Liquid ejection device

Abstract

A liquid ejecting apparatus capable of reducing the risk of lowering the detection accuracy of residual vibration due to noise generated in the generation of a drive signal. The liquid ejecting apparatus includes a first ejecting portion having a first piezoelectric element, which is driven by a drive signal to thereby eject liquid; a drive signal generating portion that generates the drive signal; a first selecting portion that performs a selecting operation of whether or not to apply a voltage of each of a plurality of drive waveforms included in the drive signal to the first piezoelectric element, based on a print data signal; a residual vibration detecting portion that detects residual vibration of the first ejecting portion after the voltage of a first drive waveform among the plurality of drive waveforms is applied to the first piezoelectric element; and a control portion that generates the print data signal, the control portion stopping the drive signal generating portion when the residual vibration detecting portion detects the residual vibration.

Description

Technical Field

[0001] This invention relates to a liquid ejection device. Background Technology

[0002] In inkjet printers and other liquid ejection devices that use piezoelectric elements, such as piezoelectric effect elements, to print images and text, liquid ejection devices are known to employ piezoelectric elements. Each piezoelectric element is provided corresponding to one of multiple ejection sections in an ink ejection head, and each is driven according to a drive signal, thereby ejecting a predetermined amount of ink from the nozzle of the ejection section at a predetermined time, forming dots on a medium such as paper.

[0003] In such liquid ejection devices, the following situation exists: due to increased viscosity of the ink filled in the ejection section, air bubbles mixed into the ejection section, etc., ejection abnormalities occur, causing ink to be unable to be ejected normally from the ejection section. If ejection abnormalities occur, the predetermined points formed on the medium will not be formed correctly, and the image quality will degrade. Conventionally, the following techniques are known: after driving the ejection section, residual vibration in the ejection section is detected, and the ejection state of the ink in the ejection section is determined based on the detection result. The degree of residual vibration varies depending on the viscosity of the ink, and the viscosity of the ink varies depending on the temperature. Therefore, Patent Document 1 discloses a liquid ejection device that can change the inspection timing of residual vibration according to temperature, thereby unifying the judgment criteria for ejection state and simplifying the inspection sequence.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2019-116057

[0005] However, the signal generated by residual vibration is very small. Therefore, there is a risk that the noise generated in the generation of the high-voltage drive signal will affect the detection of residual vibration and reduce the detection accuracy. Summary of the Invention

[0006] The liquid ejection device of the present invention comprises:

[0007] The first ejection section has a first piezoelectric element, which is driven by a drive signal to eject liquid;

[0008] A drive signal generation unit generates the drive signal;

[0009] The first selection unit performs a selection action based on the printed data signal to select whether to apply the voltage of each of the multiple drive waveforms included in the drive signal to the first piezoelectric element.

[0010] The residual vibration detection unit detects the residual vibration of the first ejector after the voltage of the first driving waveform (one of the plurality of driving waveforms) is applied to the first piezoelectric element; and

[0011] The control unit generates the printing data signal.

[0012] When the residual vibration detection unit detects the residual vibration, the control unit stops the drive signal generation unit. Attached Figure Description

[0013] Figure 1 This is a diagram showing a simplified structure of a liquid ejection device.

[0014] Figure 2 This is a diagram showing the lower surface of the head.

[0015] Figure 3 This is a block diagram showing the electrical structure of the liquid ejection device.

[0016] Figure 4 This is a diagram showing a simplified structure corresponding to a nozzle.

[0017] Figure 5 This is a diagram showing the waveforms of the drive signals COMA and COMB.

[0018] Figure 6 This is a diagram showing the waveform of the drive signal VOUT.

[0019] Figure 7 This is a diagram showing the structure of the switching circuit.

[0020] Figure 8 This is a diagram showing the decoded content in the decoder.

[0021] Figure 9 This is a diagram showing the structure of the selection circuit.

[0022] Figure 10 This is a diagram showing the circuit configuration of the drive circuit.

[0023] Figure 11 It is a diagram used to illustrate the operation of the drive circuit.

[0024] Figure 12 This is a diagram showing the structure of the inspection circuit.

[0025] Figure 13 This is a diagram used to illustrate the operation of the measurement unit.

[0026] Figure 14 This is a diagram illustrating an example of decision logic based on the decision unit.

[0027] Figure 15 This is a diagram illustrating an example of the operation of the liquid ejection device according to the first embodiment.

[0028] Figure 16 This is a diagram illustrating an example of the operation of the liquid ejection device according to the second embodiment.

[0029] Figure 17 This is a diagram illustrating another example of the operation of the liquid ejection device according to the second embodiment.

[0030] Explanation of reference numerals in the attached figures

[0031] 1…Liquid ejection device, 3…Moving mechanism, 4…Conveying mechanism, 20…Head unit, 21…Head, 24…Slide carriage, 31…Slide carriage motor, 32…Slide carriage guide shaft, 33…Timing belt, 40…Platform, 41…Conveyor motor, 42…Conveyor roller, 50, 50a-1~50a-4, 50b-1~50b-4…Drive circuit, 60…Piezoelectric element, 70, 70-1~70-4…Switching circuit, 80, 80-1~80-4…Inspection Circuit, 81…waveform shaping unit, 82…measuring unit, 83…determination unit, 90…temperature sensor, 100…control board, 110…drive signal generation unit, 111…control unit, 112…power supply circuit, 120…residual vibration detection unit, 190…cable, 220…selection control unit, 222…shift register, 224…latch circuit, 226…decoder, 230…selection circuit, 232a, 232b, 232c…logic inverting circuit, 234a, 234b, 234c… Transmission gates; 236a, 236b, 236c… Level shifter circuits; 500… Integrated circuit device; 510… Modulation unit; 511… DAC; 512… Adder; 513… Adder; 514… Comparator; 515… Logic inverting circuit; 516… Integrator attenuator; 517… Attenuator; 520… Gate driver; 521… First gate driver; 522… Second gate driver; 540… Boost circuit, 550…output circuit, 560…low-pass filter, 570…first feedback circuit, 572…second feedback circuit, 580…reference voltage generation unit, 600…ejection unit, 601…piezoelectric element, 611, 612…electrodes, 621…vibrating plate, 631…cavity, 632…nozzle plate, 641…reservoir, 650…nozzle array, 650a~650h…first nozzle array~eighth nozzle array, 651…nozzle, 661…supply port. Detailed Implementation

[0032] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The drawings are provided for ease of explanation. It should be noted that the embodiments described below are not intended to unduly limit the scope of the invention as defined in the claims. Furthermore, the structures described below are not necessarily essential components of the present invention.

[0033] 1. First Implementation Method

[0034] 1-1. Overview of the liquid ejection device

[0035] As an example of the liquid ejection device involved in this embodiment, the printing apparatus is an inkjet printer that ejects ink based on image data supplied from an external host computer, thereby forming ink dot groups on a printing medium such as paper, and thus printing an image (including text, graphics, etc.) corresponding to the image data.

[0036] Figure 1 This is a perspective view showing a simplified internal structure of the liquid ejection device 1 according to this embodiment. Figure 1 As shown, the liquid ejection device 1 is a serial scanning type liquid ejection device, comprising: a head unit 20 and a moving mechanism 3 that reciprocates the head unit 20 in the main scanning direction X. Although not shown in the figure, a USB port and a power port are provided on the rear surface of the liquid ejection device 1. That is, the liquid ejection device 1 is configured to connect to a computer or the like via the USB port. It should be noted that in this embodiment, the moving direction of the carriage 24 in the liquid ejection device 1 is defined as the main scanning direction X, the transport direction of the printing medium P as the secondary scanning direction Y, and the vertical direction as Z. Furthermore, the main scanning direction X, the secondary scanning direction Y, and the vertical direction Z are shown as three mutually perpendicular axes in the accompanying drawings, but the arrangement of the various structures is not necessarily perpendicular.

[0037] The moving mechanism 3 has: a carriage motor 31 that serves as the drive source for the head unit 20; a carriage guide shaft 32 that is fixed at both ends; and a timing belt 33 that extends substantially parallel to the carriage guide shaft 32 and is driven by the carriage motor 31.

[0038] The head unit 20 is configured to include a carriage 24 and a head 21 mounted on the carriage 24 opposite to the printing medium P. The carriage 24 is supported by a carriage guide shaft 32 in a manner that allows for free reciprocating motion, and is fixed to a portion of the timing belt 33. Therefore, if the carriage motor 31 rotates the timing belt 33 in both directions, the head unit 20 is guided by the carriage guide shaft 32 to reciprocate. The head 21 is used to eject droplets, i.e., ink droplets, from a plurality of nozzles, and its structure is such that various control signals are supplied via a cable 190. For example, the cable 190 may be a flexible flat cable.

[0039] Figure 2 This diagram shows the lower surface of head 21, i.e., the ink ejection surface. (See diagram below.) Figure 2As shown, on the ink ejection surface of the head 21, four nozzle plates 632 are arranged along the main scanning direction X. Each of the four nozzle plates 632 has two nozzle columns 650. Each nozzle column 650 has a plurality of nozzles 651 arranged at a predetermined interval Py along the sub-scanning direction Y. Between the two nozzle columns 650 on each nozzle plate 632, each nozzle 651 is positioned such that it is shifted by only half the interval Py in the sub-scanning direction Y. Thus, in this embodiment, eight nozzle columns 650, namely the first nozzle column 650a to the eighth nozzle column 650h, are provided on the ink ejection surface of the head 21.

[0040] In addition, such as Figure 1 As shown, the liquid ejection device 1 includes a conveying mechanism 4 that conveys the printing medium P along the sub-scanning direction Y on the table 40. The conveying mechanism 4 includes a conveying motor 41 as a drive source, and a conveying roller 42 that is rotated by the conveying motor 41 and conveys the printing medium P along the sub-scanning direction Y.

[0041] In this embodiment, the carriage 24 houses four ink cartridges 22, and the ink filled in each ink cartridge 22 is supplied to the head 21. For example, the four ink cartridges 22 are respectively filled with cyan, magenta, yellow, and black ink. It should be noted that the structure can also be as follows: each ink cartridge 22 is disposed in an ink tank, which is not mounted on the carriage 24 but is fitted to the body side, and the ink filled in each ink cartridge 22 is supplied to the head 21 via an ink tube.

[0042] When the printing medium P has been conveyed by the conveying mechanism 4, the head 21 sprays ink droplets toward the printing medium P in the vertical direction Z, thereby forming an image on the surface of the printing medium P.

[0043] 1-2. Electrical structure of the liquid ejection device

[0044] Figure 3 This is a block diagram illustrating the electrical structure of the liquid ejection device 1 according to this embodiment. Figure 3 As shown, the liquid ejection device 1 includes a control board 100 and a head unit 20. The control board 100 is fixed at a predetermined position inside the body of the liquid ejection device 1 and is connected to the head unit 20 via a cable 190.

[0045] The control board 100 is provided with a control unit 111, a power supply circuit 112 and eight drive circuits 50, namely drive circuits 50a-1 to 50a-4 and 50b-1 to 50b-4.

[0046] For example, the control unit 111 is implemented by a processor such as a microcontroller, and generates various data and signals based on various signals such as image data supplied from the host computer.

[0047] Specifically, the control unit 111 generates drive data dA1 to dA4 and dB1 to dB4 based on various signals from the host computer. This drive data is digital data that serves as the basis for the drive signals COMA-1 to COMA-4 and COMB-1 to COMB-4 of each ejection section 600 of the drive head 21. The drive data dA1 to dA4 are supplied to drive circuits 50a-1 to 50a-4, respectively, and the drive data dB1 to dB4 are supplied to drive circuits 50b-1 to 50b-4, respectively. The drive data dA1 to dA4 are digital data that define the waveforms of the drive signals COMA-1 to COMA-4, respectively, and the drive data dB1 to dB4 are digital data that define the waveforms of the drive signals COMB-1 to COMB-4, respectively.

[0048] Additionally, the control unit 111 generates output control signals OEB1 to OEB4. Output control signal OEB1 controls the generation and output of drive signals COMA-1 and COMB-1, and is supplied to drive circuits 50a-1 and 50b-1. Output control signal OEB2 controls the generation and output of drive signals COMA-2 and COMB-2, and is supplied to drive circuits 50a-2 and 50b-2. Output control signal OEB3 controls the generation and output of drive signals COMA-3 and COMB-3, and is supplied to drive circuits 50a-3 and 50b-3. Output control signal OEB4 controls the generation and output of drive signals COMA-4 and COMB-4, and is supplied to drive circuits 50a-4 and 50b-4.

[0049] Furthermore, based on various signals from the host computer, the control unit 111 generates four printing data signals SI1 to SI4, a latch signal LAT, a change signal CH, and a clock signal SCK, serving as various control signals to control the ejection of liquid from each ejection section 600. Additionally, the control unit 111 generates a check control signal TSIG, which, after the ejection section 600 is driven, indicates the start and end of residual vibration detection (i.e., residual vibration detection). The printing data signals SI1 to SI4, the latch signal LAT, the change signal CH, the clock signal SCK, and the check control signal TSIG are transmitted from the control unit 111 to the head unit 20 via cable 190.

[0050] It should be noted that, in addition to the above-described processing, the control unit 111 also monitors the scanning position of the head unit 20 and drives the carriage motor 31 based on the scanning position of the head unit 20. Therefore, the movement of the head unit 20 toward the main scanning direction X is controlled. Furthermore, the control unit 111 drives the transport motor 41. Therefore, the movement of the printing medium P toward the sub-scanning direction Y is controlled.

[0051] Furthermore, the control unit 111 causes a maintenance mechanism (not shown) to perform maintenance procedures to restore the ink ejection state of the head 21 to normal, namely cleaning and wiping.

[0052] Power supply circuit 112 generates a certain high power supply voltage VHV, a certain low power supply voltage VDD, a certain offset voltage VBS, and a ground voltage GND. For example, the high power supply voltage VHV is 42V, the low power supply voltage VDD is 3.3V, the offset voltage VBS is 6V, and the ground voltage GND is 0V. The high power supply voltage VHV, the low power supply voltage VDD, the offset voltage VBS, and the ground voltage GND are transferred from power supply circuit 112 to head unit 20 via cable 190. Additionally, the high power supply voltage VHV, the low power supply voltage VDD, and the ground voltage GND are supplied to drive circuits 50a-1 to 50a-4 and 50b-1 to 50b-4, respectively.

[0053] The drive circuits 50a-1 to 50a-4 and 50b-1 to 50b-4 generate drive signals COMA-1 to COMA-4 and COMB-1 to COMB-4 based on each of the drive data dA1 to dA4 and dB1 to dB4. For example, the drive circuits 50a-1 to 50a-4 and 50b-1 to 50b-4 convert the drive data dA1 to dA4 and dB1 to dB4 from digital to analog and then amplify them in Class D to generate drive signals COMA-1 to COMA-4 and COMB-1 to COMB-4. The drive data dA1 to dA4 and dB1 to dB4 are data that define the waveforms of the drive signals COMA-1 to COMA-4 and COMB-1 to COMB-4, respectively.

[0054] When the output control signal OEB1 is low, drive circuits 50a-1 and 50b-1 generate and output drive signals COMA-1 and COMB-1 respectively; when the output control signal OEB1 is high, the output becomes high impedance. Similarly, drive circuits 50a-2 and 50b-2 generate and output drive signals COMA-2 and COMB-2 respectively when the output control signal OEB1 is low; when the output control signal OEB1 is high, the output becomes high impedance. Likewise, drive circuits 50a-3 and 50b-3 generate and output drive signals COMA-3 and COMB-3 respectively when the output control signal OEB1 is low; when the output control signal OEB1 is high, the output becomes high impedance. Similarly, when the output control signal OEB1 is low, the drive circuits 50a-4 and 50b-4 generate and output drive signals COMA-4 and COMB-4 respectively. When the output control signal OEB1 is high, the output becomes high impedance. When the outputs of drive circuits 50a-1 to 50a-4 and 50b-1 to 50b-4 are high impedance, the drive signals COMA-1 to COMA-4 and COMB-1 to COMB-4 remain at their previous voltages due to the capacitance of each piezoelectric element 60.

[0055] It should be noted that the only differences between the drive circuits 50a-1 to 50a-4 and 50b-1 to 50b-4 are the input drive data, the output control signal, and the output drive signal. The circuit structure can be the same, and the details will be explained later.

[0056] The drive signals COMA-1 to COMA-4 and COMB-1 to COMB-4 are transferred from the control board 100 to the head unit 20 via cable 190.

[0057] The head unit 20 is equipped with four switching circuits 70, namely switching circuits 70-1 to 70-4, four inspection circuits 80, namely inspection circuits 80-1 to 80-4, and a temperature sensor 90.

[0058] Each of the drive signals COMA-1 to COMA-4, each of the drive signals COMB-1 to COMB-4, and each of the print data signals SI1 to SI4 are input to the switching circuits 70-1 to 70-4. Additionally, the same clock signal SCK, latch signal LAT, change signal CH, and check control signal TSIG are input to the switching circuits 70-1 to 70-4. The switching circuits 70-1 to 70-4 operate with a high power supply voltage VHV, a low power supply voltage VDD, and a ground voltage GND, respectively, and output drive signals VOUT to the multiple ejection sections 600 of the head 21. Specifically, the switching circuit 70-1 selects either the drive signal COMA-1 or the drive signal COMB-1 as the drive signal VOUT output based on the clock signal SCK, the print data signal SI1, the latch signal LAT, the change signal CH, and the check control signal TSIG, or neither is selected and the output is set to high impedance. Similarly, switching circuits 70-2 to 70-4 select any one of the drive signals COMA-2 to COMA-4 and COMB-2 to COMB-4 as the drive signal VOUT output based on clock signal SCK, each of the printed data signals SI2 to SI4, latch signal LAT, change signal CH, and check control signal TSIG, or they do not select any of them and set the output to high impedance.

[0059] The drive signal VOUT output by switching circuit 70-1 is applied to one end of the piezoelectric element 60 of each ejection section 600 corresponding to the first nozzle row 650a and the second nozzle row 650b. Furthermore, the drive signal VOUT output by switching circuit 70-2 is applied to one end of the piezoelectric element 60 of each ejection section 600 corresponding to the third nozzle row 650c and the fourth nozzle row 650d. Furthermore, the drive signal VOUT output by switching circuit 70-3 is applied to one end of the piezoelectric element 60 of each ejection section 600 corresponding to the fifth nozzle row 650e and the sixth nozzle row 650f. Furthermore, the drive signal VOUT output by switching circuit 70-4 is applied to one end of the piezoelectric element 60 of each ejection section 600 corresponding to the seventh nozzle row 650g and the eighth nozzle row 650h. The other end of each piezoelectric element 60 is supplied with the same offset voltage VBS. Furthermore, the piezoelectric element 60 is displaced according to the potential difference between the drive signal VOUT and the offset voltage VBS, and ink is ejected from the nozzle 651 in an amount corresponding to the displacement. Alternatively, the piezoelectric element 60 is displaced according to the potential difference between the drive signal VOUT and the offset voltage VBS, and ink is not ejected from the nozzle 651, resulting in residual vibration in the ejection section 600.

[0060] Furthermore, switching circuit 70-1, based on printing data signal SI1 and inspection control signal TSIG, switches whether one end of the piezoelectric element 60 of each ejector section 600 corresponding to the first nozzle row 650a or the second nozzle row 650b is electrically connected to inspection circuit 80-1. Similarly, switching circuit 70-2, based on printing data signal SI2 and inspection control signal TSIG, switches whether one end of the piezoelectric element 60 of each ejector section 600 corresponding to the third nozzle row 650c or the fourth nozzle row 650d is electrically connected to inspection circuit 80-2. Similarly, switching circuit 70-3, based on printing data signal SI3 and inspection control signal TSIG, switches whether one end of the piezoelectric element 60 of each ejector section 600 corresponding to the fifth nozzle row 650e or the sixth nozzle row 650f is electrically connected to inspection circuit 80-3. Similarly, the switching circuit 70-4 switches whether to electrically connect one end of the piezoelectric element 60 of each ejection section 600 provided corresponding to the seventh nozzle column 650g or the eighth nozzle column 650h to the inspection circuit 80-4 based on the printing data signal SI4 and the inspection control signal TSIG.

[0061] Specifically, switching circuits 70-1 to 70-4 select the ejector section 600 of the inspection object that is in the ejection state based on each of the printing data signals SI1 to SI4. Hereinafter, the ejector section 600 of the inspection object that is in the ejection state is referred to as the "ejector section 600 of the inspection object", and the ejector section 600 of the inspection object that is not in the ejection state is referred to as the "ejector section 600 of the non-inspection object". In addition, based on the inspection control signal TSIG, switching circuits 70-1 to 70-4 electrically connect one end of the piezoelectric element 60 of the ejector section 600 of the inspection object to each of the inspection circuits 80-1 to 80-4, and electrically disconnect one end of the piezoelectric element 60 of the ejector section 600 of the non-inspection object from each of the inspection circuits 80-1 to 80-4. Then, with one end of the piezoelectric element 60 of each of the four ejector parts 600 of the object under inspection electrically connected to each of the inspection circuits 80-1 to 80-4, the object under inspection signals PO1 to PO4 appearing at each end of the piezoelectric element 60 of each of the four ejector parts 600 of the object under inspection are input to each of the inspection circuits 80-1 to 80-4.

[0062] It should be noted that the circuit structures of switching circuits 70-1 to 70-4 can also be the same, and the details will be explained later.

[0063] The inspection circuits 80-1 to 80-4 are input with the inspection control signal TSIG and each of the inspection target signals PO1 to PO4, and are operated by being supplied with a low power supply voltage VDD and a ground voltage GND. Synchronized with the inspection control signal TSIG, the inspection circuits 80-1 to 80-4, based on each of the inspection target signals PO1 to PO4, apply a drive signal VOUT to the piezoelectric element 60 of the ejection section 600 of the inspection target, and then detect the residual vibration of the ejection section 600. Further, based on the detection result of the residual vibration, the inspection circuits 80-1 to 80-4 determine the ejection state of the ink in the ejection section 600 of the inspection target, and output determination result signals RS1 to RS4 indicating the determination result. The determination result signals RS1 to RS4 are transmitted from the head unit 20 to the control unit 111 via cable 190.

[0064] It should be noted that the circuit structure of inspection circuits 80-1 to 80-4 can also be the same, and the details will be explained later.

[0065] The control unit 111 performs processing corresponding to the judgment result signals RS1 to RS4. For example, if at least one of the judgment result signals RS1 to RS4 indicates that the ejector 600 has an ejection malfunction, the control unit 111 can display an error message on the display (not shown) of the liquid ejection device 1. Additionally, the control unit 111 can also generate control signals to cause a maintenance mechanism (not shown) to perform maintenance processing, and can also generate printing data signals SI1 to SI4 for supplementary recording processing of printing on the printing medium P by replacing the ejector 600 with an ejector 600 that has an ejection malfunction.

[0066] Temperature sensor 90 operates by being supplied with a low power supply voltage VDD and a ground voltage GND, detects the temperature of head 21, and outputs a temperature signal VTEMP indicating the temperature of head 21. For example, temperature sensor 90 can be located inside head 21 or on the outer surface of head 21. The temperature signal VTEMP is transmitted from head unit 20 to control unit 111 via cable 190.

[0067] The control unit 111 generates drive data dA1 to dA4 and dB1 to dB4 for correcting drive signals COMA-1 to COMA-4 and COMB-1 to COMB-4 based on the temperature signal VTEMP. In this embodiment, the drive signal VOUT used to eject ink from each ejection unit 600 in order to print an image based on image data onto the printing medium P is generated based on drive signals COMA-1 to COMA-4. Then, the control unit 111 changes the drive data dA1 to dA4 according to the value (voltage level or digital value) of the temperature signal VTEMP so that the amount of ink ejected from each ejection unit 600 is a constant amount that does not change with temperature. Specifically, the lower the temperature of the ejection section 600, the higher the viscosity of the ink, and the more difficult it is for the ink to be ejected from the nozzle 651. Therefore, the control unit 111 generates drive data dA1 to dA4 in such a way that the lower the temperature of the ejection section 600, i.e. the temperature of the head 21 indicated by the temperature signal VTEMP, the larger the amplitude of the drive signals COMA-1 to COMA-4.

[0068] It should be noted that in this embodiment, the drive circuits 50a-1 to 50a-4 and 50b-1 to 50b-4 constitute a drive signal generation unit 110. This drive signal generation unit 110 generates a drive signal COM-1 composed of drive signals COMA-1 and COMB-1, a drive signal COM-2 composed of drive signals COMA-2 and COMB-2, a drive signal COM-3 composed of drive signals COMA-3 and COMB-3, and a drive signal COM-4 composed of drive signals COMA-4 and COMB-4. Furthermore, the inspection circuits 80-1 to 80-4 constitute a residual vibration detection unit 120. This residual vibration detection unit 120 detects the residual vibration of the ejection section 600 after the drive signal COMB is applied to the piezoelectric element 60.

[0069] 1-3. Structure of the ejector section

[0070] Figure 4 This is a diagram showing a simplified structure corresponding to an ejector section 600 of the head 21. (See diagram for example.) Figure 4 As shown, the head 21 includes an ejector 600 and a storage unit 641.

[0071] The storage device 641 is configured for each color of ink separately, and the ink is introduced into the storage device 641 from the supply port 661. It should be noted that the ink is supplied from the ink cartridge 22 to the supply port 661.

[0072] The ejection section 600 includes a piezoelectric element 60, a vibrating plate 621, a cavity 631, and a nozzle 651. The vibrating plate 621 is displaced by the piezoelectric element 60, which is disposed on its upper surface, and functions as a diaphragm that expands / contracts the internal volume of the ink-filled cavity 631. The nozzle 651 is disposed on a nozzle plate 632 and is an opening communicating with the cavity 631. The cavity 631 is filled with liquid, i.e., ink, and its internal volume changes due to the displacement of the piezoelectric element 60. The nozzle 651 communicates with the cavity 631 and ejects the ink from the cavity 631 as droplets according to the change in the internal volume of the cavity 631. Thus, because the piezoelectric element 60 is driven, the ejection section 600 ejects ink from the nozzle 651.

[0073] Figure 4 The piezoelectric element 60 shown is constructed by clamping a piezoelectric body 601 between a pair of electrodes 611 and 612. For this piezoelectric body 601, depending on the voltage applied by the electrodes 611 and 612, the electrodes 611 and 612, as well as the vibrating plate 621, interact with... Figure 4 Together with the central portion, it flexes vertically relative to the two end portions. Specifically, a drive signal VOUT is applied to one end of the piezoelectric element 60, namely electrode 611, and an offset voltage VBS is applied to the other end of the piezoelectric element 60, namely electrode 612. Furthermore, the piezoelectric element 60 is configured such that if the voltage of the drive signal VOUT decreases, it flexes upward; conversely, if the voltage of the drive signal VOUT increases, it flexes downward. In this configuration, if it flexes upward, the internal volume of cavity 631 expands, so ink is introduced from reservoir 641; conversely, if it flexes downward, the internal volume of cavity 631 shrinks, and depending on the degree of shrinkage, ink is ejected from nozzle 651.

[0074] It should be noted that the piezoelectric element 60 is not limited to the structure shown in the figure; it can be any type that can deform the piezoelectric element 60 to eject a liquid such as ink. Furthermore, the piezoelectric element 60 is not limited to buckling vibration; it can also be a structure that uses so-called longitudinal vibration.

[0075] Furthermore, the piezoelectric element 60 is provided corresponding to the cavity 631 and nozzle 651 in the head 21, and is also consistent with the description below. Figure 7 The selection circuit 230 shown is correspondingly provided. Therefore, the piezoelectric element 60, cavity 631, nozzle 651 and selection circuit 230 are arranged such that each nozzle 651 is provided separately.

[0076] 1-4. Structure of driving signals

[0077] In this embodiment, a drive signal COMA-1 is prepared to enable droplets ejected from each nozzle 651, which is included in the first nozzle row 650a or the second nozzle row 650b, to exhibit four gray levels: "large point," "medium point," "small point," and "no recording," for a single point. One cycle of the drive signal COMA-1 has a first half pattern and a second half pattern. The structure is such that, in one cycle, the drive signal COMA-1 is selected according to the gray level to be represented in the first and second halves, and supplied to the piezoelectric element 60 corresponding to each nozzle 651. Furthermore, in this embodiment, in order to "inspect" the ejection section 600 of the object to be inspected among the ejection sections 600 corresponding to the first nozzle row 650a or the second nozzle row 650b, a drive signal COMB-1 is prepared in addition to the drive signal COMA-1. In addition, in this embodiment, drive signals COMA-2 to COMA-4 are prepared for the same purpose as drive signal COMA-1, and COMB-2 to COMB-4 are prepared for the same purpose as drive signal COMB-1.

[0078] It should be noted that the waveforms of drive signals COMA-1 to COMA-4 differ slightly due to the different types of ink ejected, but their basic structure remains the same. Similarly, although the waveforms of drive signals COMB-1 to COMB-4 differ slightly, their basic structure remains the same. Therefore, in the following explanations, drive signals COMA-1 to COMA-4 will be collectively referred to as drive signal COMA, drive signals COMB-1 to COMB-4 will be collectively referred to as drive signal COMB, and drive signal COM-1 (composed of drive signals COMA-1 and COMB-1), drive signal COM-2 (composed of drive signals COMA-2 and COMB-2), drive signal COM-3 (composed of drive signals COMA-3 and COMB-3), and drive signal COM-4 (composed of drive signals COMA-4 and COMB-4) will be collectively referred to as drive signal COM.

[0079] Figure 5 This is a diagram showing the waveforms of the drive signals COMA and COMB. (For example...) Figure 5 As shown, the drive signal COMA is a waveform that makes the following waveforms continuous: a trapezoidal waveform Adp1 configured during the period T1 from the rise of the pulse of the latch signal LAT to the rise of the pulse of the change signal CH, and a trapezoidal waveform Adp2 configured during the period T2 from the rise of the pulse of the change signal CH to the rise of the next pulse of the latch signal LAT. The period consisting of period T1 and period T2 is taken as the period Ta, and for each period Ta, a new point is formed on the printing medium P.

[0080] In this embodiment, the trapezoidal waveforms Adp1 and Adp2 are different waveforms. Trapezoidal waveform Adp1 is such that, when supplied to one end of the piezoelectric element 60, a predetermined amount, specifically a moderate amount, of ink is ejected from the nozzle 651 corresponding to the piezoelectric element 60. Trapezoidal waveform Adp2 is such that, when supplied to one end of the piezoelectric element 60, a smaller amount, specifically a small amount, of ink is ejected from the nozzle 651 corresponding to the piezoelectric element 60.

[0081] The drive signal COMB has a trapezoidal waveform Bdp1 configured throughout the entire cycle Ta. The trapezoidal waveform Bdp1 is the waveform used to drive the piezoelectric element 60 in a manner that prevents ink droplets from being ejected from the nozzle 651 if the trapezoidal waveform Bdp1 is supplied to one end of the piezoelectric element 60.

[0082] It should be noted that the trapezoidal waveforms Adp1, Adp2, and Bdp1 all have the same voltage Vc at the start and end of the timing. That is, the trapezoidal waveforms Adp1, Adp2, and Bdp1 each begin and end with voltage Vc. The control unit 111 generates drive data dB1 to dB4 and dB1 to dB4 in a manner that the lower the temperature of the ejector 600 (indicated by the temperature signal VTEMP) of the head 21, the higher the voltage Vc.

[0083] Each ejector section 600 ejects ink by driving the piezoelectric element 60 via a drive signal COM composed of drive signals COMA and COMB. In this embodiment, a drive signal VOUT, which includes a drive waveform selected from multiple drive waveforms, namely trapezoidal waveforms Adp1, Adp2, and Bdp1, included in the drive signal COM, is applied to the piezoelectric element 60.

[0084] Figure 6 It is a diagram showing the waveform of the drive signal VOUT corresponding to each of "large point", "medium point", "small point", "non-recording" and "check".

[0085] like Figure 6 As shown, the drive signal VOUT corresponding to the "large dot" becomes a waveform that makes the trapezoidal waveform Adp1 of the drive signal COMA in period T1 and the trapezoidal waveform Adp2 of the drive signal COMA in period T2 continuous. If this drive signal VOUT is supplied to one end of the piezoelectric element 60, then within the period Ta, medium and small amounts of ink are ejected twice from the nozzle 651 corresponding to the piezoelectric element 60. Therefore, the respective inks adhere to the printing medium P and combine to form a large dot.

[0086] The drive signal VOUT corresponding to the "midpoint" becomes the trapezoidal waveform Adp1 of the drive signal COMA during period T1, and becomes the previous voltage Vc due to the high impedance during period T2, maintained by the capacitance of the piezoelectric element 60. If the drive signal VOUT is supplied to one end of the piezoelectric element 60, a moderate amount of ink is ejected from the nozzle 651 corresponding to the piezoelectric element 60 only during period T1 during period Ta. Therefore, the ink adheres to the printing medium P, forming the midpoint.

[0087] The drive signal VOUT corresponding to the "small dot" becomes the previous voltage Vc due to the capacitance of the piezoelectric element 60 during period T1, and becomes the trapezoidal waveform Adp2 of the drive signal COMA during period T2. If the drive signal VOUT is supplied to one end of the piezoelectric element 60, then during period Ta, a small amount of ink is ejected from the nozzle 651 corresponding to the piezoelectric element 60 only during period T2. Therefore, the ink adheres to the printing medium P, forming a small dot.

[0088] The drive signal VOUT corresponding to "non-recording" becomes high impedance during periods T1 and T2, and thus remains at the previous voltage Vc due to the capacitance of the piezoelectric element 60. If the drive signal VOUT is supplied to one end of the piezoelectric element 60, no ink is ejected from the nozzle 651 corresponding to the piezoelectric element 60 during period Ta. Therefore, the ink does not adhere to the printing medium P, and no dots are formed.

[0089] The drive signal VOUT corresponding to "inspection" becomes the trapezoidal waveform Bdp1 of the drive signal COMB during periods TS1 and TS3, and becomes high impedance during period TS2. Here, periods TS1, TS2, and TS3 are defined by the inspection control signal TSIG. Specifically, the inspection control signal TSIG is a signal indicating the start of the detection of residual vibration of each ejector section 600 by the inspection circuits 80-1 to 80-4, and has a first pulse PL1 with a predetermined period Ta for the start timing of residual vibration detection. In addition, the inspection control signal TSIG is a signal indicating the end of the detection of residual vibration of each ejector section 600 by the inspection circuits 80-1 to 80-4, and has a second pulse PL2 with a predetermined period Ta for the end timing of residual vibration detection. Furthermore, the period Ta is divided into: period TS1 from the rise of the latch signal LAT pulse to the rise of the first pulse PL1, period TS2 from the rise of the first pulse PL1 to the rise of the second pulse PL2, and period TS3 from the rise of the second pulse PL2 to the rise of the next pulse of the latch signal LAT.

[0090] If the drive signal VOUT for inspection is supplied to one end of the piezoelectric element 60, the ejector portion 600 having the piezoelectric element 60 will, during period TS1, experience a rapid expansion of cavity 631 as the potential of the drive signal VOUT rises, followed by a rapid contraction of cavity 631 as the potential of the drive signal VOUT falls. Subsequently, if the rise in the potential of the drive signal VOUT ends and becomes a constant potential, cavity 631 will repeatedly expand and contract while returning to its original volume. However, at this time, residual vibrations that decay over time are generated in cavity 631 and added to the piezoelectric element 60. Based on these residual vibrations, the electromotive force of the piezoelectric element 60 changes, and a residual vibration waveform appears in the drive signal VOUT during period TS2. Details will be explained later. In this embodiment, in inspection circuits 80-1 to 80-4, the ejection state of the ejector portion 600 of the inspection object is determined based on the residual vibration waveform appearing in the drive signal VOUT.

[0091] In this embodiment, within each cycle Ta, for each ejection section 600, one or both of the following processes can be performed: printing processing to supply a drive signal VOUT for "large dot", "medium dot", "small dot" or "non-recording", and inspection processing to supply a drive signal VOUT for "inspection" and to determine the ejection state. The liquid ejection device 1 forms an image corresponding to image data on the printing medium P by repeatedly performing printing processing within multiple cycles Ta, either continuously or intermittently.

[0092] For example, for each of the plurality of cycles Ta, any one of the ejector units 600 that is supplied with a "non-recording" drive signal VOUT during the printing process can instead be supplied with a "checking" drive signal VOUT. In this embodiment, the liquid ejection device 1 has four inspection circuits 80-1 to 80-4, which can perform inspection processing on a maximum of M×4 ejector units 600 in parallel with the printing process when an image corresponding to the image data is formed on the printing medium P within M cycles Ta.

[0093] Additionally, for example, the inspection process can be performed during periods when printing is not required, such as the period from the end of printing one page to the start of printing the next page in the case of multi-page printing. If the inspection mode has been set, it can be performed separately from the printing process.

[0094] It should be noted that, Figure 5 The drive signals COMA and COMB shown are just one example. In fact, depending on the moving speed of the head unit 20, the printing medium P, the structure of the ejector 600, the viscosity of the ink, etc., a wide variety of pre-prepared combinations of waveforms can be used.

[0095] Furthermore, an example was described here where the piezoelectric element 60 bends upwards as the voltage decreases. However, if the voltage supplied to electrodes 611 and 612 is reversed, the piezoelectric element 60 will bend downwards as the voltage decreases. Therefore, in the structure where the piezoelectric element 60 bends downwards as the voltage decreases, Figure 5 The illustrated drive signals COMA and COMB are waveforms that have been flipped based on the voltage Vc.

[0096] 1-5. Structure of the switching circuit

[0097] Next, the structure of the switching circuit 70 will be explained. Figure 7 This diagram shows the structure of the switching circuit 70. Hereinafter, printing data signals SI1 to SI4 will be used as printing data signals SI, drive signals COMA-1 to COMA-4 as drive signals COMA, drive signals COMB-1 to COMB-4 as drive signals COMB, and inspection target signals PO1 to PO4 as inspection target signals PO. Figure 7 As shown, the switching circuit 70 includes a selection control unit 220 and a plurality of selection circuits 230.

[0098] The selection control unit 220 is supplied with a clock signal SCK, a print data signal SI, a latch signal LAT, a change signal CH, and a check control signal TSIG. In the selection control unit 220, groups of shift registers 222, latch circuits 224, and decoders 226 are provided corresponding to each of the piezoelectric elements 60. That is, the number of groups of shift registers 222, latch circuits 224, and decoders 226 in one switching circuit 70 is the same as the total number m of nozzles 651 included in the two nozzle rows 650.

[0099] The print data signal SI is a 3-bit print data (SIH, SIM, SIL) for each of the m ejector sections 600, including any one of “large dot”, “medium dot”, “small dot”, “non-recording” and “inspection”, totaling 3m bits of signal.

[0100] The printing data signal SI is a signal synchronized with the clock signal SCK and corresponds to the nozzle 651. For each printing data signal SI, the 3 bits of printing data (SIH, SIM, SIL) are temporarily held by a shift register 222.

[0101] More specifically, the structure is as follows: shift registers 222 of the same stage as the piezoelectric element 60 are cascaded together, and the serially supplied printed data signal SI is sequentially transferred to the next stage according to the clock signal SCK.

[0102] It should be noted that, in order to distinguish shift register 222, it is sequentially labeled as level 1, level 2, ..., level m from the upstream side of the supplying printed data signal SI.

[0103] Each of the m latch circuits 224 latches the 3-bit printed data (SIH, SIM, SIL) held in each of the m shift registers 222 during the rise of the latch signal LAT.

[0104] Each of the m decoders 226 decodes the 3-bit printed data (SIH, SIM, SIL) latched by each of the m latch circuits 224. During each specified period T1 and T2 of the latch signal LAT and the change signal CH, a selection signal Sa is output. During each specified period TS1, TS2, and TS3 of the latch signal LAT and the check control signal TSIG, selection signals Sb and Sc are output, which define the selection in the selection circuit 230.

[0105] Figure 8 This is a diagram showing the decoded content in decoder 226. (Example) Figure 8 As shown, if the latched 3-bit printed data (SIH, SIM, SIL) shows a "large dot" (1, 1, 0), the decoder 226 sets the logic level of the selection signal Sa to high during periods T1 and T2 and outputs it, and sets the logic levels of the selection signals Sb and Sc to low during periods TS1, TS2, and TS3 and outputs them.

[0106] Additionally, if the 3-bit printed data (SIH, SIM, SIL) shows a "midpoint" (1, 0, 0), the decoder 226 sets the logic level of the selection signal Sa high during period T1, sets it low during period T2, and outputs it. It also sets the logic levels of the selection signals Sb and Sc low during periods TS1, TS2, and TS3 and outputs them.

[0107] Additionally, if the 3-bit printed data (SIH, SIM, SIL) shows "small dots" (0, 1, 0), the decoder 226 sets the logic level of the selection signal Sa low during period T1 and outputs it, sets it high during period T2 and outputs it, and sets the logic levels of the selection signals Sb and Sc low during periods TS1, TS2, and TS3 and outputs them.

[0108] Additionally, if the 3-bit printed data (SIH, SIM, SIL) shows "not recorded" (0, 0, 0), the decoder 226 sets the logic level of the selection signal Sa low during periods T1 and T2 and outputs it, and sets the logic levels of the selection signals Sb and Sc low during periods TS1, TS2, and TS3 and outputs them.

[0109] Additionally, if the 3-bit printed data (SIH, SIM, SIL) shows "Check" (1, 1, 1), the decoder 226 sets the logic level of the selection signal Sa low during periods T1 and T2 and outputs it, sets the logic level of the selection signal Sb high during periods TS1 and TS3 and low during period TS2 and outputs it, and sets the logic level of the selection signal Sc low during periods TS1 and TS3 and high during period TS2 and outputs it.

[0110] The selection circuit 230 is provided for each corresponding piezoelectric element 60. That is, the number of selection circuits 230 in a switching circuit 70 is the same as the total number m of nozzles 651 included in the two nozzle rows 650.

[0111] Figure 9 This is a diagram showing the structure of a selection circuit 230 corresponding to the piezoelectric element 60.

[0112] like Figure 9 As shown, the selection circuit 230 includes: logic inverting circuits 232a, 232b, and 232c; transmission gates 234a, 234b, and 234c; and level shifting circuits 236a, 236b, and 236c.

[0113] The selection signal Sa from decoder 226 is a low logic amplitude signal, which is level-shifted to a high logic amplitude selection signal sax by level shifting circuit 236a. Similarly, the selection signal Sb is a low logic amplitude signal, which is level-shifted to a high logic amplitude selection signal sbx by level shifting circuit 236b. Likewise, the selection signal Sc is a low logic amplitude signal, which is level-shifted to a high logic amplitude selection signal scx by level shifting circuit 236c. As an example, the low level of low logic amplitude is 0V and the high level is 3.3V, while the low level of high logic amplitude is 0V and the high level is 42V.

[0114] The selection signal Sax from level shift circuit 236a is supplied to the positive control terminal of transmission gate 234a, and is logically inverted by logic inverting circuit 232a and supplied to the negative control terminal of transmission gate 234a. Similarly, the selection signal Sbx from level shift circuit 236b is supplied to the positive control terminal of transmission gate 234b, and is logically inverted by logic inverting circuit 232b and supplied to the negative control terminal of transmission gate 234b. Likewise, the selection signal Scx from level shift circuit 236c is supplied to the positive control terminal of transmission gate 234c, and is logically inverted by logic inverting circuit 232c and supplied to the negative control terminal of transmission gate 234c.

[0115] A drive signal COMA is supplied to the input terminal of transmission gate 234a, and a drive signal COMB is supplied to the input terminal of transmission gate 234b. The output terminals of transmission gates 234a and 234b are connected to each other and connected to one end of the piezoelectric element 60 in the ejection section 600.

[0116] Furthermore, the input terminal of transmission gate 234c and the output terminals of transmission gates 234a and 234b are connected together to one end of the piezoelectric element 60 in the ejection section 600. For example... Figure 7 As shown, the output of transmission gate 234c is connected in common with the output of transmission gate 234c of all other selection circuits 230 of switching circuit 70.

[0117] If the selection signal Sax of transmission gate 234a is high, it enables conduction between the input and output terminals; if the selection signal Sax is low, it disables conduction between the input and output terminals. Hereinafter, conduction will be referred to as "on," and discontinuation as "off." Similarly, transmission gates 234b and 234c enable or disable conduction between their input and output terminals based on the selection signals Sbx and Scx, respectively.

[0118] When transmission gate 234a is opened, the drive signal COMA is supplied as drive signal VOUT to one end of the piezoelectric element 60. When transmission gate 234b is opened, the drive signal COMB is supplied as drive signal VOUT to one end of the piezoelectric element 60. In addition, when transmission gate 234c is opened, the inspection target signal PO, which has a waveform based on the residual vibration generated in the ejection section 600, is output to the inspection circuit 80.

[0119] As mentioned above, the logic levels of the selection signals Sa, Sb, and Sc are determined based on the various printed data (SIH, SIM, SIL) included in the printed data signal SI. The drive signal VOUT output from the selection circuit 230 becomes... Figure 6 The voltage of any of the driving waveforms shown. That is, the selection circuit 230 selects whether to apply the voltage of each of the multiple driving waveforms, namely trapezoidal waveforms Adp1, Adp2, and Bdp1, included in the driving signal COM composed of driving signals COMA and COMB, to the piezoelectric element 60 based on the printed data signal SI. Specifically, the selection circuit 230 selects whether to apply the voltage of trapezoidal waveform Adp1 to the piezoelectric element 60 during period T1, and whether to apply the voltage of trapezoidal waveform Adp2 to the piezoelectric element 60 during period T2, according to the selection signal Sa. The transition from period T1 to period T2 is performed by changing the signal CH, so the changing signal CH is a signal used to switch the selection operation of the selection circuit 230.

[0120] 1-6. Structure of the driving circuit

[0121] Next, the drive circuit 50 will be described. Hereinafter, drive data dA1 to dA4 will be referred to as drive data dA, drive data dB1 to dB4 as drive data dB, output control signals OEB1 to OEB4 as output control signals OEB, drive signals COMA-1 to COMA-4 as drive signals COMA, and drive signals COMB-1 to COMB-4 as drive signals COMB.

[0122] Figure 10 This is a diagram showing the circuit configuration of the drive circuit 50. (See diagram for example.) Figure 10 As shown, the drive circuit 50 includes: an integrated circuit device 500, an output circuit 550, a first feedback circuit 570, and a second feedback circuit 572.

[0123] Integrated circuit device 500 is an integrated circuit device that outputs amplified control signals as gate signals to each of the first transistor M1 and the second transistor M2 based on k-bit drive data dA or dB input via terminals In1 to Ink. Therefore, integrated circuit device 500 includes: DAC 511, adder 512, adder 513, comparator 514, logic inverting circuit 515, integrating attenuator 516, attenuator 517, first gate driver 521, second gate driver 522, boost circuit 540, and reference voltage generation unit 580. DAC is short for Digital to Analog Converter.

[0124] The reference voltage generation unit 580 generates a reference voltage on the high voltage side, namely the first reference voltage DAC_HV, and a reference voltage on the low voltage side, namely the second reference voltage DAC_LV, and supplies them to DAC511.

[0125] DAC511 converts k bits of the drive data dA or dB of the specified drive signal COMA into the original drive signal Aa, which is the voltage between the first reference voltage DAC_HV and the second reference voltage DAC_LV, and supplies it to the input (+) of adder 512. It should be noted that the maximum and minimum values ​​of the voltage amplitude of the original drive signal Aa are determined by the first reference voltage DAC_HV and the second reference voltage DAC_LV, respectively. The signal after amplification of this voltage becomes the drive signal COMA or drive signal COMB. That is to say, the original drive signal Aa is the target signal before it becomes the drive signal COMA or drive signal COMB. As an example, the voltage amplitude of the original drive signal Aa is in the range of 1 to 2V.

[0126] The integrator 516 is the voltage input to terminal Out via terminal Vfb, that is, it attenuates and integrates the drive signal COMA and supplies it to the input terminal (-) of adder 512.

[0127] Adder 512 supplies the signal Ab, which is the voltage at input terminal (-) minus the voltage at input terminal (+) and the integrated voltage, to the input terminal (+) of adder 513.

[0128] It should be noted that the power supply voltage from the DAC511 to the logic inverter circuit 515 is from... Figure 4 The power supply circuit 112 shown supplies a low power supply voltage VDD, for example, a low amplitude 3.3V. Therefore, the voltage of the original drive signal Aa is at most 2V, while the voltage of the drive signal COMA can exceed 40V. Therefore, in order to match the amplitude range of the two voltages when calculating the deviation, the voltage of the drive signal COMA is attenuated by the integrator attenuator 516.

[0129] Attenuator 517 attenuates the high-frequency components of the drive signal COMA input via terminal Ifb and supplies them to the input terminal (-) of adder 513. Adder 513 supplies the voltage As, obtained by subtracting the voltage at input terminal (-) from the voltage at input terminal (+), to comparator 514. The function of attenuator 517 is to adjust the modulation gain, i.e., the sensitivity. That is, in conjunction with the drive data dB or dB, the frequency and duty cycle of the modulation signal Ms will change, but attenuator 517 will adjust these changes.

[0130] The voltage of the signal As output from adder 513 is the voltage of the original drive signal Aa minus the attenuated voltage of the signal supplied to terminal Vfb, and also minus the attenuated voltage of the signal supplied to terminal Ifb. Therefore, it can be said that the voltage of signal As based on adder 513 is a signal obtained by correcting the deviation obtained by subtracting the attenuated voltage of drive signal COMA or drive signal COMB output from terminal Out from the voltage of the original drive signal Aa, which is the target, using the high-frequency component of drive signal COMA or drive signal COMB.

[0131] Comparator 514 outputs a pulse-modulated signal Ms based on the subtraction voltage from adder 513 in the following manner: More specifically, comparator 514 outputs a modulated signal Ms that is high when the signal As output from adder 513 is a voltage rise, and is low when it is below the voltage threshold Vt1; if the signal As is a voltage fall, it is low when it is below the voltage threshold Vt2. It should be noted that, as described later, the voltage thresholds are set to a relationship of Vth1 > Vth2.

[0132] The modulated signal Ms, based on comparator 514, is logic-flipped by logic inverting circuit 515 and supplied to second gate driver 522. On the other hand, the modulated signal Ms, without logic flipping, is supplied to first gate driver 521. Therefore, the logic levels supplied to first gate driver 521 and second gate driver 522 are mutually exclusive.

[0133] The logic levels supplied to the first gate driver 521 and the second gate driver 522 can also be timed in a way that they are not actually high at the same time, that is, timed in a way that the first transistor M1 and the second transistor M2 are not turned on at the same time.

[0134] However, the modulation signal mentioned here, in a narrow sense, refers to the modulation signal Ms. But if we consider it as a signal pulse-modulated according to the original driving signal Aa, then the negation signal of the modulation signal Ms is also included in the modulation signal. That is to say, the modulation signal pulse-modulated according to the original driving signal Aa includes not only the modulation signal Ms, but also the signal that flips the logic level of the modulation signal Ms and the timing control signal.

[0135] It should be noted that adder 512, adder 513, comparator 514, logic inverting circuit 515, integrator attenuator 516, and attenuator 517 function as the modulation section 510 that modulates the original driving signal Aa and generates the modulation signal Ms.

[0136] The first gate driver 521 shifts the output signal of comparator 514 (i.e., the low logic amplitude level) to a high logic amplitude and outputs it from terminal Hdr. The power supply voltage of the first gate driver 521 is applied via terminal Bst for the high-order side and via terminal Sw for the low-order side. Terminal Bst is connected to one end of capacitor C5 and the cathode of diode D1 for reverse current prevention. Terminal Sw is connected to the source of the first transistor M1, the drain of the second transistor M2, the other end of capacitor C5, and one end of inductor L1. The anode of diode D1 is connected to terminal Gvd and is supplied with the voltage Vm output by boost circuit 540. Therefore, the potential difference between terminal Bst and terminal Sw is the potential difference across capacitor C5, that is, approximately equal to the voltage Vm. For example, voltage Vm is 7.5V.

[0137] The second gate driver 522 operates on a lower potential side than the first gate driver 521. The second gate driver 522 shifts the output signal of the logic inverter circuit 515 (i.e., the low logic amplitude level) to a high logic amplitude level, outputting it from the terminal Ldr. For example, the low level of the low logic amplitude is 0V and the high level is 3.3V, while the low level of the high logic amplitude is 0V and the high level is 7.5V. Of the power supply voltage of the second gate driver 522, the high-order side is supplied with a voltage Vm, and the low-order side is supplied with a ground voltage GND supplied from the power supply circuit 112 via the ground terminal Gnd. That is, the ground terminal Gnd is grounded through a ground wire.

[0138] For example, the first transistor M1 and the second transistor M2 are N-channel FETs. FET is an abbreviation for Field Effect Transistor. In the first transistor M1 on the high-potential side, a high power supply voltage VHV supplied from the power supply circuit 112 is applied to the drain, and the gate is connected to the terminal Hdr via resistor R1. For the second transistor M2 on the low-potential side, the gate is connected to the terminal Ldr via resistor R2, and the source is grounded through the ground wire.

[0139] Therefore, when the first transistor M1 is off and the second transistor M2 is on, the voltage at terminal Sw becomes 0V, and a voltage Vm is applied to terminal Bst. On the other hand, when the first transistor M1 is on and the second transistor M2 is off, a high power supply voltage VHV is applied to terminal Sw, and a voltage VHV+Vm is applied to terminal Bst.

[0140] In other words, the first gate driver 521 uses capacitor C5 as a floating power supply. Depending on the operation of the first transistor M1 and the second transistor M2, the reference potential, i.e., the potential of terminal Sw, will change to 0V or a high power supply voltage VHV. Therefore, a low-level output will show an amplified control signal near 0V, and a high-level output will show an amplified control signal near voltage Vm; or a low-level output will show an amplified control signal near high power supply voltage VHV, and a high-level output will show an amplified control signal near voltage VHV+Vm. Conversely, the reference potential of the second gate driver 522, i.e., the potential of the ground terminal Gnd, is fixed at 0V regardless of the operation of the first transistor M1 and the second transistor M2. Therefore, a low-level output will show an amplified control signal near 0V, and a high-level output will show an amplified control signal near voltage Vm.

[0141] It should be noted that the first gate driver 521 and the second gate driver 522 function as gate drivers 520 that generate amplification control signals based on the modulation signal Ms. Additionally, the first transistor M1 and the second transistor M2 function as amplifier circuits that generate amplified modulation signals after amplifying the modulation signal Ms.

[0142] The other end of inductor L1 is the output terminal Out in the drive circuit 50, from which drive signal COMA or drive signal COMB is supplied to each of the selection circuits 230.

[0143] Terminal Out is connected to one end of capacitor C1, one end of capacitor C2, and one end of resistor R3, respectively. The other end of capacitor C1 is grounded via a ground wire. Therefore, inductor L1 and capacitor C1 function as a low-pass filter 560 that smooths (demodulates) the amplified modulation signal appearing at the connection point of the first transistor M1 and the second transistor M2 and generates a drive signal.

[0144] The other end of resistor R3 is connected to terminal Vfb and one end of resistor R4, the other end of which is supplied with a voltage Vh. Thus, at terminal Vfb, the drive signal COMA or drive signal COMB from terminal Out, having passed through the first feedback circuit 570 composed of resistors R3 and R4, is pulled up and fed back.

[0145] On the other hand, the other end of capacitor C2 is connected to one end of resistor R5 and one end of resistor R6. The other end of resistor R5 is grounded via a ground wire. Therefore, capacitor C2 and resistor R5 function as a high-pass filter, allowing high-frequency components above the cutoff frequency of the drive signal COMA or drive signal COMB from terminal Out to pass through. It should be noted that, for example, the cutoff frequency of the high-pass filter is set to approximately 9MHz.

[0146] Additionally, the other end of resistor R6 is connected to one end of capacitor C4 and one end of capacitor C3. The other end of capacitor C3 is grounded via a ground wire. Therefore, resistor R6 and capacitor C3 function as a low-pass filter, allowing low-frequency components below the cutoff frequency of the signal passing through the aforementioned high-pass filter to pass through. It should be noted that, for example, the cutoff frequency of the LPF is set to approximately 160MHz.

[0147] The cutoff frequency of the high-pass filter is set to be lower than that of the low-pass filter. Therefore, the high-pass filter and the low-pass filter function as bandpass filters that allow the high-frequency components of the predetermined frequency domain included in the drive signal COMA or drive signal COMB to pass through.

[0148] The other end of capacitor C4 is connected to terminal Ifb of integrated circuit device 500. Thus, at terminal Ifb, the DC component of the high-frequency component of the drive signal COMA or drive signal COMB, which is composed of capacitor C2, resistor R5, resistor R6, capacitor C3, and capacitor C4 and functions as the aforementioned bandpass filter, is cut off and fed back.

[0149] However, the drive signal COMA or COMB output from terminal Out is a signal smoothed by passing the amplified and modulated signal in terminal Sw (the connection point between the first transistor M1 and the second transistor M2) through a low-pass filter composed of inductor L1 and capacitor C1. After being integrated and subtracted via terminal Vfb, the drive signal COMA or COMB is fed back to adder 512, thus oscillating at a frequency determined by the sum of the delay caused by the smoothing effect of inductor L1 and capacitor C1 and the delay caused by the integrator attenuator 516—that is, the feedback delay and the feedback transfer function.

[0150] However, the feedback path via terminal Vfb has a large delay, so there are cases where feedback via terminal Vfb alone cannot raise the frequency of the self-excited oscillation to a level that can adequately ensure the accuracy of the drive signal COMA or drive signal COMB.

[0151] Therefore, in this embodiment, in addition to the path via terminal Vfb, a path is also provided for feeding back the high-frequency components of the drive signal COMA or drive signal COMB via terminal Ifb, thereby reducing the delay from the perspective of the overall circuit. Thus, compared to the case where there is no path via terminal Ifb, the frequency of signal As obtained by adding the high-frequency components of drive signal COMA to signal Ab is increased to a level that sufficiently ensures the accuracy of drive signal COMA or drive signal COMB.

[0152] Figure 11 This diagram illustrates the correlation between the waveforms of signal As and modulation signal Ms and the original driving signal Aa.

[0153] like Figure 11 As shown, signal As is a triangular wave, and its oscillation frequency varies according to the voltage of the original driving signal Aa. Specifically, it is at its highest when the voltage of the original driving signal Aa is at its intermediate value, and it decreases as the voltage of the original driving signal Aa increases or decreases from the intermediate value.

[0154] Furthermore, if the voltage of the original driving signal Aa is near its midpoint, the slope of the triangular wave in signal As is approximately equal during the upward movement of the voltage rise and the downward movement of the voltage fall. Therefore, the duty cycle of the modulation signal Ms, obtained by comparing signal As with voltage thresholds Vt1 and Vt2 via comparator 514, is approximately 50%. If the voltage of the original driving signal Aa increases from its midpoint, the downward slope of signal As becomes gentler. Therefore, the period during which the modulation signal Ms is high becomes relatively longer, and the duty cycle increases. On the other hand, as the voltage of the original driving signal Aa decreases from its midpoint, the upward slope of signal As becomes gentler. Therefore, the period during which the modulation signal Ms is high becomes relatively shorter, and the duty cycle decreases.

[0155] Therefore, the modulation signal Ms becomes a pulse density modulation signal as follows. That is, the duty cycle of the modulation signal Ms is approximately 50% at the midpoint of the voltage of the original driving signal Aa, increases as the voltage of the original driving signal Aa becomes higher than the midpoint, and decreases as the voltage of the original driving signal Aa becomes lower than the midpoint.

[0156] The first gate driver 521 turns the first transistor M1 on / off based on the modulation signal Ms. That is, if the modulation signal Ms is high, the first gate driver 521 turns on the first transistor M1; if the modulation signal Ms is low, the first gate driver 521 turns off the first transistor M1. The second gate driver 522 turns the second transistor M2 on / off based on the logic toggle signal of the modulation signal Ms. That is, if the modulation signal Ms is high, the second gate driver 522 turns off the second transistor M2; if the modulation signal Ms is low, the second gate driver 522 turns on the second transistor M2.

[0157] Therefore, the voltage of the drive signal COMA or drive signal COMB, which is smoothed by the amplified modulation signal at the connection point of the first transistor M1 and the second transistor M2, increases as the duty cycle of the modulation signal Ms increases and decreases as the duty cycle decreases. As a result, the drive signal COMA or drive signal COMB is controlled and output as a signal that amplifies the voltage of the original drive signal Aa.

[0158] The drive circuit 50 uses pulse density modulation, which has the advantage of being able to achieve a greater range of duty cycle variations compared to pulse width modulation with a fixed modulation frequency.

[0159] In other words, the minimum positive and negative pulse widths that the circuit as a whole can handle are limited by its circuit characteristics. Therefore, in pulse width modulation with a fixed frequency, only a predetermined range can be ensured as the duty cycle variation width, such as from 10% to 90%. In contrast, in pulse density modulation, as the voltage of the original driving signal Aa moves away from its midpoint, the oscillation frequency decreases. Therefore, in the region where the voltage of the original driving signal Aa is higher, the duty cycle can be increased; conversely, in the region where the voltage of the original driving signal Aa is lower, the duty cycle can be decreased. Thus, in self-oscillating pulse density modulation, a wider range can be ensured as the duty cycle variation width, such as from 5% to 95%.

[0160] Furthermore, the drive circuit 50 includes a drive signal COMA or drive signal COMB, a modulation signal Ms, and a signal path for transmitting the amplified modulation signal. It is a self-excited oscillation circuit, unlike externally excited oscillation circuits which require generating high-frequency transmission waves. Therefore, it has the following advantages: integration of parts other than those dealing with high-voltage circuits, i.e., the integrated circuit device 500, is easier.

[0161] Furthermore, in the drive circuit 50, the feedback path for the drive signal COMA or drive signal COMB includes not only the path via terminal Vfb, but also a path via terminal Ifb that feeds back the high-frequency component. Therefore, the delay is reduced from the perspective of the overall circuit. Consequently, the frequency of the self-oscillation increases, allowing the drive circuit 50 to generate the drive signal COMA or drive signal COMB with high accuracy.

[0162] It should be noted that when the output control signal OEB input from the terminal oeb of the integrated circuit device 500 is low, the first gate driver 521 and the second gate driver 522 respectively turn on / off the first transistor M1 and the second transistor M2 according to the logic level of the modulation signal Ms. Thus, the drive circuit 50 performs self-oscillation and outputs a drive signal COMA or a drive signal COMB from the terminal Out.

[0163] On the other hand, when the output control signal OEB is high, the first gate driver 521 and the second gate driver 522 forcibly turn off the first transistor M1 and the second transistor M2 respectively, regardless of the logic level of the modulation signal Ms. As a result, the terminal Out becomes high impedance, and the drive signal COMA or drive signal COMB remains at its previous voltage due to the capacitance of the piezoelectric element 60. Therefore, the control unit 111 can also set the output control signal OEB high during a period when the voltage of the drive signal COMA or drive signal COMB is constant, for example, during the period of voltage Vc, thereby stopping the self-oscillation operation of the drive circuit 50. Thus, by setting the period during which the output control signal OEB is high, the power consumption of the drive circuit 50 is reduced, and the noise generated by the operation of the drive circuit 50 is also reduced.

[0164] return Figure 10 ,exist Figure 10 In the example shown, resistor R1, resistor R2, first transistor M1, second transistor M2, capacitor C5, diode D1, and low-pass filter 560 are configured as an output circuit 550 that generates a drive signal COMA or a drive signal COMB based on an amplified control signal and outputs it to the capacitive load, i.e., the piezoelectric element 60.

[0165] The boost circuit 540 supplies power to the gate driver 520. Figure 10 In the example shown, the boost circuit 540 boosts the low power supply voltage VDD supplied from the power supply terminal Vdd based on the ground voltage GND of the ground terminal Gnd, and generates a voltage Vm that becomes the power supply voltage on the high potential side of the second gate driver 522. The boost circuit 540 can be constructed using a charge pump circuit, a switching regulator, etc., but the case of using a charge pump circuit can suppress noise generation compared to the case of using a switching regulator. Therefore, the drive circuit 50 can generate the drive signal COMA or drive signal COMB with higher accuracy, and can control the voltage applied to the piezoelectric element 60 with high precision, thus improving the liquid ejection accuracy. Furthermore, since the power generation section of the gate driver 520 is miniaturized by using a charge pump circuit, it can be mounted in the integrated circuit device 500. Compared to the case where the power generation section of the gate driver 520 is constructed outside the integrated circuit device 500, the overall circuit area of ​​the drive circuit 50 can be significantly reduced. It should be noted that the boost circuit 540 can also be included in... Figure 3 The power supply circuit 112 is shown.

[0166] The drive circuit 50 configured in this way converts the drive data dA or dB from digital to analog, amplifies it in Class D, and then generates a drive signal COMA or a drive signal COMB. Here, the drive data dA and dB can be analog signals, as long as they define the waveform of the drive signals COMA and COMB. Furthermore, the drive circuit 50 can amplify the signal waveform defined by the drive data dA or dB and output the drive signal COMA or drive signal COMB. Therefore, the drive circuit 50 can also generate the drive signal COMA or drive signal COMB by amplifying the signal waveform defined by the drive data dA or dB in Class A, Class B, or Class AB.

[0167] 1-7. Check the circuit structure

[0168] Next, the structure of the inspection circuit 80 will be described. Hereinafter, the inspection target signals PO1 to PO4 will be referred to as inspection target signals PO, and the judgment result signals RS1 to RS4 will be referred to as judgment result signals RS.

[0169] Figure 12 This is a diagram showing the structure of the inspection circuit 80. (As shown...) Figure 12 As shown, the inspection circuit 80 includes a waveform shaping unit 81, a measurement unit 82, and a determination unit 83.

[0170] The waveform shaping unit 81 removes noise components from the inspection target signal PO through a low-pass filter or a band-pass filter, and outputs the residual vibration signal NVT obtained by amplifying the amplitude of the inspection target signal PO through an operational amplifier and resistors.

[0171] The residual vibration signal NVT, output by the waveform shaping unit 81, is input to the measurement unit 82. During the period TS2 specified by the inspection control signal TSIG, the period, amplitude, etc. of the residual vibration signal NVT are measured.

[0172] The determination unit 83 determines the ejection state of the ejection section 600 of the inspection object based on the period, amplitude, etc. of the residual vibration signal NVT measured by the measurement unit 82, and outputs a determination result signal RS indicating the determination result. The determination result signal RS can be a signal indicating the presence or absence of ejection abnormality, or it can be a signal that includes information on the cause of the ejection abnormality.

[0173] Figure 13 This is a timing diagram used to illustrate the operation of the measuring unit 82. For example... Figure 13 As shown, if TS2 starts and the supply of the residual vibration signal NVT begins, the measurement unit 82 compares the residual vibration signal NVT with the following potentials: the potential of the center level of the amplitude of the residual vibration signal NVT, i.e., the threshold potential Vth2; the threshold potential Vth1, which is higher than the threshold potential Vth2; and the threshold potential Vth3, which is lower than the threshold potential Vth2. Then, the measurement unit 82 generates the following signals: a comparison signal Cmp1 that is high when the potential of the residual vibration signal NVT is higher than the threshold potential Vth1; a comparison signal Cmp2 that is high when the potential of the residual vibration signal NVT is higher than the threshold potential Vth2; and a comparison signal Cmp3 that is high when the potential of the residual vibration signal NVT is lower than the threshold potential Vth3.

[0174] Then, after the start time t0 of period TS2, the measurement unit 82 measures the time Tp from the moment t1 when the comparison signal Cmp2 initially drops to a low level and then rises to a high level to the moment t2 when the comparison signal Cmp2 drops to the next low level and then rises to a high level.

[0175] For example, the measurement unit 82 can count the number of pulses of the clock signal SCK between time t1 and time t2, and set the count value as time Tp.

[0176] Furthermore, if the amplitude of the residual vibration signal NVT is small, it is anticipated that an ejection abnormality may occur in the ejection section 600 of the object under inspection, such as the cavity 631 not being filled with ink. Here, the measuring unit 82 sets the amplitude determination value Ap to "1" when the potential of the residual vibration signal NVT is above the threshold potential Vth1 and the comparison signal Cmp1 is high during the period from time t1 to time t2, and when the potential of the residual vibration signal NVT is below the threshold potential Vth3 and the comparison signal Cmp3 is high during the period from time t1 to time t2. Otherwise, the amplitude determination value Ap is set to "0".

[0177] Although the ejection section 600 performs the action of ejecting ink droplets, the ink droplets are not ejected normally from the nozzle 651. That is to say, the following points can be listed as reasons for the ejection abnormality: (1) air bubbles are mixed into the cavity 631, (2) the viscosity of the ink in the cavity 631 increases due to the drying of the ink in the cavity 631, etc., and (3) foreign objects such as paper scraps adhere to the outlet of the nozzle 651.

[0178] First, with air bubbles mixed in within cavity 631, the total weight of the ink filling cavity 631 decreases, and the inertia is expected to decrease. Furthermore, with air bubbles adhering near nozzle 651, the diameter of nozzle 651 is considered to increase to the diameter of the air bubble, and the acoustic impedance is expected to decrease. Therefore, compared to a normal ejection state, the frequency of residual vibration increases when ejection abnormalities occur due to air bubbles mixed in cavity 631. Consequently, time Tp becomes smaller than the predetermined threshold time Tth2.

[0179] Next, as the ink near nozzle 651 dries and its viscosity increases, the ink within cavity 631 becomes trapped inside cavity 631. Under these conditions, it is conceivable that the acoustic impedance will increase. Therefore, with the ink viscosity near nozzle 651 within cavity 631 increasing, the frequency of residual vibration decreases compared to the normal ejection state. Consequently, time Tp becomes greater than the predetermined threshold time Tth4.

[0180] Next, when foreign matter such as paper scraps adheres to the vicinity of the nozzle 651 exit, ink will seep out from the cavity 631 through the foreign matter, so it is conceivable that inertia will increase. Furthermore, it is conceivable that the fibers of the paper scraps adhering to the vicinity of the nozzle 651 exit will cause an increase in acoustic impedance. Therefore, when foreign matter such as paper scraps adheres to the vicinity of the nozzle 651 exit, the frequency of residual vibration becomes lower compared to the case where the ejection state is normal. Therefore, time Tp becomes greater than the predetermined threshold time Tth3 but less than the threshold time Tth4.

[0181] Therefore, in the absence of any ejection abnormality caused by the reasons mentioned in (1) to (3) above, that is, when time Tp is above the threshold time Tth2 and below the threshold time Tth3, the ejection state of the ejection section 600 is judged to be normal.

[0182] As described above, the determination unit 83 can determine the ejection state of the ejection section 600 of the inspection object based on the time Tp corresponding to the period of the residual vibration and the amplitude determination value Ap of the residual vibration.

[0183] Figure 14 This diagram illustrates an example of the determination logic for the ejection state of the ejection unit 600 based on the determination unit 83. Figure 14 In the example, if the amplitude determination value Ap is "0", the determination unit 83 determines that some ejection abnormality, such as unfilled ink, has occurred in the cavity 631, even though it cannot identify the specific cause, and sets the determination result signal RS to "5". Alternatively, if the amplitude determination value Ap is "1", the determination unit 83 determines the ejection state of the ejection unit 600 based on time Tp. That is, if time Tp is less than the threshold time Tth2, the determination unit 83 determines that the ejection unit 600 has an ejection abnormality due to air bubbles and sets the determination result signal RS to "2". Furthermore, if time Tp is above the threshold time Tth2 and below the threshold time Tth3, the determination unit 83 determines that the ejection state of the ejection unit 600 is normal and sets the determination result signal RS to "1". Additionally, if time Tp is more than the threshold time Tth3 and below the threshold time Tth4, the determination unit 83 determines that the ejection unit 600 has an ejection abnormality due to foreign matter adhesion and sets the determination result signal RS to "3". In addition, if the time Tp is greater than the threshold time Tth4, the determination unit 83 determines that the ejection unit 600 has caused an ejection abnormality due to increased viscosity, and sets the determination result signal RS to "4".

[0184] It should be noted that the determination result signal RS generated by the determination unit 83 is in Figure 14 In the example, the information consists of five values ​​from "1" to "5". However, for example, it could also be information with two values ​​indicating the presence or absence of an ejection anomaly. Furthermore, the determination unit 83 could also use only the time Tp and a portion of the amplitude determination value Ap in the generation of the determination result signal RS.

[0185] In this way, the inspection circuit 80 detects the residual vibration of the ejector section 600 after the voltage of the trapezoidal waveform Bdp1 included in the drive signal COMB is applied to the piezoelectric element 60, and determines the ejection state of the ejector section 600 of the object under inspection based on the residual vibration.

[0186] 1-8. Operation of the liquid ejection device

[0187] Next, regarding the operation of the liquid ejection device 1 in the first embodiment, refer to... Figure 15 Please provide an explanation.

[0188] The printing data signal SI and the clock signal SCK are supplied serially in sync and are sequentially transferred in shift registers 222 corresponding to the nozzles. Then, if the supply of the clock signal SCK stops, each of the shift registers 222 holds the 3-bit printing data (SIH, SIM, SIL) corresponding to the nozzle 651. It should be noted that the printing data signal SI is supplied in the order corresponding to the final m-level, ..., 2nd-level, 1st-level nozzles in the shift registers 222.

[0189] Here, if the latch signal LAT rises, each of the latch circuits 224 latches all 3 bits of printed data (SIH, SIM, SIL) held in the shift register 222. Figure 15 In the diagram, LT1, LT2, ..., LTm represent 3-bit printed data (SIH, SIM, SIL) latched by latch circuits 224 corresponding to shift registers 222 of levels 1, 2, ..., m.

[0190] Decoder 226, based on the latched 3-bit printed data (SIH, SIM, SIL), within each of periods T1 and T2, adjusts the logic level of the selection signal Sa to... Figure 8 The output content shown will, within each of TS1, TS2, and TS3, select the logic levels of signals Sb and Sc. Figure 8 Output the content shown.

[0191] In other words, when the printed data (SIH, SIM, SIL) is (1, 1, 0), the decoder 226 sets the selection signal Sa to high level, high level during periods T1 and T2, and sets the selection signals Sb and Sc to low level, low level, low level during periods TS1, TS2, and TS3. Conversely, when the printed data (SIH, SIM, SIL) is (1, 0, 0), the decoder 226 sets the selection signal Sa to high level, low level during periods T1 and T2, and sets the selection signals Sb and Sc to low level, low level, low level during periods TS1, TS2, and TS3. Conversely, when the printed data (SIH, SIM, SIL) is (0, 1, 0), the decoder 226 sets the selection signal Sa to low level, high level during periods T1 and T2, and sets the selection signals Sb and Sc to low level, low level, low level during periods TS1, TS2, and TS3. Furthermore, when the printed data (SIH, SIM, SIL) is (0, 0, 0), the decoder 226 sets the selection signal Sa to low level, low level during periods T1 and T2, and sets the selection signals Sb and Sc to low level, low level, low level during periods TS1, TS2, and TS3. Conversely, when the printed data (SIH, SIM, SIL) is (1, 1, 1), the decoder 226 sets the selection signal Sa to low level, low level during periods T1 and T2, sets the selection signal Sb to high level, low level, high level during periods TS1, TS2, and TS3, and sets the selection signal Sc to low level, high level, low level during periods TS1, TS2, and TS3.

[0192] When the printed data (SIH, SIM, SIL) is (1, 1, 0), the selection circuit 230 selects the trapezoidal waveform Adp1 of the drive signal COMA because the selection signal Sa is high during period T1, and selects the trapezoidal waveform Adp2 of the drive signal COMA because Sa is high during period T2. Furthermore, the selection circuit 230 does not select the drive signal COMB because the selection signal Sb is low during periods TS1, TS2, and TS3. As a result, a... Figure 6 The drive signal VOUT corresponding to the "large point" is shown.

[0193] When the printed data (SIH, SIM, SIL) is (1, 0, 0), the selection circuit 230 selects the trapezoidal waveform Adp1 of the drive signal COMA because the selection signal Sa is high during period T1, and does not select the drive signal COMA because Sa is low during period T2. Furthermore, the selection circuit 230 does not select the drive signal COMB because the selection signal Sb is low during periods TS1, TS2, and TS3. As a result, a... Figure 6The drive signal VOUT corresponding to the "midpoint" is shown.

[0194] When the printed data (SIH, SIM, SIL) is (0, 1, 0), selection circuit 230 does not select drive signal COMA because selection signal Sa is low during period T1, and selects the trapezoidal waveform Adp2 of drive signal COMA because selection signal Sa is high during period T2. Furthermore, selection circuit 230 does not select drive signal COMB because selection signal Sb is low during periods TS1, TS2, and TS3. As a result, a... Figure 6 The driving signal VOUT corresponding to the "small dot" is shown.

[0195] When the printed data (SIH, SIM, SIL) is (0, 0, 0), selection circuit 230 does not select drive signal COMA because selection signal Sa is low during periods T1 and T2. Furthermore, selection circuit 230 does not select drive signal COMB because selection signal Sb is low during periods TS1, TS2, and TS3. As a result, this generates... Figure 6 The drive signal VOUT shown corresponds to "non-recording".

[0196] When the printed data (SIH, SIM, SIL) is (1, 1, 1), selection circuit 230 does not select drive signal COMA because selection signal Sa is low during periods T1 and T2. Furthermore, selection circuit 230 does not select the trapezoidal waveform Bdp1 of drive signal COMB because selection signal Sb is high during periods TS1 and TS3, and it does not select drive signal COMB because selection signal Sb is low during period TS2. As a result, during periods TS1 and TS3, [the following occurs]. Figure 6 The drive signal VOUT corresponding to "inspection" is shown. Additionally, during periods TS1 and TS3, the selection circuit 230 closes transmission gate 234c because the selection signal Sc is low, and during period TS2, the selection signal Sc is high, thus opening transmission gate 234c. As a result, the inspection target signal PO is generated during period TS2.

[0197] During period TS2, the inspection circuit 80 detects the residual vibration of the ejection part 600 of the inspection object, and during period Tx including period TS3, it sends the data of the residual vibration detection result, i.e. the judgment result signal RS, to the control unit 111.

[0198] In this case, during TS2, the inspection circuit 80 detects the residual vibration of the ejection section 600 of the object being inspected. Since the residual vibration is small, there is a risk that the detection accuracy of the residual vibration detection unit 120 will decrease if it is affected by noise. In particular, the drive circuit 50 generates high-voltage drive signals COMA and COMB through the switching operation of the first transistor M1 and the second transistor M2. Therefore, it is necessary to ensure that the switching noise of the drive circuit 50 does not affect the detection of residual vibration.

[0199] Therefore, in this embodiment, when the residual vibration detection unit 120, composed of inspection circuits 80-1 to 80-4, detects residual vibration, the control unit 111 stops the drive signal generation unit 110, composed of drive circuits 50-1 to 50-4. For example, the control unit 111 may also start the residual vibration detection unit 120 to detect residual vibration after stopping the drive signal generation unit 110. Alternatively, the control unit 111 may also release the stop of the drive signal generation unit 110 after stopping the residual vibration detection unit 120.

[0200] Specifically, such as Figure 15 As shown, after the control unit 111 stops the drive circuit 50 by setting the output control signal OEB from low to high, it starts the detection of residual vibration in the inspection circuit 80 by checking the first pulse PL1 of the check control signal TSIG. Then, after the control unit 111 stops the detection of residual vibration in the inspection circuit 80 by checking the second pulse PL2 of the check control signal TSIG, it sets the output control signal OEB from high to low to release the stop of the drive circuit 50. Thus, the drive circuit 50 stops during the period TS2 from the rise of the first pulse PL1 to the rise of the second pulse PL2, thereby reducing the risk of decreased detection accuracy based on residual vibration in the inspection circuit 80.

[0201] It should be noted that the start of residual vibration detection based on the residual vibration detection unit 120 and the stop of the drive signal generation unit 110 can also be performed simultaneously. That is, the timing of the output control signal OEB changing from a low level to a high level can also be simultaneous with the timing of the rise of the first pulse PL1 of the check control signal TSIG. Furthermore, the end of residual vibration detection based on the residual vibration detection unit 120 can also be simultaneous with the release of the stop of the drive signal generation unit 110. That is, the timing of the output control signal OEB changing from a high level to a low level can also be simultaneous with the timing of the rise of the second pulse PL2 of the check control signal TSIG.

[0202] Furthermore, such as Figure 9As shown, in each selection circuit 230, high logic amplitude selection signals Sax, Sbx, and Scx are input to logic inverting circuits 232a, 232b, and 232c, respectively. When the logic levels of selection signals Sax, Sbx, and Scx change, a large through current flows through logic inverting circuits 232a, 232b, and 232c, respectively. In this embodiment, there are four ejector sections 600 that are to be inspected within each cycle Ta. In contrast, the other majority of ejector sections 600 can perform ejection operations based on the trapezoidal waveforms Adp1 and Adp2 of the drive signal COMA. Therefore, if the logic level of the selection signal Sax changes, through current flows simultaneously through the majority of logic inverting circuits 232a, which may become significant noise for the residual vibration of the ejector section 600 to be inspected. Furthermore, the logic level of the selection signal Sax can change when the selection operation based on the trapezoidal waveforms Adp1 and Adp2 of the selection circuit 230 is switched by changing the signal CH.

[0203] Therefore, the control unit 111 allows switching of the selection operation of the selection circuit 230 corresponding to the non-inspection target ejection section 600 only during the period when the residual vibration detection unit 120 is not detecting residual vibration. In other words, the control unit 111 prohibits switching of the selection operation of the selection circuit 230 corresponding to the non-inspection target ejection section 600 during the period when the residual vibration detection unit 120 is detecting residual vibration. That is to say, the control unit 111 keeps the change signal CH fixed at a low level during the period TS2 when the inspection circuit 80 detects the residual vibration of the inspection target ejection section 600. For example, as Figure 15 As shown, during the period TS3 following period TS2, after the period Tx in which the inspection circuit 80 sends the determination result signal RS ends, the control unit 111 generates a pulse of the change signal CH. Therefore, during period TS2, no switching of selection operations occurs in each selection circuit 230, thus reducing the risk of decreased detection accuracy based on residual vibration of the inspection circuit 80.

[0204] It should be noted that the ejector section 600 of the object being inspected is an example of the "first ejector section" of the present invention, and the piezoelectric element 60 provided in the ejector section 600 of the object being inspected is an example of the "first piezoelectric element" of the present invention. Furthermore, the selection circuit 230, which selects any one of multiple drive waveforms, namely trapezoidal waveforms Adp1, Adp2, and Bdp1, based on the printing data signal SI, and applies it to the piezoelectric element 60 provided in the ejector section 600 of the object being inspected, is an example of the "first selection section" of the present invention. Furthermore, the drive signal COM, composed of drive signals COMA and COMB that drive the piezoelectric element 60 of the ejector section 600 of the object being inspected, is an example of the "drive signal" of the present invention. Furthermore, the trapezoidal waveform Bdp1 of the drive signal COMB is an example of the "first drive waveform". Furthermore, the ejector section 600 of the object not being inspected, which is supplied with the same drive signal COM as the ejector section 600 of the object being inspected, is an example of the "second ejector section" of the present invention, and the piezoelectric element 60 provided in this non-object ejector section 600 is an example of the "second piezoelectric element" of the present invention. Furthermore, the selection circuit 230, which outputs the drive signal VOUT to the piezoelectric element 60 of the non-inspection object ejection section 600, is an example of the "second selection section" of the present invention.

[0205] 1-9. Effects

[0206] As described above, in the liquid ejection device 1 according to the first embodiment, the control unit 111 stops the drive signal generation unit 110 when the residual vibration detection unit 120 detects residual vibration. For example, after stopping the drive signal generation unit 110, the control unit 111 starts the residual vibration detection unit 120 to detect residual vibration, and after stopping the residual vibration detection unit 120 to stop the residual vibration detection, it releases the stop of the drive signal generation unit 110. That is, the drive signal generation unit 110 is stopped before the residual vibration detection unit 120 starts detecting residual vibration, and the residual vibration detection unit 120 stops detecting residual vibration before the drive signal generation unit 110 starts operating. Therefore, the drive signal generation unit 110 stops during the period when the residual vibration detection unit 120 performs residual vibration detection. As a result, according to the liquid ejection device 1 according to the first embodiment, the risk of a decrease in the detection accuracy of residual vibration based on the residual vibration detection unit 120 due to the switching noise generated by the drive signal generation unit 110 is reduced.

[0207] Furthermore, in the liquid ejection device 1 according to the first embodiment, the control unit 111 allows switching of the selection operation of the selection circuit 230 corresponding to the ejection unit 600 that is not under inspection only during periods when the residual vibration detection unit 120 is not detecting residual vibration. Therefore, according to the liquid ejection device 1 according to the first embodiment, during the period when the residual vibration detection unit 120 is detecting residual vibration, the switching of the selection operation of each selection circuit 230 does not occur. Thus, the risk of a decrease in the detection accuracy of residual vibration based on the residual vibration detection unit 120 due to noise generated by each selection circuit 230 is reduced.

[0208] 2. Second Implementation Method

[0209] Hereinafter, for the liquid ejection device according to the second embodiment, the same reference numerals are used for the same structural elements as in the first embodiment, and the descriptions that are repeated in the first embodiment are omitted. The descriptions will mainly focus on the contents that are different from the first embodiment.

[0210] Similar to the liquid ejection device 1 according to the first embodiment, in the liquid ejection device 1 according to the second embodiment, the control unit 111 stops the drive signal generation unit 110 composed of drive circuits 50-1 to 50-4 when the residual vibration detection unit 120, which is composed of inspection circuits 80-1 to 80-4, detects residual vibration. For example, the control unit 111 may also start the residual vibration detection unit 120 to detect residual vibration after stopping the drive signal generation unit 110. In addition, the control unit 111 may also release the stop of the drive signal generation unit 110 after the residual vibration detection unit 120 ends the detection of residual vibration. Furthermore, the control unit 111 allows the switching of the selection operation of the selection circuit 230 corresponding to the ejection unit 600 that is not under inspection only during the period when the residual vibration detection unit 120 is not detecting residual vibration.

[0211] However, in the liquid ejection device 1 according to the first embodiment, if the judgment result signal RS sent by the inspection circuit 80 to the control unit 111 becomes erroneous data due to the switching noise of the drive circuit 50, there is a risk that the processing of the control unit 111 corresponding to the judgment result signal RS will become inappropriate.

[0212] Therefore, in the liquid ejection device 1 according to the second embodiment, the control unit 111 further stops the drive signal generation unit 110 when the residual vibration detection unit 120 sends the data of the residual vibration detection result, i.e., the determination result signal RS. For example, the control unit 111 may stop the residual vibration detection unit 120 after stopping the drive signal generation unit 110, start the residual vibration detection unit 120 to detect residual vibration, and after the residual vibration detection unit 120 ends the residual vibration detection, release the stop of the drive signal generation unit 110 after the residual vibration detection unit 120 sends the data of the residual vibration detection result, i.e., the determination result signal RS.

[0213] That is to say, such as Figure 16 As shown, after the control unit 111 sets the output control signal OEB from low to high and stops the drive circuit 50, it starts the residual vibration detection of the inspection circuit 80 by checking the first pulse PL1 of the check control signal TSIG, and stops the residual vibration detection of the inspection circuit 80 by checking the second pulse PL2 of the check control signal TSIG. During the period Tx, which includes the period TS3 after the residual vibration detection period TS2, the inspection circuit 80 sends the residual vibration detection result data, i.e., the judgment result signal RS, to the control unit 111. Then, after the period Tx ends, the control unit 111 sets the output control signal OEB from high to low and releases the stop of the drive circuit 50. After releasing the stop of the drive circuit 50, it generates a pulse of the change signal CH.

[0214] Alternatively, for example, the control unit 111 may start the residual vibration detection unit 120 to detect residual vibration after stopping the drive signal generation unit 110, and release the stop of the drive signal generation unit 110 after stopping the residual vibration detection unit 120. Then, after stopping the drive signal generation unit 110 again, the residual vibration detection unit 120 sends the residual vibration detection result data, i.e., the judgment result signal RS. After the transmission ends, the stop of the drive signal generation unit 110 is released.

[0215] For example, such as Figure 17As shown, after the control unit 111 stops the drive circuit 50 by setting the output control signal OEB from low to high, it starts the residual vibration detection of the inspection circuit 80 by checking the first pulse PL1 of the check control signal TSIG, and stops the residual vibration detection of the inspection circuit 80 by checking the second pulse PL2 of the check control signal TSIG. Then, the control unit 111 releases the stop of the drive circuit 50 by setting the output control signal OEB from high to low, and generates a pulse of the latch signal LAT. With the pulse of the latch signal LAT, the next cycle Ta begins as the cycle Ta ends. In the next cycle Ta, after the control unit 111 stops the drive circuit 50 by setting the output control signal OEB from low to high, the inspection circuit 80 sends the residual vibration detection result data, i.e., the judgment result signal RS, to the control unit 111 during the period Tx. Then, after the period Tx ends, the control unit 111 releases the stop of the drive circuit 50 by setting the output control signal OEB from high to low.

[0216] exist Figure 16 as well as Figure 17 In either case, during the period TS2 from the rise of the first pulse PL1 to the rise of the second pulse PL2, the drive circuit 50 stops, thus reducing the risk of decreased detection accuracy based on residual vibration of the inspection circuit 80. Furthermore, during period TS2, no switching of selection actions occurs in the selection circuits 230, further reducing the risk of decreased detection accuracy based on residual vibration of the inspection circuit 80. Moreover, during period Tx, the drive circuit 50 stops, thus reducing the risk that the determination result signal RS becomes erroneous data. Furthermore, Figure 16 The situation and Figure 17 In comparison, the control unit 111 sets the output control signal OEB from low level to high level less often and from high level to low level less often, thus simplifying the control of the drive circuit 50 based on the control unit 111.

[0217] The other components and functions of the liquid ejection device 1 according to the second embodiment are the same as those of the liquid ejection device 1 according to the first embodiment, so its illustrations and descriptions are omitted.

[0218] As described above, in the liquid ejection device 1 according to the second embodiment, the control unit 111 stops the drive signal generation unit 110 when the residual vibration detection unit 120 detects residual vibration. For example, after stopping the drive signal generation unit 110, the control unit 111 starts the residual vibration detection unit 120 to detect residual vibration, and after stopping the residual vibration detection unit 120 to stop the residual vibration detection, it releases the stop of the drive signal generation unit 110. Therefore, according to the liquid ejection device 1 according to the second embodiment, the drive signal generation unit 110 stops during the period when the residual vibration detection unit 120 is detecting residual vibration, so the risk of a decrease in the detection accuracy of residual vibration based on the residual vibration detection unit 120 due to the switching noise generated by the drive signal generation unit 110 is reduced.

[0219] Furthermore, in the liquid ejection device 1 according to the second embodiment, the control unit 111 allows switching of the selection operation of the selection circuit 230 corresponding to the ejection unit 600 that is not under inspection only during periods when the residual vibration detection unit 120 is not detecting residual vibration. Therefore, according to the liquid ejection device 1 according to the second embodiment, during the period when the residual vibration detection unit 120 is detecting residual vibration, the switching of the selection operation of each selection circuit 230 does not occur. Thus, the risk of a decrease in the detection accuracy of residual vibration based on the residual vibration detection unit 120 due to noise generated by each selection circuit 230 is reduced.

[0220] Furthermore, in the liquid ejection device 1 according to the second embodiment, the control unit 111 stops the drive signal generation unit 110 when the residual vibration detection unit 120 sends the residual vibration detection result data, i.e., the determination result signal RS. Therefore, according to the liquid ejection device 1 according to the second embodiment, since the drive signal generation unit 110 stops during the period when the residual vibration detection unit 120 sends the residual vibration detection result data, the risk of the residual vibration detection result data being erroneous due to the switching noise generated by the drive signal generation unit 110 is reduced.

[0221] For example, the control unit 111 may, after stopping the drive signal generation unit 110, start the residual vibration detection unit 120 to detect residual vibration, and after stopping the residual vibration detection unit 120 and sending the residual vibration detection result data, i.e., the judgment result signal RS, the control unit 111 may release the stop of the drive signal generation unit 110. In this way, the number of times the drive signal generation unit 110 is stopped and released is reduced, thus simplifying the control unit 111's control of the drive signal generation unit 110.

[0222] 3. Variations

[0223] In the above embodiments, the inspection circuit 80 is disposed in the head unit 20, but at least a portion of the inspection circuit 80 may also be disposed in the control board 100.

[0224] Furthermore, in the embodiments described above, the determination unit 83 of the inspection circuit 80 determines the ejection state of the ejection section 600 of the inspection target. However, the control unit 111 may also have at least a portion of the functions of the determination unit 83. For example, the inspection circuit 80 may also... Figure 13 as well as Figure 14 The time Tp and amplitude determination value Ap shown are sent to the control unit 111 as data of the residual vibration detection result. The control unit 111 determines the ejection state of the ejection section 600 of the object under inspection based on the time Tp and amplitude determination value Ap. Alternatively, the inspection circuit 80 may output a residual vibration signal NVT to the control unit 111, and the control unit 111 may determine the ejection state of the ejection section 600 of the object under inspection based on the residual vibration signal NVT.

[0225] In addition, in the above embodiments, the four inspection circuits 80-1 to 80-4 perform residual vibration detection within the same period, but they can also perform residual vibration detection within different periods.

[0226] Furthermore, in the above embodiments, the control unit 111 stops and releases the eight drive circuits 50a-1 to 50a-4 and 50b-1 to 50b-4 at the same timing by outputting control signals OEB1 to OEB4, but it can also do so at different timings. For example, when the detection of residual vibration based on the inspection circuit 80-1 is unlikely to be affected by noise caused by the operation of drive circuits 50a-2, 50a-3, 50a-4, 50b-2, 50b-3, and 50b-4, the control unit 111 can, when enabling the inspection circuit 80-1 to detect residual vibration, not stop drive circuits 50a-1 and 50b-1 by outputting control signal OEB1, but simultaneously stop drive circuits 50a-2, 50a-3, 50a-4, 50b-2, 50b-3, and 50b-4 by outputting control signals OEB2, OEB3, and OEB4.

[0227] In addition, in the above embodiments, the liquid ejection device 1 has eight drive circuits 50 and four inspection circuits 80, but the number of drive circuits 50 and inspection circuits 80 is not limited to this.

[0228] Furthermore, in the embodiments described above, it was explained that the ejector section 600 of the object to be inspected does not eject ink even when driven by the drive signal COMB. However, it is also possible to increase the amplitude of the drive signal COMB to cause ink to be ejected from the ejector section 600. The larger the amplitude of the drive signal COMB, the larger the amplitude of the residual vibration, thus improving the judgment accuracy. In this case, for example, residual vibration detection processing can be performed in an inspection mode where no printing processing is performed.

[0229] Furthermore, in the embodiments described above, the control board 100 and the head unit 20 are connected via a single cable 190, but they can also be connected via multiple cables. Additionally, various signals can be wirelessly transmitted from the control board 100 to the head unit 20. That is, the control board 100 and the head unit 20 can also be connected without the cable 190.

[0230] In addition, in the above embodiments, the drive circuit 50 is disposed on the control board 100, but it may also be disposed on the head unit 20.

[0231] Furthermore, in the above embodiments, a portion or all of the waveform of the drive signal COMA is selected to generate the drive signal VOUT corresponding to "large point," "medium point," "small point," and "non-recording," and a portion of the drive signal COMB is selected to generate the drive signal VOUT corresponding to "inspection." However, the method for generating the drive signal VOUT applied to each piezoelectric element 60 is not limited to this, and various methods can be applied. For example, drive waveforms of multiple drive signals can be combined to generate the drive signal VOUT corresponding to "large point," "medium point," "small point," "non-recording," and "inspection." Alternatively, for example, the drive signal VOUT corresponding to "large point," "medium point," "small point," "non-recording," and "inspection" can be generated depending on whether multiple drive waveforms included in a single drive signal are selected.

[0232] Furthermore, in the above embodiments, serial scanning inkjet printers that print on printing media by moving the head are exemplified as liquid ejection devices. However, the present invention can also be applied to line printhead inkjet printers that print on printing media by not moving the head.

[0233] The present invention has been described above with reference to these embodiments or modifications, but it is not limited to these embodiments or modifications and can be implemented in various ways without departing from its spirit. For example, the embodiments and modifications described above can be appropriately combined.

[0234] This invention includes structures that are substantially identical to those described in the embodiments (e.g., structures with the same function, method, and result, or structures with the same purpose and effect). Additionally, this invention includes structures obtained by replacing non-essential parts of the structures described in the embodiments. Furthermore, this invention includes structures capable of achieving the same effects as the structures described in the embodiments, and structures capable of achieving the same purpose as the structures described in the embodiments. Additionally, this invention includes structures incorporating known techniques into the structures described in the embodiments.

[0235] The following content is derived from the above implementation methods and variations.

[0236] One method of liquid ejection device includes:

[0237] The first ejection section has a first piezoelectric element, which is driven by a drive signal to eject liquid;

[0238] A drive signal generation unit generates the drive signal;

[0239] The first selection unit performs a selection action based on the printed data signal to select whether to apply the voltage of each of the multiple drive waveforms included in the drive signal to the first piezoelectric element.

[0240] The residual vibration detection unit detects the residual vibration of the first ejector after the voltage of the first driving waveform (one of the plurality of driving waveforms) is applied to the first piezoelectric element; and

[0241] The control unit generates the printing data signal.

[0242] When the residual vibration detection unit detects the residual vibration, the control unit stops the drive signal generation unit.

[0243] According to this liquid ejection device, the drive signal generation unit stops during the residual vibration detection period of the residual vibration detection unit. Therefore, the risk of the residual vibration detection accuracy of the residual vibration detection unit decreasing due to the noise generated by the drive signal generation unit is reduced.

[0244] One embodiment of the liquid ejection device may also be:

[0245] After stopping the drive signal generation unit, the control unit causes the residual vibration detection unit to begin detecting the residual vibration.

[0246] According to this liquid ejection device, the drive signal generation unit is stopped before the residual vibration detection unit starts detecting residual vibration. Therefore, the risk of the detection accuracy of residual vibration based on the residual vibration detection unit decreasing due to the noise generated by the drive signal generation unit is reduced.

[0247] One embodiment of the liquid ejection device may also be:

[0248] After the control unit causes the residual vibration detection unit to stop detecting the residual vibration, it releases the stop of the drive signal generation unit.

[0249] According to this liquid ejection device, the residual vibration detection unit finishes detecting residual vibration before the drive signal generation unit starts operating. Therefore, the risk of the residual vibration detection unit's detection accuracy decreasing due to noise generated by the drive signal generation unit is reduced.

[0250] One embodiment of the liquid ejection device may also be:

[0251] The residual vibration detection unit sends the detection results of the residual vibration to the control unit.

[0252] When the residual vibration detection unit sends the data, the control unit stops the drive signal generation unit.

[0253] According to this liquid ejection device, during the period when the residual vibration detection unit sends the data of the residual vibration detection result, the drive signal generation unit stops, so the risk that the data of the residual vibration detection result will be erroneous due to the noise generated by the drive signal generation unit is reduced.

[0254] One embodiment of the liquid ejection device may also be:

[0255] After stopping the drive signal generation unit, the control unit causes the residual vibration detection unit to start detecting the residual vibration. After stopping the residual vibration detection unit and sending the data, the control unit releases the stop of the drive signal generation unit.

[0256] According to this liquid ejection device, the number of times the drive signal generation unit stops and stops is reduced, thus simplifying the control of the drive signal generation unit based on the control unit.

[0257] One possible embodiment of the liquid ejection device is:

[0258] The second ejection section has a second piezoelectric element, which is driven by the driving signal to eject liquid; and

[0259] The second selection unit, based on the printed data signal, performs a selection operation to determine whether to apply the voltages of the plurality of driving waveforms to the second piezoelectric element.

[0260] The control unit allows the switching of the selection action of the second selection unit only during periods when the residual vibration detection unit does not detect the residual vibration.

[0261] According to this liquid ejection device, during the period when the residual vibration detection unit performs residual vibration detection, the selection operation of the second selection unit will not be switched. Therefore, the risk of the detection accuracy of residual vibration based on the residual vibration detection unit decreasing due to the noise generated by the second selection unit is reduced.

Claims

1. A liquid ejection device, characterized in that, have: The first ejection section has a first piezoelectric element, which is driven by a drive signal to eject liquid; A drive signal generation unit generates the drive signal; The first selection unit performs a selection action based on the printed data signal to select whether to apply the voltage of each of the multiple drive waveforms included in the drive signal to the first piezoelectric element. The residual vibration detection unit detects the residual vibration of the first ejector after the voltage of the first driving waveform among the plurality of driving waveforms is applied to the first piezoelectric element. as well as The control unit generates the printing data signal. When the residual vibration detection unit detects the residual vibration, the control unit stops the drive signal generation unit. After stopping the drive signal generation unit, the control unit causes the residual vibration detection unit to begin detecting the residual vibration. After the control unit causes the residual vibration detection unit to stop detecting the residual vibration, it releases the stop of the drive signal generation unit.

2. The liquid ejection device according to claim 1, characterized in that, The residual vibration detection unit sends the detection results of the residual vibration to the control unit. When the residual vibration detection unit sends the data, the control unit stops the drive signal generation unit.

3. The liquid ejection device according to claim 2, characterized in that, After stopping the drive signal generation unit, the control unit causes the residual vibration detection unit to start detecting the residual vibration. After stopping the residual vibration detection unit and sending the data, the control unit releases the stop of the drive signal generation unit.

4. The liquid ejection device according to claim 1, characterized in that, The liquid ejection device includes: The second ejection section has a second piezoelectric element, which is driven by the driving signal to eject liquid. as well as The second selection unit, based on the printed data signal, performs a selection operation to determine whether to apply the voltages of the plurality of driving waveforms to the second piezoelectric element. The control unit allows the switching of the selection action of the second selection unit only during periods when the residual vibration detection unit does not detect the residual vibration.

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