JP6708811B2 - Liquid ejecting apparatus and image forming apparatus - Google Patents

Description

The present invention relates to a liquid ejection device and an image forming apparatus.

There is known an image forming apparatus that forms and outputs an image by ejecting ink droplets onto a sheet-shaped medium. Such an image forming apparatus includes a liquid ejection device for ejecting ink droplets. Such an image forming apparatus is generally called an inkjet printer. 2. Description of the Related Art There is known an inkjet printer in which a liquid ejection device is arranged at a position facing a peripheral surface of a drum member that conveys a sheet-shaped medium in order to form an image at high speed and with high quality.

In the image forming apparatus as described above, there is a problem that "wrinkles are generated" in the sheet-shaped medium wound around the drum member and conveyed. For the purpose of solving this problem, there is known an inkjet printer that winds a sheet-shaped medium conveyed by a drum member around a drum member while applying tension (back tension) in a direction opposite to the conveying direction (for example, See Patent Document 1).

The inkjet printer disclosed in Patent Document 1 uses a suction pump to apply back tension to a sheet-shaped medium. Negative pressure by a suction pump is used to apply back tension to the sheet-shaped medium at a position where wrinkles are likely to occur during transport.

When the sheet-shaped medium is wound around the drum member to be conveyed, a guide plate is arranged so that the sheet-shaped medium is not separated from the drum member, and the sheet-shaped medium is conveyed along the guide plate.

According to the technique disclosed in Patent Document 1, in order to apply a negative pressure to the sheet-shaped medium conveyed along the guide plate, it is necessary to lift the sheet-shaped medium to a position that is affected by the negative pressure of the suction pump. is there. When the sheet medium is sucked while being lifted in this manner, wrinkles are likely to occur on the sheet medium. Therefore, the conventionally known technique has a further problem in preventing the wrinkles of the sheet-shaped medium.

The present invention has been made in view of the above problems, and an object thereof is to prevent wrinkles from being generated when a sheet-shaped medium is conveyed.

In order to solve the above problems, one embodiment of the present invention is a liquid ejection apparatus including a recording head that ejects a liquid onto a sheet-shaped medium, wherein the sheet-shaped medium is wound around a peripheral surface in the ejection direction of the liquid. A printing drum that conveys the sheet-shaped medium, a pressing roller that presses the sheet-shaped medium against the peripheral surface of the printing drum to bring the sheet-shaped medium into close contact, a conveyance drum that delivers the sheet-shaped medium to the printing drum, and the printing drum from the conveyance drum. When the rear end of the sheet-shaped medium is transferred to the sheet-shaped medium, a nip pressure is applied to the sheet-shaped medium between the printing drum and the conveying drum, and the peripheral speed of the conveying drum is set to the peripheral speed of the printing drum. set to be slower than the back tension applying mechanism that causes the peripheral speed difference to the conveyor drum and the printing drum, characterized by the Ruco equipped with.

According to the present invention, it is possible to prevent wrinkles from being generated when a sheet-shaped medium is conveyed.

It is a schematic diagram showing composition of one embodiment of a liquid discharge device concerning the present invention. It is a side view which shows the structure of the image recording part which concerns on this embodiment schematically. It is a figure which shows the mode of conveyance of the sheet-shaped medium which concerns on this embodiment. It is a figure which shows the example of a structure of the back tension provision mechanism which concerns on this embodiment. It is a figure which shows another example of a structure of the back tension provision mechanism which concerns on this embodiment. It is a figure which shows another example of a structure of the back tension provision mechanism which concerns on this embodiment. It is a figure which shows another example of a structure of the back tension provision mechanism which concerns on this embodiment. It is a figure which shows another example of a structure of the back tension provision mechanism which concerns on this embodiment. It is the schematic which shows the structure of the transfer cylinder which concerns on this embodiment. It is a bottom view showing an example of composition of a back tension providing mechanism concerning this embodiment. It is a bottom view which shows another structure of the back tension provision mechanism which concerns on this embodiment.

Hereinafter, embodiments of the liquid ejection apparatus and the image forming apparatus according to the present invention will be described. The liquid ejection apparatus according to the present invention is an apparatus including a recording head mounted inside an image forming apparatus. A print drum is arranged at a position facing the recording head of the liquid ejection device. The printing drum realizes image formation by ink droplets ejected from the recording head while winding and transporting a sheet-shaped medium. The sheet-shaped medium that is wound around the peripheral surface of the printing drum and conveyed is supplied from a paper feed tray. A transfer drum is used to transfer the sheet-shaped medium in the paper feed tray to the print drum. That is, the image forming apparatus according to the present invention includes a liquid ejection device, and is configured to convey the sheet-shaped medium to a position facing the recording head of the liquid ejection device by the printing drum and the conveyance drum to form an image. There is.

The recording head included in the liquid ejecting apparatus receives the supply of the ink liquid from the ink tanks which are divided for each color required for forming a color image, and ejects the ink droplets toward the sheet-shaped medium. The sheet-like medium may be one that can be carried by a drum member such as a carrying drum or a printing drum, and can form an image by fixing the ink droplets ejected from the recording head. For example, plain paper is a typical example, but the present invention is not limited to this. The sheet-like medium includes recording media such as OHP sheets and sheet-like media such as prepregs and copper foils in addition to paper, and includes all media that can be conveyed by the drum member.

The liquid ejection apparatus and the image forming apparatus according to the present invention include a mechanism that applies a nip pressure to the sheet-shaped medium between the printing drum and the transport drum. Further, it is provided with a mechanism for applying back tension to the sheet-like medium by adjusting the rotational speeds of the printing drum and the conveying drum and making the peripheral speeds of the peripheral surfaces of the printing drum and the conveying drum different. The gist of the present invention is to include a mechanism for uniformly applying the back tension due to the difference in nip pressure and the peripheral speed as described above to the entire sheet medium.

Embodiments of an image forming apparatus and a liquid ejection apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an overall configuration of an inkjet printer 10 which is an embodiment of the present invention. In FIG. 1, an inkjet printer 10 is an inkjet type image forming apparatus that ejects ink droplets onto a sheet P to form an image and output the image. The paper P according to the present embodiment is assumed to be general plain paper.

The inkjet printer 10 includes a paper feed unit 20 that feeds a paper P, a treatment liquid application unit 30 that applies a predetermined treatment liquid to the print surface that is the front surface of the paper P, and a cyan (C) ink on the print surface of the paper P. , Magenta (M), yellow (Y), and black (K) ink droplets are ejected by the inkjet head 44 to draw a color image, and the ink droplets ejected on the paper P are recorded. An ink drying unit 50 for drying, a fixing unit 60 for fixing the image recorded on the paper P, and a collecting unit 70 for collecting the paper P are configured.

Each of the processing liquid application unit 30, the image recording unit 40, the ink drying unit 50, and the fixing unit 60 serves as a transporting unit for the paper P and includes a first transport drum 31 and an image recording drum 41 that is a second transport drum. And a third transport drum 51 and a fourth transport drum 61. Further, the inkjet printer 10 includes a transfer drum, which is a conveyance drum, between the treatment liquid application unit 30 and the image recording unit 40, between the image recording unit 40 and the ink drying unit 50, and between the ink drying unit 50 and the fixing unit 60. 100 are arranged.

The transfer cylinder 100 is a rotary transfer unit arranged between the above-mentioned units. The sheet P is conveyed between the first to fourth conveying drums by the transfer drum 100, and is subjected to processing in each part of the treatment liquid applying section 30, the image recording section 40, the ink drying section 50, and the fixing section 60. To be done.

Each of the above-mentioned transport drums is a member formed in a cylindrical shape and has a dimension in the axial direction corresponding to the width of the paper P. Each of the above-mentioned transport drums is provided with an individual drive means, and is rotationally driven by this. The first to fourth transport drums constituting each processing unit rotate counterclockwise in FIG. The transfer cylinder 100, which is a rotary transfer unit, rotates in a clockwise direction in FIG. The paper P is wound around the outer peripheral surface of each rotating transport drum, and thus is transported from the paper feed unit 20 toward the collection unit 70.

A gripper G serving as a holding unit that holds the paper P is provided on the peripheral surface of each of the above-described transport drums. The sheet P is conveyed while being gripped by the gripper G at the leading end. The grippers G are installed, for example, at 180° intervals in each of the transport drums. As a result, it is possible to convey two sheets of paper with one rotation.

Further, each of the first to fourth transport drums is provided with a suction holding mechanism that holds the paper P wound around the outer peripheral surface by suction. In this example, the air pressure (negative pressure) is used to suck and hold the paper P on the outer peripheral surface. Therefore, a large number of suction holes are formed on the outer peripheral surface of each conveying drum. The back surface of the sheet P is sucked through the suction holes and is suction-held on the outer peripheral surface of each conveying drum. For the suction holding mechanism, a method using static electricity can also be used.

A gripper G that is a holding unit that holds the paper P is also provided on the peripheral surface of the transfer drum 100. The sheet P is conveyed while being gripped by the gripper G at the leading end. The grippers G are installed at 180° intervals, for example, at two locations on the outer peripheral portion of the transfer drum 100. As a result, it is possible to convey two sheets of paper with one rotation.

Arc-shaped guide plates 102 are installed on the lower portions of the transfer cylinders 100 along the conveyance path of the paper P, respectively. The sheet P conveyed by the transfer drum 100 is conveyed while being guided by the guide plate 102 on the back surface (the surface opposite to the printing surface).

Hereinafter, the embodiment of the present invention will be described focusing on the image recording drum 41 that constitutes the image recording unit 40 and the transfer drum 100 that feeds the paper P to the image recording drum 41.

FIG. 2 is a side view schematically showing the configuration of the paper transport mechanism in the image recording unit 40. In FIG. 2, the image recording unit 40 includes an image recording drum 41 that is a printing drum that conveys the paper P, and a pressing roller 42 that brings the paper P that is conveyed to the image recording drum 41 into close contact with the peripheral surface of the image recording drum 41. , Are provided. The image recording unit 40 also includes an inkjet head 44 (44C, 44M, 44Y, 44K) that constitutes a liquid ejection device that ejects ink droplets onto the paper P conveyed by the image recording drum 41. That is, the ejection direction of the ink droplets from the inkjet head 44 is the direction in which the paper P is adsorbed and held.

The image recording drum 41 receives the paper P conveyed by the transfer drum 100, which constitutes the conveying means, at a predetermined receiving position while rotating around the axis. The image recording drum 41 conveys the received paper P along an arc-shaped conveyance path. At this time, the paper P is adsorbed and held on the outer peripheral surface. A large number of suction holes are formed in a fixed pattern on the peripheral surface of the image recording drum 41. By sucking air from the inside through the suction holes, the paper P wound on the outer peripheral surface is removed. The sheet P is conveyed while being attracted and held, and is conveyed in a predetermined direction.

The pressing roller 42 is composed of a rubber roller (a roller whose outer peripheral portion is covered with rubber) having a width substantially the same as the width of the image recording drum 41, and is arranged at the upstream position of the inkjet head 44 with respect to the conveyance direction of the paper P. It

The pressing roller 42 is rotatably supported by bearings at both ends of the shaft portion, and is arranged in parallel with the image recording drum 41. That is, the pressing roller 42 is arranged orthogonal to the conveyance direction of the paper P. Since the pressing roller 42 is arranged in a state of being urged toward the image recording drum 41, the pressing roller 42 is pressed against the outer peripheral surface of the image recording drum 41, and a nip pressure is applied to the paper P by this pressure. ..

Here, the structure of the transfer cylinder 100 will be described. FIG. 9 is a perspective view schematically showing the structure of the transfer drum 100. As shown in FIG. 9, the transfer cylinder 100 is provided with a plurality of disc-shaped members each having a notch 101 in a part of its outer periphery, and has a form in which the plurality of disc-shaped members are coaxially penetrated. There is. The disk-shaped member rotates in the circumferential direction according to the rotation of the shaft. A gripper G is arranged in the cutout portion 101.

Next, the transfer of the paper P between the transfer drum 100 and the image recording drum 41 will be described. FIG. 3 is a side view showing how the paper P is transferred from the transfer drum 100 to the image recording drum 41. In FIG. 3, when the paper P is transferred from the transfer drum 100 to the image recording drum 41, the front end of the paper P held by the gripper G of the transfer drum 100 is changed to the gripper G provided in the image recording drum 41. Let The diameter of the portion of the transfer drum 100 is D1.

As shown in FIG. 3, in the delivery portion of the paper P, the gap between the peripheral surface of the image recording drum 41 and the peripheral surface of the transfer drum 100 is formed with a size that allows the paper P to pass through. The gap may be formed so that the sheet P can pass even if it is thick to some extent (even if it is thick paper).

Next, in the present embodiment, the back tension applying mechanism 200, which is a structure for preventing the occurrence of wrinkles when the paper P is conveyed, will be described. FIG. 4 is a side view showing a schematic configuration of the back tension applying mechanism 200. FIG. 10 is a bottom view showing a schematic configuration of the back tension applying mechanism 200. As shown in FIG. 4, the back tension applying mechanism 200 includes a cam 201, a contact plate 202 that abuts on the cam surface of the cam 201, a spring 203, and a fixing unit 206 that fixes the end of the spring 203. And a cam mechanism configured as described above.

Further, as shown in FIG. 10, the cam 201 is installed on the rotating shaft of the transfer drum 100, and the cam 201 also rotates in the same direction as the transfer drum 100 rotates. The rotating shaft of the transfer cylinder 100 is supported by the bearing holder 207. The bearing holder 207 has a structure that moves in the same direction when the transfer cylinder 100 is moved in the direction toward the image recording drum 41 and in the direction away from the image recording drum 41.

The peripheral surface of the cam 201 contacts the contact plate 202. The backing plate 202 is fixed to the inner wall of the housing of the inkjet printer 10. One end of a spring 203, which is an elastic member, is fixed to the rotating shaft of the transfer cylinder 100. The other end of the spring 203 is fixed to the fixing means 206. The fixing means 206 is a protruding portion formed on the inner wall of the housing of the inkjet printer 10.

The restoring force of the spring 203 urges the transfer drum 100 toward the image recording drum 41. The force against the biasing force is generated when the cam 201 is pressed against the contact plate 202. As shown in FIG. 4, when the cam 201 rotates, the relative position of the peripheral surface of the transfer drum 100 to the image recording drum 41 changes depending on the relationship between the outer peripheral surface of the cam 201 and the surface of the contact plate 202. For example, the peripheral surface of the transfer cylinder 100 is as shown by the movement track 100a. That is, the relative positions of the peripheral surfaces of the transfer drum 100 and the image recording drum 41 facing each other periodically approach or move away from each other.

As described above, the back tension applying mechanism 200 is configured by assembling the biasing mechanism that cooperates with the spring 203 as the biasing means, the contact plate 202 as the anti-biasing means, and the cam 201 as the bias adjusting means. Has been done. By the back tension applying mechanism 200, the transfer cylinder 100 rotates while being biased in a direction to approach the image recording drum 41. The size of the clearance between the peripheral surface of the transfer drum 100 and the peripheral surface of the image recording drum 41 changes according to the rotation of the cam 201.

Like the movement trajectory 100a of the peripheral surface of the transfer drum 100 shown by the dotted line in FIG. 4, the diameter of the peripheral surface of the transfer drum 100 is the first outer diameter R1 and the second outer diameter due to the action of the back tension applying mechanism 200. It changes periodically between R2. That is, the back tension applying mechanism 200 includes an outer diameter changing mechanism that moves the position of the peripheral surface of the transfer drum 100, which is a conveying drum, with respect to the image recording drum 41, which is a printing drum.

When the diameter of the peripheral surface of the transfer drum 100 is the first outer diameter R1, the leading end of the sheet P is transferred from the transfer drum 100 to the image recording drum 41. That is, when the diameter of the peripheral surface of the transfer drum 100 becomes the first outer diameter R1, the paper P is held between the transfer drum 100 and the image recording drum 41. As a result, the paper P is transferred from the transfer drum 100 to the image recording drum 41.

When the diameter of the peripheral surface of the transfer drum 100 is the second outer diameter R2, the rear end of the sheet P is separated from the transfer drum 100 and transferred to the image recording drum 41. That is, when the diameter of the peripheral surface of the transfer drum 100 becomes the second outer diameter R2, the paper P is conveyed from the transfer drum 100 to the image recording drum 41.

As in the movement trajectory 100a of the transfer drum 100, the first outer diameter R1 is larger than the second outer diameter R2, and the second outer diameter is larger than when the diameter of the peripheral surface of the transfer drum 100 is the first outer diameter R1. When the diameter is R2, the gap between the peripheral surface of the transfer drum 100 and the peripheral surface of the image recording drum 41 becomes narrower. Therefore, when the trailing edge of the paper P passes through the gap between the image recording drum 41 and the transfer drum 100, the paper P is transferred to the image recording drum 41 by the spring force of the spring 203 of the back tension applying mechanism 200. It is nipped between the body 100 and conveyed.

When the rear end of the paper P is nipped between the transfer drum 100 and the peripheral surface of the image recording drum 41, the rotation speeds of the transfer drum 100 and the image recording drum 41 are differentiated so that the transfer drum 100 and the image recording drum 41 are rotated. Causes a difference in peripheral speed. Here, the rotation speed of the image recording drum 41 is set to be higher than the rotation speed of the transfer drum 100. In other words, the rotation speed of the transfer drum 100 is set to be lower than the rotation speed of the image recording drum 41.

According to the back tension applying mechanism 200 that operates as described above, the nip pressure by the spring 203 is applied to the paper P at the timing when the rear end of the paper P is transferred from the transfer drum 100 to the image recording drum 41, and the peripheral speed difference is caused. A dynamic friction force is applied. The dynamic frictional force generated by the difference between the nip pressure and the peripheral speed is the source of applying back tension (tensile force in the direction opposite to the transport direction) to the paper P. Due to this back tension, when the paper P is transferred from the transfer drum 100 to the image recording drum 41, a tension directed in a direction opposite to the moving direction of the paper P is applied to the rear end of the paper P. As a result, it is possible to prevent the occurrence of wrinkles that are likely to occur when the paper P is delivered. That is, according to the back tension applying mechanism 200 according to the present embodiment, wrinkles on the paper P are obtained by using a simple configuration without using a negative pressure device (suction device) for applying the back tension to the paper P. Can be prevented.

At the timing when the diameter of the peripheral surface of the transfer drum 100 reaches the first outer diameter R1, the front end of the paper P is transferred from the transfer drum 100 to the image recording drum 41. At this time, there is no peripheral speed difference between the transfer drum 100 and the image recording drum 41, and the peripheral surfaces are moved at the same speed.

Next, another embodiment of the image forming apparatus and the liquid ejection apparatus according to the present invention will be described. FIG. 5 is a side view showing a schematic configuration of the back tension applying mechanism 200a according to the present embodiment. FIG. 11 is a bottom view showing a schematic configuration of the back tension applying mechanism 200a. As shown in FIG. 5, the back tension applying mechanism 200a moves while fixing the cam 201, the contact plate 202 that contacts the cam surface of the cam 201, the spring 203, the motor 204, and the end of the spring 203. And a moving means 208.

Both ends of the spring 203 are fixed in the pulled state as described above. Due to the restoring force of the spring 203, the transfer cylinder 100 is in a state of being applied with a tension for approaching the image recording drum 41.

By the operation of the motor 204, which is an electric motor, the moving means 208 moves the end of the spring 203 back and forth toward the passing cylinder 100. As a result, the end of the spring 203 moves toward and away from the transfer cylinder 100 and reciprocates. In this way, the biasing force applied to the transfer drum 100 by the spring 203 changes. By controlling the operation of the motor 204, the gap between the peripheral surfaces of the transfer drum 100 and the image recording drum 41 can be adjusted. As a result, the nip pressure applied to the paper P can be changed appropriately.

Next, still another embodiment of the image forming apparatus and the liquid ejection apparatus according to the present invention will be described. The back tension applying mechanism 200b according to the present embodiment uses the air cylinder 205 instead of the spring 203 to adjust the relative distance between the transfer drum 100 and the image recording drum 41. As shown in FIG. 6, the cam 201 provided on the rotating shaft of the transfer drum 100 is fixed so as to rotate together with the transfer drum 100. The cam surface of the cam 201 is fixed so as to abut the contact plate 202. The air cylinder 205 applies a force that pushes the rotating shaft of the transfer drum 100 toward the image recording drum 41.

The rotating shaft of the transfer cylinder 100 is pressed by the pressing force of the air cylinder 205, and the cam 201 is pressed against the contact plate 202. When the rotation of the cam 201 increases the resisting force against the pressing plate 202, the rotating shaft of the transfer cylinder 100 is displaced toward the air cylinder 205.

Due to the relative difference between the force generated by the rotation of the cam 201 and the force applied to the transfer cylinder 100 by the air cylinder 205, the peripheral surface of the transfer cylinder 100 changes periodically. This periodic change is as shown in the movement locus 100a shown in FIG.

That is, by adjusting the air pressure of the air cylinder 205, the peripheral surface of the transfer drum 100 facing the image recording drum 41 can be moved. With the air cylinder 205, the above nip pressure can be adjusted. The air pressure in the air cylinder 205 may be adjusted by a regulator or an electropneumatic regulator.

Next, still another embodiment of the image forming apparatus and the liquid ejection apparatus according to the present invention will be described. The back tension applying mechanism 200c according to the present embodiment, like the spring 203 and the air cylinder 205 described above, adjusts the clearance between the transfer drum 100 and the peripheral surface of the image recording drum 41 by a mechanical operation, and the nip. It does not adjust the pressure. The back tension applying mechanism 200c is arranged such that the elastic body 209 is attached to a part of the peripheral surface of the transfer drum 100 so as to adjust the gap between the transfer drum 100 and the peripheral surface of the image recording drum 41 and to adjust the nip pressure. Adjust.

The elastic body 209 is made of, for example, a material having elastic force such as rubber or sponge, which deforms when an external force is applied but returns to its original state by a restoring force. As shown in FIG. 7A, the elastic body 209 is not provided around the gripper G that holds the leading end of the paper P on the peripheral surface of the transfer drum 100.

As shown in FIG. 7A, when the front end of the paper P is transferred from the transfer drum 100 to the image recording drum 41, the peripheral speed of the transfer drum 100 and the peripheral speed of the image recording drum 41 are set to the same speed. The velocities of the transfer drum 100 and the image recording drum 41 are adjusted by an adjusting unit included in the liquid ejecting apparatus or the image forming apparatus.

The adjusting unit independently controls the rotation speed of the image recording drum 41 and the rotation speed of the transfer drum 100. The adjusting unit controls the peripheral speed of the image recording drum 41 and the peripheral speed of the transfer drum 100 to be different at a predetermined timing.

As shown in FIG. 7B, when the rear end of the paper P is passed from the transfer drum 100 to the image recording drum 41, the elastic body 209 passes through the gap between the transfer drum 100 and the image recording drum 41. The elastic body 209 is installed in the. The elastic body 209 is thicker than the gap between the transfer drum 100 and the image recording drum 41, and applies a nip pressure to the sheet P by a restoring force corresponding to the amount of bending when passing through the gap.

Further, at the timing of transferring the rear end of the paper P from the transfer drum 100 to the image recording drum 41, the rotation speeds of the transfer drum 100 and the image recording drum 41 are adjusted to be different. At this time, the peripheral speed of the transfer drum 100 is slower than the peripheral speed of the image recording drum 41. As a result, as described above, the dynamic frictional force is applied to the paper P, and the back tension is applied to the paper P.

Therefore, the back tension applying mechanism 200c according to the present embodiment includes, in addition to the elastic body 209, an adjusting unit that separately adjusts the rotational drive of the transfer drum 100 and the image recording drum 41. The adjusting unit adjusts the rotational speeds of the transfer drum 100 and the image recording drum 41 according to the phase of the transfer drum 100 to generate the dynamic frictional force as described above.

When the leading end of the paper P is transferred from the transfer drum 100 to the image recording drum 41, the adjusting unit sets the peripheral speed of the transfer drum 100 and the peripheral speed of the image recording drum 41 to the same speed. On the other hand, when the rear end of the paper P is transferred from the transfer drum 100 to the image recording drum 41, the peripheral speed of the transfer drum 100 and the peripheral speed of the image recording drum 41 are set to different speeds. This speed difference causes the dynamic frictional force described above. The wrinkles of the paper P can be prevented by the dynamic friction force and the nip pressure.

Next, still another embodiment of the liquid ejection device according to the present invention will be described. The back tension applying mechanism 200d according to the present embodiment is configured using a spring 203 and a tension guide 210, as shown in FIG. In the present embodiment, the tension guide 210 is wound around the part of the peripheral surface of the transfer drum 100 and arranged.

The tension guide 210 has such a thickness that it can pass with the paper P in the gap formed between the transfer drum 100 and the image recording drum 41 by the bias of the spring 203. When the tension guide 210 along with the paper P passes through the gap between the transfer drum 100 and the image recording drum 41, a nip pressure is applied to the paper P by the thickness of the tension guide 210 and the bias of the spring 203. That is, when the rear end of the paper P is transferred from the transfer drum 100 to the image recording drum 41, the nip pressure on the paper P is applied by the tension guide 210 and the spring 203.

As shown in FIG. 8A, when the front end of the paper P is transferred from the transfer drum 100 to the image recording drum 41, the peripheral speed of the transfer drum 100 and the peripheral speed of the image recording drum 41 are set to the same speed. .. As shown in FIG. 8B, when the trailing edge of the paper P is passed from the transfer drum 100 to the image recording drum 41, the peripheral speed of the transfer drum 100 and the peripheral speed of the image recording drum 41 are set to different speeds.

Due to the peripheral speed difference as described above, a dynamic frictional force is applied to the paper P, and a back tension is applied to the paper P. Therefore, the back tension applying mechanism 200d according to the present embodiment includes, in addition to the elastic body 209, an adjusting unit that separately adjusts the rotational drive of the transfer drum 100 and the image recording drum 41. The adjusting unit adjusts the rotational speeds of the transfer drum 100 and the image recording drum 41 according to the phase of the transfer drum 100 to generate the dynamic frictional force as described above.

That is, when the front end of the paper P is transferred from the transfer drum 100 to the image recording drum 41, the adjusting unit adjusts the peripheral speed of the transfer drum 100 and the peripheral speed of the image recording drum 41 to the same speed. On the other hand, when the rear end of the paper P is transferred from the transfer drum 100 to the image recording drum 41, the adjusting unit adjusts the peripheral speed of the transfer drum 100 and the peripheral speed of the image recording drum 41 to different speeds. As a result, a dynamic frictional force is applied to the paper P, and the occurrence of wrinkles on the paper P is prevented.

10 Inkjet Printer 20 Paper Feeding Section 30 Treatment Liquid Applying Section 31 First Conveying Drum 40 Image Recording Section 41 Image Recording Drum 42 Pressing Roller 44 Inkjet Head 50 Ink Drying Section 51 Third Conveying Drum 60 Fixing Section 61 Fourth Conveying Drum 70 Recovery Part 100 Transfer cylinder 102 Guide plate 200 Back tension applying mechanism 201 Cam 202 Contact plate 203 Spring 204 Motor 205 Air cylinder 206 Elastic body 207 Bearing holder 208 Moving means 209 Elastic body 210 Tension guide

JP2012-184044A

Claims (9)

A liquid ejecting apparatus comprising a recording head for ejecting a liquid onto a sheet-shaped medium,
A printing drum that winds and conveys the sheet-shaped medium around a peripheral surface in the liquid ejection direction;
A pressing roller that presses the sheet-shaped medium against the peripheral surface of the printing drum to bring it into close contact;
A transport drum that transfers the sheet-shaped medium to the printing drum,
A nip pressure is applied to the sheet medium between the print drum and the transport drum when the rear end of the sheet medium is transferred from the transport drum to the print drum, and the peripheral speed of the transport drum is also increased. was set to be slower than the peripheral speed of the printing drum, the back tension applying mechanism that causes the peripheral speed difference to the conveyor drum and the printing drum, a liquid discharge apparatus characterized by and Turkey provided with .. The back tension applying mechanism,
The liquid ejecting apparatus according to claim 1, further comprising an outer diameter changing mechanism that moves a position of a peripheral surface of the transport drum relative to the printing drum. The outer diameter changing mechanism is a cam mechanism that changes the relative position of the rotating shaft of the transport drum and the printing drum,
The liquid ejecting apparatus according to claim 2, further comprising an urging mechanism that applies an urging force in a direction in which the peripheral surface of the printing drum and the peripheral surface of the transport drum are brought close to each other. The outer diameter changing mechanism causes the gap between the transport drum and the print drum to move from the transport drum to the print drum more than when the front end portion of the sheet-shaped medium passes from the transport drum to the print drum. The liquid ejecting apparatus according to claim 2, wherein the rear end portion of the sheet-shaped medium is narrowed when passed over . There is no difference between the rotation speed of the print drum and the rotation speed of the transport drum when the leading end of the sheet-shaped medium is passed from the transport drum to the print drum, and the sheet-shaped medium is transferred from the transport drum to the print drum. the direction of conveyance drum is slow, it liquid ejection apparatus according to any one of claims 1 to 4, characterized in than said printing drum when the rear end portion is passed in. The liquid ejecting apparatus according to claim 3, wherein the urging mechanism includes an elastic member having an elastic force, and an electric motor that varies a restoring force of the elastic member. The liquid ejecting apparatus according to claim 3, wherein the urging mechanism includes an air cylinder. The back tension applying mechanism,
The liquid ejecting apparatus according to claim 1, further comprising an elastic body attached to the transport drum. An image forming apparatus having a liquid ejection device including a recording head for ejecting a liquid onto a sheet-like medium, wherein the liquid ejected by the recording head forms an image on the sheet-like medium and outputs the image.
An image forming apparatus, wherein the liquid ejecting apparatus is the liquid ejecting apparatus according to any one of claims 1 to 8.