Print head and liquid ejecting apparatus

Abstract

The invention provides a printing head and a liquid ejecting apparatus capable of realizing high detection speed of residual vibration. A print head includes: a first pressure chamber whose volume varies according to a drive signal; the first nozzle is communicated with the first pressure chamber and sprays liquid; a first piezoelectric element that outputs a first residual vibration signal corresponding to a first residual vibration generated by a volume change of the first pressure chamber; a first switching circuit, one end of which is input with the drive signal and the other end of which is electrically connected to the first piezoelectric element, the first switching circuit switching whether or not to supply the drive signal to the first piezoelectric element; the first residual vibration detection circuit outputs a first residual vibration detection signal corresponding to the first residual vibration signal, and one end of the first residual vibration detection circuit is electrically connected with one end of the first switching circuit; and the other end of the first residual vibration detection circuit is electrically connected with the other end of the first switching circuit.

Description

Technical Field

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

[0002] In a liquid ejection device that ejects ink from an ejection portion by being driven by a piezoelectric element, 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 Laid-Open No. 2015-039856 Summary of the Invention

[0004] However, when detecting residual vibration generated after the piezoelectric element is driven, the technology described in Patent Document 1 is not sufficient from the perspective of further improving the detection speed, and there is room for further improvement.

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

[0006] a first pressure chamber, the volume of which changes according to a driving signal;

[0007] a first nozzle, connected to the first pressure chamber and spraying liquid;

[0008] a first piezoelectric element outputting a first residual vibration signal corresponding to a first residual vibration generated by a volume change of the first pressure chamber;

[0009] a first switch circuit having one end to which the drive signal is input and the other end electrically connected to the first piezoelectric element, the first switch circuit switching whether to supply the drive signal to the first piezoelectric element; and

[0010] a first residual vibration detection circuit, outputting a first residual vibration detection signal corresponding to the first residual vibration signal;

[0011] One end of the first residual vibration detection circuit is electrically connected to one end of the first switch circuit, and the other end of the first residual vibration detection circuit is electrically connected to the other end of the first switch circuit.

[0012] One aspect of the liquid ejection device according to the present invention comprises:

[0013] A driving circuit outputting a driving signal;

[0014] a first pressure chamber, the volume of which changes according to a driving signal;

[0015] a first nozzle, connected to the first pressure chamber and spraying liquid;

[0016] a first piezoelectric element outputting a first residual vibration signal corresponding to a first residual vibration generated by a volume change of the first pressure chamber;

[0017] a first switch circuit having one end to which the drive signal is input and the other end electrically connected to the first piezoelectric element, the first switch circuit switching whether to supply the drive signal to the first piezoelectric element; and

[0018] a first residual vibration detection circuit, outputting a first residual vibration detection signal corresponding to the first residual vibration signal;

[0019] One end of the first residual vibration detection circuit is electrically connected to one end of the first switch circuit, and the other end of the first residual vibration detection circuit is electrically connected to the other end of the first switch circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a diagram showing a schematic structure of a liquid ejecting device.

[0021] Figure 2 It is a diagram showing a schematic structure of a discharge unit.

[0022] Figure 3 This is an exploded perspective view of the print head.

[0023] Figure 4 yes Figure 3 Cross-sectional view of line Aa in .

[0024] Figure 5 1 is a diagram showing an example of signal waveforms of the drive voltage signal COM, the latch signal LAT, the conversion signal CH, and the test timing signal TSIG.

[0025] Figure 6 1 is a diagram showing an example of the functional configuration of a drive signal selection circuit.

[0026] Figure 7 This is a diagram showing an example of the decoded content in the decoder.

[0027] Figure 8 This is a diagram showing the configuration of a selection circuit corresponding to one ejection unit.

[0028] Figure 9 : is a diagram showing an example of the configuration of a residual vibration detection circuit.

[0029] Figure 10 This is a diagram showing an example of the operation of the drive signal selection circuit.

[0030] Figure 11 This is a diagram showing an example of the configuration of a waveform information output circuit.

[0031] Figure 12 This is a diagram for explaining the operation of the waveform information output circuit.

[0032] Figure 13 1 is a diagram showing an example of the residual vibration signals Vout1 and Vout2.

[0033] Figure 14 This is a diagram showing an example of a calculation model that assumes simple harmonic vibration of residual vibration generated in the pressure chamber CB1 , the pressure chamber CB2 , or the vibration plate 304 .

[0034] Figure 15 This is a diagram for explaining the relationship between the viscosity of ink and the signal waveforms of the residual vibration signals Vout1 and Vout2.

[0035] Figure 16 It is a diagram for explaining the signal waveforms of the residual vibration signals Vout1 and Vout2 when bubbles are mixed in the pressure chambers CB1 and CB2.

[0036] Figure 17 1 is a diagram showing an example of a signal waveform of the residual vibration signal Vout when the ejection portion is normal.

[0037] Figure 18 1 is a diagram showing an example of a signal waveform of the residual vibration signal Vout when abnormal viscosity increase occurs in the discharge portion.

[0038] Figure 19 1 is a diagram showing an example of a signal waveform of the residual vibration signal Vout when an abnormal bubble mixing occurs in the ejection portion.

[0039] Description of Reference Numerals

[0040] 1: Liquid ejection device, 2: Control unit, 3: Liquid container, 4: Transport unit, 5: Ejection unit, 6: Circulation unit, 10: Drive module, 11: Control circuit substrate, 15: Cable, 20: Ejection module, 21: Print head, 22: Head chip, 23: Head circuit substrate, 24: Flexible substrate, 41: Transport motor, 42: Transport roller, 50: Drive circuit, 60a, 60b: Piezoelectric element, 100: Control circuit, 200: Drive signal selection circuit, 201 : integrated circuit, 220: selection control circuit, 222: shift register, 224: latch circuit, 226: decoder, 230: selection circuit, 232a, 232b: logic inversion circuit, 234a, 234b: transmission gate, 240: residual vibration detection circuit, 300: waveform information output circuit, 302: connecting plate, 303: pressure chamber substrate, 304: vibration plate, 305: storage chamber forming substrate, 308: wiring substrate, 310: reset circuit, 32 0: Maximum voltage acquisition circuit, 330: Minimum voltage acquisition circuit, 340: Cycle acquisition circuit, 341: Counter circuit, 350: Opening, 351: Supply port, 352: Discharge port, 360: Nozzle substrate, 361, 362: Plastic sheet, 600: Discharge unit, C1, C2, C11-C13, C21-C23: Capacitors, CB1, CB2: Pressure chambers, CP1: Comparator, D11, D21: Diodes, INV1: Logic inversion Circuit, Ln: nozzle array, N: nozzle, OP1, OP11, OP12, OP21, OP22: amplifier circuit, P: medium, PW1: power supply circuit, R1~R6: resistors, RA1: supply flow channel, RA2: discharge flow channel, RB1: supply flow channel, RB2: discharge flow channel, RK1, RK2: connecting flow channel, RN: nozzle flow channel, RR1, RR2: connecting flow channel, SW1, SW2, SW11~SW13, SW21~SW23: switches. DETAILED DESCRIPTION

[0041] Below, preferred embodiments of the present invention are described using the accompanying drawings. The accompanying drawings are used for ease of explanation. It should be noted that the embodiments described below are not intended to unduly limit the contents of the present invention as described in the claims. In addition, not all of the structures described below are necessarily essential components of the present invention.

[0042] 1. Structure of liquid ejection device

[0043] Figure 1 1 is a diagram showing a schematic structure of the liquid ejecting device 1. Figure 1As shown, the liquid ejection device 1 is a so-called line-type inkjet printer, which ejects ink, an example of a liquid, onto the medium P being transported by the transport unit 4 at a desired timing, thereby forming a desired image on the medium P. It should be noted that the liquid ejection device 1 is not limited to a line-type inkjet printer and may also be a serial-type inkjet printer. Furthermore, the liquid ejection device 1 is not limited to an inkjet printer and may also be a colorant ejection device used in the manufacture of color filters for liquid crystal displays, etc., an electrode material ejection device used in the formation of electrodes for organic EL displays, FEDs (surface emitting displays), etc., a bio-organic material ejection device used in the manufacture of biochips, etc., or a three-dimensional modeling device or a printing and dyeing device. In the following description, the direction in which the medium P is transported may sometimes be referred to as the transport direction, and the width direction of the transported medium P may be referred to as the scanning direction.

[0044] like Figure 1 As shown, the liquid ejecting device 1 includes a control unit 2 , a liquid container 3 , a transport unit 4 , a plurality of ejecting units 5 , and a circulation unit 6 .

[0045] The control unit 2 includes processing circuits such as a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), and storage circuits such as semiconductor memory. The control unit 2 outputs signals for controlling various elements of the liquid ejection device 1 based on image data supplied from an external device such as a host computer (not shown) located outside the liquid ejection device 1.

[0046] The liquid container 3 stores ink, an example of a liquid, which is supplied to the ejection unit 5. Specifically, the liquid container 3 stores inks of various colors, such as black, cyan, magenta, yellow, red, and gray, to be ejected onto the medium P. Examples of the liquid container 3 include ink cartridges, bag-shaped ink packs formed of a flexible film, and refillable ink tanks.

[0047] The circulation unit 6 supplies ink stored in the liquid container 3 to the ejection unit 5 based on the circulation control signal Ctrl-P output by the control unit 2. Furthermore, the circulation unit 6 recovers ink discharged from the ejection unit 5 based on the circulation control signal Ctrl-P output by the control unit 2. Specifically, the circulation unit 6 recirculates the ink within the liquid ejection device 1. Such a circulation unit 6 can be configured, for example, by including a pump or the like that generates a flow of ink within the liquid ejection device 1.

[0048] The conveying unit 4 includes a conveying motor 41 and conveying rollers 42. The conveying unit 4 receives a conveying control signal Ctrl-T from the control unit 2. The conveying motor 41 is driven based on the conveying control signal Ctrl-T, and the conveying rollers 42 rotate in response to the drive of the conveying motor 41. The rotation of the conveying rollers 42 conveys the medium P in the conveying direction.

[0049] Each of the multiple ejection units 5 includes a driver module 10 and an ejection module 20. Each of the multiple ejection units 5 receives a corresponding image information signal IP output by the control unit 2 and is supplied with ink stored in the liquid container 3. The driver module 10 controls the operation of the ejection module 20 based on the image information signal IP. Consequently, the ejection module 20 ejects the ink supplied from the liquid container 3 at a predetermined timing in accordance with the control of the driver module 10.

[0050] In the liquid ejection device 1 of this embodiment, the ejection modules 20 included in each of the multiple ejection units 5 are aligned and positioned along the scanning direction so as to extend beyond the width of the medium P. The drive modules 10 included in each of the multiple ejection units 5 eject ink from the ejection modules 20 in synchronization with the transport of the medium P. The ink ejected from each of the multiple ejection modules 20 lands at a desired location on the medium P, thereby forming a desired image on the medium P.

[0051] Next, the schematic structure of the discharge unit 5 will be described. Figure 2 : is a diagram showing a schematic structure of the ejection unit 5. Figure 2 As shown, the discharge unit 5 includes a drive module 10 and a discharge module 20. In the discharge unit 5, the drive module 10 and the discharge module 20 are electrically connected via a cable 15. A flexible flat cable (FFC) or a flexible printed circuit (FPC) can be used as the cable 15 that electrically connects the drive module 10 and the discharge module 20. Alternatively, the drive module 10 and the discharge module 20 can be electrically connected using a BtoB (Board to Board) connector, rather than the cable 15. Alternatively, both the cable 15 and the BtoB connector can be used.

[0052] The driver module 10 includes a control circuit substrate 11, a driver circuit 50, and a control circuit 100. The control circuit substrate 11 is a printed circuit board having one or more wiring layers, and can be a glass epoxy substrate, a glass polyimide substrate, or the like. The various components that make up the driver module 10, including the driver 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, on which the various components that make up the driver module 10 are mounted, can consist of a single printed circuit board or multiple printed circuit boards.

[0053] The control circuit 100 is a processor that includes processing circuits such as a CPU and FPGA, and storage circuits such as semiconductor memory. The control circuit 100 receives an image information signal IP output by the control unit 2. Based on the input image information signal IP, the control circuit 100 generates and outputs signals for controlling the operation of the drive module 10 and the ejection module 20.

[0054] Specifically, the control circuit 100 generates a clock signal SCK, a latch signal LAT, a conversion signal CH, a test timing signal TSIG, and print data signals SI1 to SIn based on the input image information signal IP, and outputs them to the ejection module 20 .

[0055] In addition, the control circuit 100 generates a basic drive signal dA and outputs it to the drive circuit 50. The drive circuit 50 generates a drive voltage signal COM and outputs it to the ejection module 20. The drive voltage signal COM includes a signal waveform specified by the input basic drive signal dA. Specifically, the control circuit 100 generates a basic drive signal dA of a digital signal and outputs it to the drive circuit 50. After converting the basic drive signal dA of the input digital signal into an analog signal, the drive circuit 50 performs Class D amplification on the converted analog signal to generate the drive voltage signal COM. The drive circuit 50 outputs the generated drive voltage signal COM to the ejection module 20. That is, the control circuit 100 outputs the basic drive signal dA that specifies the signal waveform of the drive voltage signal COM output by the drive circuit 50. It should be pointed out that the basic drive signal dA can be any signal that can specify the signal waveform of the drive voltage signal COM, and can also be an analog signal. In addition, as long as the drive circuit 50 can amplify the signal waveform specified by the basic drive signal dA to generate the drive voltage signal COM, it can also generate the drive voltage signal COM by performing class A amplification, class B amplification, or class AB amplification instead of or in addition to class D amplification.

[0056] In addition, the driving circuit 50 generates a reference voltage signal VBS and outputs it to the ejection module 20. The reference voltage signal VBS is a signal that specifies a reference potential for driving the piezoelectric elements 60a and 60b described later. The voltage value of such a reference voltage signal VBS can be, for example, the ground potential, or 5.5V, 6V, etc. It should be noted that Figure 2 The driving circuit 50 in the figure generates the reference voltage signal VBS and outputs it to the ejection module 20 . However, the reference voltage signal VBS may be generated by a constant voltage output circuit (not shown) configured separately from the driving circuit 50 .

[0057] Furthermore, waveform information signals WFS11 to WFS1m, WFS21 to WFS2m, ..., and WFSn1 to WFSnm are input from the ejection module 20 (described later) to the control circuit 100. Based on each of the input waveform information signals WFS11 to WFS1m, WFS21 to WFS2m, ..., and WFSn1 to WFSnm, the control circuit 100 determines whether the ejection state of ink ejected from the ejection module 20 is normal. Details of the waveform information signals WFS11 to WFS1m, WFS21 to WFS2m, ..., and WFSn1 to WFSnm input to the control circuit 100, as well as a method for determining whether the ejection state of ink ejected from the ejection module 20 is normal based on the waveform information signals WFS11 to WFS1m, WFS21 to WFS2m, ..., and WFSn1 to WFSnm, will be described below.

[0058] The ejection module 20 includes print heads 21-1 to 21-n, a head circuit board 23, and waveform information output circuits 300-11 to 300-1m, 300-21 to 300-2m, ..., 300-n1 to 300-nm. Furthermore, each print head 21-1 to 21-n includes a head chip 22, a flexible substrate 24, and a drive signal selection circuit 200. Furthermore, each head chip 22 of each print head 21-1 to 21-n includes an ejection unit 600-1 to 600-m, and each ejection unit 600-1 to 600-m includes a piezoelectric element 60a or 60b.

[0059] The ejection module 20 receives the clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, print data signals SI1 to SIn, drive voltage signal COM, and reference voltage signal VBS output from the driving module 10 .

[0060] The head circuit board 23 transmits the input clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, print data signals SI1 to SIn, drive voltage signal COM, and reference voltage signal VBS to the corresponding print heads 21-1 to 21-n. The head circuit board 23 is a printed circuit board having one or more wiring layers, and can be, for example, a glass epoxy substrate or a glass polyimide substrate.

[0061] Specifically, the head circuit substrate 23 transmits the clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, printing data signal SI1~SIn, drive voltage signal COM and reference voltage signal VBS among the input clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, printing data signal SI1~SIn, drive voltage signal COM and reference voltage signal VBS to the print head 21-1, and transmits the clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, printing data signal SIn, drive voltage signal COM and reference voltage signal VBS to the print head 21-n.

[0062] Of the clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, print data signal SI1, drive voltage signal COM, and reference voltage signal VBS input to print head 21-1, the clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, print data signal SI1, and drive voltage signal COM are input to drive signal selection circuit 200 of print head 21-1. Drive signal selection circuit 200 of print head 21-1 selects or deselects a signal waveform included in drive voltage signal COM based on the input clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, and print data signal SI1, thereby generating and outputting drive voltage signals Vin-1 to Vin-m.

[0063] The drive voltage signals Vin-1 to Vin-m output by the drive signal selection circuit 200 of the print head 21-1 are supplied to the corresponding ejection units 600-1 to 600-m included in the head chip 22 of the print head 21-1. Specifically, the drive voltage signal Vin-1 of the drive signal selection circuit 200 is supplied to one end of the piezoelectric elements 60a and 60b included in the ejection unit 600-1 included in the head chip 22 of the print head 21-1, while the drive voltage signal Vin-m is supplied to one end of the piezoelectric elements 60a and 60b included in the ejection unit 600-1 included in the head chip 22 of the print head 21-1. At this time, the reference voltage signal VBS is commonly supplied to the other end of the piezoelectric elements 60a and 60b included in each of the ejection units 600-1 to 600-m included in the head chip 22 of the print head 21-1. The piezoelectric elements 60a and 60b included in each of the ejection units 600-1 to 600-m of the head chip 22 of the print head 21-1 are driven based on the potential difference between the voltage value of the corresponding driving voltage signals Vin-1 to Vin-m supplied to one end and the voltage value of the reference voltage signal VBS supplied to the other end. The ejection units 600-1 to 600-m of the print head 21-1 eject an amount of ink corresponding to the driving of the piezoelectric elements 60a and 60b.

[0064] Furthermore, in the ejection units 600-1 to 600-m of the head chip 22 of the print head 21-1, residual vibrations are generated after the piezoelectric elements 60a and 60b included in each are driven. The piezoelectric elements 60a and 60b included in each of the ejection units 600-1 to 600-m of the head chip 22 of the print head 21-1 are displaced in response to the residual vibrations generated in the corresponding ejection units 600-1 to 600-m. The piezoelectric elements 60a and 60b included in each of the ejection units 600-1 to 600-m of the print head 21-1 output residual vibration signals Vout-1 to Vout-m corresponding to the displacements. These residual vibration signals Vout-1 to Vout-m are input to the drive signal selection circuit 200 of the print head 21-1. Then, the drive signal selection circuit 200 of the print head 21 - 1 generates residual vibration detection signals NVT- 1 to NVT-m corresponding to the input residual vibration signals Vout- 1 to Vout-m, and outputs them from the print head 21 - 1 .

[0065] Specifically, a signal corresponding to the residual vibration generated in the ejection section 600-1 after driving the piezoelectric elements 60a and 60b included in the ejection section 600-1 of the head chip 22 of the print head 21-1 is input as a residual vibration signal Vout-1 to the drive signal selection circuit 200 of the print head 21-1. Furthermore, a signal corresponding to the residual vibration generated in the ejection section 600-m after driving the piezoelectric elements 60a and 60b included in the ejection section 600-m of the head chip 22 of the print head 21-1 is input as a residual vibration signal Vout-m to the drive signal selection circuit 200 of the print head 21-1. The drive signal selection circuit 200 of the print head 21-1 then generates a residual vibration detection signal NVT-1 corresponding to the input residual vibration signal Vout-1 and outputs it from the print head 21-1. The drive signal selection circuit 200 of the print head 21-1 also generates a residual vibration detection signal NVT-m corresponding to the input residual vibration signal Vout-m and outputs it from the print head 21-1.

[0066] The drive signal selection circuit 200 included in the print head 21 - 1 may be configured as an integrated circuit device and mounted on the flexible substrate 24 included in the print head 21 - 1 using a COF (Chip On Film).

[0067] Furthermore, among the clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, print data signal SIn, drive voltage signal COM, and reference voltage signal VBS input to the print head 21-n, the clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, print data signal SIn, and drive voltage signal COM are input to the drive signal selection circuit 200 of the print head 21-n. The drive signal selection circuit 200 of the print head 21-n selects or deselects a signal waveform included in the drive voltage signal COM based on the input clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, and print data signal SIn, thereby generating and outputting drive voltage signals Vin-1 to Vin-m.

[0068] The drive voltage signals Vin-1 to Vin-m output by the drive signal selection circuit 200 of the print head 21-n are supplied to the corresponding ejection units 600-1 to 600-m included in the head chip 22 of the print head 21-n. Specifically, the drive voltage signal Vin-1 of the drive signal selection circuit 200 of the print head 21-n is supplied to one end of the piezoelectric elements 60a and 60b included in the ejection unit 600-1 included in the head chip 22 of the print head 21-n, while the drive voltage signal Vin-m is supplied to one end of the piezoelectric elements 60a and 60b included in the ejection unit 600-1 included in the head chip 22 of the print head 21-n. At this time, the reference voltage signal VBS is commonly supplied to the other end of the piezoelectric elements 60a and 60b included in each of the ejection units 600-1 to 600-m included in the head chip 22 of the print head 21-n. The piezoelectric elements 60a and 60b included in the ejection units 600-1 to 600-m of the head chip 22 of the print head 21-n are driven by the potential difference between the voltage value of the corresponding driving voltage signals Vin-1 to Vin-m supplied to one end and the voltage value of the reference voltage signal VBS supplied to the other end. The ejection units 600-1 to 600-m of the print head 21-n eject an amount of ink corresponding to the driving of the piezoelectric elements 60a and 60b.

[0069] Furthermore, in the ejection units 600-1 to 600-m of the head chip 22 of the print head 21-n, residual vibrations are generated after the piezoelectric elements 60a and 60b included in each are driven. The piezoelectric elements 60a and 60b included in each of the ejection units 600-1 to 600-m of the head chip 22 of the print head 21-n are displaced in response to the residual vibrations generated in the corresponding ejection units 600-1 to 600-m. The piezoelectric elements 60a and 60b included in each of the ejection units 600-1 to 600-m of the print head 21-n output residual vibration signals Vout-1 to Vout-m corresponding to the displacements. These residual vibration signals Vout-1 to Vout-m are input to the drive signal selection circuit 200 of the print head 21-n. Then, the drive signal selection circuit 200 of the print head 21 - n generates residual vibration detection signals NVT- 1 to NVT-m corresponding to the input residual vibration signals Vout- 1 to Vout-m, and outputs them from the print head 21 - n.

[0070] Specifically, a signal corresponding to the residual vibration generated in the ejection section 600-1 of the head chip 22 of the print head 21-n after driving the piezoelectric elements 60a and 60b included in the ejection section 600-1 is input as a residual vibration signal Vout-1 to the drive signal selection circuit 200 of the print head 21-n. Furthermore, a signal corresponding to the residual vibration generated in the ejection section 600-m of the head chip 22 of the print head 21-n after driving the piezoelectric elements 60a and 60b included in the ejection section 600-m is input as a residual vibration signal Vout-m to the drive signal selection circuit 200 of the print head 21-n. The drive signal selection circuit 200 of the print head 21-n then generates a residual vibration detection signal NVT-1 corresponding to the input residual vibration signal Vout-1 and outputs it from the print head 21-n. The drive signal selection circuit 200 of the print head 21-n then generates a residual vibration detection signal NVT-m corresponding to the input residual vibration signal Vout-m and outputs it from the print head 21-n.

[0071] The drive signal selection circuit 200 included in the print head 21 - n may be configured as an integrated circuit device and mounted on the flexible substrate 24 included in the print head 21 - n by COF.

[0072] The waveform information output circuits 300 - 11 to 300 - 1 m , 300 - 21 to 300 - 2 m , . . . , and 300 - n1 to 300 - nm are mounted on the head circuit board 23 .

[0073] The waveform information output circuits 300-11 to 300-1m receive the latch signal LAT and the residual vibration detection signals NVT-1 to NVT-m output by the print head 21-1. The waveform information output circuits 300-11 to 300-1m acquire the waveform information of the input residual vibration detection signals NVT-1 to NVT-m at each cycle specified by the latch signal LAT and generate waveform information signals WFS11 to WFS1m containing the acquired waveform information. The waveform information output circuits 300-11 to 300-1m then output the generated waveform information signals WFS11 to WFS1m to the control circuit 100 of the drive module 10.

[0074] Specifically, the waveform information output circuit 300-11 receives input of the residual vibration detection signal NVT-1 output by the print head 21-1. The waveform information output circuit 300-11 then acquires waveform information of the input residual vibration detection signal NVT-1 output by the print head 21-1 at each cycle specified by the latch signal LAT, and outputs a waveform information signal WFS11 including the acquired waveform information. In other words, the waveform information output circuit 300-11 acquires waveform information of a signal corresponding to the residual vibration of the ejection unit 600-1 included in the head chip 22 of the print head 21-1 at each cycle specified by the latch signal LAT, and outputs the waveform information signal WFS11 including the acquired waveform information to the control circuit 100.

[0075] Furthermore, the waveform information output circuit 300-1m receives input of the residual vibration detection signal NVT-m output by the print head 21-1. The waveform information output circuit 300-1m then acquires waveform information of the input residual vibration detection signal NVT-m output by the print head 21-1 at each cycle specified by the latch signal LAT and outputs a waveform information signal WFS1m including the acquired waveform information. Specifically, the waveform information output circuit 300-1m acquires waveform information of a signal corresponding to the residual vibration of the ejection unit 600-m included in the head chip 22 of the print head 21-1 at each cycle specified by the latch signal LAT and outputs the waveform information signal WFS1m including the acquired waveform information to the control circuit 100.

[0076] Similarly, waveform information output circuits 300-n1 to 300-nm receive inputs of latch signal LAT and residual vibration detection signals NVT-1 to NVT-m output by print head 21-n. Waveform information output circuits 300-n1 to 300-nm acquire waveform information of the input residual vibration detection signals NVT-1 to NVT-m at each cycle specified by latch signal LAT, and generate waveform information signals WFSn1 to WFSnm including the acquired waveform information. Waveform information output circuits 300-n1 to 300-nm then output the generated waveform information signals WFSn1 to WFSnm to control circuit 100 of drive module 10.

[0077] Specifically, the waveform information output circuit 300-n1 obtains the waveform information of the residual vibration detection signal NVT-1 output by the print head 21-n in each cycle specified by the latch signal LAT, and outputs the waveform information signal WFS11 including the obtained waveform information. The waveform information output circuit 300-nm obtains the waveform information of the residual vibration detection signal NVT-m output by the print head 21-n in each cycle specified by the latch signal LAT, and outputs the waveform information signal WFS11 including the obtained waveform information. In other words, the waveform information output circuit 300-n1 obtains the waveform information of the signal corresponding to the residual vibration of the ejection part 600-1 possessed by the head chip 22 of the print head 21-n in each cycle specified by the latch signal LAT, and outputs the waveform information signal WFSn1 including the obtained waveform information to the control circuit 100. The waveform information output circuit 300-nm obtains the waveform information of the signal corresponding to the residual vibration of the ejection part 600-m possessed by the head chip 22 of the print head 21-n in each cycle specified by the latch signal LAT, and outputs the waveform information signal WFSnm including the obtained waveform information to the control circuit 100.

[0078] Specifically, the waveform information output circuits 300-11 to 300-1m, 300-21 to 300-2m, ..., 300-n1 to 300-nm individually acquire waveform information corresponding to the residual vibration of each of the ejection units 600-1 to 600-m included in the head chips 22 of the respective print heads 21-1 to 21-n, and generate waveform information signals WFS11 to WFS1m, WFS21 to WFS2m, ..., WFSn1 to WFSnm corresponding to the acquired waveform information. The waveform information output circuits 300-11 to 300-1m, 300-21 to 300-2m, ..., 300-n1 to 300-nm then output the generated waveform information signals WFS11 to WFS1m, WFS21 to WFS2m, ..., WFSn1 to WFSnm to the control circuit 100 included in the drive module 10.

[0079] The control circuit 100 determines whether the ink ejection states of the ejection units 600-1 to 600-m included in the head chips 22 of the print heads 21-1 to 21-n are normal based on the input waveform information signals WFS11 to WFS1m, WFS21 to WFS2m, . . . , WFSn1 to WFSnm.

[0080] Here, the waveform information output circuits 300-11 to 300-1m may be configured as a single integrated circuit device or may be configured from discrete components. Furthermore, the waveform information output circuits 300-11 to 300-1m may be mounted together with the drive signal selection circuit 200 on an integrated circuit device that constitutes the drive signal selection circuit 200 included in the print head 21-1. Furthermore, if the waveform information output circuits 300-11 to 300-1m are configured as an integrated circuit device, the integrated circuit device may be mounted on the flexible substrate 24 included in the print head 21-1 using a COF.

[0081] Similarly, the waveform information output circuits 300-n1 to 300-nm may be configured as a single integrated circuit device or as discrete components. Furthermore, the waveform information output circuits 300-n1 to 300-nm may be mounted together with the drive signal selection circuit 200 on an integrated circuit device that constitutes the drive signal selection circuit 200 included in the print head 21-n. Furthermore, if the waveform information output circuits 300-n1 to 300-nm are configured as an integrated circuit device, the integrated circuit device may be mounted on the flexible substrate 24 included in the print head 21-n using a COF.

[0082] Here, print heads 21-1 to 21-n all have the same structure and, when distinction is not necessary, may be simply referred to as print head 21. The following description assumes that the print head 21 receives inputs such as a clock signal SCK, a latch signal LAT, a conversion signal CH, a test timing signal TSIG, print data signals SI (SI1 to SIn), a drive voltage signal COM, and a reference voltage signal VBS, and outputs residual vibration detection signals NVT-1 to NVT-m. Furthermore, the following description assumes that the residual vibration detection signals NVT-1 to NVT-m output by the print head 21 are input to waveform information output circuits 300-1 to 300-m, 300-21 to 300-2m, ..., 300-n1 to 300-nm. At this time, it is assumed that the waveform information output circuit 300-1 is input with the residual vibration detection signal NVT-1 output by the print head 21, the waveform information output circuit 300-1 outputs the waveform information signal WFS1 corresponding to the residual vibration detection signal NVT-1, and the waveform information output circuit 300-m is input with the residual vibration detection signal NVT-m output by the print head 21, and the waveform information output circuit 300-m outputs the waveform information signal WFSm corresponding to the residual vibration detection signal NVT-m for explanation.

[0083] The waveform information output circuits 300-1 to 300-m all have the same configuration and, when distinction is not necessary, may be simply referred to as the waveform information output circuit 300. In this description, it is assumed that the waveform information output circuit 300 receives the residual vibration detection signals NVT-1 to NVT-m output from the print head 21 as input and outputs the waveform information signal WFS as the waveform information signals WFS1 to WFSm.

[0084] The ejection units 600-1 to 600-m included in the print head 21 all have the same structure and, unless otherwise required, are simply referred to as ejection units 600. Specifically, the description assumes that the print head 21 includes a plurality of ejection units 600, namely, m ejection units 600. Furthermore, the description assumes that the ejection units 600 are supplied with drive voltage signals Vin as drive voltage signals Vin-1 to Vin-m, and that the ejection units 600 output residual vibration signals Vout as residual vibration signals Vout-1 to Vout-m.

[0085] 2. Print head structure

[0086] Next, the structure of the print head 21 will be described. Figure 3 is an exploded perspective view of the print head 21. Figure 4 yes Figure 3 . Here, in the following description, mutually orthogonal X-axis, Y-axis, and Z-axis are used for description. In addition, in the following description, the starting point side of an arrow along the X-axis in the figure may be referred to as the -X side, and the front end side may be referred to as the +X side. The starting point side of an arrow along the Y-axis in the figure may be referred to as the -Y side, and the front end side may be referred to as the +Y side. The starting point side of an arrow along the Z-axis in the figure may be referred to as the -Z side, and the front end side may be referred to as the +Z side.

[0087] like Figure 3 and Figure 4 As shown, the print head 21 includes a head chip 22 and a flexible substrate 24. The head chip 22 includes a nozzle substrate 360, flexible sheets 361 and 362, a communication plate 302, a pressure chamber substrate 303, a vibration plate 304, and a reservoir forming substrate 305.

[0088] The nozzle substrate 360 ​​is a plate-shaped member that is elongated along the Y axis and extends approximately parallel to the XY plane defined by the X and Y axes. M nozzles N are formed on the nozzle substrate 360. The nozzles N are through-holes formed in the nozzle substrate 360. These M nozzles N are arranged side by side along the Y axis on the nozzle substrate 360 ​​to form a nozzle array Ln on the nozzle substrate 360. The term "approximately parallel" is not limited to being completely parallel; it also includes conditions that are considered parallel to account for errors and other factors.

[0089] The connecting plate 302 is located on the -Z side of the nozzle substrate 360. The connecting plate 302 is a plate-shaped member that extends along the Y axis and is generally parallel to the XY plane. Formed on the connecting plate 302 are a supply flow channel RA1, a discharge flow channel RA2, M connecting flow channels RK1, M connecting flow channels RK2, M connecting flow channels RR1, M connecting flow channels RR2, and M nozzle flow channels RN, which serve as a portion of the flow channel through which ink flows.

[0090] The supply channel RA1 is located on the +X side of the connecting plate 302 and extends along the Y direction. The discharge channel RA2 is located on the -X side of the connecting plate 302 and extends along the Y direction. At this time, the supply channel RA1 and the discharge channel RA2 are formed to be roughly line symmetrical with the Z axis passing through the nozzle N as the symmetry axis. The M connecting channels RK1 are located on the -X side of the supply channel RA1 and are arranged side by side along the Y direction. The M connecting channels RR1 are located on the -X side of the M connecting channels RK1 arranged side by side along the Y direction and are arranged side by side along the Y direction. The M connecting channels RK2 are located on the +X side of the discharge channel RA2 and on the -X side of the M connecting channels RR1 arranged side by side along the Y direction and are arranged side by side along the Y direction. The M connecting channels RR2 are located on the +X side of the M connecting channels RK2 arranged side by side along the Y direction and on the -X side of the M connecting channels RR1 arranged side by side along the Y direction and are arranged side by side along the Y direction. At this time, the connecting flow channel RK1 and the connecting flow channel RK2 are formed to be approximately line-symmetrical about the Z axis passing through the nozzle N, and the communicating flow channel RR1 and the communicating flow channel RR2 are formed to be approximately line-symmetrical about the Z axis passing through the nozzle N. The nozzle flow channel RN connects the communicating flow channel RR1 and the communicating flow channel RR2 corresponding to the common nozzle N. In addition, when the communicating plate 302 is viewed from the Z direction, the nozzle substrate 360 ​​is fixed to the communicating plate 302 so that the nozzle N is located approximately at the center of the nozzle flow channel RN in the X direction.

[0091] The pressure chamber substrate 303 is located on the -Z side of the connecting plate 302 and is fixed to the connecting plate 302. The pressure chamber substrate 303 is a plate-shaped component that is elongated in the Y-axis direction and extends approximately parallel to the XY plane. M pressure chambers CB1 and M pressure chambers CB2 are formed on the pressure chamber substrate 303 as part of the flow path for ink flow. The pressure chambers CB1 and CB2 are arranged approximately line-symmetrically about the Z-axis passing through the nozzle N.

[0092] The m pressure chambers CB1 correspond one-to-one to the m nozzles N and are arranged side by side along the Y-axis. Furthermore, each of the m pressure chambers CB1 communicates with the connecting flow channel RK1 and the communication flow channel RR1 corresponding to the common nozzle N. Specifically, when viewed along the Z-axis, the +X-side end of the pressure chamber CB1 communicates with the connecting flow channel RK1, and the -X-side end communicates with the communication flow channel RR1. In other words, the pressure chamber CB1 connects the connecting flow channel RK1 and the communication flow channel RR1 corresponding to the common nozzle N.

[0093] Similarly, the m pressure chambers CB2 correspond one-to-one with the m nozzles N and are located on the -X side of the m pressure chambers CB1 arranged side by side along the Y axis. Furthermore, each of the m pressure chambers CB2 communicates with the connecting flow channel RK2 and the communicating flow channel RR2 corresponding to the common nozzle N. Specifically, when viewed along the Z axis, the -X end of the pressure chamber CB2 communicates with the connecting flow channel RK2, and the +X end communicates with the communicating flow channel RR2. In other words, the pressure chamber CB2 connects the connecting flow channel RK2 and the communicating flow channel RR2 corresponding to the common nozzle N.

[0094] The vibration plate 304 is located on the -Z side of the pressure chamber substrate 303 and is fixed to the pressure chamber substrate 303 in a manner that seals the pressure chambers CB1 and CB2. The vibration plate 304 is a plate-shaped component that is elongated in the Y direction and extends approximately parallel to the XY plane. It is a component that can vibrate elastically. In addition, m piezoelectric elements 60a and m piezoelectric elements 60b are arranged side by side on the -Z side of the vibration plate 304. The m piezoelectric elements 60a are arranged side by side along the Y axis on the -Z side of the vibration plate 304. In addition, the m piezoelectric elements 60b are arranged side by side along the Y axis on the -X side of the m piezoelectric elements 60a arranged side by side along the Y axis on the -Z side of the vibration plate 304. In other words, a row of m piezoelectric elements 60a and a row of m piezoelectric elements 60b are arranged side by side on the -Z side of the vibration plate 304.

[0095] The storage chamber forming substrate 305 is located on the -Z side of the connecting plate 302. The storage chamber forming substrate 305 is a component that is elongated in the Y direction and includes an opening 350. In addition, the storage chamber forming substrate 305 is fixed to the connecting plate 302 in such a manner that the pressure chamber substrate 303, the vibration plate 304, and the wiring substrate 308 are located on the inner side of the opening 350. In addition, the storage chamber forming substrate 305 includes a supply flow channel RB1, a discharge flow channel RB2, a supply port 351, and a discharge port 352. The supply flow channel RB1 is connected to the supply flow channel RA1. The discharge flow channel RB2 is connected to the discharge flow channel RA2. The supply port 351 is connected to the supply flow channel RB1. The discharge port 352 is connected to the discharge flow channel RB2. Then, by the action of the circulation unit 6, the ink stored in the liquid container 3 is supplied to the supply port 351. In this way, ink is supplied to the head chip 22. The ink supplied to the head chip 22 flows inside the head chip 22 by the operation of the circulation unit 6 and is recovered through the discharge port 352. That is, the ink supplied to the head chip 22 is returned by the operation of the circulation unit 6.

[0096] On the -Z side of the vibration plate 304, the flexible substrate 24 is electrically connected to the vibration plate 304 on the -X side of the row of m piezoelectric elements 60a and on the +X side of the row of m piezoelectric elements 60b. That is, the flexible substrate 24 is electrically connected to the vibration plate 304 between the row of m piezoelectric elements 60a and the row of m piezoelectric elements 60b provided on the vibration plate 304. In this case, the flexible substrate 24 is preferably electrically connected to the vibration plate 304 so that the distance between the flexible substrate 24 and the row of m piezoelectric elements 60a and the distance between the flexible substrate 24 and the row of m piezoelectric elements 60b are substantially equal.

[0097] An integrated circuit 201 is COF-mounted on the flexible substrate 24. The drive signal selection circuit 200 is mounted on the integrated circuit 201. That is, the integrated circuit 201 outputs corresponding drive voltage signals Vin to the piezoelectric elements 60a and 60b included in each of the m ejection units 600.

[0098] Specifically, the flexible substrate 24 transmits the clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, print data signal SI, drive voltage signal COM, and reference voltage signal VBS to the print head 21. The clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, print data signal SI, drive voltage signal COM, and reference voltage signal VBS transmitted by the flexible substrate 24 are input to the integrated circuit 201. Based on the input clock signal SCK, latch signal LAT, conversion signal CH, inspection timing signal TSIG, print data signal SI, and drive voltage signal COM, the integrated circuit 201 selects or deselects the signal waveform of the drive voltage signal COM, thereby generating and outputting the drive voltage signal Vin corresponding to each of the m ejection units 600.

[0099] The driving voltage signal Vin output by the integrated circuit 201 is transmitted through the flexible substrate 24 and supplied to the corresponding piezoelectric element 60a included in the ejection unit 600. This drives the piezoelectric elements 60a and 60b included in the corresponding ejection unit 600 so that they are displaced along the Z axis. The driving of the piezoelectric elements 60a and 60b causes the vibration plate 304 to displace along the Z axis. This displacement of the vibration plate 304 changes the volume of the pressure chambers CB1 and CB2. Consequently, the internal pressures of the pressure chambers CB1 and CB2 change in accordance with the volume changes of the pressure chambers CB1 and CB2.

[0100] Here, the drive voltage signal Vin is transmitted through a wiring pattern formed on the flexible substrate 24, branched at the vibration plate 304, and then supplied to the piezoelectric elements 60a and 60b, respectively. This eliminates the need for separate wiring patterns on the flexible substrate 24 for transmitting the drive voltage signal Vin to the piezoelectric element 60a and for transmitting the drive voltage signal Vin to the piezoelectric element 60b. As a result, the flexible substrate 24 can be miniaturized.

[0101] In the print head 21 configured as described above, the structure including the piezoelectric elements 60 a and 60 b , the pressure chambers CB1 and CB2 , the communication flow paths RR1 and RR2 , and the nozzles N included in the head chip 22 corresponds to the above-mentioned ejection unit 600 .

[0102] That is, the print head 21 of this embodiment includes: a pressure chamber CB1, the volume of which changes according to a driving voltage signal Vin based on a driving voltage signal COM; a pressure chamber CB2, the volume of which changes according to a driving voltage signal Vin based on a driving voltage signal COM; a nozzle N, which is connected to the pressure chamber CB1 and the pressure chamber CB2 and ejects ink; a piezoelectric element 60a, which is driven in response to a driving voltage signal Vin based on the driving voltage signal COM, so that the volume of the pressure chamber CB1 changes; and a piezoelectric element 60b, which is driven in response to a driving voltage signal Vin based on the driving voltage signal COM, so that the volume of the pressure chamber CB2 changes.

[0103] Furthermore, in the print head 21, the ink flowing out of pressure chamber CB1 in response to the decrease in its volume and the ink flowing out of pressure chamber CB2 in response to the decrease in its volume merge on the -Z side of the nozzle N. The ink that merges on the -Z side of the nozzle N is then ejected from the nozzle N. Therefore, the print head 21 of this embodiment can achieve improved drive capability compared to a structure in which a single piezoelectric element ejects ink filling a single pressure chamber. As a result, the print head 21 of this embodiment can increase the amount of ink ejected and achieve stable ejection characteristics even when using high-viscosity ink.

[0104] Here, in the following description, it is assumed that when the voltage value of the drive voltage signal Vin input to the print head 21 decreases, the center portions of the corresponding piezoelectric elements 60a and 60b are displaced along the Z-axis toward the -Z side, and when the voltage value of the drive voltage signal Vin input to the print head 21 increases, the center portions of the corresponding piezoelectric elements 60a and 60b are displaced along the Z-axis toward the +Z side. It should be noted that the relationship between the voltage value of the drive voltage signal Vin and the displacement of the piezoelectric elements 60a and 60b is not limited to this. It can also be configured such that when the voltage value of the drive voltage signal Vin input to the print head 21 decreases, the center portions of the corresponding piezoelectric elements 60a and 60b are displaced along the Z-axis toward the +Z side, and when the voltage value of the drive voltage signal Vin input to the print head 21 increases, the center portions of the corresponding piezoelectric elements 60a and 60b are displaced along the Z-axis toward the -Z side.

[0105] 3. Structure and operation of the drive signal selection circuit

[0106] 3.1 Signal waveform of driving voltage signal COM

[0107] Next, the structure and operation of the drive signal selection circuit 200, which outputs the drive voltage signal Vin corresponding to each of the m ejection units 600 by selecting or deselecting the signal waveform included in the drive voltage signal COM, will be described. The details of the drive signal selection circuit 200 will be described first with an example of the signal waveforms of the drive voltage signal COM, latch signal LAT, conversion signal CH, and test timing signal TSIG input to the drive signal selection circuit 200. Figure 5 1 is a diagram showing an example of signal waveforms of the drive voltage signal COM, the latch signal LAT, the conversion signal CH, and the test timing signal TSIG.

[0108] The control circuit 100 outputs a pulse signal as a latch signal LAT, whose logic level remains high for a predetermined period, at a timing corresponding to the transport position of the medium P. In the following description, the pulse signal output by the control circuit 100 as the latch signal LAT is referred to as a latch pulse. During the period in which the control circuit 100 outputs the latch pulse as the latch signal LAT, a desired dot is formed on the medium P. This period is the period in which the logic level of the latch signal LAT remains high for a predetermined period. In the following description, the period in which the logic level of the latch signal LAT remains high and the control circuit 100 outputs the latch pulse as the latch signal LAT is referred to as the dot formation period Cp. It should be noted that if the liquid ejection device 1 is a serial inkjet printer, the control circuit 100 may output the latch pulse as the latch signal LAT at a timing corresponding to the scanning position of the print head that ejects ink, in addition to the transport position of the medium P.

[0109] The driving voltage signal COM includes a driving voltage signal ComA and a driving voltage signal ComB. The driving voltage signal ComA includes a driving waveform Adp1 and a driving waveform Adp2 in the dot formation period Cp. The driving waveform Adp1 is a signal waveform that starts when the voltage value is voltage vc, changes in the voltage value so as to drive the piezoelectric elements 60a and 60b, and ends when the voltage value is voltage vc. When the driving waveform Adp1 is supplied to the piezoelectric elements 60a and 60b, a specified amount of ink is ejected from the nozzle N of the corresponding ejection unit 600. The driving waveform Adp2 is a signal waveform that starts when the voltage value is voltage vc, changes in the voltage value so as to drive the piezoelectric elements 60a and 60b, and ends when the voltage value is voltage vc. When the driving waveform Adp2 is supplied to the piezoelectric elements 60a and 60b, less ink than the specified amount is ejected from the nozzle N of the corresponding ejection unit 600.

[0110] That is, the driving voltage signal ComA includes a signal waveform for causing ink to be ejected from the nozzles N included in the ejection unit 600. Here, in the following description, when the driving waveform Adp1 is supplied to the piezoelectric elements 60a and 60b, a predetermined amount of ink ejected from the corresponding nozzles N is sometimes referred to as a medium amount, and when the driving waveform Adp2 is supplied to the piezoelectric elements 60a and 60b, an amount of ink ejected from the corresponding nozzles N that is less than the predetermined amount is sometimes referred to as a small amount.

[0111] The drive voltage signal ComB includes a drive waveform Bdp1 and a drive waveform Bdp2 during the dot formation period Cp. The drive waveform Bdp1 is a signal waveform that begins at a voltage value of voltage vc, changes in voltage value so that the piezoelectric elements 60a and 60b are driven to such an extent that ink is not ejected from the corresponding nozzle N, and then ends at a voltage value of voltage vc. When this drive waveform Bdp1 is supplied to one end of the piezoelectric elements 60a and 60b, the ink near the nozzle N vibrates to such an extent that ink is not ejected from the nozzle N included in the corresponding ejection unit 600. This alleviates concerns about increased viscosity of the ink near the opening of the nozzle N of the ejection unit 600. The drive waveform Bdp2 is a signal waveform whose voltage value is constant at voltage vc. When this drive waveform Bdp2 is supplied to one end of the piezoelectric elements 60a and 60b, the piezoelectric elements 60a and 60b are not driven, and therefore, ink is not ejected from the corresponding ejection unit 600.

[0112] That is, the driving voltage signal ComB includes a signal waveform for preventing an increase in ink viscosity by vibrating the ink near the nozzle N included in the ejection unit 600, preventing the ink from being ejected from the nozzle N. In the following description, the action of preventing an increase in ink viscosity by vibrating the ink near the opening of the nozzle N of the ejection unit 600 may be referred to as microvibration.

[0113] The control circuit 100 outputs a pulse signal whose logic level is high for a certain period as the conversion signal CH when the signal waveform included in the drive voltage signal ComA switches from the drive waveform Adp1 to the drive waveform Adp2 and when the signal waveform included in the drive voltage signal ComB switches from the drive waveform Bdp1 to the drive waveform Bdp2. In the following description, the pulse signal output by the control circuit 100 as the conversion signal CH is referred to as a conversion pulse.

[0114] Specifically, the control circuit 100 outputs a conversion pulse as the conversion signal CH between the period during which the voltage value of the driving waveform Adp1 changes so as to drive the piezoelectric elements 60a, 60b and the period during which the voltage value of the driving waveform Adp2 changes so as to drive the piezoelectric elements 60a, 60b, and after the period during which the voltage value of the driving waveform Adp2 changes so as to drive the piezoelectric elements 60a, 60b has passed. In the following description, the period from the output of the latch pulse as the latch signal LAT to the output of the conversion pulse as the conversion signal CH in the dot formation period Cp is referred to as the driving period Pp1, and the period from the output of the conversion pulse as the conversion signal CH to the output of the latch pulse as the latch signal LAT is referred to as the driving period Pp2. That is, the conversion signal CH divides the dot formation period Cp into a driving period Pp1 and a driving period Pp2, wherein the driving period Pp1 is configured with a driving waveform Adp1 included in the driving voltage signal ComA and a driving waveform Bdp1 included in the driving voltage signal ComB, and the driving period Pp2 is configured with a driving waveform Adp2 included in the driving voltage signal ComA and a driving waveform Bdp2 included in the driving voltage signal ComB.

[0115] In this embodiment, the control circuit 100 is described as outputting a single conversion signal CH corresponding to both the drive voltage signal ComA and the drive voltage signal ComB. However, the control circuit 100 may separately output the conversion signal CH corresponding to the drive voltage signal ComA and the conversion signal CH corresponding to the drive voltage signal ComB. Furthermore, the control circuit 100 may output two or more conversion pulses as the conversion signal CH during the dot formation period Cp, depending on the number of signal waveforms included in the drive voltage signals ComA and ComB.

[0116] Based on the residual vibration generated in the ejection unit 600, the control circuit 100 outputs a pulse signal whose logic level is high for a certain period of time as a check timing signal TSIG that specifies the timing for checking whether the ejection state of ink ejected from the ejection module 20 including the ejection unit 600 is normal. In the following description, the pulse signal output by the control circuit 100 as the check timing signal TSIG is referred to as a check pulse.

[0117] Specifically, after the control circuit 100 inputs a latch pulse as the latch signal LAT, the voltage value of the driving voltage signal ComB changes, and then, at a predetermined timing, outputs a check pulse as the check timing signal TSIG. Furthermore, after the control circuit 100 outputs a check pulse as the check timing signal TSIG at a predetermined timing after the voltage value of the driving voltage signal ComB changes, the control circuit 100 outputs a check pulse as the check timing signal TSIG again after a predetermined period. In the following description, the period from the output of the latch pulse as the latch signal LAT to the output of the check pulse as the check timing signal TSIG in the dot formation period Cp is referred to as the check period Ps1, the period from the output of the check pulse as the check timing signal TSIG that specifies the end of the check period Ps1 to the next output of the check pulse as the check timing signal TSIG is referred to as the check period Ps2, and the period from the output of the check pulse as the check timing signal TSIG that specifies the end of the check period Ps2 to the next output of the latch pulse as the latch signal LAT is referred to as the check period Ps3. That is, the inspection timing signal TSIG divides the dot formation period Cp into inspection periods Ps1, Ps2, and Ps3. Therefore, the control circuit 100 checks whether the ink ejection state from the ejection module 20 including the ejection unit 600 is normal based on the residual vibration generated in the ejection unit 600 during the inspection period Ps2.

[0118] That is, the driving circuit 50 outputs a driving voltage signal COM including a driving voltage signal ComA and a driving voltage signal ComB to the driving signal selection circuit 200, wherein the driving voltage signal ComA includes driving waveforms Adp1 and Adp2, and the driving voltage signal ComB includes driving waveforms Bdp1 and Bdp2. The driving signal selection circuit 200 selects or deselects the driving waveforms Adp1 and Adp2 and the driving waveforms Bdp1 and Bdp2 during the driving periods Pp1 and Pp2, respectively, thereby generating a driving voltage signal Vin and supplying it to one end of the piezoelectric elements 60a and 60b of the corresponding ejection portion 600.

[0119] Furthermore, during the inspection period Ps2, the drive signal selection circuit 200 acquires a residual vibration signal Vout corresponding to the residual vibration generated in the ejection unit 600 and outputs it as a residual vibration detection signal NVT. The waveform information output circuit 300 then acquires waveform information of the residual vibration detection signal NVT and outputs a waveform information signal WFS including the acquired waveform information to the control circuit 100. Based on the input waveform information signal WFS, the control circuit 100 then checks whether the ink ejection status of the corresponding ejection unit 600 and the ejection module 20 including the ejection unit 600 is normal.

[0120] It should be pointed out that Figure 5 The signal waveform of the driving voltage signal COM shown is an example. The driving circuit 50 may also output a driving voltage signal COM including a signal waveform of various shapes corresponding to the type of ink ejected, the type of medium P on which the ink lands, etc. In addition, the driving circuit 50 may also generate a driving voltage signal COM including a signal waveform corresponding to each of the print heads 21-1 to 21-n, and output it to the corresponding print heads 21-1 to 21-n. In addition, the timing of the control circuit 100 outputting the conversion pulse as the conversion signal CH and the timing of outputting the check pulse as the check timing signal TSIG are not limited to Figure 5 An example is shown.

[0121] 3.2 Structure of the drive signal selection circuit

[0122] A specific example of the configuration of the drive signal selection circuit 200 will be described. Figure 6 2 is a diagram showing an example of the functional structure of the drive signal selection circuit 200. Figure 6 1 and 2 also illustrate m ejection units 600, ie, ejection units 600-1 to 600-m, driven by the driving voltage signal Vin output by the driving signal selection circuit 200. Figure 6 As shown, the driving signal selection circuit 200 includes a selection control circuit 220 , m selection circuits 230 , and m residual vibration detection circuits 240 .

[0123] The selection control circuit 220 receives inputs of the clock signal SCK, the print data signal SI, the latch signal LAT, the conversion signal CH, and the inspection timing signal TSIG. Based on the inputs of the clock signal SCK, the print data signal SI, the latch signal LAT, the conversion signal CH, and the inspection timing signal TSIG, the selection control circuit 220 generates selection signals Sa and Sb at predetermined logic levels during the drive periods Pp1 and Pp2, respectively, and outputs them to the corresponding selection circuits 230. Furthermore, the selection control circuit 220 generates inspection enable signals OE at predetermined logic levels during the inspection periods Ps1, Ps2, and Ps3, respectively, and outputs them to the corresponding residual vibration detection circuits 240.

[0124] The selection control circuit 220 includes a set of shift registers 222, latch circuits 224, and decoders 226 provided corresponding to the ejection units 600-1 to 600-m of the print head 21. In other words, the selection control circuit 220 includes at least m sets of shift registers 222, latch circuits 224, and decoders 226.

[0125] The print data signal SI includes three bits of print data SId [SIH, SIM, SIL] serially corresponding to each of the M ejection units 600. The three bits of print data SId [SIH, SIM, SIL] are used to select which of the large dot LD, medium dot MD, small dot SD, and non-recording ND to form on the medium P, or to perform a status check CD to check the ejection status of the ink ejected from the ejection unit 600. That is, the print data signal SI is a serial signal of at least 3m bits.

[0126] The print data signal SI is input to the selection control circuit 220 in synchronization with the clock signal SCK. The m shift registers 222 of the selection control circuit 220 hold 3-bit print data SId [SIH, SIM, SIL] included in the input print data signal SI, corresponding to the ejection units 600-1 to 600-m.

[0127] Specifically, m shift registers 222 are cascade-connected, corresponding to each of the ejection units 600-1 to 600-m. The print data signal SI, serially input to the selection control circuit 220, is transferred sequentially to the subsequent stages of the m cascade-connected shift registers 222 in synchronization with the clock signal SCK. Then, by stopping the supply of the clock signal SCK to the selection control circuit 220, the m shift registers 222 retain the 3-bit print data SId [SIH, SIM, SIL] corresponding to the ejection units 600-1 to 600-m. It should be noted that in the following description, to distinguish the m cascade-connected shift registers 222, they may be referred to as stage 1, stage 2, ..., and stage m, starting from the upstream side of the supply of the print data signal SI toward the downstream side.

[0128] Each of the m latch circuits 224 collectively latches the 3-bit print data [SIH, SIM, SIL] held by the corresponding shift register 222 when a latch pulse serving as the latch signal LAT is input.

[0129] The print data SId [SIH, SIM, SIL] latched by the m latch circuits 224 is input to the corresponding decoder 226. Each of the m decoders 226 decodes the input print data SId [SIH, SIM, SIL], generates selection signals Sa and Sb of logic levels corresponding to large dots LD, medium dots MD, small dots SD, and non-recording ND, and outputs them to the corresponding selection circuit 230. Furthermore, the decoder 226 generates a check enable signal OE of logic level corresponding to the status check CD and outputs it to the corresponding residual vibration detection circuit 240.

[0130] Figure 7 2 is a diagram showing an example of the decoding content in the decoder 226. Figure 7As shown, when the decoder 226 is input with the printing data SId[SIH, SIM, SIL]=[1, 1, 0] corresponding to the large dot LD, the logic level of the selection signal Sa is set to the H, H level in the driving period Pp1, Pp2, the logic level of the selection signal Sb is set to the L, L level in the driving period Pp1, Pp2, and the logic level of the inspection enable signal OE is set to the L, L, L level in the inspection period Ps1, Ps2, Ps3.

[0131] In addition, when the decoder 226 is input with the printing data SId[SIH, SIM, SIL]=[1, 0, 0] corresponding to the midpoint MD, the logic level of the selection signal Sa is set to the H, L levels during the driving periods Pp1 and Pp2, the logic level of the selection signal Sb is set to the L, L levels during the driving periods Pp1 and Pp2, and the logic level of the inspection enable signal OE is set to the L, L, L levels during the inspection periods Ps1, Ps2, and Ps3.

[0132] In addition, when the decoder 226 is input with the printing data SId[SIH, SIM, SIL]=[0, 1, 0] corresponding to the small dot SD, the logic level of the selection signal Sa is set to L, H levels during the driving periods Pp1 and Pp2, the logic level of the selection signal Sb is set to L, L levels during the driving periods Pp1 and Pp2, and the logic level of the inspection enable signal OE is set to L, L, L levels during the inspection periods Ps1, Ps2, and Ps3.

[0133] In addition, when the decoder 226 is input with the printing data SId[SIH, SIM, SIL]=[0, 0, 0] corresponding to non-recording ND, the logic level of the selection signal Sa is set to L, L level in the driving period Pp1, Pp2, the logic level of the selection signal Sb is set to H, H level in the driving period Pp1, Pp2, and the logic level of the inspection enable signal OE is set to L, L, L level in the inspection period Ps1, Ps2, Ps3.

[0134] In addition, when the decoder 226 is input with the printing data SId[SIH, SIM, SIL]=[1, 1, 1] corresponding to the status check CD, the logic level of the selection signal Sa is set to L, L level in the driving period Pp1, Pp2, the logic level of the selection signal Sb is set to H, H level in the driving period Pp1, Pp2, and the logic level of the inspection enable signal OE is set to L, H, L level in the inspection period Ps1, Ps2, Ps3.

[0135] As described above, the selection control circuit 220 generates the selection signals Sa and Sb and the inspection enable signal OE at the logic levels corresponding to the m ejection units 600 based on the logic levels of the print data SId [SIH, SIM, SIL]. The selection control circuit 220 then outputs the generated selection signals Sa and Sb at the logic levels to the corresponding selection circuit 230 and outputs the generated inspection enable signal OE at the logic level to the corresponding residual vibration detection circuit 240.

[0136] The selection circuits 230 are provided corresponding to each of the ejection units 600-1 to 600-m. That is, the drive signal selection circuit 200 includes m selection circuits 230. Each of the m selection circuits 230 receives drive voltage signals ComA and ComB as the drive voltage signal COM. Each of the m selection circuits 230 then generates a drive voltage signal Vin corresponding to the drive voltage signal COM based on the logic levels of the input selection signals Sa and Sb, and outputs the signal to the corresponding ejection unit 600. Figure 8 1 is a diagram showing the configuration of the selection circuit 230 corresponding to one of the ejection units 600-1 to 600-m. Figure 8 As shown, the selection circuit 230 has logic inversion circuits 232a, 232b and transmission gates 234a, 234b.

[0137] The select signal Sa is supplied to the positive control terminal of transmission gate 234a and, after its logic level is inverted by logic inversion circuit 232a, is also supplied to the negative control terminal of transmission gate 234a. Thus, when the logic level of select signal Sa is high, conduction occurs between one end of transmission gate 234a and the other end. When the logic level of select signal Sa is low, conduction occurs between one end of transmission gate 234a and the other end. Furthermore, drive voltage signal ComA is supplied to one end of transmission gate 234a. Thus, transmission gate 234a selects or deselects the signal waveform of drive voltage signal ComA input to one end based on the logic level of select signal Sa, and outputs the signal waveform from the other end.

[0138] The select signal Sb is supplied to the positive control terminal of transmission gate 234b and, after its logic level is inverted by logic inversion circuit 232b, is also supplied to the negative control terminal of transmission gate 234b. Thus, when the logic level of select signal Sb is high, one end of transmission gate 234b is conductive to the other end. When the logic level of select signal Sb is low, one end of transmission gate 234b is non-conductive. Furthermore, drive voltage signal ComB is supplied to one end of transmission gate 234b. Thus, transmission gate 234b selects or deselects the drive voltage signal ComB input to one end based on the logic level of select signal Sb, and outputs the signal waveform from the other end.

[0139] In the selection circuit 230, the other end of the transmission gate 234a and the other end of the transmission gate 234b are interconnected. The other ends of the interconnected transmission gates 234a and 234b are electrically connected to the corresponding piezoelectric elements 60a and 60b included in the ejection unit 600. Thus, the selection circuit 230 supplies the signal obtained by the transmission gate 234a selecting or not selecting the signal waveform of the drive voltage signal ComA and the signal obtained by the transmission gate 234b selecting or not selecting the signal waveform of the drive voltage signal ComB as the drive voltage signal Vin to the corresponding piezoelectric elements 60a and 60b included in the ejection unit 600.

[0140] Furthermore, the selection circuit 230 receives input of a residual vibration signal Vout. This residual vibration signal Vout is generated by driving the piezoelectric elements 60a and 60b included in the corresponding ejection unit 600 after the driving voltage signal Vin is supplied to the piezoelectric elements 60a and 60b, based on the residual vibration generated in the ejection unit 600. Specifically, the other ends of the transmission gates 234a and 234b receive the residual vibration signal Vout corresponding to the residual vibration generated in the piezoelectric elements 60a and 60b.

[0141] The selection circuit 230 outputs the voltage value of one end of the transmission gate 234b, that is, the voltage value of the driving voltage signal ComB supplied to one end of the transmission gate 234b, as the residual vibration reference signal Vo1 to the corresponding residual vibration detection circuit 240, and outputs the voltage value of the other end of the transmission gate 234b, that is, the voltage value of the residual vibration signal Vout supplied to the other end of the transmission gate 234b, as the residual vibration detection signal Vo2 to the corresponding residual vibration detection circuit 240.

[0142] Here, in the following description, conduction between one end and the other end of the transmission gates 234a and 234b may be referred to as “ON”, and non-conduction between one end and the other end of the transmission gates 234a and 234b may be referred to as “OFF”.

[0143] Furthermore, in transmission gates 234a and 234b, one or more N-channel MOS (Metal Oxide Semiconductor) transistors and one or more P-channel MOS transistors are complementarily connected. In other words, transmission gates 234a and 234b include transistor elements. At least some of the transistor elements included in transmission gates 234a and 234b are driven in the linear region while transmission gates 234a and 234b are on.

[0144] The residual vibration detection circuits 240 are provided to correspond to m selection circuits 230, each corresponding to one of the ejection units 600-1 to 600-m. That is, the drive signal selection circuit 200 includes m residual vibration detection circuits 240. Each of the m residual vibration detection circuits 240 receives as input the residual vibration reference signal Vo1 and the residual vibration detection signal Vo2 output by the corresponding selection circuit 230. Based on the waveforms of the input residual vibration reference signal Vo1 and the residual vibration detection signal Vo2, each of the m residual vibration detection circuits 240 generates and outputs a residual vibration detection signal NVT corresponding to the residual vibration generated in the corresponding ejection unit 600.

[0145] Figure 9 : is a diagram showing an example of the configuration of the residual vibration detection circuit 240. The residual vibration detection circuit 240 includes capacitors C1 and C2, resistors R1, R2, R3, R4, R5, and R6, switches SW1 and SW2, and an amplifier circuit OP1.

[0146] The residual vibration reference signal Vo1 is input to one end of the capacitor C1. The other end of the capacitor C1 is electrically connected to one end of the resistor R1. In addition, the other end of the resistor R1 is supplied with a ground potential. That is, the capacitor C1 and the resistor R1 constitute a high-pass filter circuit. As the output of the high-pass filter circuit constituted by the capacitor C1 and the resistor R1, the other end of the capacitor C1 and one end of the resistor R1 are electrically connected to one end of the resistor R2. The other end of the resistor R2 is electrically connected to one end of the resistor R3 and is electrically connected to the negative input terminal of the amplifier circuit OP1. The other end of the resistor R3 is electrically connected to the output terminal of the amplifier circuit OP1.

[0147] The residual vibration detection signal Vo2 is input to one end of the capacitor C2. The other end of the capacitor C2 is electrically connected to one end of the resistor R4. In addition, the other end of the resistor R4 is supplied with a ground potential. That is, the capacitor C2 and the resistor R4 constitute a high-pass filter circuit. As the output of the high-pass filter circuit composed of the capacitor C2 and the resistor R4, the other end of the capacitor C2 and one end of the resistor R4 are electrically connected to one end of the resistor R5. The other end of the resistor R5 is electrically connected to one end of the resistor R6 and is electrically connected to the + side input terminal of the amplifier circuit OP1. The other end of the resistor R6 is electrically connected to the + terminal of the power supply circuit PW1, and the - terminal of the power supply circuit PW1 is supplied with a ground potential.

[0148] In residual vibration detection circuit 240 configured as described above, a signal obtained by reducing the DC component included in residual vibration reference signal Vo1 via a high-pass filter circuit formed by capacitor C1 and resistor R1 is input to the negative input terminal of amplifier circuit OP1. A signal obtained by superimposing bias voltage signal VB output by power supply circuit PW1 on a signal obtained by reducing the DC component included in residual vibration detection signal Vo2 via a high-pass filter circuit formed by capacitor C2 and resistor R4 is input to the positive input terminal of amplifier circuit OP1. Consequently, amplifier circuit OP1 outputs a residual vibration detection signal NVT by adding a signal obtained by amplifying the difference between the signal input to the negative input terminal and the signal input to the positive input terminal at an amplification factor determined by the resistance values ​​of resistors R3 and R2, and the voltage value of bias voltage signal VB, i.e., voltage vb.

[0149] As the residual vibration signal Vout is generated by the displacement of the piezoelectric elements 60a and 60b due to the residual vibration generated in the ejection unit 600, the charge generated by the displacement of the piezoelectric elements 60a and 60b due to the residual vibration is transmitted through the transmission gate 234b to the wiring to which the drive voltage signal ComB is applied. At this time, the current signal generated by the movement of the charge accompanying the residual vibration is converted into a voltage signal by the on-resistance of the transmission gate 234b. In other words, a potential difference corresponding to the residual vibration generated in the corresponding ejection unit 600, i.e., a potential difference corresponding to the residual vibration signal Vout output by the corresponding ejection unit 600, is generated between one end and the other end of the transmission gate 234b.

[0150] The selection circuit 230 outputs the voltage value at one end of the transmission gate 234b as the residual vibration reference signal Vo1, and outputs the voltage value at the other end of the transmission gate 234b as the residual vibration detection signal Vo2. The residual vibration detection circuit 240 differentially amplifies the residual vibration reference signal Vo1 and the residual vibration detection signal Vo2, thereby generating a signal obtained by amplifying the potential difference based on the residual vibration generated at both ends of the transmission gate 234b, and generating a residual vibration detection signal NVT which is an amplified signal of the residual vibration signal Vout to be output from the corresponding ejection portion 600, and outputs the signal to the control circuit 100.

[0151] Switch SW1 has one end electrically connected to the other end of capacitor C1 and one end of resistor R1, while its other end is supplied with ground potential. A signal obtained by inverting the logic level of the test enable signal OE via logic inversion circuit INV1 is input to its control end. Consequently, the switch SW1 becomes non-conductive when a low-level signal is input to the control end, and conductive when a high-level signal is input to the control end. That is, when a high-level test enable signal OE is input to residual oscillation detection circuit 240, the switch SW1 becomes non-conductive between one end and the other end. When a low-level test enable signal OE is input to residual oscillation detection circuit 240, the switch SW1 becomes conductive between one end and the other end.

[0152] Switch SW2 has one end electrically connected to the other end of capacitor C2 and one end of resistor R4, while its other end is supplied with ground potential. A signal obtained by inverting the logic level of the test enable signal OE via logic inversion circuit INV1 is input to its control end. Consequently, switch SW2 becomes non-conductive when a low-level signal is input to the control end, and conductive when a high-level signal is input to the control end. That is, when a high-level test enable signal OE is input to residual oscillation detection circuit 240, switch SW2 becomes non-conductive between one end and the other end. When a low-level test enable signal OE is input to residual oscillation detection circuit 240, switch SW2 becomes conductive between one end and the other end.

[0153] Such switches SW1 and SW2 are configured by including N-channel MOS transistors.

[0154] When a low-level check enable signal OE is input to residual vibration detection circuit 240 configured as described above, one end of switch SW1 is conductively connected to the other end, preventing residual vibration reference signal Vo1 from being supplied to the negative input terminal of amplifier circuit OP1. Meanwhile, one end of switch SW2 is conductively connected to the other end, preventing residual vibration detection signal Vo2 from being supplied to the positive input terminal of amplifier circuit OP1. Consequently, residual vibration detection circuit 240 does not generate residual vibration detection signal NVT, which is amplified from residual vibration signal Vout output from the corresponding ejection unit 600.

[0155] On the other hand, when a high-level check enable signal OE is input to residual vibration detection circuit 240, one end of switch SW1 becomes non-conductive with the other end, thereby supplying residual vibration reference signal Vo1 to the negative input terminal of amplifier circuit OP1. Meanwhile, one end of switch SW2 becomes non-conductive with the other end, thereby supplying residual vibration detection signal Vo2 to the positive input terminal of amplifier circuit OP1. Consequently, residual vibration detection circuit 240 generates residual vibration detection signal NVT, which is amplified from residual vibration signal Vout output from the corresponding ejection unit 600, and outputs it to control circuit 100.

[0156] Specifically, while the high-level inspection enable signal OE is input, the residual vibration detection circuit 240 acquires the residual vibration signal Vout output from the corresponding ejection unit 600 and outputs a residual vibration detection signal NVT corresponding to the acquired residual vibration signal Vout to the control circuit 100. In other words, the residual vibration detection circuit 240 generates and outputs the residual vibration detection signal NVT by shaping the signal waveform of the residual vibration signal Vout by reducing the DC component using a high-pass filter circuit and performing amplification.

[0157] Here, in the following description, conduction between one end and the other end of the switches SW1 and SW2 may be referred to as “ON”, and non-conduction between one end and the other end of the switches SW1 and SW2 may be referred to as “OFF”.

[0158] The operation of the driving signal selection circuit 200 configured as described above will be described in detail. Figure 10 This diagram illustrates an example of the operation of the drive signal selection circuit 200. The print data signal SI is serially supplied to the drive signal selection circuit 200 in synchronization with the clock signal SCK. The print data signal SI input to the drive signal selection circuit 200 is sequentially transferred to the subsequent shift register 222 in synchronization with the clock signal SCK. Then, by stopping the supply of the clock signal SCK to the drive signal selection circuit 200, each of the m shift registers 222 holds 3-bit print data SId [SIH, SIM, SIL] corresponding to the m ejection units 600.

[0159] Then, when the latch signal LAT rises, the latch circuits 224 latch the print data SId [SIH, SIM, SIL] held in the shift register 222. Figure 10 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 .

[0160] Decoder 226 presses Figure 7 The decoder 226 decodes the latched print data SId[SIH, SIM, SIL]. Then, the decoder 226 outputs the Figure 7 The logic levels of the selection signals Sa, Sb and the inspection enable signal OE are shown.

[0161] Specifically, when the printing data SId[SIH, SIM, SIL] = [1, 1, 0], the decoder 226 sets the logic level of the selection signal Sa to H, H levels during the driving periods Pp1 and Pp2, sets the logic level of the selection signal Sb to L, L levels during the driving periods Pp1 and Pp2, and sets the logic level of the inspection enable signal OE to L, L, L levels during the inspection periods Ps1, Ps2, and Ps3.

[0162] The selection signals Sa and Sb output by the decoder 226 are input to the selection circuit 230. As a result, the selection circuit 230 selects the drive waveform Adp1 of the drive voltage signal ComA in the drive period Pp1 and the drive waveform Adp2 of the drive voltage signal ComA in the drive period Pp2. As a result, the drive signal selection circuit 200 outputs the same waveform as the one in the dot formation period Cp. Figure 10 The driving voltage signal Vin corresponding to the large dot LD is shown. When the driving voltage signal Vin corresponding to the large dot LD is supplied to the ejection unit 600, a medium amount of ink is ejected from the ejection unit 600 during the driving period Pp1, and a small amount of ink is ejected during the driving period Pp2. Consequently, during the dot formation period Cp, the medium amount of ink and the small amount of ink ejected from the ejection unit 600 land on the medium P and combine. Thus, during the dot formation period Cp, a large dot LD is formed on the medium P.

[0163] Furthermore, the inspection enable signal OE output by the decoder 226 is input to the residual vibration detection circuit 240. Consequently, the switches SW1 and SW2 included in the residual vibration detection circuit 240 are controlled to be on during the inspection periods Ps1, Ps2, and Ps3. Consequently, the residual vibration detection circuit 240 outputs a signal having a constant voltage value of voltage vb, independent of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. Specifically, when the print data SId[SIH, SIM, SIL] = [1, 1, 0], the residual vibration detection circuit 240 does not acquire the residual vibration signal Vout corresponding to the residual vibration generated in the corresponding ejection unit 600, and does not output the residual vibration detection signal NVT corresponding to the residual vibration signal Vout.

[0164] In addition, when the printing data SId[SIH, SIM, SIL] = [1, 0, 0], the decoder 226 sets the logic level of the selection signal Sa to H, L levels during the driving periods Pp1 and Pp2, sets the logic level of the selection signal Sb to L, L levels during the driving periods Pp1 and Pp2, and sets the logic level of the inspection enable signal OE to L, L, L levels during the inspection periods Ps1, Ps2, and Ps3.

[0165] The selection signals Sa and Sb output by the decoder 226 are input to the selection circuit 230. Thus, the selection circuit 230 selects the drive waveform Adp1 of the drive voltage signal ComA during the drive period Pp1 and does not select any signal waveform during the drive period Pp2. As a result, the drive signal selection circuit 200 outputs the same signal waveform as the one in the dot formation period Cp. Figure 10 The driving voltage signal Vin corresponding to the midpoint MD shown in FIG. When the driving voltage signal Vin corresponding to the midpoint MD is supplied to the ejection unit 600, a moderate amount of ink is ejected from the ejection unit 600 during the driving period Pp1, and no ink is ejected during the driving period Pp2. That is, during the dot formation period Cp, the moderate amount of ink ejected from the ejection unit 600 lands on the medium P. Thus, during the dot formation period Cp, the midpoint MD is formed on the medium P.

[0166] Furthermore, the inspection enable signal OE output by the decoder 226 is input to the residual vibration detection circuit 240. Consequently, the switches SW1 and SW2 included in the residual vibration detection circuit 240 are controlled to be on during the inspection periods Ps1, Ps2, and Ps3. Consequently, the residual vibration detection circuit 240 outputs a signal having a constant voltage value of voltage vb, independent of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. Specifically, when the print data SId[SIH, SIM, SIL] = [1, 0, 0], the residual vibration detection circuit 240 does not acquire the residual vibration signal Vout corresponding to the residual vibration generated in the corresponding ejection unit 600, and does not output the residual vibration detection signal NVT corresponding to the residual vibration signal Vout.

[0167] In addition, when the printing data SId[SIH, SIM, SIL] = [0, 1, 0], the decoder 226 sets the logic level of the selection signal Sa to L, H levels during the driving periods Pp1 and Pp2, sets the logic level of the selection signal Sb to L, L levels during the driving periods Pp1 and Pp2, and sets the logic level of the inspection enable signal OE to L, L, L levels during the inspection periods Ps1, Ps2, and Ps3.

[0168] The selection signals Sa and Sb output by the decoder 226 are input to the selection circuit 230. As a result, the selection circuit 230 does not select any signal waveform in the driving period Pp1, and selects the driving waveform Adp2 of the driving voltage signal ComA in the driving period Pp2. As a result, the driving signal selection circuit 200 outputs the same waveform as that in the dot formation period Cp. Figure 10 The driving voltage signal Vin corresponding to the small dot SD shown in FIG. When the driving voltage signal Vin corresponding to the small dot SD is supplied to the ejection unit 600, no ink is ejected from the ejection unit 600 during the driving period Pp1, and a small amount of ink is ejected during the driving period Pp2. That is, during the dot formation period Cp, the small amount of ink ejected from the ejection unit 600 lands on the medium P. Thus, during the dot formation period Cp, the small dot SD is formed on the medium P.

[0169] Furthermore, the inspection enable signal OE output by the decoder 226 is input to the residual vibration detection circuit 240. Consequently, the switches SW1 and SW2 included in the residual vibration detection circuit 240 are controlled to be on during the inspection periods Ps1, Ps2, and Ps3. Consequently, the residual vibration detection circuit 240 outputs a signal having a constant voltage value of voltage vb, independent of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. Specifically, when the print data SId[SIH, SIM, SIL] = [0, 1, 0], the residual vibration detection circuit 240 does not acquire the residual vibration signal Vout corresponding to the residual vibration generated in the corresponding ejection unit 600, and does not output the residual vibration detection signal NVT corresponding to the residual vibration signal Vout.

[0170] In addition, 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 driving period Pp1, Pp2, sets the logic level of the selection signal Sb to H, H level in the driving period Pp1, Pp2, and sets the logic level of the inspection enable signal OE to L, L, L level in the inspection period Ps1, Ps2, Ps3.

[0171] The selection signals Sa and Sb output by the decoder 226 are input to the selection circuit 230. Thus, the selection circuit 230 selects the driving waveform Bdp1 of the driving voltage signal ComB in the driving period Pp1 and the driving waveform Bdp2 of the driving voltage signal ComB in the driving period Pp2. As a result, the driving signal selection circuit 200 outputs the same waveform as that in the dot formation period Cp. Figure 10The driving voltage signal Vin corresponding to the non-recording ND is shown. When the driving voltage signal Vin corresponding to the non-recording ND is supplied to the ejection unit 600, ink is not ejected from the ejection unit 600 during the dot formation period Cp, and no dots are formed on the medium P. At this time, micro-vibration is performed in the corresponding ejection unit 600.

[0172] Furthermore, the inspection enable signal OE output by the decoder 226 is input to the residual vibration detection circuit 240. Consequently, the switches SW1 and SW2 included in the residual vibration detection circuit 240 are controlled to be on during the inspection periods Ps1, Ps2, and Ps3. Consequently, the residual vibration detection circuit 240 outputs a signal having a constant voltage value vb, independent of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. Specifically, when the print data SId[SIH, SIM, SIL] = [0, 0, 0], the residual vibration detection circuit 240 does not acquire the residual vibration signal Vout corresponding to the residual vibration generated in the corresponding ejection unit 600, and does not output the residual vibration detection signal NVT corresponding to the residual vibration signal Vout.

[0173] In addition, 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 levels in the driving periods Pp1 and Pp2, sets the logic level of the selection signal Sb to H, H levels in the driving periods Pp1 and Pp2, and sets the logic level of the inspection enable signal OE to L, H, L levels in the inspection periods Ps1, Ps2, and Ps3.

[0174] The selection signals Sa and Sb output by the decoder 226 are input to the selection circuit 230. Thus, the selection circuit 230 selects the driving waveform Bdp1 of the driving voltage signal ComB in the driving period Pp1 and the driving waveform Bdp2 of the driving voltage signal ComB in the driving period Pp2. As a result, the driving signal selection circuit 200 outputs the same waveform as that in the dot formation period Cp. Figure 10 The driving voltage signal Vin corresponding to the non-recording ND is shown. When the driving voltage signal Vin corresponding to the non-recording ND is supplied to the ejection unit 600, ink is not ejected from the ejection unit 600 during the dot formation period Cp, and no dots are formed on the medium P. At this time, micro-vibration is performed in the corresponding ejection unit 600.

[0175] Furthermore, the inspection enable signal OE output by decoder 226 is input to residual vibration detection circuit 240. Consequently, switches SW1 and SW2 of residual vibration detection circuit 240 are controlled to be on during inspection period Ps1, off during inspection period Ps2, and on during inspection period Ps3. Consequently, residual vibration detection circuit 240 outputs a signal having a constant voltage value of voltage vb during inspection period Ps1, independent of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. During inspection period Ps2, residual vibration detection circuit 240 outputs residual vibration detection signal NVT, which is a signal obtained by adding voltage vb to a differentially amplified signal of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. During inspection period Ps3, residual vibration detection circuit 240 outputs a signal having a constant voltage value of voltage vb, independent of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. In other words, when the voltage value of the drive voltage signal ComB fluctuates during inspection period Ps2 and then reaches a predetermined value, the residual vibration detection circuit 240 outputs a residual vibration detection signal NVT corresponding to the residual vibration signal Vout corresponding to the residual vibration generated in the corresponding ejection unit 600. Specifically, when the print data SId[SIH, SIM, SIL] = [1, 1, 1], the residual vibration detection circuit 240 obtains the residual vibration signal Vout corresponding to the residual vibration generated in the corresponding ejection unit 600 and outputs the residual vibration detection signal NVT corresponding to the residual vibration signal Vout.

[0176] As described above, the drive signal selection circuit 200 selects or deselects the drive waveforms Adp1 and Adp2 included in the drive voltage signal ComA and the drive waveforms Bdp1 and Bdp2 included in the drive voltage signal ComB in the drive voltage signal COM output by the drive circuit 50 based on the clock signal SCK, the printing data signal SI, the latch signal LAT and the conversion signal CH, thereby generating a drive voltage signal Vin and supplying it to the corresponding ejection unit 600. In addition, based on the clock signal SCK, the printing data signal SI, the latch signal LAT and the inspection timing signal TSIG, the residual vibration signal Vout corresponding to the residual vibration generated in the ejection unit 600 after the drive voltage signal Vin is supplied to the ejection unit 600 is obtained, and outputted to the control circuit 100 as the residual vibration detection signal NVT.

[0177] That is, the ejection unit 600 of the print head 21 of this embodiment includes a piezoelectric element 60a and a piezoelectric element 60b. The piezoelectric element 60a outputs a signal corresponding to the residual vibration generated by the volume change of the pressure chamber CB1, and the piezoelectric element 60b outputs a signal corresponding to the residual vibration generated by the volume change of the pressure chamber CB2. The drive signal selection circuit 200 of the print head 21 includes a transmission gate 234b and a residual vibration detection circuit 240. One end of the transmission gate 234b is input with the drive voltage signal ComB, and the other end is output with the drive voltage signal ComB. Electrically connected to the piezoelectric elements 60a and 60b, the transmission gate 234b switches whether the drive voltage signal ComB is supplied to the piezoelectric elements 60a and 60b. The residual vibration detection circuit 240 outputs a residual vibration detection signal NVT corresponding to the residual vibration signal Vout. This residual vibration signal Vout is a composite signal of the residual vibration generated by the volume change of the pressure chamber CB1 and the residual vibration generated by the volume change of the pressure chamber CB2, output by the piezoelectric element 60a. Furthermore, in the drive signal selection circuit 200 included in the print head 21, one end of the residual vibration detection circuit 240 is electrically connected to one end of the transmission gate 234b, and the other end is electrically connected to the other end of the transmission gate 234b.

[0178] In the print head 21 configured as described above, a potential difference is generated across the transmission gate 234b, corresponding to the residual vibration signal Vout corresponding to the charge output by the piezoelectric elements 60a and 60b in response to the residual vibration generated in the ejection unit 600 and the resistance value of the on-resistance of the transmission gate 234b. The residual vibration detection circuit 240 of this embodiment has one end electrically connected to one end of the transmission gate 234b and the other end electrically connected to the other end of the transmission gate 234b. Therefore, the potential difference across the transmission gate 234b can be detected. In other words, the residual vibration detection circuit 240 of this embodiment can detect the residual vibration signal Vout corresponding to the residual vibration generated in the ejection unit 600 while the transmission gate 234b, which switches whether or not to supply the drive voltage signal ComB to the ejection unit 600, remains on. In other words, during the inspection period Ps1 during which the driving voltage signal Vin corresponding to the driving voltage signal ComB is supplied to the piezoelectric elements 60a and 60b, and during the inspection period Ps2 during which the piezoelectric elements 60a and 60b output the residual vibration signal Vout corresponding to the residual vibration generated in the ejection portion 600, one end and the other end of the transmission gate 234b are controlled to be turned on.

[0179] As a result, the printhead 21 of this embodiment does not need to control the conduction states of the transmission gates 234a and 234b to a specific state for acquiring the residual vibration signal Vout generated in the ejection unit 600. In other words, the printhead 21 of this embodiment can acquire the residual vibration signal Vout generated in the ejection unit 600 without controlling the conduction states of the transmission gates 234a and 234b to a state specifically for acquiring the residual vibration signal Vout corresponding to the residual vibration generated in the ejection unit 600. In other words, the printhead 21 of this embodiment can acquire the residual vibration signal Vout generated in the ejection unit 600 while maintaining the conduction states of the transmission gates 234a and 234b in any of the following states: large dot LD, medium dot MD, small dot SD, or non-recording ND (micro-vibration). Consequently, the speed of detecting the residual vibration generated in the ejection unit 600 after the piezoelectric elements 60a and 60b are driven can be further increased.

[0180] Here, in the print head 21 of this embodiment, it is assumed that one end of the residual vibration detection circuit 240 is electrically connected to one end of the transmission gate 234b, and the other end is electrically connected to the other end of the transmission gate 234b, and when the driving waveform Bdp1 for performing micro-vibration is supplied to the corresponding ejection part 600 as the driving voltage signal Vin, the residual vibration signal Vout corresponding to the residual vibration generated in the ejection part 600 is obtained for explanation, but it is not limited to this.

[0181] For example, it may also be that one end of the residual vibration detection circuit 240 is electrically connected to one end of the transmission gate 234a, and the other end is electrically connected to the other end of the transmission gate 234a, and the control circuit 100 outputs a check pulse of the check timing signal TSIG as the start of the specified check period Ps2 when the voltage value of the driving voltage signal ComA changes and then reaches a certain timing, thereby supplying the corresponding ejection part 600 with the driving waveform Adp1 for ejecting a medium degree of ink or the driving waveform Adp2 for ejecting a small degree of ink as the driving voltage signal Vin, and obtaining the residual vibration signal Vout corresponding to the residual vibration generated in the ejection part 600.

[0182] However, as shown in this embodiment, it is preferable that, when a drive waveform Bdp1 that causes micro-vibration is supplied as the drive voltage signal Vin to the corresponding ejection unit 600, the residual vibration detection circuit 240 obtains a residual vibration signal Vout corresponding to the residual vibration generated in the ejection unit 600, and the control circuit 100 determines the ejection state of ink from the corresponding ejection unit 600 based on the residual vibration signal Vout obtained by the residual vibration detection circuit 240. In other words, when the residual vibration detection circuit 240 obtains the residual vibration signal Vout, the drive voltage signal Vin supplied to the corresponding ejection unit 600 is preferably a micro-vibration waveform that causes micro-vibration to vibrate the vicinity of the nozzle N to such an extent that ink is not ejected from the nozzle N.

[0183] The residual vibration generated in the ejection unit 600 varies depending on the state of ink stored in the pressure chambers CB1 and CB2 that constitute the printhead 21, and the state of ink flowing in the communication channels RR1 and RR2, as well as the nozzle channel RN. Details will be described later. By acquiring a residual vibration signal Vout corresponding to the residual vibration generated in the ejection unit 600 when a microvibration waveform that performs microvibration that prevents ink from being ejected from the corresponding nozzle N is supplied, the likelihood that changes in the state of ink stored in the pressure chambers CB1 and CB2, and changes in the state of ink flowing in the communication channels RR1 and RR2, as well as the nozzle channel RN, caused by ink ejection from the nozzle N, will affect the residual vibration generated in the ejection unit 600. This improves the accuracy of acquiring the residual vibration signal Vout corresponding to the residual vibration, which is acquired by the residual vibration detection circuit 240, and thus improves the accuracy of determining the ejection state of ink ejected from the ejection unit 600 based on the residual vibration signal Vout acquired by the residual vibration detection circuit 240.

[0184] In addition, in the print head 21 of the present embodiment, it is assumed that the volume of the pressure chamber CB1 is changed by driving the piezoelectric element 60a, and the volume of the pressure chamber CB2 is changed by driving the piezoelectric element 60b, and the piezoelectric element 60a outputs a signal corresponding to the residual vibration generated by the volume change of the pressure chamber CB1, and the piezoelectric element 60b outputs a signal corresponding to the residual vibration generated by the volume change of the pressure chamber CB2. However, the piezoelectric element that changes the volume of the pressure chamber CB1 and the piezoelectric element that outputs the signal corresponding to the residual vibration generated by the volume change of the pressure chamber CB1 may also be different piezoelectric elements, and the piezoelectric element that changes the volume of the pressure chamber CB2 and the piezoelectric element that outputs the signal corresponding to the residual vibration generated by the volume change of the pressure chamber CB2 may also be different piezoelectric elements.

[0185] However, as shown in the print head 21 of this embodiment, it is preferable that the piezoelectric element that changes the volume of pressure chamber CB1 and the piezoelectric element that outputs a signal corresponding to the residual vibration generated by the volume change of pressure chamber CB1 are the same piezoelectric element, and the piezoelectric element that changes the volume of pressure chamber CB2 and the piezoelectric element that outputs a signal corresponding to the residual vibration generated by the volume change of pressure chamber CB2 are the same piezoelectric element. This can reduce the number of piezoelectric elements included in the print head 21, allowing for a more compact print head 21.

[0186] That is, the print head 21 preferably has a piezoelectric element 60a and a piezoelectric element 60b, the piezoelectric element 60a outputs a signal corresponding to the residual vibration generated by the volume change of the pressure chamber CB1, and the piezoelectric element 60b outputs a signal corresponding to the residual vibration generated by the volume change of the pressure chamber CB2, the piezoelectric elements 60a and 60b are displaced according to the driving waveform Bdp1 of the driving voltage signal ComB, the volume of the pressure chamber CB1 changes according to the displacement of the piezoelectric element 60a, and the volume of the pressure chamber CB2 changes according to the displacement of the piezoelectric element 60b.

[0187] 4. Structure and operation of residual vibration output circuit

[0188] Next, the configuration and operation of the waveform information output circuit 300 that acquires waveform information of the residual vibration detection signal NVT input from the residual vibration detection circuit 240 and outputs a waveform information signal WFS including the acquired waveform information will be described. Figure 11 3 is a diagram showing an example of the structure of the waveform information output circuit 300. Figure 11 As shown, the waveform information output circuit 300 includes a reset circuit 310 , a maximum voltage value acquisition circuit 320 , a minimum voltage value acquisition circuit 330 , and a period acquisition circuit 340 .

[0189] The latch signal LAT is input to the reset circuit 310. The reset circuit 310 also outputs reset signals RST1 and RST2, whose logic levels vary according to the input latch signal LAT, and an acquisition signal AS.

[0190] The reset signal RST1 is a signal whose logic level is high at the rising edge of the latch pulse, which serves as the latch signal LAT, and then changes to a low level after a predetermined period. The acquisition signal AS is a signal whose logic level changes to high after the reset signal RST1 changes to a low level, and then changes to a low level after a predetermined period. The reset signal RST2 is a signal whose logic level changes to high after the acquisition signal AS changes to a low level, and then changes to a low level after a predetermined period. The period during which the reset signal RST1 is logic-high, the period during which the acquisition signal AS is logic-high, and the period during which the reset signal RST2 is logic-high are all included in the inspection period Ps1.

[0191] The maximum voltage value acquisition circuit 320 includes amplifier circuits OP11 and OP12 , a diode D11 , capacitors C11 and C12 , and switches SW11 , SW12 , and SW13 .

[0192] The residual vibration detection signal NVT is input to the +-side input terminal of the amplifier circuit OP11. The anode terminal of the diode D11 is electrically connected to the output terminal of the amplifier circuit OP11. The cathode terminal of the diode D11 is electrically connected to the --side input terminal of the amplifier circuit OP11. In addition, the cathode terminal of the diode D11 is electrically connected to one end of the capacitor C11, one end of the switch SW11, and one end of the switch SW12. The other end of the capacitor C11 and the other end of the switch SW11 are supplied with a ground potential. One end of the capacitor C12, one end of the switch SW13, and the +-side input terminal of the amplifier circuit OP12 are electrically connected to the other end of the switch SW12. The other end of the capacitor C12 and the other end of the switch SW13 are supplied with a ground potential. The --side input terminal of the amplifier circuit OP12 is electrically connected to the output terminal of the amplifier circuit OP12. That is, the amplifier circuit OP12 constitutes a voltage follower circuit. The maximum voltage value acquisition circuit 320 configured as described above outputs a signal corresponding to the maximum voltage value of the input residual vibration detection signal NVT in a predetermined period from the output terminal of the amplifier circuit OP12 constituting the voltage follower circuit as the maximum voltage signal Vmax.

[0193] Furthermore, a reset signal RST2 is input to the control terminal of switch SW11. When the logic level of reset signal RST2 input to the control terminal is high, one end of switch SW11 is conductive, while when the logic level of reset signal RST2 input to the control terminal is low, one end of switch SW11 is not conductive. Consequently, the conductive connection between one end of switch SW11 discharges the charge stored in capacitor C11 to ground potential. As a result, the voltage value at one end of capacitor C11 is reset to ground potential.

[0194] The acquisition signal AS is input to the control terminal of switch SW12. When the logic level of acquisition signal AS input to the control terminal is high, one end of switch SW12 is conductive, while when the logic level of acquisition signal AS input to the control terminal is low, one end of switch SW12 is not conductive. Thus, by conductively connecting one end of switch SW12 to the other end, the charge accumulated in capacitor C11 is also accumulated in capacitor C12.

[0195] A reset signal RST1 is input to the control terminal of switch SW13. When the logic level of reset signal RST1 input to the control terminal is high, one end of switch SW13 is conductive, while when the logic level of reset signal RST1 input to the control terminal is low, one end of switch SW13 is not conductive. Consequently, the conductive connection between one end of switch SW13 discharges the charge stored in capacitor C12 to ground potential. As a result, the voltage value at one end of capacitor C12 is reset to ground potential.

[0196] Here, in the following description, conduction between one end and the other end of each of the switches SW11 , SW12 , and SW13 may be referred to as “ON”, and non-conduction between one end and the other end of the switches SW11 , SW12 , and SW13 may be referred to as “OFF”.

[0197] The minimum voltage value acquisition circuit 330 includes amplifier circuits OP21 and OP22 , a diode D21 , capacitors C21 and C22 , and switches SW21 , SW22 , and SW23 .

[0198] The residual vibration detection signal NVT is input to the positive input terminal of amplifier circuit OP21. The cathode terminal of diode D21 is electrically connected to the output terminal of amplifier circuit OP21. The anode terminal of diode D21 is electrically connected to the negative input terminal of amplifier circuit OP21. Furthermore, the anode terminal of diode D21 is electrically connected to one end of capacitor C21, one end of switch SW21, and one end of switch SW22. The other end of capacitor C21 is supplied with ground potential. The other end of switch SW21 is supplied with voltage signal VDD. Here, the voltage value of voltage signal VDD, i.e., voltage vd, is preferably greater than the voltage value of bias voltage signal VB, i.e., voltage vb. One end of capacitor C22, one end of switch SW23, and the positive input terminal of amplifier circuit OP22 are electrically connected to the other end of switch SW22. The other end of capacitor C22 and the other end of switch SW23 are supplied with ground potential. The negative input terminal of amplifier circuit OP22 is electrically connected to the output terminal of amplifier circuit OP22. In other words, amplifier circuit OP22 constitutes a voltage follower circuit. The minimum voltage value acquisition circuit 330 configured as described above outputs a signal corresponding to the minimum voltage value of the input residual vibration detection signal NVT in a predetermined period from the output terminal of the amplifier circuit OP22 constituting the voltage follower circuit as the minimum voltage signal Vmin.

[0199] Furthermore, a reset signal RST2 is input to the control terminal of switch SW21. When the logic level of reset signal RST2 input to the control terminal is high, one end of switch SW21 is conductive, while when the logic level of reset signal RST2 input to the control terminal is low, one end of switch SW21 is not conductive. Consequently, the conductive connection between one end of switch SW21 accumulates a predetermined charge corresponding to voltage signal VDD in capacitor C21. Consequently, the voltage value at one end of capacitor C21 is reset to the voltage value of voltage signal VDD, i.e., voltage vd.

[0200] The acquisition signal AS is input to the control terminal of switch SW22. When the logic level of acquisition signal AS input to the control terminal is high, one end of switch SW22 is conductive, while when the logic level of acquisition signal AS input to the control terminal is low, one end of switch SW22 is not conductive. Thus, by conductively connecting one end of switch SW22 to the other end, the charge accumulated in capacitor C21 is also accumulated in capacitor C22.

[0201] A reset signal RST1 is input to the control terminal of switch SW23. When the logic level of reset signal RST1 input to the control terminal is high, one end of switch SW23 is conductive, while when the logic level of reset signal RST1 input to the control terminal is low, one end of switch SW23 is not conductive. Consequently, the conductive connection between one end of switch SW23 discharges the charge stored in capacitor C22 to ground potential. As a result, the voltage value at one end of capacitor C22 is reset to ground potential.

[0202] Here, in the following description, conduction between one end and the other end of each of the switches SW21 , SW22 , and SW23 may be referred to as “ON”, and non-conduction between one end and the other end of the switches SW21 , SW22 , and SW23 may be referred to as “OFF”.

[0203] The period acquisition circuit 340 includes a comparator CP1 and a counter circuit 341 .

[0204] The residual vibration detection signal NVT is input to the positive input terminal of the comparator CP1. The voltage signal VREF is input to the negative input terminal of the comparator CP1. Consequently, the comparator CP1 generates a periodic pulse signal CYP and outputs it from its output terminal to the counter circuit 341. The periodic pulse signal CYP goes high when the voltage value of the residual vibration detection signal NVT at the positive input terminal is greater than the voltage value of the voltage signal VREF at the negative input terminal, and goes low when the voltage value of the residual vibration detection signal NVT at the positive input terminal is less than the voltage value of the voltage signal VREF at the negative input terminal.

[0205] Here, the voltage value of the voltage signal VREF, i.e., the voltage vref, is a voltage value close to the voltage value of the bias voltage signal VB, i.e., the voltage vb, and may be stored, for example, in a storage circuit (not shown) included in the control circuit 100. Furthermore, the voltage value of the voltage signal VREF, i.e., the voltage vref, may be changed according to the operating status and operating environment of the liquid ejection device 1.

[0206] After the logic level of reset signal RST1 changes from high to low, counter circuit 341 measures the period from when the logic level of input cyclic signal CYC changes from high to low and then back to high, or from when the logic level of input cyclic signal CYC changes from low to high and then back to low, and stores the measurement result as measurement result information CT. Then, when the logic level of acquisition signal AS changes from low to high, counter circuit 341 generates and outputs cyclic signal CYC including the stored measurement result information CT. Using a clock circuit (not shown), counter circuit 341 measures and stores the period from when the logic level of cyclic signal CYC changes from high to low and then back to high, or from when the logic level of cyclic signal CYC changes from low to high and then back to low.

[0207] As described above, the waveform information output circuit 300 outputs the maximum voltage signal Vmax output by the maximum voltage value acquisition circuit 320, the minimum voltage signal Vmin output by the minimum voltage value acquisition circuit 330, and the period signal CYC output by the period acquisition circuit 340 as waveform information of the input residual vibration detection signal NVT. That is, the maximum voltage signal Vmax, the minimum voltage signal Vmin, and the period signal CYC are included in the waveform information signal WFS, which includes the waveform information of the residual vibration detection signal NVT.

[0208] Next, the operation of the waveform information output circuit 300 will be described. Figure 12 This figure is used to explain the operation of the waveform information output circuit 300. In describing the operation of the waveform information output circuit 300, in the following description, any dot formation cycle Cp during which the status check CD is executed in the target ejection unit 600 is referred to as a dot formation cycle Cp(i), a dot formation cycle Cp following the dot formation cycle Cp(i) during which the status check CD is not executed in the target ejection unit 600 is referred to as a dot formation cycle Cp(i+1), and a dot formation cycle Cp preceding the dot formation cycle Cp(i) during which the status check CD is not executed in the target ejection unit 600 is referred to as a dot formation cycle Cp(i-1). In addition, in the following description, the signal held by one end of capacitor C11 is referred to as voltage signal Vc11, the signal held by one end of capacitor C12 is referred to as voltage signal Vc12, the signal held by one end of capacitor C21 is referred to as voltage signal Vc21, the signal held by one end of capacitor C22 is referred to as voltage signal Vc22, the maximum voltage value of the residual vibration detection signal NVT input to the waveform information output circuit 300 is referred to as voltage vmax, and the minimum voltage value of the residual vibration detection signal NVT input to the waveform information output circuit 300 is referred to as voltage vmin.

[0209] During the dot formation cycle Cp(i-1), the state check CD is not performed on the ejection unit 600. Therefore, immediately before the control circuit 100 outputs a latch pulse as the latch signal LAT, indicating the end of the dot formation cycle Cp(i-1), the residual vibration detection circuit 240 outputs a signal to the waveform information output circuit 300 whose voltage value is constant at voltage vb, independent of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. To this end, immediately before the control circuit 100 outputs a latch pulse as the latch signal LAT, indicating the end of the dot formation cycle Cp(i-1), voltage vb is held at one end of capacitor C11 as voltage signal Vc11, and voltage vb is held at one end of capacitor C21 as voltage signal Vc21.

[0210] Furthermore, just before the control circuit 100 outputs a latch pulse as latch signal LAT, indicating the end of the predetermined dot formation period Cp(i-1), a signal output by the residual vibration detection circuit 240, whose voltage value is constant at voltage vb, is also input to the positive input terminal of the comparator CP1. At this time, the negative input terminal of the comparator CP1 receives voltage signal VREF, whose voltage value is constant at voltage vref. Consequently, the comparator CP1 outputs a signal with a constant logic level of high or low as the periodic pulse signal CYP.

[0211] The control circuit 100 then outputs a latch pulse as latch signal LAT, which specifies the end of dot formation period Cp(i-1) and the start of dot formation period Cp(i). The latch signal LAT output by the control circuit 100 is input to the reset circuit 310 of the waveform information output circuit 300. At the rising edge of the latch pulse input as latch signal LAT, the reset circuit 310 sets the logic level of the output reset signal RST1 to a high level. This turns on switches SW13 and SW23. As a result, the charge stored in capacitor C12 is discharged to ground potential via switch SW13, and the charge stored in capacitor C22 is discharged to ground potential via switch SW23. In other words, one end of capacitor C12 and one end of capacitor C22 are both supplied with ground potential.

[0212] Then, the reset circuit 310 sets the logic level of the reset signal RST1 it outputs to a low level. This turns off switches SW13 and SW23. As a result, one end of capacitor C12 is held at ground potential as voltage signal Vc12, and one end of capacitor C22 is held at ground potential as voltage signal Vc22. In other words, based on the logic level of the reset signal RST1 output by the reset circuit 310, the waveform information output circuit 300 resets the voltage values ​​of voltage signal Vc12 held at one end of capacitor C12 and voltage signal Vc22 held at one end of capacitor C22 to a predetermined voltage value, namely, ground potential.

[0213] After setting the logic level of the output reset signal RST1 to a low level, the reset circuit 310 sets the logic level of the output acquisition signal AS to a high level. This turns on switches SW12 and SW22. As a result, the charge held by capacitor C11 flows into capacitor C12 via switch SW12, and the charge held by capacitor C21 is transferred to capacitor C22 via switch SW22. Specifically, the voltage vb held at one end of capacitor C11 as voltage signal Vc11 is supplied to one end of capacitor C12, and the voltage vb held at one end of capacitor C21 as voltage signal Vc21 is supplied to one end of capacitor C22.

[0214] Then, the reset circuit 310 sets the logic level of the output acquisition signal AS to a low level. This turns off switches SW12 and SW22. As a result, voltage vb is held at one end of capacitor C12 as voltage signal Vc12, and voltage vb is held at one end of capacitor C22 as voltage signal Vc22. In other words, based on the logic level of the acquisition signal AS output by the reset circuit 310, the waveform information output circuit 300 takes the voltage value of voltage signal Vc11 held at one end of capacitor C11 into one end of capacitor C12 as voltage signal Vc12, where it is held at one end of capacitor C12. Furthermore, the waveform information output circuit 300 takes the voltage value of voltage signal Vc21 held at one end of capacitor C21 into one end of capacitor C22 as voltage signal Vc22, where it is held at one end of capacitor C22.

[0215] After setting the logic level of the output acquisition signal AS to a low level, the reset circuit 310 sets the logic level of the output reset signal RST2 to a high level. This turns on switches SW11 and SW21. As a result, the charge stored in capacitor C11 is discharged to ground potential via switch SW11, while a charge corresponding to the voltage value of voltage signal VDD, i.e., voltage vd, is stored in capacitor C21 via switch SW21. Specifically, ground potential is supplied to one end of capacitor C11, while voltage vd is supplied to one end of capacitor C21 as voltage signal Vc21.

[0216] Then, the reset circuit 310 sets the logic level of the output reset signal RST2 to a low level. This turns off switches SW11 and SW21. As a result, one end of capacitor C11 holds ground potential as voltage signal Vc11, and one end of capacitor C21 holds voltage vd as voltage signal Vc21. In other words, based on the logic level of reset signal RST2, the waveform information output circuit 300 resets the voltage value of voltage signal Vc11 held at one end of capacitor C11 to a predetermined voltage value, namely ground potential, and resets the voltage value of voltage signal Vc21 held at one end of capacitor C21 to a predetermined voltage value, namely voltage vd.

[0217] The control circuit 100 then outputs a check pulse as the check timing signal TSIG. Consequently, the residual vibration detection circuit 240 outputs a residual vibration detection signal NVT corresponding to the residual vibration generated in the corresponding ejection unit 600, namely, the residual vibration detection signal NVT obtained by differentially amplifying the residual vibration reference signal Vo1 and the residual vibration detection signal Vo2 input from the corresponding selection circuit 230 and adding the voltage vb, to the waveform information output circuit 300. Specifically, the control circuit 100 outputs a check pulse as the check timing signal TSIG, thereby inputting the residual vibration detection signal NVT corresponding to the residual vibration generated in the corresponding ejection unit 600 to the waveform information output circuit 300.

[0218] The residual vibration detection signal NVT input to the waveform information output circuit 300 is supplied to the positive input terminal of the amplifier circuit OP11. The amplifier circuit OP11 outputs a signal having the same potential as the input residual vibration detection signal NVT from its output terminal. When the voltage value of the signal output by the amplifier circuit OP11 is greater than the voltage value of the voltage signal Vc11 held at one end of the capacitor C11, the signal output by the amplifier circuit OP11 is supplied to the one end of the capacitor C11 via a diode D11. On the other hand, when the voltage value of the signal output by the amplifier circuit OP11 is less than the voltage value of the voltage signal Vc11 held at one end of the capacitor C11, the signal output by the amplifier circuit OP11 is blocked by the diode D11. Therefore, the maximum voltage value of the signal output by the amplifier circuit OP11, i.e., the maximum voltage value of the residual vibration detection signal NVT, i.e., voltage vmax, is held at one end of the capacitor C11 as the voltage signal Vc11. That is, the maximum voltage value acquisition circuit 320 acquires the maximum voltage value of the residual vibration detection signal NVT, ie, the voltage vmax, as waveform information of the residual vibration detection signal NVT, and stores it at one end of the capacitor C11 as the voltage signal Vc11 .

[0219] Furthermore, the residual vibration detection signal NVT input to the waveform information output circuit 300 is also supplied to the positive input terminal of the amplifier circuit OP21. The amplifier circuit OP21 outputs a signal at the same potential as the input residual vibration detection signal NVT from its output terminal. When the voltage value of the signal output by the amplifier circuit OP21 is lower than the voltage value of the voltage signal Vc21 held at one end of the capacitor C21, the charge held at one end of the capacitor C21 is discharged via the diode D21 and the amplifier circuit OP21. Consequently, the voltage value of the voltage signal Vc21 held at one end of the capacitor C21 drops to the voltage value of the signal output by the amplifier circuit OP21. On the other hand, when the voltage value of the signal output by the amplifier circuit OP21 is higher than the voltage value of the voltage signal Vc21 held at one end of the capacitor C21, the charge held at one end of the capacitor C21 is not discharged via the diode D21 and the amplifier circuit OP21. In this case, the voltage value of the voltage signal Vc21 held at one end of the capacitor C21 does not change. Therefore, the minimum voltage value of the signal output by amplifier circuit OP21, i.e., the minimum voltage value of residual vibration detection signal NVT, i.e., voltage vmin, is held at one end of capacitor C21 as voltage signal Vc21. Specifically, minimum voltage value acquisition circuit 330 acquires voltage vmin, i.e., the minimum voltage value of residual vibration detection signal NVT, as waveform information of residual vibration detection signal NVT, and holds it at one end of capacitor C21 as voltage signal Vc21.

[0220] Furthermore, the residual vibration detection signal NVT input to the waveform information output circuit 300 is also supplied to the positive input terminal of the comparator CP1. Consequently, the comparator CP1 outputs a periodic pulse signal CYP. This periodic pulse signal CYP becomes high when the voltage value of the residual vibration detection signal NVT also supplied to the positive input terminal is greater than the voltage value vref of the voltage signal VREF also supplied to the negative input terminal, and becomes low when the voltage value of the residual vibration detection signal NVT also supplied to the positive input terminal is less than the voltage value vref of the voltage signal VREF also supplied to the negative input terminal.

[0221] As described above, the residual vibration detection signal NVT is a signal obtained by differentially amplifying the residual vibration reference signal Vo1 and the residual vibration detection signal Vo2 and adding the signal to the voltage vb. Therefore, the voltage value of the residual vibration detection signal NVT varies with the residual vibration of the ejection unit 600, with the voltage vb serving as the reference potential. Furthermore, the voltage value of the voltage signal VREF, i.e., the voltage vref, is approximately the voltage value of the bias voltage signal VB, i.e., the voltage vb. Therefore, the period of the logic level switching of the periodic pulse signal CYP corresponds to the period of the residual vibration detection signal NVT.

[0222] The counter circuit 341 measures the time required for the logic level of the input periodic pulse signal CYP to change, and stores it as measurement result information CT. Figure 12 In the example shown, counter circuit 341 measures the time it takes for the logic level of input periodic signal CYC to change from high to low and then back to high, that is, the time required for the logic level of one cycle of periodic signal CYC to change, and stores this information as measurement result information CT. However, counter circuit 341 may also measure the time it takes for the logic level of input periodic signal CYC to change from high to low and store this information as measurement result information CT, or may measure the time required for the logic level of two or more cycles of periodic signal CYC and store this information as measurement result information CT. In other words, period acquisition circuit 340 acquires measurement result information CT corresponding to the period of residual vibration detection signal NVT as waveform information of residual vibration detection signal NVT, and stores this information in counter circuit 341.

[0223] That is, the period acquisition circuit 340 outputs the period signal CYC according to the comparison result of the voltage value of the voltage signal VREF, ie, the voltage vref, and the voltage value of the residual vibration detection signal NVT.

[0224] The control circuit 100 then outputs a latch pulse as latch signal LAT, which specifies the end of dot formation period Cp(i) and the start of dot formation period Cp(i+1). The latch signal LAT output by the control circuit 100 is input to the reset circuit 310 of the waveform information output circuit 300. At the rising edge of the latch pulse input as latch signal LAT, the reset circuit 310 sets the logic level of the output reset signal RST1 to a high level. One end of capacitor C12 is supplied with ground potential, and one end of capacitor C22 is supplied with ground potential. The reset circuit 310 then sets the logic level of the output reset signal RST1 to a low level, thereby maintaining ground potential at one end of capacitor C12 as voltage signal Vc12, and maintaining ground potential at one end of capacitor C22 as voltage signal Vc22. In other words, the voltage values ​​of voltage signal Vc12 and voltage signal Vc22 maintained at one end of capacitor C12 and C22 are reset to a predetermined voltage value, namely, ground potential.

[0225] After setting the logic level of the output reset signal RST1 to a low level, the reset circuit 310 sets the logic level of the output acquisition signal AS to a high level. Consequently, the maximum voltage value of the residual vibration detection signal NVT, or voltage vmax, held at one end of capacitor C11 as voltage signal Vc11, is supplied to one end of capacitor C12, while the minimum voltage value of the residual vibration detection signal NVT, or voltage vmin, held at one end of capacitor C21 as voltage signal Vc21, is supplied to one end of capacitor C22. In other words, the voltage vmax held at one end of capacitor C11 as voltage signal Vc11 is transferred to one end of capacitor C12, while the voltage vmin held at one end of capacitor C21 as voltage signal Vc21 is transferred to one end of capacitor C22. The reset circuit 310 then sets the logic level of the output acquisition signal AS to a low level, causing capacitor C12 to hold voltage vmax as voltage signal Vc12, and capacitor C22 to hold voltage vmin as voltage signal Vc22.

[0226] Voltage vmax, which is the voltage signal Vc12 held in capacitor C12, undergoes impedance conversion in amplifier circuit OP12 and is output as maximum voltage signal Vmax. Voltage vmin, which is the voltage signal Vc22 held in capacitor C12, undergoes impedance conversion in amplifier circuit OP22 and is output as minimum voltage signal Vmin. Voltage vmax, which is output as the maximum voltage signal Vmax from waveform information output circuit 300, is one piece of waveform information of residual vibration detection signal NVT corresponding to residual vibration generated in the corresponding ejection unit 600 during dot formation period Cp(i), and corresponds to the maximum amplitude of residual vibration detection signal NVT. Voltage vmin, which is output as the minimum voltage signal Vmin from waveform information output circuit 300, is one piece of waveform information of residual vibration detection signal NVT corresponding to residual vibration generated in the corresponding ejection unit 600 during dot formation period Cp(i), and corresponds to the minimum amplitude of residual vibration detection signal NVT.

[0227] Furthermore, when the logic level of the output acquisition signal AS is set to a high level by the reset circuit 310, the counter circuit 341 generates a periodic signal CYC, which is output from the waveform information output circuit 300. This periodic signal CYC includes the measurement result information CT stored as waveform information of the residual vibration detection signal NVT. The periodic signal CYC output from the waveform information output circuit 300, including the measurement result information CT stored as waveform information of the residual vibration detection signal NVT, is one piece of waveform information of the residual vibration detection signal NVT corresponding to the residual vibration generated in the corresponding ejection unit 600 during the dot formation period Cp(i), and corresponds to the period of the residual vibration detection signal NVT.

[0228] Specifically, the waveform information output circuit 300 acquires a maximum voltage signal Vmax corresponding to the maximum voltage of the residual vibration detection signal NVT, a minimum voltage signal Vmin corresponding to the minimum voltage of the residual vibration detection signal NVT, and a periodic signal CYC corresponding to the period of the residual vibration detection signal NVT as waveform information of the residual vibration detection signal NVT corresponding to the residual vibration generated in the corresponding ejection unit 600 during the dot formation period Cp(i). The waveform information output circuit 300 then outputs a waveform information signal WFS including this acquired waveform information to the control circuit 100.

[0229] As described above, the waveform information output circuit 300 includes: a maximum voltage value acquisition circuit 320, which maintains the maximum voltage value of the residual vibration detection signal NVT in the point formation period Cp as the maximum voltage signal Vmax; a minimum voltage value acquisition circuit 330, which maintains the minimum voltage value of the residual vibration detection signal NVT in the point formation period Cp as the minimum voltage signal Vmin; and a period acquisition circuit 340, which outputs a period signal CYC corresponding to the period of the residual vibration detection signal NVT, and includes: switches SW11 and SW13, which reset the maximum value of the residual vibration detection signal NVT maintained by the maximum voltage value acquisition circuit 320; and switches SW21 and SW23, which reset the minimum value of the residual vibration detection signal NVT maintained by the minimum voltage value acquisition circuit 330.

[0230] 5. Residual vibration signal

[0231] Next, a specific example of residual vibration generated in the discharge unit 600, which is the inspection target, after the drive voltage signal Vin is supplied to the discharge unit 600, and a specific example of a residual vibration signal Vout corresponding to this residual vibration will be described. The liquid discharge device 1 of this embodiment obtains the residual vibration signal Vout and determines the state of the corresponding discharge unit 600 based on the residual vibration detection signal NVT corresponding to the obtained residual vibration signal Vout. The residual vibration signal Vout is a signal corresponding to the residual vibration generated in the discharge unit 600 after the piezoelectric elements 60a and 60b included in the discharge unit 600 are driven by the drive voltage signal Vin including the drive waveform Bdp1.

[0232] Specifically, in the liquid ejection device 1 of this embodiment, the piezoelectric elements 60a and 60b included in the corresponding ejection unit 600 are each driven by a drive voltage signal Vin including a drive waveform Bdp1. This driving of the piezoelectric elements 60a and 60b causes the vibration plate 304 to displace, and the internal pressure of the pressure chambers CB1 and CB2 changes due to the displacement of the vibration plate 304. By maintaining a constant voltage value for the drive voltage signal Vin supplied to the piezoelectric elements 60a and 60b, damped vibrations are generated in the vibration plate 304 in response to the changes in the internal pressure of the pressure chambers CB1 and CB2. At this time, the damped vibrations generated in the vibration plate 304 cause the piezoelectric elements 60a and 60b to displace. Consequently, charge corresponding to this displacement is released from the piezoelectric elements 60a and 60b. The signal corresponding to the charge released from the piezoelectric elements 60a and 60b due to the damped vibrations generated in the vibration plate 304 corresponds to the residual vibration signal Vout. Here, in the following description, the signal corresponding to the charge output by the piezoelectric element 60a along with the attenuation signal of the vibration plate 304 is sometimes referred to as the residual vibration signal Vout1, and the signal corresponding to the charge output by the piezoelectric element 60b along with the attenuation signal of the vibration plate 304 is sometimes referred to as the residual vibration signal Vout2.

[0233] Figure 13 : is a diagram showing an example of residual vibration signals Vout1 and Vout2. Figure 13 As shown, the signal waveforms of residual vibration signals Vout1 and Vout2 are attenuated vibration waveforms whose voltage amplitude decreases over time due to the damped vibration generated in vibration plate 304 as the internal pressures of pressure chambers CB1 and CB2 change. Waveform information such as amplitude and period included in the attenuated vibration waveforms of residual vibration signals Vout1 and Vout2 changes depending on the state of ink stored in pressure chambers CB1 and CB2 and the state of ink flowing in communication channel RR1 and nozzle channel RN.

[0234] Here, the relationship between the waveform information of the residual vibration signals Vout1 and Vout2 and the state of the ink stored in the pressure chambers CB1 and CB2 and the state of the ink flowing in the communication channels RR1 and RR2 and the nozzle channel RN is described using a calculation model. Figure 14This diagram illustrates an example of a calculation model that considers the simple harmonic vibration of residual vibrations generated in pressure chambers CB1 and CB2 or the vibrating plate 304. As previously described, the piezoelectric elements 60a and 60b are displaced by the supply of the drive voltage signal Vin. This displacement of the piezoelectric elements 60a and 60b also causes the vibrating plate 304 to displace. Consequently, the volume of the corresponding pressure chambers CB1 and CB2 changes with the displacement of the vibrating plate 304. At this time, a portion of the ink filling the pressure chambers CB1 and CB2 is ejected from the nozzles N due to the pressure generated within the pressure chambers CB1 and CB2.

[0235] During this series of actions to eject ink from the nozzle N, the vibration plate 304 freely vibrates at a natural frequency determined by the shape of the ink flow channel, the flow channel resistance r due to the ink's viscosity, the inertia m caused by the weight of the liquid within the flow channel, and the compliance C of the vibration plate 304. The piezoelectric elements 60a and 60b are displaced in response to the free vibration generated in the vibration plate 304. The charge signal generated by the displacement of the piezoelectric element 60a is output as a residual vibration signal Vout1, and the charge signal generated by the displacement of the piezoelectric element 60b is output as a residual vibration signal Vout2.

[0236] The calculation model of the residual vibration generated in the vibration plate 304 can be expressed by pressure p, inertia m, compliance C and flow resistance r. Figure 14 The step response of the circuit shown when a pressure p is applied is given by the following equations (1) to (3).

[0237]

[0238]

[0239]

[0240] Figure 15 : is a diagram for explaining the relationship between the viscosity of ink and the signal waveforms of the residual vibration signals Vout1 and Vout2. Figure 15 In the figure, the horizontal axis shows time, and the vertical axis shows the magnitude of the residual vibration. Figure 15 In FIG, as the viscosity of the ink, the signal waveform when the viscosity ratio is 1.0 is illustrated as waveform a1, the signal waveform when the viscosity ratio is 1.4 is illustrated as waveform a2, the signal waveform when the viscosity ratio is 1.8 is illustrated as waveform a3, and the signal waveform when the viscosity ratio is 2.2 is illustrated as waveform a4.

[0241] like Figure 15As shown, when the viscosity of the stored ink increases and the viscosity ratio increases, the amplitude and attenuation rate of the residual vibration signals Vout1 and Vout2 change. Specifically, as the viscosity of the ink stored in pressure chambers CB1 and CB2, the ink flowing in the connecting flow channels RR1 and RR2 and the nozzle flow channel RN, and the ink near the nozzle N increases, the flow channel resistance r increases. Consequently, the amplitude of the attenuated vibration generated by the vibration plate 304 decreases, and the attenuation rate increases. As a result, when the stored ink undergoes abnormal viscosity increase, the corresponding residual vibration signals Vout1 and Vout2 decrease in amplitude and increase in attenuation rate.

[0242] in addition, Figure 16 This is a diagram for explaining the signal waveforms of the residual vibration signals Vout1 and Vout2 when bubbles are mixed in the pressure chambers CB1 and CB2. Figure 16 In the figure, the horizontal axis shows time, and the vertical axis shows the magnitude of the residual vibration. Figure 16 In the figure, the signal waveform of the normal state in which no bubbles are mixed into the pressure chambers CB1, CB2, the connecting flow channels RR1, RR2 and the nozzle flow channel RN is illustrated as waveform b1, and an example of the signal waveform when bubbles are mixed into any of the pressure chambers CB1, CB2, the connecting flow channels RR1, RR2 and the nozzle flow channel RN is illustrated as waveform b2.

[0243] like Figure 16 As shown, when bubbles are mixed into the pressure chambers CB1 and CB2, the connecting flow passages RR1 and RR2, and the nozzle flow passage RN, the vibration frequency of the residual vibration signals Vout1 and Vout2 increases. Specifically, when bubbles are mixed into the interior of the pressure chambers CB1 and CB2, the connecting flow passages RR1 and RR2, the nozzle flow passage RN, and the nozzle N, the inertia m, which is equivalent to the weight of the stored ink, decreases by an amount corresponding to the mixed bubbles. Therefore, when the inertia m decreases, the angular velocity ω increases, as shown in equation (2). As a result, the vibration period of the residual vibration generated by the vibration plate 304 shortens, resulting in an increase in the vibration frequency and a shortened period of the residual vibration signals Vout1 and Vout2.

[0244] As described above, when a viscosity abnormality (increased ink viscosity) or a bubble mixing abnormality (bubble mixing) occurs in the pressure chamber CB1, the communication channel RR1, the nozzle channel RN, etc., the waveform information such as the amplitude and period of the residual vibration signal Vout1 changes. Similarly, when a viscosity abnormality or bubble mixing abnormality occurs in the pressure chamber CB2, the communication channel RR2, the nozzle channel RN, etc., the waveform information such as the amplitude and period of the residual vibration signal Vout2 changes. Therefore, based on the waveform information such as the amplitude and period of the residual vibration signals Vout1 and Vout2, the state of the ejection unit 600 including the piezoelectric elements 60a and 60b that output the residual vibration signals Vout1 and Vout2 can be determined.

[0245] Here, assuming that the drive signal selection circuit 200 independently acquires both the residual vibration signal Vout1 and the residual vibration signal Vout2, and the control circuit 100 independently calculates waveform information such as the amplitude and period of the residual vibration signal Vout1 and the amplitude and period of the residual vibration signal Vout2, it is possible to determine the state of the discharge unit 600 even if the discharge unit 600 includes the pressure chamber CB1 and the pressure chamber CB2. However, in a configuration where the discharge unit 600 includes the pressure chamber CB1 and the pressure chamber CB2, when both the residual vibration signal Vout1 and the residual vibration signal Vout2 are independently acquired and the state of the discharge unit 600 is determined, the drive signal selection circuit 200 needs a structure for switching between acquiring the residual vibration signal Vout1 and acquiring the residual vibration signal Vout2. As a result, the integrated circuit 201 on which the drive signal selection circuit 200 is mounted may be larger.

[0246] In contrast, in the liquid ejection device 1 of this embodiment, the drive signal selection circuit 200 obtains the residual vibration signal Vout, which is a composite of the residual vibration signal Vout1 and the residual vibration signal Vout2, and outputs the residual vibration detection signal NVT corresponding to the residual vibration signal Vout. Consequently, the waveform information output circuit 300 obtains the waveform information of the residual vibration detection signal NVT and outputs it as the waveform information signal WFS to the control circuit 100. The control circuit 100 determines the state of the ejection unit 600 based on the input waveform information signal WFS. This eliminates the need for a structure for switching between obtaining the residual vibration signal Vout1 corresponding to the pressure chamber CB1 and obtaining the residual vibration signal Vout2 corresponding to the pressure chamber CB2, enabling miniaturization of the integrated circuit 201 in which the drive signal selection circuit 200 is mounted.

[0247] Next, an example of the signal waveform of the residual vibration signal Vout obtained by combining the residual vibration signal Vout1 and the residual vibration signal Vout2 will be described.

[0248] Figure 17 : is a diagram showing an example of a signal waveform of the residual vibration signal Vout when the ejection unit 600 is normal. Figure 17 In the figure, the horizontal axis represents time, and the vertical axis represents the magnitude of the residual vibration. Figure 17 The residual vibration signal Vout shown is an example of a signal waveform of the residual vibration signal Vout input to the drive signal selection circuit 200 when the pressure chamber CB1 corresponding to the piezoelectric element 60a is normal and the pressure chamber CB2 corresponding to the piezoelectric element 60b is normal. Figure 17 The residual vibration signal Vout1 and the residual vibration signal Vout2 are also shown in the figure.

[0249] like Figure 17 As shown, when the pressure chamber CB1 corresponding to piezoelectric element 60a is normal and the pressure chamber CB2 corresponding to piezoelectric element 60b is normal, the residual vibration signal Vout1 output by piezoelectric element 60a and the residual vibration signal Vout2 output by piezoelectric element 60b have substantially identical signal waveforms. Specifically, when the drive voltage signal Vin is input to piezoelectric elements 60a and 60b, the same residual vibration is generated in the region of the vibration plate 304 corresponding to piezoelectric element 60a and the region of the vibration plate 304 corresponding to piezoelectric element 60b. Therefore, when the pressure chamber CB1 corresponding to piezoelectric element 60a and the pressure chamber CB2 corresponding to piezoelectric element 60b are normal, the residual vibration signals Vout1 and Vout2 have substantially identical signal waveforms. Therefore, the residual vibration signal Vout having a period substantially equal to that of the residual vibration signal Vout1 and the residual vibration signal Vout2 and an amplitude greater than that of the residual vibration signal Vout1 and the residual vibration signal Vout2 is input into the driving signal selection circuit 200 as a composite wave of the residual vibration signal Vout1 and the residual vibration signal Vout2.

[0250] Figure 18 : is a diagram showing an example of a signal waveform of the residual vibration signal Vout when abnormal viscosity increase occurs in the discharge portion 600. Figure 18 In the figure, the horizontal axis represents time, and the vertical axis represents the magnitude of the residual vibration. Figure 18 The residual vibration signal Vout shown is an example of a signal waveform of the residual vibration signal Vout input to the drive signal selection circuit 200 when the pressure chamber CB1 corresponding to the piezoelectric element 60a is normal and the ink stored in the pressure chamber CB2 corresponding to the piezoelectric element 60b has abnormal viscosity increase. Figure 18 In addition to the residual vibration signal Vout1 and the residual vibration signal Vout2, the figure also shows the residual vibration signal Vout1 and the residual vibration signal Vout2. Figure 17The residual vibration detection signal NVout is a residual vibration signal Vout when the ejection unit 600 is normal.

[0251] like Figure 18 As shown, when the pressure chamber CB1 corresponding to the piezoelectric element 60a is normal and a viscosity increase abnormality occurs in the pressure chamber CB2 corresponding to the piezoelectric element 60b, the amplitude of the residual vibration signal Vout2 output by the piezoelectric element 60b becomes smaller than the amplitude of the residual vibration signal Vout1 output by the piezoelectric element 60a. Specifically, the driving voltage signal Vin is input to the piezoelectric elements 60a and 60b. At this time, a residual vibration with an amplitude smaller than the residual vibration generated in the area of ​​the vibration plate 304 corresponding to the piezoelectric element 60b is generated. Therefore, when the pressure chamber CB1 corresponding to the piezoelectric element 60a is normal and a viscosity increase abnormality occurs in the pressure chamber CB2 corresponding to the piezoelectric element 60b, the amplitude of the residual vibration signal Vout2 becomes smaller than the amplitude of the residual vibration signal Vout1. Therefore, the residual vibration signal Vout having a period substantially equal to that of the residual vibration signal Vout1 and the residual vibration signal Vout2 and having an amplitude smaller than that of the residual vibration detection signal NVout is input as a composite wave of the residual vibration signals Vout1 and Vout2 to the driving signal selection circuit 200 .

[0252] Figure 19 : is a diagram showing an example of a signal waveform of the residual vibration signal Vout when an abnormal bubble mixing occurs in the ejection portion 600. Figure 19 In the figure, the horizontal axis represents time, and the vertical axis represents the magnitude of the residual vibration. Figure 19 The residual vibration signal Vout shown is an example of a signal waveform of the residual vibration signal Vout input to the drive signal selection circuit 200 when the pressure chamber CB1 corresponding to the piezoelectric element 60a is normal and the pressure chamber CB2 corresponding to the piezoelectric element 60b has an abnormal bubble mixing. Figure 19 In addition to the residual vibration signal Vout1 and the residual vibration signal Vout2, the figure also shows the residual vibration signal Vout1 and the residual vibration signal Vout2. Figure 17 The residual vibration detection signal NVout is a residual vibration signal Vout when the ejection unit 600 is normal.

[0253] like Figure 19As shown, when pressure chamber CB1 corresponding to piezoelectric element 60a is normal and a bubble mixing anomaly occurs in pressure chamber CB2 corresponding to piezoelectric element 60b, the frequency of residual vibration signal Vout2 output by piezoelectric element 60b increases and its period shortens relative to residual vibration signal Vout1 output by piezoelectric element 60a. Specifically, a drive voltage signal Vin is input to piezoelectric elements 60a and 60b. At this time, residual vibration with a shorter period is generated in the region of vibrating plate 304 corresponding to piezoelectric element 60b than in the region of vibrating plate 304 corresponding to piezoelectric element 60a. Therefore, when pressure chamber CB1 corresponding to piezoelectric element 60a is normal and a bubble mixing anomaly occurs in pressure chamber CB2 corresponding to piezoelectric element 60b, the period of residual vibration signal Vout2 becomes shorter than that of residual vibration signal Vout1. Consequently, residual vibration signal Vout, which has a different period and frequency from residual vibration detection signal NVout, is input to drive signal selection circuit 200 as a composite wave of residual vibration signals Vout1 and Vout2.

[0254] As described above, when both the pressure chamber CB1 corresponding to residual vibration signal Vout1 and the pressure chamber CB2 corresponding to residual vibration signal Vout2 are normal, the period and amplitude of residual vibration signal Vout, the composite wave of residual vibration signals Vout1 and Vout2, are both within the specified range. In contrast, when the viscosity of the ink stored in at least one of the pressure chambers CB1 corresponding to residual vibration signal Vout1 and CB2 corresponding to residual vibration signal Vout2 increases, the amplitude of residual vibration signal Vout decreases compared to when both pressure chambers CB1 corresponding to residual vibration signal Vout1 and CB2 corresponding to residual vibration signal Vout2 are normal. Furthermore, when bubbles enter at least one of the pressure chambers CB1 corresponding to residual vibration signal Vout1 and CB2 corresponding to residual vibration signal Vout2, the period of residual vibration signal Vout falls outside the specified range when both pressure chambers CB1 corresponding to residual vibration signal Vout1 and CB2 corresponding to residual vibration signal Vout2 are normal. That is, when an abnormality occurs in at least one of the pressure chamber CB1 corresponding to the residual vibration signal Vout1 and the pressure chamber CB2 corresponding to the residual vibration signal Vout2 , the amplitude and period of the residual vibration signal Vout change.

[0255] In the liquid ejection device 1 of this embodiment, the drive signal selection circuit 200 acquires and amplifies the residual vibration signal Vout, thereby outputting a residual vibration detection signal NVT corresponding to the residual vibration signal Vout. The waveform information output circuit 300 acquires, as waveform information for the residual vibration detection signal NVT, a maximum voltage signal Vmax corresponding to the maximum voltage of the residual vibration detection signal NVT, a minimum voltage signal Vmin corresponding to the minimum voltage of the residual vibration detection signal NVT, and a periodic signal CYC corresponding to the period of the residual vibration detection signal NVT. The waveform information output circuit 300 then outputs a waveform information signal WFS containing the acquired waveform information to the control circuit 100. The control circuit 100 calculates at least one of the amplitude and period of the residual vibration signal Vout based on the maximum voltage signal Vmax, the minimum voltage signal Vmin, and the periodic signal CYC included in the input waveform information signal WFS, thereby determining the ejection status of ink ejected from the ejection unit 600 to be inspected.

[0256] It should be noted that, in addition to acquiring the maximum voltage signal Vmax, the minimum voltage signal Vmin, and the period signal CYC, the waveform information output circuit 300 may also acquire various waveform information of the residual vibration detection signal NVT. Then, in addition to calculating the amplitude and period of the residual vibration detection signal NVT based on the maximum voltage signal Vmax, the minimum voltage signal Vmin, and the period signal CYC, the control circuit 100 may also determine whether ink is being ejected normally from the nozzle N, as the ejection status of ink ejected from the nozzle N of the ejection unit 600, based on the various acquired waveform information. Furthermore, the amplitude of the residual vibration signal Vout includes, for example, the attenuation rate that can be calculated based on the amplitude, and the period of the residual vibration signal Vout includes, for example, the frequency and phase that can be calculated based on the period.

[0257] Here, the drive waveform Bdp1 is an example of a drive signal, and the drive voltage signals ComB, COM, and Vin that include the drive waveform Bdp1 are also examples of drive signals. Furthermore, the pressure chambers CB1 and CB2 included in the ejection unit 600-1 are examples of first pressure chambers, the nozzle N included in the ejection unit 600-1 is an example of a first nozzle, the piezoelectric elements 60a and 60b included in the ejection unit 600-1 are examples of first piezoelectric elements, the residual vibration generated in the ejection unit 600-1 is an example of first residual vibration, and the residual vibration signal Vout output from the ejection unit 600-1 is an example of a first residual vibration signal. Furthermore, the transmission gate 234b included in the selection circuit 230 corresponding to the ejection unit 600-1 is an example of a first switching circuit, the residual vibration detection circuit 240 corresponding to the ejection unit 600-1 is an example of a first residual vibration detection circuit, and the residual vibration detection signal NVT output by the residual vibration detection circuit 240 corresponding to the ejection unit 600-1 is an example of a first residual vibration detection signal. Furthermore, the pressure chambers CB1 and CB2 included in the ejection unit 600-2 are examples of second pressure chambers, the nozzle N included in the ejection unit 600-2 is an example of a second nozzle, the piezoelectric elements 60a and 60b included in the ejection unit 600-2 are examples of second piezoelectric elements, the residual vibration generated in the ejection unit 600-2 is an example of a second residual vibration, and the residual vibration signal Vout output from the ejection unit 600-2 is an example of a second residual vibration signal. Furthermore, the transmission gate 234b included in the selection circuit 230 corresponding to the ejection unit 600-2 is an example of a second switch circuit, the residual vibration detection circuit 240 corresponding to the ejection unit 600-2 is an example of a second residual vibration detection circuit, and the residual vibration detection signal NVT output by the residual vibration detection circuit 240 corresponding to the ejection unit 600-2 is an example of a second residual vibration detection signal. Furthermore, the inspection period Ps1 is an example of a first timing, and the inspection period Ps2 is an example of a second timing.

[0258] 6. Effects

[0259] In the liquid ejection device 1 of this embodiment configured as described above, the print head 21 includes a transmission gate 234b and a residual vibration detection circuit 240. One end of the transmission gate 234b receives a drive voltage signal ComB including a drive waveform Bdp2 that generates residual vibration in the ejection unit 600, while the other end is electrically connected to the ejection unit 600. The residual vibration detection circuit 240 outputs a residual vibration detection signal NVT corresponding to a residual vibration signal Vout. This residual vibration signal Vout is a signal corresponding to the residual vibration generated in the ejection unit 600. Furthermore, in the print head 21, one end of the residual vibration detection circuit 240 is electrically connected to one end of the transmission gate 234b, and the other end is electrically connected to the other end of the transmission gate 234b.

[0260] In the printhead 21 configured as described above, a potential difference is generated across the transmission gate 234b corresponding to the resistance value of the transmission gate 234b's on-resistance and the residual vibration signal Vout. The residual vibration detection circuit 240 detects the potential difference across the transmission gate 234b. This residual vibration signal Vout is a signal corresponding to the charge output by the piezoelectric elements 60a and 60b in response to the residual vibration generated in the ejection unit 600. Since the residual vibration detection circuit 240 detects the potential difference across the transmission gate 234b, the printhead 21 does not need to control the conduction state of the transmission gate 234b to a specific state for detecting the residual vibration signal Vout generated in the ejection unit 600. In other words, the printhead 21 of this embodiment can detect the residual vibration signal Vout generated in the ejection unit 600 without having to control the conduction state of the transmission gate 234b to a state specifically for detecting the residual vibration signal Vout corresponding to the residual vibration generated in the ejection unit 600. Therefore, it is possible to further increase the speed of detecting the residual vibration generated in the ejection portion 600 after the piezoelectric elements 60 a and 60 b are driven.

[0261] Furthermore, in the liquid ejection device 1 of this embodiment, the print head 21 includes a residual vibration detection circuit 240 corresponding to each of the m ejection units 600. This allows for individual acquisition of a residual vibration signal Vout corresponding to the residual vibration generated in the ejection unit 600 after the piezoelectric elements 60a and 60b included in each of the m ejection units 600 are driven. In other words, the residual vibration signals Vout corresponding to the residual vibration generated in the ejection unit 600 after the piezoelectric elements 60a and 60b included in each of the m ejection units 600 are driven can be acquired in parallel. Consequently, the detection speed of the residual vibration generated in the ejection unit 600 after the piezoelectric elements 60a and 60b are driven can be further increased.

[0262] Furthermore, in the liquid ejection device 1 of this embodiment, in the print head 21, the residual vibration detection circuits 240 corresponding to each of the m ejection units 600 acquire residual vibration signals Vout corresponding to the residual signal generated when the piezoelectric elements 60a and 60b are supplied with the drive waveform Bdp1 that causes the ejection units 600 to microvibrate. Specifically, the residual vibration detection circuits 240 acquire residual vibration signals Vout corresponding to the residual vibrations generated during periods when ink is not being ejected from the ejection units 600. This improves the accuracy of acquiring the residual vibration signals Vout by the residual vibration detection circuits 240, and improves the accuracy of determining the ejection status of ink from the ejection units 600 based on the acquired residual vibration signals Vout.

[0263] Furthermore, in the liquid ejection device 1 of this embodiment configured as described above, in the ejection module 20, the piezoelectric element 60a of the print head 21 outputs a residual vibration signal Vout1 corresponding to the residual vibration generated by the volume change of the pressure chamber CB1, and the piezoelectric element 60b outputs a residual vibration signal Vout2 corresponding to the residual vibration generated by the volume change of the pressure chamber CB2. The residual vibration detection circuit 240 then acquires a residual vibration signal Vout corresponding to the residual vibration signals Vout1 and Vout2 and outputs a residual vibration detection signal NVT obtained by waveform-shaping the acquired residual vibration signal Vout. The maximum voltage value acquisition circuit 320 outputs the maximum voltage value of the residual vibration detection signal NVT during the dot formation period Cp as a maximum voltage signal Vmax. The minimum voltage value acquisition circuit 330 outputs the minimum voltage value of the residual vibration detection signal NVT during the dot formation period Cp as a minimum voltage signal Vmin. The period acquisition circuit 340 outputs a period signal CYC corresponding to the period of the residual vibration detection signal NVT.

[0264] That is, the ejection module 20 of this embodiment can directly acquire the amplitude and period of the residual vibration detection signal NVT corresponding to the residual vibration signal Vout, where the residual vibration signal Vout is a signal corresponding to the acquired residual vibration. Thus, in the ejection module 20 of this embodiment, even if the amplitude and period of the residual vibration signal Vout are difficult to acquire due to the ejection unit 600 having the pressure chambers CB1 and CB2, the waveform information of the residual vibration detection signal NVT can be acquired with high precision without performing processing such as A / D conversion. Therefore, in the ejection module 20 of this embodiment, the waveform information of the residual vibration generated in the ejection unit 600 after the piezoelectric elements 60a and 60b are driven can be acquired with high precision and high speed.

[0265] 7. Modifications

[0266] In the liquid ejection device 1 of the present embodiment described above, a configuration is described in which the ejection unit 600 for ejecting ink includes the pressure chamber CB1 and the pressure chamber CB2. However, the configuration of the ejection unit 600 for ejecting ink is not limited thereto. For example, one pressure chamber may be provided for each nozzle N, or three pressure chambers may be provided for each nozzle N. Even with such a configuration, the same operational effects are achieved.

[0267] In addition, in the liquid ejection device 1 of the present embodiment described above, the waveform information output circuit 300 is described as obtaining the maximum voltage signal Vmax corresponding to the maximum voltage value of the residual vibration detection signal NVT in the point formation period Cp and the minimum voltage signal Vmin corresponding to the minimum voltage value of the residual vibration detection signal NVT in the point formation period Cp, but the waveform information output circuit 300 can also obtain the maximum voltage signal Vmax corresponding to the maximum voltage value of the residual vibration detection signal NVT and the minimum voltage signal Vmin corresponding to the minimum voltage value according to each vibration period of the residual vibration detection signal NVT, and calculate the attenuation rate of the amplitude as the waveform information of the residual vibration detection signal NVT based on the multiple maximum voltage signals Vmax and multiple minimum voltage signals Vmin obtained.

[0268] Specifically, the periodic pulse signal CYP outputted by the comparator CP1 is inputted to the reset circuit 310 included in the waveform information output circuit 300 instead of or in addition to the latch signal LAT.

[0269] When the logic level of the input periodic pulse signal CYP changes from high to low, the reset circuit 310 controls switch SW12 to be on for a predetermined period, and then controls switch SW12 from on to off. Furthermore, after controlling switch SW12 from on to off, the reset circuit 310 controls switch SW11 to be on for a predetermined period, and then controls switch SW11 from on to off. Furthermore, when the logic level of the input periodic pulse signal CYP changes from low to high, the reset circuit 310 controls switch SW13 to be on for a predetermined period, and then controls switch SW13 from on to off. Consequently, the maximum voltage value acquisition circuit 320 maintains the maximum voltage value at one end of capacitor C13 for each vibration cycle of the residual vibration detection signal NVT, and outputs this value from the maximum voltage value acquisition circuit 320 as the maximum voltage signal Vmax.

[0270] Furthermore, when the logic level of the input periodic pulse signal CYP changes from low to high, the reset circuit 310 controls switch SW22 to be on for a predetermined period, and then controls switch SW22 from on to off. Furthermore, after controlling switch SW22 from on to off, the reset circuit 310 controls switch SW21 to be on for a predetermined period, and then controls switch SW21 from on to off. Furthermore, when the logic level of the input periodic pulse signal CYP changes from high to low, the reset circuit 310 controls switch SW23 to be on for a predetermined period, and then controls switch SW23 from on to off. Thus, the minimum voltage value acquisition circuit 330 maintains a minimum voltage value at one end of the capacitor C23 for each vibration cycle of the residual vibration detection signal NVT, and outputs this value from the minimum voltage value acquisition circuit 330 as the minimum voltage signal Vmin.

[0271] The control circuit 100 then holds the maximum voltage signal Vmax output by the maximum voltage value acquisition circuit 320 during the period when the periodic pulse signal CYP output by the comparator CP1 is at a low level, and holds the minimum voltage signal Vmin output by the minimum voltage value acquisition circuit 330 during the period when the periodic pulse signal CYP output by the comparator CP1 is at a high level. This allows the control circuit 100 to acquire the maximum voltage signal Vmax corresponding to the maximum voltage value and the minimum voltage signal Vmin corresponding to the minimum voltage value of the residual vibration detection signal NVT for each vibration cycle of the residual vibration detection signal NVT.

[0272] In the liquid ejection device 1 of the modified example configured as described above, the attenuation rate of the amplitude of the residual vibration detection signal NVT can be calculated using both the maximum and minimum voltage values ​​of the residual vibration detection signal NVT. In this case, the control circuit 100 can obtain approximately twice as much amplitude information as when the attenuation rate of the amplitude of the residual vibration detection signal NVT is calculated using only the maximum or minimum voltage values ​​of the residual vibration detection signal NVT. In addition to the aforementioned effects, the attenuation rate of the amplitude of the residual vibration detection signal NVT, which serves as waveform information, can be calculated with high precision. As a result, the accuracy of determining the ejection status of ink ejected from the corresponding ejection unit 600 is further improved.

[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 without departing from the spirit and scope of the present invention. For example, the above embodiments can be appropriately combined.

[0274] The present invention includes structures that are substantially the same as the structures described in the embodiments (for example, structures that have the same functions, methods, and results, or structures that have the same purpose and effect). Furthermore, the present invention includes structures in which non-essential portions of the structures described in the embodiments are replaced. Furthermore, the present invention includes structures that can produce the same effects as the structures described in the embodiments, or structures that can achieve the same purpose. Furthermore, the present invention includes structures in which known technologies are added to the structures described in the embodiments.

[0275] The following are derived from the above-mentioned embodiments.

[0276] One aspect of the print head is:

[0277] a first pressure chamber, the volume of which changes according to a driving signal;

[0278] a first nozzle, connected to the first pressure chamber and spraying liquid;

[0279] a first piezoelectric element outputting a first residual vibration signal corresponding to a first residual vibration generated by a volume change of the first pressure chamber;

[0280] a first switch circuit having one end to which the drive signal is input and the other end electrically connected to the first piezoelectric element, the first switch circuit switching whether to supply the drive signal to the first piezoelectric element; and

[0281] a first residual vibration detection circuit, outputting a first residual vibration detection signal corresponding to the first residual vibration signal;

[0282] One end of the first residual vibration detection circuit is electrically connected to one end of the first switch circuit, and the other end of the first residual vibration detection circuit is electrically connected to the other end of the first switch circuit.

[0283] According to the print head, it has a first switching circuit and a first residual vibration detection circuit, one end of the first switching circuit is input with a driving signal, and the other end is electrically connected to the first piezoelectric element, the first piezoelectric element outputs a first residual vibration signal corresponding to the first residual vibration generated by the volume change of the first pressure chamber, the first residual vibration detection circuit outputs a first residual vibration detection signal corresponding to the first residual vibration signal, one end of the first residual vibration detection circuit is electrically connected to one end of the first switching circuit, and the other end is electrically connected to the other end of the first switching circuit.

[0284] In the printhead constructed as described above, a potential difference is generated across the first switch circuit corresponding to the resistance value of the first switch circuit's on-resistance and the first residual vibration signal. The first residual vibration signal is a signal corresponding to the charge output by the first piezoelectric element in response to the first residual vibration generated by the volume change of the first pressure chamber. The first residual vibration detection circuit then detects the potential difference across the first switch circuit. In other words, the first residual vibration detection circuit can detect the first residual vibration signal without switching the on-state of the first switch circuit. Therefore, in the printhead described above, the first residual vibration signal can be detected without having to control the on-state of the first switch circuit to a state specifically for obtaining the first residual vibration signal. Consequently, the speed of detecting the residual vibration generated by driving the first piezoelectric element can be further increased.

[0285] In one aspect of the above-mentioned print head, there may also be:

[0286] The first piezoelectric element is displaced according to the driving signal,

[0287] The volume of the first pressure chamber changes according to the displacement of the first piezoelectric element.

[0288] According to this print head, the first piezoelectric element changes the volume of the first pressure chamber and obtains the first residual vibration signal. Therefore, there is no need to separately provide a dedicated structure for changing the volume of the first pressure chamber, resulting in a compact print head.

[0289] In one aspect of the above-mentioned print head, there may also be:

[0290] At a first timing when the volume of the first pressure chamber changes according to the driving signal and at a second timing when the first piezoelectric element outputs the first residual vibration signal corresponding to the first residual vibration, one end and the other end of the first switch circuit are controlled to be conductive.

[0291] According to this print head, the first residual vibration detection circuit can obtain the first residual vibration signal without switching the conduction state of the first switch circuit. Therefore, there is no need to control the conduction state of the first switch circuit to a state dedicated to obtaining the first residual vibration signal. As a result, the detection speed of the residual vibration generated after the first piezoelectric element is driven can be further increased.

[0292] In one aspect of the above-mentioned print head, there may also be:

[0293] The first switch circuit includes a transistor element,

[0294] At the first timing, the transistor element is driven in a linear region.

[0295] In one aspect of the above-mentioned print head, it may also be:

[0296] The driving signal is a micro-vibration waveform that vibrates liquid near the first nozzle to such an extent that the liquid is not ejected from the first nozzle.

[0297] According to this print head, the liquid stored in the first pressure chamber is not ejected when the first residual vibration detection circuit acquires the first residual vibration signal. Therefore, the first residual vibration detection circuit can acquire the first residual vibration signal with high accuracy.

[0298] In one aspect of the above-mentioned print head, it may include:

[0299] a second pressure chamber, the volume of which changes according to the driving signal;

[0300] a second nozzle, connected to the second pressure chamber and spraying liquid;

[0301] a second piezoelectric element outputting a second residual vibration signal corresponding to a second residual vibration generated by a volume change of the second pressure chamber;

[0302] a second switch circuit having one end to which the drive signal is input and the other end electrically connected to the second piezoelectric element, the second switch circuit switching whether to supply the drive signal to the second piezoelectric element; and

[0303] a second residual vibration detection circuit outputting a second residual vibration detection signal corresponding to the second residual vibration signal;

[0304] One end of the second residual vibration detection circuit is electrically connected to one end of the second switch circuit, and the other end of the second residual vibration detection circuit is electrically connected to the other end of the second switch circuit.

[0305] In this printhead, the first residual vibration detection circuit acquires a first residual vibration signal corresponding to the first residual vibration generated in the first pressure chamber, while the second residual vibration detection circuit acquires a second residual vibration signal corresponding to the second residual vibration generated in the second pressure chamber. This allows the first residual vibration signal to be acquired by the first residual vibration detection circuit and the second residual vibration detection circuit to be acquired by the second residual vibration detection circuit in parallel. Consequently, even with a printhead having multiple pressure chambers, the residual vibration detection speed can be further increased.

[0306] One aspect of the liquid ejection device includes:

[0307] A driving circuit outputting a driving signal;

[0308] a first pressure chamber, the volume of which changes according to the driving signal;

[0309] a first nozzle, connected to the first pressure chamber and spraying liquid;

[0310] a first piezoelectric element outputting a first residual vibration signal corresponding to a first residual vibration generated by a volume change of the first pressure chamber;

[0311] a first switch circuit having one end to which the drive signal is input and the other end electrically connected to the first piezoelectric element, the first switch circuit switching whether to supply the drive signal to the first piezoelectric element; and

[0312] a first residual vibration detection circuit, outputting a first residual vibration detection signal corresponding to the first residual vibration signal;

[0313] One end of the first residual vibration detection circuit is electrically connected to one end of the first switch circuit, and the other end of the first residual vibration detection circuit is electrically connected to the other end of the first switch circuit.

[0314] According to the liquid ejection device, the print head has a first switching circuit and a first residual vibration detection circuit, one end of the first switching circuit is input with a driving signal, and the other end is electrically connected to the first piezoelectric element, the first piezoelectric element outputs a first residual vibration signal corresponding to the first residual vibration generated by the volume change of the first pressure chamber, the first residual vibration detection circuit outputs a first residual vibration detection signal corresponding to the first residual vibration signal, one end of the first residual vibration detection circuit is electrically connected to one end of the first switching circuit, and the other end is electrically connected to the other end of the first switching circuit.

[0315] In the print head constructed as described above, a potential difference corresponding to the resistance value of the on-resistance of the first switching circuit and the first residual vibration signal is generated at both ends of the first switching circuit. The first residual vibration signal is a signal corresponding to the charge output by the first piezoelectric element based on the first residual vibration generated by the volume change of the first pressure chamber.

[0316] The first residual vibration detection circuit then detects the potential difference across the first switch circuit. In other words, the first residual vibration detection circuit can detect the first residual vibration signal without switching the conductive state of the first switch circuit. Therefore, in a liquid ejection device having the above-described printhead, the first residual vibration signal can be detected without having to control the conductive state of the first switch circuit to a state specifically for detecting the first residual vibration signal. Consequently, the detection speed of the residual vibration generated by driving the first piezoelectric element can be further increased.

[0317] In one aspect of the liquid ejection device, it may also be:

[0318] The first piezoelectric element is displaced according to the driving signal,

[0319] The volume of the first pressure chamber changes according to the displacement of the first piezoelectric element.

[0320] According to this liquid ejection device, the first piezoelectric element changes the volume of the first pressure chamber and obtains the first residual vibration signal. Therefore, there is no need to separately set up a dedicated structure for changing the volume of the first pressure chamber. As a result, the print head can be made small.

[0321] In one aspect of the liquid ejection device, it may also be:

[0322] At a first timing when the volume of the first pressure chamber changes according to the driving signal and at a second timing when the first piezoelectric element outputs the first residual vibration signal corresponding to the first residual vibration, one end and the other end of the first switch circuit are controlled to be conductive.

[0323] According to the liquid ejection device, the first residual vibration detection circuit can obtain the first residual vibration signal without switching the conduction state of the first switch circuit. Therefore, there is no need to control the conduction state of the first switch circuit to a state dedicated to obtaining the first residual vibration signal. As a result, the detection speed of the residual vibration generated after the first piezoelectric element is driven can be further increased.

[0324] In one aspect of the liquid ejection device, it may also be:

[0325] The first switch circuit includes a transistor element,

[0326] At the first timing, the transistor element is driven in a linear region.

[0327] In one aspect of the liquid ejection device, it may also be:

[0328] The driving signal is a micro-vibration waveform that vibrates liquid near the first nozzle to such an extent that the liquid is not ejected from the first nozzle.

[0329] According to this liquid ejection device, the liquid stored in the first pressure chamber is not ejected when the first residual vibration detection circuit acquires the first residual vibration signal. Therefore, the first residual vibration detection circuit can acquire the first residual vibration signal with high accuracy.

[0330] In one aspect of the liquid ejection device, the device may include:

[0331] a second pressure chamber, the volume of which changes according to the driving signal;

[0332] a second nozzle, connected to the second pressure chamber and spraying liquid;

[0333] a second piezoelectric element outputting a second residual vibration signal corresponding to a second residual vibration generated by a volume change of the second pressure chamber;

[0334] a second switch circuit having one end to which the drive signal is input and the other end electrically connected to the second piezoelectric element, the second switch circuit switching whether to supply the drive signal to the second piezoelectric element; and

[0335] a second residual vibration detection circuit outputting a second residual vibration detection signal corresponding to the second residual vibration signal;

[0336] One end of the second residual vibration detection circuit is electrically connected to one end of the second switch circuit, and the other end of the second residual vibration detection circuit is electrically connected to the other end of the second switch circuit.

[0337] In this liquid ejection device, the first residual vibration detection circuit acquires a first residual vibration signal corresponding to the first residual vibration generated in the first pressure chamber, and the second residual vibration detection circuit acquires a second residual vibration signal corresponding to the second residual vibration generated in the second pressure chamber. This allows the first residual vibration signal to be acquired by the first residual vibration detection circuit and the second residual vibration detection circuit to be acquired by the second residual vibration detection circuit in parallel. Consequently, even with a printhead having multiple pressure chambers, the residual vibration detection speed can be further increased.

Claims

1. A print head, characterized in that: have: a first pressure chamber, the volume of which changes according to a driving signal; a first nozzle, connected to the first pressure chamber and spraying liquid; a first piezoelectric element outputting a first residual vibration signal corresponding to a first residual vibration generated by a volume change of the first pressure chamber; a first switch circuit, one end of which is input with the driving signal and the other end of which is electrically connected to the first piezoelectric element, the first switch circuit switching whether to supply the driving signal to the first piezoelectric element; as well as a first residual vibration detection circuit, outputting a first residual vibration detection signal corresponding to the first residual vibration signal; One end of the first residual vibration detection circuit is electrically connected to one end of the first switch circuit, and the other end of the first residual vibration detection circuit is electrically connected to the other end of the first switch circuit.

2. The print head according to claim 1, wherein The first piezoelectric element is displaced according to the driving signal, The volume of the first pressure chamber changes according to the displacement of the first piezoelectric element.

3. The print head according to claim 1, wherein At a first timing when the volume of the first pressure chamber changes according to the driving signal and at a second timing when the first piezoelectric element outputs the first residual vibration signal corresponding to the first residual vibration, one end and the other end of the first switch circuit are controlled to be conductive.

4. The print head according to claim 3, wherein: The first switch circuit includes a transistor element, At the first timing, the transistor element is driven in a linear region.

5. The print head according to claim 1, wherein: The driving signal is a micro-vibration waveform that vibrates liquid near the first nozzle to such an extent that the liquid is not ejected from the first nozzle.

6. The print head according to any one of claims 1 to 5, characterized in that The print head has: a second pressure chamber, the volume of which changes according to the driving signal; a second nozzle, connected to the second pressure chamber and spraying liquid; a second piezoelectric element outputting a second residual vibration signal corresponding to a second residual vibration generated by a volume change of the second pressure chamber; a second switch circuit, one end of which is input with the driving signal and the other end of which is electrically connected to the second piezoelectric element, the second switch circuit switching whether to supply the driving signal to the second piezoelectric element; as well as a second residual vibration detection circuit outputting a second residual vibration detection signal corresponding to the second residual vibration signal; One end of the second residual vibration detection circuit is electrically connected to one end of the second switch circuit, and the other end of the second residual vibration detection circuit is electrically connected to the other end of the second switch circuit.

7. A liquid ejection device, characterized in that: have: A driving circuit outputting a driving signal; a first pressure chamber, the volume of which changes according to the driving signal; a first nozzle, connected to the first pressure chamber and spraying liquid; a first piezoelectric element outputting a first residual vibration signal corresponding to a first residual vibration generated by a volume change of the first pressure chamber; a first switch circuit, one end of which is input with the driving signal and the other end of which is electrically connected to the first piezoelectric element, the first switch circuit switching whether to supply the driving signal to the first piezoelectric element; as well as a first residual vibration detection circuit, outputting a first residual vibration detection signal corresponding to the first residual vibration signal; One end of the first residual vibration detection circuit is electrically connected to one end of the first switch circuit, and the other end of the first residual vibration detection circuit is electrically connected to the other end of the first switch circuit.

8. The liquid ejection device according to claim 7, wherein: The first piezoelectric element is displaced according to the driving signal, The volume of the first pressure chamber changes according to the displacement of the first piezoelectric element.

9. The liquid ejection device according to claim 7, wherein: At a first timing when the volume of the first pressure chamber changes according to the driving signal and at a second timing when the first piezoelectric element outputs the first residual vibration signal corresponding to the first residual vibration, one end and the other end of the first switch circuit are controlled to be conductive.

10. The liquid ejection device according to claim 9, wherein: The first switch circuit includes a transistor element, At the first timing, the transistor element is driven in a linear region.

11. The liquid ejecting device according to claim 7, wherein: The driving signal is a micro-vibration waveform that vibrates liquid near the first nozzle to such an extent that the liquid is not ejected from the first nozzle.

12. The liquid ejecting device according to any one of claims 7 to 11, wherein: The liquid ejection device comprises: a second pressure chamber, the volume of which changes according to the driving signal; a second nozzle, connected to the second pressure chamber and spraying liquid; a second piezoelectric element outputting a second residual vibration signal corresponding to a second residual vibration generated by a volume change of the second pressure chamber; a second switch circuit, one end of which is input with the driving signal and the other end of which is electrically connected to the second piezoelectric element, the second switch circuit switching whether to supply the driving signal to the second piezoelectric element; as well as a second residual vibration detection circuit outputting a second residual vibration detection signal corresponding to the second residual vibration signal; One end of the second residual vibration detection circuit is electrically connected to one end of the second switch circuit, and the other end of the second residual vibration detection circuit is electrically connected to the other end of the second switch circuit.

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