JP2015006952A - Transfer device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer device which transfers printing mediums while maintaining a proper head gap by using a simple structure.SOLUTION: An ink jet printer 1 having a transfer device includes: a transfer belt 21 which transfers paper P while moving below an ink jet head 12; a pair of intermediate rollers 26 which is disposed in at least one of the upstream side and the downstream side of the ink jet head 12 in a transfer direction of the paper P, sandwiches the transfer belt 21, and rotates following the transfer belt 21; and a head gap adjustment part 4 which adjusts height positions of the pair of intermediate rollers 26.

Description

  The present invention relates to a transport device that transports a print medium.

  2. Description of the Related Art Conventionally, a line-type inkjet printing apparatus that discharges ink from an inkjet head to a sheet while conveying the sheet is known. As a paper transport mechanism in a line-type inkjet printing apparatus, there is a paper transport mechanism that transports paper by a transport belt.

  In such a paper transport mechanism, there is an air adsorption system as one of the systems for causing the paper to follow the transport belt. The air adsorption method is a method of conveying a sheet while adsorbing the sheet onto the conveyance belt with an adsorption force generated in the suction hole by sucking air through a suction hole formed in the conveyance belt. As another method, there is an electrostatic adsorption method. The electrostatic adsorption method is a method of conveying a sheet while adsorbing the sheet to a conveyance belt by electrostatic force. Still another method is a roller nip method. The roller nip method is a method in which a conveying belt is nipped (clamped) and a sheet is conveyed while being pressed against the conveying belt by a plurality of pairs of rollers driven by the conveying belt.

  Also, there is a paper transport mechanism disclosed in Patent Document 1 that does not use a transport belt. The paper transport mechanism disclosed in Patent Document 1 includes a platen disposed for each inkjet head, and a group of rollers disposed on the upstream side and the downstream side of the platen. Each roller group includes a driving roller and two driven rollers that are in contact with the central vertical line of the driving roller on the upstream side and the downstream side, respectively. As a result, the paper transport mechanism of Patent Document 1 can transport the paper so that it is in close contact with the platen, and keeps the distance between the inkjet head and the paper constant.

JP 2011-121223 A

  However, in the air suction method and the electrostatic suction method described above, the structure of the apparatus is complicated and enlarged due to the structure for generating the suction force on the conveyor belt. In addition, a high flatness is required for the structure under the head, which increases the manufacturing cost.

  In the roller nip method described above, since one roller of each roller pair is fixed, an appropriate head gap may not be obtained due to roller component tolerance, assembly error, or the like. Also in the technique of Patent Document 1, since each platen is fixed, an appropriate head gap may not be obtained due to its assembly error.

  The head gap is the distance between the ejection surface of the inkjet head and the paper transport surface. If the head gap is not appropriate, ink landing deviation may occur, and the print image quality may deteriorate. In addition, the paper may come into contact with the inkjet head.

  The present invention has been made in view of the above, and an object of the present invention is to provide a transport apparatus that can transport a print medium while maintaining an appropriate head gap with a simple configuration.

  In order to achieve the above object, the transport device according to the present invention is characterized by a transport belt that transports a print medium while moving below the inkjet head, and an upstream side and a downstream side of the inkjet head in the transport direction of the print medium. An intermediate roller pair that is disposed on at least one of the rollers and that is driven to rotate while sandwiching the conveyance belt, and an adjustment unit that adjusts the height position of the intermediate roller pair.

  According to the characteristics of the conveying device according to the present invention, the head gap is adjusted by adjusting the height position of the intermediate roller pair. As a result, the print medium can be conveyed while maintaining an appropriate head gap with a simple configuration without using highly accurate parts.

1 is a schematic configuration diagram of an inkjet printing apparatus according to a first embodiment. It is a top view of the principal part of the inkjet printing apparatus shown in FIG. 2 is a flowchart for explaining the operation of the inkjet printing apparatus shown in FIG. 1. It is a schematic block diagram of the inkjet printing apparatus which concerns on the modification 1 of 1st Embodiment. It is a schematic block diagram of the inkjet printing apparatus which concerns on the modification 2 of 1st Embodiment. It is a schematic block diagram of the inkjet printing apparatus which concerns on 2nd Embodiment.

  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, and the description thereof is omitted or simplified. However, it should be noted that the drawings are schematic and different from the actual ones. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, 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 includes 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.

[First Embodiment]
FIG. 1 is a schematic configuration diagram of an ink jet printing apparatus according to a first embodiment of the present invention, and FIG. 2 is a plan view of a main part of the ink jet printing apparatus shown in FIG. In the following description, the direction orthogonal to the paper surface of FIG. 1 is the front-rear direction, and the front surface direction is the front. Further, as shown in FIG. 1, when viewed from the front, the top, bottom, left, and right are the top, bottom, left, and right directions. In FIG. 1, the direction from left to right is the conveyance direction of the paper P. In the following description, upstream and downstream mean upstream and downstream in the transport direction.

  As shown in FIGS. 1 and 2, the inkjet printing apparatus 1 according to the first embodiment includes a head unit 2, a transport unit 3, a head gap adjustment unit 4, a head gap detection unit 5, and a control unit. 6. Note that the transport device includes each unit except for the head unit 2.

  The head unit 2 prints an image by ejecting ink onto the paper P transported by the transport unit 3. The head unit 2 includes a head holder 11 and an inkjet head 12.

  The head holder 11 is a box that holds the inkjet head 12. A plurality of openings (not shown) are formed at predetermined positions on the bottom surface of the head holder 11. A head module 13 of an ink jet head 12 to be described later is inserted and fixed in this opening.

  The inkjet head 12 ejects ink. The inkjet head 12 includes a plurality of head modules 13. In the present embodiment, the ink jet head 12 includes six head modules 13.

  The six head modules 13 are arranged in a staggered manner. Specifically, the six head modules 13 are arranged in the front-rear direction, and are alternately arranged in the transport direction of the paper P every other one. The head module 13 is inserted through the opening on the bottom surface of the head holder 11 and attached so that the lower end protrudes downward from the bottom surface of the head holder 11. The head module 13 has a plurality of nozzles formed on the ejection surface (lower surface) 13a, and ejects ink from the nozzles.

  The transport unit 3 transports the paper P that is a print medium. The transport unit 3 is disposed below the head unit 2. The conveying unit 3 includes a conveying belt 21, a driving roller 22, a driving motor 23, a driven roller 24, a spring 25, an intermediate roller pair 26, a spring 27, paper pressing rollers 28A, 28B, and 28C, a spring 29A, 29B, 29C.

  The transport belt 21 is an annular belt for transporting the paper P. The conveyor belt 21 is stretched around a driving roller 22 and a driven roller 24. The conveyance belt 21 conveys the paper P on the paper conveyance surface 21a to the right while rotating in the clockwise direction in FIG. The sheet conveying surface 21 a is the upper surface of the conveying belt 21 that faces the inkjet head 12 between the driving roller 22 and the driven roller 24.

  The driving roller 22 rotates and moves the conveyor belt 21. The driving roller 22 supports the conveying belt 21 together with the driven roller 24. The drive roller 22 is disposed on the downstream side of the inkjet head 12. The drive roller 22 is rotationally driven by a drive motor 23.

  The driven roller 24 supports the conveying belt 21 together with the driving roller 22, and is driven to rotate by the driving roller 22 via the conveying belt 21. The driven roller 24 is disposed at the same height as the drive roller 22 on the upstream side of the inkjet head 12. The driven roller 24 is given a leftward elastic force by a spring 25. As a result, tension is applied to the conveyor belt 21.

  The intermediate roller pair 26 presses the conveyed paper P against the paper transport surface 21 a of the transport belt 21. The intermediate roller pair 26 is for adjusting the head gap. The head gap is a distance between the ejection surface 13a of the head module 13 of the inkjet head 12 and the paper transport surface 21a. The intermediate roller pair 26 is disposed in the vicinity of the upstream side of the inkjet head 12 between the driving roller 22 and the driven roller 24. The intermediate roller pair 26 nips (nips) the conveyance belt 21 and rotates following the conveyance belt 21. The intermediate roller pair 26 includes an upper roller 31 and a lower roller 32.

  The upper roller 31 is disposed on the paper conveyance surface 21 a of the conveyance belt 21 in the vicinity of the upstream side of the inkjet head 12. The upper roller 31 is formed in a cylindrical shape extending in the front-rear direction. The length of the upper roller 31 is longer than the length of the transport belt 21 in the front-rear direction. The upper roller 31 has a rotating shaft 31a rotatably supported by a pair of rotating members 42 and 43 of the head gap adjusting unit 4 described later. Thereby, the upper roller 31 is movable in the vertical direction.

  The lower roller 32 is disposed below the upper roller 31 with the conveyance belt 21 in between. The lower roller 32 is formed in the same shape as the upper roller 31. An upper elastic force is applied to the lower roller 32 by a spring 27. Thus, the lower roller 32 nips the conveyor belt 21 with the upper roller 31 and moves in the vertical direction following the upper roller 31.

  The paper pressing rollers 28 </ b> A, 28 </ b> B, 28 </ b> C press the conveyed paper P against the paper transport surface 21 a of the transport belt 21. The paper pressing rollers 28A, 28B, and 28C are formed in the same shape as the upper roller 31. The paper pressing roller 28A is disposed on the upper side of the driven roller 24 with the conveying belt 21 in between. The paper pressing roller 28B is disposed on the upper side of the driving roller 22 with the conveying belt 21 interposed therebetween. The paper pressing roller 28 </ b> C is disposed on the paper transport surface 21 a of the transport belt 21 in the vicinity of the downstream side of the inkjet head 12. A downward elastic force is applied to the paper pressing rollers 28A, 28B, and 28C by springs 29A, 29B, and 29C. As a result, the paper pressing rollers 28A, 28B, and 28C come into contact with the conveyance belt 21 and are driven to rotate by the conveyance belt 21.

  The head gap adjusting unit 4 adjusts the head gap. Specifically, the head gap adjusting unit 4 adjusts the height position (position in the vertical direction) of the intermediate roller pair 26. When the height position of the intermediate roller pair 26 varies, the height position of the conveying belt 21 at the nip point of the intermediate roller pair 26 varies. As a result, the height position of the sheet transport surface 21a immediately below the inkjet head 12 varies. Therefore, the head gap is adjusted by adjusting the height position of the intermediate roller pair 26. The head gap adjustment unit 4 includes a rotation shaft 41, a pair of rotation members 42 and 43, and an adjustment motor 44.

  The rotation shaft 41 is made of a long member extending in the front-rear direction. The rotation shaft 41 is rotatably supported at the left end portion of the head holder 11. The front end portion and the rear end portion of the rotation shaft 41 protrude to the outside of the front surface and the rear surface of the head holder 11, respectively.

  The rotating members 42 and 43 move the upper roller 31 of the intermediate roller pair 26 in the vertical direction. The rotating members 42 and 43 are formed in an elongated plate shape. The rotating members 42 and 43 are disposed on the outer side of the front surface and the outer surface of the rear surface of the head holder 11, respectively. Front end portions and rear end portions of the rotation shaft 31a of the upper roller 31 are rotatably supported at one end portions of the rotating members 42 and 43, respectively. The other end portions of the rotating members 42 and 43 are fixed to the front end portion and the rear end portion of the rotating shaft 41 protruding from the head holder 11, respectively.

  The adjustment motor 44 rotates the rotation shaft 41. Thereby, the rotation members 42 and 43 rotate.

  The head gap detector 5 is for detecting a head gap. The head gap detector 5 is disposed at the same height as the ejection surface 13 a of the inkjet head 12. In the left-right direction, the head gap detector 5 is disposed between the intermediate roller pair 26 and the inkjet head 12. In the front-rear direction, the head gap detector 5 is disposed at the center of the head holder 11. The head gap detection unit 5 measures the distance H to the paper conveyance surface 21 a of the conveyance belt 21. The head gap detection unit 5 includes a distance measuring sensor.

  The control unit 6 controls the operation of each unit of the inkjet printing apparatus 1. The control unit 6 includes a CPU, RAM, ROM, hard disk, and the like.

  Next, the operation of the inkjet printing apparatus 1 will be described.

  FIG. 3 is a flowchart for explaining the operation of the inkjet printing apparatus 1. The process of the flowchart of FIG. 3 starts when a print job is input to the inkjet printing apparatus 1.

  When a print job is input, the control unit 6 acquires the current head gap in step S1 of FIG.

  Specifically, the control unit 6 causes the head gap detection unit 5 to measure the distance H to the paper transport surface 21a, and acquires the measured value as the current head gap. Here, the sheet conveying surface 21 a may be inclined with respect to the horizontal plane between the intermediate roller pair 26 and the driving roller 22. For this reason, the distance H measured by the head gap detector 5 may not exactly match the head gap, which is the distance between the ejection surface 13a of the inkjet head 12 and the paper transport surface 21a. However, since the head gap detector 5 is in the vicinity of the inkjet head 12, the distance H measured by the head gap detector 5 can be regarded as the head gap.

  Next, in step S2, the control unit 6 determines whether or not the current head gap acquired in step S1 is appropriate.

  Specifically, the control unit 6 obtains a difference between the current head gap value acquired in step S1 and the set value of the head gap corresponding to the paper type used for printing. The control unit 6 determines that the current head gap is appropriate when the difference is equal to or smaller than the threshold value, and determines that the current head gap is not appropriate when the difference is larger than the threshold value. Here, the control unit 6 can acquire the paper type from the paper information included in the print job. The control unit 6 stores a head gap setting value for each paper type in advance.

  When it is determined that the current head gap is appropriate (step S2: YES), in step S3, the control unit 6 performs printing.

  Specifically, the control unit 6 rotates the drive roller 22 by the drive motor 23. As a result, the conveyor belt 21 rotates in the clockwise direction in FIG. Further, the control unit 6 feeds the paper P from a paper feeding unit (not shown). Accordingly, the transport unit 3 transports the fed paper P. In the transport unit 3, the paper P is pressed to the paper transport surface 21 a by the paper pressing roller 28 </ b> A, the upper roller 31 of the intermediate roller pair 26, and the paper pressing rollers 28 </ b> B and 28 </ b> C, while following the movement of the transport belt 21. It is conveyed to. The control unit 6 causes the ink jet head 12 to eject ink onto the paper P transported by the transport unit 3. As a result, an image is printed on the paper P.

  If it is determined in step S2 that the current head gap is not appropriate (step S2: NO), in step S4, the controller 6 adjusts the head gap.

  Specifically, the control unit 6 drives the adjustment motor 44 of the head gap adjustment unit 4. Thereby, the rotating shaft 41 rotates and the rotating members 42 and 43 rotate. As a result, the intermediate roller pair 26 moves in the vertical direction, and the head gap changes. For example, when the current head gap value acquired in step S1 is smaller than the set value of the head gap corresponding to the paper type, the control unit 6 causes the rotating shaft 41 to rotate clockwise in FIG. Rotate to Accordingly, the rotating members 42 and 43 are rotated in the clockwise direction in FIG. 1, and the intermediate roller pair 26 pushes down the conveying belt 21. As a result, the head gap is widened. The control unit 6 adjusts the height position of the intermediate roller pair 26 by the head gap adjustment unit 4 so that the measurement value of the head gap detection unit 5 becomes the set value of the head gap corresponding to the paper type.

  When the adjustment of the head gap in step S4 is completed, the control unit 6 proceeds to step S3 and executes printing.

  As described above, in the inkjet printing apparatus 1, the head gap is adjusted according to the height position of the intermediate roller pair 26. Thereby, in the inkjet printing apparatus 1, the paper P can be conveyed by maintaining a proper head gap with a simple configuration without using high-precision components. As a result, occurrence of ink landing deviation and contact of the paper P with the inkjet head 12 can be suppressed.

  In the inkjet printing apparatus 1, the paper pressing rollers 28 </ b> A, 28 </ b> B, and 28 </ b> C press the paper P against the transport belt 21, thereby preventing the paper P from being lifted. Thereby, the occurrence of ink landing deviation and the contact of the paper P with the inkjet head 12 can be further suppressed.

  The arrangement of the intermediate roller pair 26 and the paper pressing roller 28C may be interchanged. That is, the intermediate roller pair 26 may be disposed in the vicinity of the downstream side of the inkjet head 12, and the paper pressing roller 28 </ b> C may be disposed in the vicinity of the upstream side of the inkjet head 12.

  Further, the number and arrangement of the paper pressing rollers are not limited to the example of FIG.

(Modification 1 of the first embodiment)
FIG. 4 is a schematic configuration diagram of an ink jet printing apparatus according to Modification 1 of the first embodiment.

  As illustrated in FIG. 4, the inkjet printing apparatus 1 </ b> A according to the first modification has a configuration in which a fan 46 is added to the inkjet printing apparatus 1 according to the first embodiment illustrated in FIG. 1. Further, in the ink jet printing apparatus 1 </ b> A, a large number of through holes (not shown) are formed over the entire surface of the transport belt 21.

  The fan 46 generates a downward airflow. The fan 46 is disposed between the driving roller 22 and the driven roller 24.

  In the inkjet printing apparatus 1A, during the printing operation, the control unit 6 drives the fan 46 to generate a downward airflow. As a result, a negative pressure is generated in the through hole in the paper conveyance surface 21 a of the conveyance belt 21. The transport belt 21 transports the paper P while adsorbing and holding the paper P by this negative pressure.

  Thus, in the ink jet printing apparatus 1A, the paper P can be adsorbed to the transport belt 21, so that the paper P can be prevented from being lifted. Thereby, the occurrence of ink landing deviation and the contact of the paper P with the inkjet head 12 can be further suppressed.

(Modification 2 of the first embodiment)
FIG. 5 is a schematic configuration diagram of an ink jet printing apparatus according to Modification 2 of the first embodiment.

  As illustrated in FIG. 5, the inkjet printing apparatus 1 </ b> B according to the second modification replaces the inkjet unit 1 according to the first embodiment illustrated in FIG. 1 by replacing the conveyance unit 3 with a conveyance unit 51. In this configuration, an adjustment unit 52 and a head gap detection unit 53 are added.

  The conveyance unit 51 has a configuration in which the paper pressing roller 28C and the spring 29C are omitted, and an intermediate roller pair 56 and a spring 57 are added to the conveyance unit 3 in the first embodiment.

  The intermediate roller pair 56 has the same configuration as the intermediate roller pair 26. The intermediate roller pair 56 is disposed in the vicinity of the downstream side of the inkjet head 12 between the driving roller 22 and the driven roller 24. An upward elastic force is applied to the lower roller 32 of the intermediate roller pair 56 by a spring 57.

  The head gap adjusting unit 52 adjusts the height position of the intermediate roller pair 56. The head gap adjustment unit 52 has the same configuration as the head gap adjustment unit 4.

  The head gap detection unit 53 includes a distance measuring sensor similar to the head gap detection unit 5. The height position of the head gap detector 53 and the position in the front-rear direction are the same as those of the head gap detector 5. In the left-right direction, the head gap detection unit 53 is disposed between the inkjet head 12 and the intermediate roller pair 56.

  In the ink jet printing apparatus 1B, the head gap is adjusted by adjusting the height positions of the pair of intermediate rollers 26 and 56 by the head gap adjusting units 4 and 52. When performing printing, the control unit 6 determines that the distance Hu measured by the head gap detection unit 5 and the distance Hd measured by the head gap detection unit 53 are intermediate values such that the head gap is set according to the paper type. The height positions of the roller pairs 26 and 56 are adjusted.

  Thereby, in the inkjet printing apparatus 1B, the paper conveyance surface 21a can be made into a horizontal surface under the inkjet head 12. FIG. Therefore, an appropriate head gap can be set with higher accuracy.

  In the second modification, as in the first modification described above, the conveyance belt 21 may be formed with a plurality of through holes, and the fan 46 may be provided.

[Second Embodiment]
FIG. 6 is a schematic configuration diagram of an ink jet printing apparatus according to the second embodiment.

  As shown in FIG. 1, the inkjet printing apparatus 1C according to the second embodiment includes a head unit 61, a transport unit 62, head gap adjustment units 63A and 63B, head gap detection units 64A and 64B, and a control. Part 65.

  The head unit 61 prints an image by ejecting ink onto the paper P conveyed by the conveyance unit 62. The head unit 61 includes a head holder 71 and two inkjet heads 12. The head holder 71 holds the inkjet head 12 in the same manner as the head holder 11 in the first embodiment. The head holder 71 holds two inkjet heads 12 that are spaced apart from each other in the left-right direction.

  The transport unit 62 transports the paper P. The transport unit 62 is disposed below the head unit 61. The conveying unit 62 includes a conveying belt 21, a driving roller 22, a driving motor 23, a driven roller 24, paper pressing rollers 28A and 28B, springs 29A and 29B, driven rollers 72 and 73, a spring 74, An intermediate support roller 75, a paper pressing roller 76, a spring 77, intermediate roller pairs 78A and 78B, and springs 79A and 79B are provided.

  The driven rollers 72 and 73 are spaced apart from each other in the left-right direction below the driving roller 22 and the driven roller 24 and are disposed at the same height. The conveyor belt 21 is stretched around the driving roller 22, the driven roller 24, and the driven rollers 72 and 73. The driven rollers 72 and 73 are driven to rotate by the transport belt 21. The driven roller 72 is given an elastic force in the lower left direction by a spring 74. As a result, tension is applied to the conveyor belt 21.

  The intermediate support roller 75 supports the conveyance belt 21 at an intermediate position between the driving roller 22 and the driven roller 24. The upper end of the intermediate support roller 75 is the same height as the upper end of the drive roller 22 and the upper end of the driven roller 24. The intermediate support roller 75 is formed in the same shape as the paper pressing rollers 28A and 28B. The intermediate support roller 75 rotates following the conveyance belt 21.

  The paper pressing roller 76 presses the transported paper P against the paper transport surface 21 a of the transport belt 21. The paper pressing roller 76 is disposed on the upper side of the intermediate support roller 75 with the conveying belt 21 interposed therebetween. The paper pressing roller 76 is formed in the same shape as the paper pressing rollers 28A and 28B. A downward elastic force is applied to the paper pressing roller 76 by a spring 77. As a result, the paper pressing roller 76 contacts the conveyance belt 21 and rotates following the conveyance belt 21.

  The intermediate roller pair 78A, 78B has the same configuration as the intermediate roller pair 26 in the first embodiment. An upward elastic force is applied to the lower roller 32 of the intermediate roller pair 78A and the lower roller 32 of the intermediate roller pair 78B by springs 79A and 79B, respectively. The intermediate roller pair 78 </ b> A is disposed in the vicinity of the upstream side of the upstream inkjet head 12. The intermediate roller pair 78 </ b> B is disposed in the vicinity of the upstream side of the downstream inkjet head 12 on the downstream side of the intermediate support roller 75 and the paper pressing roller 76.

  The head gap adjusting units 63A and 63B have the same configuration as the head gap adjusting unit 4 in the first embodiment. The head gap adjustment unit 63 </ b> A adjusts the head gap in the upstream inkjet head 12. Specifically, the head gap adjustment unit 63A adjusts the height position of the intermediate roller pair 78A. The head gap adjusting unit 63B adjusts the head gap in the downstream inkjet head 12. Specifically, the head gap adjusting unit 63B adjusts the height position of the intermediate roller pair 78B.

  The head gap detectors 64A and 64B are composed of distance measuring sensors similar to the head gap detector 5 in the first embodiment. The height positions of the head gap detectors 64A and 64B and the positions in the front-rear direction are the same as those of the head gap detector 5 in the first embodiment. In the left-right direction, the head gap detector 64A is disposed between the intermediate roller pair 78A and the upstream inkjet head 12. The head gap detector 64B is disposed between the intermediate roller pair 78B and the downstream inkjet head 12.

  The control unit 65 controls the operation of each unit of the inkjet printing apparatus 1C. The control unit 65 includes a CPU, RAM, ROM, hard disk, and the like.

  In the ink jet printing apparatus 1C, when performing printing, the control unit 65 uses the head gap adjustment unit 63A to perform an intermediate operation so that the distance Ha measured by the head gap detection unit 64A becomes the set value of the head gap according to the paper type. The height position of the roller pair 78A is adjusted. Further, the control unit 65 adjusts the height position of the intermediate roller pair 78B by the head gap adjustment unit 63B so that the distance Hb measured by the head gap detection unit 64B becomes a set value of the head gap according to the paper type. To do.

  When the adjustment of the head gap is completed, the control unit 65 rotates the drive roller 22 by the drive motor 23 and rotates the transport belt 21 in the clockwise direction. Further, the control unit 65 feeds the paper P from a paper feeding unit (not shown). In the transport unit 62, the paper P is pressed by the paper transport surface 21a by the paper pressing roller 28A, the upper roller 31 of the intermediate roller pair 78A, the paper pressing roller 76, the upper roller 31 of the intermediate roller pair 78B, and the paper pressing roller 28B. Following the movement of the conveyor belt 21, it is conveyed rightward. The control unit 65 causes ink to be ejected from the inkjet head 12 onto the paper P transported by the transport unit 62. As a result, an image is printed on the paper P.

  As described above, in the second embodiment, the head gap is adjusted by adjusting the height positions of the pair of intermediate rollers 78A and 78B for each of the two inkjet heads 12. Thereby, in the inkjet printing apparatus 1 </ b> C having the two inkjet heads 12, the sheet P can be conveyed while maintaining an appropriate head gap with a simple configuration without using high-precision components.

  Also in the second embodiment, similarly to the first modification of the first embodiment described above, the conveyor belt 21 may be provided with a large number of through holes, and the fan 46 may be provided.

  Further, a configuration in which the pair of intermediate rollers 78A and 78B and the head gap adjusting units 63A and 63B are disposed on the downstream side of each inkjet head 12 may be employed.

  In addition to the upstream side, the intermediate roller pair, the head gap adjusting unit, and the head gap detecting unit are provided on each of the inkjet heads 12 in addition to the upstream side as in the second modification of the first embodiment described above. May be provided.

  Even when there are three or more inkjet heads, an intermediate support roller and a paper pressing roller are arranged between the inkjet heads as in the second embodiment, and an intermediate roller pair and a head gap are adjusted for each inkjet head. And a head gap detector may be provided.

[Other embodiments]
As described above, the present invention has been described according to the first and second embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the first and second embodiments, the head gap is adjusted by adjusting the height position of the intermediate roller pair, but it may be used in combination with other head gap adjusting means. For example, you may use together the mechanism which adjusts a head gap by raising / lowering a conveyance part with respect to a head unit.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

1, 1A, 1B, 1C Inkjet printing device 2, 61 Head unit 12 Inkjet head 3, 51, 62 Conveying unit 4, 52, 63A, 63B Head gap adjusting unit 5, 53, 64A, 64B Head gap detecting unit 6, 65 Control unit 21 Conveying belt 26, 56, 78A, 78B Intermediate roller pair 46 Fan

Claims (1)

A conveyor belt that conveys the print medium while moving under the inkjet head;
An intermediate roller pair that is disposed on at least one of the upstream side and the downstream side of the inkjet head in the conveyance direction of the print medium, and sandwiches the conveyance belt to rotate following the conveyance belt;
An adjustment unit that adjusts the height position of the intermediate roller pair.