Conveyor device

Abstract

To provide a conveyance device which can reduce an airflow generated during conveyance of a sheet, while alleviating the floating of the sheet.SOLUTION: A conveyance belt 21 includes a plurality of belt holes 21a, and conveys a sheet. A platen 26 is disposed on the lower side of the conveyance belt 21, and includes a plurality of suction holes 32 whose area in plan view is smaller than the belt hole 21a. A suction part allows the sheet to be adsorbed to the conveyance belt 21 by sucking the air via the suction holes 32 and the belt holes 21a.SELECTED DRAWING: Figure 3

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 type inkjet printing device that ejects ink from an inkjet head onto a sheet while conveying the sheet, a conveying device that adsorbs and holds the sheet on a conveying belt by air suction and conveys it is used (see Patent Document 1).

[0003] In an inkjet printing device using the air suction type conveying device as described above, an air flow is generated by air suction during the conveyance of the sheet. Due to the influence of this air flow, satellites (also referred to as ink mist), which are minute droplets generated when ink is ejected from the inkjet head, are washed away and land on the margin portion of the sheet, and there is a risk of soiling (mist soiling) of the printed matter.

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

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, if the output of the fan is reduced, the adsorption force on the paper conveyance belt may decrease, and the paper may float from the conveyance belt. If the paper floats, the paper may come into contact with the inkjet head, resulting in damage to the inkjet head or ink adhesion stains on the printed matter. Also, the floating of the paper may be detected as a conveyance jam, and the paper conveyance may stop.

[0007] The present invention has been made in view of the above, and an object thereof is to provide a conveyance device that can reduce the airflow generated during sheet conveyance while reducing the floating of the sheet.

Means for Solving the Problems

[0008] To achieve the above object, the conveyance device of the present invention includes a conveyance belt having a plurality of belt holes for conveying a sheet, a member disposed on the side opposite to the side on which the sheet of the conveyance belt is placed and having a plurality of suction holes having a smaller planar 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 conveyance belt.

Effects of the Invention

[0009] According to the conveyance device of the present invention, it is possible to reduce the floating of the sheet while reducing the airflow generated during sheet conveyance.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent parts and components throughout the drawings are denoted by the same or equivalent reference numerals.

[0012] The embodiments shown below illustrate devices and the like for embodying the technical idea of this invention, and the technical idea of this invention does not specify the materials, shapes, structures, arrangements, etc. of each component part as the following. The technical idea of this invention can be variously modified within the scope of the claims.

[0013] FIG. 1 is a schematic configuration diagram of an inkjet printing apparatus provided with a conveying device according to an embodiment of the present invention. FIG. 2 is a plan view of the inkjet printing apparatus shown in FIG. 1. FIG. 3 is a partially enlarged plan view of the conveying unit of the inkjet printing apparatus shown in FIG. 1. FIG. 4 is a partially enlarged cross-sectional view of the conveying unit taken along line A-A of FIG. 3. In the following description, the direction perpendicular to the plane of FIG. 1 is defined as the front-rear direction, and the front side of the plane of the drawing is defined as the front. Also, the up, down, left, and right directions in the plane of FIG. 1 are defined as the up-down and left-right directions. In FIG. 1, the direction from left to right is the paper conveyance direction. In the following description, upstream and downstream mean upstream and downstream in the paper conveyance direction.

[0014] As shown in FIGS. 1 and 2, the inkjet printing apparatus 1 according to the present embodiment includes a printing unit 2 and a conveying unit (corresponding to a conveying device) 3.

[0015] The printing unit 2 prints an image on a sheet P conveyed by the conveying unit 3. The printing unit 2 includes a plurality of line heads 11. In the present embodiment, the printing unit 2 includes four line heads 11.

[0016] The line head 11 discharges ink onto the sheet P to print an image. The four line heads 11 discharge inks of different colors (for example, black, cyan, magenta, and yellow). The four line heads 11 are arranged in parallel along the paper conveyance direction (left-right direction) above the conveying unit 3. Each line head 11 has a plurality of inkjet heads 12. In the present embodiment, each line head 11 has six inkjet heads 12.

[0017] In the line head 11, the inkjet heads 12 are arranged in a staggered manner along the front-rear direction. That is, in each line head 11, six inkjet heads 12 arranged along the front-rear direction are arranged with their positions in the left-right direction shifted alternately.

[0018] The inkjet head 12 has a plurality of nozzles (not shown) that open to a discharge surface 12a, which is a lower surface facing the conveyance surface 21b of a conveyance belt 21 described later, and discharges ink from the nozzles.

[0019] The conveyance unit 3 conveys a sheet P (corresponding to a sheet) fed from a sheet feeding unit (not shown) while adsorbing and holding it by air suction.

[0020] The conveyance unit 3 includes a conveyance belt 21, a drive roller 22, driven rollers 23 to 25, a platen (corresponding to a member) 26, a platen plate 27, a suction unit 28, and a plurality of sheet pressing rollers 29.

[0021] The conveyance belt 21 adsorbs and holds the sheet P and conveys it. The conveyance belt 21 is an endless belt wound around the drive roller 22 and the driven rollers 23 to 25. A large number of belt holes 21a are formed in the conveyance belt 21. The conveyance belt 21 adsorbs and holds the sheet P on the conveyance surface 21b by the suction 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 sheet 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 rotates (moves endlessly) in the clockwise direction in FIG. 1 to convey the adsorbed and held sheet P in the conveyance direction from left to right.

[0022] The belt holes 21a are arranged at a predetermined pitch (interval) K in each row along the conveyance direction (left - right direction). Also, two adjacent rows of belt holes 21a in the sheet width direction (front - rear direction) orthogonal to the conveyance direction are arranged so as to be shifted by half a pitch in the left - right direction. That is, the belt holes 21a are arranged in a staggered pattern.

[0023] The drive roller 22 rotates the conveyor belt 21. The drive roller 22 is rotationally driven by a motor (not shown). The driven rollers 23 to 25 support the conveyor belt 21 together with the drive roller 22. The driven rollers 23 to 25 rotate in a driven manner with respect to the conveyor belt 21. The driven roller 23 is arranged at the same height as the drive roller 22 and to the left of the drive roller 22. The driven rollers 24 and 25 are arranged at the same height and spaced apart from each other in the left-right direction below the drive roller 22 and the driven roller 23.

[0024] The platen 26 is arranged on the lower side of the conveyor belt 21 (the side opposite to the conveying surface 21b) between the drive roller 22 and the driven roller 23, and is a plate-like member that slidably supports the conveyor belt 21. The platen 26 has a plurality of recesses 31 and a plurality of suction holes 32.

[0025] The recess 31 is formed by digging downward toward the back surface (lower surface) on the surface (upper surface) of the platen 26 on the conveyor belt 21 side. The recess 31 is a portion where air is sucked by the drive of the fan 38 to generate a negative pressure. The recess 31 is formed in a rectangular shape in plan view 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 recess 31 are both equal to or greater than the diameter D of the belt hole 21a. That is, "D ≤ L and D ≤ W". Here, the diameter D of the belt hole 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 belt hole 21a.

[0026] The recesses 31 are arranged at a predetermined pitch along the left-right direction. Also, two rows of recesses 31 adjacent to each other in the front-back direction are arranged so as to be shifted by half a pitch in the left-right direction. That is, the recesses 31 are arranged in a staggered pattern on the surface of the platen 26. The pitch of the recesses 31 in the front-back direction is equal to the pitch of the belt holes 21a in the front-back direction. The recesses 31 are arranged at positions where the belt holes 21a of the conveyor belt 21 pass through.

[0027] Here, among the belt holes 21a of the conveyor belt 21 and the recesses 31 of the platen 26, when the upstream belt hole 21a of the two belt holes 21a adjacent to each other in the left - right direction reaches the downstream end of the recess 31 with which the upstream belt hole 21a overlaps, the downstream belt hole 21a of the two belt holes 21a adjacent to each other in the left - right direction is formed so as to pass downstream of the recess 31 adjacent to the downstream side of the recess 31 with which the upstream belt hole 21a overlaps.

[0028] Specifically, the belt holes 21a and the recesses 31 are formed so as to satisfy "K≧R and D≦L".

[0029] Here, as shown in FIG. 2, R is the distance between the upstream end of the upstream recess 31 and the downstream end of the downstream recess 31 among the 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 the two recesses 31 adjacent to each other in the left - right direction. The wall 33 separates the adjacent recesses 31 in the left - right direction.

[0030] Also, the belt holes 21a and the recesses 31 are formed such that the planar view area (opening area) of the belt holes 21a is equal to or less than the planar view area of the recesses 31.

[0031] The suction holes 32 are holes for sucking air from the recesses 31. The suction holes 32 are formed so as to penetrate from a part of the bottom surface of the recesses 31 to the back surface of the platen 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 such that the planar view area is smaller than that of the belt holes 21a. The planar view area A of the suction holes 32 is preferably 0.8 mm 2 or less. Also, the ratio V / A of the volume V [mm 2 of the recesses 31 to the planar view area A [mm 3 of the suction holes 32 is preferably 45.5 or less. Here, assuming the depth of the recess 31 is H, V = L×W×H.

[0032] The platen plate 27 is a plate-shaped member disposed below the platen 26 and supporting the platen 26 via a plurality of spacers 36. The platen plate 27 is formed with a plurality of through holes 27a for allowing the air sucked by the fan 38 to pass therethrough. The planar view area of the through holes 27a is larger than the planar view area of the belt holes 21a and the planar view area A of the suction holes 32.

[0033] The suction unit 28 sucks air through the suction holes 32 and the belt holes 21a and adsorbs the sheet P to the conveyor belt 21. The suction unit 28 includes a chamber 37 and a fan 38.

[0034] The chamber 37 forms a negative pressure chamber for generating an adsorption force in the belt holes 21a of the conveyor belt 21. The chamber 37 is provided on the back surface side of the platen plate 27 between the drive roller 22 and the driven roller 23.

[0035] The fan 38 exhausts air from the chamber 37. Thereby, the fan 38 sucks air through the suction holes 32 and the belt holes 21a to generate an adsorption force in the belt holes 21a, and adsorbs the sheet P to the conveyor belt 21.

[0036] The sheet pressing roller 29 presses the sheet P conveyed by the conveyor belt 21 against the conveying surface 21b. The sheet pressing roller 29 rotates following the rotating conveyor belt 21.

[0037] Next, the operation of the inkjet printing apparatus 1 will be described.

[0038] When performing printing with the inkjet printing apparatus 1, first, the drive roller 22 and the fan 38 start driving.

[0039] Due to the driving of the drive roller 22, the conveyor belt 21 rotates in the clockwise direction in FIG. 1 and moves in the conveying direction of the sheet P between the drive roller 22 and the driven roller 23. When the conveyor belt 21 rotates, the belt holes 21a pass over the recess 31 of the platen 26 from left to right.

[0040] On the other hand, when the exhaust from the chamber 37 is performed by driving the fan 38, a negative pressure is generated in the chamber 37.

[0041] Since the recess 31 communicates with the chamber 37 through the suction hole 32 and the through hole 27a of the platen plate 27, when a negative pressure is generated in the chamber 37, a negative pressure is generated in the recess 31 where the belt holes 21a do not overlap and are blocked by the conveyor belt 21. The recess 31 where the belt holes 21a overlap is open to the atmosphere through the belt holes 21a, and no negative pressure is generated.

[0042] After the driving of the driving roller 22 and the fan 38 is started, when the paper P is fed from a paper feeding unit (not shown) to the conveying unit 3, some of the belt holes 21a are covered by the fed paper P. Since the recess 31 where the belt holes 21a covered by the paper P overlap is blocked by the conveyor belt 21 and the paper P, the recess 31 is in a negative pressure state. As a result, an adsorption force is generated in the belt holes 21a, and the paper P is adsorbed to the belt holes 21a.

[0043] The conveyor belt 21 adsorbs and holds the paper P on the conveying surface 21b by the adsorption force generated in the belt holes 21a covered by the paper P. The conveyor belt 21 rotates in the clockwise direction in FIG. 1 to convey the adsorbed and held paper P to the right.

[0044] The inkjet head 12 ejects ink onto the paper P conveyed by the conveyor belt 21 to print an image. The printed paper P is discharged by a paper discharge unit (not shown).

[0045] Here, Fig. 5 shows the generation state of the negative pressure in the recess 31 near the leading end (downstream end) of the conveyed sheet P. In the example of Fig. 5, K = R. In this case, at the timing when the entire one belt hole 21a overlaps with one recess 31, the belt holes 21a overlap with every other recess 31 in the left - right direction. In this case, as shown in Fig. 5, it is possible to set the state such that a negative pressure is generated in the recess 31 adjacent to the downstream side of the recess 31 with which the belt hole 21a on the most leading - end side of the sheet P among the belt holes 21a covered by the sheet P overlaps.

[0046] Different from this embodiment, Fig. 6 shows an example of the generation state of the negative pressure in the recess 31 near the leading end of the conveyed sheet P in the case where the interval between the belt holes 21a in the conveyance direction is equal to the interval between the recesses 31. In this case, no negative pressure is generated in the recess 31 adjacent to the downstream side of the recess 31 with which the belt hole 21a on the most leading - end side of the sheet P among the belt holes 21a covered by the sheet P overlaps.

[0047] Therefore, in the configuration of Fig. 6, a gap is formed between the upper end surface of the downstream - side wall 33 of the recess 31 and the conveyance belt 21, and air may flow into the recess 31 with which the belt hole 21a on the most leading - end side of the sheet P among the belt holes 21a covered by the sheet P overlaps from the recess 31 adjacent to its downstream side. As a result, a loss of the negative pressure in the recess 31 with which the belt hole 21a on the most leading - end side of the sheet P among the belt holes 21a covered by the sheet P overlaps may occur. As a result, the adsorption force of the sheet P to the conveyance belt 21 may decrease at the leading end portion of the sheet P.

[0048] Also, in the configuration of Fig. 6, when the belt hole 21a on the most leading - end side of the sheet P among the belt holes 21a covered by the sheet P overlaps with the recess 31, the recess 31 is blocked and the generation of the negative pressure in the recess 31 starts. Therefore, the generation of the adsorption force by the belt hole 21a with respect to the leading end portion of the sheet P may be delayed with respect to the arrival of the leading end portion of the sheet P at the recess 31. Also due to this, the adsorption force of the sheet P to the conveyance belt 21 may decrease at the leading end portion of the sheet P.

[0049] When the adsorption force of the sheet P to the conveying belt 21 decreases, the sheet P may float from the conveying belt 21. When the sheet P floats, the sheet P may come into contact with the inkjet head 12, resulting in damage to the inkjet head 12 or the like. In addition, the floating of the sheet P may be detected as a conveyance jam, and the sheet conveyance may be stopped.

[0050] On the other hand, in the inkjet printing apparatus 1 of the present embodiment, as described above, among the belt holes 21a covered with the sheet P, the belt holes 21a do not overlap with the recess 31 adjacent to the downstream side with respect to the recess 31 where the entire belt holes 21a at the most leading end side of the sheet P overlap. For this reason, the said recessed part is obstruct | occluded by the conveyance belt 21, and negative pressure is produced | generated.

[0051] Therefore, it is possible to suppress the formation of a gap between the upper end surface of the downstream side wall 33 of the recess 31 where the belt holes 21a at the most leading end side of the sheet P overlap among the belt holes 21a covered with the sheet P and the conveying belt 21. Therefore, in the recess 31 where the belt holes 21a at the most leading end side of the sheet P overlap among the belt holes 21a covered with the sheet P, the pressure loss due to the inflow of air from the recess 31 adjacent to the downstream side thereof is suppressed.

[0052] In addition, in the inkjet printing apparatus 1, the recess 31 where the belt holes 21a at the most leading end side of the sheet P overlap next among the belt holes 21a covered with the sheet P is already in a state where negative pressure is generated. For this reason, it is possible to suppress the occurrence of the adsorption force by the belt holes 21a with respect to the leading end portion of the sheet P from being delayed with respect to the arrival of the leading end portion of the sheet P at the recess 31.

[0053] Therefore, in the inkjet printing apparatus 1, a decrease in the adsorption force of the sheet P to the conveying belt 21 at the leading end portion of the sheet P is suppressed. As a result, the floating of the sheet P from the conveying belt 21 is suppressed.

[0054] Here, as described above, since "D ≤ W", the recess 31 is prevented from being open to the atmosphere and losing negative pressure by a part of the belt holes 21a in the rows adjacent in the front-rear direction to the row of the belt holes 21a passing through the recess 31 overlapping with the recess 31.

[0055] Also, as described above, since the suction holes 32 having a smaller area in plan view than the belt holes 21a are formed in the platen 26, it is possible to reduce the air flow due to the air suction of the suction portion 28 while suppressing a reduction in the suction force in the belt holes 21a.

[0056] Here, the area of the belt holes 21a in plan view contributes to the suction force (= negative pressure × area in plan view) in the belt holes 21a. For this reason, reducing the area of the belt holes 21a in plan view to reduce the air flow due to air suction leads to a reduction in the suction force in the belt holes 21a. On the other hand, in the inkjet printing apparatus 1, the air flow due to air suction is reduced by the suction holes 32 having a smaller area in plan view than the belt holes 21a. Here, since the flow path resistance of the suction holes 32 having a smaller area in plan view than the belt holes 21a dominates the air flow due to air suction, the air flow due to air suction can be reduced by the suction holes 32.

[0057] Therefore, as described above, it is possible to reduce the air flow due to the air suction of the suction portion 28 while suppressing a reduction in the suction force in the belt holes 21a. As a result, it is possible to reduce the floating of the sheet P from the conveyor belt 21 and reduce the air flow generated during the conveyance of the sheet P. By reducing this air flow, it is possible to reduce the mist contamination of the printed matter caused by the satellite (ink mist) generated during the ink ejection from the inkjet head 12 flowing and landing on the margin portion of the sheet P.

[0058] Here, the strength of the air flow due to air suction and the degree of mist contamination of the printed matter corresponding thereto differ depending on the area A of the suction holes 32 in plan view. The results of an experiment in which the amount of mist contamination was measured for each area A of the suction holes 32 in plan view are shown in FIG. 7. Also, examples of printed images in the cases where the amount of mist contamination is 3.5, 4.0, 4.5, 5.0, 6.0, and 7.0 are shown in FIG. 8.

[0059] As shown in FIG. 8, if the amount of mist stain is 4.5 or less, the mist stain is of a level that cannot be visually recognized. On the other hand, as shown in FIG. 7, by setting the planar view area A of the suction hole 32 to 0.8 mm 2 or less, the amount of mist stain becomes 4.5 or less. Therefore, the planar view area A of the suction hole 32 is preferably 0.8 mm 2 or less. However, for the planar view area A of the suction hole 32, there is a minimum area according to the suction ability of the suction portion 28.

[0060] An experiment for measuring the above-described amount of mist stain will be described.

[0061] First, while the paper P is being conveyed by the conveying unit 3, a chart 41 shown in FIG. 9 is printed by one line head 11. The chart 41 is formed by arranging six patch columns 43, which are columns of patches 42 arranged at equal intervals along the left-right direction, at equal intervals in the front-rear direction. The patch 42 is a solid image of a square with a predetermined size. Six inkjet heads 12 in the line head 11 print each patch column 43 one by one. After the chart 41 is printed, the printed chart 41 is read by a scanner to generate read data.

[0062] Here, at the time of printing the chart 41, mist stains due to the influence of the air flow by air suction mainly occur in the vicinity of the leading end side of the patch 42 on the most leading end side (downstream side) in the conveyance direction of the paper P, and in the vicinity of the trailing end side of the patch 42 on the most trailing end side (upstream side).

[0063] Therefore, the luminance of each pixel in the region Ea adjacent to the leading end side of the patch 42 on the most leading end side of each patch column 43 and the region Eb adjacent to the trailing end side of the patch 42 on the most trailing end side of each patch column 43 in the read data of the chart 41 is calculated. Here, as shown in FIG. 10, the region Ea is the region on the leading end side (downstream side) in the conveyance direction of the paper P among the regions around the patch 42. The region Eb is the region on the trailing end side (upstream side) in the conveyance direction of the paper P.

[0064] Next, the standard deviation of the luminance in each of the regions Ea and Eb where the luminance of each pixel is calculated is calculated. As the degree of mist contamination increases, the variation in luminance increases, so the standard deviation of the luminance increases.

[0065] Then, the average value of the standard deviations of the luminance of the calculated regions Ea and Eb is calculated as the above-described mist contamination amount.

[0066] In the experiment whose results are shown in FIG. 7, the volume V of the recess 31 is the same regardless of the value of the planar-view area A of the suction hole 32. It has been confirmed that the volume V of the recess 31 has almost no influence on the mist contamination amount.

[0067] Next, the ratio V / A of the volume V [mm 2 of the recess 31 to the planar-view area A [mm 3 of the suction hole 32 will be described.

[0068] As described above, in the inkjet printing apparatus 1, when the sheet P is conveyed, the recess 31 where the most leading belt hole 21a of the belt holes 21a covered by the sheet P overlaps next is already in a state where negative pressure is generated. Thereby, it is possible to suppress a delay in the generation of the adsorption force by the belt hole 21a with respect to the leading end portion of the sheet P with respect to the arrival of the leading end portion of the sheet P at the recess 31, and to suppress the floating of the sheet P from the conveyance belt 21.

[0069] In such an inkjet printing apparatus 1, if V / A is too large, there is a possibility that sufficient negative pressure cannot be generated in the recess 31 with respect to the arrival of the leading end portion of the sheet P at the recess 31. For this reason, it is desirable to appropriately set V / A.

[0070] In the inkjet printing apparatus 1, the results of an experiment in which the sheet floating height, which is the height of the leading end portion of the sheet P from the conveyance surface 21b, is measured while changing the value of V / A are shown in FIGS. 10 and 11.

[0071] In this experiment, the paper floating height was measured for each of the cases where V / A = 25.5, V / A = 45.5, and V / A = 63.8. In each case, V = 12.75 mm 3 was set. And when V / A = 25.5, A = 0.5 mm 2 ; when V / A = 45.5, A = 0.28 mm 2 ; when V / A = 63.8, A = 0.2 mm 2 was set.

[0072] The conveyance position in Fig. 11 is the position on the conveyance surface 21b in the conveyance direction (left - right direction). Fig. 12 is a diagram showing the paper floating height at the predetermined position S shown in Fig. 11. The position S is the position below a certain line head 11. In Fig. 11, the position where the paper floating height is almost 0 (zero) corresponds to the position where the paper pressing roller 29 is arranged.

[0073] As shown in Figs. 10 and 11, in the case of V / A = 25.5 and the case of V / A = 45.5, the floating of the paper P is relatively small, and in the case of V / A = 63.8, the floating of the paper P is relatively large. From this, it is preferable that V / A ≤ 45.5. However, the volume V [mm 3 has a substantial lower limit because it requires the adsorption force accompanying the necessary negative pressure generation, and the value of V / A also has a substantial lower limit.

[0074] As described above, in the inkjet printing apparatus 1, the suction holes 32 having a smaller planar view area than the belt holes 21a are formed in the platen 26. Thereby, while suppressing the reduction of the adsorption force at the belt holes 21a, the air flow due to the air suction of the suction portion 28 can be reduced. As a result, while reducing the floating of the paper P from the conveyance belt 21, the air flow generated during the conveyance of the paper P can be reduced. For this reason, while reducing the floating of the paper P from the conveyance belt 21, the mist contamination of the printed matter can be reduced.

[0075] Also, in the inkjet printing apparatus 1, the planar view area A of the suction holes 32 is 0.8 mm 2The following is preferable. Thereby, the airflow generated during the conveyance of the paper P can be further reduced. For this reason, the mist stain on the printed matter can be further reduced.

[0076] Also, the ratio V / A of the volume V [mm 2 of the recess 31 to the planar area A [mm 3 of the suction hole 32 is preferably 45.5 or less. Thereby, it is possible to suppress a delay in the generation of negative pressure in the recess 31 with respect to the tip of the paper P reaching the recess 31. As a result, a delay in the generation of the adsorption force by the belt hole 21a is suppressed, so that the floating of the paper P from the conveyance belt 21 is further suppressed.

[0077] In the above-described embodiment, the configuration in which the belt holes 21a and the recesses 31 are formed so as to satisfy “K≧R and D≦L” is shown, but the present invention is not limited thereto. For example, as shown in FIG. 6, a configuration in which the interval between the belt holes 21a and the interval between the recesses 31 in the conveyance direction are equal may be employed. Even in such a configuration, since the suction holes 32 having a smaller planar area than the belt holes 21a are formed in the platen 26, it is possible to reduce the floating of the paper P from the conveyance belt 21 and reduce the airflow generated during the conveyance of the paper P. Further, even in such a configuration, by setting V / A to 45.5 or less, the time during which negative pressure is generated in the recess 31 can be shortened compared to the case where V / A is greater than 45.5, and the floating of the paper P from the conveyance belt 21 can be suppressed.

[0078] Also, in the above-described embodiment, the configuration in which the suction holes 32 having a smaller planar area than the belt holes 21a are formed in the recesses 31 of the platen 26 is shown, but the present invention is not limited thereto. For example, the suction holes 32 of the platen 26 may have a larger planar area than the belt holes 21a, and the through holes 27a of the platen plate 27 may be formed as suction holes having a smaller planar area than the belt holes 21a. Any member may be used as long as it is arranged between the portion between the driving roller 22 and the driven roller 23 of the conveyance belt 21 and the suction portion 28 and has a plurality of suction holes having a smaller planar area than the belt holes 21a.

[0079] In the above-described embodiment, the belt holes 21a are circular in plan view and the recesses 31 are rectangular in plan view. However, the shapes of the belt holes 21a and the recesses 31 are not limited to this.

[0080] In the above-described embodiment, an inkjet printing apparatus for transporting paper has been described. However, the present invention is not limited to this, and any transport apparatus for transporting a sheet may be used.

[0081] The present invention is not limited to the above-described embodiment as it is, and at the implementation stage, components can be modified and embodied without departing from the gist thereof. Also, various inventions can be formed by appropriately combining a plurality of components disclosed in the above-described embodiment. For example, some components may be deleted from all the components shown in the embodiment.

[0082] [Appendix] This application discloses the following inventions.

[0083] (Appendix 1) A transport belt having a plurality of belt holes and transporting a sheet, A member disposed on the side opposite to the side on which the sheet of the transport belt is placed and having a plurality of suction holes having a smaller planar area than the belt holes, A suction unit that sucks air through the suction holes and the belt holes to adsorb the sheet to the transport belt A transport apparatus characterized by comprising:

[0084] (Appendix 2) The transport apparatus according to Appendix 1, characterized in that the planar area of the suction holes is 0.8 mm 2 or less.

[0085] (Appendix 3) The member is formed on the surface on the side of the transport belt and has a plurality of recesses in which the suction holes open, and supports the transport belt. The volume V [mm 2 of the recess with respect to the planar area A [mm 3The conveying device according to appended claim 1 or 2, characterized in that the ratio V / A is 45.5 or less.

Explanation of Signs

[0086] 1 Inkjet printing device 2 Printing unit 3 Conveying unit 11 Line head 12 Inkjet head 21 Conveying belt 21a Belt hole 21b Conveying surface 26 Platen 27 Platen plate 28 Suction unit 31 Recess 32 Suction hole 37 Chamber 38 Fan

Claims

**Claim 1**: A conveying belt having a plurality of belt holes for conveying a sheet, a member disposed on the side opposite to the side on which the sheet of the conveying belt is placed and having a plurality of suction holes having a smaller planar 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, wherein the member is formed on the surface on the conveying belt side and has a plurality of recesses in which the suction holes open, and supports the conveying belt. The ratio V / A of the volume V [mm ２ of the recess to the planar area A [mm ３ of the suction hole is 45.5 or less, and the conveying device is characterized by this. **Claim 2**: The conveying device according to claim 1, wherein the planar area of the suction holes is 0.8 mm 2 or less.

Images