JP2011195296A - Paper floating detection device, paper conveying device, and image recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively and reliably detect the floating of paper, particularly, the high-speed floating of the rear end of the paper by a simple structure.SOLUTION: This paper floating detection device 300 comprises a paper pressing roller 42 for pressing paper P on a conveying surface. In the paper floating detection device, a light emitting unit 310 and a light receiving unit 312 which are disposed so as to face each other with a conveying path interposed therebetween are disposed near the downstream side of the paper pressing roller 42 in the conveying direction so that the optical axis L of a detection beam emitted from the light emitting unit 310 and received by the light receiving unit 312 is generally perpendicular to the conveying direction. The paper floating detection device detects that the paper P to be conveyed shields the detection beam to detect the floating of the paper P from the conveying surface. A paper floating suppression means 320 which hardly floats a part of the rear end of the paper P to be conveyed in the lateral direction is installed between the paper pressing roller 42 in the conveying path and the position of the optical axis L of the detection beam.

Description

  The present invention relates to a sheet floating detection apparatus, a sheet conveying apparatus, and an image recording apparatus, and more particularly to a sheet floating detecting apparatus, a sheet conveying apparatus, and an image recording apparatus that detect sheet floating in an inkjet recording unit in an inkjet printing system. .

  2. Description of the Related Art Conventionally, an image forming apparatus has an inkjet head in which a large number of nozzles (ink discharge ports) are arranged, and a recording medium is conveyed relative to the inkjet head, and ink is directed from the nozzle toward the recording medium. 2. Related Art Inkjet recording apparatuses (inkjet printers) that form images on a recording medium by ejecting them as ink droplets are known.

  In such an ink jet recording apparatus, when the ink jet head and the recording medium are relatively transported, the nozzles of the ink jet head are very close to the recording medium being transported, so that the recording medium passes near the ink jet head. When the recording medium is lifted from the transport surface, the ink hitting height is different, resulting in poor image quality, the recording medium rubbing against the nozzle surface and damaging the nozzle surface, or the recording medium colliding with the nozzle. In some cases, dirt may adhere to the recording medium, or paper dust may clog the nozzles, resulting in problems such as ejection failure.

  Therefore, conventionally, for example, a lifting detection device that detects the lifting amount of the recording medium is provided, and when a lifting of a predetermined amount or more of the recording paper is detected, an alarm is issued or the conveyance of the recording medium is stopped. Like to do.

  For example, in Japanese Patent Laid-Open No. 2004-228688, the paper floating is detected by detecting with an optical sensor that the paper floating detection plate has been rotated by abutting the floating paper against the lower end of the paper floating detection plate. An image recording apparatus having a recording medium floating detection unit is described.

  Japanese Patent Application Laid-Open No. 2004-228561 describes whether or not the end of the recording medium floats and the end of the recording medium based on a profile indicating the relationship between the amount of reflected light in the scanning direction of the recording medium and the position of the reflective optical sensor. A recording apparatus having a reflective optical sensor provided on a carriage for detecting the position of the recording medium is described.

  Further, for example, Patent Document 3 describes an ink jet printer in which pressing of a nip roller against a conveyance roller is released when a floating detection device including a floating detection plate and a photo sensor detects floating of a recording medium on a platen. Has been.

JP 2006-341474 A JP 2006-240138 A JP 2006-231557 A

  However, in the case of the above-mentioned Patent Document 1, when the paper is floating, the floating detection plate rotates directly in contact with the floating portion, and the optical sensor receives the light blocked by the floating detection plate. Although the floating of the paper is detected, there is no description that a roller or the like is additionally arranged so that the response speed of the optical sensor can follow. Further, in this method, when the detection position is in the vicinity of the conveyance table and the sheet pressing roller, it is very difficult in terms of working distance to provide a member that rotates in contact with the sheet. In addition, if the rotating member is a weak member that rotates at the waist of a light paper, there is a possibility that it will break when a jam occurs. No longer reacts, and there is a problem that paper floating cannot be detected.

  Further, the one described in Patent Document 2 reflects light on a recording medium, receives the reflected light by a reflection type light receiving sensor, and measures the received light intensity to detect the floating of the recording medium. Although it has been disclosed that the measurement data collection speed is slow enough not to affect the responsiveness of the reflective optical sensor, there is no description of the arrangement of a roller or the like for detecting floating.

  Moreover, although the thing of the said patent document 3 detects the floating of a recording medium with a photo sensor, and there is description that the nip roller which presses a recording medium separates and detects a floating, when it detects, the floating There is no disclosure regarding a technique for reliably detecting the above.

  In addition, the paper is pressed against the paper carrier by the rollers and is held by the paper carrier, and is transported near the head. However, the paper may curl away from the carrier, be transported by drums, or lift the paper. When the sheet holding force to the sheet transport table is poor, the trailing end of the sheet may be separated from the sheet pressing roller and at the same time may jump up at a high speed due to the strong repulsive force of the sheet.

  The problem at this time will be described with reference to the drawings. FIG. 6 is a side view showing the periphery of the paper floating detection device provided in the vicinity of the inkjet head. In FIG. 6, a sheet 902 is conveyed on the conveyance table 900 as indicated by an arrow A, and ink is ejected from the inkjet head 904 onto the sheet 902 to draw an image. A paper pressing roller 906 is disposed on the upstream side of the ink jet head 904 and presses the paper 902 against the transport table 900. A paper floating detection device (not shown) is disposed between the paper pressing roller 906 and the inkjet head 904.

  This sheet floating detection device is configured such that light in an optical path formed by a light emitting element and a light receiving element arranged in a direction substantially perpendicular to the sheet conveying direction (arrow A direction) on the sheet conveying surface is blocked by the sheet. In this case, it is detected that the paper is floating. FIG. 6 shows a cross section of the optical path (optical axis) by reference numeral 908.

  At this time, if the sheet 902 is curled away from the transport table 900, the sheet trailing edge 902a is separated from the sheet pressing roller 906 and at the same time, as indicated by an arrow B in FIG. Jump up at high speed. As shown in FIG. 6, when the entire trailing edge 902a of the sheet (the entire width direction) jumps at a high speed at the same time, the cross section of the sheet 902 momentarily crosses the optical path 908. There is a problem that cannot be detected.

  In this case, if the sheet 902 is conveyed as it is without detecting sheet floating, the sheet 902 comes into contact with the nozzle surface 910 of the inkjet head 904.

  On the other hand, it is conceivable to increase the detection speed electrically in order to detect such a high-speed floating at the rear end of the paper at a high speed, but it becomes difficult to separate it from noise. After all, there is a problem that it is difficult to detect high-speed floating.

  Note that Patent Document 2 and Patent Document 3 do not describe a technique for detecting a recording medium that floats at high speed.

  The present invention has been made in view of such circumstances, and has a simple structure and a low cost, and can reliably detect sheet floating, particularly high-speed floating at the trailing edge of the sheet, and sheet conveyance. An object is to provide an apparatus and an image recording apparatus.

  In order to achieve the object, the invention described in claim 1 has a sheet pressing roller for pressing the sheet onto the conveying surface, and is opposed to each other across a conveying path for conveying the sheet in a predetermined conveying direction. The conveyance of the paper pressing roller is arranged such that the optical axis of the detection light emitted from the light projection unit and received by the light reception unit is substantially perpendicular to the conveyance direction. A sheet floating detection device that is disposed in the vicinity of a downstream side of the sheet and detects the lifting of the sheet from the conveyance surface by detecting that the sheet being conveyed blocks the detection light, the sheet being conveyed A sheet floating suppression means for making it difficult to lift a part in the width direction of the rear end portion is provided between the sheet pressing roller of the transport path and the position of the optical axis of the detection light. Providing paper floating detection device is characterized in that to detect the paper floating immediately after separating the paper pressing rollers.

  As a result, the force that causes the entire trailing edge width direction of the sheet after the separation of the sheet pressing roller to float simultaneously is prevented from floating by the sheet lifting restraining means so that only a part in the sheet width direction is lifted. By twisting the paper to be tried and increasing the detection area of the paper with respect to the detection light, it is possible to reliably detect the paper floating.

  According to a second aspect of the present invention, the sheet floating suppression means is a roller or a guide plate that presses a part of the sheet against the transport surface.

  According to a third aspect of the present invention, the sheet floating restraining means is a fluid spraying means for spraying a fluid onto a part of the sheet.

  As a result, the detection area of the paper can be increased with a simple configuration, and the paper floating can be reliably detected.

  According to a fourth aspect of the present invention, the portion where the sheet floating suppressing means makes it difficult to lift a part of the sheet is closer to the end in the width direction than the center in the width direction of the rear end of the sheet. Features.

  As a result, as seen from the optical axis direction of the detection light for detecting the paper floating, the paper floating is surely detected by using the light shielding area due to the paper that expands due to the paper springing up and the twisting of the paper caused by pressing one point. be able to.

  Similarly, in order to achieve the above object, the invention according to claim 5 includes a sheet pressing roller that presses the sheet onto the conveyance surface, and sandwiches a conveyance path for conveying the sheet in a predetermined conveyance direction. A light projecting unit and a light receiving unit that are arranged to face each other are arranged in the vicinity of the downstream side of the transport direction of the paper pressing roller, and by detecting that the transported paper blocks the detection light, A paper floating detection device for detecting a lift from the transport surface, wherein an optical axis of detection light emitted from the light projecting unit and received by the light receiving unit is inclined at a predetermined angle with respect to a direction perpendicular to the transport direction There is provided a paper floating detection device characterized in that it is configured as described above.

  According to a sixth aspect of the present invention, the transport surface is a drum transport surface that rotates and transports the paper while holding the paper on a peripheral surface thereof, and the predetermined angle is 0.3 ° to 3 °. It is characterized by.

  Accordingly, it is possible to reliably detect the floating of the trailing edge of the sheet at low cost without the need for a sheet floating suppressing unit such as a roller, a guide plate, or a fluid spraying unit for making it difficult to lift only a part of the sheet.

  Similarly, in order to achieve the above object, the invention according to claim 7 provides a paper conveyance device comprising the paper floating detection device according to any one of claims 1 to 6. .

  Similarly, in order to achieve the above-mentioned object, the invention according to claim 8 is characterized in that a transport base for transporting a sheet in a predetermined transport direction while holding the sheet on the front transport surface, and the sheet on the transport surface. A sheet pressing roller to be pressed, and a light projecting unit and a light receiving unit which are disposed in the vicinity of the sheet pressing roller downstream in the transport direction so as to face each other across the transport path for transporting the paper, and are emitted from the light projecting unit. A paper lift detection device that detects the lifting of the paper from the transport surface by detecting that the paper has blocked the detection light received by the light receiving unit, and a holding force for holding the paper on the transport surface Means for controlling the distribution in the sheet width direction between the sheet pressing roller and the sheet floating detection device in the conveyance path, and a rear end portion of the sheet to be conveyed The holding force is increased for a part of the direction to suppress simultaneous floating in the width direction of the trailing edge of the sheet immediately after the sheet is separated from the sheet pressing roller, and the trailing edge of the sheet presses the sheet pressing roller. Provided is a sheet conveying device characterized in that the sheet floating immediately after being separated is detected.

  As a result, it is possible to reliably detect high-speed jumping of the paper after the paper pressing roller is separated, and to take appropriate measures when the paper floating is detected.

  According to a ninth aspect of the present invention, the holding force for holding the sheet on the transport table is a vacuum suction force, and the suction force is increased for a part in the width direction of the rear end portion of the transported sheet. It is characterized by that.

  In addition, as shown in claim 10, the holding force for holding the paper on the transport table is an electrostatic attracting force, and electrostatic attracting coating is applied to a part of the transported paper and the rear end width direction. Characterized by strengthening.

  Thus, by controlling the holding force for holding the paper originally provided in the transport table, it is possible to make it difficult to lift a part in the paper trailing edge width direction without the need for special paper floating suppression means, Reliable sheet floating detection is possible.

  Similarly, in order to achieve the above object, an invention according to claim 11 provides an image recording apparatus comprising the sheet conveying device according to claims 7 to 10.

  As a result, it is possible to reliably detect the paper floating due to the high-speed jumping of the paper after the paper pressing roller is separated, so that it is possible to maintain the image quality.

  As described above, according to the present invention, the force to lift the entire trailing edge width direction of the sheet after the separation of the sheet pressing roller is lifted only by a part in the sheet width direction by the sheet floating suppressing means. By making it difficult, the sheet that is going to float at the same time is twisted, and the detection area of the sheet with respect to the detection light is increased, so that the sheet floating can be detected reliably.

1 is a schematic configuration diagram illustrating an overall configuration of an embodiment of an image recording apparatus in which a paper conveyance device including a paper floating detection device according to the present invention is incorporated. It is a block diagram which shows schematic structure of the control system of the image recording apparatus of this embodiment. FIG. 2 is a schematic configuration diagram illustrating a first embodiment of a paper floating detection device and a paper transport device including the same in an image recording unit, where (a) is a side view and (b) is a front view. The outline of 2nd Embodiment of the paper floating detection apparatus in an image recording part and a paper conveying apparatus provided with the same is shown, (a) is a side view, (b) is a front view. FIG. 6 is a perspective view of the vicinity of an image recording drum showing a schematic configuration of a third embodiment of a sheet floating detection device. It is a side view which shows the periphery of the paper floating detection apparatus provided in the vicinity of the inkjet head which shows the conventional problem.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, with reference to the accompanying drawings, a paper floating detection device, a paper transport device, and an image recording device according to the present invention will be described in detail.

  FIG. 1 is a schematic configuration diagram showing an overall configuration of an embodiment of an image recording apparatus in which a paper conveyance device having a paper floating detection device according to the present invention is incorporated.

  As shown in FIG. 1, an image recording apparatus 10 according to the present embodiment is a drawing apparatus that draws by an inkjet method using aqueous ink (ink containing water in a solvent) on a sheet of paper (recording medium) P. A paper feeding unit 20 that feeds the paper P, a processing liquid application unit 30 that applies a predetermined processing liquid to the printing surface (drawing surface) of the paper P, and cyan (C) and magenta (M ), Yellow (Y), and black (K) ink droplets are ejected from the inkjet head, and an image recording unit 40 that draws a color image, and ink drying that dries the ink droplets deposited on the paper P. The image forming apparatus includes a unit 50, a fixing unit 60 that fixes an image recorded on the paper P, and a collection unit 70 that collects the paper P.

  Conveying drums 31, 41, 51, 61 are provided in the processing liquid application unit 30, the image recording unit 40, the ink drying unit 50, and the fixing unit 60 as the conveying means for the paper P, respectively. The paper P is transported by the transport drums 31, 41, 51, 61 through the processing liquid application unit 30, the image recording unit 40, the ink drying unit 50, and the fixing unit 60.

  Each of the transport drums 31, 41, 51, 61 is formed corresponding to the sheet width, and is rotated by being driven by a motor (not shown) (rotates counterclockwise in FIG. 1). A gripper G is provided on the peripheral surface of each of the transport drums 31, 41, 51, 61, and the paper P is transported with the leading end gripped by the gripper G. In the present embodiment, grippers G are provided at two positions spaced apart by 180 ° on the peripheral surfaces of the respective transport drums 31, 41, 51, 61, so that two sheets can be transported by one rotation. Has been.

  In addition, a large number of suction holes are formed on the peripheral surfaces of the transport drums 31, 41, 51, 61, and the back surface of the paper P is vacuum-sucked from the suction holes, so that the transport drums 31, 41, 51 and 61 are held on the outer peripheral surface. In the present embodiment, the sheet P is vacuum-sucked and held on the outer peripheral surface of each of the transport drums 31, 41, 51, 61. It can also be set as the structure hold | maintained by suction on the outer peripheral surface of 31,41,51,61.

  Transfer cylinders 80, 90, and 100 are disposed between the treatment liquid applying unit 30 and the image recording unit 40, between the image recording unit 40 and the ink drying unit 50, and between the ink drying unit 50 and the fixing unit 60, respectively. Has been. The paper P is conveyed between the respective parts by the transfer cylinders 80, 90, 100.

  Each of the transfer cylinders 80, 90, and 100 includes transfer cylinder main bodies 81, 91, and 101 configured by a frame, and a gripper G provided on the transfer cylinder main bodies 81, 91, and 101. The transfer drum main bodies 81, 91, 101 are formed corresponding to the paper width, and are driven to rotate by a motor (not shown) and rotate clockwise in FIG. Thereby, the gripper G rotates on the same circumference. The paper P is transported with the gripper G gripping the leading end. In the present embodiment, the pair of grippers G are disposed at symmetrical positions with the rotation axis interposed therebetween, and are configured to be able to transport two sheets of paper P in one rotation.

  Under the transfer cylinders 80, 90, 100, arc-shaped guide plates 83, 93, 103 are arranged along the transport path of the paper P. The sheet P conveyed by the transfer cylinders 80, 90, 100 is conveyed while being guided by the guide plates 83, 93, 103 on the back surface (the surface opposite to the print surface).

  Further, dryers (hot air drying means) 84, 94, and 104 that blow hot air toward the paper P conveyed by the transfer drum 80 are disposed inside the transfer drums 80, 90, and 100. The hot air blown from the dryers 84, 94, 104 is blown against the printing surface of the paper P conveyed by the transfer cylinders 80, 90, 100.

  The paper P fed from the paper feeding unit 20 is transferred to the conveyance drum 31 of the processing liquid application unit 30, and is conveyed from the conveyance drum 31 of the processing liquid application unit 30 through the transfer drum 80 to the conveyance drum of the image recording unit 40. Passed to 41. Then, the image is transferred from the transfer drum 41 of the image recording unit 40 to the transfer drum 51 of the ink drying unit 50 via the transfer drum 90, and transferred from the transfer drum 51 of the ink drying unit 50 to the transfer drum 100 via the transfer drum 100. Delivered to the drum 61. Then, the paper is transferred from the conveyance drum 61 of the fixing unit 60 to the collection unit 70. In this series of conveyance processes, the paper P is subjected to required processing, and an image is formed on the printing surface.

  The paper P is transported to the transport drums 31, 41, 51, 61 with the print surface facing outward, and is transported to the transfer drums 80, 90, 100 with the print surface facing inward. Is done.

  Hereinafter, the configuration of each unit of the image recording apparatus 10 of the present embodiment will be described in detail.

<Paper Feeder>
The paper feeding unit 20 includes a paper feeding device 21, a paper feeding tray 22, and a transfer cylinder 23, and continuously feeds the sheets P one by one to the processing liquid application unit 30.

  The paper feeding device 21 feeds the paper P stacked in a magazine (not shown) one by one to the paper feeding tray 22 one by one from the top.

  The paper feed tray 22 sends out the paper P fed from the paper feeder 21 toward the transfer cylinder 23.

  The transfer cylinder 23 receives the paper P sent out from the paper feed tray 22, transports it along a predetermined transport path, and transfers it to the transport drum 31 of the treatment liquid application unit 30.

  As the paper P, a general-purpose printing paper that is not an inkjet dedicated paper is used.

<Processing liquid application part>
The processing liquid application unit 30 applies a predetermined processing liquid to the printing surface of the paper P. The treatment liquid application unit 30 applies a predetermined treatment liquid to a conveyance drum (hereinafter referred to as a treatment liquid application drum) 31 that conveys the paper P and a print surface of the paper P that is conveyed by the treatment liquid application drum 31. A treatment liquid application device 32 is provided.

  The treatment liquid application drum 31 receives the paper P from the transfer drum 23 of the paper supply unit 20 (holds and receives the leading edge of the paper P with the gripper G), and rotates to convey the paper P.

  The treatment liquid application device 32 applies a treatment liquid having a function of aggregating the color material in the ink to the printing surface of the paper P conveyed by the treatment liquid application drum 31. The treatment liquid application device 32 is constituted by, for example, a coating device that applies a treatment liquid to a roller, and presses and contacts the application roller with the treatment liquid applied to the peripheral surface against the surface of the paper P, thereby printing the printing surface of the paper P. The treatment liquid is applied to By applying ink in advance by applying such a treatment liquid, feathering and bleeding can be suppressed and high-quality printing can be performed even when general-purpose printing paper is used. . In addition, the treatment liquid application device 32 may be configured to be applied using a droplet discharge head similar to an inkjet head described later, or to be applied by spraying.

  According to the treatment liquid application unit 30 configured as described above, the paper P is conveyed along a predetermined conveyance path by the treatment liquid application drum 31, and the treatment liquid is applied from the treatment liquid application device 32 to the print surface in the conveyance process. Is done. The paper P with the treatment liquid applied to the printing surface is then transferred from the treatment liquid application drum 31 to the transfer cylinder 80 at a predetermined position.

  Here, as described above, a dryer 84 is installed inside the transfer drum 80, and hot air is blown out toward the guide plate 83. The paper P is blown with hot air on the print surface in the process of being conveyed from the treatment liquid application unit 30 to the image recording unit 40 by the transfer cylinder 80, and the treatment liquid applied to the print surface is dried (processing liquid). The solvent component therein is removed by evaporation).

<Image recording unit>
The image recording unit 40 ejects ink droplets of C, M, Y, and K colors on the printing surface of the paper P, and draws a color image on the printing surface of the paper P. The image recording unit 40 presses the conveyance drum (hereinafter referred to as an image recording drum) 41 that conveys the paper P and the printing surface of the paper P that is conveyed by the image recording drum 41, and the back surface of the paper P is imaged. A paper pressing roller 42 that is in close contact with the peripheral surface of the recording drum 41, a paper floating detection device 300 that detects the floating of the paper P that has passed through the paper pressing roller 42, and inks of C, M, Y, and K colors on the paper P It includes inkjet heads 44C, 44M, 44Y, and 44K that discharge droplets.

  The image recording drum 41 receives the paper P from the transfer cylinder 80 and rotates to convey the paper P. At this time, as described above, the paper P is conveyed while being held by suction on the outer peripheral surface of the image recording drum 41. Accordingly, the sheet P has an arc-shaped surface (area from receiving the sheet P from the transfer cylinder 80 and delivering the sheet P to the transfer cylinder 90) defined by the outer peripheral surface of the image recording drum 41 as a conveyance surface. It is transported along a transport path set on the transport surface. Note that the conveyance path passes through the center of the image recording drum 41 and is set corresponding to the width of the paper P.

  The sheet pressing roller 42 is installed in the vicinity of the sheet receiving position of the image recording drum 41 (the position where the sheet P is received from the transfer drum 80). It is pressed against the circumferential surface. The sheet P transferred from the transfer cylinder 80 to the image recording drum 41 is nipped by passing through the sheet pressing roller 42, and the back surface is in close contact with the outer peripheral surface of the image recording drum 41.

  The paper floating detection device 300 detects the floating of the paper P that has passed through the paper pressing roller 42 (a certain level of floating from the outer peripheral surface of the image recording drum 41). The sheet floating detection device 300 irradiates a laser beam (detection beam) across the image recording drum 41 at a predetermined height from the outer peripheral surface (conveyance surface) of the image recording drum 41, and detects the presence or absence of the light shielding. Thus, the floating of the paper P is detected. That is, when the paper P is lifted, the laser light is shielded by the paper P. Therefore, the float of the paper P is detected by detecting whether the laser light is shielded. The configuration of the paper floating detection device 300 will be described in detail later.

  The four inkjet heads 44C, 44M, 44Y, and 44K are arranged at the rear stage of the paper floating detection device 300, and are arranged at regular intervals along the paper P conveyance path. The inkjet heads 44C, 44M, 44Y, and 44K are constituted by line heads corresponding to the paper width, and ink droplets of corresponding colors are directed toward the image recording drum 41 from the nozzle rows formed on the nozzle surfaces. Discharge.

  According to the image recording unit 40 configured as described above, the paper P is transported along a predetermined transport path by the image recording drum 41. The paper P transferred from the transfer cylinder 80 to the image recording drum 41 is first nipped by the paper pressing roller 42 and brought into close contact with the outer peripheral surface of the image recording drum 41. Next, the presence or absence of floating is detected by the paper floating detection device 300, and then ink droplets of each color of C, M, Y, K are ejected from the inkjet heads 44C, 44M, 44Y, 44K onto the printing surface, A color image is drawn on the printing surface.

  Here, in the image recording apparatus 10 of the present embodiment, water-based ink in which a plastic resin is dispersed in ink is used for each color. Even when such water-based ink is used, since the predetermined processing liquid is applied to the paper P as described above, high-quality drawing is performed without causing feathering or bleeding. be able to.

  Further, when the floating of the paper P is detected by the paper floating detection device 300, the conveyance is stopped and an alarm is issued.

  The paper P on which the image is drawn is transferred to the transfer drum 90, transported along a predetermined transport path by the transfer drum 90, and transferred to the transport drum 51 of the ink drying unit 50. As described above, the transfer drum 90 is provided with the dryer 94 therein, and hot air is blown out toward the guide plate 93. The ink drying process is performed in the ink drying unit 50 at the subsequent stage, but the paper P is also subjected to the drying process when being conveyed by the transfer cylinder 90.

  Although not shown, the image recording unit 40 includes a maintenance unit that performs maintenance of the inkjet heads 44C, 44M, 44Y, and 44K. The inkjet heads 44C, 44M, 44Y, and 44K are necessary. Accordingly, it is configured to move to the maintenance unit and receive the required maintenance.

<Ink drying section>
The ink drying unit 50 dries the liquid component remaining on the paper P after image recording. The ink drying unit 50 includes a transport drum (hereinafter referred to as an ink drying drum) 51 that transports the paper P, and an ink drying device 52 that performs a drying process on the paper P transported by the ink drying drum 51. Configured.

  The ink drying drum 51 receives the paper P from the transfer cylinder 90 and rotates to convey the paper P.

  The ink drying device 52 is constituted by, for example, a dryer (in this embodiment, it is constituted by three dryers arranged along the conveyance path of the paper P) and is conveyed by the ink drying drum 51. By blowing hot air toward the paper P, the ink is dried (liquid components present on the paper are evaporated).

  According to the ink drying unit 50 configured as described above, the paper P is conveyed by the ink drying drum 51. Then, hot air is blown from the ink drying device 52 onto the printing surface during the conveyance process, and the ink applied to the printing surface is dried.

  The paper P that has passed through the ink drying device 52 is then transferred from the ink drying drum 51 to the transfer cylinder 100 at a predetermined position. Then, it is transported along a predetermined transport path by the transfer drum 100 and transferred to the transport drum 61 of the fixing unit 60.

  In addition, as described above, the dryer 104 is installed in the transfer drum 100, and hot air is blown out toward the guide plate 103. Accordingly, the paper P is also subjected to a drying process when being transported by the transfer drum 100.

<Fixing part>
The fixing unit 60 heats and presses the paper P to fix the image recorded on the print surface. The fixing unit 60 includes a transport drum (hereinafter, referred to as a fixing drum) 61 that transports the paper P, heat rollers 62 and 63 that apply heat and pressure to the paper P transported by the fixing drum 61, and a post-drawn image. An in-line sensor 64 that detects the temperature, humidity, and the like of the paper P and captures a drawn image is provided.

  The fixing drum 61 receives the paper P from the transfer cylinder 100 and rotates to convey the paper P.

  The heat rollers 62 and 63 heat and press the ink applied to the printing surface of the paper P, thereby welding the thermoplastic resin dispersed in the ink and forming a film of the ink. At the same time, deformation such as cockling and curling generated on the paper P is corrected. Each of the heat rollers 62 and 63 is formed to have substantially the same width as the fixing drum 61 and is heated to a predetermined temperature by a built-in heater. Further, the heat rollers 62 and 63 are pressed and brought into contact with the peripheral surface of the fixing drum 61 with a predetermined pressing force by a pressing unit (not shown). The sheet P passes through the heat rollers 62 and 63 and is heated and pressed by the heat rollers 62 and 63.

  The in-line sensor 64 includes a thermometer, a hygrometer, a CCD line sensor, and the like, detects the temperature, humidity, and the like of the paper P conveyed by the fixing drum 61 and captures an image drawn on the paper P. Based on the detection result of the in-line sensor 64, abnormalities in the apparatus, defective ejection of the head, and the like are checked.

  According to the fixing unit 60 configured as described above, the paper P is transported by the fixing drum 61, and in the transport process, the heat rollers 62 and 63 are pressed against the print surface to be heated and pressurized. As a result, the thermoplastic resin dispersed in the ink is welded to form a film of the ink. At the same time, the deformation generated in the paper P is corrected.

  Thereafter, the sheet P subjected to the fixing process is transferred from the fixing drum 61 to the collecting unit 70 at a predetermined position.

<Recovery Department>
The collection unit 70 collects the sheets P on which a series of printing processes have been performed on the stacker 71 and collects them. The collection unit 70 receives the paper P collected from the fixing drum 61 and the stacker 71 that collects the paper P from the fixing drum 61, conveys the paper P on a predetermined conveyance path, and discharges the paper P to the stacker 71. 72.

  The paper P fixed by the fixing unit 60 is transferred from the fixing drum 61 to the paper discharge conveyor 72, conveyed to the stacker 71 by the paper discharge conveyor 72, and collected in the stacker 71.

  Next, a control system of the image recording apparatus 10 of the present embodiment will be described.

  FIG. 2 is a block diagram showing a schematic configuration of a control system of the image recording apparatus 10 of the present embodiment.

  As shown in FIG. 2, the image recording apparatus 10 includes a system controller 200, a communication unit 201, an image memory 202, a conveyance control unit 203, a paper feed control unit 204, a processing liquid application control unit 205, an image recording control unit 206, an ink A drying control unit 207, a fixing control unit 208, a collection control unit 209, an operation unit 210, a display unit 211, a warning unit 212, and the like are provided.

  The system controller 200 functions as a control unit that performs overall control of each unit of the image recording apparatus 10 and also functions as a calculation unit that performs various calculation processes. The system controller 200 includes a CPU, a ROM, a RAM, and the like, and operates according to a predetermined control program. The ROM stores a control program executed by the system controller 200 and various data necessary for control.

  The communication unit 201 includes a required communication interface and transmits / receives data to / from a host computer connected to the communication interface.

  The image memory 202 functions as a temporary storage unit for various data including image data, and data is read and written through the system controller 200. Image data captured from the host computer via the communication unit 201 is stored in the image memory 202.

  The conveyance control unit 203 includes conveyance drums 31, 41, 51, 61 that are conveyance means for the paper P in the processing liquid application unit 30, the image recording unit 40, the ink drying unit 50, and the fixing unit 60, a transfer drum 80, 90 and 100 are controlled.

  That is, while controlling the drive of the motor which drives each conveyance drum 31,41,51,61, opening / closing of the gripper G with which each conveyance drum 31,41,51,61 was equipped is controlled.

  Similarly, the driving of the motor that drives each transfer drum 80, 90, 100 is controlled, and the opening / closing of the gripper G provided in each transfer drum 80, 90, 100 is controlled.

  Each of the transport drums 31, 41, 51, 61 is provided with a mechanism for sucking and holding the paper P on the peripheral surface, and therefore controls the drive of the suction holding mechanism (in this embodiment, the paper P is loaded). Since vacuum suction is performed, the drive of the vacuum pump as the negative pressure generating means is controlled.)

  Further, since each of the transfer cylinders 80, 90, 100 is provided with the dryers 84, 94, 104, the driving (heating amount and blowing amount) is controlled.

  The driving of the transport drums 31, 41, 51, 61 and the transfer drums 80, 90, 100 is controlled according to commands from the system controller 200.

  The paper feed control unit 204 controls the drive of each unit (the paper feed device 21, the transfer drum 23, etc.) constituting the paper feed unit 20 in accordance with a command from the system controller 200.

  The processing liquid application control unit 205 controls driving of each unit (processing liquid application device 32 and the like) constituting the processing liquid application unit 30 in accordance with a command from the system controller 200.

  The image recording control unit 206 controls driving of each unit (paper pressing roller 42, ink jet heads 44C, 44M, 44Y, 44K, etc.) constituting the image recording unit 40 in accordance with a command from the system controller 200.

  The ink drying control unit 207 controls driving of each unit (such as the ink drying device 52) constituting the ink drying unit 50 in accordance with a command from the system controller 200.

  The fixing control unit 208 controls driving of each unit (the heat rollers 62 and 63, the inline sensor 64, etc.) constituting the fixing unit 60 in accordance with a command from the system controller 200.

  The collection control unit 209 controls the drive of each unit (the paper discharge conveyor 72 and the like) constituting the collection unit 70 in response to a command from the system controller 200.

  The operation unit 210 includes necessary operation means (for example, operation buttons, a keyboard, a touch panel, and the like), and outputs operation information input from the operation means to the system controller 200. The system controller 200 executes various processes in accordance with the operation information input from the operation unit 210.

  The display unit 211 includes a required display device (for example, an LCD panel), and displays required information on the display device in response to a command from the system controller 200.

  The warning unit 212 includes a patrol lamp, a speaker, and the like, and performs necessary warning operations (lighting of the patrol lamp, generation of an alarm sound from the speaker, etc.) in response to a command from the system controller 200.

  Note that, as described above, the image recording unit 40 includes the paper floating detection device 300, and the floating of the paper P is detected. The detection result of the floating of the paper P by the paper floating detection device 300 is output to the system controller 200. When the floating of the paper P is detected, the system controller 200 determines that a conveyance abnormality has occurred, instructs the conveyance control unit 203 to stop conveyance of the paper P, and performs a required warning operation on the warning unit 212. Instruct to do.

  Further, as described above, the image data to be recorded on the paper P is taken into the image recording apparatus 10 from the host computer via the communication unit 201 and stored in the image memory 202. The system controller 200 performs necessary signal processing on the image data stored in the image memory 202 to generate dot data, and controls the driving of each inkjet head of the image recording unit 40 according to the generated dot data. An image represented by the image data is recorded on a sheet.

  The dot data is generally generated by performing color conversion processing and halftone processing on image data. The color conversion process is a process of converting image data expressed in sRGB or the like (for example, RGB 8-bit image data) into ink amount data of each color of ink used in the image recording apparatus 10 (in this embodiment, C , M, Y, and K ink amount data. The halftone process is a process of converting the ink amount data of each color generated by the color conversion process into dot data of each color by a process such as error diffusion.

  The system controller 200 performs color conversion processing and halftone processing on the image data to generate dot data for each color. Then, the image represented by the image data is recorded on the paper by controlling the driving of the corresponding inkjet head in accordance with the dot data of each color to be generated.

  Next, a printing (drawing) operation by the image recording apparatus 10 will be described.

  When a paper feed command is output from the system controller 200 to the paper feeding device 21, the paper P is fed from the paper feeding device 21 to the paper feeding tray 22. The paper P fed to the paper feed tray 22 is transferred to the processing liquid application drum 31 of the processing liquid application unit 30 via the transfer cylinder 23.

  The paper P delivered to the treatment liquid application drum 31 is conveyed along a predetermined conveyance path by the treatment liquid application drum 31, passes through the treatment liquid application device 32 in the conveyance process, and the treatment liquid is applied to the printing surface. The

  The sheet P to which the processing liquid is applied is transferred from the processing liquid applying drum 31 to the transfer cylinder 80, transported along a predetermined transport path by the transfer cylinder 80, and transferred to the image recording drum 41 of the image recording unit 40. . Then, hot air is blown onto the print surface from a dryer 84 installed inside the transfer drum 80 during the conveyance process by the transfer drum 80, and the treatment liquid applied to the print surface is dried.

  The paper P transferred from the transfer cylinder 80 to the image recording drum 41 first passes through the paper pressing roller 42, is nipped by the paper pressing roller 42, and is brought into close contact with the outer peripheral surface of the image recording drum 41. Thereafter, the presence or absence of the sheet P is detected by the sheet floating detection device 300. Here, when the floating of the sheet P is detected, it is determined that the conveyance abnormality of the sheet P has occurred, the conveyance is stopped, and a necessary warning is issued. On the other hand, when the floating of the paper P is not detected, the ink is transported as it is, and ink droplets of each color of CMYK are ejected from each of the inkjet heads 44C, 44M, 44Y, 44K. Thereby, a color image is drawn on the printing surface. Thereafter, the paper P on which the image is drawn is transferred from the image recording drum 41 to the transfer cylinder 90.

  The paper P delivered to the transfer cylinder 90 is conveyed along a predetermined conveyance path by the transfer cylinder 90 and is transferred to the ink drying drum 51 of the ink drying unit 50. Then, hot air is blown onto the printing surface from a dryer 94 installed inside the transfer drum 90 during the conveyance process, and the ink applied to the printing surface is dried.

  The paper P delivered to the ink drying drum 51 is transported along a predetermined transport path by the ink drying drum 51, and hot air is blown from the ink drying device 52 to the print surface in the course of transport, and the liquid remaining on the print surface. The ingredients are dried.

  The dried paper P is transferred from the ink drying drum 51 to the transfer drum 100, transferred along a predetermined transfer path, and transferred to the fixing drum 61 of the fixing unit 60. Then, hot air is blown onto the print surface from the dryer 104 installed inside the transfer drum 100 during the transfer process by the transfer drum 100, and the ink applied to the print surface is further dried.

  The paper P delivered to the fixing drum 61 is transported along a predetermined transport path by the fixing drum 61, and is heated and pressed by the heat rollers 62 and 63 in the transport process, so that the image recorded on the printing surface is fixed. Is done. Thereafter, the paper P is delivered from the fixing drum 61 to the paper discharge conveyor 72 of the collection unit 70, conveyed to the stacker 71 by the paper discharge conveyor 72, conveyed to the stacker 71, and discharged into the stacker 71. .

  As described above, in the image recording apparatus 10 according to the present embodiment, the paper P is transported by drum, and the processing liquid is applied to the paper P, the processing liquid is dried, the ink droplets are ejected, dried, and fixed in the transport process. A predetermined image is recorded on the paper P by performing each of these processes.

  Hereinafter, detection of sheet floating will be described. In the method of detecting paper floating according to the present invention, in order to reliably detect high-speed floating at the rear end of the paper, a part of the paper between the paper pressing roller and the paper floating detection sensor is pressed to press the paper. Only the portion other than the location is floated, and the area of the paper that blocks the detection light is increased so that the paper lift can be reliably detected.

<First Embodiment>
As described above, in the image recording apparatus 10 of the present embodiment, the paper floating detection device 300 is incorporated in the image recording unit 40, and the floating of the paper P is detected before ink ejection.

  FIG. 3 is a schematic configuration diagram illustrating a first embodiment of a paper floating detection device and a paper transport device including the same in the image recording unit 40, FIG. 3A is a side view, and FIG. 3B is a front view. FIG.

  As shown in FIG. 3A, in the image recording unit 40, ink is ejected from the inkjet head 44 (44C, 44M, 44Y, 44K) onto the paper P conveyed by the image recording drum 41. The image is drawn.

  The front end of the paper P is gripped by a gripper G (not shown here) provided on the peripheral surface of the image recording drum 41 and is vacuum-sucked by a number of suction holes formed on the peripheral surface of the image recording drum 41. And conveyed. A sheet pressing roller 42 is provided on the upstream side in the conveyance direction of the sheet P so as to face the circumferential surface of the image recording drum 41, and the back surface of the sheet P is in close contact with the circumferential surface of the image recording drum 41.

  In addition, a paper floating detection device 300 is provided between the inkjet head 44 and the paper pressing roller 42.

  As shown in FIG. 3B, the paper floating detection device 300 includes a light projecting unit 310 that emits detection light (laser light) L, and a light receiving unit 312 that receives the detection light L emitted from the light projecting unit 310. And is configured. In addition, in FIG.3 (b), the display of the inkjet head 44 is abbreviate | omitted.

  The light projecting unit 310 and the light receiving unit 312 constitute a paper floating detection unit that detects the floating of the paper P. The light projecting unit 310 and the light receiving unit 312 are disposed to face each other across the image recording drum 41 (they are disposed to face each other across the conveyance direction path of the paper P).

  The light projecting unit 310 is attached to the main body frame of the image recording apparatus 10 via a bracket (not shown). The light projecting unit 310 includes a light projecting element, and emits detection light L from the light projecting element toward the light receiving unit 312.

  Here, the detection light L is emitted in a direction substantially parallel to the rotation axis of the image recording drum 41 (a direction substantially perpendicular to the conveyance direction of the paper P) and from the outer peripheral surface (conveyance surface) of the image recording drum 41. The light is emitted so as to pass through a position at a predetermined height. Therefore, the light projecting unit 310 is installed so as to satisfy this condition. FIG. 3A shows a cross section of the optical axis of the detection light L.

  The system controller 200 controls the driving of the light projecting unit 310 to control the emission of the detection light L.

  The light receiving unit 312 is attached to the main body frame of the image recording apparatus 10 via a bracket (not shown). The light receiving unit 312 includes a light receiving element (for example, a transmissive photoelectric element), and receives the detection light L emitted from the light projecting unit 310 by the light receiving element. The light receiving element is provided to face the light projecting element of the light projecting unit 310, is substantially parallel to the rotation axis of the image recording drum 41 from the light projecting element, and is at a predetermined height from the outer peripheral surface of the image recording drum 41. The emitted detection light L is received.

  Information (amount of received light) of the detection light L by the light receiving unit 312 is output to the system controller 200. The system controller 200 determines whether or not the paper P is lifted based on the light reception information of the detection light L by the light receiving unit 312. Specifically, the preset threshold value is compared with the received light amount, and when the received light amount is equal to or less than the threshold value, it is determined that the detection light L is blocked by the paper P, and the paper P is lifted. judge.

  When paper floating is detected, a detection signal is output to give a warning or an instruction such as a brake for stopping the conveyance.

  In the present embodiment, in order to reliably detect the high-speed floating of the trailing edge of the sheet, the sheet floating detection apparatus 300 between the sheet pressing roller 42 and the sheet floating detection apparatus 300 is configured as described above. A part of the paper P is pressed so that only the part other than the place where the paper P is pressed is lifted so that the area of the paper P that blocks the detection light L is increased.

  That is, as shown in FIG. 3A, a paper floating stopper (paper floating suppression means) 320 is provided between the paper pressing roller 42 and the detection light L of the paper floating detection device 300. The paper floating stopper 320 presses only a part of the paper P against the image recording drum 41, and prevents the entire end of the paper P in the width direction from being separated from the conveyance surface (outer peripheral surface) of the image recording drum 41. The location where the paper P is pressed and the location where the paper P is lifted are created. As a result, when the paper P is lifted, the area where the lifted paper P blocks the detection light L is increased so that high-speed floating can be easily detected.

  As shown in FIG. 3B, the sheet floating stopper 320 presses the sheet P conveyed by being sucked and held on the image recording drum 41 against the image recording drum 41 in a part in the width direction. In the example shown in FIG. 3B, the paper floating stopper 320 presses a part of the paper P slightly to the left of the center in the width direction against the conveyance surface of the image recording drum 41. As a result, when the paper P is separated from the paper pressing roller 42 as shown in FIG. 3A, the portion of the paper P close to the paper lift stopper 320 is not lifted from the transport surface as shown in FIG. 3B. Although not, it floats at the right end Pt far from the paper float stopper 320. At this time, when viewed from the light projecting unit 310 side, the right end Pt of the sheet P that has floated has a large area.

  As a result, in the present embodiment, even when the paper P has a curl such that the entire edge width direction of the paper P jumps simultaneously at a high speed, a part of the paper P in the edge width direction is partially Since the floating stopper 320 is pressed down, the entire end portion of the paper P does not jump up at a high speed at the same time. That is, a portion that is pressed by the paper floating stopper 320 and does not float, and a portion that floats because it is far from the paper floating stopper 320 are generated, and a portion where the paper P floats is oblique with respect to the detection light L, and an area that blocks the detection light L is Since it becomes large, it is possible to reliably detect sheet floating.

  The sheet floating stopper 320 is not particularly limited, and may be, for example, a roller or a guide plate as shown in FIG. However, in the case of the guide plate, it is preferable that the paper P side is rounded (R shape) so as not to damage the paper P. Further, in order to reduce the contact area with the paper P, a star wheel or the like may be used.

  The location where the paper floating stopper 320 is installed is not fixed, but a moving means may be provided so that the location where the paper floating stopper 320 presses a part of the paper P can be adjusted as appropriate.

  As described above, according to the present embodiment, the sheet P has a simple structure in which the force to lift the entire sheet P after the sheet pressing roller 42 is pressed by the sheet floating stopper 320 only at one position in the width direction of the sheet P. The detection area for the detection light L can be increased, and sheet floating can be reliably detected simply and at low cost.

Second Embodiment
Next, a second embodiment will be described.

  Similarly to the first embodiment described above, this embodiment also holds a part of the sheet P between the sheet pressing roller 42 and the sheet floating detection device 300 in order to reliably detect high-speed floating at the trailing edge of the sheet. Thus, only the portion other than the place where the paper P is pressed is floated so as to increase the area of the paper P that blocks the detection light L. However, in the present embodiment, a fluid such as air is sprayed on only one point of the paper P between the paper pressing roller 42 and the paper floating detection device 300 so as to suppress the floating of the single paper P. is there.

  FIG. 4 shows an outline of a second embodiment of a paper floating detection device in the image recording unit 40 and a paper transport device provided with the device.

  FIG. 4A is a side view, and FIG. 4B is a front view. The same members as those in FIG. 3 described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 4A, the image recording unit 40 includes an image recording drum 41 and an ink jet head 44, and the ink from the ink jet head 44 is conveyed to the paper P held and adsorbed by the image recording drum 41. To draw an image.

  In addition, a paper pressing roller 42 is provided on the upstream side of the inkjet head 44, and a paper floating detection device 300 (detection light L) is provided between the inkjet head 44 and the paper pressing roller 42.

  As shown in FIG. 4B, the sheet floating detection device 300 emits a detection light (laser light) L and a light receiving unit 310 that receives the detection light L emitted from the light projection unit 310. The unit 312 is configured so as to be opposed to each other across the conveyance path of the paper P.

  It is determined from the amount of light received by the light receiving unit 312 that the sheet P has been lifted and the detection light L has been blocked, and the occurrence of sheet floating is detected.

  Further, in the present embodiment, as shown in FIG. 4A, a fluid spraying means 330 is provided as a paper floating stopper between the paper floating detection device 300 (detection light L) and the paper pressing roller 42. . As the fluid spraying means 330, for example, an air nozzle is used, and air is blown onto one point of the paper P, and the paper P is applied to the transport surface of the image recording drum 41 by air pressure so that the paper P at that point does not float. Press it.

  As described above, even when a fluid such as air is sprayed onto one point of the paper P to press the one point of the paper P, it is the same as when the paper P is pressed by mechanical means such as a roller as in the first embodiment. It has the effect of.

  That is, by blowing a fluid such as air on only one point of the sheet P, the sheet P is pressed when the sheet P has curl in a direction away from the conveyance surface by suppressing the floating of the sheet P at that point. Since the area of the lifted paper P that blocks the detection light L increases when viewed from the light projecting unit 310 side, the paper lift can be reliably detected.

  In this embodiment, the installation position of the fluid spraying unit 330 may not be fixed, but a moving unit may be provided so that the position at which the fluid spraying unit 330 sprays the fluid onto the paper P can be adjusted.

  As described above, according to the present embodiment, a force that causes the entire width direction of the sheet edge of the sheet P after the separation of the sheet pressing roller 42 to be lifted can be sprayed from a place away from a fluid such as air. The detection area of the paper P can be increased without damaging the conveying means, the paper floating stopper, and the like due to jamming and the like, and reliable paper floating detection can be performed.

<Third Embodiment>
Next, a third embodiment will be described.

  In this embodiment, the light projecting unit and the light receiving unit are arranged to face each other with the paper transport path interposed therebetween, and the paper floats when the paper shields the optical axis of the light receiving unit and the light receiving amount of the light receiving unit falls below a certain threshold value. In the configuration for detecting the image, as in each of the embodiments described above, by pressing only one portion of the sheet, the area of the sheet blocking the optical axis viewed from the optical axis direction is not increased, but the direction of the optical axis is simply changed. Thus, the area of the sheet that blocks the optical axis viewed from the optical axis direction is increased without requiring a means for pressing only one part of the sheet, and the sheet floating is reliably detected.

  FIG. 5 is a perspective view of the vicinity of the image recording drum showing a schematic configuration of the sheet floating detection device of the present embodiment.

  As shown in FIG. 5, in the present embodiment, the detection light L is projected at a predetermined angle with respect to a direction (axial direction of the image recording drum 41) perpendicular to the transport direction of the paper P. The light projecting unit 310 and the light receiving unit 312 are arranged.

  Thus, even if the entire width direction of the trailing edge of the paper P is lifted simultaneously by slightly tilting the optical axis of the detection light L from the axial direction of the image recording drum 41, the optical axis of the detection light L is the paper. Since the sheet P is not parallel to the paper surface, the area of the sheet P that blocks the detection light L can be increased to reliably detect sheet floating.

  The predetermined angle is not particularly limited, but for example, it is preferable to incline about 0.3 ° to 2 °.

  According to this embodiment, the roller and guide plate of the paper floating stopper of the first embodiment described above or the fluid spraying means of the second embodiment are unnecessary, and high-speed floating of the trailing edge of the paper is ensured at low cost. Can be detected.

  Further, when the present embodiment is combined with the first embodiment or the second embodiment and a part of the paper P is pressed, the optical axis of the detection light L is set with respect to the axial direction of the image recording drum 41. May be tilted.

  Further, as shown in FIG. 5, the method of inclining the detection light L is not limited to the one in which the light receiving unit 312 is disposed at a position higher than the light projecting unit 310. The optical axis of the detection light L may be tilted by disposing this at a position higher than the light receiving unit 312.

  Further, the light projecting unit 310 and the light receiving unit 312 may not be fixedly installed, but a moving means may be provided for each so that the positions of the light projecting unit 310 and the light receiving unit 312 can be adjusted. Alternatively, the light projecting unit 310 and the light receiving unit 312 may be fixed, an optical system may be provided for each of them, and the optical axis of the detection light L may be inclined by the optical system.

<Other embodiments>
In the first embodiment described above, a sheet floating stopper made of a roller or a guide plate or the like is used as the sheet floating suppression unit, and a part of the sheet is pressed against the conveying surface. However, the sheet floating stopper is used as the conveying surface. It is good also as an aspect provided in the place a little lifted from.

  In the first and second embodiments described above, in order to make it difficult to lift only a part of the trailing edge of the sheet in the width direction, a separate sheet floating stopper is provided. However, as other embodiments, In particular, without using such a member, by using the mechanism that the conveying apparatus originally has, it is difficult to lift only a part of the rear end of the sheet in the width direction at low cost.

  For example, as in the above-described example, when the image recording drum 41 sucks and holds the paper P on the transport surface by vacuum suction, the suction force can be controlled in the width direction of the paper P and the transported paper By increasing the suction force only in a part in the width direction of the rear end portion, it is possible to make it difficult to lift only a portion in the width direction of the rear end portion of the paper P. Also by this, the same effect as the case where the sheet floating stopper is used as in the above example can be obtained.

  In addition, in the case where the image recording drum 41 is electrostatically attracted and holds the paper P on the transport surface, for example, only a part in the width direction of the rear end portion of the transported paper is subjected to electrostatic suction coating. By strengthening, it is possible to make it difficult to lift only a part in the width direction of the rear end portion of the paper P.

  Further, the method of controlling the sheet suction force of the image recording drum 41 to distribute the suction force in the sheet width direction may be combined with the method using the sheet floating stopper in each of the above-described embodiments. Good.

  The sheet floating detection device, the sheet conveyance device, and the image recording device of the present invention have been described in detail above. However, the present invention is not limited to the above examples, and various improvements can be made without departing from the gist of the present invention. It goes without saying that or may be modified.

  DESCRIPTION OF SYMBOLS 10 ... Image recording apparatus, 20 ... Paper feed part, 21 ... Paper feed apparatus, 22 ... Paper feed tray, 23 ... Transfer cylinder, 30 ... Processing liquid application part, 31 ... Conveyance drum (processing liquid application drum), 32 ... Processing Liquid applicator, 40 ... image recording unit, 41 ... transport drum (image recording drum), 42 ... paper pressing roller, 44C, 44M, 44Y, 44K ... inkjet head, 50 ... ink drying unit, 51 ... transport drum (ink drying) Drum), 52 ... ink drying device, 60 ... fixing unit, 61 ... transport drum (fixing drum), 70 ... collection unit, 200 ... system controller, 201 ... communication unit, 202 ... image memory, 203 ... transport control unit, 204 DESCRIPTION OF REFERENCE SYMBOLS: Paper feed control unit 205 ... Processing liquid application control unit 206 ... Image recording control unit 207 ... Ink drying control unit 208 ... Fixing control unit 209 ... Recovery control unit 210 , 211... Display unit, 212 .. Warning unit, 300. (optical axis)

Claims (11)

A light-emitting unit and a light-receiving unit that have a paper pressing roller that presses the paper onto the conveyance surface and are disposed opposite to each other across a conveyance path that conveys the paper in a predetermined conveyance direction are emitted from the light projection unit. The detection light received by the light receiving unit is disposed in the vicinity of the downstream of the paper pressing roller in the transport direction so that the optical axis of the detection light is substantially perpendicular to the transport direction, and the transported paper transmits the detection light. A paper floating detection device that detects the lifting of the paper from the conveying surface by detecting the blockage,
A sheet floating suppressing means for making it difficult to lift a part in the width direction of the trailing edge of the conveyed sheet is provided between the sheet pressing roller of the conveying path and the position of the optical axis of the detection light, A paper floating detection apparatus, wherein a paper floating immediately after the trailing edge separates the paper pressing roller is detected.   The sheet floating detection device according to claim 1, wherein the sheet floating suppressing unit is a roller or a guide plate that presses a part of the sheet against the conveyance surface.   The sheet floating detection device according to claim 1, wherein the sheet floating suppressing unit is a fluid spraying unit that sprays a fluid onto a part of the sheet.   4. The portion of the sheet floating suppressing unit that makes it difficult to lift a part of the sheet is closer to the end in the width direction than the center in the width direction of the rear end of the sheet. The paper floating detection device according to claim 1. A sheet pressing roller that presses the sheet onto the conveying surface; and a light projecting unit and a light receiving unit that are arranged opposite to each other across a conveying path that conveys the sheet in a predetermined conveying direction. A paper floating detection device that is arranged in the vicinity of the downstream in the transport direction and detects the lifting of the paper from the transport surface by detecting that the transported paper blocks the detection light,
An apparatus for detecting sheet floating, wherein an optical axis of detection light emitted from the light projecting unit and received by the light receiving unit is inclined by a predetermined angle with respect to a direction perpendicular to the transport direction.   The said conveyance surface is a drum conveyance surface which carries out rotation conveyance, hold | maintaining the said paper on the surrounding surface, and the said predetermined angle is 0.3 degrees-3 degrees, It is characterized by the above-mentioned. Paper float detection device.   A paper conveyance device comprising the paper floating detection device according to claim 1. A conveyance stand for holding the sheet on the conveyance surface of the sheet and conveying the sheet in a predetermined conveyance direction;
A paper pressing roller for pressing the paper onto the transport surface;
The projector includes a light projecting unit and a light receiving unit that are opposed to each other across the transport path for transporting the paper in the vicinity of the downstream of the paper pressing roller in the transport direction, and are emitted from the light projecting unit and received by the light receiving unit. A paper floating detection device for detecting the lifting of the paper from the conveying surface by detecting that the paper blocks the detection light.
Means for controlling the distribution of the holding force for holding the paper on the transport surface in the paper width direction between the paper pressing roller and the paper floating detection device in the transport path;
The holding force is strengthened for a part in the width direction of the trailing edge of the conveyed paper to suppress simultaneous floating in the width direction of the trailing edge of the paper immediately after the paper is separated from the paper pressing roller. And a sheet conveying device that detects sheet floating immediately after the trailing edge of the sheet separates the sheet pressing roller.   9. The holding force for holding the paper on the transport table is a vacuum suction force, and the suction force is strengthened for a part in the width direction of the rear end of the transported paper. Paper transport device.   9. The holding force for holding the sheet on the transport table is an electrostatic adsorption force, and electrostatic adsorption coating is strengthened for a part of the sheet to be conveyed and the rear end width direction. The paper transport device described in 1.   An image recording apparatus comprising the sheet conveying device according to claim 7.

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