JP4192726B2 - Inkjet image forming apparatus - Google Patents

Description

  The present invention relates to an inkjet image forming apparatus.

  In recent years, the spread of color documents in offices is remarkable, and various output devices have been proposed. Among them, downsizing is possible, and the low-cost inkjet method is used as a powerful recording method in various output devices.

  A print head used in such an ink jet system includes energy generating means, means for converting the energy into ink discharge force, an ink discharge port, and an ink path communicating with the discharge port. Examples of energy generating means include means using an electromechanical transducer such as a piezo element, means for heating ink with an electrothermal transducer having a heating resistor to generate bubbles, and discharging the ink by generating these bubbles, etc. There is.

  The latter print head using an electrothermal conversion element is not only capable of arranging ink discharge ports at a high density because the electrothermal conversion element is small, but also has a semiconductor integrated circuit as a manufacturing technique thereof. Since the manufacturing technique can be diverted, it is possible to reduce the size of the print head having a large number of high-precision ink discharge ports and to manufacture the print head at low cost.

  However, at present, a printing method called serial scan, in which the printing head is reciprocated while carrying recording paper and printing is performed line by line to form an image, is mainly prevalent. Although this method can be reduced in size and cost, there is a drawback that multiple scans are required to form an image over the entire paper, and the printing speed is slow. It is extremely easy to retract the head to a position that does not face the means for transporting the ink, and the head recovery means that is the fate of the ink jet method (dummy jet mechanism and implementation timing for preventing ink nozzle clogging, in the standby state) There is an advantage that the mounting of the cap for maintaining the ink characteristics, the cleaning of the head, etc.) is easy.

  However, in order to improve the printing speed, it is necessary to reduce the number of scans. For this purpose, it is essential to lengthen the print head. The thing which pushed this to the limit is a printing system having a paper-width printing head, a so-called full line head system.

  The full-line head system is an ink jet printing apparatus using a paper width print head in which a large number of ejection openings are arranged over the same length as the width of the recording paper. The print head is fixed and the recording paper is opposed to this. Recording is performed by moving.

  This method does not require the reciprocal movement of the head, so that it can achieve higher productivity than the short head scanning type, but a new device is required to implement the above-described head recovery means.

  As an example, there is a head recovery operation in which the entire head is detached from the printing surface and the recovery means is moved to perform the recovery operation (see, for example, Patent Documents 1 and 2).

  However, since this method cannot perform a recovery operation (dummy jet) during a continuous printing operation, there is a problem that productivity, which is a merit of the full line head method, is lowered. Further, in the method described in Patent Document 2, the maintenance mechanism is complicated and the apparatus is increased in size, and it is difficult to reduce the size of the apparatus due to the necessity of a belt circumference longer than the paper size. Further, the attracting electric field between the head and the paper may affect the flight trajectory of the drop and cause a printing defect. Also, dust floating in the machine adheres to the head, paper, and belt due to the influence of the adsorption electric field.

  Alternatively, a method has been proposed in which an opening is provided in a part of the belt-shaped recording medium conveying unit and a recovery unit is provided inside the conveying unit (see, for example, Patent Document 3).

  In this method, dummy jets are possible during the printing operation, and the maintenance operation is simple. However, stress concentrates on the opening, which may cause deformation or breakage of the belt. Therefore, stable operation for a long time becomes difficult. In addition, since the belt circumferential length larger than the paper size + opening length (> head size) is required, it is difficult to reduce the size of the apparatus.

  In addition, there has been proposed a system in which an opening having a shutter unit is provided in a part of a cylindrical recording medium rotating and conveying unit, and a recovery unit is disposed inside the cylindrical rotating and conveying unit (see, for example, Patent Document 4).

  In this method, a dummy jet is possible during the printing operation, but the suction electric field between the head and the paper may affect the flight trajectory of the drop and may cause a printing failure. Further, the problem that dust floating in the machine adheres to the head, paper, and belt due to the influence of the adsorption electric field is the same as that of the method described in Patent Document 2. In addition, since the drum circumferential length greater than the paper size + opening length (> head size) is required, the problem that it is difficult to reduce the size of the apparatus is the same as the method described in Patent Document 3. Furthermore, in a combination with a recording head in which nozzles are arranged two-dimensionally (three or more rows), the nozzle-paper spacing is not uniform, and special head control is required to correct this.

As a paper transport method, there is a conventional method of holding the paper 118 on the transport belt 120 while being pressed by the star wheel 100 as shown in FIG. 9, but in this method, the paper 118 of the portion where printing is performed on the upstream side. Image failure is likely to occur due to contact with the downstream star wheel 100 before the ink of the ink is dried. Paper dust is generated by contact between the star wheel 100 and the paper 118. The holding force of the paper 118 on the conveyor belt 120. Since the paper is weak, there is a drawback that the paper 118 is easily displaced or inclined during conveyance.
Japanese Patent Laid-Open No. 10-00776 (FIG. 2, pages 3 to 4) Japanese Patent No. 2834451 (FIG. 1, pages 2 to 4) Japanese Patent Laid-Open No. 10-00776 (FIG. 2, pages 3 to 4) Japanese Patent No. 2834451 (FIG. 1, pages 2 to 4)

  In consideration of the above-described facts, an object of the present invention is to provide a full-line head type ink jet image forming apparatus that can reliably hold and convey a sheet and does not use a complicated head recovery mechanism.

  The inkjet image forming apparatus according to claim 1, wherein a plurality of first recording heads arranged at a predetermined interval in a direction orthogonal to a conveyance direction of the recording medium, and the recording in the first non-printing area of the first recording head. A first conveyor belt that is disposed along the medium conveyance direction, conveys the recording medium, and is provided downstream of the first conveyance belt in the conveyance direction, and is arranged in a plurality at a predetermined interval in the first non-printing area. An inkjet image comprising: the second recording head that is arranged; and a second conveyance belt that is disposed in a second non-printing area of the second recording head along the conveyance direction of the recording medium and conveys the recording medium. In the forming apparatus, an adsorbing unit that adsorbs a sheet to at least one of the first conveying belt and the second conveying belt is provided.

    In the invention with the above configuration, since it is a full-line head type one-pass printing, high productivity can be obtained, and the entire paper can be used as a printing area, and a plurality of physically divided heads are used. As a result, the yield in manufacturing the head is improved, the cost can be reduced, and the sheet is sucked and conveyed by the conveying means, so that the inkjet image forming apparatus can be reliably held and conveyed.

  According to a second aspect of the present invention, in the ink jet image forming apparatus, the suction unit is a friction charging member that comes into contact with the transport belt.

  In the invention having the above configuration, since the friction charging member is brought into contact with the transport belt as means for attracting the sheet to the transport means, the inkjet image forming apparatus including the sheet suction means that is simple in structure, low in cost, and hardly breaks down. can do.

  According to a third aspect of the present invention, in the ink jet image forming apparatus, the suction unit is a charging member that generates a potential between the transport belt and a sheet.

  In the invention with the above configuration, the charging member such as a charging roller that generates a potential between the conveyance belt and the sheet is used as a means for adsorbing the sheet to the conveyance unit, thereby suppressing wear of the charging member and the conveyance belt and ensuring Inkjet image forming apparatus capable of adsorbing an appropriate sheet can be obtained.

  According to a fourth aspect of the present invention, in the ink jet image forming apparatus, the suction unit is a negative pressure applying unit that generates a suction force in a suction hole formed in the transport belt.

  In the invention with the above configuration, it is possible to provide an ink-jet image forming apparatus that is capable of reliably adsorbing paper with a simple configuration and that hardly causes dust or the like in the apparatus to be adsorbed to the conveyance belt.

  According to a fifth aspect of the present invention, there is provided an ink jet image forming apparatus provided with a peeling unit for peeling the paper adsorbed on the first conveyance belt or the second conveyance belt.

  In the invention having the above-described configuration, the conveyance belt and the paper are separated by separating the paper and the conveyance belt by the peeling unit, so that an inkjet image forming apparatus without a conveyance failure can be obtained.

  Since the present invention has the above-described configuration, a full-line head type inkjet image forming apparatus that can reliably hold and convey paper and does not use a complicated head recovery mechanism can be obtained.

  1 to 4 show a printing mechanism portion of the inkjet image forming apparatus according to the first embodiment of the present invention.

  FIG. 1 is a perspective view of a printing mechanism portion of the inkjet image forming apparatus according to the first embodiment.

  The ink jet image forming apparatus of the present embodiment is provided with a print recording means 12 corresponding to a long head having a print section divided in the paper width direction.

  The print recording unit 12 is a recording unit that divides a print region in a direction perpendicular to the conveyance direction of the paper 18 (= paper width direction) into a plurality of portions and prints every other divided print region.

  This is a paper width head in which a single row of ink nozzles are arranged as in the past, or a staggered arrangement in the main scanning direction, and the ink nozzles are arranged without gaps in a direction perpendicular to the paper transport direction. Instead of the staggered arrangement head, every other printing area for each recording means is arranged, and the printing area and the non-printing area are alternately arranged in one printing recording means 12. Therefore, in order to cover the entire paper width, at least two print recording means 12 are required for one side of the paper 18.

  In the inkjet image forming apparatus 10 of this embodiment, two print recording means 12 are used for each color of ink. In the case of full color, yellow (Y), magenta (M), cyan (C), black ( K) four color printing recording means 12 are required, so that the whole apparatus requires eight printing recording means 12.

  In FIG. 2, Y0, M0, C0, K0, Y1, M1, C1, and K1 correspond to the eight print recording means 12.

  Here, the print recording means 12 that covers and prints the same print area among the print areas divided in the paper width direction is defined as one print set 14. That is, since two print recording means 12 are used for each color as described above, the number of print sets is also two. That is, Y0 to K0 in FIG. 1 are the upstream print set 14, and Y1 to K1 are the downstream print set 14.

  The divided print areas in the paper width direction are set at equal intervals. As a result, when the print set 14 is arranged by shifting in the paper width direction by the width of the divided print area at the time of placement in the inkjet image forming apparatus, the print recording means can be used regardless of whether the ink color is single color or full color. The same components can be used as the components constituting the component 12, for example, the ink nozzles.

  FIG. 3 shows the relationship between the print recording means 12 and the print area of the paper 18.

  As an example, Y1 color will be described. As shown in FIG. 3A, the entire sheet 18 is divided into two areas A and B, Y0 being Y (yellow) print recording means 12 on the upstream side, and downstream on the downstream side. Y1 is arranged. Y0 which is the print recording means 12 is a set of unit recording heads having a print width WA capable of covering the area A, and similarly Y1 is a set of unit recording heads having a print width WB capable of covering the area B. On Y0, the interval between the unit recording heads in the sheet width direction (= the width of the non-printing area) is set to be equal to or slightly smaller than the printing width WA, and is arranged at equal intervals. Similarly on Y1, the interval in the paper width direction between the unit recording heads is set to be equal to or slightly smaller than the print width WB, and arranged at equal intervals.

  The print areas A and B on the paper 18 can be printed without a gap by arranging the Y0 and Y1 so as to be shifted by the print width of the unit recording head so that the respective print areas cover the non-print areas. Can be an area. At this time, if the interval in the paper width direction between the unit recording heads Y0 and Y1 (= the width of the non-printing area) is set slightly smaller than the printing widths WA and WB, the Y0 and Y1 printing areas overlap. Generation of white streaks or the like between the print areas A and B can be prevented.

  In the case of full color, the above relationship is the same for all of the four colors Y, M, C, and K. Therefore, the same relationship is applied to all the eight print recording means 12 (= Y0 to K1) constituting the two print sets 14. Holds.

  Next, the head recovery means will be described.

  As shown in FIGS. 1 and 2, the head recovery means 36 is arranged at a position facing each print recording means 12 across the conveyance surface of the paper 18. That is, it is disposed at a position where the above-described transport belt 20 is not present.

  The head recovery means 36 has both a cap function for the head for preventing the ejection openings of the ink nozzles from adhering during standby and a dummy jet function for preventing clogging of the ink nozzles.

  When printing on the paper 18, since the paper 18 passes between the print recording means 12 and the head recovery means 36, the head recovery means 36 reaches a position where it does not contact the surface of the paper 18 facing the head recovery means 36. Descends. While image printing is not being performed, the print recording means 12 is capped to prevent ink drying, so that the head recovery means 36 is raised so that the head recovery means 36 is in close contact with the print recording means 12.

  A dummy jet is performed as necessary in the interval from the end of printing of the paper 18 until the next paper 18 is conveyed. At that time, the head recovery means 36 descends so as not to interfere with the next paper 18 and receives a dummy jet from the print recording means 12.

  At this time, the moving mechanism of the head recovery means 36 may have an individual mechanism for each head recovery means 36, or each head recovery means 36 is disposed on a common base plate, and the base plate It may be a mechanism that moves itself.

  Next, a paper conveying method will be described.

  In this embodiment, as shown in FIG. 1, the paper 18 is transported by the transport belt 20 that spans the non-printing area of the printing set 14 described above. Since the non-printing areas are alternately arranged with the printing areas, a plurality of conveying belts 20 are laid at equal intervals in the paper width direction.

  Further, since the two print sets 14 are arranged so as to be shifted by the width of the region divided in the paper width direction, the arrangement of the conveying belt 20 is staggered.

  Each group of conveying belts 20 corresponding to each printing set 14 is spanned via one common roller.

  The shared roller is connected to the drive motor 24 directly or through a gear or the like, and serves as a drive roller 26 that is a drive source of each of the conveying belts 20 group. Thereby, the conveyance speed of the upstream and downstream conveyance belts 20 group can be made common (V = constant), and an image failure due to a conveyance speed difference between the upstream and downstream conveyance belts 20 group at the time of paper conveyance can be prevented. The printing quality in the printing set 14 can be stabilized.

  Further, the drive roller 26 has an encoder (not shown) on the roller shaft, and a drive for suppressing rotation unevenness of the drive roller 26 caused by eccentricity of the shaft and gear of the drive motor 24 and the shaft of the drive roller 26. It constitutes a roller control means.

  The control means of the drive roller 26 reads the difference from the ideal rotational speed of the shaft of the drive roller 26, that is, the eccentric error component from the individual encoder signal at the time of rotation, and gives the motor information to cancel the difference. To control eccentricity. At this time, if a stepping motor is used as the drive motor 24, high-performance sheet conveyance control can be performed.

  At the other end of the transport belt 20 group, that is, at the end not on the drive roller 26, the transport belt 20 is held by each driven roller 28.

  In this embodiment, the transport belt 20 is made of an insulator such as rubber or a plastic sheet, and charging rods 16 made of glass rods, nylon, or the like are provided at positions where all the transport belts 20 come into contact.

  While the conveyor belt 20 is rotationally driven to convey the paper 18, the charging rod 16 continues to contact the conveyor belt 20 and charges the conveyor belt 20 made of an insulator by frictional charging. When the belt is not charged during standby or the like, the outer peripheral glass rod or the like may be separated from the belt.

  A registration roll 22 that transports the paper 18 to the transport belt 20 in a timely manner is provided upstream of the transport belt 20, and a loop is formed in the paper 18 with the preceding roll to remove the skew of each sheet. Thus, an accumulator (sheet storage section) 24 is formed to feed the sheet 18 to the conveyor belt 20. The material of the registration roll 22 is a metal roll on the lower side and a rubber roll on the upper side, and the rubber roll is the driving side.

  Further, a roll is disposed in the suction portion of the paper 18 and the transport belt 20 to assist the suction. As a result, the sheet 18 is adsorbed straight to the conveyor belt 20 toward the printing unit.

  The downstream conveying belt 20 is also charged by the same mechanism as that on the upstream side, and adsorbs the paper 18. During the printing operation, the paper 18 is attracted to the conveyance belt 20, and there is no danger of contact between the print recording means 12 and the paper 18, and the flatness and conveyance accuracy of the paper 18 are maintained. Obtainable.

  After the printing, when the paper 18 is peeled from the conveyance belt 20 to be discharged from the printing unit, a static eliminator 32 is disposed further downstream of the conveyance belt 20 on the downstream side to neutralize the charging and the paper 18 is conveyed to the conveyance belt. The paper 18 and the belt are separated using a peeling claw 30 which is a mechanical peeling means in a state in which the paper 18 is easily peeled off. Alternatively, instead of the static eliminator 32, a grounded static eliminator brush 34 or the like may be disposed near the peeling claw 30 to temporarily neutralize the charge.

  Further, a separation claw 30 is also provided at a location where the paper 18 crosses from the upstream conveying belt 20 to the downstream conveying belt 20 so that the paper 18 can be smoothly separated from the upstream conveying belt 20 and easily moved downstream. You may do it.

  In the system of this embodiment, the suction unit of the paper 18 does not affect the ink droplets ejected from the print recording unit 12. For this reason, since there is no adverse effect on the position system in which the ink droplets land on the paper 18, there is no possibility of causing image position shift or color shift.

  FIG. 4 shows a printing mechanism portion of an inkjet image forming apparatus according to the second embodiment of the present invention.

  As described above, the sheet 18 nipped and conveyed by the registration roller 22 is held by the conveyance belt 20. The conveyor belt 20 is made of an insulator and is wound around a drive roller 26 and a driven roller 28.

  The conveying belt 20 is applied with an electric potential of several hundred to several thousand volts from the back surface of the belt by the charging roller 38 on the upstream side. When the sheet 18 reaches the nip portion of the grounded conductive roller 40 provided on the surface of the conveyance belt 20, the sheet 18 and the conveyance belt 20 are in a more closely contacted state and are held by the electrostatic adsorption force. The paper 18 is conveyed in close contact with the conveyance belt 20. Further, electrostatic adsorption of the paper 18 is also performed on the downstream side by the same mechanism.

  As a result, during the printing operation, the sheet 18 and the conveying belt 20 are conveyed in close contact with each other, so that the positional accuracy of the sheet 18 with respect to the print recording unit 12 is reliably maintained, and the skew, registration misalignment, and floating of the sheet 18 are ensured. It is possible to prevent image quality degradation accompanying the above.

  In the first and second embodiments, the example in which the conveyor belt 20 is formed of an insulator has been shown. However, the present invention is not limited to this, and the two layers in which the front surface of the conveyor belt 20 is formed of an insulating layer and the back surface is formed of a conductive layer. The conveyor belt 20 may be configured by a belt made of the above. Further, as a method of applying the charge, a configuration in which the sheet 18 is directly charged and is attracted to the conveyance belt 20 may be employed. Further, the static eliminator 32 may be disposed in the paper peeling unit 30.

  Even in this method, the suction means of the paper 18 does not affect the ink droplets ejected from the print recording means 12 as in the first embodiment. For this reason, since there is no adverse effect on the position system or the like where the ink droplets land on the paper 18, there is no possibility of causing image position shift or color shift.

  FIG. 5 shows a printing mechanism portion of an inkjet image forming apparatus according to the third embodiment of the present invention.

  As shown in FIG. 5, the conveying belt 20 wound around the drive roller 26 and the driven roller 28 is made of a so-called porous material having numerous holes, and has air permeability.

  Further, the material of the belt may be made of a steel sheet having a large number of holes in addition to rubber, plastic and the like. A duct 42 for sucking air is stretched under the conveyor belt 20, and the end of the duct 42 is connected to a suction fan 44.

  The structure of the duct 42 is shown in FIGS. 6 is a plan view seen from above (from the direction of the print recording means 12), FIG. 7 is a side view seen from the downstream side in the transport direction of the paper 18, and FIG. 8 is a perspective view.

  As shown in FIGS. 6, 7, and 8, the duct 42 is provided with an air intake hole 46 in a portion that contacts the conveyor belt 20 in order to enhance suction, and sucks air through the conveyor belt 20 to adsorb the paper 18. It is structured to be held by the conveyor belt 20.

  When the suction fan 44 is operated, a negative pressure is generated inside the duct 42 and air is sucked through the transport belt 20, so that a negative pressure is generated on the surface of the transport belt 20. When the paper 18 is transported, the paper 18 is sucked by the negative pressure on the surface of the transport belt 20, and the paper 18 is sucked and attracted to the transport belt 20.

  At this time, if the air permeability of the conveying belt 20 is insufficient, the conveying belt 20 is sucked and adsorbed to the duct 42, so that the conveying belt 20 itself needs to be formed of a material having excellent air permeability as described above. . In addition to a porous material, the conveyance belt 20 may simply have a plurality of vent holes.

  Since the duct 42 is not provided in the most downstream portion of the transport belt 20, the suction force to the paper 18 by the transport belt 20 does not work beyond that. Therefore, the paper 18 and the conveyance belt 20 can be easily separated by providing the peeling claw 30 at the tip.

  In this structure, suction through the conveyance belt 20 is not performed directly below the print recording means 12. Accordingly, it is possible to suppress ink permeation unevenness caused by sucking the paper 18 from the back side.

  As described above, the full-color inkjet recording apparatus having a plurality of colors capable of full-color printing has been described. However, it goes without saying that the requirements of the present invention can be applied to a recording apparatus having a printing recording means for only a single color instead of full color.

  Also, the inkjet image forming apparatus has been described as a printer that receives print information from outside the image forming apparatus. However, a so-called inkjet type copy that has an image reading apparatus such as a scanner and prints document information read by the image reading apparatus. The effect of the present invention is also effective in the machine.

1 is a perspective view showing an inkjet image forming apparatus according to a first embodiment of the present invention. It is a side view which shows the internal structure of the inkjet image forming apparatus which concerns on the 1st form of this invention. FIG. 2 is a plan view showing a recording head arrangement of the inkjet image forming apparatus according to the first embodiment of the present invention. It is a side view which shows the internal structure of the inkjet image forming apparatus which concerns on the 2nd form of this invention. It is a side view which shows the internal structure of the inkjet image forming apparatus which concerns on the 3rd form of this invention. It is a top view which shows the internal structure of the inkjet image forming apparatus which concerns on the 3rd form of this invention. It is a side view which shows the internal structure of the inkjet image forming apparatus which concerns on the 3rd form of this invention. It is a perspective view which shows the internal structure of the inkjet image forming apparatus which concerns on the 3rd form of this invention. It is a side view which shows the paper holding means of the conventional inkjet image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inkjet image forming apparatus 12 Print recording means 14 Print set 16 Charging rod 18 Paper 20 Conveyor belt 22 Registration roller 24 Accumum 26 Drive roller 28 Driven roller 30 Peeling claw 32 Static elimination device 34 Static elimination brush 36 Recovery means 38 Charging roller 40 Conductive roller 42 Duct 44 Suction fan 46 Air intake hole

Claims (5)

A plurality of first recording heads arranged at a predetermined interval in a direction orthogonal to the recording medium conveyance direction; and a first non-printing area of the first recording head arranged along the conveyance direction of the recording medium, A first conveying belt for conveying a recording medium;
A plurality of second recording heads provided downstream of the first conveying belt in the conveying direction and arranged in the first non-printing area at a predetermined interval; and the recording medium in the second non-printing area of the second recording head An inkjet image forming apparatus provided with a second conveyor belt that is disposed along a conveyance direction of the recording medium and that conveys the recording medium.
An inkjet image forming apparatus, comprising: an adsorbing unit that adsorbs a sheet to at least one of the first conveying belt and the second conveying belt.   The inkjet image forming apparatus according to claim 1, wherein the suction unit is a frictional charging member that contacts the conveyance belt.   The inkjet image forming apparatus according to claim 1, wherein the suction unit is a charging member that generates a potential between the conveyance belt and a sheet.   The inkjet image forming apparatus according to claim 1, wherein the suction unit is a negative pressure applying unit that generates a suction force in a suction hole formed in the conveyance belt.   5. The ink jet image forming apparatus according to claim 1, further comprising a peeling unit for peeling the paper adsorbed on the first conveyance belt or the second conveyance belt.

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