JP2006272720A - Inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely remove dust such as paper powder or the like on or near a printing medium when the printing medium is attracted on a carrying belt charged in a stripe-shape and is supplied to an inkjet printer. <P>SOLUTION: When the printing medium 2 supplied from gate rollers 23 is supplied onto the endless belt 1 which is alternately charged to a positive and a negative polarities into a stripe-shape to be attracted and carried, a first and a second dust attracting rollers 13, 14 are arranged on the upstream side in the printing medium carrying direction of a printing region, the first dust attracting rollers 13 are applied with the potential of a negative electrode to attract the dust charged to positive polarity near the printing medium 2, while the second dust attracting rollers 14 are applied with the potential of a positive electrode to attract and remove the dust charged to negative polarity near the printing medium 2. The dust attracting rollers 13, 14 are simultaneously applied with alternative potential to finely vibrating the dust to facilitate attraction. Furthermore, the dust attracting rollers 13, 14 are prevented from getting into complete close contact with the printing medium 2 to allow attraction of only dust effectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention adsorbs and conveys a printing medium such as recording paper onto the surface of a conveying belt, and discharges, for example, fine particles (dots) of liquid ink of a plurality of colors onto the printing medium to draw predetermined characters and images. The present invention relates to an inkjet printer.

Such an inkjet printer is generally inexpensive and can easily obtain a high-quality color printed matter. Accordingly, along with the widespread use of personal computers and digital cameras, it has become widespread not only in offices but also in general users.
In such an ink jet printer, a moving body called a carriage or the like in which an ink cartridge and an ink discharge head (generally called an ink jet head) are integrally provided is generally a direction perpendicular to the paper feed direction on a print medium. By driving the actuator while reciprocating, the liquid ink fine particles are ejected (jetted) from the nozzles formed in the ink jet head, thereby outputting minute ink dots on the print medium, A desired printed matter is created by drawing an image. The carriage is equipped with four color (yellow, magenta, cyan) ink cartridges including black (black) and an inkjet head for each color, so that not only monochrome printing but also full-color printing combining each color is easy. (Furthermore, 6 colors, 7 colors, or 8 colors in which light cyan, light magenta, etc. are added to these colors are also put into practical use).

   Also, in this type of inkjet printer in which printing is executed while the inkjet head on the carriage is reciprocated in the direction (width direction of the print medium) perpendicular to the paper feed direction, the entire page is printed neatly. In addition, since it is necessary to reciprocate the inkjet head several tens of times to 100 times or more, it takes much printing time compared with other types of printing apparatuses such as laser printers and copying machines using electrophotographic technology. There are drawbacks.

  On the other hand, in an ink jet printer of a type in which a long ink jet head having the same dimensions as the width of the printing paper is arranged and a carriage is not used, it is not necessary to move the ink jet head in the width direction of the printing paper, so-called one pass. Therefore, high-speed printing similar to that of the laser printer is possible. The former inkjet printer is generally referred to as a “multi-pass inkjet printer”, and the latter inkjet printer is generally referred to as a “line head inkjet printer”.

  By the way, in this type of line head type ink jet printer, a configuration in which a print medium is adsorbed and conveyed by an endless belt for conveyance is often used. On the other hand, dust mainly composed of paper dust adheres to a printing medium such as printing paper, and when this paper dust adheres to the nozzles of the inkjet head, an ink ejection problem such as a flying curve occurs. The flight curve means that the ink droplets ejected from the nozzle do not fly on the ideal trajectory and deviate from the ideal output position (also referred to as the landing position). In particular, in a line head type ink jet printer, since printing is performed in a so-called one pass, a printing result is remarkably lowered only by an ink ejection failure occurring in one of a large number of nozzles.

Therefore, in the ink jet printer described in Patent Document 1 below, dust such as paper dust is blown off by blowing air onto the print medium in an oblique direction toward the moving direction of the ink jet head. In Patent Document 1, the print medium is grounded as necessary to remove static electricity.
Japanese Patent Laid-Open No. 2003-118095

  However, in the prior art described in Patent Document 1, air is blown to the print medium and dust such as paper dust is blown away, so that it is blown further forward in front of the head movement. In other words, it was not possible to completely define the destination of the blown-up paper dust and the like, and there were many things that fell again in the vicinity of the head nozzle, which was unreliable. Further, as described in Patent Document 1, dust such as paper dust adheres to a belt or a printing medium due to electrostatic force, but in Patent Document 1, paper dust or the like that is actually desired to be removed. No measures were taken to remove or control the charged charge of the dust itself, so the reliability of removing paper dust and the like was insufficient. In any case, the ink jet printer described in Patent Document 1 has a problem that dust such as paper dust on the printing medium cannot be removed reliably.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide an ink jet printer capable of reliably removing dust such as paper dust on a print medium. is there.

  [Invention 1] In order to solve the above-mentioned problem, the ink jet printer of Invention 1 adsorbs and conveys a print medium to the surface of the conveyance belt by electrostatic force, and ejects ink droplets from the nozzles to the print medium for printing. A first dust adsorbing roller that adsorbs dust charged on the surface of the print medium and in the vicinity of the positive electrode while rotating synchronously with the print medium on the surface of the transport belt to be conveyed, A second dust adsorbing roller that adsorbs dust charged on the surface of the printing medium and in the vicinity of the negative electrode while rotating synchronously with the printing medium on the surface of the conveying belt that is charged to the positive electrode and conveyed. It is characterized by.

  According to the ink jet printer of the first aspect of the present invention, the charged dust is adsorbed on the print medium surface and the positive electrode in the vicinity thereof by the first dust adsorbing roller charged on the negative electrode, and the second dust adsorbing roller charged on the positive electrode is adsorbed. Because of the configuration that adsorbs dust charged on the surface of the print medium and the negative electrode in the vicinity of the print medium, it is possible to reliably remove dust charged on both the positive and negative poles regardless of whether the transport belt is charged on either the positive or negative pole. Can do.

[Invention 2] The ink jet printer of Invention 2 is characterized in that, in the ink jet printer of Invention 1, the charged dust is adsorbed such that the first and second dust adsorbing rollers do not completely adhere to the print medium. It is what.
In the ink jet printer according to the second aspect of the present invention, the first and second dust suction rollers are configured to suck the charged dust so that the first and second dust suction rollers do not completely adhere to the print medium. Only the dust can be reliably removed without being attracted to the suction roller.

[Invention 3] The inkjet printer of Invention 3 is characterized in that, in the inkjet printer of Invention 2, an AC potential is applied to the first and second dust suction rollers.
In the ink jet printer according to the third aspect of the invention, by applying an alternating potential to the first and second dust suction rollers, fine vibration can be generated on the surface of the print medium and dust in the vicinity thereof. Even when charged, dust can be lifted and removed reliably.

Next, an embodiment of an inkjet printer according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an ink jet printer according to the present embodiment. Reference numeral 1 in the figure denotes an endless belt for conveying a printing medium 2 such as printing paper. As described above, the printing medium 2 is a sheet material made of a high resistance material such as printing paper or an OHP sheet. The endless belt 1 is also an endless belt having a surface made of a material as described later and made of a high resistance material. The endless belt 1 is wound around a driving roller 3 disposed at the left end portion in the figure and a driven roller 4 disposed at the right end portion in the figure. The drive roller 3 is rotated in the direction of the arrow in the figure by a drive source (not shown), and the print medium 2 is attracted from the right side of the figure in a state where the endless belt 1 is charged by the charging roller described later. Transport to the left, that is, in the direction of the arrow. The driven roller 4 is grounded in order to set the charging potential to a predetermined value. The tension of the endless belt 1 is adjusted by a configuration such as using a tension roller (not shown) to expand the belt downward in the figure, or pulling either the driving roller 3 or the driven roller 4 outward with a spring, etc. It's not going out.

  A charging roller 7 as a charging unit is in contact with the endless belt 1 so as to face the driven roller 4, and an AC power supply 8 is connected to the charging roller 7. The arrangement of the charging roller 7 corresponds to immediately before the feeding position of the printing medium 2. As described above, the charging roller 7 charges the surface of the endless belt 1 by alternately applying positive (+) and negative (−) polar charges to the print medium 2 by the charged charges. The print medium 2 is attracted to the surface of the endless belt 1 by electrostatic force due to the charge on the endless belt 1 side of the print medium 2 and the charge on the surface of the endless belt 1 due to the dielectric polarization. Note that alternately forming positive (+) and negative (−) charging regions on the surface of the endless belt 1 is also referred to as stripe charging. Specific examples of the stripe charging include those described in Japanese Patent Application Laid-Open No. 2003-103857, for example. The charging roller 7 is pressed against the endless belt 1 by a spring (not shown).

  A paper pressing roller 9 may be disposed above the driven roller 4 as shown. The paper pressing roller 9 is urged downward by a spring (not shown) and has a function of pressing the print medium 2 against the endless belt 1 on the driven roller 4. Since the printing medium 2 has irregularities of about 10 to several tens of μm, and there are wrinkles, warping, sagging, and bending, the printing medium 2 can be obtained by feeding the printing medium 2 onto the endless belt 1. It does not adhere to. Therefore, after the print medium 2 is mounted on the outer peripheral surface of the charged endless belt 1 and then pressed against the endless belt 1 by the paper pressing roller 9, the outer surface of the endless belt 1 is caused by the dielectric polarization as described above. The adsorbed print medium 2 is further closely adhering and transported with a higher adsorbing force, and improves the surface smoothness of the print medium 2 and improves the uniformity of the gap with the head nozzle. Will also improve. A gate roller 23 is disposed upstream of the paper pressing roller 9 in the conveyance direction of the printing medium 2. The gate roller 23 adjusts the timing at which the print medium 2 fed from the paper feed unit 24 is fed onto the endless belt 1 and corrects the bending of the print medium 2 in the conveyance direction, so-called skew. Note that reference numeral 25 in the figure denotes a paper discharge unit for discharging the print medium 2.

   Reference numeral 11 in FIG. 1 denotes an inkjet head. This ink jet head 11 has four colors of yellow (Y), magenta (M), cyan (C), and black (K), or six colors obtained by adding light magenta (Lm) and light cyan (Lc) to these, or blue For each color of a necessary combination of a plurality of colors such as 6 colors including (B) and red (R), and further 7 colors including gray, the printing medium 2 is arranged in a shifted direction. . Ink is supplied to each inkjet head 11 from an ink tank of each color (not shown) via an ink supply tube. Each inkjet head 11 is formed with a plurality of nozzles in a direction intersecting with the transport direction of the print medium 2, and by ejecting a necessary amount of ink droplets from these nozzles to necessary places as appropriate, the print medium 2. A minute ink dot is formed and output on the top. By performing this for each color, it is possible to perform so-called one-pass printing by passing the print medium 2 adsorbed on the endless belt 1 once. That is, the area where the inkjet head 11 is disposed corresponds to the print area.

There are various methods for ejecting and outputting ink from each nozzle of the ink jet head, such as a piezo method and a thermal method, and any ink output method can be applied to the present invention.
A plane forming portion 12 is provided below the inkjet head 11 constituting the printing area so as to face the inkjet head 11. The plane forming unit 12 is generally called a platen, and regulates the flat surface of the print medium 2 when ejecting ink droplets from the inkjet head 11.

The endless belt 1 uses a polyamide-based synthetic fiber, polyester, polyurethane, PET, polycarbonate, a fluorine-based resin such as silicon-based or PVDF-based resin as a base resin, and carbon black or conductive filler mixed therein The volume resistance value is adjusted to about 10 ⁵ to 10 ⁸ Ω · cm, and the volume resistance value is set to 10 ¹² Ω · cm or more, and an insulating layer having a thickness of about several μm to 20 μm is adhered thereto. The total thickness is selected to be 0.05 to 0.5 mm, more preferably about 0.1 to 0.2 mm in consideration of durability and flexibility, high-speed charging and static elimination characteristics, and the like. As a material of the insulating layer, for example, a general synthetic resin such as polyurethane, polyimide, or silicon rubber may be used, and nylon, polyvinylidene fluoride, polyvinylidene chloride, or the like may be used. On the other hand, the endless belt 1 is charged by applying an AC potential to the charging roller 7. When the surface of the endless belt 1 is charged (+) (−) alternately in stripes by the charging roller 7 and the print medium 2 is mounted on the surface, dielectric polarization occurs in the thickness direction in the print medium 2 made of an insulator. The print medium 2 is attracted to the surface of the endless belt 1 by the electrostatic force generated by the charge on the surface of the endless belt 1 and the charge on the endless belt 1 side in the dielectrically polarized print medium 2. In particular, stripe charging by applying an alternating potential has almost the same amount of positive and negative charges when viewed as the entire surface, and therefore the print medium 2 peeled off the endless belt 1 after printing is not charged macroscopically. Alternatively, there is an advantage that it is easy to release charges.

  In the present embodiment shown in FIG. 1, a second dust suction roller 14 is provided on the upstream side of the inkjet head 11 in the print medium conveyance direction, and further, a first dust suction roller 13 is provided on the upstream side thereof. On the opposite side of the first and second dust suction rollers 13 and 14 with the endless belt 1 interposed therebetween, backup rollers 15 are disposed. An AC potential and a (−) DC potential are applied to the first dust adsorbing roller 13, and the average value thereof is higher than the (−) potential of the endless belt charged in a striped manner. An AC potential and a (+) DC potential are applied to the second dust suction roller 14, and the average value thereof is higher than the (+) potential of the endless belt 1 charged in a striped manner. Further, a scraper 16 is in contact with each of the first and second dust suction rollers 13 and 14, and a dust receiver 17 is disposed below each scraper 16.

  The endless belt 1 may be charged in stripes with both positive and negative polarities, and it is unknown whether the positive or negative dust is charged on the printing medium 2 or in the vicinity thereof. The charged dust is adsorbed by the first dust suction roller 13 to which a higher (−) potential is applied. The dust charged to (−) is adsorbed by the second dust adsorbing roller 14 to which a higher (+) potential is applied. The dust adsorbed on the first and second dust suction rollers 13 and 14 is scraped off by the scraper 16 and collected in the dust receiver 17. The AC potential is applied to the first and second dust adsorbing rollers 13 and 14 because the electric field continuously fluctuates in a short time to give fine vibrations to the dust, and the print medium 2 and the endless belt. This is to facilitate peeling from 1. At this time, dust such as paper dust having a small mass and a small contact area with the printing medium 2 and the endless belt 1 is easily moved because it is subjected to vibration due to an alternating potential on the whole. Furthermore, the printing medium 2 adsorbed on the entire surface of the endless belt 1 is hardly moved because only a part of the entire volume is subjected to vibration due to an alternating potential. Therefore, it is possible to remove only dust such as paper dust.

  In any roller, the voltage obtained by superimposing the alternating current potential and the direct current potential should not exceed 2000 V at the maximum (leakage discharge may occur if it exceeds 2000 V). The AC frequency is preferably 500 to 3000 Hz. If the frequency is within this range, dust such as paper dust is easy to follow and move, while the print medium 2 and the endless belt 1 having a relatively large mass are difficult to follow and no unnecessary noise is generated. The alternating current waveform does not matter. A similar effect can be expected with a sine wave, a rectangular wave, or a triangular wave. Even if only a direct current potential is applied without applying an alternating current potential, there is an effect of adsorbing and removing dust such as paper dust. In this case, the direct current potential is greater than the belt charging potential (500 to 1200 V) and is 2000 V or less.

  Various forms of the first and second dust suction rollers 13 and 14 are shown in FIG. These dust adsorbing rollers 13 and 14 include a conductive shaft such as stainless steel (not shown), an abutting portion 21 for pressing the printing medium 2, and a dielectric portion 22 slightly smaller in diameter than that. Specifically, the ring-shaped butting portion 21 is fitted and fixed to the outer periphery of the dielectric portion 22. Alternatively, the abutting portion 21 and the dielectric portion 22 may be connected in the axial direction. The abutting portion 21 is for maintaining the dielectric portion 22 in a non-contact state with the print medium 2 while pressing the print medium 2, and the length in the axial direction is as short as about 3 mm or less. Further, it is desirable that the abutting portion 21 presses slightly inside both ends of the print medium 2 in the width direction (direction perpendicular to the transport direction). This is because the print medium 2 is pressed down so as not to be lifted, and at the same time, it is desired to adsorb dust such as paper dust that is generated when the print medium 2 is cut and remains near the end of the print medium 2. This is in order not to hold it down. 2A is an example in which the width of the print medium 2 is one type, and FIGS. 2B and 2C are examples in the case of corresponding to the widths of a plurality of types of print media 2, respectively. The inner side of the two width direction ends can be pressed slightly. In the case of the configuration of FIG. 2b and FIG. 2c, among the printing tooth plates 2 of several kinds of dimensions, the wide one is pressed not only slightly inside the both ends in the width direction but also several places near the center. It hardly affects the effect of adsorbing and removing dust such as powder. This is because dust such as paper dust is less near the center than in the vicinity of the end of the print medium 2. In particular, in FIG. 2c, the abutting portion 21 has a tapered cross section so that dust such as paper dust is not suppressed as much as possible. It is also effective to chamfer the tip of the abutting portion 21. Further, the abutting portion 21 itself may have a spur shape.

The dielectric portion 22 is composed of an inner middle resistance layer and a surface insulating layer. As the material of the medium resistance layer, general synthetic resins such as chloroprene rubber, urethane rubber, butadiene rubber, acrylonitrile butadiene rubber, styrene butadiene rubber, ethylene propylene rubber, acrylic rubber, and fluoro rubber can be used as a base material. Then, for example, carbon black or conductive filler is mixed into these base materials, and the entire volume resistance value is adjusted to about 10 ⁵ Ω · cm. Hardness does not matter. The insulating layer may be made of, for example, a general synthetic resin such as polyurethane, polyimide, or silicon rubber. When considering the removability of dust by the scraper 16, nylon, polyvinylidene fluoride, polyvinylidene chloride, or the like is used. Also good. The resistance value of the insulating layer is at least 10 ¹² Ω · cm, preferably 10 ¹⁵ Ω · cm or more in volume resistance. The thickness of the insulating layer is preferably thinner considering the reaction of charge generation at the time of dielectric polarization by an alternating potential, for example, 10 to 200 μm, preferably 10 to 50 μm. The material of the abutting portion 21 may be a general insulating plastic, but in order to reduce the chargeability of the surface that contacts the printing medium 2, a fluorinated polymer such as PTFE, a fluorinated epoxy resin, a fluorinated polyimide, or the like. Alternatively, an insulating material having a low dielectric constant such as an olefin-based or polystyrene-based hydrocarbon-based polymer may be used.

  As described above, according to the ink jet printer of this embodiment, the charged dust is adsorbed on the surface of the printing medium 2 and the positive electrode in the vicinity thereof by the first dust adsorbing roller 13 charged on the negative electrode, and is charged on the positive electrode. In addition, since the second dust suction roller 14 sucks dust charged on the surface of the printing medium 2 and the negative electrode in the vicinity thereof, the positive and negative poles can be used regardless of whether the transport endless belt 1 is charged with positive or negative polarity. Charged dust can be reliably removed. In particular, when the conveying endless belt 1 is charged in a striped manner, dust can be reliably removed by the ink jet printer of this embodiment.

In addition, since the first and second dust suction rollers 13 and 14 are configured to suck the charged dust so that they are not completely in close contact with the print medium 2, the print medium 2 is placed in the first and second dust suction rollers 13, Only the dust can be reliably removed without being adsorbed by 14.
Further, by applying an AC potential to the first and second dust suction rollers 13 and 14, fine vibration can be generated on the surface of the printing medium 2 and dust in the vicinity thereof, so that the conveying endless belt 1 is charged. Even if it is, it becomes possible to remove dust reliably.

FIG. 3 shows another embodiment of a configuration for cleaning the first dust suction roller 13 on behalf of the first and second dust suction rollers 13 and 14. In this embodiment, another individual cleaning roller 18 is brought into contact with the dust suction roller 13, the scraper 16 is brought into contact with the cleaning roller 18, and a dust receiver 17 is disposed below the scraper 16. The cleaning roller 18 is applied with a direct current (−) potential that is larger than the maximum sum of the alternating current potential and the direct current potential applied to the dust adsorbing roller 13. The cleaning roller 18 is configured by covering the surface of a medium resistance material having a volume resistance of about 10 ⁵ Ω · cm with a relatively hard material having a volume resistance of 10 ¹² Ω · cm or more. It abuts only on the butting portion 21 of the. Accordingly, dust such as paper dust adsorbed on the dust adsorbing roller 13 is adsorbed by the cleaning roller 18 having a larger potential difference, and further scraped off by the scraper 16 and collected in the dust receiver 17. In this way, it is not necessary to create the scraper 16 having a complicated shape for avoiding the abutting portion 21 and contacting only the dielectric portion 22 to which dust such as paper dust is adsorbed. This can also be applied to the second dust suction roller 14 with the same configuration as the polarity of the applied DC potential and (+).

The polarity of the DC potential applied to the first dust suction roller 13 and the second dust suction roller 14 may be reversed from the setting in the above embodiment. Regardless of the order, it is necessary to support both (+) potential and (−) potential.
The ink jet printer of the present invention is not limited to a line head type ink jet printer, but can be applied to a multi-pass type ink jet printer.

1 is a front view illustrating a schematic configuration of an embodiment of an inkjet printer according to the present invention. It is explanatory drawing of the various form of the dust adsorption roller of FIG. It is a block diagram of the dust adsorption roller cleaner which shows other embodiment of the inkjet printer of this invention.

Explanation of symbols

  1 is an endless belt, 2 is a printing medium, 3 is a driving roller, 4 is a driven roller, 7 is a charging roller, 8 is an AC power supply, 9 is a paper pressing roller, 11 is an inkjet head, 12 is a plane forming unit, and 13 is a first forming unit. 1 dust suction roller, 14 second dust suction roller, 15 backup roller, 16 scraper, 17 dust receiving, 18 cleaning roller, 23 gate roller, 24 paper feed unit, 25 paper delivery unit

Claims (3)

  In an ink jet printer that performs printing by adsorbing a print medium to the surface of a conveyance belt by electrostatic force and discharging ink droplets from the nozzles to the print medium, the negative electrode is charged on the surface of the conveyance belt to be conveyed A first dust adsorbing roller that adsorbs dust charged on the surface of the printing medium and the positive electrode in the vicinity thereof while rotating synchronously with the printing medium, and synchronous with the printing medium on the surface of the conveying belt charged with the positive electrode and conveyed. An ink jet printer comprising: a second dust adsorbing roller that adsorbs dust charged on the surface of the print medium and a negative electrode in the vicinity thereof while rotating.  The inkjet printer according to claim 1, wherein the charged dust is sucked so that the first and second dust suction rollers do not completely adhere to the printing medium.   The inkjet printer according to claim 2, wherein an AC potential is applied to the first and second dust suction rollers.

Images