JP2007301867A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit a deterioration in print quality by suppressing a variation in conveying speed in printing near the end part of a sheet of recording paper in an image forming apparatus corresponding to a frameless print. <P>SOLUTION: A press roller 33 is arranged through a press roller holder 34 with facing a paper supply roller 32 which conveys the recording paper P to the printing position. An auxiliary roller 36 is mounted at the second end of a wire spring member 37 whose first end 37a is connected to the press roller holder 34. The auxiliary roller 36 presses the rear end of the recording paper leaving the press roller 33 to the paper supply roller 32 and applies a loading to the spinning of a paper discharge roller 38. Thereby, a variation in the conveying speed of the recording paper is suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus capable of printing up to the end of recording paper.

  In recent years, an inkjet image forming apparatus (hereinafter referred to as an inkjet printer) has been required to cope with so-called borderless printing in which printing is performed up to the end of a recording sheet as well as high image quality close to photographic image quality. In general, in an inkjet printer, a paper feed roller is provided on the upstream side of the print head, and a paper discharge roller is provided on the downstream side. The conveyance speed of the paper discharge roller is set slightly higher than the conveyance speed of the paper supply roller so that the recording paper does not loosen between the paper supply roller and the paper discharge roller. Therefore, when the recording paper is being conveyed by the paper feed roller and the paper discharge roller, a slight load is applied to the paper discharge roller side. However, when the end portion of the recording paper is removed from the paper feed roller, the load applied to the paper discharge roller is instantaneously released. Since the roller shaft into which the paper discharge roller is press-fitted is supported by the bearing, rattle exists between the roller shaft and the bearing. Further, backlash is present in the gear that rotationally drives the paper discharge roller. Therefore, if the rotation load of the paper discharge roller is momentarily released due to the end of the recording paper being removed from the paper feed roller, the recording paper conveyance speed will fluctuate instantaneously. As a result, in the vicinity of the rear end of the recording paper, the recording paper and the print head cannot be synchronized, causing a problem that color unevenness occurs and print quality deteriorates.

  In order to suppress such problems, (i) when forming an image in the vicinity of the trailing edge of the recording paper, the conveyance amount of the recording paper is reduced, and (ii) a large load due to friction or the like is constantly applied to the paper discharge roller. Measures such as suppressing fluctuations in the recording sheet conveyance speed when the trailing end of the recording sheet deviates from the paper feed roller have been studied. However, in the case of (i), the printing speed is reduced. In the case of (ii), the mechanical load of the paper discharge roller is increased, so that the burden on the motor for driving the paper discharge roller is increased. There is.

In order to obtain good print quality while avoiding such adverse effects, Patent Document 1 provides an auxiliary roller for preventing the trailing edge of the recording paper from jumping on the downstream side of the pressing roller, and the recording paper conveyance speed. An image forming apparatus in which fluctuations in the above are suppressed is shown. Patent Document 2 discloses an image forming apparatus in which an auxiliary roller is provided on the downstream side of the print head to prevent the trailing edge of the recording paper from jumping up. Further, Patent Document 3 discloses an image in which fluctuations in the conveyance speed of the recording paper are suppressed by temporarily releasing the pressing force on the discharge roller side immediately before the trailing edge of the recording paper passes the paper feed roller. A forming device is shown. Further, in Patent Document 4, the recording roller can be stably conveyed to the vicinity of the print head by configuring the pressing roller facing the paper feeding roller to be movable along the peripheral surface of the paper feeding roller. An image forming apparatus is shown.
Japanese Patent Laying-Open No. 2005-22242 JP 2005-262835 A JP 2005-153147 A JP-A-8-12124

However, in the image forming apparatus disclosed in Patent Document 1, the auxiliary roller is rotatably supported with respect to the roller holder, and can be moved up and down together with the roller holder by the biasing force of the coil spring. For this reason, it is difficult to optimize the pressing force of the auxiliary roller independently of the pressing roller, and fluctuations in the recording paper conveyance speed cannot be effectively suppressed.
Further, in the image forming apparatuses disclosed in Patent Documents 2 to 4, the configuration of the apparatus is complicated, resulting in an increase in cost.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of effectively suppressing fluctuations in the conveyance speed of a recording sheet with a simple and inexpensive configuration. .

  In order to achieve the above object, the invention of claim 1 includes a paper feed tray for holding the loaded recording paper, a first transport means for transporting the recording paper held in the paper feed tray into the apparatus, An image forming unit that forms an image on the recording paper conveyed by the first conveying unit, a second conveying unit that conveys the recording paper on which the image is formed by the image forming unit to the outside of the apparatus, and the second conveying unit A paper discharge tray on which the transported recording paper is deposited and a frame for supporting each of the above-described parts. The image forming means includes an ink cartridge filled with ink, and the ink cartridge is attached to the recording paper. A carrier that reciprocates in a direction perpendicular to the transport direction; and a carrier driving unit that drives the carrier. The first transport unit is configured to transfer the recording paper held in the paper feed tray to the apparatus. A pick roller to be fed to the printing unit, a paper feed roller for transporting the recording paper sent by the pick roller to an image forming position by the image forming means, a roller driving means for driving the pick roller and the paper feed roller, and a recording paper A pressure roller that presses against the paper feed roller, a pressure roller holder that is rotatably supported by the frame while rotatably holding the pressure roller, and the pressure roller that presses the pressure roller holder against the paper feed roller In the image forming apparatus having a holder urging unit that urges in the direction, a plurality of pressing roller holders are arranged in parallel to the paper feed roller, and the first conveying unit is on the downstream side of the pressing roller. The auxiliary roller disposed opposite to the paper feed roller on the upstream side of the ink cartridge and the first end are coupled to the pressing roller holder, and the second end The auxiliary roller is rotatably supported and the wire spring member biases the auxiliary roller in the direction of the paper feed roller. The width of the auxiliary roller is smaller than the width of the pressing roller, and recording is performed. When the trailing edge of the paper is removed from the pressing roller, the auxiliary roller applies a load to the second conveying unit by pressing the recording paper in the direction of the paper feeding roller, and when printing near the end of the recording paper, In this way, fluctuations in the conveyance speed of the sheet can be suppressed and deterioration in print quality can be prevented.

  According to a second aspect of the present invention, a first conveying unit that conveys recording paper into the apparatus, an image forming unit that forms an image on the recording paper conveyed by the first conveying unit, and an image is formed by the image forming unit. And a second conveying unit that conveys the recording paper to the outside of the apparatus. The first conveying unit presses the recording paper against the paper feeding roller, and feeds the recording paper to an image forming position by the image forming unit. In the image forming apparatus having the pressing roller that presses and the pressing roller holder that rotatably holds the pressing roller, the first transport unit is a downstream side of the pressing roller and an upstream side of the ink cartridge. Auxiliary rollers disposed opposite to each other and one end portion are coupled to the pressing roller holder, and the other end portion rotatably supports the auxiliary roller and urges the auxiliary roller toward the paper feed roller. And when the rear end of the recording paper comes off the pressing roller, the auxiliary roller applies a load to the second conveying means by pressing the recording paper in the direction of the paper feeding roller, and the trailing end of the recording paper. When printing the vicinity, it is possible to suppress a change in the conveyance speed of the recording paper and to prevent a decrease in print quality.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the width of the auxiliary roller is smaller than the width of the pressing roller.

  According to the first aspect of the present invention, when the trailing edge of the recording paper is removed from the pressing roller, the auxiliary roller applies a load to the second conveying unit by pressing the recording paper in the direction of the paper feeding roller. When printing the vicinity of the end of the recording paper, fluctuations in the conveyance speed of the recording paper are suppressed. As a result, it is possible to prevent a decrease in print quality. Further, since the auxiliary roller is attached to the pressing roller holder via the wire spring member, the auxiliary roller is pressed against the paper feed roller by the elastic force of the wire spring member. Accordingly, although the configuration is simple, the pressing force of the auxiliary roller can be set independently of the pressing force of the pressing roller, and fluctuations in the conveyance speed of the recording paper can be effectively suppressed. Moreover, since the width dimension of the auxiliary roller is smaller than the width dimension of the pressing roller, the mass of the auxiliary roller can be reduced, and the auxiliary roller and the pressing roller holder can be elastically elastic using a simple wire spring. Thus, it becomes possible to suppress the cost increase of the apparatus. Further, since the pressing roller holder is supported by the frame, the auxiliary roller can be accurately positioned, and the load applied to the second conveying means can be stabilized. Thereby, the fluctuation | variation of the conveyance speed of a recording paper can be suppressed further.

  According to the second aspect of the present invention, when the trailing edge of the recording paper is removed from the pressing roller, the auxiliary roller applies a load to the second conveying means by pressing the recording paper in the direction of the paper feeding roller. When printing the vicinity of the end of the recording paper, fluctuations in the conveyance speed of the recording paper are suppressed. As a result, it is possible to prevent a decrease in print quality. Further, since the auxiliary roller is attached to the pressing roller holder via the wire spring member, the auxiliary roller is pressed against the paper feed roller by the elastic force of the wire spring member. Therefore, although the configuration is simple, the pressing force of the auxiliary roller can be set independently of the pressing force of the pressing roller, and the fluctuation of the recording paper conveyance speed can be effectively suppressed.

  According to the invention of claim 3, since the width dimension of the auxiliary roller is formed smaller than the width dimension of the pressing roller, the mass of the auxiliary roller can be reduced, and the auxiliary roller can be assisted by using a simple wire spring member. It becomes possible to elastically couple the roller and the pressing roller holder, and it becomes possible to suppress the cost increase of the apparatus.

  An ink jet printer as an example of an image forming apparatus according to the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an ink jet printer. The ink jet printer 1 includes a paper feed tray 2 that holds a loaded recording paper P, a transport mechanism 3 that transports the recording paper P held in the paper feed tray 2, and a recording paper transported by the transport mechanism 3. An image forming unit (image forming unit) 4 that forms an image on P, a paper discharge tray 5 on which recording paper P on which an image is formed by the image forming unit 4 is stacked, a transport mechanism 3 and an image forming unit 4 are accommodated. And a control unit that controls the transport mechanism 3 and the image forming unit 4.

  In the transport mechanism 3, an image is formed by the first transport mechanism (first transport unit) 3 a that transports the recording paper P held on the paper feed tray 2 to an image forming position by the image forming unit 4 and the image forming unit 4. A second transport mechanism (second transport means) 3b for transporting the recording paper to the paper discharge tray 5, a feed motor (roller drive means) 30 for driving the first transport mechanism 3a and the second transport mechanism 3b, and the like. Composed.

  The image forming unit 4 reciprocates in the main scanning direction B (see FIG. 3) orthogonal to the conveyance direction A (sub-scanning direction) of the recording paper P while supporting the ink cartridge 40 filled with ink and the ink cartridge 40. A moving carrier 41, a carrier driving motor (carrier driving means) 42 for driving the carrier 41, and the like are configured. A print head 43 that ejects ink onto the recording paper P is provided on the lower surface of the ink cartridge 40. The carrier 41 is supported by a shaft 44 disposed in parallel to the main scanning direction so as to be reciprocally movable, and is driven by the carrier drive motor 42 to move. The output of the carrier drive motor 42 is transmitted to the carrier 41 via a belt or the like. An image is formed on the recording paper P by ejecting ink from the print head 43 in synchronization with the drive of the feed motor 30 and the carrier drive motor 42 under the control of the control unit.

  FIG. 2 shows a schematic configuration of the first transport mechanism 3a and the second transport mechanism 3b. The first transport mechanism 3 a is provided on the upstream side of the print head 43 and a pick roller 31 (see FIG. 1) that sends the recording paper P placed on the paper feed tray 2 to the inside of the apparatus main body. A paper feed roller 32 that feeds the recording paper P sent to the print head 43 side, a pressure roller 33 that presses the recording paper P against the paper feed roller 32, and a pressure roller holder that rotatably holds the pressure roller 33. 34, a holder urging spring 35 that urges the pressing roller holder 34, an auxiliary roller 36 disposed opposite to the paper feed roller 32, a wire spring member 37 that rotatably supports the auxiliary roller 36, and the like. It is configured. The pressing roller 33 and the holder biasing spring 35 are attached to both ends of the pressing roller holder 34. The pressing roller holder 34 is rotatably supported by the frame 50, and the holder biasing spring 35 biases the pressing roller holder 34 in the direction C in which the pressing roller 33 is pressed against the paper feed roller 32. The second transport mechanism 3b includes a paper discharge roller 38 that transports the recording paper P on which an image is formed to the paper discharge tray 5, a star wheel 39 that presses the recording paper P against the paper discharge roller 38, and the like. Yes.

  FIG. 3 shows the configuration of the paper feed roller 32 and its periphery. A pressure roller 33 and an auxiliary roller 36 are disposed on the peripheral surface of the paper feed roller 32 via a pressure roller holder 34. A plurality of pressing roller holders 34 are arranged in parallel to the paper feed roller 32 (in the main scanning direction B). A pair of pressing rollers 33 is attached to the tip of the pressing roller holder 34, and an auxiliary roller 36 is disposed between the pressing rollers 33. The width dimension of the auxiliary roller 36 is smaller than the width dimension of the pressing roller 33. The auxiliary roller 36 is attached to the pressing roller holder 34 via a wire spring member 37. The wire spring member 37 is formed, for example, by bending a metal wire having an appropriate elastic modulus, and its first end 37a is coupled to the pressing roller holder 34 and its second end 37b is the auxiliary roller 36. Is supported rotatably. In this embodiment, the pressing force of the pressing roller 33 is mainly determined by the spring constant of the holder biasing spring 35 and the length of the arm of the pressing roller holder 34, and the pressing force of the auxiliary roller 36 is mainly the wire spring member 37. Determined by the spring constant. Accordingly, the pressing force of the pressing roller 33 and the pressing force of the auxiliary roller 36 can be set independently.

  As described above, according to the ink jet printer 1 of the present embodiment, the auxiliary roller 36 presses the recording paper P in the direction of the paper feed roller 32 when the trailing edge of the recording paper P is detached from the pressing roller 33. Since a load is applied to the second transport mechanism 3b, fluctuations in the transport speed of the recording paper P are suppressed when the vicinity of the end portion of the recording paper P is printed. As a result, it is possible to prevent a decrease in print quality. Further, since the auxiliary roller 36 is attached to the pressing roller holder 34 via the wire spring member 37, the auxiliary roller 36 is pressed against the paper feed roller 32 by the elastic force of the wire spring member 37. Accordingly, although the configuration is simple, the pressing force of the auxiliary roller 36 can be set independently of the pressing force of the pressing roller 33, and the fluctuation in the conveyance speed of the recording paper P can be effectively suppressed. . Further, since the width dimension of the auxiliary roller 36 is smaller than the width dimension of the pressing roller 33, the mass of the auxiliary roller 36 can be reduced, and a simple wire spring member 37 is used. The pressure roller holder 34 can be elastically coupled, and the cost increase of the inkjet printer 1 can be suppressed. Further, since the pressing roller holder 34 is supported by the frame 50, the auxiliary roller 36 can be accurately positioned, and the load applied to the second transport mechanism 3b can be stabilized. Thereby, the fluctuation | variation of the conveyance speed of the recording paper P can be suppressed further.

  In addition, this invention is not restricted to the structure of the said embodiment, What is necessary is just the structure by which the auxiliary roller 36 is attached to the press roller holder 34 via the wire spring member 37 at least. A star wheel may be used instead of the auxiliary roller 36.

1 is a diagram illustrating a configuration of an ink jet printer that is an example of an image forming apparatus according to an embodiment of the present disclosure. FIG. FIG. 3 is a side view illustrating a schematic configuration of a first transport mechanism and a second transport mechanism of the printer. The perspective view which shows the structure of a paper feed roller and its peripheral part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printer 2 Paper feed tray 3 Conveyance mechanism 3a 1st conveyance mechanism (1st conveyance means)
3b Second transport mechanism (second transport means)
4 Image forming unit (image forming means)
DESCRIPTION OF SYMBOLS 5 Paper discharge tray 31 Pick roller 32 Paper feed roller 33 Press roller 34 Press roller holder 35 Holder biasing spring 36 Auxiliary roller 37 Wire spring member 38 Paper discharge roller 39 Star wheel 40 Ink cartridge 41 Carrier 43 Print head

Claims (3)

A paper feed tray for holding the loaded recording paper, a first transport means for transporting the recording paper held in the paper feed tray into the apparatus, and forming an image on the recording paper transported by the first transport means An image forming unit, a second conveying unit that conveys the recording paper on which an image is formed by the image forming unit to the outside of the apparatus, a paper discharge tray on which the recording paper conveyed by the second conveying unit is deposited, A frame for supporting each of the above parts,
The image forming means includes an ink cartridge filled with ink, a carrier mounted with the ink cartridge and reciprocating in a direction orthogonal to the conveyance direction of the recording paper, and carrier driving means for driving the carrier. Have
The first transport unit feeds the recording paper held in the paper feed tray into the apparatus, and feeds the recording paper fed by the pick roller to an image forming position by the image forming unit. A paper roller, roller driving means for driving the pick roller and paper feed roller, a pressure roller for pressing the recording paper against the paper feed roller, and the frame being rotatable while holding the pressure roller. An image forming apparatus having a pressing roller holder supported by the pressing roller holder and a holder urging unit that urges the pressing roller holder in a direction in which the pressing roller is pressed against the paper feeding roller.
A plurality of the pressing roller holders are arranged in parallel to the paper feed roller,
The first conveying means includes an auxiliary roller disposed on the downstream side of the pressure roller and upstream of the ink cartridge so as to face the paper feed roller, and a first end portion of the pressure roller on the pressure roller holder. A wire spring member that is coupled and rotatably supports the auxiliary roller at the second end, and biases the auxiliary roller in the direction of the paper feed roller;
A width dimension of the auxiliary roller is formed smaller than a width dimension of the pressing roller,
When the trailing edge of the recording paper is removed from the pressing roller, the auxiliary roller presses the recording paper in the direction of the paper feeding roller to apply a load on the second conveying means, and prints the vicinity of the end of the recording paper. In this case, an image forming apparatus is characterized in that a change in the conveyance speed of the recording paper can be suppressed to prevent a decrease in print quality. First conveying means for conveying recording paper into the apparatus, image forming means for forming an image on the recording paper conveyed by the first conveying means, and recording paper on which an image is formed by the image forming means Second conveying means for conveying to
The first transport unit includes a paper feed roller that transports the recording paper to an image forming position by the image forming unit, a pressure roller that presses the recording paper against the paper feed roller, and a pressure that rotatably holds the pressure roller. In an image forming apparatus having a roller holder,
The first conveying means is connected to the auxiliary roller disposed opposite to the paper feed roller on the downstream side of the pressure roller and upstream of the ink cartridge, and one end portion thereof coupled to the pressure roller holder. A wire spring member that rotatably supports the auxiliary roller at the other end and urges the auxiliary roller in the direction of the paper feed roller;
When the trailing edge of the recording paper is removed from the pressing roller, the auxiliary roller presses the recording paper in the direction of the paper feeding roller to apply a load on the second conveying means, and prints the vicinity of the end of the recording paper. In this case, an image forming apparatus is characterized in that a change in the conveyance speed of the recording paper can be suppressed to prevent a decrease in print quality.   The image forming apparatus according to claim 2, wherein a width dimension of the auxiliary roller is smaller than a width dimension of the pressing roller.

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