JP5048413B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including a rotating body that holds a recording medium.

  In general, a printer / fax / copier or an image forming apparatus that combines these functions includes, for example, a recording head composed of a liquid ejection head that ejects ink droplets, and a recording medium (hereinafter also referred to as “paper”, but a material). In addition, a medium, a recording medium, a transfer material, a recording paper, etc. are also used synonymously.) While transporting the ink, ink is adhered to the paper to form an image (recording, printing, printing, printing) Are also used synonymously.)

  The “image forming apparatus” means an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. “Formation” means not only giving an image having a meaning such as a character or a figure to a recording medium but also giving an image having no meaning such as a pattern to the recording medium. In addition, “ink” is not limited to ink in a narrow sense, but means a liquid that can form an image.

As such an image forming apparatus, there are an apparatus using a rotating body (drum) as a conveying means for conveying a recording medium (see Patent Document 1), an apparatus using a conveying belt (see Patent Documents 2 to 4), and the like. .
JP 2004-174742 A JP 2006-256864 A JP 2005-263332 A JP 2006-232512 A

  By the way, it is difficult for the image forming apparatus using a rotating body (drum) to transport the recording medium described above to hold a stiff recording medium or a thick recording medium on the circumferential surface of the rotating body. There is a problem that there is.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to make it possible to form an image on a thick paper or a recording medium that is difficult to hold with a rotating body.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head unit comprising a plurality of recording heads arranged side by side with a plurality of nozzles for discharging droplets;
A rotating body that holds and conveys a recording medium on which an image is formed by the recording head, on a peripheral surface;
A linear conveyance path for linearly conveying the recording medium;
Switching means for switching between the path for holding the recording medium on the peripheral surface of the rotating body and the linear transport path;
The recording head is capable of forming an image on both the recording medium transported while being held on the circumferential surface of the rotating body and the recording medium transported through the linear transport path,
When forming an image on the recording medium transported along the linear transport path, the nozzle surfaces of the plurality of recording heads are arranged on substantially the same surface,
When forming an image on the recording medium that is held and conveyed by the peripheral surface of the rotating body, the nozzle surface of the recording head is displaced in a direction along the peripheral surface of the rotating body. The configuration.

An image forming apparatus according to the present invention includes:
A recording head unit comprising a plurality of recording heads arranged side by side with a plurality of nozzles for discharging droplets;
A rotating body that holds and conveys a recording medium on which an image is formed by the recording head, on a peripheral surface;
A conveyance belt that is wrapped around at least two rollers that convey and hold the recording medium on the surface, and
The peripheral surface of the rotating body and the surface of the transport belt are arranged opposite to each other, and the recording medium can be transferred between the rotating body and the transport belt,
The recording head can form an image on any of the recording media in a state of being held on the peripheral surface of the rotating body and in a state of being held on the surface of the transport belt ,
When forming an image on the recording medium held by the conveyor belt, the nozzle surfaces of the plurality of recording heads are arranged on substantially the same surface,
When forming an image on the recording medium held on the circumferential surface of the rotating body, the nozzle surfaces of the plurality of recording heads are displaced in a direction along the circumferential surface of the rotating body. <Br / > Configuration.

By the present invention lever, an image can be formed even for a strong recording medium having difficulty cardboard and hips be held in rotating body.

Embodiments of the present invention will be described below with reference to the accompanying drawings. A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic explanatory view showing a main configuration of the image forming apparatus according to the embodiment.
In this image forming apparatus, a paper feed tray 2 that accommodates a paper (recording medium) 1 is disposed at the bottom, and the paper 1 is separated from the paper feed tray 2 one by one by a pickup roller 3, and is indicated by an arrow 101. Thus, the paper is conveyed in the vertical direction by the conveying roller pairs 4 and 5, further changed in the horizontal direction by the conveying roller pair 6, conveyed in the direction of the arrow 102, and sent to the image forming unit (printing unit) 7.

  In the image forming unit, a drum 10 that is a rotating body that winds and holds the paper 1 around a circumferential surface, and a recording head unit 11 that faces the circumferential surface of the drum 10 are disposed. The drum 10 is disposed so as to be rotatable in the direction of a broken line arrow (counterclockwise in the figure) in a state where the sheet 1 is held on the peripheral surface by air suction, static electricity, tip chucking of a recording medium, or the like. The recording head unit 11 includes a line type recording head 12y having nozzles for discharging liquid droplets of different colors, for example, liquid droplets of yellow (Y), magenta (M), cyan (C), and black (K). 12m, 12c, and 12k (referred to as “recording head 12” when colors are not distinguished) are integrally supported by the support member 13.

  Further, a separation claw 14 for separating the paper 1 from the drum 10 is slidably disposed on the downstream side of the image forming unit. When the paper 1 is continuously held on the drum 10, the separation claw 14 is in an inoperative position ( The position is indicated by the broken line in the figure. When the image formation on the paper 1 is completed, the separation claw 14 swings to the position indicated by the solid line, the drum 10 releases the holding state of the paper 1, and the paper 1 is separated from the drum 10 by the separation claw 14. Then, it is conveyed linearly in the direction of the arrow 103.

  Here, when performing reverse printing on the printing surface or duplex printing, the sheet 1 on which an image is formed on one side is conveyed in a downward direction indicated by an arrow 104 and is fed into the duplex unit 15. When reverse paper discharge is performed, the paper is sent toward a pair of paper discharge rollers (for example, composed of a roller and a spur) 16 and discharged to a paper discharge tray (not shown) in the direction of an arrow 105. Further, when performing double-sided printing, the paper is again fed into the pair of conveying rollers 5 through the double-sided unit 15 and is again conveyed to the printing unit. The duplex unit 15 includes transport rollers 15a and 15b and transport roller pairs 15c and 15d.

  Further, the paper feed tray 20 and the paper feed roller 21 that feed the paper to the pair of transport rollers 6 and the paper that is guided and linearly transported in a state where the separation claw 14 is in the separation position, is transported as it is in the paper discharge direction. A pair of paper rollers 22 is arranged to form a straight conveyance path (a path indicated by arrows 102 and 103) from the paper feed tray 20 to the pair of paper discharge rollers 22 between the recording head unit 11 and the drum 10. .

  In this case, the separation claw 14 serves as a switching unit that switches between a path for holding the paper on the peripheral surface of the drum 10 and a straight conveyance path, and swings to the separation position side indicated by the solid line when the straight conveyance path is used. The drum 10 serves as a support member (platen) that supports the sheet conveyed on the straight conveyance path from the lower side at a position facing the recording head unit 11.

  With this configuration, when image formation is performed on normal paper 1, paper 1 is fed from the paper feed tray 2, wound around the peripheral surface of the drum 10, and the paper 1 is held on the peripheral surface of the drum 10. The liquid droplets of the respective colors are ejected from the recording head 12 while being rotated in order to form an image on the paper 1. Note that when printing is performed a plurality of times for the purpose of preventing ink bleeding and increasing the resolution, the droplets from the recording head 12 are again retained while the paper 1 is held on the drum 10 in order to obtain positional accuracy for the plurality of times of printing. It is preferable to form an image by ejecting the liquid.

  On the other hand, when using thick paper or paper that is stiff and difficult to wind (hold) around the drum 10 (hereinafter referred to as “specific paper”), the paper feed tray 20 carries the transport roller. While transporting between the recording head unit 11 and the drum 10 in pairs 6, droplets are ejected by the recording head 12 to form an image, while transporting on a linear transport path passing over the separation claw 14 at the separation position, The paper is conveyed in the paper discharge direction by the paper discharge roller pair 22 and discharged to a paper discharge tray (not shown).

  Here, when a specific sheet is conveyed linearly and an image is formed by the recording head unit 11, it is preferable to perform printing a plurality of times by moving the specific sheet back and forth linearly in order to increase the resolution. For the reciprocating movement of the specific paper, for example, a suction port 10a that is sucked in the region facing the recording head unit 11 of the drum 10 is provided, and the specific paper is adsorbed with a weak adsorbing force and is swung on the drum 10. A discharge port 10b for discharging the airflow is provided on the separation claw 14 side so that the specific sheet can be peeled off.

  In this way, a recording head in which a plurality of nozzles for discharging droplets are arranged side by side, and the recording head is opposed to the circumferential surface, and the recording head forms an image with the recording head and holds the recording medium on the circumferential surface to convey the recording medium. A linear transport path for linearly transporting the recording medium, and a switching means for switching between a path for holding the recording medium on the peripheral surface of the rotating body and a linear transport path. It is possible to form an image on both the recording medium that is held and transported by the surface and the recording medium that is transported by the linear transport path, so that it is difficult to hold the card with thick paper or waist Image formation can be performed even on strong recording media

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic explanatory view showing the main configuration of the image forming apparatus according to the embodiment.
In this image forming apparatus, a paper feed tray 2 that accommodates a paper (recording medium) 1 is disposed at the bottom, and the paper 1 is separated from the paper feed tray 2 one by one by a pickup roller 3, and is indicated by an arrow 101. Thus, the sheet is conveyed in the vertical direction by the conveying roller pair 4, further changed in the horizontal direction by the conveying roller pair 6, conveyed in the direction of the arrow 102, and sent to the image forming unit (printing unit) 7.

  The image forming unit is provided with a conveyor belt 31 that circulates around the rollers 32 and 33 that convey the paper 1 fed from the conveyance roller pair 6 while holding the sheet 1 on the surface. A drum 10 that is a rotating body that rotates while holding the paper 1 similar to that of the first embodiment on the peripheral surface facing the front surface (however, the rotation direction is clockwise in the figure) is disposed.

  The sheet 1 can be held on the surface of the transport belt 31 by airflow suction or electrostatic suction, or may not be performed until it is sucked only by placement. In addition, a heating unit may be incorporated in at least one of the rollers 32 and 33 around which the transport belt 31 is wound so as to promote the drying of the ink attached to the paper 1.

  The drum 10 transfers the paper 1 held on the surface of the conveyor belt 31 and winds and holds the paper 1 around the circumferential surface. As described above, the sheet 1 can be held on the peripheral surface of the drum 10 by air suction, static electricity, sheet tip chucking, and the like. In this case, the sheet 1 is not held on the transport belt 31. As a result, the leading edge of the paper 1 can be held on the circumferential surface of the drum 10 without being disturbed.

  Here, a plurality of blowing holes 31 a are provided in the conveying belt 31, and a duct 34 is provided inside the conveying belt 31. When the paper 1 is transferred from the conveying belt 31 to the drum 10, the conveying belt 31 passes through the blowing hole 31 a through the duct 34. The airflow is blown out to assist in the transfer and holding to the drum 10. By blowing out from the blowing hole 31 a of the conveyance belt 31 at the timing when the leading edge of the sheet 1 comes into contact with the peripheral surface of the drum 10, the leading edge of the sheet 1 can be reliably held on the peripheral surface of the drum 10.

  The recording head unit 11 has the same configuration as that of the first embodiment, and also has a position facing the peripheral surface of the drum 10 (a position shown by a solid line) and a position facing the surface of the transport belt 31 (shown by a broken line). Position).

  Then, the sheet 1 separated from the peripheral surface of the drum 10 is transported by the transport belt 31 and sent in the direction of the arrow 107, and is discharged to a discharge tray (not shown). In the case of performing duplex printing, the sheet 1 on which an image is formed on one side is conveyed in a downward direction indicated by an arrow 108 by a conveyance roller 37 on the downstream side of the conveyance belt 31, and is sent into the duplex reversing unit 38 to be printed on both sides. The paper is fed from the reversing unit 38, changed in direction by the transport roller 39, and sent to the transport roller pair 6 through the transport rollers 40, 41, 42, and 43 in contact with the surface of the transport belt 31, and again to the image forming unit. Transport is performed.

  Further, a paper feed tray 20 and a paper feed roller 21 that linearly feed paper to the transport roller pair 6 are provided.

  With this configuration, when an image is formed on a normal sheet 1, the recording head unit 11 is placed at a position facing the drum 10, the sheet 1 is fed from the sheet feed tray 2 and fed onto the transport belt 31. The paper 1 is transferred from the surface of the transport belt 31 to the peripheral surface of the drum 10 and wound, and droplets of each color are discharged from the recording head 12 while rotating the paper 1 while holding the paper 1 on the peripheral surface of the drum 10. Form an image on top. Note that when printing is performed a plurality of times for the purpose of preventing ink bleeding and increasing the resolution, the droplets from the recording head 12 are again retained while the paper 1 is held on the drum 10 in order to obtain positional accuracy for the plurality of times of printing. It is preferable to form an image by ejecting the liquid. Thereafter, the sheet 1 is transferred from the peripheral surface of the drum 10 onto the conveyance belt 31, and the sheet 1 is conveyed in the paper discharge direction by the conveyance belt 31.

  On the other hand, when using special paper that is difficult to wrap around cardboard or the drum 10 circumferential surface, the recording head unit 11 is placed at a position facing the surface of the transport belt 31 and transported by feeding from the paper feed tray 20. While holding a specific sheet on the surface of the belt 31, the recording head 12 discharges droplets to form an image, which is conveyed in the paper discharge direction.

  As described above, a recording head in which a plurality of nozzles for discharging droplets are arranged side by side, a rotating body that holds and conveys a recording medium on which an image is formed by the recording head, and a recording medium are held on the surface. A conveying belt that is looped around at least two rollers that convey the recording medium, and the circumferential surface of the rotating body and the surface of the conveying belt are arranged to face each other, so that the recording medium is rotated and the conveying belt. Since the image can be formed on any recording medium that is held on the peripheral surface of the rotating body and held on the surface of the conveyor belt, it is held on the rotating body. Therefore, it is possible to form an image on a thick paper or a recording medium having a low stiffness.

Next, a third embodiment of the present invention will be described with reference to FIGS.
When the recording head unit 11 is oscillated and displaced as in the second embodiment so that the position facing the drum 10 and the position facing the conveyance belt 31 can be taken, as shown in FIG. By simply changing the direction of the head unit 11, the nozzle surfaces of the four recording heads 12 (surfaces on which nozzles for discharging liquid droplets) are formed when facing the drum 10 and when facing the conveyor belt 31. The distance from the recording medium to the recording medium is slightly different, and there may be a positional deviation or the like when the ink droplets ejected from the recording head 12 land on the recording medium during image formation.

Therefore, as shown in FIG. 3, in the recording head unit 11, when facing the surface of the conveyance belt 31, the nozzle surfaces of the four recording heads 12 are substantially the same surface (same as in FIG. 4). When facing the circumferential surface, the posture (angle) and position of each recording head 12 can be changed so that the nozzle surfaces of the four recording heads 12 are in a direction along the circumferential surface of the drum 10. By adopting such a configuration, it is possible to reduce the positional deviation of the landing droplets. Note that the posture and position of the recording head 12 can be adjusted by displacing a circular gear or a spacer between the recording heads 12.

Next, a fourth embodiment of the present invention will be described with reference to FIGS.
Here, in the second embodiment, the droplet ejection timing from each recording head 12 is corrected based on the distance and angle without changing the posture (angle) and position of the recording head 12 of the recording head unit 11. I am doing so.

  That is, as shown in FIG. 5, when the recording head unit 11 faces the conveyance belt 31, the nozzle surfaces of the recording heads 12 and the conveyance belt 31 are substantially parallel, so that the discharge from the recording heads 12 of each color is performed. Thus, the landing intervals d1 of the droplets 120y, 120m, 120c, and 120k that land on the recording medium are kept the same.

  On the other hand, as shown in FIG. 6, when the recording head unit 11 faces the peripheral surface of the drum 10, even if the interval between the recording heads 12 for each color is the same, the ejection is performed from the recording head 12 for each color. The landing intervals of the droplets landed on the recording medium are different as the interval d3 between the recording heads 12y and 12m and between the recording heads 12c and 12k, and the interval d4 between the recording heads 12m and 12c. The distance from the nozzle surface of the head 12 to the peripheral surface of the drum 10 is different. Therefore, the landing positions are adjusted by correcting (adjusting) the discharge timing of the droplets discharged from each recording head 12.

Here, the landing distance difference to be considered in correcting the droplet discharge timing will be described with reference to FIG. 7 by taking the recording heads 12k and 12c as an example.
In FIG. 7, the radius from the center O of the drum 10 is R, the nozzle interval between the recording head 12k and the recording head 12c (landing interval in the state of FIG. 5) is d1, and the recording head 12k and the recording head 12c are centered on the drum 10. If the angle formed by the landing position is θ, and the angle formed by the point where the center line of the recording head unit 11 with respect to the center of the drum 10 intersects the center of the drum 10 and the landing position of the recording head 12k is σ, the difference in landing distance is It is calculated by such calculation.

  The landing positions can be adjusted by correcting the droplet discharge timing based on the relationship between the distance obtained as described above and the ink droplet velocity. The distance difference can also be obtained by automatic calculation using CAD drawing.

  Further, it is possible to obtain the landing distance difference when one recording head 12 has two nozzle rows as shown in FIG. Here, with reference also to FIG. 9, a landing distance difference to be taken into consideration for correcting the landing speed between the two nozzle arrays of the recording heads 12k and 12c or 12y and 12m is calculated. Since the center line of the recording head unit 11 is on the extension of the axis of the rotating body 10, the distances from the recording heads 12k and 12y, 12c and 12m to the rotating body 10 in FIG.

  The difference in distance is calculated as described above, and the landing position can be corrected based on the droplet discharge timing from the relationship between the ink droplet velocity and the distance.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
In this embodiment, the recording heads 12 held by the recording head unit 11 are arranged in a posture matching the peripheral surface of the drum 10, and the distance between the nozzle surface of each recording head 12 and the peripheral surface of the drum 11 is set. Each recording head 12 is the same.

  When the recording head unit 11 is placed at a position facing the conveyance belt 31, the distance between the nozzle surface of each recording head 12 and the surface of the conveyance belt 31 is different for each recording head 12. The droplet discharge timing is corrected based on the distance difference between the surface and the surface of the conveyor belt 31 and the angle, and the landing position is adjusted.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
In this embodiment, the position of each recording head 12 held in the recording head unit 11 can be changed when the recording head unit 11 is displaced between a position facing the drum 10 and a position facing the conveyance belt 31. Thus, the distance between the nozzle surface of each recording head 12 and the peripheral surface of the drum 11 can be the same when facing the drum 10, and the nozzle surface of each recording head 12 and the surface of the transport belt 31 when facing the transport belt 31. The distance between and can be the same. Thereby, landing position deviation can be reduced.

  11 is set based on the position of the recording head 12 facing the drum 10 as shown in FIG. 11, and when forming an image with the transport belt 31, the difference in distance between the recording head 12 of each color and the transport belt 31 is determined as a droplet. A configuration in which correction is performed at the discharge timing may also be adopted. In other words, since the frequency of printing on the specific paper is less than the case of printing on the normal paper, the state in which the recording head 12 faces the drum 10 can be prioritized.

It is a typical explanatory view showing a 1st embodiment of the present invention. It is typical explanatory drawing which shows 2nd Embodiment of this invention. It is typical explanatory drawing which shows 3rd Embodiment of this invention. It is a typical explanatory view for the comparison explanation of a 3rd embodiment similarly. FIG. 6 is an explanatory diagram for explaining a landing position when the recording head faces the conveyance belt. It is explanatory drawing with which it uses for description of a landing position when a recording head is similarly facing the rotary body. It is explanatory drawing with which it uses for description of calculation of the distance difference in the case of performing correction | amendment of landing position deviation similarly. FIG. 5 is an explanatory diagram for explaining landing positions when there are two nozzle rows of the recording head. FIG. 5 is an explanatory diagram for explaining calculation of a distance difference when correcting landing position deviation when there are two nozzle rows of the recording head. It is a typical explanatory view showing a 4th embodiment of the present invention. It is typical explanatory drawing which shows 5th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Drum 11 ... Recording head unit 12y, 12m, 12c, 12k ... Recording head 14 ... Separation claw (switching means)
31 ... Conveyor belt

Claims (5)

A recording head unit comprising a plurality of recording heads arranged side by side with a plurality of nozzles for discharging droplets;
A rotating body that holds and conveys a recording medium on which an image is formed by the recording head, on a peripheral surface;
A linear conveyance path for linearly conveying the recording medium;
Switching means for switching between the path for holding the recording medium on the peripheral surface of the rotating body and the linear transport path;
The recording head is capable of forming an image on both the recording medium transported while being held on the circumferential surface of the rotating body and the recording medium transported through the linear transport path,
When forming an image on the recording medium transported along the linear transport path, the nozzle surfaces of the plurality of recording heads are arranged on substantially the same surface,
The nozzle surface of the recording head is displaced in a direction along the peripheral surface of the rotating body when an image is formed on the recording medium that is held and conveyed by the peripheral surface of the rotating body. Image forming apparatus.   2. The image forming apparatus according to claim 1, wherein the straight conveyance path is a conveyance belt that conveys the recording medium while holding the recording medium on a surface. A recording head unit comprising a plurality of recording heads arranged side by side with a plurality of nozzles for discharging droplets;
A rotating body that holds and conveys a recording medium on which an image is formed by the recording head, on a peripheral surface;
A conveyance belt that is wrapped around at least two rollers that convey and hold the recording medium on the surface, and
The peripheral surface of the rotating body and the surface of the transport belt are arranged opposite to each other, and the recording medium can be transferred between the rotating body and the transport belt,
The recording head can form an image on any of the recording media in a state of being held on the peripheral surface of the rotating body and in a state of being held on the surface of the transport belt,
When forming an image on the recording medium held by the conveyor belt, the nozzle surfaces of the plurality of recording heads are arranged on substantially the same surface,
When forming an image on the recording medium held on the circumferential surface of the rotating body, the nozzle surfaces of the plurality of recording heads are displaced in a direction along the circumferential surface of the rotating body. An image forming apparatus.   4. The image forming apparatus according to claim 2, wherein the recording head unit is held on a position where an image is formed on the recording medium held on a peripheral surface of the rotating body and on a surface of the conveying belt. An image forming apparatus, wherein the image forming apparatus is displaceably disposed at a position where an image is formed on the recording medium.   5. The image forming apparatus according to claim 4, comprising a plurality of recording heads that eject droplets of different colors, wherein each recording head forms an image on the recording medium on the circumferential surface of the rotating body. Between the nozzle surface having the nozzle and the peripheral surface of the rotating body, and the nozzle surface having the nozzle and the conveyance belt when forming an image on the recording medium on the surface of the conveyance belt. An image forming apparatus, wherein the image forming apparatus is displaceably arranged so that a distance between the surface and the surface is the same.

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