JP2013059998A - Image forming apparatus - Google Patents

Abstract

An object of the present invention is to prevent paper jamming around a droplet discharge head with an inexpensive configuration without using a complicated device, and to keep the height of the device low.
A liquid discharge head that discharges liquid droplets onto a recording medium and a carriage that moves the liquid discharge head in the main scanning direction are disposed with the liquid droplet discharge direction of the liquid discharge head facing upward. In an image forming apparatus that discharges droplets toward a sheet 12 conveyed above the liquid discharge head 7, the sheet 12 disposed above is supported from below when the carriage 3 moves in the main scanning direction. A recording medium support having a belt member 210 that prevents the liquid discharging head 7 from coming into contact with the liquid discharge head 7 is provided.
[Selection] Figure 4

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus that forms an image on a recording medium that is conveyed above the liquid ejection head with ink droplets from a liquid ejection head that ejects ink droplets upward.

  As an image forming apparatus, there is an ink jet image forming apparatus that includes a liquid discharge head that discharges ink droplets as droplets, and discharges ink droplets from the liquid discharge head onto a recording medium such as paper to form an image. The liquid discharge head of such an image forming apparatus includes a plurality of nozzles corresponding to the respective colors for discharging, for example, yellow, cyan, magenta, and black color inks. In addition, the liquid discharge head includes an individual liquid chamber and an individual flow path provided corresponding to each nozzle, a pressure generating unit that pressurizes ink in each individual liquid chamber, a common liquid chamber that supplies ink to each individual liquid chamber, and A common flow path is provided.

  In the liquid discharge head, pressure is applied to the ink by a pressure generating means arranged in the individual liquid chamber, and the ink packed inside is discharged as an ink droplet from the discharge port (nozzle). As the pressure generating means, a piezoelectric actuator, a thermal actuator, an electrostatic actuator, or the like is used.

  Each individual liquid chamber is supplied with ink from the common liquid chamber via the ink supply path, and the ink supplied from the outside to the common liquid chamber via the ink supply port is separated from the common liquid chamber. Distribute to chamber and nozzle.

  In this liquid discharge head, nozzles are clogged even if minute foreign matters or bubbles are mixed, and discharge failure occurs. As a means for discharging bubbles staying in the liquid discharge head, for example, a mechanism that presses a cap formed of an elastic body and sucks the inside of the liquid discharge head is employed. Such bubbles are caused by air leakage in the ink supply path, backflow of air from the nozzles, precipitation of air dissolved in the ink, and generation of bubbles in the liquid ejection head (common liquid chamber, individual liquid chamber). It occurs more.

  Here, as an ink jet image forming apparatus, there is an apparatus having a liquid discharge head with a discharge port surface (nozzle surface) facing downward. In this type of image forming apparatus, the liquid ejection head is mounted on a scanning carriage that can be driven in the main scanning direction, and forms an image on a sheet conveyed under the carriage. As a sheet conveying apparatus for conveying a sheet, a roller pair disposed upstream and downstream of the conveyance path with the sheet interposed therebetween, an electrostatic adsorption belt, an air suction apparatus, or the like is employed.

  Patent Document 1 and Patent Document 2 disclose an image forming apparatus in which nozzles of a liquid discharge head are arranged facing downward.

  Further, the image forming apparatus according to Patent Document 1 includes a jam prevention belt for the purpose of preventing carriage jamming due to paper floating, folding, cockling, and the like, and this belt also serves as a carriage driving belt. Yes.

  Further, the image forming apparatus according to Patent Document 2 discloses an apparatus in which a belt is formed of a flexible film and the film is set along a carriage so that the film does not move in the horizontal direction when the carriage is scanned. ing.

  As described above, in an image forming apparatus provided with a liquid discharge head, it is necessary to discharge bubbles in order to eliminate the adverse effects of bubbles on ink discharge. In a liquid discharge head that discharges ink droplets downward, the liquid chamber is located above the nozzle, so that bubbles accumulate on the upper surface of the liquid chamber by buoyancy. For this reason, bubbles may not be easily sucked and discharged, and a large amount of ink must be discarded to discharge the bubbles.

  In view of this, an image forming apparatus that ejects ink droplets upward from nozzles has been proposed in order to improve bubble discharge performance in the liquid ejection head. In this type of image forming apparatus, bubbles in the nozzle rise by buoyancy and accumulate near the nozzle outlet, so that the amount of ink consumed for discharging the bubble may be small.

  Patent Documents 3 and 4 disclose an image forming apparatus including a liquid discharge head that discharges ink droplets upward. Patent Document 3 discloses a configuration in which the idle discharge receiving surface forms a slope toward the discharge port for the purpose of preventing ink dripping from idle discharge. Further, Patent Document 4 discloses a heater provided with a heater for evaporating ink in an empty discharge receiver for the purpose of preventing ink dripping from empty discharge.

  Here, in the image forming apparatus in which the nozzles of the liquid discharge head are arranged upward, the carriage travels below the paper, so that the paper needs to be stably arranged above the liquid discharge head. Therefore, a suction device that sucks the paper upward is employed. If such a suction device is not provided, the paper will be caught by the liquid discharge head when the paper moves downward, and a paper jam (jam) will occur. FIG. 22 is a schematic diagram illustrating a state in which the sheet is in contact with the liquid ejection head device.

  In the liquid discharge head 310, a nozzle 320 is arranged upward. The liquid ejection head 310 is held by the carriage 330, and the carriage 330 is driven along the main scanning direction (arrow A in the figure) along the guide rod 340. The sheet S is guided by the upstream-side transport roller 350 and the downstream-side transport roller 360, and is transported in the sub-scanning direction above the liquid discharge head 310. Here, when the sheet S is conveyed by the upstream-side conveyance roller 350, the leading end Sa hangs down due to its own weight or the like and comes into contact with the carriage 330, as shown in FIG. 22B. Become.

  As a suction device for preventing the paper from sagging, there is one that uses electrostatic suction force. FIG. 23 is a cross-sectional view showing a liquid discharge head in a conventional image forming apparatus. In this example, an electrostatic belt device 370 is disposed as a suction device, and the sheet S is conveyed upward (arrow B in FIG. 23) and conveyed in the sub-scanning direction (arrow C in the drawing). The electrostatic belt device 370 charges the belt member 371 running around the two rollers 372 and 373 to a predetermined voltage by the charging roller 374, and sucks the sheet to the belt member 371.

  In this example, since the sheet S is attracted to the upper side by the electrostatic belt device 370, it can be prevented that the sheet S hangs down and contacts the carriage to cause a jam. As the suction device, an air suction device or the like is used instead of the charging suction belt.

  However, in the above-described suction device, the adsorption force may decrease due to long-term use. In addition, when a configuration for sucking air is employed as a suction device, some malfunction may occur, such as a reduction in suction force due to clogging, and in such a case, jamming cannot be prevented.

  Furthermore, when using a suction device, it is expensive to install the suction device. In addition, it is necessary to control this suction device, which complicates the control of the image forming apparatus. Then, the suction device must be arranged in the space above the sheet, and there is a problem that the height of the image forming apparatus increases and the cost increases.

  The present invention has been made in view of the above points, and can prevent paper jamming around the liquid discharge head with a low-cost configuration without using a complicated device and keep the height of the device low. It is an object of the present invention to provide an image forming apparatus that can be used.

  An image forming apparatus according to the present invention includes a liquid ejection head that includes nozzles and ejects liquid droplets onto a recording medium, and the liquid ejection head mounted on the liquid ejection head in a main scanning direction orthogonal to the conveyance direction of the recording medium. A carriage that moves, wherein the nozzle of the liquid ejection head is disposed upward and the droplets are ejected toward the recording medium that is transported above the liquid ejection head. A recording medium support that supports the recording medium disposed above when moving in the main scanning direction from below and prevents the recording medium from dripping downward and coming into contact with the liquid ejection head. Features.

  According to the present invention, it is possible to reduce the manufacturing cost and reduce the height of the image forming apparatus and prevent the paper from being jammed by the liquid discharge head.

1 is a schematic diagram illustrating a cross section of an image forming apparatus according to Embodiment 1. FIG. 2 is a bottom view of the image forming apparatus. FIG. FIG. 3 is a perspective view showing a recording medium support of the image forming apparatus. FIG. 4 is a cross-sectional view corresponding to the line CC in FIG. 3. 3A and 3B show a recording medium support of an image forming apparatus according to Embodiment 2, in which FIG. 5A is a perspective view and FIG. 5B is a cross-sectional view corresponding to the line EE in FIG. 4A and 4B show a recording medium support of an image forming apparatus according to Embodiment 3, wherein FIG. 5A is a perspective view, and FIG. 5B is a cross-sectional view corresponding to the line FF in FIG. 6 is a perspective view showing a recording medium support of an image forming apparatus according to Embodiment 4. FIG. 8A and 8B illustrate a recording medium support of the image forming apparatus illustrated in FIG. 7, in which FIG. 7A is an exploded perspective view, and FIG. 7B is a cross-sectional view corresponding to line GG in FIG. 7A and 7B illustrate a recording medium support of an image forming apparatus according to Embodiment 5, in which FIG. 5A is a perspective view and FIG. 5B is a cross-sectional view corresponding to line HH in FIG. FIG. 10 is a perspective view illustrating a recording medium support of an image forming apparatus according to a sixth embodiment. It is sectional drawing corresponded in the JJ line | wire in FIG. FIG. 3 is a schematic diagram illustrating a drawing method of an image forming apparatus equipped with a recording medium support according to an embodiment of the present invention. 9A and 9B show a recording medium support of an image forming apparatus according to Embodiment 7, in which FIG. 9A is a perspective view and FIG. 9B is a cross-sectional view corresponding to the line KK in FIG. 9A and 9B show a recording medium support of an image forming apparatus according to an eighth embodiment, where FIG. 9A is a perspective view and FIG. 9B is an end view taken along line LL in FIG. It is a schematic diagram explaining the example of a shape of a caterpillar-shaped recording medium support body. FIG. 10 is a perspective view showing a recording medium support of an image forming apparatus according to Embodiment 9. FIG. 17 shows an example of attachment of the caterpillar recording medium support of FIG. 16 to a carriage, (a) is an exploded perspective view, and (b) is a cross-sectional view corresponding to line MM in (a). . FIG. 10 shows a recording medium support of an image forming apparatus according to Embodiment 10, wherein (a) is a perspective view and (b) is an end view taken along line NN in (a). FIG. 12 is a perspective view showing a recording medium support of an image forming apparatus according to Embodiment 11. FIG. 14 is a diagram illustrating a recording medium support of an image forming apparatus according to Embodiment 12, where (a) is a cross-sectional view and (b) is a perspective view. It is a figure which shows the recording medium support body of the image forming apparatus which concerns on Embodiment 13, (a) is a perspective view, (b) is an expanded sectional view equivalent to the PP line in (a). It is a perspective view showing a liquid discharge head in a conventional image forming apparatus. It is a schematic diagram showing a suction device in a conventional image forming apparatus.

  An image forming apparatus according to an embodiment for carrying out the present invention will be described.

<Embodiment 1>
Hereinafter, an image forming apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. The image forming apparatus according to the present embodiment is an ink jet recording apparatus that ejects ink droplets upward.

  First, the basic structure of the image forming apparatus 100 according to the first embodiment will be described. FIG. 1 is a schematic diagram illustrating a cross section of the image forming apparatus according to the first embodiment, and FIG. 2 is a bottom view of the image forming apparatus. The image forming apparatus 100 includes an image forming unit 110 that forms an image on a sheet 12, a paper feeding unit 120 that stores the sheet 12, a transport unit 130 that transports the sheet 12 to the image forming unit 110, and an imaged sheet. 12 is discharged.

  The image forming unit 110 includes liquid discharge heads 7Y, 7C, 7M, and 7Bk that discharge yellow (Y), cyan (C), magenta (M), and black (Bk) ink as ink droplets, and a liquid discharge head 7Y. , 7C, 7M, and 7Bk. The image forming unit 110 includes a main scanning motor 4 and drives the carriage 3 in the main scanning direction (see FIG. 2 and in the X direction in FIG. 3 and the like).

  Guide rods 8 spanning the left and right side plates 101 (not shown in FIG. 1; see FIG. 3) hold the carriage 3 so that it can move in the main scanning direction. In addition, the image forming unit 110 includes a conveyance guide 21 that holds the loaded paper 12 from above. Further, the image forming unit 110 supports the sheet 12 disposed above when the carriage 3 moves in the main scanning direction from below, and prevents the sheet 12 from dripping downward and coming into contact with the liquid ejection head 7. The recording medium support 200 is provided. Hereinafter, when the liquid discharge heads 7Y, 7C, 7M, and 7Bk are described without distinguishing colors, they are simply referred to as the liquid discharge head 7.

  The main scanning motor 4 drives the timing belt 5 that spans between the driving pulley 6A and the driven pulley 6B. Thus, the main scanning motor 4 moves and scans the carriage 3 attached to the timing belt 5 in a direction penetrating the paper surface (main scanning direction). Guide bushes (bearings) 3 a and 3 a are arranged between the carriage 3 and the guide rod 8.

  In the carriage 3, the ink discharge ports of the four liquid discharge heads 7Y, 7C, 7M, and 7Bk are arranged side by side in a direction intersecting the main scanning direction, and the ink droplet discharge direction is set vertically upward.

  The liquid ejection head 7 can use a thermal actuator that utilizes liquid film boiling using a piezoelectric actuator such as a piezoelectric element or an electrothermal transducer such as a heating resistor as energy generating means for ejecting ink. . Similarly, the liquid discharge head 7 can be a shape memory alloy actuator using a metal phase change due to a temperature change, an electrostatic actuator using an electrostatic force, or the like.

  The carriage 3 is equipped with a liquid discharge head tank (not shown) for each color for supplying each color ink to each liquid discharge head 7Y, 7C, 7M, 7Bk. The liquid discharge head tank is replenished and supplied with ink from a main tank (ink cartridge) (not shown) via an ink supply tube.

  In addition to the liquid discharge head 7 that discharges ink droplets, a liquid discharge head that discharges a fixing processing liquid (fixing ink) that reacts with the ink to improve the fixability of the ink can be provided.

  The nozzles of the liquid discharge head 7 are likely to be clogged with nozzles due to drying. For this reason, when the carriage 3 is not in operation, such as when the machine is stopped due to an error during printing or when the power is turned off, the nozzle surface of the liquid discharge head 7 is covered with a cap (not shown) for moisture retention. Yes. The cap is disposed in a cleaning mechanism or the like, and the cleaning mechanism is disposed at either the left or right end of the apparatus.

  The paper feed unit 120 includes a paper feed cassette 10 that stores the paper 12. The paper feed cassette 10 includes a paper stacking unit (pressure plate) 11, a paper feed roller 13, and a separation pad 14. The paper feed roller 13 conveys the paper 12 from the paper stacking unit 11. The separation pad 14 is disposed to face the paper feed roller 13 and is made of a material having a large friction coefficient. The separation pad 14 is pressed against the paper feed roller 13, and the paper feed roller 13 separates and transports the paper 12 from the paper stacking unit 11 one by one.

  The transport unit 130 transports the paper 12 fed from the paper feed unit 120 to the image forming unit 110, and further transports the paper 12 in the sub-scanning direction perpendicular to the ink droplet ejection nozzle surface of the liquid ejection head 7. The conveyance unit 130 includes conveyance roller pairs 26 and 27, a reverse guide unit 15, a sheet presence / absence detection sensor 45 that detects the leading edge of the sheet 12, and conveyance roller pairs 26 and 27. The transport unit 130 also includes a paper reversing unit 16 that reverses the paper 12 when performing duplex printing on the paper 12.

  In the conveyance unit 130, the sub-scanning motor 31 drives the conveyance roller 27 with the timing belt 32 and the timing roller 33.

  In the image forming apparatus 100, the conveyance state of the paper 12 is detected by the encoder 36. As shown in FIG. 2, the encoder 36 includes a disc type encoder sheet 34 and an encoder sensor 35. A disc-shaped encoder sheet 34 is disposed on the shaft of the conveying roller 27. In the disk-type encoder sheet 34, light transmitting portions and light non-transmitting portions are formed alternately. The transmitting portion and the non-transmitting portion of the disk-type encoder sheet 34 are detected by the encoder sensor 35, and the conveyance of the paper 12 is controlled based on the detection information.

  Further, the position of the carriage 3 is detected by an encoder sheet 42 disposed in front of the carriage 3. The encoder sheet 42 includes light transmitting portions and light non-transmitting portions that are alternately formed on the side surfaces, and the transmitting portions and the non-transmitting portions are detected by an encoder sensor (not shown) including a transmission type photosensor. . Based on this detection information, the drive of the carriage 3 is controlled.

  The paper discharge unit 140 discharges the paper 12 recorded by the liquid discharge head 7. The paper discharge unit 140 includes a pair of paper discharge rollers 52 and 53 and a paper discharge tray 54 that stocks the paper 12 to be discharged.

  In the image forming apparatus 100 configured as described above, the paper 12 is separated and fed one by one from the paper feeding unit 120, and the paper 12 fed in the horizontal direction is guided by the reverse guide unit 15 to change the direction. After that, when the leading edge of the paper 12 is detected by the paper presence / absence detection sensor 45, the paper 12 is transported onto the transport guide 21.

  In the image forming apparatus 100, the liquid ejection heads 7Y, 7C, 7M, and 7Bk are driven based on image signals input from the host apparatus while moving the carriage 3. Thus, ink droplets are ejected onto the stopped paper 12 to record one line, and after the paper 12 is conveyed by a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the paper 12 has reached the recording area, the recording operation is finished and the paper 12 is discharged onto the paper discharge tray 54.

  As for the relationship between the scanning direction of the carriage 3 and printing, there are a unidirectional recording mode in which an image is formed only during scanning in one direction and a bidirectional recording mode in which an image is formed in both scanning in both directions. Whether this is set according to the designation from the user or the print image or only one of the modes is performed can be selected as appropriate.

  Next, the recording medium support 200 of the image forming apparatus 100 according to the first embodiment will be described. 3 is a perspective view showing a recording medium support of the image forming apparatus according to the first embodiment, and FIG. 4 is a cross-sectional view corresponding to the line DD in FIG. As shown in FIG. 3, the recording medium support 200 includes a belt member 210 that is a belt-like thin plate member, and two rollers 270 and 280 around which the belt member 210 is wound. The belt member 210 can be made of a hard synthetic resin thin plate material.

  Both end portions of the belt member 210 are fixed to the carriage 3 with the liquid discharge heads 7Y, 7C, 7M, and 7Bk interposed therebetween. As a result, the belt member 210 has an annular shape together with the carriage 3, and the belt member 210 surrounds the lower side from both sides of the carriage 3 (see FIG. 7 for the schematic overall structure). For this reason, the belt member 210 moves so as to circulate even if the carriage 3 moves, and the belt member 210 is always disposed on the outer side in the main scanning direction from both sides of the carriage 3.

  Since the belt member 210 has such a structure, the belt member 210 can support the sheet 12 that has been suspended downward so as not to contact the carriage 3 or the liquid discharge head 7. In addition, the sheet 12 conveyed to the upper surface 211 of the belt member 210 comes into contact with the sheet member 12 and functions as a conveying unit that guides the sheet 12.

  In the image forming apparatus 100 according to the first embodiment, as illustrated in FIG. 4, when the paper 12 comes into contact with the upper surface 211 of the belt member 210, the gap W between the liquid ejection head 7 and the thickness dimension of the belt member 210. Is formed. For this reason, even if the leading end of the inserted paper 12 hangs down, it does not come into contact with the carriage 3 or the liquid discharge head 7. Even when the ink ejection force from the liquid ejection head 7 is strong, the conveyance guide 21 supports the sheet 12 so that the sheet 12 does not rise unnecessarily.

  The belt member 210 is configured as a toothed belt, a sprocket meshed with teeth formed inside the belt member 210 is disposed, and the carriage 3 can be driven by the belt member 210.

<Embodiment 2>
Next, an image forming apparatus according to the second embodiment will be described. The image forming apparatus according to the second embodiment includes the following recording medium support 230. 5A and 5B show a recording medium support of the image forming apparatus according to the second embodiment. FIG. 5A is a perspective view, and FIG. 5B is a cross-sectional view corresponding to the line EE in FIG.

  As shown in FIG. 5A, the recording medium support 230 extends the upstream end of the belt member 231 in the sub-scanning direction (Y axis) downward (Z axis), that is, toward the carriage 3, and has an inclined surface. 232 is formed. Further, as shown in FIG. 5B, the liquid ejection head 7 is disposed on the downstream side of the tip of the inclined surface 232. Other configurations of the image forming apparatus are basically the same as those of the image forming apparatus 100 according to the first embodiment.

  According to the image forming apparatus according to the second embodiment, the inclined surface 232 of the recording medium support 230 can suppress the ear folding of the conveyed paper 12. Further, even if the leading end of the paper 12 transported from the pair of transport rollers 26 and 27 hangs down, the front end of the paper 232 can be scooped up to effectively prevent a paper jam. Further, since the liquid discharge head 7 is disposed on the downstream side of the inclined surface 232, the paper 12 does not contact the liquid discharge head 7.

<Embodiment 3>
Next, an image forming apparatus according to Embodiment 3 will be described. The image forming apparatus according to the third embodiment includes the following recording medium support 240. 6A and 6B show a recording medium support of an image forming apparatus according to Embodiment 3. FIG. 6A is a perspective view, and FIG. 6B is a cross-sectional view corresponding to the line FF in FIG.

  As shown in FIG. 6A, the recording medium support 240 has the upstream end and the downstream end in the sub-scanning direction (Y axis) of the belt member 241 directed downward (Z axis), that is, toward the carriage 3. The inclined surfaces 242 and 243 are formed. In this example, the width dimension and the inclination angle in the Y direction of the inclined surfaces 242 and 243 are the same, and the sheet 12 is not in contact with the liquid ejection head 7 as shown in FIG. The liquid discharge head 7 is disposed inside the two inclined surfaces 242 and 243. Other configurations of the image forming apparatus are basically the same as those of the image forming apparatus 100 according to the first embodiment.

  According to the image forming apparatus according to the third embodiment, when double-sided printing is performed on the paper 12, the paper 12 once image-formed is transported to the paper reversing unit 16 (indicated by a dashed line in FIG. 6B). It is possible to scoop up the leading edge of the paper 12 that returns on the inclined surface 243. For this reason, it is possible to effectively prevent paper jams during normal printing and duplex printing.

<Embodiment 4>
Next, an image forming apparatus according to Embodiment 4 will be described. The image forming apparatus according to the fourth embodiment includes the following recording medium support 250. FIG. 7 is a perspective view showing a recording medium support of the image forming apparatus according to the fourth embodiment, FIG. 8 is a view showing the recording medium support of the image forming apparatus shown in FIG. 7, and (a) is an exploded perspective view. (B) is sectional drawing equivalent to the GG line in (a).

  The recording medium support 250 forms inclined surfaces 252 and 253 when the belt member 251 is attached to the carriage 3 at both ends thereof. The inclined surfaces 252 and 253 extend downward along the liquid ejection head 7 side in the main scanning direction. The inclined surfaces 252 and 253 are formed by attaching the belt member 251 to the inclined surfaces 3b and 3c arranged at both ends of the carriage 3 in the main scanning direction.

  The belt member 251 is attached to the carriage 3 using screws 255 and a pressing member 256. As shown in FIGS. 8A and 8B, inclined surfaces 3b and 3c and screw holes 3d are formed on both sides of the carriage 3 in the X direction. Then, the belt member 251 is attached to the carriage 3 with the screw 255 and the pressing member 256. In a state where the screw 255 is fixed to the carriage 3, it is preferable that the nozzle forming surface 7 a of the liquid discharge head 7 does not protrude from the upper surface of the screw 255.

  According to the image forming apparatus according to the fourth embodiment, contact between the paper 12 and the carriage 3 can be prevented when the carriage 3 moves in the main scanning direction. This is effective when the carriage 3 moves over the paper 12 and returns. When the carriage 3 is returned, the end of the sheet 12 hanging downward is scooped up by the inclined surfaces 252 and 253 to prevent the sheet 12 from being jammed. Therefore, it is possible to know that a paper jam (carriage jam) is prevented during the main scanning.

<Embodiment 5>
Next, an image forming apparatus according to Embodiment 5 will be described. The image forming apparatus according to Embodiment 5 includes the following recording medium support 260. 9A and 9B show a recording medium support of the image forming apparatus according to the fifth embodiment. FIG. 9A is a perspective view, and FIG. 9B is a cross-sectional view corresponding to the line HH in FIG.

  In the recording medium support 260, a paper contact portion 262, an inclined surface 263, and an inclined surface 263 are provided on the belt member 261. The sheet contact portion 262 maximizes the separation distance from the nozzle forming surface 7a of the liquid ejection head 7 (arrow d in FIG. 9B). The inclined surface 263 is formed on the upstream side of the paper contact portion 262, and the guide surface 264 is formed on the downstream side of the paper contact portion 262.

  As shown in FIG. 9B, the sheet contact portion 262 is disposed on the upstream side of the region where the liquid ejection head 7 is disposed (region K in the figure), and is formed in parallel with the nozzle formation surface 7 a of the liquid ejection head 7. .

  The inclined surface 263 has the same configuration as the inclined surface of the belt member according to each of the embodiments described above, and scoops up the paper 12 when the paper 12 being conveyed is hanging down.

  The inclined surface 263 is formed so as to be inclined toward the carriage 3 (downward) from the paper contact portion 262 toward the upstream side in the sub-scanning direction. Further, the guide surface 264 is formed to be inclined toward the carriage 3 (downward) from the paper contact portion 262 toward the downstream side in the sub-scanning direction. Here, the height of the lowermost portion of the guide surface 264 is desirably the same as or higher than the nozzle formation surface 7 a of the liquid discharge head 7. This is to prevent the paper 12 in contact with the guide surface 264 from coming into contact with the liquid ejection head 7.

  In an image forming apparatus in which a recording medium support is disposed, when the recording medium support comes into contact with the image forming surface of the paper, the drying of the ink is slow or the penetration of the ink into the paper is slow. The ink rubs and image degradation occurs.

  In the image forming apparatus according to the fifth embodiment, the paper contact unit 262 supports the paper 12 in an unimaged region (region L in FIG. 9B) where no ink is applied. For this reason, even if the belt member 261 comes into contact with the paper 12 during image formation, image rubbing does not occur.

  The paper 12 is supported by the guide surface 264 between the paper contact portion 262 and the paper discharge roller pairs 52 and 53, and paper jamming in the main scanning direction can be prevented even if the paper 12 hangs down.

  The sheet conveyance path at a position facing the liquid ejection head 7 may be oblique. In other words, the configuration may not be such that the paper is always conveyed in the horizontal direction.

<Embodiment 6>
FIG. 10 is a perspective view showing a recording medium support of the image forming apparatus according to Embodiment 6, and FIG. 11 is a cross-sectional view corresponding to the line JJ in FIG. The basic configuration is substantially the same as that shown in FIGS. 3 and 4, but in this embodiment, the caterpillar recording medium support 300 is arranged so that the head side of the carriage 3 is an end. It is fixed. The same or similar parts as those in the example of FIG. 3 are given the same reference numerals (the same applies to the following embodiments). The sheet 12 is placed on the caterpillar-shaped recording medium support 300 by its own weight, and its surface becomes an image forming surface. When the ink ejection force from the liquid ejection head 7 is strong, as shown in FIG. 1, the transport guide 21 (located at a position facing the liquid ejection head 7 and the caterpillar recording medium support 300). Since it supports, the paper 12 does not float unnecessarily.

  When the recording medium support 300 has a caterpillar configuration as in the present embodiment, it is easy to cope with changing the length. Moreover, since the number of dedicated parts does not increase, the initial investment amount can be suppressed. Further, even when an accident such as a scratch occurs, it is only necessary to remove and replace the caterpillar member in which the problem has occurred, and further, it is only necessary to access only the replacement part, so that the disassembling work is facilitated. Of course, since the caterpillar can be formed of a molded product, it becomes easy to connect another part such as a spur (described later).

FIG. 12 is a schematic diagram for explaining a drawing method in the image forming apparatus on which the caterpillar-shaped recording medium support 300 according to the present embodiment is mounted.
In a general serial type image forming apparatus, as shown in (a) → (b), the carriage 3 moves in the main scanning direction (X direction which is the left-right direction in FIG. 12) (see FIG. 2) and liquid ejection is performed simultaneously. The head 7 ejects ink onto the paper 12 to print the image p. Next, the paper 12 moves in the sub-scanning direction (Y direction which is the vertical direction in FIG. 12) as shown in (b) → (c), and the image is drawn again as shown in (c) → (d). When the paper 12 moves (sub-scanning direction), the carriage 3 stops, and when the carriage 3 moves (main scanning direction), the paper 12 stops.

<Embodiment 7>
13A and 13B show a recording medium support of an image forming apparatus according to Embodiment 7, wherein FIG. 13A is a perspective view and FIG. 13B is a cross-sectional view corresponding to the line KK in FIG. . In the present embodiment, the position of the topmost portion of the caterpillar-shaped recording medium support 300 in the height direction becomes the image forming surface (image forming position), and the caterpillar is secured in order to secure a gap between the liquid ejection head 7 and the image forming surface. The top of the recording medium support 300 is positioned above the nozzle surface of the liquid discharge head 7.

  Also in this embodiment, as in the embodiment shown in FIG. 5A, the recording medium support 300 has the upstream end in the sub-scanning direction (Y-axis) of each caterpillar 331 below (Z-axis), that is, the carriage. 3, and an inclined surface 332 is formed. And as shown in FIG.13 (b), the liquid discharge head 7 is arrange | positioned downstream from the front-end | tip of the inclined surface 332. FIG.

  According to the seventh embodiment, the inclined surface 332 of the recording medium support 300 can suppress the ear folding of the conveyed paper 12. Further, even when the leading edge of the sheet 12 conveyed from the conveying roller pair 26 and 27 hangs down, the leading edge where the inclined surface 232 hangs down is scooped up, and a paper jam can be effectively prevented. In addition, since the liquid discharge head 7 is arranged on the downstream side of the inclined surface 332, the paper 12 does not contact the liquid discharge head 7.

<Eighth embodiment>
14A and 14B show a recording medium support of the image forming apparatus according to the eighth embodiment. FIG. 14A is a perspective view, and FIG. 14B is an end view taken along line LL in FIG.

  The caterpillar-shaped recording medium support 300 according to the present embodiment is formed with inclined surfaces 332a and 332b that are inclined downward on both the upstream and downstream sides of the sheet 12 in the conveyance direction of the sheet 12 of each caterpillar 331. . The inclination angle is preferably the same angle and width (width in the Y direction) for the inclined surfaces 332a and 332b. When printing the last line during double-sided printing or single-sided printing, the rear end of the paper 12 during single-sided conveyance is conveyed downstream in the conveyance direction (Y direction in the figure) of the carriage 3 and then switched back. The inclined surface 332b can scoop the leading edge of the paper 12 in the transport direction after switchback. Therefore, it is possible to prevent paper jams during normal printing or double-sided printing. The liquid discharge head 7 is disposed so as not to protrude from the inclined surfaces 332a and 332b in order to prevent interference with the front end of the paper 12.

  FIG. 15 is a schematic diagram for explaining an example of a caterpillar 331 that can be used in the present embodiment. As described above, the inclined surfaces 332a and 332b are formed on both ends in the main scanning direction (X direction) of each caterpillar 331, and in order to easily connect the adjacent caterpillars 331 to each other, A convex portion 333 and a concave portion 334 are formed in the central portion. The caterpillar 331 shown in FIGS. 15A to 15C shows a basic shape, but FIGS. 15D to 15F show the outermost edge of the caterpillar 331 (all the edges constituting the outer periphery or The edge is chamfered 331a so that the paper 12 is not caught. That is, the caterpillar recording medium support 300 moves on the lower surface of the sheet during the main scanning operation, and the sheet 12 moves on the caterpillar recording medium support 300 during the sub-scanning operation. It is preferable that the sheet 12 is not caught at each edge of the sheet. For example, not only the outermost edge in the main scanning direction and the sub-scanning direction but also the edges of the center of the convex portion 333 and the concave portion 334 in the main scanning direction are chamfered.

<Ninth Embodiment>
FIG. 16 is a perspective view showing a recording medium support of the image forming apparatus according to the ninth embodiment, and FIG. 17 is a perspective view showing an example of attaching the caterpillar recording medium support of FIG. In the present embodiment, the part on which the liquid ejection head 7 of the carriage 3 is mounted is recessed downward in the Z direction perpendicular to the surface formed by the main scanning direction (X direction) and the sub scanning direction (Y direction). The ends in the main scanning direction serve as attachment portions for the caterpillar-shaped recording medium support 300, and inclined surfaces 3a and 3a are formed at both ends in the main scanning direction of the recessed portion.

  When the carriage 3 moves in the main scanning direction, the end of the paper 12 in the main scanning direction may be located near the liquid discharge head 7, and at this time, the end surface of the paper 12 hangs down, so that the carriage 3 The inclined surfaces 3a and 3a can scoop the end surface of the paper 12 when scanned in the reverse direction. Accordingly, the left and right edges of the paper 12 in the main scanning direction (X direction) can be scooped during main scanning, and paper jamming (carriage jam) in the main scanning direction can be prevented.

  As shown in FIG. 17, the fixing member 350 for attaching the caterpillar recording medium support 300 to the carriage 3 is formed with a fixing hole 352 for inserting and fixing a fastening member 351 such as a screw. . Of course, it is preferable that the upper surface of the fastening member 351 does not protrude from the upper surface of the liquid discharge head 7 in a state where the fixing member 350 of the recording medium support 300 is fixed by the fastening member 351. In FIG. 17, the fixing member 350 is a dedicated component, but a hole may be provided in one of the other caterpillars 331 constituting the caterpillar-shaped recording medium support 300 to replace the fixing member 350.

<Embodiment 10>
18A and 18B show a recording medium support of the image forming apparatus according to the tenth embodiment. FIG. 18A is a perspective view, and FIG. 18B is an end view taken along line NN in FIG. In this embodiment, the caterpillar-shaped recording medium support 300 has a deformed trapezoidal cross-sectional shape, and the top surface 360a slides on the image forming surface of the paper 12 during image formation. For this reason, if the ink discharged onto the paper 12 is slowly dried and penetrated, the image is rubbed (see the description of FIGS. 12 and 12). Therefore, the top surface 360a of the caterpillar recording medium support 300 is used as a gap securing support portion (hereinafter, denoted by reference numeral 360a) for securing a gap between the liquid ejection head 7 and the image forming surface, and the gap securing support portion 360a. The inclined surface provided on the downstream side of the inclined surface 360b provided on the upstream side in the conveyance direction of the paper 12 (from right to left in FIG. 18B) is longer in the conveyance direction of the paper 12, and the inclination is also gentle. The guide surface portion 360c is formed.

  Therefore, on the upstream side in the Y direction of the liquid ejection head 7 (the non-image forming portion side), the gap is secured (paper supported) by the gap securing support portion 360a, so that the recording medium support 300 slides during image formation. Also, image blurring can be prevented. Further, between the gap securing support portion 360a and the paper discharge roller 52 and the paper discharge roller 53, a guide surface portion 360c for preventing the paper from drooping should prevent the paper 12 in the main scanning direction from being dropped. Clogging can be prevented. In this embodiment, the height of the lowermost portion of the guide surface portion 360c is preferably the same as or above the nozzle surface of the liquid discharge head 7.

<Embodiment 11>
FIG. 19 is a perspective view illustrating a recording medium support of the image forming apparatus according to the eleventh embodiment. The caterpillar recording medium support 300 of the present embodiment assumes that the carriage 3 rubs against the paper 12 when the carriage 3 moves in the main scanning direction (X direction). A spur-shaped roller 370 that rotates in the main scanning direction is disposed on the surface of the caterpillar 331 that is in sliding contact with the sheet. That is, for example, the position of the gap securing support portion 360a shown in FIG. 18 does not rub the print because it rubs the region before drawing, but the noise due to friction with the paper 12 or the surface of the gap securing support portion 360a itself. There is concern about wear. In view of this, the roller 370a is arranged to reduce the contact area with the paper 12 mainly for the purpose of preventing abnormal noise and wear. In addition, the roller 370a may not be a spur shape but a disc shape. Further, in order to eliminate the restriction of the rotation direction, a spherical roller 370b is formed as shown in FIGS. 19B and 19C, or a spherical shape having a protrusion on the surface as shown in FIG. 19D. A roller 370c may be used.

<Twelfth embodiment>
20A and 20B are diagrams illustrating a recording medium support of the image forming apparatus according to the twelfth embodiment. FIG. 20A is a cross-sectional view, and FIG. 20B is a perspective view. In this embodiment, while the paper 12 is conveyed from the roller pair 26 and 27 to the paper discharge roller 52 and the paper discharge roller 53, the paper 12 is rubbed on the recording medium support 300 (particularly, the image is drawn). On the downstream side of the sheet conveyance with respect to the liquid ejection head 7, the sheet is conveyed by the so-called stiffness of the sheet 12. For a sheet such as a thin sheet that easily hangs down, for example, the embodiment shown in FIG. In this configuration, there is a possibility that the sheet cannot be sandwiched between the pair of the discharge roller 52 and the discharge roller 53 on the downstream side of the liquid discharge head 7. Therefore, the liquid discharge head 7 can support the sheet surface more. The paper support rollers 370a and 370b are disposed both upstream and downstream in the paper transport direction (Y direction) of the paper transport roller 370b on the downstream side in the paper transport direction. straight For those, the ink ejected on the sheet may in some cases still wet, it is desirable to that of spur-like as shown.

  In the configuration of the present embodiment, the gap between the liquid ejection head 7 and the image forming surface is determined by the protruding amount of the rollers 370a and 370b, and the caterpillar recording medium support 300 supports the hanging paper, The main role is holding the rollers 370a and 370b. In addition, since the present embodiment is intended to prevent the paper 12 from being rubbed with the recording medium support 300, it may be unnecessary when the paper 12 is stiff. This is an embodiment of a configuration effective for an image forming apparatus mainly for printing on a sheet that easily hangs down, such as thin paper. Further, as shown in FIG. 20B, only the spur-shaped paper support roller 370b may be provided.

<Embodiment 13>
21A and 21B are diagrams showing a recording medium support of the image forming apparatus according to the thirteenth embodiment. FIG. 21A is a perspective view, and FIG. 21B is an enlarged cross-sectional view corresponding to the line P-P in FIG. is there. This embodiment has both functions of Embodiments 11 and 12, and each caterpillar 331 is connected with a spherical roller 380a and a spherical roller 380b provided with a spur-like protrusion in the Y direction. And can be rotated without being restricted in the main scanning direction and the sub-scanning direction, that is, without any restriction in the rotation direction. Regarding the arrangement of the rollers, it is desirable to arrange them on the upstream side and the downstream side of the liquid discharge head 7, respectively, and it is desirable that the roller on the downstream side is spur-like and the friction with the paper is steeper.

3: Carriage 7: Liquid ejection heads 7Y, 7C, 7M, 7Bk: Liquid ejection head 7a: Nozzle forming surface 8: Guide rod 10: Paper feed cassette 11: Paper stacking section 12: Paper 26, 27: Transport roller pair 52, 53: Paper discharge roller pair 54: Paper discharge tray 100: Image forming apparatus 110: Image forming unit 120: Paper feed unit 130: Transport unit 140: Paper discharge unit 200: Recording medium support 210: Belt member 230: Recording medium support Body 231: Belt member 232: Inclined surface 240: Recording medium support 241: Belt member 242, 243: Inclined surface 250: Recording medium support 251: Belt member 252, 253: Inclined surface 260: Recording medium support 261: Belt Member 262: Paper contact portion 263: Inclined surface 264: Guide surface 270: Roller 300: Recording medium support 331: Caterer La 332: inclined surface 332a: inclined surface 332b: inclined surface 333: protrusions 334: recessed portion 350: fixing member 351: fastener 352: fixing hole 360a: top surface (gap-supporting portion)
360b: inclined surface 360c: guide surface portion 370, 370a to 370c: roller 380a, 380b: roller p: image

Japanese Utility Model Publication No. 05-041816 JP 2010-006603 A JP 2001-334121 A JP 2002-011893 A

Claims (10)

A liquid discharge head for discharging liquid droplets onto a recording medium;
A carriage that mounts the liquid ejection head and moves the liquid ejection head in a main scanning direction orthogonal to the conveyance direction of the recording medium,
In the image forming apparatus in which the droplet discharge direction of the liquid discharge head is arranged upward and the droplets are discharged toward the recording medium conveyed above the liquid discharge head.
A recording medium support is provided that supports the recording medium disposed above when the carriage moves in the main scanning direction from below and prevents the recording medium from dripping downward and coming into contact with the liquid ejection head. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the recording medium support is a belt-shaped member.   The image forming apparatus according to claim 1, wherein the recording medium support has a function as a conveyance surface portion that contacts when the recording medium is conveyed.   The image forming apparatus according to claim 1, wherein the recording medium support has a function of a drive belt that drives the carriage in a main scanning direction.   The image forming apparatus according to claim 2, wherein a dimension of the recording medium support in the sub-scanning direction is larger than a dimension of the liquid discharge head in the sub-scanning direction.   The image forming apparatus according to claim 1, wherein an upper side surface of the recording medium support is disposed above a position where a liquid droplet ejection port of the liquid ejection head is installed.   The image forming apparatus according to claim 1, wherein an upstream end of the recording medium support in the sub-scanning direction is inclined downward.   The image forming apparatus according to claim 1, wherein an upstream end and a downstream end in the sub-scanning direction of the recording medium support are inclined downward.   9. The two joint portions for joining the recording medium support to the liquid discharge head are inclined downward along the liquid discharge head side in the main scanning direction. The image forming apparatus according to any one of the above. The recording medium support is formed on the upstream side in the sub-scanning direction from the arrangement region of the liquid ejection head, and a sheet contact portion that maximizes the separation distance from the nozzle formation surface of the droplet ejection head;
10. The image forming apparatus according to claim 1, further comprising a guide surface inclined toward the liquid discharge head along a downstream direction in the sub-scanning direction from the sheet contact portion. .