JP2008110530A - Conveying apparatus and image forming apparatus - Google Patents

Abstract

An object of the present invention is to minimize impact generated on a recording sheet, prevent occurrence of uneven printing, and obtain a high-quality printing result.
A guide member is disposed between a line head and a spur roller, and guides a recording sheet from the line head toward the spur roller. The guide member is arranged in a conveyance direction of the recording sheet. It has an inclined portion 28 a that leads the tip portion to the nip portion N of the spur roller 24, and the inclined portion 28 a is from above the end portion on the spur roller 24 side of the line head 11 and from the nip portion N of the spur roller 24. Also on the side of the line head 11, the shape is the gentlest slope toward the position where the protrusion 24 a of the spur roller 24 is not exposed.
[Selection] Figure 4

Description

  The present invention relates to a conveyance device and an image forming apparatus that can reduce impact when a recording medium is fed to a conveyance roller, and more specifically, to a specific medium that guides a recording medium toward the conveyance roller. The present invention relates to a technique provided with a shaped guide member.

  Conventionally, as an example of an image forming apparatus, a recording sheet (recording medium) is conveyed to the position of a print head, and ink (liquid) in an ink liquid chamber (liquid chamber) is generated by a heating resistor (energy generation element) of the print head. Inkjet printers are known in which an image is formed on a recording paper by ejecting ink as droplets from a nozzle. In particular, the line head type ink jet printer in which the nozzles for ejecting ink are arranged in a length corresponding to the width of the recording paper eliminates the need to move the print head in the main scanning direction by the line head. Therefore, vibration and noise can be reduced and the printing speed can be greatly increased.

  In order to improve the printing quality in such an ink jet printer, it is necessary to stably move the recording paper at a position away from the print head by a predetermined distance. Therefore, in general, the rotation speed of a plurality of conveyance rollers that convey the recording paper is controlled to convey the recording paper at a constant speed and a constant tension. Further, the impact when the recording paper enters the conveying roller is prevented from acting on the recording paper. In particular, in a line head type ink jet printer, printing is continuously performed without moving the print head, so that streaks and unevenness are likely to occur in the printing result, and it is necessary to transport the recording paper with higher accuracy.

Here, various techniques are known for reducing the rush shock of the recording paper to the conveyance roller and achieving stable movement of the recording paper while maintaining a predetermined distance from the print head (for example, (See Patent Document 1, Patent Document 2, and Patent Document 3).
JP-A-5-281635 JP 7-271126 A Japanese Patent Laid-Open No. 9-141954

  According to the technique described in Patent Document 1, recording paper can be smoothly conveyed by the first roller pair and the second roller pair, and the first roller pair and the second roller pair can be selectively opened and closed. Since the first roller pair or the second roller pair into which the recording paper enters is opened, the occurrence of an impact when the recording paper enters the first roller pair and the second roller pair is prevented. Can do.

  Further, according to the technique described in Patent Document 2, a conveyance guide plate that is curved so that the recording paper forms a gentle loop is formed between the upstream and downstream conveyance roller pairs, and the recording is performed in the middle of the conveyance guide plate. Since the auxiliary conveying roller pair that moves up and down according to the slack and tension of the paper is installed, not only can the recording paper of a size smaller than the distance between the upstream conveying roller pair and the downstream conveying roller pair be conveyed, The loop can absorb the speed difference between the upstream and downstream conveying roller pairs and the shock at the time of entering the conveying roller pair.

  Furthermore, according to the technique described in Patent Document 3, the recording sheet is pressed against the capstan by a pinch roller and conveyed by the frictional force generated by the rotation of the capstan, but during printing on the recording sheet, the capstan Since the pinch roller and the pinch roller are not pressure-bonded, it is possible to reduce fluctuations in the conveyance load when the recording paper enters between the capstan and the pinch roller.

As described above, various technologies that can reduce the rush shock of the recording sheet to the conveyance roller have been disclosed.
However, the techniques disclosed in Patent Documents 1 to 3 are structurally complicated and cause a cost increase. In particular, when the recording paper is warped due to the manufacturing process or the storage state, and the paper is fed with the leading edge of the recording paper warped upward as it is, the techniques disclosed in Patent Documents 1 to 3 are applied. However, stable conveyance is not always possible. That is, a shock caused by the collision between the leading edge of the warped recording sheet and the conveyance roller may cause conveyance unevenness and adversely affect the printing result.

  Further, in the line head type ink jet printer, the nozzles are arranged over a plurality of rows so as to correspond to the width of the recording paper, and in order to perform printing by continuously ejecting ink without stopping the conveyance of the recording paper, There is a problem that it is easily affected by warping of the recording paper. For this reason, the recording paper is placed on the conveyor belt and moved so that fluctuations in tension due to the speed difference between the plurality of conveying rollers and shocks when the recording paper enters the conveying rollers do not act on the recording paper. There is also a line head type ink jet printer which can be stably conveyed.

FIG. 7 is a partial side view showing an outline of such a conventional line head type ink jet printer 110 (image forming apparatus).
As shown in FIG. 7, the inkjet printer 110 is disposed so as to face the line head 111 and a line head 111 (print head) that forms an image on a recording paper P (recording medium). A spur roller 124 (which is disposed downstream of the line head 111 in the transport direction (arrow direction) of the recording paper P and is driven to rotate in contact with the transport belt 125. And a guide member 128 that guides the recording paper P toward the spur roller 124. The spur roller 124 has a protrusion 124 a for conveying the recording paper P, and the guide member 128 has an inclined portion 128 a (introduction portion) for guiding the recording paper P.

  In order to form an image on the recording paper P by the ink jet printer 110 shown in FIG. 7, Y (yellow), M (magenta), C from the nozzles of the line head 111 while continuously conveying the recording paper P in the direction of the arrow. Each ink of four colors (cyan) and K (black) is ejected. On the other hand, the recording paper P is moved by the transport belt 125 that maintains the driving speed constant. Therefore, the recording paper P is stably transported at a constant transport speed a, and each ink droplet lands on the recording paper P without any change in tension acting on the recording paper P, and there are no streaks or unevenness. A high-quality color image is formed.

  Here, as shown in FIG. 7A, if the recording paper P is not warped, the recording paper P conveyed at the conveying speed a in the direction of the arrow by the conveying belt 125 is printed while being printed. As shown to b), it sends out to the downstream of the line head 111. FIG. Then, the leading edge of the recording paper P is guided to the nip portion N where the spur roller 124 grips the recording paper P, and the recording paper P is sandwiched between the spur roller 124 and the transport belt 125 and discharged at the transport speed a. . Since the spur roller 124 is in point contact with the protruding portion 124a on the outer periphery and the surface of the printed recording paper P, the ink droplets that have landed on the recording paper P are not transferred or otherwise transferred.

  However, when the leading edge of the recording paper P is warped upward, the leading edge abuts on the inclined portion 128a of the guide member 128, and slides downward along the inclined portion 128a as the recording paper P is conveyed. It is guided to the nip portion N of the spur roller 124. When the leading edge of the recording paper P comes into contact with the inclined portion 128a of the guide member 128, the recording paper P may be shocked. In particular, in the line head type inkjet printer 110, when a shock is given during the conveyance of the recording paper P, the relative speed between the line head 111 and the recording paper P temporarily varies, and ink droplets are initially scheduled. Since the landing is shifted from the appropriate position, printing unevenness occurs at that location.

FIG. 8 is a side view showing the relationship between the recording paper P and the guide member 128 in the conventional line head type inkjet printer 110 shown in FIG.
As shown in FIG. 8, when the leading edge of the recording paper P is warped upward, the leading edge first contacts the inclined portion 128 a of the guide member 128. Then, after sliding down along the inclined portion 128a, the leading edge of the recording paper P reaches the nip portion N of the spur roller 124.

  Here, since the recording paper P is transported by the transport belt 125 at the transport speed a, the transport speed is also a. Therefore, when the leading end of the recording paper P collides with the inclined portion 128a of the fixed guide member 128, the brake is applied to the recording paper P that is placed on the transport belt 125 and moved at the transport speed a. And an impact occurs. The impact becomes stronger as the leading edge of the recording paper P warps and the collision angle with the inclined portion 128a of the guide member 128 increases. In the conventional line head type ink jet printer 110, the impact is increased in the recording paper P. Print irregularities (streaks).

  Therefore, the problem to be solved by the present invention is to enable the recording paper to be stably conveyed with a simple configuration, to minimize the impact when the leading edge of the recording paper collides with the guide member, and to prevent uneven printing. It is to prevent generation and obtain a high-quality printing result.

The present invention solves the above-described problems by the following means.
The invention according to claim 1, which is one of the present invention, is arranged on the downstream side in the transport direction of the recording medium from the print head for forming an image on the recording medium, and grips the recording medium. And a transport roller for transporting the recording medium on which an image is formed by the print head, and is disposed between the print head and the transport roller, and the recording medium is transferred from the print head to the transport roller. A guide member that guides the recording medium to the nip portion of the transport roller, and the guide member includes an introduction portion that guides a leading end portion in a conveyance direction of the recording medium. The portion is on the print head side from the nip portion of the transport roller from above the end portion on the transport roller side of the print head, and the outermost periphery of the transport roller is exposed. Characterized in that towards the free position is a shape which is most gentle slope.

  According to a fourth aspect of the present invention, which is another aspect of the present invention, a print head for forming an image on a recording medium, and a downstream side of the printing head in the conveyance direction of the recording medium. A nip portion for gripping the recording medium, and a transport roller for transporting the recording medium on which an image is formed by the print head; and a recording roller disposed between the print head and the transport roller. An image forming apparatus including a guide member that guides a medium from the print head toward the transport roller, wherein the guide roller is disposed in the transport direction of the recording medium in the nip portion of the recording medium. An introduction portion that guides a leading end portion, and the introduction portion is located above the end portion of the print head on the conveyance roller side, and is located above the nip portion of the conveyance roller. A head side, wherein the outermost periphery of the transfer roller has a shape which becomes the most gentle slope toward the position not exposed.

(Function)
According to the first and fourth aspects of the present invention, the guide member has an introduction portion that guides the leading end portion in the conveyance direction of the recording medium to the nip portion of the conveyance roller. From the upper side of the end portion on the side of the transport roller, the shape is such that the slope is the gentlest toward the print head side from the nip portion of the transport roller toward the position where the outermost periphery of the transport roller is not exposed.
For this reason, the leading end of the recording medium collides with the guide member at the introduction portion of the guide member at the most gentle inclination, and the collision angle between the introduction portion of the guide member and the recording medium is small. Then, the leading end of the recording medium is guided as far as possible to the nip portion by the introduction portion of the guide member, and the recording medium is conveyed without reducing the conveying speed.

According to the above invention, even if the leading end of the recording medium collides with the introduction portion of the guide member, the collision angle is small and the leading end of the recording medium is guided to the nip portion closest to the conveyance speed, and the recording medium Therefore, the impact generated on the recording medium is greatly reduced.
In particular, even when the leading end of the recording medium is warped upward, the recording medium can be guided to the nip portion of the transport roller without applying an impact.
Therefore, the occurrence of uneven printing can be prevented and a high quality printing result can be obtained.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the following embodiments, as an image forming apparatus of the present invention, a line head type ink jet printer 10 having a line head 11 (corresponding to a print head in the present invention) corresponding to the print width is taken as an example. The inkjet printer 10 is compatible with A4 size color, and the transport roller of the present invention is mounted on the inkjet printer 10.

  Further, in the following embodiment, the liquid ejected from the line head 11 is ink, the liquid chamber containing the ink is the ink liquid chamber 12, and a very small amount (for example, several picoliters) of ink ejected from the nozzle 18 is contained. Ink droplet. Furthermore, in the following embodiment, the heating resistor 13 is used as an energy generating element for discharging ink, and the heating resistor 13 also constitutes one surface (bottom wall portion) of the ink liquid chamber 12. ing.

  Since the ink jet printer 10 according to the following embodiment is compatible with A4 size color, the ink liquid chamber 12, the heating resistor 13, and the nozzle 18 of the line head 11 have an A4 size print width for each color. There are quite a few. Note that all the ink liquid chambers 12 containing the same color ink are communicated by a common ink flow path.

FIG. 1 is a partial perspective view showing a line head 11 in the ink jet printer 10 of the present embodiment.
As shown in FIG. 1, the line head 11 is configured by laminating a barrier layer 16 on a semiconductor substrate 15 that is a substrate member 14, and bonding a nozzle sheet 17 having nozzles 18 to the barrier layer 16. Yes. In FIG. 1, for convenience of explanation, the nozzle sheet 17 is shown in an exploded manner.

  Here, the semiconductor substrate 15 is made of silicon, glass, ceramics, or the like. The heating resistor 13 is deposited on one surface (the upper surface in FIG. 1) of the semiconductor substrate 15 by using a fine processing technique for manufacturing semiconductors and electronic devices (for example, a material that becomes the heating resistor 13). Is formed by a sputtering method using plasma, and is electrically connected to an external circuit through a conductor portion (not shown) formed on the semiconductor substrate 15 in the same manner.

  The barrier layer 16 is formed on the side of the heating resistor 13 in the semiconductor substrate 15, and is formed by patterning with a photosensitive resin in a portion excluding the peripheral portion of the heating resistor 13. That is, the barrier layer 16 is made of, for example, a photosensitive cyclized rubber resist or an exposure-curing dry film resist, and is laminated on the entire surface of the semiconductor substrate 15 on which the heating resistor 13 is formed, and then is exposed to photolithography. The process is formed by removing unnecessary portions.

  Furthermore, the nozzle sheet 17 is formed by, for example, an electroforming technique using nickel (Ni) so that a plurality of circular nozzles 18 are arranged. Then, the positions of the nozzles 18 on the nozzle sheet 17 and the positions of the heating resistors 13 on the semiconductor substrate 15 are precisely aligned, that is, the nozzles 18 are positioned precisely so as to face the heating resistors 13. And bonded onto the barrier layer 16.

  Therefore, each ink liquid chamber 12 is constituted by the semiconductor substrate 15, the barrier layer 16, and the nozzle sheet 17 so as to surround the heating resistor 13. That is, the semiconductor substrate 15 and the heating resistor 13 constitute the top wall of the ink liquid chamber 12, the barrier layer 16 constitutes three side walls of the ink liquid chamber 12, and the nozzle sheet 17 serves as the ink liquid chamber 12. Configure the bottom wall. In FIG. 1, the vertical relationship of the line head 11 is reversed so that the positional relationship between each heating resistor 13 and each nozzle 18 becomes clear.

  Each ink liquid chamber 12 has an opening region in the lower right direction in FIG. 1, and this opening region communicates with a common ink flow path. Therefore, the ink in the ink tank (not shown) passes through the common ink flow path and is supplied into each ink liquid chamber 12 from each opening region.

  In order to form an image on the recording paper P that is a recording medium using such a line head 11, the heating resistor 13 is selectively driven by a command from a control unit (not shown), and the ink Discharge energy is applied to the ink stored in the liquid chamber 12. Further, the recording paper P is continuously conveyed while maintaining a position away from the nozzle sheet 17 by a predetermined distance. Then, the ink is ejected as ink droplets from the nozzle 18 and landed at a predetermined position on the recording paper P to perform printing. In the present embodiment, such a line head 11 has a four-row configuration corresponding to each color of Y (yellow), M (magenta), C (cyan), and K (black). Printing is possible.

  That is, ink of each color is supplied from four color ink tanks (not shown) connected to the line heads 11 of each row, and the ink is stored in the ink liquid chamber 12, and then the heating resistance is based on the print data. If a pulse current is passed through the body 13 for a short time (for example, 1 to 3 μsec), the heating resistor 13 is rapidly heated, and bubbles due to film boiling are generated in the ink in the portion in contact with the heating resistor 13. Then, a predetermined volume of ink is pushed away by the expansion of the bubbles, and an ink having a volume equivalent to the pushed-off ink is ejected as ink droplets from the nozzle 18 and is continuously conveyed onto the recording paper P. Landing and printing in color.

FIG. 2 is a cross-sectional view showing the line head type inkjet printer 10 of the present embodiment.
As shown in FIG. 2, the inkjet printer 10 includes a paper feed tray 31 and a paper discharge tray 32 for the recording paper P, a transport device 20 for the recording paper P, and the like. Further, four detachable ink tanks 33 corresponding to the respective colors of Y (yellow), M (magenta), C (cyan), and K (black), and the ink tanks 33 are respectively connected to each color ink ( A line head 11 for discharging ink droplets) is mounted.

  In order to perform printing with the inkjet printer 10 shown in FIG. 2, first, the recording paper P is fed from the paper feed tray 31 as indicated by the arrow, and the recording paper P is fed into the transport device 20. Subsequently, the recording paper P is continuously and precisely conveyed by the conveying device 20 below the line head 11 while maintaining a predetermined distance. At the same time, ink of four colors (ink droplets) is appropriately ejected from the line head 11 based on the printing information, and characters, images, and the like are printed on the recording paper P in color. The printed recording paper P is discharged onto the paper discharge tray 32.

FIG. 3 is a cross-sectional view showing the conveyance device 20 mounted on the inkjet printer 10 of the present embodiment shown in FIG.
As shown in FIG. 3, the conveying device 20 includes a driving roller 21, a pinch roller 22, a driven roller 23, a spur roller 24 (corresponding to the conveying roller in the present invention), a conveying belt 25, a platen 26, a retainer sheet 27, And a guide member 28.

  In the transport device 20 shown in FIG. 3, a driving roller 21 and a pinch roller 22 are disposed upstream of the line head 11 in the transport direction (arrow direction) of the recording paper P, and a driven roller 23 and a spur roller on the downstream side thereof. 24 are arranged. An endless conveyance belt 25 is stretched between the driving roller 21 and the driven roller 23 so that the recording paper P can be placed on the conveyance belt 25 and conveyed. Yes. In addition, the pinch roller 22 contacts and rotates on the upstream side of the line head 11 with respect to the conveyor belt 25, and the spur roller 24 contacts and rotates on the downstream side.

  Here, the drive roller 21 drives the conveyor belt 25, and the rotation speed is controlled to be constant by a control unit (not shown). On the other hand, the conveyor belt 25 is composed of a timing belt which is a transmission belt with teeth (flat teeth, helical teeth, or mountain teeth), and moves in a state where there is no slip and noise. For this reason, the driving roller 21 causes the conveyor belt 25 to rotate gently at a constant speed with the driven roller 23.

  A platen 26 is arranged so as to face the line head 11. The platen 26 supports the recording paper P conveyed toward the line head 11, and has a plurality of ribs 26 a arranged at regular intervals, and each rib 26 a serves as a reference surface of the recording paper P. Forming. That is, in the print area where the four color inks (ink droplets) are respectively ejected from the line head 11, the recording paper P moves on the ribs 26a which are reference surfaces.

  Such movement of the recording paper P is performed by the pinch roller 22, the spur roller 24, and the conveyance belt 25. That is, the pinch roller 22 feeds the recording paper P fed from the paper feed tray 31 (see FIG. 2) and placed on the transport belt 25. Therefore, the recording paper P sandwiched between the pinch roller 22 is conveyed toward the ribs 26a (printing area) of the platen 26 by the rotation of the conveying belt 25.

  Further, the line head 11 facing the platen 26 has a nozzle 18 (see FIG. 1) at a predetermined pitch and the entire length in the sheet width direction of the recording sheet P of the maximum size (A4 size in this embodiment) that can be printed. They are arranged in a straight line. Therefore, when printing, ink droplets can be continuously ejected onto the recording paper P moving at a constant speed by the transport belt 25 without moving the line head 11 in the paper width direction. It is possible to print on.

  Then, the printing is executed and the recording paper P sent out to the downstream side of the platen 26 is now sandwiched between the spur roller 24. The spur roller 24 has a plurality of protrusions 24a that contact the image forming surface of the recording paper P on its outer periphery, and plays a role of preventing deterioration in image quality. That is, the spur roller 24 is provided with a protrusion 24a over the entire circumference of the outer peripheral edge, and the protrusion 24a and the surface of the printed recording paper P are in point contact with each other, thereby landing on the recording paper P. The recording paper P can be conveyed without the transferred ink droplets being transferred elsewhere. Therefore, the recording paper P sandwiched between the spur roller 24 by the rotation of the transport belt 25 is transported to the paper discharge tray 32 (see FIG. 2) while maintaining the print quality.

  3 has a configuration in which the pinch roller 22 and the spur roller 24 are driven to rotate while being pressed against the transport belt 25, and the pinch roller 22 and the spur roller 24 are driven by themselves. I don't have a source. Therefore, the recording paper P is transported at a constant speed according to the constant rotation speed of the transport belt 25 by the driving roller 21, and when the recording paper P enters or leaves the pinch roller 22 or the spur roller 24. However, basically no speed difference is generated, and conveyance unevenness can be suppressed.

  In addition, a retainer sheet 27 is disposed in the transport device 20 illustrated in FIG. 3 in order to prevent the recording paper P from being jammed and to further improve the landing accuracy of the ink droplets ejected from the line head 11. The retainer sheet 27 is disposed upstream of the line head 11 in the conveyance direction (arrow direction) of the recording paper P, and presses the recording paper P toward the platen 26 over the entire width of the recording paper P. It plays a role.

  Here, the retainer sheet 27 is a plate-like member formed of a sheet-like resin material having flexibility, and supports the upstream side in the conveyance direction of the recording paper P and the downstream side extends toward the line head 11. It is a pressing contact portion 27a. As shown in FIG. 3, the pressing contact portion 27 a extends to a position immediately before a portion (the portion of the nozzle 18 shown in FIG. 1) from which the ink (ink droplet) is ejected from the line head 11. Even when the recording paper P is conveyed in a state of being warped upward, the recording paper P is prevented from being lifted from the platen 26 and the distance from the line head 11 is kept constant. High quality printing results are obtained.

  However, when the leading edge of the recording paper P passes the pressing contact portion 27a of the retainer sheet 27, the pressing by the retainer sheet 27 does not work, and the leading edge of the recording paper P warps upward again. When the leading edge of the recording paper P reaches the guide member 28 in this state, it collides with the inclined portion 28a (corresponding to the introduction portion in the present invention) of the guide member 28. Therefore, as in the case of the guide member 128 in the conventional line head type ink jet printer 110 shown in FIGS. 7 and 8, if the collision angle between the leading edge of the recording paper P and the inclined portion 128a is large, the impact is recorded during printing. Propagation in the conveyance direction of the paper P causes an instantaneous slowdown of the conveyance speed, and causes uneven printing.

In this case, if the recording paper P without warping is used, the impact is small, the conveyance unevenness is suppressed, and the print quality is not deteriorated.
However, it is normal for the recording paper P to warp due to the manufacturing process and storage state of the recording paper P. In particular, a glossy photographic paper or the like warps due to paper quality problems. Many are seen. In other words, it is ideal that a completely flat recording sheet P is fed, but in reality, a recording sheet P without warping is rare. Further, since the recording paper P is once pressed against the conveying belt 25 by the pressure contact force of the pinch roller 22, even if the recording paper P is warped, the pinch roller 22 can correct the warp to some extent. There are also limits.
Therefore, the transport device 20 in the ink jet printer 10 of the present embodiment uses the guide member 28 that can reduce the occurrence of impact even when the recording paper P having warpage is transported.

FIG. 4 is a side view showing the conveying device 20 mounted on the inkjet printer 10 of the present embodiment shown in FIG.
As shown in FIG. 4A, a guide member 28 and a spur roller 24 are arranged downstream of the line head 11 in the conveyance direction (right direction in FIG. 4) of the recording paper P (not shown). ing. The spur roller 24 is driven to rotate while being in pressure contact with the conveying belt 25, and has a plurality of protrusions 24 a that contact the image forming surface of the recording paper P on the outer periphery. Further, the guide member 28 has an inclined portion 28 a that guides the leading end of the recording paper P to the spur roller 24.

  Here, the guide member 28 is formed by resin molding such as ABS (acrylonitrile butadiene styrene) or POM (polyacetal) integrally with the support member 29 that supports the rotating shaft 24b of the spur roller 24. The rotating shaft 24 b of the spur roller 24 is supported by the bearing portion 29 a of the support member 29. That is, the support member 29 is provided with a plurality of bearing portions 29a that support the rotation shaft 24b of the spur roller 24, and the guide member 28 is integrated so as to sandwich the spur roller 24 incorporated therein. Yes.

  4B, the inclined portion 28a of the guide member 28 has a nip portion N (protrusion of the spur roller 24) of the spur roller 24 from above the end portion of the line head 11 on the spur roller 24 side. The portion 24a is inclined more gently toward the position closer to the line head 11 than the portion of the recording paper P that is being conveyed) toward the position where the outermost periphery of the spur roller 24 (the tip of the protruding portion 24a) is not exposed. It has a shape. And it is connected with the horizontal part 28b before the nip part N by the curve.

  The inclined portion 28a of the guide member 28 will be described in more detail. The interval between the side surface of the line head 11 and the side surface of the guide member 28 is 0.5 mm as a practical minimum interval. 28 a is connected to the side surface of the guide member 28 by a curve, and starts from the lower surface of the line head 11 by 0.5 mm. Therefore, the starting point of the inclined portion 28a is above the lower surface of the line head 11, and the inclined portion 28a is at the position where the inclination is the gentlest.

  Further, the distance between the horizontal portion 28b of the guide member 28 and the upper surface of the conveying belt 25 is the thickness of the recording paper P assumed to be used + α (0.3 mm), and the inclined portion 28a has the guide member 28. The end point is determined so as to pass through a position 0.2 to 0.5 mm away from the protrusion 24a of the spur roller 24. Therefore, the end point of the inclined portion 28a is a position where the protruding portion 24a of the spur roller 24 is not exposed and is as close as possible to the nip portion N, and the inclined portion 28a has the most gentle inclination.

As described above, the guide member 28 has the inclined portion 28a and the horizontal portion 28b that guide the leading end portion in the conveyance direction of the recording paper P to the nip portion N where the spur roller 24 grasps the recording paper P, and the inclined portion 28a. Is the most gentle slope between the line head 11 and the spur roller 24 so as not to expose the protrusion 24a of the spur roller 24. That is, the inclined portion 28a of the recording paper P is formed by making the inclined portion 28a where the leading end of the recording paper P collides with the guide member 28 has the gentlest inclination and bringing the end point of the inclined portion 28a as close as possible to the nip portion N. The collision angle with respect to is reduced, and the conveyance speed of the recording paper P is not lowered. Therefore, the recording paper P can be reliably conveyed while minimizing shock caused by the leading edge of the recording paper P colliding with the inclined portion 28a of the guide member 28.
Then, next, such an effect | action by the inclination part 28a of the guide member 28 is demonstrated in detail.

FIG. 5 is a side view showing the conveyance of the recording paper P by the conveyance device 20 mounted on the inkjet printer 10 of the present embodiment shown in FIG.
FIG. 6 is a side view showing the relationship between the recording paper P, the guide member 28 and the spur roller 24 in the transport device 20 mounted on the ink jet printer 10 of the present embodiment shown in FIG.
In the transport device 20 shown in FIGS. 5 and 6, a guide member 28 and a spur roller 24 are disposed on the downstream side of the line head 11 in the transport direction of the recording paper P.

  Here, FIG. 5A shows a state in which the recording paper P whose leading end is warped upward is conveyed from the upstream side of the guide member 28 and the spur roller 24 from the left to the right as indicated by arrows. That is, as shown in FIG. 5A, the recording paper P is printed by the line head 11, and then the tip of the recording paper P abuts on the inclined portion 28a of the guide member 28, and the arrow P extends along the inclined portion 28a. To be guided.

  FIG. 5B shows a state in which the recording paper P is conveyed and the leading end thereof is guided by the inclined portion 28 a of the guide member 28. That is, the leading edge of the recording paper P slides downward on the inclined portion 28a of the guide member 28 as shown in FIG. Here, the inclined portion 28a is shaped so as to be the gradual inclination from the upper side of the end of the line head 11 on the spur roller 24 side toward the position where the protruding portion 24a of the spur roller 24 is not exposed. Therefore, the collision angle between the inclined portion 28a of the guide member 28 and the leading edge of the recording paper P is reduced. Since the conveyance speed of the recording paper P hardly changes, the recording paper P is fed between the spur roller 24 and the conveyance belt 25 without applying an impact.

  Next, FIG. 6A shows a state where the leading edge of the recording paper P is fed between the spur roller 24 and the conveyance belt 25. That is, as shown in FIG. 6A, the recording paper P is smoothly guided as indicated by an arrow without any impact by the inclined portion 28a of the guide member 28 with almost no change in the conveying speed. When the leading edge of the recording paper P reaches the lowermost portion of the inclined portion 28a, the recording paper P is then continuously conveyed through the horizontal portion 28b connected to the inclined portion 28a by a curve, and is supplied by the line head 11. Printing is executed. Note that the recording paper P does not collide with the protruding portion 24a of the spur roller 24 until the leading edge of the recording paper P reaches the lowermost portion of the inclined portion 28a.

  Then, as shown in FIG. 6A, the leading end of the recording paper P collides with the protruding portion 24 a of the spur roller 24 near the nip portion N. Here, the protrusion 24a of the spur roller 24 with which the leading edge of the recording paper P collides is an inclined side L2 formed at a small angle with respect to the conveyance direction (arrow direction) of the recording paper P. Therefore, even if the leading edge of the recording paper P collides with the protrusion 24a before the nip N, the leading edge slides down the inclined side L2, and the conveyance speed (the horizontal component of the rotational peripheral speed a) by the spur roller 24 is recorded. Nipping is performed at substantially the same point as the conveyance speed a of the paper P. As a result, the impact caused by the leading edge of the recording paper P colliding with the protrusion 24a of the spur roller 24 is minimized, and the recording paper P is moved to the spur roller 24 in a state where the conveyance speed a of the recording paper P hardly changes. Can enter.

  FIG. 6B shows a state in which the recording paper P has entered the spur roller 24. That is, the leading edge of the recording paper P is guided to the nip portion N of the spur roller 24, and the recording paper P is sandwiched between the spur roller 24 and the conveyance belt 25 and discharged. Since the spur roller 24 is in point contact with the acute protrusion 24a and the surface of the printed recording paper P, the ink droplets that have landed on the recording paper P by the line head 11 are not transferred. Absent.

Thus, even if the leading edge of the recording paper P is warped, it collides with the inclined portion 28a of the guide member 28 and the protrusion 24a of the spur roller 24 at a small angle. The impact applied to the recording paper P and the fluctuation of the transport speed a at the time of collision are greatly reduced, and transport unevenness during printing is prevented.
Therefore, regardless of whether or not the recording paper P is warped, the recording paper P does not experience a slow conveyance speed a and can be stably conveyed, and high-quality printing without streaks or unevenness is always achieved. The result can be obtained.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to embodiment mentioned above, For example, the following various deformation | transformation is possible.
(1) In this embodiment, the guide member 28 and the support member 29 are integrally formed by resin molding such as ABS (acrylonitrile butadiene styrene) or POM (polyacetal). Both may be separated. Further, the molding resin is not limited at all, and may be a metal material.

  (2) In the present embodiment, the line head type ink jet printer 10 including the line head 11 corresponding to the print width is taken as an example of the image forming apparatus. However, the image forming apparatus is not limited to the line head type and is arranged in the width direction of the recording paper P. A serial head system in which printing is performed by moving it may be used. The present invention can also be applied to a thermal printer, various types of copying machines, and the like.

It is a fragmentary perspective view which shows the line head in the inkjet printer of this embodiment. 1 is a cross-sectional view illustrating a line head type inkjet printer according to an embodiment. It is sectional drawing which shows the conveying apparatus mounted in the inkjet printer of this embodiment. It is a side view which shows the conveying apparatus mounted in the inkjet printer of this embodiment. It is a side view showing conveyance of a recording paper by a conveyance device mounted in the ink jet printer of this embodiment. It is a side view which shows the relationship between the recording paper in the conveyance apparatus mounted in the inkjet printer of this embodiment, a guide member, and a spur roller. It is a partial side view showing an outline of a conventional line head type ink jet printer. FIG. 10 is a side view showing a relationship between a recording sheet and a guide member in a conventional line head type ink jet printer.

Explanation of symbols

10 Inkjet printer (image forming device)
11 Line head (print head)
12 Ink liquid chamber (liquid chamber)
13 Heating resistor (energy generating element)
18 Nozzle 20 Conveying Device 21 Driving Roller 22 Pinch Roller 23 Followed Roller 24 Spur Roller (Conveying Roller)
24a Protruding part 24b Rotating shaft 25 Conveying belt 26 Platen 27 Retainer sheet 28 Guide member 28a Inclined part (introducing part)
28b Horizontal portion 29 Support member 29a Bearing portion P Recording paper (recording medium)

Claims (6)

A recording medium that is disposed downstream of the print head that forms an image on the recording medium in the conveyance direction of the recording medium, has a nip portion that grips the recording medium, and on which the image is formed by the print head A transport roller for transporting
A guide device that is disposed between the print head and the transport roller and guides a recording medium from the print head toward the transport roller;
The guide member has an introduction portion that guides a leading end portion in the conveyance direction of the recording medium to the nip portion of the conveyance roller.
The introduction portion is from above the end portion of the print head on the conveyance roller side, toward the print head side from the nip portion of the conveyance roller, and toward a position where the outermost periphery of the conveyance roller is not exposed. A conveying device characterized by a shape having the gentlest inclination. In the conveyance apparatus of Claim 1,
The conveyance device, wherein the guide member is formed integrally with a support member that supports a rotation shaft of the conveyance roller. In the conveyance apparatus of Claim 1,
The transport roller has a plurality of protrusions on the outer periphery thereof that contact the image forming surface of the recording medium,
The conveyance device, wherein the introduction portion of the guide member has a shape toward a position where the protrusion of the conveyance roller is not exposed. A print head for forming an image on a recording medium;
A transport roller that is disposed downstream of the print head in the transport direction of the recording medium, has a nip portion that grips the recording medium, and transports the recording medium on which an image is formed by the print head;
An image forming apparatus comprising: a guide member disposed between the print head and the transport roller and guiding a recording medium from the print head toward the transport roller;
The guide member has an introduction portion that guides a leading end portion in the conveyance direction of the recording medium to the nip portion of the conveyance roller.
The introduction portion is from above the end portion of the print head on the conveyance roller side, toward the print head side from the nip portion of the conveyance roller, and toward a position where the outermost periphery of the conveyance roller is not exposed. An image forming apparatus characterized by having a shape with the gentlest inclination. The image forming apparatus according to claim 4.
The image forming apparatus, wherein the print head ejects liquid in a liquid chamber from a nozzle by an energy generating element to form an image on a recording medium. The image forming apparatus according to claim 4.
The image forming apparatus, wherein the print head forms an image on a recording medium continuously conveyed.

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