Sheet discharge device and image forming device

Abstract

To improve sheet loading performance.SOLUTION: A sheet discharge device includes: a discharge part that discharges a sheet in a sheet discharge direction; a sheet support part that supports the sheet discharged by the discharge part; a first static elimination unit that is arranged downstream of the discharge part in the sheet discharge direction and removes charge from the surface of the sheet; and a second static elimination unit that is arranged downstream of the first static elimination unit in the sheet discharge direction and removes charge from the surface of the sheet. The first static elimination unit has a plurality of first static elimination parts arranged side by side at a first pitch in a cross direction intersecting the sheet discharge direction, and the second static elimination unit has a plurality of second static elimination parts arranged side by side at a second pitch different from the first pitch in the cross direction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a sheet discharge device that discharges sheets and an image forming apparatus including the same. [Background technology]

[0002] Conventionally, an image forming apparatus has been proposed in which a sheet on which a toner image is formed and which is discharged by a pair of discharge rollers is discharged by a first discharge unit and a second discharge unit (see Patent Document 1). In the conveyance direction, the first discharge unit is disposed downstream and above the pair of discharge rollers, and the second discharge unit is disposed upstream and below the pair of discharge rollers. The first and second discharge units discharge the top and bottom surfaces of the sheet. The first and second discharge units each have a plurality of discharge brushes arranged in the sheet width direction, which is perpendicular to the sheet conveyance direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-030917 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the speed and functionality of image forming devices have increased, resulting in an increase in the amount of static electricity carried to the discharge tray per unit time via discharged sheets. As a result, the first and second static elimination units described in Patent Document 1 mentioned above may not be able to effectively remove the charge on the sheets, and there may be cases where the sheets attract or repel each other, causing problems with the stackability of the sheets on the discharge tray.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet discharge device that can improve the sheet stacking efficiency. [Means for solving the problem]

[0006] One aspect of the present invention is a sheet discharge device comprising: a discharge section that discharges a sheet in a sheet discharge direction; a sheet support section that supports the sheet discharged by the discharge section; a first de-ionization unit that is arranged downstream of the discharge section in the sheet discharge direction and removes charge from the surface of the sheet; and a second de-ionization unit that is arranged downstream of the first de-ionization unit in the sheet discharge direction and removes charge from the surface of the sheet, wherein the first de-ionization unit has a plurality of first de-ionization sections arranged side by side at a first pitch in a cross direction that intersects the sheet discharge direction, and the second de-ionization unit has a plurality of second de-ionization sections arranged side by side in the cross direction at a second pitch that is different from the first pitch.

[0007] Another aspect of the present invention is a sheet discharge device comprising: a discharge section that discharges a sheet in a sheet discharge direction; a sheet support section that supports the sheet discharged by the discharge section; a first de-ionization unit that is arranged downstream of the discharge section in the sheet discharge direction and that removes charge from the surface of the sheet; and a second de-ionization unit that is arranged downstream of the first de-ionization unit in the sheet discharge direction and that removes charge from the surface of the sheet, wherein the first de-ionization unit includes a plurality of upstream de-ionization units arranged side by side in a cross direction that intersects the sheet discharge direction, the plurality of upstream de-ionization units having first upstream de-ionization units and second upstream de-ionization units that are adjacent to each other in the cross direction; the second de-ionization unit includes a plurality of downstream de-ionization units arranged side by side in the cross direction, the plurality of downstream de-ionization units having first downstream de-ionization units and second downstream de-ionization units that are adjacent to each other in the cross direction; and wherein the distance between the first upstream de-ionization unit and the second upstream de-ionization unit in the cross direction is different from the distance between the first downstream de-ionization unit and the second downstream de-ionization unit. [Effects of the Invention]

[0008] According to the present invention, the sheet stacking capacity can be improved. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic overall view showing a cross-sectional configuration of an image forming apparatus according to a first embodiment. [Figure 2] 1A is a perspective view showing a sheet discharge device, FIG. 1B is a perspective view showing a sheet discharge device main body, and FIG. 1C is a perspective view showing an extension unit. [Figure 3] FIG. 2A is a front view showing a first static eliminating unit, and FIG. 2B is a front view showing a second static eliminating unit. [Figure 4] FIG. [Figure 5] FIG. 10(a) is a front view showing a first static eliminating unit according to a second embodiment, and FIG. 10(b) is a front view showing a second static eliminating unit. DETAILED DESCRIPTION OF THE INVENTION

[0010] First Embodiment [Overall configuration] First, a first embodiment of the present invention will be described. Fig. 1 is an overall schematic diagram showing a cross-sectional configuration of an image forming apparatus 100 according to the first embodiment. The image forming apparatus 100 has an image forming section 140 that forms an image on a sheet S, which is a recording material, a feeding unit 110, a fixing device 150, a sheet discharge device 200, and an image reading device 102. The image forming apparatus 100 also has an apparatus main body 101, which is a housing that houses the image forming section 140.

[0011] The image forming apparatus includes printers, copiers, facsimiles, and multifunction peripherals, and refers to an apparatus that forms an image on a sheet used as a recording medium based on image information input from an external PC or image information read from an original. In addition, an image forming apparatus may be connected to accessories such as an optional feeder, an image reader, and a sheet processing device in addition to the main body having an image forming function, and the entire system connected with such accessories is also a type of image forming apparatus.

[0012] The image forming section 140 is an electrophotographic unit of an intermediate transfer tandem type in which image forming stations Y, M, C, and Bk that form toner images of four colors are arranged along an intermediate transfer belt 145 .

[0013] The sheets S are stored in a cassette 111 provided at the bottom of the apparatus main body 101, and are fed one by one by a feeding unit 110. 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, which are recording materials, can be a variety of sheets of different sizes and materials, such as 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.

[0014] The sheet S fed from the feeding unit 110 has its skew corrected by the skew correction device 120, and is transported toward the transfer nip 130 at a timing synchronized with the toner image formation process by the image forming section 140. The transfer nip 130 as a transfer section 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, and transports the sheet while nipping it.

[0015] In parallel with the above-described process of transporting the sheet S to the transfer nip 130, the image forming unit 140 executes 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 unit such as a charging roller, and a developing unit 143, which serves as a developing unit. The image forming unit 140 also includes an exposure device 142 disposed below the four photosensitive drums 141. In the toner image formation process, the charging unit 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 on 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.

[0016] 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 transfer nip 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 transfer nip 130.

[0017] The sheet S that has passed through the transfer nip 130 is transported to the fuser 150. The fuser 150 has a fuser roller 155 that has a built-in heater, and a pressure roller 156 that contacts the fuser roller 155 with a predetermined pressure. The fuser roller 155 is driven by a drive source such as a motor (not shown), and the pressure roller 156 is rotated by the fuser roller 155. The fuser 150 applies pressure and heat to the toner image on the sheet S while nipping and transporting the sheet S with a fuser nip 157 that serves as a fuser formed by the fuser roller 155 and the pressure roller 156. This melts the toner, and the toner adheres after passing through the fuser nip, resulting in a fixed image on the sheet S.

[0018] The sheet S that has passed through the fixing unit 150 is guided by a first guide member 151 to either a first discharge path 230 toward a first discharge roller pair 160 or a second discharge path 240 toward a second discharge roller pair 161. When images are formed on both sides of the sheet S, the sheet S with an image formed on its first side is guided by the first guide member 151 toward the second discharge roller pair 161 and conveyed toward the outside of the apparatus by the second discharge roller pair 161. When the trailing end of the sheet S in the conveying direction passes through the second guide member 152, the second discharge roller pair 161 reverses the conveying direction of the sheet S and sends the sheet S into a double-sided conveying path 180. The portion of the sheet S that protrudes outside the apparatus main body 101 during the reversing operation by the second discharge roller pair 161 is supported by a second discharge tray 171. The sheet S reaches the skew correction device 120 again via the double-sided conveying path 180, and after skew correction and timing correction, passes through the transfer nip 130 and the fixing device 150, where an image is formed on the second side.

[0019] A sheet discharge device 200 is provided downstream of the fixing device 150 in the sheet conveying direction, which discharges the sheet S outside the apparatus, i.e., outside the apparatus main body 101. The sheet discharge device 200 has a first discharge roller pair 160, a second discharge roller pair 161, a first discharge tray 170, and a second discharge tray 171.

[0020] When discharging the sheet S, the sheet S sent out from the fixing unit 150 is guided by the first guide member 151 to the first discharge roller pair 160, and is then discharged to the outside of the apparatus main body 101 by the first discharge roller pair 160. A first discharge tray 170 is provided on the upper part of the apparatus main body 101, and the sheet S discharged by the first discharge roller pair 160 is stacked (supported) on the first discharge tray 170. The upper surfaces of the first discharge tray 170 and the second discharge tray 171 have inclined surfaces 170a and 171a that slope upward toward the downstream side in the sheet discharge direction DD. The sheet S stacked on the first discharge tray 170 or the second discharge tray 171 slides due to its own weight along the inclined surfaces (170a and 171a) of the first discharge tray 170 or the second discharge tray 171 toward the upstream side in the sheet discharge direction DD. Alignment surfaces 170b, 171b extending in the vertical direction (gravity direction) are provided on the upstream side of the first discharge tray 170 and the second discharge tray 171 in the sheet discharge direction DD. The sheet S discharged to the outside of the apparatus slides along the inclined surface (170a, 171a) of the first discharge tray 170 or the second discharge tray 171. Then, the rear end of the sheet S hits the alignment surface (170b, 171b), thereby aligning the position of the sheet S stacked on the first discharge tray 170 or the second discharge tray 171.

[0021] The image forming apparatus 100 includes an image reading device 102 mounted on an upper portion of the 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 first 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.

[0022] Furthermore, the image forming unit 140 described above is an example of an image forming unit, and for example, a direct transfer type electrophotographic unit that transfers a toner image formed on a photosensitive member onto a sheet without using an intermediate transfer member may be used.

[0023] [Sheet ejection device] Next, the sheet discharge device 200 will be described with reference to Figures 2(a) to 2(c). Figure 2(a) is a perspective view showing the sheet discharge device 200. Figure 2(b) is a perspective view showing the sheet discharge device main body 210. Figure 2(c) is a perspective view showing the extension unit 300.

[0024] As shown in Fig. 2(a), the sheet discharge device 200 has a sheet discharge device main body 210 and an extension unit 300. As shown in Fig. 2(b), the sheet discharge device main body 210 has a discharge frame 210a, a first discharge roller pair 160 as a discharge section, and a second discharge roller pair 161 disposed above the first discharge roller pair 160. The first discharge roller pair 160 and the second discharge roller pair 161 discharge the sheet S in a sheet discharge direction DD.

[0025] The sheet discharge device main body 210 also has a first static elimination unit 220 disposed downstream in the sheet discharge direction DD of the first discharge roller pair 160, and an upper static elimination unit 220U disposed downstream in the sheet discharge direction DD of the second discharge roller pair 161. The upper static elimination unit 220U has a configuration similar to that of the first static elimination unit 220 described below, and removes charges from the surface of the sheet S discharged by the second discharge roller pair 161.

[0026] In this embodiment, four first discharge roller pairs 160 and four second discharge roller pairs 161 are arranged side by side in a width direction W that intersects with the sheet discharge direction DD. However, the number of first discharge roller pairs 160 and second discharge roller pairs 161 is not limited to four, and may be one to three, or four or more. In this embodiment, the width direction W as the intersecting direction is a direction perpendicular to the sheet discharge direction DD, but it may be any direction that intersects with the sheet discharge direction DD.

[0027] The first discharge roller pair 160 has a drive roller 160a as a first roller and a driven roller 160b as a second roller that rotates following the drive roller 160a. The driven roller 160b forms a nip 165 with the drive roller 160a to sandwich and transport the sheet S. Similarly, the second discharge roller pair 161 has a drive roller 161a and a driven roller 161b that rotates following the drive roller 161a.

[0028] The discharge frame 210a has a slit 291 extending in the width direction W, and a hole 292 disposed below the slit 291. The hole 292 is provided in approximately the center in the width direction W of the discharge frame 210a.

[0029] As shown in FIG. 2C, the extension unit 300 includes an extension frame 310 and a second static eliminating unit 320. The extension frame 310 includes an engagement portion 311 that engages with the discharge frame 210a of the sheet discharge device main body 210, and a hole 312. The hole 312 is aligned with the hole 292 of the discharge frame 210a when the engagement portion 311 is engaged with the discharge frame 210a. The hole 292, 312 are fastened with fastening members such as screws, thereby fixing the extension unit 300 to the sheet discharge device main body 210. The extension unit 300 is configured to be detachable from the sheet discharge device main body 210, and may be attached or detached depending on the media transported by the image forming apparatus 100.

[0030] When the sheet S is discharged from the first discharge path 230, the surface of the sheet S discharged to the outside of the apparatus body 101 (see FIG. 1) by the first discharge roller pair 160 has its charges removed by the first charge removal unit 220 and the second charge removal unit 320. In this embodiment, "removal of charges" is also referred to as "elimination of charges" and means that the amount of charge on the surface of the sheet S is reduced by charge removal. In other words, in charge removal, it is not necessary to remove all of the charges on the sheet S, and it is sufficient if only a portion of the charges on the sheet S can be removed.

[0031] [Configuration of the first static elimination unit and the second static elimination unit] Next, the configurations of the first static eliminating unit 220 and the second static eliminating unit 320 will be described with reference to Figures 3(a), 3(b) and 4. Figure 3(a) is a front view showing the first static eliminating unit 220, and Figure 3(b) is a front view showing the second static eliminating unit 320. Figure 4 is a cross-sectional view showing the sheet discharge device 200.

[0032] As shown in FIG. 3(a), the first static eliminating unit 220 has a support portion 222 made of stainless steel (SUS: Steel Use Stainless) and multiple static eliminating brushes 221 made of stainless steel. Stainless steel is a steel material with a chromium content of 10.5% or more and a carbon content of 1.2% or less in iron. The multiple static eliminating brushes 221 serving as the multiple first static eliminating portions and multiple upstream static eliminating portions are supported by the support portion 222 serving as the first support portion and are arranged side by side in the width direction W at a first pitch p1. For example, the multiple static eliminating brushes 221 include a static eliminating brush 221a serving as a first upstream static eliminating portion and a static eliminating brush 221b serving as a second upstream static eliminating portion that are adjacent to each other in the width direction W. The distance between these static eliminating brushes 221a and 221b is the first pitch p1.

[0033] 3(b), the second static eliminating unit 320 has a support portion 322 as a second support portion, and a plurality of static eliminating brushes 321 supported by the support portion 322 and arranged side by side in the width direction W at a second pitch p2 that is shorter than the first pitch p1. For example, the plurality of static eliminating brushes 321 have a static eliminating brush 321a as a first downstream static eliminating portion and a static eliminating brush 321b as a second downstream static eliminating portion that are adjacent to each other in the width direction W. The distance between these static eliminating brushes 321a and 321b is a second pitch p2, which is different from the first pitch p1.

[0034] The plurality of second static eliminating units and the plurality of static eliminating brushes 321 serving as the plurality of downstream static eliminating units are made of amorphous metal fiber, which is an amorphous metal material. For example, the amorphous metal fiber is made of Al-based amorphous or Co-Fe-Cr-Si-B-based amorphous. The support unit 322 is made of, for example, stainless steel or amorphous metal. That is, the support units 222, 322, the plurality of static eliminating brushes 221, and the plurality of static eliminating brushes 321 are all conductive. The support units 222, 322 are grounded via a metal frame or the like of the image forming apparatus 100. The static eliminating brushes 221, 321 are made of a plurality of wires extending in the direction of gravity G, and are referred to as "brushes" regardless of the material.

[0035] The area in which the plurality of first charge-removing brushes 221 and the plurality of second charge-removing brushes 321 are arranged is longer in the width direction W than the width of the largest size sheet that can be used in the image forming apparatus 100. Therefore, the first charge-removing unit 220 and the second charge-removing unit 320 remove electric charges from the entire surface of the sheet S that passes through the first discharge path 230 and is discharged by the first discharge roller pair 160.

[0036] Generally, increasing the pitch of multiple static elimination brushes increases the effectiveness of each individual static elimination brush in eliminating the charge on the sheet, but this creates areas between two adjacent static elimination brushes where static cannot be eliminated, resulting in uneven charge levels on the sheet surface.

[0037] Therefore, in this embodiment, the pitch p1 of the plurality of static eliminating brushes 221 of the first static eliminating unit 220 is made different from the pitch p2 of the plurality of static eliminating brushes 321 of the second static eliminating unit 320. More specifically, the pitch p1 of the plurality of static eliminating brushes 221 of the first static eliminating unit 220 is set to be longer than the pitch p2 of the plurality of static eliminating brushes 321 of the second static eliminating unit 320.

[0038] This improves the static elimination effect of the multiple static elimination brushes 221 of the first static elimination unit 220 arranged upstream in the sheet discharge direction DD. Therefore, it is possible to effectively remove electric charges from sheets, even for ultra-thin paper, coated paper, and the like, which tend to have a relatively large amount of charge. Furthermore, because the pitch p2 is shorter than the pitch p1, it is possible to eliminate electric charges remaining on the sheets S so as to reduce unevenness in the electric charges by the multiple static elimination brushes 321 of the second static elimination unit 320 arranged downstream in the sheet discharge direction DD. Therefore, it is possible to prevent sheets stacked on the discharge tray 170 from attracting or repelling each other due to the electric charges on the sheets S, thereby improving the stackability of the sheets S.

[0039] In this embodiment, the multiple static elimination brushes 321 of the second static elimination unit 320 are made of amorphous metal fibers. Amorphous metal fibers have very low electrical resistance and high conductivity. In other words, static elimination brushes made of amorphous metal fibers have higher static elimination performance than static elimination brushes made of stainless steel. Therefore, even if the multiple static elimination brushes 321 are arranged in the width direction W at a pitch p2 shorter than the pitch p1, they can maintain high static elimination performance by being made of amorphous metal fibers.

[0040] 4, a pair of upstream discharge rollers 154 is disposed between the fixing unit 150 and the pair of discharge rollers 160 in the sheet discharge direction DD. The sheet S is transported by the pair of upstream discharge rollers 154 and guided by the first guide member 151 toward the first discharge path 230, and is guided to the first discharge roller pair 160 by the transport guides 231a and 231b that form the first discharge path 230. Upstream of the first discharge roller pair 160 in the sheet discharge direction DD, the position of the sheet S is regulated by the pair of upstream discharge rollers 154, the first guide member 151, and the transport guides 231a and 231b, and the movement trajectory (transport trajectory) of the sheet S does not change significantly.

[0041] On the other hand, downstream of the discharge roller pair 160 in the sheet discharge direction DD, the sheet S sandwiched between the discharge roller pair 160 is not held by any member, and the conveying posture may fluctuate, for example, within an area AR surrounded by a dashed line in Fig. 4. Therefore, the sheet S is discharged onto the first discharge tray 170 serving as a sheet support portion, while allowing for fluctuations (shaking) in the movement trajectory within the area AR.

[0042] 4, the deviation width of the sheet S in the sheet height direction (gravity direction, vertical direction) in the area AR increases toward the downstream side in the sheet discharge direction DD. For example, the deviation width B2 of the sheet S at the static elimination position of the second static elimination unit 320 is larger than the deviation width B1 of the sheet S at the static elimination position of the first static elimination unit 220.

[0043] The static elimination effect of a static elimination brush also varies depending on the material of the static elimination brush. For example, the effective distance of a static elimination brush made of stainless steel and a static elimination brush made of amorphous metal fiber differs, with the amorphous metal fiber static elimination brush having a relatively longer effective distance. Therefore, in this embodiment, a first static elimination unit 220 having a static elimination brush 221 made of stainless steel is disposed upstream in the sheet discharge direction DD where the wobble width (B1) of the sheet S is small. Furthermore, a second static elimination unit 320 having a static elimination brush 321 made of amorphous metal fiber is disposed downstream in the sheet discharge direction DD where the wobble width (B2) of the sheet S is large.

[0044] Therefore, even in the second static eliminating unit 320 provided downstream of the first static eliminating unit 220 in the sheet discharge direction DD, the response of static eliminating performance to changes in the position of the sheet S can be improved, and an appropriate static eliminating effect can be expected. Therefore, the stackability of the sheet S can be improved.

[0045] As described above, in this embodiment, there are provided the first static eliminating unit 220 and the second static eliminating unit 320 disposed downstream in the sheet discharge direction DD of the first static eliminating unit 220. By making the pitches and materials of these static eliminating brushes 221, 321 different from each other, it is possible to effectively eliminate static electricity from sheets while accommodating various types of sheets, and it is possible to improve the sheet stackability.

[0046] In this embodiment, the charge removal brushes 221, 321 are arranged so as not to come into contact with the surface of the sheet S discharged by the discharge roller pair 160. Even when the charge removal brushes 221, 321 are arranged in this manner, corona discharge causes charge to be released from the surface of the sheet S to the charge removal brushes 221, 321, thereby eliminating charge from the sheet S. Furthermore, because the sheet S does not come into contact with the charge removal brushes 221, 321, damage to the sheet and the image formed on the sheet can be suppressed. It is preferable that the charge removal brushes 221, 321 do not come into contact with the surface of the sheet S discharged by the discharge roller pair 160, but they may come into contact with it.

[0047] <Second embodiment> Next, a second embodiment of the present invention will be described. In the second embodiment, the pitch of the static eliminating brushes of the first static eliminating unit 220 and the second static eliminating unit 320 of the first embodiment is changed. Therefore, the same components as those of the first embodiment will be omitted from the illustration or will be described by using the same reference numerals in the drawings. Fig. 5(a) is a front view showing a first static eliminating unit 220B according to the second embodiment, and Fig. 5(b) is a front view showing a second static eliminating unit 320B.

[0048] 5(a), the first static eliminating unit 220B has a plurality of static eliminating brushes 221B as a plurality of first static eliminating sections that are supported by a support portion 222 and arranged side by side in the width direction W at a third pitch p3. The second static eliminating unit 320B has a plurality of static eliminating brushes 321B as a plurality of second static eliminating sections that are supported by a support portion 322 and arranged side by side in the width direction W at a fourth pitch p4. The third pitch p3 as the first pitch is longer than the fourth pitch p4 as the second pitch. That is, in the present embodiment as well, the pitches of the static eliminating brushes of the first static eliminating unit 220B and the second static eliminating unit 320B are made different from each other, as in the first embodiment.

[0049] Therefore, the plurality of charge eliminating brushes 221B of the first charge eliminating unit 220B can effectively reduce unevenness in the charge on the sheet S. Furthermore, the plurality of charge eliminating brushes 321B of the second charge eliminating unit 320B can effectively remove the charge on the sheet even for ultra-thin paper, coated paper, and the like, which tend to have a relatively large amount of charge. Therefore, it is possible to effectively eliminate charge on the sheet while dealing with various types of sheets, and the sheet stackability can be improved.

[0050] Also in this embodiment, as in the first embodiment, the plurality of static elimination brushes 221B of the first static elimination unit 220B are made of SUS, and the plurality of static elimination brushes 321B of the second static elimination unit 320B are made of amorphous metal fibers.

[0051] In any of the above-described embodiments, the materials of the static elimination brushes 221, 221B of the first static elimination units 220, 220B and the static elimination brushes 321, 321B of the second static elimination units 320, 320B are not limited to those described above. That is, the static elimination brushes 221, 221B of the first static elimination units 220, 220B are not limited to stainless steel, but may be made of, for example, amorphous metal fiber or other conductive bristle materials. Furthermore, the static elimination brushes 321, 321B of the second static elimination units 320, 320B are not limited to amorphous metal fiber, but may be made of stainless steel or other conductive bristle materials. Other conductive bristle materials include composite materials that arbitrarily combine resins such as nylon, acrylic, and polyester, carbon, and metal.

[0052] Furthermore, the support parts 222 and 322 are not limited to those described above. For example, the support parts 222 and 322 may be made of conductive tape, conductive resin, metal, or the like.

[0053] In addition, in all of the above-described embodiments, the materials of the static eliminating brushes 221, 221B of the first static eliminating units 220, 220B and the static eliminating brushes 321, 321B of the second static eliminating units 320, 320B are different from each other, but this is not limiting. For example, the materials of the static eliminating brushes 221, 221B of the first static eliminating units 220, 220B and the static eliminating brushes 321, 321B of the second static eliminating units 320, 320B may be the same.

[0054] In any of the above-described embodiments, the first static eliminating units 220, 220B and the second static eliminating units 320, 320B are both disposed on the drive roller 160a side with respect to the sheet sandwiched by the nip portion 165 of the discharge roller pair 160, but this is not limiting. For example, the first static eliminating units 220, 220B and the second static eliminating units 320, 320B may be disposed on the driven roller 160b side with respect to the sheet sandwiched by the discharge roller pair 160. Furthermore, the first static eliminating units 220, 220B and the second static eliminating units 320, 320B may be disposed on the drive roller 160a side and the driven roller 160b side with respect to the sheet sandwiched by the discharge roller pair 160. Furthermore, the positions of the drive roller 160a and the driven roller 160b may be interchanged.

[0055] In addition, in all of the above-described embodiments, the sheet discharge device 200 has two static eliminating units, a first static eliminating unit and a second static eliminating unit, but this is not limited to this. For example, the sheet discharge device 200 may have three or more static eliminating units downstream of the discharge roller pair 160 in the sheet discharge direction DD. Furthermore, the sheet discharge device 200 may have one or more static eliminating units upstream of the discharge roller pair 160 in the sheet discharge direction DD. Furthermore, the sheet discharge device 200 is not limited to a static eliminating unit having a static eliminating brush, and may have a static eliminating sheet made of a conductive sheet or a static eliminating tape made of a conductive tape. The static eliminating sheet and static eliminating tape may be provided on the opposite side of the sheet sandwiched between the discharge roller pair 160 from the first static eliminating unit and the second static eliminating unit.

[0056] In addition, in any of the above-described embodiments, the extension unit 300 is provided only on the first discharge path 230 side and not on the second discharge path 240 side, but this is not limiting. For example, the extension unit 300 may be provided only on the second discharge path 240 side, or the extension unit 300 may be provided on both the first discharge path 230 and the second discharge path 240.

[0057] In addition, in all of the above-described embodiments, the pitch of each of the static eliminating brushes of the first static eliminating unit 220 and the second static eliminating unit 320 is defined, but the pitch does not necessarily have to be the same for all of the static eliminating brushes of each static eliminating unit. For example, the multiple static eliminating brushes 221 of the first static eliminating unit 220 are arranged side by side at a first pitch p1, but a manufacturing error of ±5% for the first pitch p1 may be taken into consideration. The second pitch p2 is also the same as the first pitch p1.

[0058] In addition, although the above-described embodiments have been described using an electrophotographic image forming apparatus 100, the present invention is not limited to this. For example, the present invention can also be applied to an inkjet image forming apparatus that forms an image on a sheet by ejecting ink liquid from nozzles. [Explanation of symbols]

[0059] 100: image forming apparatus / 140: image forming section / 160: discharge section (pair of discharge rollers) / 160a: first roller (drive roller) / 160b: second roller (driven roller) / 165: nip section / 170: sheet support section (first discharge tray) / 200: sheet discharge device / 220, 220B: first static elimination unit / 221, 221B: multiple first static elimination sections (multiple static elimination brushes) / 221a: first upstream static elimination section (static elimination brush) / 221b: second upstream static elimination section (static elimination brush) / 222: first support portion (support portion) / 320, 320B: second static elimination unit / 321, 321B: multiple second static elimination portions (multiple static elimination brushes) / 321a: first downstream static elimination portion (static elimination brush) / 321b: second downstream static elimination portion (static elimination brush) / 322: second support portion (support portion) / DD: sheet discharge direction / G: gravity direction / p1, p3: first pitch, distance (third pitch) / p2, p4: second pitch, distance (fourth pitch) / S: sheet / W: width direction (cross direction)

Claims

1. a discharge section that discharges the sheet in a sheet discharge direction; a sheet support portion that supports the sheet discharged by the discharge portion; a first static elimination unit disposed downstream of the discharge unit in the sheet discharge direction, the first static elimination unit eliminating charges on the surface of the sheet; a second static elimination unit disposed downstream of the first static elimination unit in the sheet discharge direction and configured to eliminate charges on the surface of the sheet, the first static eliminating unit has a plurality of first static eliminating sections arranged side by side at a first pitch in a cross direction intersecting the sheet discharge direction, the second static eliminating unit has a plurality of second static eliminating portions arranged side by side at a second pitch different from the first pitch in the intersecting direction; A sheet discharge device characterized by:

2. the first pitch is longer than the second pitch; 2. The sheet ejection device according to claim 1.

3. The first pitch is shorter than the second pitch.

2. The sheet ejection device according to claim 1.

4. The plurality of first static eliminating units are made of a material different from that of the plurality of second static eliminating units.

2. The sheet ejection device according to claim 1.

5. the plurality of first static eliminating units are made of stainless steel, the plurality of second static eliminating portions are made of an amorphous metal material; 5. The sheet ejection device according to claim 4.

6. the first static eliminating unit has a first support portion that supports the plurality of first static eliminating portions and has conductivity; the second static eliminating unit supports the plurality of second static eliminating parts and has a second support part having conductivity; 2. The sheet ejection device according to claim 1.

7. the discharge section includes a first roller and a second roller that forms a nip portion with the first roller to sandwich and transport the sheet, the first static eliminating unit and the second static eliminating unit are both disposed on the first roller side with respect to the sheet sandwiched by the nip; 2. The sheet ejection device according to claim 1.

8. the plurality of first static eliminating units and the plurality of second static eliminating units extend in the direction of gravity; 2. The sheet ejection device according to claim 1.

9. a discharge section that discharges the sheet in a sheet discharge direction; a sheet support portion that supports the sheet discharged by the discharge portion; a first static elimination unit disposed downstream of the discharge unit in the sheet discharge direction, the first static elimination unit eliminating charges on the surface of the sheet; a second static elimination unit disposed downstream of the first static elimination unit in the sheet discharge direction and configured to eliminate charges on the surface of the sheet, the first static eliminating unit includes a plurality of upstream static eliminating sections arranged side by side in a cross direction intersecting the sheet discharge direction, the plurality of upstream static eliminating sections including a first upstream static eliminating section and a second upstream static eliminating section adjacent to each other in the cross direction; the second static eliminating unit includes a plurality of downstream static eliminating sections arranged side by side in the intersecting direction, the plurality of downstream static eliminating sections including a first downstream static eliminating section and a second downstream static eliminating section adjacent to each other in the intersecting direction, a distance between the first upstream static eliminating unit and the second upstream static eliminating unit in the cross direction is different from a distance between the first downstream static eliminating unit and the second downstream static eliminating unit; A sheet discharge device characterized by:

10. an image forming unit that forms an image on a sheet; and the sheet discharge device according to claim 1 , which discharges a sheet on which an image has been formed by the image forming unit. An image forming apparatus characterized by:

Images