JP2006160472A - Sheet material conveying device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To overcome the disadvantage of causing a recording failure due to contact of a floating part with a recording head by preventing a sheet material from being floated due to air remainder even in the case of conveying an air impermeable sheet material using a belt. <P>SOLUTION: In this sheet material conveying device, the sheet material is sucked to a conveying belt and conveyed. A means for sucking the sheet material to the conveying belt is a suction means for sucking the sheet material sequentially from the leading end of the sheet material 18 in the conveying direction toward the trailing end and from one point at the leading edge to both side parts in the conveying width direction, or from one side end in the width direction at the leading edge of the sheet material in the conveying direction toward the trailing end and from one side end toward the other side end. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sheet material conveying apparatus that adsorbs and conveys a sheet material to a conveying belt, and an image forming apparatus including the sheet material conveying apparatus.

  An image forming apparatus such as a printer, a copier, or a facsimile forms an image having a dot pattern on a sheet material (recording medium) such as paper or a plastic thin plate based on image information. This image forming apparatus can be divided into an ink jet type, a wire dot type, a thermal type, a laser beam type, and the like according to a recording method, and the ink jet type discharges ink from a recording head to a sheet material such as recording paper. It is configured to form an image.

  In an image forming apparatus, it is necessary to transport a sheet material from a paper feed unit such as a cassette to a paper discharge unit through an image forming unit (recording unit). In that case, the conveyance of the sheet material is always controlled at a constant timing after the paper is fed until an image is formed and discharged. Among these, from paper feeding to image formation, the image forming position on the sheet material is affected, so that particularly accurate conveyance is required. Also, during image formation, if the sheet material conveyance speed is not constant, the image magnification will be deviated, causing the image to expand and contract. In particular, in the case of an image forming apparatus using a plurality of recording heads such as for color, a deviation occurs between images recorded by the respective image forming units. This shift appears as a color shift in the case of a color image forming apparatus, and causes image defects. In order to prevent such a problem, it is necessary to accurately transmit the conveying force of the conveying unit controlled with high accuracy to the sheet material.

  Conventionally, various transport means have been proposed as a transport system taking such points into consideration. For example, there is a method in which a sheet material is sent out by a roller pair, and a conveyance direction is regulated by a guide. In this method, since the sheet material is sent out by the pressure between the rollers, the conveying force is strong and the method is simple and reliable. However, it is necessary to arrange the roller pairs at intervals shorter than the minimum length of the sheet material to be used. For example, it is not suitable for transporting a postcard or a business card size sheet material. Further, it cannot be used when it is necessary to keep the recording surface in a non-contact state, such as from the transfer by an electrophotographic drum to the fixing.

  As a transport device that solves these problems, a transport device that uses an endless belt (endless belt) and causes a sheet material to adhere to the endless belt by electrostatic attraction has been proposed. In the belt type conveying device by electrostatic adsorption, in particular in the case of a color image forming apparatus using a plurality of recording heads (image forming means), in order to make the image forming position of each recording head accurate, the belt It is necessary to keep the conveyance speed of the machine precise. In addition, it is necessary to keep the sheet material in close contact with the conveying member (belt, drum, etc.) so as not to shift or float. As means for that purpose, as disclosed in JP-A-50-31828, JP-B-3-48100, and JP-A-2000-247476, a pair of conductive electrodes (adsorptive force generating means) is provided on a conveyance belt carrying recording paper. There is known a method in which a recording paper is applied to generate an electrostatic force by applying an electric charge to adsorb a recording paper.

  In the ink jet recording apparatus having such a conveying means, the recording paper fed from the paper feeding apparatus is conveyed by the electrostatic adsorption means (conductive electrode) as described above provided on the conveying belt in the recording area. It is sucked and held on the belt surface and conveyed while being recorded by the recording head. A typical configuration for this is described in Japanese Patent Laid-Open No. 2000-247476. 16 and 17 are diagrams showing a schematic configuration of a conveying apparatus having such a conveying belt, in which (a) is a schematic plan view and (b) is a schematic side view.

  In FIGS. 16 and 17, the conveyance belt 101 formed of an endless belt is hung on three rollers: a driving roller 102, a conveyance roller 103, and a pressure roller 104 that urges the conveyance belt 101 to have a predetermined tension. It has been turned. The rotational driving force of the driving motor 105 is transmitted to the driving roller 102 via the belt 106, and the driving roller rotates at a predetermined speed to cause the transport belt 101 to travel. A high voltage is applied from the power supply brush 107 to the plurality of electrodes 110. A positive or negative high voltage is applied to the power supply brush 107 by the high voltage generator 108 (power is supplied).

  18 is an enlarged schematic partial plan view showing a portion D1 in FIG. 16, and FIG. 19 is a schematic side view of the power supply brush 107 in FIGS. FIG. 18 shows an electrode pattern (shaded portion) arranged below the surface layer of the conveyor belt 101. In FIG. 18, the electrode 110 includes a plurality of positive electrodes 110A and a plurality of negative electrodes 110B. Each positive electrode 110A and each negative electrode 110B extend in a direction orthogonal to the conveyance direction of the conveyance belt 101, and are alternately arranged at predetermined intervals in the conveyance direction of the conveyance belt. The potential difference between the positive electrode 110A and the negative electrode 110B is set to be about several kilovolts. The negative electrode 110B may be connected to a ground potential or applied with a negative voltage. This depends on mounting conditions such as required functions and performance of actual equipment. What is necessary is just to select suitably.

  A power-supplied portion 110A1 is formed at the widthwise end of the transport belt 101 of the positive electrode 110A, and a power-supplied portion 110B1 is formed at the width-direction end of the transport belt 101 of the negative electrode 110B. The voltage supply from the power supply brush 107 to the positive electrode 110A and the negative electrode 110B is performed from these power supply parts 110A1 and 110B1. Further, these power-supplied portions 110A1 and 110B1 are disposed so as to be reachable from openings 101a and 101b formed in the surface layer of the conveyor belt 101. When the brush of the power supply brush 107 comes into contact with the power-supplied portions 110A1 and 110B1 through the openings 101a and 101b, power is supplied to the electrodes 110 (the positive electrode 110A and the negative electrode 110B). An area where a potential difference is generated between the positive electrode 110A and the negative electrode 110B when power is supplied is an adsorption area. FIG. 16 shows the adsorption area 112.

  Since the sheet material such as recording paper is a dielectric material such as paper, when the sheet material that has entered from the upstream side in the conveyance direction of the conveyance belt 101 and is placed on the belt reaches the adsorption region 112, an adsorption force is generated. It is polarized by the electric field generated in the electrode 110 as a means. As a result, an electrostatic force attracting each other is generated between the sheet material and the conveyance belt 101, and the sheet material is adsorbed and supported on the conveyance belt 101.

  However, the adsorptive power of the sheet material due to the comb-like electrode pattern such as the electrode 110 shown in FIGS. 16 to 19 is not necessarily distributed uniformly. That is, the spatial distribution of the density of the lines of electric force formed at the part without the electrode, the end part of the electrode, the center part of the electrode, etc. is changed, and the adsorption force is not constant. It has been experimentally found that this attractive force is relatively strong at the end of the electrode and relatively weak at the portion without the electrode. Therefore, it is necessary to consider the positional relationship between the sheet material and the electrode so as to ensure a sufficient adsorbing force at the end of the sheet material where turning is likely to occur.

  On the other hand, when the sheet material is conveyed by the belt, if the suction force at the edge of the sheet material is insufficient, the conveyance belt and the edge of the sheet material are in close contact with each other due to the shape of the warp of the edge. It may not be. When such a phenomenon occurs when a component or a mechanism such as a recording head exists near the upper portion of the transport belt as in an inkjet recording apparatus, for example, the sheet material being transported is transferred to these component or mechanism. There is a risk of contact. When the sheet material being conveyed comes into contact with an adjacent component or the like, the flatness of the sheet material is lost rapidly or partially at the contact portion, which may cause conveyance failure. Further, when the sheet material and the recording head come into contact with each other, there may be a problem in the printing capability of the recording head.

  That is, as shown in FIGS. 16 to 19, the conventional electrode pattern is formed in a direction orthogonal to the conveying direction of the sheet material, and the front end portion of the sheet material carried on the traveling conveyor belt and the electrode No particular attention was paid to the positional relationship. For this reason, the end portion of the sheet material cannot be turned up, and there is a problem in the transportability.

  Therefore, in Japanese Patent Laid-Open No. 2000-247476 (Patent Document 1), it is possible to generate a stable suction force even at the end portion of the sheet material, and from an electrode pattern that is not easily affected by the gap direction of the sheet material. A conveying belt provided with the attraction force generating means is disclosed. A belt conveyance device and an image forming apparatus using the conveyance belt have the following configurations. That is, a belt member having a carrying surface for carrying a sheet material, a plurality of counter electrodes arranged in an adsorption force generation region at a central portion in the conveyance width direction of the belt member, and the belt member that supplies power to the counter electrode. An attracting force generating means having a power-feeding portion disposed at at least one end in the transport width direction, and the sheet material can be transported by electrostatically attracting to the attracting force generating region of the carrying surface of the belt member In the transport belt, the plurality of counter electrodes have a region formed obliquely with respect to the transport width direction of the belt member.

Similarly, Japanese Patent Laid-Open No. 2000-60168 (Patent Document 2) discloses a configuration of a conveyor belt for solving the problem of suppressing the floating of the leading end of the sheet material. 20 and 21 are schematic plan views showing an outline of two examples of such a conveyor belt. 20 and FIG. 21 both electrostatically adsorb the recording medium by applying positive and negative voltages alternately to the electrode pattern formed with a certain gap on the surface of the conveyor belt 10. Each of the electrodes is configured to be inclined in a zigzag manner with respect to the width direction of the substrate of the conveyance belt so that at least one end in the conveyance direction of the recording medium is adsorbed in the conveyance belt conveyed in this manner. Yes.
JP 2000-247476 A JP2000-60168

  However, the conventional techniques as described above have the following problems. That is, in Patent Document 1, the contact position of the sheet material with respect to the conveyance belt and the suction start position are not limited, and when the front end of the sheet material comes into contact with the conveyance belt, an adsorption force may act on the entire front end. In this case, the suction force acts on the entire contact area from the suction start position, and the suction force acts on the entire contact area even when the conveyance belt travels and the contact area increases. If the suction force is activated from the moment when the sheet material comes into contact with the conveyance belt in a state where the sheet material is waved or curled due to changes in the environment such as temperature and humidity, the sheet material is deformed into a convex shape with respect to the conveyance belt. Then, there is a possibility that the sheet material is adsorbed while air remains in the portion sandwiched between the inner surface of the convex portion and the upper surface of the conveying belt.

  If the sheet material is plain paper that allows gas to pass through, even if air remains at the start of adsorption, the air will slip through the surface of the sheet material due to the adsorption force between the conveyor belt and the sheet material, so there is no air left. It is possible to adsorb with. However, in the case of a sheet material such as photographic coated paper (Canon product name: Professional Photo Paper PR-101) that is difficult to allow air to pass through, the air remaining between the conveyance belt and the sheet material passes through the sheet material. In this case, it remains between the conveying belt and the sheet material, and only that portion becomes convex and floats. And this convex-shaped part may contact the discharge surface of an inkjet head, etc., and a recording defect may generate | occur | produce.

  Also, in Patent Document 2, since the contact start position of the sheet material with respect to the conveyance belt and the position of the electrode that is supplied with power and generates an attracting force are not clear, the sheet material that hardly allows air to pass therethrough as in Patent Document 1. In this case, air may remain between the conveying belt and the sheet material and float in a convex shape, and this floating portion may come into contact with the ejection surface of the inkjet head and cause a recording defect. .

  The present invention has been made in view of such a technical problem, and the object of the present invention is to prevent the sheet material from floating due to the air remaining even when the belt transport is performed on a sheet material that is difficult to pass air. It is an object of the present invention to provide a sheet material conveying apparatus and an image forming apparatus capable of eliminating the inconvenience that a floating portion comes into contact with a recording head or the like to cause a recording defect.

  In order to achieve the above object, the present invention provides a sheet material conveying apparatus that adsorbs and conveys a sheet material to a conveying belt, wherein the adsorbing means for adsorbing the sheet material to the conveying belt is provided from the leading end in the conveying direction of the sheet material. It is characterized by being an adsorbing means that adsorbs in order toward the rear end and at one end of the front end toward both end portions in the conveyance width direction.

In order to achieve the above object, the present invention provides a sheet material conveying apparatus that adsorbs and conveys a sheet material to a conveyance belt, wherein an adsorption means for adsorbing the sheet material to the conveyance belt is provided at a front end of the sheet material in the conveyance direction. The adsorbing means adsorbs in order from one end of the width direction to the rear end and from one end to the other end.

  According to the present invention, in the sheet material conveying apparatus that adsorbs and conveys the sheet material to the conveying belt, the adsorbing means that adsorbs the sheet material to the conveying belt moves from the leading end in the conveying direction of the sheet material to the rear end and the leading end. Since it is constructed so as to be sequentially adsorbed from one place to the both side ends in the conveyance width direction, the air between the sheet material and the conveyance belt is conveyed while being pushed out in both the conveyance direction rear side and the conveyance width direction. Therefore, even when a sheet material that is difficult to pass air is conveyed by a belt, the sheet material can be prevented from floating due to the remaining air, and the floated portion contacts the recording head or the like, resulting in a recording failure. And a sheet material conveying apparatus capable of reducing the gap between the sheet material and the image forming means and improving the image quality of the recorded image. Forming apparatus is provided.

  Embodiments of the present invention will be specifically described below with reference to the drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings. FIG. 1 is a schematic perspective view showing an embodiment of an image forming apparatus provided with a sheet material conveying apparatus according to the present invention. FIG. 2 is a schematic perspective view showing the belt unit in FIG. In the present embodiment, the case where the image forming apparatus in which the sheet material conveying apparatus according to the present invention is used is an inkjet recording apparatus will be described as an example.

  In FIG. 1, an ink jet recording apparatus according to the present embodiment is a belt as a sheet material conveying system including a conveying belt 1 including an endless belt that adsorbs and conveys a sheet material such as recording paper as a recording medium by static electricity. A unit 30 is provided. An image forming means 6 for forming an image on the sheet material conveyed in the direction of the arrow by the conveyance belt 1 is disposed on the belt unit 30. A belt cleaning unit 5 is provided below the belt unit 30 for wiping off and adhering substances such as ink adhering to the transport belt 1. The image forming means 6 is composed of a full-line multi-head system having a structure in which a plurality of full-line heads 6a to 6f that form images by discharging ink onto a sheet material are held by a head frame.

  The head frame holding the full line heads 6a to 6f, which are image forming means 6 for color recording, is driven up and down substantially vertically by a motor (not shown). When recording is not performed, the head frame is raised to a position spaced upward from the conveyor belt 1, and a cap unit (not shown) is disposed between the conveyor belt 1 and the full line heads 6a to 6f. By capping, the ink in the vicinity of the ejection openings of the heads 6a to 6f is prevented from being dried. Further, the full line heads 6a to 6f are arranged in the order of the respective ink colors of black, yellow, cyan, light cyan, magenta, and light magenta from the upstream side in the conveyance direction (arrow direction) of the conveyance belt 1.

  As shown in FIGS. 1 and 2, the belt unit 30 includes a conveying belt 1 that adsorbs and conveys a sheet material by static electricity, a driving roller 2 that drives the conveying belt 1, and a driven that is driven by the movement of the conveying belt 1. A roller 3 and a tension roller 4 for applying tension to prevent slack between the driving roller 2 and the driven roller 3 of the conveyor belt 1, and the conveyor belt 1 is connected to the rollers 2, 3, 4. Constructed by winding.

  FIG. 3 is a partial longitudinal sectional view of a part of the conveyor belt 1 shown in FIG. 2 and 3, the conveyor belt 1 is formed by embedding a first electrode 9a and a second electrode 9b made of conductive metal, which is an adsorbing means or an adsorbing force generating means, in a belt base material 9c made of a resin material. Is covered with a surface layer 9d. As a material of the belt equipment 9c, for example, a polymer synthetic resin material such as polyethylene, polycarbonate, polyimide, or the like is used. As shown in FIG. 2, the first electrode 9 a and the second electrode 9 b have a strip shape, and are bent so as to protrude toward the upstream side in the transport direction at a substantially central portion in the width direction of the transport belt 1. The plurality of first electrodes 9a and second electrodes 9b are alternately arranged in parallel with a predetermined gap. As shown in FIG. 2, the plurality of first electrodes 9 a and second electrodes 9 b form a comb-teeth shape that is bent in a direction substantially orthogonal to the transport direction.

  The surface layer 9d is made of a fluorine-based synthetic resin such as PVDF capable of resistance control in order to generate an optimal electrostatic force. FIG. 2 is also a diagram showing an electrode pattern of the conveyance belt of the present embodiment. At the end of each electrode 9a, 9b in the belt width direction, a power-supplied portion, which is a portion that contacts a power supply brush for applying a voltage to the electrode, is provided so as to be contactable from the back of the belt. The power-supplied part (first power-supplied part) 8a of the first electrode 9a is formed so as to be contactable from the back surface of the left end part in the transport direction of the transport belt 1, and the power-supplied part (second power-supplied part) 8b of the second electrode 9b. Is formed so as to be contactable from the back surface of the conveyance belt 1 at the right end in the conveyance direction.

  Each of the power-supplied parts 8a and 8b is exposed from the back surface of the conveyor belt 1 by providing an opening in the belt base material 9c, and can be contacted. The conductive power supply brushes 7a and 7b for voltage application are configured to contact the power supplied parts 8a and 8b through the openings with a predetermined pressure. Each of the power supply brushes 7a and 7b serving as a power supply unit is fixed to a frame (not shown) in a space inside the conveyor belt 1 formed of an endless belt wound around the rollers 2, 3 and 4, and generates a high voltage (not shown). Connected to the instrument. A positive high voltage (0.5 to 1.5 kV) from a high voltage generator (not shown) is applied to the power-supplied part 8a by a power supply brush 7a, and the power-supplied part 8b is applied by a power supply brush 7b. A negative high voltage (−0.5 to −1.5 kV) from a high voltage generator (not shown) is applied.

The material of the power supply brush 7 is preferably a conductive material having a volume resistivity of 10 ⁵ Ωcm or less. When a voltage is applied to the electrodes 9a and 9b, an electric force is generated in the direction of the arrow in FIG. 3, and electric lines of force are formed. Then, due to the potential difference between the electrode 9a and the electrode 9b, an adsorption force is generated above the conveying belt 1, and the sheet material is adsorbed on the conveying belt. In FIG. 2, the electrodes 9a and 9b are electrodes to which a high voltage is applied, and the electrode 9 is an electrode to which no high voltage is applied. Therefore, the electrodes 9a and 9b are applied to the sheet material. Adsorption force acts. Even if different electrodes come into contact with the power supply brushes 7a and 7b due to the movement of the conveyor belt 1, the suction force generation region does not change greatly, and the suction force is generated almost in the region of the electrodes 9a and 9b.

  4 is a schematic perspective view showing a state in which the conveyor belt 1 is cleaned with a rubber blade in the belt cleaning unit 5 in FIG. 1, and FIG. 5 is an absorber in the belt cleaning unit 5 in FIG. It is a typical perspective view which shows a state when absorbing and removing the liquid on a rubber blade. As shown in FIG. 1, the belt cleaning unit 5 for cleaning the transport belt 1 is attached so as to follow the rotating shaft of the driving roller 2.

  4 and 5, the belt cleaning unit 5 has a web 31 for collecting foreign matters such as paper dust on the conveyor belt 1. The web 31 prevents foreign matters such as paper dust on the conveyor belt 1 from going downstream from the web 31. The web 31 is made of a non-woven fabric whose surface has been impregnated with a surfactant to improve the liquid absorption capability, and has a width wider than the recording width of the full line heads 6 a to 6 f and narrower than the width of the transport belt 1. The web 31 is bonded to the core bars 32 and 33 at the front end and the rear end, respectively, and most of the web 31 is wound around the core bar 33 as shown in FIGS. 4 and 5.

  The web 31 is driven in a direction opposite to the moving direction (conveying direction) of the conveying belt 1 by rotating the mandrel 32 with a driving source (not shown), and is wound on the mandrel 32. Go. In addition, the web 31 is wound around the web roller 21 and the shaft 25 in the middle thereof, and is supported so as to rub against the conveyance surface of the conveyance belt 1. In the present embodiment, the web 31 is composed of a nonwoven fabric with enhanced liquid absorption capability. The material of the web 31 is not limited to this. That is, the web 31 is capable of collecting foreign matters such as paper dust on the conveyor belt 1 and does not generate foreign matters due to friction with the conveyor belt 1 and does not repel the cleaning liquid. Any material can be used as long as it is absorbable and resistant to ink, and any material having these characteristics may be used.

  The web roller 21 has a cylindrical shape, and a cleaning liquid supply port 24 is provided on an end surface thereof. The cylindrical surface of the web roller 21 is provided with a plurality of holes communicating with the cleaning liquid supply port 24 in the length direction. A tube (not shown) is connected to the cleaning liquid supply port 24, and the cleaning liquid can be supplied from the tube to the cylindrical surface of the web roller 21 through the cleaning liquid supply port 24 and the plurality of holes. A cleaning liquid receiver 35 is disposed on the lower surface side of the web roller 21, and the overflowing cleaning liquid is received by the cleaning liquid receiver 35 so as not to diffuse into the apparatus main body. A discharge port 36 for discharging the cleaning liquid accumulated in the cleaning liquid receiver 35 is provided on the bottom surface of the cleaning liquid receiver 35. A tube (not shown) is connected to the discharge port 36, and the overflowing cleaning liquid is discharged into the waste liquid through the tube. It is collected in the tank.

A web facing plate 71 is disposed on the opposite side of the conveyor belt 1 to face the web roller 21. The web facing plate 71 is fixed to a frame (not shown) so as to come into surface contact with the back surface of the conveyor belt 1. The web facing plate 71 prevents flapping of the conveyor belt 1 and promotes the web 31 to be pressed against the conveyor belt 1.
A rubber blade 41 for wiping off the liquid on the conveyor belt 1 is disposed on the downstream side in the moving direction of the conveyor belt 1 of the web roller 21 in the belt cleaning unit 5. The rubber blade 41 is formed of a plate-like urethane rubber, has a thickness of about 1.5 mm, and a width that is slightly narrower than the width of the web 31. The rubber blade 41 is fixed to the blade base 40.

  The base end portion of the blade base 40 is fixed to a rotation support plate 43 that is rotatably supported by the shaft 25 at both left and right side portions thereof. The rotation support plate 43 is connected to a drive source (not shown). When the rotation support plate 43 is driven to rotate, the rubber blade 41 as shown in FIG. 4 operates to wipe the liquid on the conveyor belt, and the liquid adhering to the rubber blade 41 as shown in FIG. It is possible to take two positions, that is, a cleaning position where the light is absorbed and removed by the absorber 42. The length of the absorber 42 is selected to be slightly longer than the rubber blade 41 so that the entire tip of the rubber blade 41 can be contacted. This absorbent body 42 is a porous polyurethane absorbent body, and in this embodiment, since it requires liquid absorption and ink resistance, it is formed by the product name Ruby Cell (manufactured by Toyo Polymer). However, the material of the absorber 42 is not limited to these as long as it has liquid absorption and ink resistance.

  Further, the absorber 42 is rotatably supported by a support member (not shown) so that the two positions shown in FIGS. 4 and 5 can be taken in accordance with the rotation of the rubber blade 41. As a result, after the rubber blade 41 comes into contact with the transport belt 1 and wipes off the adhering liquid on the transport belt, the rubber blade 41 is scraped by the rubber blade 41 when the contact with the transport belt 1 is released. Thus, the liquid adhering to the tip portion can be absorbed and removed by the absorber 42. Further, when the liquid wiping operation on the transport belt 1 is not performed, the tip of the rubber blade 41 can always be kept clean.

  Further, as shown in FIGS. 4 and 5, a blade facing plate 72 is disposed on the opposite side of the conveying belt 1 so as to face the rubber blade 41. As with the web facing plate 71, the blade facing plate 72 is fixed to a frame (not shown) so as to be in surface contact with the back surface of the transport belt 1. The blade facing plate 72 is disposed in a positional relationship such that the conveyance belt 1 is sandwiched between the blade blade 41 and the tip of the rubber blade 41, so that even when the conveyance belt rotates at high speed, In addition to preventing fluttering, the ink and cleaning liquid adhering to the transport belt 1 can be reliably removed.

6 to 14 are schematic perspective views showing an operation when the sheet material 18 is adsorbed and conveyed by the belt unit 30, and FIG. 6 shows a state where the sheet material is conveyed to the front of the belt unit. FIG. 7 shows a state when the sheet material is further conveyed from the state of FIG. 6 and the leading end of the sheet material reaches a position where it contacts the conveying belt.
FIG. 8 shows a state where the sheet material is further conveyed from the state of FIG. 7 and an adsorption force acting region from the conveyance belt is formed on the sheet material, and FIG. 9 further conveys the sheet material from the state of FIG. As a result, the adsorption force acting region for the sheet material is slightly expanded.

FIG. 10 shows a state when the sheet material is further conveyed from the state of FIG. 9 and the adsorption force action area for the sheet material further expands to reach both end portions, and FIG. 11 shows the state of the sheet material from the state of FIG. The state when the sheet is further conveyed and the adsorption force acting area from the conveyance belt with respect to the sheet material further extends rearward is shown.
FIG. 12 shows a state where the sheet material is further conveyed from the state of FIG. 11 and the adsorption force acting region from the conveyance belt to the sheet material reaches almost the entire region of the sheet material.
FIG. 13 shows a state when the sheet material is further conveyed from the state of FIG. 12 and the adsorption force acting area on the sheet material is in a limited range at the rear end portion, and FIG. 14 shows the state from the state of FIG. The state when the material is further conveyed and the sheet material is separated from the conveying belt and discharged is shown.

  Next, an operation when the sheet material 18 is attracted to the belt unit 30 and conveyed by using FIG. 6 to FIG. 14 will be described. 6 to 14 show a state in which the A4 size sheet material 18 is conveyed from the upstream side of the belt unit 30, is adsorbed to the conveyance belt 1, and is discharged to the downstream side.

  In FIG. 6, a sheet material 18 such as recording paper or a plastic thin plate is conveyed to the front of the belt unit 30 by a sheet feeding device (not shown), and the sheet material is conveyed in parallel and at the same height as the upper surface of the conveyance belt 1. Has been. At this time, the conveying belt 1 composed of an endless belt travels by receiving drive transmission from the driving roller 2, and at the same time, the power supply units (power supply brushes) 7a and 7b and the power supplied units 8a and 8b are connected by a high voltage generator (not shown). A high voltage starts to be applied to the electrodes 9a and 9b. A voltage of +1.0 kV is applied to the first electrode 9a in contact with the power supply brush 7a in the power supplied portion 8a, and a voltage of −1.0 kV is applied to the second electrode 9b in contact with the power supply brush 7b in the power supplied portion 8b on the opposite side. Is applied. Then, as shown in FIG. 6, an adsorption force for adsorbing the sheet material is generated in the region of the electrode portions 9a and 9b to which a voltage is applied.

  When the sheet material 18 is further conveyed from the state of FIG. 6 and reaches the position where the leading end of the sheet material 18 contacts the conveying belt 1 as shown in FIG. 7, the portion that is in contact with the electrode that generates the suction force Is only the central portion at the front end of the sheet material 18, and therefore, the region 50 </ b> A where the suction force is generated on the sheet material 18 is only the central portion at the front end of the sheet material 18. As described above, the configuration of the belt unit 30, the shape of the electrodes 9a and 9b, and the positional relationship between the power supply brushes 7a and 7b serving as power supply units are as follows. It is set so that the adsorption force acts only on the center of the tip of the material.

When the sheet material 18 is further conveyed and has a positional relationship as shown in FIG. 8, the range in which the suction force from the conveyance belt 1 acts on the sheet material is a portion of a region 50B in FIG. The area 50B in FIG. 8 extends to the rear end side of the sheet material 18 as compared with the area 50A shown in FIG. Spread in the direction.
When the sheet material 18 is further conveyed and has a positional relationship as shown in FIG. 9, the range in which the suction force from the conveyance belt 1 acts on the sheet material is a portion of a region 50C in FIG. The area 50C in FIG. 9 expands closer to the rear end of the sheet material 18 than the area 50B shown in FIG. Spread in the direction.

  When the sheet material 18 is further conveyed and has a positional relationship as shown in FIG. 10, the range in which the suction force from the conveyance belt 1 acts on the sheet material is a portion of a region 50D in FIG. The area 50D in FIG. 10 extends to the rear end of the sheet material 18 as compared with the area 50C shown in FIG. Then, the sheet material spreads in the direction of the conveyance width of the sheet material in a direction toward (approaching) from both sides to the both end portions, and the entire front end of the sheet material 18 is adsorbed at the position shown in FIG.

  When the sheet material 18 is further conveyed and has a positional relationship as shown in FIG. 11, the range in which the suction force from the conveyance belt 1 acts on the sheet material is a portion of a region 50E in FIG. The region 50E in FIG. 11 extends to a position closer to the rear end of the sheet material 18 than the region 50D illustrated in FIG. In FIG. 11, a triangular region 50 </ b> D having the full width of FIG. 10 as the base extends as it is to the rear of the sheet material 18. That is, the attracting force generation region in FIG. 11 is further expanded by a region corresponding to a quadrangle whose longitudinal and lateral directions are the distance moved and the width of the sheet material 18 as compared with the region 50D shown in FIG.

  When the sheet material 18 is further conveyed and has a positional relationship as shown in FIG. 12, the range in which the suction force from the conveyance belt 1 acts on the sheet material is an area 50F in FIG. The region 50F in FIG. 12 extends over almost the entire area of the sheet material 18, and the sheet material is adsorbed over almost the entire area. However, from the position in FIG. 12, an area that is not attracted is generated and spreads, contrary to the time of the suction start. That is, from the state of FIG. 12, the non-adsorbed region goes from the center of the front end of the sheet material 18 to the rear of the sheet material, and from the center to the both side ends in the conveyance width direction of the sheet material ( It spreads in the direction of approaching.

When the sheet material 18 is further conveyed and the positional relationship shown in FIG. 13 is obtained, the range in which the suction force from the conveyance belt 1 acts on the sheet material is a region 50G in FIG. The region 50G in FIG. 13 is reduced only to both end portions on the rear end of the sheet material 18, and therefore the sheet material is adsorbed only on both end portions on the rear end.
When the sheet material 18 is further conveyed, the positional relationship is finally as shown in FIG. In the state of FIG. 14, the sheet material 18 is separated from the conveyor belt 1 and is discharged out of the apparatus main body.

  According to the embodiment described above, the sheet material 18 to be conveyed by the belt has the suction area by the conveyance belt 1 so that the adsorption region gradually extends toward the rear side from the central portion of the leading end of the sheet material and toward both side ends. It is conveyed while being attracted to the conveyor belt 1. Accordingly, the sheet material 18 is adsorbed so as to push out the air between the sheet material and the conveyance belt 1 not only toward the rear in the conveyance direction but also toward both end portions. For this reason, the residual air between the sheet material 18 and the conveyance belt 1 during the adsorption conveyance can be reduced or eliminated.

As a result, even a sheet material that has good surface properties such as glossy paper and hardly permeates gas can be adsorbed and transported without interposing air between the sheet material and the transport belt. The floating of the sheet material inside can be eliminated, and the disturbance of the recorded image due to the friction between the sheet material and the structural parts such as the recording head can be eliminated.
In addition, since the sheet material does not float, the sheet material and the recording head can be arranged closer to each other, and the flying distance of the ejected ink in the case of inkjet recording can be shortened. Provided is a recording apparatus that can form an image without greatly shifting the landing position of the ink droplet from the desired position even when “flection” that is ejected obliquely occurs, and can record with higher image quality. The

  In the present embodiment, at the position where the sheet material 18 starts to contact the conveyance belt 1, the suction force is generated from the central portion of the front end of the sheet material, but this is because the sheet material contacts the conveyance belt. After the sheet is conveyed for a predetermined distance in the state, the position of the power supply brush or the shape of the electrode of the conveying belt may be changed so that an attracting force is generated from the center of the leading end of the sheet material. Further, if the position of the power supply brush does not change, the shape may be changed so that the angle of the bent portion of the electrode is increased. Similar effects can be obtained by such a configuration.

  Furthermore, the position of the power supply brush and the shape of the electrode of the conveyor belt are changed so that the suction force acts in the area with a certain width at the tip of the sheet material at the position where the sheet material starts to contact the conveyor belt. You may do it. In this case, if the position of the power supply brush does not change, the shape may be changed so that the angle of the bent portion of the electrode becomes smaller. In any case, the region where the adsorption force acts on the sheet material is further toward the rear side of the sheet material and gradually spreads in the direction toward both end portions. Therefore, the belt can be transported without interposing air, and the same effect as the present embodiment can be obtained.

  Furthermore, in order to adsorb the sheet material so as to push out the air between the sheet material and the conveyance belt more reliably, the sheet material is surely adsorbed directly under the inkjet head on the most upstream side in the conveyance direction. In order to achieve this, the power supply brush is arranged so that the suction force acts from the center of the front end of the sheet material at the position where the front end of the sheet material starts to contact the conveying belt as shown in FIG. It is preferable to determine the position and the shape of the electrode.

  FIG. 15 is a schematic plan view showing the main configuration of the second embodiment of the sheet material conveying apparatus according to the present invention. In FIG. 15, two power supply brushes, a first power supply brush 7 a and a second power supply brush 7 b, are arranged on one side (left side in the drawing) of the transport belt 1. Two types of electrodes, the first electrode 9a and the second electrode 9b, are arranged in a plurality of pairs with a predetermined gap alternately in the transport direction. In the present embodiment, the electrodes 9a and 9b are arranged so as to be inclined at the same angle in the transport direction from one side end of the transport belt 1 to the other side end. A first power-supplied portion 8a that contacts only the first power supply brush 7a is formed at one end (left side in the figure) of the first electrode 9a, and a second power supply is provided at one end (left side in the figure) of the second electrode 9b. A second power-supplied portion 8b that contacts only the brush 7b is formed. That is, each power-supplied part is applied such that a voltage is applied to the first electrode 9a only from the first power supply brush 7a, and a voltage is applied to the second electrode 9b only from the second power supply brush 7b. 8a and 8b are formed so as not to remove the belt equipment.

  Although this embodiment is different from the above-described first embodiment in the points described above, the other parts have substantially the same configuration, and corresponding parts are denoted by the same reference numerals. Also in the present embodiment, the suction force is generated between the sheet material 18 and the conveyance belt 1 in the regions of the first electrode 9a and the second electrode 9b that are in contact with the power supply brushes 7a and 7b. Further, FIG. 15 shows a state at the time when the conveyed sheet material 18 is first conveyed in contact with the conveying belt 1, and at this time, the suction force is generated on the sheet material 18 in the region 50P. Only. In the case of the present embodiment, the suction region 50P is only the right end portion with respect to the conveyance direction at the front end of the sheet material 18.

  When the sheet material 18 is conveyed in the direction of the arrow from the position of FIG. 15, the electrodes 9a and 9b that contact the power supply brushes 7a and 7b are sequentially switched, but the adsorption force generation region on the conveyance belt 1 is substantially the same place. Therefore, the suction force generation region for the sheet material 18 gradually extends toward the rear side in the conveying direction and toward one end portion in the width direction (left end portion in the illustrated example). As a result, an action (air discharge force) is generated that pushes air between the conveyance belt 1 and the sheet material 18 not only in the direction toward the rear in the conveyance direction but also in the direction toward the left end, It becomes possible to make the conveyance belt 1 more closely contact.

  Also in the present embodiment, as in the case of the first embodiment, the feeding brush 7a, so that the suction force acts on the sheet material after the conveying belt 1 and the sheet material 18 are in contact and conveyed for a while. The position of 7b and the shape of the electrode pattern (electrodes 9a and 9b) may be changed. Furthermore, even if the positions of the power supply brushes 7a and 7b and the shape of the electrode pattern are changed so that the suction force acts in a range wider than the region 50P shown in FIG. good.

  Further, in the present embodiment, the power supply portions 8a and 8b are formed by bending the vicinity of the end of the electrode pattern 9 (9a and 9b) to a relatively small angle, but the pattern of each electrode is almost linear as a whole. Therefore, the operation of embedding the electrode member in the belt base material when manufacturing the transport belt can be performed more easily than in the first embodiment. Further, the shape (pattern) of each electrode may be completely straight without being bent at the parts to be fed 8a and 8b.

  According to the embodiment described above, in the sheet material conveying apparatus that adsorbs and conveys the sheet material to the conveying belt, the adsorbing means that adsorbs the sheet material to the conveying belt is directed from the front end to the rear end in the conveying direction of the sheet material. In addition, since it is configured so as to be sequentially adsorbed from one point of the leading end toward both end portions in the conveyance width direction, the air between the sheet material and the conveyance belt is pushed out in both the conveyance direction rear side and the conveyance width direction. Therefore, even when a sheet material that is difficult to pass air is conveyed by a belt, the sheet material can be prevented from being lifted by the remaining air, and the lifted portion contacts the recording head or the like to cause a recording failure. In addition, the sheet material can improve the image quality of the recorded image by reducing the gap between the sheet material and the image forming means. Feeding device and image forming apparatus is provided.

  In the above-described embodiment, the present invention has been described by taking an example of an image recording apparatus having a line-type image forming unit composed of a full line head or the like. However, the present invention performs main scanning movement with respect to a sheet material. The present invention can be similarly applied to an image forming apparatus of another recording form such as a serial type image forming apparatus using an image forming unit, and has the same effect. In the above-described embodiment, the case where the recording method of the image forming apparatus is an ink jet type has been described as an example. However, the present invention is not limited to a recording method such as a thermal transfer type, a thermal type, a laser beam irradiation type, or a wire dot type. It can be applied regardless of the method, and has the same effect.

1 is a schematic perspective view illustrating an embodiment of an image forming apparatus including a sheet material conveying device according to the present invention. It is a typical perspective view which shows the belt unit in FIG. FIG. 3 is a partial vertical cross-sectional view in which a part of the conveyance belt 1 in FIG. 2 is cut in the conveyance direction. It is a typical perspective view which shows a state when the conveyance belt is cleaned with the rubber blade in the belt cleaning unit in FIG. FIG. 2 is a schematic perspective view showing a state when the liquid on the rubber blade is absorbed and removed by the absorber in the belt cleaning unit in FIG. 1. FIG. 6 is a schematic perspective view showing a state in which the sheet material is conveyed to the front of the belt unit. FIG. 7 is a schematic perspective view showing a state when the sheet material is further conveyed from the state of FIG. 6 and the leading end of the sheet material reaches a position in contact with the conveyance belt. FIG. 8 is a schematic perspective view showing a state when the sheet material is further conveyed from the state of FIG. 7 and an adsorption force action region from the conveyance belt for the sheet material is formed. FIG. 9 is a schematic perspective view illustrating a state in which the sheet material is further conveyed from the state of FIG. 8 and an adsorption force action region for the sheet material is slightly expanded. FIG. 10 is a schematic perspective view showing a state when the sheet material is further conveyed from the state of FIG. 9 and the adsorption force action area for the sheet material further expands to reach both end portions. FIG. 11 is a schematic perspective view showing a state when the sheet material is further conveyed from the state of FIG. 10 and the adsorption force acting region from the conveyance belt with respect to the sheet material further expands rearward. FIG. 12 is a schematic perspective view showing a state when the sheet material is further conveyed from the state of FIG. 11 and an adsorption force acting region from the conveyance belt with respect to the sheet material reaches almost the entire area of the sheet material. FIG. 13 is a schematic perspective view showing a state when the sheet material is further conveyed from the state of FIG. 12 and the adsorption force acting region on the sheet material is in a limited range of the rear end portion. FIG. 14 is a schematic perspective view showing a state when the sheet material is further conveyed from the state of FIG. 13 and the sheet material is separated from the conveyance belt and discharged. It is a typical top view which shows the principal part structure of 2nd Embodiment of the sheet material conveying apparatus by this invention. It is a typical top view which shows one structural example of the conventional belt conveyance type sheet | seat conveyance apparatus. FIG. 17 is a schematic side view of the sheet material conveying device of FIG. 16. It is a typical fragmentary top view which expands and shows the D1 part in FIG. FIG. 19 is a schematic side view of the power supply brush in FIGS. 16 to 18. It is explanatory drawing which shows an example of the electrode pattern of the conveyance belt of the conventional sheet material conveying apparatus. It is explanatory drawing which shows another example of the electrode pattern of the conveyance belt of the conventional sheet material conveying apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conveyor belt 2 Drive roller 3 Driven roller 4 Tension roller 5 Belt cleaning unit 6 (6a-6f) Image formation means (full line head)
7 (7a, 7b) Feeding part (feeding brush)
8 (8a, 8b) Power-supplied part (first power-supplied part, second power-supplied part)
9 (9a, 9b) Electrode (first electrode, second electrode)
9c Substrate 9d Surface layer 18 Sheet material 21 Web roller 40 Blade base 41 Rubber blade 42 Absorber 43 Rotating support plate 71 Web facing plate 72 Blade facing plate 50A-50G, 50P Sheet material adsorption area

Claims (9)

In the sheet material conveying apparatus that adsorbs and conveys the sheet material to the conveying belt,
The adsorbing means for adsorbing the sheet material to the conveying belt is an adsorbing means that adsorbs the sheet material in order from the leading end to the rear end in the conveying direction and from one point of the leading end to both side ends in the conveying width direction. There is a sheet material conveying device. In the sheet material conveying apparatus that adsorbs and conveys the sheet material to the conveying belt,
The adsorption force generating means for adsorbing the sheet material to the conveyance belt first applies an adsorption force at the center of the front end of the sheet material when or after the sheet material contacts the conveyance belt, and the sheet As the contact area between the sheet and the conveyor belt increases, the region where the suction force acts is from the leading edge of the sheet material in the conveying direction toward the rear edge and from one point of the leading edge toward both side edges in the conveying width direction. A sheet material conveying device characterized by generating an adsorption force so as to spread in order. In the sheet material conveying apparatus that adsorbs and conveys the sheet material to the conveying belt,
The conveyor belt is an endless belt that extends in the width direction of the belt, and is provided with a plurality of electrodes having a power-supplied portion in contact with the power feeding portion at an end in the belt width direction at intervals in the conveyance direction;
The plurality of electrodes provided on the transport belt are inclined upstream in the transport direction from the power-supplied portion to a predetermined position in the belt width direction, and transport from the predetermined position in the middle to the other side end. Inclining downstream in the direction,
When the power-supplied part of each electrode comes to a power supply start position where it comes into contact with the power supply part, the predetermined position of the electrode is at a position where the conveyance belt and the leading edge of the sheet material first contact each other, or a sheet A sheet material conveying apparatus, which is located downstream of the material conveying direction.   The sheet material conveying device according to any one of claims 1 to 3, wherein the one halfway portion is a substantially central portion in the belt width direction. In the sheet material conveying apparatus that adsorbs and conveys the sheet material to the conveying belt,
An adsorbing means for adsorbing the sheet material to the conveyance belt is directed from one end in the width direction to the rear end at the front end in the conveyance direction of the sheet material and from the one end to the other end. The sheet material conveying apparatus is characterized by being an adsorption means for sequentially adsorbing. When the sheet material comes into contact with the conveyance belt, an adsorption force acts on one end portion in the conveyance width direction of the sheet material,
As the contact area between the sheet material and the conveyor belt increases, the region where the attractive force acts is directed from the one end to the rear end in the conveyance width direction at the front end in the conveyance direction of the sheet material and conveyed from the one end. The sheet material conveying device according to claim 5, wherein the sheet material conveying device spreads in order toward the other end portion in the direction width direction. In the sheet material conveying apparatus that adsorbs and conveys the sheet material to the conveying belt,
The transport belt is an endless belt that extends in the belt width direction, and is provided with a plurality of electrodes having a power-feeding portion that comes into contact with the power feeding portion at an end portion in the belt width direction, with an interval in the transport direction.
The plurality of electrodes provided on the conveyor belt are provided so as to be inclined such that one end portion in the belt width direction is located on the upstream side in the conveyance direction from the other end portion,
When the power supplied portion of each electrode pattern comes to a power supply start position in contact with the power supply portion, a portion located on the most upstream side in the transport direction at one end portion of the electrode of the transport belt has the transport belt and the A sheet material conveying apparatus, wherein the leading edge of the sheet material is in a position where it first contacts or is located further downstream in the sheet material conveying direction.   An image forming apparatus comprising: an image forming unit that forms an image on a sheet material based on image information; and the sheet material conveying device according to claim 1.   The image forming apparatus according to claim 8, wherein the image forming unit is an ink jet recording head that performs recording by discharging ink from the recording head to a sheet material.

Images