JP5397145B2 - Inkjet printer - Google Patents

Description

  The present invention relates to an inkjet printer.

  2. Description of the Related Art Conventionally, an inkjet printer that records an image on a recording medium by ejecting ink droplets from an inkjet head is known that includes a drying unit that dries the recording medium after image formation (see, for example, Patent Document 1). This drying unit quickly dries the ink droplets that land on the recording medium to prevent image transfer when the recording medium after image formation is overlaid or rolled up. This is an essential configuration for an ink jet printer that performs the above.

  By the way, there are various types of inks used in ink jet printers, such as organic solvents and UV curable resins, but they have excellent image quality and little generation of VOC (Volatile Organic Compounds). For these reasons, water-based inks using water as a main solvent have become mainstream.

  However, since water has a larger heat of vaporization than organic solvents and UV curable resins, when using water-based ink, the load on the drying section is greater than when using other types of ink, There is a problem that power consumption increases. Therefore, there has been a demand for a technique for reducing energy consumption (energy consumed by the entire apparatus) necessary for drying the recording medium.

JP 2001-150649 A

  An object of the present invention is to provide an ink jet printer capable of reducing energy consumption necessary for drying a recording medium.

In order to solve the above problems, an invention according to claim 1 is an inkjet printer,
An inkjet head that forms an image by ejecting ink droplets onto a recording medium;
A drying unit for drying the recording medium on which an image is formed by the inkjet head by exposing the recording medium to a dry gas inside;
A heat pump having a heat absorbing portion and a heat radiating portion;
After the gas exhausted from the drying unit is led to the heat absorption unit and the heat dissipation unit in this order and passed therethrough, a gas circulation path that leads to the drying unit again,
A heat exchanger for exchanging heat between the gas before and after passing through the heat absorption part;
It is characterized by providing.

The invention according to claim 2 is the inkjet printer according to claim 1,
The apparatus further comprises a blower that circulates the gas in the gas circulation path and depressurizes the inside of the drying unit to a pressure lower than atmospheric pressure.

The invention according to claim 3 is the ink jet printer according to claim 1 or 2,
Heat pump control means for controlling the amount of heat transfer between the heat absorbing part and the heat radiating part in the heat pump is provided.

The invention according to claim 4 is the ink jet printer according to claim 3,
The heat pump control means maintains a constant temperature of the gas introduced into the drying unit through the gas circulation path.

The invention according to claim 5 is the inkjet printer according to claim 3 or 4,
The heat pump control means maintains a constant temperature of the gas discharged from the drying unit through the gas circulation path.

Invention of Claim 6 is an inkjet printer as described in any one of Claims 1-5,
A flow rate control means for controlling the flow rate of the gas introduced into the drying section through the gas circulation path is provided.

The invention according to claim 7 is the ink jet printer according to claim 6,
The flow rate control unit controls a flow rate of a gas introduced into the drying unit when the recording medium is dried according to an amount of ink droplets ejected to the recording medium by the inkjet head. .

Invention of Claim 8 is an inkjet printer as described in any one of Claims 1-7,
The gas circulation path is provided with an outside air introduction valve capable of introducing outside air between the drying section and the heat absorption section.

The invention according to claim 9 is the inkjet printer according to any one of claims 1 to 8,
The gas circulation path is provided with a gas discharge valve capable of discharging gas to the outside air between the heat radiating section and the drying section.

The invention according to claim 10 is the ink jet printer according to any one of claims 1 to 9,
A preheating unit that preheats the recording medium before the image is formed by the inkjet head by exposing it to the heated gas inside;
At least a part of the gas that has passed through the heat radiating portion is guided to the preheating portion.

The invention according to claim 11 is the ink jet printer according to claim 10,
At least a part of the gas discharged from the preheating unit is guided to the drying unit.

  According to the first aspect of the present invention, the heat pump having the heat absorbing portion and the heat radiating portion, and the gas discharged from the drying portion in this order to the heat absorbing portion and the heat radiating portion are passed in this order, and then again led to the drying portion. Since it is provided with a circulation path, the heat energy contained in the gas discharged from the drying unit is recovered by the heat absorption unit, and the gas is circulated to the drying unit while the gas is heated by the heat dissipation unit using this thermal energy. Can do. Therefore, the energy contained in the exhaust from the drying section can be effectively used to reduce the energy consumption necessary for drying the recording medium.

Further, when the gas discharged from the drying unit is cooled by the heat absorption unit, the solvent of the ink contained in this gas can be extracted as a drain. Therefore, the organic solvent contained in the ink solvent can be safely recovered.
Furthermore, since a heat exchanger that exchanges heat between the gas before and after passing through the endothermic part is provided, the temperature of the gas before passing through the endothermic part decreases, and the gas after passing (before passing through the heat dissipating part) Temperature rises. As a result, the power required for driving the heat pump can be reduced, and as a result, the energy consumption required for drying the recording medium can be reduced.

  According to the second aspect of the present invention, since the inside of the drying unit is depressurized to a pressure lower than the atmospheric pressure, even when a large amount of dry gas is flowed into the drying unit, the recording medium to the drying unit is Dry gas does not leak from the inlet or the like and hit the inkjet head. Accordingly, it is possible to prevent the ink near the ink discharge port of the ink jet head from being dried and causing a discharge failure, changing the discharge direction of the ink droplets, and scattering of the satellite ink droplets to contaminate the recording medium.

  According to the third aspect of the present invention, since the amount of heat transfer between the heat absorbing part and the heat radiating part in the heat pump is controlled, the heat energy exchanged between the heat absorbing part and the heat radiating part and the gas is appropriately adjusted. As a result, the temperature of the gas introduced into the drying section and the temperature of the gas discharged from the drying section can be appropriately adjusted. Therefore, the energy consumption necessary for drying the recording medium can be adjusted as appropriate.

  According to the invention described in claim 4, since the temperature of the gas introduced into the drying section through the gas circulation path is kept constant, for example, when the outside air temperature is high and the heat radiation from the device is small, the energy consumption is reduced. Can be reduced.

  According to the fifth aspect of the present invention, since the temperature of the gas discharged from the drying section through the gas circulation path is kept constant, for example, when the amount of ink droplets landed on the recording medium is small, the energy consumption Can be reduced.

  According to the sixth aspect of the present invention, since the flow rate of the gas introduced into the drying section through the gas circulation path is controlled, the energy consumption required for drying the recording medium can be adjusted as appropriate.

  According to the seventh aspect of the invention, the flow rate of the gas introduced into the drying unit when the recording medium is dried is controlled according to the amount of ink droplets ejected onto the recording medium by the inkjet head. For example, when the amount of ejected ink droplets is small, the energy consumption required for drying the recording medium can be minimized by reducing the gas flow rate.

  According to the eighth aspect of the invention, the gas circulation path is provided with the outside air introduction valve capable of introducing outside air between the drying section and the heat absorption section. Outside air can be introduced to adjust the temperature and flow rate of the circulating gas as appropriate.

  According to the ninth aspect of the present invention, the gas circulation path is provided with the gas discharge valve capable of discharging the gas to the outside air between the heat radiating section and the drying section. The gas can be discharged by opening and closing and the temperature and flow rate of the circulating gas can be adjusted as appropriate.

  According to the tenth aspect of the invention, since the preheating unit that preheats the recording medium before the image is formed by the inkjet head is provided, drying of the recording medium can be promoted. In addition, since at least a part of the gas that has passed through the heat radiating portion is led to the preheating portion, the thermal energy contained in the gas discharged from the drying portion can be effectively used for preheating the recording medium.

  According to the eleventh aspect of the present invention, at least a part of the gas discharged from the preheating unit is guided to the drying unit, so that the thermal energy contained in the gas discharged from the preheating unit is effectively used for drying the recording medium. can do.

It is a conceptual diagram which shows the principal part of the inkjet printer which concerns on this invention. It is a block diagram which shows the control structure of an inkjet printer. It is a conceptual diagram which shows the principal part of the inkjet printer in a 1st modification. It is a conceptual diagram which shows the principal part of the inkjet printer in a 2nd modification.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a conceptual diagram showing a main part of an ink jet printer 1 according to the present invention.
As shown in FIG. 1, the ink jet printer 1 includes an ink jet head 2, a transport belt 3, a drying unit 4, a heat pump 5, and a gas circulation path 6.

  The ink jet head 2 has a plurality of nozzles (not shown) that eject ink as fine ink droplets, and ejects ink droplets onto a recording medium supported by the conveyor belt 3 to form an image. In the present embodiment, water-based ink using water as a main solvent is used as the ink ejected from the inkjet head 2.

  The conveyance belt 3 is stretched around a pair of conveyance rollers 31, 31, and the recording medium supported on the upper surface by feeding along with the rotation of the conveyance rollers 31, 31 is referred to as an arrow Z direction (hereinafter referred to as conveyance direction Z). ). The recording medium conveyed by the conveyance belt 3 is not particularly limited, and may be paper, fabric, or a resin film.

  The drying unit 4 is formed in a hollow casing shape, and is disposed downstream of the inkjet head 2 in the transport direction Z. On both side walls in the transport direction Z of the drying unit 4, insertion holes 4 a through which the transport belt 3 is inserted are provided. As will be described later, the drying unit 4 is configured such that a dried gas (air) is introduced through a gas circulation path 6, and a recording medium on which an image is formed by the ink jet head 2 is dried inside. Expose to dry.

  The heat pump 5 includes an evaporator 51 as a heat absorption unit, a condenser 52 as a heat dissipation unit, an expansion valve 53, and a compressor 54, and a heat medium is configured to circulate these. . In this heat pump 5, the heat medium (gas phase) compressed by the compressor 54 is condensed and liquefied by the condenser 52, expanded by the expansion valve 53, evaporated by the evaporator 51, and then again compressed by the compressor 54. The process of compressing is repeated. In this process, the evaporator 51 absorbs the heat of vaporization of the heat medium and cools it, and the condenser 52 releases the heat of liquefaction and heats it. Further, the evaporator 51 is provided with a drain valve 55 that discharges moisture contained in the gas cooled by the evaporator 51 as a drain. As will be described later, the drain valve 55 can discharge the ink solvent contained in the gas (air) discharged from the drying unit 4 as a drain.

  The gas circulation path 6 is a pipe disposed so as to guide the gas (air) discharged from the drying unit 4 to the evaporator 51 and the condenser 52 in this order and pass them to the drying unit 4 again. is there. The gas circulation path 6 communicates the first pipe 61 that communicates the drying unit 4 and the evaporator 51, the second pipe 62 that communicates the evaporator 51 and the condenser 52, and the condenser 52 and the drying unit 4. The third pipe 63 is configured.

Among these, in the first pipe 61, the air in the gas circulation path 6 is circulated in the direction of the arrow X (hereinafter referred to as the circulation direction X), and the inside of the drying unit 4 is reduced to a pressure lower than the atmospheric pressure. The blower 7 is provided. In addition, the first pipe 61 is provided with an outside air introduction valve 81 capable of introducing outside air on the upstream side in the circulation direction X from the blower 7.
The third pipe 63 is provided with a gas discharge valve 82 that can discharge air to the outside air.

  Next, the control configuration of the inkjet printer 1 will be described. FIG. 2 is a block diagram illustrating a control configuration of the inkjet printer 1.

As shown in this figure, the ink jet printer 1 includes a control unit 10 that controls each unit to execute image recording on a recording medium.
Specifically, the control unit 10 is configured to be able to control operations of the inkjet head 2, the transport rollers 31 and 31, the heat pump 5, the blower 7, the outside air introduction valve 81, and the gas discharge valve 82.

Next, the operation of the inkjet printer 1 will be described.
When the image recording is started, first, the control unit 10 drives the blower 7 to circulate the air in the gas circulation path 6 in the circulation direction X, and the drying unit 4 is set to a pressure lower than the atmospheric pressure. Reduce pressure. In addition, the control unit 10 controls the operation of the heat pump 5 to start the heat transfer between the evaporator 51 and the condenser 52. Then, the air in the gas circulation path 6 is cooled by the evaporator 51, dehumidified, and then heated by the condenser 52, so that it becomes dry heated air and is introduced into the drying unit 4.

  At this time, the control unit 10 adjusts the temperature of the air in the drying unit 4 by controlling the amount of heat transfer between the evaporator 51 and the condenser 52, and also controls the output of the blower 7. The flow rate of air introduced into the drying unit 4 through the gas circulation path 6 is adjusted. Further, in addition to these controls, the control unit 10 can also adjust the temperature and flow rate of the air in the drying unit 4 by controlling the openings of the outside air introduction valve 81 and the gas discharge valve 82. Thus, the drying capacity in the drying unit 4 is adjusted as appropriate by the control unit 10.

  In this case, the control unit 10 may control the temperature of the air introduced into the drying unit 4 through the gas circulation path 6 (drying unit inlet temperature) to be constant or the drying unit through the gas circulation path 6. Control may be performed to keep the temperature of the air discharged from 4 (drying section outlet temperature) constant. Further, the control unit 10 may control the air flow rate to the drying unit 4 so as to keep both the drying unit inlet temperature and the drying unit outlet temperature constant. At this time, the control unit 10 predicts the amount of ink droplets ejected onto the recording medium based on the input data of the image, and the drying unit 4 when drying the recording medium according to the amount of ink droplets. It is preferable to adjust the flow rate of the air introduced into the.

  Then, the control unit 10 controls the operation of the conveyance rollers 31 and 31 to convey the recording medium on the conveyance belt 3 in the conveyance direction Z, and controls the operation of the inkjet head 2 to eject ink droplets onto the recording medium. To form an image on the recording medium.

  The recording medium on which the image is formed is conveyed to the inside of the drying unit 4 through the insertion hole 4a, and exposed to the dry heated air in the drying unit 4 to dry the ink droplets. The dried recording medium is conveyed outside the drying unit 4 and discharged to a discharge tray (not shown).

  At this time, the air discharged from the drying unit 4 to the evaporator 51 as the air circulates in the gas circulation path 6 contains the solvent of the vaporized ink. The vaporized solvent is condensed during the cooling process in the evaporator 51 and is discharged as drain through the drain valve 55.

  According to the above inkjet printer 1, the heat energy contained in the air discharged from the drying unit 4 is recovered by the evaporator 51, and the air is dried by heating the air by the condenser 52 using this heat energy. It can be circulated to part 4. Therefore, the energy contained in the exhaust from the drying unit 4 can be effectively used to reduce the energy consumption necessary for drying the recording medium.

  Further, when the air discharged from the drying section 4 is cooled by the evaporator 51, the ink solvent contained in the air can be discharged as a drain. Even if it is a water-based ink, since some organic solvents are contained as a solvent, such a solvent can be discharged as drain without being released into the atmosphere. It can be recovered safely.

  Further, since the inside of the drying unit 4 is depressurized to a pressure lower than the atmospheric pressure, even when a large amount of dry air flows through the drying unit 4, the dry air leaks out from the insertion hole 4a and the inkjet head. Never hit 2. Therefore, it is possible to prevent ink near the nozzles of the ink jet head 2 from being dried and causing ejection failure, changing the ejection direction of ink droplets, and scattering of satellite ink droplets to contaminate the recording medium.

  Further, since the amount of heat transfer between the evaporator 51 and the condenser 52 is controlled, the heat energy exchanged between the evaporator 51 and the condenser 52 and the air is appropriately adjusted, and consequently the drying unit 4. The temperature of the air introduced into the air and the temperature of the air discharged from the drying unit 4 can be appropriately adjusted. Therefore, the energy consumption necessary for drying the recording medium can be adjusted as appropriate.

  Moreover, since the temperature of the air introduced into the drying part 4 through the gas circulation path 6 is kept constant, for example, when the outside air temperature is high and the heat radiation from the apparatus is small, energy consumption can be reduced.

  Further, since the temperature of the air discharged from the drying unit 4 through the gas circulation path 6 is kept constant, for example, when the amount of ink droplets that have landed on the recording medium is small, energy consumption can be reduced.

  Further, since the flow rate of the air introduced into the drying unit 4 through the gas circulation path 6 is controlled, the energy consumption necessary for drying the recording medium can be adjusted as appropriate.

  Further, since the flow rate of air introduced into the drying unit 4 when the recording medium is dried is controlled according to the amount of ink droplets ejected onto the recording medium by the inkjet head 2, for example, the ejected ink When the amount of drops is small, the energy consumption necessary for drying the recording medium can be minimized by reducing the air flow rate.

  Further, by controlling the opening degree of the outside air introduction valve 81 and the gas discharge valve 82, the temperature and flow rate of the circulating air can be appropriately adjusted. Thereby, for example, even when the heating temperature in the condenser 52 is higher than the set value when the cooling temperature in the evaporator 51 is lowered in order to reliably recover the solvent of the ink, The temperature of the air after passing through the condenser 52 can be lowered without changing the cooling temperature in the evaporator 51.

[Modification 1]
Then, the 1st modification of the inkjet printer 1 in the said embodiment is demonstrated. In addition, the same code | symbol is attached | subjected to the component similar to the said embodiment, and the description is abbreviate | omitted.

FIG. 3 is a conceptual diagram showing a main part of the ink jet printer 1A.
As shown in this figure, the ink jet printer 1 </ b> A includes a preheating unit 11 and a gas circulation path 6 </ b> A instead of the gas circulation path 6.

  The preheating unit 11 is formed in a casing shape having a hollow inside, and is disposed upstream of the inkjet head 2 in the transport direction Z. On both side walls of the preheating unit 11 in the transport direction Z, insertion holes 11a through which the transport belt 3 is inserted are provided. The preheating unit 11 is configured so that heated gas is introduced through the gas circulation path 6A, and the recording medium before the image is formed by the ink jet head 2 is exposed to the heated gas in advance. Heat.

  The gas circulation path 6 </ b> A includes a first pipe 61 and a second pipe 62 similar to those of the above embodiment, a fourth pipe 64 that communicates the condenser 52 and the preheating unit 11, and the preheating unit 11 and the drying unit 4. It is comprised from the 5th piping 65 connected. Among these, the 4th piping 64 guides at least one part of the air which passed the condenser 52 to the preheating part 11, and the 5th piping 65 dries at least one part of the air discharged | emitted from the preheating part 11. It leads to part 4. The fourth pipe 64 is provided with a gas discharge valve 82 similar to that in the above embodiment. However, this gas discharge valve 82 may be provided in the fifth pipe 65.

According to the above inkjet printer 1A, since the preheating unit 11 that preheats the recording medium before the image is formed is provided, drying of the recording medium can be promoted.
Further, since at least a part of the air that has passed through the condenser 52 is guided to the preheating unit 11, the thermal energy contained in the air discharged from the drying unit 4 can be effectively used for preheating the recording medium.

  Further, since at least a part of the air discharged from the preheating unit 11 is guided to the drying unit 4, the thermal energy contained in the air discharged from the preheating unit 11 can be effectively used for drying the recording medium.

[Modification 2]
Next, a second modification of the ink jet printer 1 in the above embodiment will be described. In addition, the same code | symbol is attached | subjected to the component similar to the said embodiment, and the description is abbreviate | omitted.

FIG. 4 is a conceptual diagram showing a main part of the inkjet printer 1B.
As shown in this figure, the ink jet printer 1 </ b> B includes a heat exchanger 12 that performs heat exchange between gases before and after passing through the evaporator 51.

  According to the above inkjet printer 1B, since the heat exchanger 12 that performs heat exchange between the gas before and after passing through the evaporator 51 is provided, the temperature of the air before passing through the evaporator 51 is lowered and passed. After that (before passing through the condenser 52), the temperature of the air rises. Thereby, the power required for driving the heat pump 5 can be reduced, and consequently, the energy consumption required for drying the recording medium can be reduced.

  It should be noted that the present invention should not be construed as being limited to the above-described embodiment and the first and second modifications thereof, and can of course be modified or improved as appropriate.

  For example, in the above-described embodiment and the first and second modifications thereof, water-based ink is used. However, the ink is not limited to water-based ink. For example, ultraviolet curable ink, oil-based ink, solvent-based ink, conductive Ink, semiconductor ink, etc. can also be used.

The heat pump 5 is not particularly limited as long as the heat transfer is performed by the evaporator 51 and the condenser 52 to save energy, and other types of heat pumps that are conventionally known may be applied.
In addition, the ink jet printer 1B in the second modified example may include the heat exchanger 12 provided in the ink jet printer 1A including the preheating unit 11 in the first modified example.

  In addition, the outside air introduction valve 81 is provided on the upstream side in the circulation direction X with respect to the blower 7 in the first pipe 61, but is not particularly limited thereto, for example, on the downstream side in the circulation direction X with respect to the blower 7. You may provide with an external air introduction fan.

  Hereinafter, the present invention will be described more specifically with reference to examples.

  As examples and comparative examples of the present invention, energy consumption (power consumption) necessary for drying the recording medium was determined under the following conditions.

<1 Example>
An image was recorded on a recording medium using the inkjet printer 1 under the following image forming conditions and drying conditions.

<1.1 Image formation conditions>
Image formation was performed at a printing speed of 10 m ² / min while ejecting 14 ml / m ^{2 of} water-based ink containing 70% of volatile components (mainly water) from the inkjet head 2 onto the recording medium.
The required amount of dry water (the amount of volatile components that must be dried) at this time is (14 [ml / m ² ] × 70 [%] / 100 × 10 [m ² / min] = 98 [ml / min]. ≒) 1.6 g / sec.
Further, the required drying power corresponding to the required amount of dry water (the power required for drying all volatile components) is 4.1 kW with water as the volatile component.

<1.2 Drying conditions>
The gas introduction temperature at the inlet of the drying unit 4 was 70 ° C., and the gas flow rate circulating through the gas circulation path 6 was 9 m ³ / min. At this time, the gas discharge temperature at the outlet of the drying unit 4 was 40 ° C., and the cooling temperature in the evaporator 51 was 10 ° C.

<2 Comparative example>
In a conventional inkjet printer having a drying section, a recording medium on which an image was formed under the same image forming conditions as in the examples was dried with dry air heated by a heater. In the drying section, the outside air at 20 ° C. was heated with a heater, and the recording medium was dried with dry air at an inlet temperature of 70 ° C. and a flow rate of 9 m ³ / min, as in the example.

<3 results>
In the example, the recording medium could be sufficiently dried, and the ink solvent could be almost recovered by the evaporator 51. Moreover, the power consumption of the heat pump 5 was 4 kW.
On the other hand, in the comparative example, the power consumption of the heater was 9 kW.

<4 Summary>
From the above results, the power consumption of 2.2 times (≈ 9 / 4.1) of the required drying power was required in the comparative example, whereas the power consumption substantially equal to the required drying power was calculated in the example. It can be seen that the recording medium can be dried. That is, it can be seen that by providing the heat pump 5, the energy consumption required for drying the recording medium can be reduced to 45% (1 / 2.2 × 100).

1, 1A, 1B Inkjet printer 2 Inkjet head 4 Drying unit 5 Heat pump 6, 6A Gas circulation path 7 Blower 10 Control unit (heat pump control means, flow rate control means)
11 Preheating part 12 Heat exchanger 51 Evaporator (heat absorption part)
52 Condenser (heat dissipation part)
81 Outside air introduction valve 82 Gas discharge valve

Claims (11)

An inkjet head that forms an image by ejecting ink droplets onto a recording medium;
A drying unit for drying the recording medium on which an image is formed by the inkjet head by exposing the recording medium to a dry gas inside;
A heat pump having a heat absorbing portion and a heat radiating portion;
A gas circulation path for guiding the gas discharged from the drying unit to the heat absorbing unit and the heat radiating unit in this order and passing the gas to the drying unit;
A heat exchanger for exchanging heat between the gas before and after passing through the heat absorption part;
An ink jet printer comprising:   The inkjet printer according to claim 1, further comprising a blowing unit that circulates the gas in the gas circulation path and depressurizes the inside of the drying unit to a pressure lower than atmospheric pressure.   The inkjet printer according to claim 1, further comprising a heat pump control unit configured to control a heat transfer amount between the heat absorbing unit and the heat radiating unit in the heat pump.   4. The ink jet printer according to claim 3, wherein the heat pump control means maintains a constant temperature of the gas introduced into the drying unit through the gas circulation path.   5. The ink jet printer according to claim 3, wherein the heat pump control unit maintains a constant temperature of the gas discharged from the drying unit through the gas circulation path.   The inkjet printer according to claim 1, further comprising a flow rate control unit configured to control a flow rate of the gas introduced into the drying unit through the gas circulation path.   The flow rate control unit controls a flow rate of a gas introduced into the drying unit when the recording medium is dried according to an amount of ink droplets ejected to the recording medium by the inkjet head. The ink jet printer according to claim 6.   The said gas circulation path is provided with the external air introduction valve which can introduce external air between the said drying part and the said heat absorption part, It is any one of Claims 1-7 characterized by the above-mentioned. Inkjet printer.   The gas circulation path is provided with a gas discharge valve capable of discharging gas to the outside air between the heat radiating unit and the drying unit. The inkjet printer according to item. A preheating unit that preheats the recording medium before the image is formed by the inkjet head by exposing it to the heated gas inside;
The inkjet printer according to claim 1, wherein at least a part of the gas that has passed through the heat radiating unit is guided to the preheating unit.   The inkjet printer according to claim 10, wherein at least a part of the gas discharged from the preheating unit is guided to the drying unit.

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