JP2011062822A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To overcome the problem of image degradation because of uniting of dots when the dots adjoining in a medium transfer direction are formed by nozzles of the same nozzle array. <P>SOLUTION: The image forming apparatus includes a recording head 102 in which two nozzle arrays 112A and 112B that eject liquid droplets of the same color are arranged staggering. Oscillation generating mechanisms 135 and 135 which move rollers 133 and 132 back and forth in an axial direction are provided on one axial ends of the rollers 133 and 132 around which a transfer belt 131 is stretched, and elastic members 136 and 136 are provided on the other axial ends. A paper 100 is made movable back and forth in a nozzle array direction to the recording head 102 via the transfer belt 131. At the time of image formation, the paper 100 and the recording head 102 are oscillated relatively in the nozzle array direction, whereby adjoining dots in a dot array of the same color formed in the paper transfer direction of the paper 100 are formed by liquid droplets ejected from different nozzle arrays 112A and 112B. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that includes a liquid discharge head for discharging droplets in a recording head.

  As an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, a plotter, and a complex machine of these, for example, an ink jet recording apparatus is known as an image forming apparatus of a liquid discharge recording method using a recording head for discharging ink droplets. . This liquid discharge recording type image forming apparatus means that ink droplets are transported from a recording head (not limited to paper, including OHP, and can be attached to ink droplets and other liquids). Yes, it is also ejected onto a recording medium or a recording medium, recording paper, recording paper, etc.) to form an image (recording, printing, printing, and printing are also used synonymously). And a serial type image forming apparatus that forms an image by ejecting liquid droplets while the recording head moves in the main scanning direction, and a line type head that forms images by ejecting liquid droplets without moving the recording head There are line type image forming apparatuses using

  In the present application, the “image forming apparatus” of the liquid ejection method is an apparatus that forms an image by ejecting liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, or the like. In addition, “image formation” means not only that an image having a meaning such as a character or a figure is applied to the medium, but also an image having no meaning such as a pattern is applied to the medium (simply liquid It also means that a droplet hits the medium). The “ink” is not limited to what is called ink, and is not particularly limited as long as it becomes a liquid when ejected. For example, a DNA sample, a resist, a pattern material, etc. Is also included. In addition, the “image” is not limited to a planar one, but includes an image given to a three-dimensionally formed image, and an image formed by three-dimensionally modeling a solid itself.

  In a liquid discharge type image forming apparatus, in order to increase resolution (high density) and improve productivity (printing speed), droplets (pixels) discharged from nozzles adjacent to a recording head The density has increased and the discharge timing (time difference) has also become shorter. For this reason, the droplets that form adjacent dots landed on the paper are easily united. When adjacent droplets coalesce, the result is the same as landing a large droplet, and ink bleeding is particularly noticeable, reducing pixel density and image resolution such as feathering and bleeding. Not only that, but also the deterioration of the image density due to the deep ink penetration depth and the image deterioration such as the promotion of the image back-through (enhanced back-through density) are caused.

  In this case, in the serial type image forming apparatus, the multi-scan is performed to shift the droplet discharge timing of the adjacent pixels in the main scanning direction, or the adjacent pixels in the sub scanning direction are discharged by the interlace method in the sub scanning direction. By adopting a configuration such as shifting the droplet discharge timing of the pixels, the droplets of adjacent pixels are united.

  As a technique related to the present invention, for example, Patent Document 1 discloses a technique in which a line type ink jet head is moved by a minute movement amount and printing is performed with a resolution of 1/2 the nozzle pitch.

  As for vibration or movement of the head in the nozzle array direction, those disclosed in Patent Documents 2 to 4 are known.

JP 08-310049 A JP 2009-18491 A JP 2005-104037 A JP 2006-76024 A

  In the vibration in the nozzle row direction as described above, it is possible to make the white stripe inconspicuous or raise the resolution higher than the nozzle arrangement density by shifting the landing points of the droplets ejected from the same nozzle.

  However, in simple vibration printing, dots adjacent in the recording medium conveyance direction are ejected from the same nozzle row, and therefore, it is not possible to make a difference in ejection timing. That is, for example, adjacent to the recording medium conveyance direction of the dot Da1 printed by the nozzle A1, for example, the dot Da2 ejected from the nozzle A2 adjacent to the nozzle A1 in the same nozzle row as the nozzle A1 is formed. The formation timing of the dots Da1 and Da2 is exactly the same as the case where the dots Da1 and Da2 are continuously formed by the nozzle A1. Therefore, even if such continuous printing is performed, it is impossible to prevent the droplets forming adjacent dots in the recording medium conveyance direction from being unified.

  The present invention has been made in view of the above problems, and an object of the present invention is to prevent deterioration in image quality due to unification of adjacent dots without increasing the size of the liquid discharge head such as increasing the number of nozzles. To do.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A liquid discharge head having a plurality of nozzle rows for discharging droplets;
Conveying means for conveying a recording medium in a direction orthogonal to the nozzle row direction of the liquid ejection head;
Vibration generating means for relatively vibrating the recording medium and the liquid ejection head in the nozzle row direction,
A plurality of nozzle rows that discharge droplets of the same color are arranged,
When forming an image, the recording medium and the liquid discharge head are relatively vibrated in the nozzle array direction, and the same color dot array formed in the recording medium transport direction is ejected from a nozzle array in which adjacent dots are different. It was set as the structure formed with the formed droplet.

  Here, the plurality of nozzle rows that discharge droplets of the same color may be arranged so as not to overlap each other in the recording medium conveyance direction.

  Moreover, it can be set as the structure provided with the means to change the amplitude of the said vibration.

  Further, the conveying means has roller members arranged on the upstream side and the downstream side in the recording medium conveying direction of the liquid ejection head, the vibration generating means is provided on one of the shaft ends of the roller member, and the elastic member is provided on the other side. It can be configured as provided.

  Further, the conveying means has roller members arranged on the upstream side and the downstream side in the recording medium conveying direction of the liquid ejection head, and the vibration generating means is provided at both shaft ends of the roller member. it can.

  Further, the roller member may be a roller member around which a conveyance belt that sucks and conveys the recording medium is wound.

  Further, the conveying means may be a rotating body around which the recording medium is wound, and the vibration generating means may be provided on at least one of the shaft ends of the rotating body.

  Further, the vibration generating means may include an electrostrictive element or a giant magnetostrictive element.

  According to the image forming apparatus of the present invention, when a plurality of nozzle rows that eject droplets of the same color are arranged and image formation is performed, the recording medium and the liquid ejection head are relatively vibrated in the nozzle row direction. Since the dot rows of the same color formed in the recording medium transport direction are formed by droplets in which adjacent dots are ejected from different nozzle rows, for example, liquid ejection having nozzle rows of a normal staggered arrangement Even if the head is used, adjacent dots in the recording medium conveyance direction can be formed with droplets from different nozzle arrays, and image quality deterioration due to coalescence of adjacent dots without increasing the size of the liquid discharge head Can be prevented.

1 is an explanatory front view of an image forming apparatus according to a first embodiment of the present invention. It is plane explanatory drawing of the conveyance unit of the apparatus. FIG. 4 is an explanatory diagram of a bottom surface of a recording head. It is a block explanatory drawing explaining the outline | summary of the control part of the apparatus. It is explanatory drawing with which it uses for operation | movement description of the same embodiment. It is a plane explanatory view of the conveyance unit concerning a 2nd embodiment of the present invention. It is front explanatory drawing similarly. It is a plane explanatory view of the conveyance unit concerning a 3rd embodiment of the present invention. It is front explanatory drawing similarly. It is front explanatory drawing with which it uses for description of 4th Embodiment of this invention. It is explanatory drawing with which it uses for operation | movement description of the same embodiment. It is explanatory drawing with which it uses for description of an effect | action of 5th Embodiment of this invention. It is explanatory drawing with which it uses for description of the other example of the embodiment. It is a flowchart with which it uses for description of the complementary control of a non-discharge nozzle similarly. It is a plane explanatory view of an image forming device concerning a 6th embodiment of the present invention. It is front explanatory drawing similarly. FIG. 10 is an explanatory plan view of an image forming apparatus according to a seventh embodiment of the present invention. It is explanatory drawing with which it uses for operation | movement description of 6th, 7th embodiment of this invention. It is explanatory drawing with which it uses for other effect | action description of 6th, 7th embodiment of this invention. It is a plane explanatory view of an image forming device concerning an 8th embodiment of the present invention. It is a plane explanatory view of an image forming device concerning a 9th embodiment of the present invention. It is explanatory drawing of the drive waveform with which it uses for description of an effect | action of 8th Embodiment of this invention. It is explanatory drawing of the drive waveform with which it uses for operation | movement description of 9th Embodiment of this invention. It is explanatory drawing of the other drive waveform with which it uses for description of an effect | action of 8th Embodiment of this invention. It is explanatory drawing with which it uses for description of an effect | action of 10th Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS. 1 is an explanatory front view of the image forming apparatus, FIG. 2 is an explanatory plan view of the transport unit, and FIG. 3 is an explanatory bottom view of the recording head.
The image forming apparatus includes a recording head unit 101 as an image forming unit that forms an image by ejecting liquid droplets onto a sheet 100 that is a recording medium, a transport unit 103 that is a transport unit that transports the sheet 100, and a sheet. A paper feed tray 104 that accommodates 100 is provided.

  The recording head unit 101 is composed of a line type liquid discharge head having a nozzle row in which a plurality of nozzles for discharging droplets are arranged in a length corresponding to the paper width. Yellow (Y), magenta (M), cyan (C) and black (K) ink droplets are provided with recording heads 102y, 102m, 102c, and 102k (hereinafter referred to as “recording head 102” when colors are not distinguished).

  As shown in FIG. 3, one recording head 102 has two nozzle rows 112A and 112B in which a plurality of nozzles 111 that discharge droplets of the same color are arranged. The nozzle rows 112A and 112B stagger the nozzles 111. By arranging the plurality of nozzle rows that discharge droplets of the same color, they are arranged so as not to overlap each other in the recording medium conveyance direction. The arrangement direction (nozzle arrangement direction) of the nozzles 111 is referred to as “nozzle row direction”. In addition, the arrangement pitch of the nozzles 102 in the nozzle row direction is a pitch at which a required resolution can be obtained.

  The conveyance unit 103 includes a conveyance belt 131 that is an endless belt that adsorbs and conveys the paper 100, and the conveyance belt 131 is arranged between the conveyance roller 132 and the tension roller 133 so as to circulate. Yes. The paper 100 can be held on the transport belt 131 by, for example, a structure that performs electrostatic suction, suction by suction of air, or other known transport means. Further, a conveying means using a roller pair can also be used.

  The paper 100 accommodated in the paper feed tray 104 is separated one by one by a pick-up roller 141 that can swing between the side shown by the solid line for releasing the conveyance and the broken line for carrying the paper, and is fed downstream by the paper feeding roller 142a. The sheet 100 conveyed to the sheet feeding unit 142 constituted by the separation roller 142b and separated into one sheet by the sheet feeding unit 142 is sent to the intermediate conveyance roller pair 145 via the conveyance path 144, and is conveyed to the intermediate conveyance The roller pair 145 is transported from the transport path 146 through the transport path 147 to the transport belt 131 of the transport unit 103 via the transport roller 148.

  Then, the ink is transported by the circular movement of the transport belt 131 and droplets of each color are ejected from the recording heads 102 of the recording head unit 101 to form an image, which is then discharged to a paper discharge tray (not shown).

Next, details of the transport unit 103 will be described with reference to FIG. FIG. 2 is an explanatory plan view of the transport unit.
The conveying roller 132 and the tension roller 133 for driving the conveying belt 131 are provided with a vibration generating mechanism 135 as vibration generating means for vibrating the rollers 132 and 133 in the axial direction at one shaft end 132a and 133a. An elastic coupling 136 is provided as an elastic member at the ends 132b and 133b, and the main body frame 137 is rotatably held by a holding member 138 such as a bearing.

  Here, as an actuator constituting the vibration generating mechanism 135, an electrostrictive element such as a piezo element, a super magnetostrictive element that generates vibration by a magnetic force, a solenoid, or the like can be used. Here, the conveying roller 132 and the tension roller 133 are vibrated, but it is sufficient if the recording head unit 101 and the paper 100 can be relatively vibrated in the nozzle row direction. For example, the recording head unit 101 itself may be vibrated. .

Next, an overview of the control unit will be described with reference to the block explanatory diagram of FIG.
The control unit 500 includes a main control unit (system controller) 501 including a microcomputer that also serves as a vibration control unit that controls vibrations according to the present invention, which controls the entire image forming apparatus, an image memory, a communication interface, and the like. Yes. The main control unit 501 sends print data to the print control unit 502 in order to form an image on a sheet based on image data transferred from an external information processing apparatus (host side) and various command information.

  Based on the print data signal received from the main control unit 501, the print control unit 502 generates data for driving pressure generating means for ejecting droplets from each head 102 of the recording head unit 101. Various signals necessary for the transfer of the data and confirmation of the transfer are transferred to the head driver 503, and a storage unit as drive waveform data storage means, a D / A converter for D / A converting the drive waveform data, and It includes a drive waveform generation unit composed of a voltage amplifier, a current amplifier, etc., and a selection means for selecting a drive waveform to be given to the head driver 503, and is composed of one drive pulse (drive signal) or a plurality of drive pulses (drive signal). A drive waveform is generated and output to the head driver 503 to drive-control each recording head 102.

  Further, the main control unit 501 drives and controls a paper feed motor 505 that moves the conveyor belt 131 around via a motor driver 504.

  Further, the main control unit 501 drives and controls the actuator of the vibration generating mechanism 135 via the driver 508 during image formation, and reciprocates (vibrates) the transport belt 131 in the nozzle arrangement direction.

  The main control unit 501 receives detection signals from a sensor group 506 including various sensors, and performs input / output of various information and exchange of display information with the operation unit 507.

Next, the operation of the embodiment configured as described above will be described.
First, when vibration is generated by the vibration generating mechanism 135, the transport roller 132 and the tension roller 133 both vibrate in the axial direction (nozzle row direction). At this time, by synchronizing the vibrations so that the vibration periods and amplitudes of both rollers 132 and 133 are matched, the conveyance belt 131 and the paper 100 are moved relative to the recording head 102 with the same period and amplitude as the rollers 132 and 133. It vibrates relatively in the nozzle row direction.

  Here, the vibration period in the nozzle row direction of the paper is twice the drive period, the amplitude is 1/4 of the nozzle pitch P (MAX-MIN is 1/2 of the nozzle pitch P: see FIG. 5), and the nozzle By separating the inter-column distance by 2n dots (n is a natural number), as shown in FIG. 5A, the dots formed by the nozzle row 112A, the DA, and the dots DB formed by the nozzle row 112B are the nozzle rows. The direction positions can be the same, and the dots DA and DB adjacent in the paper transport direction can be formed by different nozzle rows 112A and 112B. When dots are formed by the nozzle rows 112A and 112B without applying vibration, the result is as shown in FIG.

  Note that, here, the two nozzle rows are shown as being arranged with a deviation of 1/2 the nozzle pitch P, but the nozzle positions of the two nozzle rows may be arranged in the recording medium conveyance direction. In such a case, if the distance between the nozzle rows is (2n + 1) dots (n is a natural number), the vibration cycle in the nozzle row direction is twice the drive cycle and the amplitude is the nozzle pitch as in the above case. By setting 1/4 of P, the same image can be formed.

  In this way, when a plurality of nozzle rows that eject droplets of the same color are arranged and image formation is performed, the recording medium and the liquid ejection head are relatively vibrated in the nozzle row direction, and the recording medium is conveyed in the conveyance direction. The formed dot rows of the same color are formed by droplets ejected from different nozzle rows of adjacent dots. For example, even if a liquid discharge head having a normal staggered nozzle row is used, recording is performed. Adjacent dots in the medium transport direction can be formed with droplets from different nozzle rows, and the nozzle rows are doubled and the liquid discharge head is not enlarged, which is associated with coalescence of adjacent dots. Degradation of image quality can be prevented.

  More specifically, when vibration is not generated, the arrangement of dots DA and DB formed by the nozzle rows 112A and 112B is as shown in FIG. That is, in the transport direction, dots formed from ink droplets ejected from the same nozzle are continuously arranged, and ink droplets from the same nozzle are ejected at the head drive frequency (usually several tens of kHz), so ink is almost simultaneously with landing. The droplets coalesce, and the coalescence of the ink droplets causes beading, a decrease in image density, a deterioration in the back-through density, and the like.

  On the other hand, when vibration is generated, the arrangement of the dots DA and DB formed by the nozzle rows 112A and 112B is the amount of movement of the paper 100 in the nozzle row direction as shown in FIG. It will shift. Thereby, since the distance between dots from the same nozzle is increased, ink droplets do not coalesce, and the image density can be improved, the back-through density can be reduced, and beading can be suppressed.

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 is an explanatory plan view of a transport unit for explaining the embodiment, and FIG. 7 is an explanatory front view.
Here, the conveyance unit 203 includes conveyance rollers 232 and 233 arranged on the upstream side and the downstream side in the sheet conveyance direction of the recording head unit 101, and conveys the continuous sheet 200 while applying tension in the conveyance direction. A vibration generating mechanism 135 is provided at one of the shaft ends of the paper transport rollers 232 and 233, and an elastic coupling 136 is provided at the other shaft end.

  By synchronizing the vibrations of the two rollers 232 and 233 by the vibration generating mechanisms 135 and 135, the entire sheet 200 tensioned between the rollers can be reciprocally vibrated in the direction perpendicular to the transport direction (nozzle arrangement direction). it can.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 8 is an explanatory plan view of a transport unit for explaining the embodiment, and FIG. 9 is an explanatory front view.
Here, as a transport unit for transporting the paper 100, a drum-shaped rotating body 303 that rotates while carrying the paper 100 on the surface is provided. A vibration generating mechanism 135 is provided at one end of the rotating body 303 as in the above embodiment, and an elastic coupling 136 is provided at the other end.

  By vibrating the rotating body 303 by the vibration generating mechanism 135, the paper 100 can be reciprocally vibrated in the direction orthogonal to the transport direction (nozzle arrangement direction).

  In each of the above embodiments, the vibration generating mechanism 135 can be arranged at both the shaft ends. The drive control of the vibration generating mechanism 135 will be described later.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In addition, FIG. 10 is a schematic front view for explaining the embodiment.
Here, two recording head units 101A and 101B are provided, the recording heads 122 and 123 of the recording head units 101A and 101B have one nozzle array, and the nozzle array and the recording head of the recording head 122 of the recording head unit 101A. The nozzle row of the recording head 123 of the unit 101B is shifted in the nozzle row direction by 1/2 nozzle pitch. The transport unit 103 has the same configuration as that of the first embodiment.

  Here, the period of vibration in the nozzle array direction of the paper is twice the driving period, the amplitude is 1/4 of the nozzle pitch P (MAX-MIN is 1/2 of the nozzle pitch P: see FIG. 11), and the nozzle By separating the inter-column distance by 2n dots (n is a natural number), as shown in FIG. 11A, the adjacent dots DA in the paper transport direction are the recording head unit 101A and the dot DB is the recording head unit 101B. Therefore, the same effect as that of the above embodiment can be obtained. Note that FIG. 11B shows a dot arrangement in the case of not vibrating.

  Note that, here, the two nozzle rows are shown as being arranged with a deviation of 1/2 the nozzle pitch P, but the nozzle positions of the two nozzle rows may be arranged in the recording medium conveyance direction. In such a case, if the distance between the nozzle rows is (2n + 1) dots (n is a natural number), the vibration cycle in the nozzle row direction is twice the drive cycle and the amplitude is the nozzle pitch as in the above case. By setting 1/4 of P, the same image can be formed.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
FIG. 12A shows an image formed by the recording head 101A in the fourth embodiment. Here, the recording head 101B is configured to be largely separated from the recording head 101A in the recording medium conveyance direction, and FIG. 12A shows a state where an image of the recording head 101B is not yet formed.

  Here, FIG. 12B shows an image formed by the recording head 101 </ b> A when the black arrow nozzles fail to eject (the dot positions to be formed by the ejecting nozzles are “non-ejection dots”). As white circles.) In this case, when the image of the recording head 101B is formed after that, dots formed from other nozzles are formed on the same line in the transport direction as shown in FIG. It becomes difficult. However, non-ejection nozzles (missing nozzles) are further detected, and as shown in FIG. 12D, the nozzles adjacent to the nozzles causing the missing nozzles are detected from the dots D (dots DA and DB in this example). In addition, white stripes can be made inconspicuous by ejecting large droplets that form relatively large dots Dl (formed by the head 101B, but the dots DB are shown in different shades).

  Such processing becomes possible only when dots adjacent in the recording medium conveyance direction are shot with different nozzle rows. That is, by ejecting adjacent nozzles in the recording medium conveyance direction with a time difference, it is possible to detect ejection failure due to the first nozzle row, and to subsequently eject large dots D1 between the defective nozzles. The non-ejection nozzle detection means may be a known means such as one in which an image sensor such as a CCD is arranged along the nozzle arrangement direction or one using laser light emitted along the nozzle row direction.

  Further, here, processing for changing the amplitude of vibration can be performed instead of driving the large dot D1. Specifically, if the amplitude is increased when non-ejection detection is performed, the recording positions of the non-ejection nozzles are separated from each other, and white spots are not conspicuous. In the case of vibration with an amplitude of 1/4 of the normal nozzle pitch P (MAX-MIN is 1/2 of the nozzle pitch P), the non-ejection positions are arranged in a zigzag pattern diagonally as shown in FIG. However, if the amplitude is changed to 3/4 of the nozzle pitch P (MAX-MIN is 3/2 of the nozzle pitch P), the non-ejection positions are separated as shown in FIG.

  Also, by arranging a plurality of nozzle rows so that they do not overlap with each other in the recording medium conveyance direction, it is difficult for ink of adjacent dots to coalesce on a recording medium with good permeability. Can stop the vibration and perform recording with an amplitude of 0 (when arranged side by side in the recording medium conveyance direction, dots cannot be formed between the nozzles, so that the solid is filled without vibration. Can't). By doing in this way, when vibration is unnecessary, a vibration can be stopped and consumption of useless electric power can be suppressed.

Here, an example of control for forming an image by complementing the nozzle from the detection of the non-ejection nozzle will be described with reference to FIG.
First, non-ejection detection is performed. If there is a missing nozzle, the missing nozzle Xn is specified, the droplet size of the dot data of the nozzle Xn is determined, and if the droplet size of the dot data of the nozzle Xn is a small droplet, the nozzle If the dot data of the nozzle Xn-1 or Xn + 1 adjacent to Xn is changed to a medium droplet, and the droplet size of the dot data of the nozzle Xn is a medium droplet, the dot data of the nozzle Xn-1 or Xn + 1 adjacent to the nozzle Xn is changed If the droplet size of the dot data of the nozzle Xn is a large droplet, the dot data of the nozzle Xn−1 or Xn + 1 adjacent to the nozzle Xn is changed to a medium droplet.

  Then, the vibration of the transport unit is started, the transport of the paper is started, the image is formed while transporting the paper, and the paper is discharged. After that, if there is next data, it is determined whether or not non-ejection detection is performed. When non-ejection detection is not performed, the conveyance unit vibration and image formation are performed in the same manner, and when non-ejection detection is performed, nozzle recovery operation is performed. After discharge, non-discharge detection is performed.

  Here, non-ejection detection is carried out before the recording operation, but non-ejection detection is performed at the time of ejection of image formation in the first nozzle row, and the droplet size change is reflected in the ejection operation by the second nozzle row. May be. In such a case, it is preferable that the two nozzle arrays are separated from each other.

  Further, such processing does not require pre-recording processing and can greatly improve the work efficiency, but there is a problem that the non-ejection of the second nozzle row cannot be corrected. In order to improve this, a process for confirming only the second row before the recording operation is performed, and the non-ejection detection result in the second row is promptly fed back. It is useful to change the drop size of the rows. Even in such a case, the production efficiency is greatly improved as compared with the case where the recording operation is started after the ejection failure of all the nozzles.

  Such a configuration can be similarly applied to the configurations of the first to third embodiments.

  In each of the above embodiments, the number of nozzle rows is not limited to two. For example, the same effect can be obtained by combining dots ejected from three or more nozzles and arranging them in the recording medium conveyance direction. it can.

Next, a sixth embodiment of the present invention will be described with reference to FIGS. 15 is an explanatory plan view of the image forming apparatus according to the embodiment, and FIG. 16 is an explanatory front view.
In this image forming apparatus, a single-sheet recording medium 1 of the same size is stacked on a paper supply bank 2 and picked up by a pickup roller 3 one by one from the top in accordance with a printing command, and then passes through a separation roller pair 4. By doing so, the sheets are separated one by one, pass through the conveying roller pair 5, and the leading edge of the recording medium 1 reaches the registration roller pair 6. At this time, the rotation of the registration roller pair 6 is stopped. When it is detected in front of the resist registration 7 that the leading edge of the recording medium 1 is in contact with the upstream side of the nip position of the registration roller pair 6, the conveyance of the conveyance roller pair 5 is also temporarily stopped, and the object in a state in which a loop is drawn. Registration of the leading edge of the recording medium 1 is performed.

  Thereafter, the registration roller pair 6 is activated again, and after passing the registration sensor 8, it is detected that the leading edge of the recording medium 1 has reached a predetermined position.

  Further, after passing through the conveying roller pair 9, the recording medium 1 guided by the guide plates 10 and 11 has a rotational torque generated by the motor 17 and its motor pulley 15 due to the timing belt 16 and the shaft portion 13-of the driving roller 13. 3 by a driving roller 14 attached to 3, a conveying force of a conveying belt 12 stretched around a driven roller 18, a driven roller 18, and a front spur 19 disposed opposite to the upper side of the driven roller 18. 1 can be transported without slipping, and by detecting the timing at which the leading edge of the recording medium 1 has passed the head sensor front 25, the line-type liquid discharge is accurately performed at a desired position on the predetermined recording medium 1. An ink droplet image is formed by passing through a recording head (unit) 23 including the head.

  Note that the ink in the unstable state accumulated in the head 23 is discharged to the printing tray 24 disposed opposite to the nozzle surface of the recording head 23 with the conveyance belt 12 interposed therebetween, as appropriate at intervals of the printing timing. Since the hole in which the pattern is formed is opened, the hole is ejected when the hole passes through the nozzle of the predetermined head 23. Therefore, the conveyor belt 12 is made of ink. There is no defacement.

  When the recording medium 1 is further transported, it is covered by the negative pressure of the suction fan 21 disposed below the transport belt 12 and upstream of the head 23 and the suction fan 22 disposed downstream. The recording medium 1 is given further conveying force, and the recording medium 1 is discharged to the paper discharge unit 26 without slipping by the driving roller 13 and the spur 20 disposed opposite to the upper side thereof. The

  The material of the conveyor belt 12 is preferably a material having a friction coefficient as high as possible in order to prevent slippage relative to the recording medium 1, and vulcanized rubber is generally used. An elastomer or a material obtained by processing a sheet made of a polymer material into a belt shape is used.

  Further, the roller 31 of the conveying roller pair 9 has a degree of freedom in the axial direction with respect to the shaft portion 32, but a retaining ring 29 is fixedly attached to both sides of the roller 31 to the shaft portion 32, There is a compressed spring 30 between the roller 31 and the roller 31, and the roller 31 is in a neutral position by the spring pressure. This is a system in which the individual rollers 31 are not provided with the spring 30 and the retaining ring 29, and the rollers fixed to the shaft portion 32 are integrally provided with a degree of freedom in the axial direction and are held in a neutral position by the spring. May be.

  Although a mechanism for transmitting torque is not shown in the conveying roller pair 9, torque is transmitted to at least one of the roller pair 9 at an angular speed synchronized with the conveying speed of the recording medium 1. On the other hand, by installing a one-way clutch (not shown) in the shaft contact portion of the roller 31, the shaft portion 32 and the roller 31 are not necessarily integrated, but have a degree of freedom in the axial direction, and a recording medium in a predetermined direction. The structure which can perform the torque transmission which conveys 1 may be sufficient.

  Further, the spur 19 and spur 20 have a degree of freedom in the axial direction with respect to the shaft portion 32, but a retaining ring 29 is fixed to the shaft portion 32 on both sides of the spur 19 and spur 20. There is a spring 30 compressed between the spur 19 and after the spur 20, and the pre-spur 19 and the spur 20 are in neutral positions by the spring pressure. The spur 19 and the spur 20 are not provided with the spring 30 and the retaining ring 29 before the spur 19 as described above, and the spur 19 and the spur 20 are integrated with the shaft portion 32 and have a degree of freedom in the axial direction. A system in which the spring is kept in the neutral position may be used.

  Then, giant magnetostrictive actuators 35 and 37 comprising giant magnetostrictive elements as vibration generating means for reciprocating (vibrating) the recording medium 1 with respect to the recording head 23 in the nozzle row direction (direction orthogonal to the medium conveying direction) are provided. ing.

  That is, the driving roller 13 and the driven roller 18 are provided with a driving roller 13 and a driven roller 18 at a shaft end portion, and a driven roller 18 at a bonding portion 18-1, respectively. The actuator 35 and the actuator 37 are connected. A driver 39 and a driver 41 for driving the actuators 35 and 37 simultaneously drive the actuators 35 and 37 in the same direction at the same timing. In the actuator 35 and the actuator 37, the amount of distortion expansion / contraction of the magnetostrictive element changes according to the signal current waveform signal transmitted to the driver 39 and the driver 41, respectively.

  In other words, in the giant magnetostrictive element type actuator, the amount of distortion of the giant magnetostrictive element actuator in the center is determined according to the value of the current flowing through the coil, and it can be expanded and contracted according to the current direction, so any amount of expansion and contraction is possible It is said that the frequency response can follow up to a higher range than the solenoid system described later.

Next, a seventh embodiment of the present invention will be described with reference to FIG. FIG. 17 is an explanatory plan view of the image forming apparatus according to the embodiment.
Here, in the image forming apparatus of the sixth embodiment, a solenoid as a vibration generating means for reciprocating (vibrating) the recording medium 1 with respect to the recording head 23 in the nozzle row direction (direction orthogonal to the medium conveying direction). 43 and 45 are provided.

  That is, a joint portion 13-1 and a follower roller joint portion 18-1 are provided at the shaft end portions of the driving roller 13 and the driven roller 18, and a plunger portion 13-5 and a plunger portion 18-5 are provided on the respective shafts. Directly connected, a solenoid 43 and a solenoid 44 are provided. A driver 45 and a driver 46 for driving the solenoids 43 and 44 are simultaneously driven in the same direction at the same timing.

  In the solenoid method, the plunger is not indicated by the reference sign due to the current flowing in the coil, but there is a base with a truncated cone-shaped concave surface to efficiently loop the magnetic field generated in the coil on the plunger, When a force that attracts a certain convex portion 13-5 or a truncated cone-shaped convex portion at the tip of the plunger portion 18-5 is generated and no current flows, the force is exerted in a separating direction by the action of a compression spring (not shown). In order to perform the operation | movement which arises, the roller parts 13-4 and 18-4 can be reciprocated by a current waveform.

  The actuator may be a solenoid actuator as described above, or a piezo-type actuator that oscillates in response to a pulse signal (not shown). The giant magnetostrictive actuator described above that can control the amount of expansion and contraction according to the flowing current is preferable.

  In the sixth and seventh embodiments described above, the driving roller 13 and the driven roller 18 move in the axial direction in accordance with the drive of the actuator, and the conveying belt 12 stretched on the driving roller 13 and the driven roller 18 also move in the axial direction as a unit. Accordingly, the spur 19 and spur 20 having the degree of freedom in the axial direction are also moved, and the recording medium 1 nipped therebetween also reciprocates. Furthermore, the recording medium 1 is also niped on the upstream side of the rear end side, and the conveying roller pair 29 having a degree of freedom in the axial direction follows the same movement.

  Since the pulley 14 does not move in the axial direction with respect to the movement of the shaft portion 13-3 of the driving roller 13, the one-way clutch portion 14 that can freely slide in the axial direction and transmit torque to the pulley 14. -1 may be installed.

The operation of the sixth and seventh embodiments described above will be described with reference to FIGS. 18 and 19 as well.
Here, as shown in FIGS. 18 and 19, the recording head 23 has a nozzle row in which nozzles nz1 to nz9 are arranged in one row. In consideration of ease of illustration, only one nozzle row of the “plurality of nozzle rows” is focused on, and only the image by this nozzle row is shown.
First, when the recording medium 1 is not vibrated (not reciprocated) in the nozzle arrangement direction, as shown in FIG. 18A, images from time series L1 to L7 are generated by ink droplets ejected from the nozzles nz1 to nz9. An image is formed according to the main / sub-scanning conveyance locus of the recording medium 1 in the formed state. Miracles in the transport direction of the recording medium 1 in the time series L1 to L7 at this time are arranged on a straight line as shown by individual arrow vectors. Accordingly, the arrangement of the ink droplets ejected from the nozzles nz1 to nz9 of the recording head 23 is also in a state of being arranged linearly with no amplitude in the main scanning direction.

On the other hand, as shown in the sixth embodiment, when a giant magnetostrictive element type actuator that can be expanded and contracted only by an actuator on one side of the shaft is used, the actuator is as shown in FIG.
That is, the miracles in the transport direction of the recording medium 1 from time series L1 to L7 are arranged on a straight line as indicated by the individual arrow vectors, but in the nozzle arrangement direction, the nozzle position of the head 23 shown in the locus L1. This is printed when the recording medium 1 is moved in the nozzle arrangement direction to the lower side, and when the recording medium 1 is transported and moved in the nozzle arrangement direction to the upper side from the nozzle position of the recording head 23 shown in the locus L2. This series of operations is repeated after printing and locus L3.

  By this operation, the amount conveyed in the nozzle arrangement direction is set to ½ of the nozzle pitch to the nozzle nz2 adjacent to the nozzle nz1. Therefore, the amplitude is 1/4 of the nozzle pitch, and the reciprocating operation is performed between +1/4 in the upward direction and -1/4 in the downward direction.

  This operation can be performed when a giant magnetostrictive element type actuator that can be expanded and contracted only by an actuator on one side of the shaft is used. However, as will be described later, an actuator that moves the rotating shaft in the axial direction is used. In the case of being independently provided at both end portions of the shafts and capable of being driven individually, the same operation can be performed by alternately operating the solenoids at both ends even in the solenoid system.

In the sixth and seventh embodiments, an operation as shown in FIG. 19 can be performed.
That is, printing is performed when the recording medium 1 is transported and moved above the nozzle position of the recording head 23 while moving from the initial state of the locus L1 in the nozzle row direction to the locus L2. The trajectory L3 is again returned to the initial position similar to that of the trajectory L1, and thereafter, this series of operations is repeated.

  In this operation, the amount of movement in the nozzle row direction is 1/2 of the nozzle pitch. Therefore, the operation range is 1/2 of the nozzle pitch, and the reciprocating operation is performed between +1/2 in one direction (upward in the figure) from the initial state. Note that this operation example is similar to the operation shown in FIG.

Next, an eighth embodiment of the present invention will be described with reference to FIG. FIG. 20 is an explanatory plan view of the image forming apparatus according to the embodiment.
Here, at both shaft ends of the driving roller 13 and the driven roller 18, a conical driving roller pivot (a bearing-type pivot having a conical tip) 13-1, a pivot 13-2, and a driven roller pivot 18 are provided. -1 and a pivot 18-2 are provided, and at the apex portion of the pivots 13-1, 13-2, 18-1, 18-2 in a conical concave shape at a position in contact with the tip of the axis. Giant magnetostrictive actuators 35 to 38 are installed so as to be in contact with each other. The drivers 39 to 42 that drive the actuators 35 to 38 can be driven at independent timings.

  It should be noted that the pivot end of the shaft end and the shape of the actuator recessed in a conical shape are such that both the shaft end portions of the drive roller 13 and the driven roller 18 rotate, whereas the actuator is secondary when rotated. Since there is concern about harmful wear and induction of malfunction, it is necessary to fix the contact, so it is necessary to suppress relative contact as much as possible. In this case, the pivot bearing method is adopted as the point contact method with the shaft core. However, the present invention is not limited to this, and the method is limited as long as the structure transmits only the operation in the axial direction without transmitting the rotational torque. Not.

Next, a ninth embodiment of the present invention will be described with reference to FIG. FIG. 21 is an explanatory plan view of the image forming apparatus according to the embodiment.
Here, solenoids 43 to 46 are provided at both shaft ends of the driving roller 13 and the driven roller 18, respectively, and the solenoids 47 to 50 are provided.

Next, drive waveforms for driving the actuator of the vibration generating means in the eighth embodiment will be described with reference to FIG.
First, in the drive waveform of FIG. 22A, when a giant magnetostrictive actuator is used at both shaft ends and a desired stroke corresponding to the increase / decrease of the current value is determined as the drive waveform, the current value is expressed as Ia and Ib. Both values are shown in the same direction.

  That is, until time t1, the value of the current flowing through the giant magnetostrictive actuators 35, 37 is as low as Ia, so the giant magnetostrictive actuators 35, 37 are shortened, and the value of the current passed through the giant magnetostrictive actuators 36, 38 is as high as Ib. Therefore, the giant magnetostrictive actuators 36 and 38 are long. In this way, by performing the push / pull operation from both ends of the shaft, the roller portion 13-4 and the roller portion 18-4 are instantaneously moved in the axial direction (nozzle arrangement direction). The recording medium 1 also moves reliably.

  Thereafter, the current value flowing through the giant magnetostrictive actuators 35 and 37 from time point t1 to time point t2 is switched from Ia to Ib, and the current value flowing through the giant magnetostrictive actuators 36 and 38 is simultaneously switched from Ib to Ia. Keep the state and print at least one line between them.

  Further, between time t3 and time t4, the current value flowing through the giant magnetostrictive actuators 35 and 37 again changes from Ib to Ia, and the current value sent through the giant magnetostrictive actuators 36 and 38 changes simultaneously from Ia to Ib, and the next line is switched. Keep that state until you print it.

  By repeating this cycle sequentially, every time printing is performed, the recording medium is transported in the medium transport direction, and at the same time, an operation of repeating a constant period of vibration in the nozzle arrangement direction is performed.

  First, in the drive waveform of FIG. 22B, when a giant magnetostrictive actuator is used at both shaft ends and a desired stroke corresponding to the increase / decrease of the current value is determined as the drive waveform, the current direction is the reverse current value + Ic. And −Ic, the current directions are opposite to each other.

  That is, from the initial state to the time point t1, the current value flowing through the giant magnetostrictive actuators 35, 37 is 0, and the current value flowing through the giant magnetostrictive actuators 36, 38 is also zero. The power is not supplied.

  Thereafter, between time t1 and time t2, the value of current flowing through the giant magnetostrictive actuators 35, 37 is switched from 0 to + Ic, and the value of current flowing through the giant magnetostrictive actuators 36, 38 is simultaneously switched from 0 to -Ic until time t3. Keep this state and print at least one line between them.

  From time t2 to time t3, the current value flowing through the giant magnetostrictive actuators 35 and 37 flows in the direction of + Ic, the giant magnetostrictive actuators 35 and 37 become longer, and the current value passed through the giant magnetostrictive actuators 36 and 38 is -Ic. Therefore, the giant magnetostrictive actuators 36 and 38 are shortened, so that the push / pull operation is performed from both ends of the shaft, and the roller portion 13-4 and the roller portion 18-4 are instantaneously operated in the axial main scanning direction. As a result, the belt 12 and the recording medium 1 also move reliably.

  When the absolute value of the current value is set to | + Ic | = | −Ic |, the operation stroke of the giant magnetostrictive element is also equal, and the push / pull operation is performed from both ends of the shaft. Since the section 18-4 instantaneously operates in the axial main scanning direction, the belt 12 and the recording medium 1 also operate reliably.

  Further, between time t3 and time t4, the current value flowing through the giant magnetostrictive actuators 35 and 37 again changes from + Ic to 0, and the current value passed through the giant magnetostrictive actuators 36 and 38 changes simultaneously from -Ic to zero. The position is determined when the actuators 35 to 38 return to the initial neutral state. Thereafter, this neutral state continues until time t5, during which at least one line is printed.

  The time point t5 is the same operation as the time point t1 and is repeated in the same cycle until the printing operation is completed thereafter. By repeating this cycle sequentially, the recording medium is conveyed in the medium conveyance direction each time printing is performed. At the same time, an operation of repeating a constant period of vibration in the nozzle arrangement direction is performed.

Next, drive waveforms for driving the actuator of the vibration generating means in the ninth embodiment will be described with reference to FIG.
In this driving waveform, when a solenoid is used at both shaft ends, when a predetermined stroke is determined by flowing a current value Id, the current value is set to two values of 0 and Id, and the opposite end shafts are provided. Each solenoid is alternately switched between 0 and Id to allow current to flow.

  That is, from the initial state to the time point t1, the current value flowing through the solenoids 43 and 45 is 0, and the current value flowing through the solenoids 44 and 46 is also 0, so that all the solenoids 43 to 46 are not initially energized. So it is in a neutral position.

  Thereafter, the current value that flows through the solenoids 43 and 45 from time t1 to time t2 changes from 0 to Id, and the current value that flows through the solenoids 44 and 46 remains 0, so that the solenoids 43 and 45 flow at time t2. 21 is moved upward in FIG. 21, and from time t2 to time t3, only the solenoids 43 and 45 on one side of the shafts of both ends flow with the current value Id, so only one side is moved. Since the solenoids 44 and 46 at this time are not energized, the solenoids 44 and 46 move away from each other, and the roller unit 13-4 and the roller unit 18-4 are instantaneously axially moved (nozzle row direction). As a result, the belt 12 and the recording medium 1 also move reliably.

  The state is maintained between time t2 and time t3, and at least one line is printed during that time.

  Furthermore, between time t3 and time t4, the solenoids 43 and 45 are positioned by returning to the neutral position of the initial state by the restoring force of the compression spring (not shown) by reducing the current value to 0. This neutral state then continues until time t5.

  At time t5, only the solenoids 44 and 46 on one side out of both end shafts on the opposite side to the time t1 have a current value of Id and are pulled only on one side, and the solenoids 43 and 45 at this time are not energized. For this reason, the belt 12 and the recording medium 1 are reliably moved by the time point t6 by moving in the separating direction and reliably moving the roller portion 13-4 and the roller portion 18-4 in the axial direction. It will be.

  Thereafter, the state is maintained between time t6 and time t7, and at least one line is printed during that time.

  Further, between time t7 and time t8, the solenoids 44 and 46 are positioned by returning to the neutral position of the initial state by the restoring force of the compression spring (not shown) by reducing the current value to 0. This neutral state then continues until time t9.

  The time point t9 is the same operation as the time point t1 and is repeated in the same cycle until the printing operation is completed thereafter. By repeating this cycle sequentially, the recording medium is conveyed in the medium conveyance direction each time printing is performed. At the same time, an operation of repeating a constant period of vibration in the nozzle row direction is performed.

Next, another example of the drive waveform for driving the actuator of the vibration generating means in the eighth embodiment will be described with reference to FIG.
Here, the actuators 35 to 38 are driven and controlled at a predetermined timing and speed profile.

  That is, although the current value flowing through the giant magnetostrictive actuators 36 and 38 from time t1 to time t2 is about to switch from 0 to + Ic, the current value passed through the giant magnetostrictive actuators 35 and 37 is still 0. Then, the delay time until the time point t1a is allowed to switch to -Ic, and the operation of all the giant magnetostrictive actuators 35 to 38 is completed by the time point t3.

  In this way, by slightly shifting the timing of starting the operation of the giant magnetostrictive actuators on both end shafts, the play amount generated during the strokes on both ends is removed, so that there is no excess play until time t2. The effect of reducing the residual vibration is expected for the operation. Thereafter, at least one line is printed from the time t2 to the time t3, and the operation during that time is the same as described above, and is therefore omitted.

  Further, the giant magnetostrictive actuator B35 and the giant magnetostrictive actuator A35 and the giant magnetostrictive actuator A at the time t3 ′ during which the current value flowing through the giant magnetostrictive actuator B36 and the giant magnetostrictive actuator D38 is about to switch from + Ic to 0 between the time t3 and the time t4. The value of the current passed through C37 has already been switched from -Ic to 0 and completed.

  In this way, by slightly shifting the timing of completion of the operation of the giant magnetostrictive elements on both end shafts, the play amount generated during the strokes on both ends is removed, so that there is no excess play until time t4. The effect of reducing the residual vibration is expected for the operation.

  Thereafter, the operation from time t4 to time t5 is the same as that in FIG.

Next, a tenth embodiment of the present invention will be described with reference to FIG.
Here, the vibration operation is started on the basis of a detection signal from the sensor head front 27 serving as a leading edge detecting means for detecting that the leading edge of the recording medium has arrived.
That is, at the time t1, the sensor head 27 detects the leading edge of the recording medium 1, and the actuator (vibration generating means) starts operating after the time t2 has elapsed. Do not reciprocate.

  When the time point t3 is reached, the leading edge of the recording medium 1 reaches the recording position of the recording head 23, and ejection of ink droplets of an appropriate image is started.

  Although the front 27 of the sensor head detects the rear end of the recording medium 1 at time t4, since the rear end of the recording medium 1 is not reached at the position of the head 23, the printing operation and the actuator operation are continued. At the time t5, the printing operation is terminated at a position where the rear end of the recording medium 1 passes the recording position of the head 23 or a position slightly ahead of it. If the printing operation is performed even after the trailing edge of the recording medium 1 has passed, ink droplets are directly ejected onto the conveying belt 12 to cause fouling, so that a margin trailing edge merging of a certain printing range is provided.

  Thereafter, the actuator operation is also stopped and stopped at time t6. Although not shown, the actuator operation is continued until at least the recording medium is completely separated from the ink discharge sub-scanning position of the recording head 23.

DESCRIPTION OF SYMBOLS 1 Recording medium 12 Conveyor belt 13 Roller 18 Roller 35, 36, 37, 38 Giant magnetostrictive actuator (vibration generating means)
43, 44, 45, 46 Solenoid (vibration generating means)
100 Recording medium (paper)
DESCRIPTION OF SYMBOLS 101 Recording head unit 102 Recording head 103 Conveying unit 131 Conveying belt 132 Roller 133 Roller 135 Vibration generating mechanism (vibration generating means)
136 Elastic member (elastic coupling)

Claims (8)

A liquid discharge head having a plurality of nozzle rows for discharging droplets;
Conveying means for conveying a recording medium in a direction orthogonal to the nozzle row direction of the liquid ejection head;
Vibration generating means for relatively vibrating the recording medium and the liquid ejection head in the nozzle row direction,
A plurality of nozzle rows that discharge droplets of the same color are arranged,
When forming an image, the recording medium and the liquid discharge head are relatively vibrated in the nozzle array direction, and the same color dot array formed in the recording medium transport direction is ejected from a nozzle array in which adjacent dots are different. An image forming apparatus formed with the formed droplets.   The image forming apparatus according to claim 1, wherein the plurality of nozzle rows that discharge the same color droplets are arranged so as not to overlap each other in a recording medium conveyance direction.   The image forming apparatus according to claim 1, further comprising means for changing an amplitude of the vibration.   The conveying means has roller members arranged on the upstream side and the downstream side in the recording medium conveying direction of the liquid discharge head, and the vibration generating means is provided on one of the shaft ends of the roller member and the elastic member is provided on the other side. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The transport unit includes roller members disposed on the upstream side and the downstream side in the recording medium transport direction of the liquid ejection head, and the vibration generating unit is provided on both shaft ends of the roller member. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 4, wherein the roller member is a roller member wound around a conveyance belt that sucks and conveys the recording medium.   The image according to any one of claims 1 to 3, wherein the conveying means is a rotating body around which the recording medium is wound, and the vibration generating means is provided on at least one of shaft ends of the rotating body. Forming equipment.   The image forming apparatus according to claim 1, wherein the vibration generating unit includes an electrostrictive element or a giant magnetostrictive element.

Images