JP2840244B2 - Sheet material transport device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sheet conveying apparatus. More specifically, for example, in an image forming apparatus such as an electronic copier, a laser beam printer (LBP), or an electrostatic recording device, the image is introduced between a pair of image-fixing rollers that are driven to rotate and exits through the pair of rollers. In order to relay the incoming image-fixed sheet material (transfer paper, recording paper, etc.) and feed it to a discharge tray or the like, it is arranged next to the image fixing roller pair (downstream of the image fixing roller pair in the sheet material conveyance direction). The sheet conveying apparatus is suitable as a sheet conveying means to be provided. 2. Description of the Related Art For the sake of convenience, a description will be given of an example of a sheet conveying means disposed next to an image fixing roller pair in an image forming apparatus as described above. FIG. 11 shows the general means configuration. That is, 101 and 102 are heat fixing roller pairs or pressure fixing roller pairs as image fixing roller pairs, 104 and 105 are sheet discharge roller pairs as sheet material splicing conveyance means disposed next to the image fixing roller pair, Reference numeral 103 denotes a sheet guide plate (sheet path) disposed between the image fixing roller pairs 101 and 102 and the discharge roller pairs 104 and 105, and reference numeral 106 denotes a discharge tray. In the image fixing roller pair 101/102, in this case, the upper roller 101 is a fixing roller, the lower roller 102 is a backup roller, and the two rollers are in contact with each other with a predetermined pressing force, and It is rotationally driven at a predetermined peripheral speed in the indicated direction. A sheet material P on which an image (unfixed image) is formed on the upper surface side by an image forming unit (not shown) is introduced between the image fixing roller pairs 101 and 102 and passes therethrough. Fixing or pressure fixing is performed. The sheet material P that has exited between the image fixing roller pairs 101 and 102 is introduced between the sheet discharge roller pairs 104 and 105 through the sheet material guide plate 103, and is conveyed and discharged to the sheet discharge tray 106. In the pair of paper discharge rollers 104 and 105, the lower roller 104 is a hard rubber drive roller and is driven to rotate at a predetermined peripheral speed in the direction indicated by the arrow. The upper roller 105 is a driven roller made of resin, and is constantly urged against the lower drive roller 104 by a spring member 107 such as a leaf spring. When the sheet material is not interposed between the rollers 104, the upper resin roller 105 is driven to rotate by the rotation of the drive roller 104 due to the direct contact frictional force with the lower drive roller 104.
When the sheet material is introduced between the rollers 104, 105, the sheet material is pressed by the lower drive roller 104 by the upper resin roller 105, and receives a conveying force corresponding to the rotational peripheral speed of the drive roller 104. Transported. The upper resin roller rotates following the conveyance of the sheet material by the contact frictional force with the upper surface of the conveyance sheet material. In this way, the sheet material having undergone image fixing from the pair of image fixing rollers 101 and 102 is relayed and conveyed by the pair of discharge rollers 104 and 105 and discharged to the discharge tray 106. In the above description, the sheet material P that exits the image fixing roller pairs 101 and 102 and is conveyed by the discharge roller pairs 104 and 105 loosens between the image fixing roller pairs 101 and 102 and the discharge roller pairs 104 and 105. If slack occurs, the sheet material output to the paper output tray 106 is likely to wrinkle.To prevent this, the rotational peripheral speed of the paper output roller pair 104/105 is set to be lower than that of the image fixing roller pair 101/102. Is also set to a predetermined speed so that tension is applied to the sheet material portion between the image fixing roller pair 101/102 and the paper discharge roller pair 104/105. [Problems to be Solved by the Invention] However, the paper discharge roller pair configured as described above, that is, the sheet material conveying device has the following problems. (1) The rotational peripheral speed of the pair of paper discharge rollers 104 and 105 is set to 10 to apply tension to the sheet material for the aforementioned purpose.
Since the speed is set faster than that of 1 ・ 102, the conveyance speed of the sheet material may be slightly changed before and after the leading edge of the sheet material reaches the discharge roller pair 104 ・ 105 in the image forming process. In some cases, the formed image may have an adverse effect such as blurring. (2) Depending on the thickness of the sheet material used, a pair of paper discharge rollers
Since the sheet material feeding force of 104 and 105 is determined, when a thick and strong sheet material is used, an excessively strong tension is applied, and abrasion damage due to roller slip, a guide mark, and the like are easily caused on the sheet material surface. (3) Since the pair of rollers 104 and 105 rotate while contacting each other even when the sheet material is not introduced between them, the wear of both rollers progresses with time, and the diameter of the roller is reduced due to the wear, so that the rotating circumference is reduced. The speed gradually decreases, and eventually becomes equal to or less than the rotational peripheral speed of the pair of image fixing rollers 101 and 102, and between the pair of image fixing rollers 101 and 102 and the pair of discharge rollers 104 and 105. The effect of applying tension to the sheet material is lost. The present invention is to provide a sheet conveying apparatus which does not cause the above-described problems. [Means for Solving the Problems] The present invention relates to a roller which is disposed downstream of a fixing roller for fixing a toner image to a sheet material and is driven to rotate at a peripheral speed higher than the rotational peripheral speed of the fixing roller. A sheet material guide member opposed to the roller having a plurality of convex ribs parallel to the sheet material conveyance direction, wherein the roller enters non-contact between the convex ribs and is fed from the fixing roller. One side of the sheet material comes into contact with the convex rib, and the other side comes into contact with the roller and is conveyed by the rotational force of the roller. When the sheet material is being conveyed, at least the sheet of the roller The portion in contact with the sheet material has a smaller radius according to the stiffness of the sheet material than when the sheet material is not conveyed, and when the sheet material is not conveyed, the roller is connected to the sheet material guide. For members However, there is provided a sheet material conveying device wherein the convex rib is not in contact with the convex rib. [Operation] The roller diameter changes according to the strength of the introduced sheet material regardless of whether the strength of the introduced sheet material is strong or weak by adopting the above-described sheet material conveying apparatus configuration. The sheet material is conveyed without affecting the image quality. When no sheet material is introduced and the sheet material is not conveyed, the roller and the sheet material guide member are kept in a non-contact state or a light contact state with each other, so that the wear progressing speed of the roller over time can be reduced, and the roller can be used for a long time. It is possible to maintain a necessary and appropriate sheet material transport condition state. [Embodiment] FIG. 2 shows a means for connecting a sheet material conveying device 1 or 2 according to the present invention to an image-fixed sheet material which passes through a pair of image fixing rollers 21 and 22 and feeds the sheet material to a paper discharge tray 23. 1 is a schematic diagram of an example of an LBP (laser beam printer) incorporated as an apparatus. (1) LBP Configuration / Imaging Operation The configuration / imaging operation of the LBP itself in this example is out of the gist of the present invention, and therefore will be described only briefly. Reference numeral 10 denotes a photosensitive drum that is driven to rotate at a predetermined peripheral speed in the direction indicated by the arrow, and the surface of the drum 10 is uniformly positively or negatively charged by a contact charging roller 11 as charging means. Semiconductor laser, polygon mirror, spherical lens,
An electrostatic latent image corresponding to the image information to be recorded is sequentially formed by receiving the laser beam scanning exposure L corresponding to the image information to be recorded by the laser scanner 12 including an F-θ lens or the like. The latent image is then developed as a toner image by the developing sleeve 13a of the developing device 13. On the other hand, only the uppermost sheet material of the sheet materials (transfer paper) P stacked and set on the multi-feed tray 15 is drawn into the printer by the paper feed roller 16 and the separation pad 17, and
The toner image formed on the surface of the drum 10 on the surface of the fed sheet material is fed to the transfer roller 19 by the paper feed roller 16 and the conveying roller 18 and fed to the opposite portion of the drum 10 and the transfer roller 19. The transfer is sequentially performed by the applied bias voltage and the pressing force of the roller. The sheet material to which the toner image has been transferred is separated from the surface of the drum 10, and is guided by guide plates 20 and 20 and is driven to rotate at a predetermined peripheral speed in a direction indicated by an arrow (a heat fixing roller pair or a pressure fixing roller pair). The transfer toner image is thermally fixed or pressure-fixed by being introduced between the fixing rollers 21 and 22 and passing between the pair of rollers. An image-fixed sheet material that passes between the image fixing roller pairs 21 and 22 is spliced by a sheet material transport device 1 and 2 according to the present invention, which will be described later, and is discharged onto a discharge tray 23. The cleaning device 14 cleans the surface of the drum 10 after the transfer of the toner image.
The cleaning blade 14a wipes and removes the untransferred toner and other contaminants, cleans the surface, and repeatedly performs image formation. In the printer of this embodiment, the four image forming process devices of the photosensitive drum 10, the charging roller 11, the developing device 13, and the cleaning device 14 are collectively used as a process cartridge 30 which can be freely attached to and detached from a predetermined mounting portion in the printer. Are assembled together with a predetermined mutual positional relationship to the housing (frame body). In the printer of this embodiment, the right end side in the drawing is the front side, and the front plate 40 is tilted forward and downward with respect to the printer main body around the support shaft A on the lower side, and freely raised and closed as shown in the figure. It is. The feed roller 16, transfer roller 19, guide plate 20, image fixing roller pairs 21 and 22, and sheet material conveying devices 1 and 2 are assembled inside the front plate 40 which can be freely opened and closed. The operation of attaching and detaching the process cartridge 30 and the inspection / maintenance of the inside of the printer are performed by opening the front plate 40 to open the inside of the printer largely. Reference numeral 41 denotes a sheet material introduction port provided at a position on the bottom of the printer corresponding to the position of the nip between the feed roller 16 and the transport roller 18 described above. When an optional sheet material feeding device (not shown) is used in combination with the printer, the sheet material P 'fed from the sheet material feeding device enters the printer from the sheet material inlet 41 described above. , Guide plate 41a / 4
In 1a, the sheet is held in the nip portion between the feed roller 16 and the transport roller 18, and thereafter, the image is transferred and transferred through the printer along the same path as that for the sheet P fed from the multi-feed tray 15 described above. After the fixing process, the sheet is discharged onto the sheet discharge tray 23. (2) Sheet Material Conveying Apparatus (FIG. 1) FIG. 1 shows a state in which an image-fixed sheet material coming out between the image fixing roller pairs 21 and 22 is spliced and sent to the paper discharge tray 23 as described above. FIG. 3 is a detailed view of the sheet material conveying devices 1 and 2; FIG. 3A is a part of a front view (view from the sheet material exit side); FIG. 3B is a diagram (B)-(B) of FIG. ) Is a cross-sectional view along the line, (C) is a cross-sectional view of a state in which the sheet material is introduced and the sheet is being conveyed, and (D) and (E) are strains of the introduced sheet material. FIG. 6 is a diagram illustrating a deformed state of a roller based on a difference between the rollers. A roller shaft 1A is rotatably supported by a bearing member (not shown). The roller 1 is made of a soft and elastic porous material such as a rubber sponge and is integrally fixed to the shaft 1A. The roller 1 may be made of a soft, solid-walled rubber or resin having elastic deformability. The rotational force of a drive source (not shown) is transmitted to the shaft 1A via power transmission means (not shown) such as gears, and the shaft 1A, that is, the roller 1, is rotated at a predetermined speed higher than the rotational peripheral speed of the image fixing roller pair 21/22. (A) It is driven to rotate clockwise in FIG. The sheet material guide member 2 is arranged and supported immovably so as to approach and oppose the roller 1, and guides a plurality of convex ribs 2 </ b> A parallel to the sheet material conveyance direction on the lower surface side which is the sheet material passing side. A predetermined interval is provided along the length of the member 2. Roller 1 is in a state in which both side portions on the upper surface side are in non-contact with the side of the convex rib between adjacent convex ribs 2A, and the sheet material is not introduced between roller 1 and guide member 2. , The upper surface of the roller is not in contact with the lower surface of the guide member 2. Therefore, the radius r of the roller 1 when the sheet material is not introduced and the sheet material is not conveyed is the rotation center line O of the roller 1 and the convex rib on the lower surface of the guide member 2 when the introduced sheet material is conveyed. The shortest distance h of the distance from the portion where the sheet material contacts 2A
(Figure (B)). Thus, between the roller 1 and the guide member 2, the sheet material P
In the state of FIGS. (A) and (B) in which no roller is introduced, the roller 1 rotates without contacting the lower surface of the guide member 2 or the convex rib 2A. In this state, when the sheet material P is introduced between the roller 1 and the guide member 2 from the image fixing roller pair 21/22 side, the introduced sheet material P becomes the roller 1 as shown in FIGS. Between the upper surface of the guide member 2 and the protruding rib 2A on the lower surface of the guide member 2, and is conveyed to the discharge tray 23 side by the rotation force of the roller 1 to be discharged. Image fixing roller pair 21 and 22, roller 1
As described above, since the rotational speed of the roller 1 is set to be higher than that of the pair of image fixing rollers 21 and 22, a moderate tension is applied to the sheet material portion between the guide member 2 and the sheet material portion. Does not occur. In the above-described sheet material conveyance state, the upper surface side of the roller 1 receives the pressing force due to the above-mentioned biting of the sheet material P, and is deformed r ₁ · r ₂ in the diameter reducing direction as shown in FIGS. Its degree of deformation is large as r ₁ of if stronger is leaving introducing the sheet material P (D) view smaller than the r ₁ as r ₂ of the paper is weak if (E) diagrams. Although the sheet material conveyance force by the roller 1 increases as the degree of deformation of the roller 1 increases,
The range of deformation is limited to a certain size, and the sheet material is moved between the roller 1 and the guide member 2 so as not to be larger than the sheet conveying force on the upstream side in the sheet conveying direction of the pair of image fixing rollers 21 and 22 at the maximum. Even when there is P, the same conveyance speed as when there is no sheet material can be maintained. That is, the sheet material P is placed between the roller 1 and the guide member 2.
As a result of the deformation of the sheet material P in the radial direction as described above in accordance with the strength of the strain when the sheet material is introduced, scars on the surface of the conveyed sheet material can be prevented, and the process speed is changed. The sheet material can be conveyed without the need. (3) Other Embodiments FIGS. 3 (A) and (B) Example In this embodiment, a guide member 2 is provided on its lower surface with a concave groove 2B having a larger radius of curvature than the roller 1 and having a circular cross section. The upper surface of the roller 1 is inserted into the groove 2B, and the upper surface of the roller 1 is extremely lightly brought into contact with the ceiling surface of the groove 2B. is there. The guide member 2 of the present embodiment does not have the convex rib 2A as in FIG. (A) surface is the state when the sheet material is not introduced,
FIG. 2B shows a state in which the sheet material P is introduced and conveyed. The upper surface side of the roller 1 is the introduced sheet material
It is deformed in the radial direction as shown in FIG. 8B according to the strength of the saw, and the same operation and effect as those in the example of FIG. 1 can be obtained. 4 (A) and 4 (B) Example This example is a modification of the above FIGS. 3 (A) and 3 (B),
The upper surface of the roller 1 is slightly separated from the ceiling surface of the concave groove 2B of the guide member 2 in a non-contact manner, and the two members 2.1 are arranged vertically. (A) illustrates a state where the sheet material is not introduced, and (B) illustrates a state where the sheet material P is introduced and the conveyance is performed. The upper surface side of the roller 1 is deformed in the diameter reducing direction in accordance with the strength of the stiffness of the introduced sheet material P, and the same operation and effect as those of the examples of FIGS. 1 and 3 are obtained. 5 to 10 Example The same effect can be obtained even if the roller 1 is not a regular cylinder (cylinder). FIGS. 5 to 9 each show a rotating member roller 1 having a side or cross-section cross-shuriken shape, and FIG. 10 shows a rotating member having a number of protrusions on a peripheral surface of a side or cross-sectional gear shape. This is a roller 1. In each of the examples shown in FIGS. 5, 6, 8, and 10, the guide member 2 is provided with a convex rib 2A on the lower surface side similarly to the example in FIG. Convex rib
While being in contact with 2A, it is conveyed by the rotational force of the roller 1. In each of the examples shown in FIGS. 7 and 9, the guide member 2 is not provided with a convex rib, and the upper surface of the introduced sheet material P contacts the substantially entire back surface of the guide member 2 while rotating the roller 1. Conveyed by. The roller 1 in each of the examples of FIGS. 5 and 10 rotates without contact with any of the lower surface of the guide member 2 and the convex rib 2A when the sheet material is not introduced. 6 and 7, when no sheet material is introduced, the roller 1 rotates while the tips of the outwardly projecting fins of the cross contact the lower surface of the guide member 2. When the tip of each outwardly projecting fin comes into contact with the lower surface of the guide member 2, it flexes against elasticity and passes while rubbing the lower surface of the guide member. 8 (A), (B), and FIG. 9, the guide member 2 corresponding to the position of the roller 1 is provided with a through-hole 2C. When there is no fin, the tips of the outwardly projecting fins of the cross rotate through the through holes 2C without contacting the lower surface of the guide member 2. As described above, any of the examples shown in FIGS.
The same operation and effect as those of the example shown in FIGS. In each embodiment shown in FIGS. 1, 4, 5, 8, 9, and 10, when there is no sheet material introduced between the roller and the guide member, Since the roller rotates without contacting the lower surface of the guide member and the convex rib, the progress of wear of the roller and the guide member over time is suppressed to a small extent, and a proper sheet material transport required for a long period of time. The condition can be stably maintained. [Effects of the Invention] As described above, according to the sheet material conveying apparatus of the present invention, it is possible to stably maintain a necessary appropriate sheet material conveying condition state for a long period of time without causing the above-described problems and to convey the sheet material. In an image forming apparatus such as the one described above, an image-fixed sheet material coming out from between image-fixing roller pairs can be spliced and disposed next to the image-fixing roller pairs in order to be sent out to a paper output tray or the like. It is effective and appropriate as a sheet material conveying means to be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the apparatus, wherein FIG. 1 (A) is a front view of a main part, FIG. 1 (B) is a cross-sectional view, and FIG. (D) and (E) are partially cutaway front views when conveying a sheet material, FIG. 2 is a schematic diagram of an example of a laser beam printer using the apparatus of the embodiment, Third
FIGS. (A) and (B), FIGS. 4 (A) and (B), FIGS. 5, 6, 7, 8 (A) and (B), FIGS. 9, 10 Is a block diagram of a device of another embodiment, and FIG. 11 is a block diagram of a conventional device. Reference numeral 1 denotes a sheet material conveying rotary roller, 2 a sheet material guide member, 2A a convex rib, 2B a concave groove, 2C a through hole, 21/22 a pair of image fixing rollers, and 23 a paper output tray.

Claims (1)

(57) [Claims] A roller disposed downstream of the fixing roller for fixing the toner image to the sheet material, and driven to rotate at a peripheral speed higher than the rotational peripheral speed of the fixing roller; and a plurality of convex ribs parallel to the sheet material conveying direction. A sheet material guide member opposed to the provided roller, wherein the roller is in non-contact between the convex ribs,
The sheet material sent from the fixing roller has one surface in contact with the convex rib and the other surface in contact with the roller and is conveyed by the rotational force of the roller. At least a portion of the roller that is in contact with the sheet material has a smaller radius according to the stiffness of the sheet material than when the sheet material is not being conveyed, and the roller is not conveyed when the sheet material is not conveyed. Is a non-contact state between the sheet material guide member and the convex rib. 2. When the sheet material is not transported, the radius of the roller is
2. The sheet conveying apparatus according to claim 1, wherein the distance from the rotation center line of the roller when the sheet is conveyed to a portion where the sheet comes into contact is larger than the shortest distance. 3. 3. The sheet conveying apparatus according to claim 1, wherein the roller is a flexible elastic porous material.