Print head and liquid discharge device

Abstract

To provide a print head capable of increasing the detection speed of residual vibration.SOLUTION: A print head comprises: a first pressure chamber whose volume changes according to a drive signal; a first nozzle which communicates with the first pressure chamber and discharges liquid; a first piezoelectric element which outputs 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 which has one end to which the drive signal is input, and has the other end electrically connected to the first piezoelectric element, and which switches whether the drive signal is supplied to the first piezoelectric element; and a first residual vibration detection circuit which outputs a first residual vibration detection signal corresponding to the first residual vibration signal. The first residual vibration detection circuit has one end electrically connected to one end of the first switch circuit and the other end electrically connected to the other end of the first switch circuit.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a printhead and a liquid ejection device. [Background technology]

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

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-039856 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in terms of further increasing the detection speed when detecting residual vibrations that occur after the piezoelectric element is driven, the technology described in Patent Document 1 is not sufficient, and there is room for further improvement. [Means for solving the problem]

[0005] One aspect of the print head according to the present invention is a first pressure chamber whose volume changes in response to a drive signal; a first nozzle communicating with the first pressure chamber and discharging 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 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 or not the drive signal is supplied to the first piezoelectric element; a first residual vibration detection circuit that outputs a first residual vibration detection signal corresponding to the first residual vibration signal; Equipped with The first residual vibration detection circuit has one end electrically connected to one end of the first switch circuit and the other end electrically connected to the other end of the first switch circuit.

[0006] One aspect of the liquid ejection device according to the present invention is a drive circuit that outputs a drive signal; a first pressure chamber whose volume changes in response to the drive signal; a first nozzle communicating with the first pressure chamber and discharging 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 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 or not the drive signal is supplied to the first piezoelectric element; a first residual vibration detection circuit that outputs a first residual vibration detection signal corresponding to the first residual vibration signal; Equipped with The first residual vibration detection circuit has one end electrically connected to one end of the first switch circuit and the other end electrically connected to the other end of the first switch circuit. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a liquid ejection device. [Figure 2] FIG. 2 is a diagram illustrating a schematic configuration of a discharge unit. [Figure 3] FIG. 2 is an exploded perspective view of a print head. [Figure 4] FIG. 4 is a cross-sectional view taken along line Aa in FIG. [Figure 5] 10A and 10B are diagrams illustrating examples of signal waveforms of a drive voltage signal COM, a latch signal LAT, a change signal CH, and a test timing signal TSIG. [Figure 6] FIG. 2 is a diagram illustrating an example of a functional configuration of a drive signal selection circuit. [Figure 7] FIG. 10 is a diagram showing an example of the decoded content in the decoder. [Figure 8] FIG. 10 is a diagram showing the configuration of a selection circuit corresponding to one discharge portion. [Figure 9] FIG. 2 is a diagram illustrating an example of the configuration of a residual vibration detection circuit. [Figure 10] FIG. 10 is a diagram illustrating an example of the operation of a drive signal selection circuit. [Figure 11] FIG. 2 is a diagram illustrating an example of the configuration of a waveform information output circuit. [Figure 12] 10A and 10B are diagrams for explaining the operation of a waveform information output circuit. [Figure 13] 5A and 5B are diagrams illustrating examples of residual vibration signals Vout1 and Vout2. [Figure 14] 10 is a diagram showing an example of a calculation model of simple harmonic motion assuming residual vibration occurring in the pressure chamber CB1, the pressure chamber CB2, or the diaphragm 304. FIG. [Figure 15] 10A and 10B are diagrams for explaining the relationship between the viscosity of ink and the signal waveforms of residual vibration signals Vout1 and Vout2. [Figure 16] 10A and 10B are diagrams for explaining the signal waveforms of residual vibration signals Vout1 and Vout2 when air bubbles are mixed into pressure chambers CB1 and CB2. [Figure 17] 10 is a diagram showing an example of the signal waveform of a residual vibration signal Vout when the ejection unit is normal. FIG. [Figure 18] 10 is a diagram showing an example of the signal waveform of a residual vibration signal Vout when an abnormality in viscosity increase occurs in a discharge section. FIG. [Figure 19] 10 is a diagram showing an example of the signal waveform of a residual vibration signal Vout when an abnormality due to air bubbles entering the discharge section occurs. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present invention will be described below with reference to the drawings. The drawings used are for the convenience of explanation. Note that the embodiments described below do not unduly limit the content of the present invention as defined in the claims. Furthermore, not all of the configurations described below are necessarily essential components of the present invention.

[0009] 1. Configuration of the liquid ejection device FIG. 1 is a diagram illustrating a schematic configuration of a liquid ejection device 1. As shown in FIG. 1, the liquid ejection device 1 is a so-called line-type inkjet printer that forms a desired image on a medium P transported by a transport unit 4 by ejecting ink, as an example of a liquid, at a desired timing. Note that the liquid ejection device 1 is not limited to a line-type inkjet printer, but may also be a serial-type inkjet printer. Furthermore, the liquid ejection device 1 is not limited to an inkjet printer, but may also be a color material ejection device used in manufacturing color filters for liquid crystal displays and the like, an electrode material ejection device used in forming electrodes for organic electroluminescence displays (EL) displays, FEDs (face-emitting displays), and the like, a bioorganic material ejection device used in manufacturing biochips, a three-dimensional modeling device, a textile printing device, or the like. Hereinafter, the direction in which the medium P is transported may be referred to as the transport direction, and the width direction of the transported medium P may be referred to as the scanning direction.

[0010] As shown in FIG. 1, the liquid ejection device 1 includes a control unit 2, a liquid container 3, a transport unit 4, a plurality of ejection units 5, and a circulation unit 6.

[0011] The control unit 2 is composed of a CPU (Central Processing Unit) and an FPGA (Field Programmable Gate Array). The control unit 2 includes a processing circuit such as a BLE Gate Array, and a storage circuit such as a semiconductor memory. The control unit 2 outputs signals to control each element of the liquid ejection device 1 based on image data supplied from an external device such as a host computer (not shown) provided outside the liquid ejection device 1.

[0012] The liquid container 3 stores ink as an example of a liquid to be supplied to the ejection unit 5. Specifically, the liquid container 3 stores ink of a plurality of colors to be ejected onto the medium P, such as black, cyan, magenta, yellow, red, and gray. As such a liquid container 3, an ink cartridge, a bag-shaped ink pack made of a flexible film, an ink tank that can be refilled with ink, or the like can be used.

[0013] The circulation unit 6 supplies the 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. The circulation unit 6 also recovers the ink discharged from the ejection unit 5 based on the circulation control signal Ctrl-P output by the control unit 2. In other words, the circulation unit 6 circulates the ink in the liquid ejection device 1. Such a circulation unit 6 can be configured to include, for example, a pump that generates the flow of ink in the liquid ejection device 1.

[0014] The transport unit 4 has a transport motor 41 and a transport roller 42. A transport control signal Ctrl-T output by the control unit 2 is input to the transport unit 4. The transport motor 41 is driven based on the transport control signal Ctrl-T, and the drive of the transport motor 41 causes the transport roller 42 to rotate. The rotation of the transport roller 42 transports the medium P along the transport direction.

[0015] Each of the multiple ejection units 5 has a drive module 10 and an ejection module 20. A corresponding image information signal IP output by the control unit 2 is input to each of the multiple ejection units 5, and ink stored in the liquid container 3 is supplied to each of the multiple ejection units 5. The drive module 10 controls the operation of the ejection module 20 based on the image information signal IP. As a result, the ejection module 20 ejects ink supplied from the liquid container 3 at a predetermined timing according to the control of the drive module 10.

[0016] In the liquid ejection device 1 of this embodiment, the ejection modules 20 of each of the multiple ejection units 5 are aligned along the scanning direction so as to be equal to or greater than the width of the medium P. The drive modules 10 of each of the multiple ejection units 5 cause the ejection modules 20 to eject ink in synchronization with the transport of the medium P. The ink ejected from each of the multiple ejection modules 20 lands at a desired position on the medium P. This forms a desired image on the medium P.

[0017] Next, a schematic configuration of the discharge unit 5 will be described. FIG. 2 is a diagram showing a schematic configuration of the discharge unit 5. As shown in FIG. 2, the discharge unit 5 has a driving module 10 and a discharge module 20. In the discharge unit 5, the driving module 10 and the discharge module 20 are electrically connected via a cable 15. Here, a flexible flat cable (FFC) or a flexible printed circuit (FPC) can be used as the cable 15 that electrically connects the driving module 10 and the discharge module 20. Furthermore, the driving module 10 and the discharge module 20 may be electrically connected by a BtoB (Board to Board) connector without using the cable 15, or may be electrically connected by using the cable 15 and the BtoB connector in combination.

[0018] The drive module 10 has a control circuit board 11, a drive circuit 50, and a control circuit 100. The control circuit board 11 is a printed circuit board having one or more wiring layers, and a glass epoxy board, a glass polyimide board, or the like can be used. The control circuit board 11 is mounted with the elements that make up the drive module 10, including the drive circuit 50 and the control circuit 100. Note that the control circuit board 11 on which the elements that make up the drive module 10 are mounted may be made up of a single printed circuit board or multiple printed circuit boards.

[0019] The control circuit 100 is a processor and includes a processing circuit such as a CPU or FPGA, and a storage circuit such as a 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.

[0020] Specifically, the control circuit 100 generates a clock signal SCK, a latch signal LAT, a change 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.

[0021] The control circuit 100 also generates a reference drive signal dA and outputs it to the drive circuit 50. The drive circuit 50 generates a drive voltage signal COM including a signal waveform defined by the input reference drive signal dA and outputs it to the ejection module 20. Specifically, the control circuit 100 generates the reference drive signal dA as a digital signal and outputs it to the drive circuit 50. The drive circuit 50 converts the input digital reference drive signal dA into an analog signal and then generates the drive voltage signal COM by class-D amplifying the converted analog signal. The drive circuit 50 outputs the generated drive voltage signal COM to the ejection module 20. In other words, the control circuit 100 outputs the reference drive signal dA that defines the signal waveform of the drive voltage signal COM output by the drive circuit 50. Note that the reference drive signal dA may be an analog signal as long as it is a signal that can define the signal waveform of the drive voltage signal COM. Furthermore, the drive circuit 50 is only required to generate the drive voltage signal COM by amplifying the signal waveform defined by the basic drive signal dA, and may 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.

[0022] The drive circuit 50 also generates a reference voltage signal VBS and outputs it to the discharging module 20. The reference voltage signal VBS is a signal with a constant voltage value that defines a reference potential for driving the piezoelectric elements 60a and 60b, which will be described later. The voltage value of such a reference voltage signal VBS may be, for example, ground potential, or may be 5.5 V or 6 V. Note that while FIG. 2 illustrates the drive circuit 50 generating the reference voltage signal VBS and outputting it to the discharging module 20, the reference voltage signal VBS may also be generated by a constant voltage output circuit (not shown) that is configured separately from the drive circuit 50.

[0023] Furthermore, waveform information signals WFS11 to WFS1m, WFS21 to WFS2m, ..., WFSn1 to WFSnm are input to the control circuit 100 from the ejection modules 20, which will be described later. The control circuit 100 determines whether or not the ink ejection state from the ejection modules 20 is normal based on each of the input waveform information signals WFS11 to WFS1m, WFS21 to WFS2m, ..., WFSn1 to WFSnm. Details of the waveform information signals WFS11 to WFS1m, WFS21 to WFS2m, ..., WFSn1 to WFSnm input to the control circuit 100 and details of a method for determining whether or not the ink ejection state from the ejection modules 20 is normal based on the waveform information signals WFS11 to WFS1m, WFS21 to WFS2m, ..., WFSn1 to WFSnm will be described later.

[0024] The ejection module 20 includes print heads 21-1 to 21-n, a head circuit board 23, and , 300-n1 to 300-nm. Each of print heads 21-1 to 21-n has a head chip 22, a flexible substrate 24, and a drive signal selection circuit 200. Each of head chips 22 included in each of print heads 21-1 to 21-n has ejection units 600-1 to 600-m, and each of ejection units 600-1 to 600-m includes piezoelectric elements 60a and 60b.

[0025] The ejection module 20 receives the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signals SI1 to SIn, drive voltage signal COM, and reference voltage signal VBS output by the drive module 10.

[0026] The head circuit board 23 transmits the input clock signal SCK, latch signal LAT, change 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 may be made of, for example, a glass epoxy board or a glass polyimide board.

[0027] Specifically, of the input clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signals SI1 to SIn, drive voltage signal COM, and reference voltage signal VBS, head circuit board 23 propagates the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SI1, drive voltage signal COM, and reference voltage signal VBS to print head 21-1, and propagates the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SIn, drive voltage signal COM, and reference voltage signal VBS to print head 21-n.

[0028] Of the clock signal SCK, latch signal LAT, change 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, change signal CH, inspection timing signal TSIG, print data signal SI1, and drive voltage signal COM are input to print head 21-1's drive signal selection circuit 200. The drive signal selection circuit 200 of print head 21-1 selects or deselects the signal waveform included in the drive voltage signal COM based on the input clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, and print data signal SI1, thereby generating and outputting drive voltage signals Vin-1 to Vin-m.

[0029] Drive voltage signals Vin-1 to Vin-m output by drive signal selection circuit 200 of print head 21-1 are supplied to corresponding ejection units 600-1 to 600-m of head chip 22 of print head 21-1. Specifically, of drive voltage signals Vin-1 to Vin-m output by drive signal selection circuit 200 of print head 21-1, drive voltage signal Vin-1 is supplied to one end of piezoelectric elements 60a, 60b included in ejection unit 600-1 of head chip 22 of print head 21-1, and drive voltage signal Vin-m is supplied to one end of piezoelectric elements 60a, 60b included in ejection unit 600-m of head chip 22 of print head 21-1. At this time, a reference voltage signal VBS is commonly supplied to the other end of the piezoelectric elements 60a, 60b included in each of the ejection units 600-1 to 600-m of the head chip 22 of the print head 21-1. The piezoelectric elements 60a, 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 in accordance with the potential difference between the voltage value of the corresponding drive 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. An amount of ink corresponding to the drive of the piezoelectric elements 60a, 60b is ejected into the ejection units of the print head 21-1. Ink is ejected from 600-1 to 600-m.

[0030] Furthermore, residual vibrations occur in the ejection sections 600-1 to 600-m of the head chip 22 of the print head 21-1 after the piezoelectric elements 60a and 60b included therein are driven. The piezoelectric elements 60a and 60b included in the ejection sections 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 sections 600-1 to 600-m. The piezoelectric elements 60a and 60b included in the ejection sections 600-1 to 600-m of the print head 21-1 output residual vibration signals Vout-1 to Vout-m corresponding to the displacement. These residual vibration signals Vout-1 to Vout-m are input 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 residual vibration detection signals NVT-1 to NVT-m according to the input residual vibration signals Vout-1 to Vout-m, and outputs them from the print head 21-1.

[0031] Specifically, after piezoelectric elements 60a, 60b included in ejector 600-1 of head chip 22 of print head 21-1 are driven, a signal corresponding to the residual vibration occurring in ejector 600-1 is input as residual vibration signal Vout-1 to drive signal selection circuit 200 of print head 21-1, and after piezoelectric elements 60a, 60b included in ejector 600-m of head chip 22 of print head 21-1 are driven, a signal corresponding to the residual vibration occurring in ejector 600-m is input as residual vibration signal Vout-m to drive signal selection circuit 200 of print head 21-1. Drive signal selection circuit 200 of print head 21-1 then generates residual vibration detection signal NVT-1 corresponding to the input residual vibration signal Vout-1 and outputs it from print head 21-1, and generates residual vibration detection signal NVT-m corresponding to the input residual vibration signal Vout-m and outputs it from print head 21-1.

[0032] The drive signal selection circuit 200 of the print head 21-1 is configured as an integrated circuit device, and is mounted on the flexible substrate 24 of the print head 21-1. On Film) may be implemented.

[0033] Of the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SIn, drive voltage signal COM, and reference voltage signal VBS input to print head 21-n, the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SIn, and drive voltage signal COM are input to print head 21-n's drive signal selection circuit 200. The drive signal selection circuit 200 of print head 21-n selects or deselects the signal waveform included in the drive voltage signal COM based on the input clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, and print data signal SIn, thereby generating and outputting drive voltage signals Vin-1 to Vin-m.

[0034] 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 of the head chip 22 of the print head 21-n. Specifically, of the drive voltage signals Vin-1 to Vin-m output by the drive signal selection circuit 200 of the print head 21-n, the drive voltage signal Vin-1 is supplied to one end of the piezoelectric elements 60a, 60b included in the ejection unit 600-1 of the head chip 22 of the print head 21-n, and the drive voltage signal Vin-m is supplied to one end of the piezoelectric elements 60a, 60b included in the ejection unit 600-m of 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, 60b included in each of the ejection portions 600-1 to 600-m of the head chip 22 of the print head 21-n. Piezoelectric elements 60a, 60b are driven in response to the potential difference between the voltage value of corresponding drive voltage signals Vin-1 to Vin-m supplied to one end and the voltage value of reference voltage signal VBS supplied to the other end. An amount of ink corresponding to the driving of these piezoelectric elements 60a, 60b is ejected from ejection portions 600-1 to 600-m of print head 21-n.

[0035] Furthermore, residual vibrations occur in the ejection sections 600-1 to 600-m of the head chip 22 of the print head 21-n after the piezoelectric elements 60a and 60b included therein are driven. The piezoelectric elements 60a and 60b included in the ejection sections 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 sections 600-1 to 600-m. The piezoelectric elements 60a and 60b included in the ejection sections 600-1 to 600-m of the print head 21-n output residual vibration signals Vout-1 to Vout-m corresponding to the displacement. These residual vibration signals Vout-1 to Vout-m 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 then generates residual vibration detection signals NVT-1 to NVT-m according to the input residual vibration signals Vout-1 to Vout-m, and outputs them from the print head 21-n.

[0036] Specifically, after piezoelectric elements 60a, 60b included in ejector 600-1 of head chip 22 of print head 21-n are driven, a signal corresponding to the residual vibration occurring in ejector 600-1 is input as residual vibration signal Vout-1 to drive signal selection circuit 200 of print head 21-n, and after piezoelectric elements 60a, 60b included in ejector 600-m of head chip 22 of print head 21-n are driven, a signal corresponding to the residual vibration occurring in ejector 600-m is input as residual vibration signal Vout-m to drive signal selection circuit 200 of print head 21-n. Drive signal selection circuit 200 of print head 21-n then generates residual vibration detection signal NVT-1 corresponding to the input residual vibration signal Vout-1 and outputs it from print head 21-n, and generates residual vibration detection signal NVT-m corresponding to the input residual vibration signal Vout-m and outputs it from print head 21-n.

[0037] The drive signal selection circuit 200 of the print head 21-n may be configured as an integrated circuit device and mounted on the flexible substrate 24 of the print head 21-n by COF mounting.

[0038] The waveform information output circuits 300-11 to 300-1m, 300-21 to 300-2m, . . . , 300-n1 to 300-nm are mounted on the head circuit board 23.

[0039] 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 waveform information of the input residual vibration detection signals NVT-1 to NVT-m at intervals defined by the latch signal LAT, and generate waveform information signals WFS11 to WFS1m that include 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.

[0040] Specifically, the waveform information output circuit 300-11 receives the residual vibration detection signal NVT-1 output by the print head 21-1. The waveform information output circuit 300-11 acquires waveform information of the residual vibration detection signal NVT-1 output by the print head 21-1 at each cycle defined 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 section 600-1 of the head chip 22 of the print head 21-1 at each cycle defined by the latch signal LAT, and outputs a waveform information signal WFS11 including the acquired waveform information. The information signal WFS11 is output to the control circuit 100.

[0041] The waveform information output circuit 300-1m also receives the residual vibration detection signal NVT-m output by the print head 21-1. The waveform information output circuit 300-1m acquires waveform information of the input residual vibration detection signal NVT-m output by the print head 21-1 at each cycle defined by the latch signal LAT, and outputs a waveform information signal WFS1m including the acquired waveform information. That is, the waveform information output circuit 300-1m acquires waveform information of a signal corresponding to the residual vibration of the ejection portion 600-m of the head chip 22 of the print head 21-1 at each cycle defined by the latch signal LAT, and outputs a waveform information signal WFS1m including the acquired waveform information to the control circuit 100.

[0042] Similarly, the waveform information output circuits 300-n1 to 300-nm receive the latch signal LAT and the residual vibration detection signals NVT-1 to NVT-m output by the print head 21-n. The 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 intervals defined by the latch signal LAT, and generate waveform information signals WFSn1 to WFSnm containing the acquired waveform information. The waveform information output circuits 300-n1 to 300-nm then output the generated waveform information signals WFSn1 to WFSnm to the control circuit 100 of the drive module 10.

[0043] Specifically, the waveform information output circuit 300-n1 acquires waveform information of the residual vibration detection signal NVT-1 output by the print head 21-n at each period defined by the latch signal LAT and outputs a waveform information signal WFS11 including the acquired waveform information, and the waveform information output circuit 300-nm acquires waveform information of the residual vibration detection signal NVT-m output by the print head 21-n at each period defined 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-n1 acquires waveform information of a signal corresponding to the residual vibration of the ejection section 600-1 of the head chip 22 of the print head 21-n at each period defined by the latch signal LAT, and outputs a waveform information signal WFSn1 including the acquired waveform information to the control circuit 100, while the waveform information output circuit 300-nm acquires waveform information of a signal corresponding to the residual vibration of the ejection section 600-m of the head chip 22 of the print head 21-n at each period defined by the latch signal LAT, and outputs a waveform information signal WFSnm including the acquired waveform information to the control circuit 100.

[0044] That is, the waveform information output circuits 300-11 to 300-1m, 300-21 to 300-2m, ..., 300-n1 to 300-nm individually acquire waveform information of signals corresponding to the residual vibration of each of the ejection portions 600-1 to 600-m of the head chips 22 of the 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 of the drive module 10.

[0045] Based on the input waveform information signals WFS11 to WFS1m, WFS21 to WFS2m, ..., WFSn1 to WFSnm, the control circuit 100 individually determines whether the ink ejection state from each of the ejection sections 600-1 to 600-m of the head chips 22 of the print heads 21-1 to 21-n is normal or not.

[0046] Here, the waveform information output circuits 300-11 to 300-1m may be configured as a single integrated circuit device or may be configured as discrete components. 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 waveform information output circuits 300-11 to 300-1m. In addition, when the waveform information output circuits 300-11 to 300-1m are configured as integrated circuit devices, the integrated circuit devices may be mounted on the flexible substrate 24 of the print head 21-1 by COF mounting.

[0047] Similarly, the waveform information output circuits 300-n1 to 300-nm may be configured as a single integrated circuit device or may be configured with discrete components. Furthermore, the waveform information output circuits 300-n1 to 300-nm may be mounted together with the drive signal selection circuit 200 in an integrated circuit device that constitutes the drive signal selection circuit 200 of the print head 21-n. Furthermore, when the waveform information output circuits 300-n1 to 300-nm are configured as integrated circuit devices, the integrated circuit device may be mounted on the flexible substrate 24 of the print head 21-n using COF mounting.

[0048] Here, print heads 21-1 to 21-n all have the same configuration, and when there is no need to distinguish between them, they may be simply referred to as print head 21. Furthermore, print head 21 will be described as receiving clock signal SCK, latch signal LAT, change signal CH, test timing signal TSIG, print data signal SI as print data signals SI1 to SIn, drive voltage signal COM, and reference voltage signal VBS, and outputting residual vibration detection signals NVT-1 to NVT-m. Furthermore, the residual vibration detection signals NVT-1 to NVT-m output by print head 21 will be described as being input to waveform information output circuits 300-1 to 300-m as waveform information output circuits 300-11 to 300-1m, 300-21 to 300-2m, ..., 300-n1 to 300-nm. At this time, the residual vibration detection signal NVT-1 output by the print head 21 is input to the waveform information output circuit 300-1, which outputs a waveform information signal WFS1 corresponding to the residual vibration detection signal NVT-1, and the residual vibration detection signal NVT-m output by the print head 21 is input to the waveform information output circuit 300-m, which outputs a waveform information signal WFSm corresponding to the residual vibration detection signal NVT-m.

[0049] Furthermore, the waveform information output circuits 300-1 to 300-m all have the same configuration, and when there is no need to distinguish between them, they may be simply referred to as waveform information output circuit 300. In this case, the following description will be given assuming that the waveform information output circuit 300 receives the residual vibration detection signal NVT as the residual vibration detection signals NVT-1 to NVT-m output by the print head 21, and outputs the waveform information signal WFS as the waveform information signals WFS1 to WFSm.

[0050] Furthermore, the ejection sections 600-1 to 600-m of the print head 21 all have the same configuration, and when there is no need to distinguish between them, they will be simply referred to as ejection section 600. That is, the print head 21 will be described as having a plurality of ejection sections 600, m in number. The description will be given assuming that the ejection sections 600 are supplied with a drive voltage signal Vin as drive voltage signals Vin-1 to Vin-m, and that the ejection sections 600 output a residual vibration signal Vout as residual vibration signals Vout-1 to Vout-m.

[0051] 2. Print head structure Next, the structure of the print head 21 will be described. Figure 3 is an exploded perspective view of the print head 21, and Figure 4 is a cross-sectional view taken along line Aa in Figure 3. The following description will be made using mutually perpendicular X, Y, and Z axes. In the following description, the starting side of an arrow along the illustrated X axis will be referred to as the -X side, and the tip side as the +X side. The starting side of an arrow along the illustrated Y axis will be referred to as the -Y side, and the tip side as the +Y side. The starting side of an arrow along the illustrated Z axis will be referred to as the -Z side, and the tip side as the +Z side.

[0052] As shown in FIGS. 3 and 4, the print head 21 includes a head chip 22 and a flexible The head chip 22 also includes a nozzle substrate 360, compliance sheets 361 and 362, a communication plate 302, a pressure chamber substrate 303, a vibration plate 304, and a reservoir chamber forming substrate 305.

[0053] The nozzle substrate 360 ​​is a plate-like member that is elongated along the Y axis and extends substantially parallel to the XY plane formed by the X and Y axes. m nozzles N are formed in the nozzle substrate 360. The nozzles N are through-holes formed in the nozzle substrate 360. These m nozzles N are arranged in parallel along the Y axis on the nozzle substrate 360 ​​to form a nozzle row Ln on the nozzle substrate 360. Here, "substantially parallel" does not necessarily mean completely parallel, but also includes cases where the nozzles can be considered parallel when errors and the like are taken into consideration.

[0054] The communicating plate 302 is located on the -Z side of the nozzle substrate 360. The communicating plate 302 is a plate-shaped member that is long along the Y axis and extends approximately parallel to the XY plane. In this communicating plate 302, a supply flow path RA1, a discharge flow path RA2, m connection flow paths RK1, m connection flow paths RK2, m communication flow paths RR1, m communication flow paths RR2, and m nozzle flow paths RN are formed as part of the flow paths through which ink flows.

[0055] The supply flow path RA1 is located on the +X side of the communicating plate 302 and extends along the Y direction. The discharge flow path RA2 is located on the -X side of the communicating plate 302 and extends along the Y direction. The supply flow path RA1 and the discharge flow path RA2 are formed to be approximately symmetrical with respect to the Z axis passing through the nozzle N. The m connection flow paths RK1 are located on the -X side of the supply flow path RA1 and are arranged side by side along the Y direction. The m communication flow paths RR1 are located on the -X side of the m connection flow paths RK1 arranged side by side along the Y direction and are arranged side by side along the Y direction. The m connection flow paths RK2 are located on the +X side of the discharge flow path RA2 and on the -X side of the m communication flow paths RR1 arranged side by side along the Y direction and are arranged side by side along the Y direction. The m communication flow paths RR2 are located on the +X side of the m connection flow paths RK2 arranged side by side along the Y direction and on the -X side of the m communication flow paths RR1 arranged side by side along the Y direction and are arranged side by side along the Y direction. In this case, the connection flow paths RK1 and RK2 are formed so as to be approximately line-symmetrical about the Z axis that passes through the nozzle N, and the communication flow paths RR1 and RR2 are formed so as to be approximately line-symmetrical about the Z axis that passes through the nozzle N. The nozzle flow path RN communicates with the communication flow paths RR1 and RR2 that correspond to a common nozzle N. The nozzle substrate 360 ​​is fixed to the communication plate 302 so that the nozzle N is located approximately in the center of the nozzle flow path RN in the X direction when the communication plate 302 is viewed from the Z direction.

[0056] The pressure chamber substrate 303 is located on the -Z side of the communication plate 302 and is fixed to the communication plate 302. The pressure chamber substrate 303 is a plate-like member that is long in the Y-axis direction and extends approximately parallel to the XY plane. In this pressure chamber substrate 303, m pressure chambers CB1 and m pressure chambers CB2 are formed as part of the flow path through which ink flows. In this case, the pressure chambers CB1 and CB2 are formed so as to be approximately symmetrical with respect to the Z-axis that passes through the nozzle N.

[0057] The m pressure chambers CB1 correspond one-to-one to the m nozzles N and are arranged side by side along the Y axis. Each of the m pressure chambers CB1 is communicated with a connecting flow channel RK1 and a communicating flow channel RR1 corresponding to the common nozzle N. Specifically, when viewed from the Z axis, the +X side end of the pressure chamber CB1 is communicated with the connecting flow channel RK1 and the -X side end is communicated with the communicating flow channel RR1. In other words, the pressure chamber CB1 communicates with the connecting flow channel RK1 corresponding to the common nozzle N and the communicating flow channel RR1.

[0058] Similarly, the m pressure chambers CB2 correspond one-to-one to the m nozzles N, are located on the -X side of the m pressure chambers CB1 arranged side by side along the Y axis, and are arranged side by side along the Y axis. Each of the m pressure chambers CB2 has a connecting flow channel RK2 and a communicating flow channel RK3 corresponding to a common nozzle N. RR2. Specifically, when viewed from the Z-axis, the pressure chamber CB2 has an end on the -X side that communicates with the connecting flow channel RK2 and an end on the +X side that communicates with the communicating flow channel RR2. In other words, the pressure chamber CB2 communicates with the connecting flow channel RK2 that corresponds to the common nozzle N and the communicating flow channel RR2.

[0059] 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 so as to close the pressure chambers CB1 and CB2. The vibration plate 304 is a plate-shaped member that is elongated in the Y direction and extends approximately parallel to the XY plane, and is a member that can elastically vibrate. On the -Z side of the vibration plate 304, m piezoelectric elements 60a and m piezoelectric elements 60b are arranged side by side. The m piezoelectric elements 60a are arranged side by side along the Y axis on the -Z side of the vibration plate 304. The m piezoelectric elements 60b are also arranged side by side along the Y axis on the -Z side of the vibration plate 304, on the -X side of the m piezoelectric elements 60a arranged side by side along the Y axis. That is, on the -Z side of the vibration plate 304, a row of m piezoelectric elements 60a and a row of m piezoelectric elements 60b are arranged side by side.

[0060] The reservoir chamber forming substrate 305 is located on the -Z side of the communication plate 302. The reservoir chamber forming substrate 305 is a member that is elongated in the Y direction and includes an opening 350. The reservoir chamber forming substrate 305 is fixed to the communication plate 302 so that the pressure chamber substrate 303, the vibration plate 304, and the wiring substrate 308 are located inside the opening 350. The reservoir chamber forming substrate 305 also includes a supply flow path RB1, a discharge flow path RB2, a supply port 351, and a discharge port 352. The supply flow path RB1 communicates with the supply flow path RA1. The discharge flow path RB2 communicates with the discharge flow path RA2. The supply port 351 communicates with the supply flow path RB1. The discharge port 352 communicates with the discharge flow path RB2. The circulation unit 6 operates to supply ink stored in the liquid container 3 to the supply port 351. This causes ink to be supplied to the head chip 22. Furthermore, the ink supplied to head chip 22 flows inside head chip 22 due to the operation of circulation unit 6, and is collected via outlet 352. That is, the ink supplied to head chip 22 is circulated due to the operation of circulation unit 6.

[0061] The flexible substrate 24 is electrically connected to the diaphragm 304 on the -Z side surface of the diaphragm 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 diaphragm 304 between the row of m piezoelectric elements 60a and the row of m piezoelectric elements 60b provided on the diaphragm 304. In this case, it is preferable that the flexible substrate 24 is electrically connected to the diaphragm 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 approximately equal.

[0062] An integrated circuit 201 is mounted on the flexible substrate 24 by COF mounting. The above-mentioned drive signal selection circuit 200 is mounted on the integrated circuit 201. That is, the integrated circuit 201 outputs a corresponding drive voltage signal Vin to the piezoelectric elements 60a, 60b of each of the m ejection units 600.

[0063] That is, the flexible substrate 24 propagates the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SI, drive voltage signal COM, and reference voltage signal VBS that are input to the print head 21. Of the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SI, drive voltage signal COM, and reference voltage signal VBS propagated by the flexible substrate 24, the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SI, and drive voltage signal COM are input to the integrated circuit 201. The integrated circuit 201 controls the drive voltage based on the input clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, and print data signal SI. By selecting or not selecting the signal waveform of the signal COM, the driving voltage signal Vin corresponding to each of the m ejection sections 600 is generated and output.

[0064] The drive voltage signal Vin output by the integrated circuit 201 propagates through the flexible substrate 24 and is supplied to the piezoelectric element 60a included in the corresponding ejection section 600. This drives each of the piezoelectric elements 60a, 60b included in the corresponding ejection section 600 so that they are displaced along the Z axis. Driving the piezoelectric elements 60a, 60b displaces the vibration plate 304 along the Z axis, and the displacement of the vibration plate 304 changes the volumes of the pressure chambers CB1, CB2. The internal pressures of the pressure chambers CB1, CB2 change in accordance with the change in the volumes of the pressure chambers CB1, CB2.

[0065] Here, the drive voltage signal Vin propagates through a wiring pattern formed on the flexible substrate 24, branches at the diaphragm 304, and is then supplied to each of the piezoelectric elements 60a and 60b. This eliminates the need to provide, on the flexible substrate 24, a wiring pattern for propagating the drive voltage signal Vin to the piezoelectric element 60a and a wiring pattern for propagating the drive voltage signal Vin to the piezoelectric element 60b, individually. As a result, the flexible substrate 24 can be made smaller.

[0066] In the print head 21 configured as above, the configuration including the piezoelectric elements 60a and 60b, pressure chambers CB1 and CB2, communication channels RR1 and RR2, and nozzles N included in the head chip 22 corresponds to the ejection section 600 described above.

[0067] That is, the print head 21 of this embodiment has a pressure chamber CB1 whose volume changes in response to a drive voltage signal Vin based on a drive voltage signal COM, a pressure chamber CB2 whose volume changes in response to a drive voltage signal Vin based on a drive voltage signal COM, a nozzle N that communicates with the pressure chamber CB1 and the pressure chamber CB2 and ejects ink, a piezoelectric element 60a that is driven in response to a drive voltage signal Vin based on the drive voltage signal COM and changes the volume of the pressure chamber CB1, and a piezoelectric element 60b that is driven in response to a drive voltage signal Vin based on the drive voltage signal COM and changes the volume of the pressure chamber CB2.

[0068] In the print head 21, ink flowing out of pressure chamber CB1 in response to the decrease in volume of pressure chamber CB1 and ink flowing out of pressure chamber CB2 in response to the decrease in volume of pressure chamber CB2 join together on the -Z side of nozzle N. The ink joined on the -Z side of nozzle N is then ejected from nozzle N. Therefore, the print head 21 of this embodiment can achieve higher driving performance than a configuration in which one piezoelectric element ejects the ink filled inside one pressure chamber. As a result, the print head 21 of this embodiment can increase the amount of ink ejected and can achieve stable ejection characteristics even when using highly viscous ink.

[0069] 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 central portions of the corresponding piezoelectric elements 60a, 60b are displaced along the Z axis to the -Z side, and when the voltage value of the drive voltage signal Vin input to the print head 21 increases, the central portions of the corresponding piezoelectric elements 60a, 60b are displaced along the Z axis to the +Z side. Note that the relationship between the voltage value of the drive voltage signal Vin and the displacement of the piezoelectric elements 60a, 60b is not limited to this, and it may be configured such that when the voltage value of the drive voltage signal Vin input to the print head 21 decreases, the central portions of the corresponding piezoelectric elements 60a, 60b are displaced along the Z axis to the +Z side, and when the voltage value of the drive voltage signal Vin input to the print head 21 increases, the central portions of the corresponding piezoelectric elements 60a, 60b are displaced along the Z axis to the -Z side.

[0070] 3. Configuration and operation of the drive signal selection circuit 3.1 Signal waveform of drive voltage signal COM Next, we will explain the configuration and operation of the drive signal selection circuit 200, which selects or deselects a signal waveform included in the drive voltage signal COM to output a drive voltage signal Vin corresponding to each of the m discharge units 600. Before explaining the details of the drive signal selection circuit 200, we will first explain examples of the signal waveforms of the drive voltage signal COM, latch signal LAT, change signal CH, and test timing signal TSIG input to the drive signal selection circuit 200. Figure 5 is a diagram showing examples of the signal waveforms of the drive voltage signal COM, latch signal LAT, change signal CH, and test timing signal TSIG.

[0071] The control circuit 100 outputs a pulse signal as the latch signal LAT, whose logic level remains high for a fixed 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 will be referred to as a latch pulse. Desired dots are formed on the medium P during a period in which the logic level of the latch signal LAT remains high for a fixed period and the control circuit 100 outputs a latch pulse as the latch signal LAT. In the following description, the period in which the logic level of the latch signal LAT remains high and the control circuit 100 outputs a latch pulse as the latch signal LAT will be referred to as a dot formation period Cp. Note that if the liquid ejection device 1 is a serial inkjet printer, the control circuit 100 may output a 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.

[0072] The drive voltage signal COM includes a drive voltage signal ComA and a drive voltage signal ComB. The drive voltage signal ComA includes a drive waveform Adp1 and a drive waveform Adp2 in a dot formation period Cp. The drive waveform Adp1 is a signal waveform that starts at a voltage vc, changes to drive the piezoelectric elements 60a and 60b, and then ends at the voltage vc. When this drive waveform Adp1 is supplied to the piezoelectric elements 60a and 60b, a predetermined amount of ink is ejected from the nozzle N of the corresponding ejection unit 600. The drive waveform Adp2 is a signal waveform that starts at a voltage vc, changes to drive the piezoelectric elements 60a and 60b, and then ends at the voltage vc. When this drive waveform Adp2 is supplied to the piezoelectric elements 60a and 60b, a smaller amount of ink than the predetermined amount is ejected from the nozzle N of the corresponding ejection unit 600.

[0073] That is, the drive voltage signal ComA includes a signal waveform for ejecting ink from the nozzle N included in the ejection unit 600. In the following description, a predetermined amount of ink ejected from the corresponding nozzle N when the drive waveform Adp1 is supplied to the piezoelectric elements 60a, 60b may be referred to as a medium amount, and an amount of ink smaller than the predetermined amount ejected from the corresponding nozzle N when the drive waveform Adp2 is supplied to the piezoelectric elements 60a, 60b may be referred to as a small amount.

[0074] The drive voltage signal ComB includes drive waveforms Bdp1 and Bdp2 during the dot formation period Cp. The drive waveform Bdp1 is a signal waveform that starts at a voltage vc, changes so that the piezoelectric elements 60a and 60b are driven to a level that prevents ink from being ejected from the corresponding nozzle N, and then ends at a 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 included in the corresponding ejection unit 600 vibrates to a level that prevents ink from being ejected from the nozzle N. This reduces the risk of an increase in the viscosity of the ink near the opening of the nozzle N in the ejection unit 600. The drive waveform Bdp2 is a signal waveform with a constant 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.

[0075] That is, the driving voltage signal ComB causes ink to be ejected from the nozzles N included in the ejection unit 600. The signal waveform includes a signal waveform for preventing an increase in the viscosity of the ink by not ejecting the ink but vibrating the ink in the vicinity of the nozzle N. Here, in the following description, the operation of vibrating the ink in the vicinity of the opening of the nozzle N of the ejection unit 600 to prevent an increase in the viscosity of the ink may be referred to as micro-vibration.

[0076] The control circuit 100 outputs a pulse signal whose logic level is high for a certain period as the change signal CH at the timing when the signal waveform included in the drive voltage signal ComA is switched from drive waveform Adp1 to drive waveform Adp2 and at the timing when the signal waveform included in the drive voltage signal ComB is switched from drive waveform Bdp1 to drive waveform Bdp2. Here, in the following explanation, the pulse signal output by the control circuit 100 as the change signal CH will be referred to as a change pulse.

[0077] Specifically, the control circuit 100 outputs a change pulse as the change signal CH at a timing between a period during which the voltage value of the drive waveform Adp1 changes to drive the piezoelectric elements 60 a, 60 b and a period during which the voltage value of the drive waveform Adp2 changes to drive the piezoelectric elements 60 a, 60 b, and at a timing after the period during which the voltage value of the drive waveform Adp2 changes to drive the piezoelectric elements 60 a, 60 b has elapsed. Here, in the following explanation, the period within the dot formation period Cp from when a latch pulse is output as the latch signal LAT to when a change pulse is output as the change signal CH is referred to as the drive period Pp1, and the period from when a change pulse is output as the change signal CH to when a latch pulse is output as the latch signal LAT is referred to as the drive period Pp2. That is, the change signal CH divides the dot formation period Cp into a drive period Pp1 in which the drive waveform Adp1 included in the drive voltage signal ComA and the drive waveform Bdp1 included in the drive voltage signal ComB are arranged, and a drive period Pp2 in which the drive waveform Adp2 included in the drive voltage signal ComA and the drive waveform Bdp2 included in the drive voltage signal ComB are arranged.

[0078] In this embodiment, the control circuit 100 outputs one change signal CH corresponding to both the drive voltage signal ComA and the drive voltage signal ComB, but the control circuit 100 may also output a change signal CH corresponding to the drive voltage signal ComA and a change signal CH corresponding to the drive voltage signal ComB separately. Also, the control circuit 100 may output two or more change pulses as the change signal CH in the dot formation cycle Cp, depending on the number of signal waveforms included in the drive voltage signals ComA and ComB.

[0079] The control circuit 100 outputs a pulse signal whose logic level is high for a certain period of time as a test timing signal TSIG that specifies the test timing for testing whether or not the ink discharge state from the discharge module 20 including the discharge unit 600 is normal, based on the residual vibration generated in the discharge unit 600. Here, in the following description, the pulse signal that the control circuit 100 outputs as the test timing signal TSIG will be referred to as a test pulse.

[0080] Specifically, after a latch pulse is input as the latch signal LAT, the control circuit 100 changes the voltage value of the drive voltage signal ComB, and then outputs a test pulse as the test timing signal TSIG at the timing when the voltage value becomes constant. Also, after the control circuit 100 outputs a test pulse as the test timing signal TSIG at the timing when the voltage value of the drive voltage signal ComB changes and then becomes constant, it outputs a test pulse as the test timing signal TSIG again after a certain period of time has passed. Here, in the following explanation, the period from when the latch pulse as the latch signal LAT is output to when the test pulse as the test timing signal TSIG is output within the dot formation period Cp is referred to as the test period Ps1, and the test pulse as the test timing signal TSIG that defines the end of the test period Ps1 is output. The period from when the test pulse as the test timing signal TSIG that defines the end of the test period Ps2 is output until the next test pulse as the test timing signal TSIG is output is called the test period Ps2, and the period from when the test pulse as the test timing signal TSIG that defines the end of the test period Ps2 is output until the next latch pulse as the latch signal LAT is output is called the test period Ps3. In other words, the test timing signal TSIG divides the dot formation period Cp into test periods Ps1, Ps2, and Ps3. Then, based on the residual vibration generated in the ejector 600 during the test period Ps2, the control circuit 100 performs an inspection to determine whether the ink ejection state from the ejection module 20 that includes the ejector 600 is normal.

[0081] That is, the drive circuit 50 outputs a drive voltage signal COM including a drive voltage signal ComA including drive waveforms Adp1 and Adp2 and a drive voltage signal ComB including drive waveforms Bdp1 and Bdp2 to the drive signal selection circuit 200, and the drive signal selection circuit 200 generates a drive voltage signal Vin by selecting or deselecting the drive waveforms Adp1 and Adp2 and the drive waveforms Bdp1 and Bdp2 during each of the drive periods Pp1 and Pp2, and supplies this to one end of the piezoelectric elements 60a and 60b of the corresponding ejection section 600.

[0082] Furthermore, during the test period Ps2, the drive signal selection circuit 200 acquires a residual vibration signal Vout corresponding to the residual vibration generated in the ejection section 600 and outputs it as a residual vibration detection signal NVT. Then, the waveform information output circuit 300 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. Then, based on the input waveform information signal WFS, the control circuit 100 performs an inspection to determine whether the ink ejection state from the corresponding ejection section 600 and the ejection module 20 including that ejection section 600 is normal.

[0083] 5 is an example, and the drive circuit 50 may output the drive voltage signal COM including various signal waveforms depending on the type of ink to be ejected and the type of medium P on which the ink will land. Alternatively, the drive circuit 50 may generate a drive voltage signal COM including a signal waveform corresponding to each of the print heads 21-1 to 21-n and output the signal to the corresponding print head 21-1 to 21-n. The timing at which the control circuit 100 outputs a change pulse as the change signal CH and the timing at which the control circuit 100 outputs a test pulse as the test timing signal TSIG are not limited to the example shown in FIG.

[0084] 3.2 Configuration of the drive signal selection circuit A specific example of the configuration of the drive signal selection circuit 200 will be described. Fig. 6 is a diagram showing an example of the functional configuration of the drive signal selection circuit 200. Fig. 6 also shows m ejection units 600, ejection units 600-1 to 600-m, which are driven by the drive voltage signal Vin output by the drive signal selection circuit 200. As shown in Fig. 6, the drive signal selection circuit 200 includes a selection control circuit 220, m selection circuits 230, and m residual vibration detection circuits 240.

[0085] A clock signal SCK, a print data signal SI, a latch signal LAT, a change signal CH, and a test timing signal TSIG are input to the selection control circuit 220. Based on the input clock signal SCK, print data signal SI, latch signal LAT, change signal CH, and test timing signal TSIG, the selection control circuit 220 generates selection signals Sa and Sb that have predetermined logic levels during the drive periods Pp1 and Pp2, respectively, and outputs these to the corresponding selection circuits 230. Also, the selection control circuit 220 generates a test enable signal OE that has a predetermined logic level during the test periods Ps1, Ps2, and Ps3, and outputs this to the corresponding residual vibration detection circuit 240.

[0086] The selection control circuit 220 has a set of a shift register 222, a latch circuit 224, and a decoder 226 provided corresponding to each of the ejection units 600-1 to 600-m of the print head 21. In other words, the selection control circuit 220 has at least m sets of the shift register 222, the latch circuit 224, and the decoder 226.

[0087] The print data signal SI includes 3-bit print data SId[SIH, SIM, SIL] serially corresponding to each of the m ejection units 600, for selecting which dot to form on the medium P (large dot LD, medium dot MD, small dot SD, or non-printing ND), or whether to execute a status inspection CD that inspects the ink ejection status from the ejection units 600. In other words, the print data signal SI is a serial signal of at least 3m bits.

[0088] The print data signal SI is input to the selection control circuit 220 in synchronization with the clock signal SCK. The m shift registers 222 included in the selection control circuit 220 hold the 3-bit print data SId [SIH, SIM, SIL] included in the input print data signal SI, corresponding to the ejection sections 600-1 to 600-m.

[0089] Specifically, m shift registers 222 are connected in cascade to correspond to the respective ejection units 600-1 to 600-m. The print data signal SI input serially 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. When the supply of the clock signal SCK to the selection control circuit 220 is stopped, the m shift registers 222 hold the 3-bit print data SId[SIH, SIM, SIL] corresponding to the ejection units 600-1 to 600-m. In the following description, to distinguish between the m cascade-connected shift registers 222, they may be referred to as stage 1, stage 2, ..., stage m, in order from the upstream side to the downstream side where the print data signal SI is supplied.

[0090] Each of the m latch circuits 224 latches the 3-bit print data SId [SIH, SIM, SIL] held in the corresponding shift register 222 all at once when a latch pulse is input as a latch signal LAT.

[0091] The print data SId[SIH, SIM, SIL] latched by the m latch circuits 224 is input to the corresponding decoders 226. Each of the m decoders 226 decodes the input print data SId[SIH, SIM, SIL] and generates selection signals Sa, Sb of logic levels corresponding to large dots LD, medium dots MD, small dots SD, and non-printing ND, which are output to the corresponding selection circuit 230. Also, each decoder 226 generates an inspection enable signal OE of logic level corresponding to status inspection CD, which is output to the corresponding residual vibration detection circuit 240.

[0092] Fig. 7 is a diagram showing an example of the decoded content in decoder 226. As shown in Fig. 7, when print data SId[SIH,SIM,SIL]=[1,1,0] corresponding to large dots LD is input, decoder 226 sets the logic level of selection signal Sa to H,H levels during drive periods Pp1 and Pp2, sets the logic level of selection signal Sb to L,L levels during drive periods Pp1 and Pp2, and sets the logic level of inspection enable signal OE to L,L,L levels during inspection periods Ps1, Ps2, and Ps3.

[0093] Furthermore, when print data SId[SIH, SIM, SIL]=[1, 0, 0] corresponding to a medium dot MD is input, the decoder 226 sets the logic level of the selection signal Sa to H, L levels during the drive periods Pp1, Pp2, sets the logic level of the selection signal Sb to L, L levels during the drive periods Pp1, Pp2, and sets the logic level of the inspection enable signal OE to L, L, L levels during the inspection periods Ps1, Ps2, Ps3.

[0094] Furthermore, when print data SId[SIH, SIM, SIL]=[0, 1, 0] corresponding to a small dot SD is input, the decoder 226 sets the logic level of the selection signal Sa to L, H levels during the drive periods Pp1, Pp2, sets the logic level of the selection signal Sb to L, L levels during the drive periods Pp1, Pp2, and sets the logic level of the inspection enable signal OE to L, L, L levels during the inspection periods Ps1, Ps2, Ps3.

[0095] Furthermore, when print data SId[SIH, SIM, SIL]=[0,0,0] corresponding to non-recording ND is input, the decoder 226 sets the logic level of the selection signal Sa to L, L levels during the drive periods Pp1 and Pp2, sets the logic level of the selection signal Sb to H, H levels during the drive 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.

[0096] Furthermore, when print data SId[SIH, SIM, SIL]=[1,1,1] corresponding to the status inspection CD is input, the decoder 226 sets the logic level of the selection signal Sa to L, L levels during the drive periods Pp1, Pp2, sets the logic level of the selection signal Sb to H, H levels during the drive periods Pp1, Pp2, and sets the logic level of the inspection enable signal OE to L, H, L levels during the inspection periods Ps1, Ps2, Ps3.

[0097] As described above, based on the logic level of the print data SId [SIH, SIM, SIL], the selection control circuit 220 generates selection signals Sa, Sb and an inspection enable signal OE of logic levels corresponding to each of the m ejection sections 600. Then, the selection control circuit 220 outputs the selection signals Sa, Sb of the generated logic levels to the corresponding selection circuits 230, and outputs the inspection enable signal OE of the generated logic level to the corresponding residual vibration detection circuit 240.

[0098] A selection circuit 230 is provided corresponding to each of the ejection units 600-1 to 600-m. That is, the drive signal selection circuit 200 has m selection circuits 230. Drive voltage signals ComA and ComB are input as the drive voltage signal COM to each of the m selection circuits 230. Each of the m selection circuits 230 generates a drive voltage signal Vin corresponding to the drive voltage signal COM in accordance with the logic levels of the input selection signals Sa and Sb, and outputs the drive voltage signal Vin to the corresponding ejection unit 600. FIG. 8 is a diagram showing the configuration of a selection circuit 230 corresponding to one of the ejection units 600-1 to 600-m. As shown in FIG. 8, the selection circuit 230 has logic inversion circuits 232a and 232b and transfer gates 234a and 234b.

[0099] The selection signal Sa is supplied to the positive control terminal of the transfer gate 234a, and after its logic level is inverted by the logic inverter circuit 232a, is also supplied to the negative control terminal of the transfer gate 234a. When the logic level of the selection signal Sa is high, the transfer gate 234a is conductive between one end and the other end, and when the logic level of the selection signal Sa is low, the transfer gate 234a is non-conductive between the one end and the other end. The drive voltage signal ComA is also supplied to one end of the transfer gate 234a. Based on the logic level of the selection signal Sa, the transfer gate 234a selects or non-selects the signal waveform of the drive voltage signal ComA input to one end and outputs it from the other end.

[0100] The selection signal Sb is supplied to the positive control terminal of the transfer gate 234b, and after its logic level is inverted by the logic inverter circuit 232b, is also supplied to the negative control terminal of the transfer gate 234b. When the logic level of the selection signal Sb is high, the transfer gate 234b is conductive between one end and the other end, and when the logic level of the selection signal Sb is low, the transfer gate 234b is non-conductive between one end and the other end. The drive voltage signal ComB is supplied to one end of the transfer gate 234b, which selects or deselects the signal waveform of the drive voltage signal ComB input to one end based on the logic level of the selection signal Sb and outputs it from the other end.

[0101] In the selection circuit 230, the other end of the transfer gate 234a and the other end of the transfer gate 234b are connected to each other. The other ends of the connected transfer gates 234a and 234b are electrically connected to the piezoelectric elements 60a and 60b included in the corresponding ejection section 600. As a result, the selection circuit 230 supplies, as the drive voltage signal Vin, a signal indicating that the transfer gate 234a has selected or not selected the signal waveform of the drive voltage signal ComA, and a signal indicating that the transfer gate 234b has selected or not selected the signal waveform of the drive voltage signal ComB, to the piezoelectric elements 60a and 60b included in the corresponding ejection section 600.

[0102] Furthermore, the selection circuit 230 receives a residual vibration signal Vout, which is generated when the piezoelectric elements 60a, 60b included in the corresponding ejection unit 600 are supplied with and driven by the drive voltage signal Vin, and the piezoelectric elements 60a, 60b are driven in response to residual vibrations generated in the ejection unit 600. That is, the other ends of the transfer gates 234a, 234b are supplied with the residual vibration signal Vout, which is generated in response to residual vibrations generated in the piezoelectric elements 60a, 60b.

[0103] The selection circuit 230 outputs the voltage value of one end of the transfer gate 234b, which is the voltage value of the drive voltage signal ComB supplied to one end of the transfer gate 234b, as a residual vibration reference signal Vo1 to the corresponding residual vibration detection circuit 240, and also outputs the voltage value of the other end of the transfer gate 234b, which is the voltage value of the residual vibration signal Vout supplied to the other end of the transfer gate 234b, as a residual vibration detection signal Vo2 to the corresponding residual vibration detection circuit 240.

[0104] In the following description, conduction between one end and the other end of the transfer gates 234a and 234b may be referred to as "on," and non-conduction between one end and the other end of the transfer gates 234a and 234b may be referred to as "off."

[0105] Each of the transfer gates 234a and 234b includes one or more N-channel metal oxide semiconductor (MOS) transistors and one or more P-channel MOS transistors connected in a complementary manner. That is, each of the transfer gates 234a and 234b includes transistor elements. At least some of the transistor elements included in each of the transfer gates 234a and 234b operate in a linear region while the transfer gates 234a and 234b are turned on.

[0106] A residual vibration detection circuit 240 is provided corresponding to each of the m selection circuits 230 provided corresponding to each of the ejection units 600-1 to 600-m. That is, the drive signal selection circuit 200 has m residual vibration detection circuits 240. A residual vibration reference signal Vo1 and a residual vibration detection signal Vo2 output by the corresponding selection circuit 230 are input to each of the m residual vibration detection circuits 240. Then, each of the m residual vibration detection circuits 240 generates and outputs a residual vibration detection signal NVT corresponding to the residual vibration occurring in the corresponding ejection unit 600, in accordance with the signal waveforms of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2.

[0107] 9 is a diagram showing an example of the configuration of the residual vibration detection circuit 240. The residual vibration detection circuit 240 has capacitors C1 and C2, resistors R1, R2, R3, R4, R5, and R6, switches SW1 and SW2, and an amplifier circuit OP1.

[0108] A 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. The other end of the resistor R1 is supplied with ground potential. In other words, the capacitor C1 and the resistor R1 form a high-pass filter circuit. The output of the high-pass filter circuit formed 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 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.

[0109] A 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. The other end of the resistor R4 is supplied with a ground potential. In other words, the capacitor C2 and the resistor R4 form a high-pass filter circuit. The output of the high-pass filter circuit formed by 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 also electrically connected to the positive input terminal of the amplifier circuit OP1. The other end of the resistor R6 is electrically connected to the positive terminal of the power supply circuit PW1, and the negative terminal of the power supply circuit PW1 is supplied with a ground potential.

[0110] In the residual vibration detection circuit 240 configured as described above, a signal in which the DC component contained in the residual vibration reference signal Vo1 has been reduced by a high-pass filter circuit configured with capacitor C1 and resistor R1 is input to the negative input terminal of amplifier circuit OP1, and a signal in which the bias voltage signal VB output by power supply circuit PW1 is superimposed on a signal in which the DC component contained in the residual vibration detection signal Vo2 has been reduced by a high-pass filter circuit configured with capacitor C2 and resistor R4 is input to the positive input terminal of amplifier circuit OP1. As a result, amplifier circuit OP1 outputs a signal in which the difference between the signal input to the negative input terminal and the signal input to the positive input terminal is amplified by an amplification factor determined by the resistance values ​​of resistors R3 and R2, and voltage vb, which is the voltage value of the bias voltage signal VB, is added to the amplified signal as the residual vibration detection signal NVT.

[0111] The residual vibration signal Vout is generated by the displacement of the piezoelectric elements 60a, 60b due to the residual vibration generated in the ejection unit 600, and the charge generated in association with the displacement of the piezoelectric elements 60a, 60b due to the residual vibration propagates through the wiring to which the drive voltage signal ComB is applied via the transfer gate 234b. At this time, the current signal generated by the movement of charge due to the residual vibration is converted into a voltage signal by the on-resistance of the transfer gate 234b. In other words, a potential difference corresponding to the residual vibration generated in the corresponding ejection unit 600, that is, 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 transfer gate 234b.

[0112] The selection circuit 230 outputs the voltage value at one end of the transfer gate 234b as a residual vibration reference signal Vo1, and outputs the voltage value at the other end of the transfer gate 234b as a 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 to generate a residual vibration detection signal NVT, which is a signal obtained by amplifying the potential difference based on the residual vibration generated at both ends of the transfer gate 234b and is an amplified residual vibration signal Vout output from the corresponding ejection section 600, and outputs the signal to the control circuit 100.

[0113] One end of the switch SW1 is electrically connected to the other end of the capacitor C1 and one end of the resistor R1, the other end is supplied with ground potential, and a signal obtained by inverting the logic level of the inspection enable signal OE by the logic inverter circuit INV1 is input to the control end. The one end and the other end of the switch SW1 are then made non-conductive when a low-level signal is input to the control end. , and becomes conductive when a high-level signal is input to the control terminal. That is, when a high-level inspection enable signal OE is input to the residual vibration detection circuit 240, one end and the other end of the switch SW1 become non-conductive, and when a low-level inspection enable signal OE is input to the residual vibration detection circuit 240, one end and the other end of the switch SW1 become conductive.

[0114] One end of the switch SW2 is electrically connected to the other end of the capacitor C2 and one end of the resistor R4, the other end is supplied with ground potential, and a signal obtained by inverting the logic level of the test enable signal OE by the logic inverter INV1 is input to the control end. The one and other ends of the switch SW2 are made non-conductive when a low-level signal is input to the control end, and are made 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 the residual vibration detection circuit 240, the one and other ends of the switch SW2 are made non-conductive, and when a low-level test enable signal OE is input to the residual vibration detection circuit 240, the one and other ends of the switch SW2 are made conductive.

[0115] Such switches SW1 and SW2 are configured to include N-channel MOS transistors.

[0116] When a low-level inspection enable signal OE is input to the residual vibration detection circuit 240 configured as described above, one end and the other of the switch SW1 are conductive, so that the residual vibration reference signal Vo1 is not supplied to the negative input terminal of the amplifier circuit OP1, and one end and the other of the switch SW2 are conductive, so that the residual vibration detection signal Vo2 is not supplied to the positive input terminal of the amplifier circuit OP1. Therefore, the residual vibration detection circuit 240 does not generate a residual vibration detection signal NVT obtained by amplifying the residual vibration signal Vout output from the corresponding discharge unit 600.

[0117] On the other hand, when a high-level inspection enable signal OE is input to the residual vibration detection circuit 240, one end and the other end of the switch SW1 become non-conductive, so that the residual vibration reference signal Vo1 is supplied to the negative input terminal of the amplifier circuit OP1, and one end and the other end of the switch SW2 become non-conductive, so that the residual vibration detection signal Vo2 is supplied to the positive input terminal of the amplifier circuit OP1. Therefore, the residual vibration detection circuit 240 generates a residual vibration detection signal NVT by amplifying the residual vibration signal Vout output from the corresponding discharge unit 600, and outputs the amplified residual vibration signal NVT to the control circuit 100.

[0118] That is, during the period when a 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 reduces the DC component using a high-pass filter circuit and amplifies it to generate and output a residual vibration detection signal NVT in which the signal waveform of the residual vibration signal Vout is shaped.

[0119] In the following description, conduction between one end and the other end of switches SW1 and SW2 may be referred to as "on," and non-conduction between one end and the other end of switches SW1 and SW2 may be referred to as "off."

[0120] The operation of the drive signal selection circuit 200 configured as described above will be described in detail below. Fig. 10 is a diagram showing 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, when the supply of the clock signal SCK to the drive signal selection circuit 200 is stopped, each of the m shift registers 222 holds 3-bit print data SId[SIH, SIM, SIL] corresponding to the m ejection sections 600.

[0121] Thereafter, when the latch signal LAT rises, the latch circuits 224 simultaneously latch the print data SId[SIH, SIM, SIL] held in the shift register 222. Here, LT1, LT2, ..., LTm shown in Figure 10 indicate the print data SId[SIH, SIM, SIL] held in the 1st, 2nd, ..., mth stages of the shift register 222 and latched by the corresponding latch circuit 224.

[0122] The decoder 226 decodes the latched print data SId [SIH, SIM, SIL] as shown in Fig. 7. Then, during the dot formation period Cp, the decoder 226 outputs the selection signals Sa, Sb and the inspection enable signal OE at the logic levels shown in Fig. 7.

[0123] Specifically, when the print data SId[SIH, SIM, SIL] = [1, 1, 0], the decoder 226 sets the logic level of the selection signal Sa to H, H levels during the drive periods Pp1 and Pp2, sets the logic level of the selection signal Sb to L, L levels during the drive 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.

[0124] 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 during the drive period Pp1, and selects the drive waveform Adp2 of the drive voltage signal ComA during the drive period Pp2. As a result, the drive signal selection circuit 200 outputs the drive voltage signal Vin corresponding to the large dot LD shown in FIG. 10 during the dot formation period Cp. When the drive voltage signal Vin corresponding to this large dot LD is supplied to the ejection unit 600, a medium amount of ink is ejected from the ejection unit 600 during the drive period Pp1, and a small amount of ink is ejected during the drive period Pp2. Then, 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. As a result, a large dot LD is formed on the medium P during the dot formation period Cp.

[0125] Furthermore, the test enable signal OE output by the decoder 226 is input to the residual vibration detection circuit 240. As a result, the switches SW1 and SW2 of the residual vibration detection circuit 240 are controlled to be on during the test periods Ps1, Ps2, and Ps3. Therefore, the residual vibration detection circuit 240 outputs a signal with a constant voltage value of voltage vb, regardless of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. In other words, 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 section 600, and does not output the residual vibration detection signal NVT corresponding to the residual vibration signal Vout.

[0126] Furthermore, when the print data SId[SIH, SIM, SIL] = [1, 0, 0], the decoder 226 sets the logic level of the selection signal Sa to H, L levels during the drive periods Pp1, Pp2, sets the logic level of the selection signal Sb to L, L levels during the drive periods Pp1, Pp2, and sets the logic level of the inspection enable signal OE to L, L, L levels during the inspection periods Ps1, Ps2, Ps3.

[0127] 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 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 drive voltage signal Vin corresponding to the medium dot MD shown in FIG. 10 during the dot formation period Cp. When the drive voltage signal Vin corresponding to this medium dot MD is supplied to the discharge unit 600, the discharge unit 600 outputs a medium dot during the drive period Pp1. A medium amount of ink is ejected during the drive period Pp1, and no ink is ejected during the drive period Pp2. That is, during the dot formation period Cp, a medium amount of ink is ejected from the ejection unit 600 and lands on the medium P. As a result, medium dots MD are formed on the medium P during the dot formation period Cp.

[0128] Furthermore, the test enable signal OE output by the decoder 226 is input to the residual vibration detection circuit 240. As a result, the switches SW1 and SW2 of the residual vibration detection circuit 240 are controlled to be on during the test periods Ps1, Ps2, and Ps3. Therefore, the residual vibration detection circuit 240 outputs a signal with a constant voltage value of voltage vb, regardless of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. In other words, 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 section 600, and does not output the residual vibration detection signal NVT corresponding to the residual vibration signal Vout.

[0129] Furthermore, when the print data SId[SIH, SIM, SIL] = [0, 1, 0], the decoder 226 sets the logic level of the selection signal Sa to L, H levels during the drive periods Pp1, Pp2, sets the logic level of the selection signal Sb to L, L levels during the drive periods Pp1, Pp2, and sets the logic level of the inspection enable signal OE to L, L, L levels during the inspection periods Ps1, Ps2, Ps3.

[0130] 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 during the drive period Pp1, and selects the drive waveform Adp2 of the drive voltage signal ComA during the drive period Pp2. As a result, the drive signal selection circuit 200 outputs the drive voltage signal Vin corresponding to the small dot SD shown in FIG. 10 during the dot formation period Cp. When the drive voltage signal Vin corresponding to this small dot SD is supplied to the ejection unit 600, no ink is ejected from the ejection unit 600 during the drive period Pp1, but a small amount of ink is ejected during the drive period Pp2. In other words, during the dot formation period Cp, a small amount of ink ejected from the ejection unit 600 lands on the medium P. As a result, a small dot SD is formed on the medium P during the dot formation period Cp.

[0131] Furthermore, the test enable signal OE output by the decoder 226 is input to the residual vibration detection circuit 240. As a result, the switches SW1 and SW2 of the residual vibration detection circuit 240 are controlled to be on during the test periods Ps1, Ps2, and Ps3. Therefore, the residual vibration detection circuit 240 outputs a signal with a constant voltage value of voltage vb, regardless of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. In other words, 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 section 600, and does not output the residual vibration detection signal NVT corresponding to the residual vibration signal Vout.

[0132] Furthermore, when the print data SId[SIH, SIM, SIL] = [0, 0, 0], the decoder 226 sets the logic level of the selection signal Sa to L, L levels during the drive periods Pp1 and Pp2, sets the logic level of the selection signal Sb to H, H levels during the drive 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.

[0133] 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 Bdp1 of the drive voltage signal ComB in the drive period Pp1, and selects the drive waveform Bdp2 of the drive voltage signal ComB in the drive period Pp2. As a result, the drive signal selection circuit 200 selects the drive waveform Bdp1 of the drive voltage signal ComB in the dot formation period Cp as shown in FIG. When the drive voltage signal Vin corresponding to this non-printing ND is supplied to the ejection unit 600, ink is not ejected from the ejection unit 600 in the dot formation period Cp, and no dots are formed on the medium P. At this time, the corresponding ejection unit 600 performs a slight vibration.

[0134] Furthermore, the test enable signal OE output by the decoder 226 is input to the residual vibration detection circuit 240. As a result, the switches SW1 and SW2 of the residual vibration detection circuit 240 are controlled to be on during the test periods Ps1, Ps2, and Ps3. Therefore, the residual vibration detection circuit 240 outputs a signal with a constant voltage value of voltage vb, regardless of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. In other words, 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 section 600, and does not output the residual vibration detection signal NVT corresponding to the residual vibration signal Vout.

[0135] Furthermore, when the print data SId[SIH, SIM, SIL] = [1, 1, 1], the decoder 226 sets the logic level of the selection signal Sa to L, L levels during the drive periods Pp1 and Pp2, sets the logic level of the selection signal Sb to H, H levels during the drive periods Pp1 and Pp2, and sets the logic level of the inspection enable signal OE to L, H, L levels during the inspection periods Ps1, Ps2, and Ps3.

[0136] 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 Bdp1 of the drive voltage signal ComB during the drive period Pp1, and selects the drive waveform Bdp2 of the drive voltage signal ComB during the drive period Pp2. As a result, the drive signal selection circuit 200 outputs the drive voltage signal Vin corresponding to the non-printing ND shown in FIG. 10 during the dot formation period Cp. When the drive voltage signal Vin corresponding to this non-printing 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, the corresponding ejection unit 600 performs a micro-vibration.

[0137] Furthermore, the test enable signal OE output by the decoder 226 is input to the residual vibration detection circuit 240. As a result, the switches SW1 and SW2 of the residual vibration detection circuit 240 are controlled to be on during the test period Ps1, off during the test period Ps2, and on during the test period Ps3. Therefore, during the test period Ps1, the residual vibration detection circuit 240 outputs a signal with a constant voltage value of voltage vb regardless of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2, during the test period Ps2, it outputs a residual vibration detection signal NVT obtained by adding voltage vb to a signal obtained by differentially amplifying the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2, and during the test period Ps3, it outputs a signal with a constant voltage value of voltage vb regardless of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. In other words, during the test period Ps2, at the timing when the voltage value of the drive voltage signal ComB fluctuates and then becomes constant, the residual vibration detection circuit 240 outputs the residual vibration detection signal NVT that corresponds to the residual vibration signal Vout that corresponds to the residual vibration generated in the corresponding ejection section 600, and that corresponds to the residual vibration reference signal Vo1 and the residual vibration detection signal Vo2. In other words, when the print data SId[SIH, SIM, SIL]=[1,1,1], the residual vibration detection circuit 240 acquires the residual vibration signal Vout that corresponds to the residual vibration generated in the corresponding ejection section 600, and outputs the residual vibration detection signal NVT that corresponds to the residual vibration signal Vout.

[0138] As described above, the drive signal selection circuit 200 selects the drive waveforms Adp1 and Adp2 included in the drive voltage signal ComA of the drive voltage signal COM output by the drive circuit 50 based on the clock signal SCK, the print data signal SI, the latch signal LAT, and the change signal CH. A drive voltage signal Vin is generated by selecting or deselecting the drive waveforms Bdp1 and Bdp2 included in the drive voltage signal ComB and supplied to the corresponding ejection section 600. Based on the clock signal SCK, print data signal SI, latch signal LAT, and inspection timing signal TSIG, a residual vibration signal Vout corresponding to the residual vibration generated in the ejection section 600 after the drive voltage signal Vin is supplied to the ejection section 600 is obtained and output to the control circuit 100 as a residual vibration detection signal NVT.

[0139] That is, the ejection section 600 of the print head 21 of this embodiment includes a piezoelectric element 60a that outputs a signal corresponding to the residual vibration caused by the volume change of the pressure chamber CB1, and a piezoelectric element 60b that outputs a signal corresponding to the residual vibration caused by the volume change of the pressure chamber CB2. The drive signal selection circuit 200 of the print head 21 includes a transfer gate 234b that receives the drive voltage signal ComB at one end and is electrically connected at the other end to the piezoelectric elements 60a and 60b, and switches whether or not the drive voltage signal ComB is supplied to the piezoelectric elements 60a and 60b, and a residual vibration detection circuit 240 that outputs a residual vibration detection signal NVT corresponding to a residual vibration signal Vout that is a combination of a signal output by the piezoelectric element 60a that is corresponding to the residual vibration caused by the volume change of the pressure chamber CB1, and a signal output by the piezoelectric element 60b that is corresponding to the residual vibration caused by the volume change of the pressure chamber CB2. In the drive signal selection circuit 200 of the print head 21, one end of the residual vibration detection circuit 240 is electrically connected to one end of the transfer gate 234b, and the other end is electrically connected to the other end of the transfer gate 234b.

[0140] In the print head 21 configured as described above, a potential difference is generated across the transfer gate 234b depending on the resistance value of the on-resistance of the transfer gate 234b and the residual vibration signal Vout depending on the charge output by the piezoelectric elements 60a and 60b in response to residual vibration generated in the ejection section 600. The residual vibration detection circuit 240 of this embodiment has one end electrically connected to one end of the transfer gate 234b and the other end electrically connected to the other end of the transfer gate 234b, so it can obtain the potential difference across the transfer gate 234b. In other words, the residual vibration detection circuit 240 of this embodiment can obtain the residual vibration signal Vout depending on the residual vibration generated in the ejection section 600 while the transfer gate 234b, which switches whether or not to supply the drive voltage signal ComB to the ejection section 600, remains on. In other words, during the inspection period Ps1 in which the drive voltage signal Vin corresponding to the drive voltage signal ComB is supplied to the piezoelectric elements 60a, 60b, and during the inspection period Ps2 in which the piezoelectric elements 60a, 60b output a residual vibration signal Vout corresponding to the residual vibration generated in the ejection section 600, one end and the other end of the transfer gate 234b are controlled to be conductive.

[0141] As a result, the print head 21 of this embodiment does not need to control the conduction states of the transfer gates 234a and 234b to a specific state for acquiring the residual vibration signal Vout generated in the ejection section 600. That is, the print head 21 of this embodiment can acquire the residual vibration signal Vout generated in the ejection section 600 without controlling the conduction states of the transfer gates 234a and 234b to a state specialized for acquiring the residual vibration signal Vout corresponding to the residual vibration generated in the ejection section 600. In other words, the print head 21 of this embodiment can acquire the residual vibration signal Vout generated in the ejection section 600 while maintaining the conduction states of the transfer gates 234a and 234b controlled to one of large dot LD, medium dot MD, small dot SD, or non-printing ND in which slight vibration is executed. Therefore, the speed at which residual vibration generated in the ejection section 600 is detected after the piezoelectric elements 60a and 60b are driven can be further increased.

[0142] In the print head 21 of this embodiment, one end of the residual vibration detection circuit 240 is electrically connected to one end of the transfer gate 234b, and the other end is electrically connected to the other end of the transfer gate 234b, and the residual vibration detection circuit 240 outputs a minute vibration to the corresponding ejection section 600 as a drive voltage signal Vin. In the above description, the residual vibration signal Vout corresponding to the residual vibration generated in the ejection section 600 is acquired when the drive waveform Bdp1 that executes the movement is supplied, but the present invention is not limited to this.

[0143] For example, the residual vibration detection circuit 240 has one end electrically connected to one end of the transfer gate 234a and the other end electrically connected to the other end of the transfer gate 234a, and the control circuit 100 outputs a test pulse as a test timing signal TSIG that defines the start of the test period Ps2 at the timing when the voltage value of the drive voltage signal ComA fluctuates and then becomes constant, thereby obtaining a residual vibration signal Vout corresponding to the residual vibration generated in the ejection section 600 when a drive waveform Adp1 that ejects a medium amount of ink or a drive waveform Adp2 that ejects a small amount of ink is supplied as the drive voltage signal Vin to the corresponding ejection section 600.

[0144] However, as shown in this embodiment, when a drive waveform Bdp1 that executes micro-vibrations is supplied as the drive voltage signal Vin to the corresponding ejection section 600, the residual vibration detection circuit 240 preferably acquires a residual vibration signal Vout corresponding to the residual vibration generated in the ejection section 600, and the control circuit 100 determines the ink ejection state from the corresponding ejection section 600 based on the residual vibration signal Vout acquired by the residual vibration detection circuit 240. In other words, when the residual vibration detection circuit 240 acquires the residual vibration signal Vout, the drive voltage signal Vin that is supplied to the corresponding ejection section 600 is preferably a micro-vibration waveform that executes micro-vibrations that vibrate the vicinity of the nozzle N to the extent that ink is not ejected from the nozzle N.

[0145] As will be described in detail later, the residual vibration generated in the ejection unit 600 changes depending on the state of ink stored in the pressure chambers CB1 and CB2 that constitute the print head 21 and the state of ink flowing through the communicating channels RR1 and RR2 and the nozzle channel RN. By acquiring a residual vibration signal Vout corresponding to the residual vibration generated in the ejection unit 600 when a micro-vibration waveform that executes micro-vibration that does not cause ink to be ejected from the corresponding nozzle N is supplied, the risk that changes in the state of ink stored in the pressure chambers CB1 and CB2 that occur as a result of ink being ejected from the nozzle N and changes in the state of ink flowing through the communicating channels RR1 and RR2 and the nozzle channel RN will contribute to the residual vibration generated in the ejection unit 600 is reduced. This improves the accuracy of acquiring the residual vibration signal Vout corresponding to the residual vibration acquired by the residual vibration detection circuit 240, and the accuracy of determining the state of ink ejection from the ejection unit 600 based on the residual vibration signal Vout acquired by the residual vibration detection circuit 240.

[0146] Furthermore, in the print head 21 of this embodiment, the piezoelectric element 60a is driven to change the volume of the pressure chamber CB1, the piezoelectric element 60b is driven to change the volume of the pressure chamber CB2, and the piezoelectric element 60a outputs a signal corresponding to the residual vibration caused by the change in volume of the pressure chamber CB1, and the piezoelectric element 60b outputs a signal corresponding to the residual vibration caused by the change in volume 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 caused by the change in volume of the pressure chamber CB1 may be different piezoelectric elements, and the piezoelectric element that changes the volume of the pressure chamber CB2 may be different piezoelectric elements.

[0147] However, as shown in the print head 21 of this embodiment, it is preferable to use the same piezoelectric element for both the piezoelectric element that changes the volume of pressure chamber CB1 and the piezoelectric element that outputs a signal corresponding to the residual vibration caused by the volume change of pressure chamber CB1, and to use the same piezoelectric element for both the piezoelectric element that changes the volume of pressure chamber CB2 and the piezoelectric element that outputs a signal corresponding to the residual vibration caused by the volume change of pressure chamber CB2. This makes it possible to reduce the number of piezoelectric elements in the print head 21, thereby enabling the print head 21 to be made more compact.

[0148] That is, the print head 21 has a piezoelectric element 60a that outputs a signal corresponding to the residual vibration generated in response to a change in the volume of the pressure chamber CB1, and a piezoelectric element 60b that outputs a signal corresponding to the residual vibration generated in response to a change in the volume of the pressure chamber CB2, and it is preferable that the piezoelectric elements 60a and 60b are displaced in response to the drive waveform Bdp1 of the drive voltage signal ComB, and the volume of the pressure chamber CB1 changes in response to the displacement of the piezoelectric element 60a, and the volume of the pressure chamber CB2 changes in response to the displacement of the piezoelectric element 60b.

[0149] 4. Configuration and operation of the residual vibration output circuit Next, we will explain the configuration and operation of a 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. Fig. 11 is a diagram showing an example of the configuration of the waveform information output circuit 300. As shown in Fig. 11, the waveform information output circuit 300 has a reset circuit 310, a maximum voltage value acquisition circuit 320, a minimum voltage value acquisition circuit 330, and a period acquisition circuit 340.

[0150] A latch signal LAT is input to the reset circuit 310. Furthermore, the reset circuit 310 outputs reset signals RST1 and RST2, the logic levels of which change according to the input latch signal LAT, and an acquisition signal AS.

[0151] The reset signal RST1 is a signal whose logic level becomes high at the rising edge of the latch pulse of the latch signal LAT and then becomes low after a certain period of time has passed. The acquisition signal AS is a signal whose logic level becomes high after the reset signal RST1 becomes low and then becomes low after a certain period of time has passed. The reset signal RST2 is a signal whose logic level becomes high after the acquisition signal AS becomes low and then becomes low after a certain period of time has passed. Here, the period during which the reset signal RST1 is at a high logic level, the period during which the acquisition signal AS is at a high logic level, and the period during which the reset signal RST2 is at a high logic level are all included in the inspection period Ps1.

[0152] 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.

[0153] The residual vibration detection signal NVT is input to the positive 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 one end of the capacitor C11, one end of the switch SW11, and one end of the switch SW12. A ground potential is supplied to the other end of the capacitor C11 and the other end of the switch SW11. The other end of the switch SW12 is electrically connected to one end of the capacitor C12, one end of the switch SW13, and the positive input terminal of the amplifier circuit OP12. A ground potential is supplied to the other end of the capacitor C12 and the other end of the switch SW13. The negative input terminal of the amplifier circuit OP12 is electrically connected to the output terminal of the amplifier circuit OP12. In other words, the amplifier circuit OP12 constitutes a voltage follower circuit. The maximum voltage value acquisition circuit 320 configured as described above outputs, as a maximum voltage signal Vmax, a signal corresponding to the maximum voltage value of the input residual vibration detection signal NVT during a predetermined period, which is the signal from the output terminal of the amplifier circuit OP12 that constitutes a voltage follower circuit.

[0154] A reset signal RST2 is input to the control end of the switch SW11. When the logic level of the reset signal RST2 input to the control end is high, the switch SW11 is electrically connected between one end and the other end. When the signal is at a low level, there is no conduction between one end and the other end. When the switch SW11 is turned on, the charge stored in the capacitor C11 is released toward the ground potential. This resets the voltage value at one end of the capacitor C11 to the ground potential.

[0155] An acquisition signal AS is input to the control end of the switch SW12. When the logical level of the acquisition signal AS input to the control end is high, the switch SW12 is conductive between one end and the other end, and when the logical level of the acquisition signal AS input to the control end is low, the switch SW12 is non-conductive between the one end and the other end. When the one end and the other end of the switch SW12 are conductive, the charge stored in the capacitor C11 is also stored in the capacitor C12.

[0156] A reset signal RST1 is input to the control end of the switch SW13. When the logic level of the reset signal RST1 input to the control end is high, the switch SW13 is conductive between one end and the other end, and when the logic level of the reset signal RST1 input to the control end is low, the switch SW13 is non-conductive between one end and the other end. When the switch SW13 is conductive between one end and the other end, the charge stored in the capacitor C12 is released toward the ground potential. This resets the voltage value of one end of the capacitor C12 to the ground potential.

[0157] In the following description, when there is conduction between one end and the other end of each of the switches SW11, SW12, and SW13, this state may be referred to as "on," and when there is no conduction between one end and the other end of the switches SW11, SW12, and SW13, this state may be referred to as "off."

[0158] 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.

[0159] The residual vibration detection signal NVT is input to the positive input terminal of the amplifier circuit OP21. The cathode terminal of the diode D21 is electrically connected to the output terminal of the amplifier circuit OP21. The anode terminal of the diode D21 is electrically connected to the negative input terminal of the amplifier circuit OP21. The anode terminal of the diode D21 is also electrically connected to one end of a capacitor C21, one end of a switch SW21, and one end of a switch SW22. The other end of the capacitor C21 is supplied with a ground potential. The other end of the switch SW21 is supplied with a voltage signal VDD. Here, the voltage vd of the voltage signal VDD is preferably equal to or greater than the voltage vb of the bias voltage signal VB. The other end of the switch SW22 is electrically connected to one end of the capacitor C22, one end of the switch SW23, and the positive input terminal of the amplifier circuit OP22. The other end of the capacitor C22 and the other end of the switch SW23 are supplied with a ground potential. The negative input terminal of the amplifier circuit OP22 is electrically connected to the output terminal of the amplifier circuit OP22. That is, the amplifier circuit OP22 constitutes a voltage follower circuit. The minimum voltage value acquisition circuit 330 configured as described above outputs, as a minimum voltage signal Vmin, a signal that is the signal at the output terminal of the amplifier circuit OP22 that constitutes the voltage follower circuit and corresponds to the minimum voltage value of the input residual vibration detection signal NVT during a predetermined period.

[0160] A reset signal RST2 is input to the control end of the switch SW21. When the logic level of the reset signal RST2 input to the control end is high, the switch SW21 is conductive between one end and the other end, and when the logic level of the reset signal RST2 input to the control end is low, the switch SW21 is non-conductive between one end and the other end. When the switch SW21 is conductive between one end and the other end, a predetermined charge corresponding to the voltage signal VDD is stored in the capacitor C21. As a result, the voltage value of one end of the capacitor C21 is reset to voltage vd, which is the voltage value of the voltage signal VDD.

[0161] An acquisition signal AS is input to the control end of the switch SW22. When the logical level of the acquisition signal AS input to the control end is high, the switch SW22 is conductive between one end and the other end, and when the logical level of the acquisition signal AS input to the control end is low, the switch SW22 is non-conductive between the one end and the other end. When the one end and the other end of the switch SW22 are conductive, the charge stored in the capacitor C21 is also stored in the capacitor C22.

[0162] A reset signal RST1 is input to the control end of the switch SW23. When the logic level of the reset signal RST1 input to the control end is high, the switch SW23 is conductive between one end and the other end, and when the logic level of the reset signal RST1 input to the control end is low, the switch SW23 is non-conductive between one end and the other end. When the switch SW23 is conductive between one end and the other end, the charge stored in the capacitor C22 is released toward the ground potential. This resets the voltage value of one end of the capacitor C22 to the ground potential.

[0163] In the following description, when there is conduction between one end and the other end of each of the switches SW21, SW22, and SW23, it may be referred to as "on," and when there is no conduction between one end and the other end of the switches SW21, SW22, and SW23, it may be referred to as "off."

[0164] The period acquisition circuit 340 includes a comparator CP1 and a counter circuit 341.

[0165] 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. The comparator CP1 generates a periodic pulse signal CYP that goes high when the voltage value of the residual vibration detection signal NVT input to the positive input terminal is greater than the voltage value of the voltage signal VREF input to the negative input terminal, and goes low when the voltage value of the residual vibration detection signal NVT input to the positive input terminal is smaller than the voltage value of the voltage signal VREF input to the negative input terminal, and outputs the periodic pulse signal CYP from its output terminal to the counter circuit 341.

[0166] Here, the voltage vref, which is the voltage value of the voltage signal VREF, is a voltage value close to the voltage vb, which is the voltage value of the bias voltage signal VB, and may be stored, for example, in a memory circuit (not shown) included in the control circuit 100. Furthermore, the voltage vref, which is the voltage value of the voltage signal VREF, may be changeable depending on the operating conditions and operating environment of the liquid ejection device 1.

[0167] The counter circuit 341 measures the period during which the logic level of the input periodic signal CYC changes from high to low and then back to high after the logic level of the reset signal RST1 changes from high to low, or the period during which the logic level of the input periodic signal CYC changes from low to high and then back to low, and stores the measurement result as measurement result information CT. When the logic level of the acquisition signal AS changes from low to high, the counter circuit 341 generates and outputs the periodic signal CYC containing the stored measurement result information CT. Using a clock circuit (not shown), the counter circuit 341 measures and stores the period during which the logic level of the periodic signal CYC changes from high to low and then back to high, or the period during which the logic level of the periodic signal CYC changes from low to high and then back to low.

[0168] 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. The periodic signal CYC is included in the waveform information signal WFS, which includes waveform information of the residual vibration detection signal NVT.

[0169] Next, the operation of the waveform information output circuit 300 will be described. Fig. 12 is a diagram for explaining the operation of the waveform information output circuit 300. In explaining the operation of the waveform information output circuit 300, in the following explanation, an arbitrary dot formation period Cp in which the state inspection CD is performed in the target discharge unit 600 will be referred to as a dot formation period Cp(i), the dot formation period Cp next to the dot formation period Cp(i) in which the state inspection CD is not performed in the target discharge unit 600 will be referred to as a dot formation period Cp(i+1), and the dot formation period Cp before the dot formation period Cp(i) in which the state inspection CD is not performed in the target discharge unit 600 will be referred to as a dot formation period Cp(i-1). In addition, in the following description, the signal held at one end of capacitor C11 will be referred to as voltage signal Vc11, the signal held at one end of capacitor C12 will be referred to as voltage signal Vc12, the signal held at one end of capacitor C21 will be referred to as voltage signal Vc21, the signal held at one end of capacitor C22 will be 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 will be 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 will be referred to as voltage vmin.

[0170] During the dot formation period Cp(i-1), the state inspection CD is not performed on the target discharge section 600. Therefore, just before the control circuit 100 outputs a latch pulse that defines the end of the dot formation period Cp(i-1) as the latch signal LAT, the residual vibration detection circuit 240 outputs a signal with a constant voltage value of voltage vb to the waveform information output circuit 300, regardless of the input residual vibration reference signal Vo1 and residual vibration detection signal Vo2. Therefore, just before the control circuit 100 outputs a latch pulse that defines the end of the dot formation period Cp(i-1) as the latch signal LAT, 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.

[0171] Furthermore, just before the control circuit 100 outputs a latch pulse that defines the end of the dot formation period Cp(i-1) as the latch signal LAT, the signal whose voltage value is constant at voltage vb output by the residual vibration detection circuit 240 is also input to the positive input terminal of the comparator CP1. At this time, a voltage signal VREF whose voltage value is constant at voltage vref is input to the negative input terminal of the comparator CP1. Therefore, the comparator CP1 outputs a constant signal whose logical level is either high or low as the periodic pulse signal CYP.

[0172] The control circuit 100 then outputs, as the latch signal LAT, a latch pulse that defines the end of the dot formation period Cp(i-1) and the beginning of the 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. The reset circuit 310 sets the logic level of the reset signal RST1 it outputs to high level at the rising edge of the latch pulse input as the latch signal LAT. This turns on the switches SW13 and SW23. As a result, the charge stored in the capacitor C12 is released to ground potential via the switch SW13, and the charge stored in the capacitor C22 is released to ground potential via the switch SW23. In other words, the ground potential is supplied to one end of the capacitor C12 and one end of the capacitor C22.

[0173] Thereafter, the reset circuit 310 sets the logic level of the reset signal RST1 to low level. This turns off the switches SW13 and SW23. As a result, the ground potential is held at one end of the capacitor C12 as a voltage signal Vc12, and the ground potential is held at one end of the capacitor C22 as a voltage signal Vc22. In other words, In this case, the waveform information output circuit 300 resets the voltage value of the voltage signal Vc12 held at one end of the capacitor C12 and the voltage value of the voltage signal Vc22 held at one end of the capacitor C22 to a predetermined voltage value, that is, the ground potential, based on the logical level of the reset signal RST1 output by the reset circuit 310.

[0174] The reset circuit 310 sets the logic level of the reset signal RST1 it outputs to low level, and then sets the logic level of the acquisition signal AS it outputs to high level. This turns on the switches SW12 and SW22. As a result, the charge held in the capacitor C11 flows into the capacitor C12 via the switch SW12, and the charge held in the capacitor C21 propagates to the capacitor C22 via the switch SW22. That is, the voltage vb held at one end of the capacitor C11 as the voltage signal Vc11 is supplied to one end of the capacitor C12, and the voltage vb held at one end of the capacitor C21 as the voltage signal Vc21 is supplied to one end of the capacitor C22.

[0175] Thereafter, the reset circuit 310 sets the logic level of the acquisition signal AS it outputs to low. This turns off the switches SW12 and SW22. As a result, the voltage vb is held at one end of the capacitor C12 as the voltage signal Vc12, and the voltage vb is held at one end of the capacitor C22 as the 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 the voltage signal Vc11 held at one end of the capacitor C11 and stores it at one end of the capacitor C12 as the voltage signal Vc12, and also takes the voltage value of the voltage signal Vc22 held at one end of the capacitor C21 and stores it at one end of the capacitor C22 as the voltage signal Vc22.

[0176] The reset circuit 310 sets the logic level of the acquisition signal AS to a low level and then sets the logic level of the reset signal RST2 to a high level. This turns on the switches SW11 and SW21. As a result, the charge stored in the capacitor C11 is released to the ground potential via the switch SW11, and a charge based on the voltage vd, which is the voltage value of the voltage signal VDD, is stored in the capacitor C21 via the switch SW21. That is, the ground potential is supplied to one end of the capacitor C11, and the voltage vd is supplied as the voltage signal Vc21 to one end of the capacitor C21.

[0177] Thereafter, the reset circuit 310 sets the logic level of the reset signal RST2 it outputs to low level. This turns off the switches SW11 and SW21. As a result, ground potential is held at one end of the capacitor C11 as the voltage signal Vc11, and voltage vd is held at one end of the capacitor C21 as the voltage signal Vc21. In other words, based on the logic level of the reset signal RST2, the waveform information output circuit 300 resets the voltage value of the voltage signal Vc12 held at one end of the capacitor C11 to a predetermined voltage value, that is, ground potential, and resets the voltage value of the voltage signal Vc22 held at one end of the capacitor C21 to a predetermined voltage value, that is, voltage vd.

[0178] Thereafter, the control circuit 100 outputs a test pulse as the test timing signal TSIG. As a result, the residual vibration detection circuit 240 outputs to the waveform information output circuit 300 a residual vibration detection signal NVT corresponding to the residual vibration occurring in the corresponding discharge section 600, the residual vibration detection signal NVT being 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 a voltage vb. In other words, when the control circuit 100 outputs a test pulse as the test timing signal TSIG, the residual vibration detection signal NVT corresponding to the residual vibration occurring in the corresponding discharge section 600 is input to the waveform information output circuit 300.

[0179] 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 one end of the capacitor C11 via the diode D11. On the other hand, when the voltage value of the signal output by the amplifier circuit OP11 is smaller 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 voltage vmax, which is the maximum voltage value of the signal output by the amplifier circuit OP11 and is the maximum voltage value of the residual vibration detection signal NVT, is held as the voltage signal Vc11 at one end of the capacitor C11. That is, the maximum voltage value acquisition circuit 320 acquires the voltage vmax, which is the maximum voltage value of the residual vibration detection signal NVT, as waveform information of the residual vibration detection signal NVT, and holds it at one end of the capacitor C11 as a voltage signal Vc11.

[0180] 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 having the same potential as the input residual vibration detection signal NVT from its output terminal. If the voltage value of the signal output by the amplifier circuit OP21 is smaller 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 released via the diode D21 and the amplifier circuit OP21. As a result, the voltage value of the voltage signal Vc11 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, if the voltage value of the signal output by the amplifier circuit OP21 is greater 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 released via the diode D21 and the amplifier circuit OP21. At this time, the voltage value of the voltage signal Vc21 held at one end of the capacitor C21 does not change. Therefore, the voltage vmin, which is the minimum voltage value of the signal output by the amplifier circuit OP21 and is the minimum voltage value of the residual vibration detection signal NVT, is held as the voltage signal Vc21 at one end of the capacitor C21. In other words, the minimum voltage value acquisition circuit 330 acquires the voltage vmin, which is the minimum voltage value of the residual vibration detection signal NVT, as waveform information of the residual vibration detection signal NVT, and holds it at one end of the capacitor C21 as the voltage signal Vc21.

[0181] 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. The comparator CP1 outputs a periodic pulse signal CYP that goes to a high level when the voltage value of the residual vibration detection signal NVT also supplied to the positive input terminal is greater than voltage vref, which is the voltage value of the voltage signal VREF also supplied to the negative input terminal, and goes to a low level when the voltage value of the residual vibration detection signal NVT also supplied to the positive input terminal is smaller than voltage vref, which is the voltage value of the voltage signal VREF also supplied to the negative input terminal.

[0182] 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 voltage vb to the amplified signal. Therefore, the voltage value of the residual vibration detection signal NVT changes in accordance with the residual vibration of the corresponding ejection section 600, with voltage vb serving as a reference potential. Furthermore, voltage vref, which is the voltage value of voltage signal VREF, is a voltage value close to voltage vb, which is the voltage value of bias voltage signal VB. Therefore, the period in which the logic level of periodic pulse signal CYP switches corresponds to the period of the residual vibration detection signal NVT.

[0183] The counter circuit 341 measures the time required for the logic level of the input periodic pulse signal CYP to change, and stores the time as measurement result information CT. In the illustrated example, the counter circuit 341 measures the time required for the logic level of the input periodic signal CYC to change from high to low and then back to high again, which is the time required for the logic level to change for one period of the periodic signal CYC, and stores the result as measurement result information CT. However, the counter circuit 341 may instead measure the time required for the logic level of the input periodic signal CYC to change from high to low and store the result as measurement result information CT, or may measure the time required for the logic level to change for two or more periods of the periodic signal CYC and store the result as measurement result information CT. In other words, the period acquisition circuit 340 acquires measurement result information CT corresponding to the period of the residual vibration detection signal NVT as waveform information of the residual vibration detection signal NVT, and stores the result as measurement result information CT in the counter circuit 341.

[0184] That is, the cycle acquisition circuit 340 outputs a cycle signal CYC according to the result of comparison between the voltage vref, which is the voltage value of the voltage signal VREF, and the voltage value of the residual vibration detection signal NVT.

[0185] The control circuit 100 then outputs, as the latch signal LAT, a latch pulse that defines the end of the dot formation period Cp(i) and the start of the 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. The reset circuit 310 sets the logic level of the reset signal RST1 it outputs to high at the rising edge of the latch pulse input as the latch signal LAT. A ground potential is supplied to one end of the capacitor C12, and a ground potential is supplied to one end of the capacitor C22. The reset circuit 310 then sets the logic level of the reset signal RST1 it outputs to low, thereby holding the ground potential at one end of the capacitor C12 as a voltage signal Vc12, and holding the ground potential at one end of the capacitor C22 as a voltage signal Vc22. That is, the voltage value of the voltage signal Vc12 held at one end of the capacitor C12 and the voltage value of the voltage signal Vc22 held at one end of the capacitor C22 are predetermined voltage values ​​and are reset to the ground potential.

[0186] Thereafter, the reset circuit 310 sets the logic level of the reset signal RST1 it outputs to low level, and then sets the logic level of the acquisition signal AS it outputs to high level. As a result, voltage vmax, which is the maximum voltage value of the residual vibration detection signal NVT held as voltage signal Vc11 at one end of capacitor C11, is supplied to one end of capacitor C12, and voltage vmin, which is the minimum voltage value of the residual vibration detection signal NVT held as voltage signal Vc21 at one end of capacitor C21, is supplied to one end of capacitor C22. In other words, voltage vmax held as voltage signal Vc11 at one end of capacitor C11 is taken in by one end of capacitor C12, and voltage vmin held as voltage signal Vc22 at one end of capacitor C21 is taken in by one end of capacitor C22. Then, the reset circuit 310 sets the logic level of the acquisition signal AS it outputs to low level, causing the capacitor C12 to hold the voltage vmax as the voltage signal Vc12, and the capacitor C22 to hold the voltage vmin as the voltage signal Vc22.

[0187] The voltage vmax as the voltage signal Vc12 held in the capacitor C12 is impedance converted in the amplifier circuit OP12 and then output as the maximum voltage signal Vmax, and the voltage vmin as the voltage signal Vc22 held in the capacitor C12 is impedance converted in the amplifier circuit OP22 and then output as the minimum voltage signal Vmin. The voltage vmax output as the maximum voltage signal Vmax by the waveform information output circuit 300 is one piece of waveform information of the residual vibration detection signal NVT corresponding to the residual vibration occurring in the corresponding discharge section 600 during the dot formation period Cp(i) and corresponds to the maximum value of the amplitude of the residual vibration detection signal NVT, and the voltage vmin output as the minimum voltage signal Vmin by the waveform information output circuit 300 is one piece of waveform information of the residual vibration detection signal NVT corresponding to the residual vibration occurring in the corresponding discharge section 600 during the dot formation period Cp(i) and corresponds to the minimum value of the amplitude of the residual vibration detection signal NVT.

[0188] Furthermore, when the reset circuit 310 sets the logic level of the acquisition signal AS that it outputs to a high level, the counter circuit 341 generates a periodic signal CYC that includes measurement result information CT that is held as waveform information of the residual vibration detection signal NVT, and outputs this from the waveform information output circuit 300. This periodic signal CYC that includes measurement result information CT that is held as waveform information of the residual vibration detection signal NVT that is output by the waveform information output circuit 300 is one piece of waveform information of the residual vibration detection signal NVT that corresponds to the residual vibration that occurs in the corresponding discharge section 600 during the dot formation period Cp(i), and corresponds to the period of the residual vibration detection signal NVT.

[0189] That is, in the dot formation period Cp(i), 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 discharge section 600. The waveform information output circuit 300 then outputs a waveform information signal WFS including the acquired waveform information to the control circuit 100.

[0190] As described above, the waveform information output circuit 300 includes a maximum voltage value acquisition circuit 320 that holds the maximum voltage value of the residual vibration detection signal NVT in the dot formation period Cp as a maximum voltage signal Vmax, a minimum voltage value acquisition circuit 330 that holds the minimum voltage value of the residual vibration detection signal NVT in the dot formation period Cp as a minimum voltage signal Vmin, and a period acquisition circuit 340 that outputs a periodic signal CYC according to the period of the residual vibration detection signal NVT, as well as switches SW11 and SW13 that reset the maximum value of the residual vibration detection signal NVT held by the maximum voltage value acquisition circuit 320, and switches SW21 and SW23 that reset the minimum value of the residual vibration detection signal NVT held by the minimum voltage value acquisition circuit 330.

[0191] 5. Residual vibration signal Next, a specific example of residual vibration occurring in the ejection unit 600 being inspected after the drive voltage signal Vin is supplied to the ejection unit 600, and a specific example of residual vibration signal Vout corresponding to the residual vibration will be described. The liquid ejection device 1 of this embodiment acquires a residual vibration signal Vout corresponding to the residual vibration occurring in the ejection unit 600 after the piezoelectric elements 60a, 60b included in the ejection unit 600 are driven in accordance with the drive voltage signal Vin including the drive waveform Bdp1, and determines the state of the corresponding ejection unit 600 based on a residual vibration detection signal NVT corresponding to the acquired residual vibration signal Vout.

[0192] Specifically, in the liquid ejection device 1 of this embodiment, each of the piezoelectric elements 60a, 60b included in the corresponding ejection unit 600 is driven by supplying a drive voltage signal Vin including a drive waveform Bdp1. The driving of the piezoelectric elements 60a, 60b displaces the vibration plate 304, and the displacement of the vibration plate 304 changes the internal pressure of the pressure chambers CB1, CB2. Thereafter, the voltage value of the drive voltage signal Vin supplied to the piezoelectric elements 60a, 60b becomes constant, and a damped vibration occurs in the vibration plate 304 in response to the change in the internal pressure of the pressure chambers CB1, CB2. At this time, the damped vibration generated in the vibration plate 304 displaces the piezoelectric elements 60a, 60b. Then, electric charges corresponding to the displacement are emitted from the piezoelectric elements 60a, 60b. A signal corresponding to the electric charges emitted from the piezoelectric elements 60a, 60b due to the damped vibration generated in the vibration plate 304 corresponds to the residual vibration signal Vout. In the following description, the signal corresponding to the charge output by the piezoelectric element 60a in response to the attenuation signal of the vibration plate 304 may be referred to as the residual vibration signal Vout1, and the signal corresponding to the charge output by the piezoelectric element 60b in response to the attenuation signal of the vibration plate 304 may be referred to as the residual vibration signal Vout2.

[0193] 13 is a diagram showing an example of the residual vibration signals Vout1 and Vout2. As shown in FIG. 13, the signal waveforms of the residual vibration signals Vout1 and Vout2 are This is a damped oscillation waveform in which the voltage amplitude decreases over time in accordance with the damped oscillation occurring in the diaphragm 304 as the internal pressure changes. Waveform information such as the amplitude and period contained in the damped oscillation waveforms of these residual oscillation signals Vout1, Vout2 changes depending on the state of the ink stored in the pressure chambers CB1, CB2 and the state of the ink flowing through the communication flow path RR1 and the nozzle flow path RN.

[0194] Here, the relationship between the waveform information of the residual vibration signals Vout1 and Vout2 and the state of ink stored in the pressure chambers CB1 and CB2, and the state of ink flowing through the communication channels RR1 and RR2 and the nozzle channel RN will be explained using a calculation model. FIG. 14 is a diagram showing an example of a calculation model of simple harmonic motion that assumes residual vibration occurring in the pressure chamber CB1, the pressure chamber CB2, or the vibration plate 304. As described above, the piezoelectric elements 60a and 60b are displaced when the drive voltage signal Vin is supplied, and the vibration plate 304 is also displaced in response to the displacement of the piezoelectric elements 60a and 60b. The displacement of the vibration plate 304 then changes the volume of the corresponding pressure chambers CB1 and CB2. At this time, a portion of the ink filled in the pressure chambers CB1 and CB2 is ejected from the nozzle N in accordance with the pressure generated inside the pressure chambers CB1 and CB2.

[0195] In a series of operations for ejecting ink from such nozzle N, the vibration plate 304 freely vibrates at a natural vibration frequency determined by the flow path resistance r based on the shape of the flow path through which the ink flows and the viscosity of the ink, the inertance m due to the weight of the liquid in the flow path, and the compliance C of the vibration plate 304, and the piezoelectric elements 60a and 60b are displaced in response to the free vibration occurring in the vibration plate 304. Then, a signal of charge generated by the displacement of the piezoelectric element 60a is output as a residual vibration signal Vout1, and a signal of charge generated by the displacement of the piezoelectric element 60b is output as a residual vibration signal Vout2.

[0196] A calculation model of the residual vibration occurring in such diaphragm 304 can be expressed by pressure p, inertance m, compliance C, and flow path resistance r. Then, by calculating the step response in terms of volume velocity u when pressure p is applied to the circuit shown in Fig. 14, the following equations (1) to (3) are obtained.

[0197]

number

[0198]

number

[0199]

number

[0200] Figure 15 is a diagram illustrating the relationship between ink viscosity and the signal waveforms of residual vibration signals Vout1 and Vout2. In Figure 15, the horizontal axis represents time, and the vertical axis represents the magnitude of residual vibration. Figure 15 also illustrates the ink viscosity, with the signal waveform when the viscosity increase ratio is 1.0 represented as waveform a1, the signal waveform when the viscosity increase ratio is 1.4 represented as waveform a2, the signal waveform when the viscosity increase ratio is 1.8 represented as waveform a3, and the signal waveform when the viscosity increase ratio is 2.2 represented as waveform a4.

[0201] As shown in Figure 15, when the viscosity of the stored ink increases and the viscosity ratio increases, the residual ink The amplitude and damping rate of the vibration signals Vout1 and Vout2 change. Specifically, when the viscosity of the ink stored in the pressure chambers CB1 and CB2, the ink flowing through the communication channels RR1 and RR2 and the nozzle channel RN, the ink near the nozzle N, etc. increases, the channel resistance r increases. Therefore, the amplitude of the damped vibration generated in the vibration plate 304 decreases and the damping rate increases. As a result, when an abnormal increase in viscosity occurs in the stored ink, the amplitude of the corresponding residual vibration signals Vout1 and Vout2 decreases and the damping rate increases.

[0202] Fig. 16 is a diagram for explaining the signal waveforms of the residual vibration signals Vout1, Vout2 when air bubbles have entered the pressure chambers CB1, CB2. In Fig. 16, the horizontal axis represents time, and the vertical axis represents the magnitude of the residual vibration. Fig. 16 also shows, as waveform b1, a signal waveform in a normal state in which no air bubbles have entered the pressure chambers CB1, CB2, the communicating channels RR1, RR2, or the nozzle channel RN, and as waveform b2, an example of a signal waveform when air bubbles have entered any of the pressure chambers CB1, CB2, the communicating channels RR1, RR2, or the nozzle channel RN.

[0203] As shown in Figure 16, when air bubbles are mixed into the pressure chambers CB1 and CB2, the communication channels RR1 and RR2, and the nozzle channel RN, the vibration frequency of the residual vibration signals Vout1 and Vout2 increases. Specifically, when air bubbles are mixed into the pressure chambers CB1 and CB2, the communication channels RR1 and RR2, the nozzle channel RN, and the nozzle N, the inertance m, which corresponds to the weight of ink stored, decreases by the amount of the mixed air bubbles. When the inertance m decreases, the angular velocity ω increases, as shown in equation (2). This shortens the vibration period of the residual vibration generated in the vibration plate 304, and as a result, the vibration frequency of the residual vibration signals Vout1 and Vout2 increases and the period shortens.

[0204] As described above, when an abnormality in viscosity increase, in which the viscosity of ink increases, or an abnormality in which air bubbles are mixed in, occurs in the pressure chamber CB1, the communication flow path RR1, the nozzle flow path RN, etc., waveform information such as the amplitude and period of the residual vibration signal Vout1 changes, and similarly, when an abnormality in viscosity increase or an abnormality in which air bubbles are mixed in occurs in the pressure chamber CB2, the communication flow path RR2, the nozzle flow path RN, etc., waveform information such as the amplitude and period of the residual vibration signal Vout2 changes. Therefore, the state of the ejection unit 600, which includes the piezoelectric elements 60a and 60b that output the residual vibration signals Vout1 and Vout2, can be determined based on waveform information such as the amplitude and period of the residual vibration signals Vout1 and Vout2.

[0205] Here, if the drive signal selection circuit 200 separately acquires both the residual vibration signal Vout1 and the residual vibration signal Vout2, and the control circuit 100 separately calculates waveform information such as the amplitude and period of the residual vibration signal Vout1 and waveform information such as the amplitude and period of the residual vibration signal Vout2, it may be possible to determine the state of the discharge unit 600 even if the discharge unit 600 has a pressure chamber CB1 and a pressure chamber CB2. However, if the discharge unit 600 has a configuration in which the discharge unit 600 has a pressure chamber CB1 and a pressure chamber CB2 and separately acquires both the residual vibration signal Vout1 and the residual vibration signal Vout2 to determine the state of the discharge unit 600, the drive signal selection circuit 200 needs to be configured to switch between acquiring the residual vibration signal Vout1 or the residual vibration signal Vout2, and as a result, there is a concern that the integrated circuit 201 on which the drive signal selection circuit 200 is implemented may become larger.

[0206] In contrast to this, in the liquid ejection device 1 of this embodiment, the drive signal selection circuit 200 acquires a residual vibration signal Vout that is a combination of the residual vibration signals Vout1 and Vout2, and outputs a residual vibration detection signal NVT that corresponds to the residual vibration signal Vout. Then, the waveform information output circuit 300 acquires waveform information of the residual vibration detection signal NVT and outputs it to the control circuit 100 as a waveform information signal WFS, and the control circuit 100 determines the state of the ejection section 600 based on the input waveform information signal WFS. As a result, it is possible to determine whether to acquire the residual vibration signal Vout1 that corresponds to the pressure chamber CB1 or the residual vibration signal Vout2 that corresponds to the pressure chamber CB2. This eliminates the need for a configuration for switching between the drive signal selection circuit 200 and the integrated circuit 201, and thus makes it possible to reduce the size of the integrated circuit 201 on which the drive signal selection circuit 200 is mounted.

[0207] Next, an example of the signal waveform of the residual vibration signal Vout obtained by combining the residual vibration signals Vout1 and Vout2 will be described.

[0208] Fig. 17 is a diagram showing an example of the signal waveform of the residual vibration signal Vout when the ejection section 600 is normal. In Fig. 17, the horizontal axis represents time, and the vertical axis represents the magnitude of the residual vibration. The residual vibration signal Vout shown in Fig. 17 is an example of the 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. Note that Fig. 17 also shows the residual vibration signal Vout1 and the residual vibration signal Vout2.

[0209] 17, 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, the residual vibration signal Vout1 output by the piezoelectric element 60a and the residual vibration signal Vout2 output by the piezoelectric element 60b have substantially the same signal waveform. Specifically, when the drive voltage signal Vin is input to the piezoelectric elements 60a and 60b, similar residual vibrations are generated in the region of the diaphragm 304 corresponding to the piezoelectric element 60a and the region of the diaphragm 304 corresponding to the piezoelectric element 60b. Therefore, 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, the residual vibration signals Vout1 and Vout2 have substantially the same signal waveform. Therefore, the drive signal selection circuit 200 receives a residual vibration signal Vout as a composite wave of the residual vibration signal Vout1 and the residual vibration signal Vout2, the period of which is approximately equal to the period of the residual vibration signal Vout1 and the period of the residual vibration signal Vout2, and the amplitude of which is greater than the amplitude of the residual vibration signal Vout1 and the amplitude of the residual vibration signal Vout2.

[0210] FIG. 18 is a diagram showing an example of the signal waveform of the residual vibration signal Vout when a thickening abnormality occurs in the ejection section 600. In FIG. 18, the horizontal axis represents time, and the vertical axis represents the magnitude of the residual vibration. The residual vibration signal Vout shown in FIG. 18 is an example of the 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 a thickening abnormality occurs in the ink stored in the pressure chamber CB2 corresponding to the piezoelectric element 60b. In addition to the residual vibration signals Vout1 and Vout2, FIG. 18 also shows the residual vibration detection signal NVout, which corresponds to the residual vibration signal Vout when the ejection section 600 shown in FIG. 17 is normal.

[0211] 18, when the pressure chamber CB1 corresponding to the piezoelectric element 60a is normal and a thickening abnormality has occurred 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, a drive voltage signal Vin is input to the piezoelectric elements 60a and 60b. At this time, a residual vibration having a smaller amplitude than the residual vibration generated in the region of the vibration plate 304 corresponding to the piezoelectric element 60a is generated in the region of the vibration plate 304 corresponding to the piezoelectric element 60b. Therefore, when the pressure chamber CB1 corresponding to the piezoelectric element 60a is normal and a thickening abnormality has occurred 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 drive signal selection circuit 200 receives a residual vibration signal Vout as a composite wave of the residual vibration signal Vout1 and the residual vibration signal Vout2, whose period is approximately equal to the period of the residual vibration signal Vout1 and the period of the residual vibration signal Vout2 and whose amplitude is smaller than that of the residual vibration detection signal NVout.

[0212] 19 is a diagram showing an example of the signal waveform of the residual vibration signal Vout when an abnormality due to the inclusion of air bubbles occurs in the discharge section 600. In FIG. 19, the horizontal axis represents time, and the vertical axis represents the magnitude of the residual vibration. The residual vibration signal Vout shown in Fig. 19 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 an abnormality due to air bubble contamination occurs in the pressure chamber CB2 corresponding to the piezoelectric element 60b. In addition to the residual vibration signals Vout1 and Vout2, Fig. 19 also shows a residual vibration detection signal NVout which corresponds to the residual vibration signal Vout when the ejection section 600 shown in Fig. 17 is normal.

[0213] 19, 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 air bubble abnormality, the frequency of the residual vibration signal Vout2 output by the piezoelectric element 60b becomes higher and the period becomes shorter than the residual vibration signal Vout1 output by the piezoelectric element 60a. Specifically, the drive voltage signal Vin is input to the piezoelectric elements 60a and 60b. At this time, a residual vibration having a shorter period is generated in the region of the diaphragm 304 corresponding to the piezoelectric element 60b than the residual vibration generated in the region of the diaphragm 304 corresponding to the piezoelectric element 60a. Therefore, 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 air bubble abnormality, the period of the residual vibration signal Vout2 becomes shorter than the period of the residual vibration signal Vout1. Therefore, the drive signal selection circuit 200 receives the residual vibration signal Vout, which has a different period and frequency from the residual vibration detection signal NVout, as a composite wave of the residual vibration signal Vout1 and the residual vibration signal Vout2.

[0214] As described above, the residual vibration signal Vout, which is a composite wave of the residual vibration signals Vout1 and Vout2, has a period and amplitude that are both within predetermined ranges when the pressure chamber CB1 corresponding to the residual vibration signal Vout1 and the pressure chamber CB2 corresponding to the residual vibration signal Vout2 are both normal. In contrast, when the viscosity of the ink stored in at least one of the pressure chambers CB1 corresponding to the residual vibration signal Vout1 and CB2 corresponding to the residual vibration signal Vout2 increases, the amplitude of the residual vibration signal Vout becomes smaller than when the pressure chamber CB1 corresponding to the residual vibration signal Vout1 and the pressure chamber CB2 corresponding to the residual vibration signal Vout2 are both normal. When air bubbles are mixed in at least one of the pressure chambers CB1 corresponding to the residual vibration signal Vout1 and the pressure chamber CB2 corresponding to the residual vibration signal Vout2, the period of the residual vibration signal Vout falls outside the predetermined range that would be observed when the pressure chamber CB1 corresponding to the residual vibration signal Vout1 and the pressure chamber CB2 corresponding to the residual vibration signal Vout2 are both 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.

[0215] In the liquid ejection device 1 of this embodiment, the drive signal selection circuit 200 acquires and amplifies the residual vibration signal Vout to output a residual vibration detection signal NVT corresponding to the residual vibration signal Vout, and the waveform information output circuit 300 acquires, as waveform information of 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 including the acquired waveform information to the control circuit 100, and the control circuit 100 calculates at least one of the amplitude and period of the residual vibration signal Vout in accordance with the maximum voltage signal Vmax, minimum voltage signal Vmin, and periodic signal CYC included in the input waveform information signal WFS, thereby determining the ink ejection status from the ejection section 600 being inspected.

[0216] The waveform information output circuit 300 may acquire various waveform information of the residual vibration detection signal NVT in addition to the maximum voltage signal Vmax, the minimum voltage signal Vmin, and the periodic signal CYC. The control circuit 100 then acquires the amplitude and period of the residual vibration detection signal NVT calculated based on the maximum voltage signal Vmax, the minimum voltage signal Vmin, and the periodic signal CYC. Based on the various waveform information obtained, it may be possible to determine the state of ink ejection from the nozzle N of the ejection unit 600, such as whether ink is being ejected normally from the nozzle N. Naturally, the amplitude of the residual vibration signal Vout includes an attenuation rate and the like that can be calculated from the amplitude, and the period of the residual vibration signal Vout includes a frequency, a phase and the like that can be calculated based on the period.

[0217] Here, the drive waveform Bdp1 is an example of a drive signal, and the drive voltage signals ComB, COM, and Vin including the drive waveform Bdp1 are also an example of a drive signal. Furthermore, the pressure chambers CB1 and CB2 included in the ejection section 600-1 are an example of a first pressure chamber, the nozzle N included in the ejection section 600-1 is an example of a first nozzle, the piezoelectric elements 60a and 60b included in the ejection section 600-1 are an example of a first piezoelectric element, the residual vibration generated in the ejection section 600-1 is an example of a first residual vibration, and the residual vibration signal Vout output from the ejection section 600-1 is an example of a first residual vibration signal. Furthermore, the transfer gate 234b included in the selection circuit 230 corresponding to the ejection section 600-1 is an example of a first switch circuit, the residual vibration detection circuit 240 corresponding to the ejection section 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 section 600-1 is an example of a first residual vibration detection signal. Furthermore, the pressure chambers CB1 and CB2 included in the ejection section 600-2 are an example of a second pressure chamber, the nozzle N included in the ejection section 600-2 is an example of a second nozzle, the piezoelectric elements 60a and 60b included in the ejection section 600-2 are an example of a second piezoelectric element, the residual vibration generated in the ejection section 600-2 is an example of a second residual vibration, and the residual vibration signal Vout output from the ejection section 600-2 is an example of a second residual vibration signal. Furthermore, the transfer gate 234b of the selection circuit 230 corresponding to the ejection section 600-2 is an example of a second switch circuit, the residual vibration detection circuit 240 corresponding to the ejection section 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 section 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.

[0218] 6. Action and Effects In the liquid ejection device 1 of this embodiment configured as described above, the print head 21 has a transfer gate 234b, one end of which receives a drive voltage signal ComB including a drive waveform Bdp2 that generates residual vibration in the ejection section 600 and the other end of which is electrically connected to the ejection section 600, and a residual vibration detection circuit 240 that outputs a residual vibration detection signal NVT corresponding to a residual vibration signal Vout that corresponds to the residual vibration generated in the ejection section 600. In the print head 21, one end of the residual vibration detection circuit 240 is electrically connected to one end of the transfer gate 234b, and the other end is electrically connected to the other end of the transfer gate 234b.

[0219] In the print head 21 configured as described above, a potential difference occurs across the transfer gate 234b depending on the resistance value of the on-resistance of the transfer gate 234b and the residual vibration signal Vout depending on the charge output by the piezoelectric elements 60a, 60b in response to residual vibration generated in the ejection section 600, and the residual vibration detection circuit 240 acquires the potential difference across the transfer gate 234b. At this time, because the residual vibration detection circuit 240 acquires the potential difference across the transfer gate 234b, the print head 21 does not need to control the conduction state of the transfer gate 234b to a specific state for acquiring the residual vibration signal Vout generated in the ejection section 600. In other words, in the print head 21 of this embodiment, the residual vibration signal Vout generated in the ejection section 600 can be acquired without controlling the conduction state of the transfer gate 234b to a state specialized for acquiring the residual vibration signal Vout corresponding to the residual vibration generated in the ejection section 600. Therefore, it is possible to further increase the speed at which residual vibrations occurring in the discharge part 600 after the piezoelectric elements 60a and 60b are driven can be detected.

[0220] In the liquid ejection device 1 of this embodiment, the print head 21 has m ejection units. The m-number of ejection sections 600 each have a corresponding residual vibration detection circuit 240. This makes it possible to individually acquire, for each of the m ejection sections 600, a residual vibration signal Vout corresponding to the residual vibration generated in the ejection section 600 after the piezoelectric elements 60a, 60b included in each of the m ejection sections 600 are driven. In other words, it is possible to acquire, in parallel, the residual vibration signals Vout corresponding to the residual vibration generated in the ejection section 600 after the piezoelectric elements 60a, 60b included in each of the m ejection sections 600 are driven. This makes it possible to further increase the speed at which the residual vibration generated in the ejection section 600 after the piezoelectric elements 60a, 60b are driven can be detected.

[0221] 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 sections 600 acquire a residual vibration signal Vout corresponding to a residual signal generated when a drive waveform Bdp1 that causes the ejection sections 600 to vibrate is supplied to the piezoelectric elements 60a, 60b. In other words, the residual vibration detection circuits 240 acquire a residual vibration signal Vout corresponding to a residual vibration generated during a period when ink is not ejected from the ejection sections 600. This improves the accuracy with which the residual vibration detection circuits 240 acquire the residual vibration signal Vout, and also improves the accuracy with which the state of ink ejection from the ejection sections 600 is determined based on the acquired residual vibration signal Vout.

[0222] 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 residual vibrations occurring in response to volumetric changes in pressure chamber CB1, and the piezoelectric element 60b outputs a residual vibration signal Vout2 corresponding to residual vibrations occurring in response to volumetric changes in pressure chamber CB2. The residual vibration detection circuit 240 acquires a residual vibration signal Vout corresponding to the residual vibration signals Vout1 and Vout2 and outputs a residual vibration detection signal NVT by shaping the waveform of 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 in 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 in the dot formation period Cp as a minimum voltage signal Vmin. The period acquisition circuit 340 outputs a periodic signal CYC corresponding to the period of the residual vibration detection signal NVT.

[0223] That is, the discharge 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 corresponding to the acquired residual vibration. As a result, in the discharge module 20 of this embodiment, even if it is difficult to acquire the amplitude and period of the residual vibration signal Vout because the discharge unit 600 has a configuration including the pressure chambers CB1 and CB2, it is possible to accurately acquire waveform information of the residual vibration detection signal NVT without performing processing such as AD conversion. Therefore, the discharge module 20 of this embodiment can accurately and quickly acquire waveform information of the residual vibration generated in the discharge unit 600 after the piezoelectric elements 60a and 60b are driven.

[0224] 7. Variations In the liquid ejection device 1 of the present embodiment described above, the ejection section 600 that ejects ink has a configuration including a pressure chamber CB1 and a pressure chamber CB2, but the configuration of the ejection section 600 that ejects ink is not limited to this, and may have, for example, one pressure chamber for one nozzle N, or three pressure chambers for one nozzle N. Even with such a configuration, the same effects are achieved.

[0225] Furthermore, in the liquid ejection device 1 of this embodiment described above, the waveform information output circuit 300 has been described as acquiring a maximum voltage signal Vmax corresponding to the maximum voltage value of the residual vibration detection signal NVT in the dot formation period Cp and a minimum voltage signal Vmin corresponding to the minimum voltage value of the residual vibration detection signal NVT in the dot formation period Cp. However, the waveform information output circuit 300 may acquire a maximum voltage signal Vmax corresponding to the maximum voltage value of the residual vibration detection signal NVT for each vibration period of the residual vibration detection signal NVT. The maximum voltage signal Vmax and the minimum voltage signal Vmin corresponding to the minimum voltage value may be acquired, and the amplitude attenuation rate may be calculated as waveform information of the residual vibration detection signal NVT based on the acquired multiple maximum voltage signals Vmax and multiple minimum voltage signals Vmin.

[0226] Specifically, the reset circuit 310 included in the waveform information output circuit 300 receives the periodic pulse signal CYP output by the comparator CP1 instead of or in addition to the latch signal LAT.

[0227] The reset circuit 310 controls the switch SW12 to be on for a certain period when the logic level of the input periodic pulse signal CYP changes from high to low, and then controls the switch SW12 from on to off. After controlling the switch SW12 to be off, the reset circuit 310 controls the switch SW11 to be on for a certain period when the logic level of the input periodic pulse signal CYP changes from low to high, and then controls the switch SW11 from on to off. The reset circuit 310 controls the switch SW13 to be on for a certain period when the logic level of the input periodic pulse signal CYP changes from low to high, and then controls the switch SW13 from on to off. As a result, the maximum voltage value acquisition circuit 320 holds the maximum voltage value of the residual vibration detection signal NVT for each vibration period at one end of the capacitor C13 and outputs it as a maximum voltage signal Vmax from the maximum voltage value acquisition circuit 320.

[0228] The reset circuit 310 also controls the switch SW22 to be on for a certain period when the logic level of the input periodic pulse signal CYP changes from low to high, and then controls the switch SW22 from on to off. After controlling the switch SW22 to be off, the reset circuit 310 controls the switch SW21 to be on for a certain period when the logic level of the input periodic pulse signal CYP changes from high to low, and then controls the switch SW21 from on to off. The reset circuit 310 also controls the switch SW23 to be on for a certain period when the logic level of the input periodic pulse signal CYP changes from high to low, and then controls the switch SW23 from on to off. As a result, the minimum voltage value acquisition circuit 330 holds the minimum voltage value of the residual vibration detection signal NVT for each vibration period at one end of the capacitor C23 and outputs it as a minimum voltage signal Vmin from the minimum voltage value acquisition circuit 330.

[0229] The control circuit 100 holds the maximum voltage signal Vmax output by the maximum voltage value acquisition circuit 320 while 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 while 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 of the residual vibration detection signal NVT and the minimum voltage signal Vmin corresponding to the minimum voltage value for each vibration period of the residual vibration detection signal NVT.

[0230] In the liquid ejection device 1 of the modified example configured as described above, the amplitude attenuation rate 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 the amplitude information compared to when calculating the amplitude attenuation rate of the residual vibration detection signal NVT using either the maximum or minimum voltage value of the residual vibration detection signal NVT. This not only achieves the above-mentioned effects, but also makes it possible to accurately calculate the amplitude attenuation rate of the residual vibration detection signal NVT as waveform information, thereby further improving the accuracy of determining the ejection state of ink from the corresponding ejection unit 600.

[0231] Although the embodiments and modifications have been described above, the present invention is not limited to these embodiments and can be embodied in various forms without departing from the spirit of the present invention. For example, the above embodiments can be combined as appropriate.

[0232] The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effects). The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects as the configurations described in the embodiments or that can achieve the same purpose. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments.

[0233] The following can be derived from the above-described embodiment.

[0234] One embodiment of the print head comprises: a first pressure chamber whose volume changes in response to a drive signal; a first nozzle communicating with the first pressure chamber and discharging 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 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 or not the drive signal is supplied to the first piezoelectric element; a first residual vibration detection circuit that outputs a first residual vibration detection signal corresponding to the first residual vibration signal; Equipped with The first residual vibration detection circuit has one end electrically connected to one end of the first switch circuit and the other end electrically connected to the other end of the first switch circuit.

[0235] This print head has a first switch circuit electrically connected to a first piezoelectric element, one end of which receives a drive signal and the other end of which outputs a first residual vibration signal corresponding to a first residual vibration generated by a change in the volume of a first pressure chamber, and a first residual vibration detection circuit which outputs a first residual vibration detection signal corresponding to the first residual vibration signal, one end of the first residual vibration detection circuit being electrically connected to one end of the first switch circuit and the other end being electrically connected to the other end of the first switch circuit.

[0236] In the print head configured as described above, a potential difference is generated across the first switch circuit depending on the resistance value of the on-resistance of the first switch circuit and a first residual vibration signal depending on the charge output by the first piezoelectric element in response to the first residual vibration caused by a volume change in the first pressure chamber. The first residual vibration detection circuit then acquires the potential difference across the first switch circuit. That is, the first residual vibration detection circuit can acquire the first residual vibration signal without switching the conduction state of the first switch circuit. Therefore, in the print head described above, it is possible to acquire the first residual vibration signal without controlling the conduction state of the first switch circuit to a state specialized for acquiring the first residual vibration signal, thereby further increasing the speed at which residual vibration occurring after the first piezoelectric element is driven can be detected.

[0237] In one embodiment of the print head, the first piezoelectric element is displaced in response to the drive signal; The volume of the first pressure chamber may change in accordance with the displacement of the first piezoelectric element.

[0238] With this print head, the first piezoelectric element changes the volume of the first pressure chamber and acquires the first residual vibration signal, so there is no need to provide a separate dedicated component for changing the volume of the first pressure chamber, and as a result, the print head can be made compact.

[0239] In one embodiment of the print head, a first timing at which the volume of the first pressure chamber changes in response to the drive signal, and a second timing at which the first piezoelectric element outputs the first residual vibration signal in response to the first residual vibration; In the above, one end and the other end of the first switch circuit may be controlled to be conductive.

[0240] With this print head, the first residual vibration detection circuit can acquire the first residual vibration signal without switching the conductive state of the first switch circuit, so there is no need to control the conductive state of the first switch circuit to a state specialized for acquiring the first residual vibration signal, and as a result, it is possible to further increase the detection speed of the residual vibration that occurs after the first piezoelectric element is driven.

[0241] In one embodiment of the print head, the first switch circuit includes a transistor element; The transistor element may be driven in a linear region at the first timing.

[0242] In one embodiment of the print head, The drive signal may be a slight vibration waveform that vibrates the liquid in the vicinity of the first nozzle to such an extent that the liquid is not ejected from the first nozzle.

[0243] With this print head, when the first residual vibration detection circuit acquires the first residual vibration signal, the liquid stored in the first pressure chamber is not ejected, so the first residual vibration detection circuit can acquire the first residual vibration signal with high accuracy.

[0244] In one embodiment of the print head, a second pressure chamber whose volume changes in response to the drive signal; a second nozzle communicating with the second pressure chamber and discharging liquid; a second piezoelectric element that outputs 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 having one end to which the drive signal is input and the other end electrically connected to the second piezoelectric element, and configured to switch whether or not the drive signal is supplied to the second piezoelectric element; a second residual vibration detection circuit that outputs a second residual vibration detection signal corresponding to the second residual vibration signal; Equipped with The second residual vibration detection circuit may have one end electrically connected to one end of the second switch circuit and the other end electrically connected to the other end of the second switch circuit.

[0245] With this print head, the first residual vibration signal 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 signal detection circuit acquires a second residual vibration signal corresponding to the second residual vibration generated in the second pressure chamber, so that the first residual vibration detection circuit and the second residual vibration detection circuit can acquire the first residual vibration signal in parallel. Therefore, even with a print head having multiple pressure chambers, the residual vibration detection speed can be further increased.

[0246] One aspect of the liquid ejection device is a drive circuit that outputs a drive signal; a first pressure chamber whose volume changes in response to the drive signal; a first nozzle communicating with the first pressure chamber and discharging 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 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 or not the drive signal is supplied to the first piezoelectric element; a first residual vibration detection circuit that outputs a first residual vibration detection signal corresponding to the first residual vibration signal; Equipped with The first residual vibration detection circuit has one end electrically connected to one end of the first switch circuit and the other end electrically connected to the other end of the first switch circuit.

[0247] According to this liquid ejection device, the print head has a first switch circuit electrically connected to a first piezoelectric element, one end of which receives a drive signal and the other end of which outputs a first residual vibration signal corresponding to a first residual vibration generated by a change in volume of a first pressure chamber, and a first residual vibration detection circuit which outputs a first residual vibration detection signal corresponding to the first residual vibration signal, one end of the first residual vibration detection circuit being electrically connected to one end of the first switch circuit and the other end being electrically connected to the other end of the first switch circuit.

[0248] In a print head configured as described above, a potential difference is generated across both ends of the first switch circuit depending on the resistance value of the on resistance of the first switch circuit and the first residual vibration signal depending on the charge output by the first piezoelectric element in response to the first residual vibration caused by the volume change of the first pressure chamber.

[0249] The first residual vibration detection circuit then acquires the potential difference across the first switch circuit. That is, the first residual vibration detection circuit can acquire the first residual vibration signal without switching the conduction state of the first switch circuit. Therefore, in a liquid ejection device having the above print head, it is possible to acquire the first residual vibration signal without controlling the conduction state of the first switch circuit to a state specialized for acquiring the first residual vibration signal, thereby achieving even faster detection speed of the residual vibration that occurs after the first piezoelectric element is driven.

[0250] In one aspect of the liquid ejection device, the first piezoelectric element is displaced in response to the drive signal; The volume of the first pressure chamber may change in accordance with the displacement of the first piezoelectric element.

[0251] According to this liquid ejection device, the first piezoelectric element changes the volume of the first pressure chamber and acquires the first residual vibration signal, so there is no need to provide a dedicated configuration for changing the volume of the first pressure chamber, and as a result, a compact print head can be achieved.

[0252] In one aspect of the liquid ejection device, At a first timing when the volume of the first pressure chamber changes in response to the drive signal, and at a second timing when the first piezoelectric element outputs the first residual vibration signal in response to the first residual vibration, one end and the other end of the first switch circuit may be controlled to be conductive.

[0253] According to this liquid ejection device, the first residual vibration detection circuit can acquire the first residual vibration signal without switching the conductive state of the first switch circuit, so there is no need to control the conductive state of the first switch circuit to a state specialized for acquiring the first residual vibration signal, and as a result, the detection speed of the residual vibration generated after the first piezoelectric element is driven can be further increased.

[0254] In one aspect of the liquid ejection device, the first switch circuit includes a transistor element; The transistor element may be driven in a linear region at the first timing.

[0255] In one aspect of the liquid ejection device, The drive signal may be a slight vibration waveform that vibrates the liquid in the vicinity of the first nozzle to such an extent that the liquid is not ejected from the first nozzle.

[0256] According to this liquid ejection device, when the first residual vibration detection circuit acquires the first residual vibration signal, Furthermore, since the liquid stored in the first pressure chamber is not ejected, the first residual vibration detection circuit can acquire the first residual vibration signal with high accuracy.

[0257] In one aspect of the liquid ejection device, a second pressure chamber whose volume changes in response to the drive signal; a second nozzle communicating with the second pressure chamber and discharging liquid; a second piezoelectric element that outputs 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 having one end to which the drive signal is input and the other end electrically connected to the second piezoelectric element, and configured to switch whether or not the drive signal is supplied to the second piezoelectric element; a second residual vibration detection circuit that outputs a second residual vibration detection signal corresponding to the second residual vibration signal; Equipped with The second residual vibration detection circuit may have one end electrically connected to one end of the second switch circuit and the other end electrically connected to the other end of the second switch circuit.

[0258] According to this liquid ejection device, the first residual vibration signal 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 signal detection circuit acquires a second residual vibration signal corresponding to the second residual vibration generated in the second pressure chamber, so that the first residual vibration detection circuit and the second residual vibration detection circuit can acquire the first residual vibration signal in parallel. Therefore, even in a print head having multiple pressure chambers, the residual vibration detection speed can be further increased. [Explanation of symbols]

[0259] 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 board, 15...cable, 20...ejection module, 21...print head, 22...head chip, 23...head circuit board, 24...flexible board, 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... transfer gate, 240... residual vibration detection circuit, 300... waveform information output circuit, 302... communicating plate, 303... pressure chamber substrate, 304... vibration plate, 305... storage chamber forming substrate, 308... wiring substrate , 310... reset circuit, 320... maximum voltage value acquisition circuit, 330... minimum voltage value acquisition circuit, 340... period acquisition circuit, 341... counter circuit, 350... opening, 351... supply port, 352... discharge port, 360... nozzle substrate, 361, 362... compliance sheet, 600... discharge part, C1, C2, C11 to C13, C21 to C23... capacitor, CB1, CB2... pressure chamber, CP1... comparator, D11, D21... da Diode, INV1... logic inversion circuit, Ln... nozzle row, N... nozzle, OP1, OP11, OP12, OP21, OP22... amplifier circuit, P... medium, PW1... power supply circuit, R1 to R6... resistor, RA1... supply flow path, RA2... discharge flow path, RB1... supply flow path, RB2... discharge flow path, RK1, RK2... connection flow path, RN... nozzle flow path, RR1, RR2... communication flow path, SW1, SW2, SW11 to SW13, SW21 to SW23... switch

Claims

1. a first pressure chamber whose volume changes in response to a drive signal; a first nozzle communicating with the first pressure chamber and discharging a 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 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 or not the drive signal is supplied to the first piezoelectric element; a first residual vibration detection circuit that outputs a first residual vibration detection signal corresponding to the first residual vibration signal; Equipped with 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; A print head characterized by:

2. the first piezoelectric element is displaced in response to the drive signal; The volume of the first pressure chamber changes in accordance with the displacement of the first piezoelectric element.

2. The printhead of claim 1.

3. one end and the other end of the first switch circuit are controlled to be conductive at a first timing when the volume of the first pressure chamber changes in response to the drive signal and at a second timing when the first piezoelectric element outputs the first residual vibration signal in response to the first residual vibration.

2. The printhead of claim 1.

4. the first switch circuit includes a transistor element; At the first timing, the transistor element operates in a linear region.

4. The printhead of claim 3.

5. the drive signal has a slight vibration waveform that vibrates the liquid in the vicinity of the first nozzle to such an extent that the liquid is not ejected from the first nozzle.

2. The printhead of claim 1.

6. a second pressure chamber whose volume changes in response to the drive signal; a second nozzle communicating with the second pressure chamber and discharging liquid; a second piezoelectric element that outputs 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 having one end to which the drive signal is input and the other end electrically connected to the second piezoelectric element, and configured to switch whether or not the drive signal is supplied to the second piezoelectric element; a second residual vibration detection circuit that outputs a second residual vibration detection signal corresponding to the second residual vibration signal; Equipped with 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; 6. A printhead according to claim 1.

7. a drive circuit that outputs a drive signal; a first pressure chamber whose volume changes in response to the drive signal; a first nozzle communicating with the first pressure chamber and discharging a 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 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 or not the drive signal is supplied to the first piezoelectric element; a first residual vibration detection circuit that outputs a first residual vibration detection signal corresponding to the first residual vibration signal; Equipped with 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; A liquid ejection device characterized by:

8. the first piezoelectric element is displaced in response to the drive signal; The volume of the first pressure chamber changes in accordance with the displacement of the first piezoelectric element.

8. The liquid ejection device according to claim 7.

9. one end and the other end of the first switch circuit are controlled to be conductive at a first timing when the volume of the first pressure chamber changes in response to the drive signal and at a second timing when the first piezoelectric element outputs the first residual vibration signal in response to the first residual vibration.

8. The liquid ejection device according to claim 7.

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

11. the drive signal has a slight vibration waveform that vibrates the liquid in the vicinity of the first nozzle to such an extent that the liquid is not ejected from the first nozzle.

8. The liquid ejection device according to claim 7.

12. a second pressure chamber whose volume changes in response to the drive signal; a second nozzle communicating with the second pressure chamber and discharging liquid; a second piezoelectric element that outputs 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 having one end to which the drive signal is input and the other end electrically connected to the second piezoelectric element, and configured to switch whether or not the drive signal is supplied to the second piezoelectric element; a second residual vibration detection circuit that outputs a second residual vibration detection signal corresponding to the second residual vibration signal; Equipped with 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; 12. The liquid ejection device according to claim 7, wherein the liquid ejection device is a liquid ejection device.

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