Inkjet Printing Device

Abstract

To provide an inkjet printing device that can suppress uneven drying even in performing printing at an extremely low speed.SOLUTION: A control part 25, when a conveying speed of a continuous paper WP is higher than a predetermined threshold, brings a shutter 65 into an open state, and when the conveying speed of the continuous paper WP is below the predetermined threshold, brings the shutter 65 into a close state. Therefore, when the conveying speed is higher than the predetermined threshold, the continuous paper is dried at heat quantities for drying and when the conveying speed is below the predetermined threshold, the continuous paper is dried at minute heat quantities that are smaller in heat quantity than the heat quantities for drying. This can prevent ink discharged to the continuous paper WP from is being overdried even when performing printing at an extremely low speed, which can suppress uneven drying of the ink discharged to the continuous paper WP.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an inkjet printing apparatus that performs printing by ejecting ink onto a print medium, and more particularly to a technique for drying ink ejected onto a print medium. [Background technology]

[0002] Conventionally, this type of device includes a conveying unit, an inkjet head, and a drying unit (see, for example, Patent Document 1).

[0003] The transport section in this device transports the continuous paper. The inkjet head prints by ejecting ink onto the continuous paper being transported by the transport section. The drying section dries the ink ejected onto the continuous paper downstream of the inkjet head. The drying section includes, for example, a carbon heater and a shutter. The carbon heater applies heat to the ink ejected onto the continuous paper. The shutter is opened when heat is being applied from the carbon heater and is closed when heat is not being applied. The shutter remains open while the printing process is being performed and is closed only when an abnormality occurs in the device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-170573 A (paragraph number 0024) Summary of the Invention [Problem to be solved by the invention]

[0005] However, the conventional example having such a configuration has the following problems. That is, in the conventional device, when the process is delayed in the downstream post-processing device, the device may request the process to be temporarily stopped. In this case, when the inkjet printing method is adopted, the conveyance is not completely stopped, but, for example, the conveyance speed is decelerated from the conveyance speed specified in the printing conditions and conveyed at a constant very low speed to continue printing, and when the post-processing device cancels the request for temporary suspension, the conveyance speed is accelerated to the conveyance speed specified in the printing conditions. In this way, printing is performed continuously, but the conveyance speed of the drying section is not 0, so the shutter remains open. As a result, the ink ejected on the continuous paper becomes overdried, and there is a problem that the ink drying difference occurs between the area before the deceleration, resulting in uneven drying of the ink.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide an inkjet printing apparatus that can suppress uneven drying of ink even when printing at extremely low speeds. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention has the following configuration. That is, the invention described in claim 1 provides an inkjet printing device that ejects ink onto a printing medium to perform printing, the inkjet printing device comprising: a transport unit that transports the printing medium in a predetermined transport direction; a print head that ejects ink onto the printing medium being transported by the transport unit to perform printing; a heat source that generates heat for drying the ink ejected onto the printing medium downstream of the print head and a shutter that can be switched between an open state and a closed state, the drying unit applying, in the open state, a drying heat amount for drying the ink ejected onto the printing medium by heat from the heat source, and applying, in the closed state, a minute amount of heat less than the drying heat amount from the heat source; and a control unit that sets the shutter to the open state when the transport speed of the printing medium by the transport unit is faster than a predetermined threshold value, and sets the shutter to the closed state when the transport speed of the printing medium by the transport unit becomes equal to or lower than the predetermined threshold value. The drying unit further includes an opening / closing speed adjustment unit that adjusts the opening / closing speed of the shutter, and when the transport unit starts to decelerate from a predetermined transport speed, the control unit brings the shutter into the closed state at a low speed via the opening / closing speed adjustment unit when the transport speed reaches a threshold value, and when the transport unit starts to accelerate from an extremely low transport speed, the control unit brings the shutter into the open state at a low speed via the opening / closing speed adjustment unit when the transport speed reaches the threshold value.It is characterized by the above.

[0008] [Function and Effect] According to the invention described in claim 1, the control unit opens the shutter when the speed at which the print medium is transported by the transport unit is faster than a predetermined threshold, and closes the shutter when the speed at which the print medium is transported by the transport unit is equal to or lower than the predetermined threshold. Therefore, when the transport speed is faster than the predetermined threshold, drying is performed by the amount of drying heat, and when the transport speed is slower than the predetermined threshold, drying is performed by a minute amount of heat that is less than the amount of drying heat. Therefore, even when printing is performed at a very low speed, the ink ejected onto the print medium does not dry excessively, and uneven drying of the ink ejected onto the print medium can be suppressed.

[0010] When the transport unit starts to decelerate from a predetermined transport speed, the control unit closes the shutter at a low speed via the opening / closing speed adjustment unit when the transport speed reaches a threshold value. Also, when the transport unit starts to accelerate from an extremely slow transport speed, the control unit opens the shutter at a low speed via the opening / closing speed adjustment unit when the transport speed reaches the threshold value. Therefore, while the transport speed is changing, the amount of heat applied to the print medium from the drying unit can be gradually decreased or increased. Therefore, uneven drying of the ink while the transport speed is changing can also be suppressed.

[0011] In the present invention, it is preferable that the drying unit further includes a blowing mechanism that sends the heat generated from the heat source toward the print medium, and that in the closed state, the small amount of heat is applied by the blowing mechanism. (Claim 5) .

[0012] By blowing air from the blower mechanism of the drying section, a minute amount of heat, which is less than the amount of heat required for drying, can be applied to the print medium. Since there is no need to provide a separate heat source, costs can be reduced.

[0013] Furthermore, in the present invention, it is preferable that the drying section further includes an adjustment section which adjusts the amount of heat generated by the heat source, and the control section further includes a memory section which pre-stores a first formula in the closed state and a second formula in the open state which represent the amount of heat generated by the heat source, the amount of heat generated being variable so that it is higher the faster the conveying speed by the conveying section and lower the slower the conveying speed, and the control section operates the adjustment section so as to connect the first formula and the second formula when the shutter is brought to the closed state at a low speed and when the shutter is brought to the open state at a low speed (Claim 4).

[0014] The control unit operates the adjustment unit to connect the first formula and the second formula in the storage unit when the shutter is closed at a low speed and when the shutter is opened at a low speed. This allows the amount of heat generated by the heat source to be smoothly increased or decreased. Therefore, uneven drying of the ink when the shutter is opened and closed at a low speed can be further suppressed.

[0015] The invention described in claim 2 is an inkjet printing device that prints by ejecting ink onto a print medium, the inkjet printing device comprising: a transport unit that transports the print medium in a predetermined transport direction; a print head that prints by ejecting ink onto the print medium transported by the transport unit; and a heat source that generates heat for drying the ink ejected onto the print medium downstream of the print head, the shutter being switched between an open state and a closed state, the drying unit applying a drying heat amount for drying the ink ejected onto the print medium by heat from the heat source in the open state and applying a minute amount of heat less than the drying heat amount in the closed state; and a control unit that sets the shutter to the open state when the transport speed of the print medium by the transport unit is faster than a predetermined threshold value, and sets the shutter to the closed state when the transport speed of the print medium by the transport unit is equal to or lower than the predetermined threshold value. The control unit decelerates the conveyance of the conveying unit to an extremely slow speed when a request for temporary suspension is received from a post-processing device disposed downstream of the drying unit. It is characterized by the above.

[0016] When a request for temporary suspension is received from the post-processing device, the control unit decelerates the conveying speed of the conveying unit to an extremely slow speed, thereby maintaining the print quality when the conveying speed is returned to normal while responding to the request from the post-processing device.

[0017] The invention described in claim 3 is an inkjet printing device that prints by ejecting ink onto a print medium, the inkjet printing device comprising: a transport unit that transports the print medium in a predetermined transport direction; a print head that prints by ejecting ink onto the print medium transported by the transport unit; and a heat source that generates heat for drying the ink ejected onto the print medium downstream of the print head, the shutter being switched between an open state and a closed state, the drying unit applying a drying heat amount for drying the ink ejected onto the print medium by heat from the heat source in the open state and applying a minute amount of heat less than the drying heat amount in the closed state; and a control unit that sets the shutter to the open state when the transport speed of the print medium by the transport unit is faster than a predetermined threshold value, and sets the shutter to the closed state when the transport speed of the print medium by the transport unit is equal to or lower than the predetermined threshold value. When a request for temporary suspension is released from a post-processing device disposed downstream of the drying unit, the control unit accelerates the transport by the transport unit and sets the transport speed to a predetermined transport speed that is faster than an extremely slow speed. It is characterized by the above.

[0018] When the request for temporary suspension from the post-processing device is released, the control unit accelerates the conveying speed of the conveying unit to a predetermined conveying speed that is faster than the extremely slow speed, thereby making it possible to return the printing throughput to the original level while responding to the request from the post-processing device. Effect of the Invention

[0019] In the inkjet printing device according to the present invention, the control unit opens the shutter when the speed at which the print medium is transported by the transport unit is faster than a predetermined threshold, and closes the shutter when the speed at which the print medium is transported by the transport unit is equal to or lower than the predetermined threshold. Therefore, when the transport speed is faster than the predetermined threshold, drying occurs using the amount of drying heat, and when the transport speed is slower than the predetermined threshold, drying occurs using a minute amount of heat that is less than the amount of drying heat. Therefore, even when printing is performed at an extremely slow speed, the ink ejected onto the print medium does not dry out too much, and uneven drying of the ink ejected onto the print medium can be suppressed. [Brief description of the drawings]

[0020] [Figure 1] 1 is a diagram illustrating the overall configuration of an inkjet printing system according to an embodiment. [Diagram 2] FIG. 4 is a vertical cross-sectional view showing the configuration of the drying unit, with the shutter being closed. [Diagram 3] FIG. 2 is a vertical cross-sectional view showing the configuration of the drying unit, with the shutter in an open state. [Figure 4] 4 is a time chart showing an example of temperature control. [Diagram 5] 13A is a time chart of the transport speed, and FIG. 13B is a time chart showing the shutter state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of an inkjet printing system according to an embodiment.

[0022] The inkjet printing system according to this embodiment includes a paper feed section 1, an inkjet printing device 3, and a paper discharge section 5. The paper feed section 1 holds a roll of continuous paper WP so that it can rotate about a horizontal axis. The paper feed section 1 unwinds and supplies the continuous paper WP to the inkjet printing device 3. The inkjet printing device 3 prints by ejecting ink onto the continuous paper WP to form an image, and sends the continuous paper WP to the paper discharge section 5. The paper discharge section 5 winds up the continuous paper WP printed by the inkjet printing device 3 around the horizontal axis.

[0023] Here, the direction in which the continuous paper WP is sent out and transported by the paper feed unit 1 is defined as the transport direction X. The horizontal direction perpendicular to the transport direction X is defined as the width direction Y. The above-mentioned paper feed unit 1 is disposed upstream of the inkjet printing device 5 in the transport direction X. The above-mentioned paper discharge unit 5 is disposed downstream of the inkjet printing device 5 in the transport direction X.

[0024] The above-mentioned continuous paper WP corresponds to the "print medium" in the present invention.

[0025] The inkjet printing device 3 has a drive roller 7 on the upstream side for taking in the continuous paper WP from the paper feed section 1. The continuous paper WP taken in from the paper feed section 1 by the drive roller 7 is sent in the transport direction X by a plurality of transport rollers 9 and transported toward the paper discharge section 5 on the downstream side. A drive roller 11 is disposed between the most downstream transport roller 9 and the paper discharge section 5. This drive roller 11 sends out the continuous paper WP transported on the transport rollers 9 toward the paper discharge section 5.

[0026] The inkjet printing device 3 includes a printing unit 13, a drying unit 15, and an inspection unit 17, which are arranged in this order from the upstream side along the transport direction X between the drive roller 7 and the drive roller 11. The printing unit 12 ejects ink onto the web paper WP to perform printing. The drying unit 15 dries the ink ejected onto the web paper WP by the printing unit 13. The inspection unit 17 inspects whether the portion printed on the web paper WP is stained or missing.

[0027] The printing unit 13 includes an inkjet head 19 having a number of nozzles that eject ink onto the web paper WP. Generally, a number of inkjet heads 19 are arranged along the transport direction X of the web paper WP. For example, a total of four printing units 13 are provided, each for black (K), cyan (C), magenta (M), and yellow (Y). However, in the following description, an example will be described in which the inkjet printing device 3 includes only one printing unit 13. The printing unit 13 has a length in the width direction Y of the web paper WP that exceeds the width of the web paper WP. The printing unit 13 includes enough inkjet heads 19 to print the printing area in the width direction of the web paper WP without moving in the width direction Y.

[0028] The inkjet printing device 3 includes a control unit 25 that comprehensively controls the drive rollers 7, 11, the printing unit 13, the drying unit 15, and the inspection unit 17. The control unit 25 is directly or indirectly connected to an adjustment unit 27, a storage unit 29, and a calculation unit 31. The control unit 25 is configured by, for example, a CPU and a memory.

[0029] The adjustment unit 27 is operated by the control unit 25 to adjust the amount of heat in the drying unit 15. The storage unit 29 stores in advance a first formula and a second formula required for controlling the power, which will be described later. The calculation unit 31 performs calculations required for the operation of the adjustment unit 27 based on the first formula and the second formula stored in the storage unit 29, the conveying speed of the web paper WP, and the state of the drying unit 15, which will be described later. The control unit 25 receives print data from a host computer (not shown) and operates the above-mentioned units to print on the web paper WP. The control unit 25 operates in conjunction with post-process devices, such as a cutting device and a bookbinding device, that are arranged downstream of this inkjet printing system. For this reason, the control unit 25 receives signals from the post-process devices.

[0030] The above-mentioned conveying roller 9 and driving rollers 7 and 11 correspond to the "conveying section" in the present invention.

[0031] Next, the drying section 15 will be described in detail with reference to Fig. 2 and Fig. 3. Fig. 2 is a vertical cross-sectional view showing the configuration of the drying section, illustrating a state in which the shutter is closed. Fig. 3 is a vertical cross-sectional view showing the configuration of the drying section, illustrating a state in which the shutter is open.

[0032] The drying section 15 is configured, for example, by a pair of two housings 41. The pair of housings 41 have the same internal configuration. The pair of housings 41 are fixed to each other by a connecting frame 43. The housings 41 include a fan 45, a heater 47, and a shutter unit 49.

[0033] The housing 41 has a cylindrical shape that penetrates in the vertical direction. The fan 45 is attached to the upper part of the housing 41. The fan 45 forms an air flow from the top to the bottom. The heater 47 is attached below the fan 45. The fan 45 supplies air heated by the heater 47 toward the web paper WP. The heater 47 is attached to the housing 41 with a gap between it and the inner wall of the housing 41, which corresponds to the upstream side and the downstream side of the conveying direction X. Air from the fan 45 flows downward through this gap. The heater 47 is, for example, a halogen heater. The halogen heater efficiently extracts infrared light emitted by a halogen bulb and generates heat for drying a substance. The infrared light emitted by the heater 47 is directed toward the upper surface of the shutter unit 49.

[0034] The shutter unit 49 includes, for example, a fixed frame 51, a movable frame 53, and an air cylinder 55. The fixed frame 51 has a plurality of openings penetrating therethrough, and is attached to the lower part of the housing 41. The movable frame 53 has a plurality of openings penetrating therethrough, similar to the fixed frame 51, and is attached to the upper surface of the fixed frame 51. The movable frame 53 is attached to the upper surface of the fixed frame 51 so as to be slidable along the conveying direction X. An operating shaft of an air cylinder 55 is connected to one part of the movable frame 53. The air cylinder 55 is attached, for example, to the side of the housing 41 in a position in which the operating shaft advances and retreats in the horizontal direction. The operating shaft of the air cylinder 55 is driven to advance and retreat by supplying and exhausting air. The advance and retreat speed of the operating shaft is adjusted by the flow rate of the supplied air.

[0035] One end of a supply pipe 57 is connected to the air cylinder 55. The other end of the supply pipe 57 is connected to an air supply source. The air supply source supplies air at a predetermined pressure. An on-off valve 59 is attached to a part of the supply pipe 57. A branch pipe 61 is attached to the supply pipe 57 so as to bypass the on-off valve 59. An on-off valve 63 is attached to the branch pipe 61. The branch pipe 61 has a smaller flow path cross-sectional area than the supply pipe 57. Therefore, the flow rate when air is circulated only through the branch pipe 61 is smaller than the flow rate when air is circulated only through the supply pipe 57. The on-off valves 59 and 61 are opened and closed by the control unit 25.

[0036] Note that illustrations and explanations of the mechanism related to the exhaust when the working shaft of the air cylinder 55 is extended and retracted are omitted. Therefore, for the sake of explanation, when air is supplied to the air cylinder 55, the working shaft extends, and this state is maintained even if the opening and closing valves 59, 63 are closed thereafter. In this state, when air is supplied to the air cylinder 55, the working shaft retracts. In other words, the explanation will be given assuming that each time air is supplied to the air cylinder 55, the working shaft switches between extending and retracting.

[0037] Here, it is assumed that the shutter unit 49 is normally in the state shown in FIG. 2. In other words, normally, the operating shaft of the air cylinder 55 is in a contracted state. In this state, the opening of the movable frame 53 and the opening of the fixed frame 51 do not match in the vertical direction, and the frame of the movable frame 53 closes the opening of the fixed frame 51. Here, if the fixed frame 51 and the movable frame 53 are collectively referred to as the shutter 65, the shutter 65 is in a closed state. When the control unit 25 extends the operating shaft of the air cylinder 55 in this state, the opening of the movable frame 53 matches the opening of the fixed frame 51 in the vertical direction, as shown in FIG. 3. In other words, the shutter 65 is in an open state.

[0038] The drying section 15 thus configured can adjust the amount of heat in two major steps, depending on whether the shutter 65 is open or closed. Moreover, the amount of heat can be switched between the two steps in a short time. To finely control the amount of heat, the power applied to the heater 47 can be adjusted.

[0039] First, a large amount of heat is called a "dry heat amount." This dry heat amount occurs when the shutter 65 is open. This state is shown in FIG. 3. Therefore, the heater 47 irradiates infrared light and the fan 45 blows heated air at the same time. This allows a large amount of dry heat to be imparted to the web paper WP.

[0040] Next, a heat quantity smaller than the drying heat quantity described above is called a "small heat quantity." This small heat quantity occurs when the shutter 65 is closed. This state is shown in Figure 2. Therefore, the heater 47 does not directly irradiate the web paper WP with infrared light, and only the fan 45 blows heated air.

[0041] The control unit 25 operates the shutter unit 49 to open and close the shutter 65. At that time, the control unit 25 operates the on-off valve 59 and / or the on-off valve 63. When the control unit 25 detects an abnormality in the drying unit 15 by a temperature sensor (not shown), the control unit 25 opens the on-off valve 59 and the on-off valve 63 at the same time. This causes the shutter 65 to close instantly. When the control unit 25 opens and closes the shutter 65 at a first speed, the control unit 25 opens both the on-off valve 59 and the on-off valve 63. When the control unit 25 opens and closes the shutter 65 at a second speed slower than the first speed, the control unit 25 opens only the on-off valve 59. When the control unit 25 opens and closes the shutter 65 at a third speed slower than the second speed, the control unit 25 opens only the on-off valve 64.

[0042] The heater 47 corresponds to the "heat source" in the present invention, the fan 45 corresponds to the "blowing mechanism" in the present invention, and the supply pipe 57, the branch pipe 61, and the opening / closing valves 59 and 63 correspond to the "opening / closing speed adjustment unit" in the present invention.

[0043] The control unit 25 operates the drying unit 15 via the adjustment unit 27. The adjustment unit 27 adjusts the power applied to the heater 47 in response to an instruction from the control unit 25. That is, the adjustment unit 27 adjusts the power applied to the heater 47 to adjust the amount of heat generated by the drying unit 17. Now, reference is made to Fig. 4. Fig. 4 is a time chart showing an example of temperature control.

[0044] During the printing process described below, the control unit 25 preferably opens and closes the shutter 65 and controls the amount of heat as follows.

[0045] The storage unit 29 prestores, for example, a first formula FM1 and a second formula FM2 as shown in FIG. 4. The first formula FM1 is a formula for calculating the power to be applied to the heater 47 when the shutter 65 is closed. The second formula FM2 is a formula for calculating the power to be applied to the heater 47 when the shutter 65 is open. The first formula FM1 and the second formula FM2 are each set so that the power applied increases according to the transport speed. Since the transport speed has a certain upper limit, for example, the first formula FM1 and the second formula FM2 are set so that the heater output is also constant according to the printing speed Vp.

[0046] For example, as shown below the conveying speed on the horizontal axis in Fig. 4, a case will be described in which the shutter 65 is in a closed state at a certain conveying speed, and the conveying speed is increased and the shutter 65 is opened. In this case, the calculation unit 31 calculates a line segment (solid line in Fig. 4) that connects the first formula FM1 and the second formula FM2 according to the state of the shutter 65, from the first formula FM1 and the second formula FM2. Then, the calculation unit 31 provides the control unit 25 with a heater output according to the line segment. The control unit 25 operates the adjustment unit 27 according to the determined heater output.

[0047] 4 shows a case where the shutter 65 is changed from a closed state to an open state as the transport speed increases. However, when the shutter 65 is changed from an open state to a closed state as the transport speed decreases, the slopes of the first formula FM1 and the second formula FM2 are in opposite directions, but the calculation unit 31 calculates a line segment connecting the second formula FM2 to the first formula FM1, and provides the control unit 25 with a heater output according to the line segment.

[0048] By controlling the amount of heat in this way, it is possible to smoothly increase or decrease the amount of heat generated by the drying section 15. Therefore, as described below, it is possible to further suppress uneven drying when the shutter 65 is opened or closed at a low speed.

[0049] Here, reference is made to Fig. 5. Fig. 5(a) is a time chart of the transport speed, and Fig. 5(b) is a time chart showing the shutter state.

[0050] In this embodiment, as shown in Fig. 5(a), the print process is performed on the continuous paper WP while the conveying speed is being manipulated. Then, at time t5, a pause request is made from a post-processing device (not shown), and at time t9, the pause request is released from the post-processing device (not shown). As printing conditions, the print speed Vp is set as the normal conveying speed, and the conveying speed when a pause request is made is set to an extremely low speed Ve that is extremely lower than the print speed Vp. Also, as a threshold value for switching between opening and closing the shutter 65, a conveying speed V1 is set that is lower than the print speed Vp and higher than the extremely low speed Ve.

[0051] The control unit 25 increases the transport speed toward the printing speed Vp from time t1 to time t3 in response to an instruction to start the printing process. Then, for example, from time t3 when the transport speed Vp is reached and becomes constant, the printing unit 13 is operated to perform printing according to the transport speed Vp. At this time, the control unit 25 performs an operation on the drying unit 15 according to the transport speed via the adjustment unit 27.

[0052] Specifically, at time t1 when acceleration toward the transport speed Vp begins, power supply to the heater 47 begins. At this time, since the shutter 65 is in a closed state, the calculation unit 31 calculates the power according to the transport speed based on the first formula FM1, and the control unit 25 operates the heater unit 49 via the adjustment unit 27 according to the result. At time t2 when the transport speed reaches the threshold value V1, the control unit 25 opens the shutter 65. At this time, the control unit 25 simultaneously opens the opening / closing valves 59 and 63 to open the shutter 65 at high speed. Then, the calculation unit 31 calculates the power according to the transport speed based on the second formula FM2, and the control unit 25 operates the heater unit 49 via the adjustment unit 27 according to the result. At this time, the drying heat is applied to the print medium WP from the drying unit 15.

[0053] The on-off valves 59 and 63 that were opened to operate the shutter 65 are then closed, but the shutter 65 remains open.

[0054] From time t3, the transport speed becomes constant at the printing speed Vp. After that, at time t5, for example, the post-processing device outputs a temporary stop request to the control unit 25 because the processing in the post-processing device is delayed.

[0055] In this case, the control unit 25 starts deceleration at a predetermined deceleration at time t6 after the predetermined time, and performs transport control so that the transport speed reaches the extremely low speed Ve at time t8. At this time, it is assumed that the transport speed reaches the threshold value V1 at time t7. Then, the control unit 25 closes the shutter 65. The control unit 25 opens only the opening / closing valve 63 and starts closing the shutter 65 at a low speed from time t7, and closes it completely at time t8. At this time, the calculation unit 31 obtains a line segment connecting the second formula FM2 and the first formula FM1, and obtains the power to be applied to the heater 47 based on this line segment. The control unit 25 operates the drying unit 15 via the adjustment unit 27 based on the obtained power. Also, although the shutter 65 of the drying unit 15 is in a closed state, a small amount of heat is applied from the drying unit 15 to the printing medium WP, and the ink ejected on the printing medium WP is dried.

[0056] From time t8 to time t10, the conveying speed is set to the extremely low speed Ve. Even during this time, the control unit 25 operates the printing unit 13 to continue the printing process, albeit at an extremely low speed. At this time, the drying unit 15 is operated via the adjustment unit 27 with the power calculated by the calculation unit 31 based on the first mathematical formula FM1.

[0057] During the printing process at the very low speed Ve, for example, at time t9, the control unit 25 receives a signal to cancel the pause request from the post-processing device. Then, the control unit 25 accelerates the conveying speed from the very low speed Ve to the printing speed Vp from time t10, a predetermined time later, and controls the conveying speed to become the printing speed Vp at time t12. At this time, it is assumed that the conveying speed reaches the threshold value V1 at time t11. Then, the control unit 25 opens the shutter 65 at time t11. In detail, the control unit 25 opens only the opening / closing valve 63 and starts opening the shutter 65 at a low speed from time t11, and opens it completely at time t12. As a result, the drying heat is applied to the web paper WP in the drying unit 12, and the ink ejected on the web paper WP is dried. At this time, the calculation unit 21 obtains a line segment connecting the first formula FM1 and the second formula FM2 as shown in FIG. 4. Then, the calculation unit 21 calculates the power to be applied to the heater 47 based on this line segment. The control unit 25 operates the adjustment unit 27 according to the power calculated in this manner.

[0058] When the transport speed reaches the printing speed Vp at time t12, the control unit 25 performs the printing process in the same manner as from time t3 to time t6.

[0059] If the printing process ends immediately before time t13, the control unit 25 starts decelerating from time t13, and controls the conveyance so that the conveying speed becomes 0 at time t15. At this time, at time t14 when the conveying speed reaches the threshold value V1, the control unit 25 opens the on-off valves 59, 63 and closes the shutter 65 at high speed. At time t15, the printing process ends and the conveying speed becomes 0, so for example, the control unit 25 operates the adjustment unit 27 to set the power applied to the heater 47 to 0 and the heat amount from the drying unit 15 to 0.

[0060] As described above, the printing process is performed on the web paper WP by operating each section.

[0061] According to this embodiment, the control unit 25 opens the shutter 65 when the transport speed of the web paper WP is faster than a predetermined threshold V1, and closes the shutter 65 when the transport speed of the web paper WP is equal to or lower than the predetermined threshold V1. Therefore, when the transport speed is faster than the predetermined threshold V1, drying is performed by the amount of drying heat, and when the transport speed is slower than the predetermined threshold V1, drying is performed by a minute amount of heat that is less than the amount of drying heat. Therefore, even when printing is performed at an extremely low speed Ve, the ink ejected onto the web paper WP does not dry excessively, and uneven drying of the ink ejected onto the web paper WP can be suppressed.

[0062] When the control unit 25 starts decelerating from a predetermined transport speed, it closes the shutter 65 at a low speed via the adjustment unit 27 when the transport speed reaches the threshold V1. When the control unit 25 starts accelerating from a very low transport speed, it opens the shutter 65 at a low speed via the adjustment unit 27 when the transport speed reaches the threshold V1. Therefore, while the transport speed is changing, it is possible to gradually decrease or increase the amount of heat applied to the continuous paper WP from the drying unit 15. Therefore, it is also possible to suppress uneven drying of the ink while the transport speed is changing.

[0063] The present invention is not limited to the above-described embodiment, but can be modified as follows.

[0064] (1) In the above-described embodiment, when the drying unit 15 closes the shutter 65, a small amount of heat is applied by air blown by the fan 45. However, the present invention is not limited to this configuration. For example, a high-power heater and a low-power heater may be housed in the housing 41, and when the shutter 65 is closed, only heat from the high-power heater is blocked and only heat from the low-power heater is applied, thereby switching between the dry heat amount and the small heat amount.

[0065] (2) In the above embodiment, when the transport speed varies, the opening and closing speed of the shutter 65 is set to a low speed. However, the present invention is not limited to this opening and closing operation. In other words, when the impact of uneven drying of the ink when the transport speed varies is small, the amount of heat may be adjusted by simply adjusting the power applied to the heater 47, and the shutter 65 may be opened and closed at a high speed.

[0066] (3) In the above-described embodiment, the supply pipe 57, the branch pipe 61, and the on-off valves 59 and 63 are used to change the opening and closing speed of the shutter 65. However, the present invention is not limited to this configuration. For example, the branch pipe 61 may be omitted, and an electro-pneumatic regulator may be provided in the supply pipe 57. In this configuration, the extension and contraction speed of the operating shaft in the air cylinder 55 can be changed by varying the air flow rate according to a signal input to the electro-pneumatic regulator. Also, instead of the air cylinder 55, another actuator such as a motor may be used as the drive source of the shutter 65.

[0067] (4) In the above embodiment, the printing process is started at a very low speed in response to a signal from the post-processing device. However, the present invention does not require a signal from the post-processing device. The present invention can also be applied to a case where the printing process is started at a very low speed Ve in order to allow time for recovery after some kind of failure has occurred within the device.

[0068] (5) In the above embodiment, the drying unit 15 is described as having two heaters 47. However, the present invention is not limited to this configuration. That is, the drying unit 15 may be configured to have at least one heater 47 or three or more heaters 47.

[0069] (6) In the above embodiment, continuous paper has been used as an example of the print medium, however, the present invention can also be applied to print media such as sheets of printing paper or plastic film. [Industrial Applicability]

[0070] As described above, the present invention is suitable for an inkjet printing apparatus that ejects ink onto a print medium to perform printing, and dries the ink ejected onto the print medium. [Explanation of symbols]

[0071] 1 … Paper feed section 3 … Inkjet printing device 5 … Paper ejection section WP: Continuous paper 7,11 ... Drive roller 13 … Printing unit 15 … Drying section 17 … Inspection Department 19 ... Inkjet head 25 ... Control section 27 … Adjustment section 29 … Storage section 31… Arithmetic unit 45 … Fan 47 ... Heater 49 ... Shutter unit 55 ... Air cylinder 57 … Supply pipe 61 ... Branch pipe 59,63 … Opening and closing valve 65...Shutter FM1: First formula FM2: Second formula

Claims

1. In an inkjet printing device that prints by ejecting ink onto a print medium, a transport unit that transports the print medium in a predetermined transport direction; a print head that prints by ejecting ink onto the print medium being transported by the transport unit; a drying section for drying ink ejected onto the printing medium downstream of the print head, the drying section comprising a heat source for generating heat for drying the ink ejected onto the printing medium, and a shutter that can be switched between an open state and a closed state, in which in the open state, heat from the heat source is used to apply a drying heat quantity for drying the ink ejected onto the printing medium, and in the closed state, heat from the heat source is applied at a minute amount of heat less than the drying heat quantity; a control unit that sets the shutter to the open state when the speed at which the print medium is transported by the transport unit is faster than a predetermined threshold, and sets the shutter to the closed state when the speed at which the print medium is transported by the transport unit is equal to or lower than the predetermined threshold; Equipped with The drying unit further includes an opening / closing speed adjusting unit that adjusts an opening / closing speed of the shutter, When the conveying unit starts to decelerate from a predetermined conveying speed, the control unit brings the shutter into the closed state at a low speed via the opening / closing speed adjustment unit when the conveying speed reaches a threshold value, and when the conveying unit starts to accelerate from an extremely low conveying speed, the control unit brings the shutter into the open state at a low speed via the opening / closing speed adjustment unit when the conveying speed reaches a threshold value.

1. An inkjet printing apparatus comprising:

2. In an inkjet printing device that prints by ejecting ink onto a print medium, a transport unit that transports the print medium in a predetermined transport direction; a print head that prints by ejecting ink onto the print medium being transported by the transport unit; a drying section for drying ink ejected onto the printing medium downstream of the print head, the drying section comprising a heat source for generating heat for drying the ink ejected onto the printing medium, and a shutter that can be switched between an open state and a closed state, in which in the open state, heat from the heat source is used to apply a drying heat quantity for drying the ink ejected onto the printing medium, and in the closed state, heat from the heat source is applied at a minute amount of heat less than the drying heat quantity; a control unit that sets the shutter to the open state when the speed at which the print medium is transported by the transport unit is faster than a predetermined threshold, and sets the shutter to the closed state when the speed at which the print medium is transported by the transport unit is equal to or lower than the predetermined threshold; Equipped with The control unit decelerates the conveyance of the conveying unit to an extremely slow speed when a request for temporary suspension is received from a post-processing device disposed downstream of the drying unit.

1. An inkjet printing apparatus comprising:

3. In an inkjet printing device that prints by ejecting ink onto a print medium, a transport unit that transports the print medium in a predetermined transport direction; a print head that prints by ejecting ink onto the print medium being transported by the transport unit; a drying section for drying ink ejected onto the printing medium downstream of the print head, the drying section comprising a heat source for generating heat for drying the ink ejected onto the printing medium, and a shutter that can be switched between an open state and a closed state, in which in the open state, heat from the heat source is used to apply a drying heat quantity for drying the ink ejected onto the printing medium, and in the closed state, heat from the heat source is applied at a minute amount of heat less than the drying heat quantity; a control unit that sets the shutter to the open state when the speed at which the print medium is transported by the transport unit is faster than a predetermined threshold, and sets the shutter to the closed state when the speed at which the print medium is transported by the transport unit is equal to or lower than the predetermined threshold; Equipped with The control unit, when a request for temporary suspension is lifted from a downstream process device located downstream of the drying unit, accelerates the transport by the transport unit and sets the transport speed to a predetermined transport speed that is faster than an extremely slow speed.

4. In the inkjet printing apparatus according to claim 1, The drying unit further includes an adjustment unit that adjusts the amount of heat generated by the heat source, The control unit further includes a storage unit configured to store in advance a first formula in the closed state and a second formula in the open state, the first formula representing the amount of heat generated by the heat source being variable so as to be higher as the conveying speed by the conveying unit is faster and lower as the conveying speed is slower; The control unit operates the adjustment unit so as to connect the first mathematical equation and the second mathematical equation when the shutter is brought to the closed state at a low speed and when the shutter is brought to the open state at a low speed.

5. In the inkjet printing apparatus according to any one of claims 1 to 3, The inkjet printing apparatus, characterized in that the drying section further includes a blowing mechanism that sends the heat generated from the heat source toward the print medium, and in the closed state, the small amount of heat is applied by the blowing mechanism.

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