JP2009234781A - Image forming apparatus - Google Patents

Abstract

A sheet is conveyed while being held at a high flatness.
A support plate 2 disposed opposite to a recording head, a transport belt 3 that moves along the surface of the support plate and transports a sheet, sends out the sheet in the transport direction, and is substantially orthogonal to the transport direction of the sheet. And a tension applying device 8 that applies tension toward the outside in the width direction.
[Selection] Figure 2

Description

  The present invention relates to an image forming apparatus.

  In an image forming apparatus that transports a sheet directly under a head and discharges ink of a predetermined color to form a predetermined image on the sheet, the head is placed above an endless belt in order to cope with an increase in the size of the sheet. And placing the paper on the belt to form an image by feeding the paper directly under the head.

If the flatness of this type of paper cannot be ensured with high accuracy, the ink landing accuracy may decrease, and problems such as color unevenness may occur.
Therefore, conventionally, a method of improving the flatness of the paper by using a paper pressing roller has also been adopted. However, in this method, the paper after passing through the paper pressing roller is floated, and the ink landing accuracy cannot be maintained. There is a problem.

Therefore, in Patent Document 1, a hole communicating with the negative pressure chamber is provided in the platen (support plate) facing the head, and a hole is also provided in the belt moving along the surface of the platen. A technique for improving the flatness of a sheet by sucking the sheet with a negative pressure through the section and causing the sheet to follow the surface of the platen is disclosed.
Japanese Patent No. 3707640

However, the following problems exist in the conventional technology as described above.
When paper with paper habits such as wrinkles is conveyed, there is a possibility that the paper will be attracted in a state where the paper habits cannot be removed, and the ink landing accuracy is still sufficiently secured I couldn't.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can convey and hold a sheet with high flatness.

In order to achieve the above object, the present invention employs the following configuration.
The image forming apparatus of the present invention includes a support plate disposed opposite to the recording head, a transport belt that moves along the surface of the support plate and transports the paper, and feeds the paper in the transport direction. And a tension applying device that applies tension toward the outside in the width direction substantially orthogonal to the transport direction.
Accordingly, in the image forming apparatus of the present invention, the tension is applied to the paper in the width direction by the tension applying device, so that the paper habit of the paper can be removed and held at a high flatness.

The tension applying device includes a feed roller that rotates around an axis and presses and feeds the paper, and the feed roller includes a component facing forward in the transport direction and a component facing outward in the width direction. A configuration in which the paper is fed out in the direction of inclusion can be suitably employed.
As a result, in the present invention, in order to feed the paper pressed by the feed roller in the direction toward the outer side in the width direction, tension is applied by pulling the paper to the outer side. It becomes possible to hold.

Further, as the feed roller, it is possible to suitably adopt a configuration in which the feed roller is symmetrically arranged on both sides across the center in the width direction.
As a result, in the present invention, the sheet can be pulled to the outside stably in a balanced manner, and the sheet conveyance direction can be easily maintained.

Further, as the feed roller, it is also possible to adopt a configuration in which the paper is sandwiched between the transport belt and on the rear side in the transport direction.
Thereby, in this invention, since it pulls outward while pinching | interposing a paper, the paper habit of a paper can be removed more reliably.
In the present invention, since the pair of feed rollers are provided on the rear side in the transport direction with respect to the transport belt, the paper after removing the paper habit is fed to the transport belt.

In the present invention, it is also possible to employ a configuration in which the feed roller is disposed at a position for pressing the sheet between the support plate and the support plate via the transport belt.
Thereby, in this invention, it becomes possible to press the paper from which the paper habit has been removed against the support plate via the transport belt.

In the present invention, a configuration including a suction device that sucks the paper under negative pressure and sucks the paper onto the conveyance belt can be suitably employed.
As a result, according to the present invention, it is possible to hold the sheet with high flatness, and it is possible to improve image forming characteristics using the recording head.

Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to FIGS.
In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.

FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to the present invention.
In FIG. 1, the left-right direction is the conveyance direction of the paper P (the left direction is the front side and the right direction is the rear side), and the direction orthogonal to the paper surface is the width direction of the paper P.

  The image forming apparatus PR includes a recording head 1 disposed at a distance from each other along a conveyance direction, a platen (support plate) 2 disposed to face the recording head 1, and a surface of the platen 2 facing the recording head 1. An endless belt-like conveyor belt 3 that moves along 2A and conveys the paper P, a drive roller 4 that drives the conveyor belt 3, a driven roller 5, a tension roller 6, and a pair of feed rollers that feed the paper P 7. Mainly composed of a pair of gate rollers (feed rollers) 8 which are tension applying devices for correcting the posture and flatness of the paper P, a paper pressing roller 9 for pressing the paper P, and a suction device 10 for sucking the paper P Has been.

Each of the recording heads 1 has a nozzle hole on its lower surface, and an on-demand type ink jet recording head (droplet) that discharges ink droplets onto a facing paper P from a nozzle hole at a predetermined position based on recording data. In the present embodiment, a line type ink jet recording head is used in which nozzle holes are arranged at equal intervals in the direction perpendicular to the transport direction (width direction).
The ink droplet ejection method by the recording head 1 may be a method using a piezoelectric element or a thermal method, and is not specified in the present invention.

The feed roller 7 is connected to a rotation motor (not shown) and feeds the paper P forward in the transport direction.
The tension roller 6 applies a predetermined tension to the wound conveyor belt 3.

  The gate rollers 8 rotate around the axis and press and feed the paper P fed by the feed roller 7 and are provided in pairs so as to sandwich the paper P up and down. FIG. 2 is a schematic exploded perspective view of the image forming apparatus PR, and FIG. 3 is a plan view of the conveying belt 3 and the gate roller 8.

As shown in these drawings, the gate roller 8 feeds the axis line so that the paper P is sent out in the direction C including the component Cy in the transport direction of the paper P and the component Cx outside in the width direction substantially orthogonal to the transport direction. The platen 2 is arranged substantially symmetrically on both sides of the center in the width direction so as to be parallel to the surface 2A of the platen 2 and intersect the width direction.
More specifically, each gate roller 8 is parallel to the front surface 2A of the platen 2 and the outer side in the width direction of the paper P so that the feeding direction of the paper P is located between the front side in the transport direction and the outer side in the width direction. The end portion located at the end is disposed on the rear side in the transport direction with respect to the end portion located on the inner side.

  The gate rollers 8 also have a function of feeding the paper P onto the transport belt 3 in accordance with the start timing of image formation by the recording head 1.

The conveying belt 3 is wound around the driving roller 4 on the front side in the conveying direction, wound around the driven roller (belt roller) 5 on the rear side in the conveying direction, and wound around the tension roller 6 below the platen 2 for driving. When the roller 4 is driven (rotated), the roller 4 slides forward along the surface 2 </ b> A of the platen 2 with a predetermined tension set by the tension roller 6.
Further, as shown in FIG. 2, a plurality of through holes 3 </ b> A are formed uniformly on the entire support surface of the paper P and over the entire circumference in the transport belt 3 at intervals.

  As shown in the external perspective view of FIG. 2, the platen 2 has a rectangular plate shape in which the surface 2A is formed with a high degree of flatness, and the surface 2A has a plurality of holes spaced from each other at a predetermined pitch. The portion 2B is formed uniformly over substantially the entire surface.

A suction device 10 is provided on the lower surface 2 </ b> C side of the platen 2. In the present embodiment, as the suction device 10, three fans 10A arranged along the transport direction are used. The suction device 10 generates a negative pressure on the surface 2A through the hole 2B by rotating each fan 10A as a negative pressure generating means and causing the air to flow downward.
Actually, a fan 10A is accommodated on the lower surface 2C side of the platen 2, a negative pressure chamber communicating with the hole 2B is provided, and the air in the negative pressure chamber is discharged by the operation of the fan 10A. The negative pressure chamber becomes a negative pressure, and a negative pressure is generated on the surface 2A through the hole 2B.

  The paper pressing roller 9 is rotatable around an axis extending in the width direction, and is formed in a columnar shape that presses the paper P against the conveyance belt 3 with the driven roller 5.

Next, a printing operation (image forming operation) on the paper P by the image forming apparatus PR will be described.
The main recording operation includes a preparation process, a paper feed process, an image forming process, and a paper discharge process. In the following, description will be given in order.

(Preparation process)
In the preparation process, the fan 10A is first started. The fan 10A is always driven during the recording operation and generates a negative pressure. Further, the drive belt 4 is driven to rotate, thereby moving the transport belt 3.

(Paper feeding process)
The paper P fed by the feed roller 7 is adjusted in posture by the gate roller 8 and the flatness thereof is corrected, and is fed onto the transport belt 3 according to the start timing of the printing operation.
More specifically, each gate roller 8 rotates about an axis extending in a direction intersecting the width direction of the conveyance belt 3, and the direction C includes a component Cy in the conveyance direction and a component Cx outside in the width direction with respect to the paper P. When the paper P is sent out, the paper P is fed toward the transport belt 3 on the front side while being pulled in the width direction and applied with tension.

  When the paper P is fed onto the transport belt 3 that moves in the transport direction by the rotation of the drive roller 4, the paper P is pressed against the transport belt 3 by the paper pressing roller 9.

  When the conveyance of the sheet P proceeds and the through hole 3A of the conveyance belt 3 supporting the sheet P communicates with the hole 2B opened in the upper surface 2A of the platen 2, the negative pressure suction force by the suction device 10 is reduced to the hole. Since it acts on the paper P via 2B and the through hole 3A, the paper P is attracted to the transport belt 3 by this negative pressure suction force. Further, in the conveyance belt 3, the through-hole 3 </ b> A is not formed, and the conveyance belt 3 is adsorbed to the upper surface 2 </ b> A of the platen 2 by a negative pressure suction force in a region facing the hole 2 </ b> B of the platen 2. It will be in sliding contact.

  The paper P is removed by the gate roller 8, and the paper P adsorbed (contacted) to the conveyance belt 3 by the negative pressure suction force by the suction device 10 is fed to the position immediately below the recording head 1 by the movement of the conveyance belt 3. Paper.

(Image formation process)
The recording head 1 is a line-type ink jet recording head in which a plurality of discharge nozzles are arranged at equal intervals in the sub-scanning direction, which is the width direction. For example, four color discharge nozzles are integrally provided, and the transport direction A plurality (four in this case) are arranged at intervals.
The ink of each color is ejected from the nozzles of the recording head 1 in accordance with predetermined image forming data in synchronization with the paper P being scanned and moved immediately below the recording head 1 by the movement of the conveying belt 3. A predetermined image is formed on the paper P.
At this time, since the paper P is adsorbed to the platen 2 via the conveyor belt 3 in a state where the paper habit has been removed by the gate roller 8 in advance, the paper P is held with high flatness following the surface 2A of the platen 2. An image is formed in the state.

Thereafter, the paper P is transported while being sucked and placed on the transport belt 3 in the paper discharge step, and is discharged to the face-down tray via a guide plate, for example.
Thus, image formation on the paper P is completed.

As described above, in this embodiment, the gate roller 8 feeds the paper P forward in the transport direction and applies tension to the outer side in the width direction. Therefore, the transport belt 3 is removed with the paper p of the paper P removed. Through the platen 2.
Therefore, in the present embodiment, even when a paper habit such as a roll habit has occurred on the paper P, it can be held with high flatness without leaving the paper habit, and as a result, the ink landing from the recording head 1 It is possible to improve the accuracy and form a high quality image.

  In this embodiment, before the negative pressure suction force by the suction device 10 acts on the paper P, tension is applied by the gate roller 8 to remove the paper habit, so that the paper P is transported with the paper habit. It is possible to effectively avoid the fact that it is in close contact with 3 and it is difficult to remove the paper habit.

  As described above, the preferred embodiments according to the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to the examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  For example, in the above-described embodiment, one gate roller 8 is arranged on each side in the width direction. However, the present invention is not limited to this, and a plurality of rollers shorter than the illustrated gate roller 8 are arranged. It is good.

In the above embodiment, the gate roller 8 is provided on both sides of the sheet P, but the present invention is not limited to this, and the gate roller 8 may be provided only on one side.
For example, the gate roller 8 may be provided at a position facing the platen 2, and the paper P may be pressed against the platen 2 via the conveyance belt 3 and fed to the front side while applying tension to the paper P. .

In the above embodiment, the crossing angle of the rotation axis of the gate roller 8 serving as the tension applying device with respect to the width direction of the paper P is not particularly mentioned. The crossing angle may be set according to the size of the paper habit.
For example, for paper P having a large paper habit, by setting the crossing angle to be large, the distance (time) to be pulled outward in the width direction becomes longer during feeding to the front side in the transport direction. It can be applied to the paper P.
On the other hand, when the paper P is small, the crossing angle is set small, so that the distance (time) to be pulled outward in the width direction is shortened during feeding to the front side in the transport direction. Can be prevented from acting on the paper P.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment. 2 is a schematic exploded perspective view of the image forming apparatus. FIG. FIG. 4 is a plan view of a conveyance belt 3 and a gate roller 8.

Explanation of symbols

  P ... paper, PR ... image forming apparatus, 1 ... recording head, 2 ... platen (support plate), 2B ... hole (second hole), 3 ... conveying belt, 3A ... through hole (first hole), 5 ... driven roller (belt roller), 8 ... gate roller (tension applying device, feed roller), 9 ... paper pressing roller (contact device), 9A ... first paper pressing roller, 9B ... second paper pressing roller, 10 ... Suction device

Claims (7)

A support plate disposed opposite the recording head;
A transport belt that moves along the surface of the support plate to transport the paper;
An image forming apparatus comprising: a tension applying device that sends out the paper in the transport direction and applies a tension toward the outside in the width direction substantially orthogonal to the transport direction. The image forming apparatus according to claim 1.
The tension applying device has a feed roller that rotates around an axis and presses and feeds the paper,
The image forming apparatus, wherein the feeding roller feeds the sheet in a direction including a component facing forward in the transport direction and a component facing outward in the width direction. The image forming apparatus according to claim 2.
The image forming apparatus, wherein the feed roller is parallel to the support plate and intersects the width direction, and the axis is arranged. The image forming apparatus according to claim 2 or 3,
The image forming apparatus, wherein the feed rollers are symmetrically arranged on both sides of the center in the width direction. The image forming apparatus according to claim 2, wherein
The image forming apparatus according to claim 1, wherein the feeding roller is provided in a pair with the sheet interposed therebetween on a rear side in the transport direction with respect to the transport belt. The image forming apparatus according to claim 2, wherein
The image forming apparatus according to claim 1, wherein the feeding roller is disposed at a position where the sheet is pressed between the feeding roller and the support plate via the conveyance belt. The image forming apparatus according to any one of claims 1 to 6,
An image forming apparatus comprising: a suction device that sucks the paper under negative pressure and sucks the paper onto the conveyance belt.

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