Handling device

Abstract

The present invention provides a conveying device which can reduce the warping of a sheet while reducing the air flow generated during the conveyance of the sheet. The conveying belt (21) has a plurality of belt holes (21a) and conveys paper. The platen (26) is disposed on the lower side of the conveying belt (21) and has a plurality of suction holes (32) having a smaller plan view area than the belt holes (21a). The suction unit sucks air through the suction holes (32) and the belt holes (21a) to adsorb the paper to the conveying belt (21).

Description

Technical Field

[0001] The present invention relates to a conveying device for conveying a sheet. Background Art

[0002] As a conveying device for conveying a sheet, an air suction type conveying device is known. For example, in a line inkjet printing device that conveys paper while ejecting ink from an inkjet head onto the paper for printing, a conveying device that adsorbs and holds the paper on a conveying belt by air suction (see Patent Document 1).

[0003] In the inkjet printing device using the air suction type conveying device as described above, when the paper is conveyed, an air flow caused by air suction is generated. Under the influence of this air flow, there is a risk that minute droplets generated when the ink is ejected from the inkjet head, that is, satellite dots (also called ink mist), flow and land on the margin portion of the paper, resulting in contamination (fogging) of the printed matter.

[0004] On the other hand, by reducing the output of the fan that performs air suction to reduce the air flow, it is possible to reduce the fogging of the printed matter.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006 - 206309 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] However, if the output of the fan is reduced, the adsorption force of the paper on the conveying belt will be reduced, and there is a risk that the paper will warp from the conveying belt. If the paper warps, the paper may come into contact with the inkjet head, resulting in breakage of the inkjet head, ink adhesion contamination on the printed matter, etc. In addition, the warping of the paper is detected as a conveyance jam, and sometimes the paper conveyance stops.

[0010] The present invention has been made in view of the above circumstances, and an object thereof is to provide a conveying device that can reduce the warping of a sheet while reducing the air flow generated during the conveyance of the sheet.

[0011] Means for Solving the Problems

[0012] In order to achieve the above object, the conveying device of the present invention is characterized in that the conveying device includes: a conveying belt having a plurality of belt holes and conveying a sheet; a member disposed on the side of the conveying belt opposite to the side on which the sheet is placed and having a plurality of suction holes with a smaller plan view area than the belt holes; and a suction unit that sucks air through the suction holes and the belt holes to adsorb the sheet to the conveying belt.

[0013] Advantages of the Invention

[0014] The conveying device according to the present invention can reduce the airflow generated during the conveyance of the sheet while reducing the warping of the sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic structural diagram of an inkjet printing apparatus according to an embodiment.

[0016] Figure 2 is Figure 1 a top view of the inkjet printing apparatus shown.

[0017] Figure 3 is Figure 1 a partially enlarged top view of the conveying unit of the inkjet printing apparatus shown.

[0018] Figure 4 is along Figure 3 a partially enlarged cross-sectional view of the conveying unit taken along line A-A.

[0019] Figure 5 is a diagram showing the generation state of negative pressure in the recess near the front end of the paper.

[0020] Figure 6 is a diagram showing the generation state of negative pressure in the recess near the front end of the paper in a comparative example.

[0021] Figure 7 is a diagram showing the results of an experiment in which the amount of fogging is measured for the top view area of each suction hole.

[0022] Figure 8 is a diagram showing an example of a printed image for each amount of fogging.

[0023] Figure 9 is a diagram showing a pattern used in the experiment for measuring the amount of fogging.

[0024] Figure 10 is Figure 9 an explanatory diagram of an area around a small piece of the pattern shown.

[0025] Figure 11 is a diagram showing the results of an experiment in which the paper warping height is measured while changing the V / A value. 0]

[0026] Figure 12 is a diagram showing the paper warping height at a predetermined position on the conveying surface in the experiment of measuring the paper warping height while changing the V / A value.

[0027] Description of Reference Numerals

[0028] 1: Inkjet printing device;

[0029] 2: Printing section;

[0030] 3: Conveying section;

[0031] 11: Thread end;

[0032] 12: Inkjet head;

[0033] 21: Conveyor belt;

[0034] 21a: Hole in the belt;

[0035] 21b: Conveying surface;

[0036] 26: Imprinting plate;

[0037] 27: Imprinting plate board;

[0038] 28: Suction section;

[0039] 31: Concave portion;

[0040] 32: Suction hole;

[0041] 37: Chamber;

[0042] 38: Fan. Detailed implementation manners

[0043] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same or equivalent parts and structural elements are denoted by the same or equivalent reference numerals.

[0044] The embodiments shown below exemplify devices and the like for embodying the technical idea of the present invention, and the technical idea of the present invention does not specify the materials, shapes, structures, configurations, etc. of each structural component as the following content. The technical idea of the present invention can be variously modified based on the claims.

[0045] Figure 1 It is a schematic structural diagram of an inkjet printing device provided with a conveying device according to an embodiment of the present invention. Figure 2 It is Figure 1 A top view of the inkjet printing device shown. Figure 3 It is Figure 1 A partially enlarged top view of the conveying section of the inkjet printing device shown. Figure 4 It is a partially enlarged cross-sectional view of the conveying section along the A-A line of Figure 3 . In the following description, the direction orthogonal to the plane of Figure 1 is set as the front-rear direction, and the front direction of the plane is set as the front. In addition, the up-down, left-right directions of the plane in Figure 1 are set as the up-down, left-right directions. In Figure 1In this case, the direction from left to right is the conveyance direction of the paper. In the following description, upstream and downstream refer to upstream and downstream in the conveyance direction of the paper.

[0046] As Figure 1 , Figure 2 shown, the inkjet printing apparatus 1 according to this embodiment includes a printing unit 2 and a conveyance unit (equivalent to a conveyance device) 3.

[0047] The printing unit 2 prints an image on the paper P conveyed by the conveyance unit 3. The printing unit 2 includes a plurality of printheads 11. In this embodiment, the printing unit 2 includes four printheads 11.

[0048] The printhead 11 ejects ink onto the paper P to print an image. The four printheads 11 eject inks of different colors (for example, black, cyan, magenta, yellow). The four printheads 11 are arranged side by side in the conveyance direction (left - right direction) of the paper P above the conveyance unit 3. Each printhead 11 has a plurality of inkjet nozzles 12. In this embodiment, each printhead 11 has six inkjet nozzles 12.

[0049] In the printhead 11, the inkjet nozzles 12 are arranged in a staggered manner in the front - rear direction. That is, in each printhead 11, the six inkjet nozzles 12 arranged in the front - rear direction are arranged such that their positions in the left - right direction are alternately offset.

[0050] The inkjet nozzle 12 has a plurality of nozzles (not shown) that open on the lower surface facing the conveyance surface 21b of the conveyance belt 21 described later, that is, on the ejection surface 12a, and ejects ink from the nozzles.

[0051] The conveyance unit 3 conveys the paper while adsorbing and holding the paper (equivalent to a sheet) P supplied from a paper supply unit (not shown) by air suction.

[0052] The conveyance unit 3 includes a conveyance belt 21, a drive roller 22, driven rollers 23 - 25, an impression plate (equivalent to a member) 26, an impression plate plate 27, a suction unit 28, and a plurality of paper pressing rollers 29.

[0053] The conveyance belt 21 adsorbs, holds, and conveys the paper P. The conveyance belt 21 is an endless belt stretched over the drive roller 22 and the driven rollers 23 - 25. A plurality of belt holes 21a are formed in the conveyance belt 21. The conveyance belt 21 adsorbs and holds the paper P on the conveyance surface 21b by the adsorption force generated in the belt holes 21a due to the driving of a fan 38 of the suction unit 28 described later. The conveyance surface 21b is the surface on which the paper P of the conveyance belt 21 is placed, and is the upper surface of the horizontal portion of the conveyance belt 21 between the drive roller 22 and the driven roller 23. The conveyance belt 21 conveys the adsorbed and held paper P in the conveyance direction from left to right by rotating (circularly moving) in the Figure 1 clockwise direction in.

[0054] The perforations 21a are arranged in each column along the conveying direction (left - right direction) at a predetermined pitch (interval) K. In addition, two columns of perforations 21a adjacent to each other in the paper width direction (front - back direction) orthogonal to the conveying direction are arranged so as to be offset by half a pitch in the left - right direction. That is, the perforations 21a are arranged in a staggered pattern.

[0055] The driving roller 22 rotates the conveying belt 21. The driving roller 22 is rotationally driven by a motor (not shown). The driven rollers 23 - 25 support the conveying belt 21 together with the driving roller 22. The driven rollers 23 - 25 rotate following the rotation of the conveying belt 21. The driven roller 23 is arranged at the same height as the driving roller 22 to the left of the driving roller 22. The driven rollers 24 and 25 are arranged at the same height and separated from each other in the left - right direction below the driving roller 22 and the driven roller 23.

[0056] The embossing plate 26 is arranged below the conveying belt 21 (on the side opposite to the conveying surface 21b side) between the driving roller 22 and the driven roller 23, and is a plate - shaped member that supports the conveying belt 21 so as to be slidable. The embossing plate 26 has a plurality of concave portions 31 and a plurality of suction holes 32.

[0057] On the front surface (upper surface) of the embossing plate 26 on the side of the conveying belt 21, the concave portions 31 are formed by digging downward toward the back surface (lower surface). The concave portions 31 are parts that generate negative pressure by sucking air through the driving of the fan 38. The concave portions 31 are formed in a plan view rectangle having sides parallel to the left - right direction and sides orthogonal to the left - right direction (sides parallel to the front - back direction). The length L in the left - right direction and the length W in the front - back direction of the concave portions 31 are both equal to or larger than the diameter D of the perforations 21a. That is, it is formed as “D ≤ L and D ≤ W”. Here, the diameter D of the perforations 21a corresponds to the length in the left - right direction (conveying direction) and the length in the front - back direction (paper width direction) of the perforations 21a.

[0058] The concave portions 31 are arranged at a predetermined pitch along the left - right direction. In addition, two columns of concave portions 31 adjacent to each other in the front - back direction are arranged so as to be offset by half a pitch in the left - right direction. That is, the concave portions 31 are arranged in a staggered pattern on the front surface of the embossing plate 26. The pitch in the front - back direction of the concave portions 31 is equal to the pitch in the front - back direction of the perforations 21a. The concave portions 31 are arranged at the positions where the perforations 21a of the conveying belt 21 pass through.

[0059] Here, the perforations 21a of the conveyor belt 21 and the recesses 31 of the stamping plate 26 are formed such that when the upstream perforation 21a among two perforations 21a adjacent to each other in the left - right direction reaches the downstream end of the recess 31 that the upstream perforation 21a overlaps, the downstream perforation 21a among the two perforations adjacent to each other in the left - right direction has left at a position downstream of the recess 31 adjacent to the downstream side of the recess 31 that the upstream perforation 21a overlaps.

[0060] Specifically, the perforations 21a and the recesses 31 are formed to satisfy "K≥R and D≤L".

[0061] Here, as Figure 3 shown, R is the distance between the upstream end of the upstream recess 31 and the downstream end of the downstream recess 31 among two recesses 31 adjacent to each other in the left - right direction. In other words, the distance R is the distance between the upstream wall 33 of the upstream recess 31 and the downstream wall 33 of the downstream recess 31 among two recesses 31 adjacent to each other in the left - right direction. The wall 33 separates the recesses 31 adjacent to each other in the left - right direction.

[0062] In addition, the perforations 21a and the recesses 31 are formed such that the plan view area (opening area) of the perforations 21a is less than or equal to the plan view area of the recesses 31.

[0063] The suction holes 32 are holes for sucking air from the recesses 31. The suction holes 32 are formed to penetrate from a part of the bottom surface of the recesses 31 to the back surface of the stamping plate 26. The suction holes 32 are formed to open one by one on the bottom surface of each recess 31. The suction holes 32 are formed to have a smaller plan view area compared to the perforations 21a. The plan view area A of the suction holes 32 is preferably 0.8 mm 2 or less. In addition, the ratio V / A of the volume V [mm 3 of the recesses 31 to the plan view area A [mm 2 of the suction holes 32 is preferably 45.5 or less. Here, if the depth of the recesses 31 is set to H, then V = L×W×H.

[0064] The stamping plate support 27 is a plate - shaped member disposed below the stamping plate 26 and supporting the stamping plate 26 via a plurality of spacers 36. In the stamping plate support 27, a plurality of through - holes 27a for allowing the air sucked by the fan 38 to pass through are formed. The plan view area of the through - holes 27a is larger than the plan view area of the perforations 21a and the plan view area A of the suction holes 32.

[0065] The suction unit 28 sucks air through the suction holes 32 and the perforations 21a to adsorb the paper P to the conveyor belt 21. The suction unit 28 includes a chamber 37 and a fan 38.

[0066] The chamber 37 forms a negative pressure chamber for generating a suction force in the perforations 21a of the conveyor belt 21. The chamber 37 is provided on the back side of the impression platen plate 27 between the drive roller 22 and the driven roller 23.

[0067] The fan 38 exhausts air from the chamber 37. Thus, the fan 38 sucks air through the suction holes 32 and the perforations 21a to generate a suction force in the perforations 21a, and adsorbs the paper P to the conveyor belt 21.

[0068] The paper pressing roller 29 presses the paper P conveyed by the conveyor belt 21 against the conveying surface 21b. The paper pressing roller 29 rotates following the rotation of the conveyor belt 21.

[0069] Next, the operation of the inkjet printing apparatus 1 will be described.

[0070] When printing is performed using the inkjet printing apparatus 1, first, the drive roller 22 and the fan 38 start driving.

[0071] By driving the drive roller 22, the conveyor belt 21 rotates Figure 1 in the clockwise direction and moves in the conveying direction of the paper P between the drive roller 22 and the driven roller 23. When the conveyor belt 21 rotates, the perforations 21a pass over the recesses 31 of the impression platen 26 from left to right.

[0072] On the other hand, when air is exhausted from the chamber 37 by driving the fan 38, a negative pressure is generated in the chamber 37.

[0073] Since the recess 31 communicates with the chamber 37 via the suction holes 32 and the through holes 27a of the impression platen plate 27, when a negative pressure is generated in the chamber 37, a negative pressure is generated in the recesses 31 that are closed by the conveyor belt 21 without the perforations 21a overlapping. The recesses 31 overlapped by the perforations 21a are open to the atmosphere due to the perforations 21a, and thus are in a state where no negative pressure is generated.

[0074] After starting the driving of the drive roller 22 and the fan 38, when the paper P is supplied from a paper supply unit (not shown) to the conveying unit 3, a part of the perforations 21a is covered by the supplied paper P. The recesses 31 overlapped by the perforations 21a covered by the paper P are closed by the conveyor belt 21 and the paper P, so that the recesses 31 become in a negative pressure state. Thus, a suction force is generated in the perforations 21a, and the paper P is adsorbed to the perforations 21a.

[0075] The conveyor belt 21 adsorbs and holds the paper P on the conveying surface 21b by the suction force generated in the perforations 21a covered by the paper P. The conveyor belt 21 conveys the adsorbed and held paper P in the right direction by rotating Figure 1 in the clockwise direction.

[0076] The inkjet head 12 ejects ink onto the sheet P conveyed by the conveying belt 21 to print an image. The printed sheet P is discharged through a sheet discharging unit (not shown).

[0077] Herein, Figure 5 it represents the generation state of the negative pressure in the recess 31 near the front end (downstream end) of the conveyed sheet P. In the example of Figure 5 , K = R. In this case, when the entirety of one perforation 21a overlaps with one recess 31, the perforation 21a overlaps with the recess 31 separated by one recess 31 in the left - right direction. In this case, as shown in Figure 5 , it can be in a state where negative pressure is generated in the recess 31 adjacent to the recess 31 that overlaps with the perforation 21a on the foremost - end side of the sheet P among the perforations 21a covered by the sheet P on the downstream side.

[0078] Different from this embodiment, in the case of the structure shown in Figure 6 where the interval of the perforations 21a in the conveying direction is equal to the interval of the recesses 31, an example of the generation state of the negative pressure in the recess 31 near the front end of the conveyed sheet P is shown. In this case, negative pressure is not generated in the recess 31 adjacent to the recess 31 that overlaps with the perforation 21a on the foremost - end side of the sheet P among the perforations 21a covered by the sheet P on the downstream side.

[0079] Therefore, in the structure of Figure 6 , a gap is formed between the upper - end surface of the downstream - side wall 33 of the recess 31 that overlaps with the perforation 21a on the foremost - end side of the sheet P among the perforations 21a covered by the sheet P and the conveying belt 21. In the recess 31 that overlaps with the perforation 21a on the foremost - end side of the sheet P among the perforations 21a covered by the sheet P, air sometimes flows in from the adjacent recess 31 on its downstream side. As a result, the loss of the negative pressure in the recess 31 that overlaps with the perforation 21a on the foremost - end side of the sheet P among the perforations 21a covered by the sheet P sometimes occurs. As a result, at the front end of the sheet P, the adsorption force of the sheet P to the conveying belt 21 sometimes decreases.

[0080] In addition, in the structure of Figure 6 , since the perforation 21a on the foremost - end side of the sheet P among the perforations 21a covered by the sheet P overlaps with the recess 31, the recess 31 is closed and the generation of the negative pressure in the recess 31 starts. Therefore, the generation of the adsorption force of the perforation 21a to the front end of the sheet P sometimes delays with respect to the arrival of the front end of the sheet P at the recess 31. Sometimes, due to this situation, the adsorption force of the sheet P to the conveying belt 21 decreases at the front end of the sheet P.

[0081] If the suction force of the paper P on the conveyor belt 21 decreases, the paper P may sometimes lift from the conveyor belt 21. If the paper P lifts, the paper P may sometimes come into contact with the inkjet head 12 and cause damage to the inkjet head 12 or the like. In addition, the lift of the paper P may sometimes be detected as a conveyance jam and the paper conveyance may stop.

[0082] In contrast, in the inkjet printing apparatus 1 of the present embodiment, as described above, on the recess 31 adjacent to the recess 31 that overlaps the entire frontmost side of the perforations 21a in the perforations 21a covered by the paper P on the downstream side, the perforations 21a do not overlap. Therefore, this recess is closed by the conveyor belt 21 to generate a negative pressure 9.

[0083] Therefore, it is possible to suppress a gap from being generated between the upper end surface of the wall 33 on the downstream side of the recess 31 that overlaps the frontmost side of the perforations 21a in the perforations 21a covered by the paper P and the conveyor belt 21. Thus, in the recess 31 that overlaps the frontmost side of the perforations 21a in the perforations 21a covered by the paper P, it is possible to suppress a pressure loss caused by air flowing in from the recess 31 adjacent to its downstream side.

[0084] In addition, in the inkjet printing apparatus 1, the recess 31 that the frontmost side of the perforations 21a in the perforations 21a covered by the paper P is about to overlap next, forms a state where a negative pressure has already been generated. Therefore, it is possible to suppress a delay in the generation of the suction force of the perforations 21a on the front end portion of the paper P with respect to the arrival of the front end portion of the paper P at the recess 31.

[0085] Thus, in the inkjet printing apparatus 1, it is possible to suppress a decrease in the suction force of the paper P on the conveyor belt 21 at the front end portion of the paper P. As a result, it is possible to suppress the paper P from lifting from the conveyor belt 21.

[0086] Here, as described above, since "D≤W", it is possible to suppress the following situation: Since a part of the perforations 21a in the column adjacent to the column of the perforations 21a passing through the recess 31 in the front-rear direction overlaps on the recess 31, the recess 31 opens to the atmosphere and the negative pressure is lost.

[0087] In addition, as described above, since the suction holes 32 having a smaller plan view area than the perforations 21a are formed in the platen 26, it is possible to reduce the air flow caused by the air suction of the suction portion 28 while suppressing a decrease in the suction force in the perforations 21a.

[0088] Here, the plan view area of the perforations 21a contributes to the adsorption force (= negative pressure × plan view area) in the perforations 21a. Therefore, reducing the plan view area of the perforations 21a to reduce the air flow caused by air suction will result in a reduction in the adsorption force in the perforations 21a. In contrast, in the inkjet printing apparatus 1, the suction holes 32 having a smaller plan view area than the perforations 21a are used to reduce the air flow caused by air suction. Here, in the air flow caused by air suction, the flow path resistance of the suction holes 32 having a smaller plan view area than the perforations 21a becomes dominant, so that the air flow caused by air suction can be reduced compared to the suction holes 32.

[0089] Thus, as described above, it is possible to reduce the air flow caused by air suction of the suction portion 28 while suppressing a reduction in the adsorption force in the perforations 21a. As a result, it is possible to reduce the warping of the sheet P from the conveyance belt 21 while reducing the air flow generated during the conveyance of the sheet P. By reducing this air flow, it is possible to reduce the fogging of the printed matter caused by the satellite dots (ink mist) generated when the ink is ejected from the inkjet head 12 flowing and landing on the margin portion of the sheet P.

[0090] Here, the intensity of the air flow caused by air suction and the degree of fogging of the printed matter corresponding thereto vary depending on the plan view area A of the suction holes 32. In Figure 7 shows the results of an experiment in which the fogging amount was measured for each plan view area A of the suction holes 32. In addition, in Figure 8 shows examples of printed images when the fogging amounts are 3.5, 4.0, 4.5, 5.0, 6.0, and 7.0, respectively.

[0091] As Figure 8 shown, if the fogging amount is 4.5 or less, the fogging is at a level that cannot be visually recognized. In contrast, as Figure 7 shown, by setting the plan view area A of the suction holes 32 to 0.8 mm 2 or less, the fogging amount becomes 4.5 or less. Therefore, the plan view area A of the suction holes 32 is preferably 0.8 mm 2 or less. However, the plan view area A of the suction holes 32 has a lower limit area depending on the suction ability of the suction portion 28.

[0092] An experiment for measuring the above-described fogging amount will be described.

[0093] First, while conveying the sheet P by the conveying unit 3, printing is performed by one nozzle 11 Figure 9The pattern 41 shown. The pattern 41 is formed such that columns of small blocks 42 arranged at equal intervals in the left - right direction, i.e., small - block columns 43, are arranged side - by - side in six columns at equal intervals in the front - back direction. The small block 42 is a solid image of a square of a predetermined size. Six inkjet heads 12 in the lead 11 print the small - block columns 43 one column at a time. After printing the pattern 41, the printed pattern 41 is read by a scanning device and read data is generated.

[0094] Here, when printing the pattern 41, fogging caused by the influence of the air - suction - induced air flow mainly occurs near the front - end side (downstream side) of the small block 42 on the foremost - end side (downstream side) in the conveyance direction of the paper P and near the rear - end side (upstream side) of the small block 42 on the rearmost - end side (upstream side).

[0095] Therefore, the brightness of each pixel in the region Ea adjacent to the front - end side of the small block 42 on the front - end side of each small - block column 43 and the region Eb adjacent to the rear - end side of the small block 42 on the rear - end side of each small - block column 43 in the read data of the pattern 41 is calculated. Here, as Figure 10 shown, the region Ea is the region on the front - end side (downstream side) in the conveyance direction of the paper P in the region around the small block 42. The region Eb is the region on the rear - end side (upstream side) in the conveyance direction of the paper P.

[0096] Next, the standard deviation of the brightness of each of the regions Ea and Eb obtained by calculating the brightness of each pixel is calculated. Since the greater the degree of fogging, the greater the deviation of the brightness, the standard deviation of the brightness becomes larger.

[0097] Then, the average value of the standard deviations of the brightness of the calculated regions Ea and Eb is calculated as the above - mentioned fogging amount.

[0098] In addition, in the experiment showing the results in Figure 7 , the volume V of the concave portion 31 is the same regardless of the value of the plan - view area A of the suction hole 32. Although the influence of the volume V of the concave portion 31 on the fogging amount is almost negligible, it can still be confirmed.

[0099] Next, the ratio V / A of the volume V [mm 3 of the concave portion 31 to the plan - view area A [mm 2 of the suction hole 32 is described.

[0100] As described above, in the inkjet printing apparatus 1, when the paper P is conveyed, the concave portion 31 that the foremost - end - side perforated portion 21a of the paper P covering the perforated belt 21a overlaps next forms a state where negative pressure has been generated. Thereby, the generation of the adsorption force caused by the perforated portion 21a on the front - end portion of the paper P is suppressed from being delayed until the front - end portion of the paper P reaches the concave portion 31, and the paper P is suppressed from being lifted from the conveyance belt 21.

[0101] In the inkjet printing apparatus 1 as described above, if V / A is too large, there is a risk that when the leading edge of the sheet P reaches the recess 31, sufficient negative pressure in the recess 31 cannot be generated in time. Therefore, it is preferable to appropriately set V / A.

[0102] In Figure 10 , Figure 11 shows the results of an experiment in which, in the inkjet printing apparatus 1, while changing the value of V / A, the sheet lift height, which is the height from the transport surface 21 of the leading edge of the sheet P, is measured.

[0103] In this experiment, the sheet lift height was measured in each case of V / A = 25.5, V / A = 45.5, and V / A = 63.8. In any case, V = 12.75 mm was set. 3 . Moreover, in the case of V / A = 25.5, A = 0.5 mm was set. 2 , in the case of V / A = 45.5, A = 0.28 mm was set. 2 , in the case of V / A = 63.8, A = 0.2 mm was set. 2 .

[0104] Figure 11 The transport position in Figure 12 is the position on the transport surface 21b in the transport direction (left - right direction). Figure 11 is a graph showing the sheet lift height at a predetermined position S shown in Figure 11 . The position S is the position below a certain thread head 11. In addition, in

[0105] As Figure 10 , Figure 11 shown, in the case of V / A = 25.5 and in the case of V / A = 45.5, the lift of the sheet P is relatively suppressed, and in the case of V / A = 63.8, the lift of the sheet P becomes relatively large. Based on this, it is preferable that V / A ≤ 45.5. However, the volume V [mm 3 of the recess 31 has a substantial lower limit value in order to achieve the adsorption force accompanying the required negative pressure generation, and the value of V / A also has a substantial lower limit value.

[0106] As described above, in the inkjet printing apparatus 1, suction holes 32 having a smaller plan view area than the perforations 21a are formed in the platen 26. Thereby, it is possible to reduce the air flow caused by the air suction of the suction portion 28 while suppressing a decrease in the suction force in the perforations 21a. As a result, it is possible to reduce the warping of the sheet P from the conveyor belt 21 and to reduce the air flow generated during the conveyance of the sheet P. Therefore, it is possible to reduce the warping of the sheet P from the conveyor belt 21 and to reduce the fogging of the printed matter.

[0107] In addition, in the inkjet printing apparatus 1, the plan view area A of the suction hole 32 is preferably 0.8 mm 2 or less. Thereby, it is possible to further reduce the air flow generated during the conveyance of the sheet P. Therefore, it is possible to further reduce the fogging of the printed matter.

[0108] In addition, the volume V [mm 3 of the recess 31 to the plan view area A [mm 2 of the suction hole 32 is preferably 45.5 or less. Thereby, it is possible to suppress a delay in the generation of the negative pressure in the recess 31 when the front end portion of the sheet P reaches the recess 31. As a result, since the delay in the generation of the suction force caused by the perforations 21a is suppressed, the warping of the sheet P from the conveyor belt 21 is further suppressed.

[0109] In addition, in the above-described embodiment, the perforations 21a and the recess 31 are formed in a structure that satisfies "K ≧ R and D ≦ L", but the present invention is not limited thereto. For example, as Figure 6 shown, the structure may be such that the intervals of the perforations 21a and the recesses 31 in the conveyance direction are equal. In the structure as described above, by forming the suction holes 32 having a smaller plan view area than the perforations 21a in the platen 26, it is possible to reduce the warping of the sheet P from the conveyor belt 21 and to reduce the air flow generated during the conveyance of the sheet P. In addition, in the structure as described above, by setting V / A to 45.5 or less, even when V / A is greater than 45.5, it is possible to shorten the time for generating the negative pressure in the recess 31 and to suppress the warping of the sheet P from the conveyor belt 21.

[0110] In addition, in the above-described embodiment, the structure in which the suction holes 32 having a smaller plan view area than the perforations 21a are formed in the recesses 31 of the platen 26 is shown, but the present invention is not limited thereto. For example, the plan view area of the suction holes 32 of the platen 26 may be larger than that of the perforations 21a, and the through holes 27a of the platen plate 27 may be formed as suction holes having a smaller plan view area than the perforations 21a. It is only necessary to dispose a member having a plurality of suction holes having a smaller plan view area than the perforations 21a between the driving roller 22 and the driven roller 23 of the conveyor belt 21 and the suction portion 28.

[0111] In addition, in the above-described embodiment, the structure in which the perforations 21a are circular in plan view and the recess 31 is rectangular in plan view is shown, but the shapes of the perforations 21a and the recess 31 are not limited thereto.

[0112] In addition, in the above-described embodiment, an inkjet printing apparatus that conveys paper has been described, but the present invention is not limited thereto, and any conveyance apparatus that conveys a sheet may be used.

[0113] The present invention is not limited to the above-described embodiment itself, and structural elements can be deformed and embodied within the scope not departing from the gist thereof at the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of structural elements disclosed in the above-described embodiment. For example, several structural elements can also be deleted from all the structural elements shown in the embodiment.

[0114] [Supplementary Note]

[0115] The present application discloses the following inventions.

[0116] (Supplementary Note 1)

[0117] A conveyance apparatus, characterized in that:

[0118] The conveyance apparatus includes:

[0119] A conveyance belt having a plurality of perforations and conveying a sheet;

[0120] A member disposed on the side of the conveyance belt opposite to the side on which the sheet is placed and having a plurality of suction holes with a smaller plan view area than the perforations; and

[0121] A suction unit that sucks air through the suction holes and the perforations to adsorb the sheet to the conveyance belt.

[0122] (Supplementary Note 2)

[0123] The conveyance apparatus according to Supplementary Note 1, characterized in that the plan view area of the suction holes is 0.8 mm 2 or less.

[0124] (Supplementary Note 3)

[0125] The conveyance apparatus according to Supplementary Note 1 or 2, characterized in that:

[0126] The member has a plurality of recesses formed on the surface on the conveyance belt side for the suction holes to open and supports the conveyance belt,

[0127] and the ratio V / A of the volume V [mm 3 of the recesses to the plan view area A [mm 2 of the suction holes is 45.5 or less.

Claims

1. A conveying device, characterized in that the conveying device includes: a conveying belt having a plurality of belt holes and conveying a sheet; a member disposed on a side of the conveying belt opposite to a side where the sheet is placed and having a plurality of suction holes with a smaller plan view area than the belt holes; and a suction portion that sucks air through the suction holes and the belt holes to adsorb the sheet to the conveying belt, the member has a plurality of recesses formed on a surface on the conveying belt side for the suction holes to open, and supports the conveying belt. The volume V [mm 3 of the recess relative to the plan view area A [mm 2 of the suction hole has a ratio V / A of 45.5 or less.

2. The handling device according to claim 1, characterized in that, The top view area of the suction hole is 0.8 mm 2 or less.

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