JP2012116063A - Inkjet recording device and method for preventing dew condensation of inkjet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording device and a method for preventing dew condensation of an inkjet head by which the dew condensation of the inkjet head is prevented, and satisfactory image formation is achieved.SOLUTION: The inkjet head recording device includes: a plotting cylinder (44) that holds a recording medium (14); inkjet heads (48M, 48K, 48C and 48Y) that jet ink to the recording medium held on the plotting cylinder; a conveying means that relatively conveys the recording medium held on the holding means and the inkjet head; and a plotting cylinder cooling part (92) that is provided on a pre-stage side of the inkjet head, and applies cooling liquid to the surface of the plotting cylinder to cool the plotting cylinder so that a temperature difference between the plotting cylinder and the ink in the inkjet head may be within a temperature range in which the dew condensation does not occur on the inkjet head. Thus, the dew condensation of the inkjet head caused by the temperature difference between the temperature of the plotting cylinder in a plotting area of the inkjet head and that of the ink inside the inkjet head is prevented.

Description

  The present invention relates to an ink jet recording apparatus and a method for preventing condensation on an ink jet head, and more particularly, to a technique for preventing condensation on a nozzle surface in an ink jet head.

  Conventionally, as a general-purpose image forming apparatus, an ink jet recording apparatus that forms a desired image on a recording medium by discharging color ink from an ink jet head is known. Inkjet recording devices are managed so that the temperature of the ink within the inkjet head is within the proper range in order to maintain the viscosity of the ink within a certain range, ensure stable ejection characteristics, and form high-definition images. In addition, the ambient temperature around the inkjet head is controlled so as to fall within an appropriate range.

  On the other hand, in the process of drying the paper before or after drawing by the ink jet head, heat treatment using a heater or the like is performed. The heat generated by this heat treatment may cause condensation on the inkjet head. When the inkjet head is condensed, water droplets drip on the paper and stain the paper being drawn, while water droplets adhering to the nozzle surface enter the inside of the nozzle and change the ejection characteristics of the nozzle. Therefore, various techniques have been proposed to prevent condensation of the inkjet head.

  Patent Document 1 discloses an ink jet recording apparatus in which a member that is more likely to condense than the head is disposed in the vicinity of the head, and the member that is likely to condense is condensed to prevent the head from condensing. Patent Document 2 discloses a printing apparatus configured to be cooled each time continuous paper passes through a drying unit. Patent Document 3 discloses a base material coating device configured to cool a coated surface of a web that contacts an outer peripheral surface of a pressure drum by bringing a cooling roller close to a pressure drum that is in contact with a plate cylinder across the web. Disclosure.

  Patent Document 4 discloses a method for producing a thermal transfer image-receiving sheet in which a dye-receiving layer is formed on a substrate, having a step of cooling the receiving layer to room temperature via a cooling roll in which water is circulated. is doing. Patent Document 5 discloses an energized thermal transfer printer that includes a cooling roller that includes a heat pipe that is in rolling contact with the back surface (resistor layer) of a gravure endless ribbon and cools ink in a gravure cell in the rolling zone. is doing.

Japanese Patent Laid-Open No. 1-157860 JP 2007-196513 A JP 2010-89420 A JP 2005-88545 A JP 2002-321398 A

  However, in the dew condensation member provided in the ink jet recording apparatus described in Patent Document 1, the conditions under which the head dew condensation can be prevented are limited by the applied material. In addition, the methods described in Patent Documents 2, 4 and 5 both cool the paper (web) by contact, have a low cooling effect on the surrounding environment of the head, and cause a rapid temperature change of the impression cylinder. It is difficult to respond.

  On the other hand, the base material coating apparatus described in Patent Document 3 cools the coated surface of the web in contact with the impression cylinder by cooling the impression cylinder, and cools the base material coated on the coated surface of the web. There is a problem common to the technique of Patent Document 2 or the like in that the viscosity of the base material is increased and the effect of cooling the surrounding environment of the head is low.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an inkjet recording apparatus and an inkjet head condensation prevention method in which condensation of the inkjet head is prevented and preferable image formation is realized.

  In order to achieve the above object, an ink jet recording apparatus according to the present invention includes a holding unit that holds a recording medium, an ink jet head that ejects ink onto the recording medium held by the holding unit, and a holding unit that holds the recording medium. A transport unit that relatively transports the recorded recording medium and the ink jet head, and a temperature difference between the holding unit and the ink in the ink jet head causes condensation on the ink jet head. And a cooling unit that cools the holding unit by applying a cooling liquid to the surface of the holding unit so that the temperature range is not generated.

  According to the present invention, since the cooling liquid is applied to the surface of the holding unit that holds the recording medium and the holding unit is cooled before the image formation by the inkjet head, the inkjet head at the time of image formation by the inkjet head Condensation of the ink jet head due to a temperature difference from the impression cylinder is prevented, and preferable image formation is realized.

1 is an overall configuration diagram showing a schematic configuration of an ink jet recording apparatus according to an embodiment of the present invention. 1 is a perspective plan view showing an example of the structure of an inkjet head applied to the inkjet recording apparatus shown in FIG. Schematic plan view for explaining the nozzle arrangement of the head module that constitutes the ink jet head shown in FIG. Sectional drawing which shows the three-dimensional structure of the inkjet head shown in FIG. 1 is a block diagram showing a schematic configuration of a control system of the ink jet recording apparatus shown in FIG. 1 is a configuration diagram showing a schematic configuration of a drawing cylinder cooling unit provided in the ink jet recording apparatus shown in FIG. Explanatory drawing which illustrated typically the cooling fluid application | coating process by the drawing cylinder cooling part shown in FIG. The block diagram which shows the other aspect of the drawing cylinder cooling part shown in FIG. Explanatory drawing which illustrated typically the cooling fluid application | coating process by the drawing cylinder cooling part shown in FIG. The block diagram which shows schematic structure of the drawing part which concerns on the application example of this invention The perspective view which shows the whole structure of the drawing cylinder shown in FIG. Explanatory drawing which shows the example of an internal structure of the drawing cylinder shown in FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Overall configuration of inkjet recording apparatus]
FIG. 1 is a configuration diagram showing the overall configuration of the inkjet recording apparatus 10. The ink jet recording apparatus 10 shown in the figure forms an image on an image forming surface of a recording medium 14 based on predetermined image data using an ink containing a color material and an aggregating treatment liquid having a function of aggregating the ink. This is a two-liquid aggregation type recording apparatus.

  The ink jet recording apparatus 10 mainly includes a paper supply unit 20, a treatment liquid application unit 30, a drawing unit 40, a drying processing unit 50, a fixing processing unit 60, and a discharge unit 70. Transfer cylinders 32, 42, 52, and 62 are provided as means for delivering the recording medium 14 conveyed upstream of the treatment liquid application unit 30, the drawing unit 40, the drying processing unit 50, and the fixing processing unit 60, and the treatment liquid. As means for conveying the recording medium 14 while holding the recording medium 14 in each of the coating unit 30, the drawing unit 40, the drying processing unit 50, and the fixing processing unit 60, impression cylinders 34, 44, 54, and 64 having a drum (cylindrical) shape are provided. It has been.

  The transfer cylinders 32, 42, 52, 62 and the impression cylinders 34, 44, 54, 64 are provided with grippers 80 </ b> A, 80 </ b> B that hold the leading end portion of the recording medium 14 at predetermined positions on the outer peripheral surface. The structure for holding the front end portion of the recording medium 14 in the gripper 80A and the gripper 80B and the structure for delivering the recording medium 14 to and from the gripper provided in another impression cylinder or transfer cylinder are the same, and The gripper 80 </ b> A and the gripper 80 </ b> B are arranged at symmetrical positions that are moved 180 ° in the rotation direction of the pressure drum 34 on the outer peripheral surface of the pressure drum 34.

  When the transfer cylinders 32-62 and the impression cylinders 34, 44, 54, 64 are rotated in a predetermined direction with the gripper 80A, 80B holding the leading end of the recording medium 14, the transfer cylinders 32-62 and the impression cylinder 34 are rotated. , 44, 54, 64, the recording medium 14 is rotated and conveyed along the outer peripheral surface. In FIG. 1, only the grippers 80 </ b> A and 80 </ b> B provided in the impression cylinder 34 are denoted by reference numerals, and the reference numerals of the other impression cylinders and the transfer cylinder grippers are omitted.

  When the recording medium (sheet) 14 accommodated in the paper supply unit 20 is fed to the processing liquid application unit 30 via the paper supply tray 22, it is held on the outer peripheral surface of the impression cylinder (processing liquid cylinder) 34. A coagulation treatment liquid (hereinafter sometimes simply referred to as “treatment liquid”) is applied from the treatment liquid coating device 36 to the image forming surface of the recording medium 14 thus obtained. The “image forming surface of the recording medium 14” is an outer surface in a state where the impression cylinders 34, 44, 54, 64 are held, and is opposite to a surface held by the impression cylinders 34, 44, 54, 64. Surface.

  As an example of a configuration for applying the aggregation treatment liquid, an anilox roller that measures and measures the aggregation treatment liquid from a container in which the aggregation treatment liquid is stored, and the aggregation treatment liquid measured by the anilox roller is applied to the outer peripheral surface. And an application roller for applying the ink in contact with a recording medium. In addition, an acidic liquid can be applied to the aggregation treatment liquid. In such an embodiment, a coating roller moving mechanism that moves the coating roller in the vertical direction (the normal direction of the outer peripheral surface of the processing liquid cylinder 34) is provided, and the collision between the coating roller and the grippers 80A and 80B can be avoided. Embodiments are preferred.

  Thereafter, the recording medium 14 to which the aggregation processing liquid is applied is subjected to a solvent drying process and is sent to the drawing unit 40, and the drawing unit 40 has an area to which the aggregation processing liquid is applied (image forming area). ), Color ink is applied from the inkjet heads 48M, 48K, 48C, and 48Y, and a desired image is formed.

  That is, when the recording medium 14 coated with the aggregation treatment liquid is transferred from the transfer cylinder 42 to the impression cylinder (drawing cylinder) 44, the inkjet heads 48M, 48K, 48C, 48Y to M (magenta), based on the image data. K (black), C (cyan), and Y (yellow) inks are ejected. When ink lands on the recording medium 14, an aggregating action due to the aggregating treatment liquid appears and ink aggregates (dots) are formed.

  In the inkjet recording apparatus 10 shown in this example, the configuration of the standard colors (4 colors) of MKCY is exemplified, but the combination of ink colors and the number of colors is not limited to the present embodiment, and light ink is used as necessary. , Dark ink and special color ink may be added. For example, it is possible to add an inkjet head that discharges light-colored ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

  Further, the recording medium 14 on which the image of the color ink is formed is sent to the drying processing unit 50, where the drying processing is performed by the drying processing device 56, and the ink solvent is removed. The recording medium 14 after the drying process is sent to the fixing processing unit 60 where the fixing process using the heater 66 and the fixing roller 68 is performed. By performing the fixing process, the image formed on the recording medium 14 is hardened. In this manner, a desired image is formed on the image forming surface of the recording medium 14, and after the image is fixed on the image forming surface of the recording medium 14, the image is read by the inline sensor 82.

  In the ink jet recording apparatus 10 shown in this example, the presence or absence of ejection abnormality of the ink jet heads 48M, 48K, 48C, and 48Y is determined based on the reading result of the inline sensor 82. When the ejection abnormality of the inkjet heads 48M, 48K, 48C, 48Y is detected, droplet ejection correction and image correction are performed in order to prevent the occurrence of image abnormality due to ejection abnormality.

  Thereafter, the recording medium 14 is conveyed from the discharge unit 70 to the outside of the apparatus. The discharge unit 70 shown in FIG. 1 includes an endless conveyance chain 74 wound around the stretching rollers 72A and 72B, and a discharge tray 76 that stores the recording medium 14 after image recording. Yes. The recording medium 14 after the fixing process sent out from the fixing processing unit 60 is transported by the transport chain 74 and discharged to the discharge tray 76.

  As shown in FIG. 1, the inkjet recording apparatus 10 shown in this example includes a sheet cooling unit (cooling apparatus) 90 that cools the recording medium 14 before drawing on which the aggregation treatment liquid is applied. The sheet cooling unit 90 blows cold air to the recording medium 14 conveyed immediately below the inkjet heads 48M, 48K, 48C, and 48Y, and the temperature of the recording medium 14 entering immediately below the inkjet heads 48M, 48K, 48C, and 48Y is increased. The ink jet heads 48M, 48K, 48C, and 48Y are cooled so as to have substantially the same temperature as the ink.

  Further, on the opposite side (lower surface side) of the ink jet heads 48M, 48K, and 48C of the drawing cylinder 44, a drawing cylinder cooling unit 92 that cools the drawing cylinder by applying a cooling liquid to the drawing cylinder 44, and an outer peripheral surface of the drawing cylinder. A tray 94 is provided for receiving the discharged material when the air is discharged from a suction hole (not shown) provided in the container and the inside of the suction hole is cleaned. In the ink jet recording apparatus 10 shown in this example, a cooling medium is applied to the drawing cylinder 44 after the recording medium after drawing is transferred to the transfer cylinder 52 and before the next recording medium is transferred. The surface temperature of 44 is cooled so that the temperature of the ink is substantially the same. Thereafter, the coolant adhering to the surface of the drawing cylinder 44 is wiped off, and air is further discharged from the suction holes.

  Here, “substantially the same temperature as the temperature of the ink” is a temperature for preventing condensation on the nozzle surfaces (indicated by reference numeral 120A in FIG. 4) of the inkjet heads 48M, 48K, 48C, and 48Y. And includes at least a temperature lower than the temperature of the ink.

  Further, even when the surface temperature of the drawing cylinder 44 is set to ± 5 ° C. with respect to the ink temperature, the nozzle surfaces of the ink jet heads 48M, 48K, 48C, and 48Y can be prevented. That is, the concept of “substantially the same temperature as the ink temperature” includes a temperature range of ± 5 ° C. with respect to the ink temperature.

  Although FIG. 1 illustrates the impression cylinder conveyance method in which the recording medium is held and conveyed on the peripheral surface of the impression cylinder (cylindrical conveyance drum), the recording medium conveyance method is limited to the impression cylinder conveyance (rotary conveyance) method. Instead, a system in which the recording medium is held on a conveyance belt and moved linearly may be applied.

[Inkjet head structure]
Next, an example of the structure of the inkjet heads 48M, 48K, 48C, 48Y provided in the drawing unit 40 will be described. Since the structures of the inkjet heads 48M, 48K, 48C, and 48Y corresponding to the respective colors are common, the inkjet head (hereinafter also simply referred to as “head”) is represented by reference numeral 48 in the following. And

  FIG. 2 is a schematic configuration diagram of the head 48, and is a view (a plan perspective view of the head) in which the image forming surface of the recording medium is viewed from the head 48. FIG. The head 48 shown in the figure forms a multi-head by connecting n sub-heads 100-i (i is an integer from 1 to n) in a line. Each sub head 100-i is supported by the head cover 102 from both sides of the head 48 in the short direction. It is possible to configure a multi-head by arranging the sub-heads 100-i in a staggered manner.

  As an application example of a multi-head configured by a plurality of sub-heads, a full-line head corresponding to the entire width of a recording medium can be given. The full-line head has a plurality of nozzles (corresponding to the length (width) in the main scanning direction of the recording medium along the direction (main scanning direction) orthogonal to the moving direction (sub-scanning direction) of the recording medium. 3 is shown with reference numeral 104.). An image can be formed on the entire surface of the recording medium by a so-called single pass image recording method in which the head 48 having such a structure and the recording medium are scanned only once relatively.

  The sub head 100-i shown in FIG. 2 has a substantially parallelogram planar shape, and an overlap portion is provided between adjacent sub heads. The overlap portion is a connecting portion of the sub-heads, and is formed by nozzles in which dots adjacent to the sub-heads 100-i in the arrangement direction (the horizontal direction in FIG. 2, the main scanning direction X shown in FIG. 3) belong to different sub-heads. The

  FIG. 3 is a plan view showing the nozzle arrangement of the sub head 100-i. As shown in the figure, each sub head 100-i has a structure in which the nozzles 104 are two-dimensionally arranged, and the head including the sub head 100-i is a so-called matrix head. The sub head 100-i illustrated in FIG. 3 includes a row direction W that forms an angle α with respect to the sub scanning direction (the relative movement direction of the head 48 and the recording medium 14) Y, and the main scanning direction (the arrangement of the sub heads 100-i). (Direction) X has a structure in which a large number of nozzles 104 are arranged along a row direction V that forms an angle β with respect to X, and a substantial nozzle arrangement density in the main scanning direction X is increased.

  In FIG. 3, nozzle groups (nozzle rows) arranged along the row direction V are denoted by reference numeral 106, and nozzle groups (nozzle rows) arranged along the column direction W are denoted by reference numeral 108. ing. The matrix arrangement of the nozzles 104 is not limited to the example shown in FIG. 3, and the nozzles 104 may be arranged in the row direction along the main scanning direction X and the column direction oblique to the sub-scanning direction Y.

  FIG. 4 is a cross-sectional view showing a three-dimensional configuration of one channel of droplet discharge elements (ink chamber units corresponding to one nozzle 104) serving as a recording element unit. As shown in the figure, a head 48 (sub head 100) of this example includes a nozzle plate 120 in which nozzles 104 are formed, a flow path plate 126 in which flow paths such as a pressure chamber 122 and a common flow path 124 are formed, and the like. It consists of the structure which laminated and joined. The nozzle plate 120 forms a nozzle surface 120A of the head 48, and a plurality of nozzles 104 communicating with the respective pressure chambers 122 are two-dimensionally formed (see FIG. 3).

  The flow path plate 126 forms a side wall of the pressure chamber 122 and a flow path that forms a supply port 128 as a throttle portion (most narrowed portion) of an individual supply path that guides ink from the common flow path 124 to the pressure chamber 122. It is a forming member. For convenience of explanation, the flow path plate 126 has a structure in which one or a plurality of substrates are stacked, although it is illustrated schematically in FIG. The nozzle plate 120 and the flow path plate 126 can be processed into a required shape by a semiconductor manufacturing process using silicon as a material.

  The common flow path 124 communicates with an ink tank (not shown) as an ink supply source, and ink supplied from the ink tank is supplied to each pressure chamber 122 via the common flow path 124.

  A diaphragm 130 constituting a part of the pressure chamber 122 (the top surface in FIG. 4) includes an upper (individual) electrode 132 and a lower electrode 134, and a piezoelectric body between the upper electrode 132 and the lower electrode 134. A piezo actuator 138 having a structure in which 136 is sandwiched is joined. When the diaphragm 130 is formed of a metal thin film or a metal oxide film, it functions as a common electrode corresponding to the lower electrode 134 of the piezoelectric actuator 138. In the aspect in which the diaphragm is formed of a non-conductive material such as resin, a lower electrode layer made of a conductive material such as metal is formed on the surface of the diaphragm member.

  By applying a driving voltage to the upper electrode 132, the piezo actuator 138 is deformed to change the volume of the pressure chamber 122, and ink is ejected from the nozzle 104 due to the pressure change accompanying this. When the piezo actuator 138 returns to its original state after ink ejection, new ink is refilled into the pressure chamber 122 from the common channel 124 through the supply port 128.

As shown in FIG. 3, the ink chamber unit having such a structure is latticed in a fixed arrangement pattern along a row direction V that forms an angle β with the main scanning direction X and a column direction W that forms an angle α with respect to the sub-scanning direction Y. The high-density nozzle head of this example is realized by arranging a large number in the shape. In this matrix arrangement, when the interval between adjacent nozzles in the sub-scanning direction is L _s , the nozzles 104 are substantially equivalent to those in which the nozzles 104 are arranged linearly at a constant pitch P = L _s / tan θ in the main scanning direction. Can be handled.

[Explanation of control system]
FIG. 5 is a block diagram illustrating a schematic configuration of a control system of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 160, a system control unit 162, a conveyance control unit 164, an image processing unit 166, a head driving unit 168, and an image memory 170 and a ROM 172.

  The communication interface 160 is an interface unit that receives image data sent from the host computer 174. The communication interface 160 may be a serial interface or a parallel interface. The communication interface 160 may be equipped with a buffer memory (not shown) for speeding up communication.

  The system control unit 162 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. Furthermore, it functions as a memory controller for the ROM 172 and the image memory 170. That is, the system control unit 162 controls each unit such as the communication interface 160 and the conveyance control unit 164, performs communication control with the host computer 174, read / write control of the image memory 170 and the ROM 172, and the like. A control signal to be controlled is generated.

  Image data sent from the host computer 174 is taken into the inkjet recording apparatus 10 via the communication interface 160 and subjected to predetermined image processing by the image processing unit 166. The image processing unit 166 has a signal (image) processing function for performing various processing and correction processes for generating a print control signal from the image data, and supplies the generated print data to the head driving unit 168. It is a control unit. Necessary signal processing is performed in the image processing unit 166, and the ejection droplet amount (droplet ejection amount) and ejection timing of the head 48 are controlled via the head driving unit 168 based on the image data. Thereby, a desired dot size and dot arrangement are realized. The head driving unit 168 shown in FIG. 5 may include a feedback control system for keeping the driving conditions of the head 48 constant.

  The conveyance control unit 164 controls the conveyance timing and conveyance speed of the recording medium 14 (see FIG. 1) based on the print control signal generated by the image processing unit 166. 5 includes a motor that rotates the impression cylinders 34, 44, 54, and 64 in FIG. 1, a motor that rotates the transfer cylinders 32, 42, 52, and 62, and the recording medium 14 in the sheet feeding unit 20. A motor for the delivery mechanism, a motor for driving the stretching roller 72A (72B) of the discharge unit 70, and the like are included, and the transport control unit 164 functions as a driver for the motor.

  The image memory (temporary storage memory) 170 functions as temporary storage means for temporarily storing image data input via the communication interface 160, a development area for various programs stored in the ROM 172, and a calculation work area for the CPU. (For example, a work area of the image processing unit 166). As the image memory 170, a volatile memory (RAM) capable of sequential reading and writing is used.

  The ROM 172 stores a program executed by the CPU of the system control unit 162, various data necessary for controlling each unit of the apparatus, control parameters, and the like, and data is read and written through the system control unit 162. The ROM 172 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used. Alternatively, a removable storage medium that includes an external interface may be used.

  The inline detection unit 178 including the inline sensor 82 illustrated in FIG. 1 is a processing block including a signal processing unit that performs predetermined signal processing such as nozzle removal, amplification, and waveform shaping on the read signal output from the inline sensor 82. . The system control unit 162 determines whether there is an ejection abnormality of the head 48 based on the detection signal obtained by the inline detection unit 178.

  The inkjet recording apparatus 10 further includes a processing liquid application control unit 180, a drying processing control unit 182, a fixing processing control unit 184, a paper cooling control unit 186, and a drawing cylinder cooling control unit 188, and a system control unit 162. Are controlled in accordance with the instructions from the processing liquid application unit 30, the drying processing unit 50, the fixing processing unit 60, the paper cooling unit 90, and the drawing cylinder cooling unit 92, respectively.

  The maintenance control unit 190 comprehensively controls maintenance processing of each part of the apparatus in accordance with a command signal from the system control unit 162. The maintenance process includes maintenance (purging, suction, etc.) of the head 48 and maintenance (cleaning) of the impression cylinders 34, 44, 54, 64. The maintenance process for the drawing cylinder 44 includes a process for removing ink and the like attached to the outer peripheral surface of the drawing cylinder 44 and an air discharge for preventing the suction holes of the drawing cylinder 44 from being clogged.

  The parameter storage unit 192 stores various control parameters necessary for the operation of the inkjet recording apparatus 10. The system control unit 162 appropriately reads out parameters necessary for control and updates (rewrites) various parameters as necessary.

  The program storage unit 194 is a storage unit that stores a control program for operating the inkjet recording apparatus 10.

  The temperature detector 196 includes a temperature sensor that detects the temperature of each part of the apparatus. Based on a detection signal (temperature information) obtained from the temperature sensor, a cooling process or a heating process is performed so that the temperature of each part of the apparatus falls within a predetermined range. Examples of the temperature sensor include a sensor that detects the temperature of the ink in the head 48, a sensor that detects the environmental temperature of the head 48, a sensor that detects the temperature of the recording medium 14, and a sensor that detects the temperature of the coolant.

[Description of drawing cylinder cooling process]
(First embodiment)
Next, the drawing cylinder cooling process (condensation prevention process) in the inkjet recording apparatus 10 shown in this example will be described in detail. In the following description, the same reference numerals are given to the parts described above, and description thereof is omitted.

  FIG. 6 is a configuration diagram showing a schematic configuration of the drawing cylinder cooling unit 92. The drawing cylinder cooling unit 92 shown in the figure is in contact with the outer peripheral surface of the drawing cylinder 44 to apply the cooling liquid, the support member 204 that supports the rotating shaft 202 of the application roller 200, and the cooling liquid is stored. A coolant reservoir (water tray) 206, a tube 208 communicating with the coolant reservoir 206, a circulation pump 210 that circulates the coolant via the tube 208, and a coolant applied to the drawing cylinder 44. And a wiping unit 212 to be wiped off.

  FIG. 7 is an explanatory diagram schematically showing a cooling process in which the drawing cylinder cooling unit 92 shown in FIG. 6 applies a cooling liquid to the outer peripheral surface of the drawing cylinder 44 and cools it. As shown in the figure, in the application roller 200, a coolant holding part 200B made of a material obtained by foaming a rubber material such as ethylene propylene diene rubber (EPDG) around a metal or resin core material 200A is wound. The cooling liquid is held by the cooling liquid holding part 200 </ b> B that has a structure and is brought into contact with the outer peripheral surface of the drawing cylinder 44. The core member 200 </ b> A is supported by support members 204 (see FIG. 6, not shown in FIG. 7) from both ends, and is configured to rotate following the rotation of the drawing cylinder 44. In FIG. 7, the rotation direction of the drawing cylinder 44 and the driven rotation direction of the application roller 200 are indicated by arrow lines.

  The coating roller 200 has a length corresponding to the axial length of the drawing cylinder 44 in the axial direction, and can apply the cooling liquid at once to the entire width of the drawing cylinder 44 in the axial direction. . When the application roller 200 having such a structure is driven and rotated with respect to the drawing cylinder 44 while being pressed against the outer peripheral surface of the drawing cylinder 44 with a constant pressure, a certain amount of cooling liquid is applied to the outer peripheral surface of the drawing cylinder 44. In addition, the material which comprises the cooling fluid holding | maintenance part 200B is not limited to said material, What is necessary is just a material with favorable holding | maintenance (performance which absorbs cooling fluid) of a cooling fluid. Further, the coolant holding part 200B is preferably made of a material that elastically deforms when brought into contact with the drawing cylinder 44.

  Returning to FIG. 6, the application roller 200 is supported such that the lower half is immersed in the coolant stored in the coolant storage unit 206. That is, the lower half of the application roller 200 functions as an absorption region that absorbs the cooling liquid, and a portion that contacts the drawing cylinder 44 functions as an application area for applying the cooling liquid to the drawing cylinder 44. A support member 204 that supports the application roller 200 so as to be driven to rotate is a bearing that supports the core material (rotary shaft) 200 </ b> A of the application roller 200 on an L-shaped angle member that is fixed to the bottom surface of the coolant reservoir 206. (Not shown) is attached.

  The coolant reservoir 206 has tubes 208 attached to both ends in the longitudinal direction, and the coolant supplied from one end is discharged from the other end. Although not shown in FIG. 6, a temperature adjuster for adjusting the temperature of the coolant is provided in the vicinity of the coolant inlet of the coolant reservoir 206, and the coolant adjusted to a predetermined temperature is provided. It is configured to be supplied to the coolant storage unit 206. In addition, the aspect using the material which has heat insulation is preferable for the cooling fluid storage part 206 and the tube 208, in order to suppress the temperature change of a cooling fluid.

  The operation of the circulation pump 210 is controlled so that the coolant is circulated at a constant speed in one direction. By circulating the coolant, the temperature of the coolant is kept constant even when a temperature gradient occurs inside the coolant reservoir 206. Although illustration is omitted, the coolant is replenished from a tank (not shown) to the coolant reservoir 206 when the amount of coolant stored in the coolant reservoir 206 becomes a certain amount or less. ing.

  The wiping portion 212 is provided on the rear side of the application roller 200 (downstream side in the rotation direction of the drawing cylinder 44), has a structure in which the web 216 is wound around the roller 214, and the web 216 is attached to the outer peripheral surface of the drawing cylinder 44. The cooling liquid is wiped off in contact with the liquid. In addition, the aspect which wipes a cooling liquid with a braid | blade instead of the aspect which wipes off a cooling liquid with the web 216 is also possible.

  According to the drawing cylinder cooling unit 92 according to the first embodiment, by supplying the cooling liquid directly to the surface of the application roller 200, the cooling liquid is applied to the outer peripheral surface of the drawing cylinder 44, and by the action of the cooling liquid, The surface temperature of the drawing cylinder 44 can be lowered efficiently. In addition, the provision of the wiping unit 212 for wiping off the cooling liquid adhering to the drawing cylinder 44 prevents the occurrence of problems due to the adhesion of the cooling liquid. In addition, by providing cleaning performance to the cooling liquid (by applying a cleaning liquid having the same temperature condition as the cooling liquid), an effect of cleaning the outer peripheral surface of the drawing cylinder 44 by applying and wiping the cooling liquid is also obtained.

(Second Embodiment)
Next, another aspect of the drawing cylinder cooling unit 92 shown in FIG. 6 will be described. FIG. 8 is a configuration diagram showing a schematic configuration of a drawing cylinder cooling unit 92 ′ according to another aspect of the drawing cylinder cooling unit 92 shown in FIG. The drawing cylinder cooling unit 92 ′ illustrated in FIG. 8 includes a spraying device 220 that sprays a coolant instead of the application roller 200 illustrated in FIG. The spraying device 220 has a length corresponding to the axial length of the drawing cylinder 44 in the axial direction of the drawing cylinder 44, and a plurality of spray ports (in FIG. 8) on the surface facing the outer peripheral surface of the drawing cylinder 44. A cooling fluid spraying part 222 is formed, which is formed (not shown, indicated by reference numeral 228 in FIG. 9).

  The coolant spraying part 222 is supported by the support member 224 on the opposite side of the drawing cylinder 44 and is fixed at a predetermined interval from the outer peripheral surface of the drawing cylinder 44. The coolant spray unit 222 is connected to a pump 226 via a tube 208, and coolant is supplied from a tank (not shown) via the tube 208 and the pump 226.

  FIG. 9A is an explanatory diagram showing the arrangement of the spray ports 228 formed in the spray device 220. As shown in the figure, the coolant spraying part 222 has a structure in which a plurality of spray ports 228 are arranged at equal intervals over the length corresponding to the length of the drawing cylinder 44 in the axial direction of the drawing cylinder 44. Have. The diameter of the spray ports 228 is 20 μm to 500 μm, and the arrangement pitch of the spray ports 228 is 100 μm to 2 mm. The distance between the spray port 228 and the drawing cylinder is 10 mm to 40 mm.

  FIG. 9B is an explanatory diagram schematically showing spraying of the coolant. When cooling liquid is sprayed all at once from the plurality of spray ports 228 formed in the coolant spraying part 222 toward the outer peripheral surface of the drawing cylinder 44, the outer peripheral surface of the drawing cylinder 44 is constant over the entire length in the axial direction. An amount of cooling liquid adheres. Here, “cooling liquid spraying” is an application mode of cooling liquid in which mist droplets having a diameter of several μm or less are discharged from the spraying port 228 and adhered to the outer peripheral surface of the drawing cylinder 44. As an example of generating mist-like cooling liquid droplets, there is a method of vibrating the cooling liquid at a frequency of several MHz to several hundred MHz.

  According to the drawing cylinder cooling unit 92 ′ according to the second embodiment, the surface temperature of the drawing cylinder 44 can be efficiently lowered by the action of the cooling liquid by spraying the cooling liquid directly on the surface of the drawing cylinder 44. is there. In addition, the provision of the wiping unit 212 for wiping off the cooling liquid adhering to the drawing cylinder 44 prevents the occurrence of problems due to the adhesion of the cooling liquid.

  Further, like the drawing cylinder cooling unit 92 according to the first embodiment, by providing cleaning performance to the cooling liquid (by applying a cleaning liquid having the same temperature condition as the cooling liquid), by applying and wiping the cooling liquid An effect of cleaning the outer peripheral surface of the drawing cylinder 44 is also obtained.

[Application example]
Next, application examples of the present invention will be described. FIG. 10 is a configuration diagram showing a schematic configuration of a drawing unit 40 ′ according to an application example, and FIG. 11 is a perspective view showing an overall configuration of the drawing cylinder 44 ′ shown in FIG. FIG. 12 is an explanatory diagram of an example of the internal structure of the drawing cylinder 44 ′ shown in FIG.

  The drawing unit 40 ′ shown in FIG. 10 has a drawing area (suction area) 300 and a maintenance area (discharge area) 302. That is, the recording medium 14 is fixedly held on the outer peripheral surface in the drawing area 300, and maintenance of the drawing cylinder 44 'is executed in the maintenance area 302. As shown in FIG. 11, the drawing cylinder 44 ′ is provided with a number of suction holes in a recording medium holding area 322 where the recording medium 14 on the outer peripheral surface 320 is fixedly held. In FIG. 11, the individual illustration of the suction holes is omitted, and a dot hatch is attached to a region where the suction holes are formed.

  The suction holes have a circular shape with a diameter of 1 mm to 2 mm, and are arranged at equal intervals at an arrangement pitch of about 2 to 3 times the diameter. Further, each of the plurality of suction holes is illustrated with a vacuum pump (not shown in FIG. 11, notation in FIG. 11, with reference numeral 330 in FIG. 12) via a vacuum channel (suction channel) formed inside the drawing cylinder 44 ′. ) And a compressor (not shown in FIG. 11; indicated by reference numeral 332 in FIG. 12) via a vacuum channel (exhaust channel) (not shown) formed inside the drawing cylinder 44 ′. Connected with.

  Returning to FIG. 10, at the recording medium delivery position 304, the recording medium is delivered from the transfer cylinder 42 to the drawing cylinder 44 '. A paper pressing roller 46 is provided in the immediate vicinity of the recording medium delivery position 304 on the downstream side in the conveying direction, and the recording medium is pressed against the outer peripheral surface 306 of the drawing cylinder 44 ′ by the paper pressing roller 46.

  When the recording medium is brought into close contact with the outer peripheral surface 306 of the drawing cylinder 44 ', an adsorption pressure is generated in the suction hole, and the recording medium is sucked and fixed to the outer peripheral surface 306 of the drawing cylinder 44'. In this way, the recording medium is sent to the drawing area immediately below the ink jet heads 48M, 48K, 48C, and 48Y without being lifted from the outer peripheral surface 306 of the drawing cylinder 44 '.

  When a desired image is formed on the recording medium by the color ink ejected from each of the inkjet heads 48M, 48K, 48C, and 48Y, the recording medium is sent to a delivery position (discharge position) 306 with the transfer cylinder 52. At the delivery position 306, the vacuum suction of the recording medium is turned off, the fixed holding of the leading end of the recording medium is released, and the recording medium is delivered from the drawing cylinder 44 'to the transfer cylinder 52 through a predetermined guide.

  In this way, when the recording medium is transferred from the drawing cylinder 44 ′ to the transfer cylinder 52 at the transfer position 306, the drawing cylinder 44 ′ further rotates and the cooling liquid is applied from the drawing cylinder cooling unit 92. When the drawing cylinder 44 ′ further rotates and the recording medium holding area reaches the maintenance area 302, compressed air is supplied to a vacuum channel (not shown), and air is blown out from the suction holes of the outer peripheral surface 306. Is called.

  That is, the drawing cylinder 44 ′ is provided with a suction area 300 for sucking the recording medium during one rotation, and a discharge area 302 for supplying compressed air to the suction holes. Paper dust or ink that has entered the suction holes during drawing is provided. Mist, dust, etc. are discharged in the maintenance area 302. It is also possible to discharge the coolant that has entered the suction hole.

  FIG. 12 illustrates an example of a switching structure between the vacuum pump 330 and the compressor 332. A switching structure 334 illustrated by a solid line in FIG. 12 is fixed to a support member (not shown) of the bearing 336, a first flow path 340 connected to the vacuum pump 330 via the suction hose 338, and an exhaust gas A second flow path 344 connected to the compressor 332 via the hose 342 is provided at a symmetrical position across the rotation axis along the peripheral portion.

  The first flow path 340 is provided at a position corresponding to the suction area 300 of the drawing cylinder 44 ′, and the second flow path 344 is provided at a position corresponding to the discharge area 302 of the drawing cylinder 44 ′. Further, the connecting portion 350 of the suction hose 346, the connecting portion 352 of the suction hose 348, the connecting portion 354 of the suction hose 358, and the connecting portion 356 of the suction hose 360 are connected to the first flow path 340 and the second flow path 344, respectively. It is connectable and has a structure that is in a sealed state when not connected to the first flow path 340 and the second flow path 344.

  In FIG. 12, the connecting portion 352 is connected to the upstream end portion (the right end portion in FIG. 12) of the first flow path 340 in the recording medium conveyance direction, and the connecting portion 350 is connected to the substantially central portion of the first flow path 340. The connecting portion 354 is connected to the substantially central portion of the second flow path 344, and the connecting portion 356 is not connected to either the first flow path 340 or the second flow path 344. Has been.

  In the state shown in FIG. 12, the vacuum channel inside the drawing cylinder 44 ′ communicating with the suction hose 348 is connected to the vacuum pump 330, and suction pressure is generated in the suction hole communicating with the vacuum channel. On the other hand, the vacuum flow path inside the drawing cylinder 44 ′ communicating with the suction hose 358 is connected to the compressor 332, and air is discharged from the suction hole communicating with the vacuum flow path. In addition, since neither the vacuum pump 330 nor the compressor 332 is connected to the vacuum flow path inside the drawing cylinder 44 ′ communicating with the suction hose 360, the suction hole communicating with the vacuum flow path performs both suction and discharge. I will not.

  When the drawing cylinder 44 ′ rotates counterclockwise from the state illustrated in FIG. 12 and the connection between the connecting portion 354 of the suction hose 358 and the second flow path 344 is released, the drawing communicating with the suction hose 358 is performed. The vacuum channel inside the barrel 44 ′ is disconnected from the compressor 332, and the air discharge from the suction hole communicating with the vacuum channel is turned off.

  Further, when the drawing cylinder 44 ′ rotates counterclockwise and the connecting portion 356 of the suction hose 360 is connected to the second flow path 344, the drawing cylinder 44 ′ is connected to the vacuum flow path inside the drawing cylinder 44 ′ communicating with the suction hose 360. The compressor 332 is connected, and air is discharged from a suction hole communicating with the vacuum flow path. Similarly, when the connection between the connecting portion 352 of the suction hose 348 and the first flow path 340 is released according to the rotation of the drawing cylinder 44 ′, the vacuum flow path inside the drawing cylinder 44 ′ communicating with the suction hose 348. And the vacuum pump 330 are disconnected, and suction of the suction hole communicating with the vacuum channel is turned off.

  In this way, in the recording medium holding area that has reached the suction area 300 in accordance with the rotation of the drawing cylinder 44 ′, the suction holes are connected to the vacuum pump 330 via the vacuum flow path and the switching structure 334 of the drawing cylinder 44 ′. Then, the recording medium is vacuum-sucked. On the other hand, in the recording medium holding area that has reached the discharge area 302, the suction hole is connected to the compressor 332 via the vacuum flow path of the drawing cylinder 44 'and the switching structure 334, and air is discharged. A tray 94 (see FIG. 1) that receives the discharged discharge is provided immediately below the discharge region 302.

  In FIG. 12, the vacuum pump 330 and the compressor 332 are illustrated as separate devices, but it is also possible to use a combination pump that realizes both functions with a single device. Moreover, although the example which implement | achieves the connection switching of the vacuum pump 330 and the compressor 332 with a mechanical mechanism was illustrated in this example, another switching system is applicable. For example, a control valve is provided in each of a connection portion between the vacuum flow path inside the drawing cylinder 44 ′ and the vacuum pump 330 and a connection portion between the vacuum flow path and the compressor 332, and the vacuum flow path, the vacuum pump 330, and the compressor are provided. A mode in which the connection with 332 is switched by a control valve can be mentioned.

  According to the application example of the present invention, after the cooling liquid is wiped off, the cooling liquid entering the suction hole can be discharged by discharging the air from the suction hole, which affects the fixing and holding performance of the recording medium. Don't give.

  As described above, the ink jet recording apparatus and the condensation prevention method applied to the present invention have been described in detail, but can be appropriately changed without departing from the gist of the present invention.

[Appendix]
As can be understood from the description of the embodiment described in detail above, the present specification includes disclosure of various technical ideas including the invention described below.

  (Invention 1): A holding unit that holds a recording medium, an inkjet head that ejects ink onto the recording medium held by the holding unit, a recording medium that is held by the holding unit, and the inkjet head And a holding unit that is provided on a front side of the inkjet head, and that the temperature difference between the holding unit and the ink in the inkjet head is in a temperature range in which condensation does not occur in the inkjet head. And a cooling means for cooling the holding means by applying a cooling liquid to the surface of the ink jet recording apparatus.

  According to the present invention, since the cooling liquid is applied to the surface of the holding unit that holds the recording medium and the holding unit is cooled before the image formation by the inkjet head, the inkjet head at the time of image formation by the inkjet head Condensation of the ink jet head due to a temperature difference from the impression cylinder is prevented, and preferable image formation is realized.

  (Invention 2): In the ink jet recording apparatus according to Invention 1, the cooling means may include a cooling liquid in the holding means so that the temperature of the holding means with respect to the ink in the ink jet head is within a temperature range of ± 5 ° C. It is characterized by giving.

  According to this aspect, condensation of the ink jet head can be prevented by setting the temperature of the holding means to a temperature range of ± 5 ° C. with respect to the ink in the ink jet head.

  (Invention 3): In the ink jet recording apparatus according to Invention 1 or 2, the cooling means includes a roller member having a cylindrical shape and a structure in which a cooling liquid is held on an outer peripheral surface, and the surface of the holding means And a support means for supporting the roller member so as to contact the outer peripheral surface of the roller member.

  The roller member in such an embodiment preferably has a length corresponding to the entire width of the recording medium.

  (Invention 4): In the ink jet recording apparatus according to Invention 3, the roller member includes an absorbing member that absorbs and holds a cooling liquid on an outer peripheral surface.

  According to this aspect, it is possible to reliably apply the coolant to the surface of the holding unit by applying the contact-type coolant.

  (Invention 5): In the ink jet recording apparatus according to Invention 1 or 2, the cooling unit includes a spray member that sprays the cooling liquid onto a surface of the holding unit.

  According to this aspect, the application of the spray-type cooling liquid can reliably apply the cooling liquid to the surface of the holding means.

  (Invention 6): In the ink jet recording apparatus according to Invention 5, the spray member has a structure in which a spray port for a coolant is provided at a position facing the surface of the holding unit.

  The spray member in such an embodiment may have a structure in which a plurality of spray ports for spraying the cooling liquid are arranged over the entire width of the recording medium.

  (Invention 7): The ink jet recording apparatus according to any one of Inventions 1 to 6, further comprising a removing means for removing the cooling liquid applied to the holding means.

  The removal of the cooling liquid in such an aspect may include an aspect in which the wiping member is wiped to remove the cooling liquid from the holding means.

  (Invention 8): The ink jet recording apparatus according to any one of Inventions 1 to 7, wherein the cooling unit applies a cleaning liquid having a cleaning function to the holding unit.

  According to this aspect, it is possible to remove the dirt adhering to the holding means.

  (Invention 9): The ink jet recording apparatus according to any one of Inventions 1 to 8, wherein the holding means includes an ejection port for ejecting air onto a surface.

  In such an aspect, an aspect including an air flow path communicating with the injection port and a pressurizing unit connected to the air flow path is preferable.

  (Invention 10): In the ink jet recording apparatus according to Invention 9, the ejection port is provided in a recording medium holding area for holding the recording medium and also serves as an adsorption hole for generating an adsorption pressure applied to the recording medium. It is characterized by that.

  According to this aspect, it is possible to obtain the cleaning effect inside the suction hole along with the removal of the coolant.

  (Invention 11): In the ink jet recording apparatus according to any one of Inventions 1 to 10, the holding means has a cylindrical shape and includes an impression cylinder for holding a recording medium on an outer peripheral surface, and the conveying means is Rotating means for rotating the impression cylinder about a central axis of the impression cylinder as a rotation axis is included.

  (Invention 12): The ink jet recording apparatus according to any one of Inventions 1 to 11, further comprising a recording medium cooling means for cooling the recording medium held by the holding means.

  By cooling the recording medium together with the holding means, it is possible to effectively prevent condensation of the inkjet head.

  (Invention 13): An ink jet recording apparatus that forms an image by ejecting ink from the ink jet head to the recording medium while relatively transporting the recording medium and an ink jet head that ejects ink onto the recording medium. A method for preventing dew condensation on an ink jet head, comprising: applying a cooling liquid to a surface of a holding means for holding the recording medium and cooling the holding means before image formation by the ink jet head.

  In the present invention, the coolant may be applied by a contact method or by a spray method.

  Moreover, the aspect including the removal process which removes a cooling fluid, and the aspect which provides a washing | cleaning function to a cooling fluid are also preferable. Furthermore, an aspect including an air injection step of injecting air from an adsorption hole for applying an adsorption pressure to the recording medium is also preferable.

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 14 ... Recording medium, 40 ... Drawing part, 44 ... Drawing cylinder, 48, 48M, 48K, 48C, 48Y ... Inkjet head, 92, 92 '... Drawing cylinder cooling part, 188 ... Drawing cylinder cooling control , 200 ... Application roller, 200B ... Coolant holding part, 212 ... Wiping part, 216 ... Web, 220 ... Spraying device, 222 ... Coolant spraying part, 228 ... Spraying port

Claims (13)

Holding means for holding a recording medium;
An inkjet head for ejecting ink onto a recording medium held by the holding means;
Conveying means for relatively conveying the recording medium held by the holding means and the inkjet head;
A cooling liquid is provided on the surface of the holding unit so that a temperature difference between the holding unit and the ink in the inkjet head is within a temperature range in which condensation does not occur in the inkjet head. Cooling means for cooling the holding means;
An ink jet recording apparatus comprising:   2. The inkjet according to claim 1, wherein the cooling unit applies a cooling liquid to the holding unit such that the temperature of the holding unit with respect to the ink in the inkjet head is within a temperature range of ± 5 ° C. 3. Recording device. The cooling means includes a roller member having a cylindrical shape and a structure in which a coolant is held on the outer peripheral surface,
The inkjet recording apparatus according to claim 1, further comprising a supporting unit that supports the roller member so that an outer peripheral surface of the roller member is brought into contact with a surface of the holding unit.   The inkjet recording apparatus according to claim 3, wherein the roller member includes an absorbing member that absorbs and holds the cooling liquid on an outer peripheral surface.   The inkjet recording apparatus according to claim 1, wherein the cooling unit includes a spray member that sprays the cooling liquid onto a surface of the holding unit.   6. The ink jet recording apparatus according to claim 5, wherein the spray member has a structure in which a spray port for a coolant is provided at a position facing the surface of the holding unit.   The ink jet recording apparatus according to claim 1, further comprising a removing unit that removes the cooling liquid applied to the holding unit.   The inkjet recording apparatus according to claim 1, wherein the cooling unit applies a cleaning liquid having a cleaning function to the holding unit.   The inkjet recording apparatus according to claim 1, wherein the holding unit includes an ejection port that ejects air onto a surface.   The ink jet recording apparatus according to claim 9, wherein the ejection port is provided in a recording medium holding area for holding a recording medium, and is also used as an adsorption hole for generating an adsorption pressure applied to the recording medium. . The holding means has a cylindrical shape and includes an impression cylinder that holds a recording medium on an outer peripheral surface;
11. The ink jet recording apparatus according to claim 1, wherein the conveying unit includes a rotating unit that rotates the impression cylinder with a central axis of the impression cylinder as a rotation axis.   The inkjet recording apparatus according to claim 1, further comprising a recording medium cooling unit that cools the recording medium held by the holding unit. In an inkjet recording apparatus that forms an image by ejecting ink from the inkjet head to the recording medium while relatively transporting the recording medium and an inkjet head that ejects ink onto the recording medium.
A method for preventing dew condensation on an ink jet head, wherein a cooling liquid is applied to a surface of a holding means for holding the recording medium before image formation by the ink jet head to cool the holding means.

Images