Image forming apparatus and control method thereof

Abstract

To achieve an inkjet printing device that can change a conveying speed of print paper so that printing quality can be suppressed from deteriorating as much as possible when it is necessary to change the conveying speed.SOLUTION: An inkjet printing device is provided with a speed change condition determining part 141 that, when it is necessary to change a conveying speed of print paper, determines a speed change rate (variations in conveying speed per unit time) and a conveying speed after speed change, in consideration of at least either of a supply state of ink from an ink supply part 29 to a printing part 24 and a state of a drying part 25. A conveying control part 142 controls operation of a conveying part 28 in accordance with the speed change rate and the conveying speed after speed change determined by the speed change condition determining part 141.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and a control method thereof, and more particularly to an image forming apparatus that forms an image on the surface of a long strip-shaped substrate (such as printing paper) by ejecting ink onto the substrate, and a control method thereof. [Background technology]

[0002] Inkjet printing devices are known as one type of image forming device that forms an image on the surface of a substrate by ejecting ink onto the substrate using heat or pressure. For example, inkjet printing devices used for bookbinding typically use long, strip-shaped printing paper (continuous paper) called roll paper as the substrate. The long, strip-shaped printing paper is transported by a transport unit (transport mechanism) consisting of drive rollers and other components, and printing is performed by ejecting ink from a print head onto the transported printing paper.

[0003] When printing is performed on long strips of printing paper, the printing paper transport speed (the distance the printing paper is transported per unit time by the transport unit) first gradually increases from a state in which the device is stopped. In other words, the transport speed accelerates when printing starts. Then, when the transport speed reaches a predetermined speed, printing is performed while the transport speed is maintained at a constant speed. Thereafter, when printing is completed, the transport speed gradually decreases from the predetermined speed until the device stops. In other words, the transport speed decelerates when printing is completed. Note that while the transport speed is accelerating and decelerating, printing may or may not occur.

[0004] Incidentally, some inkjet printing devices have a plurality of settable transport speeds (printing speeds). Generally, in such inkjet printing devices, printing is normally performed with the transport speed set to the highest of the plurality of speeds available. However, while printing is being performed with the transport speed set to the highest speed, it may become necessary to slow down the transport speed for various reasons. The need to slow down the transport speed arises, for example, in the following cases (1) to (5). (1) In a configuration where the processes from printing to binding are inline, the post-processing machine cannot keep up with the speed at which printed paper is fed, and the free space in the buffer between the printing device and the post-processing machine is running out. (2) In the unwinding device (paper delivery section) that delivers the roll paper to the printing mechanism, a process called "splice" is performed to join two rolls of paper. (3) When the transfer of print data from the RIP device (rasterization processing device) to the inkjet printing device or the transfer of print data from the controller (print control device) to the printing unit does not keep up with the printing speed. (4) When the ink supply from the ink tank to the printing unit is not enough to keep up with the printing speed. (5) When the drying control of the printed paper in the drying section does not keep up with the conveying speed

[0005] For (1) above, the constraints are the buffer size and the time required for recovery. For (2) above, the constraints are the time required for splicing. For (3) above, the constraints are the time required for data preparation, the data processing capacity of the hardware, and the data transfer rate. For (4) above, the constraints are the maximum ink supply amount and the time required for switching ink tanks. For (5) above, the constraints are the time required for switching drying control and the time required for the temperature to change inside the drying unit.

[0006] For example, in an inkjet printing device that has two settable transport speeds, "high speed" and "low speed," if it becomes necessary to slow down the transport speed while printing is being performed with the transport speed set to high, the transport speed is changed from high to low. Then, printing is performed with the transport speed maintained at low speed. After that, when the situation requiring printing at low transport speed is resolved, the transport speed is changed from low to high, and printing is performed with the transport speed maintained at high speed. Note that, hereinafter, printing with the transport speed set to high will be simply referred to as "printing at high speed," and printing with the transport speed set to low will be simply referred to as "printing at low speed."

[0007] The following prior art documents are known in relation to the present invention. Japanese Patent Application Laid-Open No. 2019-51651 discloses a printing device that varies the acceleration of the conveying speed depending on the ease of expansion and contraction of the substrate to suppress tension fluctuations in the substrate and improve print quality. Japanese Patent Application Laid-Open No. 10-305953 also describes an automatic paper splicing device that varies the braking force during sudden deceleration or emergency stop depending on the density of the paper. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2019-51651 [Patent Document 2] Japanese Patent Application Publication No. 10-305953 Summary of the Invention [Problem to be solved by the invention]

[0009] However, there is a risk that sufficient quality may not be achieved when printing at low speeds or when the transport speed is being accelerated or decelerated. This will be explained with reference to Figure 22. Figure 22 shows an example of the relationship between the transport speed and the timing at which each page is printed on the front and back sides in an inkjet printing device consisting of a printer PR1 for front side printing and a printer PR2 for back side printing. Note that the numbers 1 to 17 in the columns labeled PR1 and PR2 represent page numbers.

[0010] During period T91, printing is performed with the transport speed gradually accelerating. During period T92, printing is performed at a high speed. During period T93, printing is performed with the transport speed gradually decelerating. During period T94, printing is performed at a low speed. The printed matter obtained by printing during period T92 is of high quality. The printed matter obtained by printing during periods T91, T93, and T94 is not of as good quality as the printed matter obtained by printing during period T92. The quality of the printed matter obtained by printing during period T91 depends on the acceleration rate, and generally the higher the acceleration rate, the lower the quality. The quality of the printed matter obtained by printing during period T93 depends on the deceleration rate, and generally the higher the deceleration rate, the lower the quality. The quality of the printed matter obtained by printing during period T94 depends on the transport speed, and generally the lower the transport speed, the lower the quality.

[0011] Users have a variety of printing needs. For example, they want to avoid stopping printing midway because stopping printing can result in wasted paper or the need to readjust post-processing equipment, which reduces equipment availability. They also want to print as quickly as possible to shorten printing time and improve equipment availability, and they want to ensure the highest possible quality of printed materials. Even for the same user, the priorities of these various needs can change depending on the job, for example.

[0012] Regarding acceleration and deceleration of the transport speed, there are limitations on the acceleration / deceleration rate and transport speed applicable to inkjet printing devices. This is explained below. The motor controlling the transport of the print paper has a speed range in which it resonates. Therefore, the transport speed cannot be selected arbitrarily; it is usually necessary to select the applicable transport speed from a pre-defined range. Furthermore, if the transport speed is significantly low or if the transport speed is changed suddenly, the transport of the print paper becomes unstable. As described above, to ensure the stability of the transport of the print paper, there are restrictions on the minimum transport speed, maximum acceleration rate, and maximum deceleration rate. Furthermore, the heater in the drying section that dries the printed print paper cannot be rapidly increased or decreased in temperature. Therefore, if the acceleration / deceleration rate is too high, the temperature control in the drying section cannot keep up with changes in the transport speed. Furthermore, when using multiple colors of ink, if the acceleration / deceleration rate is too high, the ink droplets will land misaligned, preventing the multiple colors from being properly overlaid. Furthermore, depending on the acceleration / deceleration rate and transport speed applied, the ink supply capacity from the ink tank to the printing section may be insufficient or the ink supply may be uneven.

[0013] When a change in the transport speed (acceleration or deceleration) is required during printing, it is preferable to determine the acceleration / deceleration rate to be applied and the transport speed after the change so that the user's requirements are met while taking into consideration limitations on the acceleration / deceleration rate and the transport speed. However, with conventional inkjet printing devices, when the need for deceleration arises, for example, the print quality may be significantly reduced by increasing the deceleration rate more than necessary or lowering the transport speed more than necessary.

[0014] The invention disclosed in JP 2019-51651 A merely suppresses tension fluctuations in the substrate, and therefore does not sufficiently suppress deterioration in print quality when the conveying speed is changed. Furthermore, JP 10-305953 A does not mention anything about quality.

[0015] Therefore, the present invention aims to realize an inkjet printing device (image forming device) that can change the conveying speed of printing paper so as to minimize degradation in print quality when it becomes necessary to change the conveying speed. [Means for solving the problem]

[0016] A first invention is an image forming apparatus including a transport unit that transports a long strip of printing medium and a printing unit that forms an image by ejecting ink onto the printing medium being transported by the transport unit, a transport control unit that controls the operation of the transport unit; an ink supply unit that supplies ink to the printing unit; a drying unit that dries the printed print medium on which the image has been formed by the printing unit; a speed change condition determination unit that, when it becomes necessary to change the transport speed, which is the distance the print medium is transported per unit time by the transport unit, determines speed change conditions including a speed change rate, which is the amount of change in the transport speed per unit time, and the transport speed after the speed change, taking into consideration at least one of the state of ink supply from the ink supply unit to the printing unit and the state of the drying unit; Equipped with The transport control unit controls the operation of the transport unit in accordance with the speed change condition determined by the speed change condition determination unit.

[0017] The second invention is the first invention, The speed change condition determination unit takes into consideration the ink supply state from the ink supply unit to the printing unit when determining the speed change rate and the transport speed after the speed change.

[0018] The third invention is the first invention, The speed change condition determining unit takes into consideration the state of the drying unit when determining the speed change rate and the transport speed after the speed change.

[0019] The fourth invention is the first invention, The speed change condition determination unit is characterized in that, when determining the speed change rate and the transport speed after the speed change, it takes into consideration both the state of ink supply from the ink supply unit to the printing unit and the state of the drying unit.

[0020] The fifth invention is the fourth invention, a high quality mode that prioritizes the quality of the image on the printed print medium and a drying performance mode that prioritizes the dryness of the printed print medium; when the high quality mode is set, the speed change condition determination unit determines the speed change rate and the transport speed after the speed change, taking into consideration the ink supply state from the ink supply unit to the printing unit with priority over the state of the drying unit; When the drying performance mode is set, the speed change condition determination unit determines the speed change rate and the transport speed after the speed change by taking into consideration the state of the drying unit more preferentially than the state of ink supply from the ink supply unit to the printing unit.

[0021] The sixth invention is any one of the third to fifth inventions, the drying unit includes a plurality of light sources that generate heat when turned on; a first table is prepared in advance, which stores the relationship between the combination of the lighting rates of the plurality of light sources and the speed change rates and the scores; Depending on the mode you've set, the conditions for the score you need will be set. The speed change condition determination unit determines the speed change rate based on the first table, taking into consideration the lighting rates of the plurality of light sources. It is characterized by:

[0022] A seventh aspect of the present invention is the sixth aspect of the present invention, The first table is created so that the higher the lighting rate of the plurality of light sources, the lower the score, and the higher the speed change rate, the lower the score. It is characterized by:

[0023] The eighth invention is any one of the second, fourth, and fifth inventions, the image forming apparatus further includes an ink supply control unit that controls an ink supply rate that indicates the degree of ink supply from the ink supply unit to the printing unit; a second table is prepared in advance, which stores the relationship between the combination of the ink supply rate and the speed change rate and the score; Depending on the mode you've set, the conditions for the score you need will be set. The speed change condition determination unit determines the speed change rate based on the second table, taking into account the ink supply rate. It is characterized by:

[0024] A ninth aspect of the present invention is the eighth aspect of the present invention, The second table is created so that the higher the ink supply rate, the lower the score, and the higher the speed change rate, the lower the score. It is characterized by:

[0025] The tenth invention is any one of the first to fourth inventions, the image forming apparatus further includes a learning device that has been trained by machine learning using the speed change conditions as input data; When it becomes necessary to change the conveying speed, the speed change condition determination unit provides the learning device with multiple sets of input data representing the speed change conditions, and determines the speed change condition corresponding to the input data when the learning device outputs output data closest to the target value as the speed change condition to be actually applied.

[0026] An eleventh aspect of the present invention is the tenth aspect of the present invention, The temperature of the drying section is adopted as the target value, The input data further includes a temperature of the drying section before a speed change. The learning device outputs a predicted temperature of the drying section after a speed change as the output data.

[0027] A twelfth invention is any one of the first to eleventh inventions, The speed change condition determination unit is characterized in that, when determining the speed change rate and the transport speed after the speed change, it further takes into account constraints based on the operation of at least one of the source of the print medium or the destination of the printed print medium.

[0028] The thirteenth invention is any one of the first to twelfth inventions, the printing unit includes a print head that ejects ink onto the print medium; The speed change condition determination unit is characterized in that, when determining the speed change rate and the transport speed after the speed change, it further takes into consideration the state of ink ejection from the print head onto the print medium.

[0029] The fourteenth invention is any one of the first to thirteenth inventions, Can be configured to one or more modes, The speed change condition determining unit changes the speed change rate and the conveying speed after the speed change according to the set mode.

[0030] The fifteenth invention is any one of the first to fourteenth inventions, a high speed, a first low speed, and a second low speed that is lower than the first low speed, as transport speeds when the transport unit transports the print medium at a constant speed; The transport control unit is characterized in that it is possible to perform deceleration from the high speed to the second low speed by dividing it into a first deceleration from the high speed to the first low speed and a second deceleration from the first low speed to the second low speed.

[0031] A sixteenth aspect of the present invention is the fifteenth aspect of the present invention, The gear change condition determination unit determines the gear change rate for the second deceleration to be higher than the gear change rate for the first deceleration.

[0032] A seventeenth aspect of the present invention is the fifteenth aspect of the present invention, The transport control unit is characterized in that, after the first deceleration, it is possible to accelerate from the first low speed to the high speed without decelerating from the first low speed to the second low speed.

[0033] An eighteenth invention is an image forming apparatus including a transport unit that transports a long strip-shaped print medium and a printing unit that forms an image by ejecting photocurable ink onto the print medium being transported by the transport unit, a transport control unit that controls the operation of the transport unit; an ink supply unit that supplies photocurable ink to the printing unit; an ultraviolet irradiation unit that cures the photocurable ink on the print medium on which the image has been formed by the printing unit by irradiating it with ultraviolet light; a speed change condition determination unit that, when it becomes necessary to change the transport speed, which is the distance the print medium is transported per unit time by the transport unit, determines speed change conditions including a speed change rate, which is the amount of change in the transport speed per unit time, and the transport speed after the speed change, taking into consideration at least one of the supply state of the photo-curable ink from the ink supply unit to the printing unit or the state of the ultraviolet irradiation unit; Equipped with The transport control unit controls the operation of the transport unit in accordance with the speed change condition determined by the speed change condition determination unit.

[0034] A nineteenth aspect of the present invention is a control method for an image forming apparatus including a transport unit that transports a long strip-shaped print medium, a printing unit that forms an image by ejecting ink onto the print medium being transported by the transport unit, an ink supply unit that supplies ink to the printing unit, and a drying unit that dries the printed print medium on which the image has been formed by the printing unit, a speed change condition determination step for determining, when it becomes necessary to change the transport speed, which is the distance the print medium is transported per unit time by the transport unit, a speed change condition including a speed change rate, which is the amount of change in the transport speed per unit time, and the transport speed after the speed change, taking into consideration at least one of the state of ink supply from the ink supply unit to the printing unit or the state of the drying unit; a transport control step of controlling the operation of the transport unit in accordance with the speed change conditions determined in the speed change condition determination step; The present invention is characterized by comprising:

[0035] A twentieth invention is a control method for an image forming apparatus including a transport unit that transports a long strip-shaped printing medium, a printing unit that forms an image by ejecting photocurable ink onto the printing medium being transported by the transport unit, an ink supply unit that supplies photocurable ink to the printing unit, and an ultraviolet irradiation unit that cures the photocurable ink on the printed printing medium on which the image has been formed by the printing unit by irradiating it with ultraviolet light, a speed change condition determination step for determining, when it becomes necessary to change the transport speed, which is the distance the print medium is transported per unit time by the transport unit, a speed change condition including a speed change rate, which is the amount of change in the transport speed per unit time, and the transport speed after the speed change, taking into consideration at least one of the supply state of the photo-curable ink from the ink supply unit to the printing unit or the state of the ultraviolet irradiation unit; a transport control step of controlling the operation of the transport unit in accordance with the speed change conditions determined in the speed change condition determination step; The present invention is characterized by comprising: [Effects of the Invention]

[0036] According to the first aspect of the present invention, the image forming apparatus is provided with a speed change condition determination unit that determines the speed change rate (the distance the print medium is transported per unit time by the transport unit) and the transport speed after the speed change when it becomes necessary to change the transport speed of the print medium. The speed change condition determination unit determines the speed change rate and the transport speed after the speed change, taking into account at least one of the state of ink supply from the ink supply unit to the printing unit and the state of the drying unit. This prevents a deterioration in print quality. As described above, an image forming apparatus is realized that can change the transport speed of the print medium when it becomes necessary to change the transport speed so as to minimize a deterioration in print quality.

[0037] According to the second invention, the ink supply state from the ink supply unit to the printing unit is taken into consideration when determining the speed change rate and the transport speed after the speed change, so that variations in ink supply are suppressed even when the transport speed is changed.

[0038] According to the third aspect of the present invention, the state of the drying section is taken into consideration when determining the speed change rate and the conveying speed after the speed change, so that even if the conveying speed is changed, the occurrence of uneven drying caused by the temperature control in the drying section not being able to keep up with the change in conveying speed is suppressed.

[0039] According to the fourth aspect of the present invention, when determining the speed change rate and the transport speed after the speed change, the ink supply state from the ink supply unit to the printing unit and the state of the drying unit are taken into consideration. Therefore, when the transport speed is changed, it is possible to suppress the occurrence of variations in ink supply and uneven drying caused by the temperature control in the drying unit not keeping up with changes in the transport speed.

[0040] According to the fifth aspect of the present invention, when image quality is important, the occurrence of variations in ink supply is effectively suppressed, and when the drying state is important, the occurrence of uneven drying is effectively suppressed.

[0041] According to the sixth aspect of the present invention, it is possible to minimize the effect that a change in the transport speed has on the dryness state of the printed print medium.

[0042] According to the seventh aspect of the present invention, it is possible to more effectively prevent the occurrence of uneven drying.

[0043] According to the eighth aspect of the present invention, it is possible to minimize the effect that a change in the transport speed has on the state of ink supply to the printing unit.

[0044] According to the ninth aspect of the present invention, it is possible to more effectively suppress the occurrence of variations in ink supply.

[0045] According to the tenth aspect of the present invention, machine learning is used when determining the speed change conditions, so that the speed change conditions can be determined taking into account past state changes when the conveying speed is changed so as to obtain the target control state.

[0046] According to the eleventh aspect of the invention, the same effects as those of the tenth aspect of the invention can be obtained.

[0047] According to the 12th aspect of the present invention, constraints based on the operation of the devices before and after the image forming device are taken into consideration when determining the speed change rate and the conveying speed after the speed change, so it is possible to prevent printing from being stopped due to, for example, an error occurring in the device before or after the speed change.

[0048] According to the thirteenth aspect of the present invention, the ink ejection state is taken into consideration when determining the speed change rate and the transport speed after the speed change, making it possible to more effectively suppress deterioration in print quality caused by changes in the transport speed.

[0049] According to the fourteenth aspect of the present invention, it is possible to change the speed change conditions when the conveying speed is changed in accordance with the user's request.

[0050] According to the fifteenth aspect, the transport speed can be changed more flexibly, and therefore a decrease in print quality caused by a change in the transport speed can be effectively suppressed.

[0051] According to the sixteenth aspect of the present invention, for example, it is possible to reduce the transport speed so as to prevent the printed print medium from drying excessively.

[0052] According to the seventeenth aspect of the present invention, the transport speed is prevented from decreasing more than necessary, and the printing time can be shortened.

[0053] According to the eighteenth aspect of the present invention, the same effects as those of the first aspect of the present invention can be obtained.

[0054] According to the nineteenth aspect of the present invention, the same effects as those of the first aspect of the present invention can be obtained.

[0055] According to the twentieth aspect of the present invention, the same effects as those of the first aspect of the present invention can be obtained. [Brief explanation of the drawings]

[0056] [Figure 1] 1 is a diagram illustrating the overall configuration of a printing system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an example of the configuration of a printing device according to the embodiment. [Figure 3] FIG. 2 is a block diagram showing a hardware configuration of the print control device in the embodiment. [Figure 4]FIG. 2 is a block diagram showing a schematic functional configuration of a print control unit in the embodiment. [Figure 5] 10 is a flowchart showing the overall processing procedure relating to the control of the transport speed for variable-speed printing in the embodiment. [Figure 6] 5 is a flowchart showing a detailed procedure for determining a deceleration condition in the embodiment. [Figure 7] FIG. 2 is a diagram schematically showing the contents held in a first table in the embodiment. [Figure 8] FIG. 3 is a diagram schematically showing the contents held in a second table in the embodiment. [Figure 9] FIG. 4 is a diagram schematically showing the contents held in a third table in the embodiment. [Figure 10] FIG. 10 is a diagram for explaining an example in which the value of the deceleration rate differs depending on the set mode in the embodiment. [Figure 11] FIG. 10 is a diagram schematically showing the contents held in a fourth table in the embodiment. [Figure 12] FIG. 10 is a diagram for explaining an example in which the value of the deceleration rate differs depending on the set mode in the embodiment. [Figure 13] FIG. 10 is a diagram for explaining an example in which the conveying speed after deceleration differs depending on the set mode in the embodiment. [Figure 14] 10 is a flowchart showing a detailed procedure for determining an acceleration condition in the embodiment. [Figure 15] FIG. 10 is a diagram showing an example of changes in conveyance speed in a first modified example of the embodiment. [Figure 16] FIG. 10 is a diagram showing an example of changes in conveyance speed in a second modified example of the embodiment. [Figure 17] FIG. 10 is a diagram showing an example of changes in conveyance speed in a third modified example of the embodiment. [Figure 18] FIG. 13 is a diagram schematically showing the contents held in a priority setting table in a fourth modified example of the embodiment. [Figure 19] FIG. 13 is a diagram illustrating a priority mode determination process in a fourth modified example of the embodiment. [Figure 20] FIG. 10 is a diagram for explaining a neural network used in a fifth modification of the embodiment. [Figure 21] 13 is a flowchart showing a procedure for determining a deceleration rate in the fifth modification of the embodiment. [Figure 22] 10A and 10B are diagrams illustrating that sufficient quality cannot be obtained in a conventional example when printing at low speed or when the conveying speed is increased or decreased. DETAILED DESCRIPTION OF THE INVENTION

[0057] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0058] <1. Overall structure> 1 is a block diagram showing the overall configuration of a printing system 1 according to an embodiment of the present invention. The printing system 1 is made up of a printing device 10, a print workflow management device 30, a RIP server 40, a web buffer 50, and a post-processing device group 52.

[0059] The printing device 10 is an image forming device that forms an image by ejecting ink onto printing paper as a printing medium. The printing device 10 is generally composed of a printing machine main body and a print control device that controls the main body. The printing device 10 in this embodiment is an inkjet printing device that prints on roll paper, which is continuous paper (continuous paper printing).

[0060] The print workflow management device 30 manages a series of processes (i.e., manages the print workflow) for printing in this printing system 1. In this regard, a computer such as a personal computer on which application software (print workflow management system) for managing the print workflow is installed functions as the print workflow management device 30.

[0061] The RIP server 40 performs RIP processing (rasterization processing) on ​​input data (vector format data) such as a PDF file. The print data generated by this RIP processing is sent from the RIP server 40 to the printing device 10.

[0062] 1, the web buffer 50 is provided between the printing device 10 and the post-processing device group 52. Printed printing paper is supplied from the printing device 10 to the post-processing device group 52 via the web buffer 50. The web buffer 50 temporarily holds printed printing paper as needed to absorb the difference in processing speed between the printing device 10 and the post-processing device group 52.

[0063] The post-processing machine group 52 is made up of n (n is a natural number) post-processing machines 52(1) to 52(n) for performing post-processing on printed printing paper. As an example, the post-processing machine group 52 is made up of a sheet cutter (trimming machine) that cuts the continuous paper printed by the printing device 10 to a specified size, a folding machine that creates quires from the printing paper cut to the specified size, a collating machine that assembles multiple quires, a stitching machine that binds the collated quires, and a three-side trimming machine that performs finishing trimming on three sides of the book (top, bottom, and fore-edge).

[0064] The printing device 10, the print workflow management device 30, and the RIP server 40 are communicably connected via a network 7 such as a LAN. Submitted data, which is data to be printed, is sent via this network 7 from a client computer (not shown) or the like.

[0065] In this printing system 1, while high-speed printing is being performed, an instruction (signal) requesting slowing down may be sent to the printing device 10 from, for example, the web buffer 50 or a post-processing device constituting the post-processing device group 52. When such an instruction is sent, the print paper transport speed is slowed down and printing is performed at a low speed. After that, when the condition requiring printing at a low transport speed is resolved, the transport speed is accelerated and printing is performed at a high speed. In this way, the printing device 10 according to this embodiment performs variable-speed printing, which allows the print paper transport speed to be changed during printing operations.

[0066] <2. Printer Configuration> 2 is a schematic diagram showing an example of the configuration of the printing device 10. As described above, the printing device 10 is made up of the printing machine main body 200 and the print control device 100 which is its controller.

[0067] The printing press main body 200 is equipped with a paper feed section 21 that supplies printing paper (here, roll paper) PA, a first drive roller 22 for transporting the printing paper PA into the printing mechanism, a plurality of support rollers 23 for transporting the printing paper PA inside the printing mechanism, a printing section 24 that ejects ink (water-based ink) onto the printing paper PA to perform printing, a drying section 25 that dries the printing paper PA after printing, an inspection section 26 that inspects the condition of the printing on the printing paper PA, and a second drive roller 27 for outputting the printing paper PA from inside the printing mechanism. Although not shown in Figure 2, the interior of the printing press main body 200 also includes an ink supply section that includes an ink tank for storing ink and supplies ink from the ink tank to the printing section 24.

[0068] 2, the printing unit 24 is composed of a C inkjet head array 24c, an M inkjet head array 24m, a Y inkjet head array 24y, and a K inkjet head array 24k, which eject C (cyan), M (magenta), Y (yellow), and K (black) inks, respectively. Each inkjet head array is composed of multiple inkjet heads (print heads) arranged in a staggered pattern. Each inkjet head includes a number of nozzles that eject ink.

[0069] The print control device 100 controls the operation of the printing press main body 200 configured as described above. When a print output instruction command is given to the print control device 100, the print control device 100 controls the operation of the printing press main body 200 so that the print paper PA is transported from the paper delivery unit 21 to the inside of the printing mechanism. Then, in the process of transporting the print paper PA, first the printing unit 24 prints on the print paper PA, then the drying unit 25 dries the print paper PA, and finally the inspection unit 26 inspects the print condition.

[0070] Although the configuration of an inkjet printing device that performs color printing has been exemplified here, the present invention can also be applied to inkjet printing devices that perform monochrome printing. Also, although the configuration of an inkjet printing device that prints on only one side of the print paper PA has been exemplified here, the present invention can also be applied to inkjet printing devices that are composed of a printing mechanism for front-side printing and a printing mechanism for back-side printing and that print on both sides of the print paper PA.

[0071] <3. Hardware configuration of print control device> FIG. 3 is a block diagram showing the hardware configuration of the print control device 100. As shown in FIG. 3, the print control device 100 includes a main body 110, an auxiliary storage device 121, an optical disk drive 122, a display unit 123, a keyboard 124, and a mouse 125. The main body 110 includes a CPU 111, a memory 112, a first disk interface unit 113, a second disk interface unit 114, a display control unit 115, an input interface unit 116, an output interface unit 117, and a network interface unit 118. The CPU 111, the memory 112, the first disk interface unit 113, the second disk interface unit 114, the display control unit 115, the input interface unit 116, the output interface unit 117, and the network interface unit 118 are connected to one another via a system bus. The auxiliary storage device 121 is connected to the first disk interface unit 113. The optical disk drive 122 is connected to the second disk interface unit 114. The display control unit 115 is connected to a display unit (display device) 123. A keyboard 124 and a mouse 125 are connected to the input interface unit 116. The printing machine main body 200 is connected to the output interface unit 117 via a communication cable. The network interface unit 118 is connected to the network 7. The auxiliary storage device 121 is a magnetic disk device or the like. An optical disk 8 serving as a computer-readable recording medium such as a CD-ROM or DVD-ROM is inserted into the optical disk drive 122. The display unit 123 is a liquid crystal display or the like. The display unit 123 is used to display information desired by the operator. The keyboard 124 and mouse 125 are used by the operator to input instructions to this printing control device 100.

[0072] The auxiliary storage device 121 stores a print control program P (a program for controlling the execution of print processing by the printing press main body 200). The CPU 111 reads the print control program P stored in the auxiliary storage device 121 into the memory 112 and executes it, thereby realizing various functions of the print control device 100. The memory 112 includes RAM and ROM. The memory 112 functions as a work area for the CPU 111 to execute the print control program P stored in the auxiliary storage device 121. The print control program P is provided by being stored in the computer-readable recording medium (non-transitory recording medium). That is, for example, a user purchases an optical disc 8 as a recording medium for the print control program P, inserts it into the optical disc drive 122, reads the print control program P from the optical disc 8, and installs it in the auxiliary storage device 121. Alternatively, the print control program P transmitted via the network 7 may be received by the network interface unit 118 and installed in the auxiliary storage device 121.

[0073] <4. Functional configuration> 4 is a block diagram showing a schematic functional configuration of the print control unit 14 that is realized by executing the print control program P on the print control device 100. The print control unit 14 includes an overall control unit 140, a conveyance control unit 142, an ink supply control unit 143, a printing control unit 144, and a drying control unit 145. The overall control unit 140 includes a speed change condition determination unit 141.

[0074] The transport control unit 142 controls the speed (transport speed) at which the transport unit 28 transports the print paper PA. In this embodiment, the transport unit 28 is realized by the paper delivery unit 21, the first drive roller 22, the multiple support rollers 23, and the second drive roller 27 (see FIG. 2).

[0075] The ink supply control unit 143 controls the degree of ink supply from the ink supply unit 29 to the printing unit 24 (ink supply rate).

[0076] The print control unit 144 controls the ejection of ink from each nozzle included in each inkjet head that constitutes the printing unit 24. Specifically, the print control unit 144 controls the timing and amount of ink ejection.

[0077] The drying control unit 145 controls the temperature (drying temperature) when the printing paper PA is dried by the drying unit 25. For example, the drying unit 25 includes multiple light sources that generate heat when turned on, and the drying control unit 145 controls the drying temperature by adjusting the lighting rate of the multiple light sources (hereinafter referred to as the "heater lighting rate").

[0078] The overall control unit 140 controls the operations of the transport control unit 142, the ink supply control unit 143, the printing control unit 144, and the drying control unit 145 based on the print data PD, the job information JI, and the speed change instruction signal SC.

[0079] When the speed change condition determination unit 141 detects the need to change the conveying speed based on the speed change instruction signal SC, it determines a speed change condition that indicates the mode of acceleration or deceleration, taking into consideration the state of ink supply from the ink supply unit 29 to the printing unit 24 and the state of the drying unit 25. In this embodiment, the speed change condition includes a speed change rate (acceleration / deceleration rate), which is the amount of change in conveying speed per unit time, and the conveying speed after the speed change. The overall control unit 140 controls the operation of the conveying control unit 142 according to the speed change condition determined by this speed change condition determination unit 141.

[0080] In this embodiment, the speed change condition determination unit 141 considers both the ink supply state and the state of the drying unit 25 when determining the speed change conditions, but is not limited to this. The speed change condition determination unit 141 only needs to consider at least one of the ink supply state and the state of the drying unit 25 when determining the speed change conditions.

[0081] <5. Variable speed printing> As described above, the printing device 10 according to this embodiment performs variable speed printing, which allows the transport speed of the printing paper to be changed during printing operations. This variable speed printing will be described in detail below.

[0082] <5.1 Overall processing flow> The overall processing procedure for controlling the transport speed for variable-speed printing will be described with reference to the flowchart shown in Fig. 5. Note that there are cases where two types of low speeds (referred to as the "first low speed" and the "second low speed," with the first low speed being faster than the second low speed) are prepared and two-stage deceleration (from a high speed to the first low speed and from the first low speed to the second low speed) or two-stage acceleration (acceleration from the second low speed to the first low speed and from the first low speed to a high speed) is performed, but here we will focus on cases where only one-stage deceleration and one-stage acceleration are performed.

[0083] First, a user (operator) selects a mode (step S100). Here, the modes are explained. Generally, printing devices have multiple modes selectable by the user to enable various printing styles. The printing process is then performed in the mode selected by the user. Unless otherwise specified, the printing device 10 in this embodiment is assumed to be equipped with a continuous printing mode that prevents printing from stopping, a high-quality mode that ensures high-quality printouts, and a drying performance mode that ensures high-quality printouts are obtained. While many printing devices generally allow the simultaneous selection of two or more modes, for the sake of convenience, this embodiment assumes that two or more modes cannot be simultaneously selected. That is, the user can select only one mode when printing. Although the user selects a mode in this embodiment, this is not a requirement. For example, if the user does not select a mode, a predetermined mode may be selected.

[0084] After the mode is selected, the printing operation is started (step S110). After the printing operation is started, the speed change condition determination unit 141 first determines the acceleration conditions (step S120). In this regard, at the start of the processing in step S120, the conveying speed is 0 or a low speed. Since printing should normally be performed at a high speed, in step S120, the acceleration rate and the conveying speed after acceleration are determined as the acceleration conditions. The determination of the acceleration conditions will be described in detail later.

[0085] Next, the conveyance speed is accelerated by conveyance control unit 142 controlling the operation of conveyance unit 28 according to the acceleration rate and the accelerated conveyance speed determined in step S120, and after the acceleration is completed, printing is performed at a constant speed (high-speed printing) (step S130). During the period when printing at a constant speed is being performed, the following steps S140 and S150 are repeated.

[0086] In step S140, it is determined whether printing of all pages based on the given print data has been completed. If the result of the determination is that printing of all pages has been completed, the entire process ends. At this time, the conveying speed is decelerated at a predetermined deceleration rate, and the operation of the conveying unit 28 stops. On the other hand, if there are any unprinted pages, the process proceeds to step S150.

[0087] In step S150, it is determined whether or not the conveying speed needs to be slowed down. If the result of the determination is that the conveying speed needs to be slowed down, the process proceeds to step S160, and if the conveying speed does not need to be slowed down, the process returns to step S140. Note that different determinations may be made depending on the set mode.

[0088] In step S160, deceleration conditions are determined by the speed change condition determination unit 141. In step S160, a deceleration rate and a conveying speed after deceleration are determined as the deceleration conditions. The determination of the deceleration conditions will be described in detail later.

[0089] Next, the conveyance speed is decelerated by conveyance control unit 142 controlling the operation of conveyance unit 28 in accordance with the deceleration rate and the conveyance speed after deceleration determined in step S160, and printing at a constant speed (low-speed printing) is performed after the deceleration is completed (step S170). During the period in which printing at a constant speed is being performed, the following steps S180 and S190 are repeated.

[0090] In step S180, it is determined whether printing of all pages based on the given print data has been completed. If the result of the determination is that printing of all pages has been completed, the entire process ends. At this time, the conveying speed is decelerated at a predetermined deceleration rate, and the operation of the conveying unit 28 stops. On the other hand, if there are any unprinted pages, the process proceeds to step S190.

[0091] In step S190, it is determined whether or not the conveying speed can be accelerated. If the result of the determination is that the conveying speed can be accelerated, the process returns to step S120, and if the conveying speed cannot be accelerated, the process returns to step S180. Note that different determinations may be made depending on the set mode.

[0092] In this embodiment, the speed change condition determination step is realized by the above steps S120 and S160, and the transport control step is realized by the above steps S130 and S170.

[0093] 5.2 Determining deceleration conditions A detailed procedure for determining the deceleration conditions will be described with reference to Fig. 6. The process for determining the deceleration conditions is performed by the gear change condition determination unit 141.

[0094] First, transport control information is acquired (step S161). In this embodiment, the transport control information acquired includes information such as the current transport speed, the maximum applicable deceleration rate, and the speed that can be set as the transport speed after deceleration.

[0095] Next, drying control information is acquired (step S162). In this embodiment, information on the current heater turn-on rate and information indicating the relationship between the heater turn-on rate and the acceleration / deceleration rate (information stored in a first table, which will be described later) are acquired. Note that a temperature sensor may be installed in the drying unit 25 to acquire information on the drying temperature.

[0096] Next, ink supply information is acquired (step S163). In this embodiment, information on the current ink supply rate, which indicates the state of ink supply from the ink supply unit 29 to the printing unit 24, and information indicating the relationship between the ink supply rate and the acceleration / deceleration rate (information stored in a second table, which will be described later) are acquired.

[0097] Next, constraint conditions are acquired (step S164). The constraint conditions here refer to conditions that constrain the setting of the deceleration rate and the conveying speed after deceleration. In this embodiment, information (information held in a third table, described later) that represents the "relationship between the conveying speed and the acceleration / deceleration rate" reflecting the constraint conditions resulting from the operation of the devices before and after the printing device 10 is acquired.

[0098] Finally, the deceleration conditions (deceleration rate and conveying speed after deceleration) are determined based on the currently set mode (the mode selected in step S100 of FIG. 5) and the information acquired in steps S161 to S164 (step S165).

[0099] 5.2.1 Deciding the deceleration rate A specific example will be given to explain how the deceleration rate is determined. However, the example shown here is merely an example and is not limiting. It is assumed that, from the viewpoint of ensuring stable transport of printing paper, there is a constraint that the acceleration / deceleration rate must be set to 70% or less.

[0100] In this embodiment, in order to determine the deceleration rate, a table 61 (hereinafter referred to as a "first table") as shown schematically in Fig. 7, a table 62 (hereinafter referred to as a "second table") as shown schematically in Fig. 8, and a table 63 (hereinafter referred to as a "third table") as shown schematically in Fig. 9 are prepared in advance. Note that the first table 61, the second table 62, and the third table 63 are held in, for example, the auxiliary storage device 121 (see Fig. 3).

[0101] The first table 61 stores the correspondence relationship between the combination of the heater lighting rate and the acceleration / deceleration rate and the score (see FIG. 7). The second table 62 stores the correspondence relationship between the combination of the ink supply rate and the acceleration / deceleration rate and the score (see FIG. 8). The third table 63 stores the correspondence relationship between the combination of the conveying speed after deceleration and the acceleration / deceleration rate and the score (see FIG. 9). P1, P2, and P3 in FIGS. 7 to 9 are scores that satisfy the relationship "P1>P2>P3." For example, P1 is 10, P2 is 5, and P3 is 0. However, the values ​​of P1, P2, and P3 may be different between the first table 61, the second table 62, and the third table 63. For example, in the example shown in FIG. 7, we will focus on the case where the heater lighting rate is 40%. In this case, for example, the score for an acceleration / deceleration rate of 30% is P1, the score for an acceleration / deceleration rate of 70% is P2, and the score for an acceleration / deceleration rate of 90% is P3.

[0102] The table used to determine the deceleration rate and the table used to determine the acceleration rate may be different. For example, two tables may be prepared as the first table 61: a table that stores the correspondence between combinations of heater turn-on rates and deceleration rates and the scores, and a table that stores the correspondence between combinations of heater turn-on rates and acceleration rates and the scores. The same applies to the second table 62 and the third table 63.

[0103] Let's take a look at the first table 61 (see Figure 7). Generally, the higher the heater turn-on rate, the greater the impact that acceleration / deceleration of the transport speed has on the drying state of the print paper, and the higher the acceleration / deceleration rate, the greater the impact that acceleration / deceleration of the transport speed has on the drying state of the print paper. Therefore, the first table 61 is created so that the higher the heater turn-on rate, the lower the score, and the higher the acceleration / deceleration rate, the lower the score.

[0104] Focus on the second table 62 (see FIG. 8). Generally, the higher the ink supply rate, the greater the effect that acceleration / deceleration of the transport speed has on the ink supply state to the printing unit 24, and the higher the acceleration / deceleration rate, the greater the effect that acceleration / deceleration of the transport speed has on the ink supply state to the printing unit 24. Therefore, the second table 62 is created so that the higher the ink supply rate, the lower the score, and the higher the acceleration / deceleration rate, the lower the score.

[0105] Focus on the third table 63 (see FIG. 9). This third table 63 is created taking into consideration constraints based on the operation of devices before and after the printing device 10 (the source of the printing paper or the destination of the printed printing paper) (for example, a post-processing machine).

[0106] With the first to third tables 61 to 63 prepared as described above, it is assumed that the post-processing machine sends an instruction to the printing device 10 to "reduce the conveying speed from 100 mpm to 30 mpm at a deceleration rate of 60%." At this time, the deceleration rate is determined, for example, as follows, depending on the currently set mode (the mode selected in step S100 of FIG. 5).

[0107] When the print continuation mode is set, the acceleration / deceleration rate closest to 60% that satisfies the following conditions is determined as the deceleration rate to be applied during the current deceleration: "The score for the combination of the current heater lighting rate and acceleration / deceleration rate is P1 or P2, and the score for the combination of the current ink supply rate and acceleration / deceleration rate is P1 or P2, and the score for the combination of the conveying speed and acceleration / deceleration rate after deceleration is P1." In this way, the deceleration rate is determined so that the requirement of not stopping printing midway is given priority over the quality of the printed matter or the dryness of the printed matter.

[0108] For example, assume that the current heater illumination rate is 30% and the current ink supply rate is 50%. In this case, the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current heater illumination rate and acceleration / deceleration rate is P1 or P2" is 0 to 90%, and the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current ink supply rate and acceleration / deceleration rate is P1 or P2" is 0 to 100%. Furthermore, since the conveying speed after deceleration based on the above instruction is 30 mpm, the acceleration / deceleration rate that satisfies the condition "the score of the combination of the conveying speed after deceleration and acceleration / deceleration rate is P1" is 35 to 100%. From the above, in this case, the deceleration rate is determined to be 60%.

[0109] Also, for example, assume that the current heater lighting rate is 70% and the current ink supply rate is 50%. In this case, the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current heater lighting rate and acceleration / deceleration rate is P1 or P2" is 0 to 50%, and the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current ink supply rate and acceleration / deceleration rate is P1 or P2" is 0 to 100%. The acceleration / deceleration rate that satisfies the condition "the score of the combination of the transport speed after deceleration and the acceleration / deceleration rate is P1" is 35 to 100%. From the above, in this case, the deceleration rate is determined to be 50%.

[0110] Furthermore, for example, assume that the current heater illumination rate is 30% and the current ink supply rate is 90%. In this case, the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current heater illumination rate and acceleration / deceleration rate is P1 or P2" is 0 to 90%, and the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current ink supply rate and acceleration / deceleration rate is P1 or P2" is 0 to 40%. The acceleration / deceleration rate that satisfies the condition "the score of the combination of the conveying speed after deceleration and the acceleration / deceleration rate is P1" is 35 to 100%. From the above, in this case, the deceleration rate is determined to be 40%.

[0111] When the drying performance mode is set, the acceleration / deceleration rate closest to 60% among the acceleration / deceleration rates that satisfy the following criteria is determined as the deceleration rate to be applied during the current deceleration: "The score for the combination of the current heater lighting rate and acceleration / deceleration rate is P1, the score for the combination of the current ink supply rate and acceleration / deceleration rate is P1 or P2, and the score for the combination of the transport speed and acceleration / deceleration rate after deceleration is P1 or P2." In this way, the deceleration rate is determined so that good drying of the printed matter is given priority over good quality of the printed matter or not stopping printing midway.

[0112] For example, assume that the current heater illumination rate is 30% and the current ink supply rate is 50%. In this case, the acceleration / deceleration rate that satisfies the condition "the score for the combination of the current heater illumination rate and acceleration / deceleration rate is P1" is 0 to 60%, and the acceleration / deceleration rate that satisfies the condition "the score for the combination of the current ink supply rate and acceleration / deceleration rate is P1 or P2" is 0 to 100%. Furthermore, since the conveying speed after deceleration based on the above instruction is 30 mpm, the acceleration / deceleration rate that satisfies the condition "the score for the combination of the conveying speed after deceleration and acceleration / deceleration rate is P1 or P2" is 15 to 100%. From the above, in this case, the deceleration rate is determined to be 60%.

[0113] Also, for example, assume that the current heater lighting rate is 70% and the current ink supply rate is 50%. In this case, the acceleration / deceleration rate that satisfies the condition "the score for the combination of the current heater lighting rate and acceleration / deceleration rate is P1" is 0 to 20%, and the acceleration / deceleration rate that satisfies the condition "the score for the combination of the current ink supply rate and acceleration / deceleration rate is P1 or P2" is 0 to 100%. The acceleration / deceleration rate that satisfies the condition "the score for the combination of the transport speed after deceleration and acceleration / deceleration rate is P1 or P2" is 15 to 100%. From the above, in this case, the deceleration rate is determined to be 20%.

[0114] Furthermore, for example, assume that the current heater illumination rate is 30% and the current ink supply rate is 90%. In this case, the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current heater illumination rate and acceleration / deceleration rate is P1" is 0 to 60%, and the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current ink supply rate and acceleration / deceleration rate is P1 or P2" is 0 to 40%. The acceleration / deceleration rate that satisfies the condition "the score of the combination of the conveying speed after deceleration and acceleration / deceleration rate is P1 or P2" is 15 to 100%. From the above, in this case, the deceleration rate is determined to be 40%.

[0115] If the current heater activation rate is 70%, the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current heater activation rate and deceleration rate is P1 or P2" is between 0 and 50%, while the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current heater activation rate and deceleration rate is P1" is between 0 and 20% (see FIG. 7). Therefore, as in the example above, when the drying performance mode is selected, the deceleration rate may be set to a lower value than when the print continue mode is selected. For example, when the print continue mode is selected, the conveyance speed is decelerated from V10 to V11 as shown by the solid line labeled 70 in FIG. 10, whereas when the dry performance mode is selected, the speed is decelerated as shown by the bold dotted line labeled 71 in FIG. 10. In the example shown in FIG. 10, deceleration as shown by the solid line labeled 70 can result in over-drying of the print paper. In contrast, deceleration as shown by the bold dotted line labeled 71 can result in a well-dried printed product.

[0116] When high quality mode is selected, the acceleration / deceleration rate closest to 60% among the acceleration / deceleration rates that satisfy the following criteria is determined as the deceleration rate to be applied during the current deceleration: "The score for the combination of the current heater lighting rate and acceleration / deceleration rate is P1 or P2, the score for the combination of the current ink supply rate and acceleration / deceleration rate is P1, and the score for the combination of the transport speed and acceleration / deceleration rate after deceleration is P1 or P2." In this way, the deceleration rate is determined so that good quality of the printed matter is given priority over the good drying state of the printed matter or not stopping printing midway.

[0117] For example, assume that the current heater illumination rate is 30% and the current ink supply rate is 30%. In this case, the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current heater illumination rate and acceleration / deceleration rate is P1 or P2" is 0 to 90%, and the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current ink supply rate and acceleration / deceleration rate is P1" is 0 to 80%. Furthermore, since the conveying speed after deceleration based on the above instruction is 30 mpm, the acceleration / deceleration rate that satisfies the condition "the score of the combination of the conveying speed after deceleration and acceleration / deceleration rate is P1 or P2" is 15 to 100%. From the above, in this case, the deceleration rate is determined to be 60%.

[0118] Also, for example, assume that the current heater lighting rate is 70% and the current ink supply rate is 30%. In this case, the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current heater lighting rate and acceleration / deceleration rate is P1 or P2" is 0 to 50%, and the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current ink supply rate and acceleration / deceleration rate is P1" is 0 to 80%. The acceleration / deceleration rate that satisfies the condition "the score of the combination of the transport speed after deceleration and acceleration / deceleration rate is P1 or P2" is 15 to 100%. From the above, in this case, the deceleration rate is determined to be 50%.

[0119] Furthermore, for example, assume that the current heater illumination rate is 30% and the current ink supply rate is 50%. In this case, the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current heater illumination rate and acceleration / deceleration rate is P1 or P2" is 0 to 90%, and the acceleration / deceleration rate that satisfies the condition "the score of the combination of the current ink supply rate and acceleration / deceleration rate is P1" is 0 to 40%. The acceleration / deceleration rate that satisfies the condition "the score of the combination of the conveying speed after deceleration and acceleration / deceleration rate is P1 or P2" is 15 to 100%. From the above, in this case, the deceleration rate is determined to be 40%.

[0120] In this embodiment, as described above, the deceleration rate is determined according to the selected mode, taking into consideration the current ink supply rate (the state of ink supply from the ink supply unit 29 to the printing unit 24) and the current heater illumination rate (the state of the drying unit 25). This prevents increases in printing time due to a decrease in the conveyance speed when the continuous printing mode is selected, effectively prevents uneven drying when the drying performance mode is selected, and effectively prevents variations in ink supply when the high quality mode is selected. Furthermore, because constraints based on the operation of devices before and after the printing device 10 are taken into consideration, printing stops due to, for example, errors occurring in the devices before and after the printing device 10 are prevented.

[0121] Although three tables (first to third tables 61 to 63) have been exemplified here, other tables may also be prepared. For example, a table 64 (hereinafter referred to as the "fourth table") as shown in Fig. 11 may be prepared, which is created taking into consideration constraints related to print control such as ink ejection control (control of the state of ink ejection from the inkjet head to the printing paper), and the deceleration rate may be determined taking into consideration the correspondence relationship (the correspondence relationship between the score and the combination of the conveyance speed after deceleration and the acceleration / deceleration rate) held in the fourth table 64. This makes it possible, for example, to more effectively suppress degradation of print quality caused by changes in conveyance speed.

[0122] In the above description, it is assumed that the available modes are the continue print mode, the high-quality mode, and the dryer performance mode. However, other modes may also be available. For example, a paper-saving mode may be provided to minimize paper waste, and the deceleration rate may be determined as follows: Regarding the deceleration of the transport speed from V20 to V21, when the continue print mode is selected, the speed is decelerated as shown by the solid line labeled 72 in FIG. 12 . When the high-quality mode or the dryer performance mode is selected, the speed is decelerated as shown by the bold dotted line labeled 73 in FIG. 12 . When the paper-saving mode is selected, the speed is decelerated as shown by the bold dashed line labeled 74 in FIG. 12 . In this way, when the paper-saving mode is selected, the deceleration rate is determined so that good print quality and good drying performance cannot be obtained, but paper waste is minimized.

[0123] 5.2.2 Determining the conveying speed after deceleration Next, how the conveying speed after deceleration is determined will be explained. However, the example shown here is merely an example and is not limiting. It is assumed that three speeds (40 mpm, 30 mpm, and 20 mpm) are prepared as settable conveying speeds after deceleration.

[0124] When the printing continuation mode or the drying performance mode is set, the conveying speed after deceleration is determined in accordance with a request from a post-processing machine or the like to the printing device 10. As in the example described above, when the post-processing machine sends an instruction to the printing device 10 to "reduce the conveying speed from 100 mpm to 30 mpm at a deceleration rate of 60%, the conveying speed after deceleration is determined to be 30 mpm.

[0125] When the high quality mode is selected, the transport speed after deceleration is determined based on a preset "relationship between ink supply rate and transport speed after deceleration." Here, it is assumed that an ink supply rate of 0% or more but less than 70% corresponds to 30 mpm, and an ink supply rate of 70% or more corresponds to 40 mpm. In this case, if the current ink supply rate is 50%, the transport speed after deceleration is determined to be 30 mpm, and if the current ink supply rate is 80%, the transport speed after deceleration is determined to be 40 mpm.

[0126] Furthermore, if the paper saving mode described above is provided and set to this paper saving mode, the conveying speed after deceleration may be set to a speed lower than the speed based on the instruction from the post-processing machine. In this case, if set to the continuous printing mode or the drying performance mode, the speed is decelerated as shown by the solid line labeled 75 in Fig. 13, if set to the high quality mode, the speed is decelerated as shown by the thick dotted line labeled 76 in Fig. 13, and if set to the paper saving mode, the speed is decelerated as shown by the thick dashed line labeled 77 in Fig. 13.

[0127] 5.3 Determining acceleration conditions A detailed procedure for determining the acceleration conditions will be described with reference to Fig. 14. Note that this process for determining the acceleration conditions is performed by the gear change condition determination unit 141, similar to the process for determining the deceleration conditions.

[0128] Steps S121 to S124 are similar to steps S161 to S164 in Fig. 6. In step S125, acceleration conditions (acceleration rate and conveying speed after acceleration) are determined based on the currently set mode (the mode selected in step S100 in Fig. 5) and the information acquired in steps S161 to S164. The acceleration rate is determined in the same manner as the deceleration rate, and the conveying speed after acceleration is usually set to the maximum speed.

[0129] Thereafter, it is determined whether or not the conveying speed can actually be accelerated under the acceleration conditions determined in step S125 (step S126). For this purpose, for example, a threshold value for the heater turn-on rate is determined, and if the current heater turn-on rate is higher than the threshold value, it is determined that acceleration is possible. If the result of the determination in step S126 is that acceleration is possible, the process proceeds to step S130 in FIG. 5, and if acceleration is not possible, the process returns to step S121. In this way, the conveying speed is changed from low to high once a state in which acceleration is actually possible is reached.

[0130] <6. Effects> According to this embodiment, the print control unit 14 is provided with a speed change condition determination unit 141 that determines the speed change rate and the post-speed change transport speed when a change in the print paper transport speed is required. The speed change condition determination unit 141 determines the speed change rate and the post-speed change transport speed taking into account the state of ink supply from the ink supply unit 29 to the printing unit 24 and the state of the drying unit 25. This makes it possible to suppress the occurrence of variations in ink supply and uneven drying caused by the temperature control in the drying unit 25 not keeping up with changes in the transport speed. As a result, deterioration in print quality is suppressed. As described above, an inkjet printing device is realized that can change the transport speed of print paper when a change in the transport speed is required in order to minimize deterioration in print quality.

[0131] <7. Variations> Modifications of the above embodiment will now be described.

[0132] <7.1 Two-stage acceleration / deceleration> In the above embodiment, attention was focused on the case where only one-stage deceleration and one-stage acceleration are performed. However, the present invention can also be applied to the case where two-stage deceleration and two-stage acceleration are performed. Note that, with a configuration that allows two-stage acceleration and deceleration, the conveying speed can be changed more flexibly, and therefore, deterioration of print quality due to changes in the conveying speed can be effectively suppressed.

[0133] <7.1.1 First Modification> First, referring to Figure 15, a first modified example of an operation example when a slowdown in the transport speed is required due to a delay in the transfer of print data (image data) from the RIP server 40 to the printing device 10 will be described. It is assumed that a slowdown in the transport speed is required because a delay in the transfer of print data has significantly reduced the amount of free space in the buffer. It is also assumed that a special mode is available that minimizes degradation in print quality while preventing printing from being stopped as much as possible. In this modified example, different operations are performed when the special mode is set and when a mode other than the special mode is set.

[0134] Regarding the deceleration of the conveying speed from V30 to V32, when a mode other than the special mode is set, deceleration is performed at a relatively high deceleration rate, as shown by the solid line labeled with reference numeral 78 in Fig. 15. At this time, the conveying speed reaches V32 at time t02.

[0135] In contrast, when the special mode is set, the conveying speed is first decelerated from V30 to V31 at a relatively low deceleration rate, as shown by the thick solid line labeled 79 in FIG. 15. Note that V31 is a speed higher than V32. After the conveying speed reaches V31 at time t01, the conveying speed is maintained at V31. Then, at time t03, it is determined whether the free space in the buffer has recovered to a predetermined threshold. If the result of the determination is that the free space in the buffer has recovered to the threshold, the conveying speed is accelerated from V31 to V30, as shown by the thick dashed line labeled 80 in FIG. 15. On the other hand, if the free space in the buffer has not recovered to the threshold, the conveying speed is further decelerated, as shown by the dotted line labeled 81 in FIG. 15, and the conveying speed reaches V32 at time t04.

[0136] As described above, this modification prevents the conveying speed from decreasing more than necessary when the special mode is set, which makes it possible to shorten the printing time when the conveying speed is increased or decreased during printing.

[0137] In the example shown in FIG. 15, V30 corresponds to the high speed, V31 corresponds to the first low speed, and V32 corresponds to the second low speed.

[0138] <7.1.2 Second Variation> 16, a second modified example will be described in which acceleration and deceleration are performed in two stages in consideration of the state of the drying section 25. In this modified example, different operations are performed when the drying performance mode is set and when a mode other than the drying performance mode is set.

[0139] Regarding the deceleration of the conveying speed from V40 to V42 and the acceleration of the conveying speed from V42 to V40, when a mode other than the drying performance mode is set, deceleration from V40 to V42 is performed at a relatively high deceleration rate, and then acceleration from V42 to V40 is performed at a relatively high acceleration rate, as shown by the solid line labeled with reference numeral 82 in Fig. 16. In this way, when a mode other than the drying performance mode is set, acceleration and deceleration are performed in one step.

[0140] In contrast, when the drying performance mode is selected, two-stage deceleration and two-stage acceleration are performed, as indicated by the bold dotted line labeled 83 in FIG. 16 . Specifically, first, at time t11, the conveying speed is decelerated at a relatively low deceleration rate. After the conveying speed reaches V41 at time t12, the conveying speed is maintained at V41. This is to wait for the heater activation rate to sufficiently decrease to prevent the printed material from drying excessively. When the heater activation rate has sufficiently decreased at time t13, the conveying speed is decelerated from V41 to V42 at a relatively high deceleration rate. After the conveying speed reaches V42 at time t14, when the condition requiring printing at a low conveying speed (V42) is resolved at time t15, the conveying speed is accelerated from V42 to V41 at a relatively high acceleration rate. After the conveying speed reaches V41 at time t16, the conveying speed is maintained at V41. This is to wait for the heater activation rate to sufficiently increase to prevent the printed material from drying insufficiently. When the heater turn-on rate increases sufficiently at time t17, the conveying speed is accelerated from V41 to V40 at a relatively low acceleration rate, and then, at time t18, the conveying speed reaches V40.

[0141] As described above, according to this modified example, when the drying performance mode is set, the conveying speed is reduced to prevent the printed matter from drying too much, and the conveying speed is increased to prevent the printed matter from drying too little.

[0142] In the example shown in FIG. 16, V40 corresponds to the high speed, V41 corresponds to the first low speed, and V42 corresponds to the second low speed.

[0143] <7.2 Example of indefinite conveying speed and acceleration / deceleration rate (third modified example)> An example in which the transport speed and acceleration / deceleration rate are inconstant will be described as the third modified example. In this modified example, the transport speed changes as shown by the solid line labeled 84 in Figure 17. The present invention can also be applied to cases in which the transport speed changes irregularly during printing.

[0144] <7.3 Example in which multiple modes can be selected (fourth modified example)> In the above embodiment, it was assumed that the continuous printing mode, high quality mode, and drying performance mode were available and the user could select only one mode. However, in reality, many printing devices allow the user to select two or more modes simultaneously. Therefore, an example in which multiple modes can be selected simultaneously will be described as the fourth modified example.

[0145] In this modified example, when a need arises to change the conveying speed while multiple modes are selected, a process for determining which mode to prioritize (hereinafter referred to as a "priority mode determination process") is performed prior to a process for determining the speed change conditions (deceleration conditions, acceleration conditions). Then, a process for determining the speed change conditions is performed based on the results of the priority mode determination process. For example, assume that a determination is made in the priority mode determination process that the high quality mode is prioritized while the continue printing mode, high quality mode, and drying performance mode are all selected. In this case, assuming that the continue printing mode and drying performance mode are not set but the high quality mode is set, the speed change conditions are determined, for example, using the same procedure as in the above embodiment. The priority mode determination process will be described below.

[0146] In order to perform the priority mode determination process, a table 65 (hereinafter referred to as the "priority setting table") as shown in FIG. 18 is prepared in advance, which holds the priorities of various control factors for each mode. More specifically, the priority setting table 65 holds, for each mode, the priorities for constraints on the preceding and following devices, transport control, drying control, ink supply control, and print control. For example, from the column indicated by the arrow labeled with reference numeral 85 in FIG. 18, it can be seen that when the high quality mode is set, the best print control is given the most importance. Also, from the row indicated by the arrow labeled with reference numeral 86 in FIG. 18, it can be seen that the best drying control is given the most importance when the drying performance mode is set among the above three modes. It is preferable that the priorities held in the priority setting table 65 can be changed by the user as needed. In addition, constraints on the front and rear devices are associated with the third table (see Figure 9), drying control is associated with the first table (see Figure 7), ink supply control is associated with the second table (see Figure 8), and printing control is associated with the fourth table (see Figure 11).

[0147] With the priority setting table 65 as described above prepared, the mode to be prioritized is determined, for example, as follows: It is assumed here that the post-processing machine sends an instruction to the printing device 10 to "reduce the conveying speed from 100 mpm to 30 mpm at a deceleration rate of 60%." It is also assumed that the current heater illumination rate is 50% and the current ink supply rate is 90%.

[0148] First, a score is calculated for each control factor (see Figure 19). For constraints on the front and rear devices, the deceleration rate is 60% and the transport speed after deceleration is 30 mpm, so the score is P1 according to Figure 9. For transport control, it is assumed that the score is uniformly set to P1. For drying control, the deceleration rate is 60% and the heater lighting rate is 50%, so the score is P2 according to Figure 7. For ink supply control, the deceleration rate is 60% and the ink supply rate is 90%, so the score is P3 according to Figure 8. For printing control, the deceleration rate is 60% and the transport speed after deceleration is 30 mpm, so the score is P2 according to Figure 11. It is assumed that the specific numerical values ​​of scores P1 to P3 are "P1 = 10, P2 = 50, P3 = 0".

[0149] Next, for each mode, the product of the score calculated as described above and the priority is calculated for each control factor. For example, for the part marked with reference numeral 87 in Fig. 19, the score (numerical value) for the constraints on the front and rear devices is 10, and the priority is 5 from Fig. 18, so the product is 50.

[0150] After calculating the product of the score and the priority, a total value is calculated for each mode. The mode with the highest total value is then adopted as the mode to be prioritized. In the example shown in FIG. 19, the total value of the high quality mode is the highest among the three modes, so the high quality mode is adopted as the mode to be prioritized. As a result, even if the continue printing mode, high quality mode, and drying performance mode are all actually selected, the deceleration conditions are determined as if the high quality mode was set.

[0151] <7.4 Example of determining gear shift conditions using machine learning (fifth modified example)> In recent years, machine learning such as deep learning has been used in various fields. Gear change conditions (deceleration conditions, acceleration conditions) can also be determined using machine learning. Therefore, an example in which the deceleration rate is determined using machine learning will be described as a fifth modified example.

[0152] In this modification, a temperature sensor is installed in the drying unit 25, and machine learning is performed using information on the drying temperature obtained from the temperature sensor. As a learning device for performing this machine learning, a neural network 150 (see FIG. 20) is prepared, which uses the drying temperature TEin at the start of deceleration, the conveying speed Vs before deceleration, the conveying speed Ve after deceleration, and the deceleration rate R as input data, and uses the drying temperature (predicted value) TE1 at the end of deceleration and the drying temperature (predicted value) TE2 one minute after the end of deceleration as output data. As the type of neural network 150, for example, a general forward propagation neural network or a convolutional neural network can be adopted.

[0153] To enable the use of the neural network 150 described above, each time the conveying speed is decelerated, it is necessary to store, for example, in a database, information on the drying temperature TEin at the start of deceleration, the conveying speed Vs before deceleration, the conveying speed Ve after deceleration, the deceleration rate R, the drying temperature (actual measured value) at the completion of deceleration, and the drying temperature (actual measured value) one minute after the completion of deceleration. The reason for using the information on the drying temperature (actual measured value) one minute after the completion of deceleration in addition to the information on the drying temperature (actual measured value) at the completion of deceleration is that it is considered that even if the desired drying temperature is reached at the completion of deceleration, the temperature may continue to change and the drying temperature may deviate from the desired drying temperature after the completion of deceleration.

[0154] In the following, the predicted value of the drying temperature at the time deceleration is completed will be referred to as the "first predicted temperature," the predicted value of the drying temperature one minute after deceleration is completed will be referred to as the "second predicted temperature," the actual measured value of the drying temperature at the time deceleration is completed will be referred to as the "first actual measured temperature," and the actual measured value of the drying temperature one minute after deceleration is completed will be referred to as the "second actual measured temperature."

[0155] Fig. 21 is a flowchart showing the procedure for determining the deceleration rate in this modified example. Of the processes of steps S200 to S240 shown in Fig. 21, the processes of steps S210 to S240 are carried out when actually determining the deceleration rate, and the process of step S200 is carried out in advance. When it becomes necessary to actually change the conveying speed, the processes of steps S210 to S240 are carried out by the speed change condition determination unit 141.

[0156] In step S200, neural network 150 is trained. The neural network 150 receives, as input data, the drying temperature TEin at the start of deceleration, the conveying speed Vs before deceleration, the conveying speed Ve after deceleration, and the deceleration rate R. A forward propagation process is then performed within the neural network 150, and a first predicted temperature TE1 and a second predicted temperature TE2 are output from the neural network 150. The first and second measured temperatures corresponding to the input data are then retrieved from the database, and the sum of the "squared error between the first predicted temperature TE1 and the first measured temperature" and the "squared error between the second predicted temperature TE2 and the second measured temperature" (i.e., the total sum of squared errors) is calculated. Then, the parameters (weighting coefficients, bias) of the neural network 150 are updated by the backpropagation method so as to minimize the total sum of squared errors. Repeated learning in this manner optimizes the parameters. As described above, before the process of actually determining the deceleration rate is performed, the neural network 150 is prepared as a learning device that has been trained by machine learning using the deceleration conditions and the like as input data.

[0157] As for the learning method in step S200, batch learning may be adopted in which all of the training data (in this example, one set of training data consists of the drying temperature TEin at the start of deceleration, the conveying speed Vs before deceleration, the conveying speed Ve after deceleration, the deceleration rate R, the first measured temperature, and the second measured temperature) is given to the neural network 150 all at once, or mini-batch learning may be adopted in which the training data is divided into multiple groups and training data is given to the neural network 150 for each group, or online learning may be adopted in which training data is given to the neural network 150 one by one.

[0158] In step S210, information on the drying temperature TEin at the start of deceleration, the conveying speed Vs before deceleration, and the conveying speed Ve after deceleration is acquired. Note that it is assumed that the conveying speed Ve after deceleration has been determined before this process is performed. It is also assumed that the target drying temperature after deceleration (hereinafter referred to as "target temperature") has been set before this process is performed.

[0159] In step S220, the information acquired in step S210, namely, the drying temperature TEin at the start of deceleration, the conveying speed Vs before deceleration, the conveying speed Ve after deceleration, and the deceleration rate R, are input to the neural network 150. Regarding the deceleration rate R, values ​​are sequentially assigned in increments of, for example, 5% within a range that satisfies the constraints related to conveyance control. For example, values ​​between 5% and 70% are assigned in increments of 5%. In this case, 14 values ​​of the deceleration rate R are sequentially input to the neural network 150. That is, multiple sets of input data representing the deceleration conditions are input to the neural network 150. Then, a first predicted temperature TE1 and a second predicted temperature TE2 are output from the neural network 150 for each value of the deceleration rate R.

[0160] In step S230, the sum of the "squared error between the first predicted temperature TE1 and the target temperature" and the "squared error between the second predicted temperature TE2 and the target temperature" (hereinafter referred to as the "temperature error" for convenience) is calculated for each value of the deceleration rate R input to the neural network 150 in step S220. In the above example, 14 temperature errors are calculated.

[0161] In step S240, the value of the deceleration rate R that resulted in the smallest temperature error among the temperature errors (14 temperature errors in the above example) found in step S230 is determined as the value of the deceleration rate to be actually applied. In other words, the value of the deceleration rate that corresponds to the input data when the output data closest to the target value (target temperature) is output from the neural network 150 is determined as the value of the deceleration rate to be actually applied.

[0162] According to this modification, for example, if it is desired to lower the drying temperature from 100° C. before deceleration to 60° C. after deceleration, the deceleration rate is determined so that the drying temperature at the completion of deceleration and the drying temperature one minute after the completion of deceleration will be close to 60° C. In this way, also in this modification, the deceleration rate when the conveying speed is decelerated is determined taking into consideration the state of the drying unit 25.

[0163] <7.5 Example in which a printing device using UV ink is used (sixth modified example)> In the above embodiment, it is assumed that printing is performed using aqueous ink, but the present invention is not limited to this. Therefore, an example in which a printing device using UV ink (ultraviolet curable ink), such as a printing device for label printing, is adopted will be described as a sixth modified example.

[0164] In this modification, UV ink is ejected from each inkjet head constituting inkjet head arrays 24c, 24m, 24y, and 24k (see FIG. 2) in the printing unit 24. Furthermore, instead of the drying unit 25, an ultraviolet irradiation unit that cures the UV ink on the printed printing paper by irradiating it with ultraviolet light is provided inside the printing mechanism. When it becomes necessary to slow down the conveying speed, the speed change condition determination unit 141 determines the deceleration rate and the conveying speed after deceleration, taking into account at least one of the state of ink supply from the ink supply unit 29 to the printing unit 24 and the state of the ultraviolet irradiation unit. Similarly, when it becomes necessary to accelerate the conveying speed, the speed change condition determination unit 141 determines the acceleration rate and the conveying speed after acceleration, taking into account at least one of the state of ink supply from the ink supply unit 29 to the printing unit 24 and the state of the ultraviolet irradiation unit.

[0165] <8.Other> The present invention is not limited to the above-described embodiment (including the modified examples), and various modifications can be made without departing from the spirit of the present invention. Furthermore, the above-described embodiment and the modified examples can be combined appropriately so as not to cause any contradiction. [Explanation of symbols]

[0166] 1. Printing system 10…Printing device 24…Printing Department 25...Drying section 28...Transport unit 29...Ink supply unit 50...Web buffer 52…Post-processing machine group 61~64...Tables 1~4 65...Priority setting table 100...printing control device 140... Overall processing unit 141...Shift condition determination unit 142...Transport control unit 143...Ink supply control unit 144...Printing control unit 145...Drying control unit 150...Neural Network 200...printing machine body P...Print control program

Claims

1. 1. An image forming apparatus comprising: a transport unit that transports a long strip of print medium; and a printing unit that forms an image by ejecting ink onto the print medium being transported by the transport unit, a transport control unit that controls the operation of the transport unit; an ink supply unit that supplies ink to the printing unit; a drying unit that dries the printed print medium on which the image has been formed by the printing unit; a speed change condition determination unit that, when it becomes necessary to change the transport speed, which is the distance the print medium is transported per unit time by the transport unit, determines speed change conditions including a speed change rate, which is the amount of change in the transport speed per unit time, and the transport speed after the speed change, taking into consideration at least one of the state of ink supply from the ink supply unit to the printing unit and the state of the drying unit; Equipped with The image forming apparatus, wherein the transport control unit controls the operation of the transport unit in accordance with the speed change condition determined by the speed change condition determination unit.

2. 2. The image forming apparatus according to claim 1, wherein the speed change condition determination unit takes into consideration a state of ink supply from the ink supply unit to the printing unit when determining the speed change rate and the transport speed after the speed change.

3. 2. The image forming apparatus according to claim 1, wherein the speed change condition determining unit takes into consideration the state of the drying unit when determining the speed change rate and the transport speed after the speed change.

4. 2. The image forming apparatus according to claim 1, wherein the speed change condition determination unit takes into consideration both the ink supply state from the ink supply unit to the printing unit and the state of the drying unit when determining the speed change rate and the transport speed after the speed change.

5. a high quality mode that prioritizes the quality of the image on the printed print medium and a drying performance mode that prioritizes the dryness of the printed print medium; when the high quality mode is set, the speed change condition determination unit determines the speed change rate and the transport speed after the speed change, taking into consideration the ink supply state from the ink supply unit to the printing unit with priority over the state of the drying unit; 5. The image forming apparatus according to claim 4, wherein when the drying performance mode is set, the speed change condition determination unit determines the speed change rate and the transport speed after the speed change by taking into consideration the state of the drying unit rather than the state of ink supply from the ink supply unit to the printing unit.

6. the drying unit includes a plurality of light sources that generate heat when turned on; a first table is prepared in advance, which stores the relationship between the combination of the lighting rates of the plurality of light sources and the speed change rate and the score; Depending on the mode you've set, the conditions for the score you need will be set.

6. The image forming apparatus according to claim 3, wherein the speed change condition determination unit determines the speed change rate based on the first table, taking into account lighting rates of the plurality of light sources.

7. The image forming device described in Claim 6, characterized in that the first table is created so that the higher the lighting rate of the multiple light sources, the lower the score, and the higher the speed change rate, the lower the score.

8. an ink supply control unit that controls an ink supply rate that indicates the degree of ink supply from the ink supply unit to the printing unit; a second table is prepared in advance, which stores the relationship between the combination of the ink supply rate and the speed change rate and the score; Depending on the mode you've set, the conditions for the score you need will be set.

6. The image forming apparatus according to claim 2, wherein the speed change condition determining section determines the speed change rate based on the second table, taking into account the ink supply rate.

9. The image forming apparatus described in Claim 8, characterized in that the second table is created so that the higher the ink supply rate, the lower the score, and the higher the speed change rate, the lower the score.

10. a learning device that has been trained by machine learning using the shift conditions as input data; 5. The image forming apparatus according to claim 1, wherein when it becomes necessary to change the conveying speed, the speed change condition determination unit provides the learning device with a plurality of sets of input data representing the speed change conditions, and determines the speed change condition corresponding to the input data when the learning device outputs output data closest to the target value as the speed change condition to be actually applied.

11. The temperature of the drying section is adopted as the target value, The input data further includes a temperature of the drying section before a speed change.

11. The image forming apparatus according to claim 10, wherein the learning device outputs a predicted temperature of the drying unit after the speed change as the output data.

12. 12. The image forming apparatus according to claim 1, wherein the speed change condition determination unit, when determining the speed change rate and the transport speed after the speed change, further takes into account constraints based on the operation of at least one of the source of the printing medium or the destination of the printed printing medium.

13. the printing unit includes a print head that ejects ink onto the print medium; 13. The image forming apparatus according to claim 1, wherein the speed change condition determination unit further considers the ink ejection state from the print head to the printing medium when determining the speed change rate and the transport speed after the speed change.

14. One or more modes can be set, 14. The image forming apparatus according to claim 1, wherein the speed change condition determination unit changes the speed change rate and the conveying speed after the speed change according to a set mode.

15. a high speed, a first low speed, and a second low speed that is lower than the first low speed, as transport speeds when the transport unit transports the print medium at a constant speed; 15. The image forming apparatus according to claim 1, wherein the conveying control unit is capable of performing deceleration from the high speed to the second low speed in two steps: a first deceleration from the high speed to the first low speed and a second deceleration from the first low speed to the second low speed.

16. 16. The image forming apparatus according to claim 15, wherein the speed change condition determining unit determines the speed change rate for the second deceleration to be higher than the speed change rate for the first deceleration.

17. 16. The image forming apparatus according to claim 15, wherein the transport control unit is capable of accelerating from the first low speed to the high speed without decelerating from the first low speed to the second low speed after the first deceleration.

18. 1. An image forming apparatus comprising: a transport unit that transports a long strip-shaped print medium; and a printing unit that forms an image by ejecting photocurable ink onto the print medium being transported by the transport unit, a transport control unit that controls the operation of the transport unit; an ink supply unit that supplies photocurable ink to the printing unit; an ultraviolet irradiation unit that cures the photocurable ink on the print medium on which the image has been formed by the printing unit by irradiating it with ultraviolet light; a speed change condition determination unit that, when it becomes necessary to change the transport speed, which is the distance the print medium is transported per unit time by the transport unit, determines speed change conditions including a speed change rate, which is the amount of change in the transport speed per unit time, and the transport speed after the speed change, taking into consideration at least one of the supply state of the photo-curable ink from the ink supply unit to the printing unit or the state of the ultraviolet irradiation unit; Equipped with The image forming apparatus, wherein the transport control unit controls the operation of the transport unit in accordance with the speed change condition determined by the speed change condition determination unit.

19. A control method for an image forming apparatus including a transport unit that transports a long strip of printing medium, a printing unit that forms an image by ejecting ink onto the printing medium being transported by the transport unit, an ink supply unit that supplies ink to the printing unit, and a drying unit that dries the printed printing medium on which an image has been formed by the printing unit, comprising: a speed change condition determination step for determining, when it becomes necessary to change the transport speed, which is the distance the print medium is transported per unit time by the transport unit, a speed change condition including a speed change rate, which is the amount of change in the transport speed per unit time, and the transport speed after the speed change, taking into consideration at least one of the state of ink supply from the ink supply unit to the printing unit or the state of the drying unit; a transport control step of controlling the operation of the transport unit in accordance with the speed change condition determined in the speed change condition determination step; 10. A method for controlling an image forming apparatus, comprising:

20. 1. A control method for an image forming apparatus comprising: a transport unit that transports a long strip-shaped print medium; a printing unit that forms an image by ejecting photocurable ink onto the print medium being transported by the transport unit; an ink supply unit that supplies photocurable ink to the printing unit; and an ultraviolet irradiation unit that cures the photocurable ink on the printed print medium on which an image has been formed by the printing unit by irradiating it with ultraviolet light, a speed change condition determination step for determining, when it becomes necessary to change the transport speed, which is the distance the print medium is transported per unit time by the transport unit, a speed change condition including a speed change rate, which is the amount of change in the transport speed per unit time, and the transport speed after the speed change, taking into consideration at least one of the supply state of the photo-curable ink from the ink supply unit to the printing unit or the state of the ultraviolet irradiation unit; a transport control step of controlling the operation of the transport unit in accordance with the speed change condition determined in the speed change condition determination step; 10. A method for controlling an image forming apparatus, comprising:

Images