JP2017043471A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printer which can reduce contact of an ink jet head to a sheet.SOLUTION: An ink jet printer includes: ink jet heads 61A-61D which discharge ink to a conveyed sheet; a plurality of head lower support rollers 26-30 which are arranged with an interval along the sheet conveyance direction on the lower side of the ink jet heads 61A-61D and support the sheet; and non-uniform electric field generation means 5 which forms a non-uniform electric field on the surfaces of the head lower support rollers 26-30. The head lower support rollers 26-30 are non-conductors. The non-uniform electric field generation means 5 includes: an electrode roller 52 which is brought into contact with the head lower support rollers 26-30; and application means 51 which applies the AC voltage to the electrode roller 52 to apply normal and reverse electric charges with a narrow interval.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an inkjet printing apparatus that prints by ejecting ink from an inkjet head.

  2. Description of the Related Art An ink jet printing apparatus that prints by ejecting ink from an ink jet head while conveying a recording medium made of long continuous paper called a web is known. In this inkjet printing apparatus for web, when the distance from the nozzle surface of the inkjet head to the web increases, the landing position deviation due to the error in the ejection direction of the head itself or the shaking of the web being conveyed at high speed becomes significant. In addition, mist and satellites increase and image quality deteriorates. Therefore, in this web ink jet printing apparatus, the nozzle surface of the ink jet head is set at a distance of 1 mm or less with respect to the web in order to improve the image quality.

  By the way, in a web inkjet printing apparatus, for example, when a user notices a danger or abnormality in a printing apparatus and presses an emergency stop button, or when a power failure or an outlet is disconnected and power is not supplied to the printing apparatus, the printing apparatus May stop suddenly during the printing process when it is physically unable to move due to a web jam or failure.

  In these cases, since the web wound in a roll shape on the uppermost stream and the lowermost stream of the web has a large inertia, even if the printing press stops suddenly, the conveyance of the web cannot be stopped suddenly. Since each roller in the printing section is not braked, when it stops suddenly, each roller will continue to rotate due to inertia, and this rotation may cause the web to slightly slack as shown in FIG. After the stop, the web moves in the direction opposite to the conveying direction due to the repulsive force, and the slack may occur.

  As a countermeasure against the sudden stop of the web when such a printing apparatus is suddenly stopped, there is a technique disclosed in Patent Document 1. In the technology of this Patent Document 1, an emergency stop of the paper feeding device is performed by forming a so-called air loop by loosening the web by its own weight between the web take-in mechanism and the web transport mechanism, and controlling this air loop as a buffer. Absorbs the progress of the web due to inertial force. Thereby, at the time of the emergency stop of a paper feeder, the damage to a web conveyance mechanism etc. is avoided by ensuring time until the operation | movement of a web conveyance mechanism stops.

JP 2012-136301 A

  However, since the technique of Patent Document 1 is a method of absorbing the progress of the web due to the inertia force by controlling the buffer, there is a problem that it cannot cope with the slackness of the web that occurs in the vicinity of the inkjet head. When such web slack or breakage occurs, there is a risk of so-called head attack in which the web contacts the ink jet head. When the web contacts the nozzle, the print surface is soiled, the nozzle meniscus is destroyed, the nozzle surface is damaged, etc. May cause problems.

  The present invention has been made in view of the above, and an object of the present invention is to provide an ink jet printing apparatus that can reduce the contact of the paper with the ink jet head at the time of an abnormal stop or the like and avoid the occurrence of problems around the ink jet head.

  In order to achieve the above object, a first feature of an ink jet printing apparatus according to the present invention is that an ink jet head that discharges ink onto a paper to be transported, and an interval along the paper transport direction below the ink jet head. It is provided with a plurality of support members arranged to be spaced and supporting paper, and an unequal electric field generating means for forming an unequal electric field on the surface of the support member.

  A second feature of the ink jet printing apparatus according to the present invention is that the support member has a guide roller that is a non-conductive material, and the non-uniform electric field generating means is in contact with the guide roller; And an application means for applying an AC voltage to the electrode roller and applying positive and reverse charges at a narrow interval.

  According to the first feature of the ink jet printing apparatus of the present invention, the gradient electric field generating means generates an unequal electric field on the surface of the support member, thereby pushing down the paper between the support members downward. Adsorption force by force can be generated. As a result, even if the paper is loosened or broken due to abnormal stoppage of paper conveyance, it is possible to suppress the approach of the paper to the ink jet head, reducing the contact of the paper with the ink jet head, and defects around the ink jet head. Can be avoided.

  According to the second feature of the ink jet printing apparatus according to the present invention, a guide roller that is a non-conductive material is provided as a support member, and an AC voltage is applied by an applying means through an electrode roller that is in contact with the guide roller, so that the gap is narrow. By applying forward and reverse charges, it is possible to generate a suction force that pushes down the paper between the support members. As a result, the unequal electric field generating means can be integrated with the support member that supports the paper, and the contact of the paper to the inkjet head is reduced without making a major change to the existing mechanism. It is possible to avoid the occurrence of problems around the inkjet head.

1 is a schematic configuration diagram of an inkjet printing apparatus according to an embodiment. It is a principal part top view of the conveyance part under a head of the inkjet printing apparatus shown in FIG. It is a control block diagram of the inkjet printing apparatus shown in FIG. It is a schematic diagram which shows the structure of the unequal electric field production | generation means of the inkjet printing apparatus shown in FIG. 2A and 2B are explanatory diagrams illustrating an operation in which a sheet is pushed down by an unequal electric field generating unit of the ink jet printing apparatus illustrated in FIG. 1, in which FIG. 1A illustrates a state during normal conveyance, and FIG. It is explanatory drawing which shows the state which a paper contacts the inkjet head by a prior art example.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals. The embodiments described below exemplify devices for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, The arrangement is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

(Configuration of inkjet printer)
FIG. 1 is a schematic configuration diagram of an ink jet printing apparatus according to an embodiment of the present invention. FIG. 2 is a plan view of the main part of the lower head transport section of the ink jet printing apparatus shown in FIG. FIG. 3 is a control block diagram of the inkjet printing apparatus shown in FIG. In the following description, the top, bottom, left, and right of the paper surface in FIG. Further, the direction orthogonal to the paper surface of FIG.

  As shown in FIG. 1, the inkjet printing apparatus 1 according to this embodiment includes a sending unit 2, an upstream buffer unit 20, an image forming unit 4, a downstream buffer unit 7, a winding unit 8, and a control. Part 9.

  The sending unit 2 is a mechanism that sends out the paper P from the paper roll 10. The paper roll 10 is a roll of paper P, which is a long continuous paper. As shown in FIGS. 1 and 3, the sending unit 2 includes a main motor 11.

  The main motor 11 is a driving unit that rotates a paper roll support shaft that rotatably supports the paper roll 10, and rotates the paper roll support shaft clockwise in FIG. The paper roll 10 rotates in the same direction by the rotation of the paper roll support shaft, and the paper P is sent out to the downstream side (right side). The paper roll support shaft is formed in a long shape extending in the front-rear direction in the figure, that is, in a direction orthogonal to the paper feeding direction.

  The upstream buffer unit 20 is a mechanism that absorbs the slack of the paper P between the sending unit 2 and the head lower conveyance unit 40. The upstream buffer unit 20 includes support rollers 16 and 17 and a dancer roller 18.

  The support rollers 16 and 17 support the paper P between the sending unit 2 and the head lower conveyance unit 40. The support rollers 16 and 17 are spaced apart from each other by a predetermined distance in the left-right direction and are disposed at the same height.

  The dancer roller 18 pushes down the paper P by its own weight between the support rollers 16 and 17. As a result, the slack of the paper P generated between the sending unit 2 and the head lower conveyance unit 40 is absorbed by the upstream buffer unit 20. The dancer roller 18 moves up and down according to the amount of slack of the paper P, and absorbs slack while maintaining the tension of the paper P.

  An outfeed motor 19 is provided on the downstream side of the upstream buffer unit 20. The outfeed motor 19 is a motor that feeds the paper P from the delivery unit 2 to the downstream side, and applies tension to the paper P. The outfeed motor 19 nips the paper P with the lower guide roller 19 a and is driven in synchronization with the main motor 11 of the paper roll 10 to absorb the slack in the upstream buffer unit 20 and A predetermined tension is applied to P.

  In the present embodiment, the second buffer unit 3 is provided on the downstream side of the upstream buffer unit 20. The second buffer unit 3 is a mechanism that absorbs slackness of the paper P sent out from the outfeed motor 19. The second buffer unit 3 includes support rollers 14 and 15 and a metal rod 13.

  The support rollers 14 and 15 are arranged at the same height with the support rollers 14 and 15 spaced apart from each other by a predetermined distance in the left-right direction, and the paper P is hung with a predetermined slack between the support rollers 14 and 15. Passed and supported. In this way, the paper P is suspended in a U-shape downward by a predetermined length by its own weight between the support rollers 14 and 15.

  The metal bar 13 is a weight suspended along the paper P suspended in a U-shape between the support rollers 14 and 15, and has a U-shape so as to hold the suspended paper P. The movement trajectory of the formed paper P is regulated from the inside.

  The image forming unit 4 mainly includes a head under transport unit 40, an unequal electric field generation unit 5, and an inkjet head unit 6.

  The head lower transport unit 40 is a mechanism that transports the paper P sent out by the sending unit 2 along a transport path below the ink jet heads 61A to 61D described later. As shown in FIGS. 1 to 3, the head lower transport unit 40 includes upstream guide rollers 21 to 25, a powder brake 41, head lower support rollers 26 to 31, a head lower transport motor 32, and a downstream guide. A roller 33 and a pair of support plates 34F and 34R are provided. The under-head transport unit 40 includes laser Doppler sensors 44 and 45 and an encoder 43 for measuring the transport speed at key points in the path.

  The upstream guide rollers 21 to 25 are rollers that guide the paper P between the upstream buffer unit 20 and the head lower support roller 26. Among the upstream guide rollers, a powder brake 41 is disposed between the rollers 21 and 22. The powder brake 41 is a mechanism that brakes the paper P, and suppresses the paper P from being sent to the inkjet head 6 side more than necessary. Of the upstream guide rollers, a tension sensor 42 is provided between the rollers 22 and 23 to measure the tension of the paper P on the upstream side of the inkjet head 6.

  The head lower support rollers 26 to 31 support the paper P below the ink jet heads 61A to 61D. A path connecting the highest points of the head lower support rollers 26 to 31 is a transport path of the paper P below the ink jet heads 61A to 61D. The head lower support rollers 26 to 31 are arranged in a parabolic shape so that the conveyance path has an upwardly convex shape with an interval along the paper conveyance direction (left-right direction). As for the head lower support rollers 26-31, each rotating shaft 26a-31a is supported by the support plates 34F and 34R.

  The head lower support roller 26 is disposed in the vicinity of the upstream side of the ink jet head 61A in the paper transport direction. The head lower support rollers 27, 28, and 29 are disposed between the inkjet heads 61A and 61B, between the inkjet heads 61B and 61C, and between the inkjet heads 61C and 61D, respectively, in the paper transport direction. In other words, the head lower support rollers 27, 28, and 29 are disposed in the vicinity of the downstream side of the inkjet heads 61A, 61B, and 61C and in the vicinity of the upstream side of the inkjet heads 61B, 61C, and 61D, respectively. The head lower support roller 30 is disposed in the vicinity of the downstream side of the ink jet head 61D in the paper transport direction. The head lower support roller 31 is disposed on the downstream side of the head lower support roller 30 in the paper transport direction.

  The under-head transport motor 32 rotates the drive roller 32a. The driving roller 32a conveys the paper P in the right direction by rotating while nipping the paper P with the upper roller 32b. The drive roller 32a is supported on the support plates 34F and 34R by the rotation shaft 32c.

  The support plates 34F and 34R rotatably support the rotation shafts 26a to 31a of the head lower support rollers 26 to 31 and the rotation shaft 32c of the drive roller 32a. The support plates 34F and 34R are spaced apart from each other in the front-rear direction across the transport path of the paper P. The downstream guide roller 33 guides the paper P between the head lower support roller 31 and the downstream buffer unit 7.

  The unequal electric field generating means 5 is a mechanism for forming an unequal electric field on the surfaces of the head lower support rollers 26 to 30, and as shown in FIG. An electrode roller 52 and an application unit 51 that applies an AC voltage to the electrode roller 52 and applies positive and reverse charges at narrow intervals are provided.

  More specifically, the surfaces of the head lower support rollers 26 to 30 serving as support members for the paper P are formed of a non-conductive material such as polyimide, and the unequal electric field generating means 5 always supports the head lower support during paper transport. Through the electrode roller 52 brought into contact with the rollers 26 to 30, as shown in FIG. 5A and FIG. As a result, an unequal electric field (an electric field in which electric lines of force are concentrated in part) is formed, and the gradient of the electric field strength is increased to generate a gradient force on the surfaces of the head support rollers 26 to 30. As a result, as shown in FIG. 5B, the paper is between the head lower support rollers 26, 27, between the head lower support rollers 27, 28, between the head lower support rollers 28, 29, and between the head lower support rollers 29, 30. An adsorption force that pushes P downward is generated. In addition, since a sufficient tension is applied to the paper P during normal conveyance, the paper P does not wrap around the head lower support rollers 26 to 30 due to this suction force as shown in FIG. .

  The application unit 51 is controlled to be turned on / off by the control unit 9 and is turned on when printing is started or turned on, and an AC voltage is always applied to the electrode roller 52 during conveyance. In particular, in the present embodiment, since the electric charge is constantly applied, the applied unequal electric field does not immediately disappear even in an abnormal stop that occurs when a power failure or the outlet is disconnected, and there is no power supply. However, immediately after the abnormal stop, the suction force that pushes the paper P downward is maintained. The application means 51 may be provided with an emergency power supply for the applied voltage for more reliable stability maintenance.

  The ink jet head unit 6 prints on the paper P conveyed on the head lower support rollers 26 to 31. The inkjet head unit 6 includes four inkjet heads 61A to 61D. In addition, the alphabetic suffixes (A to D) in the reference numerals of the ink jet heads 61A to 61D may be omitted and collectively described.

  The ink jet heads 61 </ b> A to 61 </ b> D discharge ink onto the conveyed paper P. The inkjet heads 61 </ b> A to 61 </ b> D are arranged in parallel along the conveyance direction (left-right direction) of the paper P. The inkjet heads 61A to 61D eject inks of different colors (for example, black, cyan, magenta, and yellow). Each of the inkjet heads 61 </ b> A to 61 </ b> D has six head modules 66.

  In the inkjet head 61, the head modules 66 are arranged in a staggered manner. That is, the ink jet head 61 is formed by arranging two head rows composed of three head modules 66 arranged at equal intervals in the front-rear direction so as to be shifted by a half pitch in the front-rear direction. . The head module 66 has a plurality of nozzles (not shown) arranged along the front-rear direction, and ejects ink from the nozzles.

  The downstream buffer unit 7 is a mechanism that absorbs slack of the paper P between the lower head transport unit 40 and the winding unit 8. The downstream buffer unit 7 includes support rollers 71 and 72 and a dancer roller 73.

  The support rollers 71 and 72 support the paper P between the head lower conveyance unit 40 and the winding unit 8. The support rollers 71 and 72 are arranged at the same height and spaced apart from each other by a predetermined distance in the left-right direction. The dancer roller 73 pushes down the paper P by its own weight between the support rollers 71 and 72. Thereby, the slack of the paper P generated between the head lower conveyance unit 40 and the winding unit 8 is absorbed by the downstream buffer unit 7. The dancer roller 73 moves up and down according to the amount of slack of the paper P.

  The winding unit 8 is a mechanism for winding the printed paper P. The winding unit 8 includes an infeed motor 86, an internal buffer unit 80, a downstream guide roller 84, and a winding motor 85.

  The winding motor 85 is a drive mechanism that rotates the winding shaft clockwise in FIG. The sheet P is wound around the winding shaft by the rotational drive of the winding motor 85. The take-up shaft is formed in a long shape extending in the front-rear direction, and is rotated by a take-up motor 85 to take up and hold the paper P.

  The infeed motor 86 is a drive motor that feeds the paper P fed from the downstream buffer unit 7 into the winding unit 8. An internal buffer unit is provided between the infeed motor 86 and the winding motor 85.

  The internal buffer unit 80 is a mechanism that absorbs slack of the paper P between the lower head transport unit 40 and the winding unit 8, and includes support rollers 81 and 82 and a dancer roller 83. The support rollers 81 and 82 support the paper P between the infeed motor 86 and the take-up motor 85. The support rollers 81 and 82 are arranged at the same height, spaced apart from each other by a predetermined distance in the left-right direction. The dancer roller 83 pushes down the paper P by its own weight between the support rollers 81 and 82. As a result, the slack of the paper P generated between the in-feed motor 86 and the winding unit 8 is absorbed by the downstream buffer unit 7. The dancer roller 83 moves up and down according to the amount of slack of the paper P.

  The control unit 9 controls the operation of each unit of the inkjet printing apparatus 1. The control unit 9 includes a CPU, a RAM, a ROM, a hard disk, and the like.

(Operation of inkjet printer)
Next, the operation of the inkjet printing apparatus 1 will be described.
First, the control unit 9 starts a printing operation when a print job is input. Specifically, the control unit 9 activates the main motor 11, the outfeed motor 19, the brake 41, and the winding motor 85. As a result, the paper P is conveyed from the sending unit 2 toward the winding unit 8. In the head lower conveyance unit 40, the paper P is conveyed while a tension is applied to the paper P by applying a brake to the paper P by the brake 41.

  At this time, the controller 9 also turns on the applying means 51 of the unequal electric field generating means 5, and an AC voltage is always applied to the electrode roller 52 during conveyance. As a result, the unequal electric field generating means 5 always applies an AC voltage by the applying means 51 through the electrode roller 52 brought into contact with the head lower support rollers 26 to 30 when the paper is conveyed, and positive and reverse charges are generated at narrow intervals. Will be applied. Due to the applied pressure of the electric charge, an unequal electric field (an electric field where electric lines of force are concentrated in part) is formed, and the gradient of the electric field strength is increased, so that a gradient force is generated on the surfaces of the head support rollers 26-30. As a result, the paper P is always pushed downward between the head lower support rollers 26 and 27, between the head lower support rollers 27 and 28, between the head lower support rollers 28 and 29, and between the head lower support rollers 29 and 30. To be adsorbed. In addition, since a sufficient tension is applied to the paper P during normal conveyance, the paper P does not wrap around the head lower support rollers 26 to 30 due to this suction force as shown in FIG. .

  After the conveyance speed of the paper P reaches a predetermined speed, the control unit 9 starts printing by the inkjet head 6. Specifically, the control unit 9 controls the ink jet heads 61 </ b> A to 61 </ b> D based on the print job to eject ink onto the paper P to form an image.

  Then, after the start of the printing operation, for example, when an emergency situation such as detection of meandering of the paper P occurs, the control unit 9 performs an emergency stop of the paper transport operation. Specifically, the control unit 9 stops the main motor 11, the under-head transport motor 32, the brake 41, and the winding motor 85. Here, the control unit 9 stops the main motor 11, the under-head transport motor 32, the brake 41, and the take-up motor 85, and the main motor 11, under-head transport so that the paper P is not loosened or broken. The deceleration acceleration of the motor 32 and the winding motor 85 is controlled. When this paper transport operation is completed, a series of operations are completed.

  Here, since there is an emergency in the ink jet printing apparatus 1, the behavior of the paper P is disturbed when the paper transport operation is stopped, so that the paper P is loosened or broken as shown in FIG. There is a fear. Therefore, in this embodiment, as shown in FIG. 5B, since a gradient force is generated on the surface of the head lower support rollers 26 to 30, the head between the head lower support rollers 26 and 27, The sheet P is adsorbed between the lower support rollers 27 and 28, between the head lower support rollers 28 and 29, and between the head lower support rollers 29 and 30 so as to push down the sheet P. In this embodiment, since the electric charge is constantly applied, the applied unequal electric field does not immediately disappear even in an abnormal stop that occurs when a power failure or the outlet is disconnected, and there is no power supply. However, immediately after the abnormal stop, the suction force that pushes down the paper P is maintained.

(Action / Effect)
As described above, according to the inkjet printing apparatus 1, the head lower support rollers 26 to 30 that are support members for the paper P are formed of a non-conductive material, and the electrode rollers are brought into contact with the head lower support rollers 26 to 30. The gradient force is generated on the surfaces of the lower support rollers 26 to 30 by applying an AC voltage by the applying means 51 through 52 and applying forward and reverse charges at narrow intervals. With this gradient force, it is possible to generate a suction force on the surfaces of the head lower support rollers 26 to 30 such that the paper P between the head lower support rollers 26 to 30 is pushed downward. As a result, even when the paper P is loosened or broken due to abnormal stoppage of paper conveyance, the approach of the paper P to the ink jet heads 61A to 61D can be suppressed, and the contact of the paper P with the ink jet heads 61A to 61D can be prevented. This can reduce the occurrence of problems around the inkjet heads 61A to 61D.

  In particular, in the present embodiment, since the head lower support rollers 26 to 30 that support the paper and the unequal electric field generating means are integrated, the paper to the ink jet head is not changed greatly. Therefore, it is possible to avoid the occurrence of problems around the ink jet head during an abnormal stop.

  Further, in this embodiment, since an AC voltage is always applied to the electrode roller 52 during conveyance, the applied unequal electric field is immediately generated even in an abnormal stop that occurs when a power failure or the outlet is disconnected. Even when there is no power supply, the suction force that pushes the paper P downward is maintained even after an abnormal stop. In addition, since a sufficient tension is applied to the paper P during normal conveyance, the paper P does not wrap around the head lower support rollers 26 to 30 due to this suction force.

  The present invention is not limited to the above-described embodiments as they are, but includes various embodiments that are not described herein, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

P: Paper 1 ... Inkjet printing apparatus 2 ... Sending unit 3 ... Second buffer unit 4 ... Image forming unit 5 ... Unequal electric field generating means 6 ... Inkjet head unit 7 ... Downstream buffer unit 8 ... Winding unit 9 ... Control unit DESCRIPTION OF SYMBOLS 10 ... Paper roll 11 ... Main motor 13 ... Metal rod 14, 15 ... Support roller (upstream buffer part)
16, 17 ... support roller (second buffer part)
18 ... Dancer roller (upstream buffer)
DESCRIPTION OF SYMBOLS 19 ... Outfeed motor 20 ... Upstream buffer part 21-25 ... Upstream guide roller 41 ... Brake 26a-31a ... Rotating shaft 26-30 ... Head lower support roller 32 ... Head lower conveyance motor 32a ... Drive roller 32b ... Upper roller 32c ... Rotating shaft 33 ... Downstream guide rollers 34F, 34R ... Support plate 40 ... Under-head transport unit 41 ... Powder brake 42 ... Tension sensor 51 ... Application means 52 ... Electrode roller 61 ... Inkjet heads 61A-61D ... Inkjet head 66 ... Head module 71, 72 ... support roller (downstream buffer part)
73 ... Dancer roller (downstream buffer)
80 ... internal buffer part 81, 82 ... support roller (internal buffer part)
83 ... Dancer roller (internal buffer)
84 ... Downstream guide roller 85 ... Winding motor 86 ... In-feed motor

Claims (2)

An inkjet head that ejects ink onto the conveyed paper;
Below the inkjet head, a plurality of support members arranged at intervals along the paper transport direction and supporting the paper,
An ink jet printing apparatus comprising: an unequal electric field generating means for forming an unequal electric field on the surface of the support member. The support member has a guide roller that is a non-conductive material,
The unequal electric field generating means includes
An electrode roller in contact with the guide roller;
The inkjet 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.