Head unit, liquid discharge device, and liquid discharge device control method

Abstract

To provide a head unit of which discharge part state determination accuracy is improved.SOLUTION: A head unit comprises: a discharge part which discharges liquid in response to drive of a piezoelectric element; a waveform shaping circuit to which a first residual vibration signal in response to residual vibration is inputted and which outputs a second residual vibration signal; and a determination circuit which determines the state of the discharge part. An amplifier circuit included in the waveform shaping circuit outputs an offset voltage signal from an output terminal in the first state that a first constant voltage signal is inputted to a first input terminal and a second constant voltage signal is inputted to a second input terminal, and outputs the second residual vibration signal from the output terminal in the second state that the first residual vibration signal is inputted to the first input terminal and the second constant voltage signal is inputted to the second input terminal. The determination circuit determines the state of the discharge part on the basis of the second residual vibration signal and an offset value which is the voltage of the offset voltage signal.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present invention relates to a head unit, a liquid ejection apparatus, and a control method for a liquid ejection apparatus. [Background technology]

[0002] In a liquid ejection device in which ink is ejected from an ejection section by driving a piezoelectric element, as described in Patent Document 1, a technology is known in which a signal corresponding to the residual vibration generated after the piezoelectric element is driven is detected, and the state of the ejection section is determined based on the detection result of the signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-211873 A Summary of the Invention [Problem to be solved by the invention]

[0004] When using the technology described in Patent Document 1 to detect a signal corresponding to residual vibration and determine the state of the ejection section based on the detection results, this was not sufficient in terms of further improving the accuracy of determining the state of the ejection section, and there was room for further improvement. [Means for solving the problem]

[0005] One aspect of the head unit according to the present invention is an ejection section including a piezoelectric element that is driven by a drive signal and that ejects liquid in response to the driving of the piezoelectric element; a waveform shaping circuit that receives a first residual vibration signal corresponding to the residual vibration generated by the drive signal, and outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal; A determination circuit for determining a state of the ejection unit; Equipped with the waveform shaping circuit has an amplifier circuit including a first input terminal, a second input terminal, and an output terminal; The amplifier circuit includes: In a first state in which a first constant voltage signal is input to the first input terminal and a second constant voltage signal is input to the second input terminal, an offset voltage signal is output from the output terminal; in a second state in which the first residual vibration signal is input to the first input terminal and the second constant voltage signal is input to the second input terminal, outputting the second residual vibration signal from the output terminal; The determination circuit determines a state of the ejection portion based on the second residual vibration signal and an offset value that is a voltage of the offset voltage signal.

[0006] One aspect of the liquid ejection device according to the present invention is to A head unit that ejects liquid onto a medium; A control unit for controlling an operation of the head unit; Equipped with The head unit includes: an ejection section including a piezoelectric element that is driven by a drive signal and that ejects liquid in response to the driving of the piezoelectric element; a waveform shaping circuit that receives a first residual vibration signal corresponding to the residual vibration generated by the drive signal, and outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal; A determination circuit for determining a state of the ejection unit; having the waveform shaping circuit has an amplifier circuit including a first input terminal, a second input terminal, and an output terminal; The amplifier circuit includes: In a first state in which a first constant voltage signal is input to the first input terminal and a second constant voltage signal is input to the second input terminal, an offset voltage signal is output from the output terminal; in a second state in which the first residual vibration signal is input to the first input terminal and the second constant voltage signal is input to the second input terminal, outputting the second residual vibration signal from the output terminal; The determination circuit determines a state of the ejection section based on the second residual vibration signal and an offset value.

[0007] One aspect of a method for controlling a liquid ejection device according to the present invention includes: an ejection section including a piezoelectric element that is driven by a drive signal and that ejects liquid in response to the driving of the piezoelectric element; a waveform shaping circuit having an amplifier circuit including a first input terminal, a second input terminal, and an output terminal, receiving a first residual vibration signal corresponding to the residual vibration generated by the drive signal, and outputting a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal; A determination circuit for determining a state of the ejection unit; a memory circuit in which an offset value of the second residual vibration signal is stored; A method for controlling a liquid ejection device comprising: storing, in the storage circuit as the offset value, a voltage value of an offset voltage signal output from the output terminal in a first state in which a first constant voltage signal is input to the first input terminal and a second constant voltage signal is input to the second input terminal; driving the piezoelectric element to generate the residual vibration; a step of determining a state of the ejection section based on the second residual vibration signal output from the output terminal in a second state in which the first residual vibration signal is input to the first input terminal and the second constant voltage signal is input to the second input terminal, and based on the offset value; Includes. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of a schematic configuration of a liquid ejection device. [Diagram 2] FIG. 2 is a diagram illustrating an example of a functional configuration of a liquid ejection device. [Diagram 3] FIG. 2 is a diagram showing a schematic configuration of a discharge unit. [Figure 4] 4 is a diagram showing an example of a signal waveform of a drive signal COM. FIG. [Diagram 5] FIG. 4 is a diagram illustrating an example of a functional configuration of a drive signal selection circuit. [Figure 6] FIG. 4 is a diagram illustrating an example of a functional configuration of a switching circuit. [Figure 7]FIG. 2 is a diagram showing an example of the decoded content in a decoder. [Figure 8] FIG. 2 is a diagram illustrating a configuration of a selection circuit. [Figure 9] FIG. 11 is a diagram illustrating an example of an operation of a switching circuit. [Figure 10] FIG. 2 is a diagram illustrating an example of the configuration of a first waveform shaping circuit. [Figure 11] FIG. 2 is a diagram illustrating an example of a configuration of a temperature detection circuit. [Figure 12] FIG. 4 is a diagram illustrating an example of a configuration of a discharge state determination circuit. [Figure 13] 11 is a diagram showing an example of a signal waveform of a residual vibration signal Vout. FIG. [Figure 14] FIG. 13 is a diagram showing a calculation model of simple harmonic motion assuming residual vibration occurring in a discharge portion. [Figure 15] 6 is a diagram for explaining the relationship between the viscosity of ink and the signal waveform of residual vibration. FIG. [Figure 16] 11A and 11B are diagrams for explaining the relationship between the inclusion of air bubbles and the signal waveform of residual vibration. [Figure 17] 11A to 11C are diagrams showing an example of a method for acquiring waveform information of a residual vibration signal Vnvt, and a method for determining the state of an ejection portion to be inspected. [Figure 18] 11A and 11B are diagrams illustrating a specific example of a reference potential acquisition process. [Figure 19] 11A to 11C are diagrams illustrating a specific example of a residual vibration signal acquisition process. [Figure 20] 11A to 11C are diagrams illustrating a specific example of waveform information calculation processing. [Figure 21] 11A to 11C are diagrams illustrating a specific example of a discharge portion determination process. [Figure 22] 13 is a diagram showing an example of the configuration of a modified ejection state determination circuit. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Preferred embodiments of the present invention will be described below with reference to the drawings. The drawings are used for the convenience of explanation. Note that the embodiments described below do not unduly limit the contents of the present invention described in the claims. Furthermore, not all of the configurations described below are necessarily essential components of the present invention.

[0010] 1. Overview of the liquid ejection device FIG. 1 is a diagram showing an example of a schematic configuration of a liquid ejection device 1. The liquid ejection device 1 of this embodiment is a so-called serial printing type inkjet printer in which a carriage 21 carrying print heads 22-1 to 22-n reciprocates along a scanning axis, and the print heads 22-1 to 22-n eject ink, which is an example of a liquid, onto a medium P transported along a transport direction, thereby forming a desired image on the medium P. As the medium P used in such a liquid ejection device 1, in addition to printing paper such as plain paper, any printing medium such as a resin film or fabric can be used. Note that the liquid ejection device 1 is not limited to a serial printing type inkjet printer, but may also be a line printing type inkjet printer. In addition, the liquid ejection device 1 is not limited to an inkjet printer, but may also be a color material ejection device used in manufacturing color filters such as liquid crystal displays, an electrode material ejection device used in forming electrodes for organic EL displays, FEDs (surface emission displays), etc., a bioorganic material ejection device used in manufacturing biochips, or a three-dimensional modeling device or a textile printing device.

[0011] As shown in FIG. 1, the liquid ejection device 1 includes a control unit 10, print heads 22-1 to 22-n, a moving unit 30, a transport unit 40, and an ink container 90.

[0012] The ink container 90 stores a plurality of types of ink to be ejected onto the medium P. As such an ink container 90, an ink cartridge, a bag-shaped ink pack formed of a flexible film, an ink tank that can be refilled with ink, or the like can be used.

[0013] The control unit 10 includes a processing circuit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and a storage circuit such as a semiconductor memory, and controls each element of the liquid ejection device 1.

[0014] The print heads 22-1 to 22-n are mounted on the carriage 21. A control signal Ctrl-H and a drive signal COM output by the control unit 10 are input to the print heads 22-1 to 22-n. Ink stored in an ink container 90 is supplied to the print heads 22-1 to 22-n via a tube or the like (not shown). Each of the print heads 22-1 to 22-n ejects the supplied ink onto the medium P based on the control signal Ctrl-H and the drive signal COM.

[0015] The moving unit 30 includes a carriage motor 31 and an endless belt 32. The carriage motor 31 operates based on a control signal Ctrl-C input from the control unit 10. A carriage 21 carrying print heads 22-1 to 22-n is fixed to the endless belt 32. The endless belt 32 rotates in accordance with the operation of the carriage motor 31. The carriage 21 fixed to the endless belt 32 moves in the scanning direction due to the rotation of the endless belt 32. That is, the moving unit 30 supports the carriage 21. It controls the movement of the mounted print heads 22-1 to 22-n.

[0016] The transport unit 40 includes a transport motor 41 and a transport roller 42. The transport motor 41 operates based on a control signal Ctrl-T input from the control unit 10. The transport roller 42 rotates in accordance with the operation of the transport motor 41 while sandwiching the medium P. Due to the rotation of the transport roller 42, the medium P sandwiched between the transport roller 42 is transported along the transport direction. In other words, the transport unit 40 controls the transport of the medium P.

[0017] In the liquid ejection device 1 configured as described above, the movement unit 30 controls the reciprocating movement of the carriage 21 along the scanning direction, and the transport unit 40 controls the transport of the medium P along the transport direction. Then, in conjunction with the reciprocating movement of the carriage 21 and the transport of the medium P, each of the print heads 22-1 to 22-n mounted on the carriage 21 ejects ink onto the medium P. As a result, the ink ejected from each of the print heads 22-1 to 22-n lands on any surface of the medium P, forming a desired image on the medium P.

[0018] 2. Functional configuration of the liquid ejection device Next, a description will be given of the functional configuration of the liquid ejection device 1. Fig. 2 is a diagram showing an example of the functional configuration of the liquid ejection device 1. As shown in Fig. 2, the liquid ejection device 1 includes a control unit 10 and a head unit 20.

[0019] The control unit 10 has a control circuit board 11, a drive circuit 50, and a control circuit 100. The control circuit board 11 is a printed circuit board having one or more wiring layers, and a glass epoxy board, a glass polyimide board, or the like can be used. Each element constituting the control unit 10 including the drive circuit 50 and the control circuit 100 is mounted on the control circuit board 11. The control circuit board 11 on which each element constituting the control unit 10 is mounted may be one printed circuit board or multiple printed circuit boards.

[0020] The control circuit 100 includes a processing circuit such as a CPU or FPGA, and a storage circuit such as a semiconductor memory. An image information signal including image data is input to the control circuit 100 from an external device such as a host computer provided outside the liquid ejection device 1. Based on the input image information signal, the control circuit 100 generates signals for controlling each element of the liquid ejection device 1, and outputs the signals to the corresponding elements.

[0021] Specifically, based on the input image information signal, the control circuit 100 generates a clock signal SCK, a latch signal LAT, a change signal CH, an inspection timing signal TSIG, and print data signals SI1 to SIn as control signals Ctrl-H for controlling the print heads 22-1 to 22-n, and outputs them to the head unit 20.

[0022] Moreover, the control circuit 100 generates a base drive signal dA as a control signal Ctrl-H and outputs it to the drive circuit 50. The drive circuit 50 generates a drive signal COM including a signal waveform defined by the input base drive signal dA and outputs it to the head unit 20. Specifically, the control circuit 100 generates a base drive signal dA of a digital signal and outputs it to the drive circuit 50. The drive circuit 50 converts the input base drive signal dA into a digital / analog signal, and then generates a drive signal COM by amplifying the converted analog signal by class D. Then, the drive circuit 50 outputs the generated drive signal COM to the head unit 20. That is, the base drive signal dA output by the control circuit 100 defines the signal waveform of the drive signal COM output by the drive circuit 50. Note that the base drive signal dA may be an analog signal as long as it can define the signal waveform of the drive signal COM. Furthermore, the drive circuit 50 can generate the drive signal COM by amplifying the signal waveform defined by the base drive signal dA. Therefore, the driving circuit 50 generates the driving signal COM by performing class A amplification, class B amplification, or class AB amplification instead of class D amplification. This is also fine.

[0023] Further, the drive circuit 50 generates a reference voltage signal VBS and outputs it to the head unit 20. The reference voltage signal VBS is a signal with a constant voltage value that specifies a reference potential for driving the piezoelectric element 60 of the ejection section 600 described later. The voltage value of such a reference voltage signal VBS may be, for example, the ground potential GND, or may be 5.5V or 6V. Note that, although FIG. 2 illustrates the drive circuit 50 generating the reference voltage signal VBS and outputting it to the head unit 20, the reference voltage signal VBS may be generated by a power supply circuit (not shown) configured separately from the drive circuit 50 and output to the head unit 20.

[0024] The control circuit 100 also receives a temperature abnormality signal XHOT, temperature information signals TH1 to THn, determination result signals RT1 to RTn, and abnormality information signals Err1 to Errn from the head unit 20, which will be described later. The temperature abnormality signal XHOT is a signal indicating whether or not a temperature abnormality has occurred in the print heads 22-1 to 22-n. The temperature information signals TH1 to THn are signals indicating the temperatures of the print heads 22-1 to 22-n. The determination result signals RT1 to RTn are signals indicating the state of the ejection sections 600 of the print heads 22-1 to 22-n. The abnormality information signals Err1 to Errn are signals indicating whether or not an abnormality has occurred in the ejection state determination circuits 300-1 to 300-n, which will be described later, of the head unit 20.

[0025] The control circuit 100 corrects or stops the output control signals Ctrl-H, Ctrl-C, and Ctrl-T based on the input temperature abnormality signal XHOT, temperature information signals TH1-THn, determination result signals RT1-RTn, and abnormality information signals Err1-Errn. In other words, the liquid ejection device 1 operates according to the temperature of the head unit 20 and the state of the ejection section 600. This improves the ejection accuracy of the ink ejected from the liquid ejection device 1, and as a result, improves the quality of the image formed on the medium P. The temperature abnormality signal XHOT, temperature information signals TH1-THn, determination result signals RT1-RTn, and abnormality information signals Err1-Errn input to the control circuit 100 will be described in detail later.

[0026] The head unit 20 includes print heads 22-1 to 22-n, a head wiring board 23, flexible printed circuits (FPCs) 24-1 to 24-n, drive signal selection circuits 200-1 to 200-n, and ejection state determination circuits 300-1 to 300-n. Each of the print heads 22-1 to 22-n includes a plurality of ejection sections 600, and each of the plurality of ejection sections 600 includes a piezoelectric element 60. The head unit 20 including the print heads 22-1 to 22-n is mounted on a carriage 21.

[0027] The head wiring board 23 is a printed circuit board having one or more wiring layers, and may be, for example, a glass epoxy board or a glass polyimide board. Discharge state determination circuits 300-1 to 300-n are mounted on the head wiring board 23. One end of the flexible wiring board 24-1 is electrically connected to the head wiring board 23, and the other end is electrically connected to the print head 22-1. A drive signal selection circuit 200-1 is mounted on this flexible wiring board 24-1. Similarly, one end of the flexible wiring board 24-i (i is any one of 1 to n) is electrically connected to the head wiring board 23, and the other end is electrically connected to the print head 22-i. A drive signal selection circuit 200-i is mounted on this flexible wiring board 24-i.

[0028] One end of a cable 15 is electrically connected to the head wiring board 23. The other end of the cable 15 is electrically connected to a control circuit board 11 of the control unit 10. The clock signal SCK, the latch signal LAT, the change signal CH, the inspection timing signal TSIG, the print data signals SI1 to SIn, the drive signal COM, and the reference voltage signal VBS output by the control unit 10 are propagated through the cable 15 and are then transmitted to the head wiring board 23 of the head unit 20. The temperature abnormality signal XHOT, the temperature information signals TH1 to THn, the determination result signals RT1 to RTn, and the abnormality information signals Err1 to Errn output by the head unit 20 are propagated through a cable 15 and input to the control unit 10. Such a cable 15 has a slidable configuration that allows it to follow the movement of the carriage 21, and for example, a flexible flat cable (FFC) can be used.

[0029] The clock signal SCK, the latch signal LAT, the change signal CH, the inspection timing signal TSIG, the print data signal SIi, and the drive signal COM propagated through the cable 15 propagate through the head wiring board 23 and the flexible wiring board 24-i, and are input to the drive signal selection circuit 200-i. The drive signal selection circuit 200-i generates a drive signal Vin corresponding to each of the multiple ejection units 600 of the print head 22-i by selecting or not selecting a signal waveform included in the drive signal COM based on the clock signal SCK, the latch signal LAT, the change signal CH, the inspection timing signal TSIG, and the print data signal SIi. The drive signal Vin generated by the drive signal selection circuit 200-i is supplied to one end of the piezoelectric element 60 included in the corresponding ejection unit 600. At this time, the reference voltage signal VBS propagated through the head wiring board 23 and the flexible wiring board 24-i is commonly supplied to the other end of the piezoelectric element 60 included in the multiple ejection units 600 of the print head 22-i. The piezoelectric element 60 of the print head 22-i is driven in response to the potential difference between the drive signal Vin supplied to one end and the reference voltage signal VBS supplied to the other end. In response to the driving of the piezoelectric element 60, ink is ejected from the corresponding ejection section 600.

[0030] The drive signal selection circuit 200-i also acquires a residual vibration signal Vout corresponding to the residual vibration generated after the piezoelectric element 60 of the print head 22-i is driven. The drive signal selection circuit 200-i shapes the signal waveform of the acquired residual vibration signal Vout and outputs it as a residual vibration signal NVTi. The residual vibration signal NVTi output by the drive signal selection circuit 200-i is input to the ejection state determination circuit 300-i.

[0031] Further, the drive signal selection circuit 200-i outputs a temperature information signal THi corresponding to the temperature of the drive signal selection circuit 200-i, ie, the temperature of the print head 22-i. The temperature information signal THi is input to the ejection state determination circuit 300-i, and is also input to the control circuit 100 via the cable 15.

[0032] The discharge state determination circuit 300-i determines the state of the discharge portion 600 of the print head 22-i based on the input residual vibration signal NVTi and temperature information signal THi. Then, the discharge state determination circuit 300-i generates a determination result signal RTi according to the determination result, and outputs it to the control circuit 100. The discharge state determination circuit 300-i also generates an abnormality information signal Erri indicating whether or not an abnormality has occurred in the discharge state determination circuit 300-i, and outputs it to the control circuit 100.

[0033] The drive signal selection circuits 200-1 to 200-n output a temperature abnormality signal XHOT indicating whether or not a temperature abnormality has occurred in any of the drive signal selection circuits 200-1 to 200-n. Specifically, a wire through which the temperature abnormality signal XHOT indicating whether or not a temperature abnormality has occurred in the drive signal selection circuit 200-1 propagates and a wire through which the temperature abnormality signal XHOT indicating whether or not a temperature abnormality has occurred in the drive signal selection circuit 200-i propagates are connected in a wired-OR. When a temperature abnormality has occurred in any of the drive signal selection circuits 200-1 to 200-n, the drive signal selection circuits 200-1 to 200-n change the logic level of the temperature abnormality signal XHOT propagating through the wire connected to the wired-OR to a predetermined logic level.

[0034] In the head unit 20 configured as above, the print heads 22-1 to 22- All of the flexible wiring boards 24-1 to 24-n have the same configuration, and when there is no need to distinguish them, they may be referred to as print heads 22. All of the flexible wiring boards 24-1 to 24-n have the same configuration, and when there is no need to distinguish them, they may be referred to as flexible wiring boards 24. All of the drive signal selection circuits 200-1 to 200-n have the same configuration, and when there is no need to distinguish them, they may be referred to as drive signal selection circuits 200. All of the ejection state determination circuits 300-1 to 300-n have the same configuration, and when there is no need to distinguish them, they may be referred to as ejection state determination circuits 300.

[0035] In this case, the clock signal SCK, the latch signal LAT, the change signal CH, the test timing signal TSIG, the print data signal SI as the print data signals SI1 to SIn, and the drive signal COM are input to the drive signal selection circuit 200. The drive signal selection circuit 200 generates drive signals Vin corresponding to each of the multiple ejection units 600 of the print head 22 by selecting or not selecting a signal waveform included in the drive signal COM based on the clock signal SCK, the latch signal LAT, the change signal CH, the test timing signal TSIG, and the print data signal SI, and supplies the drive signals Vin to one end of the piezoelectric elements 60 included in the corresponding ejection units 600. At this time, the reference voltage signal VBS propagated through the head wiring board 23 and the flexible wiring board 24 is input to the other end of the piezoelectric elements 60 included in the multiple ejection units 600 of the print head 22. The piezoelectric elements 60 included in the multiple ejection units 600 of the print head 22 are driven in response to the potential difference between a drive signal Vin supplied to one end and a reference voltage signal VBS supplied to the other end. An amount of ink corresponding to the drive of the piezoelectric elements 60 is ejected from the ejection units 600 of the print head 22.

[0036] Further, a residual vibration signal Vout corresponding to the residual vibration generated after the piezoelectric element 60 of the print head 22 is driven is input to the drive signal selection circuit 200. The drive signal selection circuit 200 acquires the input residual vibration signal Vout, and outputs a residual vibration signal NVT as the residual vibration signals NVT1 to NVTn corresponding to the acquired residual vibration signal Vout. The residual vibration signal NVT output by the drive signal selection circuit 200 is input to the ejection state determination circuit 300.

[0037] Moreover, the drive signal selection circuit 200 outputs a temperature information signal TH as the temperature information signals TH1 to THn indicating the temperature of the drive signal selection circuit 200. The temperature information signal TH is input to the ejection state determination circuit 300, and is also input to the control circuit 100 via the cable 15.

[0038] The discharge state determination circuit 300 determines the state of the discharge portion 600 of the print head 22 based on the residual vibration signal NVT and the temperature information signal TH. The discharge state determination circuit 300 generates a determination result signal RT as the determination result signals RT1 to RTn according to the determination result, and an abnormality information signal Err as the abnormality information signals Err1 to Errn indicating the presence or absence of an abnormality in the discharge state determination circuit 300, and outputs them to the control circuit 100.

[0039] As described above, the liquid ejection device 1 of this embodiment includes the head unit 20 that ejects liquid onto the medium P, and the control unit 10 that controls the operation of the head unit 20. The head unit 20 also includes an ejection section 600 that includes a piezoelectric element 60 driven by a drive signal COM and ejects ink in response to the driving of the piezoelectric element 60, a drive signal selection circuit 200 that receives an input of a residual vibration signal Vout corresponding to the residual vibration generated by the drive signal COM and outputs a residual vibration signal NVT that has been shaped to include the residual vibration signal Vout, and also outputs a temperature information signal TH corresponding to the temperature of the drive signal selection circuit 200, and an ejection state determination circuit 300 that determines the state of the ejection section 600.

[0040] 3. Configuration of the discharge section Next, a description will be given of the configuration of the ejection section 600 of the print head 22. Fig. 3 is a diagram showing a schematic configuration of one of the multiple ejection sections 600 of the print head 22. As shown in Fig. 3, the ejection section 600 includes a piezoelectric element 60, a vibration plate 621, a cavity 631, and a nozzle 651.

[0041] The cavity 631 is filled with ink supplied from a reservoir 641 .

[0042] The reservoir 641 is provided in common to the multiple ejection units 600 of the print head 22. Ink is introduced into the reservoir 641 from the ink container 90 via an ink flow path (not shown) and an ink supply port 661. That is, the cavity 631 is filled with ink stored in the ink container 90.

[0043] 3, the vibration plate 621 is displaced by being driven by the piezoelectric element 60 provided on the upper surface. The internal volume of the cavity 631 filled with ink expands and contracts in accordance with the displacement of the vibration plate 621. In other words, the vibration plate 621 functions as a diaphragm that changes the internal volume of the cavity 631.

[0044] The nozzle 651 is provided in the nozzle plate 632 and is an opening that communicates with the cavity 631. When the internal volume of the cavity 631 changes, an amount of ink corresponding to the change in the internal volume is ejected from the nozzle 651.

[0045] The piezoelectric element 60 has a structure in which a piezoelectric body 601 is sandwiched between a pair of electrodes 611, 612. In the piezoelectric body 601 having such a structure, the central portions of the electrodes 611, 612 are deflected in the vertical direction together with the vibration plate 621 in response to the potential difference of the voltages supplied by the electrodes 611, 612. Specifically, a drive signal Vin is supplied to one of the electrodes 611, 612 of the piezoelectric element 60. A reference potential signal that serves as a reference for the displacement of the piezoelectric element 60 is supplied to the other of the electrodes 611, 612 of the piezoelectric element 60. Then, when the voltage level of the drive signal Vin increases, the central portion of the piezoelectric element 60 is deflected upward, and when the voltage level of the drive signal Vin decreases, the central portion is deflected downward.

[0046] In the ejection section 600 configured as above, when the piezoelectric element 60 is driven to bend upward, the center of the vibration plate 621 is displaced upward, and the internal volume of the cavity 631 is expanded. As a result, ink is drawn in from the reservoir 641. On the other hand, when the piezoelectric element 60 is driven to bend downward, the center of the vibration plate 621 is displaced downward, and the internal volume of the cavity 631 is reduced. As a result, an amount of ink according to the degree of reduction is ejected from the nozzle 651.

[0047] 3, the piezoelectric element 60 may have any structure as long as it can eject ink from the ejection unit 600. Therefore, the piezoelectric element 60 is not limited to the bending vibration structure described above, and may have a longitudinal vibration structure. The piezoelectric element 60 may be configured such that the central portion bends upward when the voltage level of the drive signal Vin becomes low, and bends downward when the voltage level of the drive signal Vin becomes high.

[0048] 4. Configuration and operation of the drive signal selection circuit 4.1 Signal waveform of drive signal COM Next, a description will be given of the configuration and operation of the drive signal selection circuit 200, which outputs a drive signal Vin corresponding to each of the multiple ejection units 600 of the print head 22 by selecting or not selecting a signal waveform included in the drive signal COM. An example of the signal waveform of the drive signal COM will be described below. Fig. 4 is a diagram showing an example of the signal waveform of the drive signal COM. As shown in Fig. 4, the drive signal COM includes a drive signal ComA and a drive signal ComB.

[0049] The drive signal ComA includes signal waveforms for expressing four gradations of large dots LD, medium dots MD, small dots SD, and non-recording ND on the medium P. Specifically, the drive signal ComA includes drive waveforms Adp1 and Adp2 as signal waveforms in a period t from when the latch signal LAT rises until the next rise of the latch signal LAT.

[0050] The drive waveform Adp1 is placed in a period tp1 from the rising edge of the latch signal LAT to the rising edge of the change signal CH within the cycle t. The drive waveform Adp1 starts with a voltage value of Vc, changes so as to drive the piezoelectric element 60, and then ends with the voltage value of Vc. When this drive waveform Adp1 is supplied to one end of the piezoelectric element 60, a predetermined amount of ink is ejected from the corresponding nozzle 651.

[0051] The drive waveform Adp2 is placed in a period tp2 from the rising edge of the change signal CH to the rising edge of the latch signal LAT within the cycle t. The drive waveform Adp2 starts with a voltage value of Vc, changes so as to drive the piezoelectric element 60, and then ends with a voltage value of Vc. When this drive waveform Adp2 is supplied to one end of the piezoelectric element 60, a smaller amount of ink than a predetermined amount is ejected from the corresponding nozzle 651.

[0052] In the following description, a predetermined amount of ink ejected from a corresponding nozzle 651 when the driving waveform Adp1 is supplied to one end of the piezoelectric element 60 may be referred to as a medium amount, and a smaller amount of ink ejected from a corresponding nozzle 651 when the driving waveform Adp2 is supplied to one end of the piezoelectric element 60 may be referred to as a small amount.

[0053] The driving signal ComB includes a signal waveform for performing an inspection CD of the nozzle 651 to be inspected among the multiple nozzles 651. Specifically, the driving signal ComB includes driving waveforms Bdp1, Bdp2, and Bdp3 as signal waveforms in a period t.

[0054] The drive waveform Bdp1 is placed in a period ts1 from the rising edge of the latch signal LAT to the rising edge of the test timing signal TSIG within the cycle t. The drive waveform Bdp1 starts with a voltage value of Vc, changes so as to drive the piezoelectric element 60, and then ends with a voltage value of Vd. When this drive waveform Bdp1 is supplied to one end of the piezoelectric element 60, ink is not ejected from the corresponding nozzle 651, and the piezoelectric element 60 is driven so as to generate a predetermined residual vibration in the corresponding ejection portion 600.

[0055] The drive waveform Bdp2 is placed in a period t from the rising edge of the test timing signal TSIG that defines the end of the period ts1 to the rising edge of the next test timing signal TSIG within the cycle t. The drive waveform Bdp2 has a constant voltage value of voltage Vd. When this drive waveform Bdp2 is supplied to one end of the piezoelectric element 60, the piezoelectric element 60 is not driven, and therefore ink is not ejected from the corresponding nozzle 651.

[0056] The drive waveform Bdp3 is placed in a period ts3 from the rising edge of the test timing signal TSIG, which defines the end of the period ts2, to the rising edge of the next latch signal LAT within the cycle t. The drive waveform Bdp3 starts with a voltage value of Vd, and then ends when the voltage value becomes Vc. When this drive waveform Bdp3 is supplied to one end of the piezoelectric element 60, the piezoelectric element 60 is not driven, and therefore ink is not ejected from the corresponding nozzle 651.

[0057] That is, the drive circuit 50 outputs to the drive signal selection circuit 200 a drive signal COM including a drive signal ComA including drive waveforms Adp1, Adp2 for expressing four gradations of large dots LD, medium dots MD, small dots SD, and non-printing ND on the medium P, and a drive signal ComB including drive waveforms Bdp1, Bdp2, Bdp3 for performing inspection CD of the ejection section 600 including the nozzle 651 to be inspected.

[0058] Note that the signal waveform of the drive signal COM shown in FIG. 4 is just an example, and the drive signal COM may include signal waveforms of various shapes depending on the movement speed of the carriage 21 carrying the print head 22, the type of medium P on which the ink lands, the characteristics of the ink, etc.

[0059] 4.2 Configuration of the drive signal selection circuit Next, a configuration of the drive signal selection circuit 200 that generates the drive signal Vin by selecting or non-selecting a signal waveform included in the drive signal COM and outputs it to the corresponding discharge section 600 will be described. Fig. 5 is a diagram showing an example of the functional configuration of the drive signal selection circuit 200. As shown in Fig. 5, the drive signal selection circuit 200 has a switching circuit 210, a first waveform shaping circuit 240, and a temperature detection circuit 250. Such a drive signal selection circuit 200 is configured as one semiconductor device and is mounted on a flexible wiring board 24 by COF (Chip On Film).

[0060] A clock signal SCK, a latch signal LAT, a change signal CH, a test timing signal TSIG, a print data signal SI, and a drive signal COM are input to the switching circuit 210. The switching circuit 210 generates drive signals Vin corresponding to each of the multiple ejection units 600 by selecting or deselecting drive waveforms Adp1, Adp2 included in drive signal ComA of the drive signals COM and drive waveforms Bdp1, Bdp2, Bdp3 included in drive signal ComB of the drive signals COM based on the input clock signal SCK, latch signal LAT, test timing signal TSIG, change signal CH, and print data signal SI, and outputs the drive signals Vin to the corresponding ejection units 600.

[0061] Furthermore, after the piezoelectric element 60 is driven by the drive signal Vin that is output, the switching circuit 210 acquires a residual vibration signal Vout corresponding to the residual vibration generated in the discharge portion 600 by the drive of the piezoelectric element 60. The switching circuit 210 outputs the acquired residual vibration signal Vout to the first waveform shaping circuit 240.

[0062] The first waveform shaping circuit 240 extracts AC components from the input residual vibration signal Vout and amplifies the AC components to shape the signal waveform of the residual vibration signal Vout, and outputs the signal waveform as the residual vibration signal NVT. The residual vibration signal NVT output by the first waveform shaping circuit 240 is output from the drive signal selection circuit 200.

[0063] The temperature detection circuit 250 detects the temperature of the semiconductor device including the drive signal selection circuit 200 having the switching circuit 210 and the first waveform shaping circuit 240. Then, the temperature detection circuit 250 generates a temperature information signal TH having a voltage value according to the temperature detection result, and outputs it from the drive signal selection circuit 200. The temperature detection circuit 250 also determines whether the temperature of the semiconductor device including the drive signal selection circuit 200 is equal to or higher than a predetermined threshold. Then, when the temperature of the semiconductor device including the drive signal selection circuit 200 is equal to or higher than the predetermined threshold, the temperature detection circuit 250 determines that a temperature abnormality has occurred in the semiconductor device including the drive signal selection circuit 200, and outputs a temperature abnormality signal XHOT of a logic level indicating the temperature abnormality of the semiconductor device including the drive signal selection circuit 200.

[0064] As described above, the drive signal selection circuit 200 includes a first waveform shaping circuit 240 that receives the residual vibration signal Vout corresponding to the residual vibration generated by the drive signal COM and outputs a residual vibration signal NVT obtained by shaping the signal waveform of the residual vibration signal Vout, and a temperature detection circuit 250 that outputs a temperature information signal TH corresponding to the temperature of the first waveform shaping circuit 240. The temperature detection circuit 240 and the temperature detection circuit 250 are included in one semiconductor device.

[0065] 4.2.1 Switching circuit configuration A specific example of the configuration and operation of the switching circuit 210 included in the drive signal selection circuit 200 will be described. Fig. 6 is a diagram showing an example of the functional configuration of the switching circuit 210. As shown in Fig. 6, the switching circuit 210 includes a selection control circuit 220 and a plurality of selection circuits 230.

[0066] A clock signal SCK, a print data signal SI, a latch signal LAT, a change signal CH, and a test timing signal TSIG are input to the selection control circuit 220. Based on the input clock signal SCK, print data signal SI, latch signal LAT, change signal CH, and test timing signal TSIG, the selection control circuit 220 generates selection signals Sa, Sb, and Sc that are at predetermined logical levels in periods tp1, tp2, and periods ts1, ts2, and ts3, respectively, and outputs them to the corresponding selection circuits 230.

[0067] The selection control circuit 220 has a set of a shift register 222, a latch circuit 224, and a decoder 226 provided corresponding to each of the piezoelectric elements 60 of the multiple ejection units 600 of the print head 22. In the following description, the print head 22 is described as having m ejection units 600 and m piezoelectric elements 60. That is, the selection control circuit 220 has m sets of a shift register 222, a latch circuit 224, and a decoder 226. In other words, the selection control circuit 220 has m shift registers 222, m latch circuits 224, and m decoders 226.

[0068] The print data signal SI includes 3-bit print data SId[SIH, SIM, SIL] for selecting whether the piezoelectric element 60 is to be driven as the above-mentioned large dot LD, medium dot MD, small dot SD, non-recording ND, or inspection CD, serially corresponding to each of the m piezoelectric elements 60. In other words, the print data signal SI is a serial signal of a total of 3m bits or more.

[0069] The print data signal SI is input to the selection control circuit 220 in synchronization with the clock signal SCK. The m shift registers 222 of the selection control circuit 220 hold the 3-bit print data SId [SIH, SIM, SIL] included in the input print data signal SI in correspondence with the piezoelectric elements 60.

[0070] In detail, the m shift registers 222 are connected in cascade corresponding to the m piezoelectric elements 60. The print data signal SI inputted in serial to the selection control circuit 220 is sequentially transferred to the subsequent stages of the m shift registers 222 connected in cascade in synchronization with the clock signal SCK. Then, when the supply of the clock signal SCK to the selection control circuit 220 is stopped, the m shift registers 222 hold 3-bit print data SId[SIH, SIM, SIL] corresponding to the m piezoelectric elements 60. In the following description, in order to distinguish the m shift registers 222 connected in cascade, they may be referred to as 1st stage, 2nd stage, ..., mth stage in order from the upstream side to which the print data signal SI is supplied to the downstream side.

[0071] Each of the m latch circuits 224 latches the 3-bit print data SId [SIH, SIM, SIL] held in the corresponding shift register 222 simultaneously at the rising edge of the latch signal LAT.

[0072] The print data SId[SIH, SIM, SIL] latched by the m latch circuits 224 is input to the corresponding decoders 226. Each of the m decoders 226 decodes the input print data SId[SIH, SIM, SIL] and outputs large dots LD, medium dots LD, Selection signals Sa, Sb, Sc of logic levels corresponding to MD, small dot SD, non-recording ND, and inspection CD are generated and output to the corresponding selection circuits 230.

[0073] Fig. 7 is a diagram showing an example of the decoded contents in the decoder 226. As shown in Fig. 7, when print data SId[SIH, SIM, SIL]=[1, 1, 0] corresponding to a large dot LD is input, the decoder 226 sets the logic level of the selection signal Sa to H, H levels during periods tp1, tp2, sets the logic level of the selection signal Sb to L, L, L levels during periods ts1, ts2, ts3, and sets the logic level of the selection signal Sc to L, L, L levels during periods ts1, ts2, ts3.

[0074] In addition, when printing data SId[SIH, SIM, SIL]=[1, 0, 0] corresponding to medium dots MD is input, the decoder 226 sets the logical level of the selection signal Sa to H, L levels during periods tp1, tp2, the logical level of the selection signal Sb to L, L, L levels during periods ts1, ts2, ts3, and the logical level of the selection signal Sc to L, L, L levels during periods ts1, ts2, ts3.

[0075] In addition, when print data SId[SIH, SIM, SIL]=[0, 1, 0] corresponding to a small dot SD is input, the decoder 226 sets the logical level of the selection signal Sa to L, H levels during periods tp1, tp2, the logical level of the selection signal Sb to L, L, L levels during periods ts1, ts2, ts3, and the logical level of the selection signal Sc to L, L, L levels during periods ts1, ts2, ts3.

[0076] In addition, when print data SId[SIH, SIM, SIL]=[0,0,0] corresponding to non-recording ND is input, the decoder 226 sets the logic level of the selection signal Sa to L,L levels during periods tp1, tp2, the logic level of the selection signal Sb to L,L,L levels during periods ts1, ts2, ts3, and the logic level of the selection signal Sc to L,L,L levels during periods ts1, ts2, ts3.

[0077] In addition, when printing data SId[SIH, SIM, SIL]=[1,1,1] corresponding to the inspection CD is input, the decoder 226 sets the logic level of the selection signal Sa to L, L levels during periods tp1, tp2, the logic level of the selection signal Sb to H, L, H levels during periods ts1, ts2, ts3, and the logic level of the selection signal Sc to L, H, L levels during periods ts1, ts2, ts3.

[0078] As described above, the selection control circuit 220 generates the selection signals Sa, Sb, Sc of logical levels corresponding to the piezoelectric elements 60 included in each of the m ejection sections 600, based on the print data SId [SIH, SIM, SIL]. Then, the selection control circuit 220 outputs the generated selection signals Sa, Sb, Sc to the corresponding selection circuits 230.

[0079] The selection circuits 230 are provided corresponding to the m piezoelectric elements 60, respectively. That is, the switching circuit 210 has m selection circuits 230. Fig. 8 is a diagram showing the configuration of a selection circuit 230 corresponding to one piezoelectric element 60. As shown in Fig. 8, the selection circuit 230 has logic inversion circuits 232a, 232b, and 232c, and transfer gates 234a, 234b, and 234c.

[0080] The selection signal Sa is supplied to the positive control terminal of the transfer gate 234a, and is also supplied to the negative control terminal of the transfer gate 234a after its logical level is inverted by the logic inverter circuit 232a. The selection signal Sb is supplied to the positive control terminal of the transfer gate 234b, and is also supplied to the negative control terminal of the transfer gate 234b after its logical level is inverted by the logic inverter circuit 232b. The selection signal Sc is supplied to the positive control terminal of the transfer gate 234b, and is also supplied to the negative control terminal of the transfer gate 234b after its logical level is inverted by the logic inverter circuit 232b. This signal is supplied to the positive control terminal of the gate 234c, and after the logic level is inverted by the logic inverter circuit 232c, it is also supplied to the negative control terminal of the transfer gate 234c.

[0081] Further, the input terminal of the transfer gate 234a is supplied with the drive signal ComA, and the input terminal of the transfer gate 234b is supplied with the drive signal ComB. The output terminals of the transfer gates 234a and 234b are connected to each other. The output terminals of the transfer gates 234a and 234b connected to each other are electrically connected to one end of the corresponding piezoelectric element 60. The input terminal of the transfer gate 234c is electrically connected to the output terminals of the transfer gates 234a and 234b connected to each other and one end of the piezoelectric element 60. The output terminal of the transfer gate 234c is commonly connected to the output terminals of the transfer gates 234c of the m selection circuits 230 of the switching circuit 210 as shown in FIG. 6.

[0082] In the selection circuit 230 configured as above, the transfer gate 234a is conductive between the input terminal and the output terminal when the logic level of the selection signal Sa is H level, and is non-conductive between the input terminal and the output terminal when the logic level of the selection signal Sa is L level. The transfer gate 234b is conductive between the input terminal and the output terminal when the logic level of the selection signal Sb is H level, and is non-conductive between the input terminal and the output terminal when the logic level of the selection signal Sb is L level. The transfer gate 234c is conductive between the input terminal and the output terminal when the logic level of the selection signal Sc is H level, and is non-conductive between the input terminal and the output terminal when the logic level of the selection signal Sc is L level. Here, in the following description, the conductive state between the input terminal and the output terminal may be referred to as "on", and the non-conductive state between the input terminal and the output terminal may be referred to as "off".

[0083] When the transfer gate 234a is turned on, the drive signal ComA is output from the switching circuit 210 as the drive signal Vin, and when the transfer gate 234b is turned on, the drive signal ComB is output from the switching circuit 210 as the drive signal Vin. The drive signal Vin output from the switching circuit 210 is supplied to one end of the piezoelectric element 60 included in the corresponding ejection section 600. When the transfer gate 234c is turned on, the switching circuit 210 acquires a residual vibration signal Vout corresponding to a residual signal generated in the ejection section 600 as a result of driving the piezoelectric element 60. The switching circuit 210 outputs the acquired residual vibration signal Vout to the first waveform shaping circuit 240.

[0084] The operation of the switching circuit 210 configured as above will be described in detail. Fig. 9 is a diagram showing an example of the operation of the switching circuit 210. The print data signal SI is serially supplied to the switching circuit 210 in synchronization with the clock signal SCK. The print data signal SI input to the switching circuit 210 is sequentially transferred to the subsequent shift register 222 in synchronization with the clock signal SCK. Then, by stopping the supply of the clock signal SCK to the switching circuit 210, each of the m shift registers 222 holds 3-bit print data SId[SIH, SIM, SIL] corresponding to the m ejection portions 600.

[0085] Thereafter, when the latch signal LAT rises, the latch circuits 224 simultaneously latch the print data SId[SIH, SIM, SIL] held in the shift register 222. Here, LT1, LT2, ..., LTm shown in Fig. 9 indicate the print data SId[SIH, SIM, SIL] held in the 1st, 2nd, ..., mth stages of the shift register 222 and latched by the corresponding latch circuit 224.

[0086] The decoder 226 decodes the latched print data SId [SIH, SIM, SIL] as shown in Fig. 7. Then, the decoder 226 outputs the selection signals Sa, Sb, Sc at the logic levels shown in Fig. 7 during the period t.

[0087] Specifically, when the print data SId[SIH, SIM, SIL]=[1, 1, 0], the decoder 226 sets the logic level of the selection signal Sa to H, H levels during periods tp1 and tp2, sets the logic level of the selection signal Sb to L, L, L levels during periods ts1, ts2, and ts3, and sets the logic level of the selection signal Sc to L, L, L levels during periods ts1, ts2, and ts3. As a result, the selection circuit 230 selects the drive waveform Adp1 of the drive signal ComA during period tp1, and selects the drive waveform Adp2 of the drive signal ComA during period tp2. As a result, the switching circuit 210 outputs the drive signal Vin corresponding to the large dot LD shown in FIG. 9. When the drive signal Vin corresponding to this large dot LD is supplied to one end of the piezoelectric element 60, a medium amount of ink is ejected from the corresponding nozzle 651 during period tp1, and a small amount of ink is ejected during period tp2. As a result, in the period t, a medium amount of ink and a small amount of ink land on the medium P and combine with each other. As a result, a large dot LD is formed on the medium P.

[0088] When the print data SId[SIH, SIM, SIL]=[1, 0, 0], the decoder 226 sets the logic level of the selection signal Sa to H, L levels during periods tp1, tp2, sets the logic level of the selection signal Sb to L, L, L levels during periods ts1, ts2, ts3, and sets the logic level of the selection signal Sc to L, L, L levels during periods ts1, ts2, ts3. As a result, the selection circuit 230 selects the drive waveform Adp1 of the drive signal ComA during period tp1, and does not select any signal waveform of the drive signals ComA and ComB during period tp2. As a result, the switching circuit 210 outputs the drive signal Vin corresponding to the medium dot MD shown in FIG. 9. When the drive signal Vin corresponding to this medium dot MD is supplied to one end of the piezoelectric element 60, a medium amount of ink is ejected from the corresponding nozzle 651 during period tp1, and no ink is ejected during period tp2. As a result, in the period t, a medium amount of ink lands on the medium P. As a result, a medium dot MD is formed on the medium P.

[0089] When the print data SId[SIH, SIM, SIL]=[0, 1, 0], the decoder 226 sets the logic level of the selection signal Sa to L, H in the periods tp1, tp2, sets the logic level of the selection signal Sb to L, L, L levels in the periods ts1, ts2, ts3, and sets the logic level of the selection signal Sc to L, L, L levels in the periods ts1, ts2, ts3. As a result, the selection circuit 230 does not select any signal waveform of the drive signals ComA and ComB in the period tp1, and selects the drive waveform Adp2 of the drive signal ComA in the period tp2. As a result, the switching circuit 210 outputs the drive signal Vin corresponding to the small dot SD shown in FIG. 9. When the drive signal Vin corresponding to this small dot SD is supplied to one end of the piezoelectric element 60, no ink is ejected from the corresponding nozzle 651 in the period tp1, and a small amount of ink is ejected in the period tp2. As a result, in the period t, a small amount of ink lands on the medium P. As a result, a small dot SD is formed on the medium P.

[0090] When the print data SId[SIH, SIM, SIL]=[0, 0, 0], the decoder 226 sets the logic level of the selection signal Sa to L, L levels in the periods tp1 and tp2, sets the logic level of the selection signal Sb to L, L, L levels in the periods ts1, ts2, and ts3, and sets the logic level of the selection signal Sc to L, L, L levels in the periods ts1, ts2, and ts3. As a result, the selection circuit 230 does not select any signal waveform of the drive signals ComA and ComB in the period tp1, and does not select any signal waveform of the drive signals ComA and ComB in the period tp2. As a result, the switching circuit 210 outputs the drive signal Vin corresponding to the non-printing ND shown in FIG. 9. When the drive signal Vin corresponding to this non-printing ND is supplied to one end of the piezoelectric element 60, ink is not ejected from the corresponding ejection section 600 in the period tp1, and ink is not ejected in the period tp2 either. As a result, in the period t, no ink lands on the medium P. Therefore, no dots are formed on the medium P.

[0091] When the print data SId[SIH, SIM, SIL]=[1, 1, 1], the decoder 226 sets the logical level of the selection signal Sa to L, L levels during periods tp1, tp2, sets the logical level of the selection signal Sb to H, L, H levels during periods ts1, ts2, ts3, and sets the logical level of the selection signal Sc to L, H, L levels during periods ts1, ts2, ts3. As a result, the selection circuit 230 selects the drive waveform Bdp1 of the drive signal ComB during period ts1, acquires the residual vibration signal Vout corresponding to the residual vibration of the ejection section 600 during period ts2, outputs the acquired residual vibration signal Vout from the switching circuit 210, and selects the drive waveform Bdp3 of the drive signal ComB during period ts3. 9 during periods ts1 and ts3, and acquires a residual vibration signal Vout corresponding to a residual signal generated after the drive waveform Bdp1 is supplied to the piezoelectric element 60 during period ts2, and outputs the residual vibration signal Vout to the first waveform shaping circuit 240. At this time, no ink is ejected from the corresponding nozzle 651 during period t. Therefore, no ink lands on the medium P during period t. Therefore, no dots are formed on the medium P.

[0092] As described above, the switching circuit 210 generates the drive signal Vin by selecting or deselecting the drive waveforms Adp1, Adp2 included in the drive signal ComA and the drive waveforms Bdp1, Bdp2, Bdp3 included in the drive signal ComB of the drive signal COM output by the drive circuit 50 based on the clock signal SCK, the print data signal SI, the latch signal LAT, the change signal CH, and the test timing signal TSIG. Then, the switching circuit 210 supplies the generated drive signal Vin to the corresponding piezoelectric element 60, and obtains the residual vibration signal Vout corresponding to the residual signal generated after the piezoelectric element 60 is driven by the drive signal Vin, and outputs it to the first waveform shaping circuit 240.

[0093] 4.2.2 Configuration of the first waveform shaping circuit Next, a specific example of the configuration and operation of the first waveform shaping circuit 240 included in the drive signal selection circuit 200 will be described. Fig. 10 is a diagram showing an example of the configuration of the first waveform shaping circuit 240. As shown in Fig. 10, the first waveform shaping circuit 240 has a filter circuit 241, a non-inverting amplifier circuit 242, and an impedance conversion circuit 243.

[0094] The filter circuit 241 includes a capacitor C10 and a resistor R10. The residual vibration signal Vout is supplied to one end of the capacitor C10. The other end of the capacitor C10 is electrically connected to one end of the resistor R10. The other end of the resistor R10 is supplied with a ground potential. The filter circuit 241 configured as above constitutes a high-pass filter that extracts high-frequency components superimposed on the residual vibration signal Vout. In other words, the filter circuit 241 reduces low-frequency components superimposed on the residual vibration signal Vout. The filter circuit 241 may have a low-pass filter in addition to the high-pass filter.

[0095] The non-inverting amplifier circuit 242 includes an operational amplifier AM10 and resistors R11 and R12. A signal output by the filter circuit 241 is input to the positive input terminal of the operational amplifier AM10. A negative input terminal of the operational amplifier AM10 is electrically connected to one end of the resistor R11 and one end of the resistor R12. The other end of the resistor R11 is electrically connected to the output terminal of the operational amplifier AM10. A ground potential is supplied to the other end of the resistor R12. The non-inverting amplifier circuit 242 configured as above constitutes a non-inverting amplifier circuit that amplifies a signal output by the filter circuit 241 input to the positive input terminal of the operational amplifier AM10 with an amplification factor determined by the resistance values ​​of the resistors R11 and R12. That is, the non-inverting amplifier circuit 242 extracts an AC component of the residual vibration signal Vout and amplifies the amplitude of the extracted signal with an amplification factor determined by the resistance values ​​of the resistors R11 and R12.

[0096] The impedance conversion circuit 243 includes an operational amplifier AM11. A signal output by the non-inverting amplifier circuit 242 is input to a positive input terminal of the operational amplifier AM11. A negative input terminal of the operational amplifier AM11 is electrically connected to an output terminal of the operational amplifier AM11. The impedance conversion circuit 243 configured as described above constitutes a so-called voltage follower circuit that outputs, from the output terminal of the operational amplifier AM11, a signal having the same signal waveform as that of a signal input to the positive input terminal of the operational amplifier AM11.

[0097] Then, the first waveform shaping circuit 240 outputs the signal output from the output terminal of the operational amplifier AM10 in the non-inverting amplifier circuit 242 and from the output terminal of the operational amplifier AM11 in the impedance conversion circuit 243 as the residual vibration signal NVT.

[0098] As described above, in the first waveform shaping circuit 240, the filter circuit 241 removes low-frequency noise and DC components from the residual vibration signal Vout, and the non-inverting amplifier circuit 242 amplifies the amplitude of the residual vibration signal Vout from which low-frequency components such as DC components have been removed, thereby generating a residual vibration signal NVT with a shaped waveform of the residual vibration signal Vout. That is, the first waveform shaping circuit 240 has an operational amplifier AM10 that amplifies the residual vibration signal Vout and outputs it as the residual vibration signal NVT, and resistors R11 and R12 that set the amplification factor of the operational amplifier AM10.

[0099] At this time, the operational amplifier AM10 and resistors R11 and R12 of the first waveform shaping circuit 240 are configured as one semiconductor device including the drive signal selection circuit 200. Although details will be described later, the residual vibration signal Vout corresponding to the residual vibration of the discharge section 600 to be inspected, which is output by the switching circuit 210, includes a signal of an electromotive force generated by the displacement of the piezoelectric element 60 due to the residual vibration generated in the discharge section 600 after the drive signal COM is supplied to the piezoelectric element 60. Therefore, the residual vibration signal Vout corresponding to the residual vibration is a signal of a weak damped vibration and is easily affected by noise. In the first waveform shaping circuit 240 of this embodiment, the filter circuit 241 removes low-frequency noise and DC components from the residual vibration signal Vout, thereby extracting AC components caused by the damped vibration generated in the discharge section 600 to be inspected, thereby improving the waveform accuracy of the residual vibration signal Vout. The signal whose waveform accuracy has been improved by the filter circuit 241 is then amplified by the non-inverting amplifier circuit 242, thereby improving resistance to noise. That is, the first waveform shaping circuit 240 outputs the residual vibration signal NVT obtained by shaping the signal waveform of the residual vibration signal Vout, in which the influence of noise and the like has been reduced and resistance to noise has been improved.

[0100] At this time, the impedance conversion circuit 243 converts the impedance of the residual vibration signal NVT output by the non-inverting amplifier circuit 242. This can increase the stability of the residual vibration signal NVT output by the first waveform shaping circuit 240, and can also reduce the risk of malfunction of the ejection section 600 due to the operation of the ejection state determination circuit 300 when determining the state of the ejection section 600 based on the residual vibration signal NVT.

[0101] By configuring such a first waveform shaping circuit 240 together with the switching circuit 210 as one semiconductor device, the residual vibration signal Vout can be amplified in the vicinity of the ejection section 600 including the piezoelectric element 60. That is, the propagation path of the residual vibration signal Vout can be shortened. This further reduces the possibility that noise will be superimposed on the residual vibration signal Vout corresponding to the residual vibration, which is a signal of weak damped vibration, and the waveform accuracy of the residual vibration signal Vout acquired by the first waveform shaping circuit 240 can be improved. As a result, the waveform accuracy of the residual vibration signal NVT output by the drive signal selection circuit 200 is improved.

[0102] 4.2.3 Temperature detection circuit configuration Next, a specific example of the configuration and operation of the temperature detection circuit 250 will be described. 1 is a diagram showing an example of the configuration of a detection circuit 250. Here, the drive signal selection circuits 200-1 to 200-n all have the same configuration. Therefore, the temperature detection circuits 250 included in each of the drive signal selection circuits 200-1 to 200-n also have the same configuration. Therefore, in the following description, when the temperature detection circuits 250 included in each of the drive signal selection circuits 200-1 to 200-n are to be distinguished from one another, the temperature detection circuit 250 included in the drive signal selection circuit 200-1 may be referred to as the temperature detection circuit 250-1, and the temperature detection circuit 250 included in the drive signal selection circuit 200-n may be referred to as the temperature detection circuit 250-n.

[0103] 11 is a diagram showing an example of the configuration of the temperature detection circuit 250. As shown in FIG. 11, the temperature detection circuit 250 includes a reference voltage generation circuit 251, a comparator CM21, a transistor Q21, diodes D21-1 to D21-k, and resistors R21 and R22. A voltage signal Vdd1 having a constant voltage value is supplied to the temperature detection circuit 250. The voltage signal Vdd1 input to the temperature detection circuit 250 may be generated based on a band gap reference of a semiconductor device including the temperature detection circuit 250, or may be generated by a power supply circuit (not shown) provided outside the temperature detection circuit 250.

[0104] The voltage signal Vdd1 input to the temperature detection circuit 250 is input to a reference voltage generation circuit 251, one end of a resistor R21, and one end of a resistor R22. The reference voltage generation circuit 251 transforms the voltage value of the input voltage signal Vdd1 to generate a voltage signal Vref with a constant voltage value. The voltage signal Vref generated by the reference voltage generation circuit 251 is input to the positive input terminal of the comparator CM21. The other end of the resistor R21 is electrically connected to the anode terminal of a diode D21-1. The cathode terminal of the diode D21-1 is electrically connected to the anode terminal of a diode D21-2, the cathode terminal of the diode D21-2 is electrically connected to the anode terminal of a diode D21-3, and the cathode terminal of a diode D21-i (i is any one of 1 to k-1) is electrically connected to the anode terminal of a diode D21-(i+1). That is, the diodes D21-1 to D21-k are connected in series. At this time, the anode terminal of the diode D21-1 provided at one end of the diodes D21-1 to D21-k connected in series is electrically connected to the other end of the resistor R21, and the ground potential is supplied to the cathode terminal of the diode D21-k provided at the other end of the diodes D21-1 to D21-k connected in series.

[0105] Then, a signal at the connection point where the other end of resistor R21 and the anode terminal of diode D21-1 are electrically connected, and the voltage value of the signal is the sum of the forward voltages of diodes D21-1 to D21-k connected in series, is input as a voltage signal Vdet to the negative input terminal of comparator CM21 and is output from temperature detection circuit 250 as a temperature information signal TH.

[0106] The comparator CM21 operates using the potential difference between the voltage signal Vdd1 supplied to the high potential power supply terminal and the ground potential signal supplied to the low potential power supply terminal as a driving source. The output terminal of the comparator CM21 is electrically connected to the gate terminal of the transistor Q21. The drain terminal of the transistor Q21 is electrically connected to the other end of the resistor R22, and the ground potential is supplied to the source terminal of the transistor Q21. The signal of the drain terminal of the transistor Q21 is output from the temperature detection circuit 250 as the temperature abnormality signal XHOT.

[0107] In the temperature detection circuit 250 configured as above, the forward voltages of the diodes D21-1 to D21-k decrease when the temperature of the diodes D21-1 to D21-k increases. That is, the voltage value of the voltage signal Vdet and the voltage value of the temperature information signal TH are the temperatures of the diodes D21-1 to D21-k, and D21-k varies depending on the temperature of the semiconductor device constituting the drive signal selection circuit 200 including D21-k. In other words, the temperature detection circuit 250 outputs a temperature information signal TH according to the temperature of the semiconductor device constituting the drive signal selection circuit 200 including the switching circuit 210, the first waveform shaping circuit 240, and the temperature detection circuit 250.

[0108] Furthermore, a voltage signal Vdet, which is the temperature of the diodes D21-1 to D21-k and has a voltage value corresponding to the temperature of the semiconductor device constituting the drive signal selection circuit 200 including the diodes D21-1 to D21-k, is also input to the negative input terminal of the comparator CM21. The comparator CM21 compares the voltage value of the voltage signal Vref input to the positive input terminal with the voltage value of the voltage signal Vdet input to the negative input terminal. If the voltage value of the voltage signal Vdet is greater than the voltage value of the voltage signal Vref, the comparator CM21 outputs an L level signal of the ground potential, and if the voltage value of the voltage signal Vdet is smaller than the voltage value of the voltage signal Vref, the comparator CM21 outputs an H level signal of the voltage value of the voltage signal Vdd1.

[0109] Here, the voltage value of the voltage signal Vref output by the reference voltage generating circuit 251 is set to the voltage value of the voltage signal Vdet input to the comparator CM21 when the temperature of the diodes D21-1 to D21-k is the highest within the temperature range in which the diodes D21-1 to D21-k can stably operate. That is, the comparator CM21 outputs an L level signal when the temperature of the diodes D21-1 to D21-k is within the temperature range in which the diodes D21-1 to D21-k can stably operate, and outputs an H level signal when the temperature of the diodes D21-1 to D21-k exceeds the temperature range in which the diodes D21-1 to D21-k can stably operate. The voltage value of the voltage signal Vref output by the reference voltage generating circuit 251 only needs to be a voltage value that can determine whether the temperatures of the diodes D21-1 to D21-k and the temperature of the semiconductor device including the diodes D21-1 to D21-k are normal or not, and is not limited to being defined based on the temperature range in which the diodes D21-1 to D21-k can operate stably.

[0110] The signal output by the comparator CM21 is input to the gate terminal of the transistor Q21. When an L-level signal is input to the gate terminal of the transistor Q21, the transistor Q21 makes the drain terminal and the source terminal non-conductive. As a result, the temperature detection circuit 250 outputs an H-level temperature abnormality signal XHOT. On the other hand, when an H-level signal is input to the gate terminal of the transistor Q21, the transistor Q21 makes the drain terminal and the source terminal conductive. As a result, the temperature detection circuit 250 outputs an L-level temperature abnormality signal XHOT. That is, when the temperature of the semiconductor device including the diodes D21-1 to D21-k is within a temperature range in which the diodes D21-1 to D21-k can stably operate and the temperature of the semiconductor device including the diodes D21-1 to D21-k is within a predetermined range, the temperature detection circuit 250 outputs an H-level temperature abnormality signal XHOT, and when the temperature of the semiconductor device including the diodes D21-1 to D21-k exceeds the temperature range in which the diodes D21-1 to D21-k can stably operate and exceeds the predetermined range, the temperature detection circuit 250 outputs an L-level temperature abnormality signal XHOT.

[0111] Here, as shown in FIG. 11, the wirings through which the temperature detection circuits 250-1 to 250-n output the temperature abnormality signal XHOT are commonly connected. Then, when a temperature abnormality occurs in any of the temperature detection circuits 250-1 to 250-n, the drain terminal and the source terminal of the transistor Q21 of the temperature detection circuit 250 in which the temperature abnormality occurs are controlled to be conductive. That is, in the temperature detection circuits 250-1 to 250-n, the wirings through which the temperature abnormality signal XHOT propagates are connected to a wired-OR. Then, when a temperature abnormality occurs in any of the temperature detection circuits 250-1 to 250-n, the wirings through which the temperature abnormality signal XHOT is output are controlled to an L level, and when no temperature abnormality occurs in any of the temperature detection circuits 250-1 to 250-n, the wirings through which the temperature abnormality signal XHOT is output are controlled to an H level.

[0112] 5. Configuration and operation of the discharge state determination circuit 5.1 Configuration and operation of the state determination circuit Next, the configuration and operation of the discharge state determination circuit 300 that determines the state of the corresponding discharge section 600 based on the residual vibration signal NVT output by the drive signal selection circuit 200 will be described. Fig. 12 is a diagram showing an example of the configuration of the discharge state determination circuit 300. As shown in Fig. 12, the discharge state determination circuit 300 has a second waveform shaping circuit 310 and a residual vibration determination circuit 320. The discharge state determination circuit 300 determines the state of the discharge section 600 based on the residual vibration signal NVT and the temperature information signal TH.

[0113] The second waveform shaping circuit 310 has resistors R31 to R36, capacitors C31 to C33, and an operational amplifier AM31. The second waveform shaping circuit 310 receives the residual vibration signal NVT output by the drive signal selection circuit 200. The second waveform shaping circuit 310 shapes the signal waveform by extracting a signal of a predetermined frequency component from the input residual vibration signal NVT, and outputs a voltage signal Vo obtained by amplifying the shaped signal waveform. Here, when the residual vibration signal NVT input to the second waveform shaping circuit 310 is a signal based on a residual vibration signal Vout corresponding to the residual vibration generated in the discharge section 600 to be inspected, the voltage signal Vo output by the second waveform shaping circuit 310 is referred to as a residual vibration signal Vnvt. That is, when the residual vibration signal NVT based on the residual vibration signal Vout corresponding to the residual vibration generated by the drive signal COM is input, the second waveform shaping circuit 310 outputs a residual vibration signal Vnvt obtained by shaping the waveform of the residual vibration signal NVT.

[0114] A voltage signal Vdd2 having a constant voltage value is supplied to the second waveform shaping circuit 310. This voltage signal Vdd2 may be generated, for example, by a power supply circuit (not shown) provided outside the second waveform shaping circuit 310. The voltage signal Vdd2 is supplied to one end of the resistor R31. The other end of the resistor R31 is electrically connected to one end of the resistor R32. The ground potential is supplied to the other end of the resistor R32. The residual vibration signal NVT output by the drive signal selection circuit 200 is input to a connection point where the other end of the resistor R31 and one end of the resistor R32 are electrically connected.

[0115] One end of the resistor R33 is electrically connected to a connection point where the other end of the resistor R31 and one end of the resistor R32 are electrically connected. The other end of the resistor R33 is electrically connected to one end of the capacitor C31. The other end of the capacitor C31 is electrically connected to one end of the resistor R34, one end of the capacitor C32, and the negative input terminal of the operational amplifier AM31. A voltage signal Vdd2 is supplied to one end of the resistor R35. The other end of the resistor R35 is electrically connected to one end of the resistor R36, one end of the capacitor C33, and the positive input terminal of the operational amplifier AM31. A ground potential is supplied to the other end of the resistor R36 and the other end of the capacitor C32. The other end of the resistor R34 and the other end of the capacitor C32 are electrically connected to the output terminal of the operational amplifier AM31. That is, the second waveform shaping circuit 310 has an operational amplifier AM31 that includes a negative input terminal, a positive input terminal, and an output terminal.

[0116] The operational amplifier AM31 is driven based on a voltage signal Vdd2 input to the high-voltage power supply terminal and a ground potential input to the low-voltage power supply terminal, generates a voltage signal Vo based on a signal input to the negative input terminal and a signal input to the positive input terminal, and outputs the voltage signal Vo from the output terminal. That is, the operational amplifier AM31 includes a low-voltage power supply terminal that specifies the lower limit of the voltage value of the signal output from the output terminal, and a high-voltage power supply terminal that specifies the upper limit of the voltage value of the signal output from the output terminal, and the ground potential is input to the low-voltage power supply terminal, and a voltage signal Vdd2 that is a positive potential higher than the ground potential is input to the high-voltage power supply terminal. The operational amplifier AM31 outputs a voltage signal Vo whose voltage value changes between the ground potential and the voltage value of the voltage signal Vdd2. Here, in the following description, the signal input to the positive input terminal of the operational amplifier AM31 is referred to as a voltage signal Vp, and the negative input terminal of the operational amplifier AM31 is referred to as a voltage signal Vp. The signal input to the input terminal may be referred to as a voltage signal Vm.

[0117] In the second waveform shaping circuit 310 configured as above, the operational amplifier AM31, resistors R33, R34, and capacitor C31 function as an active high-pass filter that extracts a signal of high frequency components from the residual vibration signal NVT, inverts and amplifies the extracted signal of high frequency components, and level-shifts the reference potential based on the voltage value of the voltage signal Vp. The operational amplifier AM31, resistors R33, R34, and capacitor C32 function as an active low-pass filter that extracts a signal of low frequency components from the residual vibration signal NVT, inverts and amplifies the extracted signal of low frequency components, and level-shifts the reference potential based on the voltage value of the voltage signal Vp.

[0118] That is, the second waveform shaping circuit 310 has an active bandpass filter that removes noise components and shapes the signal waveform by extracting a signal of a predetermined range of frequency components from the input residual vibration signal NVT, and outputs a voltage signal Vo by level-shifting and inverting and amplifying the reference potential of the shaped signal based on the voltage signal Vp input to the positive input terminal of the operational amplifier AM31.

[0119] The residual vibration determination circuit 320 includes a control circuit 321, a multiplexer 322, and an AD (Analog The residual vibration determination circuit 320 has a digital to digital conversion circuit 323, a correction circuit 324, a memory circuit 326, a waveform information calculation circuit 327, and a state determination circuit 328. The residual vibration determination circuit 320 determines the state of the ejection part 600 based on the residual vibration signal Vnvt that the second waveform shaping circuit 310 outputs as a voltage signal Vo.

[0120] The control circuit 321 controls various components of the residual vibration determination circuit 320. The memory circuit 326 stores information on a predetermined determination threshold value and correction information for the residual vibration determination circuit 320 to determine the state of the discharge section 600 based on the residual vibration signal Vnvt. The memory circuit 326 also temporarily holds various signals for the residual vibration determination circuit 320 to determine the state of the discharge section 600 based on the residual vibration signal Vnvt. Such a memory circuit 326 includes a volatile memory such as a register or a RAM (Random Access Memory), and a non-volatile memory such as a ROM (Read Only Memory) or a flash memory.

[0121] The multiplexer 322 receives the voltage signal Vo output by the second waveform shaping circuit 310 and the temperature information signal TH output by the temperature detection circuit 250 of the drive signal selection circuit 200. In addition, the select signal Sel output by the control circuit 321 is input to a control terminal of the multiplexer 322. The multiplexer 322 selects the voltage signal Vo or the temperature information signal TH based on the select signal Sel input to the control terminal, and outputs the selected signal to the AD conversion circuit 323 as an acquisition signal AS.

[0122] The AD conversion circuit 323 converts the input acquisition signal AS into a digital signal at a predetermined sampling period and outputs it as an acquisition signal dAS. That is, the residual vibration determination circuit 320 includes an AD conversion circuit 323 that converts the residual vibration signal Vnvt and the temperature information signal TH, which are output as a voltage signal Vo, into digital signals. The AD conversion circuit 323 then outputs the generated acquisition signal dAS to the control circuit 321 and the correction circuit 324.

[0123] The control circuit 321 acquires the acquisition signal dAS input from the AD conversion circuit 323. Then, the control circuit 321 generates a memory control signal MC for storing the acquired acquisition signal dAS in the memory circuit 326, and outputs the memory control signal MC to the memory circuit 326. As a result, the control circuit 321 stores the acquired acquisition signal dAS in the memory circuit 326.

[0124] The control circuit 321 also includes a memory circuit 326 for reading out the correction information. The control circuit 321 generates a memory control signal MC and outputs it to the memory circuit 326. In this way, the control circuit 321 acquires the correction information. Then, the control circuit 321 generates a correction information signal CV according to the acquired correction information and outputs it to the correction circuit 324.

[0125] The correction circuit 324 receives the acquisition signal dAS output by the AD conversion circuit 323 and the correction information signal CV output by the control circuit 321. The correction circuit 324 corrects the acquisition signal dAS output by the AD conversion circuit 323 based on the correction information signal CV at a timing based on the sampling period of the AD conversion circuit 323. The correction circuit 324 then outputs the corrected acquisition signal dAS to the control circuit 321 as a detection voltage signal vn. Here, correcting at a timing based on the sampling period ideally means correcting for each sampling period of the AD conversion circuit 323, but also includes correcting for each multiple sampling periods depending on the processing load of the residual vibration determination circuit 320, etc. In other words, correcting at a timing based on the sampling period includes correcting at a timing synchronized with the sampling period of the AD conversion circuit 323.

[0126] The control circuit 321 sequentially acquires the detection voltage signal vn input from the correction circuit 324. Then, the control circuit 321 generates a memory control signal MC for storing the acquired detection voltage signal vn in the memory circuit 326. As a result, the memory circuit 326 stores a plurality of detection voltage signals vn that are sequentially corrected and output by the correction circuit 324 at a timing based on the sampling period of the AD conversion circuit 323.

[0127] The control circuit 321 also generates a memory control signal MC for reading out the multiple detected voltage signals vn stored in the memory circuit 326, and outputs the signal to the memory circuit 326. As a result, the control circuit 321 acquires the multiple detected voltage signals vn. The control circuit 321 then generates a detected voltage signal group vng including the multiple acquired detected voltage signals vn, and outputs the signal to the waveform information calculation circuit 327.

[0128] The waveform information calculation circuit 327 calculates waveform information such as the amplitude and frequency of the residual vibration signal Vnvt included in the voltage signal Vo based on the input detection voltage signal group vng. Then, the waveform information calculation circuit 327 generates a waveform information signal WI including the calculated waveform information, and outputs it to the state determination circuit 328.

[0129] Furthermore, the control circuit 321 generates a memory control signal MC for reading out a judgment threshold for judging the state of the discharge portion 600 based on the residual vibration signal Vnvt from the memory circuit 326, and outputs the signal to the memory circuit 326. In this way, the control circuit 321 acquires the judgment threshold. Then, the control circuit 321 generates a judgment threshold signal Jth including the acquired judgment threshold, and outputs the signal to the state judgment circuit 328.

[0130] The state determination circuit 328 determines the state of the ejection part 600 to be inspected based on the waveform information signal WI output by the waveform information calculation circuit 327 and the determination threshold signal Jth output by the control circuit 321, and generates and outputs a determination result signal RT according to the determination result. The determination result signal RT output by this state determination circuit 328 is output from the residual vibration determination circuit 320 and the ejection state determination circuit 300, and input to the control circuit 100.

[0131] Furthermore, when an abnormality occurs in the residual vibration determination circuit 320, the control circuit 321 generates an abnormality information signal Err indicating the occurrence of the abnormality. The abnormality information signal Err output by the control circuit 321 is output from the residual vibration determination circuit 320 and the ejection state determination circuit 300, and input to the control circuit 100.

[0132] 5.2. State judgment of the ejection unit in the judgment circuit Here, the relationship between the residual vibration generated in the discharge unit 600 and the state of the discharge unit 600 will be described. As described above, the residual vibration signal NVT and the residual vibration signal Vnvt are signals that are shaped by extracting the AC component of the residual vibration signal Vout based on the residual signal, removing noise components, and amplifying the signal with a known amplification factor. Therefore, when the amplification factor is taken into consideration when determining the state of the discharge unit 600, ideally, the state of the discharge unit 600 determined according to the residual vibration signal Vout and the state of the discharge unit 600 determined based on the residual vibration signals NVT and Vnvt will have similar determination results. Therefore, in the following description, the relationship between an example of the residual vibration signal Vout corresponding to the residual vibration generated in the discharge unit 600 and the state of the discharge unit 600 corresponding to the residual vibration signal Vout will be described, and the relationship between the residual vibration signals NVT and Vnvt obtained by shaping the waveform of the residual vibration signal Vout corresponding to the residual vibration and the corresponding state of the discharge unit 600 will be omitted.

[0133] In explaining the relationship between the residual vibration generated in the ejection section 600 and the state of the ejection section 600, first, an example of the residual vibration signal Vout corresponding to the residual vibration will be explained. Fig. 13 is a diagram showing an example of the signal waveform of the residual vibration signal Vout.

[0134] As described with reference to FIGS. 6 to 9, when determining the state of the ejection section 600 to be inspected, the control circuit 100 outputs the print data SId[SIH, SIM, SIL]=[1, 1, 1] as the print data SId corresponding to the ejection section 600 to be inspected. As a result, the switching circuit 210 supplies the drive signal Vin including the drive waveform Bdp1 to one end of the ejection section 600 to be inspected during the period ts1. The piezoelectric element 60 is driven when the drive signal Vin including the drive waveform Bdp1 is supplied to one end. The drive of the piezoelectric element 60 displaces the vibration plate 621, and the internal pressure of the cavity 631 changes due to the displacement of the vibration plate 621. Thereafter, when a constant drive signal Vin with a voltage Vd is supplied to one end of the piezoelectric element 60, the vibration plate 621 generates a damped vibration according to the change in the internal pressure of the cavity 631. At this time, the piezoelectric element 60 is displaced due to the damped vibration generated in the vibration plate 621. Then, an electromotive force is generated between the electrodes 611 and 612 of the piezoelectric element 60 due to the displacement generated in the piezoelectric element 60. That is, in the period ts1, the piezoelectric element 60 is driven, so that a weak electromotive force corresponding to the damped vibration generated in the diaphragm 621 is generated between the electrodes 611 and 612 of the piezoelectric element 60.

[0135] During the subsequent period ts2, the transfer gate 234b of the switching circuit 210 is turned off and the transfer gate 234c is turned on.

[0136] As a result, the switching circuit 210 acquires a residual vibration signal Vout corresponding to the damped vibration, the voltage amplitude of which decreases over time as shown in Fig. 13, and outputs the acquired residual vibration signal Vout to the first waveform shaping circuit 240. Then, in a period ts3, the transfer gate 234b of the switching circuit 210 is turned on and the transfer gate 234c is turned off, so that a drive signal Vin including a drive waveform Bdp3 is supplied to one end of the piezoelectric element 60. As a result, the voltage value of one end of the ejection part 600 to be inspected is controlled from voltage Vd to voltage Vc. That is, the displacement of the piezoelectric element 60 is controlled to a steady state.

[0137] The residual vibration judgment circuit 320 of this embodiment judges the state of the ejection section 600 to be inspected based on waveform information such as the amplitude and frequency of the residual vibration signal Vout corresponding to the residual vibration, and the amplitude and frequency of the residual vibration signal Vout corresponding to the residual vibration and the residual vibration signal Vnvt corresponding to the NVT.

[0138] Here, an example of the relationship between the waveform information of the residual vibration signal Vout and the state of the ejection section 600 to be inspected will be described. Fig. 14 is a diagram showing a calculation model of simple harmonic motion assuming residual vibration occurring in the ejection section 600. As described above, when the drive signal Vin is supplied to the piezoelectric element 60, This displaces the piezoelectric element 60, and the vibration plate 621 is also displaced in accordance with the displacement of the piezoelectric element 60. As a result, the volume of the cavity 631 expands and then contracts. At this time, a part of the ink filling the cavity 631 is ejected from the nozzle 651 due to the pressure generated inside the cavity 631.

[0139] During such a series of operations of the ejection unit 600, the vibration plate 621 freely vibrates at a natural vibration frequency determined by the flow path resistance r due to the shape of the flow path through which the ink flows and the viscosity of the ink, the inertance m due to the weight of the liquid in the flow path, and the compliance C of the vibration plate 621. This free vibration of the vibration plate 621 is the residual vibration generated in the ejection unit 600.

[0140] The calculation model of the residual vibration of diaphragm 621 shown in Fig. 14 can be expressed by pressure p, inertance m, compliance C, and flow path resistance r. Then, by calculating the step response in the case where pressure p is applied to the circuit shown in Fig. 14 with respect to the volume velocity u, formulas (1) to (3) are obtained.

[0141]

number

[0142]

number

[0143]

number

[0144] FIG. 15 is a diagram for explaining the relationship between the viscosity of ink and the signal waveform of residual vibration. In FIG. 15, the horizontal axis indicates time, and the vertical axis indicates the magnitude of residual vibration. When ink near the nozzle 651 dries, the viscosity of the ink increases, that is, the ink thickens. When the ink near the nozzle 651 thickens, the flow path resistance r increases. As a result, as shown in FIG. 15, the attenuation of the residual vibration increases.

[0145] FIG. 16 is a diagram for explaining the relationship between the inclusion of air bubbles and the signal waveform of the residual vibration. In FIG. 16, the horizontal axis indicates time, and the vertical axis indicates the magnitude of the residual vibration. When air bubbles are in the ink flow path or near the nozzle 651 inside the cavity 631, the inertance m, which is the liquid weight, is reduced by the amount of the inertance m compared to the normal case. When the inertance m is reduced, the angular velocity ω increases as shown in equation (2). As a result, as shown in FIG. 16, the vibration period of the residual vibration becomes shorter. In other words, the vibration frequency of the residual vibration becomes higher.

[0146] As described above, when an abnormality occurs in the ejection section 600, such as when the ink thickens near the nozzle 651 of the ejection section 600 or when air bubbles get into the cavity 631 of the ejection section 600, the vibration of the residual vibration generated in the ejection section 600 changes. Therefore, the waveform information such as frequency and amplitude differs between the residual vibration signals Vout, NVT, Vnvt generated when an abnormality occurs in the ejection section 600 and the residual vibration signals Vout, NVT, Vnvt generated when no abnormality occurs in the ejection section 600.

[0147] The residual vibration judgment circuit 320 acquires a residual vibration signal Vout corresponding to the residual vibration, which is a damped vibration generated in the ejection section 600 being inspected, and a residual vibration signal Vnvt based on the NVT, and calculates waveform information such as the amplitude and frequency of the acquired residual vibration signal Vnvt.

[0148] Then, the residual vibration determination circuit 320 determines whether the corresponding ejection unit 600 is normal or not according to the waveform information signal WI including the waveform information. Note that the state of the ejection unit 600 determined by the residual vibration determination circuit 320 is not limited to the above-mentioned ink thickening and air bubble inclusion, but may be, for example, the presence or absence of adhesion of foreign matter such as pieces of paper near the nozzle 651, the presence or absence of ink leakage due to the adhesion of the foreign matter, etc.

[0149] 5.3 Determining the condition of the discharge part based on residual vibration As described above, the residual vibration determination circuit 320 of this embodiment determines the state of the ejection unit 600 to be inspected based on waveform information of the residual vibration signal Vnvt based on the residual vibration signals Vout and NVT corresponding to the residual vibration generated after the ejection unit 600 to be inspected is driven by the drive signal COM. In this case, from the viewpoint of improving the accuracy of determining the state of the ejection unit 600 to be inspected, it is required to improve the accuracy of acquiring the waveform information of the residual vibration signal Vnvt in the residual vibration determination circuit 320.

[0150] For example, when the residual vibration determination circuit 320 acquires a period or frequency from the residual vibration signal Vnvt as waveform information, the residual vibration determination circuit 320 is required to accurately grasp the potential that is the reference for the amplitude of the residual vibration signal Vnvt because the signal waveform of the residual vibration signal Vnvt is a damped vibration waveform as shown in Fig. 13. Also, for example, when the residual vibration determination circuit 320 acquires the amplitude of the residual vibration signal Vnvt as waveform information, the residual vibration signal Vnvt is a signal obtained by amplifying the signal waveform of the residual vibration signal Vout, NVT by the non-inverting amplifier circuit 242 and the second waveform shaping circuit 310 of the first waveform shaping circuit 240, so the residual vibration determination circuit 320 is required to more accurately grasp the amplification factor of the non-inverting amplifier circuit 242 of the first waveform shaping circuit 240 and the amplification factor of the second waveform shaping circuit 310.

[0151] In the liquid ejection device 1 and head unit 20 of this embodiment, the residual vibration determination circuit 320 judges whether the residual vibration signal NVT corresponding to the residual vibration is not input to the negative input terminal of the operational amplifier AM31, and therefore, a constant potential voltage signal Vm is input to the negative input terminal of the operational amplifier AM31, and a constant potential voltage signal Vp obtained by dividing the voltage signal Vdd2 by the resistance value of resistor R35 and the resistance value of resistor R36 is input to the positive input terminal of the operational amplifier AM31. The state of the discharge part 600 is judged based on the voltage value of the voltage signal Vo output from the output terminal of the operational amplifier AM31, and the residual vibration signal Vnvt as the voltage signal Vo output from the output terminal of the operational amplifier AM31 in a state in which a residual vibration signal NVT corresponding to the residual vibration is input to the negative input terminal of the operational amplifier AM31 and a constant potential voltage signal Vp obtained by dividing the voltage signal Vdd2 by the resistance value of the resistor R35 and the resistance value of the resistor R36 is input to the positive input terminal of the operational amplifier AM31. This allows the residual vibration judgment circuit 320 to more accurately acquire the potential that is the reference for the amplitude of the residual vibration signal Vnvt. Therefore, the residual vibration judgment circuit 320 can accurately acquire the period and frequency of the residual vibration signal Vnvt, and as a result, the accuracy of judgment of the state of the discharge part 600 to be inspected in the residual vibration judgment circuit 320 is improved.

[0152] In the following description, when the residual vibration signal NVT corresponding to the residual vibration is not input to the negative input terminal of the operational amplifier AM31, the voltage signal Vo output from the output terminal of the operational amplifier AM31 may be referred to as the voltage signal Voff. That is, when the residual vibration signal NVT corresponding to the residual vibration is not input, the second waveform shaping circuit 310 outputs the voltage signal Voff as the voltage signal Vo, and when the residual vibration signal NVT corresponding to the residual vibration is input, it outputs the residual vibration signal Vnvt as the voltage signal Vo.

[0153] In the liquid ejection device 1 and head unit 20 of this embodiment, the non-inverting amplifier circuit 242 of the first waveform shaping circuit 240 is configured with a semiconductor device, and therefore polysilicon resistors are used as the resistors R11 and R12 that determine the amplification factor of the non-inverting amplifier circuit 242. However, the resistance value of the polysilicon resistor changes significantly with temperature, and therefore the amplification factor of the non-inverting amplifier circuit 242, that is, the amplitude rate of the residual vibration signals NVT and Vnvt, depends greatly on temperature. In contrast, in the liquid ejection device 1 and head unit 20 of this embodiment, the residual vibration determination circuit 320 acquires the residual vibration signal Vnvt and a temperature information signal TH corresponding to the temperature of the first waveform shaping circuit 240, and determines the state of the ejection section 600 to be inspected based on the acquired residual vibration signal Vnvt and temperature information signal TH. As a result, even if the resistance values ​​of resistors R11 and R12 change due to temperature, changing the amplification factor of non-inverting amplifier circuit 242 and changing the voltage value of the amplitude of residual vibration signal Vnvt, the amplitude of residual vibration signal Vnvt can be appropriately corrected. Therefore, the accuracy of acquiring the amplitude of residual vibration signal Vnvt in residual vibration judgment circuit 320 is improved, and as a result, the accuracy of judging the state of ejection part 600 to be inspected in residual vibration judgment circuit 320 is improved.

[0154] Here, an example of a method for acquiring waveform information of the residual vibration signal Vnvt based on the residual vibration signal Vout in the liquid ejection device 1 and head unit 20 of this embodiment, and a method for determining the state of the ejection section 600 to be inspected will be described. Fig. 17 is a diagram showing an example of a method for acquiring waveform information of the residual vibration signal Vnvt, and a method for determining the state of the ejection section 600 to be inspected.

[0155] 17, when acquiring waveform information of the residual vibration signal Vnvt and judging the state of the ejection section 600 to be inspected based on the acquired waveform information, the head unit 20 executes a reference potential acquisition process to acquire the voltage value of the voltage signal Voff as a reference potential of the amplitude of the residual vibration signal Vnvt (step S1), and executes a residual vibration signal acquisition process to acquire the voltage value of the residual vibration signal Vnvt (step S2). After that, the head unit 20 executes a waveform information calculation process to calculate the waveform information of the residual vibration signal Vnvt based on the acquired voltage value of the voltage signal Voff and the voltage value of the residual vibration signal Vnvt (step S3), and executes an ejection section judgment process to judge the state of the ejection section 600 based on the calculated waveform information of the residual vibration signal Vnvt (step S4).

[0156] Fig. 18 is a diagram showing a specific example of the reference potential acquisition process. As shown in Fig. 18, in the reference potential acquisition process, the control circuit 100 outputs a print data signal SI for controlling m transfer gates 234c of the switching circuit 210 of the drive signal selection circuit 200 to turn off. As a result, the switching circuit 210 controls the m transfer gates 234c to turn off (step S110). Therefore, the switching circuit 210 outputs a signal with a constant voltage value as the residual vibration signal Vout.

[0157] The residual vibration signal Vout, which has a constant voltage value and is output by the switching circuit 210, is blocked by a high-pass filter constituted by the filter circuit 241 of the first waveform shaping circuit 240 and the second waveform shaping circuit 310. Therefore, the residual vibration signal Vout is not supplied to the negative input terminal of the operational amplifier AM31 of the second waveform shaping circuit 310. At this time, a signal output from the output terminal of the operational amplifier AM31 is input via R34 to the negative input terminal of the operational amplifier AM31. That is, the switching circuit 210 controls the m transfer gates 234c to be turned off, so that the operational amplifier AM31 of the second waveform shaping circuit 310 constitutes a so-called voltage follower circuit that outputs from its output terminal a voltage signal Vo having the same voltage value as the voltage signal Vm input to its positive input terminal. Then, the second waveform shaping circuit 310 outputs the voltage signal Vo output from the operational amplifier AM31 to the residual vibration determination circuit 320 as a voltage signal Voff during the period in which the switching circuit 210 controls the m transfer gates 234c to be turned off.

[0158] In other words, during the period in which the switching circuit 210 controls the m transfer gates 234c to be turned off, a constant voltage signal Vm having the same voltage value as the voltage signal Vo is input to the negative input terminal of the operational amplifier AM31, a constant voltage signal Vm having a voltage value obtained by dividing the voltage signal Vdd2 by resistors R35 and R36 is input to the positive input terminal of the operational amplifier AM31, and the operational amplifier AM31 outputs a voltage signal Voff from the output terminal.

[0159] After the switching circuit 210 controls the m transfer gates 234c to be turned off, during a period in which the second waveform shaping circuit 310 outputs the voltage signal Voff as the voltage signal Vo, the control circuit 321 of the residual vibration determination circuit 320 outputs a select signal Sel that selects the voltage signal Vo as the acquisition signal AS (step S120). This causes the multiplexer 322 to select the voltage signal Vo as the acquisition signal AS. The voltage signal Vo selected as the acquisition signal AS by the multiplexer 322 is converted by the AD conversion circuit 323 into an acquisition signal dAS, which is a digital signal, and then input to the control circuit 321. That is, the control circuit 321 acquires the voltage value of the voltage signal Voff as a voltage vof based on the acquisition signal dAS (step S130).

[0160] Moreover, the control circuit 321 reads out from the storage circuit 326 a threshold voltage Vth for determining whether or not the voltage vof is normal (step S140).

[0161] Then, the control circuit 321 judges whether the voltage vof is greater than the threshold voltage Vth (step S150). If the control circuit 321 judges that the voltage vof is equal to or less than the threshold voltage Vth (N in step S150), the control circuit 321 judges that the input voltage signal Voff is normal, and stores the acquired voltage vof in the memory circuit 326 (step S160). In other words, the memory circuit 326 stores the voltage vof, which is the voltage value of the voltage signal Voff.

[0162] On the other hand, when the control circuit 321 determines that the voltage vof is greater than the threshold voltage Vth (Y in step S150), the control circuit 321 determines that the voltage vof, which is the voltage value of the input voltage signal Voff, is abnormal, and outputs an abnormality information signal Err indicating the abnormality of the voltage signal Voff (step S165). That is, when the voltage vof, which is the voltage value of the voltage signal Voff, exceeds the threshold voltage Vth, the residual vibration determination circuit 320 outputs the abnormality information signal Err.

[0163] The abnormality information signal Err output by the residual vibration determination circuit 320 is input to the control circuit 100. When the abnormality information signal Err indicating an abnormality in the voltage value of the voltage signal Voff is input, the control circuit 100 ends the reference potential acquisition process in the head unit 20. Note that the control circuit 100 may stop the operation of at least one of the liquid ejection device 1 and the head unit 20 upon ending the reference potential acquisition process in the head unit 20.

[0164] As described above, the reference potential acquisition process is a process of storing in memory circuit 326 a voltage vof, which is the voltage value of voltage signal Voff, the voltage value of which is the same as that of voltage signal Vm, output from the output terminal, in a state in which a constant voltage signal Vm, the voltage value of which is the same as that of voltage signal Vo, is input to the negative input terminal of operational amplifier AM31, and a constant voltage signal Vm, the voltage value of which is obtained by dividing voltage signal Vdd2 by resistors R35 and R36, is input to the positive input terminal.

[0165] The above-described reference potential acquisition process may be executed only once during the manufacturing stage of the liquid ejection device 1, or may be executed every time the residual vibration signal Vout is acquired. However, it may be executed based on the driving time and temperature of the liquid ejection device 1 and the head unit 20, the number of times the residual vibration signal Vout is acquired, etc. It is preferable that the above-mentioned process is executed at predetermined intervals for each of the liquid ejection device 1 and the head unit 20. In other words, it is preferable that the voltage vof, which is the voltage value of the voltage signal Voff stored in the memory circuit 326, is updated at predetermined intervals. This allows the residual vibration determination circuit 320 to update the voltage signal Voff to an optimal voltage value according to the operating state of the liquid ejection device 1 and the head unit 20 while reducing the risk of a significant increase in the processing load of the control circuit 321 associated with the reference potential acquisition process.

[0166] Furthermore, the voltage vof, which is the voltage value of the voltage signal Voff stored in the memory circuit 326, may be updateable from outside the liquid ejection device 1 via a network line, in addition to the above-mentioned reference potential acquisition process. That is, the head unit 20 includes a communication interface circuit (not shown) capable of communicating with the outside of the liquid ejection device 1, such as a communication interface circuit compatible with Ethernet communication or a communication interface circuit compatible with WiFi communication, and the voltage vof, which is the voltage value of the voltage signal Voff stored in the memory circuit 326, may be updated based on information held in a network server or the like connected to be able to communicate via the communication interface circuit.

[0167] This reduces the processing burden on the control circuit 321 associated with the reference potential acquisition process, and even if the usage environment of the liquid ejection device 1 and head unit 20 changes, or if design changes or maintenance processing is performed on the liquid ejection device 1 and head unit 20, the voltage vof stored in the memory circuit 326 can be easily and appropriately managed, thereby improving the reliability of the liquid ejection device 1 and head unit 20.

[0168] Next, the residual vibration signal acquisition process will be described. Fig. 19 is a diagram showing a specific example of the residual vibration signal acquisition process. As shown in Fig. 19, in the residual vibration signal acquisition process, the control circuit 321 of the residual vibration determination circuit 320 sets a variable j to "0" as an initialization process (step S210).

[0169] Thereafter, the control circuit 321 of the residual vibration determination circuit 320 outputs a select signal Sel for selecting the temperature information signal TH as the acquisition signal AS (step S220). As a result, the multiplexer 322 selects the temperature information signal TH as the acquisition signal AS. The temperature information signal TH selected by the multiplexer 322 as the acquisition signal AS is converted by the AD conversion circuit 323 into an acquisition signal dAS, which is a digital signal, and then input to the control circuit 321. As a result, the control circuit 321 acquires the temperature information signal TH output by the drive signal selection circuit 200. Then, the control circuit 321 generates a memory control signal MC for reading out the temperature correction value CVt corresponding to the acquired temperature information signal TH from the storage circuit 326, and outputs the signal to the storage circuit 326. That is, the control circuit 321 reads out the temperature correction value CVt corresponding to the acquired temperature information signal TH from the storage circuit 326 (step S225).

[0170] Furthermore, the control circuit 321 reads out from the storage circuit 326 the voltage vof, which is the voltage value of the voltage signal Voff stored in the storage circuit 326 in the reference potential acquisition process (step S230).

[0171] The control circuit 321 generates a correction information signal CV including the temperature correction value CVt and the voltage vof read from the memory circuit 326. Then, the control circuit 321 outputs the correction information signal CV including the generated temperature correction value CVt and the voltage vof to the correction circuit 324 (step S240).

[0172] Thereafter, the control circuit 321 outputs a select signal Sel that selects the voltage signal Vo as the acquisition signal AS (step S250), and the switching circuit 210 supplies the drive signal Vin corresponding to the inspection CD to the ejection unit 600 to be inspected (step S260). The step of supplying the liquid to the discharge portion 600 corresponds to the step of driving the piezoelectric element 60 and generating residual vibration in the discharge portion 600 to be inspected.

[0173] Then, when the test timing signal TSIG rises (step S270), the residual vibration determination circuit 320 acquires the voltage value of the residual vibration signal Vout corresponding to the residual vibration generated in the discharge section 600 being tested, and the residual vibration signal Vnvt based on the NVT.

[0174] Specifically, the piezoelectric element 60 of the ejection unit 600 to be inspected is driven by being supplied with a drive signal Vin corresponding to the inspection CD. This causes residual vibration to occur in the ejection unit 600 to be inspected. A residual vibration signal NVT obtained by shaping the signal waveform of the residual vibration signal Vout corresponding to the residual vibration generated in the ejection unit 600 to be inspected is input to the negative input terminal of the operational amplifier AM31 of the second waveform shaping circuit 310. At this time, a constant voltage signal Vp having a voltage value obtained by dividing the voltage signal Vdd2 by resistors R35 and R36 is input to the positive input terminal of the operational amplifier AM31 of the second waveform shaping circuit 310. Therefore, a signal of a predetermined range of frequency components is extracted from the residual vibration signal NVT, the signal waveform is shaped, and the reference potential of the shaped signal is level-shifted based on the voltage signal Vp input to the + input terminal of the operational amplifier AM31, and the inverted and amplified residual vibration signal Vnvt is output as a voltage signal Vo to the output terminal of the operational amplifier AM31 in the second waveform shaping circuit 310. In other words, in a state in which the residual vibration signal NVT based on the residual vibration signal Vout corresponding to the residual signal is input to the - input terminal of the operational amplifier AM31 and a voltage signal Vp with a constant voltage value is input to the + input terminal, the operational amplifier AM31 outputs the residual vibration signal Vnvt as a voltage signal Vo from the output terminal.

[0175] The residual vibration signal Vnvt as a voltage signal Vo output by the operational amplifier AM31 of the second waveform shaping circuit 310 is selected by the multiplexer 322 and input to the AD conversion circuit 323 as an acquisition signal AS. The AD conversion circuit 323 sequentially converts the voltage value of the residual vibration signal Vnvt as the input acquisition signal AS into a digital signal based on a sampling period. Then, the AD conversion circuit 323 outputs a detection voltage dvn of a digital signal according to the voltage value of the residual vibration signal Vnvt as the acquisition signal AS to the correction circuit 324 as an acquisition signal dAS. That is, the correction circuit 324 acquires the voltage value of the residual vibration signal Vnvt as the detection voltage dvn (step S272).

[0176] The correction circuit 324 corrects the acquired detected voltage dvn based on a correction information signal CV including a temperature correction value CVt and the voltage vof. Then, the correction circuit 324 outputs the acquired detected voltage signal vn to the control circuit 321 as a detected voltage signal vn[j].

[0177] Specifically, the correction circuit 324 subtracts the voltage vof from the detection voltage dvn. That is, the correction circuit 324 regards the voltage vof as the reference potential of the residual vibration signal Vnvt, and calculates the voltage value of the residual vibration signal Vnvt when the voltage vof is the reference potential, which is the potential difference from the reference potential. Then, the correction circuit 324 multiplies the calculated electrical difference between the voltage vof and the detection voltage dvn by a temperature correction value CVt corresponding to the temperature information signal TH. In this way, the correction circuit 324 corrects the variation in the amplification factor of the non-inverting amplifier circuit 242, which is the change in the resistance value due to the temperature characteristics of the resistors R11 and R12 of the non-inverting amplifier circuit 242, and outputs it as the detection voltage signal vn[j]. That is, the correction circuit 324 subtracts the voltage vof from the detection voltage dvn, and multiplies the obtained value by the temperature correction value CVt to calculate the detection voltage signal vn[j] (step S274). Then, the correction circuit 324 outputs the calculated detection voltage signal vn[j] to the control circuit 321.

[0178] The control circuit 321 generates a memory control signal MC for storing the input detected voltage signal vn[j] in the memory circuit 326, and outputs the signal to the memory circuit 326. As a result, the detected voltage signal vn[j] is stored in the memory circuit 326 (step S276).

[0179] Thereafter, the control circuit 321 judges whether the test timing signal TSIG has risen (step S278). If the control circuit 321 judges that the test timing signal TSIG has not risen (N in step S278), the control circuit 321 adds 1 to the variable i (step S280) and repeats the processes of steps S272, S274, S276, and S278 described above. That is, the AD conversion circuit 323 sequentially acquires the detection voltage dvn, which is the voltage value of the residual vibration signal Vnvt input during the period ts2, which is the period from when the inspection timing signal TSIG rises to when the inspection timing signal TSIG rises again, at a timing based on the sampling period, and the correction circuit 324 sequentially corrects the detection voltage dvn, which is the voltage value of the residual vibration signal Vnvt output by the AD conversion circuit 323, based on the temperature correction value CVt and the voltage vof, at a timing based on the sampling period of the AD conversion circuit 323, and sequentially outputs it to the control circuit 321 as the detection voltage signal vn[j]. Then, the control circuit 321 sequentially stores the input detection voltage signal vn[j] in the memory circuit 326.

[0180] Thereafter, when the control circuit 321 determines that the test timing signal TSIG has risen (Y in step S278), it determines that acquisition of the detected voltage signal vn, which is the voltage value of the residual vibration signal Vnvt during the period ts2, has been completed, and the residual vibration signal acquisition process ends.

[0181] As described above, in the residual vibration signal acquisition process, a drive signal Vin corresponding to the test CD is supplied to the test target discharge unit 600, thereby generating residual vibration in the test target discharge unit 600. As a result, a residual vibration signal NVT based on the residual vibration signal Vout corresponding to the residual vibration is input to the discharge state determination circuit 300. This residual vibration signal NVT based on the residual vibration signal Vout corresponding to the residual vibration is input to the negative input terminal of the operational amplifier AM31. At this time, a constant potential voltage signal Vp obtained by dividing the voltage signal Vdd2 by the resistance value of resistor R35 and the resistance value of resistor R36 is input to the positive input terminal of the operational amplifier AM31. When a residual vibration signal NVT based on the residual vibration signal Vout corresponding to the residual vibration is input to the negative input terminal of the operational amplifier AM31, and a constant potential voltage signal Vp obtained by dividing the voltage signal Vdd2 by the resistance value of resistor R35 and the resistance value of resistor R36 is input to the positive input terminal of the operational amplifier AM31, the operational amplifier AM31 outputs a residual vibration signal Vnvt based on the residual vibration signal NVT from the output terminal to the residual vibration judgment circuit 320.

[0182] The residual vibration determination circuit 320 sequentially acquires the voltage values ​​of the input residual vibration signal Vnvt, corrects them based on a correction information signal CV including a temperature correction value CVt and a voltage vof, and then stores them in the memory circuit 326. As a result, in the residual vibration signal acquisition process, the voltage value of the residual vibration signal Vnvt with the voltage vof as the reference potential is acquired.

[0183] Next, an example of a waveform information calculation process for calculating waveform information of the residual vibration signal Vnvt will be described. Fig. 20 is a diagram showing a specific example of the waveform information calculation process. Here, in the following description, it is assumed that p detected voltage signals vn are stored in the memory circuit 326 during the period ts2. That is, it is assumed that the detected voltage signals vn[1] to vn[p] are stored in the memory circuit 326 as the detected voltage signals vn.

[0184] When the waveform information calculation process starts, the control circuit 321 generates a memory control signal MC for reading out the detected voltage signals vn[1]-vn[p] from the memory circuit 326, and outputs it to the memory circuit 326. As a result, the control circuit 321 reads out the detected voltage signals vn[1]-vn[p] from the memory circuit 326. The control circuit 321 then generates a detected voltage signal group vng including the read out detected voltage signals vn[1]-vn[p], and outputs it to the waveform information calculation circuit 327. As a result, the waveform information calculation circuit 327 acquires the detected voltage signals vn[1]-vn[p] (step S310).

[0185] The waveform information calculation circuit 327 extracts the detection voltage signal vn at the timing when the voltage value switches from a positive value to a negative value or from a negative value to a positive value from the acquired detection voltage signals vn[1] to vn[p]. In the following description, the detection voltage signal vn at the timing when the voltage value first switches from a positive value to a negative value or from a negative value to a positive value after the rise of the inspection timing signal TSIG is referred to as the detection voltage signal vn[p1], and the detection voltage signal vn at the timing when the voltage value last switches from a positive value to a negative value or from a negative value to a positive value after the rise of the inspection timing signal TSIG, which is the s-th detection voltage signal vn at the timing when the voltage value switches from a positive value to a negative value or from a negative value to a positive value, is referred to as the detection voltage signal vn[ps]. That is, the waveform information calculation circuit 327 extracts, from the acquired detected voltage signals vn[1] to vn[p], detected voltage signals vn[p1] to vn[ps] at the timing when the voltage value switches from a positive value to a negative value or from a negative value to a positive value (step S320).

[0186] The waveform information calculation circuit 327 calculates the vibration frequency Fnvt of the residual vibration signal Vnvt based on the detected voltage signal vn[pu] (u is any one of 1 to s-2) and the detected voltage signal vn[p(u+2)] among the extracted detected voltage signals vn[p1] to vn[ps] (step S330).

[0187] Specifically, the waveform information calculation circuit 327 calculates the number of detection voltage signals vn acquired by the control circuit 321 between the detection voltage signal vn[pu] and the detection voltage signal vn[p(u+2)]. The waveform information calculation circuit 327 then calculates the time from the detection voltage signal vn[pu] to the detection voltage signal vn[p(u+2)] from the calculated number of detection voltage signals vn and the period in which the correction circuit 324 calculates the detection voltage signal vn from the detection voltage dvn, which period is based on the sampling period of the AD conversion circuit 323. The waveform information calculation circuit 327 then calculates the vibration frequency Fnvt of the residual vibration signal Vnvt based on the calculated time from the detection voltage signal vn[pu] to the detection voltage signal vn[p(u+2)], and acquires it as waveform information.

[0188] Here, as shown in step S274, the detection voltage signal vn is calculated by subtracting the voltage vof, which is the voltage value of the voltage signal Voff, from the voltage value of the residual vibration signal Vnvt. That is, the timing at which the voltage values ​​of the detection voltage signals vn[1]-vn[p] switch from a positive value to a negative value or from a negative value to a positive value corresponds to the timing at which the voltage value of the residual vibration signal Vnvt crosses the voltage value of the voltage signal Voff. That is, in steps S320 and S330, the waveform information calculation circuit 327 included in the residual vibration determination circuit 320 calculates the vibration frequency Fnvt of the residual vibration signal Vnvt as waveform information based on the voltage vof, which is the voltage value of the voltage signal Voff.

[0189] At this time, it is preferable that the waveform information calculation circuit 327 calculates the vibration frequency Fnvt of the residual vibration signal Vnvt based on the detection voltage signal vn acquired near the rising edge of the inspection timing signal TSIG that specifies the start of the inspection. As described above, since the residual vibration signal Vnvt corresponding to the residual vibration is a damped vibration, the voltage value of the residual vibration signal Vnvt converges toward the reference potential of the residual vibration signal Vnvt over time. When the waveform information calculation circuit 327 calculates the vibration frequency Fnvt of the residual vibration signal Vnvt, it is possible to detect a turning point at which the voltage value of the residual vibration signal Vnvt switches from a positive value to a negative value or from a negative value to a positive value at a stage where the residual vibration signal Vnvt has a sufficient amplitude by using the detection voltage signal vn acquired near the rising edge of the inspection timing signal TSIG. This improves the detection accuracy of the turning point, and as a result, improves the calculation accuracy of the vibration frequency Fnvt of the residual vibration signal Vnvt.

[0190] In addition, the waveform information calculation circuit 327 calculates the detected voltage signal vn[pv] (v is any one of 1 to s-1). Among the detection voltage signals vn acquired between the detection voltage signal vn[p(v+1)] and the detection voltage signal vn[p(v+1)], the detection voltage signal vn with the maximum absolute value is held as the maximum voltage value Vpek[v] (step S340). Specifically, the waveform information calculation circuit 327 holds the detection voltage signal vn with the maximum absolute value among the detection voltage signals vn acquired between the detection voltage signal vn[p1] and the detection voltage signal vn[p2] as the maximum voltage value Vpek[1], holds the detection voltage signal vn with the maximum absolute value among the detection voltage signals vn acquired between the detection voltage signal vn[pv] and the detection voltage signal vn[p(v+1)] as the maximum voltage value Vpek[v], and holds the detection voltage signal vn with the maximum absolute value among the detection voltage signals vn acquired between the detection voltage signal vn[p(s-1)] and the detection voltage signal vn[ps] as the maximum voltage value Vpek[s-1]. The maximum voltage value Vpek[v] held by the waveform information calculation circuit 327 corresponds to the amplitude at which the residual vibration signal Vnvt occurs. Then, the waveform information calculation circuit 327 calculates the attenuation rate ARnvt of the amplitude of the residual vibration signal Vnvt based on the maximum voltage values ​​Vpek[1] to Vpek[s-1] corresponding to the amplitude at which the residual vibration signal Vnvt occurs (step S350).

[0191] Then, the waveform information calculation circuit 327 generates a waveform information signal WI including the calculated vibration frequency Fnvt and amplitude attenuation rate ARnvt, and outputs it to the state determination circuit 328 (step S360).

[0192] Next, an example of the discharge unit determination process will be described. FIG. 21 is a diagram showing a specific example of the discharge unit determination process. As shown in FIG. 21, when the discharge unit determination process is started, the control circuit 321 generates a memory control signal MC for reading out the frequency threshold information Fth and the amplitude determination threshold information ARth from the storage circuit 326, and outputs it to the storage circuit 326. As a result, the control circuit 321 reads out the frequency threshold information Fth and the amplitude determination threshold information ARth from the storage circuit 326. Then, the control circuit 321 generates a determination threshold signal Jth including the frequency threshold information Fth and the amplitude determination threshold information ARth, and outputs it to the state determination circuit 328. That is, the state determination circuit 328 acquires the frequency threshold information Fth and the amplitude determination threshold information ARth (step S410). In addition, the state determination circuit 328 receives an input of a waveform information signal WI including the vibration frequency Fnvt and the amplitude attenuation rate ARnvt output by the waveform information calculation circuit 327. That is, the state determination circuit 328 acquires the vibration frequency Fnvt and the amplitude attenuation rate ARnvt of the residual vibration signal Vnvt (step S420).

[0193] Then, the state determination circuit 328 compares the acquired frequency threshold information Fth and amplitude determination threshold information ARth with the vibration frequency Fnvt and the amplitude attenuation rate ARnvt to determine the state of the ejection section 600, that is, whether or not the ejection section 600 being inspected has a drying thickening abnormality, and whether or not an air bubble mixing abnormality has occurred.

[0194] Specifically, the state determination circuit 328 determines whether the attenuation rate ARnvt of the amplitude of the residual vibration signal Vnvt is greater than the amplitude determination threshold information ARth (step S430). As described above, when the viscosity of the ink increases, the attenuation of the residual vibration signal Vnvt becomes greater. When the attenuation rate ARnvt of the amplitude of the residual vibration signal Vnvt is greater than the amplitude determination threshold information ARth (Y in step S430), the state determination circuit 328 determines that the viscosity of the ink has increased beyond the normal range, and determines that the ejection unit 600 being inspected has a dry thickening abnormality (step S435). Then, the state determination circuit 328 generates and outputs a determination result signal RT indicating that the ejection unit 600 being inspected has a dry thickening abnormality (step S460).

[0195] Furthermore, if the attenuation rate ARnvt of the amplitude of the residual vibration signal Vnvt is equal to or less than the amplitude determination threshold information ARth (Y in step S430), the state determination circuit 328 determines whether the vibration frequency Fnvt of the residual vibration signal Vnvt is greater than the frequency threshold information Fth (step S440). The frequency of the vibration signal Vnvt becomes higher. If the vibration frequency Fnvt of the residual vibration signal Vnvt is greater than the frequency threshold information Fth (Y in step S440), the state determination circuit 328 determines that air bubbles have entered the cavity 631, and determines that an air bubble-entered abnormality has occurred in the discharge unit 600 being inspected (step S445). Then, the state determination circuit 328 generates and outputs a determination result signal RT indicating that an air bubble-entered abnormality has occurred in the discharge unit 600 being inspected (step S460).

[0196] Furthermore, when the attenuation rate ARnvt of the amplitude of the residual vibration signal Vnvt is equal to or less than the amplitude determination threshold information ARth and the vibration frequency Fnvt of the residual vibration signal Vnvt is equal to or less than the frequency threshold information Fth (N in step S440), the control circuit 321 determines that the ejection unit 600 being inspected is normal. Then, the state determination circuit 328 generates and outputs a determination result signal RT indicating that the ejection unit 600 being inspected is normal (step S460).

[0197] As described above, the residual vibration judgment circuit 320 of this embodiment calculates waveform information of the residual vibration signal Vnvt based on the residual vibration signal Vnvt converted into a digital signal, the voltage vof which is the voltage value of the voltage signal Voff converted into a digital signal, and the temperature information signal TH converted into a digital signal, and judges the state of the ejection section 600 to be inspected based on the calculated waveform information.

[0198] Here, the ejection section determination process corresponds to a process of determining the state of the ejection section 600 to be inspected based on the residual vibration signal Vnvt output from the output terminal when a residual vibration signal NVT based on the residual vibration signal Vout corresponding to the residual signal is input to the negative input terminal of the operational amplifier AM31 and a constant voltage signal Vm whose voltage value is the same as the voltage signal Vo is input to the negative input terminal of the operational amplifier AM31 and a constant voltage signal Vm whose voltage value is the same as the voltage signal Voff whose voltage value is the same as the voltage signal Vm is input to the positive input terminal.

[0199] Here, the second waveform shaping circuit 310 is an example of a waveform shaping circuit, the residual vibration determination circuit 320 is an example of a determination circuit, and the AD conversion circuit 323 is an example of an analog-digital converter. Also, the operational amplifier AM31 is an example of an amplifier circuit, the negative input terminal of the operational amplifier AM31 is an example of a first input terminal, the positive input terminal of the operational amplifier AM31 is an example of a second input terminal, the output terminal of the operational amplifier AM31 is an example of an output terminal, the low-voltage side power supply terminal of the operational amplifier AM31 is an example of a first power supply input terminal, and the high-voltage side power supply terminal of the operational amplifier AM31 is an example of a second power supply input terminal.

[0200] Moreover, the residual vibration signal NVT is an example of a first residual vibration signal, the residual vibration signal Vnvt is an example of a second residual vibration signal, the abnormality information signal Err is an example of an error information signal, and the drive signal COM including the drive signals ComA and ComB is an example of a drive signal. In view of the fact that the drive signal Vin is generated by selecting or deselecting the signal waveforms of the drive signals ComA and ComB, the drive signal Vin is also an example of a drive signal. Moreover, the voltage signal Voff is an example of an offset voltage signal, and the voltage vof, which is the voltage value of the voltage signal Voff, is an example of an offset value. Moreover, during a period in which the residual vibration signal NVT corresponding to the residual signal is not input to the second waveform shaping circuit 310, the voltage signal Vm, which has a constant voltage value input to the negative input terminal of the operational amplifier AM31, is an example of a first constant voltage signal, and the voltage signal Vp, which has a constant voltage value obtained by dividing the voltage signal Vdd2 by the resistance value of the resistor R35 and the resistance value of the resistor R36, is an example of a second constant voltage signal.

[0201] In addition, the voltage value at the negative input terminal of the operational amplifier AM31 is constant and is the same as the voltage signal Vo. An example of a first state is a state in which a voltage signal Vm based on the residual vibration signal Vout corresponding to the residual signal is input to the negative input terminal of the operational amplifier AM31, a voltage signal Vp with a constant voltage value is input to the positive input terminal of the operational amplifier AM31, and a voltage signal Voff is output from the output terminal of the operational amplifier AM31 as a voltage signal Vo. An example of a second state is a state in which a residual vibration signal NVT based on the residual vibration signal Vout corresponding to the residual signal is input to the negative input terminal of the operational amplifier AM31, a voltage signal Vp with a constant voltage value is input to the positive input terminal of the operational amplifier AM31, and a residual vibration signal Vnvt is output from the output terminal of the operational amplifier AM31 as a voltage signal Vo.

[0202] 6. Effects As described above, in the liquid ejection device 1 and head unit 20 of this embodiment, when the voltage signal Vm with a constant voltage value is input to the negative input terminal and the voltage signal Vp with a constant voltage value is input to the positive input terminal, the operational amplifier AM31 of the second waveform shaping circuit 310 outputs a voltage signal Voff with a voltage value of voltage vof from its output terminal as a voltage signal Vo. Also, when the residual vibration signal NVT corresponding to the residual vibration is input to the negative input terminal as a voltage signal Vm and the voltage signal Vp with a constant voltage value is input to the positive input terminal, the operational amplifier AM31 of the second waveform shaping circuit 310 outputs a residual vibration signal Vnvt obtained by amplifying the amplitude of the residual vibration signal NVT corresponding to the residual vibration as a voltage signal Vo, using the voltage signal Vp as a reference potential from its output terminal. Then, the residual vibration judgment circuit 320 stores the voltage vof, which is the voltage value of the voltage signal Voff output by the operational amplifier AM31 of the second waveform shaping circuit 310, in the memory circuit 326, and judges the state of the ejection section 600 to be inspected based on the residual vibration signal Vnvt output by the operational amplifier AM31 of the second waveform shaping circuit 310 and the voltage vof, which is the voltage value of the voltage signal Voff stored in the memory circuit 326.

[0203] That is, the residual vibration judgment circuit 320 judges the state of the ejection part 600 based on the residual vibration signal Vnvt that oscillates with the voltage signal Vp as a reference potential, and the voltage vof that is the voltage value of the voltage signal Voff corresponding to the voltage signal Vp stored in advance. This allows the residual vibration judgment circuit 320 to accurately grasp the reference potential of the residual vibration signal Vnvt and judge the state of the ejection part 600 to be inspected. As a result, the accuracy of the judgment of the state of the ejection part 600 to be inspected in the residual vibration judgment circuit 320 is improved.

[0204] Specifically, the residual vibration judgment circuit 320 calculates the vibration frequency Fnvt, which is one of the waveform information of the residual vibration signal Vnvt that oscillates with the voltage signal Vp as a reference potential, based on the reference potential of the residual vibration signal Vnvt calculated based on the voltage vof, which is the voltage value of the voltage signal Voff corresponding to the voltage signal Vp stored in advance. This enables the residual vibration judgment circuit 320 to accurately calculate the vibration frequency Fnvt of the residual vibration signal Vnvt, improving the accuracy of judging the state of the ejection part 600 to be inspected based on the calculated vibration frequency Fnvt.

[0205] In the liquid ejection device 1 and the head unit 20 of this embodiment, the operational amplifier AM31 of the second waveform shaping circuit 310 receives the voltage signal Vo output by the operational amplifier AM31 as the voltage signal Vm with a constant voltage value during a period when the residual vibration signal NVT corresponding to the residual vibration is not input to the negative input terminal. That is, the operational amplifier AM31 of the second waveform shaping circuit 310 operates as a voltage follower circuit. At this time, the operational amplifier AM31 outputs the voltage signal Voff with the same voltage value as the voltage signal Vp from the output terminal as the voltage signal Vo. As a result, when the residual vibration determination circuit 320 calculates the vibration frequency Fnvt, which is one of the waveform information of the residual vibration signal Vnvt, the voltage vof, which is the voltage value of the voltage signal Voff stored in advance, can be used as it is as the reference potential of the residual vibration signal Vnvt. This reduces the load of calculating the vibration frequency Fnvt of the residual vibration signal Vnvt in the residual vibration determination circuit 320, and allows the vibration frequency Fnvt of the residual vibration signal Vnvt to be calculated with high accuracy.

[0206] Furthermore, in the liquid ejection device 1 and head unit 20 of this embodiment, a residual vibration signal Vout corresponding to the residual vibration generated by the drive signal COM is input, and a first waveform shaping circuit 240 and a second waveform shaping circuit 310 are provided which output a residual vibration signal Vnvt by shaping the waveform of the residual vibration signal Vout. Even when the first waveform shaping circuit 240 has an operational amplifier AM10 which amplifies the residual vibration signal Vout configured in one semiconductor device, and resistors R11 and R12 which set the amplification factor of the operational amplifier AM10, the residual vibration judgment circuit 320 judges the state of the ejection section 600 to be inspected based on the residual vibration signal Vnvt and a temperature information signal TH corresponding to the temperature of the first waveform shaping circuit 240, and the residual vibration judgment circuit 320 can accurately correct the amplification factor of the amplitude of the residual vibration signal Vout in the first waveform shaping circuit 240 using the resistance values ​​of the resistors R11 and R12, which have a large change in resistance value due to temperature. This allows the residual vibration determination circuit 320 to accurately calculate the attenuation rate ARnvt of the amplitude of the residual vibration signal Vnvt, which is waveform information of the amplitude of the residual vibration signal Vnvt. As a result, the accuracy of the determination of the state of the ejection part 600 to be inspected in the residual vibration determination circuit 320 is improved.

[0207] Furthermore, in the liquid ejection device 1 and head unit 20 of this embodiment, the residual vibration judgment circuit 320 has an AD conversion circuit 323, and converts the input residual vibration signal Vnvt, voltage signal Voff, and temperature information signal TH into digital signals, corrects them, and calculates waveform information of the residual vibration signal Vnvt. This allows the residual vibration judgment circuit 320 to directly acquire the voltage value of the input residual vibration signal Vnvt. As a result, the accuracy of calculation of the waveform information of the residual vibration signal Vnvt in the residual vibration judgment circuit 320 and the accuracy of judgment of the state of the ejection part 600 to be inspected are improved.

[0208] At this time, the residual vibration determination circuit 320 selects the residual vibration signal Vnvt, the voltage signal Voff, and the temperature information signal TH by the multiplexer 322, and converts each of the residual vibration signal Vnvt, the voltage signal Voff, and the temperature information signal TH into a digital signal by a common AD conversion circuit 323. As a result, the risk of an increase in the circuit size of the residual vibration determination circuit 320 is reduced, making it possible to miniaturize the head unit 20, and reducing the risk of errors occurring in the digital values ​​due to variations in the AD conversion circuit 323. Therefore, the accuracy of calculation of waveform information of the residual vibration signal Vnvt in the residual vibration determination circuit 320 and the accuracy of determination of the state of the ejection section 600 to be inspected are improved.

[0209] 7. Variations In the liquid ejection device 1 and head unit 20 of the present embodiment described above, the residual vibration judgment circuit 320 judges the state of the ejection section 600 based on the voltage vof, which is the voltage value of the voltage signal Voff as the voltage signal Vo output from the output terminal of the operational amplifier AM31 when a constant voltage signal Vm is input to the negative input terminal of the operational amplifier AM31 and a constant voltage signal Vp is input to the positive input terminal of the operational amplifier AM31, and on the residual vibration signal Vnvt as the voltage signal Vo output from the output terminal of the operational amplifier AM31 when a residual vibration signal NVT corresponding to the residual vibration is input to the negative input terminal of the operational amplifier AM31 and a constant voltage signal Vp is input to the positive input terminal of the operational amplifier AM31. At this time, since the residual vibration judgment circuit 320 can accurately calculate the reference potential of the amplitude of the residual vibration signal Vnvt based on the voltage vof, the calculation accuracy of the vibration frequency Fnvt of the residual vibration signal Vnvt is improved, and as a result, the judgment accuracy of the state of the ejection part 600 to be inspected is improved. In other words, it is sufficient for the residual vibration judgment circuit 320 to accurately acquire the reference potential of the residual vibration signal Vnvt.

[0210] 22 is a diagram showing an example of the configuration of a modified ejection state determination circuit 300. As shown in FIG. 22, in the modified ejection state determination circuit 300, the resistor R36 is an adjustable resistor. The control circuit 321 is configured with a variable resistance element, and the memory circuit 326 stores an assumed reference voltage Var calculated from the voltage value of the voltage signal Vdd2 and the resistance values ​​of the resistors R35 and R36. In a state in which the residual vibration signal NVT corresponding to the residual vibration is not input to the negative input terminal of the operational amplifier AM31, and therefore a constant potential voltage signal Vm is input to the negative input terminal of the operational amplifier AM31, and a constant potential voltage signal Vp obtained by dividing the voltage signal Vdd2 by the resistance value of the resistor R35 and the resistance value of the resistor R36 is input to the positive input terminal of the operational amplifier AM31, the control circuit 321 outputs a resistance value adjustment signal VR that adjusts the resistance value of the resistor R36 so that the voltage value of the voltage signal Vo output from the output terminal of the operational amplifier AM31 approaches the assumed reference voltage Var stored in the memory circuit 326. Then, the control circuit 321 stores in the memory circuit 326 the adjustment value of the resistance value of the resistor R36 when the voltage value of the voltage signal Vo output from the output terminal of the operational amplifier AM31 becomes approximately equal to the voltage value of the assumed reference voltage Var stored in the memory circuit 326.

[0211] Then, after adjusting the resistance value of resistor R36 based on the adjustment value of the resistance stored in memory circuit 326, the residual vibration judgment circuit 320 acquires a residual vibration signal Vnvt as a voltage signal Vo output from the output terminal of the operational amplifier AM31 in a state in which a residual vibration signal NVT corresponding to the residual vibration is input to the negative input terminal of the operational amplifier AM31 and a constant potential voltage signal Vp obtained by dividing the voltage signal Vdd2 by the resistance value of resistor R35 and the adjusted resistance value of resistor R36 is input to the positive input terminal of the operational amplifier AM31, calculates a vibration frequency Fnvt of the residual vibration signal Vnvt based on the acquired residual vibration signal Vnvt and an assumed reference voltage Var, and judges the state of the ejection section 600 to be inspected based on the calculated vibration frequency Fnvt.

[0212] Even in this case, the same effects as those of the above-described embodiment can be obtained. Note that instead of or in addition to resistor R36, R35 may be configured as a variable resistance element whose resistance value is adjustable.

[0213] That is, in the liquid ejection device 1 and head unit 20 of the modified example, the memory circuit 326 stores an assumed reference voltage Var which is an assumed reference potential of the residual vibration signal Vnvt, the second waveform shaping circuit 310 has a resistor R35 having one end to which a voltage signal Vdd2 is input and the other end electrically connected to the + side input terminal of the operational amplifier AM31, and a resistor R35 having one end electrically connected to the + side input terminal of the operational amplifier AM31 and the other end to which a ground potential is input, at least one of the resistors R35 and R36 includes a variable resistance element, and the residual vibration determination circuit 320 has a residual vibration signal NVT corresponding to the residual vibration not input to the - side input terminal of the operational amplifier AM31, and therefore a voltage signal Vm of constant potential is input to the - side input terminal of the operational amplifier AM31, and the voltage signal Vdd2 is input to the + side input terminal of the operational amplifier AM31 based on the resistance value of the resistor R35 and the resistor R36 In a state in which a constant potential voltage signal Vp obtained by dividing the voltage signal Vdd2 by the resistance value of resistor R35 and the adjusted resistance value of resistor R36 is input, the resistance value of resistor R36 may be adjusted so that the voltage value of the voltage signal Vo output from the output terminal of the operational amplifier AM31 approaches the assumed reference voltage Var stored in the memory circuit 326, and in a state in which a residual vibration signal NVT corresponding to the residual vibration is input to the negative input terminal of the operational amplifier AM31 and a constant potential voltage signal Vp obtained by dividing the voltage signal Vdd2 by the resistance value of resistor R35 and the adjusted resistance value of resistor R36 is input to the positive input terminal of the operational amplifier AM31, a vibration frequency Fnvt may be calculated as waveform information of the residual vibration signal NVT based on the residual vibration signal Vnvt as the voltage signal Vo output from the output terminal of the operational amplifier AM31 and the assumed reference voltage Var, and the state of the ejection section 600 to be inspected may be determined based on the calculated vibration frequency Fnvt.

[0214] In this case, the assumed reference voltage Var is an example of an assumed offset value, the voltage signal Vdd2 is an example of a third low voltage signal, the resistor R35 is an example of a first resistive element, and the resistor R36 is an example of a second resistive element.

[0215] In the above-mentioned liquid ejection device 1 and head unit 20, the temperature detection circuit 250 for detecting the temperature of the first waveform shaping circuit 240 has been described as being included in one semiconductor device constituting the drive signal selection circuit 200 together with the first waveform shaping circuit 240. However, as long as a part of the temperature detection circuit 250 can detect the temperature of the first waveform shaping circuit 240, it may be configured separately from one semiconductor device constituting the drive signal selection circuit 200. In this case, the temperature detection circuit 250 may be a printed board to which one end of the flexible wiring board 24, one end of which is electrically connected to the print head 22, is connected, and may be provided on the head wiring board 23. That is, the head unit 20 includes the print head 22 including the ejection portion 600, the flexible wiring board 24, one end of which is electrically connected to the print head 22, and the head wiring board 23, the other end of which is electrically connected to the flexible wiring board 24, and one semiconductor device constituting the drive signal selection circuit 200 may be provided on the flexible wiring board 24, and at least a part of the temperature detection circuit 250 may be provided on the head wiring board 23.

[0216] Even in this case, since the temperature detection circuit 250 is located near one of the semiconductor devices that constitute the drive signal selection circuit 200 including the first waveform shaping circuit 240, the same effects as those of the above-mentioned embodiment can be achieved.

[0217] Although the embodiments and modifications have been described above, the present invention is not limited to these embodiments, and can be embodied in various forms without departing from the spirit of the present invention. For example, the above embodiments can be appropriately combined.

[0218] The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations with the same functions, methods and results, or configurations with the same purpose and effect). The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects as the configurations described in the embodiments or that can achieve the same purpose. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments.

[0219] The following can be derived from the above-described embodiment.

[0220] One aspect of the head unit is an ejection section including a piezoelectric element that is driven by a drive signal and that ejects liquid in response to the driving of the piezoelectric element; a waveform shaping circuit that receives a first residual vibration signal corresponding to the residual vibration generated by the drive signal, and outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal; A determination circuit for determining a state of the ejection unit; Equipped with the waveform shaping circuit has an amplifier circuit including a first input terminal, a second input terminal, and an output terminal; The amplifier circuit includes: In a first state in which a first constant voltage signal is input to the first input terminal and a second constant voltage signal is input to the second input terminal, an offset voltage signal is output from the output terminal; in a second state in which the first residual vibration signal is input to the first input terminal and the second constant voltage signal is input to the second input terminal, outputting the second residual vibration signal from the output terminal; The determination circuit determines a state of the ejection portion based on the second residual vibration signal and an offset value that is a voltage of the offset voltage signal.

[0221] According to this head unit, the offset voltage signal output in the first state is a second constant The second constant voltage signal is a signal based on the voltage of the voltage signal, and the reference potential of the amplitude of the second residual vibration signal output in the second state is the second constant voltage signal. In such a head unit, the determination circuit determines the state of the ejection section based on the second residual vibration signal and an offset value that is the voltage of the offset voltage signal, so that the determination circuit can accurately grasp the reference potential of the second residual vibration signal. As a result, the accuracy of the determination of the ejection section state in the determination circuit is improved.

[0222] In one aspect of the head unit, The determination circuit includes: In the second state, waveform information of the second residual vibration signal may be calculated based on the offset value, and the state of the ejection section may be determined based on the calculated waveform information.

[0223] According to this head unit, the offset voltage signal output in the first state is a signal based on the voltage of the second constant voltage signal, and the reference potential of the amplitude of the second residual vibration signal output in the second state is the second constant voltage signal, so that the accuracy of calculation of the vibration frequency of the second residual vibration, which is waveform information of the second residual vibration, in the determination circuit is improved. As a result, the accuracy of determination of the state of the ejection section based on the waveform information in the determination circuit is improved.

[0224] In one aspect of the head unit, a memory circuit in which an assumed offset value of the second residual vibration signal is stored; the waveform shaping circuit includes a first resistor element having one end to which a third constant voltage signal is input and the other end electrically connected to the second input terminal, and a second resistor element having one end electrically connected to the second input terminal and the other end to which a ground potential is input, At least one of the first resistance element and the second resistance element includes a variable resistance element; The determination circuit includes: In the first state, a resistance value of the variable resistance element is adjusted so that the offset value approaches the assumed offset value; In the second state, waveform information of the second residual vibration signal may be calculated based on the assumed offset value, and the state of the ejection section may be determined based on the calculated waveform information.

[0225] According to this head unit, the reference potential of the amplitude of the second residual vibration signal output in the second state is the assumed offset value stored in the memory circuit, so that the determination circuit improves the calculation accuracy of the vibration frequency of the second residual vibration, which is the waveform information of the second residual vibration signal, and as a result, the determination accuracy of the state of the ejection section based on the waveform information in the determination circuit is improved.

[0226] In one aspect of the head unit, a memory circuit for storing the offset value; The offset value stored in the memory circuit may be updated at predetermined intervals.

[0227] According to this head unit, even if the characteristics change due to temperature or deterioration over time, the accuracy of the determination circuit's determination of the state of the ejection portions based on the waveform information is improved.

[0228] In one aspect of the head unit, The storage circuit may include a non-volatile memory in which the offset value is stored.

[0229] In one aspect of the head unit, A communication interface circuit capable of communicating with an external device is provided, The offset value stored in the memory circuit may be updated via the communication interface circuit.

[0230] According to this head unit, even if the characteristics change due to temperature or deterioration over time, the accuracy of the determination circuit's determination of the state of the ejection portions based on the waveform information is improved.

[0231] In one aspect of the head unit, the amplifier circuit includes a first power supply input terminal that defines a lower limit of a voltage value of a signal output from the output terminal, and a second power supply input terminal that defines an upper limit of a voltage value of a signal output from the output terminal; A ground potential is input to the first power supply input terminal, A positive potential higher than the ground potential may be input to the second power supply input terminal.

[0232] According to this head unit, even if the amplifier circuit is configured with a so-called one-way power supply, the accuracy of determining the state of the ejection section based on the waveform information in the determination circuit is improved.

[0233] In one aspect of the head unit, The determination circuit may output an error information signal when a voltage value of the offset voltage signal input in the first state exceeds a predetermined threshold voltage.

[0234] This head unit improves the reliability of the head unit.

[0235] In one aspect of the head unit, The judgment circuit may include an analog-to-digital converter that converts the second residual vibration signal into a digital signal, and may judge the state of the ejection portion based on the second residual vibration signal converted into a digital signal and the offset value.

[0236] According to this head unit, it is possible to directly acquire the voltage value of the amplitude of the second residual vibration signal, and the accuracy of determining the state of the ejection section based on the waveform information in the determination circuit is improved.

[0237] One aspect of the liquid ejection device is A head unit that ejects liquid onto a medium; A control unit for controlling an operation of the head unit; Equipped with The head unit includes: an ejection section including a piezoelectric element that is driven by a drive signal and that ejects liquid in response to the driving of the piezoelectric element; a waveform shaping circuit that receives a first residual vibration signal corresponding to the residual vibration generated by the drive signal, and outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal; A determination circuit for determining a state of the ejection unit; having the waveform shaping circuit has an amplifier circuit including a first input terminal, a second input terminal, and an output terminal; The amplifier circuit includes: In a first state in which a first constant voltage signal is input to the first input terminal and a second constant voltage signal is input to the second input terminal, an offset voltage signal is output from the output terminal; in a second state in which the first residual vibration signal is input to the first input terminal and the second constant voltage signal is input to the second input terminal, outputting the second residual vibration signal from the output terminal; The determination circuit determines a state of the ejection section based on the second residual vibration signal and an offset value.

[0238] According to this liquid ejection device, the offset voltage signal output in the first state is a signal based on the voltage of the second constant voltage signal, and the reference potential of the amplitude of the second residual vibration signal output in the second state is the second constant voltage signal. In such a liquid ejection device, the determination circuit determines the state of the ejection unit based on the second residual vibration signal and an offset value that is the voltage of the offset voltage signal, so that the determination circuit can accurately grasp the reference potential of the second residual vibration signal. As a result, the accuracy of the determination of the state of the ejection unit in the determination circuit is improved.

[0239] In one aspect of the liquid ejection device, The determination circuit includes: In the second state, waveform information of the second residual vibration signal may be calculated based on the offset value, and the state of the ejection section may be determined based on the calculated waveform information.

[0240] According to this liquid ejection device, the offset voltage signal output in the first state is a signal based on the voltage of the second constant voltage signal, and the reference potential of the amplitude of the second residual vibration signal output in the second state is the second constant voltage signal, so that the accuracy of calculation of the vibration frequency of the second residual vibration, which is waveform information of the second residual vibration, in the determination circuit is improved, and as a result, the accuracy of determination of the state of the ejection unit based on the waveform information in the determination circuit is improved.

[0241] In one aspect of the liquid ejection device, a memory circuit in which an assumed offset value of the second residual vibration signal is stored; the waveform shaping circuit includes a first resistor element having one end to which a third constant voltage signal is input and the other end electrically connected to the second input terminal, and a second resistor element having one end electrically connected to the second input terminal and the other end to which a ground potential is input, At least one of the first resistance element and the second resistance element includes a variable resistance element; The determination circuit includes: In the first state, a resistance value of the variable resistance element is adjusted so that the offset value approaches the assumed offset value; In the second state, waveform information of the second residual vibration signal may be calculated based on the assumed offset value, and the state of the ejection section may be determined based on the calculated waveform information.

[0242] According to this liquid ejection device, the reference potential of the amplitude of the second residual vibration signal output in the second state is the assumed offset value stored in the memory circuit, so that the determination circuit improves the accuracy of calculating the vibration frequency of the second residual vibration, which is waveform information of the second residual vibration signal, and as a result, the accuracy of determining the state of the ejection unit based on the waveform information in the determination circuit improves.

[0243] In one aspect of the liquid ejection device, a memory circuit for storing the offset value; The offset value stored in the memory circuit may be updated at predetermined intervals.

[0244] According to this liquid ejection device, even if the characteristics change due to temperature or deterioration over time, the accuracy of the determination circuit in determining the state of the ejection section based on the waveform information is improved.

[0245] In one aspect of the liquid ejection device, The storage circuit may include a non-volatile memory in which the offset value is stored.

[0246] In one aspect of the liquid ejection device, A communication interface circuit capable of communicating with an external device is provided, The offset value stored in the memory circuit may be updated via the communication interface circuit.

[0247] According to this liquid ejection device, even if the characteristics change due to temperature or deterioration over time, the accuracy of the determination circuit in determining the state of the ejection section based on the waveform information is improved.

[0248] In one aspect of the liquid ejection device, the amplifier circuit includes a first power supply input terminal that defines a lower limit of a voltage value of a signal output from the output terminal, and a second power supply input terminal that defines an upper limit of a voltage value of a signal output from the output terminal; A ground potential is input to the first power supply input terminal, A positive potential higher than the ground potential may be input to the second power supply input terminal.

[0249] According to this liquid ejection device, even if the amplifier circuit is configured with a so-called one-way power supply, the accuracy of the determination of the state of the ejection section based on the waveform information in the determination circuit is improved.

[0250] In one aspect of the liquid ejection device, The determination circuit may output an error information signal when a voltage value of the offset voltage signal input in the first state exceeds a predetermined threshold voltage.

[0251] According to this liquid ejection device, the reliability of the head unit is improved.

[0252] In one aspect of the liquid ejection device, The judgment circuit may include an analog-to-digital converter that converts the second residual vibration signal into a digital signal, and may judge the state of the ejection portion based on the second residual vibration signal converted into a digital signal and the offset value.

[0253] According to this liquid ejection device, it is possible to directly acquire the voltage value of the amplitude of the second residual vibration signal, and the accuracy of the determination of the state of the ejection section based on the waveform information in the determination circuit is improved.

[0254] One aspect of a method for controlling a liquid ejection device includes: an ejection section including a piezoelectric element that is driven by a drive signal and that ejects liquid in response to the driving of the piezoelectric element; a waveform shaping circuit having an amplifier circuit including a first input terminal, a second input terminal, and an output terminal, receiving a first residual vibration signal corresponding to the residual vibration generated by the drive signal, and outputting a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal; A determination circuit for determining a state of the ejection unit; a memory circuit in which an offset value of the second residual vibration signal is stored; A method for controlling a liquid ejection device comprising: storing, in the storage circuit as the offset value, a voltage value of an offset voltage signal output from the output terminal in a first state in which a first constant voltage signal is input to the first input terminal and a second constant voltage signal is input to the second input terminal; driving the piezoelectric element to generate the residual vibration; a step of determining a state of the ejection section based on the second residual vibration signal output from the output terminal in a second state in which the first residual vibration signal is input to the first input terminal and the second constant voltage signal is input to the second input terminal, and based on the offset value; Includes.

[0255] According to this liquid ejection device control method, The offset voltage signal output in the first state is a signal based on the voltage of the second constant voltage signal, and the reference potential of the amplitude of the second residual vibration signal output in the second state is the second constant voltage signal. Then, by determining the state of the ejection unit based on the second residual vibration signal and an offset value, which is the voltage of the offset voltage signal, the reference potential of the second residual vibration signal can be grasped with high accuracy. As a result, the accuracy of determining the state of the ejection unit is improved. [Explanation of symbols]

[0256] 1...liquid ejection device, 10...control unit, 11...control circuit board, 15...cable, 20...head unit, 21...carriage, 22...print head, 23...head wiring board, 24...flexible wiring board, 30...moving unit, 31...carriage motor, 32...endless belt, 40...transport unit, 41...transport motor, 42...transport roller, 50...driving circuit, 60...piezoelectric element, 90...ink container, 100...control circuit, 200...driving signal selection circuit, 210...switching circuit, 220...selection control circuit, 222...shift register, 224...latch circuit, 226...decoder, 230...selection circuit, 232a, 232b, 232c...logic inversion circuit, 234a, 234b, 234c...transfer gate, 240...first waveform shaping circuit, 241...filter circuit, 242...non-inverting amplifier circuit, 243...impedance 3, a piezoelectric element, a piezoelectric vibration detector ... Plate, 631...cavity, 632...nozzle plate, 641...reservoir, 651...nozzle, 661...ink supply port, AM10, AM11, AM31...op-amplifier, C...compliance, C10, C31 to C33...capacitor, CM21...comparator, D21-1 to D21-k...diode, P...medium, Q21...transistor, R10 to R12, R21, R22, R31 to R36...resistor

Claims

1. an ejection section including a piezoelectric element that is driven by a drive signal and that ejects liquid in response to the driving of the piezoelectric element; a waveform shaping circuit which receives a first residual vibration signal corresponding to the residual vibration generated by the drive signal, and outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal; A determination circuit for determining a state of the ejection unit; Equipped with the waveform shaping circuit has an amplifier circuit including a first input terminal, a second input terminal, and an output terminal; The amplifier circuit includes: In a first state in which a first constant voltage signal is input to the first input terminal and a second constant voltage signal is input to the second input terminal, an offset voltage signal is output from the output terminal; in a second state in which the first residual vibration signal is input to the first input terminal and the second constant voltage signal is input to the second input terminal, the second residual vibration signal is output from the output terminal; the determination circuit determines a state of the ejection portion based on the second residual vibration signal and an offset value which is a voltage of the offset voltage signal. A head unit characterized by:

2. The determination circuit includes: In the second state, waveform information of the second residual vibration signal is calculated based on the offset value, and a state of the ejection section is determined based on the calculated waveform information.

2. The head unit according to claim 1.

3. a memory circuit in which an assumed offset value of the second residual vibration signal is stored; the waveform shaping circuit includes a first resistor element having one end to which a third constant voltage signal is input and the other end electrically connected to the second input terminal, and a second resistor element having one end electrically connected to the second input terminal and the other end to which a ground potential is input, At least one of the first resistance element and the second resistance element includes a variable resistance element, The determination circuit includes: In the first state, a resistance value of the variable resistance element is adjusted so that the offset value approaches the assumed offset value; In the second state, waveform information of the second residual vibration signal is calculated based on the assumed offset value, and a state of the ejection section is determined based on the calculated waveform information.

2. The head unit according to claim 1.

4. a memory circuit for storing the offset value; The offset value stored in the memory circuit is updated at predetermined intervals.

2. The head unit according to claim 1.

5. the storage circuit includes a non-volatile memory in which the offset value is stored; 5. The head unit according to claim 4.

6. A communication interface circuit capable of communicating with an external device is provided, the offset value stored in the memory circuit is updated via the communication interface circuit; 6. The head unit according to claim 5.

7. The amplifier circuit includes a first power input that defines a lower limit of a voltage value of a signal output from the output terminal. a second power supply input terminal that defines an upper limit of a voltage value of a signal output from the output terminal, A ground potential is input to the first power supply input terminal, A positive potential higher than the ground potential is input to the second power supply input terminal.

2. The head unit according to claim 1.

8. the determination circuit outputs an error information signal when a voltage value of the offset voltage signal input in the first state exceeds a predetermined threshold voltage.

2. The head unit according to claim 1.

9. the determination circuit includes an analog-to-digital converter that converts the second residual vibration signal into a digital signal, and determines a state of the ejection section based on the second residual vibration signal converted into a digital signal and the offset value.

9. The head unit according to claim 1, wherein the first and second electrodes are arranged in a first direction.

10. A head unit that ejects liquid onto a medium; A control unit for controlling an operation of the head unit; Equipped with The head unit includes: an ejection section including a piezoelectric element that is driven by a drive signal and that ejects liquid in response to the driving of the piezoelectric element; a waveform shaping circuit which receives a first residual vibration signal corresponding to the residual vibration generated by the drive signal, and outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal; A determination circuit for determining a state of the ejection unit; having the waveform shaping circuit has an amplifier circuit including a first input terminal, a second input terminal, and an output terminal; The amplifier circuit includes: In a first state in which a first constant voltage signal is input to the first input terminal and a second constant voltage signal is input to the second input terminal, an offset voltage signal is output from the output terminal; in a second state in which the first residual vibration signal is input to the first input terminal and the second constant voltage signal is input to the second input terminal, the second residual vibration signal is output from the output terminal; the determination circuit determines a state of the ejection section based on the second residual vibration signal and an offset value. A liquid ejection device comprising:

11. The determination circuit includes: In the second state, waveform information of the second residual vibration signal is calculated based on the offset value, and a state of the ejection section is determined based on the calculated waveform information. The liquid ejection device according to claim 10 .

12. a memory circuit in which an assumed offset value of the second residual vibration signal is stored; the waveform shaping circuit includes a first resistor element having one end to which a third constant voltage signal is input and the other end electrically connected to the second input terminal, and a second resistor element having one end electrically connected to the second input terminal and the other end to which a ground potential is input, At least one of the first resistance element and the second resistance element includes a variable resistance element, The determination circuit includes: In the first state, a resistance value of the variable resistance element is adjusted so that the offset value approaches the assumed offset value; In the second state, waveform information of the second residual vibration signal is calculated based on the assumed offset value, and a state of the ejection section is determined based on the calculated waveform information. The liquid ejection device according to claim 10 .

13. a memory circuit for storing the offset value; The offset value stored in the memory circuit is updated at predetermined intervals. The liquid ejection device according to claim 10 .

14. the storage circuit includes a non-volatile memory in which the offset value is stored; The liquid ejection device according to claim 13 .

15. A communication interface circuit capable of communicating with an external device is provided, the offset value stored in the memory circuit is updated via the communication interface circuit; The liquid ejection device according to claim 14 .

16. the amplifier circuit includes a first power supply input terminal that defines a lower limit of a voltage value of a signal output from the output terminal, and a second power supply input terminal that defines an upper limit of a voltage value of a signal output from the output terminal, A ground potential is input to the first power supply input terminal, A positive potential higher than the ground potential is input to the second power supply input terminal. The liquid ejection device according to claim 10 .

17. the determination circuit outputs an error information signal when a voltage value of the offset voltage signal input in the first state exceeds a predetermined threshold voltage. The liquid ejection device according to claim 10 .

18. the determination circuit includes an analog-to-digital converter that converts the second residual vibration signal into a digital signal, and determines a state of the ejection section based on the second residual vibration signal converted into a digital signal and the offset value.

18. The liquid ejection device according to claim 10,

19. an ejection section including a piezoelectric element that is driven by a drive signal and that ejects liquid in response to the driving of the piezoelectric element; a waveform shaping circuit having an amplifier circuit including a first input terminal, a second input terminal, and an output terminal, receiving a first residual vibration signal corresponding to the residual vibration generated by the drive signal, and outputting a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal; A determination circuit for determining a state of the ejection unit; a memory circuit in which an offset value of the second residual vibration signal is stored; A method for controlling a liquid ejection device comprising: storing, in the storage circuit as the offset value, a voltage value of an offset voltage signal output from the output terminal in a first state in which a first constant voltage signal is input to the first input terminal and a second constant voltage signal is input to the second input terminal; driving the piezoelectric element to generate the residual vibration; a step of determining a state of the ejection section based on the second residual vibration signal output from the output terminal in a second state in which the first residual vibration signal is input to the first input terminal and the second constant voltage signal is input to the second input terminal, and based on the offset value; Including, A method for controlling a liquid ejection device comprising the steps of:

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