Sheet ejection device and image forming apparatus

Abstract

To provide a sheet discharger allowing for suppressing the occurrence of poor stacking resulting from a curl of a sheet.SOLUTION: A sheet discharger comprises discharge means (161) that has a nip portion clamping a sheet and discharges the sheet through the nip portion, a sheet-support part (170) that supports the sheet discharged by the discharge means, and guide means (200) provided to face an upper surface of the sheet delivered from the nip portion. The guide means has a regulation part (201a) that regulates a rear end of the sheet in a sheet discharge direction from moving in a manner of moving upward from an extension line (N) of the nip portion after passed through the nip portion.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a sheet discharge device that discharges a sheet and an image forming apparatus that forms an image on a sheet. [Background technology]

[0002] In an image forming apparatus such as a printer, copier, or multifunction device, a sheet on which an image has been formed is discharged outside the apparatus by a discharge roller or the like and loaded onto a loading section such as a discharge tray. Patent Document 1 describes a guide member that is located above a sheet loading section provided on the top surface of the main body of the image forming apparatus and has an internal reversing path for reversing sheets during double-sided printing, and that can load sheets onto its top surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-280856 Summary of the Invention [Problem to be solved by the invention]

[0004] However, after an image is formed on a sheet, the sheet edge may be curved upward (hereinafter referred to as "upward curl") depending on the configuration of the image forming mechanism, the operational settings of the image forming operation, the environmental conditions, etc. Such upward curl may cause improper stacking of the sheet discharged onto the discharge tray, etc. For example, the trailing edge of the discharged sheet in the sheet discharge direction may lean against the wall below the discharge roller pair. Also, the trailing edge of a previously discharged sheet may block the sheet discharge path, causing a collision with the leading edge of a subsequently discharged sheet.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sheet discharging device and an image forming apparatus that can prevent stacking errors caused by curling of sheets. [Means for solving the problem]

[0006] One aspect of the present invention is At the nip The sheet is clamped, In the sheet ejection direction that intersects with the vertical direction A pair of rollers for discharging the sheet a roller pair including a first roller that contacts an upper surface of the sheet at the nip portion and a second roller that contacts a lower surface of the sheet at the nip portion; a sheet support portion for supporting the sheet discharged by the roller pair; No. 1 The roller rotation axis The second perpendicular to the line connecting the roller rotation axes and The aforementioned a restricting portion disposed above a nip line passing through the nip portion, The aforementioned The restricting portion is arranged to restrict the rear end of the sheet in the sheet discharge direction from moving upward beyond the nip line after passing through the nip portion of the roller pair, and the length of the sheet in the sheet width direction perpendicular to the sheet discharge direction is defined as the sheet width, and the sheet width of the largest sheet that can be discharged by the roller pair is defined as the maximum sheet width, and the restricting portion is provided over a range equal to or greater than the maximum sheet width in the sheet width direction. Crate , an upstream end of the regulating portion in the sheet discharge direction protrudes downward below an upper end position of the first roller; The sheet ejection device is characterized by the above. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a sheet discharge device and an image forming apparatus that can suppress the occurrence of stacking errors caused by curling of sheets. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an image forming apparatus according to a first embodiment. [Figure 2] FIG. 2 is a perspective view of a discharge section according to the first embodiment. [Figure 3] FIG. 4 is a perspective view of a state in which an extension guide unit is removed from a discharge section according to the first embodiment. [Figure 4] FIG. 3 is a cross-sectional view of a discharge section according to the first embodiment. [Figure 5] FIG. 3 is a cross-sectional view of a discharge section according to the first embodiment. [Figure 6]FIG. 10 is a cross-sectional view of the discharge section in a state where the extension guide unit is not attached. [Figure 7] FIG. 10 is a diagram illustrating the rear end of the seat leaning. [Figure 8] FIG. 10 is a diagram illustrating a collision between sheets. [Figure 9] FIG. 2 is a schematic diagram of the image forming apparatus according to the first embodiment in a state where a post-processing device is attached. [Figure 10] FIG. 10 is a schematic diagram of an image forming apparatus according to a second embodiment. [Figure 11] FIG. 10 is a perspective view of a discharge section according to a second embodiment. [Figure 12] FIG. 10 is a cross-sectional view of a second discharge tray according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings.

[0010] In the following description, the vertical direction when the image forming apparatus is installed on a horizontal surface is referred to as the "up-down direction," and the direction perpendicular to the sheet transport direction in the image forming apparatus (the main scanning direction during image formation) is referred to as the "sheet width direction." [Example]

[0011] 1 is a schematic diagram showing a cross-sectional configuration of an image forming apparatus 100 according to Example 1. The image forming apparatus 100 includes an image forming unit 140 that forms an image on a sheet S, which is a recording material, and an apparatus main body 101 that is a housing that houses the image forming unit 140. The image forming unit 140 is an electrophotographic unit of an intermediate transfer tandem type in which image forming stations Y, M, C, and Bk that form four-color toner images are arranged along an intermediate transfer belt 145.

[0012] The sheets S are stacked on a lift-up device of a sheet feeding device incorporated in the lower part of the apparatus main body 101, and are fed one by one by a feeding unit 110 serving as a feeding means. The feeding unit 110 may include, for example, a feeding roller that feeds the sheets S, and a separation roller that is disposed in contact with the feeding roller and separates the sheets S fed by the feeding roller from the other sheets S by applying friction to the sheets S. Note that the sheets S serving as recording material can be a variety of sheets of different sizes and materials, including paper such as plain paper and cardboard, surface-treated sheet materials such as plastic film, cloth, and coated paper, and sheet materials with special shapes such as envelopes and index paper.

[0013] The sheet S fed from the feeding unit 110 has its skew corrected by the skew correction device 120, and is transported toward the secondary transfer unit 130 at a timing synchronized with the toner image formation process by the image forming unit 140. The secondary transfer unit 130 is a nip portion formed between a secondary transfer inner roller 131 and a secondary transfer outer roller 132 that are substantially opposed to each other with an intermediate transfer belt 145 sandwiched therebetween. The secondary transfer outer roller 132 is a transfer means in this embodiment.

[0014] In parallel with the above-described process of transporting the sheet S to the secondary transfer unit 130, the image forming unit 140 performs a toner image formation process. Each of the image forming stations Y, M, C, and Bk of the image forming unit 140 includes a photosensitive drum 141, which is a drum-shaped image carrier (electrophotographic photosensitive member), a charging means such as a charging roller, and a developing unit 143, which serves as a developing unit. Furthermore, an exposure device 142 is disposed below the four photosensitive drums 141. In the toner image formation process, the charging means uniformly charges the surface of the photosensitive drum 141, and the exposure device 142 exposes the photosensitive drum 141 based on a signal representing image information to be formed, thereby writing an electrostatic latent image onto the surface of the photosensitive drum 141. This electrostatic latent image is developed into a single-color toner image with toner supplied from the developing unit 143. As a result, toner images of four colors, yellow, magenta, cyan, and black, are formed on the surfaces of the four photosensitive drums 141.

[0015] The intermediate transfer belt 145 is driven to rotate counterclockwise in FIG. 1. The toner images carried on the four photosensitive drums 141 are sequentially transferred (primary transfer) by the primary transfer rollers 144 onto the intermediate transfer belt 145 so as to be superimposed on one another. As a result, a full-color toner image is finally formed on the intermediate transfer belt 145, and is carried by the intermediate transfer belt 145 and transported to the secondary transfer unit 130. Then, the toner image is secondarily transferred from the intermediate transfer belt 145 to the sheet S by the pressure and electrostatic bias in the secondary transfer unit 130.

[0016] The sheet S that has passed through the secondary transfer unit 130 is conveyed to a fixing device 150 that serves as a fixing means. The fixing device 150 has a pair of rotating bodies that are composed of rollers and / or belts, and a heat source such as a ceramic heater or a halogen lamp. The fixing device 150 shown in the figure has, as a pair of rotating bodies, a fixing roller 151 that serves as a heating member, and a pressure roller 152 that serves as a pressure member that contacts the fixing roller 151 with a predetermined pressure. The fixing device 150 applies pressure and heat to the toner image on the sheet S while nipping and conveying the sheet S at a nip portion (fixing nip) between the fixing roller 151 and the pressure roller 152. This melts the toner, and the toner adheres after passing through the fixing nip, resulting in a fixed image on the sheet S.

[0017] After passing through the fixing device 150, the sheet S is guided by a first switching flap 153 to either a path toward a discharge roller pair 161 or a path toward a reversing roller pair 162. When images are formed on both sides of the sheet S, the sheet S with an image formed on the first side is guided by the first switching flap 153 to the reversing roller pair 162 and conveyed by the reversing roller pair 162. When the trailing end of the sheet S in the conveying direction passes through a second switching flap 154, the reversing roller pair 162 reverses the conveying direction of the sheet S and sends the sheet S to a duplex conveying path 180. The portion of the sheet S that protrudes outside the apparatus main body 101 during the reversing operation by the reversing roller pair 162 is supported by a reversing guide 171. The sheet S reaches the skew correction device 120 again via the duplex conveying path 180, whereupon skew correction and timing correction are performed, and an image is formed on the second side by passing through the secondary transfer unit 130 and the fixing device 150.

[0018] When discharging the sheet S, the sheet S sent out from the fixing unit 150 is guided to the discharge roller pair 161 by the first switching flap 153, and is discharged to the outside of the apparatus main body 101 by the discharge roller pair 161 as a discharge means. An extension guide unit 200, which will be described later, is attached above the discharge opening where the discharge roller pair 161 is arranged, and the behavior of the sheet S discharged from the discharge roller pair 161 is regulated by the extension guide unit 200. Hereinafter, the movement direction of the sheet S when the discharge roller pair 161 discharges the sheet S is referred to as a sheet discharge direction B (leftward in FIG. 1).

[0019] An ejection tray 170 is provided on the top of the apparatus main body 101 as a sheet support unit in this embodiment, and sheets S ejected by the pair of ejection rollers 161 are stacked on the ejection tray 170. The upper surface of the ejection tray 170 is inclined upward toward the downstream side in the sheet ejection direction B, and the sheets S stacked on the ejection tray 170 slide upstream in the sheet ejection direction B along the inclination of the ejection tray 170 due to their own weight. An alignment surface 163a extending in the vertical direction is provided on the upstream side of the ejection tray 170 in the sheet ejection direction B as part of the apparatus main body 101. The sheet S sliding along the inclination of the ejection tray 170 comes into contact with the alignment surface 163a at the rear end in the sheet ejection direction B, thereby aligning the position of the sheet stack stacked on the ejection tray 170.

[0020] The image forming apparatus 100 includes an image reading device 102 mounted on an upper portion of an apparatus main body 101. The image reading device 102 includes a platen glass on which an original document is placed and an image sensor that reads an image of the original document through the platen glass. The image reading device 102 also includes an automatic document feeder that feeds original documents set in an original tray one by one and has the image read by the image sensor. The image forming apparatus 100 of this embodiment has a so-called internal discharge type configuration in which an internal discharge space 190 for sheets S is provided between the image forming unit 140 and the image reading device 102 in the vertical direction. The internal discharge type configuration has the advantage of being able to reduce the footprint of the image forming apparatus 100 as viewed from above, compared to a configuration in which, for example, the discharge tray 170 is provided on the side of the apparatus main body 101 and the sheet discharge space is located to the side of the apparatus main body 101.

[0021] The image forming unit 140 is an example of an image forming means, and may be, for example, a direct transfer electrophotographic unit that transfers a toner image formed on a photosensitive member to a sheet without using an intermediate transfer member. Furthermore, the image forming unit 140 is not limited to the electrophotographic type, and may be, for example, an inkjet printing unit or an offset printing mechanism.

[0022] (Extension guide unit) The configuration of the extension guide unit 200 will be described. Fig. 2 is a perspective view showing the discharge section 160 of this embodiment. Fig. 3 is a perspective view showing the discharge section 160 and the extension guide unit 200 in a state where the extension guide unit 200 has been removed from the apparatus main body 101. Fig. 4 is a cross-sectional view of the discharge section 160.

[0023] As shown in Fig. 2, the discharge section 160 serving as the sheet discharge device according to this embodiment includes a pair of discharge rollers 161, a discharge tray 170, and an extension guide unit 200. The pair of discharge rollers 161 is disposed at a discharge port which is an opening of the device body 101. The discharge tray 170 is supported by the device body 101 and is provided at the bottom of the internal discharge space 190 (Fig. 1). The extension guide unit 200 is detachably attached to the device body 101 near the discharge port.

[0024] In addition, above the discharge opening where the discharge roller pair 161 is arranged in the device main body 101, another opening where a reversing roller pair 162 is arranged is provided. Also, above the extension guide unit 200, a reversing guide 171 is provided so as to overlap with the extension guide unit 200 when viewed from above.

[0025] As shown in FIGS. 2 and 3, the extension guide unit 200 includes a base member 205, a guide member 201, a full-load detection flag 202, a rear end pressing flag 203, and a discharging brush 204.

[0026] 2 and 4, the guide member 201 has a guide surface 201a that faces the upper surface of the sheet S delivered from the discharge roller pair 161, and is fixed to a base member 205. The guide member 201 is made of a resin material, and the guide surface 201a is provided with a plurality of ribs that extend in a direction along the sheet discharge direction B. The length of this guide surface 201a in the sheet discharge direction B is determined in consideration of the distance that the sheet S protrudes from the nip portion of the discharge roller pair 161 when it is discharged by the discharge roller pair 161. In addition, the length of the guide surface 201a in the sheet width direction is set to be equal to or greater than the maximum sheet width on which the image forming apparatus 100 can form an image (maximum sheet width according to specifications).

[0027] The guide surface 201a is preferably disposed so as to extend substantially parallel to the nip line N of the discharge roller pair 161 as viewed in the sheet width direction. The discharge roller pair 161 of this embodiment sends out the sheet S slightly upward toward the downstream in the sheet discharge direction B. Therefore, the nip line N is inclined with respect to the horizontal direction, and the guide surface 201a is also inclined with respect to the horizontal direction at a substantially equal angle. Furthermore, the guide member 201 has an inclined surface that is continuous with the guide surface 201a on the upstream side in the sheet discharge direction B and is inclined with respect to the guide surface 201a as viewed in the sheet width direction so as to approach the nip line N from above the nip line N. This inclined surface has the effect of preventing the leading edge of the sheet S discharged by the discharge roller pair 161 from getting caught on the guide member 201.

[0028] Furthermore, it is desirable that the guide surface 201a be disposed at a position sufficiently close to the nip line N. For example, the shortest distance between the guide surface 201a and the nip line N as viewed in the sheet width direction is preferably 10 mm or less, and more preferably 5 mm or less.

[0029] The nip line N refers to a straight line that passes through the nip position where the pair of discharge rollers 161 clamp the sheet S when viewed in the sheet width direction, and that intersects perpendicularly with a line segment connecting the rotation axis of one roller and the rotation axis of the other roller. In other words, the nip line N refers to an extension line of the nip portion of a discharge means such as the pair of discharge rollers 161. When the pair of discharge rollers 161 is configured such that multiple roller members constituting one roller and multiple roller members constituting the other roller are intertwined in the sheet width direction, the nip position is the intersection of a line segment connecting two intersections of the outer peripheries of the roller members and a line segment connecting their rotation axes.

[0030] The static elimination brush 204 is provided downstream of the guide surface 201a in the sheet discharge direction B, and is a brush-shaped member made of conductive fibers or sheet pieces arranged in the sheet width direction. The static elimination brush 204 protrudes downward from the guide surface 201a and is arranged, for example, so as to intersect with the nip line N when viewed in the sheet width direction. The static elimination brush 204 is connected to the metal frame of the device main body 101 via a base member 205, for example, and is connected to ground potential, and functions as a static elimination member that removes electric charge from the sheet.

[0031] The full-load detection flag 202 and the trailing end pressing flag 203 are both pivotal members that are pivotally supported by the guide member 201 and pivot about an axis extending in the sheet width direction. The pivot axes of the full-load detection flag 202 and the trailing end pressing flag 203 are located above the nip line N. The guide surface 201a of the guide member 201 is provided with cutouts from which the full-load detection flag 202 and the trailing end pressing flag 203 protrude. When not in contact with the sheet S, the tips of the full-load detection flag 202 and the trailing end pressing flag 203 both protrude below the nip line N, and when pressed by the sheet S, they pivot upward.

[0032] The full-load detection flag 202 and the trailing-end pressing flag 203 are disposed near the center of the pair of discharge rollers 161 in the sheet width direction, within the range of the minimum sheet width (minimum sheet width according to specifications) on which the image forming apparatus 100 can form an image. However, the full-load detection flag 202 and the trailing-end pressing flag 203 are spaced apart from each other in the sheet width direction and can rotate independently. Furthermore, the full-load detection flag 202 and the trailing-end pressing flag 203 are inclined with respect to a line perpendicular to the nip line N so as to move downstream in the sheet discharge direction B as they move away from the pivot shaft when not in contact with the sheet. With this configuration, it is possible to reduce the impact sound when the leading edge of the sheet S collides with the flag while avoiding interference between the full-load detection flag 202 and the trailing-end pressing flag 203, which are pivotable members.

[0033] The full-load detection flag 202 has a shaft extending in the sheet width direction, and has a contact portion 202a at one end thereof that protrudes from the guide member 201 and contacts the upper surface of the sheets S stacked on the discharge tray 170. The shaft portion has a light-shielding portion 202b at the other end thereof. The apparatus main body 101 is provided with a full-load detection sensor 165, which is a photointerrupter that is shielded from light by the light-shielding portion 202b. The full-load detection sensor 165 as a detection portion is configured to switch a detection signal according to a rotation angle of the full-load detection flag 202. In other words, the full-load detection sensor 165 and the full-load detection flag 202 are configured to switch ON / OFF of the full-load detection sensor 165 according to whether or not the sheets S stacked on the discharge tray 170 are equal to or greater than a predetermined height. When the control portion of the image forming apparatus 100 detects a full-load state of the discharge tray 170 based on the detection signal of the full-load detection sensor 165, the control portion 202 suspends the image forming operation and notifies the user to remove the sheets S from the discharge tray 170.

[0034] The rear end pressing flag 203 has a function of pressing downward the rear end of the sheet S that has passed through the nip of the discharge roller pair 161, thereby helping the rear end of the sheet S fall onto the discharge tray 170. The rear end pressing flag 203 may be configured to be biased downward by its own weight, or may be configured to be biased downward by a spring disposed between the guide member 201 and the rear end pressing flag 203.

[0035] When the full-load detection flag 202 and the rear-end pressing flag 203 are not in contact with the sheet S, the leading edge 203a of the rear-end pressing flag 203 is located upstream of the leading edge (contact portion 202a) of the full-load detection sensor 165 in the sheet discharge direction B. This is because it is preferable that the rear-end pressing flag 203 presses the rear edge of the sheet S downward at a position closer to the nip of the discharge roller pair 161. Furthermore, the minimum distance from the leading edge 203a of the rear-end pressing flag 203 to the discharge tray 170 is set to be smaller than the minimum distance from the leading edge (contact portion 202a) of the full-load detection sensor 165 to the discharge tray 170. This prevents the rear-end pressing flag 203 from coming into contact with the sheet S on the discharge tray 170 before the full-load state is detected based on the detection result of the full-load detection sensor 165, making it impossible to properly press the rear edge of the newly discharged sheet S.

[0036] The full-load detection flag 202 is a first flag member in this embodiment, and the rear end pressing flag 203 is a second flag member in this embodiment. Note that it is also possible to omit the full-load detection flag 202 and arrange only the rear end pressing flag 203 on the extension guide unit 200.

[0037] 3, the extension guide unit 200 can be attached to and detached from the device main body 101 by sliding the base member 205 in the sheet width direction relative to the attachment portion of the device main body 101. When the base member 205 is held in the attachment portion, movement of the guide member 201 in the up-down direction and the sheet discharge direction B is restricted.

[0038] It is preferable to provide a guide shape near the light-shielding portion 202b of the full-load detection flag 202 to prevent the light-shielding portion 202b from colliding with the device main body 101 when the extension guide unit 200 is moved in the upper left direction in FIG. 3 to attach it to the device main body 101. This guide shape is configured to come into contact with the device main body 101 and rotate the full-load detection flag 202 upward by a predetermined angle from a state in which it hangs down due to its own weight, thereby preventing the light-shielding portion 202b from colliding with, for example, a corner 101c of the device main body 101. Because the full-load detection sensor 165 is an electrical component, at least a portion of its periphery is often covered by other members, and providing the above-described guide shape makes it possible to avoid collision when combining it with the light-shielding portion 202b.

[0039] (Post-treatment device) 9, by removing the extension guide unit 200, it becomes possible to mount the post-processing device 40 as a sheet processing device in the discharge space 190 inside the body of the image forming apparatus 100. In the illustrated example, the post-processing device 40 is mounted in a state where the discharge tray 170 and the reversing guide 171 are removed from the apparatus main body 101.

[0040] The post-processing device 40 includes a conveying path 41 that receives and conveys the image-formed sheets S discharged from the discharge roller pair 161, and an intermediate tray 42 on which the sheets S discharged from the conveying path 41 are temporarily stacked. The post-processing device 40 also includes a stapler 43 that binds the multiple sheets S stacked on the intermediate tray 42, and a discharge tray 44 on which the sheets S discharged from the intermediate tray 42 are stacked as deliverables. Here, the stapler 43 is exemplified as a processing unit that processes the sheets, but the post-processing device 40 may also include, for example, a punching unit that punches holes in the sheets or a center-folding unit that performs center-folding.

[0041] (Sheet behavior) Next, the behavior of the sheet S discharged by the discharge roller pair 161 will be described. Figures 4 and 6 are cross-sectional views of the discharge section 160, with Figure 5 showing the state immediately after the leading edge of the first sheet Sa has passed through the nip of the discharge roller pair 161, and Figure 6 showing the state immediately after the trailing edge of the first sheet Sa has passed through the nip of the discharge roller pair 161. Note that the illustration of the upstream side of the discharge section 160 in the sheet conveyance direction in the device main body 101 is omitted.

[0042] When the sheet is discharged by the discharge roller pair 161, the sheet Sa sent out from the fixing unit 150 (FIG. 1) is guided to the nip of the discharge roller pair 161 via a discharge path formed by a lower discharge guide 163 and an upper discharge guide 164 as shown in FIG. 4. Then, the discharge roller pair 161 discharges the sheet in a sheet discharge direction B toward above the discharge tray 170 in the internal discharge space 190. The lower discharge guide 163 is formed as an integral member with the above-mentioned alignment surface 163a.

[0043] As described above, the trailing edge pressing flag 203 and the full-load detection flag 202, which are not in contact with the sheet, protrude below the nip line N. Therefore, the leading edge of the sheet Sa that has passed through the nip of the pair of discharge rollers 161 moves while successively pushing aside the trailing edge pressing flag 203 and the full-load detection flag 202. The sheet Sa receives a force in the direction of gravity from these flag members during discharge, but due to the rigidity of the sheet Sa, the sheet Sa moves generally along the nip line N near the extension guide unit 200 until the trailing edge of the sheet Sa passes through the nip of the pair of discharge rollers 161. In particular, in this embodiment, a stiffening member is provided near the nip of the pair of discharge rollers 161 to curve the sheet Sa so that the sheet Sa has a wavy shape when viewed from downstream in the sheet discharge direction B, thereby increasing the rigidity of the sheet Sa.

[0044] When the leading edge of the sheet Sa moves away from the stiffening member, the leading edge of the sheet Sa sags due to its own weight and comes into contact with the discharge tray 170. Then, the sheet Sa is discharged in an upwardly convex arch shape while sliding against the discharge tray 170. Furthermore, the arched upper surface of the sheet Sa comes into sliding contact with the charge removal brush 204 of the extension guide unit 200, thereby removing the charge from the sheet Sa.

[0045] As shown in FIG. 5, when the trailing edge of sheet Sa leaves the nip of the discharge roller pair 161, sheet Sa begins to fall toward the discharge tray 170. At this point, when the trailing edge of sheet Sa leaves the nip of the discharge roller pair 161, sheet Sa is no longer constrained by the discharge roller pair 161, the upper discharge guide 164, and the lower discharge guide 163. Therefore, sheet Sa tends to curl according to the curl tendency of sheet Sa after image formation. Furthermore, when sheets are already stacked on the discharge tray 170, the conveyance resistance due to friction between the sheet Sa being discharged and the stacked sheets may increase depending on the degree of curl of the stacked sheets. For these reasons, the trailing edge of sheet Sa may tend to move above the nip line N immediately after leaving the nip of the discharge roller pair 161.

[0046] However, in this embodiment, an extension guide unit 200 is attached above the discharge opening where the discharge roller pair 161 is disposed, and the position of the trailing end of the sheet Sa in the vertical direction is regulated by the guide surface 201a of the guide member 201. In other words, the guide surface 201a functions as a regulating portion that regulates the trailing end of the sheet from moving upward and away from the extension line of the nip portion after passing through the nip portion of the discharge means. Then, by the time the sheet Sb following the previously discharged sheet Sa reaches the nip of the discharge roller pair 161, the trailing end of the sheet Sa has usually moved below the nip line N.

[0047] The advantage of providing such a guide surface 201a will be described using the behavior of a sheet in the discharge section 160 when the extension guide unit 200 is not attached. Figures 6, 7, and 8 are all cross-sectional views of the discharge section 160 when the extension guide unit 200 is not attached. The configurations shown in Figures 6 to 8 are the same as those in Example 1 except that the extension guide unit 200 is not attached.

[0048] 6 shows the state immediately after the trailing edge of the first sheet Sa passes through the nip of the pair of discharge rollers 161. In this configuration example, there is no extension guide unit 200, so when the trailing edge of the sheet Sa passes through the nip of the pair of discharge rollers 161, there is a possibility that the trailing edge of the sheet Sa will move above the nip line N as shown in the figure, depending on the tendency of the sheet Sa to curl. Then, the trailing edge of the sheet Sa will lean against the upper discharge guide 164, and it will take longer than usual to fall while rubbing against the upper discharge guide 164.

[0049] The sheet Sa leaning in this manner may be stacked in a state where its trailing edge leans against the alignment surface 163a and curves upward (leaning trailing edge), as shown in Fig. 7. Furthermore, if the sheet Sa leaning against the upper discharge guide 164 falls late, the leading edge of the subsequently discharged sheet Sb may collide with the leaning sheet Sa, as shown in Fig. 8, which may disrupt the alignment of the sheets stacked on the discharge tray 170.

[0050] 4 and 5, the configuration of this embodiment is provided with an extension guide unit 200 as a guide means having a regulating portion, which regulates the upward movement of the trailing edge of the sheet that has passed through the nip of the discharge roller pair 161. This makes it possible to prevent stacking problems such as the trailing edge leaning or collisions between sheets, even when discharging a curled sheet.

[0051] Furthermore, in this embodiment, the extension guide unit 200 is configured to be detachable from the apparatus main body 101. When the discharge roller pair 161 delivers the sheet to the post-processing device 40 (FIG. 9) instead of the discharge tray 170, the trailing end does not lean, and therefore there is little need to restrict the movement of the trailing end of the sheet by the guide surface 201a. On the other hand, by removing the extension guide unit 200, the installation operation of mounting the post-processing device 40 in the internal discharge space 190 and connecting it to the discharge port of the apparatus main body 101 can be more easily performed. Therefore, the configuration of this embodiment is more versatile than, for example, a case in which the extension guide unit 200 is configured as part of the apparatus main body 101.

[0052] As an alternative means for avoiding the rear end leaning and collisions between sheets, it is conceivable to increase the sheet discharge speed by the discharge roller pair 161 or to widen the interval between sheet discharges, but this raises concerns about an increase in motor drive noise and a decrease in productivity of the image forming apparatus. In contrast, in this embodiment, a simple configuration in which an extension guide unit 200 is attached near the discharge outlet makes it possible to suppress the rear end leaning and collisions between sheets. It is also possible to combine the above alternative means with the configuration of this embodiment.

[0053] In this embodiment, the pair of discharge rollers 161 discharges the sheet with the image side of the sheet facing downward, which is a so-called face-down discharge configuration. The image side, however, refers to the side of the sheet on which a toner image is formed by the image forming unit 140 (in the case of double-sided printing, the second side on which the image is formed the second time). In this configuration, the image side of the sheet is heated in the fixing unit 150 while being supported by a pressure member from the side opposite the image side, so that the sheet tends to curl upward when discharged face-down. The configuration of the discharge unit 160 described in this embodiment can be suitably applied to such a face-down discharge configuration.

[0054] However, the tendency of the sheet to curl after image formation varies depending on the operation settings of the image forming operation (single-sided / double-sided setting, sheet spacing and image forming speed setting, etc.), the environmental conditions during image formation (temperature, humidity, etc.), the material of the sheet used for image formation, etc. The tendency of the sheet to curl also varies depending on the layout of the image forming unit 140 (whether or not it is arranged for face-down discharge, etc.) and the characteristics of the mechanism used as the image forming means. Therefore, the configuration of the discharge unit 160 of this embodiment can be applied to devices other than the image forming apparatus 100 of the above-mentioned embodiment. [Example]

[0055] A second embodiment will now be described. In the first embodiment, a configuration has been described in which sheets discharged from the discharge roller pair 161 are basically stacked on the discharge tray 170, but in this embodiment, a second discharge tray is provided above the discharge tray 170. This embodiment differs from the first embodiment in that the second discharge tray has a function similar to the extension guide unit 200 of the first embodiment. Hereinafter, components with the same reference numerals as those in the first embodiment have substantially the same configuration and function as those in the first embodiment, and the following description will focus on the parts that differ from the first embodiment.

[0056] Fig. 10 is a schematic diagram showing a cross-sectional configuration of an image forming apparatus 100 according to this embodiment. Fig. 11 is a perspective view of a discharge section 160 according to this embodiment. Fig. 12 is a cross-sectional view of the discharge section 160 according to this embodiment.

[0057] 10 and 11, a second discharge tray 300 is provided above a discharge tray 170 (hereinafter referred to as a first discharge tray) similar to that of the first embodiment. The first discharge tray 170 is a first sheet support portion of this embodiment, and the second discharge tray 300 is a second sheet support portion of this embodiment.

[0058] The second discharge tray 300 is detachably attached to the device body 101 between an opening (second discharge outlet) of the device body 101 where the reversing roller pair 162 is provided and an opening (first discharge outlet) where the discharge roller pair 161 is provided in the vertical direction. The second discharge tray 300 extends downstream in the sheet discharge direction B from the device body 101 so as to overlap with the first discharge tray 170 when viewed from above. Therefore, the internal discharge space 190 is divided into a first discharge space 191 above the first discharge tray 170 and below the second discharge tray 300, and a second discharge space 192 above the second discharge tray 300 and below the image reading device 102.

[0059] Furthermore, the pair of reversing rollers 162 of this embodiment can perform not only a reversing operation for reversing a sheet but also a discharging operation for discharging the sheet onto the second discharge tray 300. In other words, the pair of discharge rollers 161 functions as a first discharging unit, and the pair of reversing rollers 162 functions as a second discharging unit. Note that the portion of the sheet that protrudes from the second discharge port to the outside of the device body 101 during the reversing operation is supported by the second discharge tray 300.

[0060] 12, a plurality of guide ribs 300a are formed on the lower surface of the second discharge tray 300 (the surface opposite to the support surface 300b that supports the sheets) at the upstream end in the sheet discharge direction B. The shape of these guide ribs 300a is the same as the ribs provided on the guide surface 201a of the first embodiment. In addition, with respect to the sheet width direction, the guide ribs 300a are arranged over a range equal to or greater than the maximum sheet width on which the image forming apparatus 100 can form an image (maximum sheet width according to specifications).

[0061] In this embodiment, when the discharge roller pair 161 discharges the sheet S, the guide rib 300a prevents the trailing edge of the sheet S that has passed through the nip of the discharge roller pair 161 from moving above the nip line N. In other words, the guide rib 300a functions as a restricting portion in this embodiment, and the second discharge tray 300 functions as a guide means in this embodiment. Therefore, as in the first embodiment, even when discharging a curled sheet, it is possible to prevent stacking problems such as the trailing edge leaning or collisions between sheets.

[0062] In addition, in this embodiment, when an accessory such as the post-processing device 40 (FIG. 9) is installed in the internal discharge space 190, removing the second discharge tray 300 also removes the guide rib 300a that is integral with the second discharge tray 300. This makes it easier to attach and detach the accessory compared to the configuration in which the extension guide unit 200 and the reversing guide 171 are removed separately in the first embodiment.

[0063] In this embodiment, the guide rib 300a that regulates the position of the sheet trailing end is formed as part of the second discharge tray 300, but the guide rib 300a may be disposed on another member (for example, the underside of the reversing guide 171 in the first embodiment). The guide rib 300a may be formed separately from the second discharge tray 300 and fixed to the second discharge tray 300 with screws or the like. The regulating portion is not limited to being formed by multiple ribs, but may also have a surface shape that expands in the sheet width direction and the sheet discharge direction. A regulating portion with such a surface shape has the advantage of being able to accommodate a wider variety of sheet sizes.

[0064] Furthermore, the second discharge tray 300 of this embodiment may be provided with a full-load detection flag 202 and / or a rear end pressing flag 203 similar to those of the first embodiment. By providing these flag members, the rear end of the sheet S that has passed through the nip of the discharge roller pair 161 can be pressed downward, thereby further suppressing the occurrence of stacking problems such as rear end leaning or collision between sheets. [Explanation of symbols]

[0065] 100...image forming apparatus / 101...apparatus main body / 132...transfer means (secondary transfer outer roller) / 140...image forming means (image forming unit) / 150...fixing means (fixing device) / 160...sheet discharge device (discharge unit) / 161...discharge means, first discharge means (discharge roller pair) / 162...second discharge means (reversal roller pair) / 170...sheet support portion (discharge tray) / 200...guide means (extension guide unit) / 201a...regulating portion (guide surface) / 202...flag member, first flag member (full-load detection flag) / 203...flag member, second flag member (rear end pressing flag) / 204...discharge member (discharge brush) / 300...guide means (second discharge tray) / 300a...regulating portion (guide rib)

Claims

1. A pair of rollers that clamp a sheet in a nip portion and discharge the sheet in a sheet discharge direction that intersects with the vertical direction, the pair of rollers having a first roller that contacts the upper surface of the sheet in the nip portion and a second roller that contacts the lower surface of the sheet in the nip portion; a sheet support portion that supports the sheet discharged by the roller pair; a regulating portion that is disposed above a nip line that perpendicularly intersects a line connecting the rotation axis of the first roller and the rotation axis of the second roller and passes through the nip portion, the regulating portion is disposed to regulate a trailing edge of the sheet in the sheet discharge direction from moving upward above the nip line after passing through the nip portion of the roller pair, The length of the sheet in the sheet width direction perpendicular to the sheet discharge direction is defined as the sheet width, and the sheet width of the largest sheet that can be discharged by the roller pair is defined as the maximum sheet width. the regulating portion is provided over a range equal to or greater than the maximum sheet width in the sheet width direction, an upstream end of the regulating portion in the sheet discharge direction protrudes downward below an upper end position of the first roller; A sheet discharge device characterized by:

2. The roller pair further includes a flag member that rotates around a rotation axis provided above the nip line, the flag member protruding below the nip line when not in contact with the sheet discharged from the roller pair.

2. The sheet ejection device according to claim 1.

3. the flag member is configured to come into contact with the seat supported by the seat support portion and to rotate in accordance with the amount of the seat supported by the seat support portion, The flag member further includes a detection unit whose detection signal changes depending on the rotation angle of the flag member.

3. The sheet ejection device according to claim 2.

4. The flag member is a first flag member, a second flag member that rotates around a rotation axis provided above the nip line and that protrudes below the nip line when not in contact with the sheet discharged from the pair of rollers; the second flag member contacts the sheet discharged from the roller pair upstream of the first flag member in the sheet discharge direction; 4. The sheet ejection device according to claim 3.

5. At least a portion of the regulating portion extends substantially parallel to the nip line when viewed in the sheet width direction.

5. The sheet ejection device according to claim 1, wherein the sheet ejection device is a sheet ejection device.

6. a discharge member for removing electric charges from the sheet discharged from the roller pair; 6. The sheet ejection device according to claim 1, wherein the sheet ejection device is a sheet ejection device.

7. Further, a discharge means for discharging the sheet above the pair of rollers is provided, the regulating portion is provided on a member having a support surface that supports the sheet discharged by the discharge unit; 7. The sheet ejection device according to claim 1, wherein the sheet ejection device is a sheet ejection device.

8. The restriction portion is fixed.

8. The sheet ejection device according to claim 1, wherein the sheet ejection device is a sheet ejection device.

9. The regulating portion has a planar shape extending in the sheet width direction.

9. The sheet ejection device according to claim 1, wherein the sheet ejection device is a sheet ejection device.

10. the regulating portion includes a plurality of ribs arranged side by side in the sheet width direction, each of which extends along the sheet discharge direction, 9. The sheet ejection device according to claim 1, wherein the sheet ejection device is a sheet ejection device.

11. an image forming means for forming an image on a sheet; and the sheet discharge device according to any one of claims 1 to 10, which discharges a sheet on which an image has been formed by the image forming unit. An image forming apparatus characterized by:

12. the regulating portion is detachable from a main body of the apparatus in which the image forming means is provided, a sheet processing device that processes the sheet discharged by the roller pair can be attached to the device body in a state where the regulating unit is detached from the device body; 12. The image forming apparatus according to claim 11.

13. the image forming means includes an image carrier, a transfer means for transferring a toner image formed on the image carrier onto an image surface of a sheet, and a fixing means for heating the toner image transferred onto the image surface to fix it to the sheet; the sheet discharge device discharges the sheet with the image surface facing downward; 13. The image forming apparatus according to claim 11 or 12.

Images