JP2873446B2 - Drying equipment for printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing drying device for drying ink printed on printing paper, which prevents overdrying of the printing paper.

[0002]

2. Description of the Related Art A printing drying apparatus is disclosed in Japanese Patent Laid-Open Publication No.
-247165. As shown in FIG. 4, the printing drying apparatus 1 has a first zone 4 and a second zone 5 that are divided into upper and lower sections with respect to the transport direction of the printing paper 3 coming out of the printing unit 2. At the outlet of the first zone 4, a first paper thermometer 6 for measuring the paper surface temperature of the printing paper 3 exiting the first zone 4 is provided. A second paper thermometer 7 for measuring the paper surface temperature is provided, the hot air temperature in the first zone 4 is controlled in accordance with the temperature measured by the first paper thermometer 6, and the second zone thermometer 7 is controlled in accordance with the temperature measured by the second paper thermometer 7. The configuration is such that the hot air temperature in the second zone 5 is controlled. The printing drying apparatus 1 is designed to prevent the occurrence of wrinkles on the printing paper 3 by drying the paper surface temperatures at the outlets of the respective zones 4 and 5 so as to be at predetermined temperatures, respectively. .

[0003]

However, when the printing drying device 1 is used, the printing paper 3 that has exited the final zone 5 may be over-dried. The printing paper 3 breaks in the folding machine 9,
There was a problem that it could not be folded neatly. Then, the inventor repeated many experiments in order to prevent overdrying of the printing paper 3. As a result, the inventor has found that even when the printing paper 3 exiting the final zone 5 is set to a predetermined temperature, the water content of the printing paper 3 decreases as the printing operation time elapses from the start of printing. . The reason why the moisture content of the printing paper 3 is reduced is that the interior wall surfaces and the like forming the interior of the zones 4 and 5 are radiated to the printing paper 3 from the interior wall surfaces and the like as the temperature rises with the elapse of the printing operation time. It is conceivable that the amount of radiant heat gradually increases with the elapse of the printing operation time, and the amount of heat equal to or more than the amount of drying heat required for drying the printing ink is transmitted to the print 3.

Further, the operation of the conventional printing drying apparatus 1 is as follows.
In order to ensure reliable ink drying and to prevent ink transfer to the cooling roll 8, the drying is often performed in an over-dried state.

Accordingly, an object of the present invention is to provide a printing dryer capable of adjusting the temperature of hot air to an optimum value while considering the moisture of the printing paper so as to prevent overdrying of the printing paper.

[0006]

The gist of the present invention is to provide a first zone drying chamber and a second zone drying chamber each having a nozzle for blowing hot air toward a printing paper passage. A first zone temperature controller for adjusting the hot air temperature of the first zone drying chamber so that the temperature difference between the detected temperature of the hot air temperature of the zone drying chamber and the set temperature of the hot air is reduced, and a second zone. A second zone temperature controller for adjusting the hot air temperature of the second zone drying chamber so that the temperature difference between the detected temperature of the paper surface temperature detector for detecting the printing paper surface temperature on the outlet side of the drying chamber and the paper surface setting temperature is reduced. A paper moisture detector for detecting the moisture content of the printing paper at the outlet side of the second zone drying chamber, and an excess of the moisture content detected by the paper moisture detector being lower than the set moisture value. When in a dry state, the detected moisture value A printing drying device being characterized in that a set temperature corrector for correcting lower the hot air setting temperature and the paper surface temperature setting in accordance with the moisture difference value between the constant water content. The moisture value referred to in this specification is the amount of moisture contained in the printing paper, and is expressed by the moisture content or the absolute amount of moisture.

According to the first aspect of the present invention, the hot air setting temperature and the paper surface setting temperature are corrected by obtaining a moisture difference value corresponding to the overdrying state of the printing paper, so that the nozzle of each zone drying chamber is reduced. By lowering the temperature of the hot air to be blown out, the amount of heat transfer to the printing paper can be reduced, and the excessively dry state can be eliminated. The present invention only reduces the amount of excessive heat transfer that overdrys the printing paper, and can ensure the amount of heat transfer necessary for drying the ink. Further, according to the present invention, since the paper surface temperature of the printing paper at the outlet of the second zone drying chamber is not higher than the paper surface setting temperature, it is possible to prevent occurrence of wrinkles on the printing paper.

[0008] The gist of the present invention is that a first zone drying chamber and a second zone drying chamber provided with a nozzle for blowing hot air toward a printing paper passage, and an outlet side of the first zone drying chamber. A first zone temperature controller for adjusting the hot air temperature in the first zone drying chamber so that the temperature difference between the detected temperature of the paper surface temperature detector for detecting the printing paper surface temperature and the paper surface setting temperature is reduced, and the second zone drying. A second zone temperature controller that adjusts the hot air temperature of the second zone drying chamber so that the temperature difference between the detection temperature of the paper surface temperature detector that detects the printing paper surface temperature on the outlet side of the chamber and the paper surface setting temperature is reduced. In the drying device for printing provided, a paper moisture detector for detecting a printing paper moisture value at an outlet side of the second zone drying chamber, and overdrying in which a moisture value detected by the paper moisture detector becomes lower than a set moisture value. When in the state, the detected moisture value A printing drying device being characterized in that a set temperature corrector for correcting lower the respective paper setting temperature in accordance with the moisture difference value between the constant water content.

According to a second aspect of the present invention, the temperature of hot air blown out from the nozzles is obtained by obtaining a water difference value corresponding to the overdry state of the printing paper and correcting the paper surface set temperature value of each zone to be low. To reduce the amount of heat transfer to the printing paper,
An excessively dry state can be eliminated. The present invention only reduces the amount of excessive heat transfer that overdrys the printing paper, and can ensure the amount of heat transfer necessary for drying the ink. Further, according to the present invention, since the paper surface temperature of the printing paper at the outlet of the drying chamber is not made higher than the paper surface setting temperature, it is possible to prevent the occurrence of wrinkles on the printing paper.

[0010] The gist of the present invention is that the temperature difference between the temperature detected by the temperature detector for detecting the hot air temperature in the second zone drying chamber and the set hot air temperature is reduced. And a second temperature control device that adjusts the hot air set temperature to be low by the set temperature corrector, and the second temperature control device is used during the low-speed printing paper feeding operation. The printing dryer according to claim 1 or 2, wherein the temperature is adjusted, and the temperature is adjusted by the second zone temperature adjusting device during a high-speed printing paper feeding operation.

According to the third aspect of the present invention, the temperature is adjusted by detecting the temperature of the hot air in the second zone drying chamber during the low speed feeding operation of the printing paper, and the outlet side of the second zone drying chamber during the high speed feeding operation of the printing paper. Optimum temperature adjustment according to each operating state can be performed by performing temperature adjustment for detecting the printing paper surface temperature.

According to a fourth aspect of the present invention, the set temperature corrector first performs the correction for the second zone drying chamber, and when this correction is insufficient, the first zone drying chamber is continued. 4. The drying device for printing according to claim 1, wherein said correction is made for the following.

According to the fourth aspect of the present invention, when overdrying of the printing paper is likely to occur in the second zone drying chamber, priority is given to correction for the second zone drying chamber, so that the optimum temperature is obtained. Can be adjusted.

According to a fifth aspect of the present invention, there is provided a drying chamber provided with a nozzle for blowing hot air toward a printing paper passage.
A printing apparatus comprising: a temperature controller that adjusts the temperature of hot air in the drying chamber so that a temperature difference between a detection temperature of a paper surface temperature detector that detects a printing paper surface temperature at an outlet side of the drying chamber and a paper surface setting temperature is reduced. In the drying device for paper, a paper moisture detector for detecting the printing paper moisture value at the outlet side of the drying chamber, and when the moisture content detected by the paper moisture detector is in an overdry state that is less than a set moisture value, A printing drying apparatus comprising: a set temperature corrector that corrects the paper surface set temperature to be low according to a water difference value between a detected water value and a set water value.

According to a fifth aspect of the present invention, the temperature of hot air blown from the nozzles is reduced by obtaining a water difference value corresponding to the overdry state of the printing paper and correcting the paper surface set temperature value to be low. As a result, the amount of heat transfer to the printing paper can be reduced, and the excessively dry state can be eliminated. The present invention only reduces the amount of excessive heat transfer that overdrys the printing paper, and can ensure the amount of heat transfer necessary for drying the ink. Further, according to the present invention, since the paper surface temperature of the printing paper at the outlet of the drying chamber is not made higher than the paper surface setting temperature, it is possible to prevent the occurrence of wrinkles on the printing paper.

[0016] The gist of the present invention is that a drying chamber provided with a nozzle for blowing hot air toward a printing paper passage;
A drying device for printing, comprising: a temperature controller that adjusts the hot air temperature such that a temperature difference between a detected temperature of a hot air temperature of the drying chamber and a set temperature of the hot air is reduced. A paper moisture detector for detecting the printing paper moisture value at the outlet side of the paper moisture detector, and when the detected moisture value of the paper moisture detector is in an overdry state where the moisture content is less than the set moisture value, the detected moisture value and the set moisture value And a set temperature corrector that corrects the hot air set temperature to a low value in accordance with the moisture difference value.

According to a sixth aspect of the present invention, the temperature of the hot air blown out from the nozzles is reduced by obtaining a water difference value corresponding to the overdry state of the printing paper and correcting the hot air set temperature value to a low value. As a result, the amount of heat transfer to the printing paper can be reduced, and the excessively dry state can be eliminated. The present invention only reduces the amount of excessive heat transfer that overdrys the printing paper, and can ensure the amount of heat transfer necessary for drying the ink.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a drying apparatus for printing according to the present invention.

(First Embodiment) FIG. 1 is a schematic view showing a first embodiment of a drying apparatus for printing according to the present invention. The printing drying device 11 according to the present embodiment is provided on the outlet side of the printing unit 2 and is configured to dry the ink printed on the printing paper 3 coming out of the printing unit 2. The printing drying device 11 includes a first zone drying chamber 14 and a second zone drying chamber 15, and blows out hot air for drying toward a printing paper passage R through which the printing paper 3 passes. Each zone drying chambers 14 and 15 have
Upper and lower hot air chambers 19 and 2 having a number of nozzles 17 and 18 for blowing hot air for drying toward the printing paper passage R.
0 is disposed so that the printing paper 3 is dried in a floating state.

The hot air chambers 19 and 20 are provided with circulation fans 21 and 22, heating devices 23 and 24, and circulation duct 2.
The hot air supply devices 29 and 30 having 5, 26 and the like are connected. The heating devices 23 and 24 are gas burners 27 and 28
The one with is used. Hot air supply devices 29, 30
The hot air blown into the chamber from the nozzles 17 and 18 of the drying chambers 14 and 15 is sucked by the circulation fans 21 and 22 through the circulation ducts 25 and 26, and the heating device 2 is heated to the optimum temperature.
3 and 24, and is sent to the hot-air chambers 19 and 20 through the circulation ducts 25 and 26, and the nozzles 17 and 18 are heated.
The hot air for drying is blown out to the printing paper 3.

The first zone drying chamber 14 is provided with a temperature control device 31 for controlling the temperature of the hot air sent to the hot air chamber 19. The temperature control device 31 detects the temperature of the hot air in the hot air chamber 19 by detecting the temperature of the hot air in the hot air chamber 19 and the detected temperature T1.
a temperature detector 33 that outputs a to the temperature indicating controller 32;
A setting device 34 for setting the hot air temperature T1b.
The temperature adjustment device 31 adjusts the hot air temperature of the hot air chamber 19 so that the temperature difference between the hot air set temperature T1c corrected by the arithmetic unit 52 of the set temperature corrector 51 described later and the detected temperature T1a becomes small. It is.

The second zone drying chamber 15 is provided with a temperature control device 36 for controlling the temperature of the hot air sent to the hot air chamber 20, a temperature control device 41, and a switching switch 35. When the printing paper is transported at a low speed, the temperature is controlled by the temperature controller 36, and when the printing paper is transported at a high speed, the temperature is controlled by the temperature controller 41. The switching switch 35 is configured such that the switching unit 46 receives the speed signal V generated by the speed detector 47 or the like of the printing unit 2 and performs switching.

The temperature control device 36 includes a gas burner 28
Temperature controller 37 for controlling the combustion of the hot air, a temperature detector 38 for detecting the temperature of the hot air in the hot air chamber 20 and outputting the detected temperature T2a to the temperature controller 37, and a hot air temperature T
And a setting device 39 for setting 2b. The temperature control device 36 determines the hot air set temperature T2c corrected by the arithmetic unit 53 of the set temperature corrector 51 described later and the detected temperature T2.
a so as to reduce the temperature difference from the hot air chamber 20.
The hot air temperature is adjusted.

The temperature control device 41 includes a gas burner 28
And a temperature instruction controller 42 for controlling the combustion of the printing paper, and detecting the temperature of the printing paper surface at the outlet side of the second zone drying chamber 15 to detect the detected temperature T.
Paper surface temperature detector 4 which outputs 3a to temperature indicating controller 42
3 and a setting device 44 for setting the paper surface temperature T3b. The temperature adjusting device 41 includes a set temperature compensator 5 described later.
The hot air temperature of the hot air chamber 20 is adjusted so that the temperature difference between the sheet temperature T3c corrected by the first arithmetic unit 54 and the detected temperature T3a becomes small.

The drying device 11 for printing adjusts the hot air temperature of the hot air chambers 19 and 20 to an optimum value while considering the moisture of the printing paper 3 at the outlet of the second zone drying chamber 15 to overdry the printing paper 3. Paper moisture detector 5 for detecting the printing paper moisture value at the outlet side of the second zone drying chamber 15 in order to prevent
6 and a set temperature corrector 51. The set temperature corrector 51 includes a setter 57 for setting a printing paper moisture value M1b that does not cause breakage of the dried printing paper 3 and a detection moisture value M1a of the paper moisture detector 56 is used as a setting moisture value M1b.
When the water content is in an excessively dry state, the detected moisture value M1
a and a moisture difference value M1c between the set moisture value M1b (M1c = M
1b-M1a) and a water difference value M1c
And computing units 52 and 53 for correcting the hot air set temperatures T1b and T2b of the setting units 34 and 39 according to the speed signal V.
And a calculator 54 that corrects the paper surface setting temperature T3b of the setting device 44 to be low according to the moisture difference value M1c and the speed signal V. Note that when it is not necessary to consider the printing paper transport speed, the computing units 52, 53, 56
Correction may be made respectively according to 1c.

The computing units 52, 53, and 54 calculate the water difference value M1c based on a predetermined rule.
, And the set temperatures T1b, T2b, T3b of the setters 34, 39, 44 are corrected with the corrected values, and the corrected set temperatures T1c, T2c, T3c are sent to the temperature indicating controllers 32, 37, 42. It is output. The rule for obtaining the correction value differs according to the type and basis weight of the printing paper 3, the physical properties and printing density of the ink, the printing paper transport speed, and the like, and thus is determined in advance by a drying test.

In the case where the overdrying of the printing paper 3 is likely to occur in the second zone drying chamber 15, the set temperature corrector 51 first performs the correction for the second zone drying chamber 15. It is preferable to configure the circuit so that the correction for the first zone drying chamber 14 is continuously performed when the correction is insufficient.

A cooling roll 8 and a folding machine 9 are provided on the outlet side of the second zone drying chamber 15, and between the cooling roll 8 and the folding machine 9, the water content of the cooled printing paper 3 is reduced. A paper moisture detector 59 and a moisture indicator 60 for detection are provided as needed.

Next, the operation of the printing drying device 11 will be described according to the printing procedure. First, the printing paper 3 unwound from an unwinding device (not shown) is passed through the printing unit 2, the printing paper path R of each of the zone drying chambers 14 and 15, the cooling roll 8, and the folder 9. Subsequently, the printing paper 3 is moved at a low speed (for example, 1
10 to 10 m / min), the hot air supply devices 29 and 30 of the zone drying chambers 14 and 15 are activated, and hot air is blown from the nozzles 17 and 18 to the printing paper 3 while the drying chambers 14 and 15 are blown. Is heated. In the second zone drying chamber 15 during the low speed operation of the printing paper, the switching switch 35 automatically receives the speed signal V and automatically enters the low speed state.
Adjust the temperature with.

A predetermined low-speed operation time (for example, 1 to 10 m
in), the speed of the printing paper 3 is increased (for example,
(50-700 m / min), and the printing operation starts. In the second zone drying chamber 15 during the high-speed printing paper feeding operation, the switching switch 35 automatically enters the high-speed state in response to the speed signal V, and exits the first zone drying chamber 15 while controlling the temperature with the temperature control device 41. The operation is performed so that the paper surface temperature of the printing paper 3 reaches the set temperature.

When the printing paper 3 exiting the second zone drying chamber 15 is going to be over-dried with the progress of the main printing operation, the zone drying chambers 14 and 15 are set to the set temperature compensator 51.
Is adjusted to prevent overdrying. That is, the set temperature corrector 51 is configured to set the moisture value M1 set by the setter 57.
b (for example, a water content of 4%) and a water difference value M1c (M1c = M1b-M1a) between the water value M1a (for example, a water content of 3%) of the printing paper 3 at the outlet of the drying chamber 15 and the hot air set temperature. T1b, T2b (for example, T1b = 100 to 15
0 ° C., T2b = 140 to 220 ° C.) and the paper surface set temperature T
3b (for example, T3b = 110 to 140 ° C.) is corrected to be low (for example, 5 to 30 ° C.) and the set temperature T1 after the correction is corrected.
c, T2c, and T3c are changed to temperature indicating controllers 32, 37, and 42.
Output to Thereby, each zone drying chamber 14, 1
5 can reduce the amount of heat transfer to the printing paper 3 by adjusting the temperature of the hot air blown from each of the nozzles 17 and 18, thereby eliminating or preventing excessive drying.

The printing drying device 11 can only reduce the amount of heat transfer that excessively dries the printing paper, and can secure the amount of heat transfer necessary for drying the ink, and can also perform the second zone drying. Since the paper surface temperature of the printing paper 3 at the outlet of the chamber 15 is not set to be equal to or higher than the paper surface setting temperature T3b, occurrence of wrinkles on the printing paper 3 can be prevented.

(Second Embodiment) FIG. 2 is a schematic diagram showing a second embodiment of the printing drying apparatus according to the present invention. The drying device for printing 61 according to the present embodiment
The difference from the first embodiment (see FIG. 1) is that the temperature detector 33 of the temperature controller 31 provided in the first zone drying chamber 14 is different.
1 (see FIG. 1) is replaced with a paper surface temperature detector 62 (see FIG. 2) that detects the paper surface temperature at the outlet side of the first zone drying chamber 14. The configuration other than this difference is substantially the same as that of the first embodiment.

(Third Embodiment) FIG. 3 is a schematic view showing a third embodiment of the printing drying apparatus according to the present invention. The printing drying device 71 according to the present embodiment
The difference from the first embodiment (see FIG. 1) is that the temperature control device 41 (see FIG. 1) provided in the second zone drying chamber 15 is omitted, and only the temperature control device 36 is provided. The configuration other than this difference is substantially the same as that of the first embodiment.

(Other Embodiments) The drying device for printing according to the present invention is not limited to the first to third embodiments, but can be changed according to printing specifications. For example, it is also possible to omit the first zone drying chamber 14 shown in FIG. 1 and use only the second zone drying chamber 15 and correct the temperature controllers 36 and 41 of the second zone drying chamber 15 with the set temperature corrector 51. It is. Furthermore, it is also possible to omit the first zone drying chamber 14 shown in FIG. 3 and use only the second zone drying chamber 15 and correct the temperature control device 36 of the second zone drying chamber 15 with the set temperature corrector 51. .

[0036]

As described in detail above, the printing drying apparatus according to the first to sixth aspects of the present invention reduces the amount of heat transfer to the printing paper according to the overdrying state of the printing paper, thereby reducing the overdrying state. Therefore, there is an excellent effect that the ink of the printing paper can be dried neatly without causing breakage in the folding machine.

In the printing drying apparatus according to the present invention, since the paper surface temperature of the printing paper at the outlet of the drying chamber is not higher than the paper surface setting temperature, occurrence of wrinkles on the printing paper is reduced. Can be prevented.

Further, in the printing drying apparatus according to the third aspect of the present invention, it is possible to adjust the temperature optimally according to the printing paper feeding speed.

The printing drying apparatus according to the fourth aspect of the present invention can control the temperature optimally for various conditions in which overdrying of the printing paper is likely to occur in the second zone drying chamber.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a printing drying apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a second embodiment of the printing dryer according to the present invention.

FIG. 3 is a schematic view showing a third embodiment of a printing drying apparatus according to the present invention.

FIG. 4 is a schematic side view showing a conventional printing drying apparatus.

[Explanation of symbols]

 14 ... First zone drying chamber 15 ... Second zone drying chamber 31 ... First zone temperature controller 36 ... Second temperature controller 41 ... Second zone temperature controller 51 ... Set temperature corrector 56 ... Paper moisture detector

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-247165 (JP, A) JP-A-58-52969 (JP, A) JP-A-3-168587 (JP, A) JP-A-4- 224953 (JP, A) Japanese Utility Model 2-44036 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B41F 23/04 F26B 13/10 F26B 21/10

Claims (6)

(57) [Claims] A first zone drying chamber and a second zone drying chamber each having a nozzle for blowing hot air toward a printing paper passage;
A first zone temperature controller for adjusting the hot air temperature of the first zone drying chamber so that the temperature difference between the detected temperature of the temperature detector for detecting the hot air temperature of the first zone drying chamber and the set hot air temperature is reduced, The second zone temperature control for adjusting the hot air temperature in the second zone drying chamber so that the temperature difference between the detected temperature of the paper surface temperature detector that detects the printing paper surface temperature at the outlet side of the two-zone drying chamber and the paper surface setting temperature is reduced. A printing water drying device comprising: a paper moisture detector for detecting a printing paper moisture value at an outlet side of the second zone drying chamber; and a detection moisture value of the paper moisture detector being smaller than a set moisture value. And a set temperature corrector for lowering the hot air set temperature and the paper surface set temperature in accordance with the difference between the detected moisture value and the set moisture value in the overdry state. Drying equipment for printing. 2. A first zone drying chamber and a second zone drying chamber each having a nozzle for blowing hot air toward a printing paper passage;
The first zone temperature that adjusts the hot air temperature of the first zone drying chamber so that the temperature difference between the detected temperature of the paper surface temperature detector that detects the printing paper surface temperature at the outlet side of the first zone drying chamber and the paper surface setting temperature becomes small. The controller and the hot air temperature of the second zone drying chamber are adjusted so that the temperature difference between the detected temperature of the paper surface temperature detector for detecting the printing paper surface temperature at the outlet side of the second zone drying chamber and the paper surface setting temperature is reduced. In a printing dryer having a second zone temperature controller, a paper moisture detector that detects a printing paper moisture value on the outlet side of the second zone drying chamber,
When the paper moisture detector is in an overdry state in which the detected moisture value is lower than the set moisture value, the setting is such that each of the sheet surface set temperatures is corrected to be low according to the moisture difference value between the detected moisture value and the set moisture value. A drying device for printing, comprising: a temperature compensator. 3. A hot air temperature of the second zone drying chamber is adjusted so that a temperature difference between a temperature detected by a temperature detector for detecting a hot air temperature of the second zone drying chamber and a set hot air temperature is reduced. A second temperature adjusting device for correcting the set temperature of the hot air to a low value by a set temperature corrector is also provided. During the low speed feeding operation of the printing paper, the temperature is adjusted by the second temperature adjusting device, and the high speed feeding operation of the printing paper is performed. 3. The printing drying device according to claim 1, wherein the temperature is sometimes adjusted by the second zone temperature adjusting device. 4. The set temperature corrector first performs the correction for the second zone drying chamber, and when the correction is insufficient, continuously performs the correction for the first zone drying chamber. 4. The drying device for printing according to 2 or 3. 5. A drying chamber provided with a nozzle for blowing hot air toward a passage for printing paper, and a detection temperature of a paper surface temperature detector for detecting a printing paper surface temperature at an outlet side of the drying chamber and a paper surface setting temperature. A printing drying device comprising a temperature control device for controlling the temperature of the hot air in the drying chamber so that the temperature difference is reduced,
A paper moisture detector for detecting a printing paper moisture value at an outlet side of the drying chamber; and setting the detected moisture value when the paper moisture detector detects an overdry state in which the detected moisture value is less than a set moisture value. A drying device for printing, comprising: a set temperature corrector for lowering the paper surface set temperature in accordance with a water difference value from a water value. 6. A drying chamber provided with a nozzle for blowing hot air toward a printing paper passage, and a temperature difference between a temperature detected by a temperature detector for detecting a temperature of the hot air in the drying chamber and a set hot air temperature is reduced. A drying device for printing provided with a temperature controller for controlling the temperature of the hot air as described above, wherein a paper moisture detector for detecting a printing paper moisture value at an outlet side of the drying chamber, and a moisture content detected by the paper moisture detector. A set temperature corrector that corrects the hot air set temperature to a low value in accordance with a moisture difference value between the detected moisture value and the set moisture value in an overdry state in which the set moisture value is less than the set moisture value. Drying device for printing.