Head unit and liquid ejecting apparatus

Abstract

The invention relates to a head unit and a liquid ejecting apparatus. The head unit includes: an ejection unit that includes a piezoelectric element driven according to a drive signal and ejects a liquid according to the driving of the piezoelectric element; a waveform shaping circuit to which a first residual vibration signal corresponding to residual vibration generated by the drive signal is input and which outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal; a temperature detection circuit that outputs a temperature information signal corresponding to the temperature of the waveform shaping circuit; and a determination circuit configured to determine a state of the ejection unit, the waveform shaping circuit including: an amplification circuit configured to amplify the first residual vibration signal; and an amplification factor setting circuit that sets the amplification factor of the amplification circuit, the waveform shaping circuit outputs a second residual vibration signal based on the signal amplified by the amplification circuit, the amplification circuit and the amplification factor setting circuit constitute a single semiconductor device, and the determination circuit determines the state of the ejection unit based on the second residual vibration signal and the temperature information signal.

Description

Technical Field

[0001] The present invention relates to a head unit and a liquid ejecting device. Background Art

[0002] In a liquid ejection device that is driven by a piezoelectric element to eject ink from an ejection portion, as described in Patent Document 1, there is known a technology for detecting a signal corresponding to residual vibration generated after the piezoelectric element is driven and determining the state of the ejection portion based on the detection result of the signal.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2005-211873

[0004] When the technology described in Patent Document 1 is used to detect a signal corresponding to the residual vibration and determine the state of the ejection unit based on the detection result, it is still insufficient from the perspective of further improving the determination accuracy of the state of the ejection unit and there is room for further improvement. Summary of the invention

[0005] One aspect of the head unit according to the present invention comprises:

[0006] The ejection unit includes a piezoelectric element driven according to a driving signal and ejects liquid according to the driving of the piezoelectric element;

[0007] a waveform shaping circuit which receives as input a first residual vibration signal corresponding to residual vibration generated by the driving signal and outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal;

[0008] a temperature detection circuit that outputs a temperature information signal corresponding to the temperature of the waveform shaping circuit; and

[0009] a determination circuit for determining a state of the ejection portion,

[0010] The waveform shaping circuit comprises: an amplifier circuit for amplifying the first residual vibration signal; and an amplification factor setting circuit for setting the amplification factor of the amplifier circuit, wherein the waveform shaping circuit outputs the second residual vibration signal based on the signal amplified by the amplifier circuit.

[0011] The amplifier circuit and the gain setting circuit are formed as a semiconductor device.

[0012] The determination circuit determines the state of the ejection portion based on the second residual vibration signal and the temperature information signal.

[0013] One aspect of the liquid ejection device according to the present invention comprises:

[0014] a head unit that sprays liquid toward the medium; and

[0015] a control unit for controlling the movement of the head unit,

[0016] The head unit has:

[0017] The ejection unit includes a piezoelectric element driven according to a driving signal and ejects liquid according to the driving of the piezoelectric element;

[0018] a waveform shaping circuit which receives as input a first residual vibration signal corresponding to residual vibration generated by the driving signal and outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal;

[0019] a temperature detection circuit that outputs a temperature information signal corresponding to the temperature of the waveform shaping circuit; and

[0020] a determination circuit for determining a state of the ejection portion,

[0021] The waveform shaping circuit comprises: an amplifier circuit for amplifying the first residual vibration signal; and an amplification factor setting circuit for setting the amplification factor of the amplifier circuit, wherein the waveform shaping circuit outputs the second residual vibration signal based on the signal amplified by the amplifier circuit.

[0022] The amplifier circuit and the gain setting circuit are formed as a semiconductor device.

[0023] The determination circuit determines the state of the ejection portion based on the second residual vibration signal and the temperature information signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram showing an example of a schematic structure of a liquid ejecting device.

[0025] Figure 2 This is a diagram showing an example of the functional configuration of the liquid ejecting device.

[0026] Figure 3 It is a diagram showing a schematic structure of a discharge unit.

[0027] Figure 4 : is a figure which shows an example of the signal waveform of the driving signal COM.

[0028] Figure 5 : is a diagram showing an example of the functional configuration of the drive signal selection circuit.

[0029] Figure 6 This is a diagram showing an example of the functional configuration of a switching circuit.

[0030] Figure 7 This is a diagram showing an example of the decoded content in the decoder.

[0031] Figure 8 It is a diagram showing the configuration of a selection circuit.

[0032] Fig. 9 This is a diagram showing an example of the operation of the switching circuit.

[0033] Fig.10 It is a diagram showing an example of the configuration of the first waveform shaping circuit.

[0034] Fig.11 It is a diagram showing an example of the configuration of a temperature detection circuit.

[0035] Fig.12 This is a diagram showing an example of the configuration of a discharge state determination circuit.

[0036] Fig.13 : is a diagram showing an example of the signal waveform of the residual vibration signal Vout.

[0037] Fig.14 This is a diagram showing a calculation model of a single vibration assuming residual vibration generated in the ejection portion.

[0038] Fig.15 This is a diagram for explaining the relationship between the viscosity of ink and the signal waveform of the residual vibration.

[0039] Fig.16 This is a diagram for explaining the relationship between the bubble mixing and the signal waveform of the residual vibration.

[0040] Fig.17 It 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 portion of the inspection object.

[0041] Fig.18 It is a diagram showing a specific example of the reference potential acquisition process.

[0042] Fig.19 It is a diagram showing a specific example of the residual vibration signal acquisition process.

[0043] Fig. 20 It is a diagram showing a specific example of the waveform information calculation process.

[0044] Fig.21 It is a diagram showing a specific example of the ejection portion determination process.

[0045] Fig. 22 It is a diagram showing an example of the configuration of a discharge state determination circuit according to a modified example.

[0046] Description of Reference Numerals

[0047] 1: liquid ejection device; 10: control unit; 11: control circuit substrate; 15: cable; 20: head unit; 21: carriage; 22: print head; 23: head wiring substrate; 24: flexible wiring substrate; 30: moving unit; 31: carriage motor; 32: endless belt; 40: conveying unit; 41: conveying motor; 42: conveying roller; 50: driving circuit; 60: piezoelectric element; 90: ink container; 100: control circuit; 200: driving unit 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: transmission gate; 240: first waveform shaping circuit; 241: filter circuit; 242: non-inverting amplifier circuit; 243: impedance conversion circuit; 250: temperature Detection circuit; 251: reference voltage generation circuit; 300: ejection state determination circuit; 310: second waveform shaping circuit; 320: residual vibration determination circuit; 321: control circuit; 322: multiplexer; 323: AD conversion circuit; 324: correction circuit; 326: storage circuit; 327: waveform information calculation circuit; 328: state determination circuit; 600: ejection unit; 601: piezoelectric body; 611, 612: electrodes; 6 21: vibration plate; 631: cavity resonator; 632: nozzle plate; 641: liquid reservoir; 651: nozzle; 661: ink supply port; AM10, AM11, AM31: operational amplifier; C: compliance; C10, C31~C33: capacitors; CM21: comparator; D21-1~D21-k: diodes; P: dielectric; Q21: transistor; R10~R12, R21, R22, R31~R36: resistors. DETAILED DESCRIPTION

[0048] The preferred embodiments of the present invention are described below using the accompanying drawings. The accompanying drawings are used for ease of description. It should be noted that the embodiments described below do not unduly limit the content of the present invention as described in the claims. In addition, not all of the structures described below are necessary components of the present invention.

[0049] Overview of liquid ejection device

[0050] Figure 1: is a diagram showing an example of a simplified structure of a liquid ejection device 1. The liquid ejection device 1 of the present embodiment is a so-called serial printing inkjet printer, wherein a carriage 21 equipped with print heads 22-1 to 22-n reciprocates along a scanning axis, and the print heads 22-1 to 22-n eject ink as an example of a liquid to a medium P transported along a transport direction, thereby forming a desired image on the medium P. As a medium P used for such a liquid ejection device 1, in addition to printing paper such as ordinary paper, any printing medium such as a resin film, cloth, etc. can be used. It should be noted that the liquid ejection device 1 is not limited to a serial printing inkjet printer, but may also be a line printing inkjet printer. In addition, the liquid ejection device 1 is not limited to an inkjet printer, but may be a colorant ejection device for manufacturing a color filter such as a liquid crystal display, an electrode material ejection device for forming electrodes of an organic EL display, a FED (surface luminous display), etc., a bio-organic ejection device for manufacturing a biochip, etc., and may also be a three-dimensional modeling device, a printing and dyeing device, etc.

[0051] like Figure 1 As shown, 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 .

[0052] The ink container 90 stores a plurality of inks to be ejected onto the medium P. As such an ink container 90, an ink cartridge, a bag-shaped ink bag formed of a flexible film, an ink tank capable of replenishing ink, or the like can be used.

[0053] The control unit 10 includes a processing circuit such as a CPU (Central Processing Unit) and 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 .

[0054] The print heads 22-1 to 22-n are mounted on the carriage 21. The control signal Ctrl-H and the drive signal COM output by the control unit 10 are input to the print heads 22-1 to 22-n. In addition, the ink stored in the ink container 90 is supplied to the print heads 22-1 to 22-n through a tube (not shown) or the like. The print heads 22-1 to 22-n eject the supplied ink onto the medium P based on the control signal Ctrl-H and the drive signal COM.

[0055] 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. The carriage 21 carrying the print heads 22-1 to 22-n is fixed to the endless belt 32. In addition, the endless belt 32 rotates with the operation of the carriage motor 31. Then, the carriage 21 fixed to the endless belt 32 moves along the scanning direction by the rotation of the endless belt 32. That is, the moving unit 30 controls the movement of the print heads 22-1 to 22-n mounted on the carriage 21.

[0056] The conveying unit 40 includes a conveying motor 41 and a conveying roller 42. The conveying motor 41 operates based on a control signal Ctrl-T input from the control unit 10. The conveying roller 42 rotates with the operation of the conveying motor 41 while clamping the medium P. The medium P clamped by the conveying roller 42 is conveyed along the conveying direction by the rotation of the conveying roller 42. That is, the conveying unit 40 controls the conveying of the medium P.

[0057] In the liquid ejection device 1 configured as above, the moving unit 30 controls the carriage 21 to reciprocate along the scanning direction, and the conveying unit 40 controls the conveying of the medium P along the conveying direction. Furthermore, the print heads 22-1 to 22-n mounted on the carriage 21 eject ink onto the medium P in conjunction with the reciprocating movement of the carriage 21 and the conveying of the medium P. Thus, the ink ejected from the print heads 22-1 to 22-n lands on any surface of the medium P, and a desired image is formed on the medium P.

[0058] 2. Functional composition of liquid ejection device

[0059] Next, the functional configuration of the liquid ejecting device 1 will be described. Figure 2 1 is a diagram showing an example of the functional structure of the liquid ejection device 1. Figure 2 As shown, the liquid ejection device 1 includes a control unit 10 and a head unit 20 .

[0060] The control unit 10 has a control circuit substrate 11, a drive circuit 50, and a control circuit 100. The control circuit substrate 11 is a printed substrate having one or more wiring layers, and a glass epoxy substrate, a glass polyimide substrate, etc. can be used. The various elements constituting the control unit 10 including the drive circuit 50 and the control circuit 100 are mounted on the control circuit substrate 11. It should be noted that the control circuit substrate 11 for mounting the various elements constituting the control unit 10 may be one printed substrate or a plurality of printed substrates.

[0061] The control circuit 100 includes a processing circuit such as a CPU and an 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. The control circuit 100 generates a signal for controlling each element of the liquid ejection device 1 based on the input image information signal, and outputs the signal to the corresponding element.

[0062] Specifically, the control circuit 100 generates a clock signal SCK, a latch signal LAT, a change signal CH, a check timing signal TSIG and a print data signal SI1~SIn based on the input image information signal as a control signal Ctrl-H for controlling the print heads 22-1~22-n, and outputs it to the head unit 20.

[0063] In addition, the control circuit 100 generates a basic 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 specified by the input basic drive signal dA, and outputs it to the head unit 20. Specifically, the control circuit 100 generates a basic drive signal dA which is a digital signal, and outputs it to the drive circuit 50. After the drive circuit 50 performs a digital / analog signal conversion on the input basic drive signal dA, it generates the drive signal COM by performing a D-class amplification on the converted analog signal. Then, the drive circuit 50 outputs the generated drive signal COM to the head unit 20. That is, the basic drive signal dA output by the control circuit 100 specifies the signal waveform of the drive signal COM output by the drive circuit 50. It should be noted that the basic drive signal dA can be an analog signal as long as it can specify the signal waveform of the drive signal COM. In addition, the drive circuit 50 can generate the drive signal COM by amplifying the signal waveform specified by the basic drive signal dA. Therefore, the drive circuit 50 may generate the drive signal COM by performing class A amplification, class B amplification, or class AB amplification instead of class D amplification.

[0064] In addition, the driving circuit 50 generates a reference voltage signal VBS and outputs it to the head unit 20. The reference voltage signal VBS is a signal whose voltage value is constant and specifies the reference potential for driving the piezoelectric element 60 of the ejection unit 600 described later. The voltage value of such a reference voltage signal VBS may be, for example, the ground potential GND, or 5.5V, 6V, etc. It should be noted that in Figure 2 In the figure, the driving circuit 50 is shown to generate the reference voltage signal VBS and output it to the head unit 20 . However, the reference voltage signal VBS may be generated by a power supply circuit (not shown) configured separately from the driving circuit 50 and output to the head unit 20 .

[0065] In addition, a temperature abnormality signal XHOT, temperature information signals TH1 to THn, determination result signals RT1 to RTn, and abnormality information signals Err1 to Errn are input to the control circuit 100 from the head unit 20 described later. The temperature abnormality signal XHOT is a signal indicating whether 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 temperature of the print heads 22-1 to 22-n. The determination result signals RT1 to RTn are signals indicating the state of the ejection unit 600 possessed by the print heads 22-1 to 22-n. The abnormality information signals Err1 to Errn are signals indicating whether an abnormality has occurred in the ejection state determination circuits 300-1 to 300-n described later possessed by the head unit 20.

[0066] 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 to THn, determination result signals RT1 to RTn, and abnormality information signals Err1 to Errn. That is, the liquid ejection device 1 operates according to the temperature of the head unit 20 and the state of the ejection portion 600. As a result, the ejection accuracy of the ink ejected from the liquid ejection device 1 is improved, and as a result, the image quality formed on the medium P is improved. It should be noted that the details of the temperature abnormality signal XHOT, temperature information signals TH1 to THn, determination result signals RT1 to RTn, and abnormality information signals Err1 to Errn input to the control circuit 100 will be described later.

[0067] The head unit 20 includes print heads 22-1 to 22-n, a head wiring substrate 23, flexible wiring substrates (FPC: Flexible Printed Circuit) 24-1 to 24-n, drive signal selection circuits 200-1 to 200-n, and ejection state determination circuits 300-1 to 300-n. In addition, the print heads 22-1 to 22-n each include a plurality of ejection units 600, and the plurality of ejection units 600 each include a piezoelectric element 60. The head unit 20 including the print heads 22-1 to 22-n is mounted on the carriage 21.

[0068] The head wiring substrate 23 is a printed substrate having one or more wiring layers, for example, a glass epoxy substrate, a glass polyimide substrate, etc. can be used. The ejection state determination circuits 300-1~300-n are mounted on the head wiring substrate 23. The flexible wiring substrate 24-1 is electrically connected to the head wiring substrate 23 at one end, and electrically connected to the print head 22-1 at the other end. The drive signal selection circuit 200-1 is mounted on the flexible wiring substrate 24-1. Similarly, the flexible wiring substrate 24-i (i is any one of 1~n) is electrically connected to the head wiring substrate 23 at one end, and electrically connected to the print head 22-i at the other end. The drive signal selection circuit 200-i is mounted on the flexible wiring substrate 24-i.

[0069] In addition, one end of the cable 15 is electrically connected to the head wiring substrate 23. The other end of the cable 15 is electrically connected to the control circuit substrate 11 of the control unit 10. The clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signals SI1~SIn, drive signal COM and reference voltage signal VBS output by the control unit 10 are propagated in the cable 15 and input to the head wiring substrate 23 of the head unit 20. In addition, the temperature abnormality signal XHOT, temperature information signals TH1~THn, determination result signals RT1~RTn and abnormality information signals Err1~Errn output by the head unit 20 are propagated in the cable 15 and input to the control unit 10. For such a cable 15, a structure having a sliding property that can follow the movement of the carriage 21, such as a flexible flat cable (FFC: Flexible Flat Cable) can be used.

[0070] The clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, printing data signal SIi and driving signal COM propagated in the cable 15 propagate in the head wiring substrate 23 and the flexible wiring substrate 24-i, and are input to the driving signal selection circuit 200-i. The driving signal selection circuit 200-i generates a driving signal Vin corresponding to each of the plurality of ejection units 600 of the print head 22-i by selecting or not selecting a signal waveform included in the driving signal COM based on the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG and printing data signal SIi. Then, the driving signal Vin generated by the driving 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 in the head wiring substrate 23 and the flexible wiring substrate 24-i is commonly supplied to the other ends of the piezoelectric elements 60 included in the plurality of ejection units 600 of the print head 22-i. Then, the piezoelectric element 60 of the print head 22 - i is driven by the potential difference between the driving signal Vin supplied to one end and the reference voltage signal VBS supplied to the other end. Ink is ejected from the corresponding ejection unit 600 by the driving of the piezoelectric element 60 .

[0071] In addition, the residual vibration signal Vout corresponding to the residual vibration generated after the piezoelectric element 60 of the print head 22-i is driven is obtained in the drive signal selection circuit 200-i. The drive signal selection circuit 200-i shapes the signal waveform of the obtained residual vibration signal Vout and then outputs it as the 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.

[0072] The drive signal selection circuit 200-i outputs a temperature information signal THi corresponding to the temperature of the print head 22-i, which is the temperature of the drive signal selection circuit 200-i. The temperature information signal THi is input to the ejection state determination circuit 300-i, propagates through the cable 15, and is input to the control circuit 100.

[0073] The ejection state determination circuit 300-i determines the state of the ejection unit 600 of the print head 22-i based on the input residual vibration signal NVTi and the temperature information signal THi. Then, the ejection state determination circuit 300-i generates a determination result signal RTi corresponding to the determination result, and outputs it to the control circuit 100. In addition, the ejection state determination circuit 300-i generates an abnormality information signal Erri indicating whether an abnormality has occurred in the ejection state determination circuit 300-i, and outputs it to the control circuit 100.

[0074] The drive signal selection circuits 200-1 to 200-n output a temperature anomaly signal XHOT indicating whether a temperature anomaly has occurred in any one of the drive signal selection circuits 200-1 to 200-n. Specifically, a wiring for propagating the temperature anomaly signal XHOT indicating whether a temperature anomaly has occurred in the drive signal selection circuit 200-1 and a wiring for propagating the temperature anomaly signal XHOT indicating whether a temperature anomaly has occurred in the drive signal selection circuit 200-i are connected in a wired OR manner. Furthermore, when a temperature anomaly has occurred in any one 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 anomaly signal XHOT propagated in the wiring connected in a wired OR manner to a predetermined logic level.

[0075] In the head unit 20 configured as above, the print heads 22-1 to 22-n are all configured in the same manner, and when there is no need to distinguish them, they are sometimes referred to as the print head 22. In addition, the flexible wiring substrates 24-1 to 24-n are all configured in the same manner, and when there is no need to distinguish them, they are sometimes referred to as the flexible wiring substrate 24. In addition, the drive signal selection circuits 200-1 to 200-n are all configured in the same manner, and when there is no need to distinguish them, they are sometimes referred to as the drive signal selection circuit 200. In addition, the ejection state determination circuits 300-1 to 300-n are all configured in the same manner, and when there is no need to distinguish them, they are sometimes referred to as the ejection state determination circuit 300.

[0076] In this case, the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SI as print data signals SI1 to SIn, and drive signal COM propagated in the head wiring substrate 23 and the flexible wiring substrate 24 are input to the drive signal selection circuit 200. Then, the drive signal selection circuit 200 selects or does not select the signal waveform included in the drive signal COM based on the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, and print data signal SI, thereby generating a drive signal Vin corresponding to each of the plurality of ejection units 600 of the print head 22, and supplies it to one end of the piezoelectric element 60 included in the corresponding ejection unit 600. At this time, the reference voltage signal VBS propagated in the head wiring substrate 23 and the flexible wiring substrate 24 is input to the other end of the piezoelectric element 60 included in the plurality of ejection units 600 of the print head 22. The piezoelectric element 60 included in the plurality of ejection units 600 of the print head 22 is driven by a potential difference between a drive signal Vin supplied to one end and a reference voltage signal VBS supplied to the other end. Ink of an amount corresponding to the driving of the piezoelectric element 60 is ejected from the ejection unit 600 of the print head 22.

[0077] In addition, a residual vibration signal Vout corresponding to the residual vibration generated after the piezoelectric element 60 included in 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 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.

[0078] The drive signal selection circuit 200 outputs a temperature information signal TH as 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 discharge state determination circuit 300, propagates through the cable 15, and is input to the control circuit 100.

[0079] The ejection state determination circuit 300 determines the state of the ejection unit 600 of the print head 22 based on the residual vibration signal NVT and the temperature information signal TH. Next, the ejection state determination circuit 300 generates the determination result signal RT as the determination result signal RT1 to RTn corresponding to the determination result and the abnormality information signal Err as the abnormality information signal Err1 to Errn indicating whether the ejection state determination circuit 300 is abnormal, and outputs them to the control circuit 100.

[0080] As described above, the liquid ejection device 1 of the present embodiment includes a head unit 20 for ejecting liquid onto a medium P and a control unit 10 for controlling the operation of the head unit 20. In addition, the head unit 20 includes an ejection unit 600, a drive signal selection circuit 200, and an ejection state determination circuit 300 for determining the state of the ejection unit 600, wherein the ejection unit 600 includes a piezoelectric element 60 driven according to a drive signal COM and ejects ink according to the drive of the piezoelectric element 60; the drive signal selection circuit 200 is input with a 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 waveform of the residual vibration signal Vout, and outputs a temperature information signal TH corresponding to the temperature of the drive signal selection circuit 200.

[0081] 3. Structure of the ejection part

[0082] Next, the configuration of the ejection unit 600 included in the print head 22 will be described. Figure 3 2 is a diagram showing a schematic structure of one of the plurality of ejection units 600 included in the print head 22. Figure 3 As shown, the ejection unit 600 includes a piezoelectric element 60 , a vibration plate 621 , a cavity resonator 631 , and a nozzle 651 .

[0083] The cavity resonator 631 is filled with ink supplied from the reservoir 641 .

[0084] The reservoir 641 is provided in common for the plurality of ejection units 600 of the print head 22. Ink is introduced from the ink container 90 into the reservoir 641 via an ink flow path and an ink supply port 661 (not shown). That is, the cavity resonator 631 is filled with ink stored in the ink container 90.

[0085] The vibration plate 621 passes through Figure 3 The piezoelectric element 60 provided on the upper surface is driven to displace. Then, the internal volume of the cavity resonator 631 filled with ink expands and contracts with the displacement of the vibration plate 621. That is, the vibration plate 621 functions as a diaphragm that changes the internal volume of the cavity resonator 631.

[0086] The nozzle 651 is an opening portion provided in the nozzle plate 632 and communicating with the cavity resonator 631. Then, as the internal volume of the cavity resonator 631 changes, the ink of an amount corresponding to the change in the internal volume is ejected from the nozzle 651.

[0087] The piezoelectric element 60 is a structure in which a piezoelectric body 601 is sandwiched by a pair of electrodes 611 and 612. In the piezoelectric body 601 having such a structure, the central portion of the electrodes 611 and 612 is bent in the vertical direction together with the vibration plate 621 according to the potential difference of the voltage supplied by the electrodes 611 and 612. Specifically, a driving signal Vin is supplied to one of the electrodes 611 and 612 of the piezoelectric element 60. In addition, a signal of a reference potential serving as a reference for displacement of the piezoelectric element 60 is supplied to the other of the electrodes 611 and 612 of the piezoelectric element 60. Then, in the piezoelectric element 60, for example, when the voltage level of the driving signal Vin becomes high, the central portion is bent upward, and when the voltage level of the driving signal Vin becomes low, the central portion is bent downward.

[0088] In the ejection unit 600 configured as above, the piezoelectric element 60 is driven in a manner of bending upward, and the central portion of the vibration plate 621 is displaced upward, and the internal volume of the cavity resonator 631 is expanded. As a result, ink is drawn from the liquid reservoir 641. On the other hand, the piezoelectric element 60 is driven in a manner of bending downward, and the central portion of the vibration plate 621 is displaced downward, and the internal volume of the cavity resonator 631 is reduced. As a result, an amount of ink corresponding to the reduction degree is ejected from the nozzle 651.

[0089] It should be noted that the piezoelectric element 60 included in the ejection unit 600 is not limited to Figure 3The structure shown in the figure can be any structure as long as it can eject ink from the ejection portion 600. Therefore, the piezoelectric element 60 is not limited to the structure of bending vibration as described above, and can also be a structure of longitudinal vibration. In addition, the piezoelectric element 60 can also be a structure in which the central part bends upward when the voltage level of the driving signal Vin becomes low, and the central part bends downward when the voltage level of the driving signal Vin becomes high.

[0090] 4. Configuration and operation of the drive signal selection circuit

[0091] 4.1 Signal waveform of driving signal COM

[0092] Next, the configuration and operation of the drive signal selection circuit 200 will be described. The drive signal selection circuit 200 outputs the drive signal Vin corresponding to each of the plurality of ejection units 600 included in the print head 22 by selecting or not selecting the signal waveform included in the drive signal COM. When the details of the drive signal selection circuit 200 are described, an example of the signal waveform of the drive signal COM input to the drive signal selection circuit 200 will be described. Figure 4 is a diagram showing an example of a signal waveform of the drive signal COM. Figure 4 As shown, the driving signal COM includes a driving signal ComA and a driving signal ComB.

[0093] The driving signal ComA includes a signal waveform for expressing four grayscales of large dot LD, middle dot MD, small dot SD and non-recording ND on the medium P. Specifically, the driving signal ComA includes driving waveforms Adp1 and Adp2 as signal waveforms in a period t after the latch signal LAT rises and before the next latch signal LAT rises.

[0094] The driving waveform Adp1 is arranged in a period tp1 from the rising edge of the latch signal LAT to the rising edge of the change signal CH in the period t. In the driving waveform Adp1, the voltage value starts with the voltage Vc, and after the voltage value changes to drive the piezoelectric element 60, the voltage value ends with the voltage Vc. When the driving waveform Adp1 is supplied to one end of the piezoelectric element 60, a predetermined amount of ink is ejected from the corresponding nozzle 651.

[0095] The driving waveform Adp2 is arranged in a period tp2 from the rising edge of the change signal CH to the rising edge of the latch signal LAT in the period t. In the driving waveform Adp2, the voltage value starts with the voltage Vc, and after the voltage value changes to drive the piezoelectric element 60, the voltage value ends with the voltage Vc. When the driving waveform Adp2 is supplied to one end of the piezoelectric element 60, ink less than a predetermined amount is ejected from the corresponding nozzle 651.

[0096] Here, in the following description, a predetermined amount of ink ejected from a corresponding nozzle 651 when a driving waveform Adp1 is supplied to one end of the piezoelectric element 60 is sometimes referred to as a medium amount, and an amount of ink ejected from a corresponding nozzle 651 that is less than a predetermined amount when a driving waveform Adp2 is supplied to one end of the piezoelectric element 60 is sometimes referred to as a small amount.

[0097] The driving signal ComB includes a signal waveform for performing inspection CD of the nozzle 651 to be inspected among the plurality of nozzles 651. Specifically, the driving signal ComB includes driving waveforms Bdp1, Bdp2, and Bdp3 as signal waveforms within a period t.

[0098] The driving waveform Bdp1 is arranged in a period ts1 from the rising edge of the latch signal LAT to the rising edge of the inspection timing signal TSIG within the period t. In the driving waveform Bdp1, the voltage value starts with the voltage Vc, and after the voltage value changes to drive the piezoelectric element 60, the voltage value ends with the voltage Vd. When the driving waveform Bdp1 is supplied to one end of the piezoelectric element 60, the ink is not ejected from the corresponding nozzle 651, but the piezoelectric element 60 is driven to generate a predetermined residual vibration in the corresponding ejection portion 600.

[0099] The driving waveform Bdp2 is arranged in a period ts2 from the rising edge of the inspection timing signal TSIG at the end of the predetermined period ts1 to the rising edge of the next inspection timing signal TSIG within the cycle t. In the driving waveform Bdp2, the voltage value is constant at the voltage Vd. When the driving waveform Bdp2 is supplied to one end of the piezoelectric element 60, the piezoelectric element 60 is not driven, and therefore, the ink is not ejected from the corresponding nozzle 651.

[0100] The driving waveform Bdp3 is arranged in a period ts3 from the rising edge of the inspection timing signal TSIG at the end of the predetermined period ts2 to the rising edge of the next latch signal LAT in the cycle t. In the driving waveform Bdp3, the voltage value starts at the voltage Vd and then ends at the voltage value Vc. When the driving waveform Bdp3 is supplied to one end of the piezoelectric element 60, the piezoelectric element 60 is not driven, and therefore, the ink is not ejected from the corresponding nozzle 651.

[0101] That is, the driving circuit 50 outputs a driving signal COM to the driving signal selection circuit 200, and the driving signal COM includes: a driving signal ComA and a driving signal ComB, wherein the driving signal ComA includes driving waveforms Adp1 and Adp2 for making four grayscales of large dot LD, middle dot MD, small dot SD and non-recording ND appear on the medium P, and the driving signal ComB includes driving waveforms Bdp1, Bdp2, and Bdp3 for executing the inspection CD of the ejection part 600 including the nozzle 651 of the inspection object.

[0102] It should be noted that Figure 4 The signal waveform of the driving signal COM shown is an example, and the driving signal COM may include signal waveforms of various shapes according to the moving speed of the carriage 21 carrying the print head 22, the type of the medium P on which the ink lands, the characteristics of the ink, and the like.

[0103] 4.2 Configuration of drive signal selection circuit

[0104] Next, the configuration of the drive signal selection circuit 200 will be described. The drive signal selection circuit 200 generates the drive signal Vin by selecting or not selecting the signal waveform included in the drive signal COM, and outputs the drive signal Vin to the corresponding ejection unit 600 . Figure 5 2 is a diagram showing an example of the functional configuration of the drive signal selection circuit 200. Figure 5 As shown, the drive signal selection circuit 200 includes 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 a semiconductor device and is mounted on a flexible wiring substrate 24 in a COF (Chip On Film) manner.

[0105] The clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, printing data signal SI and drive signal COM are input to the switching circuit 210. Based on the input clock signal SCK, latch signal LAT, inspection timing signal TSIG, change signal CH and printing data signal SI, the switching circuit 210 selects or does not select the drive waveforms Adp1 and Adp2 included in the drive signal ComA in the drive signal COM and the drive waveforms Bdp1, Bdp2 and Bdp3 included in the drive signal ComB in the drive signal COM, thereby generating drive signals Vin corresponding to the plurality of ejection units 600, respectively, and outputs the drive signals to the corresponding ejection units 600.

[0106] After the piezoelectric element 60 is driven by the output drive signal Vin, the switching circuit 210 obtains a residual vibration signal Vout corresponding to the residual vibration generated in the ejection unit 600 by the driving of the piezoelectric element 60. The switching circuit 210 outputs the obtained residual vibration signal Vout to the first waveform shaping circuit 240.

[0107] The first waveform shaping circuit 240 extracts an AC component from the input residual vibration signal Vout and amplifies it to shape the signal waveform of the residual vibration signal Vout and output it as a 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.

[0108] 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 corresponding to the detection result of the temperature, and outputs it from the drive signal selection circuit 200. In addition, the temperature detection circuit 250 determines whether the temperature of the semiconductor device including the drive signal selection circuit 200 is above a predetermined threshold value. Then, when the temperature of the semiconductor device including the drive signal selection circuit 200 is above the predetermined threshold value, 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 a temperature abnormality of the semiconductor device including the drive signal selection circuit 200.

[0109] As described above, the drive signal selection circuit 200 includes: a first waveform shaping circuit 240 and a temperature detection circuit 250, a residual vibration signal Vout corresponding to the residual vibration generated by the drive signal COM is input to the first waveform shaping circuit 240, and the first waveform shaping circuit 240 outputs a residual vibration signal NVT obtained by shaping the signal waveform of the residual vibration signal Vout, and the temperature detection circuit 250 outputs a temperature information signal TH corresponding to the temperature of the first waveform shaping circuit 240, and the first waveform shaping circuit 240 and the temperature detection circuit 250 are included in a semiconductor device.

[0110] 4.2.1 Switching Circuit Configuration

[0111] A specific example of the configuration and operation of the switching circuit 210 included in the drive signal selection circuit 200 will be described. Figure 6 2 is a diagram showing an example of the functional configuration of the switching circuit 210. Figure 6 As shown, the switching circuit 210 includes a selection control circuit 220 and a plurality of selection circuits 230 .

[0112] The clock signal SCK, the printing data signal SI, the latch signal LAT, the change signal CH, and the inspection timing signal TSIG are input to the selection control circuit 220. Based on the input clock signal SCK, the printing data signal SI, the latch signal LAT, the change signal CH, and the inspection timing signal TSIG, the selection control circuit 220 generates the selection signals Sa, Sb, and Sc of predetermined logic levels in the periods tp1 and tp2 and the periods ts1, ts2, and ts3, respectively, and outputs them to the corresponding selection circuits 230.

[0113] The selection control circuit 220 includes a group of shift registers 222, latch circuits 224, and decoders 226, which are respectively provided corresponding to the piezoelectric elements 60 of the plurality of ejection units 600 of the print head 22. Here, in the following description, it is explained that the print head 22 includes m ejection units 600, that is, m piezoelectric elements 60. That is, the selection control circuit 220 includes m groups of shift registers 222, latch circuits 224, and decoders 226. In other words, the selection control circuit 220 includes m shift registers 222, m latch circuits 224, and m decoders 226.

[0114] The print data signal SI includes, in a serial manner, 3-bit print data SId [SIH, SIM, SIL] for selecting which of the large dot LD, medium dot MD, small dot SD, non-recording ND, and inspection CD is used to drive the piezoelectric element 60, corresponding to each of the m piezoelectric elements 60. That is, the print data signal SI is a serial signal of more than 3m bits in total.

[0115] 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 included in the selection control circuit 220 hold 3-bit print data SId [SIH, SIM, SIL] included in the input print data signal SI in correspondence with the piezoelectric elements 60 .

[0116] In detail, m shift registers 222 are cascaded corresponding to m piezoelectric elements 60, respectively. The printing data signal SI input to the selection control circuit 220 in a serial manner is synchronously transmitted to the subsequent stage of the m cascaded shift registers 222 in sequence with the clock signal SCK. Then, by stopping the supply of the clock signal SCK to the selection control circuit 220, the 3-bit printing data SId [SIH, SIM, SIL] corresponding to the m piezoelectric elements 60 is maintained in the m shift registers 222. It should be noted that in the following description, in order to distinguish the m cascaded shift registers 222, they are sometimes referred to as the 1st stage, the 2nd stage, ..., the mth stage in sequence from the upstream side to which the printing data signal SI is supplied to the downstream side.

[0117] The m latch circuits 224 latch the 3-bit print data SId [SIH, SIM, SIL] held in the corresponding shift register 222 at the rising edge of the latch signal LAT.

[0118] The print data SId [SIH, SIM, SIL] latched by the m latch circuits 224 are input to the corresponding decoders 226. The m decoders 226 respectively decode the input print data SId [SIH, SIM, SIL], generate selection signals Sa, Sb, Sc of logic levels corresponding to the large dot LD, the middle dot MD, the small dot SD, the non-recording ND, and the inspection CD, and output them to the corresponding selection circuits 230.

[0119] Figure 7 2 is a diagram showing an example of the decoded content in the decoder 226. Figure 7 As shown, when the printing data SId [SIH, SIM, SIL] = [1, 1, 0] corresponding to the large dot LD is input, the decoder 226 sets the logic level of the selection signal Sa to the H, H level in the periods tp1 and tp2, sets the logic level of the selection signal Sb to the L, L, L level in the periods ts1, ts2, and ts3, and sets the logic level of the selection signal Sc to the L, L, L level in the periods ts1, ts2, and ts3.

[0120] In addition, when the printing data SId [SIH, SIM, SIL] = [1, 0, 0] corresponding to the midpoint MD is input, the decoder 226 sets the logic level of the selection signal Sa to H, L levels 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.

[0121] In addition, when the printing data SId [SIH, SIM, SIL] = [0, 1, 0] corresponding to the small dot SD is input, the decoder 226 sets the logic level of the selection signal Sa to L, H 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, ts3, and sets the logic level of the selection signal Sc to L, L, L levels in the periods ts1, ts2, ts3.

[0122] In addition, when the printing data SId [SIH, SIM, SIL] = [0, 0, 0] corresponding to the non-recording ND is input, the decoder 226 sets the logic level of the selection signal Sa to the L, L level in the periods tp1 and tp2, sets the logic level of the selection signal Sb to the L, L, L level in the periods ts1, ts2, and ts3, and sets the logic level of the selection signal Sc to the L, L, L level in the periods ts1, ts2, and ts3.

[0123] In addition, when the 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 level in the periods tp1 and tp2, sets the logic level of the selection signal Sb to H, L, H level in the periods ts1, ts2, ts3, and sets the logic level of the selection signal Sc to L, H, L level in the periods ts1, ts2, ts3.

[0124] As described above, the selection control circuit 220 generates the selection signals Sa, Sb, and Sc of the logic levels corresponding to the piezoelectric elements 60 included in the m ejection units 600 based on the print data SId [SIH, SIM, SIL]. Then, the selection control circuit 220 outputs the generated selection signals Sa, Sb, and Sc to the corresponding selection circuits 230.

[0125] The selection circuits 230 are provided corresponding to the m piezoelectric elements 60 . That is, the switching circuit 210 includes m selection circuits 230 . Figure 8 2 is a diagram showing the configuration of the selection circuit 230 corresponding to one piezoelectric element 60. Figure 8 As shown, the selection circuit 230 has logic inversion circuits 232a, 232b, 232c and transmission gates 234a, 234b, 234c.

[0126] The selection signal Sa is supplied to the positive control terminal of the transmission gate 234a, and is also supplied to the negative control terminal of the transmission gate 234a after the logic level is inverted by the logic inversion circuit 232a. The selection signal Sb is supplied to the positive control terminal of the transmission gate 234b, and is also supplied to the negative control terminal of the transmission gate 234b after the logic level is inverted by the logic inversion circuit 232b. The selection signal Sc is supplied to the positive control terminal of the transmission gate 234c, and is also supplied to the negative control terminal of the transmission gate 234c after the logic level is inverted by the logic inversion circuit 232c.

[0127] In addition, the drive signal ComA is supplied to the input end of the transmission gate 234a, and the drive signal ComB is supplied to the input end of the transmission gate 234b. Moreover, the output ends of the transmission gates 234a and 234b are connected to each other. The output ends of the interconnected transmission gates 234a and 234b are electrically connected to one end of the corresponding piezoelectric element 60. In addition, the input end of the transmission gate 234c is electrically connected to the output ends of the interconnected transmission gates 234a and 234b and one end of the piezoelectric element 60. The output end of the transmission gate 234c is as shown in FIG. Figure 6 As shown, the output terminals of the transmission gates 234 c of the m selection circuits 230 included in the switching circuit 210 are commonly connected.

[0128] In the selection circuit 230 configured as above, when the logic level of the selection signal Sa is at an H level, the input terminal and the output terminal of the transmission gate 234a become conductive, and when the logic level of the selection signal Sa is at an L level, the input terminal and the output terminal of the transmission gate 234a become non-conductive. In addition, when the logic level of the selection signal Sb is at an H level, the input terminal and the output terminal of the transmission gate 234b become conductive, and when the logic level of the selection signal Sb is at an L level, the input terminal and the output terminal of the transmission gate 234b become non-conductive. In addition, when the logic level of the selection signal Sc is at an H level, the input terminal and the output terminal of the transmission gate 234c become conductive, and when the logic level of the selection signal Sc is at an L level, the input terminal and the output terminal of the transmission gate 234c become non-conductive. Here, in the following description, the case where the input terminal and the output terminal become conductive is sometimes referred to as "conductive", and the case where the input terminal and the output terminal become non-conductive is sometimes referred to as "disconnected".

[0129] Furthermore, if the transmission gate 234a is turned on, the drive signal ComA is output from the switching circuit 210 as the drive signal Vin, and if the transmission 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 unit 600. In addition, by turning on the transmission gate 234c, the switching circuit 210 acquires a residual vibration signal Vout corresponding to the residual vibration generated in the ejection unit 600 accompanying the driving of the piezoelectric element 60. Then, the switching circuit 210 outputs the acquired residual vibration signal Vout to the first waveform shaping circuit 240.

[0130] 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 printing data signal SI is supplied to the switching circuit 210 in a serial manner in synchronization with the clock signal SCK. The printing data signal SI input to the switching circuit 210 is sequentially transmitted to the shift register 222 of the subsequent stage in synchronization with the clock signal SCK. Then, by stopping the supply of the clock signal SCK to the switching circuit 210, the 3-bit printing data SId [SIH, SIM, SIL] corresponding to the m ejection units 600 is respectively held in the m shift registers 222.

[0131] Thereafter, as the latch signal LAT rises, the latch circuit 224 latches the print data SId [SIH, SIM, SIL] held in the shift register 222 at the same time. Fig. 9 LT1 , LT2 , . . . , LTm shown represent print data SId [SIH, SIM, SIL] held by the 1st, 2nd, . . . , mth-stage shift registers 222 and latched by the corresponding latch circuits 224 .

[0132] Decoder 226 utilizes Figure 7 The decoder 226 then outputs the latched print data SId[SIH, SIM, SIL] in cycle t. Figure 7 The logic levels of the selection signals Sa, Sb, Sc are shown.

[0133] 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 the H, H level during the periods tp1 and tp2, sets the logic level of the selection signal Sb to the L, L, L level during the periods ts1, ts2, and ts3, and sets the logic level of the selection signal Sc to the L, L, L level during the periods ts1, ts2, and ts3. As a result, the selection circuit 230 selects the drive waveform Adp1 of the drive signal ComA during the period tp1, and selects the drive waveform Adp2 of the drive signal ComA during the period tp2. As a result, the switching circuit 210 outputs the same Fig. 9 The driving signal Vin corresponding to the large dot LD shown in FIG. 1 is supplied to one end of the piezoelectric element 60. When the driving signal Vin corresponding to the 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 the period tp1, and a small amount of ink is ejected from the corresponding nozzle 651 during the period tp2. As a result, in the period t, the medium amount of ink and the small amount of ink land on the medium P and combine. Thus, the large dot LD is formed on the medium P.

[0134] When the printing data SId [SIH, SIM, SIL] = [1, 0, 0], the decoder 226 sets the logic level of the selection signal Sa to the H, L level in the periods tp1 and tp2, sets the logic level of the selection signal Sb to the L, L, L level in the periods ts1, ts2, and ts3, and sets the logic level of the selection signal Sc to the L, L, L level in the periods ts1, ts2, and ts3. As a result, the selection circuit 230 selects the drive waveform Adp1 of the drive signal ComA in the period tp1, and does not select the signal waveform of any of the drive signals ComA and ComB in the period tp2. As a result, the switching circuit 210 outputs the same signal as Fig. 9 1. When the driving signal Vin corresponding to the midpoint MD is supplied to one end of the piezoelectric element 60, a medium amount of ink is ejected from the corresponding nozzle 651 during the period tp1, and ink is not ejected from the corresponding nozzle 651 during the period tp2. As a result, a medium amount of ink lands on the medium P during the period t. Thus, the midpoint MD is formed on the medium P.

[0135] 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 during the periods tp1 and tp2, sets the logic level of the selection signal Sb to L, L, L levels during the periods ts1, ts2, and ts3, and sets the logic level of the selection signal Sc to L, L, L levels during the periods ts1, ts2, and ts3. As a result, the selection circuit 230 does not select the signal waveform of any of the drive signals ComA and ComB during the period tp1, and selects the drive waveform Adp2 of the drive signal ComA during the period tp2. As a result, the switching circuit 210 outputs the same signal waveform as Fig. 9 The driving signal Vin corresponding to the small dot SD shown in FIG. 1 is supplied to one end of the piezoelectric element 60. When the driving signal Vin corresponding to the small dot SD is supplied to one end of the piezoelectric element 60, the ink is not ejected from the corresponding nozzle 651 during the period tp1, and a small amount of ink is ejected from the corresponding nozzle 651 during the period tp2. As a result, a small amount of ink lands on the medium P during the period t. Thus, the small dot SD is formed on the medium P.

[0136] When the printing data SId[SIH, SIM, SIL]=[0, 0, 0], the decoder 226 sets the logic level of the selection signal Sa to L, L level in the periods tp1 and tp2, sets the logic level of the selection signal Sb to L, L, L level in the periods ts1, ts2, ts3, and sets the logic level of the selection signal Sc to L, L, L level in the periods ts1, ts2, ts3. As a result, the selection circuit 230 does not select the signal waveform of any of the drive signals ComA and ComB in the period tp1, and does not select the signal waveform of any of the drive signals ComA and ComB in the period tp2. As a result, the switching circuit 210 outputs the same signal as Fig. 9 When the driving signal Vin corresponding to the non-recording ND is supplied to one end of the piezoelectric element 60, the corresponding ejection unit 600 does not eject ink during the period tp1, and does not eject ink from the corresponding ejection unit 600 even during the period tp2. As a result, the ink does not land on the medium P during the period t. Therefore, no dots are formed on the medium P.

[0137] When the printing data SId[SIH, SIM, SIL]=[1, 1, 1], the decoder 226 sets the logic level of the selection signal Sa to L, L level in the periods tp1 and tp2, sets the logic level of the selection signal Sb to H, L, H level in the periods ts1, ts2, ts3, and sets the logic level of the selection signal Sc to L, H, L level in the periods ts1, ts2, ts3. Thus, the selection circuit 230 selects the drive waveform Bdp1 of the drive signal ComB in the period ts1, obtains the residual vibration signal Vout corresponding to the residual vibration of the ejection unit 600 in the period ts2, and outputs the obtained residual vibration signal Vout from the switching circuit 210, and selects the drive waveform Bdp3 of the drive signal ComB in the period ts3. As a result, the switching circuit 210 outputs the drive waveform Bdp3 corresponding to the residual vibration of the ejection unit 600 in the periods ts1 and ts3. Fig. 9 The driving signal Vin corresponding to the inspection CD shown in the figure obtains the residual vibration signal Vout corresponding to the residual vibration generated after the driving waveform Bdp1 is supplied to the piezoelectric element 60 in the period ts2, and outputs it to the first waveform shaping circuit 240. At this time, in the period t, the ink is not ejected from the corresponding nozzle 651. Therefore, in the period t, the ink does not land on the medium P. Therefore, no dots are formed on the medium P.

[0138] As described above, the switching circuit 210 generates the driving signal Vin by selecting or not selecting the driving waveforms Adp1, Adp2 included in the driving signal ComA and the driving waveforms Bdp1, Bdp2, Bdp3 included in the driving signal ComB in the driving signal COM output by the driving circuit 50 based on the clock signal SCK, the printing data signal SI, the latch signal LAT, the change signal CH, and the check timing signal TSIG. Then, the switching circuit 210 supplies the generated driving signal Vin to the corresponding piezoelectric element 60, and obtains the residual vibration signal Vout corresponding to the residual vibration generated after the piezoelectric element 60 is driven with the driving signal Vin, and outputs it to the first waveform shaping circuit 240.

[0139] 4.2.2 Configuration of the first waveform shaping circuit

[0140] 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 2 is a diagram showing an example of the configuration of the first waveform shaping circuit 240. Fig.10 As shown, the first waveform shaping circuit 240 includes a filter circuit 241 , a non-inverting amplifier circuit 242 , and an impedance conversion circuit 243 .

[0141] The filter circuit 241 includes a capacitor C10 and a resistor R10. A 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. A ground potential is supplied to the other end of the resistor R10. The filter circuit 241 constructed as above constitutes a high-pass filter that extracts high-frequency components overlapping with the residual vibration signal Vout. That is, the filter circuit 241 reduces low-frequency components overlapping with the residual vibration signal Vout. It should be noted that the filter circuit 241 may also have a low-pass filter in addition to the high-pass filter.

[0142] The non-inverting amplifier circuit 242 includes an operational amplifier AM10, and resistors R11 and R12. The signal output by the filter circuit 241 is input to the + side input terminal of the operational amplifier AM10. The - side 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 output terminal of the operational amplifier AM10 is electrically connected to the other end of the resistor R11. A ground potential is supplied to the other end of the resistor R12. The non-inverting amplifier circuit 242 constructed as above constitutes a non-inverting amplifier circuit, which amplifies the signal output by the filter circuit 241 input to the + side input terminal of the operational amplifier AM10 at an amplification factor specified by the resistance values ​​of the resistors R11 and R12. That is, the non-inverting amplifier circuit 242 extracts the AC component of the residual vibration signal Vout, and amplifies the amplitude of the extracted signal at an amplification factor specified by the resistance values ​​of the resistors R11 and R12.

[0143] The impedance conversion circuit 243 includes an operational amplifier AM11. The signal output by the non-inverting amplifier circuit 242 is input to the + side input terminal of the operational amplifier AM11. In addition, the - side input terminal of the operational amplifier AM11 is electrically connected to the output terminal of the operational amplifier AM11. The impedance conversion circuit 243 configured as above constitutes a so-called voltage follower circuit, which outputs a signal having the same signal waveform as the signal waveform input to the + side input terminal of the operational amplifier AM11 from the output terminal of the operational amplifier AM11.

[0144] The first waveform shaping circuit 240 outputs the signal output from the output terminal of the operational amplifier AM10 included in the non-inverting amplifier circuit 242 , that is, the signal output from the output terminal of the operational amplifier AM11 included in the impedance conversion circuit 243 as the residual vibration signal NVT.

[0145] As described above, the first waveform shaping circuit 240 removes noise and DC components of low-frequency components of the residual vibration signal Vout through the filter circuit 241, 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 obtained by shaping the waveform of the residual vibration signal Vout. That is, the first waveform shaping circuit 240 includes 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.

[0146] At this time, the operational amplifier AM10 and the resistors R11 and R12 of the first waveform shaping circuit 240 constitute a semiconductor device including the drive signal selection circuit 200. The details will be described later. The residual vibration signal Vout corresponding to the residual vibration of the ejection part 600 of the inspection object, that is, the residual vibration signal Vout corresponding to the residual vibration output by the switching circuit 210 includes a signal of an electromotive force, which is generated by the displacement of the piezoelectric element 60 after the drive signal COM is supplied to the piezoelectric element 60, and the displacement of the piezoelectric element 60 is caused by the residual vibration generated in the ejection part 600. Therefore, the residual vibration signal Vout corresponding to the residual vibration is a signal of a weak attenuated vibration and is easily affected by noise. In the first waveform shaping circuit 240 of the present embodiment, the filter circuit 241 removes the noise and DC components of the low-frequency components from the residual vibration signal Vout, thereby extracting the AC component caused by the attenuated vibration generated in the ejection part 600 of the inspection object, thereby improving the waveform accuracy of the residual vibration signal Vout. Then, the non-inverting amplifier circuit 242 amplifies the signal whose waveform accuracy is improved by the filter circuit 241, thereby improving the tolerance to noise. That is, the first waveform shaping circuit 240 outputs the residual vibration signal NVT, which is a signal obtained by shaping the signal waveform of the residual vibration signal Vout, in which the influence of noise and the like is reduced and the tolerance to noise is improved.

[0147] 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. As a result, the stability of the residual vibration signal NVT output by the first waveform shaping circuit 240 can be improved, and the possibility of malfunction in the ejection unit 600 can be reduced by the action of the ejection state determination circuit 300 when determining the state of the ejection unit 600 based on the residual vibration signal NVT.

[0148] Such a first waveform shaping circuit 240 is constituted as a semiconductor device together with the switching circuit 210, thereby being able to amplify the residual vibration signal Vout near the ejection portion 600 including the piezoelectric element 60. That is, the propagation path of the residual vibration signal Vout can be shortened. As a result, the possibility of noise overlapping with the residual vibration signal Vout corresponding to the residual vibration can be further reduced, and the waveform accuracy of the residual vibration signal Vout obtained by the first waveform shaping circuit 240 can be improved, wherein the residual vibration signal Vout is a signal of weak attenuated vibration. As a result, the waveform accuracy of the residual vibration signal NVT output by the drive signal selection circuit 200 is improved.

[0149] 4.2.3 Composition of temperature detection circuit

[0150] Next, a specific example of the configuration and operation of the temperature detection circuit 250 will be described. Fig.11 2 is a diagram showing an example of the structure of the temperature detection circuit 250. Here, the drive signal selection circuits 200-1 to 200-n are all of the same structure. Therefore, the temperature detection circuits 250 of the drive signal selection circuits 200-1 to 200-n are also of the same structure. Therefore, in the following description, when the temperature detection circuits 250 of the drive signal selection circuits 200-1 to 200-n are distinguished, the temperature detection circuit 250 of the drive signal selection circuit 200-1 is sometimes referred to as the temperature detection circuit 250-1, and the temperature detection circuit 250 of the drive signal selection circuit 200-n is sometimes referred to as the temperature detection circuit 250-n.

[0151] Fig.11 2 is a diagram showing an example of the configuration of the temperature detection circuit 250. Fig.11 As shown, the temperature detection circuit 250 includes a reference voltage generating circuit 251, a comparator CM21, a transistor Q21, diodes D21-1 to D21-k, and resistors R21 and R22. In addition, 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 bandgap reference source 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.

[0152] The voltage signal Vdd1 input to the temperature detection circuit 250 is input to the reference voltage generating circuit 251, one end of the resistor R21, and one end of the resistor R22. The reference voltage generating circuit 251 generates a voltage signal Vref with a constant voltage value by transforming the voltage value of the input voltage signal Vdd1. Then, the voltage signal Vref generated by the reference voltage generating circuit 251 is input to the + side input terminal of the comparator CM21. In addition, the other end of the resistor R21 is electrically connected to the anode terminal of the diode D21-1. The cathode terminal of the diode D21-1 is electrically connected to the anode terminal of the diode D21-2, the cathode terminal of the diode D21-2 is electrically connected to the anode terminal of the diode D21-3, and the cathode terminal of the diode D21-i (i is any one of 1~k-1) is electrically connected to the anode terminal of the diode D21-(i+1). That is, the diodes D21-1~D21-k are connected in series. At this time, the anode terminal of the diode D21-1 at one end of the series-connected diodes D21-1 to D21-k 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 at the other end of the series-connected diodes D21-1 to D21-k.

[0153] Then, a signal at the connection point between the other end of the electrically connected resistor R21 and the anode terminal of the diode D21-1, i.e., a signal whose voltage value is the sum of the forward voltages of the diodes D21-1 to D21-k connected in series, is input to the -side input terminal of the comparator CM21 as a voltage signal Vdet, and is output from the temperature detection circuit 250 as a temperature information signal TH.

[0154] The comparator CM21 operates with the potential difference between the voltage signal Vdd1 supplied to the high potential side power supply terminal and the signal of the ground potential supplied to the low potential side 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. Then, the signal at the drain terminal of the transistor Q21 is output from the temperature detection circuit 250 as the temperature abnormality signal XHOT.

[0155] In the temperature detection circuit 250 configured as described above, the voltage value of the forward voltage of each of the diodes D21-1 to D21-k decreases 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 change according to the temperature of the diodes D21-1 to D21-k, that is, the temperature of the semiconductor device constituting the drive signal selection circuit 200 including the diodes D21-1 to D21-k. In other words, the temperature detection circuit 250 outputs the temperature information signal TH corresponding 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.

[0156] In addition, a voltage signal Vdet having a voltage value corresponding to the temperature of the diodes D21-1 to D21-k, that is, 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 -side input terminal of the comparator CM21. The comparator CM21 compares the voltage value of the voltage signal Vref input to the +side input terminal with the voltage value of the voltage signal Vdet input to the -side input terminal. And, when the voltage value of the voltage signal Vdet is larger than the voltage value of the voltage signal Vref, the comparator CM21 outputs a signal of the L level of the ground potential, and when the voltage value of the voltage signal Vdet is smaller than the voltage value of the voltage signal Vref, the comparator CM21 outputs a signal of the H level of the voltage value of the voltage signal Vdd1.

[0157] Here, the voltage value of the voltage signal Vref output by the reference voltage generating circuit 251 is set, for example, 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, 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, the comparator CM21 outputs an L-level signal, and 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 comparator CM21 outputs an H-level signal. It should be noted that the voltage value of the voltage signal Vref output by the reference voltage generating circuit 251 can be any voltage value that can determine whether the temperature 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, and is not limited to the situation where the temperature range within which the diodes D21-1 to D21-k can operate stably.

[0158] The signal output by the comparator CM21 is input to the gate terminal of the transistor Q21. When a signal of L level is input to the gate terminal, the transistor Q21 sets the drain terminal and the source terminal to non-conduction. Thus, the temperature detection circuit 250 outputs the temperature abnormality signal XHOT of H level. On the other hand, when a signal of H level is input to the gate terminal, the transistor Q21 sets the drain terminal and the source terminal to conduction. Thus, the temperature detection circuit 250 outputs the temperature abnormality signal XHOT of L level. That is, when the temperature is within the 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 the temperature abnormality signal XHOT of H level, and when the temperature exceeds the 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 exceeds the predetermined range, the temperature detection circuit 250 outputs the temperature abnormality signal XHOT of L level.

[0159] Here, if Fig.11As shown, the wiring for the temperature detection circuits 250-1 to 250-n to output the temperature abnormality signal XHOT is connected in common. Furthermore, when a temperature abnormality occurs in any one 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 turned on. That is, in the temperature detection circuits 250-1 to 250-n, the wiring for the propagation of the temperature abnormality signal XHOT is connected in a wired "OR" manner. Furthermore, when a temperature abnormality occurs in any one of the temperature detection circuits 250-1 to 250-n, the wiring for outputting the temperature abnormality signal XHOT is controlled to be at an L level, and when no temperature abnormality occurs in all the temperature detection circuits 250-1 to 250-n, the wiring for outputting the temperature abnormality signal XHOT is controlled to be at an H level.

[0160] 5. Configuration and operation of the ejection status determination circuit

[0161] 5.1 Configuration and operation of the state determination circuit

[0162] Next, the configuration and operation of the discharge state determination circuit 300 for determining the state of the corresponding discharge unit 600 based on the residual vibration signal NVT outputted from the drive signal selection circuit 200 will be described. Fig.12 2 is a diagram showing an example of the configuration of the ejection state determination circuit 300. Fig.12 As shown, the discharge state determination circuit 300 includes 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 unit 600 based on the residual vibration signal NVT and the temperature information signal TH.

[0163] The second waveform shaping circuit 310 has resistors R31 to R36, capacitors C31 to C33, and an operational amplifier AM31. The residual vibration signal NVT output by the drive signal selection circuit 200 is input to the second waveform shaping circuit 310. Then, 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, the voltage signal Vo output by the second waveform shaping circuit 310 when the residual vibration signal NVT input to the second waveform shaping circuit 310 is a signal based on the residual vibration signal Vout corresponding to the residual vibration generated in the ejection portion 600 of the inspection object 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 the residual vibration signal Vnvt obtained by shaping the waveform of the residual vibration signal NVT.

[0164] A voltage signal Vdd2 having a constant voltage value is supplied to the second waveform shaping circuit 310. The 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. A ground potential is supplied to the other end of the resistor R32. Furthermore, the residual vibration signal NVT output by the drive signal selection circuit 200 is input to a connection point electrically connecting the other end of the resistor R31 and one end of the resistor R32.

[0165] One end of the resistor R33 is electrically connected to a connection point of the other end of the electrically connected resistor R31 and one end of the resistor R32. 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 - side 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 + side 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 including a - side input terminal, a + side input terminal, and an output terminal.

[0166] Furthermore, the operational amplifier AM31 is driven based on the voltage signal Vdd2 input to the high-voltage side power supply terminal and the ground potential input to the low-voltage side power supply terminal, generates a voltage signal Vo based on the signal input to the -side input terminal and the signal input to the +side input terminal, and outputs it from the output terminal. That is, the operational amplifier AM31 includes a low-voltage side power supply terminal that specifies the lower limit of the voltage value of the signal output from the output terminal and a high-voltage side 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 side power supply terminal, and a positive potential higher than the ground potential, that is, the voltage signal Vdd2, is input to the high-voltage side power supply terminal. Furthermore, 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 +side input terminal of the operational amplifier AM31 is sometimes referred to as the voltage signal Vp, and the signal input to the -side input terminal of the operational amplifier AM31 is sometimes referred to as the voltage signal Vm.

[0167] In the second waveform shaping circuit 310 configured as above, the operational amplifier AM31, the resistors R33, R34, and the capacitor C31 function as an active high-pass filter, which extracts a signal of a high-frequency component from the residual vibration signal NVT, amplifies the signal while inverting the extracted high-frequency component, and performs level shifting on the reference potential based on the voltage value of the voltage signal Vp. In addition, the operational amplifier AM31, the resistors R33, R34, and the capacitor C32 function as an active low-pass filter, which extracts a signal of a low-frequency component from the residual vibration signal NVT, amplifies the signal while inverting the extracted low-frequency component, and performs level shifting on the reference potential based on the voltage value of the voltage signal Vp.

[0168] That is, the second waveform shaping circuit 310 has an active bandpass filter, which removes noise components by extracting a signal of a frequency component in a predetermined range from the input residual vibration signal NVT, shapes the signal waveform, and performs inversion amplification while level-shifting the reference potential of the shaped signal based on the voltage signal Vp input to the + side input terminal of the operational amplifier AM31, thereby outputting the voltage signal Vo.

[0169] The residual vibration determination circuit 320 includes a control circuit 321, a multiplexer 322, an AD (Analog to Digital) conversion circuit 323, a correction circuit 324, a storage 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 unit 600 based on the residual vibration signal Vnvt outputted as the voltage signal Vo by the second waveform shaping circuit 310.

[0170] The control circuit 321 controls various components of the residual vibration determination circuit 320. The storage circuit 326 stores information on a predetermined determination threshold value, correction information, etc., for the residual vibration determination circuit 320 to determine the state of the ejection unit 600 based on the residual vibration signal Vnvt. In addition, the storage circuit 326 temporarily holds various signals for the residual vibration determination circuit 320 to determine the state of the ejection unit 600 based on the residual vibration signal Vnvt. Such a storage circuit 326 includes a volatile memory such as a register and a RAM (Random Access Memory) and a non-volatile memory such as a ROM (Read Only Memory) and a flash memory.

[0171] The voltage signal Vo output from the second waveform shaping circuit 310 and the temperature information signal TH output from the temperature detection circuit 250 of the drive signal selection circuit 200 are input to the multiplexer 322. In addition, the selection signal Sel output from the control circuit 321 is input to the control terminal of the multiplexer 322. The multiplexer 322 selects the voltage signal Vo or the temperature information signal TH based on the selection signal Sel input to the control terminal, and outputs the selected signal to the AD conversion circuit 323 as the acquisition signal AS.

[0172] 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 the AD conversion circuit 323 that converts the residual vibration signal Vnvt and the temperature information signal TH output as the voltage signal Vo into a digital signal. And, the AD conversion circuit 323 outputs the generated acquisition signal dAS to the control circuit 321 and the correction circuit 324.

[0173] 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 storage circuit 326, and outputs it to the storage circuit 326. Thus, the control circuit 321 stores the acquired acquisition signal dAS in the storage circuit 326.

[0174] In addition, the control circuit 321 generates a memory control signal MC for reading the correction information stored in the storage circuit 326, and outputs it to the storage circuit 326. Thus, the control circuit 321 acquires the correction information. Then, the control circuit 321 generates a correction information signal CV corresponding to the acquired correction information, and outputs it to the correction circuit 324.

[0175] The acquisition signal dAS output by the AD conversion circuit 323 and the correction information signal CV output by the control circuit 321 are input to the correction circuit 324. The correction circuit 324 corrects the acquisition signal dAS output by the AD conversion circuit 323 at a timing based on the sampling cycle of the AD conversion circuit 323 based on the correction information signal CV. Then, the correction circuit 324 outputs the corrected acquisition signal dAS to the control circuit 321 as the detection voltage signal vn. Here, in an ideal case, correction at a timing based on a sampling cycle means correction at each sampling cycle of the AD conversion circuit 323, but includes a case where correction is performed in units of multiple sampling cycles according to the processing load of the residual vibration determination circuit 320, etc. That is, correction at a timing based on a sampling cycle includes a case where correction is performed at a timing synchronized with the sampling cycle of the AD conversion circuit 323.

[0176] 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 storage circuit 326. Thus, the plurality of detection voltage signals vn sequentially corrected and output by the correction circuit 324 at the timing based on the sampling cycle of the AD conversion circuit 323 are stored in the storage circuit 326.

[0177] In addition, the control circuit 321 generates a memory control signal MC for reading out the plurality of detection voltage signals vn stored in the storage circuit 326, and outputs it to the storage circuit 326. Thus, the control circuit 321 acquires the plurality of detection voltage signals vn. Then, the control circuit 321 generates a detection voltage signal group vng including the acquired plurality of detection voltage signals vn, and outputs it to the waveform information calculation circuit 327.

[0178] The waveform information calculation circuit 327 calculates the 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.

[0179] In addition, the control circuit 321 generates a memory control signal MC for reading out a determination threshold value for determining the state of the ejection unit 600 based on the residual vibration signal Vnvt from the storage circuit 326, and outputs the signal to the storage circuit 326. Thus, the control circuit 321 acquires the determination threshold value. Then, the control circuit 321 generates a determination threshold signal Jth including the acquired determination threshold value, and outputs the signal to the state determination circuit 328.

[0180] The state determination circuit 328 determines the state of the ejection unit 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 corresponding to the determination result. The determination result signal RT output by the state determination circuit 328 is output from the residual vibration determination circuit 320 and the ejection state determination circuit 300, and is input to the control circuit 100.

[0181] When an abnormality occurs in the residual vibration determination circuit 320 , the control circuit 321 generates an abnormality information signal Err indicating that an abnormality has occurred. The abnormality information signal Err output by the control circuit 321 is output from the residual vibration determination circuit 320 and the discharge state determination circuit 300 and input to the control circuit 100 .

[0182] 5.2. Determination of the state of the ejection unit in the determination circuit

[0183] Here, the relationship between the residual vibration generated in the ejection part 600 and the state of the ejection part 600 is described. As described above, the residual vibration signal NVT and the residual vibration signal Vnvt are signals obtained by extracting the AC component of the residual vibration signal Vout based on the residual signal, removing the noise component, and amplifying and shaping it at a known amplification factor. Therefore, when judging the state of the ejection part 600, when the amplification factor is added, the same judgment result can be obtained in the state of the ejection part 600 determined based on the residual vibration signal Vout and the state of the ejection part 600 determined based on the residual vibration signals NVT and Vnvt. Therefore, in the following description, an example of the residual vibration signal Vout corresponding to the residual vibration generated in the ejection part 600 and the relationship between the state of the ejection part 600 corresponding to the residual vibration signal Vout are described, and the description of 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 ejection part 600 is omitted.

[0184] When describing the relationship between the residual vibration generated in the discharge portion 600 and the state of the discharge portion 600 , first, an example of a residual vibration signal Vout corresponding to the residual vibration will be described. Fig.13 : is a diagram showing an example of the signal waveform of the residual vibration signal Vout.

[0185] If used Figure 6~Figure 9 As described, when the state of the ejection unit 600 of the inspection object is determined, the control circuit 100 outputs the printing data SId [SIH, SIM, SIL] = [1, 1, 1] as the printing data SId corresponding to the ejection unit 600 of the inspection object. As a result, the switching circuit 210 supplies the drive signal Vin including the drive waveform Bdp1 to one end of the ejection unit 600 of the inspection object 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 vibration plate 621 is displaced by the driving of the piezoelectric element 60, and the internal pressure of the cavity resonator 631 changes by the displacement of the vibration plate 621. Thereafter, when a constant drive signal Vin is supplied to one end of the piezoelectric element 60 with a voltage Vd, a damped vibration corresponding to the change in the internal pressure of the cavity resonator 631 is generated in the vibration plate 621. At this time, the piezoelectric element 60 is displaced by the damped vibration generated in the vibration plate 621. Furthermore, due to the displacement generated in the piezoelectric element 60, an electromotive force is generated between the electrodes 611 and 612 of the piezoelectric element 60. That is, during the period ts1, the piezoelectric element 60 is driven, and a weak electromotive force corresponding to the damped vibration generated in the vibration plate 621 is generated between the electrodes 611 and 612 of the piezoelectric element 60.

[0186] In the subsequent period ts2, the transmission gate 234b of the switching circuit 210 is turned off, and the transmission gate 234c is turned on.

[0187] Thus, the switching circuit 210 obtains Fig.13 The residual vibration signal Vout corresponding to the attenuated vibration whose voltage amplitude decreases with the passage of time as shown in FIG. 1 is obtained, and the obtained residual vibration signal Vout is output to the first waveform shaping circuit 240. Then, during the period ts3, the transmission gate 234b of the switching circuit 210 is turned on, and the transmission gate 234c is turned off, so that the drive signal Vin including the drive waveform Bdp3 is supplied to one end of the piezoelectric element 60. As a result, the voltage value at one end of the ejection portion 600 of the inspection object is controlled from the voltage Vd to the voltage Vc. That is, the displacement of the piezoelectric element 60 is controlled to a stable state.

[0188] The residual vibration determination circuit 320 of this embodiment determines the state of the ejection portion 600 of the inspection object based on the waveform information such as the amplitude and frequency of the residual vibration signal Vout corresponding to the residual vibration, that is, the waveform information such as the amplitude and frequency of the residual vibration signal Vout corresponding to the residual vibration and the residual vibration signal Vnvt corresponding to NVT.

[0189] Here, an example of the relationship between the waveform information of the residual vibration signal Vout and the state of the discharge portion 600 to be inspected will be described. Fig.14 6 is a diagram showing a calculation model of a single vibration assuming residual vibration generated in the ejection unit 600. As described above, by supplying the driving signal Vin to the piezoelectric element 60, the piezoelectric element 60 is displaced, and the vibration plate 621 is also displaced along with the displacement of the piezoelectric element 60. As a result, the volume of the cavity resonator 631 is expanded and then contracted. At this time, due to the pressure generated inside the cavity resonator 631, a part of the ink filling the cavity resonator 631 is ejected from the nozzle 651.

[0190] During the series of operations of the ejection unit 600, the vibration plate 621 freely vibrates at a natural vibration frequency determined by the shape of the flow path through which the ink flows, the viscosity of the ink, etc., the flow path resistance r, the inertia m based on the weight of the liquid in the flow path, and the compliance C of the vibration plate 621. The free vibration of the vibration plate 621 is the residual vibration generated in the ejection unit 600.

[0191] Fig.14 The calculation model of the residual vibration of the vibration plate 621 shown in FIG. 6 can be represented by pressure p, inertia m, compliance C, and flow path resistance r. In addition, if the volume velocity u is calculated for Fig.14 The step response when the circuit shown is applied with pressure p can be obtained by equations (1) to (3).

[0192] Mathematical formula 1

[0193]

[0194] Mathematical formula 2

[0195]

[0196] Mathematical formula 3

[0197]

[0198] Fig.15 This is a diagram for explaining the relationship between the viscosity of ink and the signal waveform of residual vibration. Fig.15 In FIG. 6 , the horizontal axis shows time, and the vertical axis shows the magnitude of residual vibration. When the ink near the nozzle 651 dries, the viscosity of the ink increases, i.e., the ink thickens. In addition, when the ink near the nozzle 651 thickens, the flow path resistance r increases. As a result, Fig.15 As shown, the attenuation of the residual vibration becomes larger.

[0199] in addition, Fig.16 This is a diagram for explaining the relationship between the bubble mixing and the signal waveform of the residual vibration. Fig.16 In the figure, time is plotted on the horizontal axis and the magnitude of residual vibration is plotted on the vertical axis. When bubbles are mixed into the cavity resonator 631, that is, the ink flow path and the vicinity of the nozzle 651, the inertia m, which is the weight of the liquid, decreases by an amount corresponding to the mixing of bubbles compared to the normal case. Furthermore, when the inertia m decreases, the angular velocity ω increases as shown in equation (2). As a result, Fig.16 As shown in FIG. 1 , the vibration period of the residual vibration becomes shorter. That is, the vibration frequency of the residual vibration becomes higher.

[0200] As described above, when abnormalities such as thickening of the ink near the nozzle 651 of the ejection unit 600 or mixing of bubbles into the cavity resonator 631 of the ejection unit 600 occur in the ejection unit 600, the vibration of the residual vibration generated in the ejection unit 600 changes. Therefore, the residual vibration signals Vout, NVT, and Vnvt generated when the abnormality occurs in the ejection unit 600 and the residual vibration signals Vout, NVT, and Vnvt generated when the abnormality does not occur in the ejection unit 600 have different waveform information such as frequency and amplitude.

[0201] The residual vibration determination circuit 320 obtains a residual vibration signal Vnvt based on a residual vibration signal Vout and NVT corresponding to the attenuated vibration, i.e., the residual vibration, generated in the ejection portion 600 of the inspection object, and calculates waveform information such as the amplitude and frequency of the obtained residual vibration signal Vnvt.

[0202] Then, the residual vibration determination circuit 320 determines whether the corresponding ejection unit 600 is normal based on the waveform information signal WI including the waveform information. It should be noted 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 bubble mixing, for example, it may also be whether there is a foreign object such as a paper sheet attached to the vicinity of the nozzle 651, whether there is ink leakage caused by the attachment of the foreign object, etc.

[0203] 5.3 Determination of the state of the ejection part based on residual vibration

[0204] As described above, the residual vibration determination circuit 320 of the present embodiment determines the state of the ejection unit 600 of the inspection object based on the waveform information of the residual vibration signal Vnvt, which is a signal based on the residual vibration signal Vout and NVT corresponding to the residual vibration generated after the ejection unit 600 of the inspection object is driven according to the drive signal COM. In this case, from the viewpoint of improving the determination accuracy of the state of the ejection unit 600 of the inspection object, it is required to improve the acquisition accuracy of the waveform information of the residual vibration signal Vnvt in the residual vibration determination circuit 320.

[0205] For example, when the residual vibration determination circuit 320 obtains the period and frequency from the residual vibration signal Vnvt as waveform information, the signal waveform of the residual vibration signal Vnvt is: Fig.13 The residual vibration determination circuit 320 is required to grasp the potential that is the reference of the amplitude of the residual vibration signal Vnvt with high accuracy. In addition, for example, when the residual vibration determination circuit 320 obtains the amplitude of the residual vibration signal Vnvt as waveform information, the residual vibration signal Vnvt is a signal obtained by amplifying the signal waveforms of the residual vibration signals Vout and NVT using the non-inverting amplifier circuit 242 and the second waveform shaping circuit 310 of the first waveform shaping circuit 240. Therefore, the residual vibration determination circuit 320 is required to grasp the amplification factor of the non-inverting amplifier circuit 242 and the second waveform shaping circuit 310 of the first waveform shaping circuit 240 with higher accuracy.

[0206] In the liquid ejection device 1 and the head unit 20 of the present embodiment, the residual vibration signal NVT corresponding to the residual vibration is not input to the -side input terminal of the operational amplifier AM31. Therefore, when the constant potential voltage signal Vm is input to the -side input terminal of the operational amplifier AM31, and the 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 +side input terminal of the operational amplifier AM31, the residual vibration determination circuit 320 determines the residual vibration based on the residual vibration signal NVT output from the output terminal of the operational amplifier AM31. The residual vibration determination circuit 320 determines the state of the ejection unit 600 based on the voltage value of the voltage signal Vo output from the output terminal of the operational amplifier AM31; and in the state where the residual vibration signal NVT corresponding to the residual vibration is input to the - side input terminal of the operational amplifier AM31, and the voltage signal Vp of a constant potential 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 + side input terminal of the operational amplifier AM31, the residual vibration determination circuit 320 determines the state of the ejection unit 600 based on the residual vibration signal Vnvt which is the voltage signal Vo output from the output terminal of the operational amplifier AM31. As a result, the residual vibration determination circuit 320 can obtain the potential which is the reference of the amplitude of the residual vibration signal Vnvt with higher accuracy. Therefore, the residual vibration determination circuit 320 can obtain the period and frequency of the residual vibration signal Vnvt with high accuracy, and as a result, the determination accuracy of the state of the ejection unit 600 to be inspected in the residual vibration determination circuit 320 is improved.

[0207] Here, in the following description, when the residual vibration signal NVT corresponding to the residual vibration is not input to the -side input terminal of the operational amplifier AM31, the voltage signal Vo output from the output terminal of the operational amplifier AM31 is sometimes referred to as the voltage signal Voff. That is, the second waveform shaping circuit 310 outputs the voltage signal Voff as the voltage signal Vo when the residual vibration signal NVT corresponding to the residual vibration is not input, and outputs the residual vibration signal Vnvt as the voltage signal Vo when the residual vibration signal NVT corresponding to the residual vibration is input.

[0208] In addition, in the liquid ejection device 1 and the head unit 20 of the present embodiment, since the non-inverting amplifier circuit 242 of the first waveform shaping circuit 240 is composed of a semiconductor device, polysilicon resistors can be used as resistors R11 and R12 that define the amplification factor of the non-inverting amplifier circuit 242. However, since the resistance value of the polysilicon resistor changes greatly due to temperature, 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 the temperature. In contrast, in the liquid ejection device 1 and the head unit 20 of the present embodiment, the residual vibration determination circuit 320 acquires the residual vibration signal Vnvt and the temperature information signal TH corresponding to the temperature of the first waveform shaping circuit 240, and determines the state of the ejection unit 600 of the inspection object based on the acquired residual vibration signal Vnvt and the temperature information signal TH. Thus, even when the amplification factor of the non-inverting amplifier circuit 242 changes due to the change in the resistance value of the resistors R11 and R12 according to the temperature, and the voltage value of the amplitude of the residual vibration signal Vnvt changes, the amplitude of the residual vibration signal Vnvt can be properly corrected. Therefore, the accuracy of obtaining the amplitude of the residual vibration signal Vnvt in the residual vibration determination circuit 320 is improved, and as a result, the accuracy of determining the state of the ejection unit 600 to be inspected in the residual vibration determination circuit 320 is improved.

[0209] 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 the head unit 20 of the present embodiment and a method for determining the state of the ejection unit 600 to be inspected will be described. Fig.17 1 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 portion 600 to be inspected.

[0210] like Fig.17 As shown, when the waveform information of the residual vibration signal Vnvt is acquired and the state of the ejection unit 600 of the inspection object is determined based on the acquired waveform information, the head unit 20 performs a residual vibration signal acquisition process (step S2) for acquiring the voltage value of the residual vibration signal Vnvt while performing a reference potential acquisition process (step S1), wherein in the reference potential acquisition process, the head unit 20 acquires the voltage value of the voltage signal Voff as a potential of the reference of the amplitude of the residual vibration signal Vnvt. Thereafter, the head unit 20 performs a waveform information calculation process for calculating 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 performs an ejection unit determination process for determining the state of the ejection unit 600 based on the calculated waveform information of the residual vibration signal Vnvt (step S4).

[0211] Fig.18 is a diagram showing a specific example of reference potential acquisition processing. Fig.18 As shown, in the reference potential acquisition process, the control circuit 100 outputs the printing data signal SI for driving the switching circuit 210 of the signal selection circuit 200 to control the m transmission gates 234c to be turned off. As a result, the switching circuit 210 controls the m transmission gates 234c to be turned off (step S110). Therefore, the switching circuit 210 outputs a signal with a constant voltage value as the residual vibration signal Vout.

[0212] The residual vibration signal Vout having a constant voltage value outputted from the switching circuit 210 is blocked by the filter circuit 241 of the first waveform shaping circuit 240 and the high-pass filter formed by the second waveform shaping circuit 310. Therefore, the residual vibration signal Vout is not supplied to the - side input terminal of the operational amplifier AM31 of the second waveform shaping circuit 310. At this time, the signal outputted from the output terminal of the operational amplifier AM31 through R34 is inputted to the - side input terminal of the operational amplifier AM31. That is, the switching circuit 210 controls the m transmission gates 234c to be turned off, and the operational amplifier AM31 of the second waveform shaping circuit 310 constitutes a so-called voltage follower circuit, which outputs a voltage signal Vo having the same voltage value as the voltage signal Vm inputted to the + side input terminal from the output terminal. Then, the second waveform shaping circuit 310 outputs the voltage signal Vo outputted from the operational amplifier AM31 as the voltage signal Voff to the residual vibration determination circuit 320 during the period when the switching circuit 210 controls the m transmission gates 234c to be turned off.

[0213] In other words, during the period when the switching circuit 210 controls the m transmission gates 234c to be disconnected, the -side input terminal of the operational amplifier AM31 is input with a constant voltage signal Vm having a voltage value that is the same as the voltage signal Vo, while the +side input terminal is input with a constant voltage signal Vm having a voltage value that is obtained by dividing the voltage signal Vdd2 using resistors R35 and R36, and the voltage signal Voff is output from the output terminal.

[0214] After the switching circuit 210 controls the m transmission gates 234c to be turned off, and during the period when 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 the selection signal Sel for selecting the voltage signal Vo as the acquisition signal AS (step S120). As a result, the multiplexer 322 selects 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 into the acquisition signal dAS as a digital signal by the AD conversion circuit 323, and then input to the control circuit 321. That is, the control circuit 321 acquires the voltage value of the voltage signal Voff as the voltage vof based on the acquisition signal dAS (step S130).

[0215] Furthermore, control circuit 321 reads threshold voltage Vth for determining whether voltage vof is normal from storage circuit 326 (step S140 ).

[0216] Then, the control circuit 321 determines whether the voltage vof is greater than the threshold voltage Vth (step S150). When the control circuit 321 determines that the voltage vof is less than the threshold voltage Vth (No in step S150), the control circuit 321 determines that the input voltage signal Voff is normal, and stores the acquired voltage vof in the storage circuit 326 (step S160). In other words, the storage circuit 326 stores the voltage value of the voltage signal Voff, that is, the voltage vof.

[0217] On the other hand, when the control circuit 321 determines that the voltage vof is greater than the threshold voltage Vth (Yes in step S150), the control circuit 321 determines that the voltage value of the input voltage signal Voff, that is, the voltage vof, is abnormal, and outputs the abnormal information signal Err indicating the abnormality of the voltage signal Voff (step S165). That is, the residual vibration determination circuit 320 outputs the abnormal information signal Err when the voltage vof, which is the voltage value of the voltage signal Voff, exceeds the threshold voltage Vth.

[0218] The abnormal information signal Err output by the residual vibration determination circuit 320 is input to the control circuit 100. The control circuit 100 ends the reference potential acquisition process in the head unit 20 by receiving the abnormal information signal Err indicating the abnormal voltage value of the voltage signal Voff. It should be noted that the control circuit 100 may stop the operation of at least one of the liquid ejection device 1 and the head unit 20 while ending the reference potential acquisition process in the head unit 20.

[0219] As described above, the reference potential acquisition processing is a process of performing the following processing, namely, when a voltage signal Vm having a constant voltage value which is the same as the voltage signal Vo is input to the -side input terminal of the operational amplifier AM31, and a voltage signal Vm having a constant voltage value which is obtained by dividing the voltage signal Vdd2 by using resistors R35 and R36 is input to the +side input terminal, the voltage value of the voltage signal Voff which is the same as the voltage signal Vm output from the output terminal, i.e., the voltage vof, is stored in the storage circuit 326.

[0220] The reference potential acquisition process described above can be performed only once during the manufacturing stage of the liquid ejection device 1, or can be performed each time the residual vibration signal Vout is acquired, but it is preferably performed in each predetermined period based on the driving time, temperature, and number of acquisitions of the residual vibration signal Vout of the liquid ejection device 1 and the head unit 20. That is, the voltage value of the voltage signal Voff stored in the storage circuit 326, that is, the voltage vof, is preferably updated according to a predetermined period. Thus, the residual vibration determination circuit 320 can be updated to the optimal voltage value of the voltage signal Voff corresponding to the operating state of the liquid ejection device 1 and the head unit 20 while reducing the possibility that the processing burden of the control circuit 321 will be greatly increased with the reference potential acquisition process.

[0221] In addition to the above-mentioned reference potential acquisition process, the voltage value of the voltage signal Voff stored in the storage circuit 326, that is, the voltage vof, can also be updated from the outside of the liquid ejection device 1 through the network line. That is, the head unit 20 may be provided with a communication interface circuit (not shown) capable of communicating with the outside of the liquid ejection device 1, such as a communication interface circuit corresponding to Ethernet communication, a communication interface circuit corresponding to WiFi communication, and the voltage value of the voltage signal Voff stored in the storage circuit 326, that is, the voltage vof, may be updated based on information stored in a network server or the like that can be communicatively connected through the communication interface circuit.

[0222] In this way, the processing burden of the control circuit 321 associated with the reference potential acquisition process can be reduced, and even when the use environment of the liquid ejection device 1 and the head unit 20 is changed, or when design changes or maintenance processing is performed on the liquid ejection device 1 and the head unit 20, the voltage vof stored in the storage circuit 326 can be easily and appropriately managed, thereby improving the reliability of the liquid ejection device 1 and the head unit 20.

[0223] Next, the residual vibration signal acquisition process will be described. Fig.19 2 is a diagram showing a specific example of residual vibration signal acquisition processing. Fig.19As shown, in the residual vibration signal acquisition process, the control circuit 321 of the residual vibration determination circuit 320 sets the variable j to “0” as an initialization process (step S210 ).

[0224] Then, the control circuit 321 of the residual vibration determination circuit 320 outputs the selection 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 as the acquisition signal AS by the multiplexer 322 is converted into a digital signal, that is, the acquisition signal dAS, by the AD conversion circuit 323, 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 it 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).

[0225] Furthermore, the control circuit 321 reads out 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, from the storage circuit 326 (step S230 ).

[0226] The control circuit 321 generates a correction information signal CV including the temperature correction value CVt and the voltage vof read out from the storage circuit 326. Then, the control circuit 321 outputs the generated correction information signal CV including the temperature correction value CVt and the voltage vof to the correction circuit 324 (step S240).

[0227] Then, the control circuit 321 outputs the selection signal Sel for selecting 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 of the inspection object (step S260). Here, in step S260, the process of the switching circuit 210 supplying the drive signal Vin corresponding to the inspection CD to the ejection unit 600 of the inspection object is equivalent to the process of driving the piezoelectric element 60 and causing residual vibration to be generated in the ejection unit 600 of the inspection object.

[0228] Then, by raising the inspection timing signal TSIG (step S270 ), the residual vibration determination circuit 320 acquires the voltage value of the residual vibration signal Vnvt based on the residual vibration signal Vout and NVT corresponding to the residual vibration generated in the discharge unit 600 to be inspected.

[0229] Specifically, the piezoelectric element 60 of the ejection part 600 of the inspection object is driven by being supplied with a driving signal Vin corresponding to the inspection CD. As a result, residual vibration is generated in the ejection part 600 of the inspection object. The 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 part 600 of the inspection object is input to the -side input terminal of the operational amplifier AM31 of the second waveform shaping circuit 310. At this time, a constant voltage signal Vp is input to the +side input terminal of the operational amplifier AM31 of the second waveform shaping circuit 310 at a voltage value obtained by dividing the voltage signal Vdd2 using the resistors R35 and R36. Therefore, at the output terminal of the operational amplifier AM31 of the second waveform shaping circuit 310, a signal of a frequency component in a predetermined range is extracted from the residual vibration signal NVT, and the signal waveform is shaped, and the residual vibration signal Vnvt obtained by level-shifting the reference potential of the shaped signal based on the voltage signal Vp input to the +-side input terminal of the operational amplifier AM31 and performing inversion amplification is output as the voltage signal Vo. In other words, the operational amplifier AM31 outputs the residual vibration signal Vnvt as the voltage signal Vo from the output terminal in a state where the residual vibration signal NVT based on the residual vibration signal Vout corresponding to the residual vibration is input to the --side input terminal and the voltage signal Vp having a constant voltage value is input to the +-side input terminal.

[0230] The residual vibration signal Vnvt of the voltage signal Vo output by the operational amplifier AM31 of the second waveform shaping circuit 310 is selected in the multiplexer 322 and input to the AD conversion circuit 323 as the acquisition signal AS. The AD conversion circuit 323 converts the voltage value of the residual vibration signal Vnvt of the acquisition signal AS input into a digital signal based on the sampling period. Then, the AD conversion circuit 323 outputs the detection voltage dvn of the digital signal corresponding to the voltage value of the residual vibration signal Vnvt as the acquisition signal AS to the correction circuit 324 as the 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).

[0231] The correction circuit 324 corrects the acquired detection voltage dvn based on the correction information signal CV including the temperature correction value CVt and the voltage vof. Then, the correction circuit 324 outputs the acquired detection voltage signal vn to the control circuit 321 as a detection voltage signal vn[j].

[0232] 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 potential difference with the reference potential, that is, the voltage value of the residual vibration signal Vnvt when the voltage vof is used as the reference potential. Then, the correction circuit 324 multiplies the calculated potential difference between the voltage vof and the detection voltage dvn by the temperature correction value CVt corresponding to the temperature information signal TH. Thus, the deviation of the amplification factor of the non-inverting amplifier circuit 242, that is, the change in the resistance value caused by the temperature characteristics of the resistors R11 and R12 of the non-inverting amplifier circuit 242, is corrected and output as the detection voltage signal vn[j]. That is, the correction circuit 324 subtracts the voltage vof from the detection voltage dvn, multiplies the obtained value by the temperature correction value CVt, and calculates 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 .

[0233] The control circuit 321 generates a memory control signal MC for storing the input detection voltage signal vn[j] in the storage circuit 326, and outputs the memory control signal MC to the storage circuit 326. Thus, the detection voltage signal vn[j] is stored in the storage circuit 326 (step S276).

[0234] Then, the control circuit 321 determines whether the inspection timing signal TSIG has risen (step S278). When the control circuit 321 determines that the inspection 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 above-mentioned processing of steps S272, S274, S276, and S278. That is, the AD conversion circuit 323 sequentially obtains the voltage value of the residual vibration signal Vnvt input during the period from the rise of the inspection timing signal TSIG to the next rise of the inspection timing signal TSIG, that is, the time period ts2, based on the timing of the sampling cycle, that is, the detection voltage dvn, and the correction circuit 324 sequentially corrects the voltage value of the residual vibration signal Vnvt output by the AD conversion circuit 323, that is, the detection voltage dvn, based on the temperature correction value CVt and the voltage vof, based on the timing of the sampling cycle of the AD conversion circuit 323, and sequentially outputs it as the detection voltage signal vn[j] to the control circuit 321. Then, the control circuit 321 sequentially stores the input detection voltage signal vn[j] in the storage circuit 326 .

[0235] Then, the control circuit 321 determines that the inspection timing signal TSIG has risen (Yes in step S278 ), and considers that the acquisition of the voltage value of the residual vibration signal Vnvt in the period ts2 , that is, the detection voltage signal vn, is completed, and the residual vibration signal acquisition process ends.

[0236] As described above, in the residual vibration signal acquisition process, the residual vibration is generated in the ejection part 600 of the inspection object by supplying the driving signal Vin corresponding to the inspection CD to the ejection part 600 of the inspection object. Thus, the residual vibration signal NVT based on the residual vibration signal Vout corresponding to the residual vibration is input to the ejection state determination circuit 300. The residual vibration signal NVT based on the residual vibration signal Vout corresponding to the residual vibration is input to the -side input terminal of the operational amplifier AM31. At this time, the 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 +side input terminal of the operational amplifier AM31. Then, the operational amplifier AM31 outputs a residual vibration signal Vnvt based on the residual vibration signal NVT to the residual vibration determination circuit 320 from the output terminal when the residual vibration signal NVT based on the residual vibration signal Vout corresponding to the residual vibration is input to the -side input terminal and the constant potential voltage signal Vp obtained by dividing the voltage signal Vdd2 using the resistance value of the resistor R35 and the resistance value of the resistor R36 is input to the +side input terminal.

[0237] The residual vibration determination circuit 320 sequentially acquires the voltage value of the input residual vibration signal Vnvt, and after performing correction based on the correction information signal CV including the temperature correction value CVt and the voltage vof, stores it in the storage circuit 326. Thus, 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.

[0238] Next, an example of a waveform information calculation process for calculating the waveform information of the residual vibration signal Vnvt will be described. Fig. 20 3 is a diagram showing a specific example of waveform information calculation processing. Here, in the following description, it is described that p detection voltage signals vn are stored in the storage circuit 326 during the period ts2. That is, it is described that the detection voltage signals vn[1] to vn[p] are stored in the storage circuit 326 as the detection voltage signal vn.

[0239] When the waveform information calculation process starts, the control circuit 321 generates a memory control signal MC for reading the detection voltage signals vn[1] to vn[p] from the storage circuit 326, and outputs it to the storage circuit 326. Thus, the control circuit 321 reads the detection voltage signals vn[1] to vn[p] from the storage circuit 326. Then, the control circuit 321 generates a detection voltage signal group vng including the read detection voltage signals vn[1] to vn[p], and outputs it to the waveform information calculation circuit 327. Thus, the waveform information calculation circuit 327 acquires the detection voltage signals vn[1] to vn[p] (step S310).

[0240] 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]. Here, 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 detection timing signal TSIG rises 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 detection timing signal TSIG rises, that is, 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 for the sth time is referred to as the detection voltage signal vn[ps]. That is, the waveform information calculation circuit 327 extracts the detection 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 from the acquired detection voltage signals vn[1] to vn[p] (step S320).

[0241] The waveform information calculation circuit 327 calculates the vibration frequency Fnvt of the residual vibration signal Vnvt based on the extracted detection voltage signal vn[pu] (u is any one of 1 to s-2) and the detection voltage signal vn[p(u+2)] among the detection voltage signals vn[p1] to vn[ps] (step S330).

[0242] 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 signals vn[pu] and the detection voltage signals vn[p(u+2)]. Then, the waveform information calculation circuit 327 calculates the time from the detection voltage signal vn[pu] to the detection voltage signal vn[p(u+2)] based on the calculated number of detection voltage signals vn and the period of the detection voltage signal vn calculated by the correction circuit 324 based on the detection voltage dvn, that is, the period based on the sampling period of the AD conversion circuit 323. Then, the waveform information calculation circuit 327 calculates the vibration frequency Fnvt of the residual vibration signal Vnvt based on the time from the calculated detection voltage signal vn[pu] to the detection voltage signal vn[p(u+2)], and acquires it as waveform information.

[0243] Here, as shown in step S274, the detection voltage signal vn is calculated by subtracting the voltage value of the voltage signal Voff, that is, the voltage vof, from the voltage value of the residual vibration signal Vnvt. That is, the timing at which the voltage value of the detection voltage signals vn[1]~vn[p] switches from a positive value to a negative value or from a negative value to a positive value is equivalent 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 value of the voltage signal Voff, that is, the voltage vof.

[0244] At this time, the waveform information calculation circuit 327 preferably calculates the vibration frequency Fnvt of the residual vibration signal Vnvt based on the detection voltage signal vn obtained near the rising edge of the inspection timing signal TSIG at the start of the specified 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 calculating the vibration frequency Fnvt of the residual vibration signal Vnvt, the waveform information calculation circuit 327 can detect the transition point where 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 in the stage where the residual vibration signal Vnvt has a sufficient amplitude by using the detection voltage signal vn obtained near the rising edge of the inspection timing signal TSIG. As a result, the detection accuracy of the transition point is improved, and as a result, the calculation accuracy of the vibration frequency Fnvt of the residual vibration signal Vnvt is improved.

[0245] In addition, the waveform information calculation circuit 327 holds the detection voltage signal vn having the largest absolute value among the detection voltage signals vn obtained between the detection voltage signal vn[pv] (v is any one of 1 to s-1) and the detection voltage signal vn[p(v+1)] as the maximum voltage value Vpek[v] (step S340 ). Specifically, the waveform information calculation circuit 327 maintains the detection voltage signal vn with the largest absolute value obtained between the detection voltage signal vn[p1] and the detection voltage signal vn[p2] as the maximum voltage value Vpek[1], maintains the detection voltage signal vn with the largest absolute value obtained between the detection voltage signal vn[pv] and the detection voltage signal vn[p(v+1)] as the maximum voltage value Vpek[v], and maintains the detection voltage signal vn with the largest absolute value obtained 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] maintained by the waveform information calculation circuit 327 is equivalent to the amplitude generated by the residual vibration signal Vnvt. 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 generated by the residual vibration signal Vnvt (step S350 ).

[0246] Then, the waveform information calculation circuit 327 generates a waveform information signal WI including the calculated vibration frequency Fnvt and the attenuation rate ARnvt of the amplitude, and outputs the waveform information signal WI to the state determination circuit 328 (step S360 ).

[0247] Next, an example of the ejection portion determination process will be described. Fig.21 2 is a diagram showing a specific example of the ejection portion determination process. Fig.21As shown in FIG. 4 , when the ejection portion determination process starts, the control circuit 321 generates a memory control signal MC for reading 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. Thus, the control circuit 321 reads 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 waveform information signal WI including the vibration frequency Fnvt and the attenuation rate ARnvt of the amplitude output by the waveform information calculation circuit 327 is input to the state determination circuit 328. That is, the state determination circuit 328 acquires the vibration frequency Fnvt and the attenuation rate ARnvt of the amplitude of the residual vibration signal Vnvt (step S420).

[0248] Then, the state determination circuit 328 determines whether drying and thickening abnormalities and bubble mixing abnormalities have occurred in the ejection part 600 of the inspection object by comparing the acquired frequency threshold information Fth and amplitude determination threshold information ARth with the vibration frequency Fnvt and the attenuation rate ARnvt of the amplitude as the state of the ejection part 600.

[0249] 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 larger. When the attenuation rate ARnvt of the amplitude of the residual vibration signal Vnvt is greater than the amplitude determination threshold information ARth (yes in step S430), the state determination circuit 328 determines that the viscosity of the ink has increased beyond the normal range, and determines that a drying and thickening abnormality has occurred in the ejection portion 600 of the inspection object (step S435). Then, the state determination circuit 328 generates and outputs a determination result signal RT indicating that a drying and thickening abnormality has occurred in the ejection portion 600 of the inspection object (step S460).

[0250] Furthermore, when the attenuation rate ARnvt of the amplitude of the residual vibration signal Vnvt is less than the amplitude determination threshold information ARth (Yes 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). As described above, when bubbles are mixed into the cavity resonator 631 of the ejection unit 600, the frequency of the residual vibration signal Vnvt becomes higher. When the vibration frequency Fnvt of the residual vibration signal Vnvt is greater than the frequency threshold information Fth (Yes in step S440), the state determination circuit 328 determines that bubbles are mixed into the cavity resonator 631, and determines that a bubble mixing abnormality has occurred in the ejection unit 600 of the inspection object (step S445). Then, the state determination circuit 328 generates and outputs a determination result signal RT indicating that a bubble mixing abnormality has occurred in the ejection unit 600 of the inspection object (step S460).

[0251] In addition, when the attenuation rate ARnvt of the amplitude of the residual vibration signal Vnvt is less than the amplitude determination threshold information ARth and the vibration frequency Fnvt of the residual vibration signal Vnvt is less than the frequency threshold information Fth (No in step S440), the control circuit 321 determines that the ejection unit 600 to be inspected is normal. Then, the state determination circuit 328 generates and outputs a determination result signal RT indicating that the ejection unit 600 to be inspected is normal (step S460).

[0252] As described above, the residual vibration determination circuit 320 of the present embodiment calculates the waveform information of the residual vibration signal Vnvt based on the residual vibration signal Vnvt converted into a digital signal, the voltage value of the voltage signal Voff converted into a digital signal, i.e., the voltage vof, and the temperature information signal TH converted into a digital signal, and determines the state of the ejection portion 600 of the inspection object based on the calculated waveform information.

[0253] Here, the ejection part determination processing is equivalent to the following process: when a residual vibration signal NVT based on a residual vibration signal Vout corresponding to the residual vibration is input to the -side input terminal of the operational amplifier AM31, and a voltage signal Vm whose voltage value is a constant voltage value obtained by dividing the voltage signal Vdd2 using resistors R35 and R36 is input to the +side input terminal, the ejection state of the ejection part 600 of the inspection object is determined based on the residual vibration signal Vnvt output from the output terminal; when a voltage signal Vm whose voltage value is the same as the voltage signal Vo and is constant is input to the -side input terminal of the operational amplifier AM31, and a voltage signal Vm whose voltage value is a constant voltage value obtained by dividing the voltage signal Vdd2 using resistors R35 and R36 is input to the +side input terminal, the ejection state of the ejection part 600 of the inspection object is determined based on the voltage value of the voltage signal Voff whose voltage value is the same as the voltage signal Vm output from the output terminal, that is, the voltage vof.

[0254] The first waveform shaping circuit 240 and the second waveform shaping circuit 310 are examples of waveform shaping circuits, the residual vibration determination circuit 320 is an example of a determination circuit, the operational amplifier AM10 is an example of an amplification circuit, the circuit including the resistor R11 and the resistor R12 is an example of a gain setting circuit, and the AD conversion circuit 323 is an example of an analog-to-digital converter.

[0255] In addition, the residual vibration signal Vout is an example of the first residual vibration signal, and the residual vibration signal Vnvt obtained by shaping the signal waveform of the residual vibration signal Vout by the first waveform shaping circuit 240 and the second waveform shaping circuit 310 is an example of the second residual vibration signal. The drive signal COM including the drive signal ComA and the drive signal ComB is an example of a drive signal. Here, considering that the drive signal Vin is generated by selecting or not selecting the signal waveforms of the drive signal ComA and the drive signal ComB, the drive signal Vin is also an example of a drive signal.

[0256] 6. Effects

[0257] In summary, in the liquid ejection device 1 and the head unit 20 of the present embodiment, the operational amplifier AM31 of the second waveform shaping circuit 310 outputs the voltage signal Voff having a voltage value of voltage vof as the voltage signal Vo from the output terminal in a state where the voltage signal Vm having a constant voltage value is input to the - side input terminal and the voltage signal Vp having a constant voltage value is input to the + side input terminal. In addition, the operational amplifier AM31 of the second waveform shaping circuit 310 outputs the residual vibration signal Vnvt obtained by amplifying the amplitude of the residual vibration signal NVT corresponding to the residual vibration as the voltage signal Vo from the output terminal with the voltage signal Vp as the reference potential in a state where the residual vibration signal NVT corresponding to the residual vibration is input to the - side input terminal as the voltage signal Vm and the voltage signal Vp having a constant voltage value is input to the + side input terminal. Then, the residual vibration judgment circuit 320 stores the voltage value of the voltage signal Voff output by the operational amplifier AM31 of the second waveform shaping circuit 310, that is, the voltage vof, in the storage circuit 326, and judges the state of the ejection part 600 of the inspection object based on the residual vibration signal Vnvt output by the operational amplifier AM31 of the second waveform shaping circuit 310 and the voltage value of the voltage signal Voff stored in the storage circuit 326, that is, the voltage vof.

[0258] That is, the residual vibration determination circuit 320 determines the state of the ejection unit 600 based on the residual vibration signal Vnvt that oscillates with the voltage signal Vp as the reference potential and the voltage value of the voltage signal Voff corresponding to the voltage signal Vp stored in advance, that is, the voltage vof. Thus, the residual vibration determination circuit 320 accurately grasps the reference potential of the residual vibration signal Vnvt and determines the state of the ejection unit 600 to be inspected. As a result, the accuracy of determining the state of the ejection unit 600 to be inspected in the residual vibration determination circuit 320 is improved.

[0259] Specifically, the residual vibration determination circuit 320 calculates the vibration frequency Fnvt as one of the waveform information of the residual vibration signal Vnvt vibrating with the voltage signal Vp as the reference potential based on the reference potential of the residual vibration signal Vnvt, wherein the reference potential of the residual vibration signal Vnvt is calculated based on the voltage value of the voltage signal Voff corresponding to the voltage signal Vp stored in advance, that is, the voltage vof. Thus, the residual vibration determination circuit 320 can calculate the vibration frequency Fnvt of the residual vibration signal Vnvt with high accuracy, and the determination accuracy of the state of the ejection portion 600 to be inspected based on the calculated vibration frequency Fnvt is improved.

[0260] In addition, in the liquid ejection device 1 and the head unit 20 of the present embodiment, during the period when the residual vibration signal NVT corresponding to the residual vibration is not input to the -side input terminal, the operational amplifier AM31 of the second waveform shaping circuit 310 is input with the voltage signal Vo output by the operational amplifier AM31 as the voltage signal Vm with a constant voltage value. 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 having the same voltage value as the voltage signal Vp as the voltage signal Vo from the output terminal. Thus, 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, it is possible to use the voltage value of the voltage signal Voff stored in advance, that is, the voltage vof, directly as the reference potential of the residual vibration signal Vnvt. Thus, the oscillation frequency Fnvt of the residual vibration signal Vnvt can be calculated with high accuracy while reducing the load of calculating the oscillation frequency Fnvt of the residual vibration signal Vnvt in the residual vibration determination circuit 320 .

[0261] In addition, in the liquid ejection device 1 and the head unit 20 of the present embodiment, there are a first waveform shaping circuit 240 and a second waveform shaping circuit 310, the first waveform shaping circuit 240 and the second waveform shaping circuit 310 are input with a residual vibration signal Vout corresponding to the residual vibration generated by the drive signal COM, and output a residual vibration signal Vnvt obtained by shaping the waveform of the residual vibration signal Vout, the first waveform shaping circuit 240 has an operational amplifier AM10 that is configured as a semiconductor device and amplifies the residual vibration signal Vout, and resistors R11 and R12 that set the amplification factor of the operational amplifier AM10. Even in this case, the residual vibration determination circuit 320 determines the state of the ejection part 600 of the inspection object based on the residual vibration signal Vnvt and the temperature information signal corresponding to the temperature of the first waveform shaping circuit 240, and the residual vibration determination circuit 320 can also accurately correct the resistance values ​​of the resistors R11 and R12 whose resistance values ​​vary greatly due to temperature, that is, the amplification factor of the amplitude of the residual vibration signal Vout in the first waveform shaping circuit 240. Thus, the residual vibration determination circuit 320 can accurately calculate the waveform information of the amplitude of the residual vibration signal Vnvt, that is, the attenuation rate ARnvt of the amplitude of the residual vibration signal Vnvt. As a result, the residual vibration determination circuit 320 can improve the determination accuracy of the state of the ejection unit 600 to be inspected.

[0262] In addition, in the liquid ejection device 1 and the head unit 20 of the present embodiment, the residual vibration determination circuit 320 has an AD conversion circuit 323, which performs correction after converting the input residual vibration signal Vnvt, the voltage signal Voff, and the temperature information signal TH into digital signals, and calculates the waveform information of the residual vibration signal Vnvt. Thus, the residual vibration determination circuit 320 can directly obtain the voltage value of the input residual vibration signal Vnvt. As a result, the calculation accuracy of the waveform information of the residual vibration signal Vnvt in the residual vibration determination circuit 320 and the determination accuracy of the state of the ejection unit 600 of the inspection object are improved.

[0263] 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 through the multiplexer 322, and converts the residual vibration signal Vnvt, the voltage signal Voff, and the temperature information signal TH into digital signals respectively through the common AD conversion circuit 323. As a result, the possibility of increasing the circuit scale of the residual vibration determination circuit 320 is reduced, the miniaturization of the head unit 20 can be achieved, and the possibility of errors in the digital value due to the deviation of the AD conversion circuit 323 is reduced. Therefore, the calculation accuracy of the waveform information of the residual vibration signal Vnvt in the residual vibration determination circuit 320 and the determination accuracy of the state of the ejection unit 600 of the inspection object are improved.

[0264] 7. Modifications

[0265] In the liquid ejection device 1 and the head unit 20 of the present embodiment described above, the residual vibration determination circuit 320 determines the state of the ejection portion 600 based on the voltage value of the voltage signal Voff as the voltage signal Vo output from the output terminal of the operational amplifier AM31, that is, the voltage vof, when a voltage signal Vm with a constant voltage value is input to the - side input terminal of the operational amplifier AM31 and a voltage signal Vp with a constant voltage value is input to the + side input terminal of the operational amplifier AM31; and determines the state of the ejection portion 600 based 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 - side input terminal of the operational amplifier AM31 and a voltage signal Vp with a constant voltage value is input to the + side input terminal of the operational amplifier AM31. At this time, the residual vibration determination circuit 320 can calculate the reference potential of the amplitude of the residual vibration signal Vnvt with high accuracy based on the voltage vof, so the calculation accuracy of the vibration frequency Fnvt of the residual vibration signal Vnvt is improved, and as a result, the determination accuracy of the state of the ejection unit 600 to be inspected is improved. That is, the residual vibration determination circuit 320 only needs to be able to obtain the reference potential of the residual vibration signal Vnvt with high accuracy.

[0266] Fig. 22 FIG. 2 is a diagram showing an example of the configuration of a discharge state determination circuit 300 according to a modified example. Fig. 22 As shown, in the ejection state determination circuit 300 of the modified example, the resistor R36 is composed of a variable resistor element whose resistance value can be adjusted, and the assumed reference voltage Var calculated based on the voltage value of the voltage signal Vdd2 and the resistance values ​​of the resistors R35 and R36 is stored in the storage circuit 326. In addition, the control circuit 321 does not input the residual vibration signal NVT corresponding to the residual vibration to the - side input terminal of the operational amplifier AM31, so when the constant potential voltage signal Vm is input to the - side input terminal of the operational amplifier AM31 and the 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 + side input terminal of the operational amplifier AM31, the resistance value adjustment signal VR for adjusting the resistance value of the resistor R36 is output so that the voltage value of the voltage signal Vo output from the output terminal of the operational amplifier AM31 is close to the assumed reference voltage Var stored in the storage circuit 326. Then, the control circuit 321 stores the adjustment value of the resistance value of the resistor R36 in the storage circuit 326 when the voltage value of the voltage signal Vo output from the output terminal of the operational amplifier AM31 becomes substantially equal to the voltage value of the assumed reference voltage Var stored in the storage circuit 326 .

[0267] Then, after adjusting the resistance value of resistor R36 based on the adjustment value of the resistance value stored in the storage circuit 326, the residual vibration signal NVT corresponding to the residual vibration is input to the -side input terminal of the operational amplifier AM31, and the 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 +side input terminal of the operational amplifier AM31. The residual vibration judgment circuit 320 obtains the residual vibration signal Vnvt as the voltage signal Vo output from the output terminal of the operational amplifier AM31, and calculates the vibration frequency Fnvt of the residual vibration signal Vnvt based on the obtained residual vibration signal Vnvt and the assumed reference voltage Var, and determines the state of the ejection part 600 of the inspection object based on the calculated vibration frequency Fnvt.

[0268] Even in this case, the same effects as those of the above-described embodiment can be achieved. It should be noted that R35 may be formed of a variable resistance element whose resistance value can be adjusted instead of or in addition to the resistor R36.

[0269] That is, the liquid ejection device 1 and the head unit 20 of the modified example may also be that the storage circuit 326 stores the assumed reference potential of the residual vibration signal Vnvt, that is, the assumed reference voltage Var, and the second waveform shaping circuit 310 has: a resistor R35, the voltage signal Vdd2 is input to one end of the resistor R35, and the other end of the resistor R35 is electrically connected to the + side input terminal of the operational amplifier AM31; and a resistor R36, one end of the resistor R36 is electrically connected to the + side input terminal of the operational amplifier AM31, and the ground potential is input to the other end of the resistor R36, at least one of the resistors R35 and R36 includes a variable resistance element, because the - side input terminal of the operational amplifier AM31 does not input the residual vibration signal VNT corresponding to the residual vibration, so the constant potential voltage signal Vm is input to the - side input terminal of the operational amplifier AM31, and the constant potential voltage is obtained by dividing the voltage signal Vdd2 by the resistance value of the resistor R35 and the resistance value of the resistor R36. When the signal Vp is input to the + side input terminal of the operational amplifier AM31, the residual vibration determination circuit 320 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 is close to the assumed reference voltage Var stored in the storage circuit 326; when the residual vibration signal NVT corresponding to the residual vibration is input to the - side input terminal of the operational amplifier 31, and the constant potential voltage signal Vp obtained by dividing the voltage signal Vdd2 by the resistance value of the resistor R35 and the adjusted resistance value of the resistor R36 is input to the + side input terminal of the operational amplifier AM31, the residual vibration determination circuit 320 calculates the vibration frequency Fnvt as the 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 potential Var, and determines the state of the ejection part 600 of the inspection object based on the calculated vibration frequency Fnvt.

[0270] In addition, in the above-mentioned liquid ejection device 1 and head unit 20, the case where the temperature detection circuit 250 for detecting the temperature of the first waveform shaping circuit 240 is included in one semiconductor device constituting the drive signal selection circuit 200 together with the first waveform shaping circuit 240 is described, but as long as a part of the temperature detection circuit 250 can detect the temperature of the first waveform shaping circuit 240, it can also be configured separately from the one semiconductor device constituting the drive signal selection circuit 200. In this case, the temperature detection circuit 250 can also be provided on the head wiring substrate 23, which is a printing substrate to which the other end of the flexible wiring substrate 24 electrically connected to the print head 22 is connected. That is, the head unit 20 may include: the print head 22 including the ejection part 600; the flexible wiring substrate 24 electrically connected to the print head 22 at one end; and the head wiring substrate 23 electrically connected to the other end of the flexible wiring substrate 24, the one semiconductor device constituting the drive signal selection circuit 200 is provided on the flexible wiring substrate 24, and at least a part of the temperature detection circuit 250 is provided on the head wiring substrate 23.

[0271] Even in this case, since the temperature detection circuit 250 is located near one semiconductor device constituting the drive signal selection circuit 200 including the first waveform shaping circuit 240, the same operational effects as those of the above-described embodiment can be achieved.

[0272] In this case, the head wiring substrate is an example of a wiring substrate.

[0273] Although the embodiments and modifications have been described above, the present invention is not limited to these embodiments, and can be implemented in various forms within the scope of the gist thereof. For example, the above embodiments can be appropriately combined.

[0274] The present invention includes substantially the same configuration as the configuration described in the embodiment (for example, a configuration with the same function, method and result or a configuration with the same purpose and effect). In addition, the present invention includes a configuration obtained by replacing a non-essential part of the configuration described in the embodiment. In addition, the present invention includes a configuration that can play the same role and effect as the configuration described in the embodiment or a configuration that can achieve the same purpose. In addition, the present invention includes a configuration obtained by adding a known technology to the configuration described in the embodiment.

[0275] The following can be derived from the above-described embodiments.

[0276] One aspect of the head unit has:

[0277] The ejection unit includes a piezoelectric element driven according to a driving signal and ejects liquid according to the driving of the piezoelectric element;

[0278] a waveform shaping circuit which receives as input a first residual vibration signal corresponding to residual vibration generated by the driving signal and outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal;

[0279] a temperature detection circuit that outputs a temperature information signal corresponding to the temperature of the waveform shaping circuit; and

[0280] a determination circuit for determining a state of the ejection portion,

[0281] The waveform shaping circuit comprises: an amplifier circuit for amplifying the first residual vibration signal; and an amplification factor setting circuit for setting the amplification factor of the amplifier circuit, wherein the waveform shaping circuit outputs the second residual vibration signal based on the signal amplified by the amplifier circuit.

[0282] The amplifier circuit and the gain setting circuit are formed as a semiconductor device.

[0283] The determination circuit determines the state of the ejection portion based on the second residual vibration signal and the temperature information signal.

[0284] According to the head unit, since the amplifier circuit and the gain setting circuit are configured as a semiconductor device, the influence of noise can be reduced along with the detection of the first residual vibration. On the other hand, due to the influence of temperature, the possibility of the gain of the amplifier circuit changing increases, and as a result, there is a possibility that the detection accuracy of the amplitude of the second residual vibration signal decreases. In contrast, according to the head unit, the determination circuit determines the state of the ejection unit based on the second residual vibration signal and the temperature information signal corresponding to the temperature of the waveform shaping circuit, and can appropriately correct the change in the gain of the amplifier circuit caused by the influence of temperature. As a result, the determination accuracy of the state of the ejection unit in the determination circuit is improved.

[0285] In one aspect of the head unit, it may be that

[0286] At least a portion of the temperature detection circuit is also enclosed in the semiconductor device.

[0287] According to this head unit, the temperature detection circuit is formed of the same semiconductor device as the amplifier circuit and the gain setting circuit, thereby enabling the head unit to be miniaturized.

[0288] In one aspect of the head unit, it may be that

[0289] The head unit comprises: a print head including the ejection portion;

[0290] a flexible wiring substrate, one end of which is electrically connected to the print head; and

[0291] a wiring substrate electrically connected to the other end of the flexible wiring substrate,

[0292] The semiconductor device is provided on the flexible wiring substrate.

[0293] At least a portion of the temperature detection circuit is provided on the wiring substrate.

[0294] In one aspect of the head unit, it may be that

[0295] The determination circuit includes an analog-to-digital converter that converts the second residual vibration signal into a digital signal, and determines the state of the ejection portion based on the second residual vibration signal converted into the digital signal and the temperature information signal.

[0296] According to this head unit, the amplitude of the residual vibration signal can be directly acquired, the acquisition accuracy of the signal waveform of the residual vibration signal is improved, and the determination accuracy of the state of the ejection portion is improved.

[0297] In one aspect of the head unit, it may be that

[0298] The analog-to-digital converter converts the temperature information signal into a digital signal.

[0299] The determination circuit determines the state of the ejection portion based on the second residual vibration signal converted into a digital signal and the temperature information signal converted into a digital signal.

[0300] According to this head unit, by converting the second residual vibration signal and the temperature information into digital signals by one analog-to-digital converter, it is possible to achieve miniaturization of the head unit.

[0301] One aspect of the liquid ejection device comprises:

[0302] a head unit that sprays liquid toward the medium; and

[0303] a control unit for controlling the movement of the head unit,

[0304] The head unit has:

[0305] The ejection unit includes a piezoelectric element driven according to a driving signal and ejects liquid according to the driving of the piezoelectric element;

[0306] a waveform shaping circuit which receives as input a first residual vibration signal corresponding to residual vibration generated by the driving signal and outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal;

[0307] a temperature detection circuit that outputs a temperature information signal corresponding to the temperature of the waveform shaping circuit; and

[0308] a determination circuit for determining a state of the ejection portion,

[0309] The waveform shaping circuit comprises: an amplifier circuit for amplifying the first residual vibration signal; and an amplification factor setting circuit for setting the amplification factor of the amplifier circuit, wherein the waveform shaping circuit outputs the second residual vibration signal based on the signal amplified by the amplifier circuit.

[0310] The amplifier circuit and the gain setting circuit are formed as a semiconductor device.

[0311] The determination circuit determines the state of the ejection portion based on the second residual vibration signal and the temperature information signal.

[0312] According to the liquid ejection device, since the amplifier circuit and the amplification factor setting circuit are configured as a semiconductor device, the influence of noise can be reduced along with the detection of the first residual vibration. On the other hand, due to the influence of temperature, the possibility of the amplification factor of the amplifier circuit changing increases, and as a result, there is a possibility that the detection accuracy of the amplitude of the second residual vibration signal decreases. In contrast, according to the liquid ejection device, the determination circuit determines the state of the ejection unit based on the second residual vibration signal and the temperature information signal corresponding to the temperature of the waveform shaping circuit, and can appropriately correct the change in the amplification factor of the amplifier circuit caused by the influence of temperature. As a result, the determination accuracy of the state of the ejection unit in the determination circuit is improved.

[0313] In one aspect of the liquid ejection device, it may be that:

[0314] At least a portion of the temperature detection circuit is included in the semiconductor device.

[0315] According to this liquid ejection device, since the temperature detection circuit is formed of the same semiconductor device as the amplifier circuit and the gain setting circuit, it is possible to achieve miniaturization of the head unit and the liquid ejection device.

[0316] In one aspect of the liquid ejection device, it may be that:

[0317] The head unit comprises:

[0318] A print head, comprising the ejection portion;

[0319] a flexible wiring substrate, one end of which is electrically connected to the print head; and

[0320] a wiring substrate electrically connected to the other end of the flexible wiring substrate,

[0321] The semiconductor device is provided on the flexible wiring substrate.

[0322] At least a portion of the temperature detection circuit is provided on the wiring substrate.

[0323] In one aspect of the liquid ejection device, it may be that:

[0324] The determination circuit includes an analog-to-digital converter that converts the second residual vibration signal into a digital signal, and determines the state of the ejection portion based on the second residual vibration signal converted into the digital signal and the temperature information signal.

[0325] According to this liquid ejection device, the amplitude of the residual vibration signal can be directly acquired, the acquisition accuracy of the signal waveform of the residual vibration signal is improved, and the determination accuracy of the state of the ejection unit is improved.

[0326] In one aspect of the liquid ejection device, it may be that:

[0327] The analog-to-digital converter converts the temperature information signal into a digital signal.

[0328] The determination circuit determines the state of the ejection portion based on the second residual vibration signal converted into a digital signal and the temperature information signal converted into a digital signal.

[0329] According to this liquid ejection device, by converting the second residual vibration signal and the temperature information into digital signals by one analog-to-digital converter, it is possible to achieve miniaturization of the head unit.

Claims

1. A head unit, characterized in that: have: The ejection unit includes a piezoelectric element driven according to a driving signal and ejects liquid according to the driving of the piezoelectric element; a waveform shaping circuit which receives as input a first residual vibration signal corresponding to residual vibration generated by the driving signal and outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal; a temperature detection circuit, outputting a temperature information signal corresponding to the temperature of the waveform shaping circuit; as well as a determination circuit for determining a state of the ejection portion, The waveform shaping circuit comprises: an amplifier circuit for amplifying the first residual vibration signal; and an amplification factor setting circuit for setting the amplification factor of the amplifier circuit, wherein the waveform shaping circuit outputs the second residual vibration signal based on the signal amplified by the amplifier circuit. The amplifier circuit and the gain setting circuit are formed as a semiconductor device. The determination circuit determines the state of the ejection portion based on the second residual vibration signal and the temperature information signal.

2. The head unit according to claim 1, characterized in that At least a portion of the temperature detection circuit is included in the semiconductor device.

3. The head unit according to claim 1, characterized in that The head unit comprises: A print head, comprising the ejection portion; a flexible wiring substrate, one end of which is electrically connected to the print head; and a wiring substrate electrically connected to the other end of the flexible wiring substrate, The semiconductor device is provided on the flexible wiring substrate. At least a portion of the temperature detection circuit is provided on the wiring substrate.

4. The head unit according to any one of claims 1 to 3, characterized in that: The determination circuit includes an analog-to-digital converter that converts the second residual vibration signal into a digital signal, and determines the state of the ejection portion based on the second residual vibration signal converted into the digital signal and the temperature information signal.

5. The head unit according to claim 4, characterized in that: The analog-to-digital converter converts the temperature information signal into a digital signal. The determination circuit determines the state of the ejection unit based on the second residual vibration signal converted into a digital signal and the temperature information signal converted into a digital signal.

6. A liquid ejection device, characterized in that: have: a head unit that sprays liquid toward the medium; and a control unit for controlling the movement of the head unit, The head unit has: The ejection unit includes a piezoelectric element driven according to a driving signal and ejects liquid according to the driving of the piezoelectric element; a waveform shaping circuit which receives as input a first residual vibration signal corresponding to residual vibration generated by the driving signal and outputs a second residual vibration signal obtained by shaping the waveform of the first residual vibration signal; a temperature detection circuit, outputting a temperature information signal corresponding to the temperature of the waveform shaping circuit; as well as a determination circuit for determining a state of the ejection portion, The waveform shaping circuit comprises: an amplifier circuit for amplifying the first residual vibration signal; and an amplification factor setting circuit for setting the amplification factor of the amplifier circuit, wherein the waveform shaping circuit outputs the second residual vibration signal based on the signal amplified by the amplifier circuit. The amplifier circuit and the gain setting circuit are formed as a semiconductor device. The determination circuit determines the state of the ejection portion based on the second residual vibration signal and the temperature information signal.

7. The liquid ejection device according to claim 6, characterized in that: At least a portion of the temperature detection circuit is included in the semiconductor device.

8. The liquid ejection device according to claim 6, characterized in that: The head unit comprises: A print head, comprising the ejection portion; A flexible wiring substrate, one end of which is electrically connected to the print head; as well as a wiring substrate electrically connected to the other end of the flexible wiring substrate, The semiconductor device is provided on the flexible wiring substrate. At least a portion of the temperature detection circuit is provided on the wiring substrate.

9. The liquid ejection device according to any one of claims 6 to 8, characterized in that: The determination circuit includes an analog-to-digital converter that converts the second residual vibration signal into a digital signal, and determines the state of the ejection portion based on the second residual vibration signal converted into the digital signal and the temperature information signal.

10. The liquid ejection device according to claim 9, characterized in that: The analog-to-digital converter converts the temperature information signal into a digital signal. The determination circuit determines the state of the ejection unit based on the second residual vibration signal converted into a digital signal and the temperature information signal converted into a digital signal.

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