Curl straightening appliance and image forming apparatus

Abstract

The challenge is to properly correct the curl of the medium. [Solution] A curl correction device 30 comprising a pair of registration rollers 26 for transporting paper 11, a winding member 32 around which the paper 11 is wound, an inlet roller 31A that contacts the paper 11 upstream of the winding member 32 in the paper transport direction, and an outlet roller 33B that contacts the paper 11 downstream of the winding member 32 in the paper transport direction, characterized in that, while the paper 11 is stretched between the inlet roller 31A and the outlet roller 33B and wound around the surface of the winding member 32, the outlet roller 33B rotates in a direction that transports the paper 11 downstream in the paper transport direction from the time the paper 11 is being transported until it stops.

Description

Technical Field

[0001] The present invention relates to a curl correction device and an image forming apparatus.

Background Art

[0002] There are image forming apparatuses that eject a liquid to form an image and feed and convey a sheet as a medium from a roll paper.

[0003] Such an image forming apparatus is provided with a curl correction device for correcting the curl of the sheet. For example, in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2018-34956), a roller-shaped correction member is provided that wraps around the outer surface of the sheet drawn out from the roll paper to correct its curl (curl). Further, a lifting prevention portion abuts against the circumferential surface on the inner surface side of the portion wrapped around the correction member of the sheet to prevent the sheet from lifting.

Summary of the Invention

Problems to be Solved by the Invention

[0004] When intermittent conveyance that repeatedly stops the conveyance of the medium is performed, during non-conveyance, the conveyance member such as a roller stops, so no tension is applied to the medium, and the medium sags. As a result, there is a problem that the curl of the medium cannot be appropriately forced.

[0005] An object of the present invention is to appropriately correct the curl of the medium.

Means for Solving the Problems

[0006] To solve the above problems, the present invention provides a curl correction device comprising: a conveying means for conveying a medium; a winding member around which the medium is wound; an upstream contact member that contacts the medium upstream of the winding member in the medium conveying direction; and a downstream roller that contacts the medium downstream of the winding member in the medium conveying direction, characterized in that, while the medium is stretched between the upstream contact member and the downstream roller and wound around the surface of the winding member, the downstream roller rotates in a direction that conveys the medium toward the downstream side in the medium conveying direction from the time of conveying the medium until it stops. [Effects of the Invention]

[0007] According to the present invention, the curl of the medium can be properly corrected. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view illustrating the overall configuration of an inkjet image forming apparatus. [Figure 2] This is a schematic side cross-sectional view of an inkjet image forming apparatus. [Figure 3] This is a side cross-sectional view showing an inkjet image forming apparatus of a different embodiment. [Figure 4] This is a side cross-sectional view showing an inkjet image forming apparatus of yet another embodiment. [Figure 5] This is a side cross-sectional view showing a different inkjet image forming apparatus from the present invention. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations will be simplified or omitted as appropriate. The following description will explain an image forming apparatus that forms an image on paper, which is an example of a medium.

[0010] Figure 1 is a perspective view illustrating the overall configuration of an inkjet image forming apparatus, and Figure 2 is a schematic side cross-sectional view of the same apparatus. The illustrated inkjet image forming apparatus is a serial-type inkjet image forming apparatus, and the image forming unit 2, curl correction device, paper feeding unit 4, etc. are arranged inside the main body 1 of the image forming apparatus. Guide rods 13 and guide rails 14 are stretched across both side plates of the image forming unit 2, and a carriage 15 is slidably held on these guide rods 13 and guide rails 14 in a direction parallel to the direction of arrow A in the figure.

[0011] As shown in Figure 1, the carriage 15 is equipped with liquid ejection heads that eject ink droplets of black (K), yellow (Y), magenta (M), and cyan (C). Each recording head is integrally provided with a sub-tank that supplies ink to the respective recording head. The main scanning mechanism that moves and scans the carriage 15 comprises a drive motor 21 located on one side in the main scanning direction, a drive pulley 22 that is rotationally driven by the drive motor 21, a driven pulley 23 located on the other side in the main scanning direction, and a belt member 24 that is wrapped between the drive pulley 22 and the driven pulley 23.

[0012] The driven pulley 23 is tensioned outward (away from the drive pulley 22) by a tension spring. The belt member 24 is partially fixed and held to a belt fixing part provided on the rear side of the carriage 15, thereby pulling the carriage 15 in the main scanning direction (direction of arrow A in the figure).

[0013] Furthermore, an encoder sheet is positioned along the main scanning direction of the carriage 15 to detect the main scanning position of the carriage 15, and the encoder sheet is read by an encoder sensor installed on the carriage 15.

[0014] In the recording area of ​​the main scanning region of the carriage 15, the paper is intermittently transported by a pair of registration rollers in a direction perpendicular to the main scanning direction of the carriage 15 (sub-scanning direction: direction of arrow B in the figure). In addition, a maintenance and recovery mechanism 18 for maintaining and recovering each recording head is located in one end region of the main scanning region. Furthermore, outside the carriage movement region in the main scanning direction, or in the other end region of the main scanning region as described above, a main cartridge 19 containing ink of each color to be supplied to the sub-tanks of the recording heads is detachably mounted to the image forming apparatus body 1.

[0015] A roll of paper 10, which is a roll-shaped medium, is set in a paper feed unit 4 located at the bottom of the main body 1 of the device. The paper feed unit 4 holds the roll of paper 10 and feeds it downstream. The paper feed unit 4 can accommodate rolls of paper 10 of different widths (direction of arrow A in the figure).

[0016] In the following explanation, the roll-shaped medium set in the paper feed unit 4 will be referred to as roll paper 10, and the continuous sheet-shaped medium unwound from the roll paper 10 will be referred to as paper 11 (see Figure 2). The direction of arrow A in Figure 1 is the width direction of the roll paper 10 and paper 11, and is also the main scanning direction in the image forming unit 2. This width direction of paper 11 is the direction along the surface of paper 11 and is perpendicular to the paper transport direction. Of the two sides of paper 11, the surface 11A corresponding to the outer surface of the roll paper 10 will be referred to as the outer surface 11A, and the surface 11B corresponding to the inner surface of the roll paper 10 will be referred to as the inner surface 11B. In the following explanation, the unwounding of paper 11 from the roll paper 10 by the rotation of the paper feed roller pair 25 and the transport of paper 11 are considered the same thing. The direction in which the paper 11 is transported is the direction in which the paper is fed out from the roll paper 10, and it is the direction in which the paper flows along the surface of the paper 11 shown in Figure 2, from the side of the roll paper 10 to the side of the image forming unit 2, and then to the paper discharge side. In the following explanation, the upstream or downstream side of the paper transport direction will be simply referred to as the upstream side or the downstream side.

[0017] In this image forming apparatus, as shown in Figure 1, the paper transported from the paper feeding unit 4 is transported from the rear to the front of the image forming apparatus body 1 by transport means such as a pair of registration rollers 26 to the recording area. Then, the carriage 15 is moved in the main scanning direction, and while intermittently feeding the paper, the recording head is driven according to the image information to eject droplets, thereby forming the required image on the paper. Furthermore, the paper after image formation is cut to a predetermined length and discharged into a paper output tray located on the front side of the apparatus body 1.

[0018] As shown in Figure 2, a pair of paper feed rollers 25 is provided in the paper feeding section 4. The pair of paper feed rollers 25 rotates with the paper 11 held in its nip, thereby feeding the paper 11, as a medium, from the roll paper 10 downstream in the paper transport direction. One of the rollers of the pair of paper feed rollers 25 is provided to be movable in the left-right direction in Figure 2, which is the direction in which it moves toward and away from the paper 11. During the image forming operation, this one roller moves away from the paper 11 (to the right in Figure 2), and the paper 11 is transported by the rotation of the registration roller pair 26.

[0019] A pair of registration rollers 26 is provided immediately upstream of the image forming unit 2. During the image forming operation, the pair of registration rollers 26 rotates and stops in sync with the timing, intermittently transporting the paper 11. This allows the image forming unit 2 to form an image at the desired position on the paper 11. The paper 11 with the image formed on it is fed out to the right side of Figure 2 (the front side of Figure 1) and discharged from the device. The pair of registration rollers 26 is included in the curl correction device 30.

[0020] A curl correction device 30 is provided downstream of the paper feeding unit 4 in the paper transport direction and upstream of the image forming unit 2. The curl correction device 30 includes an inlet roller 31A as an upstream contact member, a winding roller 32 as a winding member, and an outlet roller 33B as a downstream roller, all facing downstream in the paper transport direction. The direction indicated by arrows C1 and C2 in Figure 2 is the transport direction of the paper 11 in the curl correction device 30.

[0021] The inlet roller 31A and the winding roller 32 are formed of a rigid body such as metal. The outlet roller 33B is formed of an elastic body such as a foaming material.

[0022] The inlet roller 31A and the outlet roller 33B contact the inner surface 11B of the sheet 11 on their surfaces. The sheet 11 is spanned between the inlet roller 31A and the outlet roller 33B. Also, the winding roller 32 contacts the outer surface 11A of the sheet 11 at a position between these rollers in the sheet conveyance direction, and winds the sheet 11 around its surface.

[0023] The inlet roller 31A, the winding roller 32, and the outlet roller 33B rotate in the directions indicated by the arrows in FIG. 2 with the direction orthogonal to the plane of FIG. 2 as the axial direction. The inlet roller 31A and the winding roller 32 are driven to rotate passively when the sheet 11 is fed out downstream from the roll paper 10, for example, by the rotation of the resist roller pair 26. On the other hand, the outlet roller 33B is driven by a driving force transmitted independently from a driving source such as a motor, and rotates in the direction of conveying the sheet 11 downstream in the sheet conveyance direction. In other words, the portion of the outlet roller 33B that contacts the sheet 11 rotates in the direction from the upstream side to the downstream side in the conveyance direction of the sheet 11.

[0024] Also, a force that rotates in the direction opposite to the sheet conveyance direction is applied to the roll paper 10 of the sheet feeding unit 4. That is, a force in the direction of applying a brake to the conveyance of the sheet 11 is applied, and the sheet 11 is pulled in both directions between the roll paper 10 and the resist roller pair 26, and a tension is applied to the sheet 11.

[0025] The winding roller 32 contacts the outer surface 11A of the sheet 11 and winds the sheet 11 around its surface. Thereby, the winding roller 32 applies a force to the sheet 11 in the direction opposite to the direction in which the sheet 11 curls (particularly, the winding direction in the roll paper 10 in the present embodiment), and corrects the curl of the sheet 11. That is, it is possible to approach a straight state without curl of the sheet 11.

[0026] As described above, when the paper 11 is transported, a constant tension is applied to the paper 11 between the roll paper 10 and the registration roller pair 26. This allows the paper 11 to be stably wound onto the winding roller 32, and the curl of the paper 11 can be properly corrected.

[0027] However, in an inkjet-type image forming apparatus, the image forming unit 2 performs intermittent transport, repeatedly transporting and stopping the paper 11 in order to form an image at a desired position on the paper 11. As a result, there is a problem that slack occurs in the paper 11 when it is decelerated and stopped. For example, in the image forming apparatus 100 shown in Figure 5, which is different from the image forming apparatus of this embodiment, the inlet roller 131 and the outlet roller 133 both rotate in accordance with the transport of the paper 11, and stop rotating when the transport of the paper 11 stops. In an image forming apparatus 100 with such a configuration, when transitioning from the state of transporting the paper 11 to the stopped state, a certain amount of time is taken from the state in which the roll paper 10 is being fed out until it comes to a complete stop. As a result, slack occurs in the paper 11 as shown by the dotted line in Figure 5, and there was a problem that the curl of the paper 11 could not be stably corrected by the winding roller 132.

[0028] In contrast, in the image forming apparatus 1 of this embodiment shown in Figure 2, during the intermittent transport process of normal paper transport 11, deceleration, stopping, acceleration, and normal transport, the exit roller 33B is always rotated in a direction that transports the paper 11 downstream in the paper transport direction. In particular, even in the section from when the paper decelerates until it stops, and in the stopped section, the exit roller 33B is rotated in a direction that transports the paper 11 downstream in the paper transport direction. In other words, even when the transport speed of the paper 11 is slow, or when transport has stopped, the exit roller 33B is rotated by slipping against the paper 11, pulling the paper 11 in the transport direction (opposite side from the winding roller 32). As a result, sufficient tension can be applied to the paper 11 even in these sections, and sagging of the paper 11 can be suppressed. As a result, curling of the paper 11 can be properly corrected. In this embodiment, for example, during the intermittent transport process described above, the exit roller 33B is rotated at a constant rotational speed.

[0029] Furthermore, by forming the exit roller 33B from an elastic material, even if the paper 11 sags due to the deceleration or stopping of other rollers, the elastic deformation of the exit roller 33B can absorb the sag, allowing the paper 11 to be stably wound onto the winding roller 32. Therefore, the curl of the paper 11 can be corrected more appropriately. Also, by forming the exit roller 33B from an elastic material, the frictional force generated between the exit roller 33B and the paper 11 when the paper 11 is decelerated or stopped is reduced, allowing the exit roller 33B to slip against the paper 11 and rotate appropriately. In the process of transitioning from a stopped state to a normal transport state, the paper 11 goes from a sagging state to a taut, tensioned state. This can cause abnormal noises, such as a snapping sound, to come from the paper 11. However, by forming the exit roller 33B from an elastic material, the sagging of the paper 11 can be suppressed as described above, and abnormal noises can be suppressed.

[0030] Next, we will describe some variations of the curl straightening device 30 in order.

[0031] As shown in Figure 3, the curl correction device 30 of this embodiment includes an inlet roller 31B as an upstream roller, a winding roller 32, and an outlet roller 33A as a downstream contact member. Unlike the previously described embodiment, the inlet roller 31B is made of an elastic material such as foam and rotates in the opposite direction to the direction in which the paper 11 is transported by a drive source such as a motor. The outlet roller 33A is made of a rigid material such as metal and rotates in response to the transport of the paper 11, and does not have its own drive source.

[0032] In this embodiment, during the intermittent transport process of normal paper transport 11—from transport to deceleration to stop to acceleration to normal transport—the inlet roller 31B is always rotated in a direction that transports the paper 11 upstream in the paper transport direction. In particular, even during the paper deceleration section and the stop section, the inlet roller 31B is rotated in a direction that transports the paper 11 upstream in the paper transport direction. In other words, in these sections, the inlet roller 31B pulls the paper 11 upstream in the paper transport direction, opposite to the winding roller 32 side in the paper transport direction. This allows tension to be applied to the paper 11 not only during normal transport but also in other sections, suppressing sagging of the paper 11 and properly correcting the curl of the paper 11. Furthermore, by forming the inlet roller 31B from an elastic material, sagging of the paper 11 and the generation of abnormal noise can be suppressed. By suppressing sagging of the paper 11, the winding roller 32 can more appropriately correct the curl of the paper 11.

[0033] Furthermore, in the image forming apparatus 1 shown in Figure 4, the curl straightening apparatus 30 includes the same inlet roller 31B as in Figure 3, a winding roller 32, and the same outlet roller 33B as in Figure 2.

[0034] The inlet roller 31B and outlet roller 33B are made of elastic material, and during the intermittent transport process of normal paper transport 11—decelerating, stopping, accelerating, and then normal transport—each roller constantly rotates in the direction of the arrows in Figure 4. This allows the paper 11 to be pulled to the respective sides on the upstream and downstream sides of the winding roller 32 during sections other than when the paper 11 is being transported normally. This further suppresses sagging of the paper 11 and allows for proper correction of the curl of the paper 11. Furthermore, by making the inlet roller 31B and outlet roller 33B of elastic material, sagging of the paper 11 and the generation of abnormal noise can be further suppressed. By suppressing sagging of the paper 11, the winding roller 32 can properly correct the curl of the paper 11.

[0035] Furthermore, the rotation speed of the inlet roller 31B in Figure 3 or Figure 4, or the outlet roller 33B in Figure 2 or Figure 4, may be changed depending on the thickness of the paper 11. Specifically, as shown in Table 1 below, the rotation speed can be increased as the thickness of the paper 11 increases, such as 1.5 times the transport speed for thin paper, 2 times the transport speed for regular paper, and 2.5 times the transport speed for thick paper. This allows for stronger tensile force to be applied to the paper 11 as its rigidity increases, thereby appropriately suppressing sagging of the paper 11. Consequently, the curl of the paper 11 can be appropriately corrected by the winding roller 32. However, these values ​​are just examples and are not necessarily limited to these values. [Table 1]

[0036] Furthermore, the rotation speed of the inlet roller 31B and outlet roller 33B may be changed depending on the paper width. Specifically, as shown in Table 2 below, the rotation speed can be increased as the width of the paper 11 increases, for example, 1.5 times the transport speed when the paper width is less than 594 mm, and 2 times the transport speed when the paper width is 594 mm or more. As the paper 11 increases, the force required to pull the paper 11 increases. Therefore, this configuration can appropriately suppress sagging of the paper 11. Consequently, the curl of the paper 11 can be appropriately corrected by the winding roller 32. However, these values ​​are just examples and are not necessarily limited to these values. [Table 2]

[0037] For example, the system may be configured such that the operator inputs the thickness and width of the paper 11 into the image forming apparatus 1 to set the rotation speed of the input roller 31B and the output roller 33B, or the image forming apparatus 1 may be provided with a detection member to detect the thickness and width of the paper 11. Alternatively, the system may be configured to change the rotation speed of the input roller 31B and the output roller 33B based on a combination of both the paper thickness and paper width.

[0038] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the present invention.

[0039] The winding roller 32, the inlet roller 31A in Figure 2, and the outlet roller 33A in Figure 3 do not necessarily need to be configured to rotate in conjunction with the transport of the paper 11. For example, these components may be fixed and slide against the transported paper 11. In this case, for example, these components may have a fan shape in which only the surface that slides against the paper 11 is curved.

[0040] The medium is, for example, paper (also called "plain paper," etc.). However, the medium may also be coated paper, label paper, etc. other than paper, as well as overhead projector sheets, films, or flexible thin plates. In other words, the material of the medium can be a material to which ink droplets can adhere, to which ink can temporarily adhere, to which ink can adhere and solidify, or to which ink can adhere and penetrate. Specifically, the medium may be a recording medium such as paper, film, or cloth, an electronic circuit board, an electronic component such as a piezoelectric element (also called "piezoelectric component," etc.), a powder layer (also called "powder layer," etc.), an organ model, or a test cell, etc. Three-dimensional objects may also be formed. Thus, the material of the medium can be paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, or a combination thereof, etc., to which liquid can adhere. In addition, the liquid may include types other than ink, such as recording fluid, fixing fluid, or resin, depending on the above application.

[0041] In the terminology used in this application, image formation, recording, printing, copying, printing, and shaping are all synonymous. Furthermore, this image includes patterns such as wiring of electronic circuits, and also includes cases where wiring circuits are formed with conductive ink on a film substrate such as a flexible display or RFID tag.

[0042] Examples of the present invention are as follows: <1> A transport means for transporting the medium, A winding member around which the aforementioned medium is wrapped, An upstream contact member that contacts the medium upstream of the winding member in the medium transport direction, A curl straightening device comprising a downstream roller that contacts the medium downstream of the winding member in the medium transport direction, The curl correction device is characterized in that, with the medium stretched between the upstream contact member and the downstream roller and wrapped around the surface of the winding member, the downstream roller rotates in a direction that transports the medium toward the downstream side in the medium transport direction, from the time of transport to the time of stopping. <2> The downstream roller is an elastic body having elasticity. <1> This is the curl correction device described. <3> The upstream contact member is an upstream roller, The upstream roller rotates in a direction that transports the medium upstream in the medium transport direction, from the time of transport to the time of stopping. <1> or <2> This is the curl correction device described. <4> The upstream roller is an elastic body having elasticity. <3> This is the curl correction device described. <5> The rotational speed of the downstream roller is changed according to the thickness of the medium. <1> or <2> It is one of the curl-correcting appliances described below. <6> The rotational speed of the downstream roller is changed according to the width of the medium. <1> , <2> , <5> It is one of the curl-correcting appliances described below. <7> A transport means for transporting the medium, A winding member around which the aforementioned medium is wrapped, An upstream roller that contacts the medium upstream of the winding member in the medium transport direction, A curl straightening device comprising a downstream contact member that contacts the medium downstream of the winding member in the medium transport direction, The curl correction device is characterized in that, with the medium stretched between the upstream roller and the downstream contact member and wound around the winding member, the upstream roller rotates in a direction that transports the medium toward the upstream side in the medium transport direction, from the time of transport to the time of stopping. <8> The upstream roller is an elastic body having elasticity. <7> This is the curl correction device described. <9> The rotational speed of the upstream roller is changed according to the thickness of the medium. <7> or <8> This is the curl correction device described. <10> The rotational speed of the upstream roller is changed according to the width of the medium. <7> from <9> It is one of the curl-correcting appliances described below. <11> The rotational speed of the upstream roller and the downstream roller is changed according to the thickness of the medium. <3> or <4> This is the curl correction device described. <12> The rotational speeds of the upstream roller and the downstream roller are changed according to the width of the medium. <3> or <4> This is the curl correction device described. <13> <1> from <12> One of the curl straightening appliances listed, The image forming apparatus comprises an image forming unit that forms an image on the aforementioned medium. [Explanation of symbols]

[0043] 1. Image forming apparatus 2 Image forming unit 10. Roll paper (a medium in the form of a roll) 11 Paper (media) 26. Registr roller pair (conveying means) 30 Curl Orthodontic Appliance 31A Inlet roller (upstream contact member) 31B Inlet Roller (Upstream Roller) 32. Winding roller (winding component) 33A Outlet roller (downstream contact member) 33B Outlet roller (downstream roller) A. Width direction of the paper (width direction of the medium) C1, C2 Paper transport direction (media transport direction) [Prior art documents] [Patent Documents]

[0044] [Patent Document 1] Japanese Patent Publication No. 2018-34956

Claims

1. A transport means for transporting the medium, A winding member around which the aforementioned medium is wrapped, An upstream contact member that contacts the medium upstream of the winding member in the medium transport direction, A curl straightening device comprising a downstream roller that contacts the medium downstream of the winding member in the medium transport direction, A curl correction device characterized in that, with the medium stretched between the upstream contact member and the downstream roller and wrapped around the surface of the winding member, the downstream roller rotates in a direction that transports the medium toward the downstream side in the medium transport direction from the time of transport to the time of stopping.

2. The curl straightening device according to claim 1, wherein the downstream roller is an elastic body having elasticity.

3. The upstream contact member is an upstream roller, The curl correction device according to claim 1, wherein the upstream roller rotates in a direction that conveys the medium toward the upstream side in the medium conveying direction from the time of conveying the medium until it stops.

4. The curl straightening device according to claim 3, wherein the upstream roller is an elastic body having elasticity.

5. The curl straightening device according to claim 1, wherein the rotation speed of the downstream roller is changed according to the thickness of the medium.

6. The curl straightening device according to claim 1, wherein the rotation speed of the downstream roller is changed according to the widthwise length of the medium.

7. A transport means for transporting the medium, A winding member around which the aforementioned medium is wrapped, An upstream roller that contacts the medium upstream of the winding member in the medium transport direction, A curl straightening device comprising a downstream contact member that contacts the medium downstream of the winding member in the medium transport direction, A curl correction device characterized in that, with the medium stretched between the upstream roller and the downstream contact member and wound around the winding member, the upstream roller rotates in a direction that transports the medium toward the upstream side in the medium transport direction, from the time of transport to the time of stopping.

8. The curl straightening device according to claim 7, wherein the upstream roller is an elastic body having elasticity.

9. A curl straightening device according to any one of claims 1 to 8, An image forming apparatus comprising an image forming unit that forms an image on the aforementioned medium.

Images