Temperature control device

Abstract

To provide a temperature adjusting device which can efficiently control temperature adjustment while suppressing power consumption.SOLUTION: A temperature adjusting device includes: temperature adjusting mechanisms 22, 32, 42 which adjust a temperature of ink supplied to a line head 11 having a housing for housing a plurality of ink jet heads which are arrayed in a vertical direction and discharge the ink; and a control part 50 which controls the temperature adjusting mechanisms 22, 32, 42. The control part 50 controls the temperature adjusting mechanisms 22, 32, 42 so as to lower a heating condition to the ink supplied to the ink jet head arranged in an upper position in the vertical direction than the ink jet head arranged in a lower position in the vertical direction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a temperature adjusting device that adjusts the temperature of liquid supplied to a plurality of ejection ports that are arranged in a vertical direction. [Background technology]

[0002] 2. Description of the Related Art Conventionally, inkjet printing devices have been proposed that perform printing by ejecting ink onto a print medium.

[0003] In inkjet printing devices, the ink temperature is adjusted to 30°C to 35°C using a heater or the like to ensure that the ink temperature is suitable for printing and to suppress ink mist generated by ink ejection from the inkjet head. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-176572 Summary of the Invention [Problem to be solved by the invention]

[0005] Inkjet printing devices have been proposed that print on the sides of cardboard and other materials using multiple inkjet heads arranged vertically. Even in such inkjet printing devices, it is necessary to regulate the ink temperature to maintain the ink temperature within an appropriate range.

[0006] On the other hand, ink temperature is adjusted in the ink unit that supplies ink to each inkjet head. In the case of an inkjet printing device in which multiple inkjet heads are arranged vertically as described above, if heating is performed using heaters in multiple ink units provided for each inkjet head, the power consumption of the heaters will be added up for each inkjet head, resulting in very high power consumption.

[0007] Patent Document 1 proposes a method for preventing high power consumption when controlling multiple heat sources by dividing the duty ratio of a pulse signal for temperature control and supplying pulse signals sequentially to the multiple heat sources at staggered times.

[0008] However, if heating is controlled as described in Patent Document 1, it takes a long time for all the inkjet heads to reach a temperature at which printing is possible, which leads to a decrease in productivity.

[0009] An object of the present invention is to provide a temperature control device that can reduce power consumption and efficiently perform temperature control. [Means for solving the problem]

[0010] The temperature control device of the present invention comprises a temperature adjustment unit that adjusts the temperature of liquid supplied to a head unit having a housing that houses a plurality of ejection units arranged vertically to eject droplets, and a control unit that controls the temperature adjustment unit, and the control unit controls the temperature adjustment unit so that the heating or cooling conditions for the liquid supplied to the ejection units arranged vertically above are lower than those for the ejection units arranged vertically below. [Effects of the Invention]

[0011] According to the temperature control device of the present invention, temperature control is performed so that the heating or cooling conditions for the liquid supplied to the ejection section located vertically above are lower than those of the ejection section located vertically below, thereby reducing power consumption and enabling efficient temperature control. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an external perspective view showing a schematic configuration of an inkjet printing apparatus using an embodiment of a temperature adjustment device of the present invention; [Figure 2] Diagram showing the detailed configuration of the line head [Figure 3] FIG. 1 is a diagram showing the configuration of first to third ink units; [Figure 4] FIG. 2 is a block diagram showing the configuration of a control system of the inkjet printing apparatus shown in FIG. 1. [Figure 5] 1 is a graph showing changes in ink temperature in blocks B1 to B3 and a diagram showing duty ratios of pulse signals output to temperature adjustment mechanisms corresponding to blocks B1 to B3. [Figure 6] Diagram showing the line head cooling fan [Figure 7] 1 is a table showing an example of a control method for the upper head cooling fan, the lower head cooling fan, and the ink cooling fan of the temperature adjustment mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0013] An inkjet printing apparatus using an embodiment of a temperature control device of the present invention will be described in detail below with reference to the drawings. Figure 1 is an external perspective view showing the general configuration of inkjet printing apparatus 1. In the following description of the embodiment, the up, down, left, right, front, and rear directions indicated by arrows in Figure 1 are defined as the up, down, left, right, front, and rear directions of inkjet printing apparatus 1. The up and down directions of inkjet printing apparatus 1 are also defined as the vertical direction.

[0014] As shown in FIG. 1, the inkjet printing device 1 includes a head unit 10 and a transport unit 2.

[0015] The transport unit 2 transports the print medium P in the direction of the arrow shown in Fig. 1. The print medium P may be, for example, a box (such as a cardboard box) having a printing surface Ps that stands upright in the vertical direction, as shown in Fig. 1. However, the print medium P is not limited to a box, and may be any medium that has a printing surface that stands upright in the vertical direction.

[0016] The transport unit 2 includes a support table 3 and a transport belt unit 4. The support table 3 is a table that supports the transport belt unit 4.

[0017] The conveyor belt unit 4 includes two platen rollers and a conveyor belt that extend in a direction perpendicular to the conveyance direction of the print medium P. The two platen rollers are arranged parallel to and spaced apart in the conveyance direction of the print medium P. A circular conveyor belt is stretched between the two parallel platen rollers. The platen rollers rotate under the control of the control unit 50, which will be described later, and the conveyor belt moves, thereby conveying the print medium P.

[0018] The head unit 10 performs printing by ejecting ink onto the printing surface Ps of the print medium P transported by the transport unit 2.

[0019] 1, the head unit 10 has four line heads 11, 12, 13, and 14. The four line heads 11 to 14 are provided to extend in the vertical direction and are arranged parallel to the transport direction of the printing medium P. In this embodiment, each of the line heads 11 to 14 corresponds to a head portion of the present invention.

[0020] The four line heads 11 to 14 eject ink of C (cyan), M (magenta), Y (yellow), and K (black), respectively.

[0021] 2 is a diagram showing a detailed configuration of the line head 11. Here, the configuration of the line head 11 out of the four line heads 11 to 14 will be described, but the remaining line heads 12 to 14 have the same configuration.

[0022] The line head 11 includes six inkjet heads 11a, 11b, 11c, 11d, 11e, and 11f. In this embodiment, the inkjet heads 11a, 11b, 11c, 11d, 11e, and 11f correspond to the ejection units of the present invention.

[0023] Each of the inkjet heads 11a to 11f has a plurality of nozzles that eject ink, and the nozzles are arranged in a vertical direction. Note that the nozzle arrangement direction refers to the direction in which the nozzle row is longest, for example, when the nozzles are arranged two-dimensionally.

[0024] The six inkjet heads 11a, 11b, 11c, 11d, 11e, and 11f are provided inside a housing 11g, and the ink ejection surface of each of the inkjet heads 11a to 11f is exposed to the outside of the housing 11g. The ink ejection surface is a surface on which the ink ejection openings of the nozzles are arranged, and in this embodiment, the ink ejection surface is provided in a vertical direction.

[0025] The line head 11 also has a first head row consisting of three inkjet heads 11a, 11c, and 11e, and a second head row consisting of three inkjet heads 11b, 11d, and 11f. The first head row and the second head row are arranged adjacent to each other at different positions in the transport direction of the printing medium P.

[0026] The three inkjet heads 11a, 11c, and 11e of the first head row are arranged at a predetermined interval in the vertical direction, and the three inkjet heads 11b, 11d, and 11f of the second head row are arranged at a predetermined interval in the vertical direction.

[0027] As shown in FIG. 2, the inkjet heads 11a, 11c, and 11e of the first head row and the inkjet heads 11b, 11d, and 11f of the second head row are arranged in a staggered manner so as to be at different positions in the vertical direction.

[0028] For example, when printing a straight line extending in the vertical direction using the line head 11, the straight line is printed by ejecting ink from the first head row and the second head row at different timings.

[0029] In this embodiment, the six inkjet heads 11a to 11f included in the inkjet head 11 are divided into three blocks B1, B2, and B3 based on their vertical positions. Block B1 is the block to which the lower inkjet heads 11a and 11b belong. Block B2 is the block to which the middle inkjet heads 11c and 11d belong. Block B3 is the block to which the upper inkjet heads 11e and 11f belong.

[0030] The inkjet head 11a and the inkjet head 11b of the block B1 are connected to a common ink supply pipe 15a and a common ink discharge pipe 15b.

[0031] The ink supply pipe 15a supplies ink whose temperature has been adjusted in a first ink unit 20 (described later) to the inkjet head 11a and the inkjet head 11b in the block B1.

[0032] The ink discharge pipe 15b discharges ink that has not been ejected from the inkjet heads 11a and 11b of the block B1 and remains therein, and returns the discharged ink to the first ink unit 20.

[0033] That is, ink circulates between the inkjet head 11a and the first ink unit 20 and between the inkjet head 11b and the first ink unit 20 via the ink supply pipe 15a and the ink discharge pipe 15b.

[0034] A common ink supply pipe 15c and a common ink discharge pipe 15d are connected to the inkjet head 11c and the inkjet head 11d of the block B2.

[0035] The ink supply pipe 15c supplies ink whose temperature has been adjusted in a second ink unit 30 (described later) to the inkjet head 11c and the inkjet head 11d in the block B2.

[0036] The ink discharge pipe 15d discharges ink that has not been ejected from the inkjet head 11c and the inkjet head 11d in the block B2 and remains therein, and returns the discharged ink to the second ink unit 30.

[0037] That is, ink circulates between the inkjet head 11c and the second ink unit 30 and between the inkjet head 11d and the second ink unit 30 via the ink supply pipe 15c and the ink discharge pipe 15d.

[0038] A common ink supply pipe 15e and a common ink discharge pipe 15f are connected to the inkjet head 11e and the inkjet head 11f of the block B3.

[0039] The ink supply pipe 15e supplies ink whose temperature has been adjusted in a third ink unit 40 (described later) to the inkjet head 11e and the inkjet head 11f in the block B3.

[0040] The ink discharge pipe 15f discharges ink that has not been ejected from the inkjet head 11e and the inkjet head 11f in the block B3 and remains therein, and returns the discharged ink to the third ink unit 40.

[0041] That is, ink circulates between the ink-jet head 11e and the third ink unit 40, and between the ink-jet head 11f and the third ink unit 40 via the ink supply pipe 15e and the ink discharge pipe 15f.

[0042] In addition, head temperature sensors HS1 and HS2 are provided in the ink supply pipe 15a and ink discharge pipe 15b near the inkjet head 11a, respectively. The head temperature sensors HS1 and HS2 detect the temperature of the ink near the inkjet head 11a, thereby detecting the temperature of the inkjet head 11a.

[0043] Furthermore, head temperature sensors HS3 and HS4 are provided in the ink supply pipe 15a and ink discharge pipe 15b near the inkjet head 11b, respectively. The head temperature sensors HS3 and HS4 detect the temperature of the ink near the inkjet head 11b, thereby detecting the temperature of the inkjet head 11b.

[0044] Furthermore, head temperature sensors HS5 and HS6 are provided in the ink supply pipe 15c and ink discharge pipe 15d near the inkjet head 11c, respectively. The head temperature sensors HS5 and HS6 detect the temperature of the ink near the inkjet head 11c, thereby detecting the temperature of the inkjet head 11c.

[0045] Furthermore, head temperature sensors HS7 and HS8 are provided in the ink supply pipe 15c and ink discharge pipe 15d near the inkjet head 11d, respectively. The head temperature sensors HS7 and HS8 detect the temperature of the ink near the inkjet head 11d, thereby detecting the temperature of the inkjet head 11d.

[0046] Furthermore, head temperature sensors HS9 and HS10 are provided in the ink supply pipe 15e and ink discharge pipe 15f near the inkjet head 11e, respectively. The head temperature sensors HS9 and HS10 detect the temperature of the ink near the inkjet head 11e, thereby detecting the temperature of the inkjet head 11e.

[0047] In addition, head temperature sensors HS11 and HS12 are provided in the ink supply pipe 15e and the ink discharge pipe 15f near the inkjet head 11f, respectively. The head temperature sensors HS11 and HS12 detect the temperature of the ink near the inkjet head 11f, thereby detecting the temperature of the ink in the inkjet head 11f.

[0048] FIG. 3 is a diagram showing the configuration of the first ink unit 20, the second ink unit 30, and the third ink unit 40 described above.

[0049] The first to third ink units 20 to 40 supply ink to the blocks B1 to B3 of the line head 11, and control the temperature of the ink supplied. Specifically, the first ink unit 20 has an ink circulation mechanism 21, and the ink circulation mechanism 21 is provided with a temperature adjustment mechanism 22. In this embodiment, the temperature adjustment mechanism 22, and the temperature adjustment mechanisms 32 and 42 described below correspond to the temperature adjustment unit of the present invention.

[0050] As described above, the ink circulation mechanism 21 supplies ink to the inkjet heads 11a and 11b in the block B1 via the ink supply pipe 15a, and collects ink discharged from the inkjet heads 11a and 11b in the block B1 via the ink discharge pipe 15b. The ink circulation mechanism 21 has pipes and pumps for circulating the ink as described above, and also includes an ink tank in which new ink is stored, and supplies new ink from the ink tank.

[0051] The ink circulation mechanism 21 is provided with a temperature adjustment mechanism 22. The temperature adjustment mechanism 22 is a mechanism that adjusts the temperature of the ink circulating in the ink circulation mechanism 21, and specifically includes a heater that is pulse width modulation controlled (PWM controlled). The control unit 50 modulates the pulse width to control the temperature of the heater. The control unit 50 controls the temperature of the heater, thereby adjusting the temperature of the ink circulating in the ink circulation mechanism 21.

[0052] In this embodiment, as described above, one ink unit (temperature control mechanism) is provided for two inkjet heads, which makes it possible to reduce power consumption compared to providing an ink unit (temperature control mechanism) for each inkjet head. Note that, although in this embodiment, one ink unit (temperature control mechanism) is provided for two inkjet heads as described above, the number of inkjets per ink unit (temperature control mechanism) is not limited to two, and may be any number as long as it is less than the total number of inkjet units included in the line head (six in this embodiment).

[0053] The configurations of the ink circulation mechanism 31 of the second ink unit 30 and the ink circulation mechanism 41 of the third ink unit 40 are similar to that of the ink circulation mechanism 21 of the first ink unit 20. In addition, the configurations of the temperature adjustment mechanism 32 of the second ink unit 30 and the temperature adjustment mechanism 42 of the third ink unit 40 are similar to that of the temperature adjustment mechanism 22 of the first ink unit 20.

[0054] Furthermore, ink temperature sensors 20a and 20b are provided on the ink supply pipe 15a and ink discharge pipe 15b in the first ink unit 20, respectively. The ink temperature sensors 20a and 20b detect the temperature of the ink in the first ink unit 20, thereby detecting the temperature of the ink supplied to the inkjet head 11a and inkjet head 11b. In this embodiment, the ink temperatures detected by the ink temperature sensors 20a and 20b and the maximum and minimum temperatures detected by the head temperature sensors HS1, HS2, HS3, and HS4 described above are detected as the ink temperature of block B1. In this embodiment, the maximum and minimum values ​​are detected as the ink temperature of block B1 as described above, but an average value may also be detected.

[0055] Furthermore, ink temperature sensors 30a and 30b are provided in the ink supply pipe 15c and ink discharge pipe 15d in the second ink unit 30, respectively. The ink temperature sensors 30a and 30b detect the temperature of the ink in the second ink unit 30, thereby detecting the temperature of the ink supplied to the inkjet heads 11c and 11d. In this embodiment, the ink temperatures detected by the ink temperature sensors 30a and 30b and the maximum and minimum temperatures detected by the head temperature sensors HS5, HS6, HS7, and HS8 described above are detected as the ink temperature of block B2. As described above, the maximum and minimum values ​​are detected as the ink temperature of block B2, but an average value may also be detected.

[0056] Furthermore, ink temperature sensors 40a and 40b are provided on the ink supply pipe 15e and ink discharge pipe 15f in the third ink unit 40, respectively. The ink temperature sensors 40a and 40b detect the temperature of the ink in the third ink unit 40, thereby detecting the temperature of the ink supplied to the inkjet heads 11e and 11f. In this embodiment, the ink temperatures detected by the ink temperature sensors 40a and 40b and the maximum and minimum temperatures detected by the head temperature sensors HS9, HS10, HS11, and HS12 described above are detected as the ink temperature of block B3. As described above, the maximum and minimum values ​​are detected as the ink temperature of block B3, but an average value may also be detected.

[0057] In this embodiment, the control unit 50 controls the heating conditions for the ink supplied to each of blocks B1 to B3 based on the ink temperatures of each of blocks B1, B2, and B3. Note that, hereinafter, the ink temperatures of blocks B1 to B3 used during heating control are the minimum temperatures detected by ink temperature sensors 40a and 40b and head temperature sensors HS9, HS10, HS11, and HS12. However, the average value of the temperatures detected by these sensors may also be used.

[0058] 4 is a block diagram showing the configuration of the control system of the inkjet printing apparatus 1 of this embodiment. The control unit 50 includes a CPU (Central Processing Unit) and storage media such as semiconductor memory and a hard disk, and controls the entire inkjet printing apparatus 1. The control unit 50 controls the operation of each part of the inkjet printing apparatus 1 by executing a control program stored in advance in a storage medium such as semiconductor memory or a hard disk, and by operating electric circuits.

[0059] In particular, the control unit 50 of this embodiment controls the temperature adjustment mechanisms 22, 32, and 42 of the first to third ink units 20, 30, and 40 to independently control the temperature of ink supplied to each of blocks B1 to B3. Specifically, the control unit 50 sets lower heating conditions for ink supplied to blocks arranged vertically above than for blocks arranged vertically below. That is, in this embodiment, the lowest heating conditions are set for ink supplied to block B1, the next lowest heating conditions are set for ink supplied to block B2, and the highest heating conditions are set for ink supplied to block B3.

[0060] In this embodiment, the temperature adjustment mechanisms 22, 32, and 42 are equipped with PWM-controlled heaters, and the control unit 50 therefore controls the temperature by changing the duty ratio of the pulse signal supplied to the temperature adjustment mechanisms 22, 32, and 42. That is, the control unit 50 of this embodiment changes the heating conditions for the ink supplied to each of the blocks B1 to B3 by changing the duty ratio of the pulse signal.

[0061] The reason for changing the heating conditions according to the vertical position of each of the blocks B1 to B3 is that heating a block located vertically below heats the air around that block, and the heated air rises inside the housing 11g due to the chimney effect. This rising heated air then heats the blocks located vertically above. In this way, the blocks located vertically above are also heated by the air rising from below, so the desired ink temperature can be obtained even if the heating conditions are set low.

[0062] In this way, in this embodiment, temperature control is performed so that the heating conditions for ink supplied to blocks located vertically above are lower than those for blocks located vertically below, thereby reducing power consumption and enabling efficient temperature control.

[0063] An example of temperature control by the control unit 50 will be described below with reference to the graph shown in Fig. 5A and the table shown in Fig. 5B. Fig. 5A is a diagram showing changes in ink temperature in each of the blocks B1 to B3, and Fig. 5B is a table showing the duty ratios of pulse signals output to the temperature adjustment mechanisms 22 to 42 corresponding to each of the blocks B1 to B3. Note that the ambient temperature of the location where the inkjet printing apparatus 1 is installed is 25°C or below, and temperature control for maintaining the ink temperature at 30°C to 35°C will be described here.

[0064] First, when the inkjet printing apparatus 1 is started up, the ink temperature in blocks B1 to B3 is below 25°C, so the control unit 50 heats the heaters of the temperature adjustment mechanisms 22, 32, and 42 corresponding to all of blocks B1 to B3. At this time, as shown in Fig. 5B, the control unit 50 sets the duty ratio of the pulse signal output to the temperature adjustment mechanism 22 of block B1 to 100%, the duty ratio of the pulse signal output to the temperature adjustment mechanism 32 of block B2 to 50%, and the duty ratio of the pulse signal output to the temperature adjustment mechanism 42 of block B3 to 25%.

[0065] Then, at time t1 when the ink temperature in block B1 reaches 35°C as shown in Fig. 5A, the control unit 50 stops heating by the temperature adjustment mechanism 22 of block B1 as shown in Fig. 5B. Then, if the ink temperatures in blocks B2 and B3 are lower than 35°C at time t1 as shown in Fig. 5A, the control unit 50 sets the duty ratio of the pulse signal output to the temperature adjustment mechanism 32 of block B2 to 100% and the duty ratio of the pulse signal output to the temperature adjustment mechanism 42 of block B3 to 50%, as shown in Fig. 5B.

[0066] Thereafter, at time t1 when the ink temperature in block B2 reaches 35°C as shown in Fig. 5A, the control unit 50 stops heating by the temperature adjustment mechanism 32 of block B2 as shown in Fig. 5B. Then, if the ink temperature in block B3 is lower than 35°C at time t2 as shown in Fig. 5A, the control unit 50 sets the duty ratio of the pulse signal output to the temperature adjustment mechanism 42 of block B3 to 100%, as shown in Fig. 5B.

[0067] Thereafter, at time t3 when the ink temperature in block B3 reaches 35° C. as shown in FIG. 5A, the control unit 50 stops heating of block B3 by the temperature adjustment mechanism 42 as shown in FIG. 5B.

[0068] As described above, when the heating is controlled so that the blocks are heated sequentially from the blocks located vertically below to the blocks located vertically above, the heating effect due to the chimney effect can be obtained more efficiently, and the ink temperatures of the three blocks B1 to B3 can reach the desired range in a shorter time.

[0069] Then, as described above, once the ink temperature in all blocks B1 to B3 reaches 35°C, if the ink temperature in any block falls below 30°C, the control unit 50 sets the duty ratio of the pulse signal output to the temperature control mechanism of that block to an arbitrary value and heats that block.

[0070] Furthermore, when the ink temperature of a plurality of blocks drops below 30°C, the control unit 50 outputs pulse signals to the temperature adjustment mechanisms of those plurality of blocks to heat them, but in this case, the duty ratio of the pulse signal output to the temperature adjustment mechanism of the vertically lowest block among the plurality of blocks is set to an arbitrary maximum value, and when heating the block one level above the vertically lowest block, the duty ratio of the pulse signal output to the temperature adjustment mechanism of the block one level above is set to half of the arbitrary maximum value. Furthermore, when heating the block two levels above the vertically lowest block, the duty ratio of the pulse signal output to the temperature adjustment mechanism of the block two levels above is set to half the duty ratio of the pulse signal output to the temperature adjustment mechanism of the block one level above.

[0071] By changing the duty ratio of the pulse signal in this way, no matter what combination of the three blocks B1 to B3 is used to control heating, the maximum power consumption will not exceed 200% of that of a single block, thereby reducing power consumption.

[0072] In the above embodiment, we have explained the control method of the temperature adjustment mechanisms 22, 32, and 42 when heating the ink, but there are cases where the temperature of the inkjet head becomes high, for example, when the printing rate of a certain inkjet head is very high, and this causes the ink temperature to exceed the appropriate temperature. In such cases, a cooling process is required to lower the ink temperature.

[0073] Next, the temperature control when performing such a cooling process will be described. First, the cooling mechanism for performing the cooling process will be described.

[0074] As shown in FIG. 6, the cooling mechanism includes an upper head cooling fan 60 and a lower head cooling fan 61 for each of the line heads 11 to 14. The upper head cooling fan 60 and the lower head cooling fan 61 rotate based on a control signal from the control unit 50, generating cooling air that flows vertically from bottom to top. This cooling air cools the inkjet heads 11a to 11f, lowering the ink temperature. In this embodiment, the upper head cooling fan 60 and the lower head cooling fan 61 are PWM controlled and controlled in three stages: off, strong ON, and weak ON. Strong ON is controlled to have a higher rotation speed than weak ON.

[0075] Furthermore, the temperature adjustment mechanisms 22, 32, and 42 each include an ink cooling fan (not shown) as a cooling mechanism. The ink cooling fan rotates based on a control signal from the control unit 50, and cools the ink circulating through the ink circulation mechanisms 21, 31, and 41, respectively. The ink cooling fans of the temperature adjustment mechanisms 22, 32, and 42 are also PWM controlled and controlled in four stages: off, strong ON, medium ON, and weak ON. Strong ON is controlled to have a higher rotation speed than medium ON, and medium ON is controlled to have a higher rotation speed than weak ON.

[0076] Next, a control method for the upper head cooling fan 60, the lower head cooling fan 61, and the ink cooling fans of the temperature adjustment mechanisms 22, 32, and 42 described above during cooling processing will be described. FIG. 7 is a table showing an example of a control method for the upper head cooling fan 60, the lower head cooling fan 61, and the ink cooling fans of the temperature adjustment mechanisms 22, 32, and 42. Note that FIG. 7 shows a control method when rapid cooling is desired (for example, when the rate of increase in ink temperature is high). During normal cooling rather than rapid cooling, the control of the ink cooling fans of the temperature adjustment mechanisms 22, 32, and 42 is similar to the control shown in FIG. 7, but both the upper head cooling fan 60 and the lower head cooling fan 61 are controlled to weak ON.

[0077] The control method shown in Fig. 7 will now be described in detail. Note that, hereinafter, the ink temperatures of blocks B1 to B3 used during cooling control are the maximum temperatures detected by ink temperature sensors 40a and 40b and head temperature sensors HS9, HS10, HS11, and HS12. However, the average value of the temperatures detected by these sensors may also be used.

[0078] When the ink temperature in block B1 exceeds a preset threshold, the control unit 50 turns on the ink cooling fan of the temperature control mechanism 22 of the first ink unit 20 at high power and controls the lower head cooling fan 61 close to block B1 to high power.

[0079] In addition, when the ink temperature of block B2 becomes equal to or higher than a preset threshold, the control unit 50 turns on the ink cooling fan of the temperature control mechanism 32 of the second ink unit 30 and controls both the lower head cooling fan 61 and the upper head cooling fan 60 to weak ON.

[0080] In addition, when the ink temperature in block B3 exceeds a preset threshold, the control unit 50 turns on the ink cooling fan of the temperature control mechanism 42 of the third ink unit 40 and controls the upper head cooling fan 60 close to block B3 to high ON.

[0081] Furthermore, when the ink temperatures of blocks B1 and B2 reach or exceed a preset threshold, the control unit 50 controls the ink cooling fan of the temperature adjustment mechanism 22 of the first ink unit 20 to medium ON and controls the ink cooling fan of the temperature adjustment mechanism 32 of the second ink unit 30 to high ON. The control unit 50 also controls the lower head cooling fan 61, which is closer to block B1, to high ON and controls the upper head cooling fan 60 to low ON. The reason for increasing the rotation speed of the ink cooling fan of the temperature adjustment mechanism 32 of the second ink unit 30 to be higher than that of the ink cooling fan of the temperature adjustment mechanism 22 of the first ink unit 20, as described above, is that block B2 is more likely to become hotter than block B1 due to the chimney effect, and the cooled air flows vertically downward, so block B1 is cooled by the cooling air cooled by block B2.

[0082] Furthermore, when the ink temperatures of blocks B1 and B3 reach or exceed a preset threshold, the control unit 50 controls the ink cooling fan of the temperature adjustment mechanism 22 of the first ink unit 20 to medium ON, and controls the ink cooling fan of the temperature adjustment mechanism 42 of the third ink unit 40 to high ON. The control unit 50 also controls both the lower head cooling fan 61 and the upper head cooling fan 60 to high ON. The reason for increasing the rotation speed of the ink cooling fan of the temperature adjustment mechanism 42 of the third ink unit 40 to be higher than that of the ink cooling fan of the temperature adjustment mechanism 22 of the first ink unit 20, thereby increasing the cooling rate, is as described above.

[0083] Furthermore, when the ink temperatures of blocks B2 and B3 reach or exceed a preset threshold, the control unit 50 controls the ink cooling fan of the temperature adjustment mechanism 32 of the second ink unit 30 to medium ON and controls the ink cooling fan of the temperature adjustment mechanism 42 of the third ink unit 40 to high ON. The control unit 50 also controls the lower head cooling fan 61 to low ON and controls the upper head cooling fan 60 to high ON. The reason for increasing the rotation speed of the ink cooling fan of the temperature adjustment mechanism 42 of the third ink unit 40 to be higher than that of the ink cooling fan of the temperature adjustment mechanism 32 of the second ink unit 30, thereby increasing the cooling rate, is as described above.

[0084] Furthermore, when the ink temperatures of all of the blocks B1 to B3 are equal to or higher than a preset threshold, the control unit 50 controls the ink cooling fan of the temperature adjustment mechanism 22 of the first ink unit 20 to low ON, controls the ink cooling fan of the temperature adjustment mechanism 32 of the second ink unit 30 to medium ON, and controls the ink cooling fan of the temperature adjustment mechanism 42 of the third ink unit 40 to high ON. The control unit 50 also controls both the lower head cooling fan 61 and the upper head cooling fan 60 to high ON. As described above, the rotation speed of the ink cooling fan of the temperature adjustment mechanism 32 of the second ink unit 30 is set higher than that of the ink cooling fan of the temperature adjustment mechanism 22 of the first ink unit 20, and the rotation speed of the ink cooling fan of the temperature adjustment mechanism 42 of the third ink unit 40 is set higher than that of the ink cooling fan of the temperature adjustment mechanism 32 of the second ink unit 30, and the cooling rate is increased for blocks located vertically higher, as described above.

[0085] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiments. For example, all of the components shown in the embodiments can be appropriately combined. Naturally, various modifications and applications are possible without departing from the spirit of the invention.

[0086] The present invention further discloses the following supplementary notes. (Addendum)

[0087] In the temperature control device of the present invention, a temperature adjustment section can be provided for each of a plurality of discharge sections.

[0088] Furthermore, in the temperature control device of the present invention, the control unit can control the temperature adjustment unit so that, of the multiple ejection units included in the head unit, the ejection units located vertically downward are heated sequentially toward the ejection units located vertically upward. [Explanation of symbols]

[0089] 1. Inkjet printing device 2 Transport unit 3 Support stand 4 Conveyor belt section 10 Head Unit 11,12,13,14 Line Head 11a, 11b, 11c, 11d, 11e, 11f Inkjet head 11g housing 15a, 15c, 15e Ink supply pipes 15b, 15d, 15f Ink discharge pipe 20 First ink unit 20a, 20b, 30a, 30b, 40a, 40b Ink temperature sensor 21, 31, 41 Ink circulation mechanism 22,32,42 Temperature control mechanism 30 Second ink unit 40 Third ink unit 50 control section 60 Upper head cooling fan 61 Lower head cooling fan B1, B2, B3 Blocks HS1~HS12 head temperature sensor P Print media Ps printing side

Claims

1. a temperature adjusting unit that adjusts the temperature of liquid supplied to a head unit having a housing that houses a plurality of ejection units that eject droplets, the ejection units being arranged in a vertical direction; a control unit that controls the temperature adjustment unit, A temperature control device in which the control unit controls the temperature adjustment unit so that the heating conditions for the liquid supplied to a discharge unit located vertically above it are lower or the cooling conditions are stronger than those of a discharge unit located vertically below it.

2. The temperature control device according to claim 1 , wherein the temperature control unit is provided for each of the plurality of discharge units.

3. 3. A temperature control device as described in claim 1 or 2, wherein the control unit controls the temperature adjustment unit so that, of the multiple ejection units included in the head unit, the ejection units are heated sequentially from the ejection units located vertically below to the ejection units located vertically above.

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