JP2012246066A - Curl straightening device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct curl that may occur on paper on which an image is formed, while avoiding image irregularities, the deterioration of image quality caused by retransfer of ink or toner to the following paper, or the like.SOLUTION: A curl straightening device is arranged on the downstream side of conveyance of a recording medium in an image recording part which forms an image using the ink or the toner. The device includes: a first rotor positioned on a surface side of the recording medium which is sandwiched and carried; and a plurality of second rotors positioned on a back side of the recording medium and making contact with a portion in a different circumferential direction of the first rotor. The first rotor makes contact with the recording medium only in a range of a non-image region of both ends of the recording medium.

Description

  The present invention relates to a curl correction apparatus that corrects curl generated after an image is formed on a recording medium, and also relates to an image forming apparatus such as a printer, a facsimile machine, and a copier equipped with such a curl correction apparatus. The present invention can also be applied to other transport devices in which warpage occurs in the recording medium during transport of the recording medium.

  For example, in an ink jet recording apparatus using water-based ink, when ink is applied to a paper that is a recording medium, the surface of the paper that has absorbed the moisture of the ink expands and curls so that the paper edge faces toward the back surface. In particular, in the case where a line engine in which print heads are arranged in a line is used as an image forming unit, ink is ejected onto a recording sheet at a high speed, and moisture per unit time absorbed by the sheet increases. As a result, the curl grows more rapidly. Also, the amount of curl increases as the amount of ink attached increases. The curling of the paper after recording has an adverse effect on the subsequent paper conveyance. In other words, when the paper edge is warped in the reverse direction, the paper becomes convex toward the front surface, which is the image recording surface, and the flatness is lost, paper jam occurs, and then sorting, stapling, punching performed by the finisher In some cases, post-processing steps such as the above cannot be processed normally.

Therefore, the following measures can be considered to prevent curling:
(1) reduce moisture contained in the ink;
(2) Decreasing the amount of moisture absorbed by the paper per unit time by slowing the paper transport speed and ink ejection timing;
(3) Forcibly evaporating ink moisture using a dryer;
(4) The curl is corrected using a decurler (curl correction device).

  However, reducing the water content in the ink has the effect of reducing the ejection reliability of the print head due to problems such as viscosity. Slowing paper formation speed and ink ejection timing to slow down image formation lowers the productivity of the apparatus and lowers the performance of the apparatus. Further, when a dryer is used, there is a drawback that the energy used increases and the power consumption of the apparatus increases. Therefore, in general, curl correction is performed by disposing a curl correction device downstream of the image forming unit in the sheet conveyance direction.

  The curl correction device is mainly known as an image forming device that forms an image using toner and heat-fixes. For example, in Patent Document 1, a nip shape of a hard roller and a soft roller, or an endless belt stretched between two rollers. A configuration is disclosed in which a roller is pressed at the center and the curl of the paper is corrected by its nip shape. A configuration in which a curl correction nip is formed by rollers having different hardnesses is also known in Patent Document 2. Further, in Patent Document 3, a two-way curl including a front and rear curl in which the downstream end and the upstream end in the paper transport direction (paper discharge direction) warp and a left and right curl in which the side end perpendicular to the paper discharge direction warps. In order to correct properly, the structure which provides the curl correction part in each direction is disclosed.

  Even in the ink jet image forming apparatus, a roller pair composed of two rollers located on the front and back sides of the paper is provided, and the curl correction direction and the correction direction thereof are determined according to the image forming ink ejection data recorded on the paper. A configuration in which the strength is determined and decurling is performed is disclosed in Patent Document 4. In ink jet recording, it takes a certain amount of time for ink to dry after image formation by ink ejection. Therefore, in Patent Document 4, a drying fan is provided between the ink discharge means and the decurling unit.

  In a curl correction apparatus known in relation to a toner type image forming apparatus, a pair of rollers for performing curl correction forms a nip. Therefore, when such a curl correction apparatus is applied to an ink jet type image forming apparatus, it is applied to an image forming surface. Since the roller for decurling is brought into contact, the image forming surface may be disturbed even if a dryer such as a drying fan is used. In addition, there is a problem that the ink transferred from the image forming surface to the roller stains other image portions or is retransferred to a sheet that comes to the curl correction device later. Especially when the humidity is high in the external environment. Even in the toner type image forming apparatus, when the curl correction roller is strongly pressed against the image forming surface in the curl correction apparatus, high temperature toner may be transferred to the roller.

  In Patent Document 4, since the curl correction is performed by moving the roller pair in a direction perpendicular to the paper conveyance direction and perpendicular to the paper surface, the pressure associated therewith does not cause scratches such as scratches on the image forming surface of the paper. Therefore, it is stated that the surface of the roller pair is made of an elastic body such as rubber, or the distance between the two rollers constituting the roller pair is made larger than the thickness of the paper (the thickness including the image). Yes.

  However, simply forming the surfaces of the roller pair with an elastic body does not change the contact of the rollers with the image forming surface, and the method of adjusting the gap between the two rollers expands the surface of the paper that absorbs ink moisture. In the curl correction when curling so that the paper edge is directed toward the back surface, the roller also comes into contact with the paper surface (image forming surface). The possibility of scratches on the image forming surface is the same in toner recording.

  An object of the present invention is to provide a curl correction device capable of correcting curl that may occur on an image-formed paper while avoiding image quality deterioration such as image disturbance and retransfer of ink and toner to subsequent paper. There is to do.

  According to the present invention, the above-described problem is a curl correction apparatus that should be disposed on the downstream side of the recording medium conveyance of an image recording unit that forms an image using ink or toner, and is provided on the surface side of the recording medium to be nipped and conveyed. A first rotating body located on the back side of the recording medium, and a plurality of second rotating bodies that are in contact with different circumferential positions of the first rotating body, and the first rotating body is disposed at both ends of the recording medium. This is solved by contacting the recording medium only in the non-image area.

  According to the present invention, the first rotating body positioned on the surface side of the recording medium to be nipped and conveyed contacts the recording medium only in the range of the non-image area at both ends of the recording medium. In addition, retransfer of ink / toner from the rotating body to the next recording medium can be eliminated.

1 is a schematic view of an ink jet image forming apparatus according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure of 1st Embodiment of the curl correction apparatus which concerns on this invention, (a) is a top view, (b) is the side view seen from the paper discharge side. It is a modification of a curl correction apparatus. It is the further modification of a curl correction apparatus. It is the further modification of a curl correction apparatus. This is a curl correction apparatus having a configuration in which a roller can be moved in the axial direction so as to be compatible with various sizes of paper. It is the schematic of the inkjet type image forming apparatus provided with another curl correction apparatus. FIG. 8A is a plan view of the curl correction apparatus illustrated in FIG. 7, and FIG. 8B is a side view as viewed from the paper discharge side. It is the further modification of a curl correction apparatus. FIG. 10 is a diagram illustrating a configuration in which a roller is movable in the axial direction so as to be compatible with various paper sizes in the curl correction apparatus of FIG. 9.

  FIG. 1 is a conceptual view of the overall configuration of the ink jet recording apparatus according to the first embodiment of the present invention as seen from the front. This apparatus includes a conveyance belt unit 101 that conveys a sheet 100 that is a recording medium, a recording head unit 102 that forms an image by ejecting droplets on the sheet 100, and a paper feed tray unit 103 that accommodates the sheet 100. .

  Using a pickup roller 115 that can swing the paper 100 from the paper feed tray unit 103 (showing a position for releasing the conveyance with a solid line, showing a position for carrying it with a dotted line, and swinging between these positions), The sheets are separated one by one and conveyed to a feeding unit 120 including a sheet feeding roller 116a and a separation roller 116b that are conveyed downstream in the sheet conveying direction. Further, the sheet 100 is fed from the feeding unit 120 to the intermediate conveyance roller pair (positioning roller) 124 via the conveyance path 121, and the intermediate conveyance roller pair 124 passes the conveyance path 123 from the further conveyance path 122 as it is to the conveyance belt. Transport to unit 101. The transport belt unit 101 has a transport belt 119 that is stretched at least by a transport roller 117 and a tension roller 118 and is driven at a predetermined timing. The conveyance belt 109 is an endless belt, and the holding of the paper 100 on the belt is realized by, for example, electrostatic adsorption, adsorption by air suction, or other known conveyance means. Next, ink is ejected from the recording head unit 102 onto the paper 100 on the transport unit 101, an image is formed on the surface, and the paper is transported to the paper discharge unit.

  The recording head unit 102 includes line type liquid discharge heads having nozzle arrays in which a plurality of nozzles for discharging droplets are arranged over a length corresponding to the paper width, and are respectively yellow (Y) and magenta (M). , Cyan (C), and black (K) recording heads 102y, 102m, 102c, and 102k that discharge ink droplets of respective colors. Note that the recording head can be mounted on the carriage as a serial type image forming apparatus.

  A decurling mechanism is placed downstream of the recording head unit 102 and the conveying belt unit 101 in the sheet conveying direction. In this decurling mechanism, a first roller 130 is disposed on the side in contact with the surface (image forming surface) of the paper 100, and two opposing rollers 131 and 132 are disposed on the opposite side. The opposing rollers 131 and 132 are driven by transmitting the power from the drive motor 134 by a belt 133 wound around the motor output shaft and each opposing roller.

  The sheet 100 on which an image is formed by the recording head unit 102 starts to curl so that the front surface side expands and the back surface side warps in a direction of depression due to moisture or the like contained in the ink. However, while entering the decurling mechanism and passing between the rollers, the paper 100 is prevented from warping or offset by being curled in the direction opposite to the curling direction, and curling is suppressed. After passing through the decurling mechanism, the paper sheet 100 whose deformation has been suppressed has no problem such as a paper jam, and is sent on a paper feed path to a post-processing machine (not shown) such as paper discharge or finisher.

  FIG. 2 shows a top view (a view seen from the direction of arrow A in FIG. 1) and a side view (a view seen from the paper discharge side) of the decurling mechanism (curl correction device) of the first embodiment. The first roller 130 located on the side in contact with the image forming surface is formed with a large diameter only at both ends in a direction orthogonal to the paper conveyance direction, and contacts the opposing rollers 131 and 132 to function as a conveyance roller pair. The intermediate portion between both end portions of the first roller 130 has a small diameter so that it does not contact the opposing rollers 131 and 132 and is dimensioned so that the image portion of the paper 100 does not contact the intermediate small diameter portion ( The intermediate small diameter portion may simply be a shaft). In order to cope with various sizes of the paper 100, the large-diameter portions at both ends of the first roller 130 are configured to be movable in the axial direction on the intermediate small-diameter portion, and according to the position of the non-image area that varies depending on the size of the paper. It is possible to move (an example of the configuration will be described later). As a result, even if the dry state of the ink is incomplete and the paper 100 is sent to the decurling mechanism, the first roller 130 does not come into contact with the image forming surface, so that the image forming surface is disturbed or the ink attached to the roller Does not cause problems such as retransfer to the next sheet.

  Assuming the case where the paper is thick or its rigidity is high and the first roller 130 is not able to level to the center of the paper just by pressing both ends of the paper, the leveling with the spur 136 at the intermediate small diameter portion of the first roller 130 is assumed. The shim member 135 may be attached. The diameter of the spur 136 is smaller than the diameter of both end portions of the first roller 130. The spur 136 can come into contact with the image area. However, since the spur 136 has a small diameter, image disturbance due to the spur can be reduced as much as possible, and sliding of the image area due to other members and parts due to the occurrence of curling can be avoided. It becomes.

  In place of the spur, or in addition to the spur, by blowing air toward the paper, a smoothing effect on the whole paper can be expected. FIG. 3 is a side view of a modified example of the decurling mechanism. In this example, a fan 138 (an axial fan is shown in the figure, but may be a line-shaped blow fan) is disposed above the first roller 130, preferably in a region that does not overlap with the intermediate small diameter portion. It is attached to the main body frame 137. The paper 100 is prevented from warping upward by the airflow from the fan. The fan 138 is a non-contact pressure unit for the paper, and can enhance the decurling effect while avoiding contact with the image area.

  FIG. 4 shows a modification in which the first roller is divided into transport rollers 139 and 140 that contact the non-image area of the paper. In the case of this example, which is advantageous in terms of cost, there is no intermediate small-diameter portion over the entire width of the image forming surface, so that the fan 138 can be arranged closer to the paper 100. The conveyance rollers 139 and 140 are configured to be movable along the shafts 141 and 142, and can correspond to various sizes of the paper 100.

  Further, it is also possible to suppress the paper slip in the axial direction by attaching minute protrusions to the roller surface corresponding to the paper non-image area of the first roller, which contributes to stable stagnation. In the example of FIG. 5, the surface of the conveying rollers 143 and 144 is further provided with minute protrusions as compared with the modification of FIG. 4, and these conveying rollers 143 and 144 with protrusions come into contact with the non-image area of the sheet. Transport paper.

  FIG. 6 shows a specific configuration for allowing the large-diameter portions at both ends to move in the axial direction so as to correspond to various sizes of the paper 100 referred to in the description of the embodiment according to FIG. Of the first roller 130, the small diameter portion is passed through the shaft 145, and the large diameter portion is defined as the transport rollers 146 and 147. The positions of the conveying rollers 146 and 147 can be adjusted by moving levers 150 and 151 attached to linear actuators (DC solenoids) 148 and 149. That is, the transport rollers 146 and 147 are moved using the movement levers 150 and 151 so as to match the position of the non-image area that changes according to the size of the paper 100 and the vertical and horizontal orientations during the transport.

  FIG. 7 is a front view of the overall device configuration of the embodiment in which the curl suppressing effect is further enhanced, and FIG. 8 is a top view (viewed from the direction indicated by arrow C in FIG. 7) and a side view of the decurling mechanism of this embodiment. (Viewed from the paper discharge side). Since the overall configuration excluding the decurling mechanism is the same as that of the embodiment of FIG. 1, the same reference numerals are assigned to the same members and the description is omitted.

  The decurling mechanism in this embodiment is composed of members that are the same as those shown in FIG. 4, but facing rollers 155 and 156 that are wound around the belt 133 on the back side of the paper 100 and rotated by the drive motor 134. A plurality of rollers are evenly distributed and arranged in the axial direction, and the rollers of both opposing rollers are positioned so as to be staggered. Further, the conveyance rollers 153 and 154 as the first rollers arranged on the front surface (image forming surface) side of the paper 100 are formed such that the outer diameter is tapered larger than the inner diameter, and the entire paper is orthogonal to the paper conveyance direction. The effect of pulling in the direction to be applied can be applied to enhance the decurling effect. This taper also curls (decals) the paper portion that is not in contact with the roller. A fan 138 for blowing air toward the paper 100 is disposed between the conveying rollers 153 and 154 (an axial fan is shown in the figure, but a linear blow fan may be used). Supports pasting. Of course, the conveyance rollers 153 and 154 can be configured to be movable in the axial direction in order to correspond to various sizes of the paper. The shafts of the respective conveyance rollers can be extended in the longitudinal direction. The conveyance roller may be supported by a single shaft and provided with an axial movement mechanism (an example of the configuration will be described later). The spur 136 of FIG. 2 may be provided, or a minute protrusion may be attached to the surface of the conveyance roller.

  In the decurling mechanism of the embodiment shown in FIG. 9, the roller 159 on the back side is provided with an inclined surface in accordance with the inclined surface of the conveying rollers 158 and 161 on the side in contact with the image forming surface. In addition, minute protrusions are attached to the surfaces of the conveying rollers 158 and 161, which facilitates curling for removing curls in the sheet conveying direction, and at the same time curls in a direction perpendicular to the sheet conveying direction ( Curls that warp in the direction of the back surface can also be removed.

  The embodiment shown in FIG. 10 is an example relating to the configuration of “supporting a conveyance roller with a single shaft and providing an axial movement mechanism” mentioned in the description of the embodiments of FIGS. The conveyance rollers 163 and 169 on the side that contacts the image forming surface of the paper are inserted into the through shaft 162, and the conveyance rollers 163 and 169 are movable in the axial direction by the axial movement mechanism. The transfer rollers 166 and 167 are inserted into the transfer rollers 166 and 167, and the transfer rollers 166 and 167 are movable by the same axial movement mechanism. At this time, as in the embodiment of FIG. 6, the axial movement mechanism includes linear actuators (DC solenoids) 164 and 171 attached to the main body housing, and movement levers 168 and 170 attached to the linear actuators. It is configured with. The moving levers 168 and 170 move the conveying rollers 163 and 169 inward and outward in the axial direction, and the outer ends of the levers are caught by the conveying rollers 166 and 167 on the back side of the paper, and the conveying rollers 166 and 167 are moved in the axial direction. Move inward (center direction). Regarding the movement of the conveying rollers 166 and 167 outward in the axial direction, the conveying rollers 166 and 167 are moved by the frictional force between the surface inclinations of the conveying rollers 163 and 169 on the image forming surface side of the sheet. The positions of these rollers are controlled so as to move to the position corresponding to the width of the paper 100, that is, the non-image area.

DESCRIPTION OF SYMBOLS 100 Paper 102 Recording head unit 130 1st roller 131,132 Opposed roller 133 Belt 134 Drive motor 136 Spur 138 Fan

JP 2006-82909 A JP 2010-37077 A JP 2010-89915 A JP 2010-70342 A

Claims (9)

  A curl correction device to be arranged on the downstream side of a recording medium conveyance of an image recording unit for forming an image using ink or toner, a first rotating body located on the surface side of the recording medium to be nipped and conveyed, and a recording medium A plurality of second rotating bodies that are in contact with different circumferential positions of the first rotating body, and the first rotating body is a recording medium only in a range of non-image areas at both ends of the recording medium. A curl straightening device that is in contact.   2. The curl correction apparatus according to claim 1, wherein the first rotating body is inclined in the axial direction so as to apply a pulling force to the both ends of the recording medium.   3. The mechanism according to claim 1, further comprising a mechanism for moving a portion of the first rotating body that contacts the recording medium in an axial direction, wherein the contacting portion is moved according to a size of the recording medium. Curling straightener.   The said 1st rotary body has a large diameter part which contacts the non-image area | region of both ends of a recording medium, and these small diameter parts and a small diameter part are characterized by the above-mentioned. Curl correction device.   The said 1st rotary body has a roller part which contacts the non-image area | region of a recording medium, and a support part which cantilever-supports this roller part, The Claim 1 characterized by the above-mentioned. Curl correction device.   A spur that can come into contact with the image area of the recording medium is provided coaxially with the first rotating body, and the spur is set to be smaller than a diameter of a portion that contacts the non-image area of the first rotating body. The curl correction apparatus according to claim 1.   The curl correction apparatus according to claim 1, further comprising a plurality of minute protrusions on a surface of a portion of the first rotating body that contacts the recording medium.   The curl correction apparatus according to claim 1, further comprising a non-contact type pressurizing unit configured to suppress paper floating on an image area sandwiched between non-image areas at both ends of the recording medium.   An image forming unit that forms an image by ejecting ink onto a recording medium, and the curl correction device according to any one of claims 1 to 8 disposed on the recording medium conveyance downstream side of the image forming unit. Image forming apparatus.

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