Printing apparatus and printing method

Abstract

To provide a technique which can reduce a temperature fluctuating range of ink in a discharge head even if an amount of the ink flowing into the discharge head varies.SOLUTION: A flow quantity prediction part 93 predicts a flow quantity of ink flowing from an ink tank 311 to a discharge head 21 after a predetermined time elapses from the present time. A first heater control unit 91 controls a heater part 351 based on a flow quantity Fp1 predicated by the flow quantity prediction part 93. An outlet temperature sensor 371 measures a temperature Te3 of ink flowing from the heater part 351 to the discharge head 21. A second heater control unit 92 controls the heater part 351 based on a difference between the temperature Te3 measured by the outlet temperature sensor 371 and a preset target temperature Ttg.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a printing apparatus and a printing method.

Background Art

[0002] Conventionally, there is known a printing apparatus that forms an image on a base material by discharging ink from a discharge head while conveying the base material for continuous accounting in a roll-to-roll manner. In this type of printing apparatus, generally, viscosity control of the ink is important.

[0003] For example, when the temperature of the ink decreases, the viscosity increases, resulting in discharge unevenness, and problems such as deviation of the landing position of the ink or the occurrence of streaks may occur. Therefore, a mechanism for heating the ink may be provided for the purpose of keeping the ink temperature constant.

[0004] For example, in Patent Document 1, the ink is circulated in a circulation path connected to the 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

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the temperature of the ink in the discharge head can vary irregularly depending on the amount of ink flowing from the ink tank storing the unused ink into the discharge head. Therefore, there was a risk that the temperature variation range of the ink would become large simply by uniformly heating the ink in the discharge head.

[0007] The object of the present invention is to provide a technology that can reduce the temperature fluctuation range of the ink inside the ejection head, even when the amount of ink flowing into the ejection head fluctuates. [Means for solving the problem]

[0008] To solve the above problems, the first embodiment is a printing apparatus comprising: a conveying mechanism for conveying a long strip-shaped substrate unwound from an unwinding roller in a roll-to-roll manner; a discharge head for dispensing ink onto the surface of the substrate; an ink tank capable of storing the ink; an ink supply unit for supplying the ink from the ink tank to the discharge head; a heater unit for heating the ink flowing from the ink tank to the discharge head; and the discharge head in ink of Discharge Based on the dispensing information indicating the quantity The system includes: a flow rate prediction unit that predicts the flow rate of ink flowing from the ink tank to the ejection head after a predetermined time from the present; a first heater control unit that controls the heater unit by feedforward control based on the flow rate predicted by the flow rate prediction unit; a first temperature measurement unit that measures the temperature of the ink flowing from the heater unit to the ejection head; and a second heater control unit that controls the heater unit based on the difference between the temperature measured by the first temperature measurement unit and a preset target temperature.

[0009] A second embodiment is a printing apparatus according to the first embodiment, wherein the flow rate prediction unit predicts the flow rate based on ejection information indicating the amount of ink ejected from the ejection head.

[0010] A third embodiment is a printing apparatus according to the second embodiment, further comprising a discharge control unit that controls the discharge head based on print data, wherein the discharge information includes the print data.

[0011] The fourth embodiment is a printing apparatus according to any one of the first to third embodiments, further comprising a second temperature measuring unit for measuring the temperature of the ink in the ink tank, wherein the first heater control unit controls the heater unit based on the difference between the temperature measured by the second temperature measuring unit and a preset target temperature.

[0012] The fifth embodiment is a printing apparatus according to any one of the first to fourth embodiments, further comprising a third temperature measuring unit for measuring the temperature outside the ink tank, wherein the first heater control unit controls the heater unit based on the temperature measured by the third temperature measuring unit.

[0013] The sixth embodiment is a printing apparatus according to any one of the first to fifth embodiments, further comprising a flow rate measuring unit for measuring the flow rate of ink supplied from the ink tank to the ejection head, wherein the first heater control unit controls the heater unit based on the flow rate measured by the flow rate measuring unit.

[0014] The seventh aspect is a printing method comprising: x) a conveying step of conveying a long strip-shaped substrate unwound from an unwinding roller in a roll-to-roll manner; y) a discharge step of discharging ink from a discharge head onto the surface of the substrate; and a) the discharge Based on ejection information that shows the amount of ink ejected from the print head. The process includes a) a) a prediction step of predicting the flow rate of ink that will flow from the ink tank to the ejection head after a predetermined time from the present, b) a step of heating the ink flowing from the ink tank to the ejection head with a heater unit, and c) a step of measuring the temperature of the ink flowing from the heater unit to the ejection head, wherein step b) includes b-1) a step of controlling the heater unit by feedforward control based on the flow rate predicted by step a), and b-2) a step of controlling the heater unit based on the difference between the temperature measured by c) and a preset target temperature. [Effects of the Invention]

[0015] According to the printing apparatus of the first to sixth embodiments, the temperature fluctuation range can be reduced by controlling the heater section based on a predicted value of the ink flow rate to the ejection head.

[0016] According to the printing apparatus of the second embodiment, the flow rate can be accurately predicted based on the amount of ink ejected.

[0017] According to the printing apparatus of the third aspect, the flow rate can be accurately predicted based on the print data.

[0018] According to the printing apparatus of the fourth aspect, by controlling the heater unit based on the temperature difference between the target temperature and the temperature of the ink in the ink tank, the temperature of the ink in the ejection head can be appropriately adjusted.

[0019] According to the printing apparatus of the fifth aspect, by controlling the heater unit based on the temperature outside the ink tank, the temperature of the ink in the ejection head can be appropriately adjusted.

Brief Description of the Drawings

[0020] [Figure 1] It is a diagram showing the configuration of the printing apparatus according to the embodiment. [Figure 2] It is a block diagram showing the connection between the control unit and each part of the printing apparatus. [Figure 3] It is a control block diagram for controlling the heater unit. [Figure 4] It is a diagram showing the temperature fluctuation of the ink at the outlet position of the heater unit. [Figure 5] It is a diagram showing the correspondence between the temperature of the ink at the inlet position of the heater unit and the temperature fluctuation range.

Modes for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The components described in this embodiment are merely examples, and are not intended to limit the scope of the present invention thereto. In the drawings, for ease of understanding, the dimensions and numbers of each part may be exaggerated or simplified as necessary.

[0022] <1. Embodiment> Figure 1 is a diagram showing the configuration of a printing apparatus 1 according to an embodiment. The printing apparatus 1 is an inkjet printing apparatus. More specifically, the printing apparatus 1 transports a long, strip-shaped substrate W with a plurality of transport rollers 12 and ejects ink onto the substrate W from a plurality of ejection heads 21-24 to record an image on the surface of the substrate W. The substrate W is, for example, a flexible medium, such as printing paper, a resin film, corrugated cardboard, or a thin metal film.

[0023] As shown in Figure 1, the printing apparatus 1 comprises 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.

[0024] The conveying mechanism 10 conveys the base material W along a predetermined conveying path in a conveying direction along the longitudinal direction of the base material W. The conveying mechanism 10 has an unwinding roller 11, a plurality of conveying rollers 12, and a winding roller 13. The base material W is stretched over these rollers. The base material W is unwound from the unwinding roller 11 and conveyed along the predetermined conveying path while being supported by the plurality of conveying rollers 12. Each conveying roller 12 rotates about an axis extending in a direction perpendicular to the conveying direction, guiding the base material W downstream along the conveying path. The base material W conveyed by the plurality of conveying rollers 12 is wound onto the winding roller 13. Tension is applied to the base material W in the conveying direction. This suppresses sagging and wrinkling of the base material W during conveying.

[0025] The conveying mechanism 10 further includes motors 14 that rotate some of the rollers (hereinafter referred to as "drive rollers"). The conveying mechanism 10 may have 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 command values ​​to each motor 14 to drive them to rotate. The motors 14 then drive according to the command values, and the drive rollers rotate. As a result, the base material W is conveyed from the unwinding roller 11 to the winding roller 13.

[0026] The printing unit 20 is a processing unit that ejects ink droplets (hereinafter referred to as "ink droplets") onto the substrate W being transported by the transport mechanism 10. The printing unit 20 has a plurality (four in this example) ejection heads 21-24. The ejection heads 21-24 have the same structure as each other. The ejection heads 21-24 are arranged at intervals along the transport direction of the substrate W. The substrate W moves below the plurality of ejection heads 21-24, approximately parallel to the direction in which the plurality of ejection heads 21-24 are arranged. At this time, the surface (printing surface) of the substrate W is facing upward (towards each ejection head 21-24).

[0027] Each of the ejection heads 21-24 has an internal space capable of storing ink and multiple nozzles (not shown). The multiple nozzles are arranged on the lower surface of each ejection head 21-24 parallel to the width direction of the substrate W. Each of the multiple nozzles also has a piezoelectric element as a pressure generating element (not shown) and an ejection port that communicates with the internal space of each ejection head 21-24. When ink is ejected, ink flows down from the internal space to the vicinity of the ejection port. Then, due to the action of the piezoelectric element, the ink near the ejection port is pressurized, and droplet-shaped ink is ejected from the ejection port. The ink ejection method may also 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.

[0028] Each ejection head 21-24 ejects ink droplets of K (black), C (cyan), M (magenta), and Y (yellow), which are the color components of a multicolor image, from multiple nozzles toward the upper surface of the substrate W. Specifically, ejection head 21 ejects K-colored ink droplets as the processing material onto the upper surface of the substrate W at the first printing position P1, which is a processing position on the transport path. Ejection head 22 ejects C-colored ink droplets as the processing material onto the upper surface of the substrate W at the second printing position P2, which is a processing position downstream of the first printing position P1. Ejection head 23 ejects M-colored ink droplets as the processing material onto the upper surface of the substrate W at the third printing position P3, which is a processing position downstream of the second printing position P2. Ejection head 24 ejects Y-colored ink droplets as the processing material onto the upper surface of the substrate W at the fourth printing position P4, which is a processing position downstream of the third printing position P3.

[0029] 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 monochrome image on the upper surface of the substrate W by ejecting ink droplets. A multicolor image is then formed on the upper surface of the substrate W by superimposing the four monochrome images. In addition, each ejection head 21-24 can also print on the upper surface of the substrate W by ejecting ink droplets.

[0030] 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. Each of the multiple ink supply systems 31 is connected to the ejection heads 21-24 and supplies ink of the corresponding color to each ejection head 21-24. The ink supply systems 31 that supply ink to the ejection head 21 will be described below.

[0031] The ink supply system 31 includes an ink tank 311, piping 321, a pump 331, a flow meter 341, a heater unit 351, a tank temperature sensor 361, an outlet temperature sensor 371, and a liquid level sensor 381.

[0032] The ink tank 311 stores unused ink. One end of the piping 321 is connected to the internal space of the ejection head 21. The other end of the piping 321 is connected to the ink tank 311. The pump 331 is installed on the piping 321. The pump 331 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 piping 321 and the pump 331 are an example of an "ink supply unit" that supplies ink from the ink tank 311 to the ejection head 21. Alternatively, the ink from 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 an "ink supply unit".

[0033] The flow meter 341 is installed in the piping 321. The flow meter 341 measures the flow rate of ink flowing through the piping 321. The flow meter 341 transmits a signal indicating the measured flow rate to the control unit 9.

[0034] 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 response to the decrease in the amount of ink in the ejection head 21. As a result, the pump 331 is driven according to the drive value, and an amount of ink corresponding to the amount of ink in the ejection head 21 is supplied from the ink tank 311 to the ejection head 21. Similarly, ink is supplied to the other ejection heads 22-24 from their respective ink supply systems 31.

[0035] The heater unit 351 heats the ink supplied to the discharge head 21. The heater unit 351 is installed in the piping 321. The heater unit 351 is located between the pump 331 and the flow meter 341. The heater unit 351 heats the ink flowing through the piping 321.

[0036] The tank temperature sensor 361 (second temperature measurement unit) is installed inside the ink tank 311. The tank temperature sensor 361 measures the temperature of the ink stored in the ink tank 311. The tank temperature sensor 361 transmits a signal indicating the measured temperature to the control unit 9.

[0037] The outlet temperature sensor 371 (first temperature measurement unit) is installed in the piping 321. The outlet temperature sensor 371 is located between the heater unit 351 and the ejection head 21. The outlet temperature sensor 371 measures the temperature of the ink flowing from the heater unit 351 through the piping 321 to the ejection head 21. In this example, the outlet temperature sensor 371 is located at the outlet of the heater unit 351. Therefore, it measures the temperature of the ink immediately after it has passed through the heater unit 351. However, the outlet temperature sensor 371 may be located closer to the ejection head 21 than to the heater unit 351. The outlet temperature sensor 371 transmits a signal indicating the measured temperature to the control unit 9.

[0038] 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 level inside the ejection head 21. The liquid level sensor 381 is a non-contact sensor that detects the liquid level using, for example, ultrasound. The liquid level sensor 381 transmits a signal indicating the measured liquid level to the control unit 9.

[0039] The supply unit 30 has an outside air temperature sensor 39 (third temperature measurement unit). The outside air temperature sensor 39 is located outside the ink tank 311 and measures the outside air temperature outside the ink tank 311.

[0040] The encoder 60 is mounted on the axis of one of the multiple transport rollers 12 (in the example in Figure 1, transport roller 121). The encoder 60 detects the rotation of the transport roller 121 and outputs a continuous pulse signal synchronized with the rotation of the transport roller 121 to the control unit 9. The continuous pulse signal is data that reflects the change over time in the transport speed of the substrate W being transported by the multiple transport rollers 12, including the transport roller 121.

[0041] Camera 70 is an imaging device that photographs the printed surface (surface) of the substrate W after it has passed through the printing section 20. Camera 70 is positioned opposite the printed surface of the substrate W at the imaging position P5 downstream of the four ejection heads 21-24 in the transport path. Camera 70 has a line sensor in which multiple image sensors, such as CCDs or CMOS sensors, are arranged in the width direction. While the substrate W is being transported by the transport mechanism 10, Camera 70 acquires image data of the printed substrate W by photographing the printed surface of the substrate W at predetermined intervals. Camera 70 transmits the obtained image data to the control unit 9.

[0042] In addition to those mentioned above, the multiple sensors 80 are measuring instruments that measure the transport state of the substrate W. The multiple sensors 80 are installed at multiple measurement points along the transport path of the substrate W. Each sensor 80 acquires a measurement value at each measurement point. The measurement items of the sensors 80 can include, for example, the vertical displacement of the substrate W (amount of displacement in the direction perpendicular to the substrate W), the tension acting on the substrate W, the position of the edge of the substrate W in the width direction, etc. Multiple sensors 80 measuring the same item may be placed at multiple positions along the transport path. While the substrate W is being transported by the transport mechanism 10, the multiple sensors 80 constantly measure the state of each measurement point. The sensors 80 then transmit signals indicating the obtained measurement values ​​to the control unit 9.

[0043] Figure 2 is a block diagram showing the connections between the control unit 9 and the various parts of the printing device 1. The control unit 9 controls the operation of the printing device 1. The control unit 9 includes a processor 901, which is composed of a CPU or the like, and a storage unit 903, which is composed of RAM or a hard disk or the like. The storage unit 903 stores the program 90P and various data.

[0044] Program 90P is provided by recording medium M. Program 90P is recorded on recording medium M in a readable format by the control unit 9, which is a computer. Recording medium M is, for example, a USB (Universal Serial Bus) memory, an optical disc such as a DVD (Digital Versatile Disc), or a magnetic disc.

[0045] The control unit 9 is communicated via the motor 14 of the transport mechanism 10, the discharge heads 21-24 of the printing unit 20, and the pump 331, flow meter 341, heater unit 351, tank temperature sensor 361, outlet temperature sensor 371, liquid level sensor 381, and ambient temperature sensor 39 of the supply unit 30. The control unit 9 is also communicated via the encoder 60, camera 70, and various sensors 80.

[0046] The ejection control unit 90, first heater control unit 91, second heater control unit 92, flow rate prediction unit 93, and learning unit 94 shown in Figure 2 are functions realized by the processor 901 executing program 90P. The ejection control unit 90 controls the ejection of ink from the ejection heads 21-24 based on print data indicating the image to be printed on the substrate W. The first heater control unit 91 and the second heater control unit 92 control the heater unit 351. The functions of the first heater control unit 91, the second heater control unit 92, the flow rate prediction unit 93, and the learning unit 94 will be explained with reference to Figure 3.

[0047] <Heater section control> Figure 3 is a control block diagram for controlling the heater unit 351. The following explanation will mainly describe the case where the heater unit 351 of the ink supply system 31 connected to the ejection head 21 is controlled. The same control as shown in Figure 3 is performed in the ink supply system 31 connected to the ejection heads 22-24.

[0048] The first heater control unit 91 and the second heater control unit 92 output heater command values ​​CV1 and CV2, respectively, to the heater unit 351. For example, the heater command values ​​CV1 and CV2 are values ​​that indicate the power values ​​to be applied to the heaters provided by the heater unit 351. The heater unit 351 heats the heater according to the sum of the input heater command values ​​CV1 and CV2.

[0049] The first heater control unit 91 performs feedforward (FF) control. The first heater control unit 91 outputs a heater command value CV1 so that the temperature of the ink in the ejection head 21 reaches a preset target temperature Ttg after a predetermined time (for example, after a few seconds or tens of seconds).

[0050] Specifically, the first heater control unit 91 controls the heater unit 351 based on the flow rate predicted by the flow rate prediction unit 93. The flow rate prediction unit 93 uses a flow rate prediction model 931 to predict the flow rate Fp1 of ink that will flow into the discharge head 21 after a predetermined time. The flow rate Fp1 may be the flow rate at a future point in time, or it may be a flow rate fluctuation waveform that shows the time variation of the flow rate. The flow rate prediction model 931 is stored in the storage unit 903. The flow rate prediction model 931 outputs the flow rate Fp1 after a predetermined time from the input variable Vi.

[0051] The input variable Vi is the print pattern shown in the print data, the head drive waveform output by the control unit 9 to the ejection head 21 to drive the ejection head 21, the ink ejection count, the ink level in the ejection head 21 measured by the liquid level sensor 381, or a combination of these pieces of information. The print data showing the print pattern, the head drive waveform, the ink ejection count, and the ink level are ejection information indicating the amount of ink ejected from the ejection head 21. By using the ejection information as the input variable Vi, the flow rate after a predetermined time can be predicted with high accuracy. In particular, by including the print pattern shown in the print data as the input variable Vi, the flow rate after a predetermined time can be predicted with high accuracy.

[0052] The learning unit 94 performs machine learning to construct a flow rate prediction model 931. The control unit 9 stores the flow rate measured by the flow meter 341 in the storage unit 903. The learning unit 94 constructs the flow rate prediction model 931 by learning the relationship between the input variable Vi and the flow rate measured by the flow meter 341 a predetermined time after the time corresponding to the input variable Vi, based on a supervised machine learning algorithm.

[0053] The machine learning algorithm used in the learning unit 94 is a simple regression algorithm. A decision tree model (such as random forest or gradient boosting) or a deep learning algorithm (convolutional neural network) may be used. Furthermore, an appropriate machine learning algorithm or combination of input variables Vi may be selected depending on the type or characteristics of the ink used. The learning unit 94 may also update the flow rate prediction model 931 periodically or based on user input by performing machine learning. This update of the flow rate prediction model 931 helps to suppress its degradation.

[0054] When using a print pattern, the flow rate prediction unit 93 may generate ink ejection amount (consumption amount) as intermediate data from the density information of each color indicated by the image data. The flow rate prediction model 931 may then be configured to output a flow rate Fp1 using this intermediate data as an input variable Vi. Alternatively, the flow rate prediction model 931 may be constructed to output a flow rate Fp1 using image data as an input variable Vi. In this case, the flow rate prediction model 931 may be constructed using a supervised deep learning algorithm.

[0055] Furthermore, when using the displacement of the liquid level measured by the liquid level sensor 381, the flow rate prediction model 931 may calculate the slope (derivative value) of the ink depletion from the displacement of the liquid level measured during printing, and use this slope as the input variable Vi.

[0056] When constructing the flow rate prediction model 931, the model may include ink properties (such as viscosity, specific heat, or thermal conductivity) to make the model more versatile. In this case, one model can handle inks with various properties. Alternatively, the model may include information about the equipment configuration (for example, the volume inside the discharge head 21). In this case, one model can handle various equipment configurations.

[0057] The first heater control unit 91 receives the temperature difference DT1 (=Ttg-Te1) between the target temperature Ttg and the tank temperature Te1 measured by the tank temperature sensor 361. Based on this temperature difference DT1 and the flow rate Fp1 output by the flow rate prediction unit 93, the first heater control unit 91 outputs a heater command value CV1 so that the heater unit 351 is preheated in preparation for a temperature drop due to flow rate fluctuations.

[0058] The first heater control unit 91 may determine the heater command value CV1 based on a lookup table that defines the relationship between the flow rate Fp1 and the temperature difference DT1 and the heater command value CV1. Alternatively, the first heater control unit 91 may determine the heater command value CV1 using an inference model that takes the flow rate Fp1 and the temperature difference DT1 as inputs and outputs the heater command value CV1. This inference model may be constructed using a machine learning algorithm similar to that of the flow rate prediction model 931 described above.

[0059] As shown in Figure 3, the first heater control unit 91 may output a heater command value CV1 based on the ambient temperature Te2 measured by the ambient temperature sensor 39. The tank temperature Te1 is strongly influenced by the temperature outside the ink tank 311. Therefore, by determining the heater command value CV1 considering the ambient temperature Te2, the ink can be heated appropriately.

[0060] As shown in Figure 3, the first heater control unit 91 may output a heater command value CV1 based on the flow rate Fc1 measured by the flow meter 341. In this case, the first heater control unit 91 can determine the heater command value CV1 according to the flow rate fluctuations that may occur from the present time until a predetermined time has elapsed, thereby enabling the ink to be heated appropriately.

[0061] The first heater control unit 91 may output a heater command value CV1 based on the thermal properties of the ink (such as specific heat or thermal conductivity). The thermal properties of the ink are provided to the first heater control unit 91 based on user input. The thermal properties of the ink can greatly influence the amount of heat to be supplied. Therefore, by determining the heater command value CV1 considering the thermal properties of the ink, the ink can be heated appropriately.

[0062] The first heater control unit 91 may output a negative heater command value VC1 if the predicted flow rate Fp1 decreases. In this case, the value of the heater command value VC2 given to the heater unit 351 can be reduced, so that the amount of heating by the heater unit 351 can be reduced (or made zero) in accordance with the decrease in the predicted flow rate Fp1. This prevents the ink from being heated more than necessary when the flow rate of ink to the ejection heads 21-24 decreases.

[0063] The second heater control unit 92 performs feedback (FB) control. The FB control is preferably PID control. However, the FB control may also be PI control. The second heater control unit 92 outputs a heater command value CV2 to the heater unit 351 based on the difference value DT2 (=Ttg-Te3) between the target temperature Ttg and the ink temperature Te3 at the outlet position measured by the outlet temperature sensor 371. The second heater control unit 92 determines the heater command value CV2 so that the ink temperature Te3 at the outlet position approaches the target temperature Ttg.

[0064] Figure 4 shows the temperature fluctuation of the ink at the outlet position of the heater section 351. In Figure 4, the horizontal axis represents time, and the vertical axis represents the temperature measured by the outlet temperature sensor 371. In Figure 4, waveform G11 shows the temperature change when only FB control is performed by the second heater control section 92. Waveform G12 shows the temperature change when FF control is performed by the first heater control section 91 in addition to FB control. Also in Figure 4, waveform G2 shows the fluctuation of the ink flow rate Fc1 measured by the flow meter 341.

[0065] As shown in Figure 4, when the flow rate Fc1 increases, in both waveforms G11 and G12, the temperature Te3 decreases instantaneously before rising. However, as shown in waveform G11, with FB control alone, the heating of the heater section 351 is delayed, resulting in a large temperature fluctuation range (the difference between the maximum and minimum temperatures during one heating on / off cycle) (specifically, about 1.4°C). In contrast, as shown in waveform G12, by adding FF control to FB control, the temperature fluctuation range becomes smaller than with FB control alone (specifically, about 0.8°C). Furthermore, while waveform G11 is outside the allowable temperature range (here, 32°C ± 0.5°C), waveform G12 is almost within the allowable temperature range. Thus, by performing FF control based on the predicted flow rate Fp1, the temperature fluctuation range can be reduced.

[0066] Figure 5 shows the relationship between the ink temperature at the inlet position of the heater unit 351 and the temperature fluctuation range. In Figure 5, the horizontal axis shows the ink temperature at the inlet position (i.e., the temperature of the ink before it is heated by the heater unit 351; hereinafter referred to as "heater inlet position temperature"), and the vertical axis shows the temperature fluctuation range. In Figure 5, graph G31 shows the relationship when only FB control is performed by the second heater control unit 92, and graph G32 shows the relationship when FF control is performed by the first heater control unit 91 in addition to FB control.

[0067] As shown in Graph G31, with FB control alone, the heater inlet temperature must be set to a relatively high temperature (e.g., approximately 23°C or higher) to achieve the target temperature fluctuation range (e.g., 1°C). In contrast, as shown in Graph G32, by adding FF control to FB control, the target temperature fluctuation range can be achieved with a relatively low heater inlet temperature (e.g., approximately 16°C or higher). In other words, by combining FF control by the first heater control unit 91 and FB control by the second heater control unit 92, the heater inlet temperature requirement can be significantly relaxed. This allows for simplification of the temperature control system, such as omitting a heater to heat the ink inside the ink tank 311. However, this does not prevent the provision of a heater in the ink tank 311.

[0068] <2. Variant> Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.

[0069] For example, in the above embodiment, ink is supplied in one direction from the supply unit 30 to each discharge head 21-24. However, a circulation path may be provided to circulate the ink between the supply unit 30 and each discharge head 21-24. Alternatively, a circulation path may be provided within the discharge heads 21-24 to circulate the ink. Furthermore, a heater unit for heating the ink may be provided on the circulation path, and the first heater control unit 91 and the second heater control unit 92 may control the heater unit.

[0070] Although this invention has been described in detail, the above description is illustrative in all respects, and the invention is not limited thereto. It is understood that countless variations not illustrated can be conceived without falling outside the scope of this invention. The components described in each of the above embodiments and variations can be combined or omitted as appropriate, as long as they do not contradict each other. [Explanation of symbols]

[0071] 1 Printing device 9. Control Unit 21-24 Discharge head 39. Outdoor temperature sensor 90 Discharge control unit 91 First Heater Control Unit 92 Second Heater Control Unit 93 Flow rate prediction unit 95 Motor drive unit 311 Ink Tank 321 Piping 331 Pump 341 Flowmeter 351 Heater section 361 Tank temperature sensor 371 Outlet temperature sensor 931 Flow rate prediction model W Base material

Claims

1. A printing device, A conveying mechanism that transports a long, strip-shaped base material unwound from an unwinding roller using a roll-to-roll method, A dispensing head for dispensing ink onto the surface of the substrate, An ink tank capable of storing the aforementioned ink, An ink supply unit that supplies the ink from the ink tank to the discharge head, A heater unit that heats the ink flowing from the ink tank to the discharge head, A flow rate prediction unit predicts the flow rate of ink that will flow from the ink tank to the discharge head after a predetermined time from the present, based on discharge information indicating the amount of ink discharged from the discharge head. A first heater control unit controls the heater unit by feedforward control based on the flow rate predicted by the flow rate prediction unit, A first temperature measuring unit measures the temperature of the ink flowing from the heater unit to the ejection head, A second heater control unit controls the heater unit based on the difference between the temperature measured by the first temperature measuring unit and a preset target temperature. A printing device equipped with the following features.

2. A printing apparatus according to claim 1, The flow rate prediction unit predicts the flow rate based on ejection information indicating the amount of ink ejected from the ejection head.

3. A printing apparatus according to claim 2, Discharge control unit that controls the discharge head based on print data, Furthermore, The ejection information includes the print data, and the device is a printing apparatus.

4. A printing apparatus according to any one of claims 1 to 3, A second temperature measuring unit measures the temperature of the ink in the aforementioned ink tank. Furthermore, The printing apparatus comprises a first heater control unit which controls the heater unit based on the difference between the temperature measured by the second temperature measuring unit and a preset target temperature.

5. A printing apparatus according to any one of claims 1 to 4, A third temperature measuring unit that measures the temperature outside the ink tank, Furthermore, The printing apparatus comprises a first heater control unit which controls the heater unit based on the temperature measured by the third temperature measuring unit.

6. A printing apparatus according to any one of claims 1 to 5, A flow rate measuring unit that measures the flow rate of ink supplied from the ink tank to the discharge head. Furthermore, The first heater control unit controls the heater unit based on the flow rate measured by the flow rate measuring unit in the printing apparatus.

7. A printing method, x) A conveying process in which a long strip of base material unwound from an unwinding roller is conveyed using a roll-to-roll method, y) A dispensing step of dispensing ink from a dispensing head onto the surface of the substrate, a) A prediction step that predicts the flow rate of ink that will flow from the ink tank to the ejection head after a predetermined time from the present, based on ejection information indicating the amount of ink ejected at the ejection head. b) A step of heating the ink flowing from the ink tank to the ejection head in a heater unit, c) A step of measuring the temperature of the ink flowing from the heater unit to the ejection head. Includes, The aforementioned step b) is, b-1) A step of controlling the heater unit by feedforward control based on the flow rate predicted by step a), b-2) A step of controlling the heater unit based on the difference between the temperature measured by c) and a preset target temperature, Printing methods, including those mentioned.

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