JP6702005B2 - Sheet material conveying unit, sheet material conveying apparatus and apparatus for ejecting liquid - Google Patents

Description

  The present invention relates to a sheet material conveying unit, a sheet material conveying device, and a device for ejecting a liquid.

2. Description of the Related Art Conventionally, there is known an inkjet recording apparatus in which a recording medium such as a sheet is fixed to a conveying drum and ink is ejected toward the recording medium from a recording head arranged in the vicinity of the outer peripheral surface of the conveying drum to form an image. ing.
An air suction method is known as a method of fixing the paper to the transport drum. In this method, a thin suction plate having suction holes is wound around the surface of the conveying drum so as to be closely attached. When the inside of the transport drum is sucked by an 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 sucked by the suction plate.

However, when the air suction force is insufficient, a phenomenon of "floating" occurs in which the paper leaves the surface of the transport drum. The floating causes a large gap between heads, which is important in the inkjet method, to vary greatly, and there is a concern that a desired image cannot be obtained.
An example of floating is that the suction force is reduced due to air leakage from the suction holes that are not blocked in the case of a small size sheet. In addition, floating of the end portion of the paper (the front end portion and the rear end portion in the rotation direction of the transport drum) due to the large stiffness of the thick paper may be mentioned.

In order to suppress the floating that causes such a change in the head-to-head gap, various measures have been conventionally made.
A configuration has been proposed in which a plate groove and a suction hole of a suction plate that communicate with the drum suction groove are formed by half etching, and the plate groove is provided with a throttle portion that limits the flow rate (see, for example, Patent Document 1).
In Patent Document 1, the shape of the diaphragm portion is changed according to the sheet suction position, and the suction force is increased by increasing the flow rate especially at the trailing edge of the sheet that requires a large suction force. .. The suction holes are formed over substantially the entire range of the suction plate, in other words, over the entire longitudinal direction of the plate groove.

However, in the configuration in which the suction holes are formed over substantially the entire range of the suction plate as in Patent Document 1 and the like, when the paper becomes a small size, the suction force of the suction holes opened without being blocked by the paper is The degree of decrease is large.
When the suction force is reduced, the edges of the sheet are likely to be lifted, which causes variations in the head gap.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sheet material conveying unit capable of suppressing the floating of the sheet material with high accuracy.

According to the present invention, a drum-shaped carrier having an air suction path and a plurality of suction holes are mounted so as to be wound around the surface of the carrier, and a sheet material is adsorbed along the surface shape of the carrier. And a suction member for extending the sheet material in the widthwise direction of the sheet material, which extends in the sheet conveying direction and is orthogonal to the sheet conveying direction, and each communicates with the plurality of suction holes. a plurality of longitudinal suction grooves, anda transverse suction groove communicating with the air suction path communicated with the downstream side of the conveying direction in each of the plurality of longitudinal suction grooves, said plurality of suction holes, wherein A plurality of horizontal suction grooves and a plurality of the suction holes are arranged along the vertical suction groove at a predetermined pitch and in a plurality corresponding to each of the vertical suction grooves, each being biased upstream of the vertical suction groove in the transport direction. Among them, the distance to the suction hole closest to the lateral suction groove is twice or more the predetermined pitch.

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

It is a schematic block diagram which shows an example of the apparatus which discharges the liquid which concerns on the 1st Embodiment of this invention. FIG. 6 is a partially omitted schematic perspective view showing an example of a state in which a suction plate is attached to a transport drum. It is a partially-omitted schematic perspective view showing an example of a transport drum. It is a top view which shows an example of a suction plate, (a) is a figure which shows the lower layer which contacts a conveyance drum, (b) is a figure which shows an intermediate|middle layer, (c) is a figure which shows an upper layer. FIG. 3 is a diagram showing a suction structure of a large-sized sheet according to the present invention, (a) is a plan view showing a positional relationship between the sheet and suction holes, and (b) is a position of the negative pressure in the lateral suction groove and the lateral suction groove. It is a figure which shows the relationship with. FIG. 3 is a diagram showing a suction structure of a small-sized sheet, (a) is a plan view showing a positional relationship between the sheet of the present invention and a suction hole, and (b) is a negative pressure in the lateral suction groove and a lateral suction groove. FIG. 6C is a plan view showing the positional relationship between the sheet and the suction holes in the conventional example, and FIG. 7D is a plan view showing the relationship between the negative pressure in the lateral suction groove and the position of the lateral suction groove. FIG. It is a characteristic view which shows the relationship between the negative pressure and the air volume in a horizontal suction groove. FIG. 3A is a schematic side view showing an example of a clamping means and a tension applying member for fixing the leading end of the paper in the conveying direction to the conveying drum, FIG. It is a figure which shows the operation|movement which an additional member avoids interference with a clamping means. It is a perspective view which shows the principal part of a clamping means and a tension|tensile_strength addition member in 2nd Embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
1 to 8 show a first embodiment. FIG. 1 is an overall configuration diagram of an inkjet recording apparatus as an example of an apparatus that ejects liquid.
The inkjet recording apparatus 1 includes a sheet feeding unit 3 in which sheets 2 as sheet materials (recording media) are stacked and accommodated, a printing unit 4 as an image forming unit for ejecting ink droplets, and a drying process for drying ink images. It has a unit 5 and a discharge unit 6 for discharging and stacking the sheet 2 after the image formation.
In the present embodiment, the paper feed unit 3, the print unit 4, and the discharge unit 6 are each configured to be separable with casters, and these are combined to configure the inkjet recording apparatus 1 as a system. Not limited to this configuration, the entire inkjet recording device 1 may be configured as an integral part.

The printing unit 4 is provided with a sheet material transport unit 7 that sucks and transports the paper 2 fed from the paper feed unit 3, and a recording head 8 as a liquid ejection head.
The recording head 8 includes a recording head 8Y that ejects yellow ink, a recording head 8M that ejects magenta ink, a recording head 8C that ejects cyan ink, and a recording head 8Bk that ejects black ink. However, these are arranged along the peripheral surface of the sheet material conveying unit 7.
The recording head 8 is a full line type 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 transport unit 7 includes a transport drum 9 as a drum-shaped transport body, and a suction plate 10 as a suction member mounted so as to be wound around the outer surface of the transport drum 9. There is. The suction plate 10 has a plurality of suction holes 11 for sucking the paper 2.
As shown in FIG. 3, the transport drum 9 has rotary shafts 12 at both ends in the longitudinal direction (axial direction). The rotary shaft 12 forms a part of an air suction path by a suction means 13 such as an air pump, and a suction port 14 of the air suction path is opened on the surface of the transport drum 9.
The configuration in which the suction means 13 is connected to the air suction path of the transport drum 9 of the sheet material transport unit 7 constitutes a sheet material transport device.

As shown in FIG. 4, the suction plate 10 includes a lower layer 10A in which a lateral suction groove 15 communicating with the suction port 14 of the transport drum 9 is formed, and a sheet 2 extending in the transport direction indicated by an arrow F and orthogonal to the transport direction. Has a three-layer structure including a middle layer 10B having a plurality of vertical suction grooves 16 formed in the width direction and an upper layer 10C having a plurality of suction holes 11 communicating with each vertical suction groove 16. The lateral suction groove 15 is hereinafter also referred to as a drain groove.
The horizontal suction groove 15 and the vertical suction groove 16 may be formed in the same layer to have a two-layer structure. Further, the suction holes 11, the horizontal suction grooves 15, and the vertical suction grooves 16 may be formed on one or two plates by half etching.

FIG. 5A shows the positional relationship between the paper and the suction holes 11 and the like when a large size paper 2a is sucked and conveyed. The horizontal suction groove 15 communicates with each vertical suction groove 16 on the downstream side in the transport direction. The suction holes 11 are formed at substantially equal intervals along the longitudinal direction of each vertical suction groove 16, and are arranged on the upstream side of the vertical suction groove 16 in the conveying direction.
In other words, the entire suction structure including the horizontal suction groove 15, the vertical suction groove 16 and the suction hole 11 is formed near the rear end of the sheet 2a in the transport direction, and each suction hole 11 is formed in the transport direction of the vertical suction groove 16. It is arranged on the upstream side.

This is because the suction force is applied to the minimum necessary paper edge (rear edge) to suppress the floating of the paper, and the rear edge of the paper is efficiently adsorbed without increasing the flow rate of the air pump. Is. In order to realize this, in the present embodiment, the leading end of the paper is sandwiched between the transport drum 9 and the sandwiching means as described later.
Since all the suction holes 11 are closed by the large-sized paper 2a, there is almost no pressure loss in the drain groove 15 , and it is constant over the entire range of the drain groove 15 as shown by the broken line in FIG. 5B. Is. As in Patent Document 1, the suction holes 11 are not arranged in substantially the entire suction plate but are collectively arranged at the rear end of the sheet, so that the suction force of the air pump is not increased and the suction force is efficiently increased. Can be obtained. Even with thick paper, the floating of the rear end portion due to the curvature of the transport drum 9 and the waist force of the thick paper can be suppressed with high accuracy.

Specifically, the pitch p between the suction holes 11 in the transport direction is 5 mm, and the existence range (suction range) h of the suction holes 11 in the transport direction of the vertical suction groove 16 is about 20 mm from the rear end side of the paper. Has become. That is, the arrangement is such that the suction force is applied only to the trailing edge side of the paper.
Since the optimum value of 20 mm in the suction range varies depending on the paper size, it may be changed according to the paper used.
The drain groove 15 is located on the downstream side in the carrying direction with respect to the trailing edge of the sheet, and the vertical suction groove 16 extends from the drain groove 15 to the upstream side in the carrying direction.

The distance s between the drain groove 15 and the first suction hole 11 from the drain groove 15 toward the upstream side is 15 mm. In other words, the distance s between the horizontal suction groove 15 and the suction hole 11 closest to the horizontal suction groove 15 among the plurality of suction holes 11 corresponding to each vertical suction groove 16 is determined by the pitch of the plurality of suction holes 11 in the transport direction. It is twice (10 mm) or more than p.
By doing so, as shown in FIG. 6A, even if the size of the paper becomes small and some suction holes 11 are exposed, the pressure loss is caused by the resistance of the vertical suction groove from the suction hole to the drain groove. Occurs, and a large flow rate does not flow. Therefore, as shown in FIG. 6B, it is possible to keep the negative pressure in the drain groove slightly reduced, and a suction pressure of a level that does not cause floating even when the paper size changes is applied to the paper. It is possible to give.

When the concept of arranging the suction holes 11 over the entire range of the vertical suction groove 16 as in Patent Document 1 is applied, as shown in FIG. 6C, the suction hole 11 opened immediately near the drain groove 15 is applied. Exists. Therefore, as shown in FIG. 6C, the pressure loss in the drain groove 15 is large. The negative pressure in the drain groove 15 is about half that of FIG. 5B. That is, the resistance effect of the vertical suction groove in the present invention shown in FIGS. 6A and 6B cannot be enjoyed.
Therefore, in order to obtain the negative pressure in the drain groove 15 as shown in FIG. 6B, it is necessary to increase the output of the air pump, which leads to higher cost.

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 and the air flow based on FIG. 7.
Point A is a case of a large size sheet, and is a state in which 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, in the conventional example, the flow path resistance is reduced and the amount of air entering the drain groove is increased, so that the negative pressure in the drain groove is lower than the target value. It becomes a level.
In the present invention, since the distance between the drain groove and the closest suction hole is secured to increase the flow path resistance, the point C that exceeds the target value even if the paper size becomes small and part of the suction hole is opened. A level of negative pressure can be secured.

The fixing structure of the leading end of the sheet will be described below.
As shown in FIG. 8A, an axially extending recess 17 is formed in a part of the peripheral surface of the transport drum 9 (not shown in FIGS. 2 and 3), and the recess 17 serves as an urging member. Clamping means 19 for constantly clamping the leading end of the sheet 2 by the spring 18 to the surface of the conveying drum 9 via the suction plate 10 is provided.

The pinching means 19 is opened by a cam mechanism on the apparatus main body side at a predetermined timing to pinch the leading end of the sheet 2 and release the sheet 2 at a predetermined position.
By fixing the leading end of the sheet 2 by the sandwiching means 19, the leading edge of the sheet 2 is prevented from rising. In particular, it is possible to prevent the tip portion from being lifted by the wind pressure caused by the transportation.
A tension roller 20 is provided on the circumference of the transport drum 9 as a tension applying member for applying tension to the rear end side of the paper 2. The peripheral speed of the tension roller 20 is set lower than the peripheral speed of the transport drum 9. Therefore, the tension roller 20 exerts an action of extending the rear end side of the sheet 2 whose front end is fixed by the sandwiching means 19 so as to follow the surface shape of the transport drum 9.

The tension roller 20 makes it possible to prevent the slack of the paper 2 when the paper 2 is wound around the surface of the transport drum 9. As a result, it is possible to prevent wrinkles and floating on the rear end side in the transport direction when the paper is wound around the surface of the transport drum 9.
As shown in FIG. 8B, the tension roller 20 is separated from the transport drum 9 in synchronization with the rotation of the transport drum 9 by the cam mechanism when the holding means 19 passes when the transport drum 9 rotates. Thereby, the interference with the holding means 19 is avoided.
The tension roller 20 may be separated by using another drive source such as a motor or a solenoid.

FIG. 9 shows a second embodiment.
As shown in FIG. 9, in the present embodiment, the sandwiching means 19 is formed in a comb tooth shape, and the tension roller 20 is composed of a plurality of rollers 20a passing through between the comb teeth. In this way, the separating mechanism is unnecessary.

In the above-described embodiment, a sheet (recording medium) is illustrated as an example of the sheet material, but the present invention is not limited to this, and a sheet shape such as OHP or copper foil that can be adsorbed and conveyed along the shape of the conveying drum. All sheet materials can be targeted.
Further, in the above-described embodiment, the configuration having the sandwiching means 19 for fixing the leading end portion of the paper is illustrated, but it is not always necessary depending on the material of the sheet material.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and unless otherwise specified in the above description, the present invention described in the claims is disclosed. Various modifications and changes are possible within the scope of the purpose.
The effects described in the embodiments of the present invention merely exemplify the most preferable effects that result from the present invention, and the effects according to the present invention are limited to those described in the embodiments of the present invention. is not.

1 Inkjet recording device as device for ejecting liquid 2 Paper as sheet material 7 Sheet material transport unit 9 Transport drum as transporter 10 Suction plate as suction member 11 Suction hole 14 Air suction path 15 Horizontal suction groove 16 Vertical suction Groove 19 Clamping means 20 Tensioning member

Japanese Patent No. 5384121

Claims (8)

A drum-shaped carrier having an air suction path,
The suction holes plurality Yes, a suction member for sucking along the sheet material to the surface shape of the conveying member,
Equipped with
The suction member extends in the conveyance direction of the sheet material and forms a row in the width direction of the sheet material orthogonal to the conveyance direction, and each of the vertical suction grooves communicates with the plurality of suction holes, has a transverse suction groove communicating with the air suction path communicated with the downstream side of the conveying direction in each of the longitudinal suction grooves of the,
Wherein the plurality of suction holes, respectively by a plurality to correspond to and the respective longitudinal suction grooves at a predetermined pitch along the longitudinal suction grooves, arranged offset to the upstream side in the conveying direction of the longitudinal suction grooves, said transverse suction The sheet material conveying unit , wherein the distance between the groove and the suction hole closest to the lateral suction groove among the plurality of suction holes is at least twice the predetermined pitch . The sheet material conveying unit according to claim 1,
The sheet material transport unit , wherein the transport body has a sandwiching unit that sandwiches a front end portion of the sheet material in the transport direction . A sheet material conveying device, comprising: the sheet material conveying unit according to claim 1; and suction means connected to the air suction path. The sheet material conveying device according to claim 3,
A sheet material conveying apparatus , comprising: a tension applying member that extends the sheet material to an upstream side in the conveying direction so as to follow the surface shape of the conveying body . The sheet material conveying device according to claim 4,
A sheet material conveying device, wherein the tension applying member is a roller . The sheet material conveying device according to claim 5,
A sheet material conveying device, wherein a peripheral speed of the roller is lower than a peripheral speed of the conveying body . The sheet material conveying device according to claim 5 or 6 ,
A sheet characterized in that the transport body has a sandwiching means for sandwiching a leading end portion of the sheet material in the transport direction, and a spacing means for spacing the roller so as not to interfere with the sandwiching means when the transport body rotates. Material transport device. An apparatus for ejecting a liquid, comprising the sheet material conveying apparatus according to claim 3.

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