JP2017226491A - Sheet material transport unit, sheet material transport device and device for discharging liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet material transport unit for accurately suppressing floating of a recording medium.SOLUTION: A sheet material transport unit comprises a transport drum 9, and a suction plate 10 attached to an outer peripheral surface of the transport drum 9. On the transport drum 9, a drum suction groove 12 as an air suction path which is connected to suction means such as an air pump, is formed. The suction plate 10 has: a lower layer plate 17 on which plural plate suction grooves 16 communicated to the drum suction groove 12 are formed; porous bodies 19; and an upper layer plate 18 on which plural suction holes 4 are formed. In a small sized sheet 2, suction holes 4b which are not occluded, exist, and an air stream 20 flowing therefrom, receives fluid resistance by the porous bodies 19, for suppressing reduction of negative pressure of the plate suction groove 16.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a sheet material conveyance unit, a sheet material conveyance device, and a device for discharging a liquid.

2. Description of the Related Art Conventionally, there is known an ink jet recording apparatus that forms an image by fixing a recording medium such as paper to a conveyance drum and ejecting ink from a recording head arranged close to the outer peripheral surface of the conveyance drum toward the recording medium. ing.
An air suction method is known as a method for fixing the paper to the transport drum. In this system, a thin suction plate having a plurality of suction holes is wound around the surface of the conveying drum so as to be wound around. When the inside of the transport drum is sucked by the air pump, the suction hole of the suction plate communicating with the drum suction groove provided on the surface of the transport drum becomes negative pressure, and the sheet is adsorbed by the suction plate.

However, if the air suction force is insufficient, a phenomenon of “floating” in which the paper is separated from the surface of the transport drum occurs. There is a concern that the gap between the paper and the head, which is important in the ink jet method, greatly fluctuates between the heads, and a desired image cannot be obtained. This is because the variation in the gap between the heads affects the landing position accuracy of the ink droplets.
As an example of the float, there is a case in which the suction force is reduced due to air leakage from a suction hole that is not blocked in the case of a small-size sheet. Further, there is a lifting of a paper edge (a leading edge or a trailing edge in the rotation direction of the transport drum) due to the large stiffness of the thick paper.

Various devices have been devised in the past in order to suppress floating that leads to fluctuations in the gap between the heads.
A configuration is described in which a plurality of grooves serving as air suction paths from the air pump are arranged on the outer peripheral surface of the transport drum, and a single suction plate is wound around the outer periphery (see, for example, Patent Document 1). The suction plate is provided with plate grooves and suction holes connected to the grooves of the transport drum, and is manufactured by half-etching.
The plate groove is provided with a restricting portion for restricting the flow rate, and the restricting portion changes its shape according to the sheet suction position. In particular, a portion corresponding to the rear end portion of the sheet that requires a large suction force is configured to have a throttle portion that is larger than other regions in order to increase the suction force by increasing the flow rate.

  However, in the configuration described in Patent Document 1, there is a throttle portion at the connection point between the groove of the transport drum and the plate groove. In other words, the throttle part is located at a position away from the suction hole. For this reason, when there is a suction hole that is not closed because the paper size is reduced, the resistance of the throttle portion against the inflow of external air from the opened suction hole into the plate groove is low. As a result, the negative pressure for adsorbing the paper is reduced, and the suction force is reduced particularly in the vicinity of the opened suction hole in the peripheral portion of the paper (front end, rear end, side end, corner, etc.), There was a problem that floating was likely to occur.

  SUMMARY An advantage of some aspects of the invention is that it provides a sheet material conveyance unit capable of suppressing the floating of a recording medium with high accuracy.

In order to achieve the above object, a sheet material conveyance unit of the present invention has a drum-shaped conveyance body having an air suction path, a plurality of suction holes, and is mounted so as to be wound around the surface of the conveyance body. A suction member for adsorbing so as to conform to the surface shape of the carrier,
A plurality of suction grooves that connect the air suction path and the suction holes are formed on the side opposite to the suction holes of the suction member, and when external air flows in from the suction holes, An inflow resistance portion exists on the upstream side of the suction groove.

  ADVANTAGE OF THE INVENTION According to this invention, the sheet | seat material conveyance unit which can suppress the floating of a recording medium with high precision can be provided.

1 is a schematic configuration diagram of an example of an inkjet recording apparatus as an apparatus for ejecting a liquid according to a first embodiment of the present invention. It is a disassembled perspective view of an example of a sheet material conveyance unit showing a state before the suction plate is mounted on the conveyance drum. It is a fragmentary sectional view of the circumferential direction of a conveyance drum. It is a perspective view of a sheet material conveyance unit showing a state where a suction plate is mounted on the conveyance drum. It is a top view which shows an example of each plate which comprises a suction plate, (a) is a figure which shows a lower layer plate, (b) is a figure which shows a porous body, (c) is a figure which shows an upper layer plate. It is a fragmentary sectional view of the conveyance drum in the axial direction in a state where the suction plate is mounted on the conveyance drum. It is a characteristic view which shows the relationship between the negative pressure and air volume in a drum suction groove. It is a top view of an example of the suction plate in a 2nd embodiment. It is a top view which shows the structure of the suction plate shown in FIG. 8, (a) is a figure which shows a lower layer plate, (b) is a figure which shows an upper layer plate. FIG. 9 is a plan development view of an outer peripheral surface of a conveyance drum in a second embodiment. It is a top view which shows the positional relationship of the suction plate shown in FIG. 8, and the drum suction groove of a conveyance drum. It is an experiment graph which shows the relationship between the aspect ratio and flow volume in the shape of the suction hole of the suction plate shown in FIG. It is a top view which shows the modification of a suction plate.

Embodiments of the present invention will be described below with reference to the drawings.
First, a first embodiment will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of an ink jet recording apparatus as an apparatus for ejecting liquid.
The ink jet recording apparatus 1 includes a paper feeding unit 3 in which sheets 2 as recording media are stacked and stored, a printing unit 4 as an image forming unit by ejecting ink droplets, a drying unit 5 that dries an ink image, And a discharge unit 6 on which the sheet 2 after image formation is discharged and stacked.
In the present embodiment, the paper feed unit 3, the printing unit 4, and the discharge unit 6 are each configured to be separable with casters, and the inkjet recording apparatus 1 is configured as a system by combining them. Not only this structure but the whole inkjet recording device 1 is good also as a structure inseparable.

The printing unit 4 is provided with a sheet material conveyance unit 7 that adsorbs and conveys the sheet 2 fed from the sheet feeding unit 3 to the peripheral surface, and a recording head 8 as a liquid ejection head.
The recording head 8 includes a recording head 8Y that discharges yellow ink, a recording head 8M that discharges magenta ink, a recording head 8C that discharges cyan ink, and a recording head 8Bk that discharges black ink. These are arranged along the peripheral surface of the sheet material transport unit 7.
The recording head 8 is a full-line recording head having a length corresponding to the maximum width of the image forming area in the width direction orthogonal to the conveyance direction of the paper 2.

As shown in FIG. 2, the sheet material conveyance unit 7 is mounted so as to be wound around the surface of the conveyance drum 9 and the conveyance drum 9 as a drum-shaped conveyance body so that the sheet 2 follows the surface shape of the conveyance drum 9. And a suction plate 10 as a suction member for adsorbing on the suction plate.
The transport drum 9 has rotating shafts 11 at both ends in the longitudinal direction (axial direction), and has drum suction grooves 12 as a plurality of air suction paths on the outer peripheral surface.
The drum suction groove 12 is formed along the circumferential direction of the conveyance drum 9, and a connection hole 13 communicating with the inside of the conveyance drum 9 is formed at the circumferential end portion thereof as shown in FIG. 3. As shown in FIG. 2, the suction plate 10 has a large number of small suction holes 14 and has a shape along the peripheral surface of the transport drum 9.

The suction plate 10 has a one-piece or two-piece structure, and is fixed with gripping means (omitted) provided on the outer surface of the transport drum 9 with its distal end portion stopped in the circumferential direction.
As the drum suction groove 12 and the grip means, for example, the configuration described in Patent Document 1 can be adopted.

In FIG. 2, reference numeral 15 denotes a non-opening portion in the suction plate 10, and the non-opening portion 15 where the suction hole 14 does not exist is disposed so as to block the drum suction groove 12 portion of the transport drum 9.
FIG. 4 shows a state where the suction plate 10 is mounted on the transport drum 9.
A suction flow path communicating with the connection hole 13 is provided inside the transport drum 9. The suction flow path is an air pump provided outside the transport drum 9 via a pipe or joint provided on the side surface of the transport drum 9 and a flow path provided inside the rotation shaft 11 of the transport drum 9. It is connected to suction means such as.
When a negative pressure is generated by operating the air pump, the sheet 2 is attracted and held on the surface of the suction plate 10 through the suction holes 14.

  A sheet material conveying apparatus is configured by the sheet material conveying unit 7 and suction means such as an air pump.

As shown in FIG. 5, the suction plate 10 includes a lower layer plate 17 in which a plurality of plate suction grooves 16 as suction grooves communicating with the drum suction groove 12, an upper layer plate 18 in which suction holes 14 are formed, A porous body 19 having air permeability as an inflow resistance portion disposed between the lower layer plate 17 and the upper layer plate 18 is laminated.
The suction plate 10 is mounted on the transport drum 9 so that the longitudinal direction of the plate suction groove 16 is orthogonal to the longitudinal direction of the drum suction groove 12 of the transport drum 9.
As the porous body 19, for example, a felt material, a sponge material, a filter material, or the like can be used.

As shown in FIG. 6, when a small-size sheet 2 is sucked, there is a suction hole 4 b that is opened without being blocked by the suction hole 4 a that is blocked by the sheet 2. When the air flow 20 flows in from the suction hole 4b opened to the outside, the negative pressure in the plate suction groove 16 of the suction plate 10 is lowered, which causes the edge of the paper 2 to float.
In Patent Document 1, as described above, the plate suction groove is provided with a throttle portion at the connection portion between the drum suction groove and the plate suction groove to obtain an inflow resistance. However, since the throttle portion and the opened suction hole are separated from each other, the airflow flows into the plate suction groove before the fluid resistance action of the throttle portion is exerted, resulting in a negative pressure drop.

On the other hand, in this embodiment, the porous body 19 exists upstream from the plate suction groove 16 in the inflow direction of the airflow 20 by the external air from the opened suction hole 4b. For this reason, since the airflow 20 flowing from the opened suction hole 4b passes through the porous body 19 before entering the plate suction groove 16, fluid resistance is generated here, and the negative pressure drop of the plate suction groove 16 is suppressed. The
Since the negative pressure drop of the plate suction groove 16 is suppressed, the suction force of the suction hole 4a closed by the paper 2 is hardly reduced. For this reason, the floating of the end of the sheet 2 near the opened suction hole 4b is suppressed.
In the present embodiment, the suction plate 10 is configured by stacking two plates and the porous body 19, but the porous body structure is integrally formed on at least one of the lower layer plate 17 and the upper layer plate 18 by half-etching or the like. May be.

The difference between the present invention and the conventional example (Patent Document 1) will be schematically described based on the relationship between the negative pressure in the drain groove (drum suction groove 12) and the air volume based on FIG.
Point A is a large size paper, and is a state where all the suction holes are closed. In this case, since the flow path resistance is large, there is no difference between the present invention and the conventional example.
When the paper size is reduced and a part of the suction hole is opened, the flow path resistance is low because the throttle portion is separated from the suction hole in the conventional example. For this reason, the air volume entering the drain groove is increased, and the negative pressure in the drain groove is at a point B level lower than the target value.
In the present invention, since the flow path resistance is increased by the porous body located in the vicinity of the suction hole, even if the paper size is reduced and a part of the suction hole is opened, the negative pressure at the C point level exceeding the target value. Can be secured.

As described above, according to the present embodiment, the floating can be suppressed with high accuracy, and various sizes of paper and cardboard can be handled.
In particular, a recording medium (thick paper) that is stiffer and stronger can be sucked to the transport drum, leading to an improvement in paper handling capability. In addition, it is possible to improve the suction force at the trailing edge of the sheet, which requires a large suction force, to suppress floating, and to contribute to the improvement of the landing position accuracy by stabilizing the gap between the heads.
Since fluctuations in the gap between the heads can be suppressed with high accuracy, the image quality can be improved.

The second embodiment will be described with reference to FIGS.
The same parts as those of the above-described embodiment are denoted by the same reference numerals, and the description of the configuration and functions already described is omitted, and only the main parts will be described.
FIG. 8 is a plan view of the suction plate 22 as the suction member in the present embodiment as viewed from the side opposite to the mounting surface to the transport drum 9.
The suction plate 22 has plate suction grooves 23 as a plurality of suction grooves on the mounting surface side to the transport drum 9, and has a plurality of rectangular suction holes 24 on the surface side. Each plate suction groove 23 extends in a direction orthogonal to the rotation direction of the transport drum 9 indicated by an arrow F.

As shown in FIG. 9, the suction plate 22 has a configuration in which a lower layer plate 25 in which a plurality of plate suction grooves 23 are formed and an upper layer plate 26 in which a plurality of suction holes 24 are formed are overlapped. The plate suction groove 23 and the suction hole 24 may be formed in one plate by half-etching or the like.
As shown in FIG. 10, a drum suction groove 27 as an air suction path is formed on the surface of the transport drum 9 in parallel with the rotation direction of the transport drum 9, and one end of the drum suction groove 27 is connected to the suction means. A connection hole 28 is formed. The connection hole 28 is formed for the same purpose as the connection hole 13 in the above embodiment.

  FIG. 11 is a plan development view showing a state in which the suction plate 22 is mounted on the surface of the transport drum 9. When the drum suction groove 27 is sucked by the suction means through the connection hole 28, the plate suction groove 23 communicated with the drum suction groove 27 becomes negative pressure, and the sheet 2 is adsorbed by the suction hole 24 communicated with the plate suction groove 23. .

In this embodiment, the inflow resistance portion is the suction hole 24 itself, and the inflow resistance action is expressed by the rectangular shape of the suction hole 24.
If the aspect ratio of the suction hole 24 is large, the outer periphery of the suction hole 24 becomes longer with respect to the area, so that the ventilation resistance increases and the flow rate is limited.
FIG. 12 shows the result of an experiment examining the relationship between the aspect ratio of the suction hole and the flow rate. The horizontal axis represents the aspect ratio of the suction hole in logarithmic display, and the vertical axis represents the flow rate passing through the suction hole.
The suction hole area is fixed.

FIG. 12 shows that the ventilation resistance increases when the aspect ratio is 10 or more. Therefore, when the suction hole 24 has a shape with an aspect ratio of 10 or more, the flow rate of the air passing through the opened suction hole 24 can be reduced, and the negative pressure drop can be suppressed.
As shown in FIG. 13, the plate suction grooves 23 of the suction plate 22 may be formed in a zigzag shape, and the suction holes 24 may be arranged in a staggered pattern along the shape.
In this way, air flowing from the suction hole 24 that is opened without being blocked by the paper 2 is inhibited from flowing compared to the case where the plate suction groove 23 is straight. In combination with this, it is possible to further enhance the function of suppressing negative pressure drop.

In the present embodiment, since the inflow resistance of the suction hole 24 can be increased while increasing the flow rate of the plate suction groove 23, the suction force of the paper can be increased to suppress the floating with high accuracy, and various sizes of paper and thick paper Is possible. That is, it is possible to improve the paper handling capability.
Since fluctuations in the gap between the heads can be suppressed with high accuracy, the image quality can be improved.
In addition, since it is possible to cope with floating suppression only by the shape of the suction hole, it is possible to contribute to simplification of the configuration of the suction plate, and thus reduction of manufacturing cost.

In the above embodiment, a sheet (recording medium) is illustrated as an example of a sheet material, but the present invention is not limited to this, and is in the form of a sheet for an OHP (overhead projector) film or copper foil and follows the shape of the transport drum. Thus, all sheet materials that can be sucked and conveyed can be targeted.
Further, the present invention can be similarly applied to an apparatus that discharges liquid other than ink.

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to such specific embodiments, and unless specifically limited by the above description, the present invention described in the claims is not limited. Various modifications and changes are possible within the scope of the gist.
The effects described in the embodiments of the present invention are merely examples of the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device as apparatus which discharges liquid 2 Paper as recording medium 7 Sheet material conveyance unit 9 Conveyance drum 10, 22 Suction plate 12, 27 Drum suction groove 14, 24 as air suction path Suction hole 19 Porous material 23 Plate suction groove as suction groove

Japanese Patent No. 5384121

Claims (7)

A drum-shaped transport body having an air suction path;
A suction member that has a plurality of suction holes and is wound around the surface of the transport body, and sucks the sheet material along the surface shape of the transport body;
With
On the opposite side of the suction member from the suction hole, a plurality of suction grooves that connect the air suction path and the suction hole are formed,
A sheet material transport unit in which an inflow resistance portion exists on the upstream side of the suction groove in the inflow direction when external air flows from the suction hole. In the sheet material conveyance unit according to claim 1,
The sheet material conveyance unit, wherein the inflow resistance portion is a porous body provided between the suction hole and the suction groove. In the sheet material conveyance unit according to claim 1,
The inflow resistance portion is the suction hole itself, and the suction hole is a sheet material conveyance unit having a rectangular shape. In the sheet material conveyance unit according to claim 3,
A sheet material conveyance unit in which the suction hole has an aspect ratio of 10 or more. In the sheet material conveyance unit according to any one of claims 1 to 4,
A sheet material conveying unit in which the suction groove has a zigzag shape.   6. A sheet material conveying apparatus comprising: the sheet material conveying unit according to claim 1; and a suction unit connected to the air suction path.   The apparatus which discharges the liquid provided with the sheet | seat material conveying apparatus of Claim 6.

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