JP2013154531A - Image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device and an image forming method which suppress deterioration of images.SOLUTION: In an image forming device, a sheet passes a plurality of times immediately below an ink jet head 40 in which nozzles discharging ink are lined up in a direction orthogonal to a carrying direction of the sheet so as to record an image. The image forming device includes: a paper feeding part storing sheets; a carrying part carrying the sheets from the paper feeding part; a position adjustment part moving the ink jet head 40 in the direction in which the nozzles are juxtaposed; and a control part performing control so that a second recording path out of a plurality of image recording paths in a direction orthogonal to the movement direction of the ink jet head by the position adjustment part, which performs recording after image recording by a first recording path is located at a position sandwiching the other recording path between the first recording path and the second recording path.

Description

  Embodiments described herein relate generally to an image forming apparatus and an image forming method.

  There is known an image forming apparatus that forms an image by ejecting ink by a multi-pass method. However, in multi-pass image formation using ink, a recorded sheet may be deformed by absorbing ink. Due to the deformation of the sheet, there is a problem in that the ejected ink droplets adhere to a position different from the position where the sheet originally adheres, and image deterioration occurs.

Japanese Patent Laid-Open No. 7-60968

  The problem to be solved by the embodiments of the present invention is to provide an image forming apparatus and an image forming method that suppress image deterioration.

  In order to solve the above-described problem, an image forming apparatus according to an embodiment of the present invention is configured such that a sheet passes a plurality of times immediately below an inkjet head in which nozzles that eject ink are arranged in a line in a direction orthogonal to the sheet conveyance direction. In an image forming apparatus for recording an image, a sheet feeding unit that accommodates a sheet, a conveyance unit that conveys the sheet from the sheet feeding unit, a position adjustment unit that moves the inkjet head in the nozzle alignment direction, Of the plurality of image recording passes in the direction orthogonal to the moving direction of the inkjet head by the position adjusting unit, the second recording pass to be recorded after the image recording in the first recording pass is the first recording pass. A control unit that controls to place the other recording pass between the passes.

FIG. 2 is a side view of the inside of the image forming apparatus according to the first embodiment. 1 is a block diagram of an image forming apparatus according to a first embodiment. It is a schematic diagram of a recorded image in the first embodiment. 3 is a flowchart illustrating image formation in the first embodiment. It is a flowchart which shows the continuation of FIG. 4 in 1st embodiment. FIG. 3 is a schematic diagram of a recording image of a first recording pass in the first embodiment. FIG. 6 is a schematic diagram of a recording image of a second recording pass in the first embodiment. FIG. 6 is a schematic diagram of a recorded image of a third recording pass in the first embodiment. It is a schematic diagram of the recording image of the 4th recording pass in 1st embodiment. 10 is a flowchart of image formation in the second embodiment.

  Hereinafter, an inkjet image forming apparatus will be described as an embodiment with reference to the accompanying drawings.

(First embodiment)
The image forming apparatus according to the first embodiment records the second recording pass at a recording position where another recording pass is sandwiched between the first recording passes when performing inkjet recording by the multi-pass method.

  FIG. 1 shows an ink jet printer (hereinafter referred to as a printer) 10 which is an example of an image forming apparatus.

  The printer 10 includes a line head type in which inkjet heads are arranged in the width of the sheet and a serial type in which the inkjet head is moved relative to the sheet for each swath from the viewpoint of the arrangement of the heads. . Hereinafter, the printer 10 using a line head type inkjet head will be described.

  The printer 10 includes a housing 11, a drum 12 that is an example of an endless device housed in the housing 11, and a rotation mechanism 13 that includes a motor that rotates the drum 12.

  The drum 12 has a cylindrical portion 12a, and is rotated at a predetermined peripheral speed in the clockwise direction indicated by the arrow R1 about the shaft 14 by the rotation mechanism 13. The position of the drum 12 in the rotation direction is detected by a rotation angle sensor 15 such as an encoder. The drum 12 is made of an electrically insulating synthetic resin and has an inner peripheral surface 12b and an outer peripheral surface 12c.

  A laminated cover 20 having a metal layer 21 and a dielectric layer 22 is disposed on the outer peripheral surface 12 c of the drum 12. The laminated cover 20 is fixed to the outer peripheral surface 12c of the drum 12 by adhesion or the like. Therefore, the drum 12 and the laminated cover 20 rotate integrally around the shaft 14. The drum unit 25 is configured by the drum 12 and the laminated cover 20. The rotating drum unit 25 functions as a conveyance unit 26 for conveying the sheet S.

  The printer 10 also includes a sheet feeding unit 30, a sheet supply mechanism 31, a pressing roller 32, a charging roller 33, an ink jet head 40, a charge removal charger 41, a peeling member 42, a cleaner 43, a discharge mechanism 44, and a reversing mechanism 45. ing. The charging roller 33 applies a voltage to the supplied sheet S and causes the sheet S to adhere to the drum 12. The neutralization charger 41 neutralizes the sheet S after image formation so that the sheet S is easily peeled off from the drum 12. The cleaner 43 cleans the peripheral surface of the drum unit 25. The peeling member 42 constitutes a peeling mechanism for peeling the discharged sheet S from the drum unit 25. The charging roller 33, the peeling member 42, and the cleaner 43 include a moving mechanism 46 for separating the sheet S from the sheet S so as not to contact the image surface of the sheet S when the sheet S during multi-pass image formation passes. ing. The moving mechanism 46 is, for example, a solenoid.

  The sheet feeding unit 30 stores a plurality of sheets S. An example of the sheet S is not limited to a prescribed size sheet. For example, a resin film, a label, a plastic, or a sheet that absorbs oil-based ink may be used. The sheet supply mechanism 31 includes a pickup roller 50, a paper feed roller 51, a separation roller 52, a sheet conveyance path 53, and a registration roller pair 54. The sheets S picked up one by one by the paper feed roller 51 and the separation roller 52 are conveyed to the sheet conveyance path 53. The leading edge of the sheet S conveyed to the sheet conveyance path 53 is adjusted by the registration roller pair 54. A guide 56 for guiding the sheet S is provided between the registration roller pair 54 and the drum unit 25.

  A power circuit 58 is connected to the core of the charging roller 33. A DC voltage (for example, several thousand volts) is applied to the charging roller 33 by the power supply circuit 58.

  The inkjet head 40 has ink. The ink is, for example, a water-based ink. The inkjet head 40 is a line head that extends in the direction of the axis 14 of the drum 12. The ink jet head 40 of the present embodiment includes a plurality of nozzle holes for discharging aqueous ink. In addition, not only water-based ink but also an ink-jet head using oil-based ink or UV ink may be used.

  An example of the inkjet head 40 includes a piezoelectric element as a driving member. When a voltage is applied to the piezo element to deform the piezo element and pressure is applied to the ink, the ink is ejected from the nozzle hole. As another example of the driving member, a heating element may be employed. When the ink is heated by the heat generating element, the ink is ejected from the nozzle hole with the pressure of bubbles generated by the vaporization of the ink.

  The discharge mechanism 44 includes a conveyance guide 61, a conveyance roller 62, a paper discharge roller 63, and a paper discharge unit 64. The reversing mechanism 45 includes a plurality of reversing rollers 65 for reversing the sheet S, a reversing path 66, and the like.

  FIG. 2 is a block diagram of the printer 10. The printer 10 includes a CPU (Central Processing Unit) 100 as a control unit, a ROM (Read Only Memory) 101 that stores various programs, and a RAM (Random Access) that temporarily stores various variable data and image data. Memory) 102 and a communication interface (I / F) 103 for inputting data from outside and outputting data to the outside.

  The printer 10 is connected to the shaft 14 of the drum 12 and controls a rotation mechanism drive control unit 104 that controls a rotation mechanism 13 including a motor that rotates the drum 12, a sensor drive control unit 105 that controls the rotation angle sensor 15, a pickup A conveyance roller motor drive control unit 107 that controls a conveyance roller motor 106 that is coupled to a roller 50, a sheet feeding roller 51, a separation roller 52, a sheet conveyance path 53, and a registration roller pair 54, and a discharge roller that is coupled to a discharge roller 63 A paper discharge roller motor drive control unit 109 that controls the motor 108, a position adjustment unit 110 that adjusts the position of the inkjet head 40, an inkjet head drive control unit 111 that controls the inkjet head 40, and a movement mechanism drive control that controls the movement mechanism 46. For applying a DC voltage to the unit 112 and the charging roller 33. It has a circuit 58.

  The CPU 100 includes a ROM 101, a RAM 102, an I / F 103, a rotation mechanism drive control unit 104, a sensor drive control unit 105, a conveyance roller motor drive control unit 107, a discharge roller motor drive control unit 109, and a position adjustment unit 110 via a bus. The inkjet head drive control unit 111, the movement mechanism drive control unit 112, and the power supply circuit 58 are connected. The CPU 100 controls the movement of the inkjet head 40 via the position adjustment unit 109.

  A detection result obtained by the rotation angle sensor 15 is transmitted to the CPU 100 via the sensor drive control unit 105. The inkjet head 40 ejects ink from the inkjet head nozzles onto the sheet S based on a signal from the inkjet head drive control unit 110.

  The inkjet heads 40 are arranged in a line in the nozzle arrangement direction. The direction orthogonal to the direction in which the nozzles of the inkjet head 40 are arranged is the conveyance direction of the sheet S. The inkjet head 40 moves in the nozzle arrangement direction at a pitch smaller than the nozzle pitch. An example will be described below.

  If the nozzle pitch of the inkjet head 40 is 150 npi (nozzles per inch), the resolution of the head nozzle arrangement direction that can be recorded in one recording pass is 150 dpi (dots per inch). However, if the position of the inkjet head 40 is moved at a 1/600 inch pitch in the nozzle arrangement direction for each recording pass, the resolution in the nozzle arrangement direction of the head is 600 dpi in a recording pass of 4 degrees (four rotations of the drum). Become.

  FIG. 3 is a schematic diagram of a recorded image that forms an image in four recording passes (hereinafter referred to as four passes). In the figure, a circle enclosing a number indicates a recorded pixel (image), and a number in the circle indicates a recorded recording pass. 1 is circled in the first recording pass, 2 is circled in the second recording pass, 3 is circled in the third recording pass, 4 is circled This column is set as the fourth recording pass. As shown in FIG. 3, since the inkjet head 40 includes a plurality of nozzles, a plurality of circles in which the same numbers are circled are recorded side by side.

  Even if the nozzle pitch of the inkjet head 40 is 150 npi, recording is performed with a resolution that is an integral multiple of the number of recording passes. Here, as an example, the nozzle pitch is set to 150 npi and the resolution in the arrangement direction of the nozzles of the recorded image is set to 600 dpi. For example, the nozzle pitch may be 180 npi, and the resolution may be 300 dpi. When the nozzle pitch is Nrnpi and the number of recording passes is n, the resolution r of the recorded image is r = n · Nrdpi.

  When recording an image with ink, if the ink contacts the sheet S, the sheet S may be deformed because the ink is absorbed from the surface of the sheet S.

  The direction of deformation of the sheet when in contact with ink will be described. Since the sheet S is adsorbed on the conveyance path, it tends to occur in a direction perpendicular to the surface of the conveyance path. In this case, it is between the first recording pass and the second recording pass that the deviation between the position where recording has already been performed and the position where recording has not yet been performed may be greatest.

  That is, the recording position of the second recording pass is set so as not to be adjacent to the first recording pass during the recording by the first recording pass. The recording of the second recording pass between the recordings by the first recording pass means that one second recording pass is between two first recording passes among a plurality of second recording passes. Refers to recording.

  For example, the recording position of the second recording pass is set as the midpoint of the first recording pass. A recording position due to deformation of the sheet at a recording location where the recording position may be likely to be shifted by making the recording position of the first recording pass and the recording position of the second recording pass not adjacent to each other. It is possible to suppress deterioration in image quality due to deviation.

  4 and 5 are flowcharts showing image formation. In 300, the CPU 100 analyzes the image data for four recording passes, and in 301, sets the recording pass. The first recording pass is the first recording pass, the third recording pass is the second recording pass, the second recording pass is the third recording pass, and the fourth recording pass is the fourth recording. Set as a path.

  In 302, the CPU 100 controls the conveyance unit 26 to convey the sheet S under the inkjet head 40, and in 303, controls the inkjet head drive control unit 110 to record ink on the sheet S in the first recording pass. To do. FIG. 6 is a schematic diagram of a recorded image in the first recording pass. The first recording pass is the recording pass of the first column.

  In 304, the CPU 100 determines whether or not the recording of the first recording pass on the sheet S has been completed. If the recording of the first recording pass is not completed (No in 304), the process returns to 303, and the determination is repeated until the recording of the first recording pass is completed. When the recording of the first recording pass is completed (Yes in 304), in 305, the CPU 100 moves the inkjet head 40 to the nozzle arrangement direction, that is, the position of the second recording pass for recording the next image. The position adjustment unit 109 is controlled. The CPU 100 controls the position adjusting unit 109 to move the inkjet head 40 to the right, for example, 1/300 inch as shown in FIGS.

  In 306, the CPU 100 controls the conveyance unit 26 to convey the sheet S under the inkjet head 40. In 307, the CPU 100 controls the inkjet head drive control unit 110 to record ink droplets on the second recording path of the sheet S. Control. After recording ink droplets in the first recording pass, the CPU 100 rotates the sheet S once by the rotation of the drum 12, and after the sheet S is positioned again under the inkjet head 40, the ink is transferred to the second recording pass. The transport unit 26 and the inkjet head drive control unit 110 are controlled so as to record droplets. FIG. 7 is a schematic diagram of a recording image in the second recording pass. The image recording in the second recording pass is not recorded in the second recording pass adjacent to the conventional first recording pass, but is recorded in the third recording pass.

  In 308, the CPU 100 determines whether or not the recording of the second recording pass on the sheet S has been completed. If the recording of the second recording pass is not completed (No in 308), the process returns to 307, and the determination is repeated until the recording of the second recording pass is completed. When the recording of the second recording pass is completed (Yes in 308), in 309, the CPU 100 adjusts the position so that the inkjet head 40 moves to the nozzle arrangement direction, that is, the third recording pass for recording the next image. The unit 109 is controlled. The CPU 100 controls the position adjustment unit 109 to move the inkjet head 40 to the left, for example, 1/600 inch as shown in FIGS.

  In 310 shown in FIG. 5, the CPU 100 controls the conveyance unit 26 to convey the sheet S under the inkjet head 40, and in 311, the CPU 100 records ink droplets in the third recording path of the sheet S. The inkjet head drive control unit 110 is controlled. After recording the second recording pass, the CPU 100 rotates the sheet S once by the rotation of the drum 12, and after the sheet S is positioned again under the inkjet head 40, the CPU 100 conveys the recording to the third recording pass. The unit 26 and the inkjet head drive control unit 110 are controlled. FIG. 8 is a schematic diagram of a recording image of ink droplets in the third recording pass. The third recording pass is a conventional recording pass in the second column.

  In 312, the CPU 100 determines whether or not the recording of the third recording pass onto the sheet S is completed. If the recording of the third recording pass is not completed (No in 312), the process returns to 311 and the determination is repeated until the recording of the third recording pass is completed. When the recording of the third recording pass is completed (Yes in 312), in 313, the CPU 100 adjusts the position so that the inkjet head 40 moves to the nozzle arrangement direction, that is, the fourth recording pass for recording the next image. The unit 109 is controlled. The CPU 100 controls the position adjustment unit 109 to move the inkjet head 40 to the right, for example, 1/300 inch as shown in FIGS.

  In 314, the CPU 100 controls the conveyance unit 26 to convey the sheet S under the inkjet head 40, and in 315, the CPU 100 controls the inkjet head drive so as to record ink droplets in the fourth recording path of the sheet S. The unit 110 is controlled. After recording the third recording pass, the CPU 100 rotates the sheet S once by the rotation of the drum 12, and after the sheet S is positioned again under the inkjet head 40, the ink droplets are recorded in the fourth recording pass. The transport unit 26 and the ink jet head drive control unit 110 are controlled so as to do this. FIG. 9 is a schematic diagram of a recording image of ink droplets in the fourth recording pass. The fourth recording pass is a conventional recording pass in the fourth column.

  In 316, the CPU 100 determines whether or not the recording of the fourth recording pass onto the sheet S has been completed. If the recording of the fourth recording pass is not completed (No in 316), the process returns to 315, and the determination is repeated until the recording of the fourth recording pass is completed. When the recording in the fourth recording pass is completed (Yes in 316), in 317, the sheet S is conveyed to the paper discharge unit 64, and the image forming process ends. After the image forming process, the inkjet head 40 is returned to the initial position. For example, when the home position is the position of the first-line recording pass, the CPU 100 moves the inkjet head 40 to the left, for example, 1/150 inch.

  Although the above-described printer 10 has been described with monochrome image formation, it may be applied to color image formation. In the above-described printer 10, the drum-type image formation is described. However, the present invention is not limited to this, and the inkjet head or the sheet S on the plane, or the inkjet head and the sheet S on the plane are moved to form an image. The printer 10 may be used.

  In the above description, when water-based ink is recorded on a sheet, the image quality deterioration due to the expansion of the sheet is suppressed. However, there is a sheet that may be shrunk by absorbing the ink. The embodiment is also effective when there is a risk of shrinkage.

  In the first embodiment, image formation is described with four passes. However, the present invention is not limited to this, and any number of passes may be used as long as the number of passes is four or more. An even number of passes of 4 or more is suitable. For example, image formation may be performed by 6 passes, 8 passes, 10 passes, and 12 passes.

  By the image forming apparatus and the image forming method as described above, it is possible to make the pixel position shift due to the deformation of the sheet uniform, and to suppress the deterioration of the image.

(Second embodiment)
The control unit of the image forming apparatus according to the second embodiment controls the first recording pass to be a recording pass with a smaller ink amount than the second recording pass when performing ink jet recording by the multi-pass method. . The same components as those in the first embodiment are denoted by the same reference numerals.

  FIG. 10 is a flowchart showing image formation in the second embodiment. The CPU 100 analyzes the image data for n printing passes at 400, and sets a printing pass with a small amount of ink to be used as the first printing pass (m = 1) at 401. m is a recording pass; if m = 1, the first recording pass; if m = 2, the second recording pass; if m = 3, the third recording pass; if m = 4, the fourth recording pass. Recording pass.

  The CPU 100 controls the conveyance unit 26 to convey the sheet S under the inkjet head 40 in 402, and in 403, the inkjet head drive control unit to record ink droplets on the sheet S in the first recording pass. 110 is controlled.

  In 404, the CPU 100 determines whether or not the recording of the first recording pass is completed. If the recording of the first recording pass is not completed (No in 404), the process returns to 403 and the determination is repeated until the recording of the first recording pass is completed. When the recording of the first recording pass is completed (Yes in 404), in 405, the CPU 100 causes the position adjusting unit 109 to move the inkjet head 40 to the nozzle arrangement direction, that is, the recording pass for recording the next image. Control.

  In 406, the CPU 100 controls the conveyance unit 26 to convey the sheet S below the inkjet head 40, and in 407, records the previous recording pass + 1 recording pass on the sheet S. If the previous recording pass is the first recording pass, the second recording pass, which is the previous recording pass + 1 recording pass, is recorded on the sheet S.

  At 408, the CPU 100 determines whether or not recording of the final recording pass is completed, that is, whether m = n. If the recording of the final recording pass is not completed (m ≠ n) (No in 408), the CPU 100 proceeds to the processing of the next recording pass in 409, that is, returns to 405. The CPU 100 controls the position adjustment unit 109 and the inkjet drive control unit 110 so as to record the next recording pass unless the recording of the final recording pass is completed. When the CPU 100 determines that the recording of the final recording pass has been completed (m = n) (Yes in 408), the image processing ends.

  The second embodiment can realize image formation from two passes or more. If there are two passes, the recording pass with the smaller ink amount (first ink amount) out of the two passes is set as the first recording pass, and the ink amount (second ink amount) larger than the first recording pass is recorded. The image is recorded on the sheet S using the pass as the second recording pass.

  If there are three passes, the recording pass with the smallest amount of ink among the three passes may be the first recording pass, and any of the remaining two passes may be the second recording pass. However, the present invention is not limited to this, and the first recording pass, the second recording pass, the third recording pass, and the number of recording passes may be set so as to increase the amount of ink.

  If there are four or more passes, the second embodiment can be combined with the first embodiment. The first print pass is set as the print pass with the least ink amount, and the second print pass is set as a print pass that is not adjacent to the first print pass. For example, in the case of image formation in 4 passes, if the print pass in the second row is the print pass with the smallest ink amount, the print pass in the second row is the first print pass and the print pass in the fourth row is the first pass. The second recording pass, the first recording pass is the third recording pass, and the third recording pass is the fourth recording pass. Further, the recording position of the second recording pass may be set as the midpoint of the first recording pass.

  With the image forming apparatus and the image forming method as described above, even when there are few image recording passes, pixel positional deviation due to sheet deformation can be made uniform, and image deterioration can be suppressed. It becomes.

  Although several embodiments have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the gist of the invention, and in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Printer 12 Drum 13 Rotation mechanism 15 Sensor 26 Conveyance part 30 Paper feed part 31 Sheet supply mechanism 40 Inkjet head 44 Discharge mechanism 46 Movement mechanism 58 Power supply circuit 64 Paper discharge part 100 CPU
101 ROM
102 RAM
103 I / F
104 Rotation mechanism drive control unit 105 Sensor drive control unit 107 Transport roller motor drive control unit 109 Paper discharge roller motor drive control unit 110 Position adjustment unit 111 Inkjet head drive control unit 112 Movement mechanism drive control unit

Claims (8)

In an image forming apparatus for recording an image by passing a sheet a plurality of times immediately below an inkjet head in which nozzles for ejecting ink are arranged in a line in a direction orthogonal to the sheet conveyance direction,
A sheet feeding unit for storing sheets;
A conveying unit that conveys the sheet from the sheet feeding unit;
A position adjusting unit that moves the inkjet head in the nozzle arrangement direction;
Of the plurality of image recording passes in a direction orthogonal to the moving direction of the inkjet head by the position adjusting unit, a second recording pass to be recorded after image recording in the first recording pass is the first recording pass. A control unit that controls to place the other recording pass between the recording pass,
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the image is recorded by passing the sheet four times or more immediately below the inkjet.   The image forming apparatus according to claim 1, wherein the second recording pass is recorded at an intermediate point of the first recording pass.   The image forming apparatus according to claim 2, wherein the sheet passes an even number of times immediately below the inkjet to record an image. In an image forming apparatus for recording an image by passing a sheet a plurality of times immediately below an inkjet head in which nozzles for ejecting ink are arranged in a line in a direction orthogonal to the sheet conveyance direction,
A sheet feeding unit for storing sheets;
A conveying unit that conveys the sheet from the sheet feeding unit;
A position adjusting unit that moves the inkjet head in the nozzle arrangement direction;
Of the plurality of image recording passes in the direction orthogonal to the moving direction of the inkjet head by the position adjusting unit, an image having a first ink amount is recorded in a first recording pass, and the first ink amount is determined based on the first ink amount. A control unit that controls to record an image of the second ink amount, which is a large ink amount, in the second recording pass;
An image forming apparatus comprising:   6. The image forming apparatus according to claim 5, wherein the second recording pass is set at a position where another recording pass is sandwiched between the second recording pass and the first recording pass. In an image forming method in which an image is formed by passing a sheet a plurality of times immediately below an inkjet head in which nozzles for ejecting ink are arranged in a line in a direction orthogonal to the sheet conveyance direction.
Moving the inkjet head in the direction in which the nozzles are arranged;
Among a plurality of image recording passes in a direction orthogonal to the moving direction of the inkjet head, a second recording pass to be recorded after recording in the first recording pass is between the first recording pass. To control the position to sandwich another recording pass,
An image forming method. In an image forming method for recording an image by passing a sheet a plurality of times directly under an inkjet head in which nozzles for ejecting ink are arranged in a line in a direction orthogonal to the sheet conveyance direction,
Moving the inkjet head in the direction in which the nozzles are arranged;
Among a plurality of image recording passes in a direction orthogonal to the moving direction of the inkjet head, an image having a first ink amount is recorded in a first recording pass, and the ink amount is larger than the first ink amount. Controlling to record an image of the second ink amount in the second recording pass;
An image forming method.

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