JP2006219291A - Paper carrying device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper carrying device capable of drying paper with a simple constitution, and an image forming device having the paper carrying device. <P>SOLUTION: In this paper carrying device, a high voltage power source 50 for imparting AC bias voltage to an charging roller 26 for charging a carrier belt 21 for attracting and carrying the paper 12 by electrostatic attraction force, is arranged in a position for conducting heat generated in the high voltage power source 50 via the atmosphere to the paper 12 carried by the carrier belt 21, on the downstream side of a recording head 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus, and more particularly to a sheet conveying apparatus and an image forming apparatus provided with a conveying belt that adsorbs and conveys a sheet with electrostatic attraction force.

  As various image forming apparatuses such as printers, facsimiles, copying machines, plotters, printer / fax / copier multifunction machines, etc., a recording head constituted by a droplet discharging head for discharging a recording liquid (for example, ink) droplet is used as a carriage. The carriage is mounted, and this carriage is referred to the recording medium (hereinafter referred to as “paper”, but the material is not limited to paper, and is also referred to as recording medium, recording paper, transfer material, etc.). Are scanned in the orthogonal direction, and the recording medium is transported intermittently according to the recording width, and an image is formed on the recording medium by repeating conveyance and recording alternately (recording, printing, printing, printing) Are also used synonymously.) And a line type image forming apparatus having a line type head as a recording head.

  In an image forming apparatus using such a liquid discharge head as a recording head, it is necessary to improve the landing position accuracy of ink droplets on a sheet in order to improve image quality. The sheet is positively charged, and the sheet is attracted by an electrostatic force to keep the distance between the recording head and the sheet constant, and the sheet feed is accurately controlled to prevent sheet misalignment. Is known to prevent jamming and smearing caused by the contact between the paper and the recording head.

  On the other hand, in an image forming apparatus that uses a liquid ejection head, if the recording liquid on the paper on which the recording liquid has landed by image formation is not dried and is stacked on a paper discharge stocker or the like, image rubbing or smearing may occur. Since the image quality deteriorates, the paper is dried.

For example, in Patent Document 1, a skew correction unit in a transport unit in which a positional relationship between a supply roll unit and a take-up roll unit is horizontal is provided in a vertical direction, and a recording medium carry-in path and ink jet carried into an ink jet recording unit It is described that a guide roll unit is provided so that the recording medium unloading path to be unloaded from the recording unit is adjacent and parallel, and further an ink drying unit is provided across the recording medium unloading path and the recording medium unloading path. ing.
JP 2003-025557 A

Patent Document 2 discloses an ink jet recording head that ejects ink droplets, a transfer medium that faces the ink jet recording head and moves through a gap, a support roller member that supports the transfer medium, and the support roller member. In a transfer type ink jet recording apparatus, comprising: a driving means for driving the recording medium; and a pressure contact means positioned on the downstream side of the ink jet recording head with respect to the moving direction of the transfer medium to press the transfer medium and the recording medium. It is described that the member is composed of a heating device.
JP 7-125190 A

Further, Patent Document 3 includes a heating unit that performs non-contact heating on the surface to be printed of a recording medium and covers a range in which the heating region extends in the direction of multi-nozzle row arrangement and is larger than the printing width of the recording medium. And a heating means for heating a recording medium placed substantially flat on the conveying means.
JP 2000-195996 A

  As described above, in a paper transport device that transports paper by attracting the paper to the transport belt with electrostatic attraction, and an image forming apparatus using the same, if the paper absorbs moisture, the transport belt is driven by the moisture. There is a problem in that the electric charge is neutralized due to the charge, and a desired suction force cannot be obtained, so that it is not possible to carry the paper with high accuracy.

  In this case, it is disadvantageous in view of space saving and cost to provide a drying device used for recording liquid drying as described in Patent Documents 1 to 3 described above to dry the paper.

  The present invention has been made in view of the above problems, and an object thereof is to provide a sheet conveying apparatus capable of drying a sheet with a simple configuration and an image forming apparatus including the sheet conveying apparatus.

  In order to solve the above-described problems, the paper conveying apparatus according to the present invention is configured to apply heat generated by a high voltage power source for charging a conveying belt that adsorbs and conveys the paper by electrostatic attraction to the paper. .

  Here, the high voltage power supply can be disposed at a position where heat generated by the high voltage power supply is conducted to the sheet through the atmosphere. Or it can be set as the structure provided with the fan which ventilates the air | atmosphere around a high voltage power supply toward a paper.

  An image forming apparatus according to the present invention includes the sheet conveying device according to the present invention.

  According to the paper conveyance device and the image forming apparatus according to the present invention, the heat generated by the high voltage power source for charging the conveyance belt that adsorbs and conveys the paper with the electrostatic adsorption force is applied to the paper, so that the special heating is performed. Paper that is transported with a simple configuration can be dried without using any means, space saving and cost reduction can be achieved, and paper can be transported with high precision, so that high-quality images can be stably formed. be able to.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an image forming apparatus provided with a paper conveying apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram for explaining the overall configuration of the apparatus, FIG. 2 is a plan view for explaining a main part of the apparatus, and FIG. 3 is a front view of the main part of the apparatus.

  As shown in FIG. 2, the image forming apparatus holds a carriage 3 slidably in a main scanning direction by a guide rod 1 which is a guide member horizontally mounted on left and right side plates (not shown) and a guide stay (not shown). The main scanning motor 4 moves and scans in a direction indicated by an arrow (main scanning direction) in FIG. 2 via a timing belt 5 spanned between the driving pulley 6a and the driven pulley 6b. Note that guide bushes (bearings) 3a and 3a are interposed between the carriage 3 and the guide rod 1, respectively.

  The carriage 3 has a recording head 7 composed of four ink jet heads for ejecting ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk), with a plurality of ink ejection openings. They are arranged in a direction crossing the main scanning direction, and are mounted with the ink droplet ejection direction facing downward.

  As an ink jet head constituting the recording head 7, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. A shape memory alloy actuator to be used, an electrostatic actuator using an electrostatic force, or the like as an energy generating means for discharging ink can be used. Note that the recording head can also be configured by one or a plurality of liquid droplet ejection heads provided with a plurality of nozzle rows that eject different colors.

  The carriage 3 is also equipped with sub-tanks 8 for each color for supplying ink of each color to the recording head 7. Ink is supplied to the sub tank 8 from a main tank (ink cartridge) (not shown) via an ink supply tube 9. In addition to the recording head 7 that discharges ink droplets, a recording head that discharges a fixing treatment liquid (fixing ink) that reacts with the recording liquid (ink) to improve the fixing property of the ink can be provided.

  On the other hand, as a paper feeding unit for feeding the paper 12 stacked on the paper stacking unit (pressure plate) 11 such as a paper feeding cassette, a half-moon roller (feeding) that separates and feeds the paper 12 one by one from the paper stacking unit 11. A separation pad 14 made of a material having a large friction coefficient is provided opposite to the (paper roller) 13 and the sheet feeding roller 13, and the separation pad 14 is urged toward the sheet feeding roller 13 side.

  As a transport unit for transporting the paper 12 fed from the paper feed unit on the lower side of the recording head 7, a transport belt 21 for transporting the paper 12 by electrostatic adsorption, and a paper feed unit A counter roller 23 for transporting the paper 12 fed through the guide 22 while sandwiching it between the transport belt 21 and the paper 12 fed substantially vertically upward is changed by approximately 90 ° and copied onto the transport belt 21. The above-mentioned conveyance guide 22 for adjusting the pressure and a tip pressure roller 25 urged toward the conveyance belt 21 by a pressing member 24 are provided. In addition, a charging roller 26 as a charging unit for charging the surface of the transport belt 21 is provided.

  Here, the conveyance belt 21 is an endless or connected belt (these are referred to as “endless shape”), and is stretched between the conveyance roller 27 and a tension roller 28 to which tension is applied, and is sub-scanning motor. By rotating the conveyance roller 27 from 31 through the timing belt 32 and the timing roller 33, it is configured to circulate in the belt conveyance direction (sub-scanning direction, arrow A direction in FIG. 1) in FIG. .

  As shown in FIG. 4, the transport belt 21 includes a surface layer 21 a that forms a sheet adsorbing surface formed of a resin material having a pure thickness of about 40 μm that is not subjected to resistance control, for example, ETFE pure material, and the surface layer 21 a It has a back layer (medium resistance layer, earth layer) 21b made of the same material and subjected to resistance control by carbon.

  The thickness of the insulating layer (surface layer) 21a of the conveyor belt 21 affects the dielectric constant. When the thickness increases, the dielectric constant decreases and the amount of charge on the belt decreases when charged. According to the experiment, a desired electrostatic attraction force was obtained by setting the thickness of the surface layer 21a to 60 μm or less. However, in consideration of the range of film thickness that varies in manufacturing, scratches generated on the belt in the actual machine However, the electrostatic attraction force can be further improved by making the layer thickness as thin as possible within the range where the layer thickness does not become zero.

  Further, the thickness of the back layer (medium resistance layer, earth layer) 21b of the conveyor belt 21 does not directly affect the electrostatic action. However, as the total thickness of the belt increases, the rigidity increases and the belt is stretched on the actual machine. Sometimes it is difficult to ensure the flatness of the belt, while it cannot be made too thin to ensure the required strength. According to experiments, the thickness of the back layer 21b is preferably about 40 to 200 μm.

  In this way, by providing the resistance control layer 21b on the entire back side of the transport belt 21 as a two-layer structure, after the charge is formed on the surface layer 21a that is an insulating layer in advance, the charge is further increased when the sheet adsorbed to the belt comes into contact with it. The electrostatic attraction force between the paper and the conveyor belt 21 can be increased. For example, in the case of a single insulating layer, the adsorption force is halved compared to the case of two layers, and in the case of a single layer, the position where the paper starts to contact the belt faces the ground roller located inside the belt. However, by using two layers, such a restriction is eliminated.

  In this case, a surface resistance of 1E + 10Ω / □ or more was used as the surface layer 21a, and a surface resistance of 1E + 08Ω / □ or less was used as the back layer 21b, whereby a desired electrostatic adsorption force was obtained.

  The charging roller 26 is disposed so as to contact the surface layer of the conveyor belt 21 and rotate following the rotation of the conveyor belt 21, and applies 2.5N to both ends of the shaft as a pressing force. Further, the transport roller 27 also serves as an earth roller, is placed in contact with the middle resistance layer of the transport belt 22 and is grounded via a ground line (not shown).

  Further, as shown in FIG. 2, a slit disk 34 is attached to the shaft of the transport roller 27, and a sensor 35 for detecting the slit of the slit disk 34 is provided. An encoder 36 is configured.

  Further, as a paper discharge unit for discharging the paper 12 recorded by the recording head 7, a separation unit 41 for separating the paper 12 from the transport belt 21 and a paper discharge tray for stocking the paper 12 to be discharged. 42. A duplex unit 43 is detachably mounted on the back side of the apparatus.

  In this image forming apparatus, a high voltage power source 50 that applies an AC bias voltage to the charging roller 26 that charges the conveying belt 21 that adsorbs and conveys the paper 12 with electrostatic attraction is provided downstream of the recording head 7. On the side, the sheet 12 conveyed by the conveying belt 21 is disposed at a position where heat generated by the high voltage power source 50 is conducted through the atmosphere.

  As shown in FIGS. 5 and 6, the high voltage power supply 50 includes two DC transformers 51 and 52 disposed on a single substrate 53, and according to a control signal from the control unit 100, The rectangular wave high voltage generated by these DC transformers 51 and 52 is applied to the charging roller 26 via the high voltage cable 54.

  Note that the sheet conveying apparatus in the image forming apparatus includes the conveying belt 21, the conveying roller 27, the high voltage power supply 50, and the like.

Next, sheet conveyance in the image forming apparatus configured as described above will be described.
The paper 12 is separated and fed one by one from the paper feeding unit, and the fed paper 12 is guided by the transport guide 22 and is sequentially sandwiched between the transport belt 21, the counter roller 23, and the leading end roller 25 to be fed. Sent.

  At this time, the controller 100 alternately applies positive output and negative output from the high voltage power supply 50 to the charging roller 26, that is, by applying alternating rectangular wave high voltage, as shown in FIG. In addition, positive (positive polarity) and negative (negative polarity) charges are charged to the insulating layer 21a of the transport belt 21 at the same potential with a predetermined charging pitch (charging width).

  In this state, as shown in FIG. 7, when the paper 12 starts to contact, a magnetic force line 90 is generated from the positive charge on the belt 21 toward the negative charge on the surface of the conveyor belt 21. Due to the influence of the magnetic lines of force 90, charges having the same polarity are induced on the side of the paper 12 in contact with the transport belt 21 and the opposite side. The density of magnetic force on the side of the paper 12 in contact with the conveyance belt 21 is high, and the density of the paper 12 on the non-contact surface side with the conveyance belt 21 is sparse. At that time, a difference in charge is generated between the lower side and the upper side of the sheet 12, and a force acts in the direction in which the sheet 12 is attracted to the conveyance belt 21 (this is referred to as Maxwell stress, which is charged with positive and negative polarity) Occurs at the border of). As a result, the paper 12 is attracted to the transport belt 21, and the paper 12 is transported in the sub-scanning direction by the circular movement of the transport belt 21.

  In this way, the paper 12 is transported and stopped by the transport belt 21 that is alternately charged positively and negatively, and the recording head 7 is driven in accordance with the image signal while moving the carriage 3. One row is recorded by ejecting ink droplets. When recording for one line is completed, the conveying belt 21 is driven to convey the paper 12 by a predetermined amount, and then the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the paper 12 has reached the recording area, the recording operation is finished, and the paper 12 is discharged onto the paper discharge tray 42.

  As described above, since the high voltage power supply 50 for applying a high voltage to charge the transport belt 21 includes the DC transformers 51 and 52 as described above, the high voltage power supply 50 always generates heat during driving.

  Therefore, as shown in FIG. 1, the high voltage power supply 50 is installed at a position immediately after printing on the downstream side of the recording head 7 in the conveyance path through which the paper 12 is conveyed. The heat generated in step 1 is conducted to the paper 12 through the atmosphere, whereby the paper 12 immediately after printing is dried.

  In this way, by adopting a configuration in which heat generated by a high-voltage power source for charging a conveyance belt that adsorbs and conveys a sheet with electrostatic attraction is applied to the sheet, moisture absorption of the sheet is prevented and a desired sheet is obtained. The suction force can be ensured and the apparatus can be configured simply to reduce the cost and the size of the apparatus.

  In this case, the high voltage power supply is arranged at a position where heat generated by the high voltage power supply is conducted to the paper conveyed through the atmosphere, thereby simultaneously preventing an increase in the high voltage output current of the high voltage power supply. Can do.

  Preferably, the high voltage power supply is installed so that the portion where the heat generation of the high voltage power supply is large is close to the paper. Specifically, it is preferable that the transformer, the transformer current driving transistor and resistor, and the control IC, which are main heat-generating components of the high-voltage power supply, be close to the sheet, and thereby the sheet can be dried more effectively.

  By providing such a paper transport device, the recording paper such as ink is offset to the transport belt when double-sided printing is performed by drying the printed paper at an early stage, resulting in a decrease in electrostatic attraction force. Can be prevented.

Next, another embodiment of the present invention will be described with reference to FIG.
In this embodiment, heat generated by the high-voltage power supply 50 is conducted to the vicinity of the paper stacking unit 11 from the high voltage power supply 50 with respect to the paper 12 before being fed and fed in the paper stacking unit 11. The high voltage power supply 50 is arranged at a position where

  In this way, heat can be transferred to the paper before printing and dried, more effectively preventing moisture absorption of the paper, ensuring the desired paper adsorption force, and the apparatus having a simple configuration, Cost reduction and downsizing of the apparatus can be achieved.

Next, still another embodiment of the present invention will be described with reference to FIG.
In this embodiment, in the embodiment of FIG. 1, a fan 60 that blows air around the high voltage power supply 50 toward the paper 12 is provided, and heat generated by the high voltage power supply 50 is forcibly blown onto the paper 12. ing.

  As a result, the ink can be dried more efficiently and the productivity can be improved, and the temperature rise of the high voltage power supply can be prevented and failure can be prevented.

1 is a schematic side view illustrating an example of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the apparatus. It is front explanatory drawing of the same apparatus. It is explanatory drawing which shows an example of the conveyance belt of the apparatus. It is explanatory drawing of the part regarding charging with respect to the conveyance belt of the apparatus. FIG. 6 is an explanatory view of the conveyor belt as seen from the charging roller side. It is explanatory drawing with which it uses for description of electrostatic attraction conveyance of a paper. It is a schematic side surface explanatory drawing which concerns on other embodiment of this invention. It is a schematic side surface explanatory drawing which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Carriage 7 ... Recording head 21 ... Conveying belt 26 ... Charging roller 27 ... Conveying roller 50 ... High voltage power supply

Claims (4)

  In a paper conveying apparatus comprising a conveying belt that adsorbs and conveys a sheet with electrostatic attraction and a high voltage power source for charging the conveying belt, heat generated by the high voltage power source is applied to the sheet. Characteristic paper transport device.   2. The paper conveying apparatus according to claim 1, wherein the high voltage power source is arranged at a position where heat generated by the high voltage power source is conducted to the paper through the atmosphere.   2. The paper conveying apparatus according to claim 1, further comprising a fan that blows air around the high voltage power source toward the paper. A sheet conveying device including a conveying belt that adsorbs and conveys the sheet with electrostatic attraction force and a high voltage power source for charging the conveying belt, and the recording liquid is supplied from the recording head to the conveyed sheet. 4. An image forming apparatus for forming an image by ejecting liquid droplets, wherein the paper transport apparatus is the paper transport apparatus according to claim 1.

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