JP2005067052A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of decrease in recording speed when continuous marginless recording is performed because the action of returning a platen to the initial position every time when a recording to one recorded medium ends is required in a case where a support member to support a recorded medium is provided around a rotating platen to perform the marginless recording. <P>SOLUTION: In the platen 25, a circular arc support member 26 having an opening 27 in a part is supported around a rotating shaft 29 through an arm 28. When the radius from the center of rotation of the support member 26 is r, and the length of the circular arc of the opening 27 is L, the relationship of L<πr is satisfied. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus capable of performing marginless recording on a recording medium.

  As an image forming apparatus such as a printer, a facsimile machine, a copying machine, a printer / fax / copier multifunction machine, etc., a recording head constituted by a droplet discharge head for discharging ink droplets as represented by an ink jet printer is used for recording. There are some which perform image formation (recording) by adhering ink droplets to a recording medium while conveying the recording medium such as paper. As a droplet discharge head, a piezo type using an electromechanical conversion element such as a piezoelectric element, or an electrothermal conversion element such as a heating resistor arranged in the discharge is used to generate bubbles by boiling the ink film. There are a thermal type that ejects ink droplets and an electrostatic type that ejects ink droplets by deforming a diaphragm that forms the wall surface of the ejection chamber with an electrostatic force.

  In addition, as an image forming apparatus including a droplet discharge head, a shuttle (serial) type that records a recording medium by scanning the droplet discharge head in a direction orthogonal to the transport direction, and a droplet discharge head Is a full-line type that is fixedly arranged in a line in a direction perpendicular to the direction in which the recording medium is conveyed.

In such an image forming apparatus, the recording medium is generally conveyed by a guide having a rib that conveys the recording medium by a conveying roller and a discharge-side roller and guides the recording medium to a position facing the recording head. The structure which arrange | positions a member (platen) is employ | adopted. There is also a type that conveys a recording medium using a conveyance belt.
JP 2000-296665 A

  By the way, when an image forming apparatus using a droplet discharge head is used, the entire image (recording without margins, recording without margins) is performed on the recording medium for images such as cards, New Year's cards, and photographic images. Images may be recorded with exactly the same size. However, when trying to perform full-surface recording, high-precision positional accuracy is required between the recording medium and the droplet discharge head. However, since there are positional deviations during feeding and transport variations, the recording medium and the droplet discharge The head is misaligned, and the ink ejected from the droplet ejection head outside the recording medium adheres to the platen and the conveyance belt and becomes dirty. Further, when the next recording medium is transported while the ink adhered to the platen or the transport belt is adhered, the back surface or side surface of the recording medium is soiled.

Therefore, it is assumed that the recording can be performed with no margins at both ends of the recording medium, and the scanning range of the recording head mounted on the carriage is moved to the outside wider than the width of the recording medium to perform the recording. In addition, there is a configuration in which a mesh screen is provided on a part of the platen so that ink passes through the platen so that the top of the platen is not contaminated by ink droplets protruding from both ends of the recording medium. In addition, there is a configuration in which a through hole is provided on the platen instead of the mesh screen so that the ink does not completely interfere with the ink protruding from the edge of the recording medium.
JP-A-8-169155

In addition, there is no blank space for the recording near the front end of the recording medium to be transported because the rotating platen is located behind the recording medium and has a rotatable platen and a rotating part that rotates the platen. The platen is not contaminated by ink protruding from the edge of the recording medium during recording, and the platen is arranged at a position supporting the back surface of the recording medium during recording other than the end of the recording medium, and the rear end of the recording medium In the recording in the vicinity, the platen is rotated in the conveyance direction of the recording medium, and recording is performed so that the platen is positioned on the back side of the recording medium again, and marginless recording is performed without contamination of the platen. .
JP 2001-80145 A

There is the following thing of the same composition.
JP 2001-31261 A JP 2002-211057 A JP 2002-225357 A JP 2001-26165 A Japanese Patent Laid-Open No. 2002-361851

  However, in the image forming apparatus disclosed in Patent Document 3, for example, a rotatable platen is provided below the recording head, and the platen further has an arcuate recording medium support, When recording without margins in the vicinity of the edge of the medium, the platen is rotated so that the ink protruding from the edge does not adhere onto the platen, and recording is performed so that the platen is positioned on the back side of the recording medium. Is finished, the platen starts to rotate again and is configured to move to the initial position for the next recording medium.

  However, in the case of the configuration as described above, when continuous recording without margins is performed, the initial position recovery operation of the rotating platen must be performed for each recording medium, and the recording time (printing) is compared with the continuous processing. There is a problem that time) increases. In particular, in the case of a serial type apparatus, since it is necessary to return the recording head to the home position, this problem does not become so obvious, but in the case of a line type image forming apparatus that performs recording only by conveying the recording medium This problem will become apparent.

  Usually, in order to perform marginless recording on the edge in the direction perpendicular to the conveyance direction of the recording medium, ink is started to be ejected immediately before the edge reaches the recording area (image forming area), and borderless recording is performed. . In addition, at the rear end of the recording medium, ink is continuously ejected for a while after margins are removed from the recording area, and marginless recording is performed.

  Therefore, when the recording medium is continuously conveyed directly below the recording head by the mechanism described in Patent Document 3 described above, the platen needs to return to the initial position again. As a method of returning to the initial position, the recording medium is rotated in the conveying direction of the recording medium and returned to the original position, or rotated in the direction opposite to the conveying direction of the recording medium and returned to the initial position. It is necessary to perform an operation of returning the platen to the initial position every time one blankless recording is completed, and an operation of moving to a position for performing a blankless recording on the next recording medium. Such an operation is repeated for each recording medium, resulting in a problem that the time required for recording (printing) increases.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus that solves the problems of deterioration in recording quality and increase in recording time that occur when performing marginless recording with a rotary platen. And

  In the image forming apparatus according to the present invention, a platen having an opening on the outer peripheral surface is rotatably disposed at a position facing the recording head, and the recording medium is supported at a position away from the rotation center position of the platen by a radius r. In the image forming apparatus that performs image formation in the above state, the arc length L of the opening of the platen is configured to satisfy the relationship L <πr.

  Here, when the length of the chord with respect to the arc length L of the opening is Lg and the distance in the recording medium conveyance direction of the nozzle hole of the recording head is L1, it is preferable to satisfy the relationship of L1 <Lg. . The platen preferably has two or more openings in the rotational direction.

  Furthermore, when a plurality of recording media are continuously conveyed and marginless recording is performed in a direction perpendicular to the recording medium conveyance direction, the platen rotation direction is completed to complete the marginless recording of the plurality of recording media. It is preferable that it is a fixed direction until.

  Moreover, it is preferable to provide the absorber which absorbs a liquid inside an opening part. Furthermore, the recording head is preferably a line type head.

  According to the present invention, since the arc length L of the opening where the platen and the recording medium are not in contact with each other satisfies the relationship of L <πr, the platen can be used even when continuous marginless recording is performed. The initial position recovery time can be shortened, the recording time can be shortened, and the printing speed can be increased.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. A first embodiment of an image forming apparatus according to the present invention will be described with reference to FIGS. 1 is a schematic configuration diagram showing the overall configuration of the image forming apparatus, FIG. 2 is an explanatory side view showing the main part of the apparatus, FIG. 3 is an explanatory side view showing a platen of the apparatus, and FIG. FIG. 5 is an explanatory plan view of the platen.

  The image forming apparatus includes an image forming unit 2 inside the recording apparatus main body 1, a sub-scanning conveying unit 3 for conveying a recording medium at a position facing the image forming unit 2, and the like below the apparatus main body 1. The recording medium (hereinafter referred to as “paper”) 5 is fed from the paper feeding unit 4, and the image forming unit 2 is driven while the paper 5 is sub-scanned and transported by the sub-scan transport unit 3. After the image is formed (recorded), the paper 5 is discharged to the paper discharge tray 8 through the paper discharge conveyance unit 7.

  The image forming unit 2 includes a head holder 12 that includes a recording head 11 formed of a full-line head having a plurality of nozzle rows in which nozzle holes, which are a plurality of ejection openings, are arranged over the entire width of the recording area in a direction orthogonal to the paper conveyance direction. It is attached to. Here, the recording head 11 is a head for discharging ink of a required color, for example, a black ink droplet. However, for the convenience of illustration, one head unit is used for black, but a plurality of units corresponding to full colors such as yellow, magenta, and cyan may be configured, and the present invention is not limited to this.

  The head holder 12 is rotatably supported at one end by a shaft 13, and a protrusion 12 a formed at the other end engages with a rail 14, so that the distance between the nozzle forming surface of the recording head 11 and the paper 5. (Distance between papers) is specified.

  The sub-scanning conveyance unit 3 is below the recording head 11 and conveys the paper 5 in the sub-scanning direction with respect to the printing position by the recording head 11. Are arranged such that a conveying roller 23 and a clamping roller 24 are respectively arranged on the downstream side in the sheet conveying direction, and the sheet 5 is nipped and conveyed. A platen 25 is disposed immediately below the recording head 11. Details of the platen 25 will be described later. In addition, a start sensor 71 and an end sensor 72 that detect the presence or absence of the paper 5 are disposed on the downstream side of the transport roller 21 and the upstream side of the transport roller 23, respectively.

  The paper feed unit 4 includes a paper feed cassette 31 on which a large number of papers 5 can be stacked, a half-moon roller (paper feed roller) 32 that separates and feeds one paper 5 from the paper feed cassette 31, and a separation pad 33. , A guide member 36 for conveying and feeding the fed paper 5 to the sub-scanning conveying unit 2 is provided.

  The paper discharge unit 7 includes a pair of transport rollers 41 for transporting the paper 5 sent from the sub-scanning transport unit 3, a paper discharge roller 42 for sending the paper 5 that has been recorded to the paper discharge tray 8, and Opposing spur rollers 43 and the like are provided.

  Therefore, the details of the platen 25 will be described. The platen 25 is obtained by supporting a ring-shaped (arc-shaped) support member 26 having an opening 27 in a part thereof around an axis of rotation 29 via an arm 28. The rotation shaft 29 has a plurality of supporting members 26 in a direction orthogonal to the paper conveyance direction, for example, a distance that can support the A4 size paper 5A and the postcard size paper 5B as shown in FIG. Is placed. 1 to 3 show an example with three arms 28, FIG. 4 shows an example with two arms 28.

  Here, the opening 27 of the support member 26 of the platen 25 is a region that does not contact the paper 5 (non-contact region), and the peripheral surface of the support member 26 is a region that supports the paper 5. In this example, one opening portion 27 is provided in the rotation direction of the platen 25 and is formed so as to completely divide the support member 26 in a direction orthogonal to the paper transport direction.

  As shown in FIG. 3, when the radius from the rotation center of the support member 26 is r and the length of the arc of the opening 27 (non-contact region) is L, L <πr, It is formed to satisfy the relationship. Here, the relationship is L = πr / 2.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. The figure is a schematic block diagram of the control unit.
The control unit 100 includes a CPU 101 that controls the entire image forming apparatus, a ROM 102 that stores programs executed by the CPU 101 and other fixed data, a RAM 103 that temporarily stores image data (print data), and the like. Non-volatile memory (NVRAM) 104 for holding data even while the power is cut off, image processing for performing various signal processing and rearrangement on image data, and other input / output signals for controlling the entire apparatus And an ASIC 105 for processing.

  The control unit also includes an I / F 107 for transmitting and receiving data and signals used when receiving data from an external device, and a head drive control unit for driving and controlling the recording head 11 of the image forming unit 2. 108 and the head driver 109, a sub-scanning motor 121 for driving the transport roller 21, a platen motor 122 for driving the platen 25, and a paper feeding motor 123 for driving the paper feeding roller 32. Clutches for turning on / off the motor drive units 111, 112, 113 including a motor driver for driving the sheet feed, and the sheet feed clutch 124 for transmitting the rotation of the sheet feed motor 113 to the sheet feed roller 32 A drive unit 114 is provided.

  The control unit further includes an I / O 115 for taking in the detection signals of the above-described start sensor 71, end sensor 72, and various sensors (not shown), and for inputting and displaying information necessary for the apparatus. An operation panel 116 is connected.

  Next, when the control unit 100 receives print data or the like from an external host such as an information processing apparatus such as a personal computer, an image reading apparatus such as an image scanner, or an imaging apparatus such as a digital camera, via the external I / F 107. Is stored in the reception buffer included in the I / F 107.

  The CPU 101 reads out and analyzes the image data from the I / F 107, performs necessary image processing, data rearrangement processing, and the like in the ASIC 105, and transfers the print image data to the head drive control unit 108. Note that the generation of dot pattern data for image output based on external data may be performed by storing font data in the ROM 102, for example, or image data is converted into bitmap data by a printer driver on the external host side. The image may be developed and transferred to the image forming apparatus.

  When the head drive control unit 108 receives image data (dot pattern data) corresponding to one row of each recording head 11, the head drive control unit 108 transfers the dot pattern data for one row to the head driver 109. A predetermined drive waveform is selectively applied to the actuator means of the recording head 11 based on the pattern data for driving. As a result, droplets are ejected from the required nozzles of each recording head 11.

  At this time, the paper 5 is transported one line at a time by the sub-scanning transport unit 3 and stopped, the liquid droplets are ejected from the recording head 11 to record one line, and when the recording for one line is completed, A required image is formed on the sheet 5 by repeatedly conveying (feeding) 5 by the sub-scan conveying unit 3 for one line.

  The operation of the image forming apparatus configured as described above will be described with reference to FIGS. 7 shows a state in which the platen is in the initial position, FIG. 8 shows a state in which recording is performed on the leading edge of the first sheet, FIG. 9 shows a state in which recording is performed on the center of the first sheet, and FIG. Shows the state when recording on the trailing edge of the first sheet, and FIG. 11 shows the state when the second sheet is sent when performing marginless recording on the second sheet. ing.

  First, when printing without margins, the control unit 100 turns on the paper feed clutch 124 and transmits the rotation of the paper feed motor 123 to the paper feed roller 32 to separate and feed the paper 5 one sheet at a time. As the conveyance roller 21 is rotated by the rotation of the motor 121, the sheet 5 is sandwiched between the conveyance roller 21 and the driven roller 22 as shown in FIG. 7 in a recording area (position where recording by the recording head 11 is possible). It is transported to just before.

  As shown in FIG. 7, the platen 25 is in a standby state at an initial position where the opening (non-supporting portion) 27 faces the nozzle hole of the recording head 11.

  In this state, when the paper 5 starts to be transported to the recording area by the rotation of the transport roller 21, the platen motor 122 is driven to rotate based on the detection result of the paper 5 by the start sensor 71, and the platen 25 is rotated in the rotational direction in FIG. That is, the paper 5 is rotated in the conveyance direction. At this time, as shown in FIG. 8, the support member 26 of the platen 25 is located on the back surface of the paper 5.

  Then, when the leading edge of the paper 5 comes to just before the nozzle row of the recording head 11, the ejection of the ink droplet 11 a is started from the nozzle, and recording is started from the leading edge of the paper 5. As a result, marginless recording is performed on the sheet 5.

  At this time, the ink removed from the paper is ejected toward the opening 27 because the opening (non-supporting portion) 27 of the support member 26 is provided in the platen 25, and the surface (circumference) of the support member 26. Surface) is not stained with ink.

  Subsequently, when the sheet 5 is conveyed and recording is performed on the central portion (portion other than the edge), the platen 25 is positioned on the back surface of the sheet 5 and waits as it is as shown in FIG. At this time, for marginless recording on a side parallel to the conveyance direction of the paper 5 (an edge in a direction orthogonal to the conveyance direction), the support members 26 of the platen 25 are arranged at intervals as shown in FIGS. Since the support member 26 is disposed so as to be positioned on the back surface of the paper 5, the ink removed from the paper 5 does not adhere to the support member 26 of the platen 22 and become dirty.

  Subsequently, when the paper 5 is transported and recording without margins on the trailing edge of the paper 5 is performed, the start sensor 71 detects the passage of the trailing edge of the paper 5 and performs recording on the trailing edge of the paper 5. If it is determined that the platen 25 is rotated, the platen 25 is rotated in the same direction as the conveyance direction of the paper 5, so that the opening (non-supporting portion) 27 of the support member 26 of the platen 25 is formed on the recording head 11 as shown in FIG. Stand by in a position facing the nozzle hole.

  In this state, marginless recording is performed on the rear end portion of the sheet 5, and ink droplets continue to be ejected after the sheet 5 has been transported for a while from just below the nozzle row of the recording head 11, but the opening ( Since the non-supporting portion 27 is opposed to the nozzle holes of the recording head 11, the peripheral surface of the support member 26 of the platen 25 is not soiled by the ink that is removed from the position paper 5.

  The above describes the operation when borderless recording is performed on a single recording medium. Next, marginless recording is performed on a plurality of recording media that are continuously fed. The operation in this case will be described.

  As shown in FIG. 11, while recording is being performed on the first sheet 5a, in parallel with this, the sheet 5b for the next marginless recording is fed from the sheet cassette 31. The roller 32 is operated to feed paper, and is fed between the transport roller 21 and the driven roller 22 in the same manner as described above. FIG. 11 shows a state when recording is completed on the first sheet 5a.

  At this time, the platen 25 configured so that a part of the support member 26 arranged in an arc shape becomes an opening 27 and is not in contact with the recording medium is the length of the arc of the non-support part (opening) 27. The length L is L = πr / 2. Simultaneously with the completion of the recording of the first sheet, the second sheet 5b is waiting at the initial position, and the platen 25 is also waiting at the initial position (position in FIG. 7). For this reason, it is possible to start recording on the second sheet 5 without the operation of restoring the platen 25 to the initial position, and it is possible to continuously and smoothly record a plurality of marginless recordings thereafter.

  In the present embodiment, the arc length L of the opening (non-supporting portion) between the support members of the platen is L = πr / 2, but if L <πr, the rotation platen 25 The recovery time to the initial position can be greatly shortened, and the same effect can be obtained. However, in terms of further effectiveness, it is preferable to set L = πr / 2.

  Next, another example of the platen will be described with reference to FIGS. 12 and 13 are explanatory views of different platens as viewed from the side, and FIGS. 14 and 15 are perspective explanatory views of different platens.

  The platen 125 shown in FIG. 12 has a polygonal shape as viewed from the side, for example, an octagonal shape (a hexagonal shape, a hexagonal shape, a dodecagonal shape, or more), and one side has an opening. 127 is attached to the rotary shaft 129 via the arm 128.

In this case, when the distance from the center O of the rotating shaft 129 to the corner of the support member 126 is defined as a radius r1, and the length of the arc with respect to the radius r of the opening 127 is defined as L, L ≦ πr1
By satisfying this relationship, it is possible to obtain the same effect as in the above embodiment.

  A platen 135 shown in FIG. 13 is obtained by dividing a portion in contact with a recording medium into a plurality of parts and forming a plurality of support members 136 along a circumference 140. In this case as well, the same effect can be obtained by satisfying the relationship of L ≦ πr when the length L of the arc of the opening 137 is defined.

  The platen 145 shown in FIG. 14 is divided into two support members 146a and 146b to form two openings 147a and 147b in the rotation direction, and the support members 146 are attached to the rotation shaft 149 by the arms 148. It is.

  A platen 155 shown in FIG. 15 is obtained by attaching an arc-shaped support member 156, part of which is an opening 157, to a roller 159 that is also a rotating shaft by an arm 158.

  Any of the configurations shown in FIGS. 12 to 15 can provide the same effects as described in the above embodiment, but the polygonal configuration in which the straight portions shown in FIGS. It is difficult to keep the distance constant, and the arc shape is more effective in stably holding the recording medium.

  In this way, by setting the length L of the opening (non-supporting portion) of the support member of the platen within a range satisfying the relationship of L <πr, the length of the platen is removed from the recording medium even in the case of performing recording without margins. The liquid does not contaminate the platen support member (the peripheral surface in contact with the recording medium), and high-quality recording can be performed. In addition, when performing continuous recording without margins, the platen recovery operation for each recording can be completed in a short time, and continuous recording without margins can be performed at high speed.

Next, another embodiment of the image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 16 is an explanatory view showing a main part of the image forming apparatus, and FIG. 17 is a perspective explanatory view of a platen of the apparatus.
In this apparatus, the platen 225 has two support members 226a and 226b, and two openings 227a and 227b are formed in a 180 ° positional relationship in the rotation direction, and each support member 226a and 226b is an arm In this example, an absorber 230 that absorbs ink around the rotation shaft 229 is provided corresponding to at least the openings 227a and 227b.

  Here, when the length of the chord with respect to the arc length L of the openings 227a and 227b is Lg, and the distance in the recording medium conveyance direction of the nozzle holes of the recording head 11 is L1, the relationship of L1 <Lg is established. Openings 227a and 227b are formed so as to satisfy. Details of the distance L1 in the recording medium conveyance direction of the nozzle holes of the recording head 11 will be described later.

  The operation of this embodiment configured as described above will be described with reference to FIGS. 18 shows a state in which the platen is in the initial position, FIG. 19 shows a state in which recording is performed at the center of the first sheet, and FIG. 20 shows a state in which recording is performed at the rear end of the first sheet. Each of the states when a sheet of paper is being sent is shown.

  First, as shown in FIG. 18, when the first sheet 5 a is fed and fed by the transport roller 22, the platen 225 has an initial position where the opening 227 a (or the opening 227 b) faces the nozzles of the recording head 11. The support member 226a (or the support member 226b) is located on the back surface of the paper 5a.

  Therefore, even if the recording head 11 discharges ink droplets immediately before the leading edge of the paper 5a in this state and starts image formation, the support members 226a and 226b of the platen 225 are moved by the ink protruding from the edge of the paper 5a. It won't get dirty. And since the droplet discharged toward the opening 227a (or the opening 227b) is absorbed by the absorber 230, it is prevented from scattering.

  When recording on the sheet 5a starts, the platen 225 is rotated to the position shown in FIG. Then, until the rear end of the sheet 5a is detected by the same start sensor as in the above embodiment, the sheet 5a is conveyed with the back surface of the sheet 5a supported by the support member 226a (or 226b) of the platen 225 at this position. While being transported by the roller 21, ink droplets are ejected from the nozzles of the recording head 11 to record an image on the paper 5.

  In parallel with this, the sheet 5b for performing the next marginless recording is fed from the sheet feeding cassette with the sheet feeding roller 32 turned on, and fed between the conveying roller 21 and the driven roller 22, and the conveying roller. 21 and the driven roller 22 feed the paper 5b into the recording area.

  When the start sensor detects the passage of the trailing edge of the first sheet 5b, the platen 225 is rotated in the sheet conveying direction to the position shown in FIG. Accordingly, as shown in FIG. 20, the platen 225 is positioned so that the opening 227b (or the opening 227a) faces the nozzles of the recording head 11, and the support member 226a (or support member 226b) is placed on the back surface of the sheet 5a. The support member 226b (or the support member 226a) is positioned on the back surface of the paper 5b.

  Therefore, when marginless recording is performed on the trailing edge of the first sheet 5b, the support member 226a is moved again to the back surface of the sheet 5b, so that it is not soiled by ink droplets protruding from the edge of the sheet 5. The protruding ink droplets are absorbed by the absorber 230 and are prevented from scattering.

  At this time, the length Lg of the string with respect to the length L of the non-supporting portion (opening) 227a (227b) of the platen 225 is wider than the distance L1 between the upstream and downstream sides in the transport direction of the two nozzle rows of the recording head 11. Since it is configured, the platen support portions 266a and 226b are not contaminated by the ink ejected from the nozzles.

  Subsequently, the next sheet 5b has already been conveyed to immediately before the recording area. However, another support member 126b formed on the platen 225 supports the leading end of the next sheet 5b from below, and is continuous. Then, the marginless recording is performed on the leading edge of the sheet 5.

  As described above, since a plurality of paper non-supporting regions of the platen are configured with respect to the rotation direction and the plurality of continuous marginless recordings are performed, the rotation direction of the platen is only one direction. Even in the case of performing non-recording, a special operation for positioning the platen is unnecessary, the time required for recording can be shortened, and the speed can be increased.

  In addition, since the ink absorber is provided between the center of the platen and the support member, the back surface of the support member is not contaminated, and marginless recording that maintains quality can be performed.

  Furthermore, since the length Lg of the string with respect to the length L of the non-supporting region of the platen is configured to be larger than the inter-nozzle distance L1, the recording medium support member of the platen may be contaminated by the ink ejected from the nozzles. Absent.

Next, another example of a platen that can achieve the same effect as this embodiment will be described with reference to FIGS.
The platen 235 shown in FIG. 21 has two support members 236 a and 236 b, and two openings 237 a and 237 b are formed in a 180 ° positional relationship in the rotation direction, and the respective support members 236 a and 236 b are arms 238. Is attached to the rotary shaft 239, and the plate-shaped ink absorber 240 is provided in the openings 237a and 237b.

  The platen 255 shown in FIG. 22 is formed with two support members 256a and 256b by forming openings 257a and 257b in the cylindrical member 261, and the cylindrical member 261 so that the circumferential surface faces the openings 257a and 257b. An ink absorber 260 is provided therein, and a cylindrical member 261 is rotatably supported by a rotation shaft 269.

Here, the inter-nozzle distance L1 that defines the relationship with the string length Lg in the second embodiment will be described in relation to the recording head configuration.
First, the image forming apparatus shown in FIG. 23 is an example of a line-type image forming apparatus using a line-type head, and ejects droplets of different colors such as black, cyan, magenta, and yellow as the line-type head. Using the line heads 301 y, 301 m, 301 c, and 301 k for each color having one or a plurality of nozzle rows (these are collectively referred to as “each line head 301”), an intermediate roller 211 is disposed between the line heads 301. ing.

  In this image forming apparatus, a platen 225 is disposed corresponding to each line head 301. Therefore, as shown in FIG. 24, when two nozzle rows Na and Nb in which the nozzles N are arranged with respect to one line head 301 are formed, the space between the nozzle rows Na and Nb of each line head 301 is set. A distance in the recording medium conveyance direction is defined as a distance L1. In the case of one nozzle row, the width (distance) corresponds to the nozzle row.

  Next, the image forming apparatus shown in FIG. 25 is an example of a line type image forming apparatus using a line type head, and ejects droplets of different colors such as black, cyan, magenta, and yellow as the line type head. One line head 311 in which one or a plurality of nozzle rows for each color is formed is used.

  In this image forming apparatus, one platen 225 is arranged corresponding to the line head 311. Therefore, as shown in FIG. 26, when the nozzle rows NB, NC, NM, NY for the respective colors including the two nozzle rows Na, Nb are formed on the line head 311, they are the farthest in the recording medium conveyance direction. The distance between the nozzle rows, here, the nozzle row Na of the nozzle row NY that discharges yellow droplets on the most upstream side in the recording medium conveyance direction and the black droplets on the most downstream side in the recording medium conveyance direction. A distance between the nozzle row NB of the nozzle rows NB to be discharged is a distance L1.

  Next, the image forming apparatus shown in FIG. 27 is a serial type image forming apparatus in which a recording head is mounted on a carriage, and ejects droplets of different colors such as black, cyan, magenta, and yellow as the recording head. A recording head 321 in which a plurality of nozzle arrays NB, NC, NM, NY are formed is used.

  In this image forming apparatus, one platen 225 is arranged corresponding to the recording head 321. Therefore, as shown in FIG. 28, the distance between the nozzles N at both ends of the nozzle rows NB, NC, NM, NY211 in the recording medium conveyance direction of the recording head 321 is a distance L1. The same applies when a plurality of independent recording heads are arranged for each color.

  In each of the above embodiments, an image forming apparatus having a printer configuration is taken as an example. However, the image forming apparatus of the present invention can also be applied to a facsimile machine, a copying machine, a printer / fax / copier multifunction machine, and the like. Further, the present invention can be applied to an apparatus for discharging and recording a liquid other than ink, for example, a resist or a DNA sample in the medical field.

1 is a schematic configuration diagram illustrating an overall configuration of a first embodiment of an image forming apparatus according to the present invention. It is side surface explanatory drawing which shows the principal part of the apparatus. It is side surface explanatory drawing which shows the platen of the apparatus. It is a perspective explanatory view of the platen. It is a plane explanatory view of the platen. It is a block diagram which shows the outline | summary of the control part of the apparatus. It is explanatory drawing which shows a state when a platen exists in an initial position. FIG. 6 is an explanatory diagram illustrating a state when recording is performed on the leading edge of the first sheet. FIG. 10 is an explanatory diagram illustrating a state when recording is performed on the central portion of the first sheet. FIG. 6 is an explanatory diagram illustrating a state when recording is performed on the trailing edge of the first sheet. FIG. 10 is an explanatory diagram illustrating a state when a second sheet is being sent when marginless recording is performed on a second sheet of paper. It is side surface explanatory drawing which shows the other 1st example of the platen of the embodiment. It is side surface explanatory drawing which shows the other 2nd example of the platen of the embodiment. It is a perspective explanatory view showing other 3rd examples of the platen of the embodiment. It is side surface explanatory drawing which shows the other 4th example of the platen of the embodiment. It is explanatory drawing which shows the principal part of 2nd Embodiment of the image forming apparatus which concerns on this invention. It is a perspective explanatory view showing the platen of the same device. It is explanatory drawing which shows a state when a platen exists in an initial position. FIG. 10 is an explanatory diagram illustrating a state when recording is performed on the central portion of the first sheet. FIG. 10 is an explanatory diagram illustrating a state when a second sheet is being sent when marginless recording is performed on a second sheet of paper. FIG. 6 is a perspective explanatory view showing another first example of the platen of the same embodiment. It is a perspective explanatory view showing other 2nd examples of the platen of the embodiment. It is explanatory drawing explaining the structure of a line type image forming apparatus. It is plane explanatory drawing which looked at the nozzle surface side with which it uses for description of the distance L1 between nozzle rows in the same apparatus. It is explanatory drawing explaining the other structure of a line type image forming apparatus. It is plane explanatory drawing which looked at the nozzle surface side with which it uses for description of the distance L1 between nozzle rows in the same apparatus. FIG. 2 is an explanatory diagram illustrating a configuration of a serial type image forming apparatus. It is plane explanatory drawing which looked at the nozzle surface side with which it uses for description of the distance L1 between nozzle rows in the same apparatus.

Explanation of symbols

2 ... Image forming unit 3 ... Sub-scanning conveying unit 5 ... Paper (recording medium)
DESCRIPTION OF SYMBOLS 11 ... Recording head 21 ... Conveyance roller 25 ... Platen 26 ... Support member 27 ... Opening part (non-support area | region, non-support part)

Claims (6)

A platen having an opening on the outer peripheral surface is rotatably arranged at a position facing a recording head having a plurality of nozzle holes for discharging droplets, and a recording medium is located at a position away from the rotation center position of the platen by a radius r. In the image forming apparatus that forms an image while supporting the platen, the arc length L of the opening of the platen is:
L <πr
An image forming apparatus satisfying the relationship: 2. The image forming apparatus according to claim 1, wherein the length of the chord with respect to the arc length L of the opening is Lg, and the distance of the nozzle hole of the recording head in the recording medium conveyance direction is L1.
L1 <Lg
An image forming apparatus satisfying the relationship:   3. The image forming apparatus according to claim 1, wherein the platen has two or more openings in a rotation direction. 4.   3. The image forming apparatus according to claim 2, wherein when the plurality of recording media are continuously transported and marginless recording is performed in a direction orthogonal to the recording medium transporting direction, the platen rotates in a plurality of continuous directions. An image forming apparatus characterized in that the recording medium is in a certain direction until the recording with no margins is completed.   5. The image forming apparatus according to claim 1, further comprising an absorber that absorbs liquid inside the opening. 6. The image forming apparatus according to claim 1, wherein the recording head is a line type head.

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