JP2014005085A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of image quality such as image disturbance or retransfer of ink to subsequent sheets while suppressing curl that can occur in a sheet, without waiting for ink of a formed image on the sheet to dry, and not to perform curl correction processing to recording media which do not require curl correction.SOLUTION: An image forming apparatus comprises droplet discharging means which forms an image by discharging droplets to a sheet and conveying means which conveys a sheet from an image forming process to a subsequent process. The conveying means comprises an endless attraction belt stretched over a plurality of rollers, and contacting rollers which can be switched to be in contact with or separate from the surface of the attraction belt are provided. The contact rollers come into contact with the attraction belt at areas outside an image forming area of a sheet attracted to the attraction belt, and thereby the attraction belt is pressed by the contact rollers in such a manner that the image forming surface of the attraction belt for the sheet has a concave shape.

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, a copying machine, a plotter, or a multifunction machine having these functions. More specifically, the present invention relates to a curl correction that corrects curl that occurs after an image is formed on a recording medium. It relates to the mechanism, and can be applied to other transport devices using inkjet technology such as textile printing.

  As one type of image forming apparatus, an ink jet method using a recording head that discharges ink droplets is known, and an ink liquid is applied to a recording medium (including not only plain paper but also an OHP sheet). A droplet is ejected to form an image (recording, printing, printing, and printing are also used synonymously). The inkjet image forming apparatus includes a serial type image forming apparatus that forms an image by ejecting liquid droplets while the recording head moves in the main scanning direction, and the recording heads are arranged in a line. There is a line-type image forming apparatus using a line-type head that forms an image by discharging droplets in a non-conducting state.

  In the present application, the “image forming apparatus” of the droplet discharge method is an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, and the like. “Image formation” not only applies an image having a meaning such as a character or a figure to a medium, but also applies an image having no meaning such as a pattern to the medium (simply a liquid droplet). To land on the medium). The “ink” is not limited to what is called ink, and is not particularly limited as long as it becomes liquid when ejected, and includes, for example, a DNA sample, a resist, a pattern material, and the like. The “image” is not limited to a flat image, but also includes an image given to a three-dimensionally formed image or an image formed by three-dimensionally modeling a solid itself.

  By the way, in such an ink jet image forming apparatus, when ink is applied, the surface of the paper that has absorbed the moisture of the ink expands, and moisture between the paper surface that is the printing surface and the paper back surface that is the non-printing surface. There is a tendency to curl so that the edge of the paper faces the back side due to the difference in amount. If the paper curls after recording, it adversely affects 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.

  For this reason, in order to suppress curling that may occur when recording an image, for example, in Patent Document 1, a sheet on which an ink droplet is ejected and an image is formed is sent to a suction holding device and sucked and held while being conveyed. By doing so, it is disclosed that the moisture of the paper is dried and then sent to the next step (reversing mechanism or paper discharge unit). Furthermore, an inclined surface is formed inward on the suction holding surface of the conveyor belt at the paper inlet portion of the suction holding device, and the surface is flattened from the concave state toward the paper outlet. It is also disclosed that the curl is corrected by the above. In Patent Document 1, it is stated that the moisture of the paper is dried without reducing the productivity. However, a suction holding device is installed between the recording head (printing unit) and the next process, and this suction holding device is provided. The sheet is dried in the meantime, and is in a state of waiting until the sheet is dried, and a decrease in productivity as the entire image forming apparatus cannot be avoided. In the case of a paper type that does not require curl correction or in an environment, the decurling process is attempted, so that an unnecessary load may be applied to the paper.

  In addition, it is known that a sheet is bent by a roller or the like in a direction opposite to the curl direction to be decurled (a curl correction device or a decurler). In general, the curl correction apparatus is mainly known as an image forming apparatus that forms and heat-fixes an image using toner. A configuration is disclosed in which a pair of two rollers is used as a roller pair, and the curl correction direction and the correction strength are determined in accordance with image forming ink ejection data recorded on the paper, and the decurling process is performed. Inkjet image forming apparatuses form an image by ejecting ink droplets onto a sheet, so that it takes some time for the ink droplets that have landed on the sheet to dry, and the ink droplets that have landed on the sheet are dried. In the meantime, you have to wait and decal. In order to speed up drying in Patent Document 2, a drying fan is provided between the ink discharge means and the decurling unit.

  However, in any case, in the curl correction 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 image forming apparatus, a decurling roller is formed on the image forming surface. Even if a dryer such as a drying fan is used, the image forming surface may be disturbed. 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.

  In view of the conventional problems as described above, an object of the present invention is to prevent image distortion and subsequent recording medium while suppressing curling that may occur on the recording medium without waiting for drying of the ink formed on the recording medium. It is an object of the present invention to provide an image forming apparatus that can avoid deterioration of image quality such as retransfer of ink to a recording medium and that does not perform curl correction processing on a recording medium that does not require curl correction.

  According to the present invention, the above object includes a droplet discharge unit that discharges droplets onto a recording medium to form an image, and a transport unit that transports the recording medium from the image forming process to the recording medium to the next process. In the image forming apparatus, the conveying unit includes an endless suction belt wound around a plurality of rollers, and a contact roller capable of switching contact and separation is provided on the surface of the suction belt. The contact roller is pressed by the contact roller so that the image forming surface of the recording medium on the suction belt becomes concave when the contact roller contacts the suction belt outside the image forming area of the recording medium sucked by Solved.

  According to the present invention, the recording medium is adsorbed on the adsorption belt, and the contact roller contacts the adsorption belt outside the image forming area of the recording medium, whereby the image forming surface of the recording medium on the adsorption belt becomes concave. Therefore, decaling can be performed without waiting for the ink to dry, and the image forming productivity of the apparatus is not lowered, and contamination by ink on the recording medium can be prevented. Moreover, since the contact roller can be contacted and separated, it can be processed only on a recording medium that requires curl correction, or it can be prevented from decurling in a relatively high humidity environment where curling is difficult.

1 is a schematic view of an ink jet image forming apparatus according to an embodiment of the present invention. FIG. 2 is a plan view of the vicinity of a recording head unit in the image forming apparatus of FIG. 1. It is a conceptual diagram which shows the drive relationship of a subscanning conveyance part. It is a perspective view at the time of the state where the curl correction mechanism is not decurled. FIG. 6 is a perspective view of the decurling device in a state where it is decurled without the decurling roller coming into contact with the end of the sheet. FIG. 10 is a perspective view of the curl correcting mechanism in which the decurling roller is in contact with the end of the sheet in a decurling state. FIG. 6 is a perspective view of a curl correction mechanism in which a decurling roller is displaced according to a width of a sheet in a decurling state. FIG. 5 is a side view seen from the paper discharge side for explaining a configuration in which a decurling roller can be moved in the axial direction so as to be compatible with various sizes of paper. It is a flowchart regarding the decurling operation | movement of a curl correction mechanism. 2 is a block diagram illustrating an outline of a control unit of the image forming apparatus. FIG.

  FIG. 1 is a conceptual diagram of an overall configuration of an ink jet image forming apparatus according to an example of the present invention as viewed from the front (depicted as an image recording apparatus and further including an image reading unit, but the depiction is omitted). This apparatus includes a conveyance belt unit 3 having a conveyance belt 31 that conveys a sheet 100 as a recording medium, a recording head unit 2 that forms an image by ejecting droplets on the sheet 100, and a paper feed tray that accommodates the sheet 100. A processing liquid coating apparatus 200 as coating means for coating the processing liquid 201 on the paper 100 on the upstream side in the paper transport direction with respect to the unit 103 and the recording head unit 2, and a reversing unit 4 for inverting the paper 100 on which an image is formed. It has.

  Here, as shown in FIG. 2, the recording head unit (image forming unit) 2 of the image forming apparatus includes a carriage in which heads of respective colors are arranged in the main scanning direction by a guide rod 21 and a guide stay (not shown). 23 is movably held in the main scanning direction, and is moved and scanned in the main scanning direction using the main scanning motor 27 via a timing belt 29 spanned between the driving pulley 28A and the driven pulley 28B.

  A recording head 22 composed of droplet discharge heads that discharge droplets of the respective colors is mounted on the carriage 23, the carriage 23 is moved in the main scanning direction, and a conveyance belt unit 3 that is a sub-scan conveyance unit. Thus, a shuttle type is formed in which droplets are ejected from the recording head 22 while the paper 100 is fed in the paper conveyance direction (sub-scanning direction). In this way, instead of the serial type configuration in which the recording head for ejecting droplets while moving in the main scanning direction to form an image is mounted on the carriage, the droplets are ejected without moving the liquid ejection head. A line-type head configuration can also be adopted.

  The recording head 22 ejects yellow (Y) ink, magenta (M) ink, and cyan (C) ink, respectively, one droplet ejection head 22y, 22m, and 22c, and ejects black (K) ink, respectively. Each of the droplet discharge heads 22k1 and 22k2 is composed of a total of five droplet discharge heads (hereinafter referred to as “recording head 22” when the colors are not distinguished from each other). Ink is supplied. As the recording head 22, a piezoelectric plate is used as pressure generating means (actuator means) for pressurizing ink in the ink flow path (pressure generation chamber), and the vibration plate forming the wall surface of the ink flow path is deformed to change the ink flow path. A so-called piezo-type device that discharges ink droplets by changing the internal volume, or a so-called thermal device that discharges ink droplets with pressure generated by generating bubbles by heating ink in the ink flow path using a heating resistor. The volume of the ink flow path is changed by deforming the vibration plate by the electrostatic force generated between the vibration plate and the electrode. In this case, an electrostatic type that discharges ink droplets can be used, and the droplet discharge means is not limited to the exemplified method.

  On the other hand, although not shown, each color ink cartridge, which is a recording liquid cartridge containing Y ink, M ink, C ink, and K ink, can be detachably mounted on the cartridge mounting portion from the front side of the apparatus. Ink is supplied to the sub-tank 25 of each color. Note that the black ink is supplied to the two sub tanks 25 from one ink cartridge.

  Further, as shown in FIG. 2, a maintenance / recovery device 221 for maintaining and recovering the nozzle state of the recording head 22 is arranged in the non-printing area on one side (rear side of the apparatus) of the carriage 23 in the scanning direction. ing. The maintenance / recovery device 221 includes five moisturizing caps 222y, 222m, 222c, 222k1, and 222k2 for capping the head nozzle surfaces of the five recording heads 22 (if the colors are not distinguished, the “humidity retaining cap 222 ”, A single suction cap (not shown), a wiper blade 224 for wiping the nozzle surface of the recording head 22, and ejection of droplets that do not contribute to recording (image formation) (empty ejection). An empty discharge receiving member 225 and the like are provided.

  Furthermore, in the non-printing area on the other side of the carriage 23 in the scanning direction (the front side of the apparatus), as shown in FIG. 2, the ejection of droplets that do not contribute to recording (image formation) from the five recording heads 22 (empty ejection). An empty discharge receiving member 226 is provided. The empty discharge receiving member 226 is formed with five openings 227y, 227m, 227c, 227k1, and 227k2 corresponding to the recording head 22 (referred to as “openings 227” when colors are not distinguished).

  As shown in FIG. 3, the conveyance belt unit 3 (sub-scanning conveyance unit) is a driving roller for electrostatically attracting the sheet 100 fed from below and conveying the sheet 100 facing the recording head unit 2. The conveyance roller 32, the conveyance roller 33 that secures the plane of the image area with the roller 32, and the roller 33 as a fulcrum are rotated by the first link 36 between the solid line position and the broken line position in FIGS. An endless shape spanned between the separation roller 34 that switches the conveyance path and the tension roller 35 that is a belt tension roller that rotates between the solid line position and the broken line position around the rotation fulcrum 37a by the second link 37. An electrostatic adsorption conveyance belt 31 is provided. Further, a high voltage, which is an alternating voltage and / or a DC voltage, is applied to the conveyor belt unit 3 from a high-voltage power supply (AC and / or DC bias supply unit) (not shown) in order to charge the surface of the conveyor belt 31. A charging roller 39 as a charging means, a guide member 40 for guiding the conveyance belt 31 in a region facing the recording head unit 2, and a pressing roller (pressure roller) that presses the paper 100 against the conveyance belt 31 at a position facing the conveyance roller 32. ) 38 (It is more desirable that the surface of the press roller 38 is made conductive so that the electric charge can be dropped to the ground in order to lower the surface potential on the paper. Further, a high voltage is applied to the press roller 38 from a high voltage power source to Decurling which suppresses curling of the paper 100 on which an image is formed by the recording head unit 2. Over La 52a, and includes a 52 b, decal support roller 51a for supporting from below the electrostatic adsorption transport belt 31, and 51b, a separation roller 34 for separating curvature separation. The separation roller 34 is disposed at least at a position (predetermined minimum distance a) where the belt contacts the conveying roller 33 with tension. As a result, a stable image can be formed without changing the posture of the electrostatic attraction conveyance belt 31 in the image forming area even when the conveyance path is switched.

  The conveyance belt 31 of the conveyance belt unit 3 rotates in the sheet conveyance direction (sub-scanning direction) in FIG. 2 when the conveyance roller 32 is rotated by the sub-scanning motor 231 via the timing belt 232 and the timing roller 233. It is configured as follows. The transport belt 31 in this example is, for example, a surface layer that becomes a sheet adsorbing surface formed of a pure resin material that is not subjected to resistance control, such as ETFE pure material, and resistance control by carbon using the same material as the surface layer. However, the present invention is not limited to this, and a single-layer structure or a structure having three or more layers may be used.

  A paper feed tray unit (paper feed unit) 103 can be inserted / removed from the front side of the apparatus, and separates the paper feed cassette 104 for loading and storing a large number of paper 100 and the paper 100 in the paper feed cassette 104 one by one. A pick-up roller 115 for feeding out and a pair of conveying rollers including a paper feed roller 116a and a separation roller 116b are provided. Further, a manual feed tray 105 that manually feeds the paper 100, and a pickup roller 181 and a conveyance roller pair 182 for feeding the paper 100 one by one from the manual feed tray 105 are provided.

  The treatment liquid coating apparatus 200 includes a treatment liquid container (not shown) in which a deformable PET film containing the treatment liquid 201 is formed in a bag shape, and a pump (not shown) that pumps the treatment liquid 201 supplied from the treatment liquid container. And an application unit 210 for applying the treatment liquid 201 to the paper 100. The treatment liquid 201 in the treatment liquid container is sucked up by a pump and supplied to the liquid chamber 202 in the application unit 210 through a supply conveyance path (not shown) to prepare for application.

  The processing liquid 201 supplied to the liquid chamber 202 is confirmed by a liquid level detection sensor (not shown) provided in the liquid chamber 202 to have a liquid level height and a liquid level angle within a predetermined range. For example, an electrode pin type sensor is used as the liquid level detection sensor. The electrode pin method is a known technique and will not be described in detail here, but the liquid level is detected by energizing the electrode pins and conducting electricity between the electrode pins via the liquid. By this method, it is possible to prevent insufficient supply of the processing liquid 201 and supply of a predetermined amount or more to the liquid chamber 202.

  The application unit 210 has a transport roller 234 that conveys the paper 100, an application roller 235 that applies the processing liquid 201 to the paper 100 facing the roller, and supplies the processing liquid 201 to the application roller 235 to thin the liquid film. And a squeeze roller 236. These rollers are arranged such that the application roller 235 is in contact with the transport roller 234 and the squeeze roller 236 is in contact with the application roller 235. Then, a liquid film layer of the processing liquid 201 supplied by the squeeze roller 236 and the application roller 235 is formed, transferred to the transport roller 234 side by the rotation of the application roller 235, and applied to the paper 100.

  Here, the treatment liquid 201 is a modifying material that modifies the surface of the paper 100 by being applied to the surface of the paper 100. For example, the treatment liquid 201 is spread evenly on the paper 100 in advance, so that the moisture of the ink can quickly permeate the paper 100, the viscosity of the color component is increased, and further, the drying is also accelerated, thereby fading (feathering). , Bleeding, etc.) and back-through, and can improve productivity (number of image output per unit time) (fixing agent). In terms of composition, this treatment liquid 201 is, for example, cellulose that promotes moisture permeation with respect to a surfactant (any one of anionic, cationic, nonionic, or a mixture of two or more thereof). And the like (hydroxypropylcellulose etc.) and a solution to which a base such as talc fine powder is added. Furthermore, fine particles can be contained.

  The paper 100 stored in the paper feed cassette 104 is separated and fed one by one by a pickup roller 115, sent to an intermediate transport roller pair (positioning roller) 124 by a pair of transport rollers 116 and 126, and predetermined by the intermediate transport roller pair 124. Is sent to the processing liquid coating apparatus 200 via the paper feed conveyance path 300, and the processing liquid 201 is applied by the processing liquid coating apparatus 200.

  Here, first, a method of discharging paper with the recording surface facing downward after image formation by the recording head unit 2 will be described. The paper 100 coated with the treatment liquid 201 is conveyed to the print conveyance path 305. In the conveyance path 305, the paper 100 is fed onto the electrostatic adsorption conveyance belt 31 on which an alternating electric field or a DC electric field is formed, and is adsorbed and held by static electricity. By driving the recording head 22 based on the image signal while moving the carriage 23 with respect to the paper 100 held at the image formation start position, ink droplets are ejected onto the stopped paper 100 to make one line. When recording is completed and recording for one line is completed, the sheet 100 is intermittently conveyed so that the sheet 100 is fed by one line and the next line is recorded, and an image is formed on the sheet 100. Upon receiving a recording end signal or a signal that the trailing edge of the paper 100 has reached the recording area, the recording operation is completed.

  The sheet 100 on which the image is formed is conveyed by the circular movement of the conveyance belt 31 indicated by a solid line (FIG. 1) and separated from the conveyance belt 31 at the solid line position of the separation claw 41 via the reverse conveyance path 307, while conveying rollers. The pair 184 is conveyed to the reversing unit 4. The paper 100 transported to the reversing unit 4 is then transported to the reverse paper discharge transport path 309 by the transport roller pair 184 that rotates in the reverse direction, and is moved out of the apparatus with the recording surface facing downward by the transport roller pair 185 and transport roller pair 186. The paper is ejected.

  When the recording head unit 2 forms an image and discharges the paper with the recording surface facing upward, the process of forming an image on one side of the paper 100 is the same as when discharging the paper with the recording surface facing downward. Then, the sheet 100 on which the image is formed is conveyed by the circular movement of the conveying belt 31 indicated by a broken line, and is discharged outside the apparatus by the conveying roller pair 186 through the discharge conveying path 306 with the recording surface facing up. .

  Next, a case where images are formed on both sides of a sheet will be described. The process of forming an image on one side of the paper 100 is the same as the above two examples. The sheet 100 on which an image is formed on one side (first side) is conveyed by the circumferential movement of the conveying belt 31 indicated by a solid line and is separated from the conveying belt 31 at the position indicated by the solid line of the separation claw 41 via the reverse conveying path 307. Then, it is conveyed to the reversing unit 4 by the conveying roller pair 184. Thereafter, the separation claw 41 is switched to the broken line position, and the sheet 100 conveyed to the reversing unit 4 is conveyed to the double-sided conveyance path 304 by the conveying roller pair 184 rotating in the reverse direction, and intermediately conveyed by the conveying roller pair 193, 194, 195. It is sent to the roller pair 124, sent from the intermediate transport roller pair 124 to the processing liquid coating apparatus 200 via the paper feed transport path 300 at a predetermined timing, and the processing liquid 201 is applied again by the processing liquid coating apparatus 200.

  The sheet 100 coated with the treatment liquid 201 is image-formed on the second surface in the same process as when the image is formed on the first surface. The sheet 100 on which images are formed on both sides is conveyed by the circular movement of the conveyance belt 31 indicated by a broken line, and is discharged out of the apparatus by a pair of conveyance rollers 186 via a discharge conveyance path 306.

  Next, a mode in which paper is fed and conveyed from the manual feed tray 105 in a substantially straight line, and discharged from the image forming unit in a substantially straight line after image formation will be described. By such a manual feed mode, an image can be easily formed on special paper such as cardboard or release paper.

  The sheets 100 stacked on the manual feed tray 105 are separated and fed one by one by the pickup roller 181 and conveyed to the print conveyance path 305 by the conveyance roller pairs 182 and 183. In the conveyance path 305, the paper 100 is fed onto the electrostatic adsorption conveyance belt 31 on which an alternating electric field or a DC electric field is formed, and is adsorbed and held by static electricity. By driving the recording head 22 based on the image signal while moving the carriage 23 with respect to the paper 100 held at the image formation start position, ink droplets are ejected onto the stopped paper 100 to make one line. When recording is completed and recording for one line is completed, the sheet 100 is intermittently conveyed so that the sheet 100 is fed by one line and the next line is recorded, and an image is formed on the sheet 100. Upon receiving a recording end signal or a signal that the trailing edge of the paper 100 has reached the recording area, the recording operation is completed. The sheet 100 on which the image is formed is conveyed by the circular movement of the conveying belt 31 indicated by a broken line, and is discharged out of the apparatus by the conveying roller pair 186 through the discharge conveying path 306 with the recording surface facing up.

  Next, curl suppression of this example will be described with reference to FIGS. The decurling rollers 52a and 52b located on the downstream side of the recording head unit 2 in the sheet conveying direction are respectively decurled and retracted about the fulcrums 53a and 54a by third and fourth links 53 and 54 that are driven independently of each other. It arrange | positions so that rotation is possible. In FIG. 3, the decurling position is indicated by a solid line, and the retracting position where the decurling is not performed is indicated by a broken line. By switching the position of the decurling roller in this way, the decurling roller is not separated from the conveying belt 31 in the case of using a sheet that is relatively thick and difficult to curl, or in a relatively humid environment that is difficult to curl. Can be. Further, in this example, since the decurling is performed while being electrostatically attracted to the conveyance belt 31, a higher attracting force is required to decal under a thick paper that is difficult to electrostatically attract or in a high humidity environment that is difficult to electrostatically attract. In light of this, it is desirable not to decal paper types that do not require decals from the viewpoint of energy saving.

  In addition, a plurality of decurling rollers are provided in each of the paper conveyance direction and the paper width direction orthogonal to the paper conveyance direction, and the roller on the downstream side in the paper conveyance direction has a larger radius of curvature than the upstream roller. That is, the roller diameter of the second decurling roller 52b is larger than that of the first decurling roller 52a. This is because curling has already been suppressed by the unevenness of the electrostatic adsorption conveyance belt 31 formed by the upstream roller, and when the paper passes between the downstream decurling roller and the conveyance belt, the paper is electrostatically This is because the curvature can be easily separated from the suction conveyance belt 31. The curvature radius of the downstream roller is set large so that the sheet does not separate the curvature, so that the sheet can be sucked and conveyed more stably.

  FIG. 4 is a perspective view when not decurled. As shown in FIG. 4, the decurling rollers 52 a and 52 b stand by in a state of being separated from the electrostatic adsorption conveyance belt 31 (retracted position). On the other hand, FIG. 5 is a perspective view showing a state where the decurling rollers 52a and 52b are brought into contact with the conveying belt 31 (decaling position) and the sheet is decurled. Elastic members, for example, guide members 31a made of urethane are provided at both ends of the conveyance belt 31 in the paper width direction. By pressing the inner side of the guide member with a decal roller, it is possible to form unevenness for decurling on the belt by pressing only the belt end. The decurling roller 52 is arranged outside the end in the sheet width direction of the sheet to be passed, so that decaling can be performed without touching the image surface regardless of the sheet size.

  In contrast to the above example where the decal roller does not touch the paper edge, FIG. 6 shows a configuration in which the paper edge is pressed by the decal roller. By pressing the edge of the sheet where no image is present, the electrostatic adsorption conveyance belt 31 and the sheet can be more reliably brought into contact with each other, and can be conveyed while being decurled without any problem even with a relatively low electrostatic adsorption force.

  Another configuration example is shown in FIG. In the example of FIG. 7, in addition to the first decurling roller 52 a and the second decurling roller 52 b disposed at both ends (inside the guide member 31 a) of the electrostatic adsorption conveyance belt 31, the sheet conveyance direction is matched to the width of the sheet to be passed. Are provided with third and fourth decurling rollers 52c and 52d that are movable in a direction orthogonal to the first direction. FIG. 8 shows a specific configuration example for enabling the decurling roller to move in the axial direction so as to correspond to various paper sizes. The position of the decurling roller 52d can be adjusted by moving levers 150 and 151 that are attached to a linear actuator (DC solenoid) and pivotally support the decurling roller 52d. That is, the position of the fourth decurling roller 52d is moved using the moving levers 150 and 151 so as to match the position of the non-image area that changes according to the size of the paper and the vertical and horizontal orientations during conveyance.

  With such a configuration, it is possible to press the end of all the paper sizes to be passed through, and more reliably bring the conveyance belt 31 and the paper into close contact with each other. Can be transported.

  Next, the decurling operation in the configuration shown in FIG. 7 will be described with reference to FIG. When a print start signal is received, the presence / absence of a decurling operation is determined. If there is no decurling operation, printing is performed until the end of the printing job in a normal printing operation.

  When there is a decurling operation, a signal for determining the strength of decurling suppression is received. The decurling strength is set so that it is weak when the environment is relatively high, for example, weak when the paper is relatively thick, and weak when the paper is difficult to curl, such as inkjet paper. As a result, it is possible to prevent the occurrence of curling in the reverse direction due to the decurling operation.

  In the configuration of FIG. 7, the maximum decurling effect is obtained by applying both the upstream roller (52a or 52a and 52c) and the downstream roller (52b or 52b and 52d) perpendicular to the paper transport direction (transport belt moving direction). This is the case of contact. Next, the case where the decurling effect is large is a case where upstream rollers (52a or 52a and 52c) having a relatively small diameter are brought into contact with each other. The decurling effect is the smallest when the downstream rollers (52b or 52b and 52d) having a relatively large diameter are brought into contact with each other. The strength of the decurling effect may be selected as appropriate according to the type of paper, the environment, the amount of ink ejected on the paper, etc., and adjusted to the optimum decurling amount, and is not limited to the above description. However, if the amount of decurling is too large, curling will occur in the opposite direction, so it is desirable that the amount of decurling can be selected appropriately in stages.

  Next, it is determined whether or not to hold the edge of the paper depending on the paper type and environment. In the case of thin paper with relatively good adsorptivity or in a low humidity environment, it is not necessary to press the edge of the paper, and the decurling rollers 52a and / or 52b are selected regardless of the paper size. When pressing the end of the paper, the arrangement of the decurling rollers 52c and / or 52d is moved to a position where the end of the paper can be pressed based on the information about the end of the paper. Thereafter, the selected decurling roller 52 is brought into pressure contact with the conveyor belt 31 via the link 53 or 54 with the rotation fulcrums 53a and 54a as fulcrums. Thereafter, printing is performed by a normal printing operation, and the decurling operation is stopped upon completion of printing JOB.

  Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. The figure is a schematic block diagram of the control unit. This control unit 400 shuts off the power of the apparatus, the CPU 401 that controls the entire apparatus, the ROM 402 that stores programs executed by the CPU 401 and other fixed data, the RAM 403 that temporarily stores image data (print data), and the like. A non-volatile memory (NVRAM) 404 for holding data and ASIC 405 for processing various signal processing and rearrangement of image data and other input / output signals for controlling the entire apparatus. And a scanner control unit 406 that performs image reading by the image reading unit 11 (not shown in FIG. 1), data processing of the read image, and the like.

  The control unit 400 also has an I / F 407 for transmitting and receiving data and signals used when receiving data from an external device, and a head drive control for controlling the recording head 22 of the recording head unit 2. Section 408 and head driver 409, main scanning motor 27 for main scanning of carriage 23, sub-scanning motor 231 for rotating driving and conveying roller 32 and rotating conveying belt 31, feeding motor 45, and feeding and conveying section (feeding section) A transport motor 318 that rotates the rollers in the transport path (from the paper transport path 300 to the print transport path 305), a discharge motor 271 that rotates the rollers in the discharge transport path 306, and the rollers in the duplex transport path 304. A module including a motor driver for independently driving various motors (drive sources) such as a double-sided conveyance motor 291 to be driven. And a motor drive unit 211～215,317.

  In addition, a feeding electromagnetic clutch for independently driving the pickup rollers 115 and 181 and the conveying roller pair 116 and 182, an electromagnetic clutch for independently driving the conveying paths, and a separation claw for switching the conveying paths. A clutch drive unit 216 for driving a branch solenoid or the like (which is referred to as “clutch 241”) that swings and displaces 41, links 53 and 54 that are driven for decurling by a curl correction mechanism, and a moving lever And a decurling roller control control driving unit 311 for driving them, an adsorption conveyance control driving unit 312 for applying a high voltage to the charging roller 39 and electrostatically adsorbing the paper 100 to the conveyance belt 31, and the like.

  Further, the control unit 400 captures I / O for capturing detection signals from a temperature / humidity sensor 330 that detects temperature and humidity as environmental conditions, and detection signals from various sensors such as an image start sensor and an image end sensor (not shown). Further, an operation panel 332 for inputting and displaying information necessary for the apparatus is connected. Here, if the temperature / humidity sensor 330 is provided in the vicinity of the paper feed cassette that houses the paper 100, the temperature and humidity around the paper 100 to be fed can be detected. The amount of moisture to be obtained can be obtained, and more accurate anti-curl control can be performed. Further, if the temperature / humidity sensor 330 is provided in the vicinity of the conveyance position of the paper 100 after the image formation by the recording head 22 is completed, the temperature / humidity around the paper 100 after the image formation is completed can be detected. The dried state of the paper 100 after completion can be obtained, and more accurate curl prevention control can be performed. The temperature / humidity sensor 330 can also be provided at other conveyance path locations.

  When the original image is read by the image reading unit, the control unit 400 processes the read image and stores it in a buffer in the scanner control unit 406. In addition, when print data or the like is received from an external host such as an information processing apparatus such as a personal computer, an image reading apparatus such as an image scanner, or an imaging apparatus such as a digital camera via the external I / F 407, the I / F 407 Store in the included receive buffer. The CPU 401 reads out and analyzes the image data from the scanner control unit 406 and the I / F 407, performs necessary image processing, data rearrangement processing, and the like in the ASIC 405, and transfers the print image data to the head drive control unit 408. To do. Note that the generation of dot pattern data for image output based on external data may be performed by storing font data in the ROM 402, for example, or image data is converted into bitmap data by a printer driver on the external host side. The image may be developed and transferred to the image forming apparatus.

  When the head drive control unit 408 receives image data (dot pattern data) corresponding to one row of each recording head 22, the head drive control unit 408 transfers the dot pattern data for one row to the head driver 409. Based on the pattern data, a required drive waveform is selectively applied to the actuator means of the recording head 22 to drive it, and droplets are ejected from the required nozzles of each recording head 22.

  In the image forming apparatus configured as described above, the paper 100 is fed one by one from the paper feed tray unit 103 or the manual feed tray 105, electrostatically attracted to the transport belt 31, and the paper is moved by the circular movement of the transport belt 31. 100 is conveyed in the sub-scanning direction. Therefore, by driving the recording head 22 based on the image signal while moving the carriage 23, ink droplets are ejected onto the stopped paper 100 to record one line, and the recording for one line is completed. Then, the paper 100 is intermittently transported to form an image on the paper 100 such that the paper 100 is fed by one line and the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the paper 100 has reached the recording area, the recording operation is completed. Thereafter, as described above, the sheet 100 is sent out to the outside of the apparatus as the conveyance destination or the reverse conveyance path through the conveyance path.

2 Recording Head Unit 3 Conveying Belt Unit 4 Reversing Section 21 Guide Rod 22 Recording Head 23 Carriage 25 Subtank 27 Main Scanning Motor 29 Timing Belt 31 Electrostatic Adsorption Conveying Belt 39 Charging Roller 40 Guide Member 52 Decal Roller 53 Third Link 54 Fourth Link 100 Paper 103 Paper feed tray unit 104 Paper feed cassette 105 Manual feed tray 200 Processing liquid coating device 201 Processing liquid 210 Coating section 221 Maintenance recovery device 231 Sub-scanning motor

Japanese Patent No. 4581741 JP 2010-70342 A

Claims (5)

  An image forming apparatus comprising: a droplet discharge unit that discharges droplets onto a recording medium to form an image; and a transport unit that transports the recording medium from an image forming process to the recording medium to the next process. An image forming area of a recording medium adsorbed on the adsorbing belt, wherein the means has an endless adsorbing belt wound around a plurality of rollers, and an abutting roller capable of switching contact and separation is provided on the surface of the adsorbing belt An image forming apparatus, wherein the abutting roller is pressed by the abutting roller so that the image forming surface of the recording medium on the adsorbing belt becomes concave when the abutting roller abuts on the attracting belt.   The image forming apparatus according to claim 1, wherein contact rollers are arranged at a plurality of locations in the recording medium conveyance direction, and the diameter of the downstream contact roller is larger than the diameter of the upstream contact roller. .   The image forming apparatus according to claim 2, wherein the upstream contact roller and the downstream contact roller can contact and separate from the suction belt independently of each other.   The image forming apparatus according to claim 1, further comprising a contact roller that is movable in a direction orthogonal to the recording medium conveyance direction.   The image forming apparatus according to claim 4, wherein the movable contact roller is adjustable so as to contact an end portion of the recording medium outside the image forming area of the recording medium.

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