JP2008156012A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of sufficiently enhancing the stacking property. <P>SOLUTION: The image forming device comprises an image forming unit 2 having a printing unit 23 which feeds liquid droplets toward a paper sheet 5 to form an image corresponding to a document image, paper discharge roller pairs 78 for discharging the paper sheet 5 from the image forming unit 2, and a paper discharge tray 79 provided below the paper discharge roller pairs 78 to stack the paper sheets 5 discharged from the paper discharge roller pairs 78. An arm 178 is provided, which presses the paper sheet 5 discharged in the paper discharge tray 79 from an upper side. The arm 178 is movable to the non-contact position not being interfered with the paper sheet, the push-up position for pushing up the paper sheet 5 discharged by the paper discharge roller pairs 78, and the pressing position for pressing a paper sheet 6 on the paper discharge tray 79 from an upper side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine of these.

  In general, in an ink jet printer that forms an image on paper by supplying ink to the paper, the paper type of the paper used for image formation greatly affects the stackability. In other words, the paper printed by the ink jet printer, especially when the paper is thin, has a large curl due to the moisture of the ink, so the paper bends when the leading edge of the discharged paper reaches the paper discharge tray. There is a tendency that the stacking property is greatly affected, for example, paper is turned upside down on the tray, curled, or pushed out. If the curl of the paper is large, even if there is room to place the paper on the paper discharge tray, the end of the curled paper closes the exit side of the nip of the paper discharge roller pair that discharges the paper. The stacking property may be deteriorated because the paper discharge is obstructed.

  For this reason, there is known a technique for improving the stackability by suppressing the curling of the paper by providing a pressing member that presses the paper on the paper discharge tray from above (see, for example, Patent Documents 1 to 3).

Japanese Patent Laid-Open No. 10-250897 JP 2002-241028 A JP 2006-137571 A

  However, in any of the above prior arts, since the paper is discharged onto the paper discharge tray in a curled state, even if the paper on the paper discharge tray is pressed from above by the pressing member, the paper curl at the time of paper discharge However, there is a problem that the stackability cannot be sufficiently improved because the problem cannot be dealt with in the case of a large value.

  An object of the present invention is to obtain an image forming apparatus capable of sufficiently improving stackability.

  In order to solve the above-mentioned problem, the invention described in claim 1 is directed to an image forming unit having a printing unit that supplies liquid droplets toward a sheet to form an image corresponding to a document image, and the image forming unit. An image forming apparatus including a pair of paper discharge rollers for discharging the paper from the paper, and a paper stacking table provided below the paper discharge roller pair for stacking paper discharged from the paper discharge roller pair. A pressing member is provided for pressing the paper discharged onto the paper mounting table from above, and the pressing member holds the paper discharged by the paper discharge roller pair between the non-contact position where it does not interfere with the paper and the paper discharge roller pair. It is characterized by being provided so as to be movable between a push-up position where the paper is pushed up sideways and a press-down position where the paper on the paper placement table is pressed from above.

  According to a second aspect of the present invention, in the first aspect of the present invention, the control unit includes a control unit that controls driving of the presser member. The pressing member is stopped at either the lifting position or the pressing position.

  According to a third aspect of the present invention, in the second aspect of the present invention, any one of the non-contact position, the push-up position, and the press position of the paper discharge detection unit that detects the paper toward the paper discharge roller pair and the press member. A movement position detection unit for detecting whether the sheet is present, and when the paper discharge detection unit detects a sheet, the control unit moves the presser member from the non-contact position to the push-up position and stops at this position. After the paper detection by the paper detection unit is completed, the presser member is moved from the push-up position to the presser position and then stopped.

  The invention described in claim 4 is characterized in that, in the invention described in claim 2, the control unit changes the driving mode of the pressing member in accordance with the type of the sheet.

  In the invention described in claim 5, in the invention described in claim 4, the control unit continues to stop the presser member only at the non-contact position when the type of paper is a predetermined specific type. Either the control or the control of stopping after the pressing member at the non-contact position is moved to the pressing position after completion of paper discharge is performed.

  The invention described in claim 6 is the invention described in claim 5, further comprising a thickness detection unit that detects the thickness of the paper, and the control unit is configured such that the thickness of the paper is a predetermined thickness. Sometimes, it is determined that the type of paper is a predetermined specific type.

  The invention described in claim 7 is the invention described in claim 5, further comprising an input unit for inputting a paper type by a user's operation, and the control unit selects the paper type based on information from the input unit. It is characterized by judging.

  In the invention described in claim 8, in the invention described in claim 5, the image forming unit includes an adjustment unit that adjusts a distance between the printing unit and the sheet according to the thickness of the sheet, and the control unit includes: When the distance between the printing unit and the sheet reaches a predetermined distance, it is determined that the sheet type is a specific type determined in advance.

  The invention described in claim 9 is the invention described in claim 8, further comprising a distance detection unit that detects a distance between the printing unit and the sheet, and the control unit is configured to detect the type of the sheet based on information from the distance detection unit. It is characterized by judging.

  According to a tenth aspect of the present invention, in the invention according to the eighth aspect, the adjusting unit adjusts a distance of the printing unit with respect to the paper by being operated by a user, and a position of the operating member. And an operation position detection unit for detecting, wherein the control unit determines the type of paper based on information from the operation position detection unit.

  The invention described in claim 11 is the invention described in claim 2, further comprising a droplet amount detection unit that detects a droplet amount per unit area of the sheet, and the control unit is configured to detect the amount of droplets per unit area of the sheet. The driving mode of the presser member is changed according to the amount of liquid droplets.

  The invention described in claim 12 is the invention described in claim 11, wherein the droplet amount detection unit detects an appropriate amount of liquid per unit area on the rear end side of the sheet.

  According to a thirteenth aspect of the present invention, in the invention according to the eleventh or twelfth aspect, when the amount of liquid droplets per unit area of the paper reaches a predetermined amount, the control unit is only in the non-contact position. Either the control for continuously stopping the presser member or the control for stopping the presser member after moving the presser member at the non-contact position to the presser position after completion of paper discharge is performed.

  The invention described in claim 14 is the invention described in any one of claims 1 to 13, wherein the support member that rotatably supports the presser member and the presser member that urges the presser member in the direction of pressing the paper. An urging member is provided.

  The invention described in claim 15 is the invention described in claim 14, wherein the driving force from the driving source is transmitted to the presser member, and the presser member is moved to any one of the non-contact position, the push-up position and the presser position. A slider link mechanism for moving is provided.

  The invention described in claim 16 is the invention described in any one of claims 1 to 15, wherein the presser member is bent so that only the tip portion thereof presses the paper on the paper mounting table. It is characterized by being.

  According to a seventeenth aspect of the present invention, in the invention according to any one of the first to sixteenth aspects, the pressing member is rotatably provided with a roller for pressing the paper on the paper mounting table from above. It is characterized by.

  According to the present invention, since the presser member is provided so as to be movable to the non-contact position, the push-up position, and the press position, when the presser member is in the non-contact position, the paper discharge operation is not hindered and smooth. Paper can be discharged. Further, when the presser member is in the push-up position, the presser member pushes up the paper ejected by the pair of paper ejection rollers and deforms the paper into a wave shape (uneven shape) in the width direction. However, the curl is corrected and the paper is discharged, so that the paper can be discharged to the paper mounting table with curling of the paper suppressed, and the curled paper is prevented from blocking the exit side of the nip of the paper discharge roller pair. can do. Furthermore, when the pressing member is in the pressing position, the sheet can be pressed from above to further prevent the sheet from curling. As described above, since the curling of the sheet can be sufficiently suppressed by the pressing member at any one of the non-contact position, the pushing-up position, and the pressing position, the stacking property can be sufficiently improved.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, the overall structure of the image forming apparatus according to the first embodiment of the present invention will be described with reference to FIGS. 1 is a schematic configuration diagram showing the overall configuration of the image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a plan view of the image forming unit and the sub-scanning conveying unit of the image forming apparatus of FIG. 3 is a side view of the image forming apparatus of FIG.

  This image forming apparatus uses a so-called ink jet process, and has an image forming unit 2 for forming an image, a sub-scanning conveying unit 3 and the like inside the apparatus main body 1 (enclosure). The paper 5 is fed one by one from the paper feeding unit 4 provided at the bottom of the paper 1 and the paper 5 is conveyed by the image forming unit 2 while being conveyed at a position facing the image forming unit 2 by the sub-scanning conveying unit 3. In the case of single-sided printing after ejecting droplets of ink or the like to 5 and forming (recording) a required image (an image corresponding to the original image), the image forming unit 2 to the paper discharge stack unit 8 A paper receiving surface 79 a of a paper discharge tray (paper mounting table) 79 that is formed on the upper surface of the apparatus main body 1 through the paper discharge conveyance unit 7 disposed therebetween and stacks while receiving the paper 5 discharged from the image forming unit 2. Paper 5 is ejected on top, and ejected for duplex printing The paper is fed into the duplex unit 10 provided at the bottom of the apparatus main body 1 from the middle of the feeding unit 7, is subjected to switchback conveyance, and is again fed to the sub-scanning conveyance unit 3 to form images on both sides, and then a paper discharge tray 79. The sheet is discharged onto the sheet receiving surface 79a.

  As shown in FIG. 1, the paper discharge stack unit 8 includes a paper discharge tray 79 that receives and stacks the paper 5 discharged from the paper discharge roller pair 78. The paper discharge tray 79 is positioned below the paper discharge roller pair 78 and is inclined substantially upward downward in the paper discharge direction of the paper 5, and extends substantially vertically downward from the paper discharge roller pair 78. An end fence (rear wall) 79b that is integrally connected to the base end of the sheet receiving surface 79a and receives the rear side of the discharged paper on the sheet receiving surface 79a and aligns the rear side. ing.

  The image forming apparatus also has an image reading unit for reading an image above the paper discharge stack unit 8 above the apparatus main body 1 as an input system for image data (print data) formed by the image forming unit 2. (Scanner unit) 11 is provided. The image reading unit 11 includes a scanning optical system 15 including an illumination light source 13 and a mirror 14 and a scanning optical system 18 including mirrors 16 and 17. The scanned document image is read as an image signal by the image reading element 20 disposed behind the lens 19, and the read image signal is digitized and subjected to image processing, and the image-processed print data is printed. be able to.

  Further, this image forming apparatus uses an information processing apparatus such as an external personal computer, an image reading apparatus such as an image scanner, and an imaging apparatus such as a digital camera as an input system for image data (print data) formed by the image forming unit 2. For example, print data including image data from the host side can be received via a cable or a network, and the received print data can be processed and printed.

  Here, the image forming unit 2 of the image forming apparatus holds the carriage (printing unit) 23 movably in the main scanning direction by the guide rod 21 and a guide stay (not shown) as shown in FIG. The motor 27 moves and scans in the main scanning direction via a timing belt 29 spanned between the driving pulley 28A and the driven pulley 28B.

  A recording head 24 including a droplet discharge head for discharging droplets of each color is mounted on the carriage 23, the carriage 23 is moved in the main scanning direction, and the sheet 5 is transferred to the sheet by the sub-scanning conveyance unit 3. A shuttle type is used in which droplets are ejected from the recording head 24 while feeding in the transport direction (sub-scanning direction) to form an image. A line-type head can also be used.

  The recording head 24 has two droplet discharge heads 24k1 and 24k2 that discharge black (Bk) ink, respectively, and one each that discharges cyan (C) ink, magenta (M) ink, and yellow (Y) ink. Each of the sub-tanks 25 mounted on the carriage 23 is composed of a total of five droplet discharge heads (hereinafter referred to as “recording head 24” when the colors are not distinguished). Of ink is supplied.

  On the other hand, as shown in FIG. 1, a recording liquid cartridge containing black (Bk) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink from the front of the apparatus main body 1 to the cartridge mounting portion. Each color ink cartridge 26 can be detachably mounted, and ink is supplied from each color ink cartridge 26 to each color sub-tank 25 provided in the image forming unit 2. The black ink is supplied from one ink cartridge 26 to the two sub tanks 25.

  The recording head 24 uses a piezoelectric element as a pressure generating means (actuator means) for pressurizing the ink in the ink flow path (pressure generation chamber) to deform the vibration plate that forms the wall surface of the ink flow path. A so-called piezo type that discharges ink droplets by changing the volume in the flow channel, or discharges ink droplets with a pressure generated by heating the ink in the ink flow channel using a heating resistor to generate bubbles. The so-called thermal type, the diaphragm that forms the wall surface of the ink flow path and the electrode are placed opposite to each other, and the diaphragm is deformed by the electrostatic force generated between the vibration plate and the electrode, thereby the ink flow path inner volume It is possible to use an electrostatic type or the like that discharges ink droplets by changing the above.

Further, as shown in FIG. 2, a maintenance / recovery device 121 for maintaining and recovering the nozzle state of the recording head 24 is disposed in the non-printing area on one side of the carriage 23 in the scanning direction.
The maintenance / recovery device 121 includes five moisturizing caps 122k2, 122k1, 122c, 122m, and 122y for capping the nozzle surfaces of the five recording heads 24 (if the colors are not distinguished, the “moisturizing cap” 122 ”), a single suction cap 123, a wiper blade 124 for wiping the nozzle surface of the recording head 24, and discharge (empty discharge) of droplets that do not contribute to recording (image formation). For example, an empty discharge receiving member 125 is provided.

  Further, as shown in FIG. 2, in the non-printing area on the other side of the carriage 23 in the scanning direction, droplets that do not contribute to recording (image formation) are discharged (empty discharge) from the five recording heads 24. An empty discharge receiving member 126 is provided. The empty discharge receiving member 126 has five openings 127k2, 127k1, 127c, 127m, and 127y corresponding to the recording head 24 (referred to as “openings 127” when colors are not distinguished).

  Further, as shown in FIGS. 19 and 20, the guide lot 21 is held at its end by an eccentric rotating member 211, and the eccentric rotating member 211 has a lever (operation member) 213. When the lever 213 is operated, the eccentric rotating member 211 is rotated, and the carriage 23 is moved in parallel up and down. In the present embodiment, the guide lot 21, the eccentric rotating member 211, and the lever 213 constitute the adjusting unit 215.

  That is, in the inkjet image forming apparatus as in the present embodiment, when using thick paper such as an envelope as the paper and passing the paper, the envelope and the carriage 23 are not rubbed or stained. The height of the carriage 23 (the distance between the paper 5 and the carriage 23) is changed. Accordingly, the type of the paper 5 can be identified by the height of the carriage 23, in other words, the distance between the paper 5 and the carriage 23.

  Specifically, when the lever 213 is pushed down from the position shown in FIG. 20, the carriage 23 moves upward and is located at the position shown in FIG. On the other hand, when the lever 213 is pushed upward in this state, the carriage 23 moves downward from the position shown in FIG. 21 and is located at the position shown in FIG. Thereby, the distance between the carriage 23 and the conveyance belt 31 (in other words, the distance between the conveyance belt 31 and the carriage 23) can be adjusted.

  Further, when the lever 213 is pushed down from the position shown in FIG. 20 to the position shown in FIG. 21, the lever position detection sensor (operation position detection unit) 214 detects the lever 213. When the lever position detection sensor 214 detects the lever 213, the control unit 140, which will be described later, determines that the distance between the sheet 5 and the carriage 23 has reached a predetermined distance (if the sheet 5 is a thick sheet, an envelope, or the like). Judging) In place of the lever position detection sensor 214, a height detection sensor (distance detection unit) such as a photo sensor for detecting the height of the carriage 23 is provided, and the distance between the sheet 5 and the carriage 23 is determined by the height detection sensor. You may make it detect.

  As shown in FIG. 3, the sub-scanning conveyance unit 3 changes the conveyance direction of the sheet 5 fed vertically from the lower sheet feeding unit 4 approximately 90 degrees to the horizontal direction, and sends it to the image forming unit 2. An endless transport belt 31 laid between a transport roller 32 that is a drive roller for transporting in opposition and a driven roller 33 that is a tension roller, and an alternating power from a high-voltage power source to charge the surface of the transport belt 31. A charging roller 34 that is a charging unit to which a high voltage as a voltage is applied, a guide member 35 that guides the conveying belt 31 in a region facing the image forming unit 2, and a sheet 5 that is conveyed at a position facing the conveying roller 32 A pressing roller (pressing roller) 36 that is pressed against the belt 31 and a separation claw 37 for separating the paper 5 on which an image is formed by the image forming unit 2 from the conveying belt 31 are provided.

  The transport belt 31 of the sub-scan transport unit 3 is rotated in the paper transport direction (sub-scan direction) in FIG. 2 by rotating the transport roller 32 from the sub-scan motor 131 through the timing belt 132 and the timing roller 133. It is configured to do. The transport belt 31 includes, for example, a surface layer that is a sheet adsorbing surface formed of a pure resin material that is not subjected to resistance control, such as ETFE pure material, and a back layer that is subjected to resistance control using carbon with the same material as the surface layer. Although a two-layer structure (medium resistance layer, earth layer) is used, the structure is not limited to this, and a one-layer structure or a structure of three or more layers may be used.

  In addition, a cleaning unit (mylar is used here) 135 for removing paper dust and the like adhering to the surface of the conveyor belt 31 between the driven roller 33 and the charging roller 34, and the surface of the conveyor belt 31. A neutralizing brush 136 for removing electric charges is provided.

  The paper feed unit 4 can be inserted / removed from the front side of the apparatus main body 1. The paper feed cassette 41 that stacks and stores a large number of sheets 5 and the sheets 5 in the sheet feed cassette 41 are separated and sent out one by one. A sheet feeding roller 42 and a friction pad 43 are provided.

  The paper feed unit 4 includes a manual feed tray 46 for stacking and storing paper 5, a manual feed roller (not shown) for feeding the paper 5 one by one from the manual feed tray 46, and a lower side of the apparatus main body 1. A transport roller 48 for transporting the paper 5 fed from the paper feeding cassette or the duplex unit 10 as an option, and a transport roller 49 for feeding the fed paper 5 to the sub-scanning transport unit 3 are provided. I have. A member for feeding the sheet 5 to the sub-scanning conveying unit 3 such as the sheet feeding roller 42 is rotationally driven by a sheet feeding motor 45 including an HB type stepping motor via a sheet feeding clutch (not shown).

  The paper discharge transport unit 7 feeds the paper 5 sent out from between the paper discharge roller 71 and the spur 72, a transport roller 71 that feeds the paper 5 separated by the separation claw 37 of the sub-scanning transport unit 3, and a spur 72 that faces the transport roller 71. The lower guide portion 73 and the upper guide portion 74 that are conveyed while being guided, and the sheet 5 fed from between the lower guide portion 73 and the upper guide portion 74 are reversed through the reverse discharge path 81 that is the first conveyance path. A reversing roller pair 77 and a paper discharge roller pair 78 are provided for sending the paper to the paper discharge stack unit 8 face down.

  Each of the guide portions 73 and 74 includes a guide plate that guides the paper 5 in the horizontal direction and a transport roller that transports the paper 5 in the horizontal direction, and the paper 5 is interposed between the lower guide portion 73 and the upper guide portion 74. It is a conveyance path for conveyance.

  The reverse paper discharge path 81 includes a paper discharge guide plate 81 a, the above-described reverse roller 77 and the reverse paper discharge roller pair 78, and an arm 178 described later for pressing the paper 5 on the paper receiving surface 79 a of the paper discharge tray 79. A paper pressing mechanism 9 is provided. As shown in FIG. 5, the reverse discharge roller pair 78 includes a drive roller 78a supported by a rotation shaft 78c and a driven roller 78b that rotates with the drive roller 78a. Are arranged at intervals along each other. Similarly, four reversing roller pairs 77 are also arranged at intervals along the axis 77a. Further, as shown in FIG. 4, a paper discharge detection sensor (detecting the paper 5 going to the paper discharge roller pair 78 in front of the paper discharge roller pair 78 (upstream side of the paper discharge roller pair 78 in the paper discharge direction). A paper discharge detection unit 179 is provided.

  Further, the paper discharge transport unit 7 has a straight paper discharge path 82 which is a second transport path for discharging the paper 5 on which image formation has been performed straight up with face-up. The sheet 5 sent out from the guide portion 74 can be discharged to a straight discharge tray (straight discharge cover) 83 provided to be foldable on the other side of the apparatus body 1 through the straight discharge path 82. A switching mechanism 60 is provided on the exit side of the lower guide portion 73 and the upper guide portion 74 in order to switch between the reverse discharge path 81, the straight discharge path 82, and a double-sided conveyance path described later.

  The duplex unit 10 receives a sheet 5 conveyed by being guided by the switching mechanism 60 from the side surface of the apparatus main body 1 and conveys the sheet 5 downward. Subsequently, a horizontal feeding conveyance path 90a that conveys in the horizontal direction and a horizontal conveyance section 101b that constitutes a switchback conveyance path 90b are integrally provided.

  The vertical double-sided conveyance path 90c is provided with a double-sided entrance roller pair 91 for conveying the fed paper 5 downward and a conveyance roller pair 92 for sending it out to the horizontal taking-in conveyance path 90a. 93, and the switchback conveyance path 90b includes a double-sided exit roller 94 composed of a reverse roller for reversing and feeding the sheet 5 fed from the take-in conveyance path 90a and three double-sided conveyance roller pairs 95. Yes.

  Further, it is possible to swing the branch plate 96 for switching between the conveyance path of the sheet 5 from the take-in conveyance path 90a to the switchback conveyance path 90b and the conveyance path for refeeding from the switchback conveyance path 90b to the conveyance roller pair 48. Provided. The branch plate 96 can swing between a switchback side position shown by a solid line in FIG. 1 and a refeeding side position shown by a broken line. Further, although not shown, an image start sensor for detecting the leading edge of the sheet 5 on the upstream side in the sheet conveying direction of the image forming unit 2 and an image end for detecting the trailing end of the sheet 5 on the downstream side in the sheet conveying direction. A sensor is provided.

  Next, the sheet pressing mechanism 9 of the reverse sheet discharge path 81 will be described with reference to FIGS. 4 is a side view showing the periphery of the paper pressing mechanism 9, FIG. 5 is a perspective view showing the periphery of the paper pressing mechanism 9, and FIG. 6 is a side view showing the vicinity of the arm in an enlarged manner. FIG. 7 is a perspective view showing the vicinity of the slider of the base portion, and FIG. 8 is a view for explaining the rotation of the arm with respect to the base member.

  As shown in FIGS. 4 to 7, the sheet pressing mechanism 9 is disposed inside the end fence 79 b (on the left side of the end fence 79 a in FIG. 4), and has an arm 178 that holds the sheet 5 of the sheet discharge tray 79. A sheet pressing unit 170, a motor 173 that is a drive source of the sheet pressing unit 170, and a transmission unit 160 that transmits the driving of the motor 173 to the arm 178 are provided.

  The sheet pressing portion 170 is inserted from the inner side to the outer side of the end fence 79b through a rectangular cutout 79d formed from the upper end to the lower side of the end fence 79b (in FIG. 4, on the right side of the end fence 79a, in other words, the discharge tray 79. And a base member (support member) 177 that is formed in a rod shape and is attached so that the arm 178 can rotate by a certain amount. And a torsion coil spring (biasing member) 161 that urges the arm 178 toward the paper discharge tray 79 (in the direction of pressing the paper 5).

  The arm 178 is attached to the base member 177 substantially vertically. Further, four arms 178 are arranged side by side along the base member 177, and among these arms 178, the leftmost and rightmost arms 178 are arranged on the left side and the left side of the discharge roller pair 78. Arranged on the right side, the central two arms 178 are arranged between a pair of discharge rollers 78 adjacent to each other. Further, the notches 79d described above are formed in the end fence 79b at positions corresponding to the respective discharge roller pairs 78.

  Further, the arm 178 urged toward the paper discharge tray 79 by the torsion coil spring 161 is restricted from further rotation by the base end portion of the arm 178 contacting the base member 177. (See left arm 178 in FIG. 8). As a result, when the arm 178 is driven (which will be described later), even if the user accidentally touches the arm 178, the arm 178 resists the urging force of the torsion coil spring 161, and the sheet discharge tray. In order to escape away from 79 (see the right arm 178 in FIG. 8), it is possible to prevent a user's finger or the like from being pinched strongly between the arm 178 and the paper receiving surface 79a of the paper discharge tray 179. .

  Further, the arm 178 is bent so that only its tip end can press the paper 5 on the paper discharge tray. That is, the arm 178 is formed in a substantially L shape by bending the substantially central portion of the arm 178 toward the paper discharge tray 79 in a state where the arm 178 is attached to the base member 177. Only the leading end of the sheet 5 comes into contact with the sheet 5 on the sheet discharge tray 79 (see FIG. 13), so that the sheet 5 can be surely pressed. It should be noted that a member with a high friction coefficient such as a rubber material is provided at the tip of the arm 178, or the contact portion of the tip of the arm 178 with the paper 5 is provided with a concavo-convex shape so that the paper 5 of the arm 178 You may make it prevent the slip with respect to.

  The transmission unit 160 includes a rotary shaft 176 having a reduction gear 172 attached to both ends thereof, a crank-shaped link 171, a slider 177 </ b> A that is provided at one end of the base member 177 and is formed in a cylindrical shape having a substantially elliptical cross section. It has. A rotary shaft 176 is inserted into the slider 177A so that it can slide in the axial direction with respect to the rotary shaft 176. Further, both ends of the base member 177 are rotatably held by links 171, respectively. Each link 171 is provided with a gear 162 that meshes with a reduction gear 192 provided at both ends of the rotating shaft 176.

  In the present embodiment, the right reduction gear 192 in FIG. 5 meshes with the gear 162 and the gear 173 A provided on the drive shaft of the motor 173, and the driving force of the motor 173 passes through the reduction gear 192. Is transmitted to the link 171. Thus, the base member 177, the slider 177A, the rotating shaft 196, and the link 171 constitute the slider link mechanism 163, so that the arm 178 can move up and down as shown in FIGS.

  As a result, the arm 178 is located inside the end fence 79a and below the pair of discharge rollers 78 so as not to come into contact with the sheet 5 discharged by the discharge roller pair 78 or any sheet 5 on the discharge tray 79. And a non-contact position (position shown in FIG. 9) located at the side, and a push-up position (position shown in FIG. 11) for pushing up the paper 5 discharged by the paper discharge roller pair 78 laterally between the paper discharge roller pair 78. The paper 5 on the paper discharge tray 79 is moved from the top to a pressing position (position shown in FIG. 13).

  6 and 7, the link 171 is provided with a detection plate 171A. A non-contact position detection sensor (movement position detection unit) 174A for detecting the detection plate 171A, a push-up position detection sensor ( A movement position detection unit) 174B and a presser position detection sensor (movement position detection unit) 174C are arranged so as to surround the link 171. That is, when the detection plate 171A of the link 171 is at a position detected by the non-contact position detection sensor 174A disposed on the left side of the link 171 in FIG. 6, the arm 178 is positioned at the non-contact position shown in FIG. ing. Similarly, when the detection plate 171A is at a position detected by the push-up position detection sensor 174B disposed above the link 171 in FIG. 6, the arm 178 is located at the push-up position shown in FIG. When the detection plate 171A is at a position detected by the presser position detection sensor 174C disposed below the link 171 in FIG. 6, the arm 178 is positioned at the presser position shown in FIG.

  FIG. 15 is a block diagram showing a control system of the image forming apparatus according to the present embodiment. As shown in FIG. 15, the image forming apparatus includes a roller driving unit 164 that drives a conveyance roller 71, a reverse roller pair 77, and a paper discharge roller pair 78, a paper discharge detection sensor 179, and a non-contact position detection sensor 174A. The push-up position detection sensor 174B, the press-position detection sensor 174C, and a liquid crystal display device, etc., have a function of displaying the state and setting status of the image forming apparatus to the user and a copy for starting an image forming operation. A display / input unit 141 on which a start button, a button for setting the type of paper 5, and the like are arranged, a paper feed unit 4, sensors and drive units necessary for the paper feed unit 4, a paper discharge transport unit 7, paper discharge Sensors and driving units necessary for the transport unit 7, sensors and driving units necessary for the image reading unit 11 and the image reading unit 11, sensors and driving units necessary for the duplex unit 10 and the duplex unit 10. Control unit 140 of the microcomputer parts and are connected to the image forming apparatus by transmitting and receiving signals are controlled with respect to each unit.

  Next, the operation of the image forming apparatus will be described based on the flowcharts shown in FIGS. First, when the non-contact position detection sensor 174A detects the detection plate 171A of the link 171, that is, when the arm 178 is at the non-contact position shown in FIG. 9 (Yes in step S1), the process proceeds to step S5. On the other hand, when the non-contact position sensor 174A does not detect the detection plate 171A (No in step S1), the motor 173 rotates forward (forward drive) (step S2), and the non-contact position detection sensor 174A is linked 171. When the detection plate 171A is detected (step S3), the driving of the motor 173 is stopped (step S4), and the arm 178 is in the non-contact position shown in FIG. 9, that is, the arm 178 is inside the end fence 79a and discharging paper. Alternatively, it stops at a non-contact position where it does not interfere (contact) any paper on the paper discharge tray 79. Thus, the arm 178 does not interfere with the paper discharge operation of the paper 5 by the paper discharge roller pair 78, and the paper 5 can be smoothly discharged.

  Next, the image forming unit 2 is driven (step S5), and the sheet 5 printed by the image forming unit 2 passes through the reverse discharge path 81 and is conveyed by the reverse roller pair 77 (step). S6) When the paper 5 is detected by the paper discharge detection sensor 179 (step S7), the process proceeds to step S8.

  In step S8, it is determined whether the type of paper 5 (the type of paper to be discharged) set by the user operating the display / operation unit 141 during image formation is thick paper or envelope. . In order to determine the type of the paper 5, instead of the setting by the user described above, the lever 213 is pushed down to the position shown in FIG. Alternatively, it may be determined that an envelope or the like is used.

  If the set type of paper 5 is other than cardboard or envelope, when the push-up position detection sensor 174B detects the detection plate 171A of the link 171, that is, the arm 178 is in the non-contact position shown in FIG. (Yes in step S9), the process proceeds to step S13. On the other hand, when the push-up position sensor 174B does not detect the detection plate 171A (No in step S9), the motor 173 rotates backward (reverse drive) (step S10), and the arm 178 is moved from the state shown in FIG. 14, FIG. 13, FIG. 12 and FIG.

  When the push-up position detection sensor 174B detects the detection plate 171A of the link 171 (step S11), the drive of the motor 173 is stopped (step SS12), and the arm 178 is moved to the push-up position shown in FIG. It is positioned to the side between the nips of the pair of paper discharge rollers 78 and stops so as to block the paper discharge passage formed by the reverse paper discharge path 81.

  The paper 5 transported by the paper discharge transport unit 7 is finally discharged by the paper discharge roller pair 78. At this time, the arm 178 in the push-up position is above the nip (transport path) of the paper discharge roller pair 78. Stick out. For this reason, as shown in FIG. 19, each arm 178 pushes up the paper 5 ejected by the paper ejection roller pair 78 and deforms the paper into a wave shape (uneven shape) in the width direction. While curling, the curl is corrected and discharged. As a result, the paper 5 can be discharged onto the paper discharge tray 79 while curling of the paper 5 is suppressed, and the curled paper 5 can be prevented from closing the exit side of the nip of the paper discharge roller pair 78. As a result, it is possible to prevent the paper 5 discharged by the paper discharge roller pair 78 from pushing out the already discharged paper 5.

  A certain time T1 after the paper discharge detection sensor 179 no longer detects the paper 5 (the paper 5 is completely discharged to the paper discharge tray 79 after the paper discharge detection sensor 179 in step S13 stops detecting the paper. 11) until the motor 173 rotates forward and the presser position detection sensor 174C detects the detection plate 171A of the link 171 from the state shown in FIG. It rotates clockwise in the order shown in FIG. 13 (step S15 and step S15). Thereafter, until the presser position detection sensor 174C detects the detection plate 171A, the arm 178 rotates clockwise from the state shown in FIG. 11 in the order of FIG. 12, FIG. 13, FIG. 9, FIG. (Step S17, Step S18 and Step S19). Thereafter, when the image forming operation (printing) is continuing (No in step S20), the operations in steps S7 to S19 described above are repeated.

  Even if the rear end portion of the sheet 5 is caught by the driven roller 78b by the operation of the arm 178, the rear end portion of the sheet 5 is scraped off by the arm 178 that rotates in the order of FIGS. The sheet 5 can be reliably discharged. Thereafter, the arm 178 rotates in the order of FIGS. 12 and 13 and presses the sheet 5 on the sheet receiving surface 79a of the sheet discharge tray 79 from above. As described above, since the arm 178 presses the paper 5 from above, even if the curl of the stacked paper 5 is large, the rear end of the paper 5 blocks the exit side between the nips of the paper discharge roller pair 78. Can be prevented.

  On the other hand, when the printing of the image forming unit 2 is finished by the control unit 140 (Yes in step S20), the operation of the image forming unit 2 is stopped (step S21), and accordingly, the reverse roller pair 77 and the discharge roller pair. The driving of the rollers such as 78 is stopped (step S22). Then, the motor 173 is rotated forward to rotate the arm 178 to the non-contact position, and when the arm 178 reaches the non-contact position, the driving of the motor 173 is stopped (steps S23 to S26). By operating the arm 178 as described above, the paper 5 can be reliably stacked on the paper discharge tray 79.

  Here, as shown in FIG. 19, even if an attempt is made to deform the paper 5 in a wavy shape by the arm 178 at the push-up position, a strong paper (a predetermined specific type of paper) such as an envelope or a thick paper. In this case, the paper 5 may not bend and the paper 5 may be damaged. For this reason, when thick paper or an envelope is used as the paper 5, it is necessary to change to a mode different from the driving mode of the arm 178 described above. Specifically, during the paper discharge, the arm 178 does not move to the push-up position, and appropriate measures are taken according to the type of the paper 5.

  That is, if the type of the paper 5 set by the user is cardboard or envelope in step S8, the paper discharge detection sensor 179 stops detecting the paper 5 for a certain time T2 (discharge detection in step S7). When the time from when the sensor 179 no longer detects the paper until the time when the paper 5 is completely discharged to the paper discharge tray 79 elapses (step S14), the non-contact position detection sensor 174A detects the link 171 detection plate. When 171A is detected (Yes in step S28), the process proceeds to step S32.

  On the other hand, when the non-contact position sensor 174A does not detect the detection plate 171A (No in step S28), for example, when the arm 178 is in the presser position for the second and subsequent printings, the non-contact position detection sensor. The motor 173 rotates forward (forward drive) until 174A detects the detection plate 171A, whereby the arm 178 rotates clockwise and stops at the non-contact position shown in FIG. 9 (steps S29 to S31). As a result, the sheet 5 is discharged to the sheet discharge tray 79 as it is. When a certain time T1 has elapsed after the paper discharge detection sensor 179 no longer detects the paper 5 (step S14), the arm 178 is rotated clockwise until the presser position detection sensor 174C detects the detection plate 171A. As a result, if the rear end portion of the paper 5 blocks the exit side of the nip of the paper discharge roller pair 78, the paper 5 is scraped off and then the paper 5 on the paper discharge tray 79 is pressed.

  In this way, only the paper 5 excluding thick paper and envelopes that are unlikely to cause a stack failure is made wavy (uneven shape) so that the front end of the paper touches the paper 5 that has already been ejected and is not moved so as not to push it out. It is possible to ensure good stackability with little damage to other sheets.

  The arm 178 for improving the stackability is less effective with respect to the small size paper 5, so that even when the size is small, the same control as that for thick paper or envelope, that is, the same as step S27 to step S34. It is desirable to perform such control or not to move the arm 178 from the non-contact position. Here, in order to detect the size of the paper 5, for example, a paper detection unit (not shown) is provided in the carriage 23, and at the time of printing, the both ends of the paper 5 are detected and the operation speed of the carriage 23 and the time when both ends of the paper are detected are detected. The size can be calculated, and the operation of the arm 178 may be controlled in accordance with the paper size.

  The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the invention.

  In the above embodiment, the type of the paper 5 is determined by the user setting or the position of the carriage 23. Instead, the thickness of the paper is detected and the thickness reaches a predetermined thickness. Then, the arm 181 may be positioned at the pushed-up position.

  Specifically, as shown in FIG. 22, the solid line rotated from the reference position by being pushed by the sheet 5 passing between the reference position indicated by the alternate long and short dash line and each of the guide plates 73 and 74 to the discharge conveyance unit 7. A filler 192 that can rotate around the rotation shaft 192a, a filler detection sensor 190 that detects the filler 192 at the rotation position, and a spring that biases the filler 192 toward the reference position And a sheet thickness detecting unit 189 having an elastic member 194 such as the like.

  The filler 192 is pushed by the paper 5 and is located at the rotational position only when the paper 5 having a predetermined thickness or more passes between the guide plates 73 and 74. Based on the detected information from the filler detection sensor 190, it is determined in step S8 shown in FIG. 16 that thick paper such as an envelope is used as the paper 5. By doing so, it is possible to automatically determine the type of the paper 5 even if the user does not specify the type of the paper 5 by operating the operation unit 141.

  Further, as a means for detecting the thickness of the sheet 5, as shown in FIG. 23, instead of the sheet thickness detecting unit 189 shown in FIG. 22, the light emission disposed above the upper guide plate 74 of the sheet discharging and conveying unit 7 is used. It is also possible to use a transmissive sensor 200 that includes a portion 201 and a light receiving portion 202 that is disposed below the lower guide plate 73 and receives light from the light emitting portion 201.

  That is, when the paper 5 is not passed (normally), the light receiving unit 202 receives a certain amount of light from the light emitting unit 201, but the paper 5 is between the light emitting unit 201 and the light receiving unit 202. , The amount of light received by the light receiving unit 202 changes according to the thickness of the paper 5. Based on the amount of light received by the light receiving unit 202, the control unit 140 determines the thickness of the sheet 5 in step S8 shown in FIG. 16 and determines that a thick sheet such as an envelope is used as the sheet 5. This also makes it possible to automatically determine the type of the paper 5 without the user having to specify the type of the paper 5 by operating the operation unit 141. Needless to say, an appropriate sensor such as a so-called reflection type distance sensor can be used instead of the transmission type sensor 201 shown in FIG.

  Further, instead of controlling the arm 178 according to the type of the sheet 5 as in the above-described embodiment, the arm 178 may be controlled according to the printing rate of the sheet 5. Specifically, a paper detection sensor (not shown) is provided in the carriage 23, and an ink amount detection unit (droplet amount detection unit) 212 that detects the amount of ink ejected from each head 24 of the carriage 23 onto the paper 5 is provided. Provide.

  When the carriage 23 is moving in the main operation direction during printing, the time during which the paper detection sensor of the carriage 23 is detecting the paper 5 is measured, and the measured time and the movement speed (operation speed) of the carriage 23 are measured. ) To calculate the sheet size, and based on the sheet size and the ink amount detected by the ink amount detection unit at the time of printing, the ink amount per unit area of the sheet 5 (unit ink amount), in other words The printing rate of the paper 5 is calculated.

  The ink amount detection by the ink amount detection unit 212 may be a method of directly detecting the amount of ink ejected at the time of printing, or the ink ejection amount determined for each dot constituting the image. A method may be used in which the total amount of ink used is obtained by counting. That is, in the case of light red, it is set so that a magenta droplet apl (picoliter), a yellow droplet bpl, and cyan 0 pl (no cyan) are used. In this case, the ink amount of this dot is (a + b) pl. The other dots are similarly determined, and the sum of the ink amounts of all the dots is transmitted from the ink amount detection unit 212 to the control unit 140 as the ink amount in the image.

  When the amount of ink per unit area of the paper 5 is less than a predetermined value, that is, when the printing rate on the paper 5 is low and problems such as curling are unlikely to occur, FIG. 16 shows. Either the same control as in the case of No in step S8 or the control not to move the arm 178 from the non-contact position is performed. On the other hand, when the ink liquid amount has reached a predetermined value, the same control as in the case of Yes in step S8 shown in FIG. 16 is performed.

  Since the paper 5 that has been printed with ink dries from the front end in the transport direction after printing, curling occurs only at the rear end when the paper 5 is discharged onto the paper discharge tray 79. Therefore, it is desirable to calculate the unit ink amount of only the rear end portion of the paper 5.

  As described above, the operation of the arm 178 is performed when the printing rate of the paper 5 is relatively low and curling of the paper 5 is difficult to occur, and when the printing rate of the paper 5 is relatively high and curling of the paper 5 is likely to occur. The mode is switched, and the drive of the arm 181 can be controlled at an appropriate timing according to the printing rate of the paper 5.

  In the above-described embodiment, only the tip of the arm 178 is in contact with the paper 5, but instead, as shown in FIG. 24, a roller 178A is rotatable at the tip of the arm 178. The sheet 5 may be pressed by the roller 178A. In this case, it is possible to prevent the leading end portion of the arm 178 and the paper 5 from rubbing and damaging the paper 5 such as scratches.

1 is a schematic configuration diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a plan view of an image forming unit and a sub-scanning conveyance unit according to the embodiment. It is a side view which shows the carriage which concerns on embodiment, and its periphery. FIG. 6 is a side view showing the periphery of a paper pressing mechanism. FIG. 6 is a perspective view showing the periphery of a paper pressing mechanism. It is a side view which expands and shows the vicinity of an arm. It is a perspective view which shows the vicinity of the slider of a base part. It is a figure explaining rotation of the arm with respect to a base member. It is a figure which shows the state which the arm has stopped in the non-contact position. It is a figure for demonstrating the state which the arm is rotating. It is a figure which shows the state which the arm has stopped in the pushing-up position. It is a figure for demonstrating the state which the arm is rotating. FIG. 6 is a diagram illustrating a state where an arm is pressing a sheet from above at a pressing position. It is a figure for demonstrating the state which the arm is rotating. 1 is a block diagram illustrating a control system of an image forming apparatus according to an embodiment. 3 is a flowchart illustrating an operation flow of the image forming apparatus. 3 is a flowchart illustrating an operation flow of the image forming apparatus. 3 is a flowchart illustrating an operation flow of the image forming apparatus. It is a figure which shows the state in which the paper is pushed up by the arm in a push-up position. It is a figure explaining the position of the carriage when a lever is pushed up. It is a figure explaining the position of the carriage when a lever is pushed down. It is a figure which shows the paper thickness detection part which concerns on a modification. It is a figure which shows the transmission type sensor which concerns on a modification. It is a figure which shows the arm which concerns on a modification.

Explanation of symbols

2 Image forming section 23 Carriage (printing section)
78 discharge roller pair 79 discharge tray 141 display / input unit 140 control unit 161 torsion coil spring (biasing member)
163 Slider link mechanism 174A Non-contact position detection sensor (moving position detection unit)
174B Push-up position detection sensor (moving position detection unit)
174C Presser position detection sensor (moving position detection unit)
177 Base member (support member)
178 Arm (presser member)
178A Roller 179 Paper discharge detection sensor (paper discharge detection unit)
189 Paper thickness detector (thickness detector)
186 Drive unit 187 Arm position detection unit (distance detection unit)
213 Lever (operation member)
214 Lever position detection sensor (operation position detection unit)
215 Adjustment unit 212 Ink amount detection unit (droplet amount detection unit)

Claims (17)

An image forming unit having a printing unit for supplying droplets toward the paper to form an image corresponding to the original image, a paper discharge roller pair for discharging the paper from the image forming unit, and the paper discharge roller pair An image forming apparatus provided with a sheet stacking table on which sheets discharged from a pair of discharge rollers are stacked,
A pressing member is provided for pressing the paper discharged onto the paper mounting table from above, and the pressing member holds the paper discharged by the paper discharge roller pair between the non-contact position where it does not interfere with the paper and the paper discharge roller pair. An image forming apparatus, wherein the image forming apparatus is provided so as to be movable between a push-up position where the paper is pushed up sideward and a press-down position where the paper on the paper placement table is pressed from above.   A control unit that controls driving of the presser member is provided, and the control unit stops the presser member at any one of the non-contact position, the push-up position, and the presser position according to the paper discharge state. Item 4. The image forming apparatus according to Item 1. A paper discharge detection unit that detects a sheet toward the paper discharge roller pair, and a movement position detection unit that detects whether the presser member is in the non-contact position, the push-up position, or the presser position.
When the paper discharge detection unit detects the paper, the control unit moves the presser member from the non-contact position to the push-up position and stops at this position, and after the paper detection by the paper discharge detection unit is finished, The image forming apparatus according to claim 2, wherein the image forming apparatus is stopped after being moved from the push-up position to the presser position.   The image forming apparatus according to claim 2, wherein the control unit changes a driving mode of the pressing member according to a type of the sheet.   The control unit controls to keep the presser member stopped only at the non-contact position when the paper type is a predetermined specific type, or moves the presser member at the non-contact position to the press position after the paper discharge is completed. The image forming apparatus according to claim 4, wherein the control is performed to stop the operation after the image is stopped.   A thickness detection unit that detects the thickness of the paper, and the control unit determines that the type of the paper is a predetermined specific type when the thickness of the paper is a predetermined thickness. The image forming apparatus according to claim 5.   The image forming apparatus according to claim 5, further comprising an input unit that inputs a paper type by a user operation, wherein the control unit determines the paper type based on information from the input unit.   The image forming unit includes an adjustment unit that adjusts the distance between the printing unit and the paper according to the thickness of the paper, and the control unit determines the type of paper when the distance between the printing unit and the paper reaches a predetermined distance. The image forming apparatus according to claim 5, wherein the image forming apparatus is determined to be a predetermined specific type.   The image forming apparatus according to claim 8, further comprising a distance detection unit that detects a distance between the printing unit and the sheet, wherein the control unit determines the type of the sheet based on information from the distance detection unit.   The adjustment unit includes an operation member that adjusts the distance of the printing unit with respect to the sheet when operated by a user, and an operation position detection unit that detects the position of the operation member. 9. The image forming apparatus according to claim 8, wherein the type of paper is determined based on the information.   A droplet amount detection unit that detects a droplet amount per unit area of the sheet is provided, and the control unit changes the driving mode of the pressing member according to the amount of droplets per unit area of the sheet. The image forming apparatus according to claim 2.   The image forming apparatus according to claim 11, wherein the droplet amount detection unit detects an appropriate amount of liquid per unit area on the rear end side of the sheet.   The control unit controls to keep the pressing member stopped only at the non-contact position when the amount of liquid droplets per unit area of the paper reaches a predetermined amount, or presses the pressing member at the non-contact position after the paper discharge is completed. The image forming apparatus according to claim 11, wherein the image forming apparatus performs any one of the control of stopping after moving to the position.   14. A support member that rotatably supports the presser member and a biasing member that biases the presser member in a direction in which the paper is pressed are provided. Image forming apparatus.   15. The slider link mechanism according to claim 14, further comprising: a slider link mechanism that transmits a driving force from a driving source to the presser member and moves the presser member to any one of a non-contact position, a push-up position, and a presser position. Image forming apparatus.   16. The image forming apparatus according to claim 1, wherein only the front end portion of the pressing member is bent so as to press the sheet on the sheet placing table.   The image forming apparatus according to claim 1, wherein the pressing member is provided with a roller that presses the sheet on the sheet placing table from above.

Images