JP2012045764A - Image recording device, and drying control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image recording device and a drying control method, cooling a surface of an impression cylinder for drying paper to uniformize a temperature of the impression cylinder surface and performing optimal drying temperature control in accordance with paper types.SOLUTION: The image recording device includes: a drum temperature measuring unit measuring a surface temperature of a portion which does not come into contact with paper and a surface temperature of a portion coming contact with a paper; a heating unit heating the surface of a drum, and heating and drying a paper which is being carried; a cooling unit cooling the surface of the drum; and a temperature control unit controlling the heating unit and the cooling unit in accordance with the temperature of the paper measured by a paper temperature measuring unit when the paper is being carried, controlling the heating unit and cooling unit in accordance with the surface temperature of the portion of the drum which does not come into contact with the paper measured by the drum temperature measuring unit except when the paper is being carried, and uniformizing the temperature of the paper or the surface temperature of the portion of the drum coming into contact with the paper and the portion which does not come into contact with the paper.

Description

The present invention relates to an image recording apparatus and a drying control method.

  2. Description of the Related Art Conventionally, in an image recording apparatus that records character information or an image on a recording medium by transporting a recording medium such as recording paper in the transport direction and ejecting ink droplets or the like from a head facing the recording surface, inkjet recording In the process of drying the subsequent sheet, it is necessary to stably dry the sheet in a short time without deforming the sheet.

  It is generally known that the dryness of paper greatly depends on the basis weight of the paper (for example, 100 to 300 gsm) and the amount of ink droplets applied to the paper. The device has been devised to ensure the drying property in the case of drying conditions.

  On the other hand, when thin paper is used as the paper, under the drying conditions established based on thick paper that is difficult to dry, the paper deformation (cuckling) increases due to the excessive drying capacity, which may hinder backside paper passing Therefore, it is necessary to set the conditions of the drying apparatus in accordance with each condition.

  That is, when drying thick paper, a large-capacity heater is required to heat up to the paper temperature required to obtain the required film strength. On the other hand, in the case of drying thin paper, the drying device that supports thick paper heats the paper too much, and deformation of the paper cannot be suppressed, and there is a possibility that the rear surface transport reliability may be impaired.

  For example, based on prepress data, a digital printing machine characterized by drying control in which only a necessary portion of LEDs is turned on for a plurality of ultraviolet irradiation LEDs arranged in the width direction is disclosed (for example, Patent Documents) 1).

JP 2010-89455 A

  However, the method as described in Patent Document 1 performs drying control by turning ON / OFF the UV ink using an LED light source, and is not applicable to normal aqueous ink using water as a solvent. There is a risk of increasing the size and cost. This is also a unique ON / OFF control of drying (heat source), and there is no example that can be realized at a low cost for fine drying control especially when using thin paper.

  In general, the impression cylinder method is used for sheet-fed printing. However, when the impression cylinder rotating at high speed is used to dry the paper, the surface temperature is reduced when the surface heat is removed only from the part that is in contact with the paper. Since the next sheet is conveyed before being uniformed, it becomes more difficult to control the drying of the sheet and the drum temperature.

  Furthermore, since the film surface temperature (front surface) of a sheet during continuous JOB (such as continuous 200 sheets) also changes in the JOB, it is difficult to control the sheet surface temperature with a uniform temperature setting. Further, since the temperature change changes not only with the basis weight of the paper, but also with the paper type and environment, and also with the amount of ink ejected, drying control becomes more difficult with a uniform temperature setting.

  Currently, the impression cylinder method is generally used for sheet-fed printing, but the impression cylinder was in contact with the paper after the impression cylinder surface was deprived of vaporization heat by drying the paper because the impression cylinder rotated at high speed. The next wet paper is received before the impression cylinder surface temperature of the part becomes uniform with the surroundings. For this reason, in order to accurately control paper drying and cylinder temperature, it is necessary not only to heat the surface of the impression cylinder but also to increase or decrease the temperature of the impression cylinder surface positively.

  In addition, since the water content and the amount of heat required for drying differ depending on the type of paper as described above, finer temperature control is required to prevent cockle and secure film strength. There are no examples disclosed in this document.

  In consideration of the above-mentioned facts, the present invention provides an image recording apparatus and a drying control method for performing uniform drying control according to the type of paper by uniformizing the temperature of the pressure drum surface by cooling the surface of the pressure drum for paper drying. The task is to do.

  The image recording apparatus according to claim 1, wherein the image recording apparatus is supported so as to be rotatable about an axis, and holds and conveys a sheet on which an image is recorded, and a sheet temperature measuring unit that measures a surface temperature of the conveyed sheet. A drum temperature measuring means for measuring a surface temperature of a portion of the drum not in contact with the paper and a surface temperature of a portion in contact with the paper; heating the surface of the drum and heating the paper being conveyed; A heating means for drying, a cooling means for cooling the surface of the drum, and during paper conveyance, the heating means and the cooling means are controlled according to the temperature of the paper measured by the paper temperature measurement means, except during paper conveyance Controls the heating means and the cooling means according to the surface temperature of the portion of the drum that does not come into contact with the paper measured by the drum temperature measuring means, and the temperature of the paper or the paper Wherein the surface temperature of the portion in contact with the paper of the ram, characterized by comprising a temperature control means for equalizing the surface temperature, the portion not in contact with the paper.

  According to the above invention, the surface temperature of the drying drum is controlled by the cooling means and the heating means, and the surface temperature of the portion of the drying drum that is not in contact with the paper and the surface temperature of the portion that is in contact with the paper are made uniform so as to suppress clogging. An image recording apparatus having excellent transportability can be obtained.

  The image recording apparatus according to claim 2, wherein the temperature control unit performs duty control for controlling a length of ON / OFF time of the cooling unit in accordance with a sheet temperature measured by the sheet temperature measuring unit. It is characterized by.

  According to the invention described above, an image recording apparatus that prevents insufficient drying of the paper can be provided even with a cooling means having an excessive cooling capacity.

  The image recording apparatus according to claim 3, wherein the temperature control unit that performs ON / OFF control of the cooling unit in accordance with the sheet temperature and the drum temperature includes a threshold value between a target management upper limit temperature and a target management lower limit temperature preset for the sheet temperature. In contrast, when the paper temperature exceeds the upper limit, the heating means is controlled to increase the time for turning on the cooling means, and when the paper temperature falls below the lower limit, the heating means is controlled to increase the time for turning off the cooling means. Further, feedback control is performed in which weighting is performed according to a difference between the measured sheet temperature and a sheet target temperature that is an intermediate value between the target management upper limit temperature and the target management lower limit temperature.

  According to the above invention, by performing so-called PID control on the cooling means, it is possible to provide an image recording apparatus that performs dry drum temperature control that is quick and less likely to cause overshoot.

  According to a fourth aspect of the present invention, the temperature control means turns off the cooling means during a time when the drum is not holding paper.

  According to the above invention, since the paper is not dried during the time when the paper is not held on the impression cylinder, the paper cooling unit is turned off to prevent the apparatus from being overcooled and to reduce the power consumption.

  The image recording apparatus according to a fifth aspect is characterized in that the ON / OFF control of the cooling unit is performed by changing an amount of cooling air generated by a cooling source or changing an air direction of the cooling air.

  According to said invention, it can be set as an efficient cooling means with a simple structure.

  The image recording apparatus according to claim 6 is characterized in that the sheet temperature measuring means is a non-contact type radiation thermometer.

  According to the above invention, since there is no possibility of contact or interference with the paper or the impression cylinder by using the non-contact type thermometer, temperature measurement can be performed without affecting the paper transportability.

  The drying control method according to claim 7 is characterized in that a sheet of paper is used.

  According to the above-described invention, unlike continuous paper, an image recording apparatus that performs optimal drying control according to the type of paper while preventing excessive drying of the paper on a sheet having a large influence on transportability due to the dry state in 1 JOB. It can be.

  The drying control method according to claim 8, wherein a cooling unit that cools a surface of the drum according to a temperature of a sheet on which an image is recorded and a temperature of the drum, and the surface of the drum that is heated and transported The heating means for heating and drying the paper, and the temperature control means for controlling ON / OFF of the paper, the paper temperature exceeds the upper limit with respect to the threshold values of the target management upper limit temperature and the target management lower limit temperature set in advance for the paper temperature. Control the cooling means to increase the time to turn on the cooling means, and increase the time to turn off the cooling means when the paper temperature falls below the lower limit, the measured paper temperature and target management Feedback control is performed in which weighting is performed according to the difference between the upper limit temperature and the sheet target temperature, which is an intermediate value between the upper limit temperature and the target management lower limit temperature, and the drum target temperature set in advance is set for the drum temperature. The paper cooling means is controlled so as to increase the ON time when it is received, and increase the OFF time when it falls below the drum target temperature, and the paper temperature control means controls the surface finish of the paper and the paper surface area. The target paper temperature is set in accordance with a paper transport environment that is at least one of a quantity, a temperature and humidity inside the apparatus, and a discharge quantity of ink ejected onto the paper surface to record an image.

  According to the above invention, the cooling unit performs the DUTY control between the target management upper limit temperature and the target management lower limit temperature, thereby preventing the paper from being excessively dried and performing the optimum drying control according to the paper type. It can be set as a recording device.

  The drying control method according to claim 9, further comprising: a condition setting unit that automatically detects a sheet conveyance condition and an ink discharge amount, and the sheet temperature control unit according to the sheet conveyance condition and the ink discharge amount detected by the condition setting unit. Sets the target paper temperature.

  According to the above invention, the condition setting unit detects the paper type and the ink discharge amount, and the target temperature is set according to the detected paper type, so that the optimum recording control is performed according to the paper type and the output content. It can be a device.

  The drying control method according to claim 10 is characterized in that the sheet temperature control means sets the sheet target temperature according to a sheet conveyance condition and an ink discharge amount input by a user.

  According to the above invention, the image recording apparatus that performs optimum drying control according to the paper type and the output content by the user inputting the paper type and the ink discharge amount and setting the target temperature according to the input. can do.

  Since the present invention has the above-described configuration, the image recording apparatus and the drying control method perform uniform drying temperature control according to the paper type by uniformizing the temperature of the pressure drum surface by cooling the surface of the paper drying pressure drum, can do.

1 is a conceptual diagram illustrating an entire image recording apparatus according to an embodiment of the present invention. 1 is a conceptual diagram illustrating a main part of an image recording apparatus according to an embodiment of the present invention. It is a conceptual diagram which shows the drying part of the image recording apparatus which concerns on embodiment of this invention. It is a conceptual diagram which shows the relationship between DUTY control of the cooling means and paper temperature in the drying control method which concerns on embodiment of this invention.

  Hereinafter, an exemplary embodiment according to the present invention will be described with reference to the drawings.

<Overall configuration>

  Hereinafter, with reference to FIGS. 1 and 2, a configuration example of an ink jet image recording apparatus for carrying out the image recording method of the present invention will be described. FIG. 1 is a conceptual diagram (side surface) showing the entire apparatus, and FIG. 2 is a conceptual diagram (side surface) in which a heater and a temperature sensor are mainly described.

  The inkjet recording apparatus 1 forms a desired color image by ejecting a plurality of colors of ink from inkjet heads 172M, 172K, 172C, and 172Y onto a recording medium 122 held on the impression cylinder (drawing drum 170) of the drawing unit 114. An impression cylinder direct drawing type ink jet recording apparatus, which applies a treatment liquid onto the recording medium 122 before ink ejection and causes the treatment liquid and ink to react to form an image on the recording medium 122 (aggregation). ) Method is an on-demand type image forming apparatus.

  The ink jet recording apparatus 1 mainly includes a paper feeding unit 110, a processing liquid application unit 112, a drawing unit 114, a drying unit 116, a fixing unit 118, and a paper discharge unit 120.

  The paper supply unit 110 is a mechanism that supplies the recording medium 122 to the treatment liquid application unit 112, and the recording medium 122 that is a sheet is stacked on the paper supply unit 110. The paper feeding unit 110 is provided with a paper feeding tray 150, and the recording medium 122 is fed from the paper feeding tray 150 to the processing liquid application unit 112 one by one. In the inkjet recording apparatus 1, a plurality of types of recording media 122 having different paper types and sizes (medium sizes) can be used as the recording medium 122. In the present embodiment, a case where a sheet (cut sheet) is used as the recording medium 122 will be described.

  The processing liquid application unit 112 is a mechanism that applies the processing liquid to the recording surface of the recording medium 122. The treatment liquid contains a color material aggregating agent that agglomerates the color material in the ink applied by the drawing unit 114. When the treatment liquid and the ink come into contact with each other, the ink is separated from the color material and the solvent. Promoted.

  As shown in FIGS. 1 and 2, the processing liquid application unit 112 includes a paper feed cylinder 152, a processing liquid drum 154, and a processing liquid coating device 156. The treatment liquid drum 154 is a drum that holds the recording medium 122 and rotates and conveys it. The processing liquid drum 154 includes a claw-shaped holding means (gripper) on the outer peripheral surface thereof, and the recording medium 122 is sandwiched between the claw of the holding means and the peripheral surface of the processing liquid drum 154 so that the tip of the recording medium 122 is positioned. It can be held.

  The treatment liquid drum 154 may be provided with a suction hole on the outer peripheral surface thereof and connected to a suction unit that performs suction from the suction hole. As a result, the recording medium 122 can be held in close contact with the peripheral surface of the treatment liquid drum 154.

  A treatment liquid coating device 156 is provided outside the treatment liquid drum 154 so as to face the peripheral surface thereof. The processing liquid coating device 156 is in pressure contact with the processing liquid container in which the processing liquid is stored, the anilox roller partially immersed in the processing liquid in the processing liquid container, and the recording medium 122 on the anilox roller and the processing liquid drum 154. And a rubber roller that transfers the measured processing liquid to the recording medium 122. According to the processing liquid coating apparatus 156, the processing liquid can be applied to the recording medium 122 while being measured.

  The recording medium 122 to which the processing liquid is applied by the processing liquid applying unit 112 is transferred from the processing liquid drum 154 to the drawing drum 170 of the drawing unit 114 via the intermediate transport unit 124. The drawing unit 114 includes a drawing drum 170 and inkjet heads 172M, 172K, 172C, and 172Y. Similar to the treatment liquid drum 154, the drawing drum 170 includes a claw-shaped holding means (gripper) on its outer peripheral surface. The recording medium 122 fixed to the drawing drum 170 is conveyed with the recording surface facing outward, and ink is applied to the recording surface from the inkjet heads 172M, 172K, 172C, 172Y.

  The inkjet heads 172M, 172K, 172C, and 172Y are full-line inkjet recording heads (inkjet heads) each having a length corresponding to the maximum width of the image forming area on the recording medium 122. Is formed with a nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area. Each inkjet head 172M, 172K, 172C, 172Y is installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 122 (the rotation direction of the drawing drum 170).

  The droplets of the corresponding color ink are ejected from the respective ink jet heads 172M, 172K, 172C, 172Y toward the recording surface of the recording medium 122 held in close contact with the drawing drum 170, whereby the processing liquid application unit 112 The ink comes into contact with the treatment liquid previously applied to the recording surface, and the pigment and resin particles dispersed in the ink are aggregated to form aggregates. As a result, pigment flow or the like on the recording medium 122 is prevented, and an image is formed on the recording surface of the recording medium 122.

  The recording medium 122 on which an image is formed by the drawing unit 114 is transferred from the drawing drum 170 to the drying drum 176 of the drying unit 116 via the intermediate conveyance unit 126. The drying unit 116 is a mechanism that dries moisture contained in the solvent separated by the aggregating action. As shown in FIG. 1, the drying unit 176, a plurality of IR heaters (carbon heaters) 178, and each IR heater 178. And a hot air heater 180 disposed between the two.

  Further, a cooling unit 182 is provided for cooling the surface of the drying drum 176 to cool the surface. The drying unit 176 loses heat of vaporization by drying the recording medium 122, and the surface of the drying drum 176 whose recording surface temperature has decreased (recording medium 122. And a portion where the temperature remains high by the IR heater 178 and the warm air heater 180 because the contact is not in contact with the recording medium 122.

  Similar to the treatment liquid drum 154, the drying drum 176 includes a claw-shaped holding unit (gripper) on its outer peripheral surface, and the holding unit can hold the leading end of the recording medium 122. The temperature and amount of warm air blown from the warm air heater 180 toward the recording medium 122, and the temperature of each IR heater are detected by a temperature sensor described later, and are sent as temperature information to a control unit (not shown). Based on this temperature information, the control unit appropriately adjusts the temperature and air volume of the warm air, the temperature of each IR heater, and the cooling means, thereby realizing various drying conditions.

  The surface temperature of the drying drum 176 is set to 50 ° C. or higher. Drying is accelerated by heating from the back surface of the recording medium 122, and image destruction during fixing can be prevented. The upper limit of the surface temperature of the drying drum 176 is not particularly limited, but from the viewpoint of safety of maintenance work such as cleaning ink adhering to the surface of the drying drum 176 (preventing burns due to high temperatures). It is preferably set to 75 ° C. or lower (more preferably 60 ° C. or lower).

  Further, as described above, it has been found that the higher the drying drum temperature (the surface temperature of the drying drum 176) (the stronger the drying), the less the expansion and contraction of the recording medium 122, so that the above-described safety is not impaired. The higher the surface temperature of the drying drum 176, the less the influence of cockle. At the same time, if the temperature difference between the portion in contact with the recording medium 122 and the portion not in contact with the recording medium 122 is large, only the peripheral portion of the recording medium 122 is dried, and there is a risk of cuckling.

  The recording drum 122 is held on the outer peripheral surface of the drying drum 176 so that the recording surface of the recording medium 122 faces outward (that is, in a state where the recording surface of the recording medium 122 is convex), and is dried while being rotated and conveyed. By doing so, it is possible to prevent the recording medium 122 from being wrinkled or lifted, and to prevent drying unevenness caused by these.

  The recording medium 122 that has been dried by the drying unit 116 is transferred from the drying drum 176 to the fixing drum 184 of the fixing unit 118 via the intermediate conveyance unit 128. The fixing unit 118 includes a fixing drum 184, a first fixing roller 186, a second fixing roller 188, and an inline sensor 190.

  Like the processing liquid drum 154, the fixing drum 184 includes a claw-shaped holding unit (gripper) on the outer peripheral surface thereof, and the holding unit can hold the leading end of the recording medium 122. By the rotation of the fixing drum 184, the recording medium 122 is conveyed so that the recording surface faces outward. The fixing process by the first fixing roller 186 and the second fixing roller 188 and the inline sensor 190 are performed on the recording surface. Inspection is performed.

  The first fixing roller 186 and the second fixing roller 188 are roller members for welding resin particles (particularly self-dispersing polymer particles) in the ink by heating and pressurizing the ink to form a film of the ink. The recording medium 122 is configured to be heated and pressurized.

  Specifically, the first fixing roller 186 and the second fixing roller 188 are arranged so as to be in pressure contact with the fixing drum 184 and constitute a nip roller with the fixing drum 184. Yes. As a result, the recording medium 122 is sandwiched between the first fixing roller 186 and the second fixing roller 188 and the fixing drum 184 and is nipped at a predetermined nip pressure (for example, 0.15 MPa) to perform the fixing process. It is.

  Further, the first fixing roller 186 and the second fixing roller 188 are configured by a heating roller in which a halogen lamp is incorporated in a metal pipe such as aluminum having good thermal conductivity, and have a predetermined temperature (for example, 60 to 80 ° C.). Controlled.

  By heating the recording medium 122 with these heating rollers, thermal energy equal to or higher than the Tg (glass transition temperature) of the resin particles contained in the ink is applied, and the resin particles are melted so that the unevenness of the recording medium 122 is formed. While pressing and fixing are performed, unevenness on the surface of the image is leveled and gloss is obtained.

  The in-line sensor 190 is a measuring unit for measuring a check pattern, a moisture content, a surface temperature, a glossiness, and the like for an image fixed on the recording medium 122, and a CCD line sensor or the like is applied.

  According to the fixing unit 118, the resin particles in the thin image layer formed by the drying unit 116 are heated and pressurized by the fixing roller 188 and melted, and can be fixed to the recording medium 122. Further, the surface temperature of the fixing drum 184 is set to 50 ° C. or higher, and the drying is promoted by heating the recording medium 122 held on the outer peripheral surface of the fixing drum 184 from the back surface, thereby preventing image destruction during fixing. The image intensity can be increased by the effect of increasing the image temperature.

  As shown in FIG. 1, a paper discharge unit 120 is provided downstream of the fixing unit 118 in the recording medium conveyance direction. The paper discharge unit 120 includes a discharge tray 192. Between the discharge tray 192 and the fixing drum 184 of the fixing unit 118, a transfer drum 194, a conveying belt 196, and a stretching roller 198 are in contact with each other. Is provided. The recording medium 122 is sent to the transport belt 196 by the transfer drum 194 and discharged to the discharge tray 192.

  Further, the discharge tray 192 is provided with a cold air ejection nozzle 199, and the recording medium 122 can be cooled by blowing cold air from the cold air ejection nozzle 199.

  Although not shown in FIG. 1, in addition to the above-described configuration, the inkjet recording apparatus 1 performs processing on the ink storage tank that supplies ink to the inkjet heads 172M, 172K, 172C, and 172Y, and the treatment liquid application unit 112. In addition to a means for supplying liquid, the head maintenance unit that cleans each ink jet head 172M, 172K, 172C, 172Y (wiping, purging, nozzle suction, etc. of the nozzle surface) and the position of the recording medium 122 on the medium transport path A position detection sensor for detecting, a temperature sensor for detecting the temperature of each part of the apparatus, and the like are provided.

  When forming images on both sides, in the inkjet recording apparatus 1 of FIG. 1, after forming an image on one side (front side) of the recording medium, seasoning is performed for a predetermined time by a seasoning device (not shown). Then, the seasoned recording medium bundle is returned to the paper feeding unit 110, and further image formation is performed on the back surface. Thereby, good double-sided printing can be realized in a short time.

  The ink jet recording apparatus 1 shown in FIG. 1 may include a plurality of seasoning devices used for the discharge tray 192, and each seasoning device may be movable between the paper discharge unit 120 and the paper supply unit 110.

<Details of drying section>

  3 and 4 show details of the drying unit 116. FIG. As described above, the drying unit 116 is a mechanism for drying the water contained in the solvent separated by the aggregating action. As shown in the drawing, the drying unit 116 is interposed between the drying drum 176, the IR heater 178, and each IR heater 178. A hot air heater 180 is provided, and cooling means 182 for sending cooling air to the surface of the drying drum 176 and cooling the surface is provided.

  As an example, as shown in FIG. 3, the recording medium 122 is transferred from the drawing drum 170 to the drying drum 176 of the drying unit 116 via the intermediate conveyance unit 126 (the transfer cylinder 130). A hot air heater 180 and an IR heater 178 are provided along the outer peripheral surface of the drying drum 176 to heat the drying drum 176 and the recording medium 122 being conveyed. Further, the cooling means 182 blows cold air to the outer peripheral surface of the drying drum 176, and the temperature between a portion having a low surface temperature in contact with the recording medium 122 and a portion having a high temperature not in contact with the recording medium 122 such as both ends in the conveyance width direction. Mitigating the difference.

  The IR heater 178 may be, for example, a rod-like carbon heater that is extended along the outer peripheral surface of the drying drum 176 while maintaining a predetermined distance. The reason why carbon is used as an IR (infrared) heater is that the radiation peak is 2000 to 4000 nm in the far infrared region, and the absorption peak (near 3000 nm) overlaps with water used as a solvent for water-based ink. The point which can be overheated well is mentioned.

  Moreover, the structure of the warm air heater 180 sends hot air to the drying drum 176 by placing the hot air heater 280 in the air flow generated by the axial fan 282, for example. At this time, a temperature sensor 284 may be provided to prevent heating.

  Further, as the cooling means 182, for example, a cooling device that circulates a general refrigerant and cools the object through a heat exchanger by condensation / evaporation can be considered, but a cooling device that can be electrically turned on / off is desirable. Or various structures, such as a device using a Peltier element or a device that sends cold air with a heat exchanger simply cooled by a water flow, can be used.

  As an example of the cooling means 182, generally, an air conditioner, a spot cooler, or the like that cools a local space is preferably used. That is, anything may be used as long as heat is exchanged between the inside and outside of the inkjet recording apparatus 1 or the drying unit 116 to generate cool air inside, and an inexpensive spot cooler may be used because it is not necessary to control the humidity inside the apparatus. .

  As an example, as shown in FIG. 3, the outside air introduced from the outside of the apparatus by the air blowing means 181 is applied to the heat exchanger 183 cooled by various cooling methods, and the drying drum as indicated by the arrow C is used as cooling air having a reduced temperature. The structure which sprays on the surface of 176 may be sufficient. At this time, it is desirable that the cooling of the heat exchanger 183 can be electrically turned on / off as described above.

  As described above, for example, the thickness of the recording medium 122 is adjusted by appropriately adjusting the temperature and air volume of the warm air blown from the warm air heater 180 toward the recording medium 122, the temperature of each IR heater, and the cooling capacity of the cooling means 182. Various drying conditions are realized in accordance with various conditions such as surface finishing.

  At this time, parameters such as the type of the recording medium 122 are automatically detected by various detection means such as an optical sensor and a thickness sensor (not shown) provided in the apparatus, and may be sent to the control means as condition parameters. It may be configured to determine and manually input to the control means. Further, for example, environmental conditions such as temperature and humidity in the apparatus detected by a temperature / humidity sensor (not shown) provided in the drying unit 116 are sent to the control means as condition parameters, and the temperature and volume of the hot air and the temperature of each IR heater are sent. And it is good also as one of the condition factors at the time of adjusting the cooling capacity of the cooling means 182.

<Features and effects of this application>

  As described above, drying is accelerated by heating from the back surface of the recording medium 122, the required film strength is ensured, and the surface temperature of the drying drum 176 is set to 50 by the IR heater 178 in order to prevent image destruction during fixing. It is set to over ℃. Further, it has been found that the higher the drying drum temperature (the surface temperature of the drying drum 176) is (the stronger the drying is), the less the expansion and contraction of the recording medium 122, and therefore the surface of the drying drum 176 is not damaged. The higher the temperature, the less the influence of the cockle can be suppressed. Therefore, it is necessary to keep the surface temperature of the drying drum 176 within a predetermined range.

  However, it is inevitable that the surface temperature of the portion of the drying drum 176 that is not in contact with the recording medium 122 is also increased by simultaneously applying heat. On the other hand, when the recording medium 122 dries, the evaporation heat is taken away by the evaporated water, and the temperature of the portion of the drying drum 176 in contact with the recording medium 122 decreases.

  Since the drying drum 176 rotates at a high speed due to this temperature drop, after the surface of the drying drum 176 is deprived of heat by paper drying, the next paper (recording medium 122) is received before the surface temperature becomes uniform. Accurate paper drying control and surface temperature control of the drying drum 176 are difficult only by heating control of the heating means.

  Such a local change in the surface temperature of the drying drum 176 is, for example, a low temperature in the vicinity of the center of the recording medium 122 and a high temperature in the peripheral portion. Will be affected. In order to stabilize the backside paper passing property, it is necessary to suppress the local surface temperature change as described above. In order to solve the above problem, in the present invention, the drum temperature is made uniform by cooling the drying drum 176 with the cooling means 182.

  However, for example, when the recording medium 122 is thin and thin paper is used, the cooling capacity of the cooling means 182 corresponding to the thick paper causes the recording medium 122 to be overcooled and insufficiently dried, resulting in insufficient film strength at the fixing stage. May occur.

  Further, even during 1 JOB, the film surface temperature (front side) of the recording medium 122 (sheet paper) during continuous conveyance changes within the JOB. For this reason, even when the drying temperature setting of the drying drum 176 is a uniform temperature setting, it is difficult to control the surface temperature to be equal at the start of processing and at the end of processing.

  The drying condition of the recording medium 122 varies depending not only on the basis weight of the paper but also on the environment such as the paper type and temperature / humidity, and also on the droplet ejection amount. For this reason, even more uniform temperature setting makes it difficult to control the surface temperature to be equal at the start and end of processing.

  For this reason, the present invention monitors the surface temperature of the recording medium 122 (drying drum 176) with respect to the above-mentioned paper types and the like, the drying stability during 1 JOB, and various influence factors, and then drying under various conditions. The cooling means 182 is DUTY controlled so as to optimize the above.

  That is, as shown in FIG. 3, a temperature measuring device 290 that measures the temperature of the drying drum 176 and a temperature measuring device 292 that measures the surface temperature of the recording medium 122 are provided in the drying unit 116.

  The temperature measuring device 290 measures the surface temperature of the portion of the drying drum 176 that is not in contact with the recording medium 122, that is, the axial end portion, while the temperature measuring device 292 measures the recording medium 122 (the shaft of the drying drum 176 except during conveyance). Measure the temperature at the center of the direction). The temperature detected by each temperature measuring instrument is sent as temperature data to a control unit (not shown). The control unit performs DUTY control that finely controls the capability by turning ON / OFF the cooling unit 182 finely by taking into account the above-mentioned conditional factors such as the paper type and the temperature and humidity in the apparatus.

  As a result, the control unit lowers the temperature of the portion of the drying drum 176 that is not in contact with the recording medium 122 by the cooling by the cooling means 182. As described above, since the temperature of the portion is higher than that of the portion in contact with the recording medium 122, the local temperature difference of the drying drum 176 can be reduced by cooling the entire surface of the drying drum 176. That is, the temperature of the portion not in contact with the recording medium 122 is greatly reduced by cooling, and the temperature in the portion in contact with the recording medium 122 is low, so the temperature does not decrease much. For this reason, the temperature difference of both becomes small.

  However, since it is necessary to avoid that the temperature of the portion in contact with the recording medium 122 (or the recording medium 122 itself) is lowered by the cooling means 182 and the drying is insufficient, the portion in contact with / not in contact with the recording medium 122 In addition to controlling the surface temperature of the drying drum 176 in a direction to reduce the temperature difference, it is necessary to perform control so that the temperature of the portion in contact with the recording medium 122 (the portion where the temperature is low) does not become below a certain level.

  FIG. 4 shows the DUTY control of the cooling means 182. That is, as shown in FIGS. 5 (A) and 5 (B), when the temperature exceeds the upper limit with respect to the preset target management upper limit temperature and target management lower limit temperature with respect to the temperature of the portion not in contact with the recording medium 122. The time for turning on the cooling means 182 is increased, and when the temperature falls below the lower limit, the temperature difference Δt is controlled by controlling the driving time so as to increase the time for turning off the cooling means 182, and the target management upper limit temperature and The surface temperature of the portion not in contact with the recording medium 122 is kept between the target control lower limit temperatures.

  At this time, feedback control is performed in which weighting is performed according to the difference between the measured surface temperature of the portion not in contact with the recording medium 122 and the sheet target temperature which is an intermediate value between the target management upper limit temperature and the target management lower limit temperature. It may be.

  For example, there may be a case where the temperature of the target recording medium 122 (or the drying drum 176) does not reach the target temperature or is overcooled due to changes in temperature and humidity in the apparatus. Therefore, PI control that controls the amount of heat applied by integrating the deviation (residual deviation) between the target temperature and the measured temperature in the time axis direction, or PID control that takes into account the rate of change obtained by differentiating the change in measured temperature with time, etc. It may be used. Specifically, as shown in FIG. 5C, it is effective for a situation in which the target temperature is excessively overshooted or cannot be maintained even when the target temperature is reached.

  As described above, in the present invention, the cooling means 182 is DUTY controlled (determining the DUTY correction ratio) while measuring the surface temperature of the portion not in contact with the recording medium 122. Further, the DUTY target value (target temperature) is determined in accordance with the basis weight of the recording medium 122, the paper type, the environment such as temperature and humidity, the droplet ejection amount, and the like.

  Further, the cooling unit 182 is controlled according to the temperature of the recording medium 122 measured by the temperature measuring device 292 during the paper conveyance, and the cooling unit 182 is controlled according to the partial temperature of the drying drum 176 that does not contact the recording medium 122 except during the paper conveyance. By doing so, insufficient drying of the recording medium 122 due to overcooling can be prevented, and at the same time, the surface temperature difference of the drying drum 176 can be efficiently suppressed.

  In addition, by comparing and monitoring the temperature of the portion of the drying drum 176 that does not come into contact with the recording medium 122 measured by the temperature measuring device 290, the heat of the surface of the drying drum 176 taken away by the recording medium 122 is calculated, and continuous JOB is calculated. Stable temperature control is performed even when conditions are unstable such as inside.

  As a result, even when the thin recording medium 122 is dried while using the drying unit 116 having a drying capacity sufficient to dry the thick recording medium 122, the surface temperature difference of the drying drum 176 may cause cuckling. In addition, the drying capacity of the drying unit 116 can be adjusted to an optimum state according to various conditions 8 (basis weight of the recording medium 122, paper type, environment such as temperature and humidity, droplet ejection amount, etc.).

<Others>

  As mentioned above, although the Example of this invention was described, it cannot be overemphasized that this invention is not limited to said Example at all, and can implement in a various aspect in the range which does not deviate from the summary of this invention.

  For example, in the above embodiment, an ink jet type image recording apparatus using water-based ink using water as a solvent has been described as an example. However, the liquid to be ejected is not limited to ink for image recording / character printing, but a recording medium. Any liquid that uses a solvent or a dispersion medium soaking into the liquid can be applied to various discharge liquids.

1 Inkjet recording device 116 Drying unit 122 Recording medium 176 Drying drum (drum)
178 IR heater (heating means)
180 Hot air heater 182 Cooling means 280 Hot air heater 282 Axial fan 284 Temperature sensor 290 Temperature measuring device (drum temperature measuring means)
292 Temperature measuring instrument (paper temperature measuring means)

Claims (10)

A drum that is rotatably supported about an axis and holds and conveys paper on which an image is recorded;
Paper temperature measuring means for measuring the surface temperature of the paper being conveyed;
A drum temperature measuring means for measuring a surface temperature of a portion of the drum not in contact with the paper and a surface temperature of a portion in contact with the paper;
Heating means for heating the surface of the drum and heating and drying the paper being conveyed;
Cooling means for cooling the surface of the drum;
Controlling the heating means and the cooling means according to the temperature of the paper measured by the paper temperature measuring means during paper conveyance,
Controlling the heating means and the cooling means according to the surface temperature of the portion of the drum that does not contact the paper measured by the drum temperature measuring means except during paper conveyance;
Temperature control means for equalizing the temperature of the paper or the surface temperature of the portion of the drum that contacts the paper and the surface temperature of the portion that does not contact the paper;
An image recording apparatus comprising:
The image recording apparatus according to claim 1, wherein the temperature control unit performs duty control for controlling a length of ON / OFF time of the cooling unit in accordance with a sheet temperature measured by the sheet temperature measuring unit.
The temperature control means for controlling the ON / OFF of the cooling means according to the paper temperature and the drum temperature has exceeded the upper limit of the target management upper limit temperature and the target management lower limit temperature preset for the paper temperature. Control the heating means to increase the time to turn on the cooling means, and increase the time to turn off the cooling means when the paper temperature falls below the lower limit, the measured paper temperature and target management The image recording apparatus according to claim 2, wherein feedback control is performed in which weighting is performed in accordance with a difference between the upper limit temperature and a target sheet temperature that is an intermediate value between the upper limit temperature and the target management lower limit temperature.
The image recording apparatus according to claim 1, wherein the temperature control unit turns off the cooling unit during a time when the drum does not hold the sheet.
The image recording according to any one of claims 1 to 4, wherein the ON / OFF control of the cooling means is realized by changing an amount of cooling air generated by a cooling source or changing an air direction of the cooling air. apparatus.
The image recording apparatus according to claim 1, wherein the sheet temperature measuring unit is a non-contact type radiation thermometer.
The image recording apparatus according to claim 1, wherein a sheet of paper is used.
A cooling means for cooling the surface of the drum according to the temperature of the paper on which the image is recorded and the temperature of the drum; and a heating means for heating the surface of the drum and heating and drying the paper being conveyed. Temperature control means for ON / OFF control
When the paper temperature exceeds the upper limit with respect to the threshold values of the target management upper limit temperature and the target management lower limit temperature set in advance for the paper temperature, the time for turning on the cooling means is increased,
When the paper temperature falls below the lower limit, the cooling means is controlled so as to increase the time for turning off the cooling means,
Performs feedback control that is weighted according to the difference between the measured paper temperature and the paper target temperature, which is an intermediate value between the target management upper limit temperature and the target management lower limit temperature,
The sheet cooling means is controlled to increase the ON time when the drum temperature exceeds a preset drum target temperature, and to increase the OFF time when the drum temperature falls below the drum target temperature.
In addition, the paper temperature control means is at least one of the surface finish of the paper, the basis weight of the paper, the temperature and humidity inside the apparatus, and the ejection amount of the ink ejected onto the paper surface to record the image. A drying control method for setting the sheet target temperature in accordance with
A detection means for automatically detecting the paper conveyance environment;
The drying control method according to claim 8, wherein the temperature control unit sets the paper target temperature according to the paper conveyance environment detected by the detection unit.
9. The drying control method according to claim 8, wherein the temperature control unit sets the paper target temperature according to the paper conveyance environment input by a user.

Images