JP2006192838A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording device capable of obtaining a successful image by setting a difference in the gap of an unevenness of a sheet to be absorbed within the range of a tolerable gap level of a recording head in printing the face and the back of the sheet. <P>SOLUTION: This inkjet recording device comprises a double-side printing means to print the back of the sheet by one recording part by inverting the sheet after printing the face and also comprises a train of platen ribs consisting of a plurality of ribs for receiving the back of a recording sheet in an opposite part to the recording head. In addition, a transfer means to transfer the train of platen ribs in the width direction of the recording sheet, and a control means which controls the transfer of the position of the train of platen ribs over a distance about half the interval of the ribs, between the case of printing the face and the case of printing the back, are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using an ink jet system.

  The prior art will be described with reference to FIGS.

  First, the configuration and operation of the image forming apparatus related to single-side printing will be described with reference to FIG. Reference numeral 1 denotes a feeding roller that separates and feeds the sheets S on the feeding tray 2 one by one from the top by cooperation with a separation claw (not shown) during sheet feeding.

  As shown in FIG. 7, the fed sheet S is conveyed to a recording position by a conveying roller 3a that rotates to constitute the conveying means 3 and a driven roller 3b that rotates while being driven by pressing the sheet S against this.

  The recording unit 4 records an ink image on the sheet S conveyed by the conveying unit by an ink jet recording method. That is, the recording head 4d is mounted on a carriage 4c that can reciprocate along a guide shaft that is long in the width direction of the recording sheet S, and the recording head 4d is driven to synchronize with the reciprocating movement of the carriage 4c. Accordingly, ink droplets are ejected onto the sheet S supported on the back surface by the platen 4e to record an ink image.

  After the front side printing, the sheet S is conveyed to the sheet reversing unit 9 by stopping and reversing the conveyance with the trailing edge of the sheet S being held by the pair of the conveyance roller 3a and the driven roller 3b. By passing the loop-shaped conveyance path by the sheet reversing unit 9, the sheet S re-enters the conveyance unit 3 in a state where the front and back are reversed. When the recording unit 4 forms an ink image, the back side can be printed. When the printing on the back surface is completed, the platen 4e is retracted downward with the transport roller 3a as the center of rotation, and the discharge of the sheet to the paper discharge tray 7 is completed by rotating the transport roller in the normal direction.

When the sheet to be used is paper, an ink image is formed by ejecting ink containing water as a main component to the paper, so that the paper expands and the surface is uneven. Since the convex portion of the paper and the head are rubbed and the ink image is disturbed, wrinkle formation control means is provided.
The wrinkle formation control means will be described with reference to FIG.

  The platen 4e has ribs 4f on the paper support portion at intervals of P = 20 mm, the sheet S is supported on the top surface of the ribs, and the height of the ribs is such that the position of the paper is the minimum gap with the recording head. Is set. The portions other than the ribs of the platen are set to be about 2 mm lower than the ribs. The rib shape is parallel to the recording head at the opposing portion of the recording head and is the height of the rib, and the vicinity of the conveyance roller on the upstream side of the rib gradually increases from a position about 1 mm lower than the paper path to the height of the parallel portion. The taper shape becomes higher. The axis of the driven roller 3b is positioned about 2 mm downstream from the axis of the conveying roller 3a, the leading edge of the sheet S abuts against the tapered portion of the rib 4f, and then presses the paper against the rib 4f. . The ribs 4f are arranged at intervals of 20 mm (5, 25, 45, 65, 85, 105, 125, 145, 165, 185, 205 mm) from the left end of the A4 size sheet.

  In the above configuration, when paper is conveyed, the paper is conveyed while being pressed against the ribs. When ink is ejected from the recording head onto the paper, the paper expands due to the moisture of the ink, and the expanded portion enters a lower portion between the ribs 4f, and uneven wrinkles due to the expansion of the paper are caused by the ribs 4f. The supporting portion is convex, and the portion between the ribs is concave, so that rubbing between the paper surface and the recording head can be prevented. Convex and concave paper is conveyed and discharged in a state where there is a corrugated wave in the main scanning direction and no wave in the sub-scanning direction like a corrugated plate.

  That is, as shown in FIG. 9, the sheet is placed on the top surface of the rib 4f with convex portions at 5, 25, 45, 65, 85, 105, 125, 145, 165, 185, and 205 mm spaced from the left end of the sheet. , And the portions of 15, 35, 55, 75, 95, 115, 135, 155, 175, and 195 mm between the convex portions become concave portions, and can only be in a direction farther than the recording head, The variation in distance from the recording head to the sheet is a difference in unevenness, and by setting the portion supported by the rib 4f that is the convex portion to be the minimum gap with the recording head, the recording head and the sheet do not come into contact with each other, The gap difference between the irregularities of the paper can be within the allowable gap amount range of the recording head, which is also an effective means for images.

A technique for preventing the rubbing between the paper surface and the recording head by supporting the convex and concave portions of the irregularities caused by the expansion of the paper by the ribs is disclosed in, for example, Patent Document 1.
JP 2004-106978 A

  However, in the above-described conventional example, when the single-sided printing is finished as it is, the conveying roller 3a is reversed, the sheet S is reversed by the reversing unit 9, and the sheet is fed to the conveying unit 3 in the reversed state, the positional relationship between the convex portion and the concave portion. In the case of a low humidity environment where the amount of ink on the surface is large, the uneven shape formed on the surface has rigidity, and when conveyed as it is, the sheet is pressed against the top surface of the rib 4f by the conveying roller pair. However, the shape of the sheet does not follow the arrangement of the ribs, and the back surface of the recess is not received by the ribs 4f as shown in FIG. There is a problem in that the convex portion approaches the head, contacts the recording head, and disturbs the ink image.

  As a typical means for solving the above-mentioned problem, the platen 4e is provided with a mechanism for moving from the left to the right of the sheet, and before the back side printing, the platen 4e is moved by a distance corresponding to a half of the interval P of the rib 4f. Let it be done. As a result, the unevenness at the time of surface printing is completely replaced with the unevenness, and even if the sheet after surface printing is reversed and conveyed, the positions of the convex portions of the conveyed sheet and the ribs 4f coincide with each other. Without the fear of such contact between the sheet and the recording head, the gap difference between the irregularities of the paper can be kept within the allowable gap amount range of the recording head, as in surface printing, and a good image can be obtained.

  During double-sided printing, the sheet approaches the head and does not disturb the ink image, and the ink image is not disturbed. In this range, and a good image can be obtained.

  A first embodiment of the present invention will be described with reference to FIGS.

  First, the configuration and operation of the image forming apparatus relating to single-sided printing will be described with reference to FIG. Reference numeral 1 denotes a feeding roller that separates and feeds the sheets S on the feeding tray 2 one by one from the top by cooperation with a separation claw (not shown) during sheet feeding.

  As shown in FIG. 1A, the fed sheet S is conveyed to a recording position by a conveying roller 3a that rotates to form a conveying unit 3 and a driven roller 3b that rotates by driving the sheet S against the conveying roller 3a. The

  The recording unit 4 records an ink image on the sheet S conveyed by the conveying unit by an ink jet recording method. That is, the recording head 4d is mounted on a carriage 4c that can reciprocate along a guide shaft that is long in the width direction of the recording sheet S, and the recording head 4d is driven to synchronize with the reciprocating movement of the carriage 4c. Accordingly, ink droplets are ejected onto the sheet S supported on the back surface by the platen 4e to record an ink image.

  The recording head 4d includes a fine liquid discharge port (orifice), a liquid path, an energy action part provided in a part of the liquid path, and energy generating means for generating liquid droplet formation energy that acts on the liquid in the action part. It has.

  As an energy generating means for generating such energy, a recording method using an electromechanical transducer such as a piezo element, an energy generating means that emits heat by irradiating an electromagnetic wave such as a laser, and discharges a droplet by the action of the generated heat. Or a recording method using energy generating means for discharging a liquid by heating the liquid with an electrothermal transducer such as a heating element having a heating resistor.

  Among them, a recording head used in an ink jet recording method in which liquid is discharged by thermal energy can arrange liquid discharge ports (orifices) for discharging ink droplets to form discharge droplets at high density. Therefore, it is possible to record at a high resolution. Among them, a recording head using an electrothermal transducer as an energy generating means is advantageous because it can be easily made compact, can be easily mounted at high density, and can be manufactured at low cost.

  In the present embodiment, the ink discharge configuration is such that the electrothermal transducer is energized in accordance with the recording signal, and the ink is generated by the growth and contraction of bubbles generated in the ink using the film boiling generated in the ink by the thermal energy. The recording is performed by discharging from the discharge port.

  The recording head 4d is integrated with an ink tank for storing ink in the upper part thereof, and this is detachably attached to the carriage 4c.

  After the front side printing, the sheet S is conveyed to the sheet reversing unit 9 by stopping and reversing the conveyance with the trailing edge of the sheet S being held by the pair of the conveyance roller 3a and the driven roller 3b. By passing the loop-shaped conveyance path by the sheet reversing unit 9, the sheet S re-enters the conveyance unit 3 in a state where the front and back are reversed. When the recording unit 4 forms an ink image, the back side can be printed. When the printing on the back surface is completed, the platen 4e is retracted downward with the transport roller 3a as the center of rotation, and the discharge of the sheet to the paper discharge tray 7 is completed by rotating the transport roller in the normal direction.

  When the sheet to be used is paper, an ink image is formed by ejecting ink containing water as a main component to the paper, so that the paper expands and the surface is uneven. Since the convex portion of the paper and the head are rubbed and the ink image is disturbed, wrinkle formation control means is provided.

  The wrinkle formation control means will be described with reference to FIG.

  The platen 4e has ribs 4f on the paper support portion at intervals of P = 20 mm, the sheet S is supported on the top surface of the ribs, and the height of the ribs is such that the position of the paper is the minimum gap with the recording head. Is set. The portions other than the ribs of the platen are set to be about 2 mm lower than the ribs. The rib shape is parallel to the recording head at the opposing portion of the recording head and is the height of the rib, and the vicinity of the conveyance roller on the upstream side of the rib gradually increases from a position about 1 mm lower than the paper path to the height of the parallel portion. The taper shape becomes higher. The axis of the driven roller 3b is positioned about 2 mm downstream from the axis of the conveying roller 3a, the leading edge of the sheet S abuts against the tapered portion of the rib 4f, and then presses the paper against the rib 4f. . The ribs 4f are arranged at intervals of 20 mm (5, 25, 45, 65, 85, 105, 125, 145, 165, 185, 205 mm) from the left end of the A4 size sheet.

  In the above configuration, when paper is conveyed, the paper is conveyed while being pressed against the ribs. When ink is ejected from the recording head onto the paper, the paper expands due to the moisture of the ink, and the expanded portion enters a lower portion between the ribs 4f, and uneven wrinkles due to the expansion of the paper are caused by the ribs 4f. The supporting portion is convex, and the portion between the ribs is concave, so that rubbing between the paper surface and the recording head can be prevented. Convex and concave paper is conveyed and discharged in a state where there is a corrugated wave in the main scanning direction and no wave in the sub-scanning direction like a corrugated plate.

  That is, as shown in FIG. 3, the sheet is placed on the top surface of the rib 4f with convex portions at 5, 25, 45, 65, 85, 105, 125, 145, 165, 185, and 205 mm spaced from the left end of the sheet. , And the portions of 15, 35, 55, 75, 95, 115, 135, 155, 175, and 195 mm between the convex portions become concave portions, and can only be in a direction farther than the recording head, The variation in distance from the recording head to the sheet is a difference in unevenness, and by setting the portion supported by the rib 4f that is the convex portion to be the minimum gap with the recording head, the recording head and the sheet do not come into contact with each other, The gap difference between the irregularities of the paper can be within the allowable gap amount range of the recording head, which is also an effective means for images.

  However, if the single-sided printing is finished as it is, the conveying roller 3a is reversed, the sheet S is reversed by the reversing unit 9, and the sheet is fed to the conveying unit 3 in the reversed state, the positional relationship between the convex portion and the concave portion is reversed. In the case of a low humidity environment where the amount of ink on the surface is large, the uneven shape formed on the surface is stiff, and if it is conveyed as it is, the sheet shape will not change even if the sheet is pressed against the top surface of the rib 4f by the conveying roller pair. However, the rear surface of the recess is not received by the rib 4f as shown in FIG. The convex portion approaches the head and comes into contact with the recording head, thereby disturbing the ink image.

  Therefore, the platen 4e has a mechanism for moving from the left to the right of the sheet, and as shown in FIG. 5, has a mechanism for moving the interval 10 mm, which is half of the interval P = 20 mm between the ribs 4f, before printing on the back surface. As a result, the unevenness at the time of surface printing is completely replaced with the unevenness, and even if the sheet after surface printing is reversed and conveyed, the positions of the convex portions of the conveyed sheet and the ribs 4f coincide with each other. Without the fear of such contact between the sheet and the recording head, the gap difference between the irregularities of the paper can be kept within the allowable gap amount range of the recording head, as in surface printing, and a good image can be obtained.

  As for the movement of the platen 4e, a method of separately driving the platen 4e, or as shown in FIG. 6, the normal carriage in the width direction of the platen is in contact with the carriage on both sides outside the movement range related to printing. By providing the protrusion 4g and moving the carriage more in the right direction of the sheet than usual, it is at the back side printing position. On the contrary, a method of moving to the front surface printing position by moving the carriage more in the left direction of the sheet than usual can be considered.

  As described above, according to the present invention, in the ink jet recording system that performs recording by ejecting ink in accordance with a signal, the double-side printing unit that prints the back side in the same recording unit by inverting the paper after printing the front side. And a platen rib row arranged in a width direction of the recording sheet at a substantially equal interval in the width direction of the recording sheet and having a platen rib row composed of a plurality of ribs receiving the back side of the recording sheet. And a control means for moving the position of the platen rib row when printing the back surface to a position approximately half the gap between the ribs relative to the position of the platen rib row when printing the front surface. During double-sided printing, the sheet does not touch the recording head and touch the recording head, and the ink image is not disturbed. -Up difference can be made fit to the range of the allowable gap amount of the recording head, it is possible to obtain a good image.

BRIEF DESCRIPTION OF THE DRAWINGS The whole apparatus structure concerning 1st Example and operation | movement explanatory drawing. Explanatory drawing of a wrinkle formation means concerning 1st Example. Explanatory drawing of a wrinkle formation means concerning 1st Example. Explanatory drawing of a wrinkle formation means concerning 1st Example. Explanatory drawing of a wrinkle formation means concerning 1st Example. Explanatory drawing of a wrinkle formation means concerning 1st Example. Explanatory drawing concerning a prior art example. Explanatory drawing concerning a prior art example. Explanatory drawing concerning a prior art example. Explanatory drawing concerning a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Feed roller 2 Paper feed tray 3 Conveying means 4 Recording means 4d Recording head 4e Platen 4f Rib 7 Discharge tray

Claims (1)

  Inkjet recording method that performs recording by ejecting ink in response to a signal, and has double-sided printing means that inverts the paper after printing on the front side and prints the back side in the same recording unit. And a platen rib array composed of a plurality of ribs which are arranged at substantially equal intervals in the width direction of the recording sheet and receive the back side of the recording sheet, and a moving means for moving the platen rib array in the width direction of the recording sheet, and printing the surface An ink jet recording apparatus comprising: a control unit configured to move the position of the platen rib row at the time of printing and the position of the platen rib row at the time of printing the back surface by a distance approximately half of the rib interval.

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