JP5516714B2 - Paper discharge device and image forming apparatus - Google Patents

Description

  The present invention relates to a paper discharge device that discharges and accumulates paper on a paper discharge tray by a pair of paper discharge rollers, and in particular, discharge of an image forming apparatus such as a printer or a copy that curls the paper by using a thermal fixing method or the like. The present invention relates to a paper apparatus and an image forming apparatus having the same.

  2. Description of the Related Art Conventionally, in a fixing device that fixes a toner image in an image forming process, a sheet subjected to fixing processing by a heating roller and a pressure roller has both ends of the sheet in a direction orthogonal to the sheet discharge direction due to thermal stress and atmospheric temperature. It may curl to rise (see FIG. 10). In the paper discharge device that discharges the paper conveyed from the fixing device by the paper discharge roller and deposits the printed paper on the paper discharge tray, especially when the upward curl amount of the side portion of the stacked paper is large The leading end of the discharged paper that comes out pushes the bottom edge of the stacked paper on the paper discharge tray or sinks thereunder, so that the stacked paper may fall or the pages may be out of order. In order to solve such problems, the paper discharge tray has been enlarged or a movable paper guide has been added in the vicinity of the paper discharge roller.

For example, in Patent Document 1, a movable paper guide that is operated by a driving source such as a solenoid is provided, so that when the front end of the paper is discharged, the discharged paper is directed upward so that the stacked paper is not pushed by the front end of the paper. At the time of discharge, the trailing edge of the stacked paper is lifted and is directed downward so as not to be pushed by the leading edge of the discharged paper.
However, when the paper discharge tray is enlarged, the machine size is increased correspondingly, and when a movable paper guide as in Patent Document 1 is used, a drive source, a gear, or a spring is required, so it is necessary to secure a corresponding space. . Therefore, if a large paper discharge tray or movable paper guide is not used, further downsizing and cost reduction are possible.

In Patent Document 2, a sheet member for pressing the sheet is provided on both sides of the sheet, and the lower end of the sheet member is positioned below the nip between the sheet discharge roller from which the sheet is discharged and its opposing roller. Thus, the trailing edge of the sheet on the sheet discharge tray is prevented from being pushed by the leading end of the sheet to be discharged next.
However, in this case, since the sheet members on both ends are longer than the sheet, the sheet may be folded.

  In Patent Document 3, a waist roller, an arm member for swinging the roller, a tension spring for biasing the arm member, and the like are separately provided on the outside of the paper discharge driving roller and the paper discharge driven roller. A means for properly seating on thin paper and thick paper by a roller is disclosed. However, the cost and space for arranging the seating rollers are required.

  In Patent Document 4, two spoon-shaped filler portions installed on different axes from the axis of the pair of paper discharge rollers, a back curl detection sensor for detecting whether the loaded paper is back curled or not curled, and a full back curl A detection plate is provided to determine the presence or absence of back curl. However, the cost and space for providing these are still required.

  Patent Document 5 is a sheet pressing member in which one end is fixed to a frame member as a holding member and the other end is slidably held, and protrudes in the stacking direction between the both ends. There is disclosed a structure that has a bent portion and the bent portion is close to the surface receiving portion of the loading table. However, cost and space for providing the frame member separately from the shaft provided with the discharge roller are required.

  Patent Document 6 discloses a pressing member that is installed at a position that does not contact the leading end portion of the sheet discharged by the discharging roller but contacts the trailing end portion of the sheet that has already been discharged by the discharging roller. .

  Further, in an image forming apparatus having a paper discharge device that discharges paper conveyed from the fixing device by a paper discharge roller and deposits printed paper on a paper discharge tray, the paper is conventionally applied to the paper discharged from the paper discharge roller. In order to improve the alignment of the stack sheets, the position of the discharged sheets on the discharge tray is controlled according to the shape of the discharge tray. As a means for applying the stiffness to the sheet, a portion having a large diameter with respect to the nip portion of the discharge roller pair is often provided on the drive roller or the driven roller shaft. Also, in order to prevent the trailing edge of the paper from staying in the vicinity of the pair of paper discharge rollers and to reliably stack the paper on the paper discharge tray, the kick having a concavo-convex shape having a larger diameter than the nip portion of the paper discharge roller pair It is also practiced to kick the trailing edge of the paper with a dashi member.

On the other hand, when the curl amount of the discharged paper is large, the leading edge of the paper discharged from the rear end of the stacked paper on the paper discharge tray may be pushed, and the stacked paper may fall or the page may be out of order. For this reason, a paper presser is used to reduce the curl amount of the discharged paper with a simple configuration and to press the vicinity of the trailing edge of the stacked paper against the paper discharge tray so that the leading edge of the discharged paper does not push the trailing edge of the stacked paper. Members may be installed.
However, if the end of the paper is bent downward by adding the paper pressing member on the end side, the wavy deformation of the paper is formed in the width direction, which is a large amount for the above-mentioned paper stiffness and kicking. In some cases, the paper tends to escape from the diameter portion, and the aiming effect cannot be obtained.

  In Patent Document 7, in order to eliminate problems such as curling of the paper during ejection and pushing out of the previous paper, a wave is applied to the paper at a substantially central portion in the paper width direction of the surface of the ejection claw that is in sliding contact with the paper toward the paper ejection tray. Disclosed is a means for providing a protrusion for applying the upper deflection.

  Patent Document 8 discloses a paper pressing mechanism and a paper pressing member for suppressing curling even when the end of the paper discharged onto the in-body tray is largely curled due to the material of the paper or the moisture absorption state.

  Therefore, according to the present invention, in an image forming apparatus having a paper discharge device that discharges paper conveyed from the fixing device by a paper discharge roller and deposits printed paper on the paper discharge tray, , With a simple configuration without using a movable paper guide having a drive source or drive mechanism, even when large upward curl upwards occur on the discharged paper, the accumulated discharged paper is not bulky by the curl, and the discharge that comes out later An object of the present invention is to provide an image forming apparatus in which the leading edge of the paper does not push the bottom edge of the stacked paper on the paper discharge tray or dig into the bottom of the paper, and therefore does not cause the stacked paper to fall or out of page.

  Furthermore, the present invention provides a paper discharge device that discharges paper onto a paper discharge tray by a pair of paper discharge rollers. Stackability is also possible for various curled papers, which can prevent the paper from being bent and cause the paper to be squeezed evenly, or the trailing edge of the paper can be reliably kicked out. An object of the present invention is to provide a good paper discharge device.

In order to solve this problem, the present invention is provided with at least two paper discharge roller pairs including a rotatable upper paper discharge roller and a lower paper discharge roller, and the paper is discharged to the paper stacking section by the paper discharge roller pair. And a rotatable paper pressing means that comes into contact with the paper downstream of the nip portion of the paper discharge roller pair with respect to the paper discharge direction. The retraction unit is located between the lower end portion of the lower paper discharge roller and the upper surface of the paper stacking portion when retracted, and the paper pressing means has an end pressing portion and an inner pressing portion, and the end pressing portion At the time of maximum retraction, the front end portion of the inner side is closer to the lower discharge roller side than the common tangential direction of the upper discharge roller and the lower discharge roller. The upper discharge roller Suggest sheet discharging device for being located on the upper discharge roller side than in the direction of the common tangent of the lower discharge roller.

  The sheet pressing means is preferably lifted and retracted from the non-retracted position by a force received from the paper, and returned to the non-retracted position by gravity.

  Further, it is preferable that a diameter of the upper discharge roller is smaller than a diameter of the lower discharge roller.

  Further, it is preferable that the sheet pressing unit is rotatably supported on a rotation shaft of the upper sheet discharge roller.

  The image forming apparatus according to the present invention preferably includes the paper discharge device.

  In the paper discharge device according to the present invention, at least two inner paper discharge rollers and at least two outer paper discharge rollers attached to the rotation shaft, and at least two inner paper discharge followers respectively facing the paper discharge rollers. A roller and at least two outer paper discharge driven rollers, at least for pressing a side surface portion of the paper to be discharged disposed rotatably on the same rotation axis as the paper discharge roller and adjacent to the outside of the outer paper discharge roller. Two end-side pressing portions, and at least two inner pressing portions for pressing the side surface portion of the paper rotatably disposed adjacent to the outer side of the inner discharge roller on the same rotation shaft as the discharge roller. The inner pressing portion and the end pressing portion extend from the rotating shaft beyond the common tangent of the discharge roller and the discharge driven roller when not retracted, and the end pressing portion is the inner pressing portion. Than Long, configured to rest on the sheet deposited on the sheet stacking portion. As a result, the side portion of the paper is bent downward toward the image forming apparatus main body due to the weight of the inner pressing portion and the end-side pressing portion at the time of discharge, and the side portion of the discharged paper is particularly upward. The amount of curling of the sheet can be reduced, the contact area of the leading end of the discharged sheet with the stacked sheet is reduced, and the stacked sheet is less likely to be pushed by the leading end of the discharged sheet. Furthermore, the end side pressing portion presses and flattens the vicinity of the rear end of the stacked paper against the paper discharge tray by its own weight, so that the rear end of the stacked paper does not become bulky due to curling. Next, the leading edge of the sheet to be discharged is difficult to push the trailing edge of the accumulated paper or to get under the accumulated paper. In this way, it is possible to reliably deposit the discharged paper on the paper discharge tray without causing a paper drop or page order error even for a paper having a particularly large amount of side curl.

  In addition, with these simple configurations, it is possible to realize a high-quality image forming apparatus that does not cause paper drop or page misalignment without increasing the paper discharge tray or adding a movable guide that requires a drive source. At the same time, the apparatus can be reduced in size and cost.

It is a general view (center section) of the present invention. 1 is a schematic diagram illustrating a paper discharge device according to an embodiment of the present invention. FIG. 10 is a schematic diagram illustrating the operation of the end-side pressing portion and the details of the end-side pressing portion when discharging paper. FIG. 10 is a schematic diagram illustrating the operation of the inner pressing portion and the details of the inner pressing portion when paper is discharged. It is a schematic diagram showing the shape of the paper being discharged. It is a schematic diagram showing the shape of the paper being discharged. It is a figure which shows the large diameter part of the inner side discharge driven roller to which the uneven | corrugated shape to which the convex part of a large diameter and the recessed part of the same diameter as a nip part were arranged in the circumferential direction was attached | subjected. FIG. 6 is a schematic diagram illustrating the operation of the center pressing portion during sheet discharge and details of the center pressing portion. FIG. 6 is a schematic diagram illustrating a shape of a paper discharge driven roller. It is a schematic diagram which shows a curled paper.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
FIG. 1 is an overall view (center sectional view) of the present invention. The paper 4 fed from the paper feed cassette 27 by the paper feed roller 28 is sent out by the registration rollers 29 and 30 and reaches the transfer driving roller 31 and the transfer driven roller 32. The transfer driving roller 31 is in the intermediate transfer belt 33 and rotates the intermediate transfer belt 33.

Here, the image forming process will be described.
There are four developing units 34 (34a, 34b, 34c, 34d) containing toners of different colors as developers, and a photoreceptor 35 (35a, 35b, 35c, 35d) arranged in combination with these developing units 34. A charging roller 36 (36a, 36b, 36c, 36d) that is disposed and contacts the photoconductor 35 is provided. These are integrated to form a photoreceptor unit 37 (37a, 37b, 37c, 37d). The charging roller 36 contacts the surface of the photoconductor 35 and uniformly charges the surface of the photoconductor 35. Subsequently, the exposure device 38 exposes the surface of the photoconductor 35 with a laser beam 39 to form an electrostatic latent image on the surface of the photoconductor 35. Next, the developing device 34 visualizes the electrostatic latent image formed on the surface of the photoconductor 35 with toner, and forms a toner image on the surface of the photoconductor 35. Subsequently, a toner image is transferred from the surface of the photoreceptor 35 to the surface of the intermediate transfer belt 33.

  Through the image forming process as described above, the toner image on the intermediate transfer belt 33 is transferred to the sheet by the transfer driving roller 31 and the transfer driven roller 32, and is conveyed to the fixing device 26, and is fixed by the fixing roller 40 and the pressure roller 41. The image is fixed on the paper 4, the paper 4 is deposited on the paper discharge tray 3 by the paper discharge device 1, and printing ends.

The paper discharge device will be described with reference to FIG.
2A is a side sectional view of the paper discharge device 1, and FIG. 2B is a perspective view of the paper discharge device 1. FIG. The paper discharge device 1 of the present invention includes a paper discharge roller group 2 composed of a rotating shaft 2a and upper and lower paper discharge rollers 2b, a drive source (not shown) for driving the paper discharge roller group 2, and a discharge source. The paper discharge roller group 2 is driven and rotated by the outer discharge driven roller 5a, the inner discharge driven roller 5b, and the discharge roller group 2 which are driven by the paper roller group 2 to convey the paper 4 to the discharge tray 3. The reverse driven roller 6, the paper discharge roller group 2, the outer paper discharge driven roller 5a, and the guide 7 for conveying the paper 4 to the contact portion of the inner paper discharge driven roller 5b, the paper discharge roller group 2, and the reverse driven roller. 6, a guide 8 that conveys the paper 4 to the contact portion 6, a guide 9 that guides the paper 4 reversed by the reverse driven roller 6 to the reverse conveyance portion, and the paper 4 that has been conveyed to the paper discharge roller group 2 and the outer paper discharge driven roller. 5a and inner discharge driven roller 5 Switching guide 10 for switching between the contact portion and the paper discharge rollers 2 to the contact section of the reverse driven roller 6, consisting of the switching control mechanism (not shown) for controlling the switching guide 10.

  The paper discharge roller group 2 includes a rotation shaft 2a and outer and inner paper discharge rollers 2b. The outer and inner paper discharge rollers 2b are made of a rubber material so that the outer and inner paper discharge rollers 2b and the outer A friction force necessary for sheet conveyance is provided between the sheet 4 and the outer and inner sheet discharge rollers 2b sandwiched between contact portions of the sheet discharge driven roller 5a, the inner sheet discharge driven roller 5b, and the reverse driven roller 6. . The end pressing part 11 a and the inner pressing part 11 b are fixed to the rotating shaft 2 a of the paper discharge roller group 2 without being synchronized with the rotation operation of the paper discharge roller group 2.

Next, the operation of the end-side pressing portion 11a when discharging the paper will be described with reference to FIG.
The sheet 4 that is nipped and conveyed by the outer and inner sheet discharge rollers 2b and the outer sheet discharge driven roller 5a from the fixing device 26 has an R shape of the end side pressing portion 11a at the non-retracted position at the sheet front end 4s. It contacts the sheet conveying surface 12 with the mark (see FIG. 3 (3)). Here, when the sheet is not retracted, the end-side pressing portion 11a is lowered by its own weight when the sheet 4 is not deposited on the discharge tray 3 in the rotation locus A of the end-side pressing portion 11a, and the sheet conveying surface 12 is moved. Is placed on the stopper portion 13 of the guide 7 and when the paper 4 is accumulated on the paper discharge tray 3 in the rotation locus A of the end side pressing portion 11a, the end side pressing portion 11a is lowered by its own weight. That is, when the tip 16 of the end-side pressing portion 11a is placed on the paper 4 accumulated on the paper discharge tray 3 (see FIGS. 3 (1) and (2)).

  Here, since the end-side pressing portion 11a extends beyond the common tangent line of the paper discharge roller and the paper discharge driven roller from the rotation shaft, the end side pressing portion 11a comes into contact with the side portion of the discharged paper and exerts a downward force on the paper by its own weight. To reduce the upward side curl of the side of the paper. Further, the end-side pressing portion 11a is configured to be placed on the paper accumulated on the tray. Therefore, the vicinity of the rear end of the accumulated paper 4 is pressed against the discharge tray 3 and flattened by its own weight. Here, since the frequently used paper having the maximum printing paper width such as A4 paper, letter paper, and legal paper has a large amount of curl, the end side presser portion 11a has the inner side presser portion so that the deflection for correcting the curl is increased. It is preferable if it is longer than 11b. In this way, the trailing edge 4k of the stacked paper 4 is not bulky due to curling. Therefore, the leading edge of the next discharged paper is prevented from pushing the trailing edge 4k of the stacked paper due to curling. . Note that the front end portion 16 of the end-side pressing portion 11a is placed on the rear end portion 4k of the stacked paper when the paper is accumulated to a height of about 20 mm from the tray, for example. Otherwise, the end side holding portion 11 a is placed on the stopper portion 13 of the guide 7.

  Next, the paper 4 is further conveyed. At this time, the distal end portion 16 of the end-side pressing portion 11a is in contact with the outer and inner discharge rollers 2b at the time of maximum retraction when the positioning portion 14 of the end-side pressing portion 11a contacts the retraction stopper 15 provided on the guide 8. It is located at a distance L1 closer to the outer paper discharge driven roller 5a than the direction of the common tangent line 17 of the outer paper discharge driven roller 5a (the paper discharge direction when there is no end pressing portion 11a and inner pressing portion 11b) (FIG. 3 (2)). Therefore, the end-side holding portion 11a maintains the maximum retracted position around the rotating shaft 2a by the spring force F of the discharged paper, and the discharged paper is bent and discharged toward the paper discharge tray 3. The discharge direction is set in advance within the carry-out range A, so that the discharged paper is bent excessively toward the paper discharge tray 3, and the leading edge 4 s of the discharged paper is behind the paper 4 accumulated on the paper discharge tray 3. The end 4k is not pushed.

  When the paper trailing edge 4k of the paper 4 being discharged is removed from between the outer and inner paper discharge rollers 2b and the outer paper discharge driven roller 5a, the end-side pressing portion 11a returns to the non-retreat position (see FIG. 3 (1)). The end-side pressing portion 11a pushes down the rear end 4k of the paper 4 toward the paper discharge tray 3 or the stacked paper 4 by its own weight. The length La of the end-side pressing portion 11a is set so as to be located at a distance L2 from the rear end 4k of the stacked paper 4 and the front end portion 16 of the end-side pressing portion 11a contacts the paper 4. .

  As described above, the front end portion 16 of the end-side pressing portion 11a contacts and presses against the paper 4, so that even the paper 4 curled upward as shown in FIG. 10 accumulates on the paper discharge tray 3. The sheet trailing edge 4k of the sheet 4 is not bulky due to curling. Accordingly, the height of the stacked sheets does not exceed the common tangent line of the outer and inner discharge rollers 2b and the outer discharge driven roller 5a. It is possible to prevent the stacked sheets from falling by pushing the rear end 4k of the sheet and the occurrence of stacking failure such as page misalignment.

Next, the operation of the inner pressing portion 11b when discharging the paper will be described with reference to FIG.
Similarly to the end-side pressing portion 11a, the sheet 4 that is nipped and conveyed from the fixing device 26 between the outer and inner discharge rollers 2b and the inner discharge driven roller 5b is the inner pressing portion 11b when the leading end 4s of the sheet is not retracted. The sheet conveying surface 12 having the R shape is contacted. Here, the time of non-retraction means a state in which the inner pressing portion 11b is lowered by its own weight and the sheet conveying surface 12 is placed on the stopper portion 13 of the guide 7 (see FIG. 4A). The length Lb of the inner pressing portion 11b is determined so that the sheet trailing edge 4k of the paper 4 accumulated on the paper discharge tray 3 does not enter the rotation locus B of the inner pressing portion 11b.

  When the sheet 4 is further conveyed, the inner pressing portion 11b is pushed up around the rotation shaft 2a. At this time, at the time of maximum retraction when the positioning portion 14 of the inner pressing portion 11b contacts the maximum retraction stopper 15 provided on the guide 8, the tip portion 16 of the inner pressing portion 11b is connected to the outer and inner discharge rollers 2b. It is located on the outer side and the inner side discharge roller 2b side with respect to the direction of the common tangent line 17 of the inner side discharge driven roller 5b (the sheet discharge direction when there is no end-side pressing part 11a and inner pressing part 11b). Therefore, the inner pressing portion 11b does not reach the maximum retracted position, and the position where the leading end portion 16 is placed on the discharged paper 4 is the retracted position (see FIG. 4B).

  The paper 4 being discharged is not changed in the discharge direction by the inner pressing portion 11b, and is discharged in the vicinity of the common tangential direction of the outer and inner discharge rollers 2b and the inner discharge driven roller 5b. As described above, the inner pressing portion 11b extends from the rotating shaft beyond the common tangent line of the discharge roller and the discharge driven roller as in the case of the end-side pressing portion 11a. When the rear end 4k of the paper comes out from between the outer and inner discharge rollers 2b and the inner discharge driven roller 5b, it touches the discharged paper and applies a downward force to the paper by its own weight, The side curl is reduced, and the rear end 4k of the paper 4 is pushed toward the paper discharge tray 3 or the stacked paper 4.

  FIG. 5 shows the shape of the paper 4 being discharged, which is obtained by giving different operation ranges and shapes to the end-side pressing portion 11a and the inner pressing portion 11b in this way. FIG. 5A is a diagram viewed from the common tangential direction toward the outer and inner paper discharge rollers 2b, the outer paper discharge driven roller 5a, and the inner paper discharge driven roller 5b when wide paper is discharged. FIG. 5B similarly shows a view when a narrow sheet is discharged.

  The left and right end portions 19 of the sheet 4 are deformed in the direction of the sheet discharge tray 3 with a folding point 18 in the vicinity sandwiched between the outer and inner sheet discharge rollers 2b and the outer sheet discharge driven roller 5a (see FIG. 5). Since the paper is discharged while the paper is stiffened by this deformation, it is possible to reduce the curl amount 20 of the side portions of various curled papers including the side curled paper as shown in FIG.

  In the paper discharge device and the image forming apparatus of the present invention, the width of A4 paper, letter paper, and legal paper is set as the maximum print paper width. Then, by setting the left and right end portions 19 of these frequently used sheets to fall within the width Wa of the end-side pressing portion 11a, the sheets 4 stacked on the sheet discharge tray 3 by the sheet pressing means are arranged. The effect of pressing the rear end 4k of the sheet and the effect of reducing the side curl amount can be obtained on a frequently used sheet.

  Further, in the case of a paper having a narrow paper width such as a B5 paper and a small curl amount, by setting the paper left and right end portions 19 to fall within the width Wb of the inner pressing portion 11b, The effect on the end and side is obtained.

  In Patent Document 2, there is a possibility that the paper may be broken because the paper press on both ends is long with respect to the paper. However, according to the present invention, in addition to the end-side pressing portion that presses the end side of the paper, the inner pressing portion that presses the inner side of the paper is provided. This end-side pressing part forms a bend, and curling is reduced by applying stiffness to the paper. Further, since the end-side pressing part holds the discharged paper from above, the leading edge of the discharged paper is difficult to push the stacked paper and falls. Is prevented. Also, the inner pressing part prevents the edge of the paper from entering the inner side pressing part that sticks the paper and prevents the paper from being bent. Furthermore, the rear edge of the paper cooperates with the end pressing part. The force to push down is increased. For this reason, it is possible to cope with paper having a large width and large weight such as A4 paper and letter paper.

  In addition, by making the end side presser part longer than the inner side presser part, especially for high-use papers that have the maximum print paper width, such as A4 paper, letter paper, and legal paper, and that have a large curl amount Therefore, a large deflection for correcting the curl can be formed.

  In addition, the end-side pressing part and the inner pressing part are configured to be lifted and retracted from the non-retracted position by the force from the discharge paper, and to return to the non-retracted position by gravity, thereby easily and reliably discharging. It is possible to form a deflection in the direction of the rotation axis of the paper discharge roller with respect to the paper.

  Further, at least two end-side pressing portions and inner side pressing portions are provided, the end-side pressing portions are installed outside the pair of paper discharge rollers and the paper discharge driven roller, and the inner pressure holding portion is a pair of paper discharge rollers. And the outside of the paper discharge driven roller ensures that the desired deflection is applied to both sides of small and large paper, so the leading edge of the discharged paper does not push the trailing edge of the accumulated paper, Even on a large sheet, the sheet can be deposited on the sheet discharge tray without causing a sheet drop or page order error.

  Further, at least two end side pressing portions have the same shape, and the tip end position of the end side pressing portion at the maximum retreat is positioned on the discharge driven roller side with respect to the common tangent line of the discharge roller and the discharge driven roller. Due to the force received from the paper, the end-side pressing portion always contacts the stopper at the time of retraction when the paper is discharged, so that the end-side pressing portion continues to be in the maximum retracted state rotated about the rotation axis. For this reason, the sheet is bent and discharged toward the sheet discharge tray, and the sheet does not drop and the page order does not go wrong.

  Further, at least two inner pressing portions have the same shape, and the tip position of the inner pressing portion at the time of maximum retraction is positioned on the discharge roller side with respect to the common tangent of the discharge roller and the discharge driven roller. The retracted position of the inner pressing portion when discharging the paper depends on the position of the discharged paper, and the paper does not accumulate at an undesired position beyond the common tangent line.

  Further, at least two end side pressing portions have an R shape on the sheet feeding surface side, the leading end of the discharged paper reaches the leading end of the end side pressing portion along the R shape, and the discharged paper is separated from the discharge roller and the discharge roller. The paper is ejected to a region that is closer to the paper ejection driven roller than the common tangent line of the paper driven roller and that does not push the trailing edge of the accumulated paper on the paper ejection tray. Accurately deposited on top.

  In addition, since the left and right end portions of the paper having the maximum print paper width are within the width of the two end side holding portions, the bending of the maximum size paper is also reliably formed, and the curl of the paper The amount is reduced. Furthermore, since the left and right edge portions of the paper having the minimum print paper width are within the width of the two inner pressing portions, the bend is reliably formed at both end portions of the minimum size paper, and the curl amount of the paper Is reduced.

Figures 6-8 illustrate another embodiment of the present invention.
FIG. 6 (1) is a reference diagram when discharging a wide sheet . Similarly to the above-described embodiment, the sheet discharge roller group 2 includes a rotation shaft 2a and a sheet discharge roller 2b, and is centered on a sheet conveyance center as a conveyance reference. On the other hand, four discharge rollers 2b are arranged at symmetrical positions, the outer discharge roller 2b is in contact with the outer discharge roller 5b, and the inner discharge roller 2b is in contact with the inner discharge roller 5b. . The paper discharge roller 2b uses rubber to give the friction force necessary for paper conveyance between the paper 4 and the paper discharge roller 2b held between the contact portions of the paper discharge roller 2b and the paper discharge driven rollers 5a and 5b. ing. The sheet pressers 11 a and 11 c are rotatable on the rotation shaft 2 a of the sheet discharge roller group 2 and are held so as not to be synchronized with the rotation operation of the sheet discharge roller group 2.

In the reference example , the inner discharge driven roller 5b has a convex portion 51 having a diameter larger than the roller diameter of the nip portion in contact with the inner discharge roller 2b in the inner portion in the width direction that does not contact the inner discharge roller 2b. Have. The rotating shaft 2a includes an outer paper discharge roller 2b, which is an outer paper discharge roller pair, and two end-side pressing portions 11a arranged on the outer side of the outer paper discharge driven roller 5a, and an inner paper discharge roller pair. A total of three sheet pressing portions, that is, a central sheet pressing portion 11c disposed at the center of the sheet conveyance between the two inner discharge rollers 2b and the inner discharge driven roller 5b are disposed.

By having such a large-diameter portion 51, the discharged paper is applied an upward force by the large-diameter portion, and further, the central paper pressing portion 11c applies a downward force, so that the central portion of the discharged paper is bent. Is formed. Since the sheet is stiffened by this bending, the sheet is largely discharged forward without dropping downward at the same time as being discharged. Accordingly, sufficient curling is performed even on discharged paper having a large curl, and the discharged paper does not push out the stacked paper, so that it is possible to prevent the paper from dropping from the paper discharge tray and out of order.
As shown in FIG. 7, the large-diameter portion 51 of the inner paper discharge driven roller 5b is configured as a concave-convex shape in which large-diameter convex portions and concave portions having the same diameter as the nip portion are alternately arranged in the circumferential direction. Also good. As a result, the trailing edge of the discharged paper is caught by the convex portion of the large-diameter portion 51 and is reliably kicked out, and it is possible to enhance prevention of paper falling and page misalignment while performing aiming on the discharged paper.

  Since the large-diameter portion of the inner discharge driven roller has an uneven shape in the circumferential direction, in addition to applying stiffness to the discharged paper, the trailing edge of the discharged paper catches on the uneven portion to kick out the rear edge and A function of reliably discharging to the paper stacking unit is obtained, and no paper stays or drops in the vicinity of the discharge roller.

  Further, at least one central pressing portion for pressing the central portion of the sheet in place of the inner pressing portion suppresses bending in the width direction of the paper, and the inner discharge of the central pressing portion and the inner discharge driven roller is suppressed. The large-diameter portion provided at the inner end portion that does not come into contact with the roller ensures that the sheet is firm. Furthermore, it is possible to cope with sheets from the minimum print sheet width to the maximum print sheet width. Further, similarly to the above, the downward curling amount of the side portion of the discharged paper can be reduced by forming the downward deflection of the side portion of the paper by the end side pressing portion. The rear end of the stacked paper is not bulky due to curling by pressing against the paper discharge tray near the rear end, so that the front end of the next discharged paper is difficult to push the rear end of the stacked paper or under the stacked paper. It becomes difficult to dive.

FIG. 6 (2) shows another embodiment, and is a diagram showing when narrow paper is discharged unlike FIG. 6 (1). Here, the two inner pressing portions 11b are further disposed between the end pressing portion 11a and the central pressing portion 11c. Further, as will be described in detail later, the inner discharge driven roller 5b and the inner discharge roller 2b have a contact range along the rotation axis 2a that is narrower than the width along the rotation axis of the discharge roller width. The diameter of the end portion on the outer side in the axial direction of the roller 5b is smaller than that of the central portion. As a result, both end portions of the narrow paper are bent by the inner pressing portion 11b as shown in FIG. 6B, so that the force applied to the paper 4 is dispersed, and image damage and the like are reliably avoided. Further, since the image surface side of the paper 4 is guided along the curved smooth surface of the roller end of the driven roller 5b having a reduced diameter, abrupt folding does not occur, and image scratches are avoided. The

FIGS. 8A and 8B are diagrams on the axial projection surface, and show the operation of the center pressing portion 11c when the paper is discharged. In addition, about the edge side holding | suppressing part 11a and the inner side holding | maintenance part 11b, it is the same as the aspect shown by FIG.
The sheet 4 that is nipped and conveyed by the sheet discharge roller 2b and the sheet discharge driven roller 5b from the fixing device 26 comes into contact with the sheet conveyance surface 12 with the R shape of the center pressing portion 11c when the sheet front end 4s is not retracted. . Here, the time of non-retraction means a state in which the center pressing portion 11c is lowered by its own weight, and the sheet conveying surface 12 is placed on the stopper portion 13 of the guide 7 (see FIG. 8 (1)). The length Lc of the central pressing portion 11c is determined so that the paper trailing edge 4k of the paper 4 accumulated on the paper discharge tray 3 does not enter the rotation trajectory of the central pressing portion 11c.

  When the sheet 4 is further conveyed, the center pressing portion 11c is pushed up around the rotation shaft 2a, but the maximum retracting position where the positioning portion 14 of the center pressing portion 11c contacts the maximum retracting stopper 15 provided in the guide 8 is achieved. At the time, the front end portion 16 of the central pressing portion 11c is more than the direction of the common tangent line 17 of the paper discharge roller 2b and the paper discharge driven roller 5b (the paper discharge direction when the end side pressing portion 11a and the central pressing portion 11c are not provided). It is set so as to be between the discharge roller 2b side and the tangent line 18 of the large diameter portion 51 of the discharge driven roller 5b, which is parallel to the common tangent line 17 (see FIG. 8B). The sheet 4 being discharged has a tendency that the center portion of the sheet is bent upward by the large-diameter portion 51 between the left and right inner discharge driven rollers 5b, but the upper limit of bending is regulated by the center pressing portion 11c. The paper is stiffened by the large-diameter portion 51 and the central pressing portion 11c of the paper discharge driven roller 5b. By this sticking, the landing point on the paper 4 accumulated on the paper discharge tray at the paper leading end 4s can be moved away from the paper discharge roller pair, and the trailing edge 4k of the stacked paper is not pushed out. Therefore, it is possible to prevent the occurrence of stacking defects such as paper dropping and page misalignment.

  Further, since the central pressing portion 11c presses the sheet below the large diameter portion 51 of the discharge driven roller 5b, when the discharge driven roller 5b as shown in FIG. The end 4k is caught by the uneven shape of the large diameter portion, and the rear end 4k of the sheet is reliably kicked out. After kicking out the trailing edge of the sheet, the center pressing portion 11c pushes down the sheet 4 onto the sheet discharge tray 3 or the accumulated sheet 4 by its own weight, so that the sheet trailing edge 4k does not stay near the sheet discharge roller pair. Further, it is possible to prevent the page from being out of order due to the extrusion or the subtraction of the next sheet.

  Thus, the shape of the paper 4 being discharged obtained by giving different operation ranges and shapes to the end-side pressing portion 11a and the central pressing portion 11c is the shape shown in FIG. FIG. 6 is a view seen from the common tangential direction of the paper discharge roller 2b and the paper discharge driven rollers 5a and 5b.

  The tip of the end-side presser is supported so that it is retracted by the discharged paper from the non-retracted position that is below the common tangent line of the paper discharge roller and paper discharge driven roller, and returned to the non-retracted position after paper discharge. Thus, the side curl of the sheet can be reduced with a simple configuration, and the center pressing portion can be combined with the large-diameter portion of the inner discharge driven roller to add a stiffness near the center of the sheet. In addition, since the tip of the center pressing portion can be retracted above the common tangent of the paper discharge roller and the paper discharge driven roller, which is the direction in which the paper is discharged during retraction, the large diameter portion of the inner paper discharge driven roller It is possible to prevent the sheet from being stressed more than necessary between the center pressing portion and the center pressing portion.

  Further, in addition to the above-described effect, the tip of the center pressing portion is above the common tangent line of the paper discharge roller and the paper discharge driven roller when retracted, and is parallel to and above the common tangent line. Since the inner discharge driven roller is regulated to be positioned below the tangent line between the large-diameter portions of the inner discharge driven roller, it is possible to reliably apply the stiffness to the discharge sheet while suppressing the bending in the width direction of the sheet.

In the image forming apparatus of the present invention, A4, letter and legal paper is set as the maximum print paper width, and the left and right edges of the frequently used paper are set to be within the width of the end side pressing portion 11a. The effect of pressing the trailing edge 4k of the paper 4 accumulated on the paper discharge tray 3 by the portion 11a and the effect of reducing the curl amount are obtained with a frequently used paper.
In addition, since the large-diameter portion 51 of the paper discharge driven roller 5b that is in pressure contact with the internal paper discharge roller 2b is disposed on the paper conveyance center side, not only the maximum print paper width of A4, letter, legal, but also the minimum width paper. On the other hand, it is possible to obtain the effects of nipping by the paper discharge roller 2b and the paper discharge driven roller 5b, the stiffness by the large diameter portion of the paper discharge driven roller 5b and the center pressing portion 11c, and the sheet trailing edge kicking out.

  Since the large-diameter portion of the inner discharge driven roller is located inside the paper having the minimum print paper width, the deflection in the width direction of the paper is regulated for any size paper including the minimum print paper width to the discharge paper. This can be done.

  Furthermore, in order to prevent image damage and damage to the paper while the paper is being stiffened by the large diameter portion of the paper discharge driven roller 5b and the center pressing portion 11c, the large diameter end portion of the paper discharge driven roller 5b is tapered. The center pressing part 11c also has a tapered shape at the tip, the width is reduced from W1 to W2 toward the tip, the angle of the end of the leading edge that holds the paper is made obtuse, and an arc at the corner A shape may be added (see FIG. 8 (3)). Further, by restricting the front end position of the central pressing portion 11c at the maximum retracted position to the discharge roller 2b side with respect to the common tangent line 17 of the discharge roller 2b and the discharge driven roller 5b, the amount of pushing in the sheet is regulated and the sheet is fed. Reducing stress.

  The central pressing part located inside the large-diameter portion of the inner discharge driven roller is tapered at the tip and the tip corner is an obtuse angle. It is possible to regulate the bending of the paper in the width direction without causing damage such as, and to apply the stiffness to the discharged paper.

Next, the shape of the outer paper discharge driven roller 5a will be described with reference to FIG.
FIG. 9B is an enlarged view of the outer paper discharge driven roller 5a and the end side pressing portion 11a shown in FIG. As described above, the paper 4 being discharged is deformed with the folding point 18 in the vicinity sandwiched between the outer paper discharge roller 2b and the outer paper discharge driven roller 5a. The strongest force is applied to the position of the roller end 22 of the paper driven roller 5a. In particular, when the paper is a side curl paper as shown in FIG. 10, the tendency becomes remarkable, and there is a risk of image scratches.

  Therefore, the contact range 23 along the rotation axis 2a of the outer sheet discharge driven roller 5a and the outer sheet discharge roller 2b is made narrower than the width along the rotation axis of the sheet discharge roller width 24, and the driven roller starts from the end point 25 of the contact range 23. By reducing the diameter of the driven roller 5a to the roller end 22 of 5a, the force to the same position was eased. By making the roller end portion 22 and the folding point 18 in different places, the force applied to the paper 4 is dispersed, and image scratches and the like are reliably avoided. Further, the image surface side 21 of the paper 4 is guided along the curved and smooth surface of the roller end portion 22 of the driven roller 5a having a reduced diameter, so that a sharp fold does not occur and the image is damaged. Avoided.

  The diameter of the discharge driven roller decreases from the end point of the contact range to the end of the discharge driven roller so that the contact range of the discharge driven roller and the paper is smaller than the contact range of the discharge roller and the paper. Since the folding point of the paper sandwiched between the paper discharge driven roller and the paper discharge roller does not coincide with the end of the paper discharge driven roller, the paper is not bent sharply, and damage to the image formed on the paper is avoided. can do.

  Similarly, for the inner paper discharge driven roller 5b shown in FIGS. 5 (2) and 6 (2), the contact range along the rotation shaft 2a of the inner paper discharge driven roller 5b and the inner paper discharge roller 2b is set as the paper discharge roller. By making the width of the driven roller 5b narrower than the width along the rotation axis and reducing the diameter of the driven roller 5b from the end point of the contact range to the roller end of the driven roller 5b, the roller end and the bending point are made different places. The force applied to the paper 4 is dispersed, and image scratches are avoided.

  As described above, according to the paper discharge device of this embodiment, two types of paper pressing means are installed on the rotation shaft of the paper discharge roller group, and the shape of the paper discharge driven roller is changed to damage such as image scratches on the paper. By adopting a shape that does not give an image, the stacking property is improved with a simple configuration, and a high-quality image is guaranteed. In addition, since the image forming apparatus of the present invention includes the paper discharge device, the paper stacking property is improved with a simple configuration, and a high-quality image can be provided.

  The image forming apparatus of the present invention includes the paper discharge device, a conveying unit that feeds and conveys the paper, a transfer unit that transfers the image onto the paper, and a fixing device that heats and pressurizes the transferred image to fix the image on the paper. As a result, it is possible to provide a highly reliable apparatus that does not cause a paper drop or page out of order.

1 Paper discharge device (paper output unit)
2 discharge roller group 2a rotating shaft 2b discharge roller (upper discharge roller)
3 Output tray (paper stacking unit)
4 paper 5a, 5b paper discharge driven roller (lower paper discharge roller)
6 Reverse driven roller 7 Guide 8 Guide 9 Guide 10 Switching guide 11 Paper pressing means 11a End side pressing portion 11b Inner pressing portion 12 Paper conveying surface 13 Leaf spring 14 Positioning portion 15 Retraction stopper 16 Tip portion 17 Paper discharge roller and paper discharge Common tangent of driven roller 18 Bending point 19 Paper left and right edge 20 Curl amount 21 Image surface side 22 Roller edge 23 Contact range 24 Paper discharge roller width 25 End point 26 Fixing device 27 Paper feed cassette 28 Paper feed rollers 29, 30 Registration roller 31 Transfer driving roller 32 Transfer driven roller 33 Intermediate transfer belt 34 Developer 35 Photoconductor 36 Charging roller 37 Photoconductor unit 38 Exposure device 39 Laser light 40 Fixing roller 41 Pressure roller

JP-A-5-338899 JP 2001-270642 A JP 2002-284441 A JP 2000-26005 A JP-A-11-79519 JP 2002-249270 A Japanese Patent No. 3323661 Japanese Patent No. 4116973

Claims (5)

A paper discharge device provided with at least two paper discharge roller pairs each including a rotatable upper paper discharge roller and a lower paper discharge roller, wherein the paper is discharged to a paper stacking section by the paper discharge roller pair,
Rotating paper pressing means abutting on the paper is provided downstream of the nip portion of the paper discharge roller pair with respect to the paper discharge direction, and the front end of the paper pressing means is the lower paper discharge when not retracted. Located between the lower end of the roller and the upper surface of the paper stacking unit ,
The sheet pressing means has an end pressing portion and an inner pressing portion,
The distal end portion of the end-side pressing portion is at the lower discharge roller side with respect to the direction of the common tangent of the upper discharge roller and the lower discharge roller at the time of maximum retraction,
The front end portion of the inner pressing portion is located closer to the upper discharge roller than the common tangent direction of the upper discharge roller and the lower discharge roller at the time of maximum retraction. .   The paper discharge device according to claim 1, wherein the paper pressing unit is lifted and retracted from a non-retracted position by a force received from the discharged paper, and returned to a non-retracted position by gravity.   The paper discharge device according to claim 1, wherein a diameter of the upper paper discharge roller is smaller than a diameter of the lower paper discharge roller.   The paper discharge device according to any one of claims 1 to 3, wherein the paper pressing unit is rotatably supported on a rotation shaft of the upper paper discharge roller.   An image forming apparatus comprising the paper discharge device according to claim 1.

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