JP2007136726A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely discharge only a floating paper sheet as a waste paper sheet to stably and surely perform a recording operation thereafter without interrupting the recording operation, damaging an ink ejection face or wasting a recording paper sheet even when floating of the recording paper sheet occurs during the continuous printing operation. <P>SOLUTION: A paper floating detection means for detecting floating of a paper sheet is provided on a conveyance belt at a portion between a paper attraction start position and a first inkjet head. When floating of a paper sheet is detected by the paper floating detection means while the paper sheet is conveyed by both of a conveyance means at the upstream side and the conveyance belt, the conveying operation by at least the conveyance means at the upstream side is stopped and the conveyance operation is stopped in a condition that the paper sheet is held by the conveyance means at the upstream side by peeling the attracted paper sheet from the conveyance belt. When an antecedent paper sheet in the way of the image recording operation resides on the conveyance belt, the conveying operation by the conveyance belt and the image recording operation of the antecedent paper sheet is continuously carried out. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheet material conveyance device using a conveyance belt, and more particularly to a technique for more stably carrying a sheet material on a conveyance belt.

  In particular, the present invention relates to a sheet material conveying apparatus in an ink jet recording apparatus that performs recording by discharging ink from a recording unit to a sheet material. In particular, a sheet in an inkjet recording apparatus capable of performing high-speed printing by using a plurality of long inkjet heads having an ejection area having substantially the same width as the sheet material and ejecting ink while continuously conveying the sheet material. The present invention relates to a material conveying device.

  An image forming apparatus (an apparatus having a recording unit) such as a printer, a copying machine, or a facsimile is configured to form an image composed of a dot pattern on a recording material such as paper or a plastic thin plate based on image information. Has been. The image forming apparatus can be divided into an ink jet type, a wire dot type, a thermal type, a laser beam type, and the like according to a recording method, and the ink jet type forms an image by ejecting ink onto a recording material. It is configured.

  In the image forming apparatus, it is necessary to transport the recording material from a paper feeding unit such as a cassette to the paper discharging unit through the image forming unit (recording unit). In this case, the recording material is controlled at a constant timing from when the recording material is fed to when an image is formed and discharged. Among them, from the paper feed timing to image formation, it affects the image formation position on the recording material, so that particularly accurate conveyance is required. In addition, during image formation, if the recording material conveyance speed is not constant, the image magnification will be deviated and the image will be expanded or contracted. In particular, in the case of an image forming apparatus in which a plurality of image forming units (recording heads) such as those for color are juxtaposed, a deviation occurs between images recorded in the respective image forming units. In the case of a color image recording apparatus, this shift appears as a color shift and causes an image defect. In order to prevent such a problem, it is necessary to accurately convey the conveyance force of the conveyance means controlled accurately to the recording material.

  Conventionally, various transport means have been proposed as a transport system taking such points into consideration. For example, there is a method in which a recording material is sent out by a roller pair and is regulated in a transport direction by a guide. This method is a simple and reliable method with strong conveying force because the recording material is sent out by the pressure between the rollers.

  However, it is necessary to arrange the roller pairs at an interval shorter than the minimum length of the recording material to be used. For example, it is not suitable for feeding a postcard or business card size paper. Further, there is a problem that the recording surface cannot be used when it is necessary to keep the recording surface in a non-contact state, such as from the transfer by an electrophotographic drum to the fixing.

  As a transport apparatus that solves these problems, a transport apparatus that uses an endless belt and in which a recording material is brought into close contact with the endless belt by electrostatic attraction has been proposed. In the belt-type conveying device by electrostatic attraction, particularly in the case of a color image forming apparatus using a plurality of image forming means (recording heads), in order to make the image forming position of each image forming means accurate. It is necessary to keep the belt conveyance speed precise. In addition, it is necessary to keep the recording material in close contact with the conveying member (belt, drum, etc.) without shifting or floating.

  As the means, as described in JP-A-50-31828, JP-B-3-48100, JP-A-2000-247476, a conductive electrode pair (adsorptive force generating means) is provided on a conveying belt carrying recording paper. There is known a method in which a recording paper is applied to generate an electrostatic force by applying an electric charge to adsorb a recording paper.

  In the ink jet recording apparatus having such a recording paper conveying means, the recording paper fed by the paper feeding device is the above-described electrostatic adsorption means (conductive electrode) provided on the conveying belt in the recording area. Is sucked and held on the upper surface of the conveying belt, and is conveyed while being recorded by the recording head.

  In general, an inkjet recording apparatus includes a recording head having an ink ejection surface that ejects ink onto a recording surface of a recording medium. In this recording head, for example, the ink droplets formed by the pressure of the electromechanical transducer or the heating energy of the electrothermal transducer controlled based on the drive control signal supplied according to the image data are transferred to the ink ejection port. The ink is discharged to the recording surface of the recording medium through the forming surface. As the recording head, in order to increase the speed of the recording medium and improve the image quality of the recorded matter, the ink discharge port is formed over the entire width of the recording medium, so-called multi-nozzle lengthened one, or its In recent years, ink discharge ports formed on an ink discharge port forming surface, which are arranged at a relatively high density, for example, 1200 dpi to 2400 dpi, have been used in devices that require high image quality.

  In such an ink jet recording apparatus that requires high image quality, the distance between the recording surface of the recording medium and the ink discharge port forming surface of the recording head is slightly inclined rather than straight from the ink discharge port. In the case of forming an image with higher image quality while minimizing the influence of the deviation of the ejection, it is advantageous that the shorter is as much as possible. Also, it must always be maintained at a predetermined short distance in order to maintain stable recording.

  On the other hand, paper, which is the main non-recording medium, may be bent at the end when set in the device or paper feed unit, or it may be difficult to be electrostatically attracted depending on manufacturing variations and usage environment. was there. When such a recording medium is transported as it is by a transport belt, the distance between the recording surface of the recording medium and the ink discharge port forming surface of the recording head is small, which can cause fatal damage to the recording head. Will cause serious damage. Therefore, when the recording paper is bent or the paper floats due to poor adsorption, it is necessary to detect the abnormality quickly and prevent the jam from occurring, or if the recording paper is not between the transport belt and the recording head. If a jam occurs, quick jam processing is important.

  In order to solve such problems, inventions such as Japanese Unexamined Patent Application Publication Nos. 2002-113910 and 2002-137849 have been made.

In JP 2002-113910,
A suppression unit that suppresses the lifting of the recording surface of the recording medium in the vicinity of the recording unit including the recording head, and a displacement detection unit that detects a displacement of the suppression unit that is greater than or equal to a predetermined amount according to the lifting of the recording surface of the recording medium. In the vicinity of the recording unit, the conveyance abnormality is detected from the rise of the recording surface of the recording medium, and the recording medium conveying means is immediately stopped to prevent the recording head from being damaged by the floating of the recording medium. In addition, a recording unit moving mechanism that moves the recording unit to the retracted position when a conveyance abnormality occurs is provided, so that when the conveyance abnormality is detected, the recording unit can be moved to the retreat area to prevent damage to the recording head. It was what was made.

In JP 2002-137849 A,
A conveyance error detection means for detecting an error that stops the conveyance operation by the conveyance belt such as paper floating, a rotating body pair that is arranged on the downstream side in the conveyance direction from the conveyance belt, and that is near the rotation body pair. A recording medium detecting means arranged to detect the recording medium, and a control means for controlling a feeding operation of the belt member and a power supply voltage value by the power feeding means based on detection signals of the conveyance error detecting means and the recording medium detecting means. And when the conveyance error detection unit detects a conveyance error, the conveyance operation by the conveyance belt is stopped, and when the recording medium detection unit detects the recording medium, the power supply unit corresponding to the stacking portion of the recording medium is the conveyance unit The belt was neutralized and the recording medium was controlled to be conveyed by a pair of rotating bodies.

  In this way, after a transport error occurs on the transport belt, even if the transport operation by the transport belt is stopped, the recorded recording medium is transported downstream from the recording medium in which the transport error has occurred in the transport direction. If it is found that the liquid remains in the vicinity of the outlet, the recorded recording medium can be discharged. This means that it is difficult for the user himself to determine the presence or absence of a recorded recording medium, and if he / she does not notice the recorded recording medium, he / she would have performed the recording operation again. It is troublesome to take out the recorded recording medium from the paper discharge means in a good state without being contaminated, but if it is automatically discharged as described above, it will be convenient for the user. Met.

In order to solve the same problem, in Japanese Patent Application Laid-Open No. 9-211916, when the jam is detected by the upstream detection means and the registration sensor used as a trigger for the image forming operation detects the paper, the registration sensor The paper detected in step 1 is forcibly conveyed to the image forming position to form an image.
Japanese Patent Laid-Open No. 50-31828 Japanese Patent Publication No. 03-048100 JP 2000-247476 A JP 2002-113910 A JP 2002-137849 A JP-A-9-2111916

  However, the recording paper transport device in the conventional ink jet recording device has the following problems.

In JP 2002-113910,
Since the conveyance abnormality is detected from the rise of the recording surface of the recording medium and the recording medium conveyance means is immediately stopped, if there is a recording medium in the middle of printing preceding the recording medium in which the conveyance abnormality occurred, the recording The medium is also defective because the printing operation is performed only halfway. That is, there is a problem in that the printing medium is wasted due to the occurrence of two printing defects due to the failure of one sheet.

In JP2002-137849,
When paper floating is detected during printing, the printing is finished, and the recording paper that is being transported by the paper discharge roller is released only by that part, so that it is transported by the paper discharge roller and discharged out of the device. Although it is possible, the recording paper that is in the middle of printing is left in the electrostatic chucking state, and the recording paper in which the paper floats is left in the position sandwiched between the heads on the conveyance belt. In addition, even if the recording paper is left electrostatically adsorbed, if the printed recording paper is left unattended, the recording paper generated by the expansion and contraction of the recording paper due to the influence of moisture contained in the ejected ink Rippling phenomenon (cockling) occurs. In the ink jet recording apparatus in which the interval between the recording paper and the recording head is narrowed in order to realize high image quality, the recording paper surface comes into contact with the ejection nozzle surface even with a slight paper floating or cockling phenomenon. When the recording paper is removed, there is a possibility that the contacting nozzle surface may be scratched.

In JP-A-9-211916,
Instead of detecting a suction failure, the recording medium detected by the registration sensor is forcibly conveyed to form an image, and the floating state of the recording sheet immediately before printing is not detected.

  Therefore, the present invention is particularly suitable for an ink jet recording apparatus in which the recording medium and the ink discharge surface are narrowed in order to achieve higher image quality, even when the recording paper floats during the continuous printing operation. Only paper that has lifted the paper reliably can be discharged as waste paper without major interruptions, scratches on the ink ejection surface, or waste of recording paper. It is intended to be able to be performed reliably.

In order to achieve the above object, the ink jet recording apparatus of the present invention comprises:
A paper lift detection means for detecting paper lift is arranged between the paper suction start position on the transport belt and the first inkjet head, while the paper is transported by both the upstream transport means and the transport belt. When paper lift is detected by the paper lift detection means, at least the transport operation of the upstream transport means is stopped, and the paper is held on the upstream transport means by separating the adsorbed paper from the transport belt. In this state, the conveying operation is stopped, and when there is a sheet in the middle of the preceding image recording operation on the conveying belt, the conveying operation and the image recording operation of the preceding sheet by the conveying belt are continuously performed.

  In addition, the ink jet recording apparatus of the present invention releases the stop of the upstream conveying means after the plurality of ink jet heads are retracted in the direction away from the paper conveying belt after the preceding recording operation on the paper is completed. Thus, the sheet with the paper floating detected is conveyed to the downstream side by the upstream conveying means and the sheet conveying belt.

  In addition, the ink jet recording apparatus of the present invention is characterized in that, when a paper sheet that has been detected to float is transported by a paper transport belt, a preliminary ejection operation is performed on the paper by each ink jet head.

  In addition, the ink jet recording apparatus of the present invention returns the ink jet head to the normal recording position after the paper that has detected paper floating has passed through the ink jet head on the most downstream side, and then the paper that has been detected to have paper floating. The image which should have been recorded is recorded on the next sheet, and the recording operation is continued.

  In addition, the ink jet recording apparatus of the present invention records an image indicating that the recording operation is not a normal recording operation by a preliminary ejection operation performed on the paper with the paper floating.

The ink jet recording apparatus of the present invention configured as described above,
Even when the leading edge of the paper is detected during the continuous printing operation, only the paper that has been reliably lifted is discharged as waste paper without stopping the recording operation or damaging the head. The recording operation can be performed reliably, and the sheet with the float can be immediately identified, which is suitable for the continuous printing operation.

As described above, according to the present invention,
Even when the leading edge of the paper is detected during the continuous printing operation, only the paper that has been reliably lifted is discharged as waste paper without stopping the recording operation or damaging the head. In addition, it is possible to reliably perform the recording operation, and it is possible to immediately identify the sheet on which the floating has occurred, and to provide an ink jet recording apparatus suitable for continuous printing operation with high image quality.

  Next, embodiments of the present invention will be described with reference to the drawings.

  The ink jet recording apparatus of the present embodiment is a paper transport system mainly composed of a transport belt unit 20 composed of a transport belt 1 that sucks and transports recording paper by static electricity, and a recording paper transported in the direction of an arrow in the figure. And a full-line multi-head system composed of full-line heads 6a to 6d held by a head frame (not shown) that performs printing by discharging ink.

  FIG. 1 is a side view for explaining a configuration in the vicinity of a conveyance belt unit 20 that is a paper conveyance system of the ink jet recording apparatus according to the first embodiment of the present invention. FIG. 2 is an external view of the conveyance belt unit 20 of the present embodiment as viewed from above. The electrodes 9a and 9b are arranged inside the conveyance belt 1, and the electrodes 9a and 9b are arranged on the inner side of the conveyance belt 1 to apply voltage to the electrodes 9a and 9b. The power supply brushes 7a and 7b for applying the voltage are transmitted through.

  In the full line multi-head system, a head frame (not shown) that holds the full line heads 6a to 6d is driven in the vertical direction by a motor (not shown). When recording is not performed, the cap belt unit (not shown) is disposed in the space between the conveyor belt 1 and the full line heads 6a to 6d, away from the conveyor belt 1, and the nozzles of the full line heads 6a to 6d. Cap each head to prevent it from drying. Further, the full line heads 6a to 6d are arranged in the order of black (Bk), cyan (C), magenta (M), and yellow (Y) from the upstream side in the paper conveyance direction (arrow direction) of the conveyance belt 1. Yes.

  Next, the configuration of the conveyor belt 1 and the conveyor belt unit 20 will be described with reference to FIGS.

  As shown in FIGS. 1 and 2, the conveyance belt unit 20 includes a conveyance belt 1 that adsorbs and conveys recording paper by static electricity, a driving roller 2 that is connected to a motor (not shown) and drives the conveyance belt 1, and the movement of the conveyance belt. The conveyor belt 1 is wound around a tension roller 4 for applying tension so that the driven roller 3 and the conveyor belt 1 are not loosened between the driving roller 2 and the driven roller 3.

  Further, on the upstream side of the transport belt unit 20, a registration roller is disposed that transports the recording paper 22 transported from a paper feeder (not shown) to the transport belt unit by a roller pair. The registration roller receives driving force from a motor (not shown) and is driven and controlled independently of the conveyance belt 1.

  Next, FIG. 3 is a diagram for explaining the configuration of the conveyor belt 1 and shows a partial cross section of the conveyor belt 1.

  The conveyor belt 1 is configured such that a first electrode 9a and a second electrode 9b made of conductive metal are embedded in a belt material 9c made of a resin material, and the entire surface is covered with a surface layer 9d. The belt equipment 9c is made of a polymer synthetic resin material such as polyethylene, polycarbonate, polyimide, etc., and the first electrode 9a and the second electrode 9b have a strip shape as shown in FIG. is set up. These also form a comb-like shape facing each other in a direction substantially perpendicular to the belt conveyance direction. The surface layer 9d is made of a fluorine-based synthetic resin such as PVDF capable of resistance control in order to generate an optimal electrostatic force.

In addition, on the back surface (inner side) of the conveyor belt 1, the power-supplied part (first power-supplied part) of the first electrode 9 a is on the left end side in the transport direction of the transport belt 1, and the power is supplied to the second electrode 9 b. The portion (second power-supplied portion) is located on the right end side in the moving direction of the conveyor belt 1, and is provided so as to expose the surface of each electrode 9a, 9b by making a hole in the belt material 9c. In addition, a plurality of conductive power supply brushes 7a and 7b divided in the transport direction are provided so as to be in contact with each power-supplied part, and each is in contact with the power-supplied part with a predetermined pressure. Each power supply brush 7a, 7b is fixed to a frame (not shown) and is connected to a high voltage generator (not shown). Further, the high voltage generator controls the high voltage applied from the power supply brushes 7a and 7b to the electrodes 9a and 9b by a high voltage control device (not shown). The high voltage control device is configured to control the applied voltage for each power supply brush, and the power supply brushes 7a and 7b are used to supply power from the high voltage generator (not shown) to the first electrode 9a. A zero or positive high voltage (0.5 to 1.5 kV) is applied to the second electrode 9b, and a zero or negative high voltage (−0.5 to −1.5 kV) is applied to the power supply portion of the second electrode 9b. The power supply brushes 7a and 7b are preferably made of a conductive material having a volume resistivity of 10 ⁵ Ωcm or less.

  When a high voltage is applied to each electrode, as shown in FIG. 3A, electrostatic polarization occurs in the belt surface layer 9d, and the surface of the conveyor belt 1 has the same polarity as the electrode below it. Potential appears. FIG. 3B shows a state where the recording paper 22 is placed on the belt surface. When the recording paper 22 is placed on the conveying belt 1 on the surface of which the potential appears, electrostatic polarization occurs in the recording paper 22, and the electric potential of the polarity opposite to the surface of the conveying belt 1 is on the conveying belt 1 side of the recording paper 22. Due to this, the recording paper 22 is electrostatically attracted to the surface of the transport belt 1. At this time, on the surface of the recording paper 22 opposite to the conveying belt 1 (upper side of FIG. 3B), a potential having the same polarity as the electrode below the surface layer 9d of the conveying belt 1 appears. Become.

  FIG. 2 shows a state in which a high voltage is applied to both the first electrode 9a and the second electrode 9b from both power supply brushes 7a and 7b, and the difference from the other electrodes to which no high voltage is applied. For the sake of clarity, the electrodes to which a high voltage is applied are shown with diagonal lines. From the above-described results, the adsorbing force to the recording paper works only in the hatched portions (regions of the electrodes 9a2 to 9a9 and the electrodes 9b2 to 9b10), and the adsorbing force does not work in other portions. Even if the conveying belt 1 rotates and different electrodes come into contact with the power supply brushes 7a and 7b, the positions of the power supply brushes 7a and 7b are fixed and do not change. Therefore, as shown in FIG. The range where the attractive force is generated when the high pressure is supplied does not change greatly even if it slightly deviates due to the rotation of the conveyor belt 1 and is an area with a substantially hatched pattern.

  Next, the configuration of the full line heads 6a to 6d used in the present embodiment will be described with reference to FIG.

  FIG. 4 is a view of the full line heads 6a to 6d as viewed from the discharge nozzle side. A nozzle chip 5 having two nozzle rows 10 each having a length of 2 inches is arranged on the base plate 23, and each nozzle row 10 is formed on a sheet. They are arranged in a staggered pattern so as not to be interrupted in the direction perpendicular to the transport direction. Within each nozzle chip 5, one nozzle row 10 has nozzles arranged at a resolution of 600 dpi, and the other nozzle row 10 has a resolution of 600 dpi, but is shifted by a half pitch in the nozzle row direction. Therefore, as one nozzle chip 5, nozzles are arranged with a resolution of 1200 dpi. Accordingly, one full line head is configured to be able to record a width of 8 inches at 1200 dpi, that is, a substantially A4 width at a time.

  Next, in this embodiment, the A4 size recording paper 22 is sucked and conveyed by the conveying belt unit 20, and ink is ejected by the full line heads 6 a to 6 d to continuously form images on the recording paper 22. In the middle of the operation, an operation when a suction failure occurs on the recording paper before image formation will be described with reference to FIGS. The recording paper 22 is transported so that the longitudinal direction is the transport direction.

  As shown in FIG. 5, when the image forming operation is continuously performed, the next recording sheet 22b is registered on the preceding recording sheet 22a while the full line heads 6c and 6d are performing image formation. The recording medium 22b is conveyed from the roller 24 to the conveyance belt unit 20, and the leading end of the recording paper 22b reaches the suction force generation region 21 where the power supply brushes 7a and 7b are disposed. At this time, a high voltage is applied to the electrodes in contact with the power supply brushes 7a and 7b via the power supply brushes 7a and 7b by a high voltage generator (not shown), and the recording paper 22b is adsorbed by the principle described with reference to FIG. In the force generation area 21, it is attracted to the conveyor belt 1. FIG. 5 shows a state in which the leading end of the recording paper 22b is turned up and is not attracted to the conveyor belt 1 well. In the present embodiment, as described above, in order to minimize the influence of the deviation of the ejected ink and aim to form a higher quality image, the space between the surface of the recording paper 22 and the nozzle surfaces of the full line heads 6a to 6d. Is set to be a narrow head-paper distance of 0.5 mm. Therefore, when the leading edge of the recording sheet is turned up by 0.5 mm or more, the leading edge of the recording sheet collides with the full line head, and the recording sheet is jammed. In order to avoid this, a paper floating detection sensor 25 is arranged on the upstream side of the full line head 6a and above the suction force generation region 21, and the amount of floating at the leading edge of the recording paper is measured. The registration roller 24 is in a positional relationship such that the recording paper 22b is also conveyed by the registration roller 24 at least while the leading edge of the recording paper 22b is in front of the full line head 6a. That is, the distance from the registration roller to the full line head 6a is shorter than 297 mm in the A4 longitudinal direction.

  When the paper floating detection sensor 25 detects a certain amount of floating at the tip of the recording paper 22b, an operation different from the normal printing operation is performed. In the present embodiment, a plurality of reflective sensors are arranged in the recording paper width direction as the paper floating detection sensor 25 so that the floating state of the entire area of the recording paper can be measured. In the case of the present embodiment, if even one sensor detects a floating amount of 0.3 mm or more, it is determined to be abnormal, and an abnormal operation as described below is performed.

  In FIG. 5, when the paper floating detection sensor 25 determines that the leading edge of the recording paper 22b is 0.3 mm or more, the rotation of the registration roller 24 is stopped as shown in FIG. Thereby, at the same time, the paper feeding operation from a paper feeding device (not shown) upstream of the registration rollers is also stopped simultaneously. On the other hand, the printing operation of the conveyance belt unit 20 and the full line heads 6a to 6d is continuously performed on the preceding recording sheet 22a, and all image formation on the recording sheet 22a is completed as usual, and the sheet is conveyed downstream.

  As shown in FIG. 6, when paper floating is detected at the leading end of the recording paper 22 b, the recording paper 22 b is in a position where it can also be conveyed by the registration roller 24. Therefore, when the registration roller 24 is stopped, the recording paper 22b is adsorbed by the conveying belt 1 only at a part of the front end portion, but the front end of the recording paper 22b is removed by the rotation of the registration roller 24 being stopped. The recording paper 22b is stopped from being conveyed by the registration roller 24.

  Next, as shown in FIG. 7, immediately after the conveyance of the recording paper 22b is stopped and all image formation is completed on the preceding recording paper 22a, the full line heads 6a to 6d are integrated with a head frame (not shown). Thus, the recording paper 22b with the leading edge lifted is raised in a direction away from the conveying belt 1 to a height at which the recording paper 22b can pass. In this embodiment, it is raised by 10 mm. During this time, the preceding recording paper 22a is discharged out of the apparatus by the transport belt 1 and a downstream transport means (not shown). Also, here, the image formation on the preceding recording paper 22a is completed, and the rear end of the recording paper 22a has completely passed under the nozzle surface of the full line head 6d and is on the downstream side of the conveying belt unit 20. When the recording means 22a is transported to a position where the recording paper 22a can be transported by the transport means, a high voltage control device (not shown) applies a high voltage from the high voltage generator to the electrodes 9a and 9b via the power supply brushes 7a and 7b. Application of voltage may be stopped. As a result, the adsorption to the recording paper 22b is also released, and unnecessary friction between the rotating conveying belt 1 and the recording paper 22b is eliminated.

  Next, as shown in FIG. 8, when the full line heads 6 a to 6 d have been lifted, the registration roller 24 is rotated again to resume the conveyance of the recording paper 22 b. Here, when the application of the high voltage is stopped in the state of FIG. 7, the application of the high voltage is restarted together with the rotation of the registration roller 24, and the recording paper 22 b is attracted to the conveyance belt 1. Transport while.

  Next, as shown in FIG. 9, when the recording paper 22b passes under the full line heads 6a to 6d by being sucked by the conveying belt 1, each full line head 6a to 6d records a preliminary ejection operation. Perform on paper 22b. This is to enable the ejection operation to be resumed without any abnormality when the next recording operation is performed even if the ejection operation is not performed during the vertical movement of the full line head. At this time, in the preliminary discharge operation, discharge control is performed so that the discharge operation is performed several times to several tens of times with all the nozzles of all the full line heads 6a to 6b. Furthermore, in order to clearly notify the user that the recording paper 22b has not been used for the normal image forming operation because the leading edge of the recording sheet has floated, a preliminary discharge operation can be recognized as, for example, an X mark. Image formation. Further, when the conveyance of the recording paper 22b is resumed, the operation of the paper feeding device and the like further upstream of the registration roller 24 is performed in order to perform image formation on the next recording paper 22c which should have been performed on the recording paper 22b. The recording paper 22c is transported to the nip portion of the registration roller 24. Since the registration roller 24 controls to stop the rotation when the recording sheet 22b having the tip lifted is transported to the transport belt 1, the registration roller 24 transports the recording sheet 22c so that the leading end of the recording sheet 22c abuts the nip portion of the registration roller 24. As shown in FIG. 10, the conveying means on the upstream side of the registration roller 24 is stopped in a state where the front end of the recording paper 22 c is slightly curled at the front end so that it follows the nip of the registration roller 24. In the meantime, as shown in FIG. 10, the recording paper 22b with the leading edge lifted has completed the image formation of the mark indicating the failure due to the preliminary ejection operation, and is taken out of the apparatus by the conveying belt 1 and the conveying means on the downstream side. Be transported.

  Next, as shown in FIG. 11, the operation of returning the full line heads 6a to 6d to the height at which normal image formation is performed is performed. In this embodiment, the distance between the recording paper surface and the nozzle surface is lowered to a position where it is 0.5 mm.

  And as shown in FIG. The registration roller 24 is rotated again, and immediately after the leading edge of the recording paper 22 c is attracted to the conveyance belt 1, the presence or absence of the leading edge detection is detected by the paper floating detection sensor 25. If no tip lift is detected, the conveying operation of the registration roller 24 and the conveying belt 1 is continued, and the recording sheet 22c is conveyed to the image forming area of the full line heads 6a to 6d, and should be performed on the recording sheet 22b. Image formation.

  By repeating this operation, a continuous printing operation can be performed without greatly losing the total printing time even if the leading edge is lifted. It is possible to perform a printing operation without waste using only the recording paper that is lifted. Further, since a mark that can be recognized at a glance is formed on the recording paper that has become defective, it can be easily removed. In addition, in order to allow the printing of marks indicating defects to be used as a preliminary ejection operation, the subsequent recording operation is performed in order to use the preliminary ejection operation that enables stable subsequent recording operations. It becomes possible to carry out stably.

FIG. 3 is a perspective view illustrating a configuration in the vicinity of the conveyance belt of the image forming apparatus of the present invention. 2 is a perspective view illustrating a configuration of a belt unit of the image forming apparatus of the present invention. FIG. It is a figure explaining the structure and adsorption | suction principle of the conveyance belt of this invention. This is a full line head configuration. FIG. 4 is a diagram illustrating a sheet conveyance state and a suction area of the image forming apparatus of the present invention. FIG. 4 is a diagram illustrating a sheet conveyance state and a suction area of the image forming apparatus of the present invention. FIG. 4 is a diagram illustrating a sheet conveyance state and a suction area of the image forming apparatus of the present invention. FIG. 4 is a diagram illustrating a sheet conveyance state and a suction area of the image forming apparatus of the present invention. FIG. 4 is a diagram illustrating a sheet conveyance state and a suction area of the image forming apparatus of the present invention. FIG. 4 is a diagram illustrating a sheet conveyance state and a suction area of the image forming apparatus of the present invention. FIG. 4 is a diagram illustrating a sheet conveyance state and a suction area of the image forming apparatus of the present invention. FIG. 4 is a diagram illustrating a sheet conveyance state and a suction area of the image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conveyance belt 2 Drive roller 3 Driven roller 4 Tension roller 5 Nozzle chip 6a-6d Full line head 7a, 7b Power supply brush 9a 1st electrode,
9b Second electrode 9c Surface layer 9d Belt equipment 10 Nozzle array 20 Conveying belt unit 21 Adsorption force generation region 22a, b Recording paper 23 Base plate 24 Registration roller (upstream conveying means)
25 Paper floating detection sensor

Claims (5)

In an inkjet recording apparatus that adsorbs a sheet conveyed from an upstream conveying unit onto a conveyance belt and records an image on the sheet by a plurality of inkjet heads.
A paper lift detection means for detecting paper lift is disposed between the paper suction start position on the conveyor belt and the first inkjet head,
When paper lift is detected by the paper lift detection means while the paper is being transported by both the upstream transport means and the transport belt,
At least the transport operation of the upstream transport means is stopped, and the transport operation is stopped in a state where the paper is held on the upstream transport means by peeling the adsorbed paper from the transport belt,
An ink jet recording apparatus, wherein if there is a sheet in the middle of a preceding image recording operation on the conveying belt, the conveying operation and the image recording operation of the preceding sheet by the conveying belt are continuously performed.   After the recording operation on the preceding paper is completed, the entire plurality of inkjet heads are retracted in a direction away from the paper conveying belt, and then the upstream conveying means is released to remove the paper whose paper floating has been detected. 2. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is conveyed downstream by an upstream conveying means and a paper conveying belt.   3. An ink jet recording apparatus according to claim 2, wherein when the paper whose paper floating has been detected is transported by the paper transport belt, a preliminary ejection operation is performed on the paper by each ink jet head.   After the paper that has detected paper lift has passed through the ink jet head on the most downstream side, after returning the ink jet head to the normal recording position, the image that was supposed to be recorded on the paper that was detected to have paper lift is 4. The ink jet recording apparatus according to claim 2, wherein recording is performed on paper and the recording operation is continued.   5. The ink jet recording apparatus according to claim 3, wherein an image indicating that the normal recording operation is not performed is recorded by a preliminary ejection operation performed on the paper on which the paper float has occurred.

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