JP2018051819A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To positively remove fine mists flying in a device thereby preventing contamination in the device.SOLUTION: A printer for forming an image by discharging an ink onto a transported web W from an ink jet head unit 51 comprises non-uniform electric field generation means 5 which is located on a transport path on which the web W is transported, and forms non-uniform electric field on a surface of the web W near the ink jet head unit 51. The non-uniform electric field generation means 5 has electrode rollers 52, 52 which are brought into contact with the web W, and application means 53 which applies an AC voltage to the electrode rollers 52, 52, and applies positive and negative charges at narrow intervals. In the printer, a non-uniform electric field control unit 25c, which controls a formation operation of a non-uniform electric field by the non-uniform electric field generation means 5, is provided, whereby changing of an intensity of the non-uniform electric field or switching-on and -off of the formation operation is controlled according to a printing rate or a resolution of a formed image, a kind of a sheet and so on.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a printing apparatus that forms an image by ejecting ink from an inkjet head onto a transported printing paper such as a continuous paper such as a web or a sheet-fed printing paper cut one by one.

  2. Description of the Related Art As an ink jet printing apparatus, there is known an apparatus that prints by ejecting ink from an ink jet head while transporting a recording medium such as a long continuous paper called a web or a sheet-fed printing paper. In an ink jet printing apparatus, the ink ejected from the nozzles of the ink jet head may become so-called mist, and the inside of the apparatus may be soiled.

  Specifically, as the mist, the ink droplets ejected from the nozzles are elongated from the viscosity into a columnar shape, and the columnar shape is divided before landing on the print medium. Examples include a case where a fragment closer to the surface flies, a case where a small ink droplet is blown off by the moment when the ejected ink droplet collides with the print medium, and the like. These mists behave differently depending on their size and weight.For example, those with a relatively large size and mass reach the marking surface under their own weight, while those with a small size and light weight do not reach the marking surface. It flies by the air current inside and adheres to somewhere in the device.

  When the mist flying in the apparatus accumulates in the apparatus for a long time, the liquid accumulated in the paper path becomes a liquid pool, dripping on the print medium, or coming into contact with the print medium and rubbing. There is a risk that the seal will be soiled. In addition, if the flying mist accumulates in the driving part, electronic parts, etc., there is a possibility that it may cause a malfunction. In particular, in an industrial line-type ink jet web printing apparatus, since a large amount of continuous printing operation is continuously performed, mist accumulates in a relatively short time, and there is a possibility that trouble due to mist may appear remarkably. there were.

  Conventionally, as such mist countermeasures, for example, there are techniques disclosed in Patent Documents 1 and 2. In the liquid ejecting apparatus disclosed in Patent Document 1, after the ink ejection operation is completed, the printing medium is transported by a predetermined amount, and the ink is ejected between the previous ejection process end position and the next ejection process start position. An area to be washed away is formed, and the washing treatment is performed in this area. According to such a liquid ejecting apparatus disclosed in Patent Document 1, it is possible to adhere the liquid mist generated during the rinsing process to the blank area of the print medium. Contamination by liquid mist can be prevented.

JP 2007-062117 A

  However, in the liquid ejecting apparatus disclosed in Patent Document 1 described above, the generated mist is attached to the margin area of the print medium, so that the control during printing is complicated, and depending on the image formed However, there are cases where the margin area cannot be sufficiently obtained, and there is a problem that the application range is limited. Even a small mist that is small in size and does not reach the print medium with its own weight can cause a puddle in long-term continuous printing, which can cause the print medium to become dirty. But it needs to be actively removed.

  The present invention has been made in view of the above, and in a printing apparatus that prints by ejecting ink from an inkjet head, the mist flying in the apparatus is positively removed to prevent the inside of the apparatus from being contaminated. It is an object of the present invention to provide a printing apparatus that can be used.

  In order to achieve the above object, a first feature of the present invention is a printing apparatus that forms an image by ejecting ink from an inkjet head on a printing paper to be conveyed, and the conveyance of the printing paper is conveyed. An unequal electric field generating means is provided on the path and for forming an unequal electric field on the surface of the printing paper in the vicinity of the inkjet head.

  According to a second aspect of the present invention, the unequal electric field generation means includes an electrode roller that is in contact with the printing paper, and an application means that applies an AC voltage to the electrode roller and applies positive and reverse charges at narrow intervals. It is characterized by having.

  The third feature of the present invention is further provided with control means for controlling the operation of forming an unequal electric field by the unequal electric field generating means, wherein the control means comprises a printing rate or resolution of an image to be formed, and the printing paper. According to at least one of the types, the strength of the unequal electric field is changed or the on / off of the forming operation is controlled.

  According to the first feature of the printing apparatus of the present invention, by forming an unequal electric field on the surface of the printing paper in the vicinity of the inkjet head, a minute mist is absorbed by the attractive force of the gradient force on the printing paper. By using printing paper that can be adsorbed on the surface and always passed through the transport, mist can be adsorbed and removed from the device, avoiding accumulation of mist and formation of liquid pools, etc. In addition, it is possible to suppress the possibility that the printed surface of the printing paper is soiled by the accumulated mist and the occurrence of malfunctions such as the driving portion and the electronic component.

  According to the second feature of the printing apparatus according to the present invention, a narrow interval according to the rotation of the electrode roller and the frequency of the AC voltage is applied by applying the AC voltage through the electrode roller brought into contact with the printing paper. The forward and reverse charges can be applied.

  According to the third feature of the printing apparatus according to the present invention, the strength of the unequal electric field is changed or the formation operation is entered in accordance with either the printing rate or resolution of the image to be formed or the type of the printing paper. By controlling cutting, the mist is adsorbed on the printing surface, such as when high image quality is required for the formed image, when the printing rate is low and mist adsorption is conspicuous, or when it is glossy paper for photo. If this is not appropriate, the quality of the formed image may be prioritized by weakening or turning off the unequal electric field. In addition, when the formed image is continuously printed with a predetermined interval (margin), the unequal electric field is weakened or turned off in the image portion, and the unequal electric field is strengthened in the blank portion. Alternatively, control such as turning on may be performed to appropriately adjust the balance between the effect of mist removal and the maintenance of image quality.

1 is a schematic configuration diagram of a printing system according to an embodiment. It is a schematic block diagram of the unequal electric field production | generation means which concerns on embodiment. It is a control block diagram of the printing system which concerns on embodiment. It is explanatory drawing which shows a mode that mist is adsorb | sucked by the unequal electric field production | generation means based on embodiment. It is a flowchart figure which shows the control action of the unequal electric field production | generation means in the printing system which concerns on embodiment. It is a flowchart figure which shows the control action of the unequal electric field production | generation means in the printing system which concerns on embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. The embodiment described below exemplifies an apparatus or the like for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, The layout is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

(Configuration of printing system)
FIG. 1 is a schematic configuration diagram of a printing system 1 including a printing apparatus according to the first embodiment of the present invention. In addition, let the direction orthogonal to the paper surface of FIG. 1 be the front-back direction, and let a paper surface direction be the front. Also, the top, bottom, left, and right of the paper surface in FIG.

  As shown in FIG. 1, a printing system 1 according to the present embodiment is a roll-type printing apparatus that forms an image by ejecting ink onto a web W that is a continuous sheet to be conveyed. Is configured such that an unwinding device 2 that feeds out the web W, a printing device 3 that forms an image, and a winding device 4 that winds up the web W on which an image is formed are connected in series.

  The unwinding device 2 is a device that stores a web W that is a long print medium made of film, paper, and the like, and continuously feeds the web W to the printing device 3, upstream of the printing device 3. Is arranged. Specifically, the unwinding device 2 includes a web roll support shaft 11, a brake 12, and an unwinding device electrical unit 13.

  The web roll support shaft 11 is a shaft member that rotatably supports the web roll 16, and is pivotally supported so as to be orthogonal to the conveyance direction of the web roll 16. The web roll support shaft 11 is formed in a rod shape extending in the front-rear direction. The web roll 16 is a cylindrical body on which the web W is rolled.

  The brake 12 is a device that applies a brake to the web roll support shaft 11 by being pressed against the web roll support shaft 11 by a driving means (not shown), for example. The web between the web roll 16 and the conveyance roller 44 of the printing apparatus 3 to be described later is set by the brake 12 so that the rotation speed of the web roll support shaft 11 is equal to the feeding speed (conveyance speed) of the web W. Tension is applied to W.

  The unwinding device electrical unit 13 controls driving of the unwinding device 2 and includes a brake control unit 13 a that controls the brake 12. The brake control unit 13a is connected to the printing device electrical unit 25 on the printing device 3 side, and cooperates with the printing device electrical unit 25 to thereby transport the web W on the downstream printing device 3 or winding device 4 side. Accordingly, the operation of the brake 12 is controlled. The unwinding device electrical unit 13 includes electrical components such as a power supply unit that supplies driving power for the unwinding device 2.

  The printing apparatus 3 is a roll-type printing apparatus that prints an image on the web W by an inkjet method while conveying the web W unwound from the unwinding apparatus 2, and is disposed on the downstream side of the unwinding apparatus 2. Specifically, the printing apparatus 3 includes a conveyance unit 21 that conveys the web W, a first printing unit 22 and a second printing unit 23 that form an image forming unit, an ink circulation unit 24, and a printing device electrical unit 25. And a casing 26 serving as a main body for storing these parts.

  The conveyance unit 21 is a conveyance mechanism that continuously conveys the web W that has been unwound from the unwinding device 2, and includes guide rollers 31 to 40 that form a conveyance path of the web W and 20 head lower support members 41. And a pair of transport rollers 44, a transport motor 45 for driving the transport mechanism of the web W, a meandering correction unit 42, and an encoder 43. In the present embodiment, the head lower support member 41 is arranged so that the web W to be conveyed has an upward arch shape.

  The guide rollers 31 to 40 are roller members that guide the web W conveyed in the printing apparatus 3, and are axially supported and conveyed along the conveyance path of the web W so as to be orthogonal to the conveyance direction of the web W. As the web W moves, it is driven to rotate. The guide rollers 31 to 40 are formed in a rod shape extending in the front-rear direction and are rotatably supported.

  The guide rollers 31 and 32 are roller members that guide the web W between the unwinding device 2 and the meandering correction unit 42. The guide roller 31 is disposed in the vicinity of the left side surface of the housing 26 in the lower part of the printing apparatus 3. The guide roller 32 is disposed between the guide roller 31 and a meandering correction roller 46A of a meandering correction unit 42 described later.

  The guide rollers 33 to 39 are roller members that guide the web W between the meandering correction unit 42 and the conveyance roller 44. The guide roller 33 is disposed on the left side of a meandering correction roller 46B of a meandering correction unit 42 described later. The guide roller 34 is disposed above the guide roller 33. The guide roller 35 has the same height as the guide roller 34 and is disposed on the right side of the guide roller 34. The guide roller 36 is disposed below the guide roller 35 and at a position higher than the guide roller 33. The guide roller 37 is disposed on the left side of the guide roller 36, near the right side of the web W between the guide rollers 33 and 34, and at a position that is substantially the same height as the guide roller 36. The guide roller 38 is disposed on the lower right side of the guide roller 37. The guide roller 39 is disposed slightly below the right side of the guide roller 38.

  The guide roller 40 is a roller member that guides the web W between the transport roller 44 and the winding device 4, and the web W is sent to the winding device 4 through the guide roller 40. The guide roller 40 is disposed in the vicinity of the right side surface of the casing 26 in the lower part of the printing device 3, and the web W is connected to the web roll 17 wound on the winding device 4 side via the guide roller 40. ing.

  The head lower support member 41 is a roller member that supports the web W immediately below the first printing unit 22 and directly below the second printing unit 23. The head lower support member 41 is pivotally supported in a long shape extending in the front-rear direction, and is disposed so as to form a conveyance path for the web W. Ten head support members 41 are arranged between the guide rollers 34 and 35 that are directly under the first printing unit 22 and between the guide rollers 36 and 37 that are directly under the second printing unit 23. .

  In each of the space between the guide rollers 34 and 35 and between the guide rollers 36 and 37, the ten head lower support members 41 are arranged so as to draw a convex arch upward. As a result, the web W is stretched between the guide rollers 34 and 35 and between the guide rollers 36 and 37 and is maintained in a stable posture.

  The meandering correction unit 42 is a mechanism for correcting the meandering of the web W, and is disposed upstream of the printing units 22 and 23. Specifically, the meandering correction rollers 46A and 46B and the meandering correction roller 46A are provided. , 46B, a meandering correction motor 47 and a web sensor 48 are provided.

  The meandering correction rollers 46 </ b> A and 46 </ b> B are rollers for guiding the web W and correcting the meandering of the web W. The meandering correction rollers 46A and 46B are formed in a long shape extending in the front-rear direction. The meandering correction rollers 46A and 46B are configured such that the angle in the axial direction with respect to the front-rear direction on the horizontal plane can be adjusted. The meandering correction roller 46 </ b> A is disposed on the right side of the guide roller 32. The meandering correction roller 46B is disposed above the meandering correction roller 46A.

  The meander correction motor 47 is a drive device that rotates the meander correction rollers 46A and 46B around an axis orthogonal to the horizontal plane in order to adjust the angle of the meander correction rollers 46A and 46B with respect to the front-rear direction on the horizontal plane. is there. The web sensor 48 is a detection device that detects the position of the edge of the web W in the front-rear direction for correcting meandering. The web sensor 48 is disposed in the vicinity of the meandering correction roller 46B.

  The encoder 43 is a detection device that is connected to the guide roller 34 and outputs a pulse signal for each predetermined rotation angle of the guide roller 34. The output pulse signal of the encoder 43 is input to the printing apparatus electrical unit 25 and used for controlling the conveyance speed of the web W. The pair of transport rollers 44 are drive rollers that transport the web W toward the winding device 4 while nipping the web W, and the pair of transport rollers 44 are disposed between the guide rollers 39 and 40. . The transport motor 45 is a drive device that rotates the transport roller 44.

  The first printing unit 22 is an image forming unit that prints an image on the surface of the web W by an inkjet method. The first printing unit 22 is disposed above the web W between the guide rollers 34 and 35 and includes five inkjet head units 51 that discharge different color inks. On the other hand, the second printing unit 23 is an image forming apparatus that prints an image on the back surface of the web W. The second printing unit 23 is disposed above the web W between the guide rollers 36 and 37, and is similar to the first printing unit 22. Five inkjet head units 51 for discharging different color inks are provided. The inkjet head unit 51 has an inkjet head (not shown), and ejects ink from the nozzles of the inkjet head.

  The ink circulation unit 24 supplies ink to the inkjet head of the inkjet head unit 51 while circulating the ink along an ink circulation path (not shown). The ink circulation unit 24 includes, for each inkjet head unit 51, an ink circulation path, an ink cartridge (not shown) that supplies ink to the ink circulation path, and the like.

The housing 26 is a box-like body that houses the transport unit 21, the first printing unit 22, the second printing unit 23, the ink circulation unit 24, and the printing apparatus electrical unit 25. The unwinding device 2 is disposed on the left side of the housing 26, and the winding device 4 is disposed on the right side. Openings are provided in the side portions of these devices at locations corresponding to each other, and through these openings. A web W is inserted between the apparatuses, and is conveyed from the upstream unwinding apparatus 2 to the downstream winding apparatus 4 via the printing apparatus 3.
The winding device 4 winds the web W printed by the printing device 3. The winding device 4 is a device that includes a winding shaft 96, a winding motor 97, and a winding device electrical unit 98.

  The winding shaft 96 is a shaft member that winds and holds the web W. The winding shaft 96 is formed in a long shape extending in the front-rear direction. The winding motor 97 is a driving motor that rotates the winding shaft 96 in the clockwise direction in FIG. The web W is wound around the winding shaft 96 by the rotation of the winding shaft 96 by the winding motor 97.

  The winding device electrical unit 98 controls driving of the winding device 4. The winding device electrical section 98 includes a winding motor control unit 98 a that controls the winding motor 97. The winding motor control unit 98a is connected to the printing device electrical unit 25 on the printing device 3 side, and cooperates with the printing device electrical unit 25, so that the web W on the upstream printing device 3 or unwinding device 2 side is connected. The operation of the winding motor 97 is controlled according to the transport speed. The winding device electrical section 98 includes a power supply unit that supplies driving power for the winding device 4.

(Configuration of unequal electric field generation means)
Further, in the present embodiment, in the printing apparatus 3, an unequal electric field generating unit 5 is provided in the vicinity of the ink jet head unit 51 constituting the image forming unit. As schematically shown in FIG. 2, the unequal electric field generating means 5 applies an AC voltage to the plurality of electrode rollers 52, 52 brought into contact with the web W, and the electrode rollers 52, 52, and forward and reverse at a narrow interval. And an applying means 53 for applying the electric charge.

  The electrode rollers 52, 52 are rod-shaped members that extend in the front-rear direction and are rotatably supported by a metal roller member. In the first and second printing units 22, 23, the electrode rollers 52, 52 serve as a web W conveyance path. The web W is disposed so as to be orthogonal to the conveyance direction of the web W, is brought into contact with the upper surface of the web W to be conveyed, and is driven to rotate as the web W moves.

  The application means 53 is a power supply device that applies an AC voltage to the electrode rollers 52 and 52 that are in contact with the web W, and applies an AC voltage to the electrode rollers 52 and 52 that are rotated as the web W moves. As a result, forward and reverse charges 62 are applied to the surface of the web W at narrow intervals as shown in FIG. As a result, an unequal electric field (electric field where electric lines of force are concentrated in part) as shown by electric field lines 61 in the figure is formed on the web W, and the gradient of the electric field strength is increased, so that the gradient force is increased. Generated on the surface of W. As a result, an attracting force that attracts the mist 6 flying above the web W to the upper surface of the web W is generated.

  The application means 53 is configured such that the intensity of the unequal electric field is changed by the inequality electric field generation control unit 25c, or on / off of the forming operation is controlled. In the present embodiment, the default control is ON at the start of printing or when the power is turned on, and an AC voltage is always applied to the electrode rollers 52 and 52 at the time of conveyance, while it is formed according to the control mode. The intensity of the unequal electric field is changed or the on / off of the forming operation is controlled according to at least one of the image printing rate or resolution and the type of continuous paper.

(Configuration of printing device electrical equipment)
The printing device electrical unit 25 described above is a control unit that drives and controls each unit of the printing device 3. As shown in FIG. 3, the printing apparatus electrical unit 25 includes a head drive control unit 25 a that controls the inkjet head of each inkjet head unit 51, and a conveyance control unit 25 b that controls conveyance of the web W by the conveyance motor 45. It is connected. The transport control unit 25 b includes a meandering control unit that controls the operation of the meandering correction motor 47 and an ink circulation control unit that controls the ink circulation unit 24. Further, the printing apparatus electrical unit 25 includes a power supply unit that supplies driving power for the printing apparatus 3.

  Furthermore, the printing apparatus electrical unit 25 according to the present embodiment further includes an unequal electric field generation control unit 25c as a control unit that controls the operation of forming an unequal electric field by the unequal electric field generation unit 5. The unequal electric field generation control unit 25c is a module that changes the intensity of the unequal electric field formed by the applying means 53, or controls ON / OFF of the forming operation. In the present embodiment, the unequal electric field generation control unit 25c, in the default control, turns on the application means 53 at the start of printing or when the power is turned on, and always adds an AC voltage to the electrode rollers 52 and 52 during conveyance. While generating an unequal electric field, according to the control mode, the strength of the unequal electric field is changed according to at least one of the printing rate or resolution of the formed image and the type of continuous paper, or the formation operation is entered. It is designed to control off.

  In the present embodiment, as the control by the unequal electric field generation control unit 25c, a predetermined mode in which the control pattern is defined is prepared. As this control mode, for example, there is a low printing rate mode for reducing mist adsorption when the printing rate of an image to be formed is low or when the resolution is high. In this low printing rate mode, an image related to image formation is used. When the content of the data is analyzed and a part with a low printing rate or a part with a high resolution is included, the voltage of the applying means 53 is reduced or the application is turned off according to the part. There is also a high-quality paper mode that reduces mist adsorption when it can be determined that high-quality printing is required from the type of print media involved in image formation, such as photo paper. When the type of printing paper is detected and the paper type is a predetermined paper type such as photo paper, the voltage of the applying means 53 is reduced or the application is turned off for the whole paper.

  As another control mode, when the formed image is continuously printed with a predetermined interval (margin), the application unit 53 is controlled in accordance with the appearance of the margin between the prints. An inter-printing mode may be provided. In this inter-printing mode, the effect of removing mist is controlled by weakening or turning off the unequal electric field at the print part and increasing or turning off the unequal electric field in accordance with the appearance of the margin between prints. The balance between image quality maintenance and image quality maintenance may be adjusted as appropriate.

  In addition, in this embodiment, since many electrode rollers 52 and 52 are arrange | positioned continuously, adjacent electrode rollers 52 and 52, so that an unequal electric field may not cancel out between adjacent electrode rollers 52 and 52. In accordance with the distance between the electrodes 52 and the circumference of the electrode rollers 52 and 52, the voltage is controlled so that the period and phase of the unequal electric field coincide with each other. In this embodiment, since a method of forming images on the front and back of the web W is employed, the period and phase of the unequal electric field in the first printing unit 22 on the upstream side and the second printing unit 23 on the downstream side are employed. Are controlled so that the frequency and phase of the AC voltage applied to each of the electrode rollers 52 and 52 are controlled so as to avoid canceling the upstream electric field on the downstream side. Furthermore, since the amount of mist generated and accumulated increases toward the downstream side in the transport direction, in this embodiment, control is performed so that the intensity of the unequal electric field increases as it goes downstream.

(Operation of the printing system 1)
Next, the printing operation of the printing system 1 and the control of unequal electric field generation will be described.
When printing is performed by the printing system 1, first, the unwinding device 2, the printing device 3, and the winding device 4 start conveyance of the web W. Specifically, the control unit of the unwinding device electrical unit 13 activates the brake 12, the transport control unit of the printing device electrical unit 25 starts driving the transport motor 45, and the control unit of the winding device electrical unit 98 is The drive of the winding motor 97 is started. Thereby, the web W is conveyed from the unwinding device 2 toward the winding device 4. When the web roll support shaft 11 is braked by the brake 12 of the unwinding device 2, the web W is transported while tension is applied to the web W between the web roll 16 and the transport roller 44.

  During the conveyance of the web W, the conveyance control unit of the printing apparatus electrical unit 25 calculates the conveyance speed of the web W based on the output pulse signal of the encoder 43. The transport control unit controls the supply current to the transport motor 45 so that the difference between the calculated transport speed and the print transport speed (target speed) is eliminated. Thereby, the conveyance speed of the web W is controlled to be constant.

  Further, the transport control unit of the printing apparatus electrical unit 25 calculates the output torque of the transport motor 45 according to the current supplied to the transport motor 45. The output torque of the transport motor 45 can be calculated from the motor characteristics of the transport motor 45 in accordance with the supply current. The control unit of the unwinding device electrical unit 13 is a target torque in which the difference between the output torque of the transport motor 45 calculated by the transport control unit of the printing device electrical unit 25 and the output torque of the brake 12 corresponds to the target tension of the web W. The brake force (output torque) of the brake 12 is adjusted so as to make a difference. Thereby, the tension of the web W is controlled to be constant.

  Further, the ink circulation control unit of the printing apparatus electrical unit 25 starts the ink circulation operation by the ink circulation unit 24. After the conveyance of the web W and the ink circulation operation are started, the head drive control unit of the printing apparatus electrical unit 25 controls the inkjet heads of the inkjet head units 51 of the first and second printing units 22 and 23 to control the web W. To print the image.

  In accordance with the printing of this image, an AC voltage is applied to the electrode rollers 52 and 52 that are rotated in accordance with the movement of the web W in the vicinity of the inkjet head unit 51, so A reverse charge 62 is applied. By this application, a gradient force is generated on the surface of the web W, and the mist 6 flying above the web W is attracted to and attracted to the upper surface of the web W.

  The application of the voltage by the applying means 53 is such that the intensity of the unequal electric field is changed or the on / off of the forming operation is controlled according to various control modes. FIG. 5 is a flowchart showing a control operation in the low printing rate mode, and FIG. 6 is a flowchart showing a control operation in the high quality paper mode.

  In the present embodiment, the default control is ON when printing is started or when power is turned on, and an AC voltage is always applied to the electrode rollers 52 and 52 during conveyance. In this default control, the distance between the adjacent electrode rollers 52, 52, 52, the distance between the adjacent electrode rollers 52, 52, 52 of the electrode rollers 52, 52 is set so that the unequal electric field does not cancel out between the adjacent electrode rollers 52, 52 arranged in succession. In accordance with the circumference, the voltage is controlled to be applied so that the period and phase of the unequal electric field match each other. Further, the frequency of the AC voltage applied to each electrode roller 52, 52 so that the period and phase of the unequal electric field in the first printing unit 22 on the upstream side and the second printing unit 23 on the downstream side match each other. The phase may be controlled to avoid canceling the upstream electric field on the downstream side. Furthermore, since the generation and accumulation amount of mist increases toward the downstream side in the transport direction, the intensity of the unequal electric field is controlled to increase as it goes downstream.

Various control modes are selected based on a user operation or in response to automatic detection, and the intensity of the unequal electric field is changed or on / off of the forming operation is controlled according to the selected control mode.
In the low printing rate mode, as shown in FIG. 5, when printing is started, the contents of the image data relating to image formation are analyzed, and whether or not a low printing rate part or a high resolution part is included. Is determined (S101). When a part with a low printing rate or a part with a high resolution is included (“Y” in S101), the electrode roller is turned off at the timing when a part with a low printing rate / resolution appears (if it is already OFF). Or the voltage is reduced to weaken the electric field strength, and the mist adsorption is stopped or the adsorption force is weakened (S103). On the other hand, when a part with a low printing rate or a part with a high resolution is not included (“N” in S101), the electrode rollers 52 and 52 are turned on (in order to return to the default control at the timing when the part appears) If it is already ON, the voltage is increased, the electric field strength is increased, and mist is actively adsorbed (S102). Such control for each part is repeated until the printing is finished (“N” in S104), and when the printing is finished (“Y” in S104), the voltage application to the electrode rollers 52 and 52 is also finished.

  On the other hand, in the high quality paper mode, as shown in FIG. 6, when printing is started, the type of the printing paper is detected, and whether or not high quality printing is required, for example, the printing paper is photo paper. Is determined (S101). When it is not a predetermined paper type such as photo paper (“N” in S201), the electrode rollers 52 and 52 are turned on (if they are already on), or the voltage is increased to increase the electric field strength and actively. Mist is adsorbed (S202). On the other hand, when it is a predetermined paper type such as photo paper ("Y" in S201), the electrode roller is turned off (if it is already off) or the electric field strength is reduced by reducing the voltage, The adsorption of mist is stopped or the adsorption force is weakened (S203).

Such control for each part is repeated until printing is completed (“N” in S204). When printing is completed (“Y” in S204), application of voltage to the electrode rollers 52 and 52 is also terminated.
Thereafter, when printing of the image is finished, the ink circulation control unit of the printing apparatus electrical unit 25 finishes the ink circulation operation by the ink circulation unit 24. Further, the unwinding device 2, the printing device 3, and the winding device 4 end the conveyance of the web W. Specifically, the control unit of the unwinding device electrical unit 13 stops the brake 12, the transport control unit of the printing device electrical unit 25 stops the transport motor 45, and the control unit of the winding device electrical unit 98 winds up. The motor 97 is stopped. Thereby, a series of operation | movement is complete | finished.

(Function and effect)
As described above, according to the printing apparatus 3 according to the present embodiment, in the vicinity of the inkjet head unit 51, the gradient force is formed by forming an unequal electric field as indicated by the electric force lines 61 in the drawing on the surface of the web W. The mist can be adsorbed to the surface of the web W by the adsorbing force of the web W, and the mist 6 can be adsorbed and removed from the printing apparatus 3 using the web W that is conveyed and always passes. , Accumulation of mist and formation of liquid puddles can be avoided, and it is possible to prevent the accumulated mist from contaminating the marking surface of the web W and causing malfunctions such as driving parts and electronic components. be able to.

  In particular, in the present embodiment, the formed image can be increased by changing the strength of the unequal electric field or controlling the on / off of the forming operation according to the printing rate or resolution of the formed image, the type of the web W, and the like. When the image quality is required, the printing rate is low, mist adsorption is conspicuous, or the glossy paper is used for photo, etc. The quality of the formed image can be prioritized by turning it off or turning it off.

  The above description of the embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and various modifications can be made according to the design and the like as long as they do not depart from the technical idea of the present invention. In the above embodiment, the roll-type printing apparatus that forms an image by ejecting ink on the web W that is continuous paper has been described as an example. For example, printing is performed for each cut sheet. The present invention can also be applied to a sheet-fed printing apparatus.

W ... Web 1 ... Printing system 2 ... Unwinding device 3 ... Printing device 4 ... Winding device 5 ... Unequal electric field generating means 6 ... Mist 11 ... Web roll support shaft 12 ... Brake 13 ... Unwinding device electrical section 13a ... Brake Control unit 16, 17 ... Web roll 21 ... Conveying unit 22 ... First printing unit 23 ... Second printing unit 24 ... Ink circulation unit 25 ... Printing device electrical unit 25a ... Head drive control unit 25b ... Conveyance control unit 25c ... Unequal Electric field generation control unit 26 ... Case 31-40 ... Guide roller 41 ... Head lower support member 42 ... Meandering correction unit 43 ... Encoder 44 ... Conveying roller 45 ... Conveying motor 46A, 46B ... Meandering correction roller 47 ... Meandering correction motor 48 ... Web sensor 51 ... inkjet head unit 52, 52 ... electrode roller 53 ... mark It means 61 ... electric field lines 62 ... positive reverse charge 96 ... take-up shaft 97 ... winding motor 98 ... retractor electrical component section 98a ... winding motor control unit

Claims (3)

A printing apparatus that forms an image by ejecting ink from an inkjet head to a transported printing paper,
A printing apparatus comprising: an unequal electric field generating unit that is disposed on a printing paper conveyance path through which the printing paper is conveyed and that forms an unequal electric field on the surface of the printing paper in the vicinity of the inkjet head. The unequal electric field generating means includes
An electrode roller in contact with the printing paper;
The printing apparatus according to claim 1, further comprising an application unit that applies an AC voltage to the electrode roller and applies positive and reverse charges at a narrow interval. Further comprising control means for controlling the operation of forming an unequal electric field by the unequal electric field generating means,
The control means changes the strength of the unequal electric field or controls on / off of the forming operation according to at least one of a printing rate or resolution of an image to be formed and a type of the printing paper. The printing apparatus according to claim 1 or 2.

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