Liquid injection device

Abstract

To provide a liquid spraying device that can suppress malfunctions of near-infrared sensors. [Solution] A liquid ejection device comprising: a print head for ejecting a liquid containing a colorant onto a medium; a transport unit for transporting the medium from upstream to downstream; a heater located downstream of the print head for evaporating the liquid on the medium; and a near-infrared sensor located downstream of the print head for detecting the dry state of the medium, wherein the heater is located opposite the surface of the medium, and the near-infrared sensor has a light-emitting unit for emitting near-infrared light and a light-receiving unit for receiving near-infrared light, the light-receiving unit being located opposite the back surface of the medium.

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejecting apparatus. [Background Art]

[0002] Research and development have been conducted on liquid ejecting apparatuses.

[0003] In relation to this, there is known an inkjet printer comprising: a print head that ejects liquid onto a medium to be printed; a conveying section that conveys the medium; a heater for heating the printed medium to evaporate the liquid on the medium; and a near-infrared sensor for detecting the drying state of the liquid on the medium (see Patent Document 1). [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2019-162773 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] In an inkjet printer such as that described in Patent Document 1, the near-infrared sensor may fail to operate normally due to the influence of heat from the heater. [Means for Solving the Problem]

[0006] To solve the above problems, one aspect of the present disclosure is a liquid ejection device comprising: a print head for ejecting a liquid containing a colorant onto a medium; a transport unit for transporting the medium from upstream to downstream; a heater located downstream of the print head for evaporating the liquid on the medium; and a near-infrared sensor located downstream of the print head for detecting the dry state of the medium, wherein the heater is located facing the surface of the medium, and the near-infrared sensor has a light-emitting unit for emitting near-infrared light and a light-receiving unit for receiving near-infrared light, the light-receiving unit being located facing the back surface of the medium. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows an example of the hardware configuration of the liquid injection device 100. [Figure 2] This figure shows an example configuration of the drying section 150 of the liquid injection device 100. [Figure 3] This figure shows an example of the near-infrared absorption spectrum of water. [Figure 4] This figure shows an example of the processing flow of a liquid injection device 100 based on the water content in the ink on the medium. [Figure 5] This figure shows an example of the temporal change in the maximum output history of the second heater 119b. [Figure 6] This figure shows another example of the hardware configuration of the liquid injection device 100. [Figure 7] This figure shows another example of the configuration of the drying section 150 of the liquid injection device 100. [Figure 8] This figure shows an example of the visible light reflection spectrum of water. [Figure 9] This figure shows an example of the process flow in which the liquid injection device 100 determines the second output by patch printing. [Figure 10] This figure shows an example of a second heater 119b composed of multiple divided heaters. [Modes for carrying out the invention]

[0008] <Embodiment> The embodiments of this disclosure will be described below with reference to the drawings.

[0009] <Hardware configuration of liquid injection system> First, the hardware configuration of the liquid injection device according to the embodiment will be described using the liquid injection device 100 as an example. Figure 1 is a diagram showing an example of the hardware configuration of the liquid injection device 100.

[0010] The liquid ejection device 100 is a device that prints an image onto a medium by ejecting a liquid containing a colorant onto the medium. The colorant is, for example, a dye or a pigment, but is not limited to these. The liquid containing the colorant is a liquid in which the colorant is dissolved or mixed in a medium, for example, ink. Therefore, the liquid ejection device 100 is, for example, an inkjet printer that prints an image onto a medium by ejecting ink. However, the liquid ejection device 100 may also be a printer that ejects another liquid containing a colorant onto the medium instead of ink.

[0011] As shown in Figure 1, the liquid injection device 100 includes a control unit 101. The liquid injection device 100 also includes a CPU (Central Processing Unit) 102 that controls the entire liquid injection device 100, a ROM (Read Only Memory) 103, a RAM (Random Access Memory) 104, an NVRAM (Non-Volatile RAM) 105, and an ASIC (Application Specific Integrated Circuit) 106. The CPU 102, ROM 103, RAM 104, NVRAM 105, and ASIC 106 are connected to each other via a bus so that they can communicate with one another.

[0012] ROM 103 stores programs executed by CPU 102 and other fixed data. RAM 104 temporarily stores image data. NVRAM 105 retains data even when the power to the liquid injection device 100 is cut off. ASIC 106 processes various signal processing, image processing such as sorting, and other input / output signals for controlling the entire liquid injection device 100.

[0013] Furthermore, the control unit 101 includes an I / F (Interface) 107, a print control unit 108, a main scanning motor drive unit 109, a sub-scanning motor drive unit 110, a heater control unit 111, and an I (Input) / O (Output) 112. The control unit 101 is also connected to the operation panel 113 and the near-infrared sensor 114 in a communication manner.

[0014] Here, the operation panel 113 is an operation panel provided by the liquid injection device 100 for inputting and displaying various types of information, and consists of either hardware keys or software keys, or both, and a display. For example, the operation panel 113 is a touch panel, but is not limited to this.

[0015] The near-infrared sensor 114 is a sensor provided by the liquid spraying device 100 for detecting the dry state of the medium. The near-infrared sensor 114 has a light-emitting unit 114a that emits near-infrared light toward the medium and a light-receiving unit 114b that receives near-infrared light reflected or transmitted by the medium.

[0016] I / F 107 is an interface that transmits and receives data, signals, and the like to and from the host side. Specifically, I / F 107 receives print data and the like generated by a printer driver of a device such as an information processing apparatus, an image reading apparatus, or an imaging apparatus that functions as a host via a cable, a network, or the like. That is, the generation and output of print data to the control unit 101 may be performed by a printer driver on the host side. The CPU 102 reads and analyzes the print data in a reception buffer included in I / F 107. Then, the analyzed print data is subjected to image processing, data rearrangement processing and the like by the ASIC 106, and then transferred to the print control unit 108 and the head driver 116.

[0017] The print control unit 108 generates a drive waveform for driving the liquid ejecting head 121, and outputs image data for selectively driving pressure generating means that generates pressure for the liquid ejecting head 121 to eject liquid from nozzles and various accompanying data to the head driver 116.

[0018] Here, the liquid ejecting head 121 is a print head of the liquid ejecting apparatus 100, and ejects a liquid containing a color material onto a medium. The head driver 116 is one of the drivers included in the liquid ejecting apparatus 100. The head driver 116 acquires the various types of data described above from the print control unit 108, and drives the liquid ejecting head 121 based on the acquired various types of data.

[0019] The print control unit 108 may be configured by a computer provided with a CPU, a ROM, a RAM, and the like. The print control unit 108 is realized by the CPU executing a program stored in a ROM or the like.

[0020] The program executed by the CPU of the print control unit 108 may be provided as a file in an installable format or an executable format, recorded on a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, a DVD (Digital Versatile Disk), or the like.

[0021] Furthermore, the program executed by the CPU of the print control unit 108 may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Alternatively, the program executed by the CPU of the print control unit 108 may be configured to be provided or distributed via a network such as the Internet.

[0022] The main scanning motor drive unit 109 drives the main scanning motor 117. The main scanning motor 117 is a motor provided in the liquid injection device 100, and when driven, it moves the carriage 120 equipped with the liquid injection head 121 in the main scanning direction. The carriage 120 is a carriage provided in the liquid injection device 100 for moving the liquid injection head 121. The sub-scanning motor drive unit 110 drives the sub-scanning motor 118. The sub-scanning motor 118 is a motor provided in the liquid injection device 100, and when driven, it operates the transport member 122 that transports the medium to which the liquid is to be discharged by the liquid injection head 121. The transport member 122 is a component provided in the liquid injection device 100, and is configured, for example, to include one or more rollers. The heater control unit 111 controls the heater 119. The heater 119 is a heater provided in the liquid injection device 100 for evaporating the liquid on the medium. Therefore, the heater 119 is located downstream of the liquid injection head 121. For example, the heater 119 is an infrared heater. In this case, the heater 119 dries the liquid on the medium by radiating infrared rays. Note that the heater 119 may be of another type instead of an infrared heater. Also, the liquid injection device 100 may be configured to include other heaters in addition to the heater 119. In this case, the heater control unit 111 may also control the other heaters that the liquid injection device 100 has along with the heater 119.

[0023] The I / O 112 acquires information from the near-infrared sensor 114 and extracts information necessary for controlling the heater 119. The I / O 112 also acquires information from various sensors other than the near-infrared sensor 114. In this case, the I / O 112 extracts information necessary for controlling each part of the liquid injection device 100 from the acquired information.

[0024] Here, we will briefly describe the printing control process in the liquid injection device 100.

[0025] The CPU 102 of the liquid injection device 100 reads and analyzes the print data in the receiving buffer of the I / F 107, performs necessary image processing and data rearrangement processing using the ASIC 106, and then transfers the data to the print control unit 108.

[0026] The print control unit 108 outputs image data and drive waveforms to the head driver 116 at the required timing. Specifically, the print control unit 108 generates a drive waveform consisting of one or more drive pulses by performing a D (Digital) / A (Analog) conversion and amplification of the drive pulse pattern data stored in the ROM 103 and read by the CPU 102.

[0027] The generation of image data for image output (for example, dot pattern data) may be performed, for example, by storing font data in ROM 103, or by the host-side printer driver expanding the image data into a bitmap and transferring it to the liquid spray device 100.

[0028] The head driver 116 drives the liquid spray head 121 by selectively applying drive pulses, which constitute a drive waveform provided by the print control unit 108, to the pressure generating means of the liquid spray head 121 based on the input image data (e.g., dot pattern data).

[0029] Here, we will explain the effect of heat from the heater 119. In a liquid injection device different from the liquid injection device 100, the heat from the component corresponding to the heater 119 heats not only the medium to which the liquid is injected, but also the component corresponding to the near-infrared sensor 114. This phenomenon occurs because both of these components are located above the transport path through which the medium is transported and are in close proximity to each other. This can cause malfunction of the near-infrared sensor 114, which is undesirable.

[0030] Therefore, in the liquid injection device 100, at least the light-receiving part 114b of the near-infrared sensor 114 is positioned in a location where radiant heat from the heater 119 is difficult to transfer. Specifically, in the liquid injection device 100, the heater 119 is positioned opposite the upper surface of the medium that passes below the path through which the liquid injection head 121 moves back and forth by the carriage 120. On the other hand, in the liquid injection device 100, the light-receiving part 114b of the near-infrared sensor 114 is positioned opposite the lower surface of the medium. As a result, in the liquid injection device 100, when the medium is being transported, at least a portion of the radiant heat from the heater 119 is blocked by the medium. Consequently, the liquid injection device 100 can suppress the light-receiving part 114b from being heated by the heater 119. In other words, the liquid spraying device 100 can suppress malfunctions of the near-infrared sensor 114. Furthermore, since at least a portion of the radiant heat from the heater 119 to the light-receiving unit 114b is blocked by the medium, the liquid spraying device 100 can suppress a decrease in detection accuracy by the near-infrared sensor 114, even when an infrared heater is used as the heater 119. Note that the light-receiving unit 114b is less likely to malfunction than the light-emitting unit 114a, even if it is heated by the radiant heat from the heater 119. For this reason, the light-emitting unit 114a may be positioned facing the back surface of the medium together with the light-receiving unit 114b, or it may be positioned facing the front surface of the medium together with the heater 119. When the light-emitting unit 114a is positioned facing the back surface of the medium together with the light-receiving unit 114b, the liquid spraying device 100 can more reliably suppress the light-receiving unit 114b from being heated by the heater 119. Furthermore, if the light-emitting unit 114a is positioned facing the surface of the medium, the light-receiving unit 114b receives the transmitted light after the near-infrared light emitted from the light-emitting unit 114a has passed through the medium. In this case, the near-infrared sensor 114 is a transmissive sensor.On the other hand, when the light-emitting unit 114a is positioned facing the back surface of the medium, the light-receiving unit 114b receives the reflected light after the near-infrared light emitted from the light-emitting unit 114a has been reflected by the medium. In this case, the near-infrared sensor 114 is a reflective type sensor.

[0031] Some of the hardware components of the liquid injection device 100 function as a drying unit 150. Specifically, the near-infrared sensor 114 and the heater 119 function as a drying unit 150 in the liquid injection device 100. The drying unit 150 of the liquid injection device 100 will be described below. Figure 2 shows an example of the configuration of the drying unit 150 of the liquid injection device 100. The drying unit 150 is a drying device that dries the liquid on the medium. In the example shown in Figure 2, the near-infrared sensor 114 is a reflective sensor. The medium PP shown in Figure 2 is an example of a medium from which liquid is injected by the liquid injection head 121. The liquid Ld shown in Figure 2 is an example of a liquid injected onto the medium PP by the liquid injection head 121.

[0032] As shown in Figure 2, the drying section 150 of the liquid injection device 100 is composed of a near-infrared sensor 114 and a heater 119. The heater 119 also includes two heaters: a first heater 119a and a second heater 119b.

[0033] The first heater 119a is located upstream of the second heater 119b in the transport direction of the medium. Furthermore, the first heater 119a is located upstream of the near-infrared sensor 114 in the transport direction. Note that in Figure 2, for the sake of simplification, the light-emitting part 114a and the light-receiving part 114b of the near-infrared sensor 114 are shown together as a single triangular object. The first heater 119a adjusts the temperature of the medium. By doing so, the first heater 119a radiates infrared rays onto the liquid on the medium, raising the temperature of the medium and drying a portion of the liquid on the medium. In the example shown in Figure 2, the first heater 119a dries a portion of the liquid Ld on the medium PP.

[0034] A filter 125A is installed on the irradiation surface of the first heater 119a. The filter 125A restricts the passage of infrared radiation radiated by the first heater 119a. The first heater 119a may be integrated with the filter 125A. Alternatively, the filter 125A may not be installed on the irradiation surface of the first heater 119a.

[0035] The second heater 119b is located downstream of the first heater 119a in the conveying direction. Furthermore, the second heater 119b is located downstream of the near-infrared sensor 114 in the conveying direction. The second heater 119b radiates infrared rays to the liquid on the medium according to the degree of dryness of the liquid evaporated by the first heater 119a, thereby completely drying the liquid on the medium. In the example shown in Figure 2, the second heater 119b completely dries the liquid Ld on the medium PP.

[0036] A filter 125B is installed on the irradiation surface of the second heater 119b. The filter 125B restricts the passage of infrared radiation radiated by the second heater 119b. The second heater 119b may be integrated with the filter 125B. Alternatively, the filter 125B may not be installed on the irradiation surface of the second heater 119b.

[0037] As shown in Figure 2, the heater 119 is located downstream of the liquid injection head 121. Also, as shown in Figure 2, when the near-infrared sensor 114 is viewed from above the medium downwards, the near-infrared sensor 114 is located between the first heater 119a and the second heater 119b. As a result, the near-infrared sensor 114 can detect the degree of dryness of the liquid on the medium that has been partially dried by the first heater 119a. Consequently, the liquid injection device 100 can perform predetermined processing based on the detection result of the near-infrared sensor 114. The predetermined processing is performed to ensure that the liquid on the medium is completely dry. For example, the predetermined processing includes, but is not limited to, processing such as stopping the transport by the transport member 122 until it is determined that the liquid is dry based on the detection result of the near-infrared sensor 114, and processing the output of the second heater 119b. If the predetermined process includes stopping the transport by the transport member 122 until the near-infrared sensor 114 determines that the liquid is dry, the liquid spraying device 100 will stop transport by the transport member 122 if it determines that the liquid on the medium is not dry until the near-infrared sensor 114 determines that the liquid is dry. Then, if the liquid spraying device 100 determines that the liquid on the medium is dry, it will resume transport by the transport member 122. Here, for example, the liquid spraying device 100 determines that the liquid on the medium is dry if the degree of dryness of the liquid on the medium is such that it is estimated that it can be completely dried by the second heater 119b. On the other hand, for example, the liquid spraying device 100 determines that the liquid on the medium is not dry if the degree of dryness of the liquid on the medium is such that it is estimated that it cannot be completely dried by the second heater 119b. The degree of dryness of the liquid on the medium is represented by the water content of the liquid on the medium. The higher the water content of the liquid on the medium, the lower the degree of dryness of the liquid on the medium. In other words, the lower the water content in the liquid on the medium, the drier the liquid on the medium is. For example, the liquid injection device 100 determines that the liquid on the medium is not dry if the water content in the liquid on the medium is above a predetermined threshold TH.On the other hand, for example, the liquid injection device 100 determines that the liquid on the medium is dry if the water content in the liquid on the medium is less than the threshold TH. Therefore, if the process of increasing the output of the second heater 119b is included in the predetermined process, the output of the second heater 119b when the liquid injection device 100 determines, based on the detection result of the near-infrared sensor 114, that the water content in the liquid on the medium is less than the threshold TH (a first value), will be lower than the output of the second heater 119b when the water content in the liquid on the medium is greater than or equal to the threshold TH (a second value), based on the detection result of the near-infrared sensor 114. This means that the degree of drying of the liquid on the medium by the second heater 119b can be set to correlate with the water content in the liquid, which is useful.

[0038] Furthermore, as shown in Figure 2, since the heater 119 is positioned facing the surface of the medium together with the liquid spray head 121, the liquid spray device 100 can also obtain the effect of easily drying the liquid on the medium.

[0039] Here, Figure 3 shows an example of the near-infrared absorption spectrum of water. Note that the absorption spectrum curve shown in Figure 3 is merely a representation of characteristic parts and does not perfectly match the curve actually obtained experimentally. The horizontal axis of the graph in Figure 3 represents the wavelength of light. The vertical axis of the graph represents the near-infrared absorption rate by water. In the example shown in Figure 3, the near-infrared wavelengths that are easily absorbed by water are 1450 nm, 1940 nm, and 2900 nm. Therefore, if the near-infrared sensor 114 is a transmissive sensor, the light-emitting part 114a of the near-infrared sensor 114 is equipped with a light-emitting element that emits near-infrared light at one of the wavelengths of 1450 nm, 1940 nm, or 2900 nm. In this case, the near-infrared sensor 114 may be configured to detect the water content in the liquid on the medium using a combination of two or more of 1450 nm, 1940 nm, and 2900 nm. On the other hand, if the near-infrared sensor 114 is a transmissive sensor, the wavelength of near-infrared light emitted by the light-emitting part 114a of the near-infrared sensor 114 is determined using the reflection spectrum of near-infrared light by water, instead of using the absorption spectrum of near-infrared light by water. Specifically, in this case, the wavelength is determined to be one or a combination of several near-infrared wavelengths that are easily reflected by water. Note that in this embodiment, a diagrammatic explanation of the reflection spectrum of near-infrared light by water is omitted.

[0040] The liquid spray device 100 detects the water content in the ink on the medium based on the detection result of the near-infrared sensor 114. Alternatively, the water content in the ink on the medium may be detected by the near-infrared sensor 114. In this case, the near-infrared sensor 114 includes a processor that detects the water content in the liquid on the medium based on the intensity of light emitted by the light-emitting unit 114a and the intensity of light received by the light-receiving unit 114b. The processor then outputs information indicating the detected water content to the CPU 102. This also allows the liquid spray device 100 to determine the water content in the liquid on the medium.

[0041] <Processing of liquid injection devices based on the water content in the liquid on the medium> The following describes the processing of the liquid spraying device 100 based on the water content in the liquid on the medium, with reference to Figure 4. Figure 4 is a diagram showing an example of the processing flow of the liquid spraying device 100 based on the water content in the liquid on the medium. For example, when the liquid spraying device 100 receives a request from the host to print an image on the medium, it starts the processing shown in the flowchart in Figure 4. In the following, as an example, we will describe the case in which the liquid spraying device 100 prints an image on the medium in parallel with the processing shown in the flowchart in Figure 4. For this reason, in order to avoid making the explanation complicated, the explanation of the process by which the liquid spraying device 100 prints an image on the medium will be omitted in the flowchart shown in Figure 4. For the sake of convenience in the following explanation, the process by which the liquid spraying device 100 prints an image on the medium will be referred to as the printing process.

[0042] When the host requests printing an image onto the medium, the liquid injection device 100 starts operating the heater 119 (step S110). More specifically, in step S110, the liquid injection device 100 starts operating the first heater 119a so that the output of the first heater 119a becomes a predetermined first output, and starts operating the second heater 119b so that the output of the second heater 119b becomes a predetermined second output. The liquid injection device 100 may also be configured to start operating the heater 119 at other times.

[0043] Next, the liquid spraying device 100 starts detecting the drying state of the ink on the medium using the near-infrared sensor 114 (step S120). More specifically, in step S120, the liquid spraying device 100 starts emitting near-infrared light from the light-emitting part 114a of the near-infrared sensor 114, and starts receiving near-infrared light from the light-receiving part 114b of the near-infrared sensor 114. Note that the process in step S120 may be performed in the reverse order of the process in step S110, or it may be performed in parallel with the process in step S110.

[0044] Next, the liquid spraying device 100 detects the water content in the liquid on the medium based on the detection result of the near-infrared sensor 114. Then, the liquid spraying device 100 determines whether or not the liquid on the medium is dry based on the detected water content (step S130).

[0045] If the liquid ejection device 100 determines that the liquid on the medium is dry (step S130-YES), it determines whether the printing requested by the host has been completed (step S140). In Figure 4, the process in step S140 is indicated by "Printing complete?".

[0046] If the liquid ejection device 100 determines that the printing requested by the host has not been completed (step S140-NO), it proceeds to step S130 to determine again whether the liquid on the medium is dry or not.

[0047] On the other hand, if the liquid spray device 100 determines that the printing requested by the host has been completed (step S140-YES), it terminates the operation of the heater 119 (step S150). More specifically, in step S150, the liquid spray device 100 terminates the operation of the first heater 119a and the operation of the second heater 119b. The liquid spray device 100 may also be configured to terminate the operation of the heater 119 at other times.

[0048] Next, the liquid spraying device 100 terminates the detection of the dry state of the liquid on the medium by the near-infrared sensor 114 (step S160). More specifically, in step S160, the liquid spraying device 100 terminates the emission of near-infrared light by the light-emitting part 114a of the near-infrared sensor 114, and terminates the reception of near-infrared light by the light-receiving part 114b of the near-infrared sensor 114. Note that the process in step S160 may be performed in the reverse order of the process in step S150, or it may be performed in parallel with the process in step S150. After the process in step S160 is performed, the liquid spraying device 100 terminates the process shown in the flowchart in Figure 4.

[0049] On the other hand, if the liquid spraying device 100 determines that the liquid on the medium is dry (step S130-NO), it performs the predetermined process described above (step S170). That is, for example, in step S170, the liquid spraying device 100 stops transport by the transport member 122 in the printing process until it determines that the liquid on the medium is dry based on the detection result of the near-infrared sensor 114. Then, if the liquid spraying device 100 determines that the liquid on the medium is dry, it resumes transport by the transport member 122 in the printing process. Also, for example, in step S170, the liquid spraying device 100 increases the output of the second heater 119b to a first predetermined value. The first predetermined value may be any value that can be used as the value of the increase in the output of the second heater 119b. After the process in step S170 is performed, the liquid spraying device 100 proceeds to step S130 and determines again whether or not the liquid on the medium is dry.

[0050] As described above, the liquid spraying device 100 can perform processing according to the drying state of the liquid on the medium by using a near-infrared sensor 114 in which the light-receiving unit 114b is positioned opposite to the back surface of the medium passing below the path through which the liquid spraying head 121 moves back and forth by the carriage 120. In other words, the liquid spraying device 100 can perform processing according to the drying state of the liquid on the medium while suppressing malfunctions of the near-infrared sensor 114.

[0051] The liquid injection device 100 may also be configured to store information indicating the history of the maximum output of the second heater 119b that was operated in the flowchart shown in Figure 4. In this case, the liquid injection device 100 may be configured to set the maximum output of the second heater 119b that was operated in the previous instance as the second output of the second heater 119b that is started to operate in step S110, for example. Alternatively, in this case, the liquid injection device 100 may be configured to set the moving average of the maximum output of the second heater 119b over a predetermined number of times when the second heater 119b was operated in the past as the second output of the second heater 119b that is started to operate in step S110, for example. The predetermined number of times is, for example, 5 times, 10 times, etc., but is not limited to these. Figure 5 is a diagram showing an example of the temporal change in the history of the maximum output of the second heater 119b. The horizontal axis of the graph shown in Figure 5 shows the elapsed time by the number of prints performed by the liquid injection device 100. In Figure 5, this number is indicated by "number of jobs". The vertical axis of the graph represents the output of the second heater 119b. The curve plotted on the graph is a moving average of the maximum output of the second heater 119b plotted on the graph. This allows the liquid injection device 100 to adjust the second output in response to environmental changes over time. This is useful because it reduces the drying time of the liquid on the medium.

[0052] Furthermore, for example, the liquid spraying device 100 may, in step S170, instead of increasing the output of the second heater 119b by a first predetermined value, or in addition to increasing the output of the second heater 119b by a first predetermined value, raise the threshold value TH. This is because, for example, the higher the humidity in the room where the liquid spraying device 100 is installed, the more difficult it becomes for water to evaporate from the liquid on the medium. In this case, the liquid spraying device 100 may also be configured to store information indicating the history of the maximum value of the threshold value TH, similar to the output of the second heater 119b. This allows the liquid spraying device 100 to, for example, set the previous maximum value of the threshold value TH as the new threshold value TH each time the flowchart shown in Figure 4 is executed, or set the moving average of the threshold value TH as the new threshold value TH each time the flowchart shown in Figure 4 is executed. As a result, the liquid spraying device 100 can more reliably dry the liquid on the medium even if the environment changes over time.

[0053] <Modified examples of embodiments> The following describes modifications of the embodiment. In the modifications of the embodiment, the liquid injection device 100 may be configured to include a visible light sensor 115 along with the near-infrared sensor 114. Figure 6 shows another example of the hardware configuration of the liquid injection device 100.

[0054] The visible light sensor 115 is a sensor for detecting the color of ink on a medium. The visible light sensor 115 has a light-emitting unit 115a that emits visible light and a light-receiving unit 115b that receives visible light. Therefore, the aforementioned I / O 112 acquires information from the light-receiving unit 115b of the visible light sensor 115.

[0055] The visible light sensor 115 functions as part of the drying section 150 in the liquid injection device 100. That is, together with the near-infrared sensor 114 and the heater 119, the visible light sensor 115 functions as part of the drying section 150 in the liquid injection device 100. Figure 7 shows another example of the configuration of the drying section 150 of the liquid injection device 100.

[0056] As shown in Figure 7, the drying section 150 of the liquid injection device 100 is composed of a near-infrared sensor 114, a visible light sensor 115, and a heater 119. In the example shown in Figure 7, the near-infrared sensor 114 is a through-beam sensor.

[0057] As shown in Figure 7, both the light-emitting portion 115a and the light-receiving portion 115b of the visible light sensor 115 are positioned to face the surface of the medium as it passes below the path through which the liquid spray head 121 moves back and forth by the carriage 120. This is because, in addition to detecting the color of the liquid on the medium, the visible light sensor 115 is less susceptible to the influence of near-infrared radiation emitted from the heater 119, unlike the light-receiving portion 114b of the near-infrared sensor 114. Furthermore, when the visible light sensor 115 is viewed from above the medium looking downwards, it is positioned between the liquid spray head 121 and the first heater 119a. This allows the visible light sensor 115 to detect the color of the liquid on the medium before it is dried by the first heater 119a. As a result, the liquid spray device 100 can perform predetermined processing based on both the detection result of the visible light sensor 115 and the detection result of the near-infrared sensor 114. In this case, the predetermined process includes, for example, a process that changes the threshold TH according to the color of the liquid on the medium, but is not limited to this. Note that in Figure 7, for the sake of simplifying the diagram, the light-emitting part 115a and the light-receiving part 115b of the visible light sensor 115 are shown together as a single triangular object.

[0058] Here, the color of a liquid can be rephrased as the type of liquid. For example, ink, which is an example of a liquid, has a different water content depending on its type. Also, the color of ink can be identified by the luminance value of the ink's surface. The lower the luminance value of the ink's surface, the higher the water content in the ink. For example, yellow ink, which is an example of an ink with a high surface luminance value, has a lower content of colorant components and a higher water content compared to black ink. In other words, for example, black ink, which is an example of an ink with a low surface luminance value, has a higher content of colorant components and a lower water content compared to yellow ink.

[0059] Therefore, in a modified embodiment, the liquid spraying device 100 determines the second output of the second heater 119b for each liquid color by, for example, performing patch printing for each liquid color, and identifies the average value of the determined second outputs for each color as the second output to be used in the process of step S110 shown in Figure 4. As a result, the liquid spraying device 100 can perform the process using a second output suitable for the type of color used in printing, and can dry the liquid on the medium more efficiently.

[0060] The visible light sensor 115 can detect the color of a liquid on a medium using the visible light reflection spectrum of water, as shown in Figure 8. Figure 8 is a diagram showing an example of the visible light reflection spectrum of water. However, the curve of the reflection spectrum shown in Figure 8 is merely an illustrative diagram and does not necessarily match the curve obtained by actual experiments. The horizontal axis of the graph shown in Figure 8 represents the wavelength of light. The vertical axis of the graph represents the reflectance of visible light by water. The method for detecting the color of a liquid using the reflection spectrum may be a known method or a method to be developed in the future.

[0061] <Process in which the liquid injection device determines the second output by patch printing> Figure 9 shows an example of the process flow in which the liquid injection device 100 determines the second output by patch printing. When the liquid injection device 100 receives a predetermined second output determination process start operation, for example, it executes the process shown in the flowchart in Figure 9. In Figure 9, as an example, the case in which the first heater 119a and the second heater 119b are both operating at a time prior to the processing of step S210 shown in Figure 9 is performed.

[0062] After receiving the second output determination process start operation, the liquid spraying device 100 repeatedly performs the processes in steps S220 to S260 for each liquid color available to the liquid spraying device 100 (step S210). In Figure 9, the process in step S210 is shown as "for each liquid color". The liquid spraying device 100 may be configured to perform the processes in steps S220 to S260 for each liquid color in parallel. However, in this case, the liquid spraying device 100 may, for example, print patches for each liquid color on the medium in parallel with the medium's transport direction, or it may be equipped with the same number of near-infrared sensors 114 and visible light sensors 115 as there are liquid colors.

[0063] After the liquid color is selected in step S210, the liquid spraying device 100 prints the patch onto the medium using the liquid of the color selected in step S210 (step S220). In Figure 9, the process in step S220 is shown as "printing the patch".

[0064] Next, the liquid spraying device 100 detects the color of the patch printed in step S220 as the color of the liquid selected in step S210, based on the detection result of the visible light sensor 115 (step S230). Note that part of the process in step S230 may be performed in parallel with the process in step S220.

[0065] Next, the liquid spraying device 100 detects the water content in the patch printed in step S220 as the dry state of the patch, based on the detection result of the near-infrared sensor 114 (step S240).

[0066] Next, the liquid injection device 100 determines the output of the second heater 119b suitable for the color selected in step S210, based on the color detected in step S230 and the drying state detected in step S240 (step S250). In Figure 9, the process in step S250 is shown as "determining the heater output". The process in step S250 will now be explained in detail.

[0067] The liquid injection device 100 stores correspondence information. Correspondence information is information that associates the water content indicating the dry state with the output of the second heater 119b which was determined to be suitable for that water content in prior experiments, for each color of liquid. The correspondence information may be in table format or in a format other than table format. The correspondence information is information obtained through prior experiments, etc., and is stored in the liquid injection device 100 by the user of the liquid injection device 100. Based on the correspondence information stored in advance, the color detected in step S230, and the dry state detected in step S240, the liquid injection device 100 determines the output of the second heater 119b which is associated with the color and the water content indicating the dry state, as the output of the second heater 119b suitable for that color. The liquid injection device 100 performs the above processing as the processing in step S250.

[0068] After the processing in step S250 is completed, the liquid injection device 100 stores information indicating the output of the second heater 119b determined in step S250, associating it with the color information detected in step S230 (step S260). After the processing in step S260 is completed, the liquid injection device 100 transitions to step S210, where it selects an unselected color from the available liquid colors as the next color. If there are no unselected colors in step S210, the liquid injection device 100 terminates the repeated processing from steps S210 to S260 and transitions to step S270.

[0069] By repeating steps S210 to S260, the liquid injection device 100 can determine the output of the second heater 119b suitable for each color of liquid that the liquid injection device 100 can use.

[0070] After the repeated processing of steps S210 to S260 is completed, the liquid injection device 100 calculates the average value of the output of the second heater 119b indicated by the information stored in association with the information indicating each of the liquid colors that the liquid injection device 100 can use (step S270). That is, in step S270, the liquid injection device 100 calculates the average value of the output of the second heater 119b that is appropriate for each liquid color that the liquid injection device 100 can use. In Figure 9, the process of step S270 is shown as "calculation of average value".

[0071] Next, the liquid injection device 100 stores the average value calculated in step S270 as a second output used in the process of step S110 shown in Figure 4 (step S280), and terminates the process shown in the flowchart in Figure 9.

[0072] In the flowchart shown in Figure 9, the process in step S230 may be omitted if the liquid spraying device 100 has already identified the color of the liquid used for patch printing based on pre-received operations, etc. In this case, in step S250, the liquid spraying device 100 determines the output of the second heater 119b suitable for the color selected in step S210, based on the color identified by the operations, etc. and the drying state detected in step S240. In this case, the liquid spraying device 100 also stores information indicating the output of the second heater 119b determined in step S250 in association with information indicating the color identified by the operations, etc. in step S260.

[0073] As described above, the liquid injection device 100 can determine the second output used in step S110 shown in Figure 4 by patch printing. This allows the liquid injection device 100 to determine the second output used in step S110 shown in Figure 4 not only based on the environment of the room in which the liquid injection device 100 is installed, but also based on the color of the liquid that the liquid injection device 100 can use.

[0074] The liquid injection device 100 may be configured to execute the flowchart shown in Figure 9 each time a predetermined adjustment condition is met. The adjustment conditions are, for example, the current time matching a predetermined time, the current date and time matching a predetermined date and time, the liquid injection device 100 being activated, etc., but are not limited to these.

[0075] Furthermore, the liquid injection device 100 may be configured to determine the output of the second heater 119b suitable for the color detected in step S230 in step S250, and to determine a threshold value TH suitable for that color. In this case, for example, the liquid injection device 100 may be configured to determine the water content detected in step S240 as the threshold value TH suitable for that color, or it may be configured to determine the water content of other liquids as the threshold value TH suitable for that color. In this case, the liquid injection device 100 calculates the average value of the output of the second heater 119b suitable for each color of liquid that the liquid injection device 100 can use, and calculates the average value of the threshold value TH suitable for each color of liquid that the liquid injection device 100 can use. Then, in this case, the liquid injection device 100 stores the average value of the output of the second heater 119b calculated in step S270 as the second output used in step S110 in step S280, and stores the average value of the threshold value TH calculated in step S270 as the threshold value TH used in the processing of step S130.

[0076] Furthermore, if the water content indicating the dry state detected in step S240 is not included in the corresponding information, the liquid spraying device 100 may be configured to increase the output of the first heater 119a to a second predetermined value and repeat the repetition process of steps S210 to S260. In this case, the liquid spraying device 100 stores the maximum value of the output of the first heater 119a used in the process of the flowchart shown in Figure 9 as the first output used in the process of step S110 shown in Figure 4. As a result, the liquid spraying device 100 can more reliably dry the liquid on the medium without requiring additional work from the user, even in environments where the liquid on the patch is difficult to dry, such as when the humidity in the room where the liquid spraying device 100 is installed is too high.

[0077] Furthermore, the correspondence information may also be information that associates, for each liquid color, the water content indicating a dry state, the output of the second heater 119b which was judged to be suitable for that content in a prior experiment, and the threshold TH which was judged to be suitable for that content in a prior experiment. In this case, in step S250, the liquid injection device 100 determines the output of the second heater 119b which is associated with the color and the water content indicating that dry state, based on the correspondence information stored in advance, the color detected in step S230, and the dry state detected in step S240, as the output of the second heater 119b which is associated with that color, and also determines the threshold TH which is associated with the color and the water content indicating that dry state. Then, in step S260, the liquid injection device 100 stores information indicating the output of the second heater 119b and the threshold TH determined in step S250, in association with the information indicating the color detected in step S230. In this case, in step S270, the liquid spraying device 100 calculates the average value of the output of the second heater 119b indicated by the information stored in association with the information indicating each of the liquid colors that the liquid spraying device 100 can use, and also calculates the average value of the threshold TH indicated by the information stored in association with the information indicating each of the liquid colors that the liquid spraying device 100 can use. As a result, in step S280, the liquid spraying device 100 stores the average value of the output of the second heater 119b calculated in step S270 as the second output used in the process of step S110 shown in Figure 4, and stores the average value of the threshold TH calculated in step S270 as the threshold TH used in the process of step S130 shown in Figure 4. This allows the liquid spraying device 100 to dry the liquid on the printed medium more reliably.

[0078] <Other variations> In the liquid injection device 100 described above, the second heater 119b may be divided into multiple heaters arranged in a direction perpendicular to the transport direction in the horizontal direction, as shown in Figure 10.

[0079] Figure 10 shows an example of a second heater 119b composed of multiple divided heaters. However, Figure 10 shows the second heater 119b as viewed from below and upward. Therefore, in the example shown in Figure 10, the transported medium PP covers a portion of the second heater 119b. Also, in this example, the second heater 119b is composed of five heaters. Therefore, the liquid spraying device 100 can, for example, independently set the output of these five heaters. This means that the liquid spraying device 100 can more reliably dry the liquid on the printed medium. This is because the amount of sprayed liquid used on the medium generally differs from area to area. The liquid spraying device 100 may also be configured to include a near-infrared sensor 114 associated with each of the five heaters in order to adjust the output of each of the five heaters. In this case, the liquid spraying device 100 is equipped with five near-infrared sensors 114. Then, for each of these five near-infrared sensors 114, the processing shown in the flowchart in Figure 4 and the processing shown in the flowchart in Figure 9 are performed. However, in each of these five near-infrared sensors 114, at least the light-receiving part 114b of the light-emitting part 114a and the light-receiving part 114b is positioned to correspond to the back surface of the medium that passes below the path through which the liquid spray head 121 moves back and forth by the carriage 120. This allows the liquid spray device 100 to suppress malfunctions of each of these five near-infrared sensors 114. Furthermore, independent control of each of these five heaters is beneficial because it leads to energy saving and improved print quality.

[0080] Furthermore, the matters described above may be combined in any way.

[0081] <Note> [1] A liquid spraying device comprising: a print head for spraying a liquid containing a colorant onto a medium; a transport unit for transporting the medium from upstream to downstream; a heater located downstream of the print head for evaporating the liquid on the medium; and a near-infrared sensor located downstream of the print head for detecting the dry state of the medium, wherein the heater is positioned facing the surface of the medium, and the near-infrared sensor has a light-emitting unit for emitting near-infrared light and a light-receiving unit for receiving near-infrared light, the light-receiving unit being positioned facing the back surface of the medium. [2] The liquid injection device according to [1], wherein the heater is an infrared heater. [3] The liquid spraying device according to [1] or [2], wherein the near-infrared sensor is a reflective sensor, and the light-emitting part is located opposite the back surface of the medium. [4] The liquid spraying device according to [1] or [2], wherein the near-infrared sensor is a transmissive sensor and the light-emitting part is located opposite the surface of the medium. [5] The liquid ejection device according to any one of [1] to [4], wherein the print head is positioned opposite the surface of the medium. [6] The liquid injection device according to any one of [1] to [5], wherein the heater includes a first heater and a second heater located downstream of the first heater, and the near-infrared sensor is located downstream of the first heater. [7] A liquid spraying device according to [6], comprising a print head, a transport unit, and a control unit that controls the heater, wherein the control unit determines, based on the detection result of the near-infrared sensor, that the liquid on the medium is not dry, and stops transport by the transport unit until it determines, based on the detection result of the near-infrared sensor, that the liquid is dry. [8] The liquid injection device according to any one of [1] to [7], wherein the heater includes a first heater and a second heater located downstream of the first heater, and the near-infrared sensor is located upstream of the second heater. [9] A liquid spraying device according to any one of [1] to [8], comprising a print head, a transport unit, and a control unit for controlling the heater, wherein the output of the heater when the control unit determines, based on the detection result of the near-infrared sensor, that the water content in the liquid on the medium is a first value is lower than the output of the heater when the control unit determines, based on the detection result of the near-infrared sensor, that the water content in the liquid on the medium is a second value higher than the first value.

[0082] Although embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may be modified, replaced, deleted, etc., as long as it does not deviate from the gist of this disclosure.

[0083] Furthermore, a program to realize the function of any component in the device described above may be recorded on a computer-readable recording medium, and that program may be loaded into a computer system and executed. The device in question is, for example, the liquid injection device 100, the host of the liquid injection device 100, etc. Here, "computer system" includes hardware such as the OS (Operating System) and peripheral devices. "Computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs, CD (Compact Disk)-ROMs, and storage devices such as hard disks built into a computer system. Moreover, "computer-readable recording medium" also includes volatile memory (RAM) inside a computer system that acts as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line, which holds the program for a certain period of time.

[0084] Furthermore, the above program may be transmitted from a computer system that stores the program in a memory device or the like to another computer system via a transmission medium or by transmission waves within the transmission medium. Here, the "transmission medium" used to transmit the program refers to a medium that has the function of transmitting information, such as a network (communication network) like the Internet or a communication line (communication line) like a telephone line. Furthermore, the above program may be intended to implement only a portion of the functions described above. In addition, the above program may be a so-called differential file (differential program) that can implement the functions described above in combination with a program already recorded in the computer system. [Explanation of symbols]

[0085] 100...Liquid spray device, 101...Control unit, 105...Non-volatile memory, 108...Printing control unit, 109...Main scanning motor drive unit, 110...Sub-scanning motor drive unit, 111...Heater control unit, 113...Operation panel, 114...Near-infrared sensor, 114a, 115a...Light-emitting unit, 114b, 115b...Light-receiving unit, 115...Visible light sensor, 116...Head driver, 117...Main scanning motor, 118...Sub-scanning motor, 119...Heater, 119a...First heater, 119b...Second heater, 120...Carriage, 121...Liquid spray head, 122...Transporting member, 125A, 125B...Filter, 150...Drying unit, PP...Media

Claims

1. A print head that sprays a liquid containing colorants onto a medium, A transport unit for transporting the aforementioned medium from upstream to downstream, A heater located downstream of the print head for evaporating the liquid on the medium, A near-infrared sensor located downstream of the print head for detecting the dry state of the medium, Equipped with, The heater is positioned opposite the surface of the medium, The near-infrared sensor has a light-emitting section that emits near-infrared light and a light-receiving section that receives near-infrared light. The light-receiving unit is positioned opposite the back surface of the medium. Liquid injection device.

2. The heater is an infrared heater. The liquid injection device according to claim 1.

3. The aforementioned near-infrared sensor is a reflective sensor, The light-emitting part is located in a position facing the back surface of the medium. The liquid injection device according to claim 1.

4. The aforementioned near-infrared sensor is a transmissive sensor, The light-emitting part is located in a position facing the surface of the medium. The liquid injection device according to claim 1.

5. The print head is positioned facing the surface of the medium. The liquid injection device according to claim 1.

6. The heater includes a first heater and a second heater located downstream of the first heater. The near-infrared sensor is located downstream of the first heater. The liquid injection device according to claim 1.

7. The system includes a control unit that controls the print head, the transport unit, and the heater, If the control unit determines, based on the detection result of the near-infrared sensor, that the liquid on the medium is not dry, it stops the transport by the transport unit until it determines, based on the detection result of the near-infrared sensor, that the liquid is dry. The liquid injection device according to claim 6.

8. The heater includes a first heater and a second heater located downstream of the first heater. The near-infrared sensor is located upstream of the second heater. The liquid injection device according to claim 1.

9. The system includes a control unit that controls the print head, the transport unit, and the heater, When the control unit determines, based on the detection result of the near-infrared sensor, that the water content in the liquid on the medium is a first value, the output of the heater is lower than when the control unit determines, based on the detection result of the near-infrared sensor, that the water content in the liquid on the medium is a second value higher than the first value. The liquid injection device according to claim 1.

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