Printing device and printing method

Abstract

To provide a technology capable of appropriately adjusting temperature of an ink even when a flow rate of the ink passing through a heater varies.SOLUTION: A control waveform acquisition unit 921 acquires a control waveform CW1 generated according to an equivalent amount of time change. When a heater 351 is controlled on the basis of the control waveform CW1, a temperature waveform acquisition unit 922 acquires a temperature waveform TpW indicating a time change of temperature of an ink passing through the heater 351. A temperature waveform correction position specifying unit 923 specifies a temperature waveform correction position C1 whose temperature is different from a target temperature Ttg in the temperature waveform TpW. The control waveform correction unit 926 corrects the control waveform CW1 so as to make the temperature of the temperature waveform correction position C1 is the target temperature Ttg. An FF control unit 911 feed-forward controls the heater 351 on the basis of the corrected control waveform CW1 (corrected control waveform CW2) and a difference value between an entrance temperature Te1 and the target temperature Ttg.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a printing device and a printing method. [Background technology]

[0002] Conventionally, there has been known a printing device that forms an image on a continuous, long strip of substrate by conveying the substrate in a roll-to-roll manner and ejecting ink from an ejection head onto the surface of the substrate. In this type of printing device, ink viscosity control is generally important.

[0003] For example, if the temperature of the ink drops, the viscosity increases, causing uneven ejection, which can lead to problems such as misalignment of the ink landing position or the occurrence of streaks. For this reason, a mechanism for heating the ink is sometimes provided to keep the ink temperature constant.

[0004] For example, in Patent Document 1, ink is circulated in a circulation path connected to a discharge head, and the ink flowing through the circulation path is heated by a hot water unit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2016-055501 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the temperature of the ink inside the ejection head can fluctuate irregularly depending on the amount of ink flowing into the ejection head from an ink tank that stores unused ink. Therefore, simply heating the ink inside the ejection head uniformly could result in large fluctuations in ink temperature.

[0007] An object of the present invention is to provide a technique that can appropriately adjust the temperature of ink even when the flow rate of ink passing through a heater fluctuates. [Means for solving the problem]

[0008] In order to solve the above problem, a first aspect is a printing method including: a) a step of ejecting ink from an ejection head onto a surface of a long strip-shaped substrate while transporting the substrate along a predetermined transport path; b) a step of supplying an amount of ink corresponding to an amount of ink ejected from the ejection head from an ink tank capable of storing the ink to the ejection head; and c) a step of controlling a heater that heats the ink supplied to the ejection head in step b) based on a control waveform generated in accordance with a time change of the corresponding amount, wherein step c) includes the steps of: c1) acquiring the control waveform; and c2) controlling the heater based on a control waveform generated in accordance with a time change of the corresponding amount. c2) acquiring a temperature waveform showing a time change in temperature of the ink that has passed through the heater when the heater is controlled based on the control waveform; c3) identifying a temperature waveform correction point in the temperature waveform where the temperature differs from a predetermined target temperature; c4) correcting the control waveform so that the temperature of the temperature waveform correction point becomes the target temperature; c5) measuring a first temperature of the ink before it passes through the heater; and c6) feedforward controlling the heater based on the control waveform corrected in step c4) and a difference value between the first temperature and the target temperature.

[0009] A second aspect is the printing method of the first aspect, wherein step c4) includes: c41) a step of calculating dead time based on the equivalent amount at the time of the temperature waveform correction point; c42) a control waveform correction point identification unit that identifies the control waveform correction point to be corrected in the control waveform based on the dead time; and c43) a step of correcting the control waveform based on the control waveform correction point and the temperature waveform.

[0010] A third aspect is a printing method according to the first or second aspect, wherein step c1) includes a step of generating the control waveform based on print pattern data indicating a print pattern to be printed on the substrate.

[0011] A fourth aspect is the printing method of the third aspect, wherein the step b2) includes a step of predicting the temperature waveform based on the print pattern data and the control waveform.

[0012] A fifth aspect is the printing method of any one of the first to fourth aspects, further comprising: (d) a step of performing feedback control based on the temperature of the ink that has passed through the heater.

[0013] a control unit for controlling the heater; a control waveform acquisition unit for acquiring a control waveform generated in accordance with a change over time of the corresponding amount of ink; a temperature waveform acquisition unit for acquiring a temperature waveform showing a change over time of the temperature of the ink that has passed through the heater when the heater is controlled based on the control waveform; a temperature waveform correction portion identification unit for identifying a temperature waveform correction portion in the temperature waveform where the temperature differs from a predetermined target temperature; and a control waveform correction unit for correcting the control waveform so that the temperature of the temperature waveform correction portion becomes the target temperature; and the control unit performs feedforward control of the heater based on the control waveform corrected by the control waveform correction unit and a difference value between the first temperature and the target temperature.

[0014] A seventh aspect is the printing device of the sixth aspect, wherein the control unit further has a dead time calculation unit that calculates dead time based on the equivalent amount at the time of the temperature waveform correction point, and a control waveform correction point determination unit that identifies the control waveform correction point where the control waveform should be corrected based on the dead time, and the control waveform correction unit corrects the control waveform based on the control waveform correction point and the temperature waveform. [Effects of the Invention]

[0015] According to the printing methods of the first to fifth aspects, the control waveform is corrected in advance so that the temperature waveform reaches the target temperature, and the heater is feedforward controlled based on the corrected control waveform, thereby appropriately controlling the temperature of the ink so that the temperature of the ink actually passing through the heater reaches the target temperature.

[0016] According to the printing method of the second aspect, the control waveform is corrected taking into account the dead time corresponding to the corresponding amount, so the dead time can be compensated for, and therefore the temperature of the ink can be appropriately controlled.

[0017] According to the printing method of the third aspect, a control waveform can be generated from the equivalent amount of ink indicated by the print pattern data.

[0018] The temperature waveform can be appropriately predicted based on the print pattern data and the control waveform.

[0019] According to the printing method of the fifth aspect, the temperature of the ink can be maintained at the target temperature by feedback control.

[0020] According to the printing device of the sixth aspect, the control waveform is corrected in advance so that the temperature waveform becomes the target temperature, and the heater is feedforward controlled based on the corrected control waveform, thereby appropriately controlling the temperature of the ink so that the temperature of the ink actually passing through the heater becomes the target temperature. [Brief explanation of the drawings]

[0021] [Figure 1]FIG. 1 is a diagram illustrating a configuration of a printing apparatus according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing connections between a control unit and each unit of the printing device. [Figure 3] FIG. 2 is a diagram showing a control block for controlling a heater. [Figure 4] FIG. 10 is a diagram showing a flow of a control waveform correction process. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the components described in the embodiment are merely examples and are not intended to limit the scope of the present invention. In the drawings, the dimensions and numbers of each part may be exaggerated or simplified as necessary to facilitate understanding.

[0023] <1. Embodiment> FIG. 1 is a diagram showing the configuration of a printing device 1 according to an embodiment. The printing device 1 is a device that performs printing using an inkjet method. More specifically, the printing device 1 records an image on the surface of a long strip-shaped substrate W by ejecting ink from multiple ejection heads 21-24 onto the substrate W while transporting the substrate W using multiple transport rollers 12. The substrate W is, for example, a flexible medium, such as printing paper, a resin film, cardboard, or a thin metal film.

[0024] As shown in FIG. 1, the printing apparatus 1 includes a transport mechanism 10, a printing unit 20, a supply unit 30, an encoder 60, a camera 70, a plurality of various sensors 80, and a control unit 9.

[0025] The transport mechanism 10 transports the base material W along a predetermined transport path in a transport direction that is along the longitudinal direction of the base material W. The transport mechanism 10 has an unwinding roller 11, multiple transport rollers 12, and a winding roller 13. The base material W is stretched across these rollers. The base material W is unwound from the unwinding roller 11 and transported along the predetermined transport path while being supported by the multiple transport rollers 12. Each transport roller 12 rotates about an axis extending perpendicular to the transport direction, thereby guiding the base material W to the downstream side of the transport path. The base material W transported by the multiple transport rollers 12 is wound up by the winding roller 13. Tension is applied to the base material W in the transport direction. This prevents the base material W from sagging or wrinkling during transport.

[0026] The transport mechanism 10 further includes a motor 14 that rotates some of the rollers (hereinafter referred to as "drive rollers"). The transport mechanism 10 may include multiple motors 14. The motors 14 are electrically connected to the control unit 9. When the motors 14 are driven, the control unit 9 inputs a command value to each motor 14 to drive the motor 14 to rotate. The motor 14 then drives in accordance with the command value, causing the drive roller to rotate. As a result, the substrate W is transported from the unwinding roller 11 toward the winding roller 13.

[0027] The printing unit 20 is a processing unit that ejects ink droplets (hereinafter referred to as "ink droplets") onto the substrate W transported by the transport mechanism 10. The printing unit 20 has multiple (four in this example) ejection heads 21-24. The ejection heads 21-24 have the same structure. The ejection heads 21-24 are arranged at intervals along the transport direction of the substrate W. The substrate W moves below the multiple ejection heads 21-24, approximately parallel to the arrangement direction of the multiple ejection heads 21-24. At this time, the surface (printing surface) of the substrate W faces upward (toward each ejection head 21-24).

[0028] Each of the ejection heads 21-24 has an internal space capable of storing ink and a plurality of nozzles (not shown). The plurality of nozzles are arranged parallel to the width direction of the substrate W on the underside of each of the ejection heads 21-24. Each of the plurality of nozzles has a piezoelectric element (not shown) as a pressure-generating element and an ejection port communicating with the internal space of each of the ejection heads 21-24. When ejecting ink, ink flows down from the internal space to the vicinity of the ejection port. Then, the action of the piezoelectric element pressurizes the ink near the ejection port, causing droplets of ink to be ejected from the ejection port. The ink ejection method may be a so-called thermal method, in which a heater is used as a pressure-generating element to heat the ink near the ejection port and generate bubbles.

[0029] Each of the ejection heads 21-24 ejects ink droplets of each color—K (black), C (cyan), M (magenta), and Y (yellow)—that constitute the color components of a multicolor image from multiple nozzles toward the upper surface of the substrate W. That is, the ejection head 21 ejects K ink droplets as a treatment material onto the upper surface of the substrate W at a first printing position P1, which is a processing position on the transport path. The ejection head 22 ejects C ink droplets as a treatment material onto the upper surface of the substrate W at a second printing position P2, which is a processing position downstream from the first printing position P1. The ejection head 23 ejects M ink droplets as a treatment material onto the upper surface of the substrate W at a third printing position P3, which is a processing position downstream from the second printing position P2. The ejection head 24 ejects Y ink droplets as a treatment material onto the upper surface of the substrate W at a fourth printing position P4, which is a processing position downstream from the third printing position P3.

[0030] In this embodiment, the first printing position P1, the second printing position P2, the third printing position P3, and the fourth printing position P4 are arranged at equal intervals along the transport direction of the substrate W. The ejection heads 21-24 each record a single-color image on the upper surface of the substrate W by ejecting ink droplets. Then, a multi-color image is formed on the upper surface of the substrate W by superimposing the four single-color images. Each ejection head 21-24 can also print on the upper surface of the substrate W by ejecting ink droplets.

[0031] The supply unit 30 is a unit that supplies ink to the ejection heads 21-24. The supply unit 30 has multiple (four in this example) ink supply systems 31. The multiple ink supply systems 31 are connected to the ejection heads 21-24 respectively, and supply ink of the corresponding color to the ejection heads 21-24 respectively. The ink supply system 31 that supplies ink to the ejection head 21 will be described below.

[0032] The ink supply system 31 includes an ink tank 311 , a pipe 321 , a pump 331 , a flow meter 341 , a heater 351 , an inlet temperature sensor 361 , an outlet temperature sensor 371 , and a liquid level sensor 381 .

[0033] The ink tank 311 is capable of storing unused ink. One end of the pipe 321 is connected to the internal space of the ejection head 21. The other end of the pipe 321 is connected to the ink tank 311. The pump 331 is installed in the pipe 321. The pump 331 operates based on a drive value input from the control unit 9. This generates a flow of ink from the ink tank 311 to the ejection head 21. The pump 331 is, for example, a pump equipped with a brushless motor. The pipe 321 and the pump 331 are an example of a "supply unit" that supplies ink from the ink tank 311 to the ejection head 21. Note that the ink in the ink tank 311 may be sent to the ejection head 21 by a pressurizing mechanism that pressurizes the inside of the ink tank 311. In this case, the pressurizing mechanism functions as the "supply unit."

[0034] A primary tank that supplies ink to the ink tank 311 may be provided upstream of the ink tank 311. Ink may be supplied from the primary tank in response to a decrease in the amount of ink stored in the ink tank 311, for example.

[0035] The flow meter 341 is installed in the pipe 321. The flow meter 341 measures the flow rate of the ink flowing in the pipe 321. The flow meter 341 transmits to the control unit 9 a signal indicating the measured flow rate value FR1.

[0036] When ink droplets are ejected from the ejection head 21 toward the substrate W, the amount of ink in the ejection head 21 decreases. The control unit 9 inputs a drive value to the pump 331 in accordance with the decrease in the amount of ink in the ejection head 21. As a result, the pump 331 is driven in accordance with the drive value, and an amount of ink corresponding to the decrease (consumption) of ink in the ejection head 21 is supplied from the ink tank 311 to the ejection head 21. As with the ejection head 21, ink is also supplied to the other ejection heads 22-24 from the corresponding ink supply systems 31.

[0037] The heater 351 heats the ink supplied from the ink tank 311 to the ejection head 21 by the pump 331. The heater 351 is installed in the pipe 321. The heater 351 is located between the pump 331 and the flow meter 341. The heater 351 heats the ink flowing through the pipe 321. A flow rate value FR1 measured by the flow meter 341 corresponds to the flow rate of the ink passing through the heater 351.

[0038] The inlet temperature sensor 361 is located in a piping section of the piping 321 between the ink tank 311 and the heater 351. The inlet temperature sensor 361 is disposed at the inlet of the heater 351. The inlet temperature sensor 361 transmits a signal indicating the measured temperature to the control unit 9. The inlet temperature sensor 361 is an example of a "first temperature sensor" that measures the temperature (first temperature) of the ink flowing from the ink tank 311 to the heater 351, i.e., the ink before passing through the heater 351.

[0039] The outlet temperature sensor 371 is installed in the pipe 321. The outlet temperature sensor 371 is located between the heater 351 and the ejection head 21. The outlet temperature sensor 371 measures the temperature of the ink flowing from the heater 351 to the ejection head 21 via the pipe 321. In this example, the outlet temperature sensor 371 is provided near the outlet of the heater 351. Therefore, the outlet temperature sensor 371 measures the temperature of the ink immediately after passing through the heater 351. However, the outlet temperature sensor 371 may be located closer to the ejection head 21 than the heater 351. The outlet temperature sensor 371 transmits a signal indicating the measured temperature to the control unit 9. The outlet temperature sensor 371 measures the temperature (second temperature) of the ink flowing from the heater 351 to the ejection head 21, 22, 23, or 24, i.e., the ink that has passed through the heater 351.

[0040] The liquid level sensor 381 is a sensor for measuring the amount of ink in the ejection head 21, and measures the height of the ink liquid surface in the ejection head 21. The liquid level sensor 381 is, for example, a non-contact sensor that detects the height of the liquid surface using ultrasonic waves. The liquid level sensor 381 transmits a signal indicating the measured liquid level to the control unit 9.

[0041] The encoder 60 is attached to the shaft core of one of the plurality of conveying rollers 12 (in the example of FIG. 1, the conveying roller 121). The encoder 60 detects the rotation of the conveying roller 121 and outputs a continuous pulse signal synchronized with the rotation of the conveying roller 121 to the control unit 9. The continuous pulse signal is data reflecting a change over time in the conveying speed of the substrate W conveyed by the plurality of conveying rollers 12 including the conveying roller 121.

[0042] The camera 70 is an imaging device that captures an image of the printed surface (front surface) of the substrate W that has passed through the printing unit 20. The camera 70 is disposed facing the printed surface of the substrate W at an imaging position P5 that is downstream of the four ejection heads 21-24 on the conveyance path. The camera 70 has, for example, a line sensor in which a plurality of imaging elements, such as CCD or CMOS, are arranged in the width direction. While the substrate W is being conveyed by the conveyance mechanism 10, the camera 70 captures images of the printed surface of the substrate W at predetermined intervals, thereby acquiring image data of the printed substrate W. The camera 70 transmits the obtained image data to the control unit 9.

[0043] The multiple sensors 80 are measuring instruments that measure the transport state of the substrate W in addition to those listed above. The multiple sensors 80 are provided at multiple measurement points on the transport path of the substrate W. The sensors 80 acquire measurement values ​​at each measurement point. Measurement items of the sensors 80 may include, for example, the vertical displacement of the substrate W (the amount of displacement in a direction perpendicular to the substrate W), the tension applied to the substrate W, and the widthwise position of the edge of the substrate W. Note that the sensors 80 that measure the same item may be disposed at multiple positions on the transport path. While the substrate W is transported by the transport mechanism 10, the multiple sensors 80 constantly measure the state at each measurement point. The sensors 80 then transmit signals indicating the obtained measurement values ​​to the control unit 9.

[0044] 2 is a block diagram showing the connections between the control unit 9 and each unit of the printing device 1. The control unit 9 controls the operation of the printing device 1. The control unit 9 has a processor 91 formed of a CPU or the like, and a storage unit 93 formed of a RAM, a hard disk, or the like. The storage unit 93 stores a program 90P and various data.

[0045] The program 90P is provided by a recording medium M. The program 90P is recorded on the recording medium M so as to be readable by a control unit 9, which is a computer. The recording medium M is, for example, a USB (Universal Serial Bus) memory, an optical disk such as a DVD (Digital Versatile Disc), or a magnetic disk.

[0046] The control unit 9 is communicatively connected to the motor 14 of the transport mechanism 10, the ejection heads 21-24 of the printing unit 20, and the pump 331, flow meter 341, heater 351, inlet temperature sensor 361, outlet temperature sensor 371, and liquid level sensor 381 of the supply unit 30. The control unit 9 is also communicatively connected to the encoder 60, camera 70, and various sensors 80.

[0047] The control unit 9 controls the heater 351 so that the temperature of the ink supplied to the ejection heads 21-24 becomes a predetermined target temperature Ttg. The supply control unit 910, feedforward (FF) control unit 911, feedback (FB) control unit 912, control value correction unit 913, control waveform acquisition unit 921, temperature waveform acquisition unit 922, temperature waveform correction portion identification unit 923, dead time calculation unit 924, control waveform correction portion identification unit 925, and control waveform correction unit 926 shown in FIG. 2 are functions realized by the processor 91 executing the program 90P.

[0048] The supply control unit 910 controls the pump 331 of the supply unit 30 based on print pattern data PD1 that indicates an image to be printed on the substrate W. More specifically, the supply control unit 910 generates a pump drive waveform for controlling the pump 331. The pump drive waveform is specifically a temporal change in the control voltage applied to the pump 331. For example, if there is a portion in the print pattern data PD1 where ink consumption is relatively high, a pump drive waveform is generated so that the amount of ink supplied when printing that portion is large. Conversely, if there is a portion in the print pattern data PD1 where ink consumption is small, a pump drive waveform is generated so that the amount of ink supplied when printing that portion is small.

[0049] The FF control unit 911 performs FF control of the heater 351. The FB control unit 912 performs FB control of the heater 351. The control waveform acquisition unit 921, the temperature waveform acquisition unit 922, the temperature waveform correction portion identification unit 923, the dead time calculation unit 924, the control waveform correction portion identification unit 925, and the control waveform correction unit 926 are configured to correct the control waveform CW1 input to the FF control unit 911.

[0050] <Heater control> 3 is a diagram showing a control block for controlling the heater 351. The following explanation will mainly focus on the case where the heater 351 of the ink supply system 31 connected to the ejection head 21 is controlled. The same control as that shown in FIG. 3 is also performed in the ink supply system 31 connected to the ejection heads 22-24.

[0051] The FF control unit 911 generates an FF control value CV1 for FF control of the heater 351. The FF control value CV1 is, for example, a value indicating the power value applied to a heat source (e.g., a heating wire) in the heater 351. The FF control unit 911 receives the temperature difference ΔT1 and the corrected control waveform CW2 as input variables and outputs the FF control value CV1. The FF control unit 911 inputs the FF control value CV1 to a control value correction unit 913.

[0052] The temperature difference ΔT1 is the difference value between the target temperature Ttg and the inlet temperature Te1 measured by the inlet temperature sensor 361. The corrected control waveform CW2 is the control waveform CW1 corrected by a correction process described later.

[0053] The FB control unit 912 performs FB control on the heater 351 so that the temperature of the ink measured by the outlet temperature sensor 371 becomes a preset target temperature Ttg. The FB control is preferably PID control or PI control. The FB control unit 912 generates an FB control value CV2. The FB control value CV2 is, for example, a value indicating the power value applied to a heat source (e.g., a heating wire) in the heater 351. The FB control unit 912 outputs the FB control value CV2 based on a temperature difference ΔT2. The temperature difference ΔT2 is the difference value between the target temperature Ttg and the outlet temperature Te2 measured by the outlet temperature sensor 371.

[0054] The control value corrector 913 calculates a corrected FF control value CV1 (modified FF control value CV1a) by multiplying the FF control value CV1 by a gain G1. The gain G1 is set, for example, by a preliminary experiment carried out in advance.

[0055] 3, the control unit 9 outputs a heater command value CV3 obtained by adding the corrected FF control value CV1a and the FB control value CV2 to the heater 351. The heater 351 heats the ink in accordance with the input heater command value CV3.

[0056] <Correction process of control waveform CW1> The control waveform acquisition unit 921 uses the print pattern data PD1 as an input variable and the control waveform CW1 as an output variable. The control waveform CW1 is a waveform that is input to the FF control unit 911 so that the FF control unit 911 generates the FF control value CV1. However, in this embodiment, as described below, the FF control unit 911 generates the FF control value CV1 based on the control waveform CW1 corrected by the control waveform correction unit 926 (corrected control waveform CW2).

[0057] The print pattern data PD1 is data indicating the amount of ink used, and is information indicating an equivalent amount corresponding to the amount of ink ejected from the ejection head 21. Therefore, the control waveform CW1 is generated based on the equivalent amount (the flow rate of ink passing through the heater 351) indicated by the print pattern data PD1. When the equivalent amount increases (i.e., the ink flow rate at the heater 351 increases), the value of the control waveform is set to be large in order to increase the amount of heat applied to the ink. Conversely, when the equivalent amount decreases (when the ink flow rate decreases), the value of the control waveform is set to be small. In this way, the control waveform CW1 is generated so that the amount of heat applied by the heater 351 increases or decreases according to the ink flow rate at the heater 351.

[0058] The algorithm by which the control waveform acquisition unit 921 generates the control waveform CW1 from the print pattern data PD1 may use, for example, a physical model created in advance or machine learning. Alternatively, the control waveform acquisition unit 921 may generate a waveform (time change) of ink consumption from the print pattern data PD1 and shift that waveform toward the future on the time axis to generate the control waveform CW1.

[0059] The temperature waveform acquisition unit 922 uses the print pattern data PD1 and the control waveform CW1 as input variables and the temperature waveform TpW as an output variable. The temperature waveform TpW is data that indicates the temporal change in the predicted value of the outlet temperature Te2. The algorithm used by the temperature waveform acquisition unit 922 to generate the temperature waveform TpW may be, for example, a physical model created in advance, or machine learning.

[0060] When pre-training the machine learning model, data obtained in a preliminary experiment to determine the FF control gain G1 may be used as training data, or simulation data may be used. Training of the machine learning model may be sequential training using data obtained during printing. Alternatively, the machine learning model may be replaced as needed by performing batch training using data acquired over a certain period of time. A tree-based algorithm such as a random forest or a support vector machine may be used as the algorithm for performing machine learning.

[0061] The temperature waveform correction point identifying unit 923 uses the differential temperature waveform TsW as an input variable and the temperature waveform correction point C1 as an output variable. The differential temperature waveform TsW is the difference between the temperature waveform TpW and the target temperature Ttg. The temperature waveform correction point C1 is information indicating the point in the temperature waveform TpW where the outlet temperature Te2 (predicted value) differs from the target temperature Ttg (the point where the outlet temperature Te2 deviates from the target temperature Ttg by more than a predetermined threshold).

[0062] The print pattern data PD1, control waveform CW1, temperature waveform TpW, and differential temperature waveform TsW may be managed by a unified index value separated by a time axis. In this case, the temperature waveform correction point C1 and the control waveform correction point C2 may be values ​​that indicate the index value. This index value is information corresponding to a specific time (period).

[0063] The dead time calculation unit 924 uses the print pattern data PD1 and the temperature waveform correction point C1 as input variables and the dead time DT as an output variable. The dead time calculation unit 924 calculates the ink flow rate value FR1 (equivalent amount) at the time of the temperature waveform correction point C1 from the print pattern data PD1, and calculates the dead time DT from the calculated flow rate value FR1.

[0064] The dead time DT is the time from when the control unit 9 provides the heater 351 with a control signal (specifically, the heater command value CV3 including the modified FF control value CV1a) to when the outlet temperature sensor 371 displays the control result based on the control signal (i.e., the time until the outlet temperature Te2 begins to change). When the flow rate value FR1 increases, the ink moves relatively quickly from the heater 351 to the outlet temperature sensor 371 due to the increased flow rate. As a result, the dead time DT becomes relatively shorter. In contrast, when the flow rate value FR1 decreases, the ink flow rate decreases, and the dead time DT becomes relatively longer. In this way, the dead time DT depends on the flow rate value FR1. Therefore, the dead time DT can be appropriately estimated from the flow rate value FR1 obtained from the print pattern data PD1.

[0065] The relationship between the print pattern data PD1 and the flow rate value FR1, and the relationship between the flow rate value FR1 and the dead time DT are obtained, for example, by a preliminary experiment conducted in advance to determine the gain G1.

[0066] The control waveform correction point identifying unit 925 uses the dead time DT and the temperature waveform correction point C1 as input variables and outputs the control waveform correction point C2. The control waveform correction point identifying unit 925 identifies the control waveform correction point C2 based on the dead time DT and the temperature waveform correction point C1. Specifically, the point (time) that is located back by the dead time DT from the temperature waveform correction point C1 is set as the control waveform correction point C2.

[0067] The control waveform correction unit 926 generates a corrected control waveform CW2 by correcting the control waveform CW1. The control waveform correction unit 926 uses the print pattern data PD1, the differential temperature waveform TsW, the control waveform CW1, and the control waveform correction portion C2 as input variables, and the corrected control waveform CW2 as an output variable. The algorithm used by the control waveform correction portion identification unit 925 to generate the corrected control waveform CW2 may use, for example, a physical model created in advance, or machine learning.

[0068] When pre-training a machine learning model, data obtained from a preliminary experiment to determine the FF control gain G1 may be used as training data, or simulation data may be used. As an algorithm for performing machine learning, a tree-based algorithm such as a random forest or a support vector machine may be used.

[0069] 4 is a diagram showing the flow of the process of correcting the control waveform CW1. First, the control waveform acquisition unit 921 generates the control waveform CW1 based on the print pattern data PD1 (FIG. 4: step S10).

[0070] After the control waveform CW1 is generated, the temperature waveform acquisition unit 922 generates a temperature waveform TpW from the print pattern data PD1 and the control waveform CW1 (FIG. 4: step S11).

[0071] After the temperature waveform TpW is generated, the temperature waveform correction portion specifying unit 923 specifies a temperature waveform correction portion C1 where the temperature should be corrected based on the differential temperature waveform TsW (FIG. 4: step S12).

[0072] If there is a temperature waveform correction point C1 (FIG. 4: Yes in step S12), the dead time calculation unit 924 calculates the dead time DT (FIG. 4: step S13).

[0073] After the dead time DT is calculated, the control waveform correction portion specifying unit 925 specifies the portion of the control waveform CW1 that should be corrected (FIG. 4: step S14).

[0074] After the control waveform correction portion C2 is identified, the control waveform correction unit 926 corrects the control waveform CW1 (FIG. 4: step S15). The control waveform correction unit 926 generates the corrected control waveform CW2 using the print pattern data PD1, the control waveform CW1, the differential temperature waveform TsW, and the control waveform correction portion C2.

[0075] After the control waveform CW1 is corrected, the control unit 9 determines whether the printing process has ended (FIG. 4: step S16). If the printing process has ended, the control unit 9 ends the control flow. If the printing process has not ended, the control unit 9 executes step S11 again. Also, in step S12, if there is no temperature waveform correction portion C1 in the temperature waveform TpW (FIG. 4: No in step S12), the control unit 9 skips steps S12 to S15 and executes step S16.

[0076] <Effects> As described above, in the printing device 1, the control waveform CW1 is corrected in advance so that the temperature waveform of the outlet temperature Te2 becomes the target temperature Ttg, and FF control is performed based on the corrected control waveform CW1 (corrected control waveform CW2). As a result, the heater 351 is controlled so that the temperature of the ink actually passing through the heater 351 (outlet temperature Te2) becomes the target temperature Ttg, thereby enabling appropriate temperature control of the ink.

[0077] Furthermore, because the control waveform CW1 is corrected taking into account the dead time DT, the heater 351 can be controlled taking into account not only changes in ink flow rate but also fluctuations in the dead time DT. If control were performed using the uncorrected control waveform CW1, delays in control could occur depending on the dead time DT, since the dead time DT would not be taken into account. In contrast, by correcting the control waveform CW1 taking the dead time DT into account, heater control that compensates for the dead time DT can be achieved, allowing for appropriate ink temperature regulation.

[0078] <2. Modifications> Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

[0079] For example, in the above embodiment, the correction process for the control waveform CW1 is performed during printing, as shown in Figure 4. However, the correction process for the control waveform CW1 may be performed only once before printing. If the print pattern data PD1 is a cyclic print pattern in which the same print pattern is repeated, the control waveform CW1 may be corrected periodically according to the period.

[0080] When the print pattern data PD1 is a periodic print pattern, the control waveform acquisition unit 921 may acquire the control waveform of the actual data, and the temperature waveform acquisition unit 922 may acquire the temperature waveform TpW of the actual data.

[0081] In the above embodiment, the corrected control waveform CW2 is generated by the dead time calculation unit 924, the control waveform correction portion identification unit 925, and the control waveform correction unit 926. However, the control waveform correction unit 926 may be configured to generate the corrected control waveform CW2 using a machine learning model having a function combining these three units.

[0082] As input variables for the control waveform acquisition unit 921, the temperature waveform acquisition unit 922, the temperature waveform correction portion identification unit 923, and the dead time calculation unit 924, the drive value waveform of the pump 331 may be used instead of the print pattern data PD1.

[0083] In the above embodiment, the control unit 9 controls one heater 351 using the heater command value CV3 obtained by adding the corrected FF control value CV1a and the FB control value CV2. However, the corrected FF control value CV1a and the FB control value CV2 may be separated and used to control two heaters, respectively.

[0084] In the above embodiment, the inlet temperature Te1 near the inlet of the heater 351 is used as an input to the FF control unit 911. However, instead of the inlet temperature Te1, for example, the temperature of ink inside the ink tank 311 may be used. Also, a temperature sensor may be provided that measures the temperature of ink inside the ink tank 311. In this case, the temperature of the ink stored in the ink tank 311 can be reflected in the FF control.

[0085] In the above embodiment, the outlet temperature Te2 near the outlet of the heater 351 is used as an input to the FB control unit 912. However, instead of the outlet temperature Te2, the ink temperature inside the ejection heads 21-24 or the ink temperature inside a reservoir (not shown) provided in the ejection heads 21-24 may be used. In this case, the ink temperature at the ink ejection position can be reflected in the FB control.

[0086] In the above embodiment, ink is supplied in one direction from the supply unit 30 to each of the ejection heads 21-24. However, a circulation path for circulating ink between the supply unit 30 and each of the ejection heads 21-24 may be provided. Also, a circulation path for circulating ink within the ejection heads 21-24 may be provided. Also, a heater for heating ink may be provided on the circulation path, and the FF control unit 911 and the FB control unit 912 may control the heater.

[0087] Although the present invention has been described in detail, the above description is merely illustrative in all respects and does not limit the present invention. It is understood that countless variations not illustrated can be envisioned without departing from the scope of the present invention. The configurations described in the above embodiments and variations can be combined or omitted as appropriate as long as they are not mutually inconsistent. [Explanation of symbols]

[0088] 1 Printing device 9 Control Unit 21 Discharge head 311 Ink Tank 331 Pump (ink supply unit) 351 Heater 361 Inlet temperature sensor (first temperature sensor) 911 Feedforward control unit 912 Feedback control section 921 Control waveform acquisition unit 922 Temperature waveform acquisition section 923 Temperature waveform correction part identification part 924 Dead time calculation unit 925 Control waveform correction part identification part 926 Control waveform correction unit

Claims

1. 1. A printing method comprising: a) ejecting ink from an ejection head onto a surface of a long strip-shaped substrate while transporting the substrate along a predetermined transport path; b) supplying the ink from an ink tank capable of storing the ink to the ejection head in an amount corresponding to the amount of the ink ejected from the ejection head; c) controlling a heater that heats the ink supplied to the ejection head in step b) based on a control waveform generated based on the corresponding amount; Including, The step c) c1) obtaining the control waveform; c2) acquiring a temperature waveform indicating a change in temperature of the ink passing through the heater over time when the heater is controlled based on the control waveform; c3) identifying a temperature waveform correction point in the temperature waveform where the temperature differs from a predetermined target temperature; c4) correcting the control waveform so that the temperature of the temperature waveform correction point becomes the target temperature; c5) measuring a first temperature of the ink before passing through the heater; c6) feedforward controlling the heater based on the control waveform corrected in step c4) and a difference value between the first temperature and the target temperature; A printing method including:

2. 2. The printing method according to claim 1, The step c4) c41) calculating a dead time based on the equivalent amount at the time point of the temperature waveform correction point; c42) A control waveform correction portion specifying unit that specifies a control waveform correction portion to be corrected in the control waveform based on the dead time; c43) correcting the control waveform based on the control waveform correction portion and the temperature waveform; A printing method including:

3. 3. The printing method according to claim 1, further comprising: The printing method, wherein step c1) includes a step of generating the control waveform based on print pattern data indicating a print pattern to be printed on the substrate.

4. 4. The printing method according to claim 3, The printing method, wherein step b2) includes a step of predicting the temperature waveform based on the print pattern data and the control waveform.

5. 3. The printing method according to claim 1, further comprising: d) performing feedback control based on the temperature of the ink that has passed through the heater; The printing method further comprises:

6. an ejection head that ejects ink; an ink tank capable of storing the ink; an ink supply unit that supplies the ink from the ink tank to the ejection head in an amount corresponding to the amount of the ink ejected from the ejection head; a heater that heats the ink supplied from the ink tank to the ejection head; a first temperature sensor that detects a first temperature of the ink before passing through the heater; a control unit that controls the heater; Equipped with The control unit a control waveform acquisition unit that acquires a control waveform generated in response to the time change of the equivalent amount; a temperature waveform acquiring unit that acquires a temperature waveform that indicates a change over time in temperature of the ink that has passed through the heater when the heater is controlled based on the control waveform; a temperature waveform correction portion specifying unit for specifying a temperature waveform correction portion in the temperature waveform where the temperature differs from a predetermined target temperature; a control waveform correction unit that corrects the control waveform so that the temperature of the temperature waveform correction point becomes a target temperature; and The control unit feedforward controls the heater based on the control waveform corrected by the control waveform correction unit and a difference value between the first temperature and the target temperature.

7. 7. The printing device according to claim 6, The control unit a dead time calculation unit that calculates a dead time based on the equivalent amount at the time point of the temperature waveform correction point; a control waveform correction portion determining unit that identifies a control waveform correction portion to be corrected in the control waveform based on the dead time; and The control waveform correction unit corrects the control waveform based on the control waveform correction portion and the temperature waveform.

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