Sheet transport device and image forming apparatus

Abstract

To suppress turning up and flapping of a sheet in an inversion retreat part.SOLUTION: A sheet conveyance part 5 for conveying a sheet includes: an inversion mechanism 200 for conveying the sheet in a conveyance direction CD, and then conveying the sheet in an inversion conveyance direction RD opposite to the conveyance direction; an inversion retreat part 300 provided on the inversion mechanism, and temporarily retreating the sheet conveyed in the conveyance direction by the inversion mechanism; a double-sided conveyance part 220 for conveying the sheet conveyed in an inversion conveyance direction by the inversion mechanism; a first fan 221 provided on the double-sided conveyance part; and an inversion retreat guide member 310 provided on the inversion retreat part and guiding only one surface of the sheet, wherein the fan is arranged so as to blow air led from the double-sided conveyance part in the conveyance direction toward the inversion retreat part.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a sheet conveying device for conveying a sheet and an image forming device for forming an image on the sheet.

Background Art

[0002] Image forming devices such as printers, copiers, and multifunction devices form images on sheets used as recording materials. In the case of face-down discharge in which the surface of the sheet on which the image is formed is discharged downward or double-sided printing in which images are formed on both sides of the sheet, a reversing mechanism for reversing the front and back of the sheet is used. Patent Document 1 discloses a reversing mechanism provided with a pair of reversing rollers for performing back-and-forth conveyance of a sheet and a reversing storage unit in which the sheet is guided for back-and-forth movement. In the case of double-sided printing, a sheet on which an image has been formed on the first side by the image forming unit is switched back by the pair of reversing rollers, passes through the double-sided conveyance path, and is re-fed to the image forming unit with the first side and the second side on which an image is to be formed next being reversed.

[0003] By the way, there is an image forming device that discharges non-jammed sheets in the conveyance path to the reversing storage unit when a jam (paper jam) occurs. As a result, a plurality of sheets remaining in the conveyance path inside the image forming device are collected in the reversing storage unit, improving the jam processing performance. In an image forming device provided with such a sheet discharge mechanism, the reversing storage unit is provided with guide members only on the lower side of the conveyed sheet.

[0004] On the other hand, when double-sided printing is performed, water vapor is released from the sheet that has been switched back and conveyed to the double-sided conveyance path, causing condensation on the guide members of the double-sided conveyance path, the sheet sticking to the guide members, and jams may occur. Patent Document 2 discloses an image forming device that blows air into the double-sided conveyance path by a fan to suppress the occurrence of condensation and prevent the occurrence of jams.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-66560 [Patent Document 2] Japanese Patent Publication No. 2020-38352 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, recent image forming machines are required to print faster. In order to increase the printing speed, the overall sheet transport speed of the image forming machine must be increased, and the switchback transport speed must also be increased. However, if the guide member of the reversal and retraction section is only on the bottom side, when the switchback transport speed increases, the sheet may curl up due to air resistance, which may cause damage to the sheet or jams. [Means for solving the problem]

[0007] To solve the above problems, a sheet conveying device for conveying sheets according to one embodiment of the present invention is: A reversing unit that, after transporting the sheet in a first direction, transports the sheet in a second direction opposite to the first direction, A conveying unit for conveying sheets has a conveying path through which the sheets conveyed in the second direction by the reversing unit pass, Equipped with, The aforementioned reversal unit is A reversal and retraction section where the sheet conveyed in the first direction is temporarily retracted, The reversing and retracting section is provided on one side of the sheet. only Guide Furthermore, it is configured not to guide the other side of the sheet opposite to the aforementioned one side. Guide member and It has, The aforementioned transport unit is The air in the transport path in the transport section 、 The guide member The sheet guided by the guide member toward the other side of the sheet not guided by the guide member Air is blown along the first direction. Fans It is characterized by the following: [Effects of the Invention]

[0008] According to the present invention, the sheet transport speed can be increased while suppressing the curling and flapping of the sheet in the reversal and retraction section. [Brief explanation of the drawing]

[0009] [Figure 1] Cross-sectional view of an image forming apparatus. [Figure 2] Cross-sectional view of the sheet transport section. [Figure 3] Cross-sectional view of a conventional sheet transport unit. [Figure 4] An explanatory diagram showing the airflow of the fan that prevents the seat from lifting. [Figure 5] Figure 4 shows the double-sided transport section as viewed in the direction indicated by arrow V. [Figure 6] Cross-sectional view of the sheet transport section using a modified example. [Modes for carrying out the invention]

[0010] (Image forming apparatus) The embodiments for carrying out the present invention will be described below with reference to the attached drawings. Figure 1 is a cross-sectional view of an image forming apparatus. The image forming apparatus 1 is a color printer that forms a color image on a sheet P (recording medium) using an electrophotographic method. However, the image forming apparatus 1 is not limited to this, and may be, for example, an electrophotographic copier (e.g., a digital copier), a color LED printer, an MFP (multifunction printer), a facsimile machine, or a printing press. The image forming apparatus 1 is not limited to an electrophotographic image forming apparatus, but may also be an inkjet image forming apparatus. The image forming apparatus 1 may also be an image forming apparatus that forms a monochrome image.

[0011] The image forming apparatus 1 includes four image forming units 2Y, 2M, 2C, and 2K, a secondary transfer unit 3 (transfer unit), a fixing unit 4, and a sheet conveyance unit (sheet conveyance device) 5. The image forming unit 2Y forms a yellow image using yellow toner. The image forming unit 2M forms a magenta image using magenta toner. The image forming unit 2C forms a cyan image using cyan toner. The image forming unit 2K forms a black image using black toner. The subscripts Y, M, C, and K of the reference numerals indicate yellow, magenta, cyan, and black, respectively. In the following description, the subscripts Y, M, C, and K of the reference numerals may be omitted when not particularly necessary. The four image forming units 2Y, 2M, 2C, and 2K have the same structure except for the color of the toner (developer).

[0012] The image forming unit 2 has a photoreceptor (image carrier) 11 as a rotating photosensitive drum. Around the photoreceptor 11, a charging device 12, an exposure device 13 that functions as an image writing unit, a developing device 14, a primary transfer device 35, and a drum cleaning device 15 are arranged. Below the photoreceptor 11, an endless intermediate transfer belt (intermediate transfer body) 31 is arranged.

[0013] The intermediate transfer belt 31 is stretched over a secondary transfer inner roller 32, a driving roller 33, a tension roller 34, and the primary transfer device 35. The intermediate transfer belt 31 is rotated in the direction indicated by the arrow B in FIG. 1 during image formation. The primary transfer device 35 is arranged to face the photoreceptor 11 through the intermediate transfer belt 31. The secondary transfer inner roller 32 is arranged to face the secondary transfer outer roller 41 through the intermediate transfer belt 31, and forms a secondary transfer nip portion between the intermediate transfer belt 31 and the secondary transfer outer roller 41. The secondary transfer inner roller 32 and the secondary transfer outer roller 41 constitute the secondary transfer unit 3. The belt cleaning device 36 is arranged to face the driving roller 33.

[0014] At the bottom of the image forming apparatus 1 are feed cassettes 61, 62, and 63 for storing sheets P. The feed cassettes 61, 62, and 63 can store sheets P of different sizes. A manual feed tray 64 is located on the side of the image forming apparatus 1. Sheets P are fed from the feed cassettes 61, 62, or 63 or the manual feed tray 64 by their respective pickup rollers 61a, 62a, 63a, or 64a.

[0015] Sheets P fed from feed cassettes 61, 62, or 63 by pickup rollers 61a, 62a, or 63a in the direction indicated by arrow A are transported to registration roller pair 110 by transport roller pair 130 and pre-registration roller pair 120. Sheets P fed from manual feed tray 64 by pickup roller 64a are transported to registration roller pair 110 by pre-registration roller pair 73. Pre-registration roller pairs 120 and 73 abut the leading edge of sheet P against the nip portion of the stationary registration roller pair 110 to correct the skew of sheet P. In this way, pre-registration roller pairs 120 and 73 loop sheet P to correct its skew. Registration roller pair 110 transports sheet P to secondary transfer section 3.

[0016] In the conveying direction of the sheet P, an air adsorption conveying means 42 and a fixing unit 4 are arranged downstream of the secondary transfer unit 3. The air adsorption conveying means 42 conveys the sheet P from the secondary transfer unit 3 to the fixing unit 4. The fixing unit 4 has a fixing roller pair 50 consisting of a fixing roller 51 and a pressure roller 52. The fixing roller 51 and the pressure roller 52 are arranged facing each other to form a fixing nip. Downstream of the fixing unit 4 in the conveying direction of the sheet P, a discharge tray 65 is provided on which the sheets P with the image formed are stacked.

[0017] In the case of double-sided printing or face-down discharge, the sheet P, which has been transported from the fixing unit 4 by the fixing roller pair 53, has its transport path switched to the reversal path 83 by the switching unit 81 and is transported to the sheet transport unit (sheet transport device) 5 by the reversal first roller pair 90. The sheet transport unit 5 has a reversal mechanism 200 (reversal unit) and a double-sided transport unit 220 (transport unit). The reversal mechanism 200 is provided with a reversal retraction unit 300.

[0018] (Image formation process) The image forming process of the image forming apparatus 1 will be described. Since the image forming processes in the four image forming units 2Y, 2M, 2C, and 2K are the same, the image forming process in image forming unit 2Y, which forms a yellow image, will be described. The charging device 12Y uniformly charges the surface of the rotating photoreceptor 11Y. The exposure device 13Y irradiates the surface of the uniformly charged photoreceptor 11Y with a light beam modulated according to the signal of image information of the yellow component, forming an electrostatic latent image on the surface of the photoreceptor 11. The developing device 14Y develops the electrostatic latent image with yellow toner, making it visible as a yellow toner image. The primary transfer device 35Y applies a predetermined pressure and electrostatic bias and transfers the yellow toner image on the photoreceptor 11Y onto the intermediate transfer belt 31 (primary transfer). Toner remaining on the surface of the photoreceptor 11Y after the primary transfer is removed by the drum cleaning device 15Y.

[0019] Similarly, the magenta toner image formed by the image forming unit 11M is accurately superimposed and transferred onto the yellow toner image on the intermediate transfer belt 31. Subsequently, the cyan toner image and the black toner image are sequentially superimposed and transferred onto the magenta toner image on the intermediate transfer belt 31. As a result, a full-color toner image is formed on the intermediate transfer belt 31. The rotation of the intermediate transfer belt 31 transports the toner image on the intermediate transfer belt 31 to the secondary transfer unit 3.

[0020] The sheet P is transported from the feed cassette 61, 62, or 63 or the manual feed tray 64 to the registration roller pair 110. The registration roller pair 110 transports the sheet P to the secondary transfer section 3 so that the leading edge of the sheet P aligns with the toner image on the intermediate transfer belt 31. The secondary transfer section 3 transfers the toner image on the intermediate transfer belt 31 onto the sheet P by applying a predetermined pressure and electrostatic bias to the secondary transfer nip formed between the secondary transfer inner roller 32 and the secondary transfer outer roller 41 (secondary transfer). After secondary transfer, any toner remaining on the surface of the intermediate transfer belt 31 is removed by the belt cleaning device 36. The sheet P with the transferred toner image is transported to the fixing section 4 by the air adsorption transport means 42. The fixing section 4 pressurizes and heats the sheet P with the fixing nip formed between the fixing roller 51 and the pressure roller 52 to fix the toner image to the sheet P. The sheet P with the fixed toner image is discharged from the fixing section 4 by the fixing roller pair 53. Subsequently, the sheet P is discharged to the outside of the image forming apparatus 1 via different paths according to the paper feeding mode.

[0021] When the paper feeding mode is single-sided face-down feeding, the transport path of the sheet P is switched to the inversion path 83 by the switching unit 81, and the sheet P with an image formed on one side is transported to the inversion path 83 by the inversion first roller pair 90. Subsequently, the transport direction of the sheet P is switched to the face-down discharge path 84 by the inversion second roller pair 92, which is capable of switching the transport direction. The sheet P passes through the face-down discharge path 84 and is discharged face-down to the discharge tray 65 by the discharge roller pair 93.

[0022] When the paper feeding mode is single-sided face-up feeding, the transport path of the sheet P is switched to the face-up discharge path 82 by the switching unit 81, and the sheet P with an image formed on one side is transported to the face-up discharge path 82. The sheet P is then discharged face-up into the discharge tray 65 by the transport roller pair 91 and the discharge roller pair 93.

[0023] When the paper feeding mode is double-sided printing, the transport path of the sheet P is switched to the inversion path 83 by the switching unit 81, and the sheet P, with an image formed on the first side (one side), is transported to the inversion path 83 by the inversion first roller pair 90. After that, the sheet P is transported to the inversion mechanism 200 by the inversion second roller pair 92. The inversion mechanism 200 performs switchback transport, which switches the sheet P back. The inversion mechanism 200 transports the sheet P in the transport direction CD (first direction) by the forward rotation of the inversion third roller pair 230, and temporarily moves the sheet P to the inversion retraction unit 300. After that, the inversion mechanism 200 transports the sheet P in the inversion transport direction RD (second direction), opposite to the transport direction CD, by the reverse rotation of the inversion third roller pair 230, and transports the sheet P to the double-sided transport unit 220.

[0024] The double-sided transport unit 220 is connected to the transport roller pair 130 upstream of the secondary transfer unit 3. The double-sided transport unit 220 transports the sheet P, whose first and second (other) sides have been reversed by the reversal mechanism 200, to the transport roller pair 130. In this way, the sheet P, which has been switched back by the reversal mechanism 200, is transported again toward the transport roller pair 130 by the reversal mechanism 200 and the double-sided transport unit 220. The sheet P passes through the secondary transfer unit 3 and the fixing unit 4, and an image is formed on the second side. The transport path of the sheet P, which has images formed on both sides, is switched to the face-up discharge path 82 by the switching unit 81. The sheet P is transported to the face-up discharge path 82 and then discharged to the discharge tray 65 by the discharge roller pair 93.

[0025] (Sheet transport section) Next, the sheet conveying section (sheet conveying device) 5 will be described using Figure 2. Figure 2 is a cross-sectional view of the sheet conveying section 5. The sheet conveying section 5 has a reversing mechanism 200 and a double-sided conveying section 220. First, the reversing mechanism 200 will be described. The reversing mechanism 200 includes a reversing conveying section 201 (first conveying path), a third reversing roller pair 230, a double-sided switching flap 231 (switching member), a reversing retraction section 300, and a conveying path 227 (second conveying path) branching from the reversing conveying section 201. The sheet P guided to the reversing path 83 by the switching section 81 is conveyed from the reversing path 83 to the reversing conveying section 201 by the second reversing roller pair 92.

[0026] The reversing third roller pair 230, acting as a reversing means, is located downstream (downward in the vertical direction) of the confluence point JP where the reversing transport unit 201 and the transport path 227 merge, with respect to the transport direction CD before the switchback in the reversing transport unit 201. The reversing third roller pair 230 is, for example, driven and connected to a motor capable of forward and reverse rotation, and is configured to switch the sheet transport direction between the transport direction CD before the switchback and the reversing transport direction RD opposite to the transport direction CD. The double-sided switching flap 231 is provided at the confluence point JP where the reversing transport unit 201 and the transport path 227 merge, and restricts the sheet P being transported in the reversing transport direction RD by the reversing third roller pair 230 from flowing back into the reversing path 83. The transport path 227 is in communication with the double-sided transport path 226 of the double-sided transport unit 220. The sheet P, which is conveyed in the inverted conveying direction RD by the inverted third roller pair 230, is guided by the double-sided switching flap 231 and conveyed through the conveying path 227 to the double-sided conveying path 226 of the double-sided conveying section 220.

[0027] The double-sided conveying section 220 is equipped with multiple pairs of double-sided conveying rollers 223, a first fan 221, a second fan 225, and a double-sided conveying guide member 224. The double-sided conveying guide member 224 defines a double-sided conveying path 226 for conveying the sheet P to the conveying roller pair 130. The multiple pairs of double-sided conveying rollers 223 convey the sheet P, which has been inverted by the inverting third roller pair 230 and conveyed to the double-sided conveying section 220, toward the conveying roller pair 130.

[0028] The reversal retraction section 300, which serves as a retraction section for the sheet P, is provided downstream of the reversal third roller pair 230 with respect to the transport direction CD before the switchback in the reversal transport section 201. The reversal retraction section 300 forms a retraction area RR for temporarily retracting a portion of the sheet P when the reversal third roller pair 230 switches back the sheet P. The reversal retraction section 300 is composed of a metal reversal retraction guide member 310 (guide member) arranged to surround the retraction area RR for retracting the sheet P transported by the reversal third roller pair 230. The reversal retraction guide member 310 has a curved curved portion 310a. The reversal retraction guide member 310 forms a retraction transport path 320 in which the leading edge of the sheet P is guided to trace the inner surface of the reversal retraction guide member 310 when the sheet P is transported to retract into the retraction area RR. The reversal retraction guide member 310 is arranged on only one side of the retraction transport path 320.

[0029] Next, the use of the reversal and retraction section 300 in the event of a jam will be explained. As described above, the reversal and retraction section 300 secures a retraction area RR (space) for temporarily retracting the sheet P when the sheet P is reversed by the reversal third roller pair 230. However, when a jam occurs in the image forming apparatus 1, any sheets that can be transported to the reversal and retraction section 300 from among the sheets remaining inside the image forming apparatus 1 are transported to the reversal and retraction section 300. This allows the retraction area RR (space) inside the reversal and retraction section 300 to be used as a space for discharging (purging) sheets remaining inside the image forming apparatus 1. Since the reversal and retraction guide member 310 is located only below the purged sheet, there is an open space above the purged sheet. Because a retraction area RR is provided above the reversal and retraction guide member 310 as a space accessible to the user, the user can easily process the jam when it occurs.

[0030] Because the sheet P heated by the fixing roller pair 50 is at a high temperature, water vapor may be released from the sheet P during transport, causing condensation on the cooled reversal and retraction guide member 310. When condensation occurs on the reversal and retraction guide member 310, the condensed water can cause the sheet P to stick to the reversal and retraction guide member 310, resulting in jamming. Even if jamming does not occur, the condensed water can leave marks on the sheet P, leading to image defects. As shown in Figure 2, the transport surface of the double-sided transport guide member 224 of the double-sided transport unit 220 is provided with multiple ventilation holes 222 (multiple holes) to allow air to pass through. The first fan 221 and the second fan 225 draw air from the double-sided transport unit 220, preventing water vapor from accumulating inside the double-sided transport unit 220 and preventing condensation from occurring on the double-sided transport guide member 224. This prevents jamming and image defects on the double-sided transport guide member 224.

[0031] To increase the printing speed of the image forming apparatus 1, it is necessary to increase the overall transport speed of the sheet P in the image forming apparatus 1. The transport speed of the sheet P during the switchback operation in the image forming apparatus 1 is also higher than that of conventional image forming apparatuses. On the other hand, increasing the transport speed of the sheet P during the switchback operation can cause the sheet P in the reversal and retraction section 300 to lift up. Figure 3 is a cross-sectional view of a conventional sheet transport section 105. As shown in Figure 3, the fan 232 provided in the conventional sheet transport section 105 blows air toward the double-sided transport guide member 224. As shown by the dashed line in Figure 3, the leading edge of the sheet P being transported to the reversal and retraction section 300 may lift up due to air resistance caused by the movement of the sheet P in the transport direction CD before the switchback. When the sheet P lifts up, it can be damaged or the transport position of the sheet P may become unstable.

[0032] Therefore, in this embodiment, the sheet P is prevented from floating up by a first fan 221 located in the double-sided conveying section 220 blowing air toward the reversal and retraction section 300. Figure 4 is an explanatory diagram showing the airflow of the first fan 221 that prevents the sheet P from floating up. Figure 5 is a diagram showing the double-sided conveying section 220 as seen in the direction indicated by the arrow V in Figure 4. The double-sided conveying section 220 is equipped with multiple fans. The first fan 221 is located near the double-sided switching flap 231 in the double-sided conveying section 220. The first fan 221 has three fans 221a, 221b, and 221c arranged in the width direction W perpendicular to the reversal conveying direction RD of the sheet P in the double-sided conveying section 220. In the reversal conveying direction RD, a second fan 225 is provided downstream of the first fan 221. The second fan 225 has three fans 225a, 225b, and 225c arranged in the width direction W. The driving and stopping of the first fan 221 and the second fan 225 are controlled by a control unit 6 provided in the image forming apparatus 1.

[0033] The first fan 221 blows air drawn from the double-sided conveying section 220 toward the reversal retraction guide member 310 of the reversal mechanism 200, as indicated by arrow F1. The second fan 225 blows air drawn from the double-sided conveying section 220 toward the reversal retraction section 300, as indicated by arrow F2. The air from the first fan 221 flows toward the reversal retraction section 300, as indicated by arrow F1, and flows along the reversal retraction guide member 310 in the same direction as the conveying direction CD of the sheet P before the switchback. The air from the second fan 225 flows toward the reversal retraction section 300, as indicated by arrow F2. The airflow from the first fan 221 and the second fan 225 reduces the air resistance experienced by the leading edge of the sheet P being conveyed in the conveying direction CD, thereby preventing the sheet P from lifting up.

[0034] Furthermore, if the sheet P being transported to the reversal and retraction section 300 is a long sheet, the air from the second fan 225 may cause the sheet P to flap. Therefore, if the sheet P is a long sheet, one, two, or three of the three fans 225a, 225b, and 225c of the second fan 225 may be stopped. The control unit 6 controls the driving and stopping of the three fans 225a, 225b, and 225c of the second fan 225 according to the size of the sheet P. For example, if the sheet P is an A3 size sheet, all three fans 225a, 225b, and 225c of the second fan 225 may be stopped, and air may be blown only from the first fan 221 in the same direction CD as the transport direction of the sheet P before the switchback. By controlling the driving and stopping of the three fans 225a, 225b, and 225c of the second fan 225 according to the size of the sheet P, flapping of the sheet P can be prevented. On the other hand, the three fans 221a, 221b, and 221c of the first fan 221 should provide airflow for all types of paper, regardless of the size of the sheet P, in order to prevent the sheet P from floating up within the reversal and retraction section 300.

[0035] The first fan 221 and the second fan 225 draw air from the double-sided conveying section 220, thereby preventing condensation from forming on the double-sided conveying guide member 224 of the double-sided conveying section 220. According to this embodiment, the first fan 221 and the second fan 225, which are used to prevent condensation in the double-sided conveying section 220, prevent the sheet P from floating up, thus increasing the conveying speed of the sheet P during switchback.

[0036] In this embodiment, the first fan 221 has three fans 221a, 221b, and 221c, and the second fan 225 has three fans 225a, 225b, and 225c. However, the number of fans in the first fan 221 and the second fan 225 is not limited to three; it may be one, two, four, or five or more. Alternatively, the second fan 225 may be omitted, and only the first fan 221 may be provided in the double-sided transport unit 220. Figure 6 is a cross-sectional view of a modified sheet transport unit 205. The sheet transport unit 205 is provided with only the first fan 221, without the second fan 225. In this case, since no additional fans are required, it is possible to improve the printing speed while suppressing cost increases and power consumption increases of the image forming apparatus 1. According to this embodiment, the sheet transport speed can be increased while suppressing sheet curling and flapping in the reversal and retraction unit 300. [Explanation of symbols]

[0037] 5. Sheet transport section 200... Reversing mechanism 220... Double-sided transport unit 221...First fan 300... Reversal and Evacuation Section 310... Reversal and retraction guide member CD transport direction RD... Reverse transport direction P... Seat

Claims

1. A sheet conveying device for conveying sheets, A reversing unit that, after transporting the sheet in a first direction, transports the sheet in a second direction opposite to the first direction, The system includes a conveying section that conveys the sheet, which has a conveying path through which the sheet conveyed in the second direction by the reversing section passes, and a conveying section that conveys the sheet, The aforementioned reversal unit is A reversal and retraction section where the sheet conveyed in the first direction is temporarily retracted, The reversing and retracting section includes a guide member configured to guide only one side of the sheet and not the other side of the sheet opposite to the aforementioned side, The conveying unit has a fan that blows air in the conveying path of the conveying unit toward the other side of the sheet that is not guided by the guide member, along the first direction. A sheet conveying device characterized by the following features.

2. The aforementioned reversal unit is A first transport path through which the sheet is transported in the first direction and the second direction, A second transport path through which the sheet is transported from the reversing section to the transport section in the second direction, The system includes a switching member provided at the junction of the first transport path and the second transport path, which switches the transport path of the sheet, The sheet conveying device according to claim 1, characterized in that the fan is located near the switching member.

3. The guide member is provided to guide the sheet on the lower side of one of the surfaces of the sheet, The sheet conveying device according to claim 1 or 2, characterized in that the air from the fan flows along the first direction from above the other surface of the sheet that is not guided by the guide member, as described above.

4. The sheet conveying device according to any one of claims 1 to 3, characterized in that a space accessible to the user is provided above the guide member in the reversal and retraction section.

5. The sheet conveying device according to any one of claims 1 to 4, characterized in that the fan includes a plurality of fans arranged in a line along the conveying surface of the conveying section in a direction perpendicular to the second direction in the conveying section.

6. The sheet conveying device according to claim 5, characterized in that the conveying surface of the conveying section is provided with a plurality of holes for passing air through.

7. The sheet conveying device according to any one of claims 1 to 6, further comprising a second fan provided in the conveying section downstream of the first fan in the second direction of the conveying section.

8. The conveying section further comprises a second fan provided downstream of the first fan in the second direction of the conveying section, The sheet conveying device according to claim 5, characterized in that the second fan includes a plurality of fans arranged in a line along the conveying surface of the conveying section in a direction perpendicular to the second direction in the conveying section.

9. The sheet conveying device according to claim 7 or 8, characterized in that the second fan is arranged to blow air in the conveying path in the conveying section toward the reversal and retraction section.

10. The system further comprises a control unit that controls the driving and stopping of the first fan and the second fan. The control unit drives the second fan when transporting the first sheet, and stops the second fan when transporting the second sheet, which is longer in length in the sheet transport direction than the first sheet. A sheet conveying device according to any one of claims 7 to 9, characterized by the following:

11. The control unit drives the first fan regardless of the size of the sheet. The sheet conveying device according to feature 10.

12. An image forming unit that forms an image on a sheet, A sheet conveying device according to any one of claims 1 to 11, An image forming apparatus having

13. The sheet transport device transports the sheet on which the image is formed on one side in the first direction by the reversing unit and temporarily stores it in the reversing and retracting unit, then transports the sheet in the second direction to the transport unit by the reversing unit, and then transports the sheet from the transport unit to the image forming unit. The image forming apparatus according to claim 12, characterized in that an image is formed on the other surface of the sheet as a result.

14. The image forming apparatus according to claim 13, characterized in that the reversing unit transports sheets remaining inside the image forming apparatus to the reversing and retracting unit when a sheet jams.

Images