JP2016144912A - Droplet drying device, droplet drying program, and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a droplet drying device capable of suppressing excessive drying even in a case where recording is made at a lower transportation speed, in an image formation device of which transportation speed of a recording medium is variable.SOLUTION: An image formation device 10 controls intensity in drying at a drying part 70 so that an outlet temperature which is a temperature of an ink droplet at an outlet of a drying part 70 becomes lower as a transportation speed of a recording paper P becomes slower.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a droplet drying apparatus, a droplet drying program, and an image forming apparatus.

  In Patent Document 1, a fixing heater is applied to a recording medium according to the conveyance speed of the recording medium so that the energy applied to the recording medium from a fixing heater that fixes the ink to the recording medium becomes a predetermined amount of energy. An ink jet recording apparatus that controls the amount of heat per unit time is disclosed.

JP 2008-1113 A

  When an image forming apparatus with a variable recording medium conveyance speed is used for recording at a low conveyance speed, droplets on the recording medium are supplied with the same amount of thermal energy as before the conveyance speed is reduced. When the is dried, the drying time becomes longer and may become overdried. An object of the present invention is to suppress overdrying of a droplet as compared with a case where a predetermined amount of heat energy is supplied to the same level as before the conveyance speed is lowered to dry the droplet.

  In order to achieve the above object, the invention of the droplet drying apparatus according to claim 1 is characterized in that the drying means for drying the droplets on the recording medium to be transported and the drying as the transport speed of the recording medium decreases. Control means for controlling the drying strength of the drying means so that the outlet temperature, which is the temperature of the droplets at the outlet of the means, is lowered.

  According to a second aspect of the present invention, the controller reaches the outlet of the drying unit after the temperature of the droplet reaches a predetermined reference temperature by drying the droplet by the drying unit. The drying strength of the drying means is controlled so that the variation in the drying time until completion is included in a predetermined range.

  According to a third aspect of the present invention, the control means uses the fact that the drying strength of the drying means is approximately proportional to the temperature rise of the droplets, so that the drying strength of the drying means A temperature indicated by a predetermined temperature curve of the droplet at a time when the temperature of the droplet reaches the reference temperature at a conveyance speed, the reference temperature, and a drying intensity associated with the predetermined temperature curve; The drying strength of the drying means is controlled so as to approach the target drying strength obtained from.

  According to a fourth aspect of the present invention, the predetermined temperature curve is any one of a plurality of temperature curves, and the control means varies the drying time in each of the plurality of temperature curves. Is the reference temperature.

  According to a fifth aspect of the present invention, the control unit predetermines the droplets, and a plurality of data pairs in which the predetermined transport speed and the outlet temperature of the droplets at the predetermined transport speed are associated with each other. The predetermined temperature curve corresponding to each of the data pairs is set from the reference temperature curve when the droplets are transported at a reference transport speed and the droplets are dried at a predetermined reference dry strength, and the drying is performed. Using the fact that the drying strength of the means is approximately proportional to the temperature rise of the droplet, the temperature of the droplet indicated by each of the predetermined temperature curves at a specific time and the reference temperature curve indicate Based on the temperature of the droplet and the predetermined reference dry intensity associated with the reference temperature curve, the obtained dry intensity is associated with each of the predetermined temperature curves.

  The invention described in claim 6 further comprises receiving means for receiving each of the data pairs.

  According to a seventh aspect of the present invention, the receiving means includes at least one of a type of the recording medium, a type of the droplet, a designation state of an image forming surface on the recording medium, and a form of an image formed on the recording medium. The control unit selects the reference temperature curve corresponding to the image forming condition received by the receiving unit from a plurality of reference temperature curves.

  The invention of the droplet drying program according to claim 8 causes the computer to function as control means of the droplet drying apparatus according to any one of claims 1 to 7.

  The invention of claim 9 is an image forming apparatus according to any one of claims 1 to 7, further comprising: an ejection unit that ejects droplets onto a recording medium according to an image; a conveyance unit that conveys the recording medium; And a control means for controlling the discharge means, the transport means, and the droplet drying apparatus.

  According to the first, eighth, and ninth inventions, overdrying of the droplets is suppressed as compared with the case where the droplets are dried by supplying a predetermined amount of thermal energy to the droplets on the recording medium. There is an effect that can be.

  According to the invention of claim 2, there is an effect that it is possible to further suppress the excessive drying of the droplet as compared with the case where the drying time of the droplet exceeds the predetermined range.

  According to the invention of claim 3, the drying strength is reduced with a small amount of calculation compared with the case of obtaining the drying strength of the drying means without using the proportional relationship between the temperature rise of the droplets and the drying strength by the drying means. Can be obtained.

  According to invention of Claim 4, compared with the case where reference temperature is fixed, there exists an effect that reference temperature can be set accurately.

  According to the invention of claim 5, the effect that the temperature curve corresponding to the data pair can be set with higher accuracy than the case where the temperature curve corresponding to the data pair is set without using the reference temperature curve. Play.

  According to the invention of claim 6, compared to the case where the value of the data pair is fixed, the temperature curve corresponding to the designated recording medium transport speed and droplet outlet temperature can be set. Play.

  According to the seventh aspect of the present invention, it is possible to use a reference temperature curve corresponding to actual image forming conditions more than when the same reference temperature curve is used for each image formation.

1 is a schematic configuration diagram illustrating an example of a main configuration unit in an image forming apparatus. 1 is a diagram illustrating an example of a configuration of a main part of an electric system in an image forming apparatus. It is a flowchart which shows an example of the flow of a drying process. It is a figure which shows an example of a reference | standard temperature curve. It is a figure which shows an example of the reference | standard temperature curve corrected according to inlet_port | entrance temperature. It is a figure which shows an example of the temperature curve set from a reference temperature curve. It is a schematic diagram with which it uses for description for calculating drying acceleration time from a temperature curve. It is a schematic diagram with which it uses for description for setting the temperature curve in an operation | movement conveyance speed. It is a figure which shows an example of the side view of a drying part provided with a shutter. It is a figure which shows an example of the side view of a drying part provided with a shutter. It is a figure which shows an example of the temperature curve obtained when an operation | movement conveyance speed is changed. It is a diagram schematically showing a method for fixing ink droplets in a conventional image forming apparatus. It is a figure which shows an example of the change of the surface temperature of an ink drop at the time of changing the output of a drying part. It is a figure which shows an example of the temperature curve of an ink drop at the time of adjusting the output of a drying part with a different conveyance speed. It is a schematic diagram for demonstrating the drying time of an ink drop.

  Hereinafter, embodiments of the present invention will be described. In addition, the same code | symbol may be provided to the component and process which an action or a function bears the same function through all drawings, and the overlapping description may be abbreviate | omitted suitably.

  FIG. 12 is a diagram schematically illustrating a method for fixing ink droplets onto a recording sheet in a conventional image forming apparatus 12 that employs an inkjet method.

  For example, the ink droplet Q ejected onto the recording paper P from the print head 50 </ b> K that ejects black ink droplets is conveyed to the drying unit 70. Then, moisture of the ink droplet Q is evaporated by a heat source that irradiates thermal energy such as an IR (Infrared) heater 72 provided in the drying unit 70, and the ink droplet Q ′ that has passed through the drying unit 70 is fixed on the recording paper P.

  The fixing quality of the ink droplets Q on the recording paper P may depend on, for example, fluctuations in the surface temperature of the ink droplets Q at the outlet of the drying unit 70. This is because when the surface temperature of the ink droplet Q at the outlet of the drying unit 70 fluctuates, the evaporation amount of the water contained in the ink droplet Q also fluctuates, and the degree of fixing of the ink droplet Q to the recording paper P varies. .

  For example, when it is necessary to change the conveyance speed of the recording paper P in the image forming apparatus 12 due to the processing speed of the subsequent process following the image forming process such as folding the recording paper P after image formation, the ink droplets Q are dried. The time to pass through 70 varies. For example, as the conveyance speed of the recording paper P increases, the time for the ink droplets Q to pass through the drying unit 70 decreases. Therefore, when the energy amount of the thermal energy applied to the ink droplet Q from the drying unit 70 is a predetermined energy amount, the thermal energy received by the ink droplet Q from the drying unit 70 as the conveyance speed of the recording paper P increases. In some cases, the surface temperature (exit temperature) of the ink droplet Q at the exit of the drying unit 70, that is, the position where the drying unit 70 has finished passing through the drying range of the ink droplet Q, falls below a predetermined temperature. is there. Accordingly, the image forming apparatus 12 adjusts the drying strength, that is, the output of the IR heater 72 so that the outlet temperature of the ink droplet Q approaches a predetermined temperature when the conveyance speed of the recording paper P changes.

  Next, a method for adjusting the output of the IR heater 72 by the conventional image forming apparatus 12 when the conveyance speed of the recording paper P is changed will be described.

  FIG. 13 is a graph showing an example of a change in the surface temperature of the ink droplet Q in the drying unit 70 when the output of the IR heater 72 in the drying unit 70 is changed.

  The vertical axis of the graph illustrated in FIG. 13 represents the surface temperature of the ink droplet Q, and the horizontal axis represents the elapsed time since the drying unit 70 began to irradiate the ink droplet Q with thermal energy. For example, assuming that the rated output in the drying unit 70 is 100% output, the graph 75 is a change in the surface temperature of the ink droplet Q at 20% output, the graph 76 is a change in the surface temperature of the ink droplet Q at 40% output, and the graph 77 is The change in the surface temperature of the ink drop Q at 60% output, the graph 78 shows the change in the surface temperature of the ink drop Q at 80% output, and the graph 79 shows the change in the surface temperature of the ink drop Q at 100% output.

  As shown in FIG. 13, the increase from the initial surface temperature of each ink droplet Q represented by the graph 75 to the graph 79 at each elapsed time exceeding the elapsed time of 0 [s] is the output of the drying unit 70. It shows a change that can be regarded as changing at a similar rate to the change in. Here, the same level means a state in which the fluctuation of the value (in this case, the ratio) falls within a predetermined range.

  For example, from FIG. 13, the surface temperature of the ink droplet Q in the graph 76 (output 40%) at an elapsed time of 0.7 [s] is about 103 [° C.], and the surface temperature of the ink droplet Q in the graph 78 (output 80%). Can be read as about 176 [° C.]. Since the initial temperature is about 30 ° C., the respective temperature rise values are about 73 ° C. for graph 76 and about 146 ° C. for graph 78, and their ratio (146/73 = 2) is the output ratio (80/40). = 2). In terms of thermodynamics, when the amount of heat applied from the outside is ΔQ, the heat capacity of the ink droplet is C, and the temperature rise of the ink droplet is ΔT, this generally corresponds to ΔQ = CΔT. Therefore, the graph 78 is obtained by adding the initial temperature by multiplying the initial temperature of the surface temperature of the ink droplet Q in the graph 76 at each elapsed time exceeding 0 [s] by about twice.

  A common proportional relationship is also recognized between the output of the drying unit 70 and the ratio of the surface temperature increase of the ink droplet Q at each elapsed time exceeding 0 [s].

Therefore, if the proportional relationship is used, the surface temperature rise value (for example, T _a ) of the ink droplet Q corresponding to the output of any one of the drying units 70 at a specific elapsed time and another ink different from the surface temperature. From the ratio of the surface temperature increase value of the droplet Q (for example, temperature T _b ), the output of the drying unit 70 for setting the surface temperature increase value of the ink droplet Q to the temperature T _b in a specific elapsed time is specified.

  The initial surface temperature of the ink droplet Q at an elapsed time of 0 [s] represents the surface temperature of the ink droplet Q before the drying unit 70 starts drying the ink droplet Q, and is hereinafter referred to as “inlet temperature”. . A graph showing a change in the surface temperature of the ink droplet Q with respect to the elapsed time from the start of irradiating the ink droplet Q with the thermal energy from the drying unit 70 is referred to as a “temperature curve”, and graphs 75 to 79 are the temperature curve 75. Also referred to as a temperature curve 79.

  Here, when the conveyance speed of the recording paper P is reduced to about ½ from the current conveyance speed, for example, the outlet temperature of the ink droplet Q is determined in advance by adjusting the output of the drying unit 70 to about ½. Kept at temperature.

  FIG. 14 shows an example of a temperature curve of the ink droplet Q in the drying unit 70 when the output of the drying unit 70 is adjusted between different conveyance speeds of the recording paper P.

  The vertical axis of the temperature curve illustrated in FIG. 14 represents the surface temperature of the ink droplet Q, and the horizontal axis represents the elapsed time from the start of irradiating the ink droplet Q from the drying unit 70 with thermal energy. A temperature curve 81 represents a temperature curve of the ink droplet Q when the recording paper P transport speed is 1 [m / s], and a temperature curve 82 indicates that the recording paper P transport speed is 0.5 [m / s]. 2 represents a temperature curve of the ink droplet Q in the case of s]. The output of the drying unit 70 in the temperature curve 82 is adjusted to about ½ of the output of the drying unit 70 in the temperature curve 81.

  In this case, the thermal energy density irradiated from the drying unit 70 to the ink droplet Q under the condition corresponding to the temperature curve 82 is the thermal energy density irradiated from the drying unit 70 to the ink droplet Q under the condition corresponding to the temperature curve 81. It becomes about 1/2. However, since the conveyance speed of the recording paper P corresponding to the temperature curve 82 is set to ½ of the conveyance speed of the recording paper P corresponding to the temperature curve 81, the conveyance speed is 0.5 [m / s]. The passing time required for the ink droplet Q to enter the drying range of the drying unit 70 and pass through the drying range is twice as long as the transport speed of 1 [m / s], and the thermal energy irradiated to the ink droplet Q. The amount can be considered the same. Accordingly, in the example of FIG. 14, the outlet temperature of the ink droplet Q is about 120 [° C.] in both the temperature curve 81 and the temperature curve 82, and at first glance, the recording paper of the ink droplet Q accompanying the variation in the outlet temperature of the ink droplet Q It seems that the fluctuation of the fixing quality to P is suppressed.

  However, in practice, even if the amount of thermal energy applied to the ink droplets Q is adjusted to the same level according to the conveyance speed of the recording paper P, the recording paper P is reduced as the conveyance speed of the recording paper P is decreased. “Wrinkles” appear in P, and the recording paper P is more likely to be smeared. For example, a phenomenon that occurs when water contained in the ink droplets Q is evaporated more than necessary, that is, in the case of so-called excessive drying occurs. Sometimes.

  Accordingly, the inventor of the disclosed technique examines the cause of overdrying even when the amount of thermal energy applied to the ink droplet Q is adjusted to the same degree according to the conveyance speed of the recording paper P. The following hypothesis was obtained.

  For example, the moisture contained in the ink droplets Q evaporates from the surface of the recording paper P. To that end, it takes time for the moisture of the ink droplets Q that has penetrated the recording paper P to move to the surface of the recording paper P.

  As already described, when the conveyance speed of the recording paper P is slowed, in order to make the amount of thermal energy irradiated to the ink droplet Q the same regardless of the difference in the conveyance speed, according to the delay ratio of the conveyance speed. Thus, the amount of heat energy irradiated from the drying unit 70 to the ink droplet Q is adjusted to be small. However, in this case, the moisture of the ink droplet Q that has penetrated into the recording paper P moves to the surface of the recording paper P as compared to the initial conveying speed before the recording paper P is slowed down. More time is reserved. Accordingly, even if the same amount of heat energy is applied to the ink droplet Q, the moisture contained in the ink droplet Q is more likely to evaporate when the conveyance speed of the recording paper P is slowed down, and overdrying is likely to occur. It is thought that.

  Such movement of the moisture of the ink droplet Q to the surface of the recording paper P becomes more active when the surface temperature of the ink droplet Q is equal to or higher than a predetermined temperature (reference temperature), and the drying of the ink droplet Q is promoted. It is thought that.

FIG. 15 is a diagram showing the drying time of the ink droplet Q at the reference temperature after approximating the temperature curve 81 and the temperature curve 82 shown in FIG. 14 with straight lines for convenience of explanation. The temperature T _in indicates the inlet temperature of the ink droplet Q, the temperature T ₀ indicates the reference temperature of the ink droplet Q, and the temperature T ₁ indicates the outlet temperature of the ink droplet Q.

As shown in FIG. 15, the time (drying acceleration time) for drying the ink droplet Q at the temperature equal to or higher than the reference temperature T ₀ by the drying unit 70 is (m ₁ −m ₁₀ ) in the case of the temperature curve 81. When the conveyance speed of the recording paper P is a temperature curve 82 set to ½ of the conveyance speed indicated by the temperature curve 81, (m ₂ −m ₂₀ ).

As already described, since the output of the drying unit 70 in the temperature curve 82 is set to be smaller than the output of the drying unit 70 in the temperature curve 81, the surface temperature of the ink droplet Q on the temperature curve 82 for the same elapsed time is The surface temperature of the ink droplet Q on the temperature curve 81 is lower. That is, since the temperature curve 82 has a smaller temperature rise gradient with respect to the elapsed time than the temperature curve 81, the drying acceleration time in the temperature curve 82 (m ₂ −m ₂₀ ) is the drying acceleration in the temperature curve 81. It becomes longer than the time (m ₁ -m ₁₀ ).

  Therefore, even if the same amount of thermal energy is applied to the ink droplets Q, the drying acceleration time of the ink droplets Q becomes longer and the overdrying is likely to occur when the conveyance speed of the recording paper P is decreased. Conceivable.

  Hereinafter, an image forming apparatus that suppresses overdrying of the ink droplets Q even when the conveyance speed of the recording paper P is changed will be described.

  FIG. 1 shows an example of a schematic diagram illustrating a main configuration of an image forming apparatus 10 according to the present embodiment.

  The image forming apparatus 10 includes, for example, a control unit 20, a storage unit 30, a head driving unit 40, a print head 50, a paper feed roll 80, a discharge roll 90, a conveyance roller 100, a paper speed detection sensor 110, an operation display unit 120, and A drying device 130 is included.

  The control unit 20 controls the rotation of the transport roller 100 connected to the paper transport motor via a mechanism such as a gear by driving a paper transport motor (not shown). A long recording paper (continuous paper) P is wound as a recording medium in the paper conveyance direction on the paper feed roll 80, and the recording paper P is conveyed in the paper conveyance direction as the conveyance roller 100 rotates. The

  In addition, the control unit 20 acquires, for example, information on an image that the user wants to draw on the recording paper P, that is, user image information, which is stored in the storage unit 30, and color information for each pixel of the image included in the user image information. The head drive unit 40 is controlled based on the above. Then, the head driving unit 40 drives the print head 50 connected to the head driving unit 40 in accordance with the ejection timing of the ink droplet Q instructed by the control unit 20 to eject the ink droplet Q from the print head 50, An image corresponding to the user image information is formed on the transported recording paper P. Hereinafter, an image formed on the recording paper P according to the user image information is referred to as a user image.

  Note that the color information for each pixel of the user image information includes information that uniquely indicates the color of the pixel. In the example of this embodiment, for example, the color information for each pixel of the user image is represented by the respective densities of yellow (Y), magenta (M), cyan (C), and black (K). Other representation methods that uniquely indicate the color of the user image may be used.

  The print head 50 includes four print heads 50Y, 50M, 50C, and 50K corresponding to four colors of Y, M, C, and K, respectively, and ink discharge provided in the print head 50 for each color. A corresponding color ink droplet Q is ejected from the outlet. In addition, there is no restriction | limiting in the drive method for discharging the ink droplet Q in the print head 50, Well-known things, such as what is called a thermal system and a piezoelectric system, are applied.

  The drying device 130 includes, for example, a drying control unit 60 and a drying unit 70.

  The drying control unit 60 includes a switching element such as an FET (Field Effect Transistor) that controls the output of the IR heater 72 included in the drying unit 70. The drying control unit 60 controls the switching element based on an instruction from the control unit 20, for example, and adjusts the amount of heat energy irradiated from the IR heater 72 by changing the duty ratio of the pulse supplied to the IR heater 72. . Specifically, the output of the IR heater 72 decreases as the pulse duty ratio decreases, and the output of the IR heater 72 increases as the pulse duty ratio increases.

  The control unit 20 controls the drying control unit 60 to heat the image forming surface of the recording paper P from the drying unit 70 to dry the ink droplets Q of the user image formed on the recording paper P, and to record The ink droplet Q is fixed on the paper P. Note that the heat source included in the drying unit 70 is not limited to the IR heater 72, and may be any heat source that dries the ink droplets Q using thermal energy, such as a warm air heater.

  Thereafter, the recording paper P is transported to the discharge roll 90 with the rotation of the transport roller 100, and is taken up by the discharge roll 90.

  The paper speed detection sensor 110 is disposed, for example, at a position facing the image forming surface of the recording paper P, and detects the transport speed in the transport direction of the recording paper P. The detection method for detecting the conveyance speed of the recording paper P in the paper speed detection sensor 110 is not limited, and a known method is applied. The sheet speed detection sensor 110 is not an essential component for the image forming apparatus 10.

  For example, the operation display unit 120 receives an instruction from the user of the image forming apparatus 10 such as the conveyance speed of the recording paper P and notifies the user of various types of information regarding the operation status of the image forming apparatus 10. The operation display unit 120 includes, for example, a display button that realizes reception of an operation instruction by a program, a touch panel display on which various information is displayed, and hardware keys such as a numeric keypad or a start button.

  The ink includes water-based inks, oil-based inks that are inks whose solvent evaporates, and ultraviolet curable inks. In this embodiment, as an example, water-based inks containing an emulsion component are used. Hereinafter, the term “ink” or “ink droplet” simply means “water-based ink” or “water-based ink droplet”.

  FIG. 2 is a diagram illustrating a main configuration of an electrical system in the image forming apparatus 10. The control unit 20 is realized by the computer 20, for example.

  As shown in FIG. 2, the computer 20 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, a nonvolatile memory 204, and an input / output interface (I / O) 205. Are connected to each other via a bus 206. The I / O 205 is connected to a head drive unit 40, a drying control unit 60, a paper speed detection sensor 110, an operation display unit 120, a paper transport motor 140, and a communication line I / F (Interface) 150. Further, the print head 50 is connected to the head driving unit 40, and the drying unit 70 is connected to the drying control unit 60. The transport roller 100 is connected to the paper transport motor 140 via a driving mechanism such as a gear, and the transport roller 100 rotates as the paper transport motor 140 is driven.

  For example, the computer 20 executes a program preinstalled in the ROM 202 by the CPU 201 and controls the image forming apparatus 10 by performing data communication with each element connected to the I / O 205 according to the program.

  Here, the communication line I / F 150 is an interface for data communication with an information device such as a personal computer (not shown) connected to the communication line (not shown) and connected to the communication line. The communication line (not shown) may be in any form of wired, wireless, or a mixture of wired and wireless. For example, user image information may be received from an information device (not shown).

  The processing of the image forming apparatus 10 including the above elements is realized by software using the computer 20 by executing a program.

  Further, the program is not limited to a form that is preinstalled in the ROM 202 and may be provided in a state where it is stored in a computer-readable recording medium such as a CD-ROM or a memory card. Moreover, the form etc. which are delivered via communication line I / F150 may be sufficient.

  Next, the operation of the drying device 130 according to the present embodiment will be described in detail.

  FIG. 3 is a flowchart illustrating an example of a drying process executed by the CPU 201 of the computer 20 after ejecting the ink droplets Q from the print head 50 onto the recording paper P, for example.

The non-volatile memory 204 stores the temperature at the conveyance speed (reference conveyance speed V ₀ ) of the recording paper P serving as a predetermined reference and the output (reference drying strength H ₀ ) of the drying section 70 serving as a predetermined reference. It is assumed that the curve (reference temperature curve) is stored in the form of an equation or a table.

First, in step S10, a plurality of data pairs designated by the user are acquired from the operation display unit 120. Each of the data pairs includes a conveyance speed designated by the user and an outlet temperature at the designated conveyance speed. Here it will be described as to obtain the two data pairs D ₁ and D _2, the number of data pairs to be acquired is not limited to two, may obtain more than two data pairs. For convenience of explanation, the conveyance of the conveying speed included in the data-to-D ₁ speed V _1, the outlet temperature T ₁ of the outlet temperature in the data pair D _1, conveyed on the conveyance speed in the data pair D ₂ velocity V ₂ , the outlet temperature in the data pair D ₂ and the outlet temperature T _2.

  In step S20, for example, a reference temperature curve stored in advance in a predetermined area of the nonvolatile memory 204 is acquired.

FIG. 4 is a diagram illustrating an example of a reference temperature curve stored in the nonvolatile memory 204. The horizontal axis in FIG. 4 represents the time for heating by the dryer, and the vertical axis represents the temperature rise value (difference from the inlet temperature). Here, the reference temperature curve 83 is represented by a straight line, but is not necessarily a straight line. Assuming that the inlet temperature, which is the surface temperature of the printing portion at the moment of entering the drying portion L, is T _in , the subsequent change in the surface temperature of the printing portion is roughly the sum of the reference temperature curve 83 and T _in (T _{in the} vertical direction). Only translated). 5 shows an example of a temperature curve 83 'obtained by correcting the addition of T _in the reference temperature curve 83.

In step S30, using a reference temperature curve 83, to set a temperature curve corresponding to the data pair D ₁ obtained in step S10, a temperature curve corresponding to the data pairs D _2.

Specifically, first, the ink droplets at the transport speed V ₁ are determined from the length L of the drying range of the drying unit 70 along the transport direction of the recording paper P and the transport speed V ₁ included in the data pair D _1. Elapsed time m ₁ required for Q to finish passing after entering the drying range of the drying unit 70 is calculated. The length of the drying range of the drying unit 70 along the conveyance direction of the recording paper P (hereinafter simply referred to as “the length of the drying range of the drying unit 70”) is the drying unit along the conveyance direction of the recording paper P. In the case where it can be considered that the length is 70 or so (hereinafter simply referred to as “the length of the drying unit 70”), the length of the drying unit 70 is used instead of the length of the drying range of the drying unit 70. May be. Here, the length of the drying unit 70 will be described as the length of the drying range of the drying unit 70.

In this case, since the outlet temperature is T ₁ at the elapsed time m _1, the difference between the outlet temperature T ₁ of the inlet temperature T _in, on the reference temperature curve 83 at the elapsed time m ₁ (i.e. as a temperature rise value ) Calculate the ratio ((T ₁ −T _in ) / T _m1 ) with the temperature T _m1 .

As already described with reference to FIG. 13, the temperature curves having different outputs at the drying unit 70 at each elapsed time exceeding the elapsed time of 0 have the same ratio with respect to changes in the output of the drying unit 70. It can be regarded as changing. Therefore, by multiplying the reference temperature curve 83 by the ratio ((T ₁ −T _in ) / T _m1 ) and moving it _in parallel by T _in , the point (T _in , 0) and the point (T ₁ , m shown in FIG. A temperature curve 84 passing ₁ ) is obtained. Note that “A” in the notation of the points (A, B) indicates the surface temperature of the ink droplet Q, and “B” indicates the elapsed time since the drying unit 70 began to dry the ink droplet Q.

Furthermore, the elapsed time required for the ink droplet Q to finish passing through the drying range of the drying unit 70 at the transport speed V ₂ from the length L of the drying unit 70 and the transport speed V ₂ included in the data pair D _2. to calculate the m _2. Since the outlet temperature in the elapsed time _{m 2} is _{T 2,} and the difference between the outlet temperature _{T 2} and the inlet temperature _{T in,} and the temperature _{T m2} of the reference temperature curve 83 at the elapsed time _{m 2,} the ratio of ((T ₂ −T _in ) / T _m2 ).

Then, the reference temperature curve 83 is multiplied by the ratio ((T ₂ −T _in ) / T _m2 ) and translated by the initial temperature T _in, so that the points (T _in , 0) and the points (T ₂ ) shown in FIG. , M ₂ ), a temperature curve 85 is obtained.

Note that the output H ₁ of the drying unit 70 corresponding to the temperature curve 84 and the output H ₂ of the drying unit 70 corresponding to the temperature curve 85 are the output of the drying unit 70 and the specific elapsed time already described in FIG. Is obtained by using a proportional relationship recognized between the ratio of the surface temperature rise of the ink droplet Q to the reference temperature curve 83 (reference ratio). That is, since the output of the drying unit 70 varies in proportion to the reference ratio, the output H ₁ and the output H ₂ can be obtained from the reference drying intensity H ₀ .

  The proportional expression indicating the proportional relationship between the output of the drying unit 70 and the reference ratio is obtained in advance by an experiment with an actual machine of the drying apparatus 130, a computer simulation based on the design specifications of the drying apparatus 130, and the like. 204 is stored in advance in a predetermined area 204. Further, the proportional relationship between the output of the drying unit 70 and the reference ratio may be described by a more complicated function instead of a proportional expression, or the output in which the drying unit 70 is associated with the reference ratio For example, it may be stored in a predetermined area of the nonvolatile memory 204 as a table.

At step S40, set in the processing in step S30, the temperature curve 84 and the data vs. temperature curve 85 corresponding to D _2, corresponding to the data to-D _1, the time the surface temperature of the ink droplet Q is equal to or higher than a certain temperature Find the temperature at which

Therefore, for example, in the temperature curve 84 and the temperature curve 85, the elapsed time required for the surface temperature of the ink droplets Q to reach the common surface temperature is calculated. Here, if the elapsed time on the temperature curve 84 with respect to the common surface temperature is the elapsed time m ′ ₁ , and the elapsed time on the temperature curve 85 is the elapsed time m ′ ₂ , the ink droplets Q have the common surface temperature. In the case of the temperature curve 84, the above time is represented by (m ₁ −m ′ ₁ ), and in the case of the temperature curve 85, the time is represented by (m ₂ −m ′ ₂ ). While changing the common surface temperature until the difference between the calculated time (m ₁ −m ′ ₁ ) and the time (m ₂ −m ′ ₂ ) falls within a predetermined range, Time (m ₁ -m ′ ₁ ) and time (m ₂ -m ′ ₂ ) are calculated.

FIG. 7 is a diagram illustrating an example of the processing result in step S40. By the processing of step S40, the time _{(m 1} -m '1) and the time _{(m 2} -m' 2) is the reference temperature _{T 0} common temperature when a comparable time at the reference temperature _{T 0} ( The time Δm represented by m ₁ −m ′ ₁ ) or time (m ₂ −m ′ ₂ ) is defined as the drying acceleration time.

At step S50, obtains the conveyance speed (operating transport speed) V _x of the recording sheet P to be used in actual image formation. The operating transport speed V _x of the recording paper P may be stored in advance in a predetermined area of the nonvolatile memory 204, for example, or the operating transport speed V _x specified by the user may be acquired from the operation display unit 120. Good. Here, operational transport speed V _x is described as the conveying speed V ₁ and V ₂ are included in each of a plurality of data pairs D ₁ and D ₂ obtained in the process of step S10 are different transport speed The operation transport speed V _x may be one of the transport speeds V ₁ and V ₂ .

Next, the elapsed time until reaching the reference temperature T ₀ so that the drying acceleration time at the operation conveyance speed V _x of the acquired recording paper P is approximately the same as the drying acceleration time Δm calculated in the process of step S40. Is calculated. That is, the elapsed time is calculated such that the variation in the drying acceleration time Δm is included in a predetermined range. Therefore, first, an elapsed time m _x required for the ink droplet Q to pass through after having entered the drying range of the drying unit 70 is calculated at the acquired operation conveyance speed V _x of the recording paper P. Assuming that the length of the drying unit 70 is a length L, the elapsed time m _x is represented by m _x = L / V _x . Therefore, in order to set the drying promotion time at the operation conveyance speed V _x to Δm, the surface temperature of the ink droplet Q needs to be the reference temperature T _{0 in} the elapsed time (m _x −Δm). The elapsed time (m _x −Δm) is referred to as a reference temperature arrival time m ′ _x at the operation conveyance speed V _x .

In step S60, the point (T _in , 0), the reference temperature T ₀ calculated in the process of step S40, and the reference temperature arrival time m ′ _x at the operation transport speed V _x calculated in the process of step S50 are represented. And a temperature curve passing through the point (T ₀ , m ′ _x ).

The method of setting the temperature curve passing through the point (T _in , 0) and the point (T ₀ , m ′ _x ) is as follows: from the reference temperature curve 83, the point (T _in , 0) and the point (T ₁ , m ₁ ) According to the method of setting the temperature curve 84 passing through and the temperature curve 85 passing through the point (T _in , 0) and the point (T ₂ , m ₂ ). That is, the ₂ 'surface temperature T of the ink droplet Q in _x' elapsed time m for temperature curve 85, and the reference temperature _{T 0,} the ratio of the increment from _{T in} the _{((T 0 -T in) /} (T ' ₂ -T _in)) is calculated, multiplied by the ratio of the temperature curve _{85 ((T 0 -T in)} / (T '2 -T in)), by translating the temperature curve 85 only _{T in,} point A temperature curve corresponding to the operation conveyance speed V _x passing through (T _in , 0) and the point (T ₀ , m ′ _x ) is set.

FIG. 8 is a diagram illustrating an example of the processing result in step S60. The temperature curve 86 is a temperature curve corresponding to the operation conveyance speed V _x passing through the point (T _in , 0) and the point (T ₀ , m ′ _x ).

In step S70, in the same manner as in the process of step S30, between the output of the drying unit 70 and the ratio ((T ₀ −T _in ) / (T ′ ₂ −T _in )) calculated in the process of step S60. Is used to calculate the output H _x of the drying unit 70 corresponding to the temperature curve 86 from the output H ₂ of the drying unit 70 corresponding to the temperature curve 85.

In step S80, the switching element included in the drying control unit 60 is controlled to adjust the duty ratio of the pulse supplied to the IR heater 72, so that the output of the drying unit 70 is the target output calculated in the process of step S70. as you approach the output H _x, it controls the drying unit 70.

  For example, in the drying unit 70, a response time from when the power supplied to the drying unit 70 is controlled to when the output of the drying unit 70 approaches the output Hx calculated in the process of step S70 is allowed. There may be a drying unit 70 that is longer than a predetermined time as an upper limit of the response time. In this case, not the power supplied to the drying unit 70 but the heat itself applied to the ink droplets Q from the drying unit 70 may be controlled.

  FIG. 9 is an example of a side view of the drying unit 70 provided with a shutter 74 that shields heat between the IR heater 72 and the ink droplets Q. In the shutter 74 illustrated in FIG. 9, the central portion α of the shutter 74 along the paper transport direction is fixed to the housing of the drying unit 70 so that both ends of the shutter 74 orthogonal to the paper transport direction rotate. . The shutter 74 is connected to a motor (not shown) that controls the rotation angle of the shutter 74 via a gear or the like, and the rotation angle of the shutter 74 is controlled by controlling the rotation of the motor (not shown).

  FIG. 10 is a diagram illustrating an example when the shutter 74 of the drying unit 70 in FIG. 9 is rotated. As shown in FIG. 10, by controlling the rotation angle of the shutter 74, the amount of thermal energy shielded by the shutter 74 changes, so the amount of thermal energy applied to the ink droplet Q from the IR heater 72 is adjusted. .

Usually, as the rated output of the drying unit 70 increases, the response time when the power supplied to the drying unit 70 is controlled to vary the output of the drying unit 70 tends to increase. Therefore, depending on the electrical characteristics of the drying unit 70, as shown in FIGS. 9 and 10, for example, when the amount of thermal energy applied to the ink droplet Q is controlled using the shutter 74, the drying unit 70 is supplied. than the case of controlling the power, the output of the drying unit 70 to output H _x calculated in the processing of step S70, the sometimes brought close faster.

As described above, in the image forming apparatus 10 according to the present embodiment, even when the operation conveyance speed V _x changes, the difference in the drying acceleration time Δm at each operation conveyance speed V _x can be suppressed to a predetermined range. .

Therefore, to suppress the variation in the amount of evaporation of water contained in the ink droplets Q in each of the operational conveyor speed V _x, even when changing the conveyance speed of the recording sheet P, suppressing excessive drying of the ink droplet Q Expected to be effective.

The transport velocity V ₂ that is included in the conveyance velocity V _1, and data pair D ₂ included in the data-to-D ₁ to obtain in the processing of step S10, the minimum transport speed one is implemented in the image forming apparatus 10, the other Is preferably set to the maximum conveyance speed realized by the image forming apparatus 10. By setting the transport speed V ₁ and the transport speed V ₂ in this way, the drying unit 70 that suppresses overdrying of the ink droplets Q for any operational transport speed V _x realized by the image forming apparatus 10. Output is calculated.

  In this embodiment, continuous paper is used as an example of the recording paper P, but the type of the recording paper P is not limited to this. For example, cut paper such as A4 and A3 may be used, and the material of the recording medium represented by the recording paper P is not limited to paper, and a recording medium of a material that fixes ink droplets by heat is used. Also good.

Figure 11 is a diagram showing an example of a temperature curve when changing the operational conveyor speed V _x, performing the drying process shown in FIG. 3 in each of the operational conveyor speed V _x. As an example, the temperature curve 84 is 50 [m / min], the temperature curve 87 is 40 [m / min], the temperature curve 88 is 30 [m / min], the temperature curve 89 is 20 [m / min], and the temperature curve 85 represents the temperature curve corresponding to the operation conveying speed _{V x} of 10 [m / min]. Further, m _x1 represents the elapsed time at the outlet temperature of the temperature curve 87, m _x2 represents the elapsed time at the outlet temperature of the temperature curve 88, and m _x3 represents the elapsed time at the outlet temperature of the temperature curve 89.

As shown in FIG. 11, when executing the drying process shown in FIG. 3, with the change of the operational conveyor speed V _x, the outlet temperature of the ink droplet Q in each operational transport speed V _x is changed as shown by a dotted line 92. That is, if attention is paid to the outlet temperature of the ink droplet Q, even if the operation conveyance speed V _x is changed, in order to suppress overdrying of the ink droplet Q, as the operation conveyance speed V _x decreases, It can be seen that the output of the drying unit 70 may be controlled so that the outlet temperature of the ink droplet Q is lowered.

  The dried state of the ink droplets Q is at least one of the output of the drying unit 70, for example, the type of the recording paper P, the type of the ink droplets Q, the user image formation surface on the recording paper P, and the user image form. It also changes depending on the combination of the above image forming conditions.

  The recording paper P includes, for example, coated paper with a coating layer on the surface to realize quick drying of the ink droplets Q, recycled paper using used paper, embossed paper, plain paper, and the like, depending on the type of the recording paper P. The penetration rate of the ink droplet Q is different. Therefore, the ink droplets Q on the recording paper P may show different temperature curves depending on the type of the recording paper P to be used.

  Also, the ink droplet Q may exhibit different temperature curves depending on the components contained in the ink, such as the emulsion component content.

  Further, the amount of ink droplets Q ejected onto the recording paper P also changes depending on the image forming mode such as whether the user image is formed on one side or both sides of the recording paper P. The upper ink drop Q may exhibit a different temperature curve.

  Also, the recording paper depends on whether the user image is in the form of characters, photographs, or characters and photographs, and whether the user image is a monochrome image or a color image. Since the amount of ink droplets Q ejected onto P varies, the ink droplets Q on the recording paper P may show different temperature curves.

  Accordingly, at least one or more image formations in the predetermined area of the non-volatile memory 204, for example, the type of the recording paper P, the type of the ink droplet Q, the user image formation surface on the recording paper P, and the user image form. A plurality of temperature curves each corresponding to a combination of conditions are stored in advance, and for example, a reference temperature curve corresponding to an image forming condition designated by the user via the operation display unit 120 is stored in the nonvolatile memory 204. Alternatively, a plurality of reference temperature curves may be selected.

  In this case, a reference temperature curve that is more suitable for the actual image forming conditions is selected as compared with the case where the same reference temperature curve 83 is acquired from the nonvolatile memory 204 each time in the process of step S20 of FIG.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in each said embodiment. Various changes or improvements can be added to the above-described embodiments without departing from the gist of the invention, and forms to which the changes or improvements are added are also included in the technical scope of the present invention.

  Moreover, although this embodiment demonstrated the case where a drying process was implement | achieved by the software structure, this invention is not limited to this, For example, it is good also as a form which implement | achieves a drying process by a hardware configuration. In this case, the processing speed is expected to be higher than that of the embodiment described above.

Further, in the present embodiment, an example in which the drying process illustrated in FIG. 3 is performed by the control unit 20 has been described. However, the control unit 20 controls the conveyance of the head driving unit 40 and the recording paper P, and the drying control unit 60 is illustrated. It goes without saying that the drying process shown in FIG. 3 may be executed by the drying control unit 60 by being realized by the computer 20 shown in FIG. In this case, the drying control unit 60 may acquire a plurality of data pairs D ₁ and D ₂ and image forming conditions from the operation display unit 120 via the control unit 20, and the drying control unit 60 may receive the operation display unit. 120 may be connected, and a plurality of data pairs D ₁ and D ₂ and image forming conditions may be acquired from the operation display unit 120.

Further, as at the time of image formation start transient period from starting to form the user image on the recording sheet P by the image forming apparatus 10, to the transport speed of the recording sheet P is operated conveying speed V _x, or, imaging as at the end, the transitional period until the conveyance speed of the recording sheet P is 0 [m / s] from the operational conveyor speed V _x, where the context of drying ink droplets Q in the drying unit 70 is generated, for example, paper speed detection sensor sequentially measures the conveying speed of the recording sheet P at 110, by executing the processing in FIG 3 to show the step S50 after the conveying speed of the recording sheet P measured as the active conveying speed V _x, drying unit 70 May be controlled.

DESCRIPTION OF SYMBOLS 10 (12) ... Image forming apparatus, 20 ... Control part (computer), 30 ... Memory | storage part, 40 ... Head drive part, 50 ... Print head, 60 ... Drying control part , 70 ... Drying section, 72 ... IR heater, 74 ... Shutter, 80 ... Paper feed roll, 90 ... Discharge roll, 100 ... Conveyance roller, 110 ... Paper speed detection Sensor, 120 ... Operation display section, 130 ... Drying device, 140 ... Paper transport motor, 150 ... Communication line I / F, 201 ... CPU, 202 ... ROM, 203 ... · RAM, 204 ··· nonvolatile memory, 205 ··· I / O, 206 ··· bus, P · · · recording paper, Q · · · ink _{droplets, T} 0 · · · reference _{temperature, T} 1, _{T 2,} T x ··· outlet _{temperature, T in} ··· inlet temperature, _{V 0} · And standards transport _{velocity, V} x ··· operational transport speed

Claims (9)

A drying means for drying droplets on the recording medium to be conveyed;
Control means for controlling the drying strength of the drying means so that the outlet temperature, which is the temperature of the droplets at the outlet of the drying means, becomes lower as the conveyance speed of the recording medium becomes slower;
A droplet drying apparatus. The control means may vary a drying time from when the temperature of the droplet reaches a predetermined reference temperature due to drying of the droplet by the drying means until the droplet reaches the outlet of the drying means. The droplet drying apparatus according to claim 1, wherein the drying strength of the drying unit is controlled so as to be included in a predetermined range. The control means utilizes the fact that the drying strength of the drying means is approximately proportional to the temperature rise of the droplets, so that the drying strength of the drying means is the temperature of the droplets at the transport speed of the recording medium. To the target dry strength obtained from the temperature indicated by the predetermined temperature curve of the droplet at the time it reaches the reference temperature, the reference temperature, and the dry strength associated with the predetermined temperature curve. The droplet drying apparatus according to claim 2, wherein the drying strength of the drying unit is controlled so as to approach. The predetermined temperature curve is any one of a plurality of temperature curves,
4. The droplet drying apparatus according to claim 3, wherein the control unit uses, as the reference temperature, a temperature when each of the plurality of temperature curves includes a variation in the drying time within the predetermined range. The control means transports the droplets at a predetermined reference transport speed, and a plurality of data pairs in which a predetermined transport speed and an outlet temperature of the droplets at the predetermined transport speed are associated with each other, The predetermined temperature curve corresponding to each of the data pairs is set from the reference temperature curve when the droplet is dried at a predetermined reference dry strength, and the drying strength of the drying means is set to the droplet The temperature of the droplets indicated by each of the predetermined temperature curves at a specific time, the temperature of the droplets indicated by the reference temperature curve, and The droplet drying apparatus according to claim 4, wherein the obtained drying strength is associated with each of the predetermined temperature curves from the predetermined reference drying strength associated with the reference temperature curve. The droplet drying apparatus according to claim 5, further comprising receiving means for receiving each of the data pairs. The accepting means is an image forming condition represented by at least one of the type of the recording medium, the type of the liquid droplet, the designation state of the image forming surface of the recording medium, and the form of the image formed on the recording medium. Accept more,
The droplet drying apparatus according to claim 6, wherein the control unit selects the reference temperature curve corresponding to the image forming condition received by the receiving unit from a plurality of reference temperature curves.   A droplet drying program for causing a computer to function as control means of the droplet drying apparatus according to any one of claims 1 to 7. An ejection means for ejecting liquid droplets on a recording medium according to an image;
Conveying means for conveying the recording medium;
A droplet drying apparatus according to any one of claims 1 to 7,
Control means for controlling the ejection means, the transport means, and the droplet drying device;
An image forming apparatus.

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