JP2006189568A - Image forming apparatus and hollow carrying roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrying roll capable of suppressing the occurrence of a roll mark by crushing toner on a paper without reducing the carrying power, and to provide an image forming apparatus equipped with the transporting roll. <P>SOLUTION: The image forming apparatus is provided with a hollow ejection/reversion roll 100 and a pinch roll 102 arranged across a nip on the downstream side of the fixing roll 104 in the paper carrying direction, the roll 100 is provided with a rotating shaft 108 and a paper feed part 106 arranged around the rotating shaft 108, and formed of elastic material, and the hollow part is constituted of the rotating shaft 108 and the paper feed part 106. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hollow conveyance roll for conveying a sheet from an image forming unit of an image forming apparatus such as a printer, a copier, or a facsimile, and an image forming apparatus having the hollow conveying roll.

Usually, in an image forming apparatus such as a printer, a copying machine, or a facsimile, a fixing roll composed of a pressure roll and a heating roll is used to fix a developer image on a paper on which an image is formed in an image forming unit. Then, in order to discharge the paper to the paper discharge tray, the paper is transported to the paper discharge roll on the paper transport path in the image forming apparatus main body, and the paper is discharged to the paper discharge tray by the paper discharge roll.
The unfixed toner image formed on the paper at the transfer unit is heated and pressurized at the fixing nip portion of the fixing roll and fixed on the paper. However, the fixed image and the paper are somewhat hot even after leaving the fixing nip. When a sheet on which fixing toner is placed in a high temperature state enters the paper discharge roll, the toner is crushed. In particular, in the case of a color image, toner of three colors is formed so as to overlap, so the height of the toner on the paper is also high, and a roll mark appears when the toner is crushed. For this reason, until now, after toner fixing, it has been necessary to take a transport distance that lowers the toner temperature to the paper discharge roll. Further, in order to prevent the toner from being crushed, a low nip pressure on the conveying roll after fixing has been demanded.
On the other hand, the conveyance roll which formed the core material (base material) with a resin material etc. as a conveyance roll until now, and covered this with the concave-shaped rubber roll is disclosed (patent documents 1-1). (See Patent Document 3).

Japanese Patent No. 2887041 Japanese Patent No. 3396024 JP-A-11-217134

  However, since the hollow conveyance roll having the above-mentioned configuration has a cylindrical shape with a concave cross section, it has to be manufactured one by one with a mold and has a problem that the production cost increases. In addition, a dedicated core shape is also required, leading to increased costs. Also, the use of the above-mentioned hollow conveyance roll is intended to prevent the paper from being poor and the surroundings from being soiled by paper dust, and the above-mentioned problems after toner fixing have not been considered.

  A first object of the present invention is to improve a transport roll after fixing. Moreover, the 2nd objective of this invention is to provide the hollow conveyance roll which can be manufactured cheaply.

  In order to solve the above-mentioned problems, the present invention is characterized by having two transport rolls arranged with a nip on the downstream side of the fixing roll in the paper transport direction, and at least one of the transport rolls is rotating. An image having a shaft and a paper feed portion formed of an elastic material provided around the rotation shaft, wherein a hollow portion is formed by the rotation shaft and the paper feed portion. In the forming device. As a result, even when the paper passes through the fixing roll and the toner temperature on the paper is not lowered to the normal temperature, the nip width can be increased even if the nip pressure is lower than the normal solid roll. Can be maintained. Therefore, it is possible to suppress roll marks generated by crushing the toner on the paper without reducing the conveyance force. In addition, jamming can be avoided without changing the glossy state of the toner surface due to paper slip or the like, and toner adhesion to the pinch roll can also be suppressed. In addition, after fixing, it has been necessary to set a transport distance that lowers the toner temperature to the paper discharge roll. However, since the transport path can be made shorter than before, the M / C size is reduced and the throughput is shortened. Productivity can be improved.

  Preferably, the image forming apparatus is configured such that the transport roll is a paper discharge roll. As a result, since at least one of the paper discharge rolls is hollow, the nip width can be increased and the conveying force can be maintained even if the nip pressure is reduced below that of a normal solid roll. Paper can be discharged without deteriorating. In addition, even if a corrugation shape is added, the pressing force to the roll when transporting cardboard or the like is reduced, so that the roll mark can be reduced more remarkably.

  Preferably, the image forming apparatus is configured such that the transport roll is a reverse transport roll to a duplex unit. As a result, the nip width can be increased and the conveying force can be maintained even when the nip pressure is lower than that of a normal solid roll, so that paper slip and bending at the time of reversal can be suppressed without deteriorating image alignment on the second side. It can be reversed and conveyed.

  Preferably, an image forming apparatus in which the transport roll is disposed in a fixing unit. Accordingly, when a problem occurs in the transport roll, it is only necessary to repair or replace the fixing unit, and it is not necessary to repair or replace the entire image forming apparatus main body, and the repair cost and the replacement cost can be kept low.

  Preferably, the image forming apparatus includes a paper storage unit and a paper discharge unit at an upper portion of the paper storage unit, and includes a paper conveyance path that connects the paper storage unit and the paper discharge unit laterally. . Thereby, the whole image apparatus can be made compact, and productivity can be improved.

  Preferably, the image forming apparatus is configured such that the transport roll is disposed on the image forming surface side. As a result, the sheet curled on the sheet heating side is corrected on the side opposite to the image forming surface at the nip portion of the hollow conveyance roll, and a print with a small curl amount is obtained.

  The second feature of the present invention is that it has a rotation shaft and a paper feed portion, the rotation shaft has a convex support portion for supporting the paper feed portion, and the paper feed portion is made of an elastic material. The hollow transport roll has a cylindrical shape and has a hollow portion formed by the rotating shaft and the paper feeding portion. As a result, since the paper feeding section is cylindrical, the structure of the paper feeding section and the rotating shaft is not complicated, and the paper feeding section can be produced more easily than the concave hollow structure that is manually removed from the mold one by one. Production costs can be significantly reduced.

  The third feature of the present invention is that it has a rotary shaft and a paper feed portion, and the paper feed portion has an endless ring structure having a hollow substantially round cross section or a substantially square cross section, and is fitted into the rotary shaft. It is in the hollow conveyance roll characterized by having. As a result, since the paper feeding section has a hollow endless ring structure, the structure of the paper feeding section and the rotating shaft is not complicated, and compared with a concave hollow structure in which the paper feeding section is manually removed from the mold one by one. It can be produced easily and the production cost can be significantly reduced.

  Preferably, the paper feeding unit is a hollow conveyance roll press-fitted into the rotating shaft. Thereby, even if it does not provide the support part for supporting a paper feeding part in a rotating shaft, a paper feeding part can be fixed to a rotating shaft reliably and easily, and production cost can be restrained low.

  Preferably, the rotating shaft is a hollow conveyance roll made of metal or resin. Preferably, the paper feeding unit is a hollow conveyance roll formed of any one of silicon rubber, natural rubber, and EPDM. Thereby, since the material of a conveyance roll can use the same material as a normal solid roll, durability, such as friction abrasion, does not deteriorate compared with foaming rolls, such as sponge.

  The present invention includes an image forming apparatus having the above-described hollow conveyance roll.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of an image forming apparatus 10 according to an embodiment of the present invention.
The image forming apparatus 10 includes an image forming apparatus main body 12, and an opening / closing door 16 that is rotatable about a rotation fulcrum 14 is provided on the upper portion of the image forming apparatus main body 12.

  For example, a one-stage recording medium supply unit 18 is disposed in the lower part of the image forming apparatus main body 12. The recording medium supply unit 18 includes a recording medium supply unit main body 20 and a recording medium supply cassette 22 in which the recording medium is stored. A feed roll 24 for supplying a recording medium from the recording medium supply cassette 22 and a retard roll 26 for scooping the supplied recording medium one by one are arranged in the upper part near the rear end of the recording medium supply cassette 22.

  The conveyance path 28 is a recording medium path from the feed roll 24 to the discharge port 30 formed from the back side of the image forming apparatus main body 12 toward the inside of the image forming apparatus main body 12. The conveyance path 28 is formed substantially vertically from the recording medium supply cassette 22 to a fixing device 90 described later. A secondary transfer roll 81 and a secondary transfer backup roll 72, which will be described later, are disposed on the upstream side of the fixing device 90 in the conveyance path 28, and a resist roll 32 is disposed on the upstream side of the secondary transfer roll 81 and the secondary transfer backup roll 72. Is provided. In addition, a discharge reversing roll 34 to be described later is disposed in the fixing device 90 in the vicinity of the discharge port 30 of the conveyance path 28. The discharge reversing roll 34 is rotated forward and reverse by a drive motor (not shown).

  Therefore, the recording medium sent out from the recording medium supply cassette 22 of the recording medium supply unit 18 by the feed roll 24 is rolled by the retard roll 26 and only the uppermost recording medium is guided to the transport path 28 and temporarily registered by the registration roll 32. The developer image is transferred between a secondary transfer roll 81 and a secondary transfer backup roll 72, which will be described later, at a timing, and the transferred developer image is fixed by the fixing device 90 and discharged. The paper is discharged from the discharge port 30 to the discharge tray 36 provided on the upper part of the open / close door 16 by the reverse roll 34. In the case of duplex printing, the recording medium guided to the discharge reversing roll 34 is conveyed toward the registration roll 32 via a reversing path 95 described later when the discharge reversing roll 34 is reversed, and is again subjected to secondary transfer. The toner image is transferred between the roll 81 and the secondary transfer backup roll 72, fixed by the fixing device 90, and discharged by the normal rotation of the discharge reverse roll 34. The discharge tray 36 has a low discharge port 30 and is inclined so as to gradually become higher in the front direction (left direction in FIG. 1).

  In the image forming apparatus main body 12, for example, a rotary developing device 38 is disposed at a substantially central portion on the front side. The rotary developing device 38 includes developing units 42a to 42d that form developer images of four colors of yellow, yellow, magenta, cyan, and black in the developing unit main body 40, respectively. Rotate counterclockwise (counterclockwise in FIG. 1) about the rotary developing device center 44. Each of the developing units 42a to 42d has developing rolls 46a to 46d, and is pressed in the normal direction of the developing unit main body 40 by elastic bodies 48a to 48d such as coil springs. That is, the developing rolls 46a to 46d of the developing units 42a to 42d are arranged on the outer periphery of the developing unit main body 40 at intervals of 90 ° with the rotary developing device center 44 as the center, and come into contact with an image carrier 50 described later. The electrostatic latent image on the image carrier 50 is visualized with each color developer.

  The image bearing member 50 is disposed in contact with the rotary developing device 38. The image carrier 50 is made of, for example, a tubular aluminum pipe, and a photoconductive layer is formed on the surface thereof. By this photoconductive layer, the image carrier 50 carries an electrostatic latent image formed by a light beam such as a laser beam and a developer image visualized by a developer.

Below the image carrier 50, a charging device 52 made of, for example, a charging roll for uniformly charging the image carrier 50 is provided. Further, an image carrier cleaner 54 is in contact with the image carrier 50 on the upstream side of the charging device 52 in the rotation direction of the image carrier 50. The image carrier cleaner 54 includes, for example, a cleaning blade 56 that scrapes off the developer remaining on the image carrier 50 after primary transfer, and a developer recovery bottle 58 that recovers the developer scraped off by the cleaning blade 56. The
Note that, for example, a rib or the like is formed on the back side (right side in FIG. 1) of the developer recovery bottle 58 and is curved to form a part of the conveyance path 28 so that the recording medium is smoothly conveyed. .

  Below the rotary developing device 38, an exposure device 60 for writing a latent image on the image carrier 50 charged by the charging device 52 by a light beam such as a laser beam is disposed. Further, an intermediate transfer device 62 is provided above the rotary developing device 38. The intermediate transfer device 62 first transfers the developer image visualized by the rotary developing device 38 at the primary transfer position and conveys it to the secondary transfer position.

The intermediate transfer device 62 includes, for example, an intermediate transfer member 64 such as an intermediate transfer belt, a primary transfer roll 66, a wrap-in roll 68, a wrap-out roll 70, a secondary transfer backup roll 72, a scraper backup roll 74, and a brush backup roll 76. Is done. The intermediate transfer body 64 has elasticity, for example, and is stretched substantially flat so as to have a long side and a short side above the rotary developing device 38. The long side on the upper surface side of the intermediate transfer body 64 is stretched so as to be substantially parallel to, for example, the discharge unit 36 provided on the upper portion of the image forming apparatus main body 12. The intermediate transfer member 64 includes a wrap-in roll 68 disposed upstream of the primary transfer roll 66 below the long side of the intermediate transfer member 64, and a wrap-out roll 70 disposed downstream of the primary transfer roll 66. A primary transfer portion (having an image carrier wrap region, is wound around the image carrier 50 by a predetermined range, and is driven by the rotation of the image carrier 50 in this manner. The intermediate transfer body 64 is primarily transferred by the primary transfer roll 66 with the developer image on the image carrier 50 superimposed in the order of, for example, yellow, magenta, cyan, and black, and the primary transferred developer image is subjected to secondary transfer. It is conveyed toward the roll 81.
Note that the wrap-in roll 68 and the wrap-out roll 70 are separated from the image carrier 50.

Further, a flat surface portion (short side) is formed on the back side (right side surface in FIG. 1) of the intermediate transfer body 64 by a wrap-out roll 70 and a secondary transfer backup roll 72, and this flat surface portion is subjected to secondary transfer. It faces the conveyance path 28 as a part.
In the secondary transfer portion, the wrap-out roll 70 is arranged so that the intermediate transfer body 64 and the conveyance path 28 are at an angle of 12 °, for example.

  The scraper backup roll 74 assists the scraper 84 described later to scrape off the developer remaining on the intermediate transfer body 64 after the secondary transfer, and the brush backup roll 76 develops remaining on the intermediate transfer body 64 after the secondary transfer. A brush roll 86 described later assists in scraping off the agent.

  Above the long side of the intermediate transfer member 64, a sensor 79 such as a reflective photosensor is provided by being fixed to the back surface (inside) of the open / close door 16. The sensor 79 reads the developer patch formed on the intermediate transfer body 64, detects the position of the intermediate transfer body 64 in the rotation direction, and detects the developer density.

  A secondary transfer roll 81 faces the secondary transfer backup roll 72 of the intermediate transfer device 62 with the conveyance path 28 interposed therebetween. That is, the secondary transfer position in the secondary transfer portion is between the secondary transfer roll 81 and the secondary transfer backup roll 72, and the secondary transfer roll 81 is intermediate with the assistance of the secondary transfer backup roll 72. The developer image primarily transferred to the transfer body 64 is secondarily transferred to the recording medium at the secondary transfer position. Here, the secondary transfer roll 81 is separated from the intermediate transfer member 64 while the intermediate transfer member 64 rotates three times, that is, while the developer images of three colors of yellow, magenta, and cyan are conveyed. When the developer image is transferred, it is brought into contact with the intermediate transfer member 64.

  In addition, a predetermined potential difference is generated between the secondary transfer roll 81 and the secondary transfer backup roll 72. For example, when the secondary transfer roll 81 is set to a high voltage, the secondary transfer backup is performed. The roll 72 is connected to a ground (GND) or the like. That is, the intermediate transfer body 64 is set to a predetermined potential between the secondary transfer roll 81 and the secondary transfer backup roll 72.

  An intermediate transfer member cleaner 83 is provided in contact with the end of the intermediate transfer member 64 opposite to the image carrier. The intermediate transfer body cleaner 83 is, for example, a scraper 84 that scrapes and cleans the developer remaining on the intermediate transfer body 64 after the secondary transfer, a brush roll 86 that scrapes off the developer remaining after the cleaning by the scraper 84, and a scraper 84. And a developer recovery bottle 88 that recovers the developer scraped off by the brush roll 86. The scraper 84 is made of, for example, a stainless steel thin plate, and is applied with a voltage having a polarity opposite to that of the developer. The brush roll 86 is made of, for example, an acrylic brush that has been subjected to a conductive treatment. Further, while the intermediate transfer body 64 conveys the developer image, the scraper 84 and the brush roll 86 are separated from the intermediate transfer body 64, and they are integrated with the intermediate transfer body 64 at a predetermined timing. It is supposed to touch.

  A fixing device 90 is disposed above the secondary transfer position. The fixing device 90 includes a heating roll 92 and a pressure roll 94, and fixes the developer image secondarily transferred to the recording medium by the secondary transfer roll 81 and the secondary transfer backup roll 72 to the recording medium for fixing. It is conveyed toward a discharge reversing roll (conveying roll) 34 provided in the apparatus 90. Further, a recording medium passage port (not shown) is provided at the upper part of the fixing device 90. When double-sided printing is set, the recording medium is guided to the reversing path 95 by reversing the discharge reversing roll 34, It is conveyed toward the resist roll 32 by the conveyance rolls 96a to 96c.

  The image forming unit 98 is obtained by integrating the intermediate transfer device 62, the image carrier 50, the charging device 52, the image carrier cleaner 54, and the intermediate transfer member cleaner 83. The image forming unit 98 is disposed immediately below the discharge portion 36 of the opening / closing door 16 and is detachable from the image forming apparatus main body 12, and is attached / detached by opening the opening / closing door 16.

Next, the discharge reversing roll 34 and its surroundings according to the first embodiment of the present invention will be described.
FIG. 2 is a sectional view of the discharge reversing roll 34 according to the first embodiment of the present invention.
As shown in FIG. 2, the discharge reversing roll 34 is configured to sandwich a nip between a hollow discharge reversing roll (hollow transport roll) 100 and a lower pinch roll 102, and includes a heating roll 92 and a pressure roll 94. The fixing roll 104 is disposed on the downstream side in the sheet conveyance direction. In the image forming apparatus 10 of this embodiment, the paper transport path 28 has a so-called C path layout in which the recording medium supply unit 18 and the paper discharge roll 34 are connected laterally.

FIG. 3 shows an outer shape and a sectional view of the discharge reversing roll 34.
The discharge reversing roll 34 has an outer shape as shown in the side view of FIG. 3A. A hollow discharge roll (hollow transport roll) 100 is disposed on the upper side, and a pinch roll is disposed on the lower side. As shown in the cross-sectional view of FIG. 3B, the hollow discharge reversing roll 100 has a rotating shaft 108 and a paper feeding unit 106. The rotating shaft 108 is made of, for example, metal, and has support portions 110A and 110B that protrude in the radial direction at two locations in the axial direction and support the paper feeding portion 106. On the other hand, the paper feeding unit 106 is formed of rubber, for example, and has a cylindrical shape. In this embodiment, a position fixing portion 114 having a diameter W2 smaller than the diameter W1 of the outer portion 112 is provided in the inner portions of the support portions 110A and 110B so that the sheet feeding portion 106 is fixed in position. A hollow portion 116 is formed by the sheet feeding portion 106 and the rotating shaft 108.

  In this embodiment, as shown in FIG. 3C, the pinch roll 102 that contacts the hollow discharge reversing roll 100 has a width W5 that is narrower than the width W4 of the paper feed section 106 of the hollow discharge reverse roll 100, for example. ing. Therefore, when the pinch roll 102 presses the hollow discharge reversing roll 100, the paper feeding portion 106 of the hollow discharge reversing roll 100 has a concave shape at the center, and corrugation for maintaining the accommodation property can be added to the paper. .

  Therefore, by doing the above, even when the paper passes through the fixing roll 104 and the toner temperature on the paper is not lowered to the normal temperature, the nip pressure is lowered from the normal solid roll having no hollow. Since the nip width, that is, L1 in FIG. 2 can be increased, the conveying force can be maintained. Therefore, it is possible to suppress the roll mark generated by crushing the toner on the paper without reducing the conveying force. Further, since the conveyance force can be maintained even when the nip pressure is lowered, it is possible to discharge from thin paper to thick paper without deteriorating the capacity. Further, jamming can be avoided without changing the shine state of the toner surface due to paper slip or the like, and adhesion of toner to the pinch roll 102 can also be suppressed. Further, it has been necessary to take a transport distance that lowers the toner temperature to the paper discharge roll after fixing so far, but since the transport path can be made shorter than that, the M / C size can be reduced, and Throughput can be shortened and productivity can be improved.

  Further, the sheet feeding portion 106 of the hollow discharge reversing roll 100 is cylindrical, and can be manufactured, for example, by simply cutting a pipe-like rubber into an appropriate length. Compared to a concave hollow structure that is manually removed from the mold one by one, it can be produced easily, and the production cost can be significantly reduced.

  As shown in FIG. 4, the paper feeding unit 106 is mounted on the rotating shaft 108 by elastically deforming the paper feeding unit 106 and inserting one of the support portions 110A and 110B of the rotating shaft 108 inside the paper feeding unit 106. To do. Then, the sheet feeding unit 106 is further moved and fixed to the position fixing unit 114. At this time, the inner diameter W3 (see FIG. 3) of the sheet feeding portion 106 is smaller than the diameter W1 of the outer portion 112 of the support portions 110A and 110B of the rotating shaft 108, and is substantially the same as the diameter W2 of the position fixing portion 112. In this way, the paper feeding unit 106 can be easily attached to the rotating shaft 108.

  As shown in FIG. 1, the discharge reversing roll 34 of this embodiment serves as both a discharge roll and a reversing roll for duplex printing. When the sheet is discharged from the discharge port 30, the discharge reversing roll 34 rotates forward to convey the sheet to the discharge port 30, and is reversed when performing duplex printing, and conveys the sheet to the reversing path 95. This makes it possible to discharge from thin paper to thick paper without deteriorating the capacity, and even if a corrugation shape is added, the pressing force on the roll when transporting thick paper etc. is reduced, so it becomes more prominent Roll marks can be reduced. Further, it is possible to carry out reverse conveyance without suppressing paper slip and bending at the time of reversal and without deteriorating image alignment on the second surface.

  Note that the discharge reversing roll 34 of this embodiment is disposed in a fixing device 90 as a fixing unit. If a problem occurs in the discharge reversing roll 34 as a result, the fixing device 90 is removed from the image forming apparatus 10 and repaired or replaced, and it is not necessary to repair or replace the entire image forming apparatus 10. Can be kept low. In the discharge reversing roll 34 of this embodiment, the hollow discharge reversing roll 100 is disposed on the upper side and the pinch roll 102 is disposed on the lower side, but the vertical positions of the hollow discharge reversing roll 100 and the pinch roll 102 are changed. You may arrange. It is also possible to dispose the hollow discharge reversing roll 100 on the image forming surface side. In this case, the paper curled on the paper heating side can be corrected on the anti-image forming surface side, and a print with a small curl amount can be obtained. be able to.

Next, the discharge reversing roll 34 according to the second embodiment of the present invention will be described.
FIG. 5 shows a cross-sectional view of the hollow discharge reverse roll 100 of the discharge reverse roll 34 according to the second embodiment of the present invention.
The hollow discharge reversing roll 100 of this embodiment includes, for example, a rotation shaft 108 made of metal, and a sheet feeding unit 106 having a hollow endless ring structure formed of rubber attached to the rotation shaft and having a circular cross section. And have. In this embodiment, the rotating shaft 108 is formed with support portions 110A and 110B that protrude in the radial direction at two locations in the axial direction and support the paper feeding portion 106.

  On the other hand, the pinch roll 102 of the discharge reverse roll 34 can be the same as that of the discharge reverse roll 34 of the first embodiment shown in FIG. Accordingly, the pinch roll 102 comes into contact with the paper feeding portion 106 of the hollow discharge reverse roll 100 to deform the hollow discharge reverse roll 100 to form a nip having a wide nip width, and convey the paper.

  As a result, even when the sheet passes through the fixing roll 104 and the toner temperature on the sheet is not lowered to the normal temperature, the nip width is increased even if the nip pressure is lowered from that of a solid roll having no hollow. Therefore, the conveyance force can be maintained. Therefore, it is possible to suppress roll marks generated by crushing the toner on the paper without reducing the conveyance force. Further, jamming can be avoided without changing the shine state of the toner surface due to paper slip or the like, and toner adhesion to the pinch roll 102 can also be suppressed. In addition, after fixing, it has been necessary to take a transport distance that lowers the toner temperature to the paper discharge roll. However, since the transport path can be made shorter than that, the M / C size can be reduced, and Throughput can be shortened and productivity can be improved.

  Furthermore, in this embodiment, the paper feed unit 106 has a hollow end wrestling structure, and the structure of the paper feed unit 106 is not complicated, and a concave hollow structure in which the paper feed unit 106 is manually removed from the mold one by one. Compared to the above, production can be performed easily, and the production cost can be significantly reduced.

  In this embodiment, when the paper feeding unit 106 is mounted on the rotary shaft 108, the paper feeding unit 106 is elastically deformed to expand the inner diameter W7 of the paper feeding unit 106 more than the diameter W6 of the supporting units 110A and 110B. Attached between 110A and 110B. In this way, the paper feeding unit 106 can be easily attached to the rotating shaft 108.

Next, the discharge reversing roll 34 according to the third embodiment of the present invention will be described.
FIG. 6 shows a cross-sectional view of the hollow discharge reverse roll 100 of the discharge reverse roll 34 according to the third embodiment of the present invention.
The hollow discharge reversing roll 100 of this embodiment includes, for example, a rotating shaft 108 and a sheet feeding portion 106 that is formed of rubber and has a hollow endless ring structure that has a substantially square cross section and is attached to the rotating shaft 108. Have. The “substantially square shape” in this embodiment represents a shape having rounded corners in the cross section and other portions being linear. Here, in this embodiment, the rotating shaft 108 is made of metal, and the sheet feeding portion 106 is press-fitted into the rotating shaft 108 and fixed. As a result, the paper feed unit 106 can be reliably and easily fixed to the rotary shaft 108 without providing a support unit for supporting the paper feed unit 106 on the rotary shaft 108. Of course, a support portion may be further provided on the rotary shaft 108, and the position of the sheet feeding portion 106 can be more reliably fixed by providing the support portion.

  On the other hand, the pinch roll 102 of the discharge reverse roll 34 can be the same as that of the discharge reverse roll 34 of the first embodiment shown in FIG. Accordingly, the pinch roll 102 comes into contact with the paper feeding portion 106 of the hollow discharge reversing roll 100, and the hollow discharge reversing roll 100 is deformed to form a nip having a wide nip width and convey the paper.

  As a result, even when the sheet passes through the fixing roll 104 and the toner temperature on the sheet is not lowered to the normal temperature, the nip width is increased even if the nip pressure is lowered from that of a solid roll having no hollow. Therefore, the conveyance force can be maintained. Therefore, it is possible to suppress the roll mark generated by crushing the toner on the paper without reducing the conveying force. Further, jamming can be avoided without changing the shine state of the toner surface due to paper slip or the like, and toner adhesion to the pinch roll 102 can also be suppressed. In addition, after fixing, it has been necessary to take a transport distance that lowers the toner temperature to the paper discharge roll. However, since the transport path can be made shorter than that, the M / C size can be reduced, and Throughput can be shortened and productivity can be improved.

  Further, the paper feed unit 106 has a hollow endless ring structure, and the structure of the paper feed unit 106 is not complicated, and the paper feed unit 106 is easily produced as compared with the concave hollow structure in which the paper feed unit 106 is manually removed from the mold one by one. And production costs can be significantly reduced.

  As described above, the present invention can be used for a transport roll that can suppress a roll mark generated by crushing toner on a sheet without reducing a transport force and an image forming apparatus having the transport roll.

1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which shows the outline | summary of the discharge reverse roll vicinity which concerns on the 1st Embodiment of this invention. It is the side view and sectional drawing which show the outline | summary of the discharge reverse roll which concerns on the 1st Embodiment of this invention. It is a front perspective view which shows the outline | summary of the assembly method of the discharge reverse roll which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the outline | summary of the discharge reverse roll which concerns on other embodiment of this invention. It is sectional drawing which shows the outline | summary of the discharge reverse roll which concerns on further another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 34 Discharge reversing roll 90 Fixing apparatus 92 Heating roll 94 Pressure roll 100 Hollow discharge reversing roll 102 Pinch roll 104 Fixing roll 106 Paper feed part 108 Rotating shaft 110A, 110B Support part 112 Outer part 114 Position fixing part 116 Hollow part

Claims (12)

  There are two conveying rolls arranged on the downstream side of the fixing roll in the sheet conveying direction with a nip interposed therebetween, and at least one of the conveying rolls is a rotating shaft and an elastic material provided around the rotating shaft. An image forming apparatus comprising: a formed sheet feeding portion, wherein a hollow portion is formed by the rotation shaft and the sheet feeding portion.   The image forming apparatus according to claim 1, wherein the transport roll is a paper discharge roll.   The image forming apparatus according to claim 1, wherein the transport roll is a reverse transport roll to a duplex unit.   The image forming apparatus according to claim 1, wherein the conveyance roll is disposed in a fixing unit.   2. A sheet storage unit, and a sheet discharge unit at an upper portion of the sheet storage unit, and a sheet conveyance path that connects the sheet storage unit and the sheet discharge unit laterally. 5. The image forming apparatus according to any one of 4 to 4.   The image forming apparatus according to claim 1, wherein the transport roll is disposed on an image forming surface side.   A rotation shaft and a paper feed portion, the rotation shaft has a convex support portion for supporting the paper feed portion, the paper feed portion is formed of an elastic material and has a cylindrical shape, and the rotation shaft The hollow conveyance roll characterized by forming a hollow part with the said paper feeding part.   A hollow transport roll having a rotary shaft and a paper feed portion, wherein the paper feed portion has an endless ring structure having a hollow substantially round cross section or a substantially square cross section, and is fitted into the rotary shaft.   The hollow conveyance roll according to claim 8, wherein the paper feeding unit is press-fitted into the rotating shaft.   The hollow conveyance roll according to claim 7, wherein the rotation shaft is made of metal or resin.   The hollow conveyance roll according to any one of claims 7 to 10, wherein the paper feeding section is formed of any one of silicon rubber, natural rubber, and EPDM.   An image forming apparatus comprising the hollow conveyance roll according to claim 7.

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