JP2007039149A - Sheet carrier device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet carrier device capable of preventing the degradation of fixed image quality; and to provide an image forming device. <P>SOLUTION: A driven rotary member 110 mounted to a sheet carrier part for carrying a sheet with a toner image fixed thereon is composed of a rotator 111 contacting the sheet and having a cylindrical shape and a support shaft 120 for rotatably supporting the rotator 111. A contact area of the rotator 111 to the sheet is reduced by forming an uneven shape on a circumferential surface of the rotator 111. An insertion part 115 for inserting the support shaft 120 therein is formed in the rotator 111, and a holding part 116 for loosely fitting the support shaft 120 thereto and non-contact spaces 117 are formed at a central part of the inside of the insertion part 115 and on both side parts of the insertion part 115, respectively, whereby the insertion part 115 is prevented from contacting the support shaft 120 loosely fitted to the holding part 116 when the rotator 111 is tilted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus, and more particularly to a configuration for conveying a sheet on which a toner image is fixed.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, a facsimile, or a copier that forms an image by electrophotography, a toner image is formed on a sheet by heating and pressurizing an unfixed toner image formed on a sheet as a recording medium. Fixing means for fixing is provided.

  A sheet conveying device including a conveying roller and a discharge roller is provided for discharging the sheet on which the toner image is fixed by the fixing unit to the outside of the image forming apparatus.

  By the way, in such a sheet conveying apparatus, when a sheet immediately after heat fixing is conveyed by a fixing unit, a roller or roller has a surface on which the toner image of the sheet is formed before the heat-fixed toner image is completely cooled (image). Surface) or the surface behind it. In this case, the surface property of the contact portion is changed, or the contact portion is deprived of heat earlier than other portions, whereby the color appearance of the toner image is changed and visually recognized as a gloss difference. This is a roller trace, and this roller trace is not noticeable on plain paper, but is easily noticeable when the sheet has a high glossiness such as a transparent film for OHP (overhead projector), glossy paper, or glossy film.

  In addition, a conveyance guide composed of a plurality of ribs is provided on the downstream side of the fixing unit. When the image surface of the sheet immediately after the toner image is heated and fixed is rubbed by the conveyance guide, Scratches will occur. Note that, for example, if the curvature radius of the conveyance path is increased so that the image surface is not rubbed by the conveyance guide, the apparatus becomes large.

  In order to solve this problem, a method of reducing the radius of curvature of the conveyance path by providing a roller that is rotated by the conveyance force of the sheet on the image surface side of the conveyance path is conceivable. However, in such a method, it is necessary to use a special roller that can rotate smoothly so as not to take heat of the sheet and to apply a load to the toner image.

  Here, as such a special roller, one using a porous member, a heat insulating member, or the like may be used in order to place importance on heat insulation (see, for example, Patent Document 1).

  FIG. 8 shows an example of a heat insulating roller having such heat insulating properties. The heat insulating roller 2000 includes a metal shaft (roller shaft) 2012, a heat insulating layer 2013 formed on the peripheral surface of the metal shaft 2012, an uneven shape 2014 formed on the heat insulating layer 2013, and a heat insulating layer 2013. And a surface protective layer 2015 formed on the peripheral surface.

Japanese Patent Laying-Open No. 2004-301291 (page 8, FIG. 1)

  By the way, in order to follow and rotate such a heat insulating roller by a sheet conveying force, the heat insulating roller may be constituted by a roller main body provided with a heat insulating layer and a roller shaft that rotatably supports the roller main body. is there.

  Here, it is desirable that the resistance when the roller main body is driven to rotate by the conveying force of the sheet is small. However, in the case of this heat insulating roller, for example, when the roller shaft is longer than the roller body as shown in FIG. 8, when the roller body rotates following the sheet, the roller body tilts with respect to the roller shaft. The both ends of the roller and the roller shaft are instantaneously locked, and a galling state is obtained.

  When the roller main body and the roller shaft are thus locked, the roller main body does not rotate with the sheet conveying force, and as a result, the scratch mark is generated by the conveying guide because the image surface of the sheet is rubbed against the roller main body. Will appear, and the quality of the fixed image will deteriorate.

  In the case of such a heat insulating roller, since the heat insulating body forming the heat insulating layer is often a highly elastic body, when the heat insulating roller is in contact with the conveying roller and driven to rotate, the heat insulating roller, the sheet conveying roller, A long nip is formed in the sheet conveying direction. Here, when a long nip is formed in the sheet conveying direction as described above, if the above lock occurs, the rotation resistance due to the nip is added to the rotation resistance due to the lock. It gets bigger.

  When the rotational resistance is increased in this way, the resistance force for rotating the heat insulating roller through the sheet is increased by the rotational driving force of the sheet conveying roller. As a result, rubbing traces are generated on the image surface, and the fixed image quality is increased. Decreases.

  Accordingly, the present invention has been made in view of such a current situation, and an object of the present invention is to provide a sheet conveying apparatus and an image forming apparatus that can prevent deterioration of fixed image quality.

  The present invention provides a sheet conveying apparatus that conveys a sheet on which a toner image is fixed by a fixing unit, and includes a rotating body having a cylindrical shape that comes into contact with the sheet, and a support shaft that rotatably supports the rotating body. The driven rotating member is configured, and the rotating body of the driven rotating member includes a concavo-convex shape formed on a peripheral surface and an insertion portion into which the support shaft is inserted, and an inner central portion of the insertion portion A holding portion to which the support shaft is loosely fitted is provided, and a non-contact space configured to prevent the insertion portion from contacting the support shaft when the rotating body is inclined is provided at a side end portion of the insertion portion. It is characterized by being.

  According to the present invention, by providing the concave and convex shape on the peripheral surface of the rotating body of the driven rotating member, the contact area with the sheet is reduced, and when the rotating body is tilted, the insertion portion provided on the rotating body on the support shaft By reducing the rotational resistance of the rotator so as not to touch the roller, it is possible to suppress roller marks and scratch marks generated on the sheet on which the toner image is fixed. Thereby, it is possible to prevent the deterioration of the fixed image quality.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

  FIG. 1 is a schematic diagram showing an overall configuration of a color laser printer which is an example of an image forming apparatus provided with a sheet conveying apparatus according to a first embodiment of the present invention.

  In FIG. 1, 71 is a color laser printer, and 72 is a color laser printer main body (hereinafter referred to as a printer main body). The printer main body 72 includes an image forming unit 8 that forms an image on the sheet, a feeding unit 20 that feeds the sheet, and a sheet that transports the sheet fed from the feeding unit 20 to the image forming unit 8. A conveyance unit 10 and a fixing device 30 for fixing an image formed on the sheet are provided.

  Here, the image forming unit 8 includes a photosensitive drum 1 (1a to 1d) that is an image carrier that is arranged in the vertical direction and carries toner images of four colors of yellow, magenta, cyan, and black. . The photosensitive drum 1 is rotated counterclockwise by a rotating means (not shown).

  Further, a charging device 2 (2a to 2d), which is arranged around the photosensitive drum 1 along the rotation direction and uniformly charges the surface of the photosensitive drum, and radiates a laser beam based on the image information to be sensitized. A scanner unit 3 (3a to 3d) for forming an electrostatic latent image on the body drum is provided.

  In addition, the toner of each color of yellow, cyan, magenta, and black is attached to the electrostatic latent image to visualize the toner image, and the toner remaining on the surface of the photosensitive drum after the transfer is transferred. The cleaning means 6 (6a-6d) etc. to remove are provided. In the present embodiment, the photosensitive drum 1, the charging device 2, the developing device 4, and the cleaning unit 6 are integrally formed into a cartridge to form a process cartridge 7 (7a to 7d).

  A transfer roller 18 (18a) sandwiches the transfer conveyance belt 11 together with the four photosensitive drums 1 (1a to 1d) on the inner side of the transfer conveyance belt 11 which is an endless sheet conveyance member for conveying a sheet to be described later. To 18d) are provided.

  Here, these transfer rollers 18 are connected to a power supply for transfer bias (not shown), and positive charges are applied from the transfer rollers 18 to the sheet via the transfer conveyance belt 11. By applying the transfer bias in this manner, the negative color toner images on the photosensitive drum are sequentially transferred onto the sheet in contact with the photosensitive drum 1 to form a multicolor image. ing.

  The feeding unit 20 includes a plurality of sheets S, and includes a paper feeding cassette 21 loaded on the bottom of the printer main body, a pickup roller 22 that feeds the sheets S stored in the paper feeding cassette 21, and the like. When the image is formed, the sheet S is separated and fed one by one from the sheet feeding cassette 21 by the pickup roller 22, and then the sheet S is sent to the sheet conveying unit 10 at a predetermined timing by the registration roller pair 23. It is designed to be transported.

  The sheet conveyance unit 10 is provided with a transfer conveyance belt 11 as a sheet carrier that is stretched over the driving roller 12 and the driven rollers 13 to 15 and arranged to face all the photosensitive drums 1 (1a to 1d). I have. Here, the transfer conveyance belt 11 electrostatically attracts the sheet to the outer peripheral surface facing the photosensitive drum 1 and is circulated clockwise by the driving roller 12 so as to bring the sheet into contact with the photosensitive drum 1. It has become.

  Then, the sheet is conveyed to the transfer position by the transfer conveyance belt 11 by being electrostatically attracted to the transfer conveyance belt 11 that circulates in this way, and the toner image on the photosensitive drum 1 is transferred.

  In this embodiment, the transfer / conveying belt 11 is formed of a film-like member having a predetermined volume specific resistance and a thickness of about 150 μm. Further, the driving roller 12 and the driven rollers 13 to 15 are supported on both side frames (not shown) by ball bearings attached to shafts at both ends thereof.

  A suction roller 17 is disposed at the most upstream position of the transfer conveyance belt 11 and is in pressure contact with the driven roller 13 via the transfer conveyance belt 11. The suction roller 17 presses the sheet S to the outer periphery of the transfer conveyance belt 11 and applies a voltage to the transfer conveyance belt 11 to electrostatically adsorb the sheet S to the transfer conveyance belt 11. Yes.

  The fixing device 30 applies heat and pressure to the image formed on the sheet to fix the toner image. The fixing device 30 includes a fixing unit 30A having a fixing roller 31 and a pressure roller 32 incorporating a heating source, and a sheet to be described later. A transport device 30B is provided. The pressure roller 32 of the fixing unit 30 is pressed against the fixing roller 31 by a biasing unit (not shown), and a nip N is formed at a contact portion between the pressure roller 32 and the fixing roller 31.

  A sheet conveying device 30B is disposed on the downstream side of the fixing unit 30A. The sheet conveying device 30B includes a fixing inlet guide 33 that guides the sheet S conveyed from the transfer conveying belt 11 to the nip N, and a sheet discharge tray 60 installed on the upper surface of the apparatus main body 72. A fixing paper discharge roller pair 34 is provided for discharging upward.

  Next, an image forming operation of the color laser printer 71 configured as described above will be described.

  First, each process cartridge 7 is sequentially driven in accordance with the printing timing, and the photosensitive drum 1 is driven to rotate counterclockwise in accordance with the drive. Then, the scanner units 3 corresponding to the respective process cartridges 7 are sequentially driven. By this driving, the charging device 2 applies a uniform charge to the peripheral surface of the photoconductive drum 1, and the scanner unit 3 exposes the peripheral surface of the photoconductive drum 1 according to an image signal to perform the photoconductor drum 1. An electrostatic latent image is formed on the peripheral surface.

  Further, the latent image is developed by the developing device 4, whereby toner images of four colors of yellow, magenta, cyan, and black are formed on the surface of the photosensitive drum.

  In parallel with the toner image forming operation, the sheet S accommodated in the sheet feeding cassette 21 is picked up by the pickup roller 22, and thereafter, the leading end of the sheet S abuts against the registration roller pair 23 that has stopped rotating. Form a loop. The skew of the sheet S is corrected by forming a loop in this way.

  After that, at the timing when the leading edge of the toner image on the most upstream photosensitive drum 1a is rotated and conveyed to the contact point (transfer position) with the transfer conveyance belt 11, printing of the sheet S is started at the contact point. The registration roller pair 23 starts to rotate so that the positions match.

  As the registration roller pair 23 rotates, the sheet S is conveyed to the nip between the suction roller 17 and the transfer conveyance belt 11, and is attracted to the transfer conveyance belt 11 by the adsorption roller 17, and the photosensitive drum 1 and the transfer conveyance belt 11. Are conveyed to the transfer section where they are in pressure contact.

  Next, the toner image of each color on the photosensitive drum 1 is applied to the sheet conveyed to the transfer unit in this manner by the action of the transfer roller 18 disposed in each transfer unit and applied with a voltage having a polarity opposite to that of the toner. The images are sequentially superimposed and transferred on the sheet.

  Then, the sheet S on which the four color toner images are transferred in this way is separated from the transfer conveyance belt 11 by the curvature of the driving roller 12 and guided to the fixing inlet guide 33 to be carried into the fixing device 30. Is done. Thereafter, in the fixing device 30, the toner image is fixed on the sheet S, and the sheet S on which the toner image is fixed in this manner is discharged to the sheet discharge tray 60 by the fixing discharge roller pair 34.

  FIG. 2 is a schematic view of the fixing device 30. The fixing device 30 constitutes fixing means 30A for heating and pressurizing an unfixed toner image formed on the sheet, as shown in FIG. A fixing roller 31 and a pressure roller 32 are provided.

  Also, on the downstream side of the fixing unit 30A, a fixing discharge roller pair 34 for nipping and conveying the sheet and discharging it to the outside of the fixing device 30 and a driven roller 110 that is driven to rotate by contacting the sheet are arranged. Has been. Further, a conveyance guide 35 that guides the sheet S and supports the driven roller 110 is disposed downstream of the fixing unit 30A.

  The pair of fixing and discharging rollers 34, the driven roller 110, and the conveying guide 35 constitute a sheet conveying device 30B that conveys the sheet on which the toner image is fixed. A housing 36 of the fixing device 30 covers the fixing roller 31 and the like.

  Here, in the conveyance guide 35, the guide portion that guides the sheet S and the portion that carries the driven roller 110 may be configured by separate members. Further, the housing 36 may be configured by parts of the printer main body 72 including the fixing device 30.

  The fixing roller 31, the pressure roller 32, and the fixing paper discharge roller pair 34 are rotated by a driving unit (not shown) provided inside the fixing device 30 or outside the fixing device 30.

  With this rotation, the unfixed toner image transferred onto the surface of the sheet S carried from the transfer conveyance belt 11 is conveyed to the nip N between the fixing roller 31 and the pressure roller 32, and this nip N And the toner image is fixed. Thereafter, the sheet S on which the toner image is fixed reaches the fixing discharge roller pair 34 while being guided by the conveyance guide 35, and is thereafter nipped and conveyed by the fixing discharge roller pair 34 to be out of the printer 71. Is discharged.

  As the sheet conveying device 30B, as shown in FIG. 2B, a conveying roller 37 that is a conveying rotating body is disposed opposite to the driven roller 110, and the driven roller 110 is attached by a spring 5 that is an urging means. It may be configured to be pressed against the sheet conveying roller 37. Then, when the driven roller 110 is brought into pressure contact with the conveying roller 37 in this manner, the driven roller 110 is driven to rotate while sandwiching the sheet S together with the conveying roller 37. The transport roller 37 is provided inside the fixing device 30 or is rotated by a driving unit (not shown) provided outside the fixing device 30.

  In the present embodiment, as shown in FIG. 3, the driven roller 110, which is a driven rotating member, includes a roller body 111 that is a rotating body having a cylindrical shape in contact with a sheet, and a roller body 111 that is rotatable. And a support shaft 120 that supports the support shaft 120. Note that both ends of the support shaft 120 are held by the conveyance guide 35.

  Here, the roller body 111 is made of engineering plastic or the like and has a predetermined heat resistance temperature. A plurality of concave grooves 112 are formed on the peripheral surface of the roller body 111. Then, by forming the concave groove 112 and making the peripheral surface uneven as described above, the contact area with the sheet S can be reduced, and the heat absorption by the roller body 111 can be reduced. The portion of the roller body 111 that touches the sheet S is hereinafter referred to as a convex portion 113 in order to distinguish it from the concave groove 112.

  The concave grooves 112 are arranged on the circumferential surface of the roller body 111 with horizontal grooves 112 a parallel to the support shaft 120 and vertical grooves 112 b discontinuously and alternately provided between the horizontal grooves 112 a in the rotational direction. The reason why the vertical groove 112b is discontinuous is that if the vertical groove 112b is continuously arranged in the rotation direction, the trace on the boundary line between the vertical groove 112b and the convex 113 is continuously transferred to the image surface. This is to prevent it from being done.

  By the way, when such a driven roller 110 is used, the toner image may be slightly removed from the toner image immediately after being fixed, or paper dust generated from the sheet S may accumulate in the groove 112. . Therefore, in the present embodiment, the surface of the roller body 111, that is, the outer peripheral surface of the convex portion 113 is covered with the resin tube 114 to form a surface protective layer, whereby toner and powder are deposited in the concave groove 112. Can be prevented.

  For example, when a fluorine heat shrinkable tube having heat resistance and good releasability is used as the resin tube 114, the resin tube 114 follows the concave groove 112. As in the case where the tube 114 is not covered, the number is reduced. Further, by covering the resin tube 114, an air layer 118 is formed between the concave groove 112 and the resin tube 114 as shown in FIG.

  When the air layer 118 is formed in this way, the air layer 118 acts as a heat insulating layer, thereby improving the heat insulating property of the roller body 111 as compared with the case where the resin tube 114 is not present.

  Thus, by providing an uneven shape on the peripheral surface of the roller body 111 and reducing the contact area with the sheet S, compared to the conventional case where the surface of the roller body is configured with a smooth cylindrical surface, The amount of heat absorbed from the sheet S can be reduced, and the difference in gloss can be reduced.

  In addition, as the number of the concave grooves 112 increases and the width of the concave grooves 112 increases, the contact area between the sheet and the roller main body 111 can be reduced to reduce the amount of heat absorption, which is advantageous for the roller marks. On the other hand, the frictional force between the sheet and the roller body 111 decreases. When the frictional force is reduced and the resistance torque generated by the frictional force acting between the roller main body 111 and the support shaft 120 becomes equal to or higher than the rotational torque generated by the frictional force, the roller main body 111 stops. End up. As a result, scratch marks are generated.

  This phenomenon is likely to occur when a driven roller that is rotated by the conveying force of the sheet is provided only on one side of the sheet as shown in FIG. Therefore, the protrusion 113 has a contact area with the sheet, and the frictional force between the roller body 111 and the sheet is larger than the frictional force between the roller body 111 (a holding portion described later) and the support shaft 120. It is necessary to provide such an area.

  In FIG. 3, reference numeral 115 denotes an insertion hole formed in the roller body 111, and the support shaft 120 is inserted into the insertion hole 15 which is this insertion part. As shown in FIG. 3B, the insertion hole 115 is supported regardless of the posture of the roller body 111 and the holding portion 116 to which the support shaft 120 is loosely fitted when the roller body 111 rotates. And a non-contact space 117 formed so as not to contact the shaft 120.

  Here, the holding portion 116 is formed in the center portion inside the insertion hole 115 so that the axial direction of the roller body 111, that is, the section (length) in the width direction is narrower than the length of the roller body 111 in the width direction. ing. As shown in FIG. 4, the non-contact space 117 is formed from the end portion of the holding portion 116 that is the side end portion of the insertion hole 115 to the entrance of the insertion hole 115. Further, the diameter thereof is formed to be larger than the diameter of the holding portion 116, and the length in the axial direction is such that the edge of the entrance of the insertion hole 115 does not touch the support shaft 120 when the roller body 111 is inclined. Is formed.

  A broken line 119 in FIG. 4 is a line connecting the contact portion of the holding portion 116 with the support shaft 120 and the entrance edge 115 a of the insertion hole 115. By forming the non-contact space 117 as described above, the support shaft 120 moves toward the roller body from the broken line 119 regardless of how the roller body 111 is tilted with respect to the support shaft 120. There is no such thing. As a result, no matter how the roller body 111 is tilted with respect to the support shaft 120, the support shaft 120 does not touch the entrance edge 115 a of the insertion hole 115.

  FIG. 5 is a schematic diagram regarding the width of the holding portion 116, the width of the roller main body 111, the amount of inclination of the roller main body 111 with respect to the support shaft 120, and the couple of forces in the driven roller 110 of the present embodiment. 3 is a schematic diagram of a driven roller 1010. FIG.

  Here, in the case of the conventional driven roller 1010 shown in FIG. 6, the width (section) of the holding portion 1016 is longer than the width of the roller body 1011. The sliding frictional force between the holding portion 1016 and the support shaft 1020 is usually the same when the sliding material and load are the same.

  However, when the roller body 1011 is inclined with respect to the support shaft 1020, the roller body 1011 contacts the support shaft 1020 at both ends of the holding portion 1016, and as a result, the roller body 1011 has both ends of the holding portion 1016. A couple is generated around the midpoint of the contact point. This couple acts on the driven roller 1010 as a rotational resistance.

  In the case of the conventional driven roller 1010, the couple is generated even when the roller body 1011 is slightly tilted because the section of the holding portion 1016 is long, and the magnitude of the couple is large.

  On the other hand, in the case of the driven roller 110 according to the present embodiment, as shown in FIG. 5, the section of the holding portion 116 is shorter than the holding portion 1016 of the roller main body 1011 shown in FIG. Further, a non-contact space 117 is provided so that the support shaft 120 does not touch the entrance edge 115 a of the insertion hole 115 even if the roller body 111 is inclined.

  Thereby, even when the amount of inclination of the roller body 111 with respect to the support shaft 120 becomes large, the magnitude of the couple generated in the roller body 111 is smaller than the couple generated in the driven roller 1010 in FIG. As a result, the roller body 111 can rotate smoothly.

  Here, in the fixing device 30 of FIG. 2, the sheet S on which the toner image is fixed in the nip N formed by the fixing roller 31 and the pressure roller 32 is a conveyance guide 35 whose front end is the back surface (non-image surface) side. It is comprised so that it may be conveyed along. Then, in the case of a sheet having a weak stiffness immediately after heating and a heavy mass, such as a transparent film for an overhead projector (OHP), after passing through the nip N, tilt downward, that is, on the front side (image side). And For this reason, it contacts the driven roller 110 provided near the downstream of the nip N in the sheet conveying direction.

  At this time, since the driven roller 110 is smoothly rotated by the configuration described above, the sheet is conveyed by the driven roller 110 so that the surface side is in contact with the conveyance guide 35, so that the fixing discharge is not generated without generating a roller mark or a scratch mark. It is delivered to the paper roller pair 34.

  In this way, by providing an uneven shape on the peripheral surface of the roller body 111 and reducing the contact area with the sheet S, the amount of heat absorbed from the sheet S can be reduced, and the difference in gloss can be reduced. .

  Further, when the roller main body 111 is tilted, the support shaft 120 is configured so that the edge of the entrance of the insertion hole 115 does not touch, so that the couple (rotation resistance) that becomes the rotational load of the driven roller 110 is reduced. It is possible to prevent the surface from being rubbed. At the same time, even if the driven roller 110 tilts smoothly, even if the behavior of the sheet S changes suddenly, the driven roller 110 rotates smoothly while following this, so that stable sheet conveying performance is obtained. be able to.

  In the sheet conveying apparatus having the configuration in which the driven roller 110 shown in FIG. 2B is in contact with the conveying roller 37 and is driven to rotate, the rotational resistance force of the driven roller 110 is reduced by the configuration described above. Therefore, the urging force by the spring 5 can be reduced. As a result, it is possible to prevent generation of scratch marks and roller marks by the driven roller 110.

  Further, even when the radius of curvature of the sheet conveyance path after the fixing nip N is reduced, by using the driven roller 110 according to the present embodiment, it is possible to guide the sheet without generating a roller mark or a scratch mark. . Therefore, it is possible to contribute to downsizing of the fixing device 30.

  In addition, after the fixing nip N, by using a driven roller that can suppress roller marks and scratch marks and can share the driven roller parts and is advantageous in terms of cost, image loss can be achieved. The color laser printer 71 that does not cause the problem can be provided at low cost.

  Next, a second embodiment of the present invention will be described.

  FIG. 7 is a perspective view of a driven roller provided in the sheet conveying apparatus according to the present embodiment. 7, the same reference numerals as those in FIG. 3 indicate the same or corresponding parts.

  In FIG. 7A, the convex portion 113 is formed in a rhombus shape by intersecting grooves that draw a spiral. In addition to this, the convex portion 113 may be formed in any geometric shape such as a polygon such as a triangle or a pentagon, a round shape, or an elliptical shape.

  Moreover, (b) of FIG. 7 forms the concave groove 112 in a plurality of crater shapes. In addition to this, an irregular texture shape (not shown) may be formed by blasting the cylindrical surface of the driven roller 110.

  In this way, by forming the convex portion 113 in a rhombus shape, or by forming the concave groove 112 in a crater shape, the concave groove 112 along the sheet conveying direction can be eliminated. Thereby, in addition to the effect of 1st Embodiment mentioned above, the possibility that the edge trace of the ditch | groove 112 may come out can be eliminated.

  In the description so far, the fixing unit 30A and the sheet conveying device 30B are arranged in the housing 36 of the fixing device 30 to show an example of a unit configuration for reducing the size of the fixing device 30. The fixing unit and the sheet conveying device may be provided separately. Further, the driven roller 110 is described as having a structure that is rotatably supported by the support shaft 120 held at both ends. However, the driven roller 110 has a structure that is rotatably supported by the support shaft held at only one side. But it can also be applied.

  In the above description, a color laser printer has been described as an example of an image forming apparatus provided with a sheet conveying apparatus according to the present invention. However, the present invention can also be applied to a monochrome printer having a single photosensitive member. Further, the present invention can be applied not only to printers but also to other electrophotographic image forming apparatuses such as copying machines and facsimile machines.

1 is a schematic diagram illustrating an overall configuration of a color laser printer that is an example of an image forming apparatus including a sheet conveying device according to a first embodiment of the present invention. The figure which shows schematic structure of the said sheet conveying apparatus. FIG. 4 is a diagram illustrating a configuration of a driven roller provided in the sheet conveying apparatus. The principal part enlarged view of the roller main body which comprises the said driven roller. The schematic diagram regarding the area of the holding part of the said roller main body, the width | variety of a roller main body, the inclination amount with respect to a support shaft, and the couple at that time. The schematic diagram regarding the section of the holding | maintenance part of the roller main body in the conventional driven roller, the width | variety of a roller main body, the inclination amount with respect to a support shaft, and the couple at that time. The perspective view of the driven roller provided in the sheet conveying apparatus which concerns on the 2nd Embodiment of this invention. The figure explaining the structure of the conventional heat insulation roller.

Explanation of symbols

8 Image forming unit 30 Fixing device 30A Fixing unit 30B Sheet conveying device 31 Fixing roller 32 Pressure roller 35 Conveying guide 37 Conveying roller 71 Color laser printer 72 Color laser printer main body 110 Followed roller 111 Roller main body 112 Concave groove 113 Convex portion 114 Resin Tube 115 Insertion hole 115a Edge 116 of insertion hole Holding part 117 Non-contact space 120 Support shaft S Sheet

Claims (8)

In a sheet conveying apparatus that conveys a sheet on which a toner image is fixed by a fixing unit,
A driven rotating member configured by a rotating body having a cylindrical shape that comes into contact with the seat and a support shaft that rotatably supports the rotating body;
The rotating body of the driven rotating member includes a concavo-convex shape formed on a peripheral surface, and an insertion portion into which the support shaft is inserted,
A holding portion to which the support shaft is loosely fitted is provided at an inner central portion of the insertion portion, and the insertion portion does not contact the support shaft when the rotating body is inclined at a side end portion of the insertion portion. A sheet conveying apparatus, characterized in that a non-contact space configured as described above is provided.   The contact area between the rotating body and the sheet is such that the frictional force between the rotating body and the sheet is larger than the frictional force between the holding portion and the support shaft. The sheet conveying apparatus according to claim 1.   The sheet conveying apparatus according to claim 1, wherein a surface protective layer that follows the uneven shape is provided on a peripheral surface of the rotating body.   The sheet conveying apparatus according to claim 3, wherein the surface protective layer is formed of a resin tube.   The length of the holding part of the rotating body in the axial direction is made shorter than the length of the rotating body in the axial direction, and the diameter of the non-contact space is made larger than the diameter of the holding part, and the non-contact space 5. The length in the axial direction is set to a length that prevents the insertion portion from contacting the support shaft when the rotating body is tilted. 6. Sheet conveying device.   6. The sheet conveying apparatus according to claim 1, wherein the driven rotating member is arranged to rotate in contact with the conveyed sheet after the toner image is fixed.   6. The driven rotating member is disposed on the downstream side of the fixing unit, and is disposed so as to abut on a conveying rotating body that rotates by a driving force from a driving unit. The sheet conveying apparatus according to item 1. An image forming unit that forms a toner image and transfers the toner image to a sheet;
Fixing means for fixing the toner image transferred by the image forming unit to a sheet;
A sheet conveying device according to any one of claims 1 to 7,
An image forming apparatus comprising:

Images