Image forming device

Abstract

To suppress deterioration of image quality.SOLUTION: A sheet conveyance device 300 includes: a first conveyance path P along which a sheet is conveyed from a fixing device 150 that fixes a toner image on the sheet to an outside in a discharge direction DD; a second conveyance path Q that branches from the first conveyance path and conveys the sheet in a re-conveyance direction RD opposite to the discharge direction; and a guide member 210 that integrally forms a portion Pa that defines a part of the first conveyance path and a portion Qb that defines a part of the second conveyance path. The portion of the guide member that defines a part of the first conveyance path is provided with a surface shape part 210a that extends in a width direction perpendicular to the discharge direction.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention provides a sheet on which an image is formed. Guide material The present invention relates to an image forming apparatus provided with the above-mentioned. [Background technology]

[0002] An electrophotographic image forming apparatus forms an image on a sheet by using an electrophotographic image forming process. Examples of image forming apparatuses include copiers (e.g., digital copiers), printers (e.g., color laser beam printers, color LED printers, etc.), MFPs (multi-function peripherals), and facsimile machines. The image forming apparatus is not limited to an image forming apparatus that forms a color image, but may also be an image forming apparatus that forms a monochrome image. Sheets (recording media) on which an image is formed by an image forming apparatus include those made of any material such as paper, such as copy paper, plastic film for overhead projectors, and cloth, as well as those having any shape, such as envelopes and index sheets.

[0003] Conventionally, some image forming apparatuses are provided with an automatic double-sided printing function for forming images on both sides of a sheet. An image forming apparatus provided with an automatic double-sided printing function has a sheet transporting device that inverts a sheet on which an image has been formed on its front side (first side) by an image forming unit, and transports the sheet again to the image forming unit to form an image on its back side (second side). The sheet transporting device has a discharge path through which a sheet transported from the fixing unit to a discharge unit passes, a reversing path through which a sheet transported from the discharge unit to a re-conveying path passes, and a guide member that guides the sheet transported through the discharge path and the reversing path. A sheet with images formed on both sides and transported from the fixing unit is transported to the discharge unit through the discharge path while the front side (first side) on which the image has been formed is in contact with the guide member.

[0004] However, the image (toner image) formed on the surface of the sheet is reheated by the fixing device, and the sheet is hot immediately after it leaves the fixing device, and the image is not firmly fixed to the sheet. In particular, in the case of a color image, the temperature of the fixing device is set higher than that of a monochrome image in order to melt the toners of multiple colors and mix them evenly. Therefore, the color image on the sheet immediately after it is discharged from the fixing device is not firmly fixed to the sheet. In addition, with the miniaturization of the image forming apparatus, it becomes necessary to suddenly change the sheet conveying direction immediately after the sheet is discharged from the fixing device. In order to suddenly change the sheet conveying direction, the sheet comes into contact with the guide member with a large contact pressure. Since the image on the sheet immediately after it leaves the fixing device is not firmly fixed to the sheet, when the image on the sheet comes into contact with the guide member with a large contact pressure, there is a problem that the toner adheres to the guide member, causing sheet conveyance resistance and degrading image quality.

[0005] Patent Document 1 discloses a sheet conveying device including a branching member that is swingably provided at the branching point of a discharge path and a reversing path, and a rotating member that is rotatably provided on the branching member. The sheet discharged from the fixing unit comes into contact with the rotating member provided on the branching member and is guided to the discharge section. The rotating member comes into contact with the image on the sheet and rotates together with the sheet, so that the image is not rubbed by the branching member, and it is possible to prevent the toner of the image from adhering to the branching member. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2004-75305 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, when a rotating member is provided in addition to the branching member, as in Patent Document 1, or when a guide member is provided in the reversing path in addition to the guide member in the discharge path, there is a problem that the number of parts increases, leading to increased costs. Therefore, the guide member of the discharge path and the guide member of the reversing path are formed into an integrated guide member using resin, thereby reducing the number of parts. For the convenience of molding, the integrated guide member has multiple ribs arranged in a line in the width direction perpendicular to the sheet conveying direction. When a sheet on which an image is formed is conveyed along the integrated guide member, if the image surface of the sheet strongly abuts against the multiple ribs, a large stress is generated locally at the abutting portion, and the image is scratched along the multiple ribs, resulting in a decrease in image quality.

[0008] Therefore, the present invention can suppress the deterioration of image quality. Painting An imaging device is provided. [Means for solving the problem]

[0009] An image forming apparatus according to an embodiment of the present invention comprises: an image forming unit that forms an image; a transfer unit that transfers the image formed by the image forming unit onto a sheet; a fixing unit that fixes the image transferred by the transfer unit onto a sheet; a reversing roller that rotates in a first direction to reverse the sheet on which the image is fixed by the fixing unit and then rotates in a second direction opposite to the first direction; a first guide that guides a first surface of the sheet from the fixing unit toward the reversing roller in a sheet conveying direction; Department and a second guide that guides a second surface of the sheet reversed by the reversing roller, the second surface being opposite to the first surface; and a part integrally formed of a resin material. A guide member; The guide member Installed , The first guide portion is Sheet While bending a swinging member that can swing between a first position for guiding the sheet toward the reversing roller and a second position for guiding the sheet reversed by the reversing roller; of Yes , In the guide member, before Guide No. 1 Department teeth a plurality of first ribs arranged side by side in a width direction perpendicular to the sheet conveying direction and extending in the sheet conveying direction; A surface portion extending in the width direction and, is formed, before Guide No. 2 Department in the width direction In line A plurality of sheets are arranged and extend in the sheet conveying direction. Second The ribs are formed It is characterized by: Effect of the Invention

[0010] According to the present invention, it is possible to suppress the deterioration of image quality. [Brief description of the drawings]

[0011] [Figure 1] FIG. [Diagram 2] FIG. 2 is a diagram showing a sheet inverting unit according to the first embodiment. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] 6A and 6B are diagrams illustrating a sheet being transported in a discharge direction along a discharge path. [Figure 7] 13A and 13B are diagrams illustrating a sheet being transported in a re-transport direction along a reversing path. [Figure 8] FIG. 11 is a diagram showing a sheet inverting unit according to a second embodiment. [Figure 9] FIG. 11 is a diagram showing a sheet being conveyed in a re-conveying direction along a reversing path in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described with reference to Figures 1 to 9. Note that the dimensions, materials, shapes, and relative positions of the components described in the following embodiments of the present invention may be changed as appropriate depending on the configuration and various conditions of the device to which the present invention is applied, and are not intended to limit the scope of the present invention to only those. EXAMPLES

[0013] (Image forming device) FIG. 1 is a cross-sectional view of an image forming apparatus 100. The image forming apparatus 100 is an intermediate transfer tandem type in which four color image forming units 140Y, 140M, 140C, and 140K are arranged in line along an intermediate transfer belt 145. A sheet cassette 102 that stores a sheet S is provided at the bottom of the image forming apparatus 100. A feed roller 110 feeds the sheet S from the sheet cassette 102 in accordance with the image formation timing. The sheet S fed by the feed roller 110 is conveyed to a registration roller (skew correction device) 120 through a conveying path 112. The registration roller 120 corrects skew of the sheet S and adjusts the conveying timing of the sheet S. The sheet S is conveyed to a secondary transfer unit 130 by the registration roller 120 at a predetermined timing. The secondary transfer section 130 is formed between the intermediate transfer belt 145 and the secondary transfer outer roller 132 by the secondary transfer inner roller 131 and the secondary transfer outer roller 132 facing the secondary transfer inner roller. In the secondary transfer section 130, a predetermined pressure force and an electrostatic load bias are applied to the toner image on the intermediate transfer belt 145 and the sheet S, so that the toner image on the intermediate transfer belt 145 is transferred to the sheet S.

[0014] The toner image on the intermediate transfer belt 145 is conveyed to the secondary transfer unit 130 in synchronization with the timing at which the sheet S is conveyed to the secondary transfer unit 130. The toner image forming process will be described below. The image forming units 140Y, 140M, 140C, and 140K form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Since the image forming units 140Y, 140M, 140C, and 140K have the same structure, the image forming unit 140Y will be mainly described below. The suffixes Y, M, C, and K of the reference symbols represent yellow, magenta, cyan, and black, respectively. In the following description, the suffixes Y, M, C, and K will be omitted unless otherwise necessary.

[0015] The image forming section 140 includes a photoconductor (photosensitive drum) 141, a charging roller (charging means) 139, an exposure device 142, a developing device 143, and a primary transfer device 144. The charging roller 139 uniformly charges the surface of the rotating photoconductor 141. The exposure device 142 emits laser light to the uniformly charged surface of the photoconductor 141 in accordance with an image information signal of a corresponding color component, forming an electrostatic latent image on the surface of the photoconductor 141. The developing device 143 develops the electrostatic latent image on the photoconductor 141 with toner to form a toner image on the photoconductor 141. The toner image on the photoconductor 141 is given a predetermined pressure force and an electrostatic load bias by the primary transfer device 144, and is transferred onto an intermediate transfer belt 145.

[0016] The intermediate transfer belt 145 rotates in the counterclockwise direction indicated by the arrow A in Fig. 1. The yellow, magenta, cyan and black toner images formed by the image forming units 140Y, 140M, 140C and 140K, respectively, are transferred in a sequential, overlapping manner onto the intermediate transfer belt 145 by the primary transfer device 144. As a result, a full-color toner image is formed on the intermediate transfer belt 145 and is transported to the secondary transfer unit 130.

[0017] In the secondary transfer section 130, the full-color toner image on the intermediate transfer belt 145 is transferred to the sheet S. The sheet S to which the full-color toner image has been transferred is conveyed to the fixing device 150. The fixing device 150 has a heating roller 151 and a pressure roller 152. The heating roller 151 is heated by a heat source such as a heater. The pressure roller 152 is pressed against the heating roller 151 to form a fixing nip section. The heating roller 151 and the pressure roller 152 heat and press the sheet S passing through the fixing nip section to melt the toner, fix the toner image on the sheet S, and form a full-color image on the sheet S. The sheet S on which the image has been formed is conveyed in the discharge direction DD by a pair of discharge rollers 161 provided in the discharge section 160, and is discharged onto the discharge tray 170. This completes image formation (single-sided printing) on ​​the first surface (the surface on which the image is first formed) of the sheet S.

[0018] In the case of double-sided printing in which images are formed on both sides of the sheet S, the sheet S conveyed in the discharge direction DD by the discharge roller pair 161 passes through the inversion flapper 200 while being supported by the discharge tray 170, and then the sheet S is switched back and conveyed in the re-conveying direction RD. The discharge roller pair 161 rotates forward in a first direction to convey the sheet S in the discharge direction DD, and reverses in a second direction opposite to the first direction to convey the sheet S in the re-conveying direction RD opposite to the discharge direction DD. By the reverse rotation of the discharge roller pair 161, the sheet S is re-conveyed toward a double-sided roller pair (conveying roller pair) 181 provided in a re-conveying path 180. The sheet S is conveyed again to the registration roller 120 through the re-conveying path 180 by the double-sided roller pair 181. The registration roller 120 corrects the skew of the sheet S and adjusts the conveying timing of the sheet S to convey the sheet S to the secondary transfer unit 130. In the secondary transfer unit 130, a toner image is transferred from the intermediate transfer belt 145 to a second side of the sheet S, which is opposite to the first side. The toner image transferred to the second side of the sheet S is fixed to the sheet S by a fixing device 150. The sheet S with images formed on both sides is discharged onto a discharge tray 170 by a pair of discharge rollers 161, and double-sided printing is completed.

[0019] (Sheet conveying device) Next, a sheet inverting section 300 as a sheet conveying device of the first embodiment will be described with reference to FIG. 2. FIG. 2 is a diagram showing the sheet inverting section 300 of the first embodiment. The sheet inverting section 300 includes a discharge path (first conveying path) P extending from the fixing device 150 to the discharge section 160, and a reversing path (second conveying path) Q branching from the discharge path P and extending to the re-conveying path 180. The sheet inverting section 300 further includes a reversing flapper 200 as a branching member and a reversing guide 210 as a guide member. The reversing flapper 200 is provided downstream of the fixing device 150 in the sheet conveying direction X, in the vicinity of the branching section 190 where the reversing path Q branches from the discharge path P. The reversing guide 210 is provided downstream of the fixing device 150 in the sheet conveying direction X, and upstream of the reversing flapper 200. One end of the reversing flapper 200 is supported by the reversing guide 210 so as to be swingable by a shaft 201.

[0020] The discharge path P conveys the sheet S conveyed from the fixing device 150 that fixes the toner image on the sheet S to the image forming apparatus. 100 2, the discharge path P has a discharge path outer portion Pa on the right side upstream of the reverse flapper 200 in the sheet conveying direction X, and a discharge path inner portion Pb arranged on the left side opposite the discharge path outer portion Pa. The reverse path Q has a reverse path inner portion Qb on the left side downstream of the reverse flapper 200 in the re-conveying direction RD, and a reverse path outer portion Qa arranged on the right side opposite the reverse path inner portion Qb.

[0021] (Reversal guide) Next, the reversing guide 210 will be described with reference to Figures 2, 3, 4 and 5. As shown in Figure 2, the reversing guide 210 is disposed on the opposite side of the discharge section 160 with respect to the branching section 190 where the reversing path Q branches off from the discharge path P. The reversing guide 210 is an integrated guide member in which a discharge path outer section Pa (a section that defines a part of the discharge path P) and a reversing path inner section Qb (a section that defines a part of the reversing path Q) are integrally formed from a resin material.

[0022] FIG. 3 is a perspective view of the discharge path outer part Pa of the reversing guide 210. As shown in FIG. 3, the reversing guide 210 extends in the width direction W perpendicular to the sheet conveying direction X. The discharge path outer part Pa of the reversing guide 210 is provided with a planar part 210a extending in the width direction W. The planar part 210a has a planar shape without steps or a substantially planar shape with almost no steps. The planar part 210a is provided over almost the entire length of the reversing guide 210 in the width direction W. However, the length of the planar part 210a in the width direction W is not limited to this, and may be longer than the length in the width direction W of the maximum size of the sheet S that can be conveyed by the image forming apparatus 100. In the first embodiment, the planar part 210a is integrally formed with the reversing guide 210. Since the planar part 210a is integrally formed with the reversing guide 210, it is possible to suppress an increase in the number of parts and an increase in manufacturing costs. However, the planar portion 210a may be formed separately from the reversing guide 210 and attached to the reversing guide 210. The planar portion 210a may have a function of guiding the sheet S to the pair of discharge rollers 161.

[0023] 4 is a perspective view of the reversing path inner portion Qb of the reversing guide 210. As shown in FIG. 4, the reversing path inner portion Qb of the reversing guide 210 is provided with a plurality of ribs 210b aligned in a width direction W perpendicular to the re-conveying direction RD. The plurality of ribs 210b are arranged at narrow intervals in the width direction W. Each of the plurality of ribs 210b extends in the re-conveying direction RD and has a narrow width in the width direction W. The edges of each of the plurality of ribs 210b are curved and function as a guide portion for the sheet S.

[0024] Fig. 5 is a cross-sectional view of the reversing guide 210. As can be seen from Fig. 5, the planar portion 210a protrudes further into the discharge path P than other shaped portions formed on the same side, that is, the discharge path outer side portion Pa.

[0025] (Inverted Flapper) Next, the operation of the inverting flapper 200 will be described with reference to FIG. 2, FIG. 6, and FIG. 7. The inverting flapper 200 functions as a switching member for switching the conveying path of the sheet S. Before the leading edge of the sheet S on which the toner image is fixed by the fixing device 150 reaches the inverting flapper 200, the inverting flapper 200 waits at a closed position (standby position) CP that blocks the discharge path P, as shown in FIG. 2. When the leading edge of the sheet S conveyed in the sheet conveying direction X on the discharge path P abuts against the inverting flapper 200, the inverting flapper 200 is rotated clockwise around the shaft 201 by the stiffness and pressing force of the sheet S. The sheet S is conveyed to the discharge roller pair 161 of the discharge section 160 while rotating the inverting flapper 200. FIG. 6 is a diagram showing the sheet S conveyed in the discharge direction DD on the discharge path P. At this time, the inverting flapper 200 is located at an open position OP that opens the discharge path P. When the reversing flapper 200 is located at the open position OP, the sheet S is permitted to be conveyed from the reversing guide 210 to the discharge section 160. The reversing flapper 200 located at the open position OP functions as a guide member that guides the sheet S to the discharge section 160. In the case of single-sided printing, the sheet S is discharged to the discharge tray 170 by a pair of discharge rollers 161.

[0026] In the case of double-sided printing, the sheet S conveyed in the discharge direction DD by the discharge roller pair 161 passes the reverse flapper 200 while being supported by the discharge tray 170, and then the discharge roller pair 161 is reversed. By the reverse rotation of the discharge roller pair 161, the sheet S is conveyed toward the branching section 190 in the re-conveying direction RD opposite to the discharge direction DD. At this time, the re-conveying flapper 200 rotates by its own weight and returns to the closed position CP. Therefore, the sheet S conveyed to the branching section 190 by the reverse rotation of the discharge roller pair 161 is conveyed toward the double-sided roller pair 181 provided in the re-conveying path 180 through the re-conveying path Q without entering the discharge path P. When the re-conveying flapper 200 is located at the closed position CP, the sheet S is allowed to be conveyed from the discharge section 160 to the double-sided roller pair 181 without entering the discharge path P. FIG. 7 is a diagram showing the sheet S conveyed in the re-conveying direction RD through the re-conveying path Q. As shown in FIG. 7, the reversing flapper 200 is located in the closed position CP.

[0027] In the first embodiment, the reverse flapper 200 is configured to swing by the pressing force of the sheet S and the weight of the reverse flapper 200. However, the reverse flapper 200 may be configured to rotate by the biasing force of a spring (not shown). The reverse flapper 200 may be configured to rotate by the driving force of a solenoid (not shown) or a stepping motor (not shown) based on the detection result of a sensor (not shown) that detects the position of the sheet S.

[0028] (Sheet guiding operation in the discharge path) Next, a sheet guiding operation for guiding the sheet S transported along the discharge path P will be described. The sheet S transported along the discharge path P is transported along the discharge path outer portion Pa to the discharge section 160. In the case of single-sided printing, the non-image-formed surface of the sheet S (the surface opposite to the surface on which an image is formed) contacts the discharge path outer portion Pa of the reversing guide 210, and the sheet S is transported within the discharge path P while sliding on the discharge path outer portion Pa. In the case of double-sided printing, the first surface of the sheet S (the surface on which an image is formed) contacts the discharge path outer portion Pa, and the sheet S is transported within the discharge path P while sliding on the discharge path outer portion Pa.

[0029] In the case of double-sided printing, the sheet S is reheated by the fixing device 150, so the image-forming surface of the sheet S immediately after it leaves the fixing device 150 is hot, and the toner image is not firmly fixed to the sheet S. In particular, in the case of color printing, the temperature of the fixing device 150 is set higher than that in the case of black-and-white printing in order to melt the toners of multiple colors and mix them evenly. Therefore, in the case of color double-sided printing, the toner image is more difficult to fix to the sheet S immediately after it leaves the fixing device 150. When the toner image that is not firmly fixed to the sheet S contacts the rib provided on the reversing guide 210 in this way, local stress concentration occurs in the width direction W, and image rubbing occurs. However, according to the reversing guide 210 of the first embodiment, as shown in FIG. 6, the sheet S transported along the discharge path P mainly contacts the surface-shaped portion 210a provided on the discharge path outer portion Pa of the reversing guide 210, and slides on the surface-shaped portion 210a. This makes it possible to prevent local stress concentration in the width direction W when the sheet S contacts the planar portion 210a, and suppress deterioration of image quality. As shown in Fig. 2, a nip tangent NT of a nip portion between the heating roller 151 and the pressure roller 152, which are a pair of fixing rollers in the fixing device 150, is oriented so as to intersect with the planar portion 210a. As a result, the sheet S conveyed from the fixing device 150 mainly contacts the planar portion 210a and slides on the planar portion 210a.

[0030] (Sheet guiding operation on the reversing path) Next, a sheet guiding operation for guiding the sheet S conveyed along the reversing path Q will be described. As shown in FIG. 2, the nip tangent NA of the nip portion of the discharge roller pair 161 is oriented so as to intersect with the reversing path outer portion Qa. As a result, the sheet S forms a relatively large loop as shown in FIG. 7, and is conveyed along the reversing path outer portion Qa in the reversing path Q. That is, the sheet S is conveyed within the reversing path Q without the first surface, which is the image forming surface of the sheet S, coming into strong contact with the reversing path inner portion Qb and without sliding on the reversing path inner portion Qb. Therefore, even if the multiple ribs 210b of the reversing guide 210 are provided on the reversing path inner portion Qb, it is possible to prevent the image rubbing caused by the image forming surface of the sheet S coming into contact with the multiple ribs 210b of the reversing guide 210.

[0031] According to the first embodiment, it is possible to prevent image smearing caused by contact between the image forming surface of the sheet S and the reversing guide 210. Therefore, according to the first embodiment, it is possible to suppress deterioration of image quality. EXAMPLES

[0032] In the first embodiment, the nip tangent NA of the nip portion of the discharge roller pair 161 is oriented so as to intersect with the reversing path outer portion Qa, thereby preventing the image forming surface of the sheet S from strongly contacting the multiple ribs 210b of the reversing guide 210. In contrast, in the second embodiment, the nip tangent NB of the nip portion of the discharge roller pair 161 is oriented so as to intersect with the reversing path inner portion Qb. In the second embodiment, the same structures as those in the first embodiment are given the same reference symbols, and the description thereof will be omitted.

[0033] A sheet inverting unit 301 as a sheet conveying device of the second embodiment will be described with reference to FIG. 8. FIG. 8 is a diagram showing the sheet inverting unit 301 of the second embodiment. As shown in FIG. 8, the nip tangent NB of the nip of the discharge roller pair 161 is oriented so as to intersect with the reverse path inner portion Qb. FIG. 9 is a diagram showing the sheet S and the sheet SB conveyed in the re-conveying direction RD along the reverse path Q of the second embodiment. In FIG. 9, the sheet SB shown by the dashed line indicates, as a reference example, a sheet conveyed in the re-conveying direction RD along the reverse path Q when the conveying speed V1 of the discharge roller pair 161 is the same as the conveying speed V2 of the double-sided roller pair 181. The sheet S shown by the solid line indicates a sheet conveyed in the re-conveying direction RD along the reverse path Q when the conveying speed V1 of the discharge roller pair 161 according to the second embodiment is higher than the conveying speed V2 of the double-sided roller pair 181 (V1>V2).

[0034] If the conveying speed V1 of the discharge roller pair 161 is the same as the conveying speed V2 of the double-sided roller pair 181, the nip tangent NB of the discharge roller pair 161 is oriented so as to intersect with the reverse path inner portion Qb, so that the sheet SB is conveyed along the reverse path inner portion Qb. In this case, the first surface of the sheet SB, which is the image forming surface, strongly contacts the reverse path inner portion Qb, causing image rubbing and degrading the image quality. Therefore, in the second embodiment, while the sheet S is being conveyed in the re-conveying direction RD by the discharge roller pair 161 and the double-sided roller pair 181, the conveying speed V1 of the discharge roller pair 161 is set to be greater than the conveying speed V2 of the double-sided roller pair 181 (V1>V2). As a result, the sheet S forms a loop in the reverse path Q between the discharge roller pair 161 and the double-sided roller pair 181, as shown by the solid line in FIG. 9. Therefore, the first surface of the sheet S, which is the image forming surface of the sheet S, does not strongly contact the reversing path inner portion Qb, and does not slide on the reversing path inner portion Qb. This prevents the image forming surface of the sheet S from contacting the multiple ribs 210b of the reversing guide 210 and causing image rubbing. When the sheet S is transported in the re-conveying direction RD from the discharge roller pair 161, the reversing flapper 200 is located at the closed position CP, which allows the sheet S to be transported from the discharge section 160 to the double-sided roller pair 181 without entering the discharge path P.

[0035] According to the second embodiment, it is possible to prevent image smearing caused by contact between the image forming surface of the sheet S and the reversing guide 210. Therefore, according to the second embodiment, it is possible to suppress deterioration of image quality. [Explanation of symbols]

[0036] 150···Fuser unit 210···Inversion guide 210a...Surface shape part 300 Sheet turning section DD...Discharge direction P...Discharge path Pa... External part of discharge path Q... Reversal path Qb: Inner part of the reversing path RD...Re-feed direction S...Seat

Claims

1. an image forming unit that forms an image; a transfer unit that transfers the image formed by the image forming unit onto a sheet; a fixing unit that fixes the image transferred by the transfer unit onto a sheet; a reversing roller that rotates in a first direction to reverse the sheet on which the image is fixed by the fixing unit and then rotates in a second direction opposite to the first direction; a first guide portion that guides a first surface of the sheet from the fixing portion toward the reversing roller in a sheet conveying direction, and a second guide portion that guides a second surface of the sheet reversed by the reversing roller, the second surface being opposite to the first surface; and a guide member that is integrally formed of a resin material; a swinging member attached to the guide member and swingable between a first position where the sheet delivered from the first guide portion is guided toward the reversing roller while being curved, and a second position where the sheet is guided by the reversing roller; having In the guide member, The first guide portion is formed with a plurality of first ribs arranged side by side in a width direction perpendicular to the sheet conveying direction and extending in the sheet conveying direction, and a surface-shaped portion arranged downstream of the plurality of first ribs in the first guide portion and extending in the width direction, The second guide portion is formed with a plurality of second ribs arranged side by side in the width direction and extending in the sheet transport direction.

1. An image forming apparatus comprising:

2. A second guide member is disposed at a position opposite to the first guide portion and forms a conveying path through which a sheet passes together with the first guide member, the surface portion is inclined in a direction approaching the second guide member as it moves downstream in the sheet conveying direction, 2. The image forming apparatus according to claim 1,

3. The surface-shaped portion protrudes toward the second guide member, 3. The image forming apparatus according to claim 2,

4. The height of the plurality of second ribs is greater than the height of the plurality of first ribs, 4. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-color image forming apparatus.

5. The edges of the plurality of second ribs are curved.

5. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-color image forming apparatus.

6. The plurality of second ribs are formed from the upstream end to the downstream end of the second guide portion, 6. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

7. 7. The image forming apparatus according to claim 1, wherein a length of the planar portion in the width direction is longer than a length in the width direction of a sheet of a maximum size that can be conveyed.

8. a conveying roller for conveying the sheet conveyed by the reversing roller; a first conveying path through which a sheet passes between the fixing unit and the reversing roller; a second conveying path through which the sheet passes between the reversing roller and the conveying roller; Further comprising: When the rocking member is located at the first position, the sheet is allowed to be conveyed from the fixing unit to the reversing roller, and when the rocking member is located at the second position, the sheet is allowed to be conveyed from the reversing roller to the conveying roller without entering the first conveying path.

2. The image forming apparatus according to claim 1,

9. an opposing roller that is disposed at a position opposite to the reversing roller and that sandwiches the sheet with the reversing roller to form a nip portion and transport the sheet; a third guide member disposed at a position opposite to the guide member and forming the second transport path through which the sheet passes together with the guide member; A nip tangent of the nip portion intersects with the third guide member.

9. The image forming apparatus according to claim 8,

10. a counter roller that is disposed at a position opposite to the reversing roller and that sandwiches the sheet with the reversing roller to form a nip portion and convey the sheet; a nip tangent of the nip portion intersects with the guide member, a conveying speed of the sheet by the reversing roller is higher than a conveying speed of the sheet by the conveying roller; 9. The image forming apparatus according to claim 8,

11. The fixing unit includes a pair of fixing rollers, 11. The image forming apparatus according to claim 1, wherein a nip tangent to the nip portion of the pair of fixing rollers intersects with the planar portion.

12. 12. The image forming apparatus according to claim 1, wherein the planar portion is provided over an entire length of the guide member in the width direction.

13. 13. The image forming apparatus according to claim 1, wherein the surface shape portion guides the sheet to the reversing roller.

14. 14. The image forming apparatus according to claim 1, wherein the sheet conveyed by the fixing unit is conveyed to the reversing roller while rotating the swinging member.

Images