Liquid dispensing device

Abstract

To provide a liquid discharge device that can reduce a risk that accuracy in detecting residual vibrations may be deteriorated due to noise occurring in generating a driving signal.SOLUTION: A liquid discharge device comprises: a first discharge part that has a first piezoelectric element and discharges liquid when the first piezoelectric element is driven by a driving signal; a driving signal generating part that generates the driving signal; a first selecting part that performs selection-operation of selecting whether respective voltages of a plurality of driving waveforms included in the driving signal should be applied to the first piezoelectric element or not, on the basis of a print data signal; a residual vibration detecting part that detects residual vibrations of the first discharging part after the voltage of the first driving waveform of the plurality of driving waveforms is applied to the first piezoelectric element; and a control part that generates the print data signal. The control part stops the driving signal generating part, when making the residual vibration detecting part detect the residual vibrations.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Among liquid ejection devices such as inkjet printers that eject ink to print images and documents, those using piezoelectric elements such as piezo elements are known. The piezoelectric elements are provided corresponding to each of a plurality of ejection parts in an inkjet head, and each is driven according to a drive signal, so that a predetermined amount of ink is ejected from the nozzles of the ejection parts at a predetermined timing, and dots are formed on a medium such as paper.

[0003] In such a liquid ejection device, ejection abnormalities may occur where ink cannot be normally ejected from the ejection part due to thickening of the ink filled in the ejection part or混入 of bubbles into the ejection part. When an ejection abnormality occurs, the dots intended to be formed on the medium are not accurately formed, and the image quality deteriorates. Conventionally, a technique is known in which residual vibration, which is the vibration remaining in the ejection part after driving the ejection part, is detected, and the ejection state of the ink in the ejection part is determined based on the detection result. The degree of residual vibration varies depending on the viscosity of the ink, and since the viscosity of the ink varies depending on the temperature, Patent Document 1 discloses a liquid ejection device capable of simplifying the inspection sequence by making the determination criteria for the ejection state the same by changing the inspection timing of the residual vibration according to the temperature.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, because the signals generated by residual vibrations are minute, noise generated during the production of high-voltage drive signals may affect the detection operation of residual vibrations, potentially reducing detection accuracy. [Means for solving the problem]

[0006] The liquid dispensing device according to the present invention is A first discharge unit having a first piezoelectric element, which discharges liquid when the first piezoelectric element is driven by a drive signal, A drive signal generation unit that generates the aforementioned drive signal, A first selection unit performs a selection operation to select whether or not to apply the voltage of each of the multiple drive waveforms included in the drive signal to the first piezoelectric element based on the print data signal, A residual vibration detection unit that detects the residual vibration of the first discharge section after the voltage of the first drive waveform among the plurality of drive waveforms is applied to the first piezoelectric element, A control unit that generates the print data signal, Equipped with, The control unit, When the residual vibration detection unit is to detect the residual vibration, the drive signal generation unit is stopped. [Brief explanation of the drawing]

[0007] [Figure 1] This is a diagram showing the schematic configuration of a liquid dispensing device. [Figure 2] This is a diagram showing the underside of the head. [Figure 3] This block diagram shows the electrical configuration of a liquid dispensing device. [Figure 4] This diagram shows a schematic configuration corresponding to one discharge unit. [Figure 5] This figure shows the waveforms of the drive signals COMA and COMB. [Figure 6] This figure shows the waveform of the drive signal VOUT. [Figure 7] This is a diagram showing the configuration of the switching circuit. [Figure 8] This diagram shows the decoded content in the decoder. [Figure 9] It is a diagram showing the configuration of the selection circuit. [Figure 10] It is a diagram showing the circuit configuration of the drive circuit. [Figure 11] It is a diagram for explaining the operation of the drive circuit. [Figure 12] It is a diagram showing the configuration of the inspection circuit. [Figure 13] It is a diagram for explaining the operation of the measurement unit. [Figure 14] It is a diagram showing an example of the determination logic by the determination unit. [Figure 15] It is a diagram for explaining an example of the operation of the liquid discharge device according to the first embodiment. [Figure 16] It is a diagram for explaining an example of the operation of the liquid discharge device according to the second embodiment. [Figure 17] It is a diagram for explaining another example of the operation of the liquid discharge device according to the second embodiment.

Embodiments for Carrying Out the Invention

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

[0009] 1. First Embodiment 1-1. Outline of the Liquid Discharge Device As an example of the liquid discharge device according to the present embodiment, a printing device forms an ink dot group on a printing medium such as paper by discharging ink according to image data supplied from an external host computer, and thereby prints an image (including characters, figures, etc.) corresponding to the image data. It is an inkjet printer.

[0010] FIG. 1 is a perspective view showing a schematic configuration inside a liquid ejection device 1 according to the present embodiment. As shown in FIG. 1, the liquid ejection device 1 is a serial scan type liquid ejection device, and includes a head unit 20 and a moving mechanism 3 that reciprocates the head unit 20 in the main scanning direction X. Although not shown, 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 be connectable to a computer or the like via the USB port. In the present embodiment, in the liquid ejection device 1, the moving direction of the carriage 24 is described as the main scanning direction X, the conveyance direction of the printing medium P is described as the sub-scanning direction Y, and the vertical direction is described as Z. Also, the main scanning direction X, the sub-scanning direction Y, and the vertical direction Z are described as three mutually orthogonal axes in the drawing, but the arrangement relationship of each component is not necessarily limited to being orthogonal.

[0011] The moving mechanism 3 includes a carriage motor 31 that serves as a drive source for the head unit 20, a carriage guide shaft 32 whose both ends are fixed, and a timing belt 33 that extends substantially parallel to the carriage guide shaft 32 and is driven by the carriage motor 31.

[0012] The head unit 20 includes a carriage 24 and a head 21 mounted on the carriage 24 so as to face the printing medium P. The carriage 24 is supported by the carriage guide shaft 32 so as to be reciprocable and is fixed to a part of the timing belt 33. Therefore, when the timing belt 33 is run forward and backward by the carriage motor 31, the head unit 20 is guided by the carriage guide shaft 32 and reciprocates. The head 21 is for ejecting ink droplets, which are liquid droplets, from a large number of nozzles, and is configured to be supplied with various control signals and the like via a cable 190. The cable 190 may be, for example, a flexible flat cable.

[0013] Figure 2 shows the ink ejection surface, which is the lower surface of the head 21. As shown in Figure 2, the ink ejection surface of the head 21 is provided with four nozzle plates 632 arranged along the main scanning direction X, each having two nozzle rows 650, where a number of nozzles 651 are arranged along the sub-scanning direction Y at a predetermined pitch Py. Between the two nozzle rows 650 provided on each nozzle plate 632, each nozzle 651 is shifted by half a pitch Py in the sub-scanning direction Y. Thus, in this embodiment, the ink ejection surface of the head 21 is provided with eight nozzle rows 650, which are the first nozzle row 650a to the eighth nozzle row 650h.

[0014] Furthermore, as shown in Figure 1, the liquid dispensing device 1 includes a transport mechanism 4 that transports the printing medium P on the platen 40 in the sub-scanning direction Y. The transport mechanism 4 includes a transport motor 41 which is the drive source, and a transport roller 42 which is rotated by the transport motor 41 to transport the printing medium P in the sub-scanning direction Y.

[0015] In this embodiment, the carriage 24 houses four ink cartridges 22, and the ink filled in each ink cartridge 22 is supplied to the print head 21. For example, the four ink cartridges 22 are each filled with cyan, magenta, yellow, and black ink. Alternatively, each ink cartridge 22 may be provided in an ink tank attached to the main body instead of being mounted on the carriage 24, and the ink filled in each ink cartridge 22 may be supplied to the print head 21 via an ink tube.

[0016] When the printing medium P is transported by the transport mechanism 4, the head 21 ejects ink droplets vertically in the Z direction toward the printing medium P, thereby forming an image on the surface of the printing medium P.

[0017] 1-2. Electrical configuration of the liquid dispensing device Figure 3 is a block diagram showing the electrical configuration of the liquid dispensing device 1 according to this embodiment. As shown in Figure 3, the liquid dispensing device 1 comprises a control board 100 and a head unit 20. The control board 100 is fixed in a predetermined location inside the main body of the liquid dispensing device 1 and is connected to the head unit 20 by a cable 190.

[0018] The control board 100 is equipped 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.

[0019] 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.

[0020] Specifically, the control unit 111 generates drive data dA1~dA4 and dB1~dB4, which are digital data that form the basis of drive signals COMA-1~COMA-4 and COMB-1~COMB-4 that drive each ejection section 600 of the head 21, based on various signals from the host computer. Drive data dA1~dA4 is supplied to drive circuits 50a-1~50a-4, respectively, and drive data dB1~dB4 is supplied to drive circuits 50b-1~50b-4, respectively. Drive data dA1~dA4 is digital data that defines the waveforms of drive signals COMA-1~COMA-4, respectively, and drive data dB1~dB4 is digital data that defines the waveforms of drive signals COMB-1~COMB-4, respectively.

[0021] Furthermore, the control unit 111 generates output control signals OEB1 to OEB4. Output control signal OEB1 is a signal that controls whether or not drive signals COMA-1 and COMB-1 are generated and output, and is supplied to drive circuits 50a-1 and 50b-1. Output control signal OEB2 is a signal that controls whether or not drive signals COMA-2 and COMB-2 are generated and output, and is supplied to drive circuits 50a-2 and 50b-2. Output control signal OEB3 is a signal that controls whether or not drive signals COMA-3 and COMB-3 are generated and output, and is supplied to drive circuits 50a-3 and 50b-3. Output control signal OEB4 is a signal that controls whether or not drive signals COMA-4 and COMB-4 are generated and output, and is supplied to drive circuits 50a-4 and 50b-4.

[0022] Furthermore, based on various signals from the host computer, the control unit 111 generates four print data signals SI1 to SI4, a latch signal LAT, a change signal CH, and a clock signal SCK as multiple types of control signals to control the discharge of liquid from each discharge unit 600. The control unit 111 also generates an inspection control signal TSIG to instruct the start and end of detection of residual vibration, which is vibration remaining in the discharge unit 600 after the discharge unit 600 has been driven. The print data signals SI1 to SI4, the latch signal LAT, the change signal CH, the clock signal SCK, and the inspection control signal TSIG are transferred from the control unit 111 to the head unit 20 via cable 190.

[0023] In addition to the above processing, the control unit 111 also determines the scanning position of the head unit 20 and drives the carriage motor 31 based on the scanning position of the head unit 20. This controls the movement of the head unit 20 in the main scanning direction X. The control unit 111 also drives the transport motor 41. This controls the movement of the printing medium P in the sub-scanning direction Y.

[0024] Furthermore, the control unit 111 causes a maintenance mechanism (not shown) to perform cleaning and wiping processes, which are maintenance processes to restore the ink ejection state of the print head 21 to normal.

[0025] The power supply circuit 112 generates a constant high power supply voltage VHV, a constant low power supply voltage VDD, a constant 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, low power supply voltage VDD, offset voltage VBS, and ground voltage GND are transferred from the power supply circuit 112 to the head unit 20 by cable 190. The high power supply voltage VHV, low power supply voltage VDD, and ground voltage GND are also supplied to the drive circuits 50a-1 to 50a-4 and 50b-1 to 50b-4, respectively.

[0026] 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 the drive data dA1 to dA4 and dB1 to dB4, respectively. For example, 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 by performing digital-to-analog conversion of the drive data dA1 to dA4 and dB1 to dB4, followed by Class D amplification. 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.

[0027] The 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 at a low level, and the output becomes high impedance when the output control signal OEB1 is at a high level. Similarly, the 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 at a low level, and the output becomes high impedance when the output control signal OEB1 is at a high level. Similarly, the 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 at a low level, and the output becomes high impedance when the output control signal OEB1 is at a high level. Similarly, when the output control signal OEB1 is at a low level, the drive circuits 50a-4 and 50b-4 generate and output drive signals COMA-4 and COMB-4, respectively, and when the output control signal OEB1 is at a high level, the output becomes high impedance. When the outputs of the 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 are the voltages held immediately before the high impedance due to the capacitive properties of each piezoelectric element 60.

[0028] Note that the drive circuits 50a-1 to 50a-4 and 50b-1 to 50b-4 may have the same circuit configuration, differing only in the input drive data, output control signals, and output drive signals. Details of these will be described later.

[0029] The drive signals COMA-1 to COMA-4 and COMB-1 to COMB-4 are transmitted from the control board 100 to the head unit 20 via cable 190.

[0030] 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.

[0031] The switching circuits 70-1 to 70-4 receive the drive signals COMA-1 to COMA-4, the drive signals COMB-1 to COMB-4, and the print data signals SI1 to SI4, respectively. Additionally, the clock signal SCK, latch signal LAT, change signal CH, and check control signal TSIG are commonly input to the switching circuits 70-1 to 70-4. The switching circuits 70-1 to 70-4 operate using a high power supply voltage VHV, a low power supply voltage VDD, and a ground voltage GND, and output drive signals VOUT to each of the multiple ejection units 600 of the head 21. Specifically, the switching circuit 70-1 selects either the drive signal COMA-1 or the drive signal COMB-1 and outputs it as the drive signal VOUT 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 it outputs a high impedance signal without selecting either. Similarly, switching circuits 70-2 to 70-4 select either drive signals COMA-2 to COMA-4 or drive signals COMB-2 to COMB-4 based on the clock signal SCK, print data signals SI2 to SI4, latch signal LAT, change signal CH, and check control signal TSIG, respectively, and output them as drive signal VOUT, or they do not select any and set the output to high impedance.

[0032] The drive signal VOUT output by switching circuit 70-1 is applied to one end of the piezoelectric element 60 of each discharge unit 600 provided in correspondence with the first nozzle row 650a and the second nozzle row 650b. The drive signal VOUT output by switching circuit 70-2 is applied to one end of the piezoelectric element 60 of each discharge unit 600 provided in correspondence with the third nozzle row 650c and the fourth nozzle row 650d. The drive signal VOUT output by switching circuit 70-3 is applied to one end of the piezoelectric element 60 of each discharge unit 600 provided in correspondence with the fifth nozzle row 650e and the sixth nozzle row 650f. The drive signal VOUT output by switching circuit 70-4 is applied to one end of the piezoelectric element 60 of each discharge unit 600 provided in correspondence with the seventh nozzle row 650g and the eighth nozzle row 650h. An offset voltage VBS is commonly applied to the other end of each piezoelectric element 60. Then, the piezoelectric element 60 is displaced according to the potential difference between the drive signal VOUT and the offset voltage VBS, and an amount of ink corresponding to the displacement is ejected from the nozzle 651. Alternatively, the piezoelectric element 60 is displaced according to the potential difference between the drive signal VOUT and the offset voltage VBS, and residual vibration is generated in the ejection section 600 without ink being ejected from the nozzle 651.

[0033] Furthermore, the switching circuit 70-1 switches whether or not to electrically connect one end of the piezoelectric element 60 of each ejector unit 600, which is provided in correspondence to the first nozzle row 650a or the second nozzle row 650b, to the inspection circuit 80-1, based on the print data signal SI1 and the inspection control signal TSIG. Similarly, the switching circuit 70-2 switches whether or not to electrically connect one end of the piezoelectric element 60 of each ejector unit 600, which is provided in correspondence to the third nozzle row 650c or the fourth nozzle row 650d, to the inspection circuit 80-2, based on the print data signal SI2 and the inspection control signal TSIG. Similarly, the switching circuit 70-3 switches whether or not to electrically connect one end of the piezoelectric element 60 of each ejector unit 600, which is provided in correspondence to the fifth nozzle row 650e or the sixth nozzle row 650f, to the inspection circuit 80-3, based on the print data signal SI3 and the inspection control signal TSIG. Similarly, the switching circuit 70-4 switches whether or not to electrically connect one end of the piezoelectric element 60 of each ejection unit 600, which is provided in correspondence with the seventh nozzle row 650g or the eighth nozzle row 650h, to the inspection circuit 80-4 based on the print data signal SI4 and the inspection control signal TSIG.

[0034] Specifically, switching circuits 70-1 to 70-4 select the ejection unit 600 to be inspected based on the print data signals SI1 to SI4. Hereinafter, the ejection unit 600 to be inspected will be referred to as the "inspected ejection unit 600," and the ejection unit 600 not to be inspected will be referred to as the "non-inspected ejection unit 600." Furthermore, 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 inspected ejection unit 600 to each of the inspection circuits 80-1 to 80-4, and electrically disconnect one end of the piezoelectric element 60 of the non-inspected ejection unit 600 from each of the inspection circuits 80-1 to 80-4. Then, with one end of the piezoelectric element 60 that each of the four discharge units 600 to be inspected has electrically connected to each of the inspection circuits 80-1 to 80-4, the inspection signals PO1 to PO4 that appear at one end of the piezoelectric element 60 that each of the four discharge units 600 to be inspected are input to each of the inspection circuits 80-1 to 80-4.

[0035] Note that the circuit configurations of switching circuits 70-1 to 70-4 may be identical, and the details will be described later.

[0036] The inspection circuits 80-1 to 80-4 operate when they receive the inspection control signal TSIG and the inspection target signals PO1 to PO4, respectively, and are 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 detect the residual vibration of the ejection unit 600 after the application of the drive signal VOUT to the piezoelectric element 60 of the ejection unit 600, based on the inspection target signals PO1 to PO4. Furthermore, based on the residual vibration detection result, the inspection circuits 80-1 to 80-4 determine the ink ejection state of the ejection unit 600 and output the determination result signals RS1 to RS4, respectively. The determination result signals RS1 to RS4 are transferred from the head unit 20 to the control unit 111 via the cable 190.

[0037] Note that the circuit configurations of test circuits 80-1 to 80-4 may be identical, and the details will be described later.

[0038] The control unit 111 performs processing according to the determination result signals RS1 to RS4. For example, if at least one of the determination result signals RS1 to RS4 indicates that a discharge abnormality has occurred in the discharge unit 600, the control unit 111 may display an error message on a display (not shown) provided in the liquid discharge device 1. Alternatively, for example, the control unit 111 may generate a control signal to cause a maintenance mechanism (not shown) to perform maintenance processing, or it may generate print data signals SI1 to SI4 for performing supplementary recording processing to compensate for printing on the print medium P using a discharge unit 600 without a discharge abnormality instead of the discharge unit 600 with a discharge abnormality.

[0039] The temperature sensor 90 operates on a low power supply voltage VDD and a ground voltage GND, detects the temperature of the head 21, and outputs a temperature signal VTEMP indicating the temperature of the head 21. For example, the temperature sensor 90 may be located inside the head 21 or on the outside of the head 21. The temperature signal VTEMP is transmitted from the head unit 20 to the control unit 111 via cable 190.

[0040] The control unit 111 generates drive data dA1~dA4, dB1~dB4 to correct the drive signals COMA-1~COMA-4, COMB-1~COMB-4 based on the temperature signal VTEMP. In this embodiment, the drive signal VOUT for ejecting ink from each ejection unit 600 to print an image based on image data onto the printing medium P is generated based on the drive signals COMA-1~COMA-4. The control unit 111 then modifies the drive data dA1~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 remains constant regardless of temperature. Specifically, the lower the temperature of the ejection unit 600, the higher the viscosity of the ink and the more difficult it becomes for the ink to be ejected from the nozzle 651. Therefore, the control unit 111 generates the drive data dA1~dA4 so that the amplitude of the drive signals COMA-1~COMA-4 increases as the temperature of the ejection unit 600, i.e., the temperature of the head 21 indicated by the temperature signal VTEMP, decreases.

[0041] In this embodiment, the drive circuits 50a-1 to 50a-4 and 50b-1 to 50b-4 constitute a drive signal generation unit 110 that generates drive signal COM-1 consisting of drive signals COMA-1 and COMB-1, drive signal COM-2 consisting of drive signals COMA-2 and COMB-2, drive signal COM-3 consisting of drive signals COMA-3 and COMB-3, and drive signal COM-4 consisting of drive signals COMA-4 and COMB-4. The inspection circuits 80-1 to 80-4 constitute a residual vibration detection unit 120 that detects the residual vibration of the discharge unit 600 after the drive signal COMB is applied to the piezoelectric element 60.

[0042] 1-3. Discharge section configuration Figure 4 shows a schematic configuration corresponding to one discharge section 600 of the head 21. As shown in Figure 4, the head 21 includes the discharge section 600 and a reservoir 641.

[0043] Each ink color has its own reservoir 641, and ink is introduced into the reservoir 641 from the supply port 661. The ink is supplied from the ink cartridge 22 to the supply port 661.

[0044] The ejection unit 600 includes a piezoelectric element 60, a diaphragm 621, a cavity 631, and a nozzle 651. Of these, the diaphragm 621 is displaced by the piezoelectric element 60, which is located on its upper surface in the figure, and functions as a diaphragm that expands / contracts the internal volume of the cavity 631, where the ink is filled. The nozzle 651 is provided on the nozzle plate 632 and is an opening that communicates with the cavity 631. The cavity 631 is filled with liquid 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 in response to the change in the internal volume of the cavity 631. In this way, the ejection unit 600 ejects ink from the nozzle 651 when the piezoelectric element 60 is driven.

[0045] The piezoelectric element 60 shown in Figure 4 has a structure in which a piezoelectric body 601 is sandwiched between a pair of electrodes 611 and 612. In this structure of the piezoelectric body 601, the central part of the piezoelectric body 601, along with the electrodes 611 and 612 and the diaphragm 621, bends vertically relative to the ends in Figure 4, depending on the voltage applied by the electrodes 611 and 612. Specifically, a drive signal VOUT is applied to electrode 611, which is one end of the piezoelectric element 60, and an offset voltage VBS is applied to electrode 612, which is the other end of the piezoelectric element 60. The piezoelectric element 60 is configured to bend upward when the voltage of the drive signal VOUT is low, and downward when the voltage of the drive signal VOUT is high. In this configuration, if it bends upward, the internal volume of the cavity 631 expands, so ink is drawn in from the reservoir 641, while if it bends downward, the internal volume of the cavity 631 shrinks, and depending on the degree of shrinkage, ink is ejected from the nozzle 651.

[0046] Furthermore, the piezoelectric element 60 is not limited to the structure shown in the illustration; any type of piezoelectric element 60 that can be deformed to eject a liquid such as ink is acceptable. Also, the piezoelectric element 60 is not limited to bending vibration; a configuration using so-called longitudinal vibration is also acceptable.

[0047] Furthermore, the piezoelectric element 60 is provided in the head 21 corresponding to the cavity 631 and the nozzle 651, and is also provided corresponding to the selection circuit 230 shown in Figure 7, which will be described later. Therefore, a set of piezoelectric element 60, cavity 631, nozzle 651, and selection circuit 230 is provided for each nozzle 651.

[0048] 1-4. Drive signal configuration In this embodiment, a drive signal COMA-1 is provided to express four gradations—"large dot," "medium dot," "small dot," and "not recorded"—for a single dot using droplets discharged from each nozzle 651 in the first nozzle row 650a or the second nozzle row 650b. The drive signal COMA-1 has a first half pattern and a second half pattern in one cycle. In one cycle, the drive signal COMA-1 is selected according to the gradation to be expressed in the first half or second half and supplied to the piezoelectric element 60 provided corresponding to each nozzle 651. Furthermore, in this embodiment, a drive signal COMB-1 is also provided separately from the drive signal COMA-1 in order to "inspect" the discharge unit 600 to be inspected among the discharge units 600 provided corresponding to the first nozzle row 650a or the second nozzle row 650b. In addition, in this embodiment, drive signals COMA-2 to COMA-4 are provided for the same purpose as drive signal COMA-1, and COMB-2 to COMB-4 are provided for the same purpose as drive signal COMB-1.

[0049] Note that drive signals COMA-1 to COMA-4 have the same basic configuration, although their waveforms differ slightly due to the different types of ink being ejected. Similarly, drive signals COMB-1 to COMB-4 have the same basic configuration, even if their waveforms differ slightly. Therefore, in the following, 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 consisting of drive signals COMA-1 and COMB-1, drive signal COM-2 consisting of drive signals COMA-2 and COMB-2, drive signal COM-3 consisting of drive signals COMA-3 and COMB-3, and drive signal COM-4 consisting of drive signals COMA-4 and COMB-4 will be collectively referred to as drive signal COM.

[0050] Figure 5 shows the waveforms of the drive signals COMA and COMB. As shown in Figure 5, the drive signal COMA is a waveform formed by the succession of two trapezoidal waveforms: Adp1, which is positioned during period T1 from the rising edge of the latch signal LAT pulse to the rising edge of the change signal CH pulse, and Adp2, which is positioned during period T2 from the rising edge of the change signal CH pulse to the rising edge of the next pulse of the latch signal LAT. The period consisting of periods T1 and T2 is called the period Ta, and a new dot is formed on the printing medium P at each period Ta.

[0051] In this embodiment, the trapezoidal waveforms Adp1 and Adp2 are different waveforms from each other. Of these, the trapezoidal waveform Adp1, if supplied to one end of the piezoelectric element 60, is a waveform that causes a predetermined amount, specifically a moderate amount of ink, to be ejected from the nozzle 651 corresponding to the piezoelectric element 60. The trapezoidal waveform Adp2, if supplied to one end of the piezoelectric element 60, is a waveform that causes a smaller amount than the predetermined amount, specifically a small amount of ink, to be ejected from the nozzle 651 corresponding to the piezoelectric element 60.

[0052] The drive signal COMB has a trapezoidal waveform Bdp1 that is arranged over the entire period Ta. The trapezoidal waveform Bdp1 is a waveform that drives the piezoelectric element 60 so that if the trapezoidal waveform Bdp1 were supplied to one end of the piezoelectric element 60, no ink droplets would be ejected from the nozzle 651.

[0053] Note that the voltage at the start and end timings of the trapezoidal waveforms Adp1, Adp2, and Bdp1 are all the same, at voltage Vc. That is, the trapezoidal waveforms Adp1, Adp2, and Bdp1 each start and end at voltage Vc. The control unit 111 generates drive data dA1~dA4, dB1~dB4 such that the voltage Vc increases as the temperature of the discharge unit 600, i.e., the temperature of the head 21 indicated by the temperature signal VTEMP, decreases.

[0054] Each ejection unit 600 ejects ink when a piezoelectric element 60 is driven by a drive signal COM, which consists of drive signals COMA and COMB. In this embodiment, a drive signal VOUT, which includes a drive waveform selected from a plurality of drive waveforms, namely trapezoidal waveforms Adp1, Adp2, and Bdp1, included in the drive signal COM, is applied to the piezoelectric element 60.

[0055] Figure 6 shows the waveforms of the drive signal VOUT corresponding to "large dot," "medium dot," "small dot," "no recording," and "inspection."

[0056] As shown in Figure 6, the drive signal VOUT corresponding to the "large dot" has a waveform that is a continuation of the trapezoidal waveform Adp1 of the drive signal COMA during period T1 and the trapezoidal waveform Adp2 of the drive signal COMA during period T2. When this drive signal VOUT is supplied to one end of the piezoelectric element 60, a medium and a small amount of ink are ejected in two separate bursts from the nozzle 651 corresponding to the piezoelectric element 60 during period Ta. As a result, the inks land on the printing medium P and combine to form a large dot.

[0057] The drive signal VOUT corresponding to the "medium dot" is Adp1, a trapezoidal waveform of the drive signal COMA, during period T1, and during period T2, it becomes high impedance, so it is the voltage Vc that was held immediately before due to the capacitive properties of the piezoelectric element 60. When this drive signal VOUT is supplied to one end of the piezoelectric element 60, during period Ta, a moderate amount of ink is ejected from the nozzle 651 corresponding to the piezoelectric element 60, but only during period T1. As a result, this ink lands on the printing medium P, forming a medium dot.

[0058] The drive signal VOUT corresponding to the "small dot" is high impedance during period T1, and is therefore the voltage Vc held immediately before due to the capacitive properties of the piezoelectric element 60. During period T2, it becomes the trapezoidal waveform Adp2 of the drive signal COMA. When this drive signal VOUT is supplied to one end of the piezoelectric element 60, a small amount of ink is ejected from the nozzle 651 corresponding to the piezoelectric element 60 during period Ta, but only during period T2. As a result, this ink lands on the printing medium P, forming small dots.

[0059] The drive signal VOUT, corresponding to "non-recording," is high impedance during periods T1 and T2, and is therefore the voltage Vc immediately preceding the period held by the capacitive properties of the piezoelectric element 60. When this drive signal VOUT is supplied to one end of the piezoelectric element 60, ink is not ejected from the nozzle 651 corresponding to that piezoelectric element 60 during period Ta. As a result, no ink lands on the printing medium P, and no dots are formed.

[0060] The drive signal VOUT corresponding to "inspection" is a trapezoidal waveform Bdp1 of the drive signal COMB during periods TS1 and TS3, and is 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 that instructs the start of residual vibration detection for each discharge unit 600 by the inspection circuits 80-1 to 80-4, and has a first pulse PL1 that defines the start timing of residual vibration detection in period Ta. The inspection control signal TSIG is also a signal that instructs the end of residual vibration detection for each discharge unit 600 by the inspection circuits 80-1 to 80-4, and has a second pulse PL2 that defines the end timing of residual vibration detection in period Ta. The period Ta is then divided into three parts: TS1, the period from the rising edge of the latch signal LAT pulse to the rising edge of the first pulse PL1; TS2, the period from the rising edge of the first pulse PL1 to the rising edge of the second pulse PL2; and TS3, the period from the rising edge of the second pulse PL2 to the rising edge of the next pulse of the latch signal LAT.

[0061] When a test drive signal VOUT is supplied to one end of the piezoelectric element 60, the discharge unit 600 having the piezoelectric element 60 rapidly expands its cavity 631 in period TS1 as the potential of the drive signal VOUT increases, and then rapidly contracts as the potential of the drive signal VOUT decreases. After that, when the potential of the drive signal VOUT stops rising and reaches a constant potential, the cavity 631 returns to its original volume while repeatedly expanding and contracting. At this time, residual vibrations that decay over time are generated in the cavity 631 and applied to the piezoelectric element 60. The electromotive force of the piezoelectric element 60 changes according to these residual vibrations, and a residual vibration waveform appears in the drive signal VOUT in period TS2. As will be described in detail later, in this embodiment, the discharge state of the discharge unit 600 to be inspected is determined in the test circuits 80-1 to 80-4 based on the residual vibration waveform that appears in the drive signal VOUT.

[0062] In this embodiment, in each cycle Ta, it is possible to perform either or both of the following: a printing process that supplies a drive signal VOUT for "large dot," "medium dot," "small dot," or "not recorded" to each discharge unit 600, and an inspection process that supplies a drive signal VOUT for "inspection" and determines the discharge state. The liquid discharge device 1 forms an image on the printing medium P according to the image data by repeatedly performing the printing process over a plurality of continuous or intermittent cycles Ta.

[0063] For example, for each of these multiple periods Ta, one of the ejection units 600 that is supplied with a drive signal VOUT for "non-recording" in the printing process may be instead supplied with a drive signal VOUT for "inspection". In this embodiment, since the liquid ejection device 1 has four inspection circuits 80-1 to 80-4, when forming an image on the printing medium P corresponding to the image data over M periods Ta, it is possible to perform inspection processing on up to M × 4 ejection units 600 in parallel with the printing process.

[0064] Furthermore, the inspection process may be performed during periods when printing is not required, such as the period between the end of printing one page and the start of printing the next page in the case of multi-page printing, or it may be performed separately from the printing process when inspection mode is set.

[0065] Note that the drive signals COMA and COMB shown in Figure 5 are merely examples. In practice, various combinations of pre-prepared waveforms are used depending on the movement speed of the head unit 20, the printing medium P, the structure of the ejection unit 600, the viscosity of the ink, etc.

[0066] Furthermore, although this explanation describes an example where the piezoelectric element 60 bends upward as the voltage decreases, if the voltage supplied to electrodes 611 and 612 is reversed, the piezoelectric element 60 will bend downward as the voltage decreases. Therefore, in a configuration where the piezoelectric element 60 bends downward as the voltage decreases, the drive signals COMA and COMB exemplified in Figure 5 will have waveforms that are inverted with respect to the voltage Vc.

[0067] 1-5. Configuration of the switching circuit Next, the configuration of the switching circuit 70 will be described. Figure 7 shows the configuration of the switching circuit 70. In the following description, print data signals SI1 to SI4 will be referred to as print 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. As shown in Figure 7, the switching circuit 70 includes a selection control unit 220 and a plurality of selection circuits 230.

[0068] 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 an inspection control signal TSIG. In the selection control unit 220, a set of a shift register 222, a latch circuit 224, and a decoder 226 is provided corresponding to each piezoelectric element 60. That is, the number of sets of shift registers 222, latch circuits 224, and decoders 226 in one switching circuit 70 is the same as the total number of nozzles 651 included in the two nozzle rows 650, m.

[0069] The print data signal SI is a 3m-bit signal containing 3 bits of print data (SIH, SIM, SIL) for each of the m ejection units 600 to select one of the following: "large dot", "medium dot", "small dot", "not recorded", and "inspect".

[0070] The print data signal SI is a signal synchronized with the clock signal SCK, and the shift register 222 is configured to temporarily hold each 3 bits of print data (SIH, SIM, SIL) contained in the print data signal SI, corresponding to the nozzle 651.

[0071] In detail, the configuration consists of shift registers 222 with a number of stages corresponding to the piezoelectric element 60, connected in cascaded order, and the print data signal SI supplied serially is sequentially transferred to the subsequent stages according to the clock signal SCK.

[0072] To distinguish between the shift registers 222, they are labeled as stage 1, stage 2, ..., m, starting from the upstream side where the print data signal SI is supplied.

[0073] Each of the m latch circuits 224 latches the 3-bit print data (SIH, SIM, SIL) held in each of the m shift registers 222 on the rising edge of the latch signal LAT.

[0074] Each of the m decoders 226 decodes the 3-bit print data (SIH, SIM, SIL) latched by each of the m latch circuits 224, outputs a selection signal Sa for each period T1, T2 defined by the latch signal LAT and the change signal CH, and outputs selection signals Sb, Sc for each period TS1, TS2, TS3 defined by the latch signal LAT and the check control signal TSIG, thereby defining the selection in the selection circuit 230.

[0075] Figure 8 shows the decoding process in decoder 226. As shown in Figure 8, if the latched 3-bit print data (SIH, SIM, SIL) indicates a "large dot" (1,1,0), decoder 226 outputs the logic level of selection signal Sa as high in either period T1 or T2, and outputs the logic levels of selection signals Sb and Sc as low in either period TS1, TS2, or TS3.

[0076] Furthermore, if the 3-bit print data (SIH, SIM, SIL) indicates a "middle dot" (1,0,0), the decoder 226 outputs the logic level of the selection signal Sa as a high level during period T1 and as a low level during period T2, and outputs the logic levels of the selection signals Sb and Sc as low levels during any of periods TS1, TS2, and TS3.

[0077] Furthermore, if the 3-bit print data (SIH, SIM, SIL) indicates a "small dot" (0,1,0), the decoder 226 outputs the logic level of the selection signal Sa as a low level during period T1 and as a high level during period T2, and outputs the logic levels of the selection signals Sb and Sc as a low level during any of periods TS1, TS2, or TS3.

[0078] Furthermore, if the 3-bit print data (SIH, SIM, SIL) indicates "not recorded" (0,0,0), the decoder 226 outputs the logic level of the selection signal Sa as a low level during either period T1 or T2, and outputs the logic levels of the selection signals Sb and Sc as a low level during either period TS1, TS2, or TS3.

[0079] Furthermore, if the 3-bit print data (SIH, SIM, SIL) indicates "inspection" (1,1,1), the decoder 226 outputs the logic level of the selection signal Sa as low in both periods T1 and T2, the logic level of the selection signal Sb as high in periods TS1 and TS3 and as low in period TS2, and the logic level of the selection signal Sc as low in periods TS1 and TS3 and as high in period TS2.

[0080] A selection circuit 230 is provided corresponding to each piezoelectric element 60. That is, the number of selection circuits 230 in one switching circuit 70 is the same as the total number m of nozzles 651 included in the two nozzle rows 650.

[0081] Figure 9 shows the configuration of the selection circuit 230 corresponding to one piezoelectric element 60.

[0082] As shown in Figure 9, the selection circuit 230 includes logic inverting circuits 232a, 232b, 232c, transfer gates 234a, 234b, 234c, and level shift circuits 236a, 236b, 236c.

[0083] The selection signal Sa from decoder 226 is a low logic amplitude signal and is level-shifted by level-shift circuit 236a to a high logic amplitude selection signal sax. Similarly, the selection signal Sb is a low logic amplitude signal and is level-shifted by level-shift circuit 236b to a high logic amplitude selection signal sbx. Likewise, the selection signal Sc is a low logic amplitude signal and is level-shifted by level-shift circuit 236c to a high logic amplitude selection signal scx. As an example, the low logic amplitude ranges from 0V at the low level to 3.3V at the high level, and the high logic amplitude ranges from 0V at the low level to 42V at the high level.

[0084] The selection signal Sax from the level shift circuit 236a is supplied to the positive control terminal of the transfer gate 234a, while being logically inverted by the logic inverter circuit 232a and supplied to the negative control terminal of the transfer gate 234a. Similarly, the selection signal Sbx from the level shift circuit 236b is supplied to the positive control terminal of the transfer gate 234b, while being logically inverted by the logic inverter circuit 232b and supplied to the negative control terminal of the transfer gate 234b. Similarly, the selection signal Scx from the level shift circuit 236c is supplied to the positive control terminal of the transfer gate 234c, while being logically inverted by the logic inverter circuit 232c and supplied to the negative control terminal of the transfer gate 234c.

[0085] A drive signal COMA is supplied to the input terminal of transfer gate 234a, and a drive signal COMB is supplied to the input terminal of transfer gate 234b. The output terminals of transfer gates 234a and 234b are connected in common to one end of the piezoelectric element 60 of the discharge unit 600.

[0086] Furthermore, the input terminal of the transfer gate 234c is connected to one end of the piezoelectric element 60 of the discharge unit 600, along with the output terminals of the transfer gates 234a and 234b. As shown in Figure 7, the output terminal of the transfer gate 234c is commonly connected to the output terminals of the transfer gates 234c of all other selection circuits 230 of the switching circuit 70.

[0087] Transfer gate 234a conducts between its input and output terminals when the selection signal Sax is high level, and deconducts between its input and output terminals when the selection signal Sax is low level. Hereafter, conduction will be referred to as "on" and deconduction as "off". Similarly, transfer gates 234b and 234c switch between their input and output terminals depending on the selection signals Sbx and Scx.

[0088] When transfer gate 234a is turned on, the drive signal COMA is supplied to one end of the piezoelectric element 60 as the drive signal VOUT. When transfer gate 234b is turned on, the drive signal COMB is supplied to the other end of the piezoelectric element 60 as the drive signal VOUT. When transfer gate 234c is turned on, the inspection target signal PO, which has a waveform based on residual vibration generated in the discharge section 600, is output to the inspection circuit 80.

[0089] As described above, the logic levels of the selection signals Sa, Sb, and Sc are determined based on each print data (SIH, SIM, SIL) included in the print data signal SI, and the drive signal VOUT output from the selection circuit 230 is the voltage of one of the drive waveforms shown in Figure 6. That is, the selection circuit 230 performs a selection operation based on the print data signal SI to select whether or not to apply the voltages of each of the trapezoidal waveforms Adp1, Adp2, and Bdp1, which are multiple drive waveforms included in the drive signal COM consisting of drive signals COMA and COMB, to the piezoelectric element 60. Specifically, according to the selection signal Sa, the selection circuit 230 selects whether or not to apply the voltage of the trapezoidal waveform Adp1 to the piezoelectric element 60 during period T1, and selects whether or not to apply the voltage of the trapezoidal waveform Adp2 to the piezoelectric element 60 during period T2. The transition from period T1 to period T2 is performed by the change signal CH, so the change signal CH is a signal for switching the selection operation of the selection circuit 230.

[0090] 1-6. Drive Circuit Configuration Next, the drive circuit 50 will be described. In the following, 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.

[0091] Figure 10 shows the circuit configuration of the drive circuit 50. As shown in Figure 10, 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.

[0092] The integrated circuit device 500 outputs an amplification control signal as a gate signal to the first transistor M1 and the second transistor M2, respectively, based on k-bit drive data dA or dB input via terminals In1 to Ink. Therefore, the integrated circuit device 500 includes a DAC 511, an adder 512, an adder 513, a comparator 514, a logic inverter circuit 515, an integrating attenuator 516, an attenuator 517, a first gate driver 521, a second gate driver 522, a boost circuit 540, and a reference voltage generation unit 580. DAC stands for Digital to Analog Converter.

[0093] The reference voltage generation unit 580 generates a first reference voltage DAC_HV, which is the high-voltage side reference voltage, and a second reference voltage DAC_LV, which is the low-voltage side reference voltage, and supplies them to the DAC 511.

[0094] The DAC511 converts k-bit drive data dA or drive data dB, which defines the waveform of the drive signal COMA, into a raw 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 terminal (+) of the adder 512. The voltage amplitude of this raw drive signal Aa is determined by the maximum and minimum values ​​of the first reference voltage DAC_HV and the second reference voltage DAC_LV, respectively, and the amplified version of this voltage becomes the drive signal COMA or drive signal COMB. In other words, the raw drive signal Aa is the target signal before amplification of the drive signal COMA or drive signal COMB. As an example, the voltage amplitude of the raw drive signal Aa is approximately 1 to 2V.

[0095] The integrating attenuator 516 attenuates the voltage at terminal Out, i.e., the drive signal COMA, which is input via terminal Vfb, and integrates it, then supplies it to the input terminal (-) of the adder 512.

[0096] Adder 512 supplies a signal Ab, which is the voltage obtained by subtracting the voltage at the input terminal (-) from the voltage at the input terminal (+) and integrating the results, to the input terminal (+) of adder 513.

[0097] The power supply voltage for the circuit from DAC511 to logic inverter circuit 515 is the low power supply voltage VDD supplied from the power supply circuit 112 shown in Figure 4, which is, for example, a low amplitude 3.3V. Therefore, while the voltage of the original drive signal Aa is at most about 2V, the voltage of the drive signal COMA can exceed 40V at its maximum. To match the amplitude ranges of both voltages when calculating the deviation, the voltage of the drive signal COMA is attenuated by the integrating attenuator 516.

[0098] The attenuator 517 attenuates the high-frequency components of the drive signal COMA input via terminal Ifb and supplies them to the input terminal (-) of the adder 513. The adder 513 supplies a signal As, which is the voltage obtained by subtracting the voltage at the input terminal (-) from the voltage at the input terminal (+), to the comparator 514. The function of the attenuator 517 is to adjust the modulation gain, i.e., the sensitivity. That is, the frequency and duty cycle of the modulation signal Ms change in accordance with the drive data dA or drive data dB, and the attenuator 517 adjusts the amount of these changes.

[0099] The voltage of signal As output from adder 513 is the voltage obtained by subtracting the attenuation voltage of the signal supplied to terminal Vfb from the voltage of the original drive signal Aa, and then subtracting the attenuation voltage of the signal supplied to terminal Ifb. Therefore, the voltage of signal As from adder 513 can be described as a signal obtained by correcting the deviation obtained by subtracting the attenuation voltage of drive signal COMA or drive signal COMB output from terminal Out from the target voltage of the original drive signal Aa, with the high-frequency component of said drive signal COMA or drive signal COMB.

[0100] The comparator 514 outputs a pulse-modulated signal Ms based on the subtraction voltage from the adder 513, as follows: Specifically, the comparator 514 outputs a modulated signal Ms that becomes high level when the signal As output from the adder 513 is above the voltage threshold Vt1 if the voltage is rising, and low level when the signal As is below the voltage threshold Vt2 if the voltage is falling. As will be described later, the voltage thresholds are set in the relationship Vth1 > Vth2.

[0101] The modulated signal Ms from comparator 514 is supplied to the second gate driver 522 after being logically inverted by logic inverter circuit 515. On the other hand, the first gate driver 521 is supplied with the modulated signal Ms without undergoing logic inversion. Therefore, the logic levels supplied to the first gate driver 521 and the second gate driver 522 are mutually exclusive.

[0102] The logic levels supplied to the first gate driver 521 and the second gate driver 522 may be time-controlled so that they are not simultaneously high, i.e., so that the first transistor M1 and the second transistor M2 are not turned on at the same time.

[0103] By the way, the modulated signal referred to here is, in a narrow sense, the modulated signal Ms, but if we consider it as a signal pulse-modulated according to the original drive signal Aa, then the negative signal of the modulated signal Ms is also included in the modulated signal. In other words, the modulated signal pulse-modulated according to the original drive signal Aa includes not only the modulated signal Ms, but also the inverted logic level of the modulated signal Ms, and a timing-controlled version of it.

[0104] The adder 512, adder 513, comparator 514, logic inverter circuit 515, integral attenuator 516, and attenuator 517 function as a modulation unit 510 that modulates the original drive signal Aa to generate the modulated signal Ms.

[0105] The first gate driver 521 level-shifts the low logic amplitude output signal of the comparator 514 to a high logic amplitude and outputs it from terminal Hdr. Of the power supply voltage of the first gate driver 521, the high-voltage side is the voltage applied via terminal Bst, and the low-voltage side is the voltage applied via terminal Sw. Terminal Bst is connected to one end of capacitor C5 and the cathode electrode of diode D1 for reverse current prevention. Terminal Sw is connected to the source electrode of the first transistor M1, the drain electrode of the second transistor M2, the other end of capacitor C5, and one end of inductor L1. The anode electrode of diode D1 is connected to terminal Gvd, and the voltage Vm output by the boost circuit 540 is applied to it. Therefore, the potential difference between terminal Bst and terminal Sw is approximately equal to the potential difference across capacitor C5, i.e., the voltage Vm. As an example, the voltage Vm is 7.5V.

[0106] The second gate driver 522 operates at a lower potential than the first gate driver 521. The second gate driver 522 level-shifts the low logic amplitude output signal of the logic inverter circuit 515 to a high logic amplitude and outputs it from terminal Ldr. For example, the low logic amplitude has a low level of 0V and a high level of 3.3V, while the high logic amplitude has a low level of 0V and a high level of 7.5V. Of the power supply voltage of the second gate driver 522, voltage Vm is applied as the high-side voltage, and ground voltage GND supplied from the power supply circuit 112 via the ground terminal Gnd is applied as the low-side voltage. That is, the ground terminal Gnd is grounded.

[0107] The first transistor M1 and the second transistor M2 are, for example, N-channel type FETs. FET stands for Field Effect Transistor. In the high-side first transistor M1, a high power supply voltage VHV supplied from the power supply circuit 112 is applied to the drain electrode, and the gate electrode is connected to terminal Hdr via resistor R1. For the low-side second transistor M2, the gate electrode is connected to terminal Ldr via resistor R2, and the source electrode is grounded.

[0108] Therefore, when the first transistor M1 is off and the second transistor M2 is on, the voltage at terminal Sw is 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, the high power supply voltage VHV is applied to terminal Sw, and a voltage VHV + Vm is applied to terminal Bst.

[0109] In other words, the first gate driver 521 uses capacitor C5 as a floating power supply, and in accordance with the operation of the first transistor M1 and the second transistor M2, the potential of terminal Sw, which is the reference potential, changes to 0V or the high power supply voltage VHV. Therefore, it outputs an amplification control signal where the low level is near 0V and the high level is near voltage Vm, or where the low level is near the high power supply voltage VHV and the high level is near voltage VHV+Vm. In contrast, the second gate driver 522, regardless of the operation of the first transistor M1 and the second transistor M2, has the potential of the ground terminal Gnd, which is the reference potential, fixed at 0V. Therefore, it outputs an amplification control signal where the low level is near 0V and the high level is near voltage Vm.

[0110] The first gate driver 521 and the second gate driver 522 function as a gate driver 520 that generates an amplification control signal based on the modulation signal Ms. Furthermore, the first transistor M1 and the second transistor M2 function as an amplification circuit that generates an amplified modulation signal by amplifying the modulation signal Ms.

[0111] The other end of inductor L1 is terminal Out, which is the output terminal of this drive circuit 50, and drive signals COMA or COMB are supplied from terminal Out to each of the selection circuits 230.

[0112] Terminal Out is connected to one end of capacitor C1, one end of capacitor C2, and one end of resistor R3, respectively. Of these, the other end of capacitor C1 is grounded. 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 between the first transistor M1 and the second transistor M2 to generate a drive signal.

[0113] The other end of resistor R3 is connected to terminal Vfb and one end of resistor R4, and a voltage Vh is applied to the other end of resistor R4. As a result, the drive signal COMA or drive signal COMB, which has passed through the first feedback circuit 570 consisting of resistors R3 and R4 from terminal Out, is pulled up and fed back to terminal Vfb.

[0114] On the other hand, the other end of capacitor C2 is connected to one end of resistor R5 and one end of resistor R6. Of these, the other end of resistor R5 is grounded. Therefore, capacitor C2 and resistor R5 function as a high-pass filter that allows high-frequency components above the cutoff frequency contained in the drive signal COMA or drive signal COMB from terminal Out to pass through. The cutoff frequency of the high-pass filter is set to approximately 9MHz, for example.

[0115] Furthermore, the other end of resistor R6 is connected to one end of capacitor C4 and one end of capacitor C3. Of these, the other end of capacitor C3 is grounded. Therefore, resistor R6 and capacitor C3 function as a low-pass filter that allows low-frequency components below the cutoff frequency to pass through the signal components that have passed through the high-pass filter. The cutoff frequency of the LPF is set to approximately 160 MHz, for example.

[0116] Since the cutoff frequency of the high-pass filter is set lower than the cutoff frequency of the low-pass filter, the high-pass filter and the low-pass filter function as a band-pass filter that allows high-frequency components in a predetermined frequency range included in the drive signal COMA or drive signal COMB to pass through.

[0117] The other end of capacitor C4 is connected to terminal Ifb of the integrated circuit device 500. As a result, the DC component of the high-frequency components of the drive signal COMA or drive signal COMB, which has passed through the second feedback circuit 572 consisting of capacitor C2, resistor R5, resistor R6, capacitor C3, and capacitor C4 and functions as a bandpass filter, is cut off and fed back to terminal Ifb.

[0118] Incidentally, the drive signal COMA or drive signal COMB output from terminal Out is a signal obtained by smoothing the amplified modulated signal at terminal Sw, which is the connection point between the first transistor M1 and the second transistor M2, with a low-pass filter consisting of inductor L1 and capacitor C1. The drive signal COMA or drive signal COMB is integrated and subtracted via terminal Vfb and then fed back to adder 512, so it self-oscillates at a frequency determined by the feedback delay, which is the sum of the delay due to smoothing by inductor L1 and capacitor C1 and the delay due to integral attenuator 516, and the feedback transfer function.

[0119] However, due to the large delay in the feedback path via terminal Vfb, it may not be possible to raise the self-oscillation frequency high enough to ensure sufficient accuracy of the drive signal COMA or drive signal COMB using only feedback via terminal Vfb.

[0120] Therefore, in this embodiment, in addition to the path via terminal Vfb, a path is provided via terminal Ifb to feed back the high-frequency component of the drive signal COMA or drive signal COMB, thereby reducing the overall delay of the circuit. As a result, the frequency of signal As, obtained by adding the high-frequency component of the drive signal COMA to signal Ab, becomes high enough to ensure sufficient accuracy of the drive signal COMA or drive signal COMB compared to the case where the path via terminal Ifb does not exist.

[0121] Figure 11 shows the waveforms of signal As and modulated signal Ms in relation to the waveform of the original drive signal Aa.

[0122] As shown in Figure 11, signal As is a triangular wave, and its oscillation frequency varies depending on the voltage of the original drive signal Aa. Specifically, it is highest when the voltage of the original drive signal Aa is at its midpoint, and decreases as the voltage of the original drive signal Aa rises or falls from its midpoint.

[0123] Furthermore, in signal As, the slope of the triangular wave is approximately equal between the rising and falling voltages when the voltage of the original drive signal Aa is near the midpoint. Therefore, the duty cycle of the modulated signal Ms, which is obtained by comparing signal As with voltage thresholds Vt1 and Vt2 using comparator 514, is approximately 50%. As the voltage of the original drive signal Aa rises above the midpoint, the downward slope of signal As becomes gentler. As a result, the period during which the modulated signal Ms is at a high level becomes relatively longer, and the duty cycle increases. On the other hand, as the voltage of the original drive signal Aa falls below the midpoint, the upward slope of signal As becomes gentler. As a result, the period during which the modulated signal Ms is at a high level becomes relatively shorter, and the duty cycle decreases.

[0124] Therefore, the modulated signal Ms becomes a pulse density modulated signal as follows: The duty cycle of the modulated signal Ms is approximately 50% at the midpoint of the voltage of the original drive signal Aa, increases as the voltage of the original drive signal Aa rises above the midpoint, and decreases as the voltage of the original drive signal Aa falls below the midpoint.

[0125] The first gate driver 521 turns the first transistor M1 on or off based on the modulation signal Ms. That is, the first gate driver 521 turns the first transistor M1 on if the modulation signal Ms is high level, and turns it off if the modulation signal Ms is low level. The second gate driver 522 turns the second transistor M2 on or off based on the logic inversion signal of the modulation signal Ms. That is, the second gate driver 522 turns the second transistor M2 off if the modulation signal Ms is high level, and turns it on if the modulation signal Ms is low level.

[0126] Therefore, the voltage of the drive signal COMA or drive signal COMB, which is obtained by smoothing the amplified modulated signal at the connection point of the first transistor M1 and the second transistor M2 with inductor L1 and capacitor C1, increases as the duty cycle of the modulated signal Ms increases and decreases as the duty cycle decreases. As a result, the drive signal COMA or drive signal COMB is controlled to become a signal that is an amplified version of the original drive signal Aa, and is output accordingly.

[0127] This drive circuit 50 uses pulse density modulation, which has the advantage of allowing for a larger range of change in the duty cycle compared to pulse width modulation with a fixed modulation frequency.

[0128] In other words, the minimum positive and negative pulse widths that can be handled by the entire circuit are constrained by the circuit characteristics, so in fixed-frequency pulse width modulation, only a predetermined range of duty cycle variation, for example, from 10% to 90%, can be secured. In contrast, in pulse density modulation, as the voltage of the original drive signal Aa moves away from the midpoint, the oscillation frequency decreases, so the duty cycle can be made larger in the region where the voltage of the original drive signal Aa is high, and smaller in the region where the voltage of the original drive signal Aa is low. For this reason, in self-oscillating pulse density modulation, a wider range of duty cycle variation can be secured, for example, from 5% to 95%.

[0129] Furthermore, the drive circuit 50 includes a signal path through which the drive signal COMA or drive signal COMB, the modulation signal Ms, and the amplified modulation signal propagate, and is a self-oscillating circuit, eliminating the need for a circuit to generate a high-frequency carrier wave, as is the case with externally excited oscillation. This has the advantage of facilitating integration of parts other than the high-voltage handling circuit, i.e., the integrated circuit device 500.

[0130] In addition, the drive circuit 50 has a feedback path for the drive signal COMA or drive signal COMB that goes not only through terminal Vfb but also through terminal Ifb to feed back the high-frequency component, thus reducing the overall delay of the circuit. As a result, the self-oscillation frequency increases, enabling the drive circuit 50 to generate the drive signal COMA or drive signal COMB with high accuracy.

[0131] Furthermore, the first gate driver 521 and the second gate driver 522 turn on / off the first transistor M1 and the second transistor M2, respectively, according to the logic level of the modulation signal Ms, when the output control signal OEB input from terminal oeb of the integrated circuit device 500 is at a low level. As a result, the drive circuit 50 performs self-oscillating operation, and the drive signal COMA or drive signal COMB is output from terminal Out.

[0132] On the other hand, when the output control signal OEB is at a high level, 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, terminal Out becomes high impedance, and the drive signal COMA or drive signal COMB becomes the voltage held immediately before by the capacitive properties of the piezoelectric element 60. Therefore, the control unit 111 may set the output control signal OEB to a high level for a period of time when the voltage of the drive signal COMA or drive signal COMB is constant, for example, during the period of voltage Vc, to stop the self-oscillating operation of the drive circuit 50. Thus, by providing a period during which the output control signal OEB is at a high level, 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.

[0133] Returning to Figure 10, in the example shown in Figure 10, resistors R1 and R2, the first transistor M1, the 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 amplification control signal and outputs it to a piezoelectric element 60, which is a capacitive load.

[0134] The boost circuit 540 supplies power to the gate driver 520. In the example shown in Figure 10, the boost circuit 540 boosts the low power supply voltage VDD supplied from the power supply terminal Vdd, using the ground voltage GND of the ground terminal Gnd as a reference, to generate a voltage Vm, which becomes the high-potential power supply voltage of the second gate driver 522. The boost circuit 540 can be configured as a charge pump circuit or a switching regulator, but configuring it as a charge pump circuit suppresses noise generation more effectively than configuring it as a switching regulator. As a result, the drive circuit 50 can generate the drive signal COMA or drive signal COMB with greater accuracy, and the voltage applied to the piezoelectric element 60 can be controlled with high precision, thereby improving the liquid discharge accuracy. Furthermore, by configuring the power supply generation section of the gate driver 520 as a charge pump circuit, it has been miniaturized and can be mounted on the integrated circuit device 500. Compared to the case where the power supply generation section of the gate driver 520 is configured outside the integrated circuit device 500, the overall circuit area of ​​the drive circuit 50 can be significantly reduced. The boost circuit 540 may also be included in the power supply circuit 112 shown in Figure 3.

[0135] The drive circuit 50 configured in this way generates a drive signal COMA or drive signal COMB by performing a digital-to-analog conversion of drive data dA or drive data dB, followed by a Class D amplification. Here, the drive data dA and dB only need to define the waveforms of the drive signals COMA and COMB, and may be analog signals. Furthermore, the drive circuit 50 only needs to amplify the signal waveform defined by the drive data dA or drive data dB and output a drive signal COMA or drive signal COMB. Therefore, the drive circuit 50 may generate a drive signal COMA or drive signal COMB by performing a Class A, Class B, or Class AB amplification on the signal waveform defined by the drive data dA or drive data dB.

[0136] 1-7. Configuration of the test circuit Next, the configuration of the inspection circuit 80 will be described. In the following, 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.

[0137] Figure 12 shows the configuration of the inspection circuit 80. As shown in Figure 12, the inspection circuit 80 includes a waveform shaping unit 81, a measurement unit 82, and a determination unit 83.

[0138] The waveform shaping unit 81 removes noise components from the signal PO under inspection using a low-pass filter or a band-pass filter, and outputs a residual vibration signal NVT, which is obtained by amplifying the amplitude of the signal PO under inspection using an operational amplifier and resistors.

[0139] The measurement unit 82 receives the residual vibration signal NVT output by the waveform shaping unit 81 and measures the period, amplitude, etc. of the residual vibration signal NVT during the period TS2 specified by the inspection control signal TSIG.

[0140] The determination unit 83 determines the discharge state of the discharge unit 600 under inspection 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 representing the determination result. The determination result signal RS may be a signal indicating whether or not there is a discharge abnormality, or it may be a signal that includes information determining the cause of the discharge abnormality.

[0141] Figure 13 is a timing chart illustrating the operation of the measurement unit 82. As shown in Figure 13, when period TS2 begins and the supply of the residual vibration signal NVT begins, the measurement unit 82 compares the residual vibration signal NVT with the threshold potential Vth2, which is the potential at the amplitude center level of the residual vibration signal NVT, 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. The measurement unit 82 then generates a comparison signal Cmp1 which is high level when the potential of the residual vibration signal NVT is equal to or higher than the threshold potential Vth1, a comparison signal Cmp2 which is high level when the potential of the residual vibration signal NVT is equal to the threshold potential Vth2, and a comparison signal Cmp3 which is high level when the potential of the residual vibration signal NVT is less than the threshold potential Vth3.

[0142] The measurement unit 82 then measures the time Tp from time t1, when the comparison signal Cmp2 first falls to a low level and then rises to a high level, after the start time t0 of the period TS2, until time t2, when the comparison signal Cmp2 next falls to a low level and then rises to a high level.

[0143] 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.

[0144] Furthermore, if the amplitude of the residual vibration signal NVT is small, it is assumed that there is an abnormality in the ejection unit 600 being inspected, such as the cavity 631 not being filled with ink. Therefore, the measurement unit 82 sets the amplitude determination value Ap to "1" if, during the period from time t1 to time t2, the potential of the residual vibration signal NVT is equal to or greater than the threshold potential Vth1 and the comparison signal Cmp1 becomes high level, and during the period from time t1 to time t2, the potential of the residual vibration signal NVT is less than the threshold potential Vth3 and the comparison signal Cmp3 becomes high level; otherwise, the amplitude determination value Ap is set to "0".

[0145] Even though the ejection unit 600 has performed an operation to eject ink droplets, the nozzle 651 does not eject ink droplets properly, i.e., an ejection abnormality occurs, and the causes include (1) the inclusion of air bubbles in the cavity 631, (2) the viscosity of the ink in the cavity 631 due to drying of the ink in the cavity 631, and (3) the adhesion of foreign matter such as paper dust near the exit of the nozzle 651.

[0146] First, if air bubbles are introduced into the cavity 631, the total weight of ink filling the cavity 631 decreases, which is thought to lower the inertance. Also, if air bubbles are attached near the nozzle 651, the diameter of the nozzle 651 is considered to have increased by the size of the air bubbles, which is thought to lower the acoustic resistance. Therefore, if an abnormal ejection occurs due to air bubbles being introduced into the cavity 631, the frequency of residual vibration will be higher compared to when the ejection state is normal. As a result, time Tp will be smaller than the predetermined threshold time Tth2.

[0147] Next, if the ink near nozzle 651 dries and thickens, the ink in cavity 631 becomes trapped within the cavity 631. In such a case, it is thought that the acoustic resistance increases. Therefore, when the ink near nozzle 651 in cavity 631 thickens, the frequency of residual vibration becomes lower compared to when the ejection state is normal. As a result, time Tp becomes greater than the predetermined threshold time Tth4.

[0148] Next, if foreign matter such as paper dust adheres to the exit of nozzle 651, ink will seep out from inside cavity 631 through the foreign matter, which is thought to increase inertance. In addition, it is thought that the acoustic resistance will increase due to the fibers of the paper dust adhering to the exit of nozzle 651. Therefore, when foreign matter such as paper dust adheres to the exit of nozzle 651, the frequency of residual vibration will be lower compared to when the ejection state is normal. As a result, time Tp will be greater than the predetermined threshold time Tth3 and less than or equal to the threshold time Tth4.

[0149] Furthermore, if there are no discharge abnormalities due to the causes (1) to (3) above, that is, if time Tp is greater than or equal to threshold time Tth2 and less than or equal to threshold time Tth3, the discharge state of the discharge unit 600 is judged to be normal.

[0150] Based on the above, the determination unit 83 can determine the discharge state of the discharge unit 600 to be inspected based on the time Tp corresponding to the period of residual vibration and the residual vibration amplitude determination value Ap.

[0151] Figure 14 shows an example of the logic used by the determination unit 83 to determine the ejection state of the ejection unit 600. In the example in Figure 14, if the amplitude determination value Ap is "0", the determination unit 83 determines that some kind of ejection abnormality has occurred, such as the cavity 631 not being filled with ink, although the cause cannot be identified, and sets the determination result signal RS to "5". Also, 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. Specifically, if time Tp is less than the threshold time Tth2, the determination unit 83 determines that an ejection abnormality due to air bubbles has occurred in the ejection unit 600 and sets the determination result signal RS to "2". Also, if time Tp is greater than or equal to the threshold time Tth2 and less than or equal to 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". Furthermore, if time Tp is greater than threshold time Tth3 and less than or equal to threshold time Tth4, the determination unit 83 determines that a dispensing abnormality has occurred in the dispensing unit 600 due to foreign matter adhesion, and sets the determination result signal RS to "3". Also, if time Tp is greater than threshold time Tth4, the determination unit 83 determines that a dispensing abnormality has occurred in the dispensing unit 600 due to viscosity increase, and sets the determination result signal RS to "4".

[0152] In the example shown in Figure 14, the determination result signal RS generated by the determination unit 83 contains five values ​​ranging from "1" to "5". However, it may also contain two values ​​indicating, for example, whether or not there is a discharge abnormality. Furthermore, the determination unit 83 may use only a portion of the time Tp and amplitude determination value Ap to generate the determination result signal RS.

[0153] In this manner, the inspection circuit 80 detects the residual vibration of the discharge unit 600 after the application of the voltage of the trapezoidal waveform Bdp1 included in the drive signal COMB to the piezoelectric element 60, and determines the discharge state of the discharge unit 600 to be inspected based on the residual vibration.

[0154] 1-8. Operation of the liquid dispensing device Next, the operation of the liquid dispensing device 1 of the first embodiment will be described with reference to Figure 15.

[0155] The print data signal SI is supplied serially in synchronization with the clock signal SCK and is sequentially transferred in the shift register 222 corresponding to each nozzle. When the supply of the clock signal SCK stops, each of the shift registers 222 holds 3 bits of print data (SIH, SIM, SIL) corresponding to the nozzle 651. The print data signal SI is supplied in the order corresponding to the last m-stage, ..., 2-stage, and 1-stage nozzles in the shift register 222.

[0156] When the latch signal LAT rises, each of the latch circuits 224 simultaneously latches the 3-bit print data (SIH, SIM, SIL) held in the shift register 222. In Figure 15, LT1, LT2, ..., LTm represent the 3-bit print data (SIH, SIM, SIL) latched by the latch circuits 224 corresponding to the 1st, 2nd, ..., mth stages of the shift register 222.

[0157] The decoder 226 outputs the logic level of the selection signal Sa in the manner shown in Figure 8 for each of the periods T1 and T2, and outputs the logic levels of the selection signals Sb and Sc in the manner shown in Figure 8 for each of the periods TS1, TS2, and TS3.

[0158] Specifically, when the print 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 the selection signals Sb and Sc to low level, low level, low level during periods TS1, TS2, and TS3. Furthermore, when the print 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 the selection signals Sb and Sc to low level, low level, low level during periods TS1, TS2, and TS3. Furthermore, when the print 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 the selection signals Sb and Sc to low level, low level, low level during periods TS1, TS2, and TS3. Furthermore, if the print 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 the selection signals Sb and Sc to low level, low level, low level during periods TS1, TS2, and TS3. Also, if the print 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, the selection signal Sb to high level, low level, high level during periods TS1, TS2, and TS3, and the selection signal Sc to low level, high level, low level during periods TS1, TS2, and TS3.

[0159] When the print data (SIH, SIM, SIL) is (1,1,0), the selection circuit 230 selects the trapezoidal waveform Adp1 of the drive signal COMA during period T1 because the selection signal Sa is at a high level, and selects the trapezoidal waveform Adp2 of the drive signal COMA during period T2 because Sa is also at a high level. Furthermore, the selection circuit 230 does not select the drive signal COMB during periods TS1, TS2, and TS3 because the selection signal Sb is at a low level. As a result, the drive signal VOUT corresponding to the "large dot" shown in Figure 6 is generated.

[0160] When the print data (SIH, SIM, SIL) is (1,0,0), the selection circuit 230 selects the trapezoidal waveform Adp1 of the drive signal COMA during period T1 because the selection signal Sa is at a high level, and does not select the drive signal COMA during period T2 because Sa is low. Also, the selection circuit 230 does not select the drive signal COMB during periods TS1, TS2, and TS3 because the selection signal Sb is at a low level. As a result, the drive signal VOUT corresponding to the "middle dot" shown in Figure 6 is generated.

[0161] When the print data (SIH, SIM, SIL) is (0,1,0), the selection circuit 230 does not select the drive signal COMA during period T1 because the selection signal Sa is low level, and during period T2 because the selection signal Sa is high level, it selects the trapezoidal waveform Adp2 of the drive signal COMA. Also, the selection circuit 230 does not select the drive signal COMB during periods TS1, TS2, and TS3 because the selection signal Sb is low level. As a result, the drive signal VOUT corresponding to the "small dot" shown in Figure 6 is generated.

[0162] When the print data (SIH, SIM, SIL) is (0,0,0), the selection circuit 230 does not select the drive signal COMA because the selection signal Sa is low during periods T1 and T2. Also, 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, the drive signal VOUT corresponding to "not recording" shown in Figure 6 is generated.

[0163] When the print data (SIH, SIM, SIL) is (1,1,1), the selection circuit 230 does not select the drive signal COMA because the selection signal Sa is low level during periods T1 and T2. Also, the selection circuit 230 selects the trapezoidal waveform Bdp1 of the drive signal COMB because the selection signal Sb is high level during periods TS1 and TS3, and does not select the drive signal COMB during period TS2 because the selection signal Sb is low level. As a result, the drive signal VOUT corresponding to "inspection" as shown in Figure 6 is generated during periods TS1 and TS3. Also, the selection circuit 230 turns off the transfer gate 234c because the selection signal Sc is low level during periods TS1 and TS3, and turns on the transfer gate 234c during period TS2 because the selection signal Sc is high level. As a result, the inspection target signal PO is generated during period TS2.

[0164] During period TS2, the inspection circuit 80 detects residual vibration of the discharge unit 600 to be inspected, and during period Tx included in period TS3, it transmits a determination result signal RS, which is data of the residual vibration detection result, to the control unit 111.

[0165] Thus, period TS2 is the period during which the inspection circuit 80 detects residual vibration of the discharge section 600 to be inspected. Since the residual vibration is minute, it may be affected by noise, which could reduce the detection accuracy of the residual vibration detection unit 120. In particular, since 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, care must be taken to ensure that the switching noise of the drive circuit 50 does not affect the detection of residual vibration.

[0166] Therefore, in this embodiment, when the control unit 111 causes the residual vibration detection unit 120, which is composed of inspection circuits 80-1 to 80-4, to detect residual vibration, it stops the drive signal generation unit 110, which is composed of drive circuits 50-1 to 50-4. 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. Alternatively, the control unit 111 may release the stop on the drive signal generation unit 110 after the residual vibration detection unit 120 has finished detecting residual vibration.

[0167] Specifically, as shown in Figure 15, the control unit 111 stops the drive circuit 50 by changing the output control signal OEB from a low level to a high level, and then the first pulse PL1 of the inspection control signal TSIG causes the inspection circuit 80 to start detecting residual vibrations. Then, the control unit 111 causes the inspection circuit 80 to stop detecting residual vibrations by changing the second pulse PL2 of the inspection control signal TSIG, and then the output control signal OEB is changed from a high level to a low level to release the stop of the drive circuit 50. As a result, the drive circuit 50 is stopped during the period TS2 from the rising edge of the first pulse PL1 to the rising edge of the second pulse PL2, so the risk of a decrease in the accuracy of residual vibration detection by the inspection circuit 80 is reduced.

[0168] Furthermore, the start of residual vibration detection by the residual vibration detection unit 120 and the stop of the drive signal generation unit 110 may occur simultaneously. That is, the timing of the output control signal OEB changing from a low level to a high level may coincide with the rising edge of the first pulse PL1 of the inspection control signal TSIG. Also, the end of residual vibration detection by the residual vibration detection unit 120 and the release of the stop of the drive signal generation unit 110 may occur simultaneously. That is, the timing of the output control signal OEB changing from a high level to a low level may coincide with the rising edge of the second pulse PL2 of the inspection control signal TSIG.

[0169] Furthermore, as shown in Figure 9, in each selection circuit 230, high logic amplitude selection signals Sax, Sbx, and Scx are input to the logic inversion circuits 232a, 232b, and 232c, respectively, and when the logic levels of the selection signals Sax, Sbx, and Scx change, large through-currents flow through the logic inversion circuits 232a, 232b, and 232c, respectively. In this embodiment, in each period Ta, there are four discharge units 600 to be inspected, while many other discharge units 600 can perform discharge operations based on the trapezoidal waveforms Adp1 and Adp2 of the drive signal COMA. Therefore, when the logic level of the selection signal Sax changes, multiple through-currents flow through the logic inversion circuits 232a simultaneously, which can become significant noise for the residual vibration of the discharge units 600 to be inspected. The logic level of the selection signal Sax can change when the selection operation of the trapezoidal waveforms Adp1 and Adp2 by the selection circuit 230 is switched by the change signal CH.

[0170] Therefore, the control unit 111 allows the selection operation of the selection circuit 230 corresponding to the discharge unit 600 that is not being inspected to be switched only during periods when the residual vibration detection unit 120 is not detecting residual vibration. In other words, the control unit 111 prohibits the selection operation of the selection circuit 230 corresponding to the discharge unit 600 that is not being inspected during periods when the residual vibration detection unit 120 is detecting residual vibration. That is, the control unit 111 fixes the change signal CH to a low level during period TS2 when the inspection circuit 80 detects residual vibration of the discharge unit 600 that is being inspected. For example, as shown in Figure 15, in period TS3 following period TS2, the control unit 111 generates a pulse for the change signal CH after the period Tx in which the inspection circuit 80 transmits the judgment result signal RS has ended. As a result, no selection operation switching occurs in each selection circuit 230 during period TS2, and the risk of a decrease in the accuracy of residual vibration detection by the inspection circuit 80 is reduced.

[0171] The ejection unit 600 to be inspected is an example of the "first ejection unit" of the present invention, and the piezoelectric element 60 of the ejection unit 600 to be inspected is an example of the "first piezoelectric element" of the present invention. Furthermore, the selection circuit 230, which selects one of a plurality of drive waveforms, the trapezoidal waveform Adp1, Adp2, and Bdp1, based on the print data signal SI and applies it to the piezoelectric element 60 of the ejection unit 600 to be inspected, is an example of the "first selection unit" of the present invention. Furthermore, the drive signal COM, consisting of drive signals COMA and COMB that drive the piezoelectric element 60 of the ejection unit 600 to be 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, an ejection unit 600 that is not to be inspected and is supplied with the same drive signal COM as the ejection unit 600 to be inspected is an example of the "second ejection unit" of the present invention, and the piezoelectric element 60 of the ejection unit 600 that is not to be inspected is an example of the "second piezoelectric element" of the present invention. Furthermore, a selection circuit 230 that outputs a drive signal VOUT supplied to a piezoelectric element 60 of a discharge unit 600 that is not subject to inspection is an example of the "second selection unit" of the present invention.

[0172] 1-9. Effects As described above, in the liquid dispensing device 1 according to the first embodiment, the control unit 111 stops the drive signal generation unit 110 when it causes the residual vibration detection unit 120 to detect residual vibration. For example, after stopping the drive signal generation unit 110, the control unit 111 causes the residual vibration detection unit 120 to start detecting residual vibration, and after the residual vibration detection unit 120 finishes detecting residual vibration, it releases the stop on 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 finishes detecting residual vibration before the drive signal generation unit 110 starts operating, so the drive signal generation unit 110 is stopped during the period when the residual vibration detection unit 120 is detecting residual vibration. Therefore, according to the liquid dispensing device 1 according to the first embodiment, the risk of a decrease in the accuracy of residual vibration detection by the residual vibration detection unit 120 due to switching noise generated by the drive signal generation unit 110 is reduced.

[0173] Furthermore, in the liquid dispensing device 1 according to the first embodiment, the control unit 111 allows the selection operation of the selection circuit 230 corresponding to the dispensing unit 600 that is not subject to inspection to be switched only during periods when the residual vibration detection unit 120 is not detecting residual vibration. Therefore, according to the liquid dispensing device 1 according to the first embodiment, since no switching of the selection operation of each selection circuit 230 occurs during the period when the residual vibration detection unit 120 is detecting residual vibration, the risk of a decrease in the accuracy of residual vibration detection by the residual vibration detection unit 120 due to noise generated by each selection circuit 230 is reduced.

[0174] 2. Second Embodiment In the following description of the liquid dispensing device according to the second embodiment, the same reference numerals are used for components similar to those in the first embodiment, and explanations that overlap with those in the first embodiment are omitted. The main points to be described are the differences from the first embodiment.

[0175] Similar to the liquid dispensing device 1 according to the first embodiment, in the liquid dispensing device 1 according to the second embodiment, the control unit 111 stops the drive signal generation unit 110, which is composed of drive circuits 50-1 to 50-4, when it causes the residual vibration detection unit 120, which is composed of inspection circuits 80-1 to 80-4, to detect residual vibration. For example, the control unit 111 may start the detection of residual vibration by the residual vibration detection unit 120 after stopping the drive signal generation unit 110. Alternatively, the control unit 111 may release the stop of the drive signal generation unit 110 after the residual vibration detection unit 120 has finished detecting residual vibration. Furthermore, the control unit 111 allows the selection operation of the selection circuit 230 corresponding to the dispensing unit 600 that is not subject to inspection to be switched only during the period when the residual vibration detection unit 120 is not detecting residual vibration.

[0176] However, in the liquid dispensing device 1 according to the first embodiment, if the judgment result signal RS transmitted by the inspection circuit 80 to the control unit 111 becomes erroneous due to switching noise in the drive circuit 50, there is a risk that the processing by the control unit 111 in response to the judgment result signal RS will be inappropriate.

[0177] Therefore, in the liquid dispensing 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 transmits a determination result signal RS, which is data of the residual vibration detection result. For example, after stopping the drive signal generation unit 110, the control unit 111 may cause the residual vibration detection unit 120 to start detecting residual vibrations, and after the residual vibration detection unit 120 has finished detecting residual vibrations and transmitted a determination result signal RS, which is data of the residual vibration detection result, it may release the stop of the drive signal generation unit 110.

[0178] Specifically, as shown in Figure 16, the control unit 111 stops the drive circuit 50 by changing the output control signal OEB from a low level to a high level, then causes the inspection circuit 80 to start detecting residual vibrations with the first pulse PL1 of the inspection control signal TSIG, and causes the inspection circuit 80 to end the detection of residual vibrations with the second pulse PL2 of the inspection control signal TSIG. During the period Tx included in the period TS3 following the period TS2 in which residual vibrations are detected, the inspection circuit 80 transmits a determination result signal RS, which is the data of the residual vibration detection result, to the control unit 111. After the period Tx ends, the control unit 111 releases the stop of the drive circuit 50 by changing the output control signal OEB from a high level to a low level, and after releasing the stop of the drive circuit 50, generates a pulse of the change signal CH.

[0179] Alternatively, for example, the control unit 111 may stop the drive signal generation unit 110, then cause the residual vibration detection unit 120 to start detecting residual vibrations, then, after the residual vibration detection unit 120 has finished detecting residual vibrations, release the stop on the drive signal generation unit 110, then stop the drive signal generation unit 110 again, then have the residual vibration detection unit 120 transmit a determination result signal RS which is the data of the residual vibration detection result, and then release the stop on the drive signal generation unit 110 after the transmission is completed.

[0180] For example, as shown in Figure 17, the control unit 111 stops the drive circuit 50 by changing the output control signal OEB from a low level to a high level, then the first pulse PL1 of the inspection control signal TSIG causes the inspection circuit 80 to start detecting residual vibrations, and the second pulse PL2 of the inspection control signal TSIG causes the inspection circuit 80 to stop detecting residual vibrations. After that, the control unit 111 releases the stop of the drive circuit 50 by changing the output control signal OEB from a high level to a low level and generates a pulse of the latch signal LAT. The pulse of the latch signal LAT ends period Ta and starts the next period Ta. In the next period Ta, after the control unit 111 stops the drive circuit 50 by changing the output control signal OEB from a low level to a high level, the inspection circuit 80 transmits a judgment result signal RS, which is the data of the residual vibration detection result, to the control unit 111 during period Tx. Then, after period Tx ends, the control unit 111 releases the stop of the drive circuit 50 by changing the output control signal OEB from a high level to a low level.

[0181] In both Figure 16 and Figure 17, the drive circuit 50 is stopped during the period TS2 from the rising edge of the first pulse PL1 to the rising edge of the second pulse PL2, thus reducing the risk of reduced accuracy in residual vibration detection by the inspection circuit 80. Also, since no switching of selection operations occurs in each selection circuit 230 during period TS2, the risk of reduced accuracy in residual vibration detection by the inspection circuit 80 is reduced. Furthermore, since the drive circuit 50 is stopped during period Tx, the risk of incorrect data for the judgment result signal RS is reduced. Moreover, in the case of Figure 16, compared to Figure 17, the number of times the control unit 111 changes the output control signal OEB from low level to high level and from high level to low level is reduced, thus simplifying the control of the drive circuit 50 by the control unit 111.

[0182] Other configurations and functions of the liquid dispensing device 1 according to the second embodiment are the same as those of the liquid dispensing device 1 according to the first embodiment, and therefore their illustration and description are omitted.

[0183] As described above, in the liquid dispensing device 1 according to the second embodiment, the control unit 111 stops the drive signal generation unit 110 when it causes the residual vibration detection unit 120 to detect residual vibration. For example, after stopping the drive signal generation unit 110, the control unit 111 causes the residual vibration detection unit 120 to start detecting residual vibration, and after the residual vibration detection unit 120 has finished detecting residual vibration, it releases the stop on the drive signal generation unit 110. Therefore, according to the liquid dispensing device 1 according to the second embodiment, since the drive signal generation unit 110 is stopped during the period when the residual vibration detection unit 120 is detecting residual vibration, the risk of a decrease in the accuracy of residual vibration detection by the residual vibration detection unit 120 due to switching noise generated by the drive signal generation unit 110 is reduced.

[0184] Furthermore, in the liquid dispensing device 1 according to the second embodiment, the control unit 111 allows the selection operation of the selection circuit 230 corresponding to the dispensing unit 600 that is not subject to inspection to be switched only during periods when the residual vibration detection unit 120 is not detecting residual vibration. Therefore, according to the liquid dispensing device 1 according to the second embodiment, since no switching of the selection operation of each selection circuit 230 occurs during the period when the residual vibration detection unit 120 is detecting residual vibration, the risk of a decrease in the accuracy of residual vibration detection by the residual vibration detection unit 120 due to noise generated by each selection circuit 230 is reduced.

[0185] Furthermore, in the liquid dispensing 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 transmits a determination result signal RS, which is data of the residual vibration detection result. Therefore, according to the liquid dispensing device 1 according to the second embodiment, the drive signal generation unit 110 is stopped during the period when the residual vibration detection unit 120 transmits data of the residual vibration detection result, thus reducing the risk that the residual vibration detection result data will be incorrect due to switching noise generated by the drive signal generation unit 110.

[0186] For example, the control unit 111 may stop the drive signal generation unit 110, then have the residual vibration detection unit 120 start detecting residual vibrations, and after the residual vibration detection unit 120 has finished detecting residual vibrations and the residual vibration detection unit 120 has transmitted a determination result signal RS which is the data of the residual vibration detection result, it 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 of the drive signal generation unit 110 by the control unit 111.

[0187] 3. Variant In each of the above embodiments, the inspection circuit 80 is provided on the head unit 20, but at least a portion of the inspection circuit 80 may be provided on the control board 100.

[0188] Furthermore, in each of the above embodiments, the determination unit 83 of the inspection circuit 80 determines the discharge state of the discharge unit 600 to be inspected, but the control unit 111 may have at least some of the functions of the determination unit 83. For example, the inspection circuit 80 may transmit the time Tp and amplitude determination value Ap shown in Figures 13 and 14 as residual vibration detection result data to the control unit 111, and the control unit 111 may determine the discharge state of the discharge unit 600 to be inspected 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 discharge state of the discharge unit 600 to be inspected based on the residual vibration signal NVT.

[0189] Furthermore, in each of the above embodiments, the four inspection circuits 80-1 to 80-4 detect residual vibrations during the same period, but they may also detect residual vibrations during different periods.

[0190] Furthermore, in each of 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 using output control signals OEB1 to OEB4, but this may be done at different timings. For example, if the detection of residual vibration by the inspection circuit 80-1 is not easily affected by noise caused by the operation of the drive circuits 50a-2, 50a-3, 50a-4, 50b-2, 50b-3, and 50b-4, the control unit 111 does not need to stop the drive circuits 50a-2, 50a-3, 50a-4, 50b-2, 50b-3, and 50b-4 with output control signals OEB2, OEB3, and OEB4 when causing the inspection circuit 80-1 to detect residual vibration, while stopping the drive circuits 50a-1 and 50b-1 with output control signal OEB1.

[0191] Furthermore, in each of the above embodiments, the liquid dispensing device 1 is equipped with eight drive circuits 50 and four inspection circuits 80, but the number of drive circuits 50 and inspection circuits 80 is not limited to these.

[0192] Furthermore, in the above embodiments, it was explained that ink is not ejected even when the ejection unit 600 to be inspected is driven by the drive signal COMB. However, the amplitude of the drive signal COMB may be increased so that ink is ejected from the ejection unit 600. The larger the amplitude of the drive signal COMB, the larger the amplitude of residual vibration, thus improving the accuracy of the judgment. In this case, for example, the residual vibration detection process is performed in an inspection mode in which no printing process is performed.

[0193] Furthermore, in each of the above embodiments, the control board 100 and the head unit 20 are connected by a single cable 190, but they may be connected by multiple cables. Also, various signals may be transmitted wirelessly from the control board 100 to the head unit 20. In other words, the control board 100 and the head unit 20 do not necessarily have to be connected by cable 190.

[0194] Furthermore, in each of the above embodiments, the drive circuit 50 is provided on the control board 100, but it may also be provided on the head unit 20.

[0195] Furthermore, in the above embodiment, a part or all of the waveform of the drive signal COMA is selected to generate a drive signal VOUT corresponding to "large dot," "medium dot," "small dot," and "no recording," and a part of the drive signal COMB is selected to generate a 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, the drive waveforms of multiple drive signals may be combined to generate a drive signal VOUT corresponding to "large dot," "medium dot," "small dot," "no recording," and "inspection." Alternatively, for example, the drive signals VOUT corresponding to "large dot," "medium dot," "small dot," "no recording," and "inspection" may be generated depending on whether or not each of the multiple drive waveforms included in a single drive signal is selected. Furthermore, in the above embodiment, a serial scan type inkjet printer in which the head moves to print on the printing medium was given as an example of a liquid ejection device. However, the present invention is also applicable to line head type inkjet printers in which the head does not move to print on the printing medium.

[0196] Although embodiments and modified examples have been described above, the present invention is not limited to these embodiments or modified examples, and can be implemented in various forms without departing from its essence. For example, the above embodiments and modified examples can be combined as appropriate.

[0197] The present invention includes configurations that are substantially identical to those described in the embodiments (for example, configurations that have the same function, method, and result, or configurations that have the same purpose and effect). The present invention also includes configurations that replace non-essential parts of the configurations described in the embodiments. Furthermore, the present invention includes configurations that produce the same effects or achieve the same purpose as the configurations described in the embodiments. Finally, the present invention includes configurations that add known technology to the configurations described in the embodiments.

[0198] The following can be derived from the embodiments and modifications described above.

[0199] One embodiment of a liquid dispensing device is: A first discharge unit having a first piezoelectric element, which discharges liquid when the first piezoelectric element is driven by a drive signal, A drive signal generation unit that generates the aforementioned drive signal, A first selection unit performs a selection operation to select whether or not to apply the voltage of each of the multiple drive waveforms included in the drive signal to the first piezoelectric element based on the print data signal, A residual vibration detection unit that detects the residual vibration of the first discharge section after the voltage of the first drive waveform among the plurality of drive waveforms is applied to the first piezoelectric element, A control unit that generates the print data signal, Equipped with, The control unit, When the residual vibration detection unit is to detect the residual vibration, the drive signal generation unit is stopped.

[0200] With this liquid dispensing device, the drive signal generation unit is stopped during the period when the residual vibration detection unit detects residual vibrations. Therefore, the risk of the residual vibration detection unit's accuracy being reduced due to noise generated by the drive signal generation unit is minimized.

[0201] In one embodiment of the liquid dispensing device, The control unit, After stopping the drive signal generation unit, the residual vibration detection unit may be made to start detecting the residual vibration.

[0202] With this liquid dispensing device, the drive signal generation unit stops before the residual vibration detection unit starts detecting residual vibrations, thus reducing the risk of the residual vibration detection unit's accuracy being reduced due to noise generated by the drive signal generation unit.

[0203] In one embodiment of the liquid dispensing device, The control unit, After the residual vibration detection unit has finished detecting the residual vibration, the stop function of the drive signal generation unit may be released.

[0204] With this liquid dispensing device, the residual vibration detection unit finishes detecting residual vibrations before the drive signal generation unit starts operating, thus reducing the risk of the residual vibration detection unit's accuracy being reduced due to noise generated by the drive signal generation unit.

[0205] In one embodiment of the liquid dispensing device, The residual vibration detection unit is The data of the residual vibration detection result is transmitted to the control unit. The control unit, When the residual vibration detection unit transmits the data, the drive signal generation unit may be stopped.

[0206] With this liquid dispensing device, the drive signal generation unit is stopped during the period when the residual vibration detection unit transmits residual vibration detection result data. Therefore, the risk of the residual vibration detection result data becoming erroneous due to noise generated by the drive signal generation unit is reduced.

[0207] In one embodiment of the liquid dispensing device, The control unit, After stopping the drive signal generation unit, the residual vibration detection unit may be made to start detecting the residual vibration, and after the residual vibration detection unit has finished detecting the residual vibration, and after the residual vibration detection unit has transmitted the data, the stop of the drive signal generation unit may be released.

[0208] This liquid dispensing device reduces the number of times the drive signal generation unit is stopped and released, thus simplifying the control of the drive signal generation unit by the control unit.

[0209] One embodiment of the liquid dispensing device is: A second discharge unit having a second piezoelectric element, which discharges liquid when the second piezoelectric element is driven by the drive signal, A second selection unit performs a selection operation to select whether or not to apply the voltage of each of the plurality of drive waveforms to the second piezoelectric element based on the print data signal, Equipped with, The control unit, The switching of the selection operation of the second selection unit may be permitted only during periods when the residual vibration detection unit is not detecting the residual vibration.

[0210] With this liquid dispensing device, since there is no switching of the selection operation of the second selection unit during the period in which the residual vibration detection unit detects residual vibrations, the risk of a decrease in the accuracy of residual vibration detection by the residual vibration detection unit due to noise generated by the second selection unit is reduced. [Explanation of Symbols]

[0211] 1…Liquid dispensing device, 3…Moving mechanism, 4…Conveying mechanism, 20…Head unit, 21…Head, 24…Carriage, 31…Carriage motor, 32…Carriage guide shaft, 33…Timing belt, 40…Platen, 41…Conveying motor, 42…Conveying 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…Measurement 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 inversion circuit, 234a, 234b, 234c... Transfer gate, 236a, 236b, 236c... Level shift circuit, 500... Integrated circuit device, 510... Modulation unit, 511... DAC, 512... Adder, 513... Adder, 514... Comparator, 515... Logic inverter circuit, 516... Integral attenuator, 517... Attenuator, 520... Gate driver, 521... First gate driver, 522... Second gate driver, 54 0...Boost circuit, 550...Output circuit, 560...Low-pass filter, 570...First feedback circuit, 572...Second feedback circuit, 580...Reference voltage generation unit, 600...Discharge unit, 601...Piezoelectric element, 611, 612...Electrodes, 621...Diaphragm, 631...Cavity, 632...Nozzle plate, 641...Reservoir, 650...Nozzle row, 650a~650h...First nozzle row~Eighth nozzle row, 651...Nozzle, 661...Supply port

Claims

1. A first discharge unit having a first piezoelectric element, which discharges liquid when the first piezoelectric element is driven by a drive signal, A drive signal generation unit that generates the aforementioned drive signal, A first selection unit performs a selection operation to select whether or not to apply the voltage of each of the multiple drive waveforms included in the drive signal to the first piezoelectric element based on the print data signal, A residual vibration detection unit that detects the residual vibration of the first discharge section after the voltage of the first drive waveform among the plurality of drive waveforms is applied to the first piezoelectric element, A control unit that generates the print data signal, Equipped with, The control unit, When the residual vibration detection unit is to detect the residual vibration, the drive signal generation unit is stopped. A liquid dispensing device characterized by the following features.

2. The control unit, After stopping the drive signal generation unit, the residual vibration detection unit is instructed to start detecting the residual vibration. The liquid dispensing device according to feature 1.

3. The control unit, After the residual vibration detection unit has finished detecting the residual vibration, the stop function of the drive signal generation unit is released. The liquid dispensing device according to feature 2.

4. The residual vibration detection unit is The data of the residual vibration detection result is transmitted to the control unit. The control unit, When the residual vibration detection unit transmits the data, the drive signal generation unit is stopped. A liquid dispensing device according to any one of claims 1 to 3, characterized in that...

5. The control unit, After stopping the drive signal generation unit, the residual vibration detection unit is made to start detecting the residual vibration, and after the residual vibration detection unit has finished detecting the residual vibration, the residual vibration detection unit transmits the data, and then the stop of the drive signal generation unit is released. The liquid dispensing device according to claim 4, characterized in that...

6. A second discharge unit having a second piezoelectric element, which discharges liquid when the second piezoelectric element is driven by the drive signal, A second selection unit performs a selection operation to select whether or not to apply the voltage of each of the plurality of drive waveforms to the second piezoelectric element based on the print data signal, Equipped with, The control unit, The switching of the selection operation of the second selection unit is permitted only during the period when the residual vibration detection unit is not detecting the residual vibration. A liquid dispensing device according to any one of claims 1 to 5, characterized in that...

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