JP2006103022A - Inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus in which normal flying of ink drops from a recording head is not obstructed caused by an electric field generated by AC electrostatic charge on a carrying belt, satellite is hardly generated, a recording with a high quality is performed, and there exists no possibility of staining the recording head by an undesirable behavior of the ink drops. <P>SOLUTION: A dielectric flux detour roller 15 of a dielectric is brought into rotatable contact with a back surface side region within a prescribed range corresponding to the surface region just below a recording head 12 of an electrostatic attraction carrying belt 8 so as to generate a nip 155. The dielectric flux (electric line of force) generated from the electrostatic attraction carrying belt 8 AC-electrostatically charged is mostly detoured to the back surface side, so that the flying of the ink drops discharged from the recording head 12 is not influenced by the electric field on the surface region side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a recording head for ejecting ink droplets from an ejection port provided on an ejection surface facing a recording medium to perform recording on the recording medium, from the upstream side to the downstream side of the recording head position. In particular, the present invention relates to an ink jet recording apparatus that performs recording in the process of conveying a recording medium while adsorbing the recording medium with electrostatic force, and is particularly suitable for application to a line head type ink jet recording apparatus.

  In an inkjet recording apparatus, comprising: a recording head; and a conveyance belt that conveys the recording medium from an upstream side to a downstream side of the position of the recording head while adsorbing and holding the recording medium by an electrostatic force. In order to cope with the problem that the ink droplet does not draw the intended flight trajectory due to the electric field generated between the recording head and land at an undesired position, an electrode is provided in the vicinity of the gap between the recording head and the recording medium. By applying an alternating voltage to the electrodes, the charging of ink droplets flying from the recording head toward the recording medium is forcibly neutralized to obtain an accurate flight trajectory, thereby eliminating the disturbance of the recorded image Such a technique has already been proposed (see, for example, Patent Document 1).

Further, in recent years, an AC bias is applied to a conveyance belt that conveys a recording medium, and charging is performed such that the polarity is alternately reversed at a constant cycle along the moving direction of the conveyance belt, and between adjacent positive and negative charging portions. An electric field is generated in the vicinity of the conveyor belt so that the lines of electric force draw minute loops, and the recording medium is electrostatically adsorbed and conveyed using an electric field that does not extend far from the conveyor belt. In addition, it has also been proposed that the electric field used for electrostatic adsorption does not hinder the normal flight of ink droplets from the recording head to the recording medium (see, for example, Patent Document 2).
Japanese Unexamined Patent Publication No. 04-083644 (first page, fourth page, sixth page, FIGS. 3A and 3B) JP 2003-103857 A (paragraphs 0025 to 0030, FIGS. 3A and 3B, FIGS. 5A and 5B)

The conventional technology described above still has various problems as described below.
That is, in the technique disclosed in Patent Document 1, it is necessary to provide an electrode in the vicinity of the gap between the recording head and the recording medium, but in general, an electrode having a required size is provided in the vicinity of this narrow gap. In practice, there is a risk that the electrode and the recording medium are rubbed.
On the other hand, if the above-mentioned gap is increased in order to avoid this possibility, the required flight distance of the ink droplet is extended, so that the accuracy of the landing position is lowered and the image quality is impaired. Since the flying distance of the ink droplet has a very high correlation with the accuracy of the landing position, it is very disadvantageous for high-quality image formation if a gap between the recording head and the recording medium is increased in this type of apparatus. is there.

  On the other hand, even in the technique disclosed in Patent Document 2, if the high-quality image formation is intended and the ink discharge port of the recording head is configured to be close to the recording medium, and thus the recording medium conveyance belt, the following is performed. Raise the problem. That is, assuming that the charging polarity reversal period along the moving direction of the conveying belt is set to 4 mm, for example (the positive charging portion and the nonpolar charging portion are present in half in this 4 mm). Since the electric field (electric lines of force) is generated in an arc between adjacent regions where the charging polarity is reversed, the electric field acts quite strongly up to a position at least 2 mm away from the conveying belt surface in the absence of a recording medium. It will be.

  Naturally, the effect of the electric field does not stop at a position separated by 2 mm or more from the surface of the conveying belt, but the effect of the electric field extends so as to gradually decrease as the distance increases. When ordinary recording paper is applied as the recording medium, the dielectric constant is about 2 to 2.6 and the thickness is about 0.1 mm, so the apparent gap expansion effect is only about 0.16 mm. . This means that the action of the electric field is considerably strong up to a range of 1.84 mm away from the surface of the conveyor belt.

  The distance from the conveyance belt to the recording head has a very high correlation with the accuracy of the landing position of the ink droplet, as described above with reference to Patent Document 1, focusing on the gap between the recording head and the recording medium. Since it is set to be as small as possible and is usually set to 1 mm or less and at most about 1.5 mm, even if the conveyance belt is AC charged, it is not necessary to charge the conveyance belt with respect to the flying of ink droplets. It is difficult to sufficiently reduce the influence of the electric field.

  On the other hand, the electrostatic attraction force to the recording medium is due to the electrostatic force acting between the charge applied to the conveyance belt and the charge due to the dielectric polarization induced by the charge on the recording medium, so the surface is uniform. In order to realize adsorption by AC charging with an electrostatic force equivalent to that when electrostatically adsorbed by a charged (DC charged) conveyor belt, naturally, a charged charge equivalent to that in the case of DC is required.

  For this reason, for example, when a certain electrostatic attraction portion is macroscopically viewed from a viewpoint separated from the conveying belt by several times the charging pitch of AC charging, only a weak electric field (and therefore a low potential) exists. If this point of view is placed at a position sufficiently close to the vicinity of the conveyor belt (for example, a position close to 2 mm from the conveyor belt as in the above example), DC charging Thus, the same absolute potential as in the case of use is observed.

  In the case of AC charging, a voltage that is twice the value of one polarity of the alternating voltage changes as a value between positive and negative peaks. For example, in DC, the voltage that only requires +800 V is AC. Between the positive and negative peaks, it fluctuates with a large value of 1600 V, and this large voltage fluctuation occurs under the recording head. Therefore, the AC charging has a complicated influence on the flying of the ink droplets from the recording head as compared with the uniform DC charging, and the electric field from the conveying belt causes the ink to be in the same direction as the conveying direction of the recording medium. The flight trajectory of the droplet is bent and the landing position is shifted, and as a result, a streak pattern having a pitch corresponding to the charging pitch in AC charging may be formed on the recording medium.

  The present invention has been made paying attention to the problems in the prior art as described above, and it is not necessary to intervene a separate member such as an electrode between the recording medium and the recording head. Proper setting of the gap is not hindered, and the regular flight of ink droplets from the recording head is not hindered due to the electric field generated by AC charging of the conveyance belt, and satellites are hardly generated. An object of the present invention is to provide an ink jet recording of this type in which recording of quality can be performed and there is no possibility that the recording head (the ejection surface thereof) is soiled by an undesired behavior of ink droplets.

In order to solve the above-described problems, the present application proposes the following techniques.
(1) A recording head that records ink on the recording medium by ejecting ink droplets from an ejection port provided on the ejection surface facing the recording medium, and the position of the recording head while adsorbing and holding the recording medium by electrostatic force A conveying belt that conveys the conveying belt from the upstream side to the downstream side of the position; an AC charging mechanism that charges the conveying belt so that a charging polarity changes periodically along the conveying direction; and the recording head of the conveying belt And an electric flux bypass roller made of a dielectric material that forms a nip portion over a predetermined range by being in pressure contact with a back surface portion corresponding to the front surface portion facing the surface of the ink jet recording apparatus.

  According to the apparatus of (1), it is not necessary to intervene a separate member such as an electrode between the recording medium and the recording head, so that it is not hindered to properly select the gap between the two. In addition, the electric field due to the AC charging of the conveying belt is drawn to the back surface side by the electric flux bypass roller so that most of the electric field passes through the electric flux bypass roller side, and thus appears on the front surface side facing the recording head. The electric field (lines of electric force) is slight, and the regular flight of ink droplets is not hindered due to the electric field generated by AC charging, satellites are hardly generated, high-quality recording can be performed, and ink The possibility of contamination of the recording head due to the undesired behavior of the drops is eliminated.

(2) The ink jet bypass roller according to (1), wherein the length of the nip portion in the conveyance direction of the recording medium is set to be equal to or longer than the charging polarity change period of the conveyance belt. apparatus.
According to the apparatus of (2), in addition to the action of the apparatus of (1), the electric field (lines of electric force) appearing on the surface portion facing the recording head of the conveyor belt can be effectively reduced. it can.

(3) The electric flux bypass roller is set such that the length of the nip portion in the conveyance direction of the recording medium is greater than or equal to the length in the conveyance direction of the recording medium where the recording head faces the recording medium. (1) Inkjet recording apparatus characterized by the above-mentioned.
According to the apparatus of (3), in addition to the action of the apparatus of (1), the electric field (electric field lines) from the transport belt in a space including the planned flight trajectory of the ink droplets ejected from the recording head. Can be effectively reduced.

(4) The ink jet recording apparatus according to any one of (1) to (3), wherein the electric flux bypass roller is made of a dielectric having a relative dielectric constant equal to or higher than a relative dielectric constant of the recording medium.
According to the apparatus of (4), in addition to the action of any one of the apparatuses (1) to (3), the surface portion side on the recording medium corresponding to the region of the predetermined range more reliably. The electric field (lines of electric force) at can be reduced.

(5) The electric flux bypass roller uses any one of a polyamide-based synthetic polymer compound, polyurethane, polyimide, epoxy resin, and silicon rubber as the dielectric. The inkjet recording apparatus according to any one of (1) to (4).
According to the device of (5) above, the effect of reducing the electric field (lines of electric force) appearing on the surface portion side facing the recording head by the device according to any one of (1) to (4) above, It is possible to implement an ink jet recording apparatus that is more reliable.

(6) The inkjet recording apparatus according to any one of (1) to (5), wherein the recording head is a line head that functions in a state where a position is fixed during a recording operation.

  According to the device of (6), since the relative position between the head and the electric flux bypass roller is used in a constant state, the operation of any one of the devices (1) to (5) is performed. In particular, the present invention is preferably used, and there are fewer movable mechanisms than the configuration in which the head is serially driven, thereby simplifying the configuration and increasing the accuracy of the operation.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the drawings referred to below, for the sake of convenience, the main part that is the subject of the description is appropriately exaggerated.
FIG. 1 is a side view showing an outline of an ink jet recording apparatus to which the present invention is applied. In the figure, reference numeral 1 denotes a paper feeding unit for storing a large number of recording papers 2 as recording media, and the recording papers 2 are fed one by one from the paper feeding unit 1. The recording paper 2 fed from the paper feeding unit 1 is conveyed to the gate roller 4 by a paper feeding roller 3 that is driven to rotate by an electric motor 3a. The gate roller 4 is composed of a pair of upper and lower rollers that are in rolling contact with each other. The gate roller 4 is in a stopped or standby state until the leading edge of the recording paper 2 conveyed by the paper feeding roller 3 contacts the gate roller 4. One of the pair of rollers is rotationally driven by the electric motor 4a after the contact is made, and skew correction is performed to align the recording paper 2 with the leading end of the recording paper 2 aligned with the direction orthogonal to the transport direction. To the transport mechanism 5 as the transport means at the subsequent stage.

  A paper passage sensor 31 for optically detecting the leading edge of the recording paper 2 is provided at a position near the paper feeding roller 3 between the paper feeding roller 3 and the gate roller 4, and the recording paper is relied on the paper leading edge detection signal thereby. Control for aligning 2 is performed. The transport mechanism 5 is a driven roller 6 rotatably disposed on the gate roller 4 side, and an electric motor disposed on the paper discharge side of the recording paper 2 on the opposite side of the driven roller 6 from the gate roller 4. A driving roller 7 that is rotationally driven by a motor 7a, and an electrostatic attraction / conveying belt 8 that conveys the recording paper 2 in a wide band stretched between the driven roller 6 and the driving roller 7 while adsorbing and holding the recording paper 2 with electrostatic force. It is configured.

On the upper side of the driven roller 6, there is disposed a pressure roller 9 for pressing the recording paper 2 to the electrostatic adsorption conveyance belt 8.
The tension of the electrostatic adsorption conveyance belt 8 is adjusted by a tension roller or the like (not shown). The material of the electrostatic adsorption transport belt 8 is 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 has a volume resistance value of 10 ⁹ Ω · cm or more, more preferably 10 ¹⁵ Ω · cm or more. Further, if necessary, carbon black or a conductive filler may be mixed into the resin base material to adjust the resistance value, and the amount of retained charge when charging during the circular motion may be adjusted. The 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.

  Further, the transport mechanism 5 includes a charging roller 10 made of a conductive rubber material that is in contact with the electrostatic attraction transport belt 8 below the driven roller 6 in the figure, and an AC power source 11 is connected to the charging roller 10. The voltage from is applied. In other words, the charging roller 10 serving as a charging member in contact with the electrostatic adsorption conveyance belt and the AC power source 11 are charged, and the electrostatic adsorption conveyance belt 8 is charged so that the charging polarity periodically changes along the conveyance direction. An AC charging mechanism is configured.

  On the other hand, yellow, with respect to the recording paper 2 at a position facing the recording paper 2 that is electrostatically attracted and conveyed by the electrostatic adsorption conveyance belt 8 of the conveyance mechanism 5 while maintaining a slight gap region (for example, 1 to 2 mm). Four recording head units (ink heads) 12Y, 12M, 12C, and 12K that discharge magenta, cyan, and black ink droplets are sequentially arranged at predetermined intervals from the upstream side in the conveyance direction of the recording paper 2. .

  Each of the recording head units 12Y to 12K forms a recording region in which a large number of nozzles for ejecting ink droplets are arranged at a minute interval in a direction orthogonal to the conveyance direction of the recording paper 2, that is, the width direction of the recording paper 2. In monochrome printing, ink droplets are basically ejected only by the black recording head 12K, and ink droplets ejected by the recording heads 12Y to 12K of other colors including black are superimposed on the recording paper 2. Color printing can be performed.

  In addition, the nip portion of the electrostatic attraction / conveyance belt 8 which is directly below the recording heads 12Y to 12K and is brought into pressure contact with the back surface portion corresponding to the front surface portion facing each recording head is a predetermined portion of the back surface portion. Electric flux bypass rollers 15Y, 15M, 15C, and 15K are arranged as shown in the drawing so as to roll over the range region. The electric flux bypass rollers 15Y to 15K will be described in detail later with reference to FIG. 2, and the size and position of the recording sheet 2 in the width direction of the electric flux bypass rollers 15Y to 15K are the corresponding recording heads. It is set so as to cover the entire width of 12Y to 12K.

A peeling claw 21 is provided so as to circumscribe a belt portion corresponding to the outer periphery of the driving roller 7 located in the final section of the conveyance section by the electrostatic adsorption conveyance belt 8, and from the electrostatic adsorption conveyance belt 8 by this separation claw 21. The separated recording paper 2 is delivered from the driving roller 7 to the paper discharge unit 22 disposed on the downstream side in the conveyance direction of the recording paper 2.
FIG. 2 is a conceptual diagram for explaining the operation of the embodiment of the present invention, in which the recording head in the ink jet recording apparatus faces the electrostatic adsorption conveyance belt (at the time of the recording process) (FIG. 1). In FIG. 2, there are a plurality of corresponding portions including a portion exemplified by surrounding with a broken-line circle). In FIG. 2, the left-right direction is the moving direction of the electrostatic attraction / conveyance belt, and one of the recording heads 12Y, 12M, 12C, 12K as in the embodiment is typically indicated by reference numeral 12. One of the electric flux bypass rollers 15Y, 15M, 15C, and 15K disposed in correspondence therewith is shown with a reference numeral 15 representatively.

  FIG. 2A shows a state in which the electrostatic adsorption conveyance belt 8 is charged by the AC charging mechanism described with reference to FIG. 1 so that the charging polarity periodically changes along the conveyance direction. It is a thing. A large number of electric lines of force indicate that an electric field having a sufficient strength for electrostatically attracting the recording paper 2 is generated in the gap between the recording head 12 and the surface portion of the electrostatic attracting and conveying belt 8 facing the recording head 12. Has been. In order to ensure the accuracy of the ink droplet landing position, this gap is set to about 1 mm, and at most about 1.5 mm.

  As shown in the figure, in the state where neither the recording sheet 2 nor the electric flux detour roller 15 is present, many surfaces are generated by connecting each surface between adjacent portions where the charging polarity of the electrostatic adsorption conveyance belt 8 is reversed in an arc shape. The electric field lines extend to the recording head 12. In this state, various adverse effects are exerted on the flying of the ink droplets ejected from the recording head 12 by the electric field represented by the lines of electric force.

  FIG. 2B shows a state in which the recording paper 2 is placed on a portion facing the recording head 12 on the electrostatic adsorption conveyance belt 8 which is charged as shown in FIG. is there. As shown in the figure, even when the recording paper 2 is placed, the electric field is only slightly weakened, and the charging polarity of the electrostatic attraction / conveying belt 8 is reversed as in the case described with reference to FIG. Many electric lines of force generated by connecting the surfaces between adjacent portions in an arc shape reach the recording head 12. Therefore, an adverse effect on the flying of the ink droplet due to the electric field represented by the lines of electric force occurs to the extent that is almost the same as that described with reference to FIG.

2 (c), as already described with reference to FIG. 1, press-contacts the back surface portion of the electrostatic attraction / conveyance belt 8 directly below the recording head 12 and corresponding to the front surface portion facing the recording head 12. This shows a state where the electric flux bypass roller 15 is disposed so that the nip portion 155 of the self generated is in contact with the region of a predetermined range of the back surface portion.
In the state shown in FIG. 2C, the electric flux lines that are generated so as to connect each surface between adjacent portions where the charging polarity of the electrostatic attraction conveyance belt 8 is reversed are arcuated by the electric flux bypass roller 15. It is relatively increased as shown in the drawing so as to be drawn to the back surface side of the conveying belt 8 that is in contact, that is, the back surface side corresponding to the front surface portion of the conveying belt 8 facing the recording head 12. Thus, the lines of electric force leaking to the gap side of the surface portion with the recording head are relatively reduced. Therefore, various adverse effects on the flying of the ink droplets ejected from the recording head 12 due to the electric field generated from the transport belt 8 are greatly suppressed.

  Furthermore, the nip portion 155 generated in the electric flux detour roller 15 has at least an electric flux immediately below the recording head 12 (where the electric flux is understood in the same manner as the electric lines of force described above, and there is no problem in understanding the inventive concept. ) Can be effectively bypassed so that the back surface of the conveyor belt 8 is in contact with the back surface of the conveyor belt 8 over an area extending over one cycle related to the change in the charging polarity of the conveyor belt 8. Is recommended. For example, if the period related to the change in the charging polarity of the conveying belt 8 is 4 mm, the width of the nip portion 155 along the moving direction of the conveying belt 8 is set to 4 mm or more.

  Further, the nip portion 155 is set so that the recording head 12 comes into contact with the back surface portion of the conveying belt 8 over a predetermined range set so as to extend beyond the area facing the recording paper 2. It is desirable. This is because the surface (nozzle plate) facing the recording paper 2 of the recording head 12 is made of metal such as stainless steel, and it is easy to draw in the electric flux. This is because the electric flux generated between the recording head 12 and the surface portion of the electrostatic attraction / conveyance belt 8 facing the recording head 12 is reduced by being concentrated on the side.

The dielectric constituting the electric flux bypass roller 15 has a corresponding effect if its relative dielectric constant is larger than air (relative dielectric constant 1.0), but the relative dielectric constant of the recording paper is 1.2 to 2.6. Therefore, it is recommended to select 2.6 or more.
Specifically, for example, a polyamide-based synthetic polymer compound (relative permittivity: 3.5 to 3.9), polyurethane (relative permittivity: 4.2 to 7.6), polyimide (relative permittivity: 3.4) Epoxy resin (dielectric constant 4), silicon rubber (dielectric constant 8), etc. are applied. Any of them is an insulator, and its resistance value is preferably 10 ¹² Ω · cm or more, more preferably 10 ¹⁵ Ω · cm or more in terms of volume resistance.

FIG. 3 is a flowchart showing the operation of the embodiment of the present invention. The operation of the embodiment will be described below with reference to this flowchart.
In the apparatus according to the embodiment, at the beginning of the operation, an alternating voltage is applied to the charging roller 10 from the AC power supply 11 to charge the electrostatic adsorption conveyance belt 8 as described above (step S1).
Next, feeding of the recording paper 2 is started (step S2).

When the fed recording paper 2 reaches the electrostatic adsorption conveyance belt 8, the recording paper 2 is brought into close contact with the electrostatic adsorption conveyance belt 8 by the pressure roller 9, so that the recording paper 2 can be stably conveyed and the printing area (recording head portion). The gap between the recording paper 2 and the nozzles of the recording head portion can be appropriately maintained (step S3).
When the recording paper 2 is further conveyed by the electrostatic attraction conveyance belt 8 and reaches the recording head portion, the recording paper 2 reaches the region of the above-described nip portion 155 of the electric flux detour roller 15 at this position (region). (Step S4).

  In this region, most of the electric flux (electric field lines) generated from the electrostatic attraction and conveyance belt 8 is diverted to the electric flux detour roller 15 side (the electric flux detour roller 15 as described above is provided so that this detour occurs). Since it is disposed in contact with the electrostatic adsorption conveyance belt 8), the recording head 12 (the flight of ink droplets ejected from the nozzle plate side) is substantially affected by the electric field from the electrostatic adsorption conveyance belt 8. It is in a state that does not reach.

  As described above, a printing operation is performed in a region where the electric flux (electric field lines) generated from the electrostatic attraction / conveying belt 8 is diverted toward the electric flux detour roller 15 so that the ink droplet flight is not adversely affected by the electric field. (Printing operation) is executed (step S5). When the electrostatic attraction conveyance belt 8 rotates and the conveyance of the recording paper 2 further proceeds, the recording paper 2 eventually leaves the area of the nip 155 (step S6).

  When this state is reached, the electric field generated from the electrostatic attraction / conveyance belt 8 is distributed in a state before reaching the area of the nip 155, and the recording paper 2 is electrostatically attracted to the electrostatic attraction / conveyance belt 8. It is firmly adsorbed by force. After step S6, the recording paper 2 is not pressure-bonded by the pressure roller 9 again, but the suction by the electrostatic force is appropriate for transporting the recording paper 2, and the post-process is performed because the suction force is slightly reduced. Thus, it is convenient to separate the recording paper 2 from the electrostatic attraction / conveyance belt 8 by the peeling claw 21 (see FIG. 1) that contacts the outer peripheral surface of the electrostatic attraction / conveyance belt 8 (step S7).

The recording paper 2 separated from the electrostatic adsorption conveyance belt 8 is transferred from the driving roller 7 (see FIG. 1) to the paper discharge unit 22 disposed on the downstream side in the conveyance direction of the recording paper 2 (step S8). .
In the above, in the portion within the print area of the recording paper 2 (the area under the recording head portion), the suction action by the electrostatic force of the electrostatic attraction / conveyance belt 8 becomes extremely weak, but the nip 155 of the electric flux bypass roller 15 For example, before and after the area of about 4 mm, for example, is reliably adsorbed by the electrostatic force, the printing operation is not adversely affected. Further, the leading end portion of the recording paper 2 is transported in the printing area depending only on the upstream electrostatic adsorption force described above, but it is a short section, which is sufficient depending on the so-called paper stiffness. The position is maintained.

  As described above, according to the above-described embodiment, it is not necessary to intervene a separate member such as an electrode between the recording medium and the recording head, so that it is not hindered to optimally set the gap between the two. Further, the electric field due to the AC charging of the electrostatic conveyance belt is mostly drawn to the back surface side by the electric flux bypass roller so as to pass through the electric flux bypass roller side. The electric field (electric lines of force) that appear is slight, and the regular flight of ink droplets is not hindered due to the electric field generated by AC charging, satellites are hardly generated, and high-quality recording can be performed. In addition, the possibility of contamination of the recording head due to undesired behavior of ink droplets is also eliminated.

Furthermore, in the above-described embodiment, it is not necessary to apply a voltage from a separate power supply device to the electric flux bypass roller, so an electric circuit including a power supply or a control circuit related thereto is attached. There is no complication that must be present, and the configuration of the entire apparatus can be simplified.
Furthermore, since it is intended to weaken the electric field appearing on the recording paper side from the electrostatic attraction conveyance belt only in a narrow printing area, the electrostatic attraction force before and after the printing area and the so-called paper stiffness can be reduced. Depending on the strength, the gap between the recording head (nozzle thereof) and the recording paper in the printing area can be properly maintained.

  In addition, since the pressure roller is not used for the downstream side (that is, after the section past the printing area) away from the nip of the last-stage electric flux bypass roller, separation of the recording paper on the downstream side is ensured and easy. Can be done. The downstream side is a recording paper conveyance section after the printing operation period in which the gap uniformity is required, and the required degree of adhesion between the recording paper and the electrostatic adsorption conveyance belt is sufficient in this section. Is obtained.

  Further, in the configuration of the present invention, since it is necessary to keep the relative position constant with the recording paper sandwiched between the head and the electric flux bypass roller, the line head type ink jet recording apparatus in which the head position with respect to the printer body is fixed It is particularly suitable when applied to. However, even in this case, the head may be structured to move during cleaning such as head cleaning or during storage such as capping.

  In general, the technique proposed in the present application is effective when applied to a recording paper conveyance unit of various ink jet printers, in particular, a high-speed line head full-color machine and a facsimile machine incorporating the ink jet printer.

1 is a side view showing an outline of an ink jet recording apparatus to which the present invention is applied. It is a conceptual diagram for demonstrating the effect | action of embodiment of this invention. It is a flowchart showing operation | movement of embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Paper feed unit, 2 ... Recording paper, 3 ... Paper feed roller, 4 ... Gate roller, 5 ... Conveying mechanism, 6 ... Drive roller, 8 ... Electrostatic adsorption | suction conveyance belt, 9 ... Pressure-bonding roller, DESCRIPTION OF SYMBOLS 10 ... Charging roller, 11 ... AC power supply, 12 ... Recording head, 15 ... Electric flux detour roller, 21 ... Peeling claw, 22 ... Paper discharge unit, 155 ... Nip

Claims (6)

  A recording head that records ink on the recording medium by ejecting ink droplets from an ejection port provided on the ejection surface facing the recording medium, and an upstream side of the recording head position while adsorbing and holding the recording medium by electrostatic force A conveying belt that conveys the downstream side of the position, an AC charging mechanism that charges the conveying belt so that the charging polarity changes periodically along the conveying direction, and the recording belt of the conveying belt are opposed to the recording head. An ink jet recording apparatus comprising: an electric flux bypass roller made of a dielectric material that presses against a back surface portion corresponding to the front surface portion and forms a nip portion over a predetermined area.   The inkjet recording apparatus according to claim 1, wherein the electric flux bypass roller has a length of the nip portion in the conveyance direction of the recording medium set to be equal to or longer than a charging polarity change period of the conveyance belt. .   The length of the nip portion in the conveyance direction of the recording medium is set to be equal to or greater than the length in the conveyance direction of the recording medium where the recording head faces the recording medium. The ink jet recording apparatus according to claim 1.   The inkjet recording apparatus according to claim 1, wherein the electric flux bypass roller is made of a dielectric having a relative dielectric constant equal to or higher than a relative dielectric constant of the recording medium.   The electric flux bypass roller uses, as the dielectric, any one of a polyamide-based synthetic polymer compound, polyurethane, polyimide, epoxy resin, and silicon rubber. Item 5. The inkjet recording apparatus according to any one of Items 1 to 4. The inkjet recording apparatus according to claim 1, wherein the recording head is a line head that functions in a state where a position is fixed during a recording operation.

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