Print head and liquid ejection device

Abstract

To provide a print head enabling condition of an ejection head to be recognized and managed in more detail.SOLUTION: The print head is provided, having a driving element driven by being supplied with a driving signal and ejecting liquid by driving the driving element, the print head comprises an ejection module which includes the driving element and a nozzle for ejecting liquid, and a current detecting circuit that detects driving currents generated caused by transmission of the driving signal, wherein the current detecting circuit has a current detector that detects the driving currents as a current detection signal and a processor that controls operation of the current detecting circuit.SELECTED DRAWING: Figure 9

Description

Technical Field

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

Background Art

[0002] In a liquid ejection device such as an inkjet printer that forms an image or a document on a medium by ejecting ink as a liquid, there is known one using a drive element such as a piezoelectric element. In the liquid ejection device, the piezoelectric element is provided corresponding to each of a plurality of nozzles in a discharge head that discharges the liquid. Then, each of the plurality of piezoelectric elements is driven according to a drive signal, so that a predetermined amount of ink is ejected from the nozzle corresponding to the piezoelectric element at a predetermined timing. As a result, the liquid ejection device ejects the liquid onto the medium, and forms a desired image or character on the medium.

[0003] In such a liquid ejection device, managing the state of the discharge head that discharges the liquid is important from the viewpoint of improving the ejection accuracy of the ink onto the medium. For example, in Patent Document 1, a technique for managing the state of the discharge head such as the service life based on the number of ejection times of the ink ejected from the discharge head and the number of supply times of the drive signal to the drive element is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, from the viewpoint of grasping and managing the state of the discharge head in more detail, the technique described in Patent Document 1 is not sufficient, and there is room for improvement.

Means for Solving the Problems

[0006] One embodiment of the print head according to the present invention is: A print head having a drive element that is driven when a drive signal is supplied, and which ejects liquid by driving the drive element, A discharge module including the aforementioned drive element and a nozzle for discharging liquid, A current detection circuit for detecting the drive current generated as the drive signal propagates, Equipped with, The current detection circuit is, A current detector that detects the aforementioned drive current as a current detection signal, A processor that controls the operation of the current detection circuit in accordance with the current detection signal, It has.

[0007] One embodiment of the liquid dispensing device according to the present invention is: A print head having a drive element that is driven when a drive signal is supplied, and which ejects liquid by driving the drive element, A drive circuit that outputs the aforementioned drive signal, Equipped with, The aforementioned print head is A discharge module including the aforementioned drive element and a nozzle for discharging liquid, A current detection circuit for detecting the drive current generated as the drive signal propagates, It has, The current detection circuit is, A current detector that detects the aforementioned drive current as a current detection signal, A processor that controls the operation of the current detection circuit in accordance with the current detection signal, Includes. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram showing the schematic structure of a liquid dispensing device. [Figure 2] This diagram shows the functional configuration of a liquid dispensing device. [Figure 3] This is a diagram showing the schematic structure of the discharge section. [Figure 4]It is a diagram showing an example of the signal waveform of the drive signal COM. [Figure 5] It is a diagram showing the configuration of the drive signal selection circuit. [Figure 6] It is a diagram showing an example of the decoding content in the decoder. [Figure 7] It is a diagram showing the configuration of the selection circuit corresponding to one portion of the ejection unit. [Figure 8] It is a diagram for explaining the operation of the drive signal selection circuit. [Figure 9] It is a diagram showing an example of the configuration of the current detection circuit. [Figure 10] It is a diagram for explaining a specific example of the operation of the current detection circuit. [Figure 11] It is a diagram showing an example of the calculation operation in the CPU.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, preferred embodiments of the present invention will be described 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.

[0010] 1. Structure of the Liquid Ejection Device FIG. 1 is a diagram showing the schematic structure of the liquid ejection device 1 of the present embodiment. The liquid ejection device 1 of the present embodiment is a so-called inkjet printer that forms an image corresponding to the image data on a medium P such as paper by ejecting ink as an example of a liquid according to the image data supplied from a host computer provided outside. Note that the liquid ejection device 1 is not limited to an inkjet printer, and may be a color material ejection device used in the manufacture of color filters such as liquid crystal displays, an electrode material ejection device used in the formation of electrodes such as organic EL displays and surface emission displays, a biological organic matter ejection device used in the manufacture of biochips, and the like.

[0011] As shown in FIG. 1, the liquid ejection device 1 includes a print head 2, a moving mechanism 3, and a conveyance mechanism 4. In FIG. 1, illustration of some components such as the housing and cover of the liquid ejection device 1 is omitted.

[0012] The print head 2 has a discharge module 20 and a carriage 24. The carriage 24 is configured to be able to mount a predetermined number of ink cartridges 22 that store ink discharged from the discharge module 20. Further, the discharge module 20 has a number of nozzles, which will be described later, and is attached to the carriage 24 such that the nozzles face the medium P. Such a print head 2 discharges a predetermined amount of ink from each nozzle at a timing defined by various control signals supplied via a cable 190 such as a flexible flat cable.

[0013] The moving mechanism 3 reciprocates the carriage 24 of the print head 2 along the main scanning direction. The moving mechanism 3 has a carriage motor 31, a carriage guide shaft 32, a timing belt 33, and a linear encoder 90. Both ends of the carriage guide shaft 32 are fixed to the housing of the liquid ejection device 1 and support the carriage 24 so as to be reciprocally movable. The timing belt 33 extends substantially parallel to the carriage guide shaft 32, and a part of it is fixed to the carriage 24. The carriage motor 31 supplies a driving force to the timing belt 33. Thereby, when the carriage motor 31 makes the timing belt 33 run forward and backward, the carriage 24 fixed to the timing belt 33 is guided by the carriage guide shaft 32 and reciprocates along the main scanning direction. That is, the moving mechanism 3 reciprocates the print head 2 along the main scanning direction.

[0014] Further, the linear encoder 90 detects the scanning position of the carriage 24 in the main scanning direction and outputs it as a detection signal. The liquid ejection device 1 controls the output of the carriage motor 31 according to the information on the scanning position of the carriage 24 output by the linear encoder 90, thereby controlling the scanning position of the print head 2 along the main scanning direction.

[0015] The transport mechanism 4 transports the medium P along a sub-scanning direction that intersects the main scanning direction in which the carriage 24 reciprocates. The transport mechanism 4 includes a transport motor 41, transport rollers 42, and a platen 43. The transport motor 41 supplies driving force to the transport rollers 42. This causes the transport rollers 42 to rotate. This rotational drive of the transport rollers 42 transports the medium P along the sub-scanning direction. At this time, the medium P is supported by the platen 43. That is, the platen 43 guides the medium P, which is transported by the transport rollers 42, along the sub-scanning direction.

[0016] As shown in Figure 1, the liquid dispensing device 1 includes a capping member 81, a wiper member 82, and a flushing box 83. The capping member 81 and the wiper member 82 are located at one end within the movement range of the carriage 24 and are provided at the home position, which is the base point for the movement of the carriage 24. The capping member 81 seals the nozzle forming surface of the dispensing module 20, and the wiper member 82 wipes the nozzle forming surface. The flushing box 83 is provided at the other end of the platen 43 in the main scanning direction, at the end opposite to the home position where the carriage 24 moves. The flushing box 83 collects the ink dispensed from the dispensing module 20 during the flushing operation. Here, the flushing operation is an operation that forcibly dispenses ink from each nozzle, regardless of the image data, in order to prevent the nozzle from becoming clogged due to increased viscosity of the ink near the nozzle, or due to air bubbles entering the nozzle, which could result in an insufficient amount of ink being dispensed.

[0017] In the liquid dispensing device 1 configured as described above, the medium P is transported in the sub-scanning direction while supported by the platen 43, and the carriage 24 reciprocates along the main scanning direction in synchronization with the transport timing of the medium P. Then, ink is dispensed from the dispensing module 20 attached to the carriage 24 in synchronization with the transport of the medium P and the movement of the carriage 24. This makes it possible to land the ink at a desired position on the medium P, and as a result, a desired image can be formed on the medium P. In the following description, the sub-scanning direction in which the medium P is transported may be referred to as the transport direction.

[0018] 2. Functional configuration of the liquid dispensing device Next, the functional configuration of the liquid dispensing device 1 will be described. Figure 2 is a diagram showing the functional configuration of the liquid dispensing device 1. As shown in Figure 2, the liquid dispensing device 1 comprises a print head control circuit 10 and a print head 2. The print head control circuit 10 and the print head 2 are electrically connected via a cable 190.

[0019] The print head control circuit 10 includes a control circuit 100, a carriage motor driver 35, a transport motor driver 45, and a drive circuit 50.

[0020] Image data is supplied to the control circuit 100 from a host computer located outside the liquid dispensing device 1. The control circuit 100 generates various control signals according to the supplied image data and outputs them to each component of the liquid dispensing device 1.

[0021] Specifically, the control circuit 100 determines the current scanning position of the print head 2 based on the detection signal output by the linear encoder 90. The control circuit 100 then generates control signals CTR1 and CTR2 according to the scanning position of the print head 2. Control signal CTR1 is supplied to the carriage motor driver 35. The carriage motor driver 35 drives the carriage motor 31 according to the input control signal CTR1. Control signal CTR2 is supplied to the transport motor driver 45. The transport motor driver 45 drives the transport motor 41 according to the input control signal CTR2. In other words, the control circuit 100 controls the reciprocating movement of the print head 2 in the main scanning direction and the transport of the medium P in the sub-scanning direction.

[0022] Furthermore, the control circuit 100 generates a clock signal SCK, a print data signal SI, a latch signal LAT, a change signal CH, and a current detection control signal IDS based on the image data supplied from the host computer and the detection signal output by the linear encoder 90, and outputs them to the print head 2.

[0023] Furthermore, the control circuit 100 causes the maintenance unit 80 to perform maintenance processing to restore the ink ejection state in the ejection module 20 to normal. The maintenance unit 80 has a cleaning mechanism 810, a wiping mechanism 820, and a flushing mechanism 830. The cleaning mechanism 810 performs pumping processing as part of the maintenance processing, sucking up viscous ink, air bubbles, etc., accumulated in the ejection module 20 using a tube pump (not shown). The wiping mechanism 820 performs wiping processing as part of the maintenance processing, wiping off foreign matter such as paper dust attached near the nozzles of the ejection module 20 using a wiper member 82. The flushing mechanism 830 performs flushing operations to restore the ink ejection state in the ejection section 600 to normal.

[0024] Furthermore, the control circuit 100 outputs a base drive signal dA to the drive circuit 50. The drive circuit 50 converts the input base drive signal dA from digital to analog, and then amplifies the converted analog signal to generate a drive signal COM1. The drive circuit 50 then outputs the generated drive signal COM1 to the print head 2. Such a drive circuit 50 generates the drive signal COM1 by modulating the signal obtained by converting the base drive signal dA to an analog signal, amplifying it in class D, and demodulating it, and then outputs it to the print head 2. Here, the base drive signal dA can be any signal that defines the waveform of the drive signal COM1, and may be an analog signal. Also, the drive circuit 50 only needs to be able to amplify the waveform defined by the base drive signal dA, and may be a class A amplifier, a class B amplifier, or a class AB amplifier.

[0025] Furthermore, the drive circuit 50 generates a reference voltage signal VBS, for example, with a constant voltage of 5.5V, along with the drive signal COM1, and supplies it to the print head 2. This reference voltage signal VBS functions as the reference potential for driving the piezoelectric element 60, which will be described later. Note that the voltage value of the reference voltage signal VBS is not limited to 5.5V; for example, it may be a signal with a constant voltage value of 6V or 6.5V, or a signal that is constant at ground potential.

[0026] The print head 2 includes a current detection circuit 70 and an ejection module 20.

[0027] The current detection circuit 70 receives the drive signal COM1 and the current detection control signal IDS. The drive signal COM1 propagates through the current detection circuit 70 and is supplied to the discharge module 20 as the drive signal COM2. At this time, the current detection circuit 70 receives the drive signal COM1 when it propagates. The current detection circuit 70 detects the drive current Icom generated. Based on the detected drive current Icom and the current detection control signal IDS input from the control circuit 100, the current detection circuit 70 estimates the operating state of the print head 2, including the ejection module 20. The current detection circuit 70 then generates a current detection result signal IDR corresponding to the operating state of the print head 2 and outputs it to the control circuit 100. Based on the input current detection result signal IDR, the control circuit 100 corrects various control signals that control each part of the liquid ejection device 1, thereby controlling the operation of each component of the liquid ejection device 1 according to the operating state of the print head 2.

[0028] The discharge module 20 has a drive signal selection circuit 200 and n discharge units 600. The drive signal selection circuit 200 also includes a selection control circuit 210 and n selection circuits 230 corresponding to each of the n discharge units 600.

[0029] The selection control circuit 210 receives the clock signal SCK, print data signal SI, latch signal LAT, and change signal CH output by the control circuit 100. Based on the clock signal SCK, print data signal SI, latch signal LAT, and change signal CH, the selection control circuit 210 generates a selection signal S corresponding to each of the n selection circuits 230 and outputs it to the corresponding selection circuit 230.

[0030] Each of the n selection circuits 230 receives a drive signal COM2 and a corresponding selection signal S as inputs. Based on the input selection signal S, the selection circuit 230 generates a drive signal VOUT by selecting or deselecting the signal waveform included in the drive signal COM2. The selection circuit 230 then outputs the generated drive signal VOUT to the corresponding output unit 600.

[0031] Each of the n ejection units 600 includes a piezoelectric element 60. A drive signal VOUT, output by a corresponding selection circuit 230, is supplied to one end of the piezoelectric element 60. A reference voltage signal VBS is supplied to the other end of the piezoelectric element 60. The piezoelectric element 60 is driven according to the potential difference between the drive signal VOUT supplied to one end and the reference voltage signal VBS supplied to the other end. An amount of ink corresponding to the drive of the piezoelectric element 60 is ejected from the corresponding ejection unit 600.

[0032] As described above, the liquid dispensing device 1 of this embodiment includes a print head 2 that dispenses liquid by driving a piezoelectric element 60 which is driven by a drive signal VOUT based on a drive signal COM1, and a drive circuit 50 that outputs a drive signal COM1. Here, considering that the drive signal COM1 propagates through the current detection circuit 70 and the signal output from the current detection circuit 70 is the drive signal COM2, the drive signal COM1 output by the drive circuit 50 and the drive signal COM2 output by the current detection circuit 70 are ideally the same signal. Therefore, in the following description, when it is not necessary to distinguish between the drive signal COM1 and the drive signal COM2, they may simply be referred to as the drive signal COM.

[0033] 3. Configuration and operation of print head 2 Next, the configuration and operation of the print head 2 will be described. As mentioned above, the print head 2 has a current detection circuit 70 and an ejection module 20.

[0034] 3.1 Configuration and operation of the discharge module 20 To explain the configuration and operation of the discharge module 20, we will first describe the structure of the discharge section 600 of the discharge module 20. Figure 3 is a diagram showing the schematic structure of the discharge section 600. In addition to the discharge section 600, Figure 3 also shows the reservoir 641 and the supply port 661.

[0035] As shown in Figure 3, the discharge section 600 consists of a piezoelectric element 60, a diaphragm 621, and a cavity 63 1, and nozzle plate 632.

[0036] The piezoelectric element 60 includes a piezoelectric body 601 and electrodes 611 and 612. In the piezoelectric element 60, electrodes 611 and 612 are positioned so as to sandwich the piezoelectric body 601. The piezoelectric element 60 configured as described above is driven so that the central portion of the piezoelectric body 601 is displaced vertically in accordance with the potential difference between the voltage supplied to electrode 611 and the voltage supplied to electrode 612. In this embodiment, electrode 611 is supplied with a drive signal VOUT based on a drive signal COM, and electrode 612 is supplied with a reference voltage signal VBS of a constant potential. That is, the piezoelectric element 60 is driven so that the central portion is displaced vertically as the voltage value of the drive signal VOUT supplied to electrode 611 changes.

[0037] The diaphragm 621 is located below the piezoelectric element 60 in Figure 3. In other words, the piezoelectric element 60 is formed on the upper surface of the diaphragm 621 in Figure 3. Such a diaphragm 621 deforms vertically as it is displaced vertically due to the driving of the piezoelectric element 60.

[0038] Below the diaphragm 621 in Figure 3, a cavity 631 is located. The cavity 631 communicates with a reservoir 641, which is commonly provided to multiple ejection units 600. The reservoir 641 also communicates with a supply port 661, to which ink stored in the ink cartridge 22 is supplied. Therefore, the ink stored in the ink cartridge 22 is supplied to the inside of the cavity 631 via the supply port 661 and the reservoir 641. As a result, the inside of the cavity 631 is filled with ink stored in the ink cartridge 22. The internal volume of such a cavity 631 changes with the vertical displacement of the diaphragm 621. That is, the diaphragm 621 functions as a diaphragm that changes the internal volume of the cavity 631, and the cavity 631 functions as a pressure chamber whose pressure changes with the displacement of the diaphragm 621.

[0039] A nozzle 651 is formed on the nozzle plate 632. That is, the discharge section 600 includes a piezoelectric element 60 and a nozzle 651 that discharges ink. The nozzle 651 is an opening provided on the nozzle plate 632 and communicates with the cavity 631. Then, in response to a change in the internal volume of the cavity 631, the ink filled inside the cavity 631 is discharged from the nozzle 651. Of the surfaces of the nozzle plate 632 on which the nozzle 651 is formed, the surface facing the medium P to which the ink lands corresponds to the nozzle-forming surface described above.

[0040] In the ejection unit 600 configured as described above, when the piezoelectric element 60 is driven to bend upward, the diaphragm 621 is displaced upward. This expands the internal volume of the cavity 631, and as a result, the ink stored in the reservoir 641 is drawn into the cavity 631. On the other hand, when the piezoelectric element 60 is driven to bend downward, the diaphragm 621 is displaced downward. This reduces the internal volume of the cavity 631, and as a result, an amount of ink corresponding to the degree of reduction in the internal volume of the cavity 631 is ejected from the nozzle 651.

[0041] Furthermore, the piezoelectric element 60 is driven by a drive signal VOUT corresponding to the drive signal COM, and is not limited to the structure shown in Figure 3, as long as it is structured to eject ink from the nozzle 651 when driven.

[0042] Next, the configuration and operation of the drive signal selection circuit 200 of the ejection module 20 will be described. As mentioned above, the drive signal selection circuit 200 generates and outputs the drive signal VOUT by selecting or deselecting the signal waveform included in the drive signal COM based on the clock signal SCK, the print data signal SI, the latch signal LAT, and the change signal CH. In order to explain the configuration and operation of the drive signal selection circuit 200, we will first describe an example of the waveform of the drive signal COM input to the drive signal selection circuit 200.

[0043] Figure 4 shows an example of the signal waveform of the drive signal COM. As shown in Figure 4, the drive signal COM includes a trapezoidal waveform Adp positioned in T1 during the period from when the latch signal LAT rises until when the change signal CH rises, a trapezoidal waveform Bdp positioned in T2 during the period from when the change signal CH rises until the next change signal CH rises, and a trapezoidal waveform Cdp positioned in T3 during the period from when the change signal CH rises until when the latch signal LAT rises. The trapezoidal waveform Adp is a signal waveform that drives the piezoelectric element 60 so that a predetermined amount of ink is ejected from the ejection unit 600 corresponding to the piezoelectric element 60 when supplied to the piezoelectric element 60. The trapezoidal waveform Bdp is a signal waveform that drives the piezoelectric element 60 so that a smaller amount of ink than a predetermined amount is ejected from the ejection unit 600 corresponding to the piezoelectric element 60 when supplied to the piezoelectric element 60. The trapezoidal waveform Cdp is a signal waveform that drives the piezoelectric element 60 to the extent that no ink is ejected from the ejection unit 600 corresponding to the piezoelectric element 60 when supplied to the piezoelectric element 60. When a trapezoidal waveform Cdp is supplied to the piezoelectric element 60, the piezoelectric element 60 vibrates the ink near the nozzle opening of the corresponding discharge unit 600. This reduces the risk of an increase in ink viscosity near the nozzle opening.

[0044] Furthermore, the trapezoidal waveforms Adp, Bdp, and Cdp are signal waveforms that share a common voltage value Vc at their respective start and end timings. In other words, each of the trapezoidal waveforms Adp, Bdp, and Cdp starts and ends at voltage Vc.

[0045] In the following description, when a trapezoidal waveform Adp is supplied to the piezoelectric element 60, the predetermined amount of ink discharged from the discharge unit 600 corresponding to the piezoelectric element 60 is referred to as a medium amount, and when a trapezoidal waveform Bdp is supplied to the piezoelectric element 60, the amount of ink discharged from the discharge unit 600 corresponding to the piezoelectric element 60 that is less than the predetermined amount is referred to as a small amount. Furthermore, when a trapezoidal waveform Cdp is supplied to the piezoelectric element 60, the operation to vibrate the ink near the nozzle opening of the discharge unit 600 corresponding to the piezoelectric element 60 to prevent an increase in ink viscosity is referred to as micro-vibration. Note that the signal waveform of the drive signal COM shown in Figure 4 is just an example and is not limited to this; various combinations of waveforms may be used depending on the properties of the discharged ink, the material of the medium P to which the ink lands, etc.

[0046] In this embodiment, the print head 2 controls the amount of ink ejected from the ejection unit 600 by having the drive signal selection circuit 200 select or deselect trapezoidal waveforms Adp, Bdp, and Cdp during a period Ta that includes periods T1, T2, and T3. In other words, the dot size formed on the medium P during period Ta is controlled. This period Ta, which includes periods T1, T2, and T3, corresponds to the dot formation period during which dots of a predetermined size are formed on the medium P.

[0047] Next, the configuration and operation of the drive signal selection circuit 200, which generates the drive signal VOUT by selecting or deselecting the signal waveform included in the drive signal COM, will be described. Figure 5 is a diagram showing the configuration of the drive signal selection circuit 200. As shown in Figure 5, the drive signal selection circuit 200 has a selection control circuit 210 and n selection circuits 230.

[0048] The selection control circuit 210 receives the clock signal SCK, the print data signal SI, the latch signal LAT, and the change signal CH. Furthermore, the selection control circuit 210 is provided with a set of shift register (S / R) 212, latch circuit 214, and decoder 216, corresponding to each of the n output units 600. That is, the drive signal selection circuit 200 includes n shift registers 212, n latch circuits 214, and n decoders 216.

[0049] The print data signal SI is input to the selection control circuit 210 in synchronization with the clock signal SCK. The print data signal SI also serially contains 2 bits of print data [SIH,SIL] corresponding to each of the n ejection units 600, for selecting one of the following: "large dot LD", "medium dot MD", "small dot SD", and "no recording ND". In other words, the print data signal SI is a 2n-bit serial signal. The print data [SIH,SIL] contained in the print data signal SI is held in n shift registers 212 corresponding to the n ejection units 600. Specifically, the n shift registers 212 corresponding to the ejection units 600 are connected in cascaded order, and the serially input print data signal SI is sequentially transferred to the subsequent shift registers 212 according to the clock signal SCK. The clock signal SCK stops when the print data [SIH,SIL] is held in the corresponding shift registers 212. In other words, when the supply of the clock signal SCK is stopped, the print data [SIH, SIL] contained in the print data signal SI is held in the corresponding shift register 212. Note that in Figure 5, to distinguish between the n shift registers 212, they are labeled as stage 1, stage 2, ..., n stages in order from the upstream side where the print data signal SI is input.

[0050] Each of the n latch circuits 214 simultaneously latches the print data [SIH,SIL] held in the corresponding shift register 212 on the rising edge of the latch signal LAT. The print data [SIH,SIL] latched by the latch circuits 214 is then input to the corresponding decoder 216. Figure 6 shows an example of the decoding content in the decoder 216. The decoder 216 outputs a selection signal S of a logic level defined by the input print data [SIH,SIL] in each of the periods T1, T2, and T3. For example, if print data [SIH,SIL]=[1,0] is input to the decoder 216, the decoder 216 outputs the logic level of the selection signal S as H, L, L levels in periods T1, T2, and T3.

[0051] The selection signal S output by the decoder 216 is input to the selection circuit 230. The selection circuit 230 is provided corresponding to each of the n ejection units 600. That is, the drive signal selection circuit 200 has n selection circuits 230, the same number as the n ejection units 600. Figure 7 shows the configuration of the selection circuit 230 corresponding to one ejection unit 600. As shown in Figure 7, the selection circuit 230 includes an inverter 232, which is a NOT gate, and a transfer gate 234.

[0052] The selection signal S is input to the positive control terminal of the transfer gate 234 that is not marked with a circle, and after its logic level is inverted by the inverter 232, it is also input to the negative control terminal of the transfer gate 234 that is marked with a circle. In addition, the drive signal COM is supplied to the input terminal of the transfer gate 234. When a high-level selection signal S is input to the transfer gate 234, the input terminal and output terminal become conductive, and when a low-level selection signal S is input to the transfer gate 234, the input terminal and output terminal become non-conductive. That is, when the logic level of the selection signal S is high, the transfer gate 234 outputs the signal waveform included in the drive signal COM from its output terminal, and when the logic level of the selection signal S is low, it does not output the signal waveform included in the drive signal COM from its output terminal.

[0053] The drive signal selection circuit 200 then outputs the signal output to the output terminal of the transfer gate 234 of the selection circuit 230 as the drive signal VOUT.

[0054] Here, the operation of the drive signal selection circuit 200 will be explained using Figure 8. Figure 8 is a diagram illustrating the operation of the drive signal selection circuit 200. The print data signal SI is input to the selection control circuit 210 as a serial signal synchronized with the clock signal SCK. The print data signal SI is then synchronized with the clock signal SCK to n corresponding to n ejection units 600. The data is transferred sequentially in each of the shift registers 212. After the input of the clock signal SCK stops, the shift register 212 holds the print data [SIH, SIL] corresponding to each of the n ejection units 600. The print data signal SI is input in the order corresponding to the nth, ..., 2nd, and 1st stages of the ejection unit 600 in the shift register 212.

[0055] Then, when the latch signal LAT rises, each of the latch circuits 214 simultaneously latches the print data [SIH,SIL] held in the shift register 212. Note that LT1, LT2, ..., LTn shown in Figure 8 represent the print data [SIH,SIL] latched by the latch circuits 214 corresponding to the 1st, 2nd, ..., nth stage shift register 212.

[0056] The decoder 216 outputs the logic level of the selection signal S in each of the periods T1, T2, and T3, according to the size of the dots defined in the latched print data [SIH, SIL], as shown in Figure 6. The selection circuit 230 then generates the drive signal VOUT by selecting or deselecting the signal waveform included in the drive signal COM according to the logic level of the selection signal S output by the decoder 216.

[0057] Specifically, when the print data [SIH,SIL]=[1,1] is input to the decoder 216, the decoder 216 sets the logic level of the selection signal S to H,H,L levels during periods T1, T2, and T3. As a result, the selection circuit 230 selects the trapezoidal waveform Adp during period T1, selects the trapezoidal waveform Bdp during period T2, and does not select the trapezoidal waveform Cdp during period T3. Consequently, the drive signal selection circuit 200 outputs the drive signal VOUT corresponding to the "large dot LD".

[0058] When a drive signal VOUT corresponding to a "large dot LD" is supplied to the piezoelectric element 60 of the ejection unit 600, the ejection unit 600 ejects a moderate amount of ink during period T1, a small amount of ink during period T2, and no ink during period T3. The moderate and small amounts of ink ejected from the ejection unit 600 then land on and combine with the medium P, forming a "large dot LD" on the medium P.

[0059] Furthermore, when the print data [SIH,SIL]=[1,0] is input to the decoder 216, the decoder 216 sets the logic level of the selection signal S to H, L, L levels during periods T1, T2, and T3. As a result, the selection circuit 230 selects the trapezoidal waveform Adp during period T1, does not select the trapezoidal waveform Bdp during period T2, and does not select the trapezoidal waveform Cdp during period T3. Consequently, the drive signal selection circuit 200 outputs the drive signal VOUT corresponding to "Middle Dot MD".

[0060] When a drive signal VOUT corresponding to "medium dot MD" is supplied to the piezoelectric element 60 of the ejection unit 600, the ejection unit 600 ejects a moderate amount of ink during period T1, does not eject ink during period T2, and does not eject ink during period T3. The moderate amount of ink ejected from the ejection unit 600 then lands on the medium P, forming "medium dot MD" on the medium P.

[0061] Furthermore, when the decoder 216 receives the print data [SIH,SIL]=[0,1], the decoder 216 sets the logic level of the selection signal S to L, H, L levels during periods T1, T2, and T3. As a result, the selection circuit 230 does not select the trapezoidal waveform Adp during period T1, selects the trapezoidal waveform Bdp during period T2, and does not select the trapezoidal waveform Cdp during period T3. Consequently, the drive signal selection circuit 200 outputs the drive signal VOUT corresponding to "small dot SD".

[0062] When a drive signal VOUT corresponding to "small dot SD" is supplied to the piezoelectric element 60 of the ejection unit 600, the ejection unit 600 does not eject ink during period T1, ejects a small amount of ink during period T2, and does not eject ink during period T3. Then, the small amount of ink ejected from the ejection unit 600 lands on the medium P, forming "small dot SD" on the medium P.

[0063] Furthermore, when the decoder 216 receives the print data [SIH,SIL]=[0,0], the decoder 216 sets the logic level of the selection signal S to L,L,H levels during periods T1, T2, and T3. As a result, the selection circuit 230 does not select the trapezoidal waveform Adp during period T1, does not select the trapezoidal waveform Bdp during period T2, and selects the trapezoidal waveform Cdp during period T3. Consequently, the drive signal selection circuit 200 outputs the drive signal VOUT corresponding to "non-recorded ND".

[0064] When a drive signal VOUT corresponding to "non-recording ND" is supplied to the piezoelectric element 60 of the ejection unit 600, the ejection unit 600 does not eject ink during period T1, does not eject ink during period T2, and does not eject ink during period T3. Therefore, no ink is ejected from the ejection unit 600, and no dots are formed on the medium P, resulting in "non-recording ND".

[0065] At this time, the corresponding selection circuit 230 outputs a drive signal VOUT that includes a trapezoidal waveform Cdp. Therefore, micro-vibrations are performed. As a result, the risk of an increase in ink viscosity near the nozzle opening of the corresponding ejection unit 600 is reduced.

[0066] As described above, in the liquid dispensing device 1 of this embodiment, the dispensing module 20 has a piezoelectric element 60 that is driven when a drive signal COM is supplied, and the driving of the piezoelectric element 60 causes ink, which is an example of a liquid, to be dispensed from the nozzle 651.

[0067] 3.2 Configuration and Operation of Current Detection Circuit Next, the configuration and operation of the current detection circuit 70 will be described. Figure 9 shows an example of the configuration of the current detection circuit 70. As shown in Figure 9, the current detection circuit 70 includes a semiconductor device 700 and a current detector 710.

[0068] The current detector 710 detects the drive current Icom generated as the drive signal COM propagates, as a current detection signal DI. Such a current detector 710 may include a shunt resistor and an operational amplifier that amplifies the voltage signal, and can employ a resistance detection type current detection method that converts the current to be detected into a voltage and calculates the current value of the current to be detected from the converted voltage value, or a magnetic field detection type current detection method that calculates the current value of the current to be detected based on the magnetic field generated by the flow of the current to be detected. Furthermore, various magnetic field detection methods can be used for current detection, including a magnetic field detection method using a core material, in which a core material is placed around the wiring through which the current to be detected flows, and the current value of the current to be detected is calculated by detecting the magnetic field generated in the core material as the current to be detected flows through the wiring; a magnetic field detection method that does not use a core material, in which the current to be detected is drawn into a dedicated integrated circuit, and the current value of the current to be detected is calculated by detecting the magnetic field generated as the current to be detected flows inside the integrated circuit; and a magnetic field detection method using a magneto impedance element (MI element) that non-contactively detects the magnetic field generated as the current to be detected flows, thereby calculating the current value of the current to be detected.

[0069] In this embodiment, the current detector 710 detects the amount of drive current Icom generated as the drive signal COM drives the piezoelectric element 60. Therefore, if a loss occurs when detecting the drive current Icom, distortion will occur in the waveform of the drive signal COM, resulting in a print head error. This may worsen the ink ejection characteristics from the print head 2. Therefore, as a current detection method for detecting the amount of drive current Icom generated in conjunction with the propagation of the drive signal COM in the liquid ejection device 1, it is preferable that the method has small losses associated with detecting the amount of drive current Icom. Furthermore, considering that the current detection circuit 70 in this embodiment is provided on the print head 2, it is preferable that the current detection circuit 70 has a configuration that can be realized in a space-saving manner from the viewpoint of miniaturizing the print head 2. Taking these points into consideration, it is preferable that the current detector 710 is a magnetic field detection type using an MI element, which has small losses because it detects the current value of the drive current Icom without contact, and can be mounted in a space-saving manner because it can detect the current value of the drive current Icom with a single core component.

[0070] The semiconductor device 700 includes a CPU 701, a clock circuit 702, a timer circuit 703, a memory circuit 704, and a comparator circuit 705. The semiconductor device 700 receives a current detection control signal IDS output by the control circuit 100 and a current detection signal DI output by the current detector 710. Based on the input current detection control signal IDS and current detection signal DI, the semiconductor device 700 detects the state of the print head 2, generates a current detection result signal IDR corresponding to the detected state of the print head 2, and outputs it to the control circuit 100.

[0071] The clock circuit 702 generates a clock signal CK that defines the operating timing of each part of the semiconductor device 700 and outputs it to the CPU 701 and the timer circuit 703. Such a clock circuit 702 may be an internal clock circuit located inside the semiconductor device 700 and generating the clock signal CK, as shown in Figure 9, or it may be an external clock circuit located outside the semiconductor device 700 and including an oscillator (not shown). Furthermore, the clock circuit 702 may be partially located inside the semiconductor device 700 and partially located outside the semiconductor device 700. The clock signal CK output by the clock circuit 702 may also be supplied to various parts of the semiconductor device 700, in addition to the CPU 701 and the timer circuit 703.

[0072] A clock signal CK is input to the timer circuit 703. The timer circuit 703 generates a timer signal TC of a predetermined period by dividing or multiplying the input clock signal CK and outputs it to the CPU 701. In other words, the current detection circuit 70 has a timer circuit 703.

[0073] The memory circuit 704 stores information such as the operating status of the print head 2 and various information about the print head 2 corresponding to the current detection signal DI detected by the current detector 710, based on the memory circuit control signal MC output by the CPU 701. The memory circuit 704 also reads the stored information based on the memory circuit control signal MC output by the CPU 701 and outputs the read information to the CPU 701 as a read signal MR. The information stored in the memory circuit 704 includes, for example, the cumulative value of the drive current Icom supplied to the ejection module 20, the cumulative printing time during which the print head 2 performed the printing process, the cumulative driving time during which the print head 2 was driven, and other drive information corresponding to the operation of the print head 2, as well as judgment information used for various judgments in the current detection circuit 70. In addition to the above-mentioned drive information and judgment information, the memory circuit 704 may also include information on the execution of maintenance processes in the maintenance unit 80.

[0074] The comparison circuit 705 includes comparators 706 and 707.

[0075] The comparator 706 receives the threshold information signal Sit1 output by the CPU 701 and the current detection signal DI output by the current detector 710. The comparator 706 then determines whether the current detection signal DI is greater than or equal to the current threshold Ith1 defined by the threshold information signal Sit1. A comparison result signal Icm1, which indicates the comparison result, is generated and output to the CPU 701. The comparator 707 also receives the threshold information signal Sit2 output by the CPU 701 and the current detection signal DI output by the current detector 710. The comparator 707 then generates a comparison result signal Icm2, which indicates whether the current detection signal DI is greater than or equal to the current threshold Ith2 defined by the threshold information signal Sit2, and outputs it to the CPU 701.

[0076] In this embodiment, comparator 706 outputs a high-level comparison result signal Icm1 when the input current detection signal DI is equal to or greater than the current threshold Ith1, and comparator 707 outputs a high-level comparison result signal Icm2 when the input current detection signal DI is equal to or greater than the current threshold Ith2. For example, comparators or other comparison arithmetic units can be used as such comparators 706 and 707.

[0077] The CPU 701 controls various configurations of the semiconductor device 700, including the memory circuit 704 and the comparator circuit 705, based on the current detection control signal IDS input from the control circuit 100 and the current detection signal DI output from the current detector 710. It also determines the drive state of the print head 2 based on the current detection signal DI output from the current detector 710, the timer signal TC output from the timer circuit 703, the read signal MR read from the memory circuit 704, and the comparison result signals Icm1 and Icm2 output from the comparators 706 and 707. The CPU 701 also generates a current detection result signal IDR corresponding to the determined drive state of the print head 2 and outputs it to the control circuit 100. In addition, it generates a memory circuit control signal MC containing information corresponding to the determined drive state of the print head 2 and outputs it to the memory circuit 704. As a result, information corresponding to the drive state of the print head 2 is stored in the memory circuit 704. In other words, the CPU 701 controls the operation of the current detection circuit 70 based on the current detection signal DI corresponding to the drive current Icom. The CPU 701 may also include an A / D converter or a D / A converter that converts various input signals into digital or analog signals.

[0078] A specific example of the operation of the current detection circuit 70 configured as described above will now be explained. Figure 10 is a diagram illustrating a specific example of the operation of the current detection circuit 70. In addition to the various signals in the current detection circuit 70, Figure 10 also shows the control signal CTR1 that controls the movement of the print head 2 in the main scanning direction. Here, the forward control signal Fwd as the control signal CTR1 shown in Figure 10 is a signal to move the print head 2 from one end to the other along the main scanning direction, the reverse control signal Rev as the control signal CTR1 is a signal to move the print head 2 from the other end to the one end along the main scanning direction, and the stop control signal Stop as the control signal CTR1 is a signal to stop the print head 2. In the following explanation, the direction of movement of the print head 2 when the control circuit 100 outputs the forward control signal Fwd as the control signal CTR1 may be referred to as the forward direction, and the direction of movement of the print head 2 when the control circuit 100 outputs the reverse control signal Rev as the control signal CTR1 may be referred to as the reverse direction.

[0079] As shown in Figure 10, the image formation period during which the liquid ejection device 1 ejects ink onto the medium P to form a desired image on the medium P includes a movement direction switching period Tr and a main scanning direction movement period Tm.

[0080] The movement direction switching period Tr is the period during which the control circuit 100 outputs a stop control signal Stop as a control signal CTR1, and corresponds to the period during which the print head 2 is stopped. During this movement direction switching period Tr, the movement direction of the print head 2 is switched from the forward direction to the reverse direction, or from the reverse direction to the forward direction. Also, during the movement direction switching period Tr, the selection circuit 230 of the drive signal selection circuit 200 is controlled to be non-conductive. Therefore, the drive signal VOUT based on the drive signal COM is not supplied to the piezoelectric element 60. Consequently, the drive current generated when the drive signal COM propagates through the current detection circuit 70 during the movement direction switching period Tr The current value of Icom will be very low. Furthermore, during the movement direction switching period Tr, the drive circuit 50 may output a constant voltage signal Vc as the drive signal COM.

[0081] The main scanning direction movement period Tm is the period during which the carriage 24 included in the print head 2 moves back and forth along the main scanning direction, and includes a non-printing period To during which ink is not ejected to the medium P, and a printing period Tp during which ink is ejected to the medium P.

[0082] The non-printing period To is the period during which the print head 2 does not eject ink to the medium P and performs slight vibrations. That is, during the non-printing period To, the piezoelectric element 60 is supplied with a drive signal VOUT corresponding to the non-recording ND shown in Figure 8. At this time, the piezoelectric element 60 is slightly displaced to the extent that no ink is ejected from the corresponding nozzle 651. That is, the amount of current generated in conjunction with the drive signal COM supplied to the piezoelectric element 60 during the non-printing period To is small. Therefore, the current value of the drive current Icom generated when the drive signal COM propagates through the current detection circuit 70 during the non-printing period To is low, similar to the current value of the drive current Icom generated when the drive signal COM propagates through the current detection circuit 70 during the movement direction switching period Tr.

[0083] The printing period Tp is the period during which the print head 2 ejects ink onto the medium P. That is, during the printing period Tp, the piezoelectric element 60 is supplied with a drive signal VOUT, as shown in Figure 8, corresponding to the amount of ink ejected from the corresponding nozzle 651. At this time, the piezoelectric element 60 is significantly displaced so that ink is ejected from the corresponding nozzle 651. Therefore, the amount of current generated in conjunction with the drive signal COM supplied to the piezoelectric element 60 during the printing period Tp is sufficiently larger than the amount of current generated in conjunction with the drive signal COM when the piezoelectric element 60 is supplied with a drive signal VOUT corresponding to non-recording ND. Thus, the current value of the drive current Icom generated when the drive signal COM propagates through the current detection circuit 70 during the printing period Tp is sufficiently higher than the current value of the drive current Icom generated when the drive signal COM propagates through the current detection circuit 70 during the movement direction switching period Tr and the non-printing period To.

[0084] Here, the non-printing period To includes the period within the main scanning direction movement period Tm during which the medium P is not positioned opposite the nozzle-forming surface on which the nozzles 651 of the print head 2 are formed, and the printing period Tp includes the period within the main scanning direction movement period Tm during which the printing area of ​​the medium P is positioned opposite the nozzle-forming surface on which the nozzles 651 of the print head 2 are formed. In the following description, the area where the print head 2 is positioned during the non-printing period To may be referred to as the non-printing area, and the area where the print head 2 is positioned during the printing period Tp may be referred to as the printing area.

[0085] As described above, the comparator 706 outputs a comparison result signal Icm1 at an H level when the input current detection signal DI is greater than or equal to the current threshold Ith1 defined by the threshold information signal Sit1. The CPU 701 generates a threshold information signal Sit1 that includes a current threshold Ith1 which is smaller than the current detection signal DI corresponding to the current value of the drive current Icom generated when the drive signal COM propagates through the current detection circuit 70 during the printing period Tp, and larger than the current detection signal DI corresponding to the current value of the drive current Icom generated when the drive signal COM propagates through the current detection circuit 70 during the movement direction switching period Tr and the non-printing period To, and outputs this to the comparator 706. Therefore, during the image formation period in which the liquid ejection device 1 ejects ink onto the medium P to form a desired image on the medium P, the comparator 706 outputs a comparison result signal Icm1 at an H level during the printing period Tp, and outputs a comparison result signal Icm1 at an L level to the CPU 701 during the movement direction switching period Tr and the non-printing period To.

[0086] In other words, the comparator 706 outputs a comparison result signal Icm1 at an H level to the CPU 701 during the period when the print head 2 is ejecting ink onto the medium P, and outputs a comparison result signal Icm1 at an L level to the CPU 701 during the period when the print head 2 is not ejecting ink onto the medium P. As a result, the CPU 701 receives the comparison result signal Ic from the comparator 706. The operating status of printhead 2 is determined based on the logical level of m1.

[0087] In other words, the comparator 706 compares the current detection signal DI corresponding to the drive current Icom with the current threshold Ith1 defined by the threshold information signal Sit1, and the CPU 701 determines the operating state of the print head 2 according to the comparison result signal Icm1 output by the comparator 706. Here, the current threshold Ith1 input to the comparator 706 may be changed based on the threshold information signal Sit1 output by the CPU 701. As a result, even if the amount of current generated based on the drive signal COM changes depending on the type of ink ejected onto the medium P or the number of nozzles in the ejection module 20, the CPU 701 can accurately determine the operating state of the print head 2 according to the comparison result signal Icm1 output by the comparator 706.

[0088] As described above, the comparator 707 outputs a comparison result signal Icm2 at an H level when the input current detection signal DI is greater than or equal to the current threshold Ith2 defined by the threshold information signal Sit2. At this time, the current threshold Ith2 defined by the threshold information signal Sit2 input to the comparator 707 is set to a value that is sufficiently larger than the current detection signal DI corresponding to the current value of the drive current Icom generated when the drive signal COM propagates through the current detection circuit 70 during the printing period Tp. That is, the current threshold Ith2 defined by the threshold information signal Sit2 is greater than the current threshold Ith1 defined by the threshold information signal Sit1.

[0089] The comparator 707 then detects whether an unintended large current is being supplied to the ejection module 20 due to an abnormality in the drive current Icom generated based on the drive signal COM supplied to the print head 2. In other words, the current threshold Ith2 defined by the threshold information signal Sit2 is a threshold for determining whether the current value of the drive current Icom generated based on the drive signal COM is normal or not. If the current value of the drive current Icom is an unintended large current, the comparator 707 outputs a high-level comparison result signal Icm2 to the CPU 701.

[0090] The CPU 701 determines whether or not an abnormal current is occurring in the print head 2 based on the logic level of the comparison result signal Icm2 output by the comparator 707. If the CPU 701 determines that an abnormal current is occurring in the print head 2, it generates a current detection result signal IDR containing information indicating that an abnormal current is occurring in the print head 2 and outputs it to the control circuit 100. The control circuit 100 stops the operation of the print head 2 according to the input current detection result signal IDR. Specifically, the CPU 701 stops the ejection of ink from the print head 2 if the amount of drive current Icom based on the current detection signal DI is greater than or equal to a predetermined current threshold Ith2 which is greater than the current threshold Ith1. This allows for early detection of abnormalities in the print head 2.

[0091] Furthermore, the CPU 701 can also detect whether unintended leakage current is occurring in the piezoelectric element 60 or the drive signal selection circuit 200 of the ejection module 20, based on the amount of drive current Icom corresponding to the drive signal COM supplied to the print head 2.

[0092] Specifically, if unintended leakage current occurs in the piezoelectric element 60 or drive signal selection circuit 200 of the ejection module 20, the CPU 701 can detect whether or not unintended leakage current is occurring in the piezoelectric element 60 or drive signal selection circuit 200 of the ejection module 20 by setting a current threshold Ith2 between the amount of drive current Icom generated in conjunction with the drive signal COM when there is no unintended leakage current in the piezoelectric element 60 or drive signal selection circuit 200 of the ejection module 20 and the amount of drive current Icom generated in conjunction with the drive signal COM when there is unintended leakage current in the piezoelectric element 60 or drive signal selection circuit 200 of the ejection module 20. The accuracy of anomaly detection in the head 2 can be further improved. Here, the current threshold Ith2 input to the comparator 707 may be changeable based on the threshold information signal Sit2 output by the control circuit 100.

[0093] When ink is ejected from the print head 2, the CPU 701 calculates the cumulative value of the drive current Icom generated in conjunction with the drive signal COM supplied to the print head 2 as the cumulative drive current T-Icom, and stores the calculated cumulative drive current T-Icom in the memory circuit 704.

[0094] Specifically, the CPU 701 reads the accumulated drive current T-Icom stored in the memory circuit 704 as a read signal MR. Then, during the period when the print head 2 ejects ink onto the medium P, specifically during the period when the H-level comparison result signal Icm1 is input, the CPU 701 acquires the current value of the drive current Icom defined by the current detection signal DI at at least one of the rising and falling edges of the timer signal TC. The CPU 701 then adds the acquired drive current Icom defined by the current detection signal DI to the accumulated drive current T-Icom read from the memory circuit 704 and holds it as the new accumulated drive current T-Icom. Subsequently, at the time when the image formation period ends, the CPU 701 generates a memory circuit control signal MC to store the accumulated drive current T-Icom to be held in the memory circuit 704 and outputs it to the memory circuit 704. As a result, the accumulated drive current T-Icom calculated by the CPU 701 is stored in the memory circuit 704. In other words, the memory circuit 704 stores the cumulative value of the drive current Icom.

[0095] Furthermore, the CPU 701 reads the cumulative drive current T-Icom stored in the memory circuit 704 as a read signal MR based on the current detection control signal IDS input from the control circuit 100. Then, the CPU 701 estimates the lifespan of the print head 2 and the ejection module 20 based on the read cumulative drive current T-Icom. In other words, the CPU 701 calculates the estimated lifespan of the ejection module 20 according to the cumulative drive current T-Icom.

[0096] As described above, the piezoelectric element 60 shown in this embodiment is a capacitive load configured such that a piezoelectric body 601 is sandwiched between electrodes 611 and 612, and is displaced by the drive signal VOUT supplied to electrode 611. The amount of displacement of the piezoelectric element 60, which is such a capacitive load, also depends on the drive current Icom generated in conjunction with the drive signal COM. Therefore, by accumulating the amount of drive current Icom supplied to the print head 2 and holding it in the print head 2, the degradation state of the piezoelectric element 60 can be accurately determined from the amount of current supplied to the piezoelectric element 60 in the print head 2 and the ejection module 20 having the print head 2. The CPU 701 then estimates the lifespan of the ejection module 20 including the piezoelectric element 60 based on the degradation state of the piezoelectric element 60. This improves the calculation accuracy of the lifespan estimation of the print head 2 and the ejection module 20 having the print head 2.

[0097] Furthermore, since the cumulative drive current T-Icom, which is the cumulative value of the drive current Icom supplied to the print head 2, is stored in the memory circuit 704 included in the current detection circuit 70 of the print head 2, even when the print head 2 is to be reused, the CPU 701 can read the cumulative drive current T-Icom stored in the memory circuit 704 and calculate the estimated lifespan of the print head 2 and the ejection module 20 of the print head 2 based on the read cumulative drive current T-Icom. Then, by determining whether the print head 2 is in a condition suitable for reuse based on the calculated estimated lifespan, the risk of a reusable print head 2 being mistakenly discarded is reduced, and the risk of a print head 2 unsuitable for reuse being mistakenly installed in the liquid ejection device 1 is also reduced. In other words, more appropriate reuse of the print head 2 can be achieved.

[0098] Furthermore, the CPU 701 calculates the continuous operating time S-Time, cumulative printing time P-Time, and cumulative operating time T-Time, which indicate the operating status of the print head 2, based on the timer signal TC output by the timer circuit 703.

[0099] The continuous operation time S-Time corresponds to the period during which the print head 2 continuously ejects ink. The CPU 701 calculates the continuous operation time S-Time by determining the time during which the print head 2 continuously ejects ink based on the timer signal TC output by the timer circuit 703.

[0100] Specifically, the CPU 701 counts the number of pulses of the timer signal TC input from the timer circuit 703 during the period when the print head 2 continuously ejects ink onto the medium P, specifically, during the period when the CPU 701 receives an H-level comparison result signal Icm1. The CPU 701 then calculates the time during which the print head 2 continuously ejects ink from the number of pulses of the timer signal TC and the period of the pulses of the timer signal TC. Subsequently, the CPU 701 resets the calculated continuous operation time S-Time when the L-level comparison result signal Icm1 is input. In other words, the CPU 701 individually measures the time of each of the multiple periods during which the print head 2 continuously ejects ink during the image formation period in which the print head 2 forms an image on the medium P, as the continuous operation time S-Time.

[0101] The CPU 701 determines whether the measured continuous operation time S-Time is greater than or equal to a predetermined time threshold Tth. Based on this, the CPU 701 determines whether the print head 2 is ejecting ink only in the printing area. Specifically, if the continuous operation time S-Time exceeds the predetermined time threshold Tth, the CPU 701 determines that the period during which the print head 2 is continuously ejecting ink is long relative to the movement speed of the print head 2 and the width of the medium P to which the ink lands. In other words, if the continuous operation time S-Time exceeds the predetermined time threshold Tth, the CPU 701 determines that the print head 2 is ejecting ink in an area outside the printing area. Then, when the continuous operation time S-Time becomes greater than or equal to the predetermined time threshold Tth, the CPU 701 generates a current detection result signal IDR to stop the ejection of ink from the print head 2 and outputs it to the control circuit 100. The control circuit 100 stops the operation of the print head 2 according to the input current detection result signal IDR.

[0102] Specifically, the CPU 701 calculates the continuous operation time S-Time of the ejection module 20 based on the comparison result signal Icm1 output by the comparator 706 and the timer signal TC output by the timer circuit 703. If the calculated continuous operation time S-Time is greater than or equal to a predetermined time threshold Tth, the CPU 701 stops ejecting ink from the print head 2. This reduces the risk of the print head 2 ejecting ink in areas outside the printing area. As a result, the risk of ink ejected from the print head 2 adhering to the platen 43 is reduced. Consequently, the risk of the medium P being contaminated while being transported along the platen 43 is reduced.

[0103] Here, the time threshold Tth used by the CPU 701 to determine whether the continuous operating time S-Time is normal may be changed based on the current detection control signal IDS input from the control circuit 100. Specifically, the control circuit 100 sets the time threshold Tth according to the image data input from outside the liquid ejection device 1, the size of the medium P on which the image corresponding to the image data is formed, and the moving speed of the print head 2 along the main scanning direction. This reduces the risk of the print head 2 ejecting ink in the non-printing area regardless of the size of the medium P, and as a result, reduces the risk of soiling the platen 43 and the risk of soiling the medium P transported along the platen 43.

[0104] The cumulative printing time P-Time corresponds to the cumulative value of the time the print head 2 ejected ink onto the medium P. The CPU 701 calculates the cumulative value of the time the print head 2 ejected ink onto the medium P as the cumulative printing time P-Time based on the timer signal TC that is input during the time when the H-level comparison result signal Icm1 is continuously input, and stores the calculated cumulative printing time P-Time in the memory circuit 704.

[0105] Specifically, the CPU 701 reads the cumulative printing time P-Time stored in the memory circuit 704. The CPU 701 then counts the number of pulses of the timer signal TC input from the timer circuit 703 during the period when the print head 2 ejects ink onto the medium P, specifically during the period when the H-level comparison result signal Icm1 is input. The CPU 701 then calculates the time that the print head 2 ejected ink onto the medium P from the number of pulses of the timer signal TC and the period of the pulses of the timer signal TC. The CPU 701 adds the calculated time that the print head 2 ejected ink onto the medium P to the cumulative printing time P-Time read from the memory circuit 704 and holds it as the new cumulative printing time P-Time. Subsequently, when the image formation period ends, the CPU 701 generates a memory circuit control signal MC to store the held cumulative printing time P-Time into the memory circuit 704 and outputs it to the memory circuit 704. As a result, the cumulative printing time P-Time calculated by the CPU 701 is stored in the memory circuit 704.

[0106] The cumulative printing time P-Time calculated by the CPU 701 is used to calculate the estimated lifespan of the ejection module 20 based on the cumulative drive current T-Icom mentioned above. This allows the CPU 701 to calculate the amount of current supplied to the piezoelectric element 60 of the ejection module 20 per unit time. As a result, the degradation state of the print head 2 and the ejection module 20 of the print head 2 can be grasped with higher accuracy. In other words, the accuracy of calculating the estimated lifespan of the print head 2 and the ejection module 20 of the print head 2 is further improved.

[0107] The cumulative drive time T-Time is the time during which the print head 2 is driven, and corresponds to the cumulative value of the image formation period time during which the desired image is formed on the medium P, which includes the aforementioned movement direction switching period Tr and main scanning direction movement period Tm. The CPU 701 calculates the cumulative value of the image formation period time during which the print head 2 forms the desired image on the medium P based on the timer signal TC as the cumulative drive time T-Time, and stores the calculated cumulative drive time T-Time in the memory circuit 704.

[0108] Specifically, the CPU 701 reads the cumulative operating time T-Time stored in the memory circuit 704. The CPU 701 then counts the number of pulses of the timer signal TC input from the timer circuit 703 during the image formation period in which the print head 2 forms an image on the medium P, and calculates the duration of the image formation period from the number of pulses of the timer signal TC and the period of the pulses of the timer signal TC. The CPU 701 then adds the calculated duration of the image formation period to the cumulative operating time T-Time read from the memory circuit 704 and stores it as the new cumulative operating time T-Time. Subsequently, the CPU 701 generates a memory circuit control signal MC to store the stored cumulative operating time T-Time in the memory circuit 704 and outputs it to the memory circuit 704. As a result, the cumulative operating time T-Time calculated by the CPU 701 is stored in the memory circuit 704.

[0109] The cumulative operating time T-Time calculated by the CPU 701 is used to calculate the estimated lifespan of the ejection module 20 based on the cumulative operating current T-Icom mentioned above. This allows the CPU 701 to more accurately determine the degradation state of the ejection module 20 based on the amount of current supplied to the piezoelectric element 60 of the ejection module 20 and the total operating time of the ejection module 20. In other words, the print head 2 and the ejection of the print head 2 The accuracy of calculating the estimated lifetime of module 20 will be further improved.

[0110] In the current detection circuit 70 configured as described above, the CPU 701 calculates the cumulative drive current T-Icom, continuous operation time S-Time, cumulative printing time P-Time, and cumulative drive time T-Time in detail, with reference to Figure 11. Figure 11 shows an example of the calculation operation in the CPU 701. As shown in Figure 11, when the printing process in the liquid ejection device 1 starts, the CPU 701 initializes the continuous operation time S-Time (step S110). The CPU 701 also reads the cumulative drive current T-Icom, cumulative printing time P-Time, cumulative drive time T-Time, current thresholds Ith1 and Ith2, and time threshold Tth from the storage circuit 704 (step S120). The CPU 701 may also obtain at least one of the current thresholds Ith1 and Ith2 and time threshold Tth based on the current detection control signal IDS output by the control circuit 100.

[0111] Subsequently, the current detector 710 included in the current detection circuit 70 detects the current value of the drive current Icom, generates a current detection signal DI corresponding to the current value of the drive current Icom, and outputs it to the CPU 701. That is, the CPU 701 acquires the current detection signal DI corresponding to the current value of the drive current Icom output by the current detector 710 (step S130). Then, the CPU 701 compares the current value of the drive current Icom defined by the current detection signal DI with the current threshold Ith1 (step S140).

[0112] If the current value of the drive current Icom, defined by the current detection signal DI, is greater than the current threshold Ith1 (Y in step S140), the CPU 701 adds the current detection signal DI input from the current detector 710 to the accumulated drive current T-Icom read from the memory circuit 704 and holds it as the new accumulated drive current T-Icom (step S150). Then, the CPU 701 adds "1" to the continuous operation time S-Time (step S160) and also adds "1" to the accumulated printing time P-Time (step S170). After that, the CPU 701 compares the continuous operation time S-Time with the time threshold Tth (step S190).

[0113] On the other hand, if the current value of the drive current Icom, defined by the current detection signal DI, is smaller than the current threshold Ith1 (N in step S140), the CPU 701 initializes the continuous operating time S-Time to "0" (step S170), and then the CPU 701 compares the continuous operating time S-Time with the time threshold Tth (step S190).

[0114] If the continuous operating time S-Time is less than the time threshold Tth (Y in step S190), the CPU 701 compares the current value of the drive current Icom defined by the current detection signal DI with the current threshold Ith2 (step S200). If the current value of the drive current Icom defined by the current detection signal DI is less than the current threshold Ith2 (Y in step S200), the CPU 701 adds "1" to the cumulative operating time T-Time (step S210).

[0115] Subsequently, the CPU 701 determines whether the printing process in the liquid ejection device 1 has finished (step S220). If the printing process in the liquid ejection device 1 has not finished (N in step S220), the CPU 701 obtains a current detection signal DI corresponding to the current value of the drive current Icom output by the current detector 710 (step S130), and repeats the same steps.

[0116] On the other hand, if the continuous operating time S-Time is greater than the time threshold Tth (N in step S190), or if the current value of the drive current Icom defined by the current detection signal DI is greater than the current threshold Ith2 (Y in step S200), the CPU 701 will... A current detection result signal IDR indicating an abnormality in the drive current Icom based on the drive signal COM supplied to D2 is generated and output to the control circuit 100 (step S230).

[0117] Then, after the CPU 701 outputs a current detection result signal IDR indicating an abnormality to the control circuit 100, or when the printing process in the liquid ejection device 1 is completed (Y in step S220), the CPU 701 stores the accumulated drive current T-Icom, accumulated printing time P-Time, and accumulated drive time T-Time in the memory circuit 704 (step S240), and terminates the printing process of the liquid ejection device 1.

[0118] Here, the piezoelectric element 60 is an example of a driving element, the driving signal VOUT that drives the piezoelectric element 60 is an example of a driving signal, and the driving signal COM is also an example of a driving signal. The CPU 701 is an example of a processor. The current threshold Ith1 is an example of a first threshold, the time threshold Tth is an example of a second threshold, and the current threshold Ith2 is an example of a third threshold. The comparator 706 is an example of a first comparator, and the comparator 707 is an example of a second comparator. The timer signal TC output by the timer circuit 703 is an example of a timer output.

[0119] 4. Effects The print head 2 of the liquid ejection device 1 configured as described above includes an ejection module 20 that includes a piezoelectric element 60 and an ink ejection nozzle 651, and a current detection circuit 70 that detects a drive current Icom generated as the drive signal COM propagates. The current detection circuit 70 includes a current detector 710 that detects the drive current Icom as a current detection signal DI, and a CPU 701 that controls the operation of the current detection circuit 70 according to the current detection signal DI. In other words, the current detection circuit 70 of the print head 2 directly detects the current value of the drive current Icom supplied to the ejection module 20.

[0120] The amount of drive current Icom supplied to the ejection module 20 changes according to the operating state of the print head 2. In other words, the print head 2 in the liquid ejection device 1 of this embodiment can directly detect the amount of drive current Icom supplied to the ejection module 20 using the current detector 710 of the print head 2, thereby allowing for detailed understanding and management of the print head 2's state.

[0121] Furthermore, the piezoelectric element 60 included in the ejection module 20 of the print head 2 deteriorates in characteristics as the supplied current increases. In the print head 2 of the liquid ejection device 1 in this embodiment, the amount of drive current Icom supplied to the ejection module 20 can be directly detected, making it easy to calculate the cumulative value of the current supplied to the piezoelectric element 60 included in the ejection module 20. The print head 2 has a memory circuit 704, and the memory circuit 704 stores the cumulative value of the drive current Icom supplied to the ejection module 20. The CPU 701 calculates the estimated lifespan of the print head 2 and the ejection module 20 based on the cumulative value of the drive current Icom stored in the memory circuit 704, thereby improving the accuracy of the lifespan estimation of the print head 2 and the ejection module 20. In other words, in the print head 2 of the liquid ejection device 1 in this embodiment, This allows for a more detailed understanding and management of the estimated lifespan of printhead 2.

[0122] Furthermore, the amount of drive current Icom supplied to the print head 2 differs significantly between the printing period Tp during which the print head 2 ejects ink to the medium P, the non-printing period To during which the print head 2 does not eject ink to the medium P, and the movement direction switching period Tr. In the print head 2 of the liquid ejection device 1 in this embodiment, the amount of drive current Icom supplied to the ejection module 20 can be directly detected in the current detection circuit 70, and therefore the current detection circuit 70 compares the current detection signal DI with the current threshold Ith1 using a comparator 70. The CPU 701 has a 6 and determines the operating state of the ejection module 20 in accordance with the comparison result signal Icm1, which is the comparison result of the comparator 706, thereby enabling high-precision determination of the operating state of the print head 2 and the ejection module 20. In other words, in the liquid ejection device 1 of this embodiment, the operating state of the print head 2 can be understood and managed in more detail.

[0123] Furthermore, in the print head 2 of the liquid ejection device 1 in this embodiment, the current detection circuit 70 directly detects the amount of drive current Icom supplied to the ejection module 20. The current detection circuit 70 also has a timer circuit 703, and the CPU 701 can calculate with high accuracy the continuous operation time S-Time, during which the ejection module 20 is continuously ejecting ink, from the comparison result signal Icm1, which indicates the comparison result of the comparator 706, and the timer signal TC output by the timer circuit 703. In other words, the operating state of the print head 2 can be understood and managed in more detail as to whether or not it is ejecting ink onto the medium P. Furthermore, the CPU 701 stops the operation of the ejection module 20 depending on whether or not the calculated continuous operation time S-Time is greater than or equal to a predetermined time threshold Tth, thereby reducing the risk of the ejection module 20 ejecting ink outside the range of the medium P and reducing the risk of the ink ejected by the ejection module 20 adhering to the platen 43. This also reduces the risk of the medium P supported by the platen 43 being contaminated.

[0124] Furthermore, in the print head 2 of the liquid ejection device 1 in this embodiment, the current detection circuit 70 directly detects the amount of drive current Icom supplied to the ejection module 20, and the current detection circuit 70 has a comparator 707 that compares the current detection signal DI with the current threshold Ith2. The CPU 701 detects whether or not there is an abnormality in the print head 2 based on whether or not the amount of drive current Icom based on the current detection signal DI is equal to or greater than the current threshold Ith2. This allows for highly accurate determination of abnormal currents such as unintended leakage currents and overcurrents that may occur in the piezoelectric element 60 or drive signal selection circuit 200 of the print head 2. In other words, in the print head 2 of the liquid ejection device 1 in this embodiment, the abnormal state of the print head 2 can be grasped and managed in more detail.

[0125] Although embodiments and modifications have been described above, the present invention is not limited to these embodiments and can be implemented in various forms without departing from its spirit. For example, the above embodiments can be combined as appropriate.

[0126] The present invention includes configurations that are substantially identical to those described in the embodiments (for example, configurations with the same function, method, and result, or configurations with the same purpose and effect). Furthermore, the present invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Furthermore, the present invention includes configurations that produce the same effects or achieve the same purpose as those described in the embodiments. Furthermore, the present invention includes configurations that add known technology to the configurations described in the embodiments.

[0127] The following conclusions can be drawn from the embodiments described above.

[0128] One form of a print head is, A print head having a drive element that is driven when a drive signal is supplied, and which ejects liquid by driving the drive element, A discharge module including the aforementioned drive element and a nozzle for discharging liquid, A current detection circuit for detecting the drive current generated as the drive signal propagates, Equipped with, The current detection circuit is, A current detector that detects the aforementioned drive current as a current detection signal, A processor that controls the operation of the current detection circuit in accordance with the current detection signal, It has.

[0129] This printhead comprises an ejection module including a drive element and a nozzle for ejecting liquid, and a current detection circuit for detecting the drive current generated as the drive signal propagates. The current detection circuit includes a current detector that detects the drive current as a current detection signal, and a processor that controls the operation of the current detection circuit according to the current detection signal. This allows the amount of current supplied to the ejection module to be directly detected in the printhead. As a result, the state of the printhead 2 can be understood and managed in detail based on the detected amount of current.

[0130] In one embodiment of the print head, The current detection circuit has a storage circuit that stores the cumulative value of the drive current, The processor may calculate the estimated lifespan of the ejection module according to the cumulative value.

[0131] This printhead allows for the direct detection of the amount of current supplied to the ejection module, which significantly contributes to the lifespan of the ejection module. Therefore, based on the detected amount of current, the accuracy of estimating the lifespan of the printhead can be improved as the state of printhead 2.

[0132] In one embodiment of the print head, The current detection circuit has a first comparator that compares the current detection signal with a first threshold value. The processor may determine the operating state of the ejection module according to the comparison result of the first comparator.

[0133] With this printhead, the amount of current supplied to the ejection module, which changes depending on the operating state of the printhead, can be directly detected at the printhead. Therefore, the accuracy of determining the operating state of the printhead 2 can be improved based on the detected amount of current.

[0134] In one embodiment of the print head, The aforementioned first threshold may be modified.

[0135] This printhead allows for the use of an optimal first threshold value depending on the printhead's usage state, thereby further improving the accuracy of determining the operating state of the printhead 2 based on the detected current.

[0136] In one embodiment of the print head, The current detection circuit has a timer circuit, The processor may calculate the continuous operating time of the discharge module from the comparison result and the timer output of the timer circuit.

[0137] With this printhead, the amount of current supplied to the ejection module, which changes depending on whether the printhead is ejecting ink or not, can be directly detected at the printhead. Therefore, based on the detected amount of current, the accuracy of detecting the continuous operating time during which the ejection module continuously ejects ink can be improved as the state of printhead 2.

[0138] In one embodiment of the print head, The processor may stop discharging liquid from the nozzle if the continuous operation time is equal to or greater than a predetermined second threshold.

[0139] This print head reduces the risk of the print head ejecting ink outside of a designated area, thereby reducing the risk of contamination of the transport path and the media itself.

[0140] In one embodiment of the print head, The aforementioned second threshold may be modified.

[0141] This printhead allows for the use of an optimal second threshold depending on the printhead's usage state, further reducing the risk of contamination in the transport path and the media itself.

[0142] In one embodiment of the print head, The current detection circuit has a second comparator that compares the current detection signal with a third threshold value. The processor may stop the discharge of liquid from the nozzle if the amount of the drive current based on the current detection signal is equal to or greater than the third threshold.

[0143] This printhead allows for the direct detection of the amount of current supplied to the printhead, enabling highly accurate detection of abnormalities in the current supplied to the printhead.

[0144] One embodiment of a liquid dispensing device is: A print head having a drive element that is driven when a drive signal is supplied, and which ejects liquid by driving the drive element, A drive circuit that outputs the aforementioned drive signal, Equipped with, The aforementioned print head is A discharge module including the aforementioned drive element and a nozzle for discharging liquid, A current detection circuit for detecting the drive current generated as the drive signal propagates, It has, The current detection circuit is, A current detector that detects the aforementioned drive current as a current detection signal, A processor that controls the operation of the current detection circuit in accordance with the current detection signal, Includes.

[0145] According to this liquid ejection device, the print head comprises an ejection module including a drive element and a nozzle for ejecting liquid, and a current detection circuit for detecting the drive current generated as the drive signal propagates. The current detection circuit includes a current detector that detects the drive current as a current detection signal, and a processor that controls the operation of the current detection circuit according to the current detection signal. This allows the amount of current supplied to the ejection module to be directly detected in the print head. As a result, the state of the print head 2 can be understood and managed in detail based on the detected amount of current. [Explanation of Symbols]

[0146] 1…Liquid ejection device, 2…Print head, 3…Moving mechanism, 4…Conveying mechanism, 10…Print head control circuit, 20…Ejection module, 22…Ink cartridge, 24…Carriage, 31…Carriage motor, 32…Carriage guide shaft, 33…Timing belt, 35…Carriage motor driver, 41…Conveyor motor, 42…Conveyor roller, 43…Platen, 45…Conveyor motor driver, 50…Drive circuit, 60…Piezoelectric element, 70…Current detection circuit, 80…Maintenance unit, 81…Capping member, 82…Wiper Components, 83...Flushing box, 90...Linear encoder, 100...Control circuit, 190...Cable, 200...Drive signal selection circuit, 210...Selection control circuit, 212...Shift register, 214...Latch circuit, 216...Decoder, 230...Selection circuit, 232...Inverter, 234...Transfer gate, 600...Discharge section, 601...Piezoelectric element, 611,612...Electrodes, 621...Diaphragm, 631...Cavity, 632...Nozzle plate, 641...Reservoir, 651...Nozzle, 661...Supply port, 700...Semiconductor equipment, 701...CPU, 702...Clock circuit, 703...Timer circuit, 704...Memory circuit, 705...Comparison circuit, 706,707...Comparator, 710...Current detector, 810...Cleaning mechanism, 820...Wiping mechanism, 830...Flushing mechanism, P...Medium

Claims

1. A print head having a drive element that is driven when a drive signal is supplied, and which ejects liquid by driving the drive element, A discharge module including the aforementioned drive element and a nozzle for discharging liquid, A current detection circuit for detecting the drive current generated as the drive signal propagates, Equipped with, The current detection circuit is, A current detector that detects the aforementioned drive current as a current detection signal, A processor that controls the operation of the current detection circuit in accordance with the current detection signal, It has, The current detection circuit has a storage circuit that stores the cumulative value of the drive current, The processor calculates the estimated lifespan of the ejection module according to the cumulative value. A print head characterized by the following features.

2. The current detection circuit has a first comparator that compares the current detection signal with a first threshold value. The processor determines the operating state of the discharge module according to the comparison result of the first comparator. The print head according to feature 1.

3. A print head having a drive element that is driven when a drive signal is supplied, and which discharges liquid by driving the drive element, A discharge module including the aforementioned drive element and a nozzle for discharging liquid, A current detection circuit for detecting the drive current generated as the drive signal propagates, Equipped with, The current detection circuit is, A current detector that detects the aforementioned drive current as a current detection signal, A processor that controls the operation of the current detection circuit in accordance with the current detection signal, It has, The current detection circuit has a first comparator that compares the current detection signal with a first threshold value. The processor determines the operating state of the discharge module according to the comparison result of the first comparator. The current detection circuit has a timer circuit, The processor calculates the continuous operating time of the ejection module from the comparison result and the timer output of the timer circuit. A print head characterized by the following features.

4. The processor stops the discharge of liquid from the nozzle if the continuous operation time is equal to or greater than a predetermined second threshold. The print head according to feature 3.

5. The aforementioned second threshold can be changed. The print head according to feature 4.

6. The current detection circuit has a storage circuit for storing the cumulative value of the drive current, The processor calculates the estimated lifespan of the ejection module according to the cumulative value. A print head according to any one of claims 3 to 5.

7. The first threshold can be changed. A print head according to any one of claims 2 to 6.

8. The current detection circuit has a second comparator that compares the current detection signal with a third threshold value. The processor stops the discharge of liquid from the nozzle if the amount of the drive current based on the current detection signal is equal to or greater than the third threshold. A print head according to any one of claims 1 to 7.

9. A print head having a drive element that is driven when a drive signal is supplied, and which ejects liquid by driving the drive element, A drive circuit that outputs the aforementioned drive signal, Equipped with, The aforementioned print head is A discharge module including the aforementioned drive element and a nozzle for discharging liquid, A current detection circuit for detecting the drive current generated as the drive signal propagates, It has, The current detection circuit is, A current detector that detects the aforementioned drive current as a current detection signal, A processor that controls the operation of the current detection circuit in accordance with the current detection signal, Includes, The current detection circuit has a storage circuit that stores the cumulative value of the drive current, The processor calculates the estimated lifespan of the ejection module according to the cumulative value. A liquid dispensing device characterized by the following features.

10. A print head having a drive element that is driven when a drive signal is supplied, and which ejects liquid by driving the drive element, A drive circuit that outputs the aforementioned drive signal, Equipped with, The aforementioned print head is A discharge module including the aforementioned drive element and a nozzle for discharging liquid, A current detection circuit for detecting the drive current generated as the drive signal propagates, It has, The current detection circuit is, A current detector that detects the aforementioned drive current as a current detection signal, A processor that controls the operation of the current detection circuit in accordance with the current detection signal, Includes, The current detection circuit has a first comparator that compares the current detection signal with a first threshold value. The processor determines the operating state of the discharge module according to the comparison result of the first comparator. The current detection circuit has a timer circuit, The processor calculates the continuous operating time of the ejection module from the comparison result and the timer output of the timer circuit. A liquid dispensing device characterized by the following features.

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