Droplet ejection device

Abstract

A liquid droplet ejecting apparatus is provided. The liquid droplet ejecting apparatus includes a head that ejects liquid droplets toward a medium, a heater that heats the medium on which the liquid droplets are ejected from the head, a supply fan that blows outside air from outside of a frame that houses the head and the heater toward the inside, a temperature sensor that detects a temperature of the outside air blown by the supply fan, and a control unit that changes a set temperature of the heater to a lower temperature than a predetermined temperature when the temperature of the outside air detected by the temperature sensor is lower than the predetermined temperature.

Description

Technical Field

[0001] This invention relates to a droplet ejection device. Background Technology

[0002] A droplet ejection device having a heater for drying a liquid medium that has been ejected has been known for some time. Patent Document 1 discloses a heating device disposed downstream of a printing section that suppresses damage to the medium, such as deformation or damage, that occurs during the drying process.

[0003] For example, in order to suppress ink agglomeration, there exists a droplet ejection device that dries the ink sprayed onto the medium in the printing section immediately. However, the heating device described in Patent Document 1 is difficult to apply to such a droplet ejection device, so a droplet ejection device that suppresses medium damage during the drying of the medium in the printing section is desired.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2019-155653 Summary of the Invention

[0005] The droplet ejection device comprises: a head having a nozzle capable of ejecting droplets to a medium; a heater for heating the medium from which the droplets are ejected from the head at a position opposite to the head; a fan for blowing external air from the outside of a frame housing the head and the heater toward the inside; a temperature sensor for detecting the temperature of the external air blown by the fan; and a control unit that, if the temperature of the external air detected by the temperature sensor is lower than a preset temperature, changes the set temperature of the heater to a temperature lower than the preset temperature.

[0006] The droplet ejection device comprises: a head having a nozzle capable of ejecting droplets to a medium; a heater for heating the medium from which the droplets are ejected from the head at a position opposite to the head; a fan for blowing external air from the outside of a frame housing the head and the heater toward the inside; a humidity sensor for detecting the humidity of the external air blown by the fan; and a control unit that, if the humidity of the external air detected by the humidity sensor is lower than a preset humidity, changes the set temperature of the heater to a temperature lower than the preset temperature. Attached Figure Description

[0007] Figure 1 A side view is shown to illustrate the droplet ejection device according to the embodiment.

[0008] Figure 2 A block diagram illustrating the electrical structure of a droplet ejection device.

[0009] Figure 3 This diagram illustrates the principle of water evaporation.

[0010] Figure 4 This diagram illustrates the humidity changes inside the frame.

[0011] Figure 5 This is a table showing the relationship between external air temperature, relative humidity, heater set temperature, and water vapor pressure difference.

[0012] Figure 6 A flowchart illustrating the sequence of printing processes. Detailed Implementation

[0013] 1. Implementation Method

[0014] 1-1. Device Structure

[0015] The general structure of the droplet ejection device 11 according to the embodiment will be described. In the coordinate system shown in the drawings, the droplet ejection device 11 is a device placed on a horizontal plane, and three mutually orthogonal imaginary axes are designated as the X-axis, Y-axis, and Z-axis. The X-axis is an imaginary axis parallel to the width direction of the medium S. The Y-axis is an imaginary axis parallel to the conveying direction. The Z-axis is an imaginary axis parallel to the vertical direction.

[0016] First, with reference to the accompanying drawings, the implementation of the droplet ejection device will be described.

[0017] like Figure 1 As shown, the droplet ejection device 11 includes a frame 12. The droplet ejection device 11 includes an unwinding section 20 for unwinding a medium S and a medium support section 30 for supporting the medium S unwound from the unwinding section 20. The droplet ejection device 11 includes a conveying section 40 for conveying the medium S in a conveying direction along the medium support section 30. The droplet ejection device 11 includes a printing section 50 for printing text, photographs, or other images on the medium S, and a heating section 60 for heating the medium S printed on the printing section 50. The droplet ejection device 11 includes a winding section 70 for winding up the medium S printed by the printing section 50, and a ventilation section 80 for ventilating the interior of the frame 12.

[0018] The unwinding section 20 is configured such that a portion of it protrudes from the exterior of the frame 12. The unwinding section 20 has an unwinding shaft 21 that detachably holds the roll body R1 formed by the media S. The unwinding section 20 unwinds and releases the media S from the roll body R1 by rotating the unwinding shaft 21 that holds the roll body R1. In this embodiment, the unwinding section 20 unwinds the media S by rotating the unwinding shaft 21 counterclockwise. In this embodiment, the media S is paper.

[0019] The media support portion 30 has a first guide portion 31, a second guide portion 32, and a support portion 33, each composed of plate-shaped components. The first guide portion 31 is arranged such that a portion of it protrudes from the exterior of the frame 12. The first guide portion 31 supports the media S unwound from the unwinding portion 20, guiding it through the supply port 13 (an opening in the frame 12) and towards the interior of the frame 12. The support portion 33 is disposed inside the frame 12 and supports the media S guided by the first guide portion 31. The second guide portion 32 is arranged such that a portion of it protrudes from the exterior of the frame 12 and supports the media S passing above the support portion 33, guiding it through the discharge port 14 (an opening in the frame 12) and towards the exterior of the frame 12. That is, the first guide portion 31 is disposed upstream of the support portion 33 in the conveying direction, and the second guide portion 32 is disposed downstream of the support portion 33 in the conveying direction.

[0020] The upper surfaces of the first and second guide portions 31 and 32 are configured as guide surfaces 34 and 35 for guiding the medium S. The upper surface of the support portion 33 is configured as a support surface 36 for supporting the medium S. In this embodiment, the conveying direction of the medium S refers to the direction in which the medium S moves on the support surface 36 of the support portion 33. In this embodiment, the support portion 33 is configured such that the support surface 36 extends horizontally. The first and second guide portions 31 and 32 are configured such that a portion of the guide surfaces 34 and 35 is bent relative to the support surface 36.

[0021] The conveying unit 40 is disposed inside the frame 12. In this embodiment, the conveying unit 40 is disposed in two locations in the conveying direction: between the first guide portion 31 and the support portion 33, and between the support portion 33 and the second guide portion 32. The conveying unit 40 has a drive roller 41 capable of being driven to rotate and a driven roller 42 capable of being driven to rotate relative to the rotation of the drive roller 41. The conveying unit 40 conveys the medium S along the medium support portion 30 by rotating the drive roller 41 and the driven roller 42 while the medium S is being held in place. In this embodiment, the drive roller 41 is configured to contact the medium S from below in the vertical direction. The driven roller 42 is configured to contact the medium S from above in the vertical direction.

[0022] The printing section 50 is disposed inside the frame 12 and is configured to face the support section 33. The printing section 50 includes a guide shaft 51 extending in the width direction of the conveyed medium S, a carriage 52 supported by the guide shaft 51, and a head 53 mounted on the carriage 52. The carriage 52 is configured to be movable along the guide shaft 51. That is, the carriage 52 is configured to be movable in the width direction. Furthermore, in this embodiment, two guide shafts 51 are provided.

[0023] The head 53 is mounted on the carriage 52, protruding from the lower surface of the carriage 52. The head 53 has, for example, a plurality of nozzles 55 on its lower surface opposite the support portion 33, capable of ejecting ink, an example of a liquid, as droplets. The head 53 prints an image on the medium S by ejecting droplets from the nozzles 55 toward the medium S supported by the support portion 33. In this embodiment, the ink ejected by the head 53 is a water-based resin. The water-based resin uses water as its solvent.

[0024] The heating unit 60 includes a first heater 61 and a second heater 62, which are disposed inside the frame 12. Multiple first heaters 61 are arranged at intervals along the lower surface of the support portion 33 in the transport direction. Multiple second heaters 62 are arranged at intervals along the lower surface of the first guide portion 31 in the transport direction. The first and second heaters 61 and 62 are, for example, tube heaters arranged to extend in the width direction, and are heated by energization. The first heater 61 indirectly heats the medium S located on its upper surface, i.e., the support surface 36, by heating the support portion 33, which is located opposite the head 53, from its lower surface. That is, the first heater 61 heats the medium S from which droplets are ejected from the head 53 by heating the support portion 33. The first heater 61 promotes the fixing of the image printed on the medium S by evaporating the moisture from the droplets ejected from the head 53 onto the medium S. In this embodiment, the first heater 61 is configured to heat at a set temperature. The second heater 62 preheats the medium S before the droplets are ejected from the head 53, according to the set temperature of the first heater 61.

[0025] The take-up section 70 is configured such that a portion of it protrudes from the exterior of the frame 12. The take-up section 70 has a take-up spool 71 that detachably holds a roll R2 formed by stacking media S. This roll R2 is formed by taking up the media S, on which an image is printed, by the take-up spool 71 using droplets ejected from the head 53. In this embodiment, the take-up section 70 takes up the media S by rotating the take-up spool 71 counterclockwise.

[0026] A ventilation section 80 is disposed on the upper part of the frame 12, and is configured such that a portion of it protrudes from the outside of the frame 12. The ventilation section 80 has an intake duct 81 for drawing in outside air from the outside of the frame 12 toward the inside of the frame 12, and a blower fan 82 for blowing outside air through the intake duct 81 into the inside of the frame 12. The ventilation section 80 has a temperature sensor 83 for detecting the temperature of the outside air drawn in by the blower fan 82, and a humidity sensor 84 for detecting the humidity of the outside air drawn in by the blower fan 82. The intake duct 81 is provided to extend through both the inside and outside of the frame 12, and has an air inlet 85 opening to the outside of the frame 12 and an outlet 86 opening to the inside of the frame 12. The air inlet 85 is larger than the outlet 86. The outlet 86 is wide open along its width.

[0027] An air supply fan 82 is disposed within the air intake duct 81 near the air intake 85. In this embodiment, the air supply fan 82 is configured as an axial flow fan, for example, to supply air to the outside by rotating its blades 87. A temperature sensor 83 and a humidity sensor 84 are disposed within the air intake duct 81 near the air outlet 86 compared to the air supply fan 82. That is, the temperature sensor 83 and the humidity sensor 84 detect the temperature and humidity of the outside air flowing through the air intake duct 81 driven by the air supply fan 82.

[0028] The ventilation unit 80 drives the blower fan 82 to blow the drawn-in external air through the intake air passage 81 toward the area where the carriage 52 reciprocates inside the frame 12. The atmosphere inside the frame 12 is discharged to the outside of the frame 12 through the supply port 13 and the exhaust port 14 by the external air drawn in through the intake air passage 81. At this time, the ink fumes ejected from the head 53, paper dust generated by the medium S, and other floating objects inside the frame 12 are discharged to the outside of the frame 12 together with the atmosphere inside the frame 12. In this embodiment, the wind speed of the external air blown out from the exhaust port 86 by the blower fan 82 is set to 1.0 m / s.

[0029] Next, refer to Figure 2 The electrical structure of the droplet ejection device 11 will be explained.

[0030] The droplet ejection device 11 has a control unit 90, which performs control over the various components included in the droplet ejection device 11. The control unit 90 is configured to include a CPU (Central Processing Unit) 91, a storage unit 92, a control circuit 93, etc. The CPU 91 is connected to the storage unit 92 and the control circuit 93 via a bus.

[0031] CPU 91 is a processing unit that generates printing data for processing various input signals and receiving image data to perform printing. CPU 91 controls the droplet ejection device 11 as a whole based on the program stored in storage unit 92 and the printing data.

[0032] Storage unit 92 is a storage medium used to store the program for CPU 91 and other operating areas, and includes storage elements such as RAM (Random Access Memory) and EEPROM (Electrically Erasable Programmable Read Only Memory). Storage unit 92 stores general image processing application software for processing image data and printer driver software for generating printing data for the droplet ejection device 11 to perform printing. Furthermore, storage unit 92 stores a heater setting temperature gauge, which will be described later.

[0033] The droplet ejection device 11 includes a control unit 90 that comprehensively controls the device. The control unit 90 is connected to a temperature sensor 83 and a humidity sensor 84. The control unit 90 is configured to receive signals from the temperature sensor 83 and the humidity sensor 84. The temperature sensor 83 is configured to transmit a signal based on the detected temperature of the external air to the control unit 90. The humidity sensor 84 is configured to transmit a signal based on the detected humidity of the external air to the control unit 90.

[0034] The control unit 90 is electrically connected to the conveying unit 40, the printing unit 50, the first heater 61, the second heater 62, and the air blower 82. The control circuit 93 is configured to generate and transmit signals for controlling the operation of the conveying unit 40, the printing unit 50, the first heater 61, the second heater 62, and the air blower 82. The droplet ejection device 11 in this embodiment is configured to communicate with an external terminal, such as a personal computer. That is, the control unit 90 is configured to receive information such as image data input from an external terminal.

[0035] 1-2. The principle of water evaporation

[0036] Next, refer to Figures 3 to 5 The principle of evaporation of water contained in droplets sprayed onto medium S is explained.

[0037] like Figure 3As shown, the surface of the droplet DR sprayed onto the medium S is saturated with water vapor at 100% humidity. The troposphere LC is the surrounding environment of the medium S onto which the droplet DR is sprayed, i.e., the support 33 where the first heater 61 is located. The diffusion layer LD is a layer of atmosphere with relative humidity where the saturated water vapor on the upper surface of the droplet DR diffuses into the surrounding environment. Water molecules contained in the droplet DR move within the diffusion layer LD and evaporate into the troposphere LC as water vapor. The thickness of the diffusion layer LD varies from 1 mm to 10 mm depending on the airflow. Although the thickness of the diffusion layer LD affects the evaporation rate of water, its effect can be ignored in this embodiment because the airflow within the frame 12 flows at a fixed speed through the blower fan 82.

[0038] For the water contained in the droplet DR to evaporate, become water vapor, and move into the troposphere LC, a water vapor pressure difference is required between the water vapor pressure on the surface of the droplet DR and the water vapor pressure in the troposphere LC. In other words, the rate of water evaporation depends on this water vapor pressure difference.

[0039] like Figure 5 As shown in the first line, the surrounding environment on the support 33 when the first heater 61 is not activated is the same as the outside air temperature T1 = 27°C detected by temperature sensor 83 and the outside air relative humidity RH1 = 65% detected by humidity sensor 84. The water vapor pressure difference ed1 under this condition will be explained.

[0040] Since the surface of the droplet DR is saturated with water, the water vapor pressure is called the saturated water vapor pressure eT1. The saturated water vapor pressure eT1 is obtained by substituting the temperature T1 into equation (1).

[0041] Mathematical Formula 1

[0042]

[0043] According to equation (1), the saturated water vapor pressure eT1 at a temperature T1 = 27°C is 35.7 hPa. The water vapor pressure of the troposphere LC, i.e., the water vapor pressure eRH1 based on the relative humidity RH1, is proportional to the relative humidity RH1 and is obtained by the product of the saturated water vapor pressure eT1 and the relative humidity RH1. The water vapor pressure eRH1 at a relative humidity RH1 = 65% is 23.2 hPa. Therefore, the water vapor pressure difference ed1 when the first heater 61 is not activated is 12.5 hPa based on the difference between the saturated water vapor pressure eT1 and the water vapor pressure eRH1 of the troposphere LC. When the first heater 61 is not activated, this water vapor pressure difference ed1 becomes the driving force for the diffusion of water contained in the droplets DR sprayed onto the medium S into the troposphere LC. In addition, the water vapor pressure difference ed1 when the first heater 61 is not activated is obtained by the following equation.

[0044] Mathematical formula 2

[0045] ed1=eT1-eT1×RH1 / 100…(2)

[0046] 1-3. Humidity changes inside frame 12

[0047] Next, regarding such Figure 5 The first line shows the situation where the ambient temperature on the support 33, with a temperature T1 = 27°C and a relative humidity RH1 = 65%, is raised to a temperature T2 = 40°C by the drive of the first heater 61.

[0048] Figure 4 The solid-line cube SV27 shown represents the saturated water vapor content aT1 at temperature T1 = 27℃. The dashed-line cube AV represents the actual amount of water vapor present. The actual amount of water vapor present is called the absolute humidity aRH1. The saturated water vapor content aT1 is calculated by substituting the saturated water vapor pressure eT1 into the following formula.

[0049] Mathematical Formula 3

[0050]

[0051] According to equation (3), the saturated water vapor content aT1 at a temperature T1 = 27℃ is 25.8 g / m³. 3 The absolute humidity aRH1 is calculated by producting the saturated water vapor content aT1 and the relative humidity RH1. When the relative humidity RH1 = 65%, the absolute humidity aRH1 is 16.8 g / m³. 3 .

[0052] When the first heater 61 is driven, the temperature on the support 33 rises to the set temperature T2 of the first heater 61 = 40°C.

[0053] Figure 4 The solid-line cube SV40 shown represents the saturated water vapor quantity aT2 at temperature T2 = 40°C. The saturated water vapor pressure eT2, when the first heater 61 is driven and the temperature on the support 33 rises from T1 = 27°C to the set temperature T2 = 40°C of the first heater 61, is calculated based on temperature T2, similarly to equation (1). The saturated water vapor pressure eT2 at temperature T2 = 40°C is 73.8 hPa. The saturated water vapor quantity aT2 is calculated based on the saturated water vapor pressure eT2 and temperature T2, similarly to equation (3). The saturated water vapor quantity aT2 at temperature T2 = 40°C increases to 51.1 g / m³. 3 .

[0054] However, since the amount of water vapor present at temperature T1 = 27°C, i.e., the absolute humidity aRH1, does not change even when the temperature rises to T2 = 40°C, the relative humidity RH2 will decrease. The relative humidity RH2 is obtained by dividing the absolute humidity aRH1 by the saturated water vapor content aT2. The relative humidity decreases from RH1 = 65% to RH2 = 31.4% when the temperature rises from T1 = 27°C to T2 = 40°C. That is, the ambient environment on the support 33 changes from the temperature T1 = 27°C and relative humidity RH1 = 65% when the first heater 61 is not activated to the set temperature T2 = 40°C and relative humidity RH2 = 31.4% of the first heater 61.

[0055] The water vapor pressure eRH2 at the relative humidity RH2 when the first heater 61 is driven is calculated by the product of the saturated water vapor pressure eT2 and the relative humidity RH2. The water vapor pressure eRH2 at a relative humidity of RH2 = 31.4% is 23.2 hPa. Therefore, the water vapor pressure difference ed2 at the time the first heater 61 is driven is 50.6 hPa, calculated as the difference between the saturated water vapor pressure eT2 and the tropospheric water vapor pressure eRH2 (LC). As the water vapor pressure difference ed1 = 12.5 hPa increases to ed2 = 50.6 hPa, the rate of water evaporation also increases.

[0056] Furthermore, although, as described above, when the first heater 61 is driven, the relative humidity changes from RH1 = 65% to RH2 = 31.4%, the absolute humidity aRH1, which is the amount of water vapor contained therein, remains the same. Therefore, the water vapor pressure eRH1 calculated from the relative humidity RH1 is the same as the water vapor pressure eRH2 calculated from the relative humidity RH2. Thus, the water vapor pressure difference ed2 when the first heater 61 is driven is calculated by the following formula.

[0057] Mathematical expression 4

[0058] ed2=eT2-eT1×RH1 / 100…(4)

[0059] For example, in Figure 5 The water vapor pressure difference ed2 = 50.6 hPa shown in the first row represents the conditions under which the medium S can be dried effectively without causing damage such as wrinkling or breakage. Furthermore, with a preset external air temperature T1 of 27°C and a preset external air relative humidity RH1 of 65%, the preset temperature T2 of the first heater 61 is set to 40°C. The water vapor pressure difference ed2 = 50.6 hPa at this point serves as the index value for effectively drying the medium without causing damage.

[0060] like Figure 5 As shown in the second line, when the outside air temperature T1 is 18°C ​​lower than the preset temperature, and the first heater 61 is driven at a preset temperature T2 of 40°C, the water vapor pressure difference ed2 rises from the index value of 50.6 hPa to 60.4 hPa. If printing is performed under these conditions, the evaporation rate of the water contained in the droplets DR becomes too fast, potentially causing damage to the medium S. Therefore, the control unit 90 changes the preset temperature T2 of the first heater 61 to a temperature lower than the preset temperature. Figure 5 As shown in the sixth line, when the temperature T1 = 18°C, the water vapor pressure difference ed2 can be set to approximately the same value as the index value of 50.4 hPa by changing the set temperature T2 of the first heater 61 from the predetermined temperature of 40°C to 37.3°C.

[0061] In addition to the case where the outside air temperature T1 is 18°C, when the outside air relative humidity RH1 is 40% lower than the preset relative humidity, the control unit 90 further changes the set temperature T2 of the first heater 61 to a lower temperature. For example... Figure 5 As shown in the seventh line, when the temperature T1 = 18°C ​​and the relative humidity RH1 = 40%, the water vapor pressure difference ed2 can be set to approximately the same value as the index value of 50.5 hPa by changing the set temperature T2 of the first heater 61 from the predetermined temperature of 40°C to 35.8°C.

[0062] like Figure 5As shown in the third line, when the external air temperature T1 is 35°C, which is higher than the preset temperature, and the first heater 61 is driven at a predetermined temperature of 40°C with the set temperature T2, the water vapor pressure difference ed2 decreases from the index value of 50.6 hPa to 37.2 hPa. When printing is performed in this state, because the evaporation rate of the water contained in the droplets DR becomes too slow, the ink in the droplets DR ejected onto the medium S may condense, leading to a decrease in print quality, or it may be wound into the winding unit 70 before the medium S is dry, resulting in ink back printing. Therefore, the control unit 90 changes the set temperature T2 of the first heater 61 to a temperature higher than the predetermined temperature. Figure 5 As shown in the eighth line, when the temperature T1 = 35°C, the water vapor pressure difference ed2 can be set to approximately the same value as the index value of 50.8 hPa by changing the set temperature T2 of the first heater 61 from the predetermined temperature of 40°C to 43.2°C.

[0063] In addition to the case where the outside air temperature T1 is 35°C, when the outside air relative humidity RH1 is 90% higher than the preset relative humidity, the control unit 90 further changes the set temperature T2 of the first heater 61 to a higher temperature. For example... Figure 5 As shown in the ninth line, when the temperature T1 = 35°C and the relative humidity RH1 = 90%, the water vapor pressure difference ed2 can be set to approximately the same value as the index value of 50.8 hPa by changing the set temperature T2 of the first heater 61 from the predetermined temperature of 40°C to 46.1°C.

[0064] like Figure 5 As shown in the fourth line, when the relative humidity RH1 of the external air is 40% lower than the preset relative humidity, and the set temperature T2 of the first heater 61 is driven at a predetermined temperature of 40°C, the water vapor pressure difference ed2 rises from the index value of 50.6 hPa to 59.5 hPa. If printing is performed under these conditions, the evaporation rate of the water contained in the droplets DR becomes too fast, potentially causing damage to the medium S. Therefore, the control unit 90 changes the set temperature T2 of the first heater 61 to a temperature lower than the predetermined temperature. Figure 5 As shown in the tenth line, when the relative humidity RH1 = 40%, the water vapor pressure difference ed2 can be set to approximately the same value as the index value of 50.6 hPa by changing the set temperature T2 of the first heater 61 from the predetermined temperature of 40°C to 37.6°C.

[0065] In addition to the case where the relative humidity RH1 of the outside air is 40%, when the temperature T1 of the outside air is 18°C ​​lower than the preset temperature, the control unit 90 further changes the set temperature T2 of the first heater 61 to an even lower temperature. For example... Figure 5 As shown in the seventh line, when the relative humidity RH1 = 40% and the temperature T1 = 18°C, the water vapor pressure difference ed2 can be set to approximately the same value as the index value of 50.5 hPa by changing the set temperature T2 of the first heater 61 from the predetermined temperature of 40°C to 35.8°C.

[0066] like Figure 5 As shown in the fifth line, when the relative humidity RH1 of the external air is 90% higher than the preset relative humidity, and the set temperature T2 of the first heater 61 is driven at a predetermined temperature of 40°C, the water vapor pressure difference ed2 decreases from the index value of 50.6 hPa to 41.7 hPa. If printing is performed under these conditions, the evaporation rate of the water contained in the droplets DR becomes too fast, potentially causing damage to the medium S. Therefore, the control unit 90 changes the set temperature T2 of the first heater 61 to a temperature higher than the predetermined temperature. Figure 5 As shown in the eleventh line, when the relative humidity RH1 = 90%, the water vapor pressure difference ed2 can be set to approximately the same value as the index value of 50.8 hPa by changing the set temperature T2 of the first heater 61 from the predetermined temperature of 40°C to 42.2°C.

[0067] In addition to the case where the relative humidity RH1 of the outside air is 90%, when the temperature T1 of the outside air is 35°C, which is higher than the preset temperature, the control unit 90 further changes the set temperature T2 of the first heater 61 to a higher temperature. For example... Figure 5 As shown in the ninth line, when the relative humidity RH1 = 90 and the temperature T1 = 35°C, the water vapor pressure difference ed2 can be set to approximately the same value as the index value of 50.8 hPa by changing the set temperature T2 of the first heater 61 from the predetermined temperature of 40°C to 46.1°C.

[0068] Furthermore, the droplet ejection device 11 of this embodiment will be as follows: Figure 5 The heater set temperature table, which establishes various combinations of parameters such as the external air temperature TI and the external air relative humidity RH1, as shown in the sixth line below, and the heater set temperature T2 that makes the water vapor pressure difference ed2 an approximate index value, is stored in the storage unit 92.

[0069] 1-4. Printing Process

[0070] Next, refer to Figure 6 The printing process is explained.

[0071] In step S101, when the power supply to the droplet ejection device 11 is turned on, the control unit 90 receives the external air temperature T1 detected by the temperature sensor 83 and the relative humidity RH1 detected by the humidity sensor 84.

[0072] In step S102, the control unit 90 determines whether the temperature T1 and relative humidity RH1 are preset values. The control unit 90 compares the external air temperature T1 detected by the temperature sensor 83 with the temperature preset in the storage unit 92. Furthermore, the control unit 90 compares the external air relative humidity RH1 detected by the humidity sensor 84 with the relative humidity preset in the storage unit 92. In this embodiment, since the blower fan 82 is driven when the power to the droplet ejection device 11 is turned on, the temperature of the external air can be detected with high accuracy by the temperature sensor 83 located in the air intake channel 81. If the control unit 90 determines that the external air temperature T1 and relative humidity RH1 are preset values ​​(step S102: Yes), the process proceeds to step S103. If the control unit 90 determines that at least one of the temperature T1 and relative humidity RH1 is different from the preset value (step S102: No), the process proceeds to step S104.

[0073] In step S103, the control unit 90 drives the first heater 61 at a predetermined temperature. Furthermore, the control unit 90 drives the second heater 62 at a predetermined temperature.

[0074] In step S104, the control unit 90 refers to the heater setting temperature table stored in the storage unit 92 and calculates the setting temperature T2 of the first heater 61 based on temperature T1 and relative humidity RH1. Then, the control unit 90 changes the setting temperature of the first heater 61 from a predetermined temperature to the setting temperature T2 calculated from the heater setting temperature table and drives the first heater 61. Furthermore, the control unit 90 changes the setting temperature of the second heater 62 based on the changed setting temperature T2 of the first heater 61 and drives the second heater 62.

[0075] In step S105, the control unit 90 performs printing based on the printing data and ends the process.

[0076] Furthermore, although this embodiment describes the set temperature of the first heater 61 as the temperature obtained from the heater set temperature table, the set temperature of the first heater 61 can also be obtained by the control unit 90 calculating the set temperature T2 that makes the water vapor pressure difference ed2 the index value based on the temperature T1 and the relative humidity RH1.

[0077] Furthermore, when the interval between the set temperatures that can be set for the first heater 61, such as the 5°C scale, is large, the control unit 90 sets the temperature to the temperature that makes the water vapor pressure difference ed2 closest to the index value.

[0078] Furthermore, although it is stated that temperature sensor 83 and humidity sensor 84 are installed in ventilation section 80, temperature sensor 83 and humidity sensor 84 can also be installed on a carriage 52 or other surface that can directly detect the temperature and humidity on support section 33.

[0079] As described above, the droplet ejection device 11 according to this embodiment can achieve the following effects.

[0080] The droplet ejection device 11 includes: a head 53 that ejects droplets onto a medium S; a first heater 61 that heats the medium S at a position opposite to the head 53; a temperature sensor 83 that detects the temperature T1 of the external air blown by the blower fan 82; and a control unit 90. When the temperature T1 of the external air is lower than a preset temperature, the control unit 90 changes the set temperature of the first heater 61 to a temperature lower than the preset temperature. This suppresses the rise in the water vapor pressure difference ed2, which is the driving force for water evaporation. Therefore, it is possible to suppress media damage such as wrinkling caused by a faster drying rate of the medium S.

[0081] When the outside air temperature T1 is higher than a preset temperature, the control unit 90 changes the set temperature of the first heater 61 to a temperature higher than the preset temperature. This suppresses the decrease in the water vapor pressure difference ed2, which is the driving force for water evaporation. Therefore, it can suppress the reduction in print quality and ink backing caused by ink agglomeration due to the slower drying speed of the medium S.

[0082] The droplet ejection device 11 is equipped with a humidity sensor 84 that detects the relative humidity RH1 of the outside air. When the relative humidity RH1 of the outside air differs from a preset relative humidity, the control unit 90 further adjusts the set temperature of the first heater 61. This allows for proper drying of the medium S.

[0083] When the relative humidity RH1 of the outside air is lower than the preset humidity, the control unit 90 changes the set temperature of the first heater 61 to a lower temperature than the preset temperature. This suppresses the rise in the water vapor pressure difference ed2, which drives water evaporation. Therefore, damage to the medium, such as wrinkling, caused by the faster drying speed of the medium S can be suppressed.

[0084] When the relative humidity RH1 of the outside air is higher than a preset humidity, the control unit 90 changes the set temperature of the first heater 61 to a higher temperature than the preset temperature. This suppresses the decrease in the water vapor pressure difference ed2, which is the driving force for water evaporation. Therefore, it can suppress the reduction in print quality and ink backing caused by ink agglomeration due to the slower drying speed of the medium S.

[0085] When the outside air temperature T1 differs from the preset temperature, the control unit 90 further adjusts the set temperature of the first heater 61. This allows for proper drying of the medium S.

[0086] The droplet ejection device 11 includes a second heater 62 for heating the medium S before it is ejected from the head 53. The control unit 90 changes the set temperature of the second heater 62 according to the changed set temperature of the first heater 61. By preheating the medium S by the second heater 62, the temperature of the medium S when it is located at the support 33 can be set to the set temperature of the first heater 61.

[0087] Symbol Explanation

[0088] 11…Droplet ejection device; 12…Frame; 20…Unwinding section; 30…Media support section; 31…First guide section; 32…Second guide section; 33…Support section; 40…Conveying section; 50…Printing section; 52…Carriage; 53…Head; 55…Nozzle; 60…Heating section; 61…First heater; 62…Second heater; 70…Take-up section; 80…Ventilation section; 82…Air supply fan; 83…Temperature sensor; 84…Humidity sensor; 90…Control section; R1…Roll body; R2…Roll body; S…Media.

Claims

1. A droplet ejection device, characterized in that, have: The head has a nozzle capable of ejecting droplets into the medium; A heater that heats the medium from which the droplets are ejected from the head at a position opposite to the head; A blower fan blows outside air from the outside of the frame housing the head and the heater toward the inside; A temperature sensor that detects the temperature of the outside air blown by the fan; A humidity sensor that detects the humidity of the outside air blown by the fan; and Control Department If the humidity of the outside air detected by the humidity sensor is the preset humidity, and the temperature of the outside air detected by the temperature sensor is lower than the preset temperature, the control unit changes the set temperature of the heater to a temperature lower than the preset temperature.

2. The droplet ejection device as described in claim 1, characterized in that, If the temperature of the outside air detected by the temperature sensor is higher than the preset temperature, the control unit changes the set temperature of the heater to a temperature higher than the preset temperature.

3. A droplet ejection device, characterized in that, have: The head has a nozzle capable of ejecting droplets into the medium; A heater that heats the medium from which the droplets are ejected from the head at a position opposite to the head; A blower fan blows outside air from the outside of the frame housing the head and the heater toward the inside; A humidity sensor that detects the humidity of the outside air blown by the fan; A temperature sensor that detects the temperature of the outside air blown by the fan; and Control Department If the temperature of the outside air detected by the temperature sensor is a preset temperature, and the humidity of the outside air detected by the humidity sensor is lower than the preset humidity, the control unit changes the set temperature of the heater to a temperature lower than the preset temperature.

4. The droplet ejection device as described in claim 3, characterized in that, If the humidity of the outside air detected by the humidity sensor is higher than the preset humidity, the control unit changes the set temperature of the heater to a temperature that is higher than the preset temperature.

5. A droplet ejection device, characterized in that, have: The head has a nozzle capable of ejecting droplets into the medium; A heater that heats the medium from which the droplets are ejected from the head at a position opposite to the head; A blower fan blows outside air from the outside of the frame housing the head and the heater toward the inside; A temperature sensor that detects the temperature of the outside air blown by the fan; A humidity sensor that detects the humidity of the outside air blown by the fan; and Control Department The control unit changes the set temperature of the heater so that the water vapor pressure difference between the temperature of the outside air detected by the temperature sensor, the water vapor pressure of the outside air under the humidity detected by the humidity sensor, and the water vapor pressure that changes due to the drive of the heater approaches the index value.

6. The droplet ejection device according to any one of claims 1 to 5, characterized in that, The device includes a second heater for heating the medium before it is ejected from the head as droplets. The control unit changes the set temperature of the second heater based on the changed set temperature of the heater.

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