Liquid dispensing device and head unit

Abstract

To provide a liquid dispensing device that can achieve both improved accuracy in determining the condition of the dispensing section and reduced inspection time for the condition of the dispensing section. [Solution] A liquid dispensing device comprising: a transport unit for transporting a medium; a dispensing unit for dispensing liquid into the medium; a residual vibration detection circuit that acquires a residual vibration signal corresponding to residual vibrations generated in the dispensing unit and outputs a residual vibration detection signal corresponding to the residual vibration signal; a first conversion circuit including a comparison circuit that outputs a comparison result signal whose logic level changes according to the comparison result between the voltage value of the residual vibration detection signal and a reference voltage value; a second conversion circuit including an A / D conversion circuit that outputs a detection voltage signal obtained by converting the residual vibration detection signal into a digital signal; and a determination circuit for determining the state of the dispensing unit, wherein the determination circuit has a first determination mode for determining the state of the dispensing unit according to the comparison result signal and a second determination mode for determining the state of the dispensing unit according to the detection voltage signal.

Description

Technical Field

[0001] The present invention relates to a liquid ejection device and a head unit.

Background Art

[0002] As shown in Patent Document 1, in a liquid ejection device that forms an image on a medium by ejecting liquid from an ejection unit, a technique for determining the state of the ejection unit based on residual vibration generated in the ejection unit is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique described in Patent Document 1, there is room for improvement from the viewpoint of achieving both an improvement in the determination accuracy of the state of the ejection unit and a reduction in the inspection time of the state of the ejection unit.

Means for Solving the Problems

[0005] One aspect of the liquid ejection device according to the present invention is a conveyance unit that conveys a medium, an ejection unit that ejects liquid onto the medium, a residual vibration detection circuit that acquires a residual vibration signal corresponding to residual vibration generated in the ejection unit and outputs a residual vibration detection signal corresponding to the residual vibration signal, a first conversion circuit including a comparison circuit that outputs a comparison result signal whose logic level changes according to a comparison result between a voltage value of the residual vibration detection signal and a reference voltage value, a second conversion circuit including an A / D conversion circuit that outputs a detection voltage signal obtained by converting the residual vibration detection signal into a digital signal, a determination circuit that determines the state of the ejection unit, Equipped with, The aforementioned determination circuit is A first determination mode for determining the state of the discharge unit according to the comparison result signal, A second determination mode for determining the state of the discharge unit in accordance with the detected voltage signal, It has.

[0006] One embodiment of the head unit according to the present invention is: A dispensing unit that dispenses liquid into a medium, A residual vibration detection circuit that acquires a residual vibration signal corresponding to the residual vibration generated in the discharge section and outputs a residual vibration detection signal corresponding to the residual vibration signal, A first conversion circuit includes a comparison circuit that outputs a comparison result signal whose logic level changes according to the comparison result between the voltage value of the residual vibration detection signal and a reference voltage value, A second conversion circuit, which includes an A / D conversion circuit and outputs a detection voltage signal obtained by converting the residual vibration detection signal into a digital signal, A determination circuit for determining the state of the discharge section, Equipped with, The aforementioned determination circuit is A first determination mode for determining the state of the discharge unit according to the comparison result signal, A second determination mode for determining the state of the discharge unit in accordance with the detected voltage signal, It has. [Brief explanation of the drawing]

[0007] [Figure 1] This is a diagram showing the schematic configuration of a liquid dispensing device. [Figure 2] This diagram shows the schematic configuration of the discharge unit. [Figure 3] This figure shows an example of the signal waveform of the drive signal COM. [Figure 4] This figure shows an example of the functional configuration of a drive signal selection circuit. [Figure 5] This figure shows an example of the functional configuration of a switching circuit. [Figure 6] This figure shows an example of the content decoded by the decoder. [Figure 7] It is a diagram showing the configuration of the selection circuit. [Figure 8] It is a diagram showing an example of the operation of the switching circuit. [Figure 9] It is a diagram showing an example of the configuration of the waveform shaping circuit. [Figure 10] It is an exploded perspective view of the print head. [Figure 11] It is a cross-sectional view taken along line A-a in FIG. 10. [Figure 12] It is a diagram showing an example of the residual vibration signal. [Figure 13] It is a diagram showing an example of the calculation model of simple vibration assuming residual vibration. [Figure 14] It is a diagram showing the configuration of the residual vibration acquisition circuit. [Figure 15] It is a diagram for explaining the operation of the analog acquisition circuit. [Figure 16] It is a diagram for explaining an example of the acquisition process in which the digital acquisition circuit acquires the acquired residual vibration signal. [Figure 17] It is a diagram for explaining an example of the determination process for determining the state of the ejection unit based on the information acquired in the acquisition operation. [Figure 18] It is a diagram for explaining the method for determining the state of the ejection unit.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The drawings used are for convenience of explanation. The embodiments described below do not unduly limit the content of the present invention described in the claims. Also, not all of the configurations described below are essential constituent elements of the present invention.

[0009] 1. Configuration of the liquid ejection device Figure 1 shows a schematic configuration of the liquid ejection device 1. As shown in Figure 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 colorant ejection device used in the manufacture of color filters for liquid crystal displays, an electrode material ejection device used in the formation of electrodes for organic EL displays, FEDs (surface-emitting displays), etc., a bio-organic material ejection device used in the manufacture of biochips, etc., or a 3D modeling device or a textile printing device, etc. Here, in the following description, 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 main scanning direction.

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

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

[0012] The liquid container 3 stores ink, which is an example of the liquid supplied to the dispensing unit 5. Specifically, the liquid container 3 stores inks of multiple colors that are dispensed onto the medium P, such as black, cyan, magenta, yellow, red, and gray. Such a liquid container 3 can be an ink cartridge, a bag-shaped ink pack made of a flexible film, or an ink tank that allows for ink replenishment.

[0013] The circulation unit 6 supplies ink stored in the liquid container 3 to the dispensing unit 5 based on the control signal Ctrl-P output by the control unit 2. The circulation unit 6 also recovers ink discharged from the dispensing unit 5 based on the control signal Ctrl-P output by the control unit 2. In other words, the circulation unit 6 recirculates the ink in the liquid dispensing device 1. Such a circulation unit 6 can be configured, for example, to include a pump that generates the ink flow in the liquid dispensing device 1.

[0014] The transport unit 4 includes a transport motor 41 and transport rollers 42. The transport unit 4 receives a transport control signal Ctrl-T output by the control unit 2. The transport motor 41 is then driven based on the transport control signal Ctrl-T, and the transport rollers 42 rotate in conjunction with the drive of the transport motor 41. The rotation of the transport rollers 42 transports the medium P along the transport direction. In other words, the liquid dispensing device 1 includes a transport unit 4 that transports the medium P.

[0015] Each of the multiple ejection units 5 has a drive module 10 and an ejection module 20. Each of the multiple ejection units 5 receives a corresponding image information signal IP output by the control unit 2, and is supplied with ink stored in the liquid container 3. The 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 the ink supplied from the liquid container 3 at a predetermined timing corresponding to the control of the drive module 10.

[0016] In the liquid dispensing device 1 of this embodiment, the dispensing modules 20 of each of the multiple dispensing units 5 are arranged in a line along the main scanning direction so as to be greater than or equal to the width of the medium P. Each of the multiple dispensing units 5 then dispenses ink at a timing synchronized with the transport of the medium P. As a result, the ink dispensed from each of the multiple dispensing units 5 lands at a desired position on the medium P, forming a desired image on the medium P.

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

[0018] The drive module 10 includes 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 can be a glass epoxy substrate, a glass polyimide substrate, or the like. The control circuit board 11 includes a drive circuit. The various elements constituting the drive module 10, including circuit 50 and control circuit 100, are mounted on the circuit board 11. The control circuit board 11 on which the various elements constituting the drive module 10 are mounted may consist of one printed circuit board or multiple printed circuit boards.

[0019] The control circuit 100 is configured as one or more integrated circuit devices, including processing circuits such as a CPU or FPGA and storage circuits such as semiconductor memory. The control circuit 100 receives an image information signal IP output by the control unit 2. Based on the input image information signal IP, the control circuit 100 generates and outputs signals to control 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, an inspection 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] Furthermore, the control circuit 100 generates a base drive signal dA and outputs it to the drive circuit 50. The drive circuit 50 generates a drive signal COM, which includes a signal waveform defined by the input base drive signal dA, and outputs it to the output module 20. Specifically, the control circuit 100 generates a base drive signal dA of a digital signal and outputs it to the drive circuit 50. The drive circuit 50 converts the input base drive signal dA of a digital signal into an analog signal, and then generates the drive signal COM by class D amplification of the converted analog signal. The drive circuit 50 then outputs the generated drive signal COM to the output module 20. In other words, the base drive signal dA output by the control circuit 100 defines the signal waveform of the drive signal COM output by the drive circuit 50.

[0022] The base drive signal dA input to the drive circuit 50 can be any signal capable of defining the signal waveform of the drive signal COM, and may be an analog signal. Furthermore, the drive circuit 50 only needs to be able to generate the drive signal COM by amplifying the signal waveform defined by the base drive signal dA, and may generate the drive signal COM by using Class A, Class B, or Class AB amplification instead of Class D amplification.

[0023] Furthermore, the drive circuit 50 generates a reference voltage signal VBS and outputs it to the discharge module 20. The reference voltage signal VBS is a signal with a constant voltage value that defines the reference potential for driving the piezoelectric elements 60a and 60b of the discharge unit 600, which will be described later. The voltage value of such a reference voltage signal VBS may be, for example, ground potential GND, or it may be 5.5V or 6V, etc. In Figure 2, the drive circuit 50 is shown to generate the reference voltage signal VBS and output it to the discharge module 20, but the reference voltage signal VBS may be generated by a constant voltage output circuit or the like (not shown) configured separately from the drive circuit 50.

[0024] Furthermore, the control circuit 100 receives status signals aDS1~aDSn and dDS1~dDSn from the ejection module 20, which will be described later. Based on the input status signals aDS1~aDSn and dDS1~dDSn, the control circuit 100 acquires status information of the ejection unit 600 of the ejection module 20. Then, based on the acquired status information of the ejection unit 600, the control circuit 100 corrects the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, and print data signals SI1~SIn. This improves the ejection accuracy of the ink ejected from the ejection module 20.

[0025] The ejection module 20 includes print heads 21-1 to 21-n, a head circuit board 23, and residual vibration acquisition circuits 300-1 to 300-n. Each of the print heads 21-1 to 21-n also includes a head chip 22, a flexible substrate 24, and a drive signal selection circuit 200. Each of the head chips 22 in each of the print heads 21-1 to 21-n has multiple ejection units 600, and each of the multiple ejection units 600 This includes piezoelectric elements 60a and 60b.

[0026] The ejection module 20 receives the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signals SI1~SIn, drive signal COM, and reference voltage signal VBS, all output by the drive module 10.

[0027] The head circuit board 23 propagates the input clock signal SCK, latch signal LAT, change signal CH, check timing signal TSIG, print data signals SI1~SIn, drive signal COM, and reference voltage signal VBS to the corresponding print heads 21-1~21-n. Such a head circuit board 23 is a printed circuit board having one or more wiring layers, and can be made of, for example, a glass epoxy substrate or a glass polyimide substrate.

[0028] The head circuit board 23 propagates the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signals SI1 to SIn, drive signal COM, and reference voltage signal VBS from among the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SI1, drive signal COM, and reference voltage signal VBS to the print head 21-1.

[0029] Of the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SI1, drive signal COM, and reference voltage signal VBS input to the print head 21-1, the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SI1, and drive signal COM are input to the drive signal selection circuit 200 of the print head 21-1. Based on the input clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, and print data signal SI1, the drive signal selection circuit 200 of the print head 21-1 selects or deselects the signal waveform included in the drive signal COM, thereby generating a drive voltage signal Vin corresponding to each of the multiple ejection units 600 of the head chip 22 of the print head 21-1, and supplies it to one end of the piezoelectric elements 60a, 60b included in the corresponding ejection unit 600.

[0030] At this time, a reference voltage signal VBS is supplied to the other end of each of the piezoelectric elements 60a and 60b included in the multiple ejection units 600 of the head chip 22 of the print head 21-1. The piezoelectric elements 60a and 60b included in the multiple ejection units 600 are driven according to the potential difference between the voltage value of the drive voltage signal Vin supplied to one end and the voltage value of the reference voltage signal VBS supplied to the other end. By driving these piezoelectric elements 60a and 60b, ink is ejected from the corresponding ejection unit 600.

[0031] Furthermore, the drive signal selection circuit 200 of the print head 21-1 receives a residual vibration signal Vout corresponding to the residual vibration generated after the piezoelectric elements 60a and 60b included in the multiple ejection sections 600 of the head chip 22 of the print head 21-1 are driven. The drive signal selection circuit 200 generates an acquired residual vibration signal NVT1 corresponding to the input residual vibration signal Vout and outputs it from the print head 21-1.

[0032] The drive signal selection circuit 200 of such a print head 21-1 is configured as an integrated circuit device, and COF (Chip) is attached to the flexible substrate 24 of the print head 21-1. (On Film) It is implemented.

[0033] Similarly, the head circuit board 23 has a clock signal SCK, a latch signal LAT, a change signal CH, a check timing signal TSIG, print data signals SI1~SIn, a drive signal COM, and a reference voltage signal VBS, of which the clock signal SCK, latch signal LAT, change signal CH, check timing signal TSIG, and print data signal SIi (where i is one of 1~n) are used. The drive signal COM and the reference voltage signal VBS are propagated to the print head 21-i.

[0034] Of the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SIi, drive signal COM, and reference voltage signal VBS input to the print head 21-i, the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SIi, and drive signal COM are input to the drive signal selection circuit 200 of the print head 21-i. Based on the input clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, and print data signal SIi, the drive signal selection circuit 200 of the print head 21-i selects or deselects the signal waveform included in the drive signal COM, thereby generating a drive voltage signal Vin corresponding to each of the multiple ejection units 600 of the print head 21-i's head chip 22, and supplies it in common to one end of the piezoelectric elements 60a and 60b included in the corresponding ejection unit 600.

[0035] At this time, a reference voltage signal VBS is supplied to the other end of each of the piezoelectric elements 60a and 60b included in the multiple ejection units 600 of the head chip 22 of the print head 21-i. The piezoelectric elements 60a and 60b included in the multiple ejection units 600 are driven according to the potential difference between the voltage value of the drive voltage signal Vin supplied to one end and the voltage value of the reference voltage signal VBS supplied to the other end. By driving these piezoelectric elements 60a and 60b, ink is ejected from the corresponding ejection unit 600.

[0036] Furthermore, the drive signal selection circuit 200 of the print head 21-i receives a residual vibration signal Vout corresponding to the residual vibration generated after the piezoelectric elements 60a and 60b included in the multiple ejection sections 600 of the head chip 22 of the print head 21-i are driven. The drive signal selection circuit 200 generates an acquired residual vibration signal NVTi corresponding to the input residual vibration signal Vout and outputs it from the print head 22-i.

[0037] The drive signal selection circuit 200 of the print head 21-i is configured as an integrated circuit device and is mounted on the flexible substrate 24 of the print head 21-i using COF (Cross-Optical Fiber) mounting.

[0038] Here, the drive signal selection circuit 200 of each print head 21-1 to 21-i is not limited to being COF mounted on the corresponding flexible substrate 24, but may also be provided on the head circuit board 23. However, as shown in this embodiment, it is preferable that it be COF mounted on the corresponding flexible substrate 24. This shortens the propagation path of the drive voltage signal Vin output by the drive signal selection circuit 200 and the propagation path of the residual vibration signal Vout input to the drive signal selection circuit 200, reducing the risk of noise superimposing on the drive voltage signal Vin and the residual vibration signal Vout, and also reducing the risk of distortion in the signal waveforms of the drive voltage signal Vin and the residual vibration signal Vout due to the impedance of the propagation path. As a result, the accuracy of the signal waveform of the drive voltage signal Vin supplied to the piezoelectric elements 60a and 60b included in the corresponding ejection unit 600 is improved, the driving accuracy of the piezoelectric elements 60a and 60b is improved, and the accuracy of the control circuit 100's determination of whether the ejection unit 600 is functioning normally in response to the residual vibration signal Vout is improved.

[0039] The residual vibration acquisition circuits 300-1 to 300-n are provided on the head circuit board 23, corresponding to the print heads 21-1 to 21-n. Specifically, the residual vibration acquisition circuit 300-1 is provided corresponding to the print head 21-1, and receives the acquired residual vibration signal NVT1 output by the drive signal selection circuit 200 of the print head 21-1. The residual vibration acquisition circuit 300-1 then determines the state of the corresponding ejection unit 600 based on the input acquired residual vibration signal NVT1, and outputs state signals aDS1 and dDS1 according to the determination result.

[0040] Similarly, the residual vibration acquisition circuit 300-i is provided in correspondence with the print head 21-i, and receives the acquired residual vibration signal NVTi output by the drive signal selection circuit 200 of the print head 21-i. Based on the acquired residual vibration signal NVTi that is input, the residual vibration acquisition circuit 300-i determines the state of the corresponding ejection unit 600 and outputs state signals aDSi and dDSi according to the determination result. Such residual vibration acquisition circuits 300-1 to 300-n may be configured as individual integrated circuit devices, or they may be configured as a single integrated circuit device together with the drive signal selection circuit 200 of the corresponding print heads 21-1 to 21-n. Furthermore, some or all of the residual vibration acquisition circuits 300-1 to 300-n may be integrated with the control circuit 100 mounted on the control circuit board 11 in the drive module 10.

[0041] Here, print heads 21-1 to 21-n all have the same configuration. Therefore, in the following explanation, when it is not necessary to distinguish between print heads 21-1 to 21-n, they may simply be referred to as print head 21. In this case, print head 21 is assumed to receive a clock signal SCK, a latch signal LAT, a change signal CH, a check timing signal TSIG, print data signals SI as print data signals SI1 to SIn, a drive signal COM, and a reference voltage signal VBS, and to output acquired residual vibration signals NVT as acquired residual vibration signals NVT1 to NVTn. Furthermore, residual vibration acquisition circuits 300-1 to 300-n all have the same configuration. Therefore, in the following explanation, when it is not necessary to distinguish between residual vibration acquisition circuits 300-1 to 300-n, they may simply be referred to as residual vibration acquisition circuit 300. In this explanation, the residual vibration acquisition circuit 300 receives the acquired residual vibration signals NVT as acquired residual vibration signals NVT1 to NVTn, and outputs the state signals aDS as state signals aDS1 to aDSn and the state signals dDS1 to dDSn.

[0042] 2. Configuration and Operation of the Drive Signal Selection Circuit 2.1 Signal waveform of drive signal COM Next, we will describe the configuration and operation of the drive signal selection circuit 200, which outputs a drive voltage signal Vin corresponding to each of the multiple discharge units 600 by selecting or deselecting the signal waveform included in the drive signal COM. Before describing the details of the drive signal selection circuit 200, we will first describe an example of the signal waveform of the drive signal COM input to the drive signal selection circuit 200. Figure 3 is a diagram showing an example of the signal waveform of the drive signal COM. As shown in Figure 3, the drive signal COM includes drive signal ComA and drive signal ComB.

[0043] The drive signal ComA includes drive waveforms Adp1 and Adp2 as signal waveforms during the period t between the rise of the latch signal LAT and the next rise of the latch signal LAT.

[0044] The drive waveform Adp1 is positioned during the period tp1 within the period t, from the rising edge of the latch signal LAT to the rising edge of the change signal CH. The drive waveform Adp1 starts with a voltage value of voltage Vc, changes voltage value to drive the piezoelectric elements 60a and 60b, and then ends with a voltage value of 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 corresponding ejection unit 600.

[0045] The drive waveform Adp2 is positioned during the period tp2 of the period t, from the rising edge of the change signal CH to the rising edge of the latch signal LAT. The drive waveform Adp2 starts with a voltage value of voltage Vc, changes voltage to drive the piezoelectric elements 60a and 60b, and then ends with a voltage value of voltage Vc. When this drive waveform Adp2 is supplied to the piezoelectric elements 60a and 60b, a smaller amount of ink than a predetermined amount is ejected from the corresponding ejection unit 600.

[0046] In the following explanation, the amount of ink discharged from the corresponding discharge unit 600 when the drive waveform Adp1 is supplied to the piezoelectric elements 60a and 60b will be referred to as a medium amount, and the amount of ink discharged from the corresponding discharge unit 600 when the drive waveform Adp2 is supplied to the piezoelectric elements 60a and 60b, which is less than the predetermined amount, will be referred to as a small amount.

[0047] The drive signal ComB includes drive waveforms Bdp1, Bdp2, and Bdp3 as signal waveforms at period t.

[0048] The drive waveform Bdp1 is positioned within the period ts1, which is the period from the rising edge of the latch signal LAT to the rising edge of the inspection timing signal TSIG. The drive waveform Bdp1 starts with a voltage value Vc, changes to drive the piezoelectric elements 60a and 60b, and then ends with a voltage value Vd. When this drive waveform Bdp1 is supplied to the piezoelectric elements 60a and 60b, no ink is ejected from the corresponding ejection unit 600, and the piezoelectric elements 60a and 60b are driven to generate a predetermined vibration in the corresponding ejection unit 600.

[0049] The drive waveform Bdp2 is positioned within the period t of time t, specifically during the period ts2, from the rising edge of the inspection timing signal TSIG that defines the end of period ts1 to the rising edge of the next inspection timing signal TSIG. The drive waveform Bdp2 has a constant voltage value of voltage Vd. When this drive waveform Bdp2 is supplied to one end of the piezoelectric 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.

[0050] The drive waveform Bdp3 is positioned within the period t, specifically during the period ts3 from the rising edge of the inspection timing signal TSIG, which defines the end of period ts2, to the rising edge of the next latch signal LAT. The drive waveform Bdp3 starts with a voltage value of voltage Vd and ends when the voltage value becomes voltage Vc. When this drive waveform Bdp3 is supplied to 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.

[0051] In other words, the drive circuit 50 outputs a drive signal COM to the drive signal selection circuit 200, which includes drive signals ComA including drive waveforms Adp1 and Adp2, and drive signals ComB including drive waveforms Bdp1, Bdp2, and Bdp3. The drive signal selection circuit 200 then selects or deselects drive waveforms Adp1 and Adp2 and drive waveforms Bdp1, Bdp2, and Bdp3 to generate a drive voltage signal Vin including signal waveforms for representing four grayscale levels on the medium P: large dot LD, medium dot MD, small dot SD, and unrecorded ND, and a drive voltage signal Vin including a signal waveform for performing a state check CD to check the state of the ejection unit 600, and outputs these to the corresponding ejection unit 600.

[0052] Note that the signal waveform of the drive signal COM shown in Figure 3 is just an example, and the drive circuit 50 may output a drive signal COM that includes various signal waveforms depending on the type of ink to be ejected and the type of medium P to which the ink lands. In addition, the drive circuit 50 may generate a drive signal COM that includes a signal waveform corresponding to each of the print heads 21-1 to 21-n and output it to the corresponding print heads 21-1 to 21-n.

[0053] 2.2 Configuration of the drive signal selection circuit Next, a specific example of the configuration of the drive signal selection circuit 200 will be described. Figure 4 is a diagram showing an example of the functional configuration of the drive signal selection circuit 200. As shown in Figure 4, the drive signal selection circuit 200 has a switching circuit 210 and a waveform shaping circuit 240.

[0054] The switching circuit 210 receives the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SI, and drive signal COM. The switching circuit 210 generates a drive voltage signal Vin corresponding to each of the multiple ejection units 600 by selecting or deselecting the drive waveforms Adp1, Adp2 included in drive signal ComA and drive waveforms Bdp1, Bdp2, Bdp3 included in drive signal ComB, based on the input clock signal SCK, latch signal LAT, inspection timing signal TSIG, change signal CH, and print data signal SI. The drive voltage signal Vin generated by the switching circuit 210 is then output from the drive signal selection circuit 200.

[0055] The drive voltage signal Vin output from the drive signal selection circuit 200 is supplied to the piezoelectric elements 60a and 60b of the corresponding discharge unit 600. In the following description, when distinguishing between the drive voltage signal Vin supplied to piezoelectric element 60a and the drive voltage signal Vin supplied to piezoelectric element 60b, the drive voltage signal Vin supplied to piezoelectric element 60a may be referred to as drive voltage signal Vin1, and the drive voltage signal Vin supplied to piezoelectric element 60b may be referred to as drive voltage signal Vin2.

[0056] Furthermore, the switching circuit 210 acquires a residual vibration signal Vout corresponding to the residual vibration generated in the discharge section 600 after the piezoelectric elements 60a and 60b are driven by the drive voltage signal Vin output by the drive signal selection circuit 200.

[0057] Specifically, after a drive voltage signal Vin1 is supplied to piezoelectric element 60a and a drive voltage signal Vin2 is supplied to piezoelectric element 60b, residual vibration occurs in the discharge section 600. Piezoelectric element 60a then outputs the back electromotive force generated in response to the residual vibration as residual vibration signal Vout1, and piezoelectric element 60b then outputs the back electromotive force generated in response to the residual vibration as residual vibration signal Vout2. Therefore, the drive signal selection circuit 200 receives a residual vibration signal Vout, which is a combination of residual vibration signals Vout1 and Vout2. The switching circuit 210 acquires the input residual vibration signal Vout at a predetermined timing. The switching circuit 210 then outputs the acquired residual vibration signal Vout to the waveform shaping circuit 240.

[0058] The waveform shaping circuit 240 shapes the signal waveform of the input residual vibration signal Vout. The waveform shaping circuit 240 then outputs the shaped signal of the residual vibration signal Vout as the acquired residual vibration signal NVT. This acquired residual vibration signal NVT output by the waveform shaping circuit 240 is output from the drive signal selection circuit 200 and input to the residual vibration acquisition circuit 300.

[0059] 2.2.1 Configuration of the switching circuit A specific example of the configuration and operation of the switching circuit 210 included in the drive signal selection circuit 200 will be described. Figure 5 is a diagram showing an example of the functional configuration of the switching circuit 210. As shown in Figure 5, the switching circuit 210 includes a selection control circuit 220 and a plurality of selection circuits 230.

[0060] The selection control circuit 220 receives the clock signal SCK, the print data signal SI, the latch signal LAT, the change signal CH, and the check timing signal TSIG as inputs. Based on the input clock signal SCK, print data signal SI, latch signal LAT, change signal CH, and check timing signal TSIG, the selection control circuit 220 generates selection signals Sa, Sb, and Sc, which are at predetermined logic levels for periods tp1, tp2, and periods ts1, ts2, and ts3, respectively, and outputs them to the corresponding selection circuit 230.

[0061] The selection control circuit 220 has a set of a shift register 222, a latch circuit 224, and a decoder 226, each corresponding to one of the multiple ejection units 600 of the print head 21. Here, we will explain assuming that the print head 21 has M ejection units 600. That is, the selection control circuit 220 has M sets of the shift register 222, latch circuit 224, and decoder 226. In other words, the selection control circuit 220 has M sets of the shift register 222, latch circuit 224, and decoder 226. It has a fast register 222, M latch circuits 224, and M decoders 226.

[0062] The print data signal SI contains a 3-bit print data Sid[SIH,SIM,SIL] serially for each of the M ejector units 600, which is used to select which of the following the ejector units 600 should be driven for: the large dot LD, medium dot MD, small dot SD, non-recorded ND, or status check CD. In other words, the print data signal SI is a serial signal totaling 3M bits or more.

[0063] The print data signal SI is input to the selection control circuit 220 in synchronization with the clock signal SCK. The M shift registers 222 of the selection control circuit 220 hold the 3-bit print data Sid[SIH,SIM,SIL] contained in the input print data signal SI, corresponding to the ejection unit 600.

[0064] In detail, the M shift registers 222 are connected in cascaded order, each corresponding to one of the M ejection units 600. The print data signal SI, input serially to the selection control circuit 220, is sequentially transferred to the downstream of the M cascaded 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 3-bit print data Sid[SIH,SIM,SIL] corresponding to the M ejection units 600. In the following description, to distinguish between the M cascaded shift registers 222, they may be referred to as stages 1, 2, ..., M, in order from the upstream side to the downstream side where the print data signal SI is supplied.

[0065] Each of the M latch circuits 224 simultaneously latches the 3-bit print data Sid[SIH,SIM,SIL] held in the corresponding shift register 222 on the rising edge of the latch signal LAT.

[0066] The print data Sid[SIH,SIM,SIL] latched by the M latch circuits 224 is input to the corresponding decoder 226. Each of the M decoders 226 decodes the input print data Sid[SIH,SIM,SIL] and generates logic level selection signals Sa, Sb, Sc corresponding to large dot LD, medium dot MD, small dot SD, unrecorded ND, and status check CD, and outputs them to the corresponding selection circuit 230.

[0067] Figure 6 shows an example of the decoding content in decoder 226. As shown in Figure 6, when the decoder 226 receives the print data Sid[SIH,SIM,SIL]=[1,1,0] corresponding to the large dot LD, it sets the logic level of the selection signal Sa to H,H level during periods tp1 and tp2, the logic level of the selection signal Sb to L,L,L level during periods ts1, ts2, and ts3, and the logic level of the selection signal Sc to L,L,L level during periods ts1, ts2, and ts3.

[0068] Furthermore, when the decoder 226 receives print data Sid[SIH,SIM,SIL]=[1,0,0] corresponding to the middle dot MD, it sets the logic level of the selection signal Sa to H,L level during periods tp1 and tp2, the logic level of the selection signal Sb to L,L,L level during periods ts1, ts2, and ts3, and the logic level of the selection signal Sc to L,L,L level during periods ts1, ts2, and ts3.

[0069] Furthermore, when the decoder 226 receives print data Sid[SIH,SIM,SIL]=[0,1,0] corresponding to the small dot SD, it sets the logic level of the selection signal Sa to L and H levels during periods tp1 and tp2, and the logic level of the selection signal Sb to L and H levels during periods ts1 and ts2 The logic level of the selection signal Sc is set to L,L,L in ts3, and the logic level of the selection signal Sc is set to L,L,L in periods ts1, ts2, and ts3.

[0070] Furthermore, when the decoder 226 receives print data Sid[SIH,SIM,SIL]=[0,0,0] corresponding to non-recorded ND, it sets the logic level of the selection signal Sa to L,L level during periods tp1 and tp2, the logic level of the selection signal Sb to L,L,L level during periods ts1, ts2, and ts3, and the logic level of the selection signal Sc to L,L,L level during periods ts1, ts2, and ts3.

[0071] Furthermore, when the decoder 226 receives the printed data Sid[SIH,SIM,SIL]=[1,1,1] corresponding to the status check CD, it sets the logic level of the selection signal Sa to L,L level during periods tp1 and tp2, the logic level of the selection signal Sb to H,L,H level during periods ts1, ts2, and ts3, and the logic level of the selection signal Sc to L,H,L level during periods ts1, ts2, and ts3.

[0072] As described above, the selection control circuit 220 generates logic level selection signals Sa, Sb, and Sc corresponding to each of the M ejection units 600 based on the print data Sid[SIH, SIM, SIL]. The selection control circuit 220 then outputs the generated selection signals Sa, Sb, and Sc to the corresponding selection circuits 230.

[0073] The selection circuit 230 is provided in correspondence to each of the M discharge units 600. That is, the switching circuit 210 has M selection circuits 230. A drive signal COM is input to each of the M selection circuits 230, and it switches whether or not to output a drive voltage signal Vin corresponding to the drive signal COM to the corresponding discharge unit 600. Figure 7 is a diagram showing the configuration of a selection circuit 230 corresponding to one discharge unit 600. As shown in Figure 7, the selection circuit 230 has logic inverting circuits 232a, 232b, 232c and transfer gates 234a, 234b, 234c.

[0074] The selection signal Sa is supplied to the positive control terminal of transfer gate 234a, and after its logic level is inverted by the logic inverter circuit 232a, it is also supplied to the negative control terminal of transfer gate 234a. The selection signal Sb is supplied to the positive control terminal of transfer gate 234b, and after its logic level is inverted by the logic inverter circuit 232b, it is also supplied to the negative control terminal of transfer gate 234b. The selection signal Sc is supplied to the positive control terminal of transfer gate 234c, and after its logic level is inverted by the logic inverter circuit 232c, it is also supplied to the negative control terminal of transfer gate 234c.

[0075] Furthermore, a drive signal ComA is supplied to the input terminal of transfer gate 234a, and a drive signal ComB is supplied to the input terminal of transfer gate 234b. The output terminals of transfer gates 234a and 234b are interconnected. These interconnected output terminals of transfer gates 234a and 234b are electrically connected to the piezoelectric elements 60a and 60b of the corresponding discharge unit 600. The input terminal of transfer gate 234c is connected to the output terminals of the interconnected transfer gates 234a and 234b, and its output terminal is electrically connected to the piezoelectric elements 60a and 60b of the corresponding discharge unit 600. At this time, the output terminal of transfer gate 234c is commonly connected to the output terminals of the transfer gates 234c of the M selection circuits 230 of the switching circuit 210, as shown in Figure 5. That is, the output terminals of the transfer gates 234c of the M selection circuits 230 of the switching circuit 210 are electrically connected at this connection point.

[0076] In the selection circuit 230 configured as described above, the transfer gate 234a is When the logic level of the selection signal Sa is high, the input and output terminals conduct, and when the logic level of the selection signal Sa is low, the input and output terminals do not conduct. Similarly, for transfer gate 234b, when the logic level of the selection signal Sb is high, the input and output terminals conduct, and when the logic level of the selection signal Sb is low, the input and output terminals do not conduct. Similarly, for transfer gate 234c, when the logic level of the selection signal Sc is high, the input and output terminals conduct, and when the logic level of the selection signal Sc is low, the input and output terminals do not conduct. Hereinafter, in the following explanation, the conduction between the input and output terminals of transfer gates 234a, 234b, and 234c may be referred to as "on," and the non-conductivity between the input and output terminals may be referred to as "off."

[0077] When transfer gate 234a is turned on, drive signal ComA is output from the switching circuit 210 as drive voltage signal Vin, and when transfer gate 234b is turned on, drive signal ComB is output from the switching circuit 210 as drive voltage signal Vin. This drive voltage signal Vin output from the switching circuit 210 is supplied to the piezoelectric elements 60a and 60b of the corresponding discharge unit 600. When transfer gate 234c is turned on, the switching circuit 210 acquires a residual vibration signal Vout corresponding to the residual vibration generated in the corresponding discharge unit 600. The residual vibration signal Vout acquired by the switching circuit 210 is then input to the waveform shaping circuit 240. That is, the waveform shaping circuit 240 is electrically connected to a connection point where the output terminals of the transfer gates 234c of the M selection circuits 230 are commonly connected.

[0078] The operation of the switching circuit 210 configured as described above will now be explained in detail. Figure 8 shows an example of the operation of the switching circuit 210. The switching circuit 210 is supplied with print data signals SI serially in synchronization with the clock signal SCK. The print data signals SI input to the switching circuit 210 are sequentially transferred to the subsequent shift registers 222 in synchronization with the clock signal SCK. When the supply of the clock signal SCK to the switching circuit 210 is stopped, each of the M shift registers 222 holds 3-bit print data Sid[SIH,SIM,SIL] corresponding to the M ejection units 600.

[0079] Subsequently, when the latch signal LAT rises, each of the latch circuits 224 simultaneously latches the print data Sid[SIH,SIM,SIL] held in the shift register 222. Here, LT1, LT2, ..., LTM shown in Figure 8 represent the print data Sid[SIH,SIM,SIL] held in the 1st, 2nd, ..., Mth stage shift registers 222 and latched by the corresponding latch circuits 224.

[0080] Decoder 226 decodes the latched print data Sid[SIH,SIM,SIL] as shown in Figure 8. Then, at period t, decoder 226 outputs the logic level selection signals Sa, Sb, and Sc shown in Figure 8.

[0081] 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 level during periods tp1 and tp2, the logic level of the selection signal Sb to L,L,L level during periods ts1, ts2, and ts3, and the logic level of the selection signal Sc to L,L,L level during periods ts1, ts2, and ts3. As a result, the selection circuit 230 selects the drive waveform Adp1 of the drive signal ComA during period tp1, and the drive waveform Adp2 of the drive signal ComA during period tp2. Consequently, the switching circuit 210 outputs a drive voltage signal Vin corresponding to the large dot LD shown in Figure 8. When this drive voltage signal Vin corresponding to the large dot LD is supplied to the ejection unit 600, a moderate amount of ink is ejected from the ejection unit 600 during period tp1, and a small amount of ink is ejected during period tp2. Then, in period t, When a certain amount of ink and a small amount of ink land on the medium P and combine, a large dot LD is formed on the medium P.

[0082] 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 periods tp1 and tp2, the logic level of the selection signal Sb to L,L,L levels during periods ts1, ts2, and ts3, and the logic level of the selection signal Sc to L,L,L levels during periods ts1, ts2, and ts3. As a result, the selection circuit 230 selects the drive waveform Adp1 of the drive signal ComA during period tp1, and does not select either the signal waveform of drive signals ComA or ComB during period tp2. Consequently, the switching circuit 210 outputs a drive voltage signal Vin corresponding to the medium dot MD shown in Figure 8. When this drive voltage signal Vin corresponding to the medium dot MD is supplied to the ejection unit 600, a moderate amount of ink is ejected from the ejection unit 600 during period tp1, and no ink is ejected during period tp2. As a result, during period t, a moderate amount of ink lands on the medium P, forming a medium dot MD on the medium P.

[0083] 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 periods tp1 and tp2, the logic level of the selection signal Sb to L,L,L levels during periods ts1, ts2, and ts3, and the logic level of the selection signal Sc to L,L,L levels during periods ts1, ts2, and ts3. As a result, the selection circuit 230 does not select either the signal waveform of the drive signals ComA or ComB during period tp1, and selects the drive waveform Adp2 of the drive signal ComA during period tp2. Consequently, the switching circuit 210 outputs a drive voltage signal Vin corresponding to the small dot SD shown in Figure 8. When this drive voltage signal Vin corresponding to the small dot SD is supplied to the ejection unit 600, no ink is ejected from the ejection unit 600 during period tp1, and a small amount of ink is ejected during period tp2. As a result, at period t, a small amount of ink lands on the medium P, forming small dots SD on the medium P.

[0084] 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 level during periods tp1 and tp2, the logic level of the selection signal Sb to L,L,L level during periods ts1, ts2, and ts3, and the logic level of the selection signal Sc to L,L,L level during periods ts1, ts2, and ts3. As a result, the selection circuit 230 does not select either the signal waveform of the drive signals ComA or ComB during period tp1, nor does it select either the signal waveform of the drive signals ComA or ComB during period tp2. Consequently, the switching circuit 210 outputs a drive voltage signal Vin corresponding to the non-recorded ND shown in Figure 8. When this drive voltage signal Vin corresponding to the non-recorded ND is supplied to the ejection unit 600, no ink is ejected from the ejection unit 600 during period tp1, nor is any ink ejected during period tp2. As a result, during period t, no ink lands on the medium P, and no dots are formed on the medium P.

[0085] 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 level during periods tp1 and tp2, the logic level of the selection signal Sb to H,L,H level during periods ts1, ts2, and ts3, and the logic level of the selection signal Sc to L,H,L level during periods ts1, ts2, and ts3. As a result, the selection circuit 230 selects the drive waveform Bdp1 of the drive signal ComB during period ts1, acquires a residual vibration signal Vout corresponding to the residual vibration generated in the ejection section 600 after the piezoelectric elements 60a and 60b are driven by the drive waveform Bdp1 during period ts2, outputs the acquired residual vibration signal Vout from the switching circuit 210, and selects the drive waveform Bdp3 of the drive signal ComB during period ts3. As a result, the switching circuit 210 outputs a drive voltage signal Vin corresponding to the state inspection CD shown in Figure 8 during periods ts1 and ts3, and during period ts2, after the drive waveform Bdp1 is supplied to the discharge unit 600, the discharge unit 600 A residual vibration signal Vout corresponding to the vibrations occurring is acquired and output to the waveform shaping circuit 240. At this time, no ink is ejected from the ejection unit 600 during period t. As a result, no ink lands on the medium P during period t, and no dots are formed on the medium P.

[0086] As described above, the switching circuit 210 generates a drive voltage signal Vin by selecting or deselecting the drive waveforms Adp1 and Adp2 included in drive signal ComA and drive waveforms Bdp1, Bdp2, and Bdp3 included in drive signal ComB, which are part of the drive signal COM output by the drive circuit 50, based on the clock signal SCK, print data signal SI, latch signal LAT, change signal CH, and inspection timing signal TSIG. The switching circuit 210 then supplies the generated drive voltage signal Vin to the corresponding ejection unit 600, and acquires the residual vibration signal Vout that occurs after the drive voltage signal Vin is supplied to the ejection unit 600, and outputs it to the waveform shaping circuit 240.

[0087] 2.2.2 Configuration of the waveform shaping circuit Next, a specific example of the configuration and operation of the waveform shaping circuit 240 included in the drive signal selection circuit 200 will be described. Figure 9 shows an example of the configuration of the waveform shaping circuit 240. As shown in Figure 9, the waveform shaping circuit 240 includes a filter circuit 241, an amplification circuit 242, and an impedance conversion circuit 243.

[0088] The filter circuit 241 includes a capacitor C10 and a resistor R10. A residual vibration signal Vout is supplied to one end of the capacitor C10. The other end of the capacitor C10 is electrically connected to one end of the resistor R10. Ground potential is supplied to the other end of the resistor R10. As described above, the filter circuit 241 constitutes a high-pass filter. The filter circuit 241 extracts the high-frequency components superimposed on the residual vibration signal Vout by reducing the low-frequency components superimposed on the residual vibration signal Vout. Alternatively, the filter circuit 241 may also constitute a so-called band-pass filter, having a low-pass filter in addition to the high-pass filter, to extract signals of predetermined frequency components superimposed on the residual vibration signal Vout.

[0089] The amplification circuit 242 includes an operational amplifier AM10 and resistors R11 and R12. The signal output by the filter circuit 241 is input to the positive input terminal of the operational amplifier AM10. The negative input terminal of the operational amplifier AM10 is electrically connected to one end of resistor R11 and one end of resistor R12. The output terminal of the operational amplifier AM10 is electrically connected to the other end of resistor R11. Ground potential is supplied to the other end of resistor R12. The amplification circuit 242 configured as described above amplifies the signal output by the filter circuit 241 input to the positive input terminal of the operational amplifier AM10 with an amplification factor defined by the resistance values ​​of resistors R11 and R12. In other words, the amplification circuit 242 constitutes a non-inverting amplifier circuit that amplifies the amplitude of the signal from which the AC component of the residual oscillation signal Vout has been extracted, with an amplification factor defined by the resistance values ​​of resistors R11 and R12. Furthermore, the amplification circuit 242 only needs to be able to amplify the amplitude of the signal from which the AC component of the residual oscillation signal Vout has been extracted by a predetermined amplification factor, and is not limited to a non-inverting amplifier circuit.

[0090] The impedance conversion circuit 243 includes an operational amplifier AM11. The signal output by the amplification circuit 242 is input to the positive input terminal of the operational amplifier AM11. The negative input terminal of the operational amplifier AM11 is electrically connected to the output terminal of the operational amplifier AM11. The impedance conversion circuit 243 configured as described above constitutes a so-called voltage follower circuit, which outputs a signal with the same signal waveform as the signal input to the positive input terminal of the operational amplifier AM11 from the output terminal of the operational amplifier AM11.

[0091] The waveform shaping circuit 240 then uses the signal output from the output terminal of the operational amplifier AM10 of the amplification circuit 242, and the operational amplifier AM of the impedance conversion circuit 243. The signals output from the 11 output terminals are output as the acquired residual vibration signal (NVT).

[0092] The piezoelectric elements 60a and 60b of the discharge unit 600 under inspection are driven by a drive voltage signal Vin corresponding to the condition inspection CD, and subsequently, high-frequency damped oscillations occur in the discharge unit 600 under inspection. The piezoelectric elements 60a and 60b then output residual oscillation signals Vout1 and Vout2 corresponding to the damped oscillations that occur in the discharge unit 600 under inspection. In other words, the switching circuit 210 acquires a signal that is a composite wave of the residual oscillation signals Vout1 and Vout2, in which the signal waveform of the high-frequency damped oscillation is synthesized, as the residual oscillation signal Vout corresponding to the discharge unit 600 under inspection.

[0093] Such residual vibration signals Vout are susceptible to noise because their voltage amplitude is weak. In the waveform shaping circuit 240 of this embodiment, the filter circuit 241 removes low-frequency noise and DC components from the residual vibration signal Vout and extracts the high-frequency components contained in the residual vibration signal Vout, thereby extracting a signal corresponding to the high-frequency damped vibration generated in the discharge section 600 under inspection. Subsequently, the amplification circuit 242 amplifies the signal output by the filter circuit 241 to improve resistance to noise. Then, the impedance conversion circuit 243 converts the impedance of the signal output by the amplification circuit 242, thereby improving the stability of the acquired residual vibration signal NVT output by the waveform shaping circuit 240. As a result, the acquisition accuracy of the residual vibration signal Vout is improved, and the waveform accuracy of the acquired residual vibration signal NVT is improved.

[0094] In other words, the waveform shaping circuit 240 is a signal corresponding to the residual vibration signal Vout, and shapes the signal waveform of the input residual vibration signal Vout, thereby reducing the effects of noise and other factors, and outputting a highly stable signal with improved resistance to noise as the acquired residual vibration signal NVT.

[0095] As described above, the switching circuit 210 of the drive signal selection circuit 200 acquires a residual vibration signal Vout corresponding to the residual vibration generated in the discharge section 600, and the waveform shaping circuit 240 of the drive signal selection circuit 200 shapes the signal waveform of the residual vibration signal Vout to output an acquired residual vibration signal NVT corresponding to the residual vibration signal Vout. In other words, the drive signal selection circuit 200 acquires a residual vibration signal Vout corresponding to the residual vibration generated in the discharge section 600 and outputs an acquired residual vibration signal NVT corresponding to the residual vibration signal Vout.

[0096] 3. Printhead structure Next, the structure of the print head 21 will be described. Figure 10 is an exploded perspective view of the print head 21, and Figure 11 is a cross-sectional view of line Aa in Figure 10. Hereinafter, the explanation will use mutually orthogonal X, Y, and Z axes.In the following explanation, the starting point of the arrow along the X axis shown in the diagram will be referred to as the -X side and the tip as the +X side, the starting point of the arrow along the Y axis shown in the diagram will be referred to as the -Y side and the tip as the +Y side, and the starting point of the arrow along the Z axis shown in the diagram will be referred to as the -Z side and the tip as the +Z side.In addition, in the following explanation, the print head 21 will be described as having M ejection units 600 as multiple ejection units 600.

[0097] As shown in Figures 10 and 11, the print head 21 has a head chip 22 and a flexible substrate 24. 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 diaphragm 304, and a reservoir chamber forming substrate 305.

[0098] The nozzle substrate 360 ​​is a plate-shaped member that is elongated along the Y-axis and extends substantially parallel to the XY plane formed by the X-axis and Y-axis. M nozzles N are formed on the nozzle substrate 360. The nozzles N are through holes formed in the nozzle substrate 360. These M nozzles N are arranged side-by-side along the Y-axis on the nozzle substrate 360, thereby forming a nozzle row Ln on the nozzle substrate 360. Here, "approximately parallel" does not mean perfectly parallel, but includes cases where parallelism can be considered to exist when errors and other factors are taken into account.

[0099] The communication plate 302 is located on the -Z side of the nozzle substrate 360. The communication plate 302 is a plate-shaped member that is elongated along the Y axis and extends substantially parallel to the XY plane. The communication plate 302 has a supply channel RA1, an discharge channel RA2, M connection channels RK1, M connection channels RK2, M communication channels RR1, M communication channels RR2, and M nozzle channels RN formed on it as part of the ink flow path.

[0100] The supply channel RA1 is located on the +X side of the communication plate 302 and extends along the Y direction. The discharge channel RA2 is located on the -X side of the communication plate 302 and extends along the Y direction. In this case, the supply channel RA1 and the discharge channel RA2 are formed to be approximately symmetric with respect to the Z axis passing through the nozzle N. M connecting channels RK1 are located on the -X side of the supply channel RA1 and are arranged in parallel along the Y direction. M connecting channels RR1 are located on the -X side of the M connecting channels RK1 which are arranged in parallel along the Y direction and are arranged in parallel along the Y direction. M connecting channels RK2 are located on the +X side of the discharge channel RA2 and are located on the -X side of the M connecting channels RR1 which are arranged in parallel along the Y direction and are arranged in parallel along the Y direction. M connecting channels RR2 are located on the +X side of the M connecting channels RK2 which are arranged in parallel along the Y direction and are located on the -X side of the M connecting channels RR1 which are arranged in parallel along the Y direction and are arranged in parallel along the Y direction. In this configuration, connecting channels RK1 and RK2 are formed to be approximately symmetrical with respect to the Z-axis passing through nozzle N, and communicating channels RR1 and RR2 are formed to be approximately symmetrical with respect to the Z-axis passing through nozzle N. Nozzle channel RN connects communicating channels RR1 and RR2, which correspond to the common nozzle N. The nozzle substrate 360 ​​is fixed to the communicating plate 302 such that, when viewed from the Z-direction, nozzle N is positioned approximately in the center of nozzle channel RN in the X-direction.

[0101] 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-shaped member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane. M pressure chambers CB1 and M pressure chambers CB2 are formed in this pressure chamber substrate 303 as part of the flow path for ink. At this time, pressure chambers CB1 and CB2 are formed to be substantially symmetric with respect to the Z-axis, which passes through the nozzle N, as the axis of symmetry.

[0102] The M pressure chambers CB1 correspond one-to-one with the M nozzles N and are arranged side by side along the Y-axis. Each of the M pressure chambers CB1 communicates with a connecting channel RK1 and a communication channel RR1, which correspond to a common nozzle N. Specifically, when viewed along the Z-axis, the +X end of a pressure chamber CB1 communicates with the connecting channel RK1, and the -X end communicates with the communication channel RR1. In other words, each pressure chamber CB1 communicates with the connecting channel RK1 and the communication channel RR1, which correspond to a common nozzle N.

[0103] Similarly, the M pressure chambers CB2 correspond one-to-one with the M nozzles N and are located on the -X side of the M pressure chambers CB1 which are arranged in parallel along the Y-axis. Each of the M pressure chambers CB2 is in communication with the connecting channel RK2 and the communication channel RR2 which correspond to the common nozzle N. Specifically, when viewed along the Z-axis, the -X end of the pressure chamber CB2 is in communication with the connecting channel RK2, and the +X end is in communication with the communication channel RR2. In other words, the pressure chamber CB2 is in communication with the connecting channel RK2 and the communication channel RR2 which correspond to the common nozzle N.

[0104] The diaphragm 304 is located on the -Z side of the pressure chamber substrate 303 and closes off the pressure chambers CB1 and CB2. It is fixed to the pressure chamber substrate 303 in this manner. The diaphragm 304 is a plate-shaped member that is elongated in the Y direction and extends substantially parallel to the XY plane, and is an elastically vibrating member. On the -Z side of the diaphragm 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 diaphragm 304. The M piezoelectric elements 60b are arranged side by side along the Y axis on the -X side of the M piezoelectric elements 60a arranged side by side along the Y axis on the -Z side of the diaphragm 304. In other words, on the -Z side of the diaphragm 304, there are rows of M piezoelectric elements 60a and rows of M piezoelectric elements 60b arranged side by side.

[0105] The storage chamber forming substrate 305 is located on the -Z side of the communication plate 302. The storage chamber forming substrate 305 is an elongated member in the Y direction and includes an opening 350. The storage chamber forming substrate 305 is fixed to the communication plate 302 such that the pressure chamber substrate 303, the diaphragm 304, and the wiring substrate 308 are located inside the opening 350. The storage chamber forming substrate 305 also includes a supply channel RB1, a discharge channel RB2, a supply port 351, and a discharge port 352. The supply channel RB1 communicates with the supply channel RA1. The discharge channel RB2 communicates with the discharge channel RA2. The supply port 351 communicates with the supply channel RB1. The discharge port 352 communicates with the discharge channel RB2.

[0106] Ink stored in the liquid container 3 is supplied to the supply port 351 by the operation of the circulation unit 6. This supplies ink to the print head 22. The ink supplied to the print head 22 then flows through the inside of the print head 22 by the operation of the circulation unit 6 and is recovered through the discharge port 352. In other words, the ink supplied to the print head 22 is recirculated by the operation of the circulation unit 6.

[0107] The flexible substrate 24 is electrically connected to the diaphragm 304 on the -Z side 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 such that the distance between the flexible substrate 24 and the row of M piezoelectric elements 60a is approximately equal to the distance between the flexible substrate 24 and the row of M piezoelectric elements 60b.

[0108] An integrated circuit 201 is mounted on the flexible substrate 24 using COF (Cable Oscillator). The drive signal selection circuit 200 described above is mounted on the integrated circuit 201. The clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SI, drive signal COM, and reference voltage signal VBS propagate through the flexible substrate 24. Of the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SI, drive signal COM, and reference voltage signal VBS propagating through the flexible substrate 24, the clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, print data signal SI, and drive signal COM are input to the integrated circuit 201. Based on the input clock signal SCK, latch signal LAT, change signal CH, inspection timing signal TSIG, and print data signal SI, the integrated circuit 201 selects or deselects the signal waveform of the drive signal COM to generate a drive voltage signal Vin corresponding to each of the multiple ejection units 600. Then, the drive voltage signal Vin generated by the integrated circuit 201 propagates through the flexible substrate 24, and then drive voltage signal Vin1 is supplied to the piezoelectric element 60a included in the corresponding discharge unit 600, and drive voltage signal Vin2 is supplied to the piezoelectric element 60b included in the corresponding discharge unit 600. As a result, each of the M piezoelectric elements 60a and 60b is driven to be displaced along the Z-axis. The driving of the piezoelectric elements 60a and 60b causes the diaphragm 304 on which the piezoelectric elements 60a and 60b are mounted to be displaced along the Z-axis. The displacement of the nozzle changes the volume of pressure chambers CB1 and CB2, and the internal pressure of pressure chambers CB1 and CB2 changes in accordance with the change in volume of pressure chambers CB1 and CB2. Then, ink is ejected from nozzle N due to the change in internal pressure of pressure chambers CB1 and CB2.

[0109] Furthermore, compliance sheets 361 and 362 are located on the +Z side of the communication plate 302. Compliance sheet 361 closes the supply channel RA1 and the connecting channel RK1 formed in the communication plate 302. Such compliance sheet 361 is made up of an elastic material. This absorbs pressure fluctuations that occur in the supply channel RA1 and the connecting channel RK1 in response to changes in the internal pressure of the pressure chambers CB1 and CB2. Compliance sheet 362 closes the discharge channel RA2 and the connecting channel RK2 formed in the communication plate 302. Such compliance sheet 362 is made up of an elastic material. This absorbs pressure fluctuations that occur in the discharge channel RA2 and the connecting channel RK2 in response to changes in the internal pressure of the pressure chambers CB1 and CB2.

[0110] Here, in the print head 21, the configuration including the piezoelectric elements 60a, 60b, pressure chambers CB1, CB2, communication channels RR1, RR2, and nozzle N contained in the head chip 22 corresponds to the ejection section 600 described above.

[0111] Furthermore, after the internal pressure of pressure chambers CB1 and CB2 changes, residual vibration occurs in the discharge section 600 according to the state of the stored ink. This residual vibration in the discharge section 600 changes the internal pressure and volume of pressure chambers CB1 and CB2, causing the diaphragm 304 to displace. As a result, the piezoelectric elements 60a and 60b provided on the diaphragm 304 deform. Therefore, a back electromotive force corresponding to the deformation of piezoelectric element 60a is generated between the two terminals of piezoelectric element 60a, and a back electromotive force corresponding to the deformation of piezoelectric element 60b is generated between the two terminals of piezoelectric element 60b. The back electromotive force generated in piezoelectric element 60a propagates through the flexible substrate 24 as a residual vibration signal Vout1, and the back electromotive force generated in piezoelectric element 60b propagates through the flexible substrate 24 as a residual vibration signal Vout2. At this time, in the flexible substrate 24, the wiring through which residual vibration signal Vout1 propagates and the wiring through which residual vibration signal Vout2 propagates are electrically connected, so that residual vibration signal Vout1 and residual vibration signal Vout2 are combined in the flexible substrate 24. This combined signal of residual vibration signal Vout1 and residual vibration signal Vout2 is input as residual vibration signal Vout to the integrated circuit 201 on which the drive signal selection circuit 200 is mounted.

[0112] The drive signal selection circuit 200, implemented on the integrated circuit 201, acquires the residual vibration signal Vout input from the ejection unit 600, defined by the print data signal SI, at the timings defined by the latch signal LAT, the change signal CH, and the inspection timing signal TSIG. The drive signal selection circuit 200 then shapes the signal waveform of the acquired residual vibration signal Vout and outputs it as the acquired residual vibration signal NVT.

[0113] As described above, the ejection unit 600 of the print head 21 of this embodiment, which ejects ink onto the medium P, includes an ink ejection nozzle N, a pressure chamber CB1 communicating with the nozzle N and where ink is stored, a pressure chamber CB2 communicating with the nozzle N and where ink is stored, a piezoelectric element 60a that detects residual vibrations generated in the pressure chamber CB1 and outputs it as a residual vibration signal Vout1, and a piezoelectric element 60b that detects residual vibrations generated in the pressure chamber CB2 and outputs it as a residual vibration signal Vout2. The combined wave of the residual vibration signal Vout1 and the residual vibration signal Vout2 is output as a residual vibration signal Vout.

[0114] Here, in the print head 21 of this embodiment, the element that generates residual vibration in the pressure chamber CB1 and the element that detects the residual vibration generated in the pressure chamber CB1 are both piezoelectric elements 60a, and the element that generates residual vibration in the pressure chamber CB2 and the element that detects the residual vibration generated in the pressure chamber CB2 are The explanation will proceed assuming that both the element and the element are piezoelectric elements 60b. However, the element that generates residual vibration in pressure chamber CB1 and the element that detects the residual vibration generated in pressure chamber CB1 may be different elements, and the element that generates residual vibration in pressure chamber CB2 and the element that detects the residual vibration generated in pressure chamber CB2 may be different elements.

[0115] However, as shown in this embodiment, it is preferable that the piezoelectric element 60a generates residual vibration in the pressure chamber CB1 and detects the residual vibration generated in the pressure chamber CB1, and that the piezoelectric element 60b generates residual vibration in the pressure chamber CB2 and detects the residual vibration generated in the pressure chamber CB2. That is, it is preferable that the piezoelectric element 60a outputs a residual vibration signal Vout1 corresponding to the residual vibration generated in accordance with the change in volume of the pressure chamber CB1 and is driven according to a drive voltage signal Vin corresponding to a drive signal COM, so that the volume of the pressure chamber CB1 changes when the piezoelectric element 60a is driven, and it is preferable that the piezoelectric element 60b outputs a residual vibration signal Vout2 corresponding to the residual vibration generated in accordance with the change in volume of the pressure chamber CB2 and is driven according to a drive voltage signal Vin corresponding to a drive signal COM, so that the volume of the pressure chamber CB2 changes when the piezoelectric element 60b is driven. This makes it possible to reduce the number of piezoelectric elements 60a and 60b in the print head 21, and enables miniaturization of the print head 21.

[0116] 4.Residual vibration acquisition circuit Next, the configuration and operation of the residual vibration acquisition circuit 300 will be described. As mentioned above, the residual vibration acquisition circuit 300 determines the state of the corresponding discharge unit 600 based on the acquired residual vibration signal NVT that is input to it, and outputs state signals aDS and dDS according to the determination result. Here, in explaining the configuration and operation of the residual vibration acquisition circuit 300, the relationship between the acquired residual vibration signal NVT input to the residual vibration acquisition circuit 300, the residual vibration generated in the discharge unit 600, and the state of the discharge unit 600 will be explained.

[0117] Figure 12 shows an example of residual vibration signals Vout1 and Vout2. As shown in Figure 12, the signal waveforms of residual vibration signals Vout1 and Vout2 are damped vibration waveforms in which the voltage amplitude decreases over time in response to the damped vibrations generated in the diaphragm 304 due to changes in the internal pressure of pressure chambers CB1 and CB2. The waveform information such as amplitude, damping rate, and frequency included in the damped vibration waveforms of residual vibration signals Vout1 and Vout2 changes depending on the state of the ink stored in pressure chambers CB1 and CB2, and the state of the ink flowing through the communication channel RR1 and the nozzle channel RN.

[0118] Here, we will explain the relationship between the waveform information of the residual vibration signals Vout1 and Vout2, the state of the ink stored in the pressure chambers CB1 and CB2, and the state of the ink flowing through the communication channels RR1 and RR2 and the nozzle channel RN using a calculation model. Figure 13 is a diagram showing an example of a calculation model for simple harmonic motion assuming residual vibration occurring in the pressure chambers CB1 and CB2, or the diaphragm 304. As mentioned above, the piezoelectric elements 60a and 60b are displaced when the corresponding drive voltage signals Vin1 and Vin2 are supplied, and the diaphragm 304 is also displaced along with the displacement of the piezoelectric elements 60a and 60b. Then, the volume of the corresponding pressure chambers CB1 and CB2 changes with the displacement of the diaphragm 304. At this time, in accordance with the pressure generated inside the pressure chambers CB1 and CB2, a portion of the ink filled in the pressure chambers CB1 and CB2 is discharged from the nozzle N.

[0119] In this series of operations for ejecting ink from nozzle N, the diaphragm 304 vibrates freely at a natural vibration frequency determined by the flow resistance r based on the shape of the ink flow path 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 diaphragm 304. The piezoelectric elements 60a and 60b are displaced in accordance with the free vibration occurring in the diaphragm 304. Piezoelectric element 60a outputs a back electromotive force as a residual vibration signal Vout1 in accordance with the displacement, and piezoelectric element 60b outputs a back electromotive force as a residual vibration signal Vout2 in accordance with the displacement.

[0120] A calculation model for the residual vibration occurring in such a diaphragm 304 can be shown using pressure p, inertance m, compliance C, and flow resistance r. Then, by calculating the step response for volume velocity u when pressure p is applied to the circuit shown in Figure 13, the following equations (1) to (3) are obtained.

[0121]

number

[0122]

number

[0123]

number

[0124] Furthermore, if the viscosity of the ink stored in pressure chambers CB1 and CB2, the ink flowing through the communication channels RR1 and RR2, the nozzle channel RN, and the ink near nozzle N increases, the flow resistance r increases. At this time, according to equations (1) to (3), the frequency generated in the diaphragm 304 changes, and the damping rate of the damped vibration increases. Therefore, if a viscosity increase abnormality occurs in the stored ink, the frequency of the corresponding residual vibration signals Vout1 and Vout2 changes, and the amplitude damping rate increases. In other words, if the viscosity of the ink stored in pressure chambers CB1 and CB2 increases and the viscosity increase ratio increases, the frequency, amplitude, and damping rate of the residual vibration signals Vout1 and Vout2 change.

[0125] Furthermore, if, for example, air bubbles are introduced into the pressure chambers CB1 and CB2, the communication channels RR1 and RR2, and the nozzle channels RN and nozzle N, the inertance m, which corresponds to the weight of the stored ink, decreases by the amount of the introduced air bubbles. In this case, according to equations (1) to (3), the angular velocity ω increases, the vibration period of the residual vibration generated in the diaphragm 304 shortens, and as a result, the vibration frequencies of the residual vibration signals Vout1 and Vout2 increase. In other words, if air bubbles are introduced into the pressure chambers CB1 and CB2, the communication channels RR1 and RR2, and the nozzle channels RN, the vibration frequencies of the residual vibration signals Vout1 and Vout2 increase.

[0126] As described above, if an abnormality such as increased ink viscosity or the inclusion of air bubbles occurs in the pressure chamber CB1, communication channel RR1, and nozzle channel RN, the waveform information such as the amplitude and frequency of the residual vibration signal Vout1 changes. Similarly, if an abnormality such as increased viscosity or the inclusion of air bubbles occurs in the pressure chamber CB2, communication channel RR2, and nozzle channel RN, the waveform information such as the amplitude and frequency of the residual vibration signal Vout2 changes. Therefore, if an abnormality occurs in the state of the ejection unit 600, the waveform information of the residual vibration signal Vout, which is a composite wave of residual vibration signals Vout1 and Vout2, also changes.

[0127] The waveform shaping circuit 240 shapes the signal waveform by removing noise from the composite wave of residual vibration signals Vout1 and Vout2 and amplifying it. Therefore, the waveform information of the acquired residual vibration signal NVT input to the residual vibration acquisition circuit 300 includes information corresponding to the waveform information of residual vibration signal Vout1 and residual vibration signal Vout2. In other words, the waveform information of the acquired residual vibration signal NVT changes in accordance with the changes in the waveform information of residual vibration signals Vout1 and Vout2. The residual vibration acquisition circuit 300 adjusts the amplitude and frequency of the acquired residual vibration signal NVT. By acquiring waveform information such as wavenumber, the system determines whether the waveform information of residual vibration signals Vout1 and Vout2, including amplitude and frequency, is normal, thereby determining the state of the discharge unit 600 being inspected.

[0128] Figure 14 shows the configuration of the residual vibration acquisition circuit 300. As shown in Figure 14, the residual vibration acquisition circuit 300 has an analog acquisition circuit 310 and a digital acquisition circuit 320.

[0129] The analog acquisition circuit 310 includes comparators 311a, 311b, switches 312a, 312b, and a determination circuit 313, and generates and outputs a state signal aDS corresponding to the acquired residual vibration signal NVT.

[0130] Comparator 311a receives the acquired residual vibration signal NVT as input to its + side input terminal and the reference voltage Vref1a as input to its - side input terminal. Comparator 311a then compares the voltage value of the acquired residual vibration signal NVT input to the + side input terminal with the voltage value of the reference voltage Vref1a input to the - side input terminal, generates a comparison result signal aNVT1 whose logic level switches according to the comparison result, and outputs it to the judgment circuit 313. Specifically, comparator 311a generates a comparison result signal aNVT1 that is H level when the voltage value of the acquired residual vibration signal NVT is greater than the voltage value of the reference voltage Vref1a, and L level when the voltage value of the acquired residual vibration signal NVT is less than the voltage value of the reference voltage Vref1a, and outputs it to the judgment circuit 313.

[0131] Comparator 311b receives the acquired residual vibration signal NVT as input to its + side input terminal and the reference voltage Vref1b as input to its - side input terminal. Comparator 311b then compares the voltage value of the acquired residual vibration signal NVT input to the + side input terminal with the voltage value of the reference voltage Vref1b input to the - side input terminal, generates a comparison result signal aNVT2 whose logic level switches according to the comparison result, and outputs it to the judgment circuit 313. Specifically, comparator 311b generates a comparison result signal aNVT2 that is H level when the voltage value of the acquired residual vibration signal NVT is greater than the voltage value of the reference voltage Vref1b, and L level when the voltage value of the acquired residual vibration signal NVT is less than the voltage value of the reference voltage Vref1b, and outputs it to the judgment circuit 313.

[0132] In the following explanation, we will assume that the voltage value of the reference voltage Vref1b is greater than the voltage value of the reference voltage Vref1a.

[0133] Switch 312a has one end electrically connected to the wiring through which the comparison result signal aNVT1 propagates, the other end supplied with ground potential, and the control end input with a mask signal Msk. The conduction state between the one end and the other end of switch 312a switches according to the mask signal Msk input to the control end. For example, when a low-level mask signal Msk is input to the control end of switch 312a, the connection between the one end and the other end of switch 312a is controlled to be non-conductive. As a result, the comparison result signal aNVT1 output by comparator 311a is input to the determination circuit 313. Also, for example, when a high-level mask signal Msk is input to the control end of switch 312a, the connection between the one end and the other end of switch 312a is controlled to be conductive. At this time, the wiring through which the comparison result signal aNVT1 propagates is controlled to ground potential. Therefore, the comparison result signal aNVT1 output by the comparator 311a is not input to the determination circuit 313, and the ground potential signal is input to the determination circuit 313.

[0134] Switch 312b has one end electrically connected to the wiring through which the comparison result signal aNVT2 propagates, the other end supplied with ground potential, and the control end input with a mask signal Msk. The conduction state between the one end and the other end of switch 312b switches according to the mask signal Msk input to the control end. For example, an L level signal is input to the control end of switch 312b. When the mask signal Msk is input, the connection between one end and the other end of switch 312b is controlled to be non-conductive. As a result, the comparison result signal aNVT2 output by comparator 311b is input to the determination circuit 313. Alternatively, for example, when a high-level mask signal Msk is input to the control terminal of switch 312b, the connection between one end and the other end of switch 312b is controlled to be conductive. In this case, the wiring through which the comparison result signal aNVT2 propagates is controlled to ground potential. Therefore, the comparison result signal aNVT2 output by comparator 311b is not input to the determination circuit 313, and a ground potential signal is input to the determination circuit 313.

[0135] In other words, switches 312a and 312b switch whether or not to input the comparison result signals aNVT1 and aNVT2 to the determination circuit 313, depending on the logic level of the mask signal Msk. For example, N-channel MOS transistors can be used as such switches 312a and 312b. Here, the mask signal Msk may be, for example, a signal output by the control circuit 100, or a signal output by a signal generation circuit (not shown) of the residual vibration acquisition circuit 300. Note that the relationship between the operation of switches 312a and 312b and the logic level of the mask signal Msk is not limited to the above-described form. For example, switches 312a and 312b may conduct between one end and the other when the mask signal Msk is at a low level, and not conduct between one end and the other when the mask signal Msk is at a high level.

[0136] The determination circuit 313 receives the comparison result signal aNVT1 output by comparator 311a, the comparison result signal aNVT2 output by comparator 311b, and the clock signal CLK1 output by a clock circuit (not shown). Based on the number of clock cycles of the clock signal CLK1, the determination circuit 313 measures the length of time it takes for the logic levels of the comparison result signals aNVT1 and aNVT2 to change from L level to H level and then back to L level, and the length of time it takes for the logic levels to change from H level to L level and then back to H level. Based on the measurement results, the determination circuit 313 determines the state of the discharge unit 600.

[0137] Figure 15 is a diagram illustrating the operation of the analog acquisition circuit 310. As shown in Figure 15, at time t0 when the inspection timing signal TSIG rises, the aforementioned period ts2 begins in which the drive signal selection circuit 200 acquires a residual vibration signal Vout corresponding to the residual vibration generated in the discharge section 600 to be inspected. That is, at time t0, the acquired residual vibration signal NVT is input to the residual vibration acquisition circuit 300.

[0138] Furthermore, at time t0, the analog acquisition circuit 310 is input with a mask signal Msk at an H level. At this time, comparator 311a compares the voltage value of the input acquired residual vibration signal NVT with the voltage value of the reference voltage Vref1a and outputs a comparison result signal aNVT1 according to the comparison result, and comparator 311b compares the voltage value of the input acquired residual vibration signal NVT with the voltage value of the reference voltage Vref1b and outputs a comparison result signal aNVT2 according to the comparison result, but a constant signal at an L level is input to the judgment circuit 313.

[0139] The mask signal Msk is at a high level for a predetermined period Tmsk from time t0, when the supply of the acquired residual vibration signal NVT to the residual vibration acquisition circuit 300 begins, and then becomes low after the predetermined period Tmsk has elapsed. In other words, after time t0, the acquisition of the acquired residual vibration signal NVT by the analog acquisition circuit 310 is stopped for a period Tmsk. This makes it possible to exclude noise components that are superimposed immediately after residual vibration occurs in the discharge unit 600 under inspection, thereby improving the accuracy of the state determination of the discharge unit 600.

[0140] When a predetermined period Tmsk has elapsed from the time t0 when the inspection timing signal TSIG rises, and the logic level of the mask signal Msk switches from a high level to a low level, the judgment circuit 313 receives the comparison result signal aNVT1 output by comparator 311a and the comparison result signal aNVT2 output by comparator 311b.

[0141] Based on the clock signal CLK, the determination circuit 313 measures the length of period ta1 from time t1 when the logic level of comparison result signal aNVT1 switches from L level to H level to time t4 when the logic level of comparison result signal aNVT1 switches from H level to L level, and also measures the length of period tb1 from time t2 when the logic level of comparison result signal aNVT2 switches from L level to H level to time t3 when the logic level of comparison result signal aNVT2 switches from H level to L level. Furthermore, the determination circuit 313, based on the clock signal CLK, measures the length of period ta2 from time t4, when the logic level of comparison result signal aNVT1 switches from H level to L level, to time t5, when the logic level of comparison result signal aNVT1 switches from L level to H level, after period ta1. It also measures the length of period ta3 from time t5, when the logic level of comparison result signal aNVT1 switches from L level to H level, to time t8, when the logic level of comparison result signal aNVT1 switches from H level to L level, and measures the length of period tb3 from time t6, when the logic level of comparison result signal aNVT2 switches from L level to H level, to time t7, when the logic level of comparison result signal aNVT2 switches from H level to L level.

[0142] The determination circuit 313 then calculates the amplitude of the acquired residual vibration signal NVT based on the ratio of the length of period tb1 to the length of period ta1, and calculates the frequency of the acquired residual vibration signal NVT from the lengths of period ta1 and period ta2. It also calculates the attenuation rate of the amplitude of the acquired residual vibration signal NVT from the amplitude of the acquired residual vibration signal NVT calculated based on the ratio of the length of period tb1 to the length of period ta1, and the amplitude of the acquired residual vibration signal NVT calculated based on the ratio of the length of period tb3 to the length of period ta3. In other words, the determination circuit 313 calculates the waveform information of the acquired residual vibration signal NVT from periods ta1, ta2, ta3, tb1, and tb3.

[0143] The determination circuit 313 then determines whether the discharge unit 600 under inspection is normal or not based on whether each of the calculated waveform information is within a predetermined range. Subsequently, the determination circuit 313 generates a status signal aDS containing the determination result information and outputs it to the control circuit 100. Here, the determination circuit 313 may determine whether the discharge unit 600 under inspection is normal or not based on at least one of the frequency, amplitude, and amplitude attenuation rate of the acquired residual vibration signal NVT. That is, the determination circuit 313 may determine the state of the discharge unit 600 based on at least one of the time during which the voltage value of the acquired residual vibration signal NVT exceeds the voltage values ​​of the reference voltages Vref1a and Vref1b, and the time during which the voltage value of the acquired residual vibration signal NVT falls below the voltage values ​​of the reference voltages Vref1a and Vref1b.

[0144] Returning to Figure 14, the digital acquisition circuit 320 includes an A / D conversion circuit 321, a determination circuit 322, and a memory circuit 323, and generates and outputs a state signal dDS corresponding to the acquired residual vibration signal NVT.

[0145] The A / D conversion circuit 321 receives the clock signal CLK2 and the acquired residual vibration signal NVT as inputs. The A / D conversion circuit 321 sequentially converts the voltage value of the input acquired residual vibration signal NVT into a digital signal in synchronization with the clock signal CLK2, acquires it as a detection voltage dnvt, and outputs the detection voltage signal dNVT, which includes the acquired detection voltage dnvt, to the judgment circuit 322. The judgment circuit 322 sequentially acquires the detection voltage dnvt included in the detection voltage signal dNVT that is input in synchronization with the clock signal CLK2, and stores the information corresponding to the acquired detection voltage dnvt in the storage circuit 323. Furthermore, after the period ts2 has elapsed in which the drive signal selection circuit 200 acquires the residual vibration signal Vout corresponding to the residual vibration generated in the discharge section 600 to be inspected, the judgment circuit 322 reads out the information corresponding to the detection voltage dnvt stored in synchronization with the clock signal CLK2 from the storage circuit 323. Then, the determination circuit 322 calculates waveform information such as the amplitude and frequency of the acquired residual vibration signal NVT based on the information corresponding to the read-out detection voltage dnvt. Based on the calculated waveform information, it is determined whether the amplitude, frequency, and other parameters of the residual vibration generated in the discharge unit 600 under inspection are normal.

[0146] An example of the operation of such a digital acquisition circuit 320 will be described. Figure 16 is a diagram illustrating an example of the acquisition process in which the digital acquisition circuit 320 acquires the acquired residual vibration signal NVT, and Figure 17 is a diagram illustrating an example of the determination process in which the state of the discharge unit 600 is determined based on the information acquired in the acquisition operation.

[0147] As shown in Figure 16, when executing the acquisition process, the determination circuit 322 sets the variable j to "0" as an initialization process (step S10). Subsequently, when the inspection timing signal TSIG rises (step S11), the drive signal selection circuit 200 controls the transfer gate 234c included in the selection circuit 230 corresponding to the discharge unit 600 to be inspected to turn on. As a result, the drive signal selection circuit 200 acquires the residual vibration signal Vout corresponding to the residual vibration generated in the discharge unit 600 to be inspected and outputs the acquired residual vibration signal NVT. Therefore, the acquired residual vibration signal NVT is input to the digital acquisition circuit 320 of the residual vibration acquisition circuit 300.

[0148] The acquired residual vibration signal NVT is input to the A / D conversion circuit 321 of the digital acquisition circuit 320. The A / D conversion circuit 321 converts the voltage value of the input acquired residual vibration signal NVT into a digital signal detection voltage dnvt and outputs it as a detection voltage signal dNVT including the detection voltage dnvt (step S12).

[0149] The detection voltage signal dNVT, which includes the detection voltage dnvt output by the A / D conversion circuit 321, is input to the determination circuit 322. The determination circuit 322 stores the value obtained by subtracting the voltage value of the reference voltage Vref2 from the voltage value of the detection voltage dnvt included in the detection voltage signal dNVT as the retained voltage value snvt[j] in the storage circuit 323 (step S13). Subsequently, the determination circuit 322 determines whether or not the inspection timing signal TSIG has risen (step S14). At this time, the determination circuit 322 may determine whether or not the inspection timing signal TSIG has risen by directly detecting the inspection timing signal TSIG, or it may determine whether or not the inspection timing signal TSIG has risen based on whether or not a predetermined period has elapsed from the rising edge of the inspection timing signal TSIG that defines the start of period ts2. If the determination circuit 322 determines that the inspection timing signal TSIG is not rising (N in step S14), the determination circuit 322 adds 1 to the variable j (step S15) and repeats the processing in steps S12 to S14 described above. Here, the voltage value of the reference voltage Vref2 is preferably, for example, the voltage value of the DC component superimposed on the acquired residual vibration signal NVT.

[0150] In other words, the A / D conversion circuit 321 sequentially converts the voltage value of the acquired residual vibration signal NVT input during the period ts2, which is the period from when the inspection timing signal TSIG rises until the next time the inspection timing signal TSIG rises, into a digital signal at a timing based on the sampling period defined by the clock signal CLK2. The converted digital signal is then converted into a detection voltage dnvt and output to the determination circuit 322. The determination circuit 322 sequentially stores the signal corresponding to the input detection voltage dnvt in the storage circuit 323 at a timing based on the clock signal CLK2.

[0151] Subsequently, the determination circuit 322 determines that the inspection timing signal TSIG has risen (Y in step S14), and the drive signal selection circuit 200 controls the transfer gate 234c included in the selection circuit 230 corresponding to the discharge unit 600 to be inspected to turn off, and the acquisition process is completed.

[0152] Next, the information acquired in the acquisition operation described above is stored in the memory circuit 323. The following describes a determination process for determining the state of the discharge unit 600 to be inspected based on the held voltage value snvt[j]. In this example of the determination process shown in Figure 17, it is assumed that in the acquisition process, the A / D conversion circuit 321 acquires p detection voltages dnvt from the acquired residual vibration signal NVT. That is, it is assumed that the held voltage values ​​snvt[1] to snvt[p] are stored in the memory circuit 323.

[0153] When the determination process starts, the determination circuit 322 reads the held voltage values ​​snvt[1] to snvt[p] from the memory circuit 323 (step S21). Then, the determination circuit 322 extracts the held voltage value snvt at the timing when the voltage value switches from a positive value to a negative value, or from a negative value to a positive value, from the read held voltage values ​​snvt[1] to snvt[p]. In the following explanation, the holding voltage value snvt at the timing when the voltage value first changes from a positive value to a negative value, or from a negative value to a positive value, after the rising edge of the inspection timing signal TSIG, is referred to as the inversion voltage value vn[p1], and the holding voltage value snvt at the timing when the voltage value last changes from a positive value to a negative value, or from a negative value to a positive value, after the rising edge of the inspection timing signal TSIG, and which is the s-th timing when the voltage value changes from a positive value to a negative value, or from a negative value to a positive value, is referred to as the inversion voltage value vn[ps]. That is, the determination circuit 322 extracts the inversion voltage values ​​vn[p1] to vn[ps] at the timings when the voltage value switches from a positive value to a negative value, or from a negative value to a positive value, from the read-out holding voltage values ​​snvt[1] to snvt[p] (step S22).

[0154] Then, the determination circuit 322 calculates the frequency Fnvt of the acquired residual vibration signal NVT based on the inverted voltage value vn[pu] (where u is one of 1 to s-2) and the inverted voltage value vn[p(u+2)] from the extracted inverted voltage values ​​vn[p1] to vn[ps] (step S23).

[0155] Specifically, the determination circuit 322 calculates the number of retained voltage values ​​snvt acquired between the inverted voltage value vn[pu] and the inverted voltage value vn[p(u+2)]. Then, the determination circuit 322 calculates the time from the inverted voltage value vn[pu] to the inverted voltage value vn[p(u+2)] from the calculated number of retained voltage values ​​snvt and the sampling period of the A / D conversion circuit 321. Then, the determination circuit 322 calculates the frequency Fnvt of the acquired residual vibration signal NVT based on the calculated time from the inverted voltage value vn[pu] to the inverted voltage value vn[p(u+2)].

[0156] Furthermore, the determination circuit 322 stores the held voltage value snvt with the maximum absolute value among the held voltage values ​​snvt stored between the inverted voltage value vn[pv] (where v is one of 1 to s-1) and the inverted voltage value vn[p(v+1)] as the maximum voltage value Vpek[v] (step S24). Specifically, the determination circuit 322 stores the holding voltage value snvt with the maximum absolute value among the holding voltage values ​​snvt stored between the inverted voltage value vn[p1] and the inverted voltage value vn[p2] as the maximum voltage value Vpek[1]. Similarly, it stores the holding voltage value snvt with the maximum absolute value among the holding voltage values ​​snvt stored between the inverted voltage value vn[pv] and the inverted voltage value vn[p(v+1)] as the maximum voltage value Vpek[v], and it stores the holding voltage value snvt with the maximum absolute value among the holding voltage values ​​snvt stored between the inverted voltage value vn[p(s-1)] and the inverted voltage value vn[ps] as the maximum voltage value Vpek[s-1]. The maximum voltage value Vpek[v] held by this determination circuit 322 corresponds to the amplitude generated in the acquired residual vibration signal NVT. Then, the determination circuit 322 calculates the amplitude attenuation rate ARnvt of the acquired residual vibration signal NVT based on the maximum voltage values ​​Vpek[1] to Vpek[s-1] corresponding to the amplitude generated in the acquired residual vibration signal NVT (step S25).

[0157] Subsequently, the determination circuit 322 reads out the frequency upper threshold information FHth, the frequency lower threshold information FLth, and the amplitude determination threshold information ARth from the memory circuit 323 (step S26). Here, the upper frequency threshold information FHth, the lower frequency threshold information FLth, and the amplitude determination threshold information ARth can be set based on the frequency, amplitude, and attenuation rate of the residual vibration signal Vout, which is a composite wave of residual vibration signals Vout1 and Vout2 output by the piezoelectric elements 60a and 60b when the pressure chambers CB1 and CB2 are normal.

[0158] The determination circuit 322 then determines whether the frequency Fnvt of the calculated acquired residual vibration signal NVT is between the frequency upper threshold information FHth and the frequency lower threshold information FLth. That is, the determination circuit 322 determines whether the frequency Fnvt is less than the frequency upper threshold information FHth and greater than the frequency lower threshold information FLth (step S27). If the frequency Fnvt is greater than or equal to the frequency upper threshold information FHth, or if the frequency Fnvt is less than or equal to the frequency lower threshold information FLth (N in step S27), that is, if the frequency Fnvt of the calculated acquired residual vibration signal NVT is not between the frequency upper threshold information FHth and the frequency lower threshold information FLth, the determination circuit 322 determines that an air bubble contamination abnormality has occurred in the discharge unit 600 to be inspected (step S28), and outputs a status signal dDS containing information that an air bubble contamination abnormality has occurred in the discharge unit 600 to be inspected (step S32).

[0159] Furthermore, the determination circuit 322 determines whether the amplitude attenuation rate ARnvt of the acquired residual vibration signal NVT is greater than the amplitude determination threshold information ARth if the frequency Fnvt is smaller than the frequency upper threshold information FHth and the frequency Fnvt is larger than the frequency lower threshold information FLth (Y in step S27) (step S29). If the amplitude attenuation rate ARnvt of the acquired residual vibration signal NVT is greater than the amplitude determination threshold information ARth (Y in step S29), the determination circuit 322 determines that a viscosity abnormality has occurred in the discharge unit 600 to be inspected (step S30) and outputs a status signal dDS containing information that a viscosity abnormality has occurred in the discharge unit 600 to be inspected (step S32). Furthermore, the determination circuit 322 determines that the discharge unit 600 to be inspected is normal if the amplitude attenuation rate ARnvt of the acquired residual vibration signal NVT is less than or equal to the amplitude determination threshold information ARth (N in step S29) (step S31), and outputs a status signal dDS containing information that the discharge unit 600 to be inspected is normal (step S32). When the determination circuit 322 outputs the status signal dDS, the status determination of the discharge unit 600 based on the acquired residual vibration signal NVT in the digital acquisition circuit 320 is completed.

[0160] In other words, the determination circuit 322 determines the state of the discharge unit 600 based on the period and amplitude of the acquired residual vibration signal NVT, which is obtained based on the detection voltage signal dNVT, including the detection voltage dnvt.

[0161] As described above, the residual vibration acquisition circuit 300 includes comparators 311a and 311b that output comparison result signals aNVT1 and aNTV2 whose logic level changes according to the comparison result between the voltage value of the acquired residual vibration signal NVT and the voltage value of the reference voltage Vref2, an A / D conversion circuit 321 that outputs a detection voltage signal dNVT obtained by converting the acquired residual vibration signal NVT into a digital signal, and a determination circuit 330 including determination circuits 313 and 322 that determine the state of the discharge unit 600. The determination circuit 330 includes a mode in which the determination circuit 313 determines the state of the discharge unit 600 according to the comparison result signals aNVT1 and aNTV2, and a mode in which the determination circuit 322 determines the state of the discharge unit 600 according to the detection voltage signal dNVT.

[0162] As described above, when determining the state of the discharge unit 600 to be inspected using the analog acquisition circuit 310, the time during which the voltage value of the acquired residual vibration signal NVT is greater than or equal to a predetermined value is measured according to the number of clock cycles of the clock signal CLK1, and the determination is made based on the measurement result. Therefore, when determining the state of the discharge unit 600 to be inspected using the analog acquisition circuit 310, there is an advantage in that the state of the discharge unit 600 to be inspected can be determined in a short time, but the accuracy of acquiring waveform information of the acquired residual vibration signal NVT, in particular the accuracy of acquiring the amplitude of the acquired residual vibration signal NVT, is a concern. It is difficult to increase the degree.

[0163] On the other hand, when using the digital acquisition circuit 320 to determine the state of the discharge unit 600 to be inspected, the signal waveform of the acquired residual vibration signal NVT is converted into a digital signal, and the determination is made based on the digital signal corresponding to the voltage value of the acquired residual vibration signal NVT. Therefore, when using the digital acquisition circuit 320 to determine the state of the discharge unit 600 to be inspected, there is an advantage in that the waveform information of the acquired residual vibration signal NVT can be acquired with high accuracy because the voltage value of the acquired residual vibration signal NVT can be acquired directly. However, it is necessary to convert the signal waveform of the acquired residual vibration signal NVT into a digital signal and to perform calculation processing to calculate waveform information from the digital signal corresponding to the voltage value of the acquired residual vibration signal NVT, making it difficult to perform the state determination of the discharge unit 600 to be inspected in a short time.

[0164] In the liquid dispensing device 1 of this embodiment, the state determination of the dispensing unit 600 can be performed quickly and with high accuracy by appropriately switching between and executing state determination of the dispensing unit 600 using the analog acquisition circuit 310 and state determination of the dispensing unit 600 using the digital acquisition circuit 320.

[0165] Figure 18 is a diagram illustrating the method for determining the state of the discharge section 600 in the liquid discharge device 1 of this embodiment. When the state determination of the discharge section 600 is started, the control circuit 100 sequentially generates residual vibration in each of the M discharge sections 600 (step S40). As a result, the acquired residual vibration signal NVT corresponding to the residual vibration generated in each of the M discharge sections 600 is input to the residual vibration acquisition circuit 300. That is, the residual vibration acquisition circuit 300 sequentially acquires the acquired residual vibration signal NVT corresponding to each of the M discharge sections 600 (step S41), and outputs state signals aDS and dDS corresponding to the acquired acquired residual vibration signal NVT.

[0166] The control circuit 100 determines the state of each of the M ejection units 600 based on the state signal aDS, one of the state signals aDS and dDS output by the residual vibration acquisition circuit 300 (step S42). That is, it acquires the determination result of the state of the ejection unit 600 by the analog acquisition circuit 310. At this time, when the control circuit 100 receives a state signal aDS corresponding to the state of the ejection unit 600 to be inspected, it outputs various signals to generate residual vibration in the next ejection unit 600 to be inspected, regardless of the input of the state signal dDS. This reduces the risk that the processing of the digital acquisition circuit 320 will become the rate-limiting factor in the state detection of the M ejection units 600. As a result, the time required to detect the state of the M ejection units 600 is shortened.

[0167] The control circuit 100 determines whether there are any abnormal dispensing units 600 based on the status signal aDS corresponding to each of the M dispensing units 600 (step S43). If the control circuit 100 determines that there are no abnormal dispensing units 600 (N in step S43), the control circuit 100 terminates the status determination of the dispensing units 600. On the other hand, if the control circuit 100 determines that there are abnormal dispensing units 600 (N in step S43), the control circuit 100 generates residual vibration in the dispensing units 600 determined to be abnormal based on the status signal aDS (step S44). As a result, acquired residual vibration signals NVT corresponding to the residual vibration generated in each of the dispensing units 600 determined to be abnormal based on the status signal aDS are input to the residual vibration acquisition circuit 300. In other words, the residual vibration acquisition circuit 300 sequentially acquires the acquired residual vibration signal NVT corresponding to each of the discharge units 600 that have been determined to be abnormal based on the status signal aDS (step S45), and outputs status signals aDS and dDS corresponding to the acquired acquired residual vibration signal NVT.

[0168] Then, the control circuit 100, based on the status signal dDS of the status signals aDS and dDS output by the residual vibration acquisition circuit 300, grasps the details of the state of the discharge unit 600 that was determined to be abnormal based on the status signal aDS (step S46), and ends the state determination of the discharge unit 600.

[0169] In other words, in this embodiment, the liquid dispensing device 1 is configured such that, in a mode in which the determination circuit 313 determines the state of the dispensing unit 600 according to the comparison result signals aNVT1 and aNTV2, and in steps S40 to S42 it determines that there is an abnormality in the dispensing unit 600, the determination circuit 322 executes steps S44 to D46 in a mode in which it determines the state of the dispensing unit 600 according to the detected voltage signal dNVT. In a mode in which the determination circuit 313 determines the state of the dispensing unit 600 according to the comparison result signals aNVT1 and aNTV2, and in steps S40 to S42 it determines that there is no abnormality in the dispensing unit 600, the determination circuit 322 does not perform the state determination of the dispensing unit 600 in the mode in which it determines the state of the dispensing unit 600 according to the detected voltage signal dNVT. This makes it possible to perform the state determination of the dispensing unit 600 in a short time and with high accuracy.

[0170] The discharge unit 5 corresponds to the head unit, the transport unit 4 is an example of a transport section, the pressure chamber CB1 is an example of a first pressure chamber, the pressure chamber CB2 is an example of a second pressure chamber, the piezoelectric element 60a is an example of a first detection element, the piezoelectric element 60b is an example of a second detection element, at least one of the drive signal selection circuit 200 and the waveform shaping circuit 240 included in the drive signal selection circuit 200 is an example of a residual vibration detection circuit, the comparators 311a and 311b are examples of a comparison circuit and a first conversion circuit, the A / D conversion circuit 321 is an example of an A / D conversion circuit and a second conversion circuit, the determination circuit 330 is an example of a determination circuit, the determination circuit 313 included in the determination circuit 330 is an example of a first determination circuit, and the determination circuit 322 included in the determination circuit 330 is an example of a second determination circuit. Furthermore, residual vibration signal Vout is an example of a residual vibration signal, residual vibration signal Vout1 is an example of a first residual vibration signal, residual vibration signal Vout2 is an example of a second residual vibration signal, acquired residual vibration signal NVT is an example of a residual vibration detection signal, comparison result signals aNVT1 and aNVT2 are examples of comparison result signals, detected voltage signal dNVT is an example of a detected voltage signal, and reference voltages Vref1a and Vref1b are examples of reference voltage values. Then, a first determination mode is an example in which the determination circuit 313 included in the analog acquisition circuit 310 determines the state of the discharge unit 600 according to the comparison result signals aNVT1 and aNVT2, and a second determination mode is an example in which the determination circuit 322 included in the digital acquisition circuit 320 determines the state of the discharge unit 600 according to the detected voltage signal dNVT.

[0171] 5. Effects As described above, the liquid dispensing device 1 of this embodiment has a determination circuit 330 for determining the state of the dispensing unit 600, which has two modes: one in which the state of the dispensing unit 600 is determined according to comparison result signals aNVT1 and aNTV2 corresponding to the acquired residual vibration signals NVT output by comparators 311a and 311b; and another in which the state of the dispensing unit 600 is determined according to a detection voltage signal dNVT obtained by converting the acquired residual vibration signals NVT output by the A / D conversion circuit 321 into a digital signal.

[0172] In the mode where the state of the discharge unit 600 is determined according to the comparison result signals aNVT1 and aNTV2 corresponding to the acquired residual vibration signals NVT output by comparators 311a and 311b, the state of the discharge unit 600 can be determined according to the comparison result obtained by directly comparing the acquired residual vibration signals NVT, thus shortening the time required for the determination process, and as a result, the state determination of the discharge unit 600 can be performed in a short time. On the other hand, in the mode where the state of the discharge unit 600 is determined according to the detection voltage signal dNVT obtained by converting the acquired residual vibration signals NVT output by the A / D conversion circuit 321 into a digital signal, the state of the discharge unit 600 is determined according to the detection voltage signal dNVT obtained by converting the input acquired residual vibration signals NVT into a digital signal, thus improving the accuracy of acquiring waveform information of the acquired residual vibration signals NVT and improving the determination accuracy of the discharge unit 600.

[0173] The liquid dispensing device 1 of this embodiment has a comparator 311a, 311b that acquires waveform information of an acquired residual vibration signal NVT corresponding to a single residual vibration signal Vout, and an A / D conversion circuit 321, and a determination circuit 330 that determines the comparator By switching whether to determine the state of the dispensing unit 600 according to the comparison result signals aNVT1 and aNTV2 output by 311a and 311b, or according to the detection voltage signal dNVT output by the A / D conversion circuit 321, depending on the operating environment such as the number of dispensing units 600 to be inspected or the usage status of the liquid dispensing device 1, it becomes possible to optimally use both shortening the inspection time for the state of the dispensing unit 600 and improving the accuracy of the state determination of the dispensing unit 600. As a result, it is possible to achieve both improved accuracy in determining the state of the dispensing unit 600 and shortening the inspection time for the state of the dispensing unit 600.

[0174] Furthermore, in the liquid dispensing device 1 of this embodiment, in the mode in which the determination circuit 313 determines the state of the dispensing unit 600 according to the comparison result signals aNVT1 and aNTV2, if it determines that an abnormality has occurred in the dispensing unit 600, the determination circuit 322 determines the state of the dispensing unit 600 according to the detected voltage signal dNVT. In the mode in which the determination circuit 313 determines the state of the dispensing unit 600 according to the comparison result signals aNVT1 and aNTV2, if it determines that no abnormality has occurred in the dispensing unit 600, the determination circuit 322 does not determine the state of the dispensing unit 600 according to the detected voltage signal dNVT. This makes it possible to determine the state of only the dispensing unit 600 that has experienced an abnormality with high accuracy, and as a result, the state determination of all M dispensing units 600 can be performed in a short time and with high accuracy.

[0175] Furthermore, in the liquid dispensing device 1 of this embodiment, the dispensing unit 600 includes a nozzle N for dispensing ink, a pressure chamber CB1 communicating with the nozzle N and where ink is stored, a pressure chamber CB2 communicating with the nozzle N and where ink is stored, a piezoelectric element 60a that detects residual vibrations occurring in pressure chamber CB1 and outputs it as a residual vibration signal Vout1, and a piezoelectric element 60b that detects residual vibrations occurring in pressure chamber CB2 and outputs it as a residual vibration signal Vout2. Because the combined wave of residual vibration signals Vout1 and Vout2 is output as a residual vibration signal Vout, even if the signal waveform of the combined residual vibration signal Vout becomes complex due to an abnormality occurring in at least one of pressure chambers CB1 and CB2, the determination circuit 330 has a mode that determines the state of the dispensing unit 600 according to the detection voltage signal dNVT obtained by converting the acquired residual vibration signal NVT output by the A / D conversion circuit 321 into a digital signal, thereby enabling accurate determination of the state of the dispensing unit 600.

[0176] 6. Variations In this embodiment, it has been explained that the electromotive force generated at the electrodes of the piezoelectric elements 60a and 60b to which the drive voltage signal Vin is supplied due to residual vibrations generated in the discharge section 600 is acquired as the residual vibration signal Vout. However, the electromotive force generated at the electrodes of the piezoelectric elements 60a and 60b to which the reference voltage signal VBS is supplied due to residual vibrations generated in the discharge section 600 may also be acquired as the residual vibration signal Vout.

[0177] Although embodiments and modifications have been described above, the present invention is not limited to these embodiments and can be implemented in various forms without departing from its spirit. For example, the above embodiments can be combined as appropriate.

[0178] The present invention includes configurations that are substantially identical to those described in the embodiments (for example, configurations with the same function, method, and result, or configurations with the same purpose and effect). Furthermore, the present invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Furthermore, the present invention includes configurations that produce the same effects or achieve the same purpose as those described in the embodiments. Furthermore, the present invention includes configurations that add known technology to the configurations described in the embodiments.

[0179] The following conclusions can be drawn from the embodiments described above.

[0180] One embodiment of a liquid dispensing device is: A transport unit that transports the media, A dispensing unit for dispensing liquid into the aforementioned medium, A residual vibration detection circuit that acquires a residual vibration signal corresponding to the residual vibration generated in the discharge section and outputs a residual vibration detection signal corresponding to the residual vibration signal, A first conversion circuit includes a comparison circuit that outputs a comparison result signal whose logic level changes according to the comparison result between the voltage value of the residual vibration detection signal and a reference voltage value, A second conversion circuit, which includes an A / D conversion circuit and outputs a detection voltage signal obtained by converting the residual vibration detection signal into a digital signal, A determination circuit for determining the state of the discharge section, Equipped with, The aforementioned determination circuit is A first determination mode for determining the state of the discharge unit according to the comparison result signal, A second determination mode for determining the state of the discharge unit in accordance with the detected voltage signal, It has.

[0181] This liquid dispensing device has a determination circuit for determining the state of the dispensing section, which includes a first determination mode in which the state of the dispensing section is determined according to a comparison result signal whose logic level changes according to the comparison result between the voltage value of the residual vibration detection signal and a reference voltage value output by a first conversion circuit including a comparison circuit, and a second determination mode in which the state of the dispensing section is determined according to a detection voltage signal obtained by converting the residual vibration detection signal into a digital signal output by a second conversion circuit including an A / D conversion circuit. This makes it possible to optimally switch between detecting the state of the dispensing section in a short time and detecting the state of the dispensing section with high accuracy. As a result, it is possible to achieve both improved accuracy in determining the state of the dispensing section and a reduction in the inspection time of the dispensing section.

[0182] In one embodiment of the above-described liquid dispensing device, The aforementioned determination circuit is If it is determined in the first determination mode that an abnormality has occurred in the discharge unit, then in the second determination mode, the state of the discharge unit is determined, If it is determined in the first determination mode that no abnormality has occurred in the discharge unit, it is not necessary to perform the determination of the state of the discharge unit in the second determination mode.

[0183] This liquid dispensing device allows for highly accurate determination of only the state of the dispensing unit if an abnormality is detected in the first determination mode, and the state of the dispensing unit is determined in the second determination mode if no abnormality is detected in the first determination mode. This enables the determination of the state of all dispensing units with abnormalities to be performed quickly and with high accuracy.

[0184] In one embodiment of the above-described liquid dispensing device, The aforementioned discharge section is A nozzle for dispensing liquid, A first pressure chamber, which communicates with the nozzle and stores liquid, A second pressure chamber, which communicates with the nozzle and stores liquid, A first detection element that detects residual vibrations generated in the first pressure chamber and outputs them as a first residual vibration signal, A second detection element that detects residual vibrations generated in the second pressure chamber and outputs them as a second residual vibration signal, It has, The composite wave of the first residual vibration signal and the second residual vibration signal is output as the residual vibration signal. You may use force.

[0185] With this liquid dispensing device, even if the signal waveform of the residual vibration signal, which is a composite wave, becomes complex due to an abnormality in at least one of the first pressure chamber and the second pressure chamber, the state of the dispensing unit can be accurately determined by having a second determination mode that determines the state of the dispensing unit according to a detection voltage signal obtained by converting the residual vibration detection signal into a digital signal, which is output by a second conversion circuit including an A / D conversion circuit.

[0186] In one embodiment of the above-described liquid dispensing device, In the first determination mode, the determination circuit may determine the state of the discharge unit based on at least one of the time during which the voltage value of the residual vibration detection signal exceeds the reference voltage value, and the time during which the voltage value of the residual vibration detection signal falls below the reference voltage value.

[0187] In one embodiment of the above-described liquid dispensing device, In the second determination mode, the determination circuit may determine the state of the discharge unit according to the period and amplitude of the residual vibration detection signal acquired based on the detected voltage signal.

[0188] In one embodiment of the above-described liquid dispensing device, The determination circuit may include a first determination circuit that determines the state of the discharge unit in the first determination mode, and a second determination circuit that determines the state of the discharge unit in the second determination mode.

[0189] One form of head unit is: A dispensing unit that dispenses liquid into a medium, A residual vibration detection circuit that acquires a residual vibration signal corresponding to the residual vibration generated in the discharge section and outputs a residual vibration detection signal corresponding to the residual vibration signal, A first conversion circuit includes a comparison circuit that outputs a comparison result signal whose logic level changes according to the comparison result between the voltage value of the residual vibration detection signal and a reference voltage value, A second conversion circuit, which includes an A / D conversion circuit and outputs a detection voltage signal obtained by converting the residual vibration detection signal into a digital signal, A determination circuit for determining the state of the discharge section, Equipped with, The aforementioned determination circuit is A first determination mode for determining the state of the discharge unit according to the comparison result signal, A second determination mode for determining the state of the discharge unit in accordance with the detected voltage signal, It has.

[0190] According to this head unit, the determination circuit for determining the state of the discharge unit has a first determination mode in which the state of the discharge unit is determined according to a comparison result signal whose logic level changes according to the comparison result between the voltage value of the residual vibration detection signal and a reference voltage value output by a first conversion circuit including a comparison circuit, and a second determination mode in which the state of the discharge unit is determined according to a detection voltage signal obtained by converting the residual vibration detection signal into a digital signal output by a second conversion circuit including an A / D conversion circuit. This makes it possible to optimally switch between detecting the state of the discharge unit in a short time and detecting the state of the discharge unit with high accuracy. As a result, it is possible to achieve both improved accuracy in determining the state of the discharge unit and a reduction in the inspection time of the discharge unit.

[0191] In one aspect of the above head unit, The aforementioned determination circuit is If it is determined in the first determination mode that an abnormality has occurred in the discharge unit, then in the second determination mode, the state of the discharge unit is determined, If it is determined in the first determination mode that no abnormality has occurred in the discharge unit, it is not necessary to perform the determination of the state of the discharge unit in the second determination mode.

[0192] According to this head unit, if it is determined in the first judgment mode that there is an abnormality in the discharge unit, the state of the discharge unit is determined in the second judgment mode. If it is determined in the first judgment mode that there is no abnormality in the discharge unit, the state of the discharge unit in the second judgment mode is not performed. This makes it possible to determine only the state of the discharge unit where an abnormality has occurred with high accuracy, and to perform state determination of all multiple discharge units in a short time and with high accuracy.

[0193] In one aspect of the above head unit, The aforementioned discharge section is A nozzle for dispensing liquid, A first pressure chamber, which communicates with the nozzle and stores liquid, A second pressure chamber, which communicates with the nozzle and stores liquid, A first detection element that detects residual vibrations generated in the first pressure chamber and outputs them as a first residual vibration signal, A second detection element that detects residual vibrations generated in the second pressure chamber and outputs them as a second residual vibration signal, It has, The composite wave of the first residual vibration signal and the second residual vibration signal may be output as the residual vibration signal.

[0194] According to this head unit, even if the signal waveform of the residual vibration signal, which is a composite wave, becomes complex due to an abnormality in at least one of the first pressure chamber and the second pressure chamber, the state of the discharge unit can be accurately determined by having a second determination mode that determines the state of the discharge unit according to a detection voltage signal obtained by converting the residual vibration detection signal into a digital signal, which is output by a second conversion circuit including an A / D conversion circuit.

[0195] In one aspect of the above head unit, In the first determination mode, the determination circuit may determine the state of the discharge unit based on at least one of the time during which the voltage value of the residual vibration detection signal exceeds the reference voltage value, and the time during which the voltage value of the residual vibration detection signal falls below the reference voltage value.

[0196] In one aspect of the above head unit, In the second determination mode, the determination circuit may determine the state of the discharge unit according to the period and amplitude of the residual vibration detection signal acquired based on the detected voltage signal.

[0197] In one aspect of the above head unit, The determination circuit may include a first determination circuit that determines the state of the discharge unit in the first determination mode, and a second determination circuit that determines the state of the discharge unit in the second determination mode. [Explanation of Symbols]

[0198] 1…Liquid dispensing device, 2…Control unit, 3…Liquid container, 4…Transport unit, 5…Dispensing unit, 6…Circulation unit, 10…Drive module, 11…Control circuit board, 15…Cable, 20…Dispensing 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, 210…Switching circuit, 220…Selection control circuit, 222…Shift register -, 224...Latch circuit, 226...Decoder, 230...Selection circuit, 232a,232b,232c...Logic inverter circuit, 234a,234b,234c...Transfer gate, 240...Waveform shaping circuit, 241...Filter circuit, 242...Amplifier circuit, 243...Impedance conversion circuit, 300...Residual vibration acquisition circuit, 302...Communication plate, 303...Pressure chamber substrate, 304...Diaphragm, 305...Storage chamber forming substrate, 308...Wiring board, 310...Analog acquisition circuit, 311a,311b...Comparator, 312a,312b...Switch, 313...Decision circuit, 320…Digital acquisition circuit, 321…A / D conversion circuit, 322…Decision circuit, 323…Memory circuit, 330…Decision circuit, 350…Opening, 351…Supply port, 352…Discharge port, 360…Nozzle substrate, 361,362…Compliance sheet, 600…Discharge section, AM10,AM11…Operation amplifier, C10…Capacitor, CB1,CB2…Pressure chamber, Ln…Nozzle row, N…Nozzle, P…Media, R10~R12…Resistor, RA1,RA2…Discharge channel, RB1,RB2…Discharge channel, RK1,RK2…Connection channel, RN…Nozzle channel, RR1,RR2…Communication channel

Claims

1. A transport unit that transports the media, A dispensing unit for dispensing liquid into the aforementioned medium, A residual vibration detection circuit that acquires a residual vibration signal corresponding to the residual vibration generated in the discharge section and outputs a residual vibration detection signal corresponding to the residual vibration signal, A first conversion circuit includes a comparison circuit and outputs a comparison result signal whose logic level changes according to the comparison result between the voltage value of the residual vibration detection signal and a reference voltage value, A second conversion circuit includes an A / D conversion circuit that outputs a detection voltage signal obtained by converting the residual vibration detection signal into a digital signal, A determination circuit for determining the state of the discharge section, Equipped with, The aforementioned determination circuit is A first determination mode for determining the state of the discharge unit according to the comparison result signal, A second determination mode for determining the state of the discharge unit in accordance with the detected voltage signal, Having, A liquid dispensing device characterized by the following features.

2. The aforementioned determination circuit is If it is determined in the first determination mode that an abnormality has occurred in the discharge unit, then in the second determination mode, the state of the discharge unit is determined, If it is determined in the first determination mode that no abnormality has occurred in the discharge unit, the determination of the state of the discharge unit in the second determination mode is not performed. The liquid dispensing device according to feature 1.

3. The aforementioned discharge section is A nozzle for dispensing liquid, A first pressure chamber, which communicates with the nozzle and stores liquid, A second pressure chamber, which communicates with the nozzle and stores liquid, A first detection element that detects residual vibrations generated in the first pressure chamber and outputs them as a first residual vibration signal, A second detection element that detects residual vibrations generated in the second pressure chamber and outputs them as a second residual vibration signal, It has, The composite wave of the first residual vibration signal and the second residual vibration signal is output as the residual vibration signal. The liquid dispensing device according to feature 1.

4. In the first determination mode, the determination circuit determines the state of the discharge unit based on at least one of the time during which the voltage value of the residual vibration detection signal exceeds the reference voltage value, and the time during which the voltage value of the residual vibration detection signal falls below the reference voltage value. The liquid dispensing device according to feature 1.

5. In the second determination mode, the determination circuit determines the state of the discharge unit according to the period and amplitude of the residual vibration detection signal acquired based on the detected voltage signal. The liquid dispensing device according to feature 1.

6. The determination circuit includes a first determination circuit that determines the state of the discharge unit in the first determination mode, and a second determination circuit that determines the state of the discharge unit in the second determination mode. The liquid dispensing device according to feature 1.

7. A dispensing unit that dispenses liquid into a medium, A residual vibration detection circuit that acquires a residual vibration signal corresponding to the residual vibration generated in the discharge section and outputs a residual vibration detection signal corresponding to the residual vibration signal, A first conversion circuit includes a comparison circuit and outputs a comparison result signal whose logic level changes according to the comparison result between the voltage value of the residual vibration detection signal and a reference voltage value, A second conversion circuit includes an A / D conversion circuit that outputs a detection voltage signal obtained by converting the residual vibration detection signal into a digital signal, A determination circuit for determining the state of the discharge section, Equipped with, The aforementioned determination circuit is A first determination mode for determining the state of the discharge unit according to the comparison result signal, A second determination mode for determining the state of the discharge unit in accordance with the detected voltage signal, Having, A head unit characterized by the following features.

8. The aforementioned determination circuit is If it is determined in the first determination mode that an abnormality has occurred in the discharge unit, then in the second determination mode, the state of the discharge unit is determined, If it is determined in the first determination mode that no abnormality has occurred in the discharge unit, the determination of the state of the discharge unit in the second determination mode is not performed. The head unit according to feature 7.

9. The aforementioned discharge section is A nozzle for dispensing liquid, A first pressure chamber, which communicates with the nozzle and stores liquid, A second pressure chamber, which communicates with the nozzle and stores liquid, A first detection element that detects residual vibrations generated in the first pressure chamber and outputs them as a first residual vibration signal, A second detection element that detects residual vibrations generated in the second pressure chamber and outputs them as a second residual vibration signal, It has, The composite wave of the first residual vibration signal and the second residual vibration signal is output as the residual vibration signal. The head unit according to feature 7.

10. In the first determination mode, the determination circuit determines the state of the discharge unit based on at least one of the time during which the voltage value of the residual vibration detection signal exceeds the reference voltage value, and the time during which the voltage value of the residual vibration detection signal falls below the reference voltage value. The head unit according to feature 7.

11. In the second determination mode, the determination circuit determines the state of the discharge unit according to the period and amplitude of the residual vibration detection signal acquired based on the detected voltage signal. The head unit according to feature 7.

12. The determination circuit includes a first determination circuit that determines the state of the discharge unit in the first determination mode, and a second determination circuit that determines the state of the discharge unit in the second determination mode. The head unit according to feature 7.

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