Method for detecting the temperature of a head chip and liquid dispensing apparatus

Abstract

We provide technology to improve the accuracy of temperature detection at the head chip. [Solution] This disclosure provides a method for detecting the temperature of a head chip including a plurality of nozzles for discharging liquid, a plurality of piezoelectric elements for applying pressure to the liquid to cause the liquid to be discharged from each of the plurality of nozzles, and a temperature detection element. The method includes a temperature detection step in which the temperature of the head chip is detected using the temperature detection element during a micro-vibration application period in which a micro-vibration waveform that does not cause liquid to be discharged from the plurality of nozzles is applied to the plurality of piezoelectric elements. The temperature detection step includes a step of generating a micro-vibration waveform that includes a first waveform having a preset voltage change and a second waveform which is the inverted first waveform.

Description

Technical Field

[0001] The present disclosure relates to a method for detecting the temperature of a head chip and a liquid ejection device.

Background Art

[0002] Patent Document 1 discloses a liquid ejection head including a nozzle that ejects a liquid, a pressure chamber that communicates with the nozzle, a piezoelectric element that generates pressure fluctuations in the liquid in the pressure chamber, and a resistance wiring for detecting the temperature of the pressure chamber.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above prior art, there is a problem that noise caused by a drive signal for driving a piezoelectric element is superimposed on a temperature detection signal, resulting in a decrease in detection accuracy.

Means for Solving the Problems

[0005] According to a first aspect of the present disclosure, there is provided a method for detecting the temperature of a head chip including a plurality of nozzles that eject a liquid, a plurality of piezoelectric elements that apply pressure to the liquid to eject the liquid from the plurality of nozzles, and a temperature detection element. This method includes a temperature detection step of detecting the temperature of the head chip using the temperature detection element during a micro-vibration application period in which a micro-vibration waveform that does not eject the liquid from the plurality of nozzles is applied to the plurality of piezoelectric elements. The temperature detection step includes a step of generating the micro-vibration waveform so as to include a first waveform having a preset voltage change and a second waveform obtained by inverting the first waveform.

[0006] A second embodiment of the present disclosure provides a liquid dispensing device for dispensing liquid. The liquid dispensing device includes a head chip including a plurality of nozzles for dispensing the liquid, a plurality of piezoelectric elements for applying pressure to the liquid to cause the liquid to be dispensed from each of the plurality of nozzles, and a temperature detection element; a drive signal generation unit for generating a micro-vibration waveform that does not cause the liquid to be dispensed from the plurality of nozzles; a drive circuit for applying the micro-vibration waveform to the plurality of piezoelectric elements during a micro-vibration application period; and a temperature detection circuit for detecting the temperature of the head chip using the temperature detection element during the micro-vibration application period. The drive signal generation unit generates the micro-vibration waveform to include a first waveform having a preset voltage change and a second waveform which is the inverted first waveform.

[0007] A third embodiment of the present disclosure provides a method for detecting the temperature of a head chip, which includes a plurality of nozzles for discharging a liquid, a plurality of piezoelectric elements for applying pressure to the liquid to cause it to be discharged from each of the plurality of nozzles, and a temperature sensing element. The method comprises a temperature detection step of detecting the temperature of the head chip using the temperature sensing element during a micro-vibration application period in which a micro-vibration waveform that does not cause the liquid to be discharged from the plurality of nozzles is applied to the plurality of piezoelectric elements. The temperature detection step includes a step of generating the micro-vibration waveform to include a first waveform having a preset voltage change and a second waveform different from the first waveform. The first and second waveforms are formed so as to reduce errors in the detection result of the temperature sensing element caused by a change in the potential of the temperature sensing element due to a change in the potential of the temperature sensing element caused by a change in the potential of the first waveform, by a change in the potential of the temperature sensing element caused by a change in the potential of the second waveform.

[0008] A fourth embodiment of the present disclosure provides a liquid dispensing device for dispensing liquid. The liquid dispensing device includes a head chip including a plurality of nozzles for dispensing the liquid, a plurality of piezoelectric elements for applying pressure to the liquid to cause the liquid to be dispensed from each of the plurality of nozzles, and a temperature detection element; a drive signal generation unit for generating a micro-vibration waveform that does not cause the liquid to be dispensed from the plurality of nozzles; a drive circuit for applying the micro-vibration waveform to the plurality of piezoelectric elements during a micro-vibration application period; and a temperature detection circuit for detecting the temperature of the head chip using the temperature detection element during the micro-vibration application period. The drive signal generation unit generates the micro-vibration waveform to include a first waveform having a preset voltage change and a second waveform different from the first waveform. The first waveform and the second waveform are formed so as to reduce the error in the detection result of the temperature detection element caused by the potential change of the temperature detection element caused by the potential change of the second waveform, which is caused by the potential change of the temperature detection element. [Brief explanation of the drawing]

[0009] [Figure 1] An explanatory diagram showing the configuration of the liquid dispensing device in the embodiment. [Figure 2] Functional block diagram of the control unit and liquid dispensing head. [Figure 3] An explanatory diagram showing the arrangement of nozzle rows and temperature sensing elements. [Figure 4] Cross-sectional view of the head tip. [Figure 5] Conceptual diagram of the liquid dispensing head of the first embodiment. [Figure 6] A timing chart showing the temperature detection method in the first embodiment. [Figure 7] An explanatory diagram showing another example of a micro-vibration waveform in the first embodiment. [Figure 8] An explanatory diagram showing yet another example of a micro-vibration waveform in the first embodiment. [Figure 9] An explanatory diagram showing the micro-vibration waveform in the second embodiment. [Figure 10] Conceptual diagram of the liquid dispensing head of the third embodiment. [Figure 11] A timing chart showing the temperature detection method in the third embodiment. [Figure 12] A timing chart showing the temperature detection method in the fourth embodiment. [Modes for carrying out the invention]

[0010] A. First Embodiment: Figure 1 is an explanatory diagram showing the configuration of a liquid ejection device 400 in an embodiment. The liquid ejection device 400 is an inkjet printing device that ejects ink, which is an example of a liquid, onto a medium PM. A liquid storage unit 410 for storing ink can be attached to the liquid ejection device 400. The liquid ejection device 400 performs printing by ejecting the ink in the liquid storage unit 410 toward the medium PM. The liquid ejection device 400 comprises a liquid ejection head 100, a control unit 420, a moving mechanism 430, a transport mechanism 440, and a platen 450.

[0011] The liquid ejection head 100 has two head tips 101 and 102. However, the liquid ejection head 100 can be configured to have any number of head tips. Each of the head tips 101 and 102 is equipped with multiple nozzles 200, which eject liquid ink supplied from the liquid reservoir 410. Specific embodiments of the liquid reservoir 410 include, for example, a cartridge detachable from the liquid ejection device 400, a bag-shaped ink pack made of a flexible film, and a container such as an ink tank to which ink can be refilled. The ink ejected from the nozzles 200 lands on the medium PM. The medium PM is typically printing paper. However, the medium PM is not limited to printing paper and may be any material such as resin film or fabric.

[0012] The composition of the ink is not particularly limited. For example, it may be an aqueous ink in which a coloring material such as a dye or a pigment is dissolved in an aqueous solvent, a solvent-based ink in which the coloring material is dissolved in an organic solvent, or an ultraviolet curable ink. Further, the liquid ejection device 400 may eject other types of liquids such as paints instead of the ink.

[0013] The moving mechanism 430 includes an annular belt 432 and a carriage 434 fixed to the belt 432. The carriage 434 holds the liquid ejection head 100. The moving mechanism 430 can reciprocate the liquid ejection head 100 along the X direction by rotating the annular belt 432 in both directions.

[0014] The conveyance mechanism 440 conveys the medium PM along the Y direction during the movement of the liquid ejection head 100 by the moving mechanism 430. The Y direction is a direction orthogonal to the X direction. In the present embodiment, the X direction and the Y direction are horizontal directions. The Z direction is a direction intersecting the X direction and the Y direction. In the present embodiment, the Z direction is vertically downward. The liquid ejection head 100 ejects liquid along the Z direction while being conveyed along the X direction. The Z direction is also referred to as the "ejection direction".

[0015] The platen 450 is a support portion that supports the medium PM that receives the landing of the liquid ejected from the liquid ejection head 100. A platen heater 452 is provided on the platen 450. The platen heater 452 can heat the platen 450 to promote the drying of the liquid on the medium PM.

[0016] The control unit 420 controls the liquid ejection operation of the liquid ejection head 100. The control unit 420 controls the moving mechanism 430, the conveyance mechanism 440, and the liquid ejection head 100 to form an image on the medium PM.

[0017] FIG. 2 is a functional block diagram of the control unit 420 and the liquid ejection head 100. In FIG. 2, portions related to the temperature detection of the head chips 101 and 102 and the temperature correction of the drive signal are depicted.

[0018] The control unit 420 includes a control signal supply unit 421, a drive waveform correction unit 422, a drive waveform storage unit 423, and drive signal generation units 424 and 425.

[0019] The control unit 420 can be realized by a computer having a processor and a memory. The functions of the control signal supply unit 421 and the drive waveform correction unit 422 can be realized by the processor executing a computer program stored in the memory. However, part or all of these functions may be realized by a hardware circuit.

[0020] The control signal supply unit 421 supplies various control signals including a dot control signal SI and a dot clock signal CL to the drive circuits 71 and 72 of the liquid ejection head 100. The dot control signal SI is a signal indicating the presence or absence of dots formed on the medium PM and the dot size, and is also called a print signal. The waveform of the drive signal Vin for driving the piezoelectric element 80 to eject liquid from each nozzle 200 is determined according to the dot control signal SI. The dot clock signal CL is a signal defining the dot period.

[0021] The drive waveform correction unit 422 corrects drive waveform data DC1 and DC2 representing the waveforms of the common drive signals COM1 and COM2 according to the detected temperatures of the head chips 101 and 102. Correction data corresponding to the detected temperatures of the head chips 101 and 102 is stored in advance in the drive waveform storage unit 423. The drive waveform correction unit 422 reads first correction data from the drive waveform storage unit 423 according to the detected temperature of the first head chip 101, and corrects the drive waveform data DC1 for the first common drive signal COM1 according to the first correction data. The drive waveform correction unit 422 further reads second correction data from the drive waveform storage unit 423 according to the detected temperature of the second head chip 102, and corrects the drive waveform data DC2 for the second common drive signal COM2 according to the second correction data.

[0022] Furthermore, the drive waveform data DC1 and DC2 may be corrected according to the average value of the detected temperatures of the two head chips 101 and 102. If the temperature detection elements 31 and 32 are composed of resistance thermometers, the drive waveform data DC1 and DC2 may be corrected according to the average value of the current value of the first temperature detection element 31 and the current value of the second temperature detection element 32.

[0023] The drive signal generation units 424 and 425 generate common drive signals COM1 and COM2, respectively, using temperature-corrected drive waveform data DC1 and DC2. The common drive signals COM1 and COM2 are drive signals that are applied in common to multiple piezoelectric elements 80. In the first embodiment, the first common drive signal COM1 is applied in common to multiple piezoelectric elements 80 of the first head chip 101, and the second common drive signal COM2 is applied in common to multiple piezoelectric elements 80 of the second head chip 102.

[0024] The liquid discharge head 100 includes a drive circuit 71 for the first head chip 101, a drive circuit 72 for the second head chip 102, and a temperature detection circuit 310.

[0025] The first head chip 101 includes a plurality of piezoelectric elements 80 that apply pressure to the liquid in order to discharge the liquid from each of the plurality of nozzles 200, and a temperature detection element 301 for detecting the temperature of the first head chip 101. The second head chip 102 similarly includes a plurality of piezoelectric elements 80 and a temperature detection element 302.

[0026] The drive circuit 71 for the first head chip 101 generates drive signals Vin for driving individual piezoelectric elements 80 within the first head chip 101 in accordance with the first common drive signal COM1 and the dot control signal SI. Specifically, the drive circuit 71 generates drive signals Vin that include part or all of the waveform of the first common drive signal COM1 in accordance with the dot control signal SI for each dot period defined by the dot clock signal CL. For example, if the first head chip 101 contains 100 piezoelectric elements 80, 100 drive signals Vin are generated individually. The generation of drive signals Vin for each piezoelectric element 80 by the drive circuit 71 can be realized, for example, by the supply circuit 31 shown in Figure 4 of Japanese Patent Application Publication No. 2023-31984 disclosed by the applicant of this disclosure. The drive circuit 72 for the second head chip 102 is similar.

[0027] The temperature detection circuit 310 generates a temperature detection signal Dt1 indicating the temperature of the first head chip 101 using a temperature detection element 301. The temperature detection circuit 310 further generates a temperature detection signal Dt2 indicating the temperature of the second head chip 102 using a temperature detection element 302. The temperature detection signals Dt1 and Dt2 are supplied to the drive waveform correction unit 422 of the control unit 420.

[0028] Figure 3 is an explanatory diagram showing the arrangement of nozzle rows and temperature sensing elements. The first head chip 101 has two nozzle rows NL1 and NL2, and the second head chip 102 has two nozzle rows NL3 and NL4. Each of the nozzle rows NL1 to NL4 has nozzles 200 arranged along the Y direction. The temperature sensing element 301 of the first head chip 101 is arranged to surround the outer periphery of the two nozzle rows NL1 and NL2 of the first head chip 101. The temperature sensing element 302 of the second head chip 102 is arranged to surround the outer periphery of the two nozzle rows NL3 and NL4 of the second head chip 102. However, various other arrangements of the temperature sensing elements 301 and 302 are possible. In this embodiment, resistance thermometers are used as the temperature sensing elements 301 and 302. However, other types of temperature sensors such as thermistors, thermocouples, and IC-type temperature sensors may be used as the temperature sensing elements 301 and 302. Resistance thermometers have the advantage of being able to detect the average temperature of the area in which they are placed.

[0029] Figure 4 is a cross-sectional view of the head tip 101. The head tip 101 has a common liquid chamber 210 into which liquid is supplied from the outside, and nozzle-specific flow channels 220 connecting the common liquid chamber 210 to individual nozzles 200. The common liquid chamber 210 is provided in common to multiple nozzles 200 that constitute one nozzle row. That is, the common liquid chamber 210 temporarily stores the liquid supplied from the liquid storage unit 410 and supplies the liquid to multiple nozzle-specific flow channels 220 for multiple nozzles 200. In Figure 4, the nozzle-specific flow channels 220 for the nozzles 200 of the first nozzle row NL1 and the nozzle-specific flow channels 220 for the nozzles 200 of the second nozzle row NL2 have the same structure.

[0030] Each nozzle channel 220 has a pressure chamber 230 that applies pressure to the liquid. A piezoelectric element 80 is installed in the pressure chamber 230 to change the volume of the pressure chamber 230.

[0031] The common liquid chamber 210 and the multiple nozzle-specific flow paths 220 are mainly formed by a connecting plate 140 and a pressure chamber substrate 150. The connecting plate 140 is a laminate formed by stacking multiple plate-shaped members. The housing portion 160 and the pressure chamber substrate 150 are installed on the upper surface of the connecting plate 140. In a plan view in the Z direction, the pressure chamber substrate 150 is located inside the housing portion 160. A diaphragm 170 is installed on the upper surface of the pressure chamber substrate 150. The pressure chamber 230 is a space defined by the connecting plate 140, the diaphragm 170, and the pressure chamber substrate 150. The pressure chamber substrate 150 is formed, for example, by processing a silicon single crystal substrate using semiconductor processing technology. The connecting plate 140 can also be formed by stacking multiple silicon single crystal substrates.

[0032] A nozzle plate 120 is installed on the lower surface of the communication plate 140. The lower end of the common liquid chamber 210 is sealed with a flexible sealing film 130 made of a resin film or a thin film of metal.

[0033] A wiring board 50 is bonded to the upper surface of the diaphragm 170. The wiring board 50 is a mounting component on which multiple wirings are formed for electrically connecting the control unit 420 and the head chip 101. A drive circuit 71 for driving the piezoelectric element 80 is mounted on the wiring board 50. When the piezoelectric element 80 vibrates, the vibration is transmitted to the pressure chamber 230, causing pressure fluctuations in the pressure chamber 230. The liquid is discharged from the nozzle 200 by the pressure generated by the piezoelectric element 80. The piezoelectric element 80 has a first electrode 81, a second electrode 82, and a piezoelectric body 83 positioned between the first electrode 81 and the second electrode 82. The first electrode 81 is connected to a drive wiring 84. The wiring between the drive wiring 84 and the drive circuit 71 is not shown in the figure. The first electrode 81 is provided individually for each piezoelectric element 80. Regarding the second electrode 82 and piezoelectric element 83, one second electrode 82 and one piezoelectric element 83 are provided that are common to multiple piezoelectric elements 80 that drive one row of nozzles 200.

[0034] A temperature detection element 301 is positioned near the piezoelectric element 80. The temperature detection element 301 is positioned between the piezoelectric body 83 and the diaphragm 170. As shown in Figure 3, the temperature detection element 301 is positioned to surround the multiple nozzles 200 in a plan view. Preferably, the temperature detection element 301 is a resistance thermometer having a portion that contacts the piezoelectric body 83 of the piezoelectric element 80.

[0035] Since the temperature detection element 301 is located near the piezoelectric element 80, noise caused by the drive signal of the piezoelectric element 80 may be superimposed on the temperature detection signal Dt1, potentially degrading the detection accuracy. If the temperature detection element 301 has a portion that contacts the piezoelectric body 83, the generation of noise caused by the drive signal becomes even more pronounced. Therefore, in this embodiment, as will be described later, measures have been taken to reduce the influence of noise caused by the drive signal of the piezoelectric element 80 on the detection temperature of the head chip 101.

[0036] Figure 5 is a conceptual diagram of the liquid discharge head 100 of the first embodiment, which is a simplified representation of the configuration of the first embodiment described in Figures 1 to 4. The first drive circuit 71 generates a drive signal Vin1 to supply to each piezoelectric element 80 of the first nozzle row NL1 and a drive signal Vin2 to supply to each piezoelectric element 80 of the second nozzle row NL2, according to the first common drive signal COM1 and the dot control signal SI, at each dot period defined by the dot clock signal CL. The second drive circuit 72 generates a drive signal Vin3 to supply to each piezoelectric element 80 of the third nozzle row NL3 and a drive signal Vin4 to supply to each piezoelectric element 80 of the fourth nozzle row NL4, according to the second common drive signal COM2 and the dot control signal SI, at each dot period defined by the dot clock signal CL. The temperature detection circuit 310 generates a temperature detection signal Dt1 indicating the detected temperature of the first head chip 101 using a temperature detection element 301. The temperature detection circuit 310 further generates a temperature detection signal Dt2 indicating the temperature detected by the second head chip 102 using the temperature detection element 302.

[0037] Figure 6 is a timing chart showing the temperature detection method in the first embodiment. The horizontal axis in Figure 6 is time t. The upper part of Figure 6 shows the drive signals Vin1 and Vin2 of the first head chip 101. The drive signals Vin1 and Vin2 are depicted as having waveforms selected from the first common drive signal COM1 at all dot periods Pd. The lower part of Figure 6 shows the temperature detection signal Dt1 of the first head chip 101.

[0038] Figure 6 shows the first discharge period T1, the non-discharge period TN, and the second discharge period T2. The first discharge period T1 is the period during which the liquid discharge head 100 discharges liquid from the nozzle 200 while moving at a constant speed along the X direction in Figure 1. The second discharge period T2 is the period during which the liquid discharge head 100 discharges liquid from the nozzle 200 while moving at a constant speed in the -X direction, which is the opposite direction to the X direction. The movement path of the liquid discharge head 100 along the X direction is called the "forward path," and the movement path of the liquid discharge head 100 along the -X direction is called the "return path." The non-discharge period TN is the period for the liquid discharge head 100 to reverse its direction of movement from the forward path to the return path. There is also a non-discharge period for the liquid discharge head 100 to reverse its direction of movement from the return path to the forward path, but it is not shown in Figure 6.

[0039] During the first discharge period T1 and the second discharge period T2, at each dot period Pd, drive signals Vin1 and Vin2, whose potential changes in an uneven manner to discharge liquid from the nozzle 200 selected from the first common drive signal COM1, are applied to the piezoelectric element 80. As a result, noise biased to one side due to the drive signals Vin1 and Vin2 is generated in the temperature detection signal Dt1. Therefore, temperature detection by the temperature detection circuit 310 is not performed during these discharge periods T1 and T2.

[0040] The non-discharge period TN includes the micro-vibration period TMV. The micro-vibration period TMV is the period during which a micro-vibration waveform MV1 selected from the first common drive signal COM1 is applied to the piezoelectric element 80 for each dot period Pd. The micro-vibration waveform MV1 is a waveform with a smaller amplitude than the drive waveform for discharging liquid from the nozzle 200, and is a waveform that does not discharge liquid from the nozzle 200. The application of the micro-vibration waveform MV1 is performed to prevent the liquid from becoming thicker. It is preferable that the micro-vibration period TMV be set to cover almost the entire non-discharge period TN in order to prevent the liquid from becoming thicker. "Approximately the entire period" means a period of 90% or more. The drive signal including the micro-vibration waveform MV1 is supplied to the first electrode 81 of the piezoelectric element 80.

[0041] The micro-vibration waveform MV1 of the first embodiment is generated to include a first waveform MV1a and a second waveform MV1b. The first waveform MV1a has a preset voltage change, and the second waveform MV1b has a waveform that is an inversion of the first waveform MV1a. The term "inverted waveform" broadly includes a waveform in which the voltage change is reversed vertically around a reference potential Vref, and a waveform in which that waveform is further reversed horizontally. The reference potential Vref is a potential that is maintained for a predetermined period from the start of the common drive signal COM1 in each dot period Pd.

[0042] It is preferable that the waveform shape corresponding to a potential of the first waveform MV1a above the reference potential Vref and the waveform shape corresponding to a potential of the second waveform MV1b below the reference potential Vref are symmetrical with respect to the reference potential Vref as the axis of symmetry. Furthermore, it is preferable that the waveform shape corresponding to a potential of the first waveform MV1a below the reference potential Vref and the waveform shape corresponding to a potential of the second waveform MV1b above the reference potential Vref are symmetrical with respect to the reference potential Vref as the axis of symmetry. Moreover, it is preferable that the area of ​​the region enclosed by the reference potential Vref and the first waveform MV1a is the same as the area of ​​the region enclosed by the reference potential Vref and the second waveform MV1b.

[0043] In the example in Figure 6, the first waveform MV1a is a waveform that changes concavely from the reference potential Vref and returns to the reference potential Vref, and the second waveform MV1b is a waveform that changes convexly from the reference potential Vref and returns to the reference potential Vref. Furthermore, the first waveform MV1a and the second waveform MV1b are generated in such a way that their changing portions do not overlap and they occur sequentially.

[0044] When a micro-vibration waveform MV1 is applied, noise corresponding to the micro-vibration waveform MV1 is generated in the temperature detection signal Dt1. However, since the micro-vibration waveform MV1 is composed of a first waveform MV1a and a second waveform MV1b, which are inverted waveforms of each other, the noise from the first waveform MV1a and the noise from the second waveform MV1b are averaged out and canceled out to almost zero. As shown in an enlarged view at the bottom of Figure 6, it is preferable that the temperature detection circuit 310 performs temperature detection with multiple sampling timings t_sample having sufficiently short sampling periods so that the noise is averaged out. That is, it is preferable that multiple sampling timings t_sample for temperature detection are set at each dot period Pd. As a result, the temperature of the first head chip 101 can be detected with high accuracy. Temperature detection is performed similarly for the second head chip 102.

[0045] The temperature detection described above may be performed at one dot period Pd in ​​which the micro-vibration waveform MV1 is generated, or at multiple dot periods Pd. It may also be performed over the entire micro-vibration period TMV. The operation of the liquid dispensing device 400 during the temperature detection execution period corresponds to the operation of the "temperature detection process" in this disclosure.

[0046] Figure 7 is an explanatory diagram showing another example of a micro-vibration waveform in the first embodiment. This micro-vibration waveform MV2 consists of a first waveform MV2a, which is an inverted triangular shape that changes concavely from a reference potential Vref, and a second waveform MV2b, which is the first waveform MV2a inverted vertically. The first waveform MV2a and the second waveform MV2b are generated so that their changing portions do not overlap and occur sequentially. Since the potential change of the second waveform MV2b follows immediately after the potential change of the first waveform MV2a, it is also possible to consider the micro-vibration waveform MV2 as a single waveform. This micro-vibration waveform MV2 also produces the same effect as the micro-vibration waveform MV1 shown in Figure 6.

[0047] Figure 8 is an explanatory diagram showing yet another example of a micro-vibration waveform in the first embodiment. This micro-vibration waveform MV3 consists of a first waveform MV3a having a predetermined change and a second waveform MV3b which is the first waveform MV3a inverted in the vertical and horizontal directions, respectively. Each of the first waveform MV3a and the second waveform MV3b has a change portion that is higher than the reference potential Vref and a change portion that is lower than the reference potential Vref. It is also possible to consider the first waveform MV3a and the second waveform MV3b to be in a 180-degree rotationally symmetric relationship around a point on the line representing the reference potential Vref. This micro-vibration waveform MV3 also produces the same effect as the micro-vibration waveform MV1 shown in Figure 6.

[0048] In the above explanation, the waveforms of the common drive signals COM1 and COM2 are corrected according to the detected temperature of the head chips 101 and 102. However, the detected temperature of the head chips 101 and 102 may be used for other purposes. For example, temperature adjustment using the platen heater 452 may be performed according to the detected temperature of the head chips 101 and 102. In this case, temperature adjustment may be performed according to the average value of the detected temperatures of the head chips 101 and 102, or according to the maximum or minimum value of the detected temperature over a certain period.

[0049] In the first embodiment described above, since the temperature is detected using the temperature detection element 301 while applying a micro-vibration waveform having a first waveform and a second waveform that are inverted relative to each other to the piezoelectric element 80, the influence of noise caused by the application of the micro-vibration waveform can be suppressed, and temperature detection can be performed with high accuracy.

[0050] B. Second Embodiment: Figure 9 is an explanatory diagram showing the micro-vibration waveform in the second embodiment. The apparatus configuration of the second embodiment is the same as that of the first embodiment. The only difference between the second embodiment and the first embodiment is the shape of the micro-vibration waveform; other configurations and operations are almost the same as those of the first embodiment.

[0051] The micro-vibration waveform MV4 of the second embodiment consists of a first waveform MV4a having a preset voltage change and a second waveform MV4b having a voltage change different from that of the first waveform MV4a. The first waveform MV4a and the second waveform MV4b are not inverted waveforms of each other. However, the first waveform MV4a and the second waveform MV4b are formed so that when the micro-vibration waveform MV4 is applied to a plurality of piezoelectric elements 80, the error in the detection result of the temperature detection element 301 caused by the potential change of the temperature detection element 301 due to the potential change of the first waveform MV4a is reduced by the potential change of the temperature detection element 301 caused by the potential change of the second waveform MV4b. The micro-vibration waveforms MV1, MV2, and MV3 described in the first embodiment also have this feature. Preferably, the area of ​​the region enclosed by the reference potential Vref and the first waveform MV4a is the same as the area of ​​the region enclosed by the reference potential Vref and the second waveform MV4b.

[0052] Even when using the micro-vibration waveform MV4 of the second embodiment, the temperature of the head chip can be detected with high accuracy, just as when using the micro-vibration waveform of the first embodiment.

[0053] C. Third Embodiment: Figure 10 is a conceptual diagram of the liquid discharge head of the third embodiment. The main differences from the first embodiment shown in Figure 5 are the following two points. (1) The drive circuit 70 is configured to generate drive signals Vin1 to Vin4 for each piezoelectric element 80 in the four nozzle rows NL1 to NL4, respectively, in response to the first common drive signal COM1, the second common drive signal COM2, the dot control signal SI, and the dot clock signal CL. (2) The temperature detection circuit 310 uses the temperature detection element 301 of the first head chip 101 and the temperature detection element 302 of the second head chip 102 to generate a temperature detection signal Dt that indicates the average temperature of the first head chip 101 and the second head chip 102.

[0054] The generation of the drive signal Vin for each piezoelectric element 80 of the drive circuit 70 can be achieved, for example, by the supply circuit 31D shown in Figure 17 of Japanese Patent Application Publication No. 2023-31984 disclosed by the applicant of this disclosure.

[0055] According to the configuration shown in Figure 10, a drive signal Vin having either the waveform of the first common drive signal COM1 or the second common drive signal COM2 can be arbitrarily applied to each piezoelectric element 80 in each nozzle row. The temperature detection signal Dt indicates the average temperature of the first head chip 101 and the second head chip 102, and the drive waveform correction unit 422 corrects the drive waveform data DC1 and DC2 of the common drive signals COM1 and COM2 respectively according to the temperature detection signal Dt.

[0056] Alternatively, instead of using the average temperature of the first head chip 101 and the second head chip 102, the drive waveform data DC1 and DC2 of the common drive signals COM1 and COM2 may be corrected using either the detected temperature of the first head chip 101 or the detected temperature of the second head chip 102. For example, the drive waveform data DC1 and DC2 of the common drive signals COM1 and COM2 may be corrected using the detected temperature of the head chip that has a greater impact on the image quality of the printed material among the two head chips 101 and 102. A head chip that has a greater impact on image quality is, for example, a head chip that ejects ink with higher visibility or a head chip that uses ink more frequently.

[0057] Figure 11 is a timing chart showing the temperature detection method in the third embodiment. The upper part of Figure 11 shows the drive signal Vin1_odd applied to the piezoelectric element 80 that drives the odd-numbered nozzles 200 from the drive signal Vin1 of the first head chip 101. The middle part of Figure 11 shows the drive signal Vin1_even applied to the piezoelectric element 80 that drives the even-numbered nozzles 200 from the drive signal Vin1 of the first head chip 101. The drive signal Vin1_odd for the odd-numbered nozzles has a waveform selected from the first common drive signal COM1, and the drive signal Vin1_even for the even-numbered nozzles has a waveform selected from the second common drive signal COM2.

[0058] During the period when the temperature detection circuit 310 is performing temperature detection, a first waveform MV5a, which has a preset voltage change, is applied as a micro-vibration waveform MV5 to the piezoelectric element group for odd-numbered nozzles. Similarly, during the period when the temperature detection circuit 310 is performing temperature detection, a second waveform MV5b, which is the inverse of the first waveform MV5a, is applied to the piezoelectric element group for even-numbered nozzles. In the example in Figure 11, the first waveform MV5a is a waveform that changes concavely from the reference potential Vref, and the second waveform MV5b is a waveform that changes convexly from the reference potential Vref. Furthermore, the first waveform MV5a and the second waveform MV5b change at the same timing, and are generated so that the average voltage of the first waveform MV5a and the second waveform MV5b at any given timing is equal to the reference potential Vref.

[0059] When such a micro-vibration waveform MV5 is applied to the piezoelectric element 80, noise caused by the first waveform MV5a and noise caused by the second waveform MV5b may be generated in the temperature detection signal Dt. However, these noises cancel each other out, so the effect of the noise becomes almost zero. Therefore, in the third embodiment as well, the temperature of the head chip can be detected with high accuracy.

[0060] In the third embodiment, inverted micro-vibration waveforms were applied to the piezoelectric element groups for odd-numbered nozzles and the piezoelectric element groups for even-numbered nozzles. However, the multiple piezoelectric elements 80 included in each head chip may be classified into a first piezoelectric element group and a second piezoelectric element group according to other classification methods. For example, the first head chip 101 may be classified into a first piezoelectric element group for the first nozzle row NL1 and a second piezoelectric element group for the second nozzle row NL. The same applies to the second head chip 102. It is preferable that the number of piezoelectric elements 80 included in the first piezoelectric element group and the number of piezoelectric elements 80 included in the second piezoelectric element group are equal. Furthermore, it is preferable that during the period when the temperature detection circuit 310 is performing temperature detection, the first piezoelectric element group is not subjected to the second waveform MV5b but to the first waveform MV5a, and the second piezoelectric element group is not subjected to the first waveform MV5a but to the second waveform MV5b.

[0061] D. Fourth Embodiment: Figure 12 is a timing chart showing the temperature detection method in the fourth embodiment. The apparatus configuration of the fourth embodiment is the same as that of the first embodiment. The only differences between the fourth embodiment and the first embodiment are the shape of the micro-vibration waveform and the sampling timing for temperature detection; other configurations and operations are almost the same as those of the first embodiment.

[0062] In the fourth embodiment, the micro-vibration waveform MV6 is a waveform that changes concavely from a reference potential Vref. The sampling timing t_sample for temperature detection is set to a timing when there is no voltage change in the micro-vibration waveform MV6. In the example in Figure 12, the micro-vibration waveform MV6 occurs periodically at each dot period Pd, and the sampling timing t_sample is set to occur once at each dot period Pd so as to be a timing when there is no voltage change in the micro-vibration waveform MV6. It is preferable that the sampling timing t_sample is set before the voltage change of the micro-vibration waveform MV6 begins at each dot period Pd. The temperature detection circuit 310 can accurately detect the temperature of the head chip without being affected by noise caused by the micro-vibration waveform MV6.

[0063] E. Other forms: This disclosure is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit. For example, this disclosure can also be implemented in the following forms (aspects). The technical features in the embodiments described above that correspond to the technical features in each of the forms described below can be replaced or combined as appropriate in order to solve some or all of the problems of this disclosure, or to achieve some or all of the effects of this disclosure. Furthermore, if such technical features are not described as essential in this specification, they can be deleted as appropriate.

[0064] (1) According to a first embodiment of the present disclosure, a method is provided for detecting the temperature of a head chip including a plurality of nozzles for discharging a liquid, a plurality of piezoelectric elements for applying pressure to the liquid to cause the liquid to be discharged from each of the plurality of nozzles, and a temperature sensing element. The method includes a temperature detection step of detecting the temperature of the head chip using the temperature sensing element during a micro-vibration application period in which a micro-vibration waveform that does not cause the liquid to be discharged from the plurality of nozzles is applied to the plurality of piezoelectric elements. The temperature detection step includes a step of generating the micro-vibration waveform to include a first waveform having a preset voltage change and a second waveform obtained by inverting the first waveform. This method suppresses the effects of noise caused by the application of micro-vibration waveforms, enabling accurate temperature detection.

[0065] (2) In the above method, the same micro-vibration waveform may be applied to the plurality of piezoelectric elements, and the micro-vibration waveform may be generated such that the first waveform and the second waveform occur in sequence without overlapping. This method allows for accurate temperature detection while applying the same micro-vibration waveform to multiple piezoelectric elements.

[0066] (3) In the above method, the plurality of piezoelectric elements may be classified into a first piezoelectric element group and a second piezoelectric element group, wherein the first piezoelectric element group is subjected to the first waveform without the second waveform being applied, and the second piezoelectric element group is subjected to the second waveform without the first waveform being applied. This method allows for the cancellation of noise originating from the first waveform and noise originating from the second waveform, thus enabling accurate temperature detection.

[0067] (4) In the above method, the number of piezoelectric elements included in the first piezoelectric element group and the number of piezoelectric elements included in the second piezoelectric element group may be equal. This method allows for efficient cancellation of noise originating from the first waveform and noise originating from the second waveform.

[0068] (5) In the above method, the first waveform may start from the reference potential and end at the reference potential, and the second waveform may start from the reference potential and end at the reference potential, and the waveform shape of the first waveform corresponding to a potential of the reference potential or higher and the waveform shape of the second waveform corresponding to a potential of the reference potential or lower may be in a symmetrical relationship with respect to the reference potential as the axis of symmetry. Alternatively, the waveform shape of the first waveform corresponding to a potential of the reference potential or lower and the waveform shape of the second waveform corresponding to a potential of the reference potential or higher may be in a symmetrical relationship with respect to the reference potential as the axis of symmetry. This method allows for efficient cancellation of noise originating from the first waveform and noise originating from the second waveform.

[0069] (6) A second embodiment of the present disclosure provides a liquid dispensing device for dispensing liquid. The liquid dispensing device includes a head chip including a plurality of nozzles for dispensing the liquid, a plurality of piezoelectric elements for applying pressure to the liquid to cause the liquid to be dispensed from each of the plurality of nozzles, and a temperature detection element; a drive signal generation unit for generating a micro-vibration waveform that does not cause the liquid to be dispensed from the plurality of nozzles; a drive circuit for applying the micro-vibration waveform to the plurality of piezoelectric elements during a micro-vibration application period; and a temperature detection circuit for detecting the temperature of the head chip using the temperature detection element during the micro-vibration application period. The drive signal generation unit generates the micro-vibration waveform to include a first waveform having a preset voltage change and a second waveform which is the inverted first waveform. This liquid dispensing device detects temperature using a temperature detection element while applying a micro-vibration waveform having two inverted waveforms (first and second waveforms) to a piezoelectric element. This suppresses the effects of noise caused by the application of the micro-vibration waveform, enabling accurate temperature detection.

[0070] (7) A third embodiment of the present disclosure provides a method for detecting the temperature of a head chip, comprising a plurality of nozzles for discharging a liquid, a plurality of piezoelectric elements for applying pressure to the liquid to cause the liquid to be discharged from each of the plurality of nozzles, and a temperature sensing element. The method comprises a temperature detection step of detecting the temperature of the head chip using the temperature sensing element during a micro-vibration application period in which a micro-vibration waveform that does not cause the liquid to be discharged from the plurality of nozzles is applied to the plurality of piezoelectric elements. The temperature detection step includes a step of generating the micro-vibration waveform to include a first waveform having a preset voltage change and a second waveform different from the first waveform. The first and second waveforms are formed so as to reduce errors in the detection result of the temperature sensing element due to a change in the potential of the temperature sensing element caused by a change in the potential of the first waveform, by a change in the potential of the temperature sensing element caused by a change in the potential of the second waveform. This method suppresses the effects of noise caused by the application of micro-vibration waveforms, enabling accurate temperature detection.

[0071] (8) According to a fourth embodiment of the present disclosure, a liquid dispensing device is provided. The liquid dispensing device includes a head chip including a plurality of nozzles for dispensing the liquid, a plurality of piezoelectric elements for applying pressure to the liquid to cause the liquid to be dispensed from each of the plurality of nozzles, and a temperature detection element; a drive signal generation unit that generates a micro-vibration waveform that does not cause the liquid to be dispensed from the plurality of nozzles; a drive circuit that applies the micro-vibration waveform to the plurality of piezoelectric elements during a micro-vibration application period; and a temperature detection circuit that detects the temperature of the head chip using the temperature detection element during the micro-vibration application period. The drive signal generation unit generates the micro-vibration waveform to include a first waveform having a preset voltage change and a second waveform different from the first waveform. The first waveform and the second waveform are formed so as to reduce the error in the detection result of the temperature detection element caused by the potential change of the temperature detection element caused by the potential change of the second waveform, which is caused by the potential change of the temperature detection element. This liquid dispensing device suppresses the effects of noise caused by the application of micro-vibration waveforms, enabling accurate temperature detection.

[0072] This disclosure can also be implemented in various forms other than a method for detecting the temperature of a head chip or a liquid ejection device. For example, it can be implemented in the form of a method for correcting a common drive signal, a method for controlling a liquid ejection device, a computer program for implementing the method, and a non-temporary recording medium on which the computer program is stored. [Explanation of Symbols]

[0073] 50...Wiring board, 70, 71, 72...Drive circuit, 80...Piezoelectric element, 81...First electrode, 82...Second electrode, 83...Piezoelectric body, 84...Drive wiring, 100...Liquid discharge head, 101, 102...Head tip, 120...Nozzle plate, 130...Sealing film, 140...Communicating plate, 150...Pressure chamber substrate, 160...Housing section, 170...Diaphragm, 200...Nozzle, 210...Common liquid chamber, 220...Separate flow path for nozzles, 2 30...Pressure chamber, 301, 302...Temperature detection element, 310...Temperature detection circuit, 400...Liquid discharge device, 410...Liquid storage unit, 420...Control unit, 421...Control signal supply unit, 422...Drive waveform correction unit, 423...Drive waveform storage unit, 424, 425...Drive signal generation unit, 430...Moving mechanism, 432...Belt, 434...Carriage, 440...Conveying mechanism, 450...Platen, 452...Platen heater

Claims

1. A method for detecting the temperature of a head chip, comprising: a plurality of nozzles for discharging a liquid; a plurality of piezoelectric elements for applying pressure to the liquid to cause the liquid to be discharged from each of the plurality of nozzles; and a temperature sensing element, The system includes a temperature detection step in which a micro-vibration waveform that does not cause the liquid to be discharged from the plurality of nozzles is applied to the plurality of piezoelectric elements, and the temperature of the head chip is detected using the temperature detection element during the micro-vibration application period. The method comprises a step of generating the micro-vibration waveform such that the temperature detection step includes a first waveform having a preset voltage change and a second waveform obtained by inverting the first waveform.

2. The method according to claim 1, The same micro-vibration waveform is applied to the plurality of piezoelectric elements. The method for generating the micro-vibration waveform is such that the first waveform and the second waveform occur sequentially without overlapping.

3. The method according to claim 1, The plurality of piezoelectric elements are classified into a first piezoelectric element group and a second piezoelectric element group. A method in which the first piezoelectric element group is subjected to the first waveform without the second waveform being applied, and the second piezoelectric element group is subjected to the second waveform without the first waveform being applied.

4. The method according to claim 3, A method wherein the number of piezoelectric elements included in the first group of piezoelectric elements is equal to the number of piezoelectric elements included in the second group of piezoelectric elements.

5. The method according to claim 1, The first waveform begins at the reference potential and ends at the same reference potential. The second waveform begins at the reference potential and ends at the reference potential. The waveform shape of the first waveform corresponding to a potential above the reference potential and the waveform shape of the second waveform corresponding to a potential below the reference potential are symmetrical with respect to the reference potential as the axis of symmetry. A method wherein the waveform shape of the first waveform corresponding to a potential below the reference potential and the waveform shape of the second waveform corresponding to a potential above the reference potential are symmetrical with respect to the reference potential as the axis of symmetry.

6. A liquid dispensing device that dispenses liquid, A head chip including a plurality of nozzles for discharging the liquid, a plurality of piezoelectric elements for applying pressure to the liquid to cause the liquid to be discharged from each of the plurality of nozzles, and a temperature sensing element, A drive signal generation unit that generates a micro-vibration waveform that does not cause the liquid to be discharged from the plurality of nozzles, A drive circuit that applies the micro-vibration waveform to the plurality of piezoelectric elements during the micro-vibration application period, A temperature detection circuit that detects the temperature of the head chip using the temperature detection element during the micro-vibration application period, Equipped with, The liquid dispensing device generates the micro-vibration waveform such that the drive signal generation unit includes a first waveform having a preset voltage change and a second waveform obtained by inverting the first waveform.

7. A method for detecting the temperature of a head chip, comprising: a plurality of nozzles for discharging a liquid; a plurality of piezoelectric elements for applying pressure to the liquid to cause the liquid to be discharged from each of the plurality of nozzles; and a temperature sensing element, The system includes a temperature detection step in which a micro-vibration waveform that does not cause the liquid to be discharged from the plurality of nozzles is applied to the plurality of piezoelectric elements, and the temperature of the head chip is detected using the temperature detection element during the micro-vibration application period. The temperature detection step includes a step of generating the micro-vibration waveform so as to include a first waveform having a preset voltage change and a second waveform different from the first waveform. A method wherein the first waveform and the second waveform are formed such that the error in the detection result of the temperature detection element caused by the potential change of the temperature detection element resulting from the potential change of the first waveform is reduced by the potential change of the temperature detection element resulting from the potential change of the second waveform.

8. A liquid dispensing device that dispenses liquid, A head chip including a plurality of nozzles for discharging the liquid, a plurality of piezoelectric elements for applying pressure to the liquid to cause the liquid to be discharged from each of the plurality of nozzles, and a temperature sensing element, A drive signal generation unit that generates a micro-vibration waveform that does not cause the liquid to be discharged from the plurality of nozzles, A drive circuit that applies the micro-vibration waveform to the plurality of piezoelectric elements during the micro-vibration application period, A temperature detection circuit that detects the temperature of the head chip using the temperature detection element during the micro-vibration application period, Equipped with, The drive signal generation unit generates the micro-vibration waveform so as to include a first waveform having a preset voltage change and a second waveform different from the first waveform. A liquid dispensing device in which the first waveform and the second waveform are formed such that the error in the detection result of the temperature detection element caused by the potential change of the temperature detection element resulting from the potential change of the first waveform is reduced by the potential change of the temperature detection element resulting from the potential change of the second waveform.

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