JP2014046994A - Sheet conveyance device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet conveyance device capable of retaining a suction force while reducing friction between a conveyance belt and a suction duct, and an image forming apparatus.SOLUTION: Suction means connected to a suction duct 96, which is inserted into an endless conveyance belt having a plurality of suction holes and provided with a duct opening 95 for sucking air into a position facing the conveyance belt, sucks air through the duct opening 95 and the plurality of suction holes of the conveyance belt, to adsorb a sheet on the conveyance belt. The duct opening 95 is provided with auxiliary rollers 102 that rotate while abutting on the conveyance belt that moves while receiving a suction force of the suction means with the sheet adsorbed on the conveyance belt. An outer frame rib 104, which abuts on the conveyance belt, is provided to project toward the conveyance belt at an edge of the duct opening 95.

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus, and more particularly to an apparatus that conveys a sheet while adsorbed to an endless belt.

  2. Description of the Related Art Conventionally, some image forming apparatuses such as copying machines, facsimile machines, and laser printers form an image on a sheet by an electrophotographic method. In such an image forming apparatus, when an image is formed on a sheet, first, the photosensitive drum is exposed in accordance with image information to form an electrostatic latent image on the photosensitive drum.

  Next, the electrostatic latent image is developed with toner in a developing device to be visualized as a toner image, and the toner image is transferred to a sheet supplied from a paper feeding unit in a transfer unit. . Thereafter, the sheet is conveyed to a fixing nip between a fixing roller and a pressure roller provided in the fixing unit, and the toner image is fixed on the sheet as a permanent image.

  Incidentally, in recent years, image forming apparatuses are required to stably form high-quality images on a wide variety of sheets such as thin paper to thick paper and plain paper to coated paper. In order to meet such a demand, for example, it is necessary to stably convey a wide range of sheets from a small postcard size to an A3 full size or more for light printing and design.

  Therefore, in the conventional image forming apparatus, for example, an endless belt is provided in the conveyance path between the transfer unit and the fixing unit, and the sheet is moved by moving the endless belt in a state where the sheet is placed on the endless belt surface. Some have a pre-fixing conveyance unit for conveyance. When the sheet is conveyed by the conveyance belt in contact with the non-image surface side of the sheet in this way, the sheet is not damaged as compared with the case where the sheet is conveyed using the conveyance roller. Can be transported.

  Furthermore, as such a pre-fixing conveyance unit, there is one in which the sheet is attracted and held to the conveyance belt by negative pressure due to air suction. In such a configuration, the sheet uniformly contacts the conveyance belt. In addition, the transportability can be improved (see Patent Documents 1 and 2).

JP 2006-176265 A JP 2008-203767 A

  In an image forming apparatus including a pre-fixing conveyance unit, particularly when conveying a small-sized sheet that is less than the length (interval) between the image transfer unit and the image fixing unit, the sheet is only the conveyance belt of the pre-fixing conveyance unit. It is conveyed by. For this reason, it is essential to suck and hold the sheet stably on the conveyor belt.

  In recent years, there are various types of small-sized sheets represented by postcards and the like, and in order to reliably convey these highly rigid sheets, there is a tendency to set a high suction force in the pre-fixing conveyance unit.

  By the way, the suction mechanism in the pre-fixing transport unit is generally configured by a suction fan that is a suction source, and a suction duct 196 that is connected to a suction fan (not shown) from the lower portion of the transport belt 190 as shown in FIG. However, in such a configuration, if there is a gap between the suction duct 196 and the conveyor belt 190, a suction force loss occurs and the suction force cannot be obtained efficiently. Here, in order to reduce the loss of suction force, the duct upper end rib 99 of the duct opening 195 formed on the upper surface of the suction duct 196 and the belt inner peripheral surface 200 of the transport belt 190 facing the duct opening 195. It is necessary to reduce the distance to the gap as narrow as possible.

  Here, in order to narrow the gap, for example, when the height of the duct upper end rib 99 is the same as or higher than that of the belt inner peripheral surface 200, the conveyance belt 190 and the duct upper end rib 99 during driving are The friction between increases. If the friction with the duct upper end rib 99 increases in this way, there is a risk of excessive driving torque and damage to the belt. For this reason, the height of the duct upper end rib 99 is generally lower than the belt inner peripheral surface 200 as shown in FIG.

  However, even when the height of the duct upper end rib 99 is set, if the suction force increases, the belt inner peripheral surface 200 is pressed against the duct upper end rib 99 as shown in FIG. As shown in FIG. 12A, when the height of the duct upper end rib 99 is further reduced, the rubbing between the belt inner peripheral surface 200 and the duct upper end rib 99 can be avoided. When the force is reduced, as shown in FIG. 12B, the gap becomes wider and the suction force loss increases.

  Therefore, the present invention has been made in view of such a current situation, and provides a sheet conveying apparatus and an image forming apparatus that can maintain a suction force and reduce friction between the conveying belt and the suction duct. It is intended to do.

  The present invention provides a sheet conveying apparatus for conveying a sheet and sucking air to a position facing an endless conveying belt having a plurality of suction holes and an inner end of the conveying belt. A suction duct provided with an opening, and a suction connected to the suction duct and sucking air through the openings of the suction duct and the plurality of suction holes of the conveyor belt to attract the sheet to the conveyor belt And a roller member that rotates in contact with the conveyor belt that moves while receiving the suction force of the suction means when the sheet is sucked. Is.

  As in the present invention, by providing a roller member that abuts on the conveyor belt that moves while receiving the suction force of the suction means, the friction between the conveyor belt and the suction duct can be reduced while maintaining the suction force. it can.

1 is a perspective view of a color laser printer that is an example of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a schematic configuration of the color laser printer. FIG. 3 is a perspective view illustrating a configuration of a pre-fixing conveyance unit provided in the color laser printer. FIG. 3 is a perspective view illustrating a state where a conveyance belt is removed from the pre-fixing conveyance unit. FIG. 5 is a diagram illustrating a flow of air (atmosphere) during sheet suction by the pre-fixing conveyance unit. FIG. 3 is a control block diagram of the pre-fixing conveyance unit. 6 is a flowchart illustrating suction force switching control during sheet conveyance of the pre-fixing conveyance unit. The figure explaining the structure of the suction duct of the said pre-fixing conveyance unit. FIG. 3 is an enlarged sectional view around an auxiliary roller provided in the suction duct. The figure explaining the relationship between the distance between the outer frame rib of the suction duct and the belt inner peripheral surface, and the distance between the outer peripheral surface of the auxiliary roller and the belt inner peripheral surface. FIG. 10 is a first diagram illustrating a conventional sheet conveying apparatus. FIG. 6 is a second diagram illustrating a conventional sheet conveying apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below are illustrative of the present invention, and the dimensions, materials, shapes, and relative arrangements of the components described below are particularly specific. Unless otherwise specified, the scope of the present invention is not limited thereto.

  FIG. 1 is a perspective view of a color laser printer which is an example of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing a schematic configuration thereof. 1 and 2, 1 is a color laser printer, and 1A is a printer main body (image forming apparatus main body). Connected to one side of the printer main body 1A is a sheet processing apparatus 2 that performs a folding process, a stapling process, a punching process, a bookbinding process, and the like on the sheet output from the printer main body 1A. A buffer unit 3 having a curl correction device (not shown) is provided between the printer main body 1A and the sheet processing apparatus 2.

  The printer main body 1A includes an image forming unit 1B that forms a toner image, an intermediate transfer unit 1C, a fixing unit 45, a sheet feeding device 1D that feeds a sheet S to the image forming unit 1B, and a manual feed. A manual sheet feeding device 30 for feeding sheets is provided. The color laser printer 1 is capable of forming an image on the back surface of the sheet. For this reason, the sheet S on which the image is formed on the front surface (one surface) is reversed and is again formed in the image forming unit 1B. A re-conveying section 1E is provided for conveying the sheet.

  Here, the image forming unit 1B is arranged in a substantially horizontal direction, and four process stations 60 for forming toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (Bk), respectively. (60Y, 60M, 60C, 60K). The process station 60 carries toner images of four colors, yellow, magenta, cyan, and black, and is a photosensitive drum 61 (61Y, 61M, 61C, 61K) that is an image carrier that is driven by a stepping motor (not shown). ). Further, a charger 62 (62Y, 62M, 62C, 62K) for uniformly charging the surface of the photosensitive drum is provided.

  Furthermore, a scanner 63 (63Y, 63M, 63C, 63K) is provided that forms an electrostatic latent image on a photosensitive drum that rotates at a constant speed by irradiating a laser beam based on image information. In addition, a developing device 64 (64Y, 64M, 64C, 64K) is provided that causes yellow, magenta, cyan, and black toners to adhere to the electrostatic latent image formed on the photosensitive drum to visualize the toner image. Yes. The charger 62, the scanner 63, the developing device 64, and the like are arranged around the photosensitive drum 61 along the rotation direction.

  The sheet feeding apparatus 1D is provided at the lower part of the printer main body, and is a sheet feeding cassette 31 to 34 that is a sheet storage unit that stores the sheet S, and a pickup roller 36 that feeds the sheet S stacked and stored in the sheet feeding cassettes 31 to 34. ~ 39. The manual sheet feeding device 30 includes a manual tray 30a that is a sheet storage unit that stacks and stores sheets S, and a paper feed roller 35 that feeds the sheets S stacked on the manual tray 30a.

  When the image forming operation is started, the sheets S are separated and fed one by one from the sheet feeding cassettes 31 to 34 by the pick-up rollers 36 to 39, and then pass through the conveyance vertical path 41, and the registration roller 42. To be transported. In the case of manual sheet feeding, the sheet S stacked on the manual tray 30 a is conveyed by the sheet feeding roller 35 to the registration roller 42 through the conveyance path 40. Here, the registration roller 42 has a function of correcting skew by following the leading edge of the sheet S by creating a loop by the sheet S being abutted. Further, it has a function of conveying the sheet S to the secondary transfer unit 1F at a predetermined timing in accordance with the timing of image formation on the sheet S, that is, a toner image carried on an intermediate transfer belt described later. Yes.

  The intermediate transfer unit 1 </ b> C includes an intermediate transfer belt 67 that is rotationally driven along the arrangement direction of the process stations 60 indicated by an arrow B in synchronization with the outer peripheral speed of the photosensitive drum 61. Here, the intermediate transfer belt 67 applies an appropriate tension to the intermediate transfer belt 67 by the urging force of a driving roller 69, a driven roller 70 that forms a secondary transfer region with the intermediate transfer belt 67 interposed therebetween, and a spring (not shown). The tension roller 68 is stretched.

  The intermediate transfer belt 67 includes four primary transfer rollers 66 (66Y, 66M, 66C, and 66K) that constitute a primary transfer portion, with the intermediate transfer belt 67 sandwiched between the intermediate transfer belt 67 and the photosensitive drum 61, respectively. ing. These primary transfer rollers 66 are connected to a transfer bias power source (not shown). Then, by applying a transfer bias from the primary transfer roller 66 to the intermediate transfer belt 67, each color toner image on the photosensitive drum is sequentially transferred to the intermediate transfer belt 67 and a full color image is formed on the intermediate transfer belt 67. Is done.

  A secondary transfer roller 43 is disposed so as to face the driven roller 70. The secondary transfer roller 43 abuts on the lowermost surface of the intermediate transfer belt 67 and is conveyed by the registration roller 42. The sheet S is nipped and conveyed together with the intermediate transfer belt 67. When the sheet S passes through the nip portion between the secondary transfer roller 43 and the intermediate transfer belt 67, a bias is applied to the secondary transfer roller 43 so that the toner image on the intermediate transfer belt is transferred to the sheet S. Transcribed. The fixing device 45 fixes the toner image formed on the sheet via the intermediate transfer belt 67 to the sheet S. The sheet S holding the toner image is heated and pressed when passing through the fixing device 45. Is added to fix the toner image.

  Next, an image forming operation of the color laser printer 1 configured as described above will be described. When the image forming operation is started, first, in the process station 60Y that is the most upstream in the rotation direction of the intermediate transfer belt 67, the photosensitive drum 61Y is irradiated with laser by the scanner 63Y, and the yellow on the photosensitive drum is detected. A latent image is formed. Thereafter, the latent image is developed with yellow toner by the developing device 64Y to form a yellow toner image.

  Next, the yellow toner image thus formed on the photosensitive drum 61Y is primarily transferred to the intermediate transfer belt 67 in the primary transfer region by the transfer roller 66Y to which a high voltage is applied. Next, the toner image is constituted by the intermediate transfer belt 67 and the photosensitive drum 61M and the transfer roller 66M of the next process station 60M in which the image is formed delayed from the process station 60Y by the time the toner image is conveyed. To the primary transfer area.

  Then, the next magenta toner image is transferred onto the yellow toner image on the intermediate transfer belt by aligning the leading end of the image. Thereafter, the same process is repeated. As a result, the four color toner images are primarily transferred on the intermediate transfer belt 67, and a full-color image is formed on the intermediate transfer belt. Note that the transfer residual toner slightly remaining on the photosensitive drum is collected by the photosensitive cleaner 65 (65Y, 65M, 65C, 65K) and prepared for the next image formation again.

  In parallel with this toner image forming operation, for example, the sheets S stored in the paper feed cassettes 31 to 34 are separated and fed one by one by the pickup rollers 36 to 39 and then conveyed to the registration roller 42. The In the case of manual sheet feeding, the sheet S stacked on the manual tray 30 a is conveyed by the sheet feeding roller 35 to the registration roller 42 through the conveyance path 40. At this time, the registration roller 42 is stopped, and the skew of the sheet S is corrected by abutting the sheet S against the registration roller 42 in the stopped state. In addition, after the skew feeding is corrected, the sheet S is intermediated with the secondary transfer roller 43 by the registration roller 42 which starts rotating at the timing when the leading edge of the sheet and the toner image formed on the intermediate transfer belt 67 coincide. It is conveyed to the nip portion with the transfer belt 67.

  Then, the sheet is nipped and conveyed by the secondary transfer roller 43 and the intermediate transfer belt 67, and when the sheet passes through the nip portion between the secondary transfer roller 43 and the intermediate transfer belt 67, the bias is applied to the secondary transfer roller 43, so that the sheet The toner image on the intermediate transfer belt is secondarily transferred to S. Next, the sheet S on which the toner image is secondarily transferred is conveyed to the fixing device 45 by the pre-fixing conveyance unit 44.

  The fixing device 45 melts and fixes the toner image on the sheet S by applying a predetermined pressing force by an opposing roller or belt or the like and generally a heating effect by a heat source such as a heater. Here, when the sheet S having the fixed image obtained in this way is discharged to the sheet processing apparatus 2 as it is, the sheet S is moved to the discharge conveyance path 51 which is a conveyance path by the inner discharge roller 46. Then, the paper is discharged by the outer paper discharge roller 49.

  When double-sided image formation is performed, the sheet S is directed to the reverse guiding path 52 by a path switching unit (not shown). After that, the sheet S is pulled from the reverse guiding path 52 to the switchback path 55 by the reverse upper roller 53 and the reverse lower roller 54, and by performing a switchback operation to forward and reverse the rotation direction of the reverse lower roller 54, the leading and trailing edges are performed. Are switched and conveyed to the duplex conveyance path 47.

  Next, the sheet S is rejoined by the conveyance rollers 48 a to 48 d provided in the double-sided conveyance path 47 at the same timing as the subsequent sheet S conveyed from the pickup rollers 36 to 39 or the paper supply roller 35. Thereafter, the sheet S is sent to the secondary transfer unit 1F via the registration roller 42. The subsequent image forming process for the back surface (second surface) is the same as that for the front surface (first surface) described above.

  When the sheet S is reversely discharged, the sheet S is pulled from the reverse guide path 52 to the switchback path 55 by the reverse upper roller 53 and the reverse lower roller 54. Then, the pulled sheet S is conveyed by the reverse rotation of the reversing upper roller 53 and the reversing lower roller 54 in the direction opposite to the feeding direction with the rear end when fed in as the head, and is a reversal conveying path. It feeds into the conveyance path 56. Thereafter, the sheet S is reversed so that the downstream end in the sheet transport direction and the upstream end in the sheet transport direction are opposite to each other, and is discharged to the sheet processing apparatus 2 by the outer paper discharge roller 49.

  The sheet S guided by the paper discharge conveyance path 51 or the reverse conveyance path 56 and discharged from the printer main body 1A by the external paper discharge roller 49 is conveyed to a buffer path 81 provided in the buffer unit 3. Thereafter, the sheet S is conveyed to a finisher conveyance path 82 provided in the sheet processing apparatus 2, processed in the sheet processing apparatus 2, and discharged to the sheet discharge tray 2 a.

  FIG. 3 is a perspective view illustrating a configuration of the pre-fixing conveyance unit 44 that is a sheet conveyance device. In FIG. 3, reference numeral 83 denotes a secondary transfer roller 43 that is provided upstream of the pre-fixing transport unit 44 in the sheet transport direction and forms the secondary transfer unit 1F, and the pre-fixing transport unit 44 from the secondary transfer unit 1F. 2 is a secondary transfer unit having a conveyance guide. An entrance guide 84 is provided downstream of the pre-fixing transport unit 44 in the sheet transport direction and guides the sheet to the fixing device 45.

  The pre-fixing conveyance unit 44 includes one endless conveyance belt 90 installed at the center in the width direction orthogonal to the sheet conveyance direction of the conveyance path between the secondary transfer unit 1F and the fixing device 45, A conveyance guide 93 is provided on both sides of the conveyance belt 90 in the width direction. Here, the conveying belt 90 is wound around a driving roller 91 that receives driving from a driving source and drives the conveying belt 90 to travel, and a driven roller 92 that supports the conveying belt 90 together with the driving roller 91 with a predetermined tension. Yes. The conveyor belt 90 is provided with a plurality of suction holes 94.

  Further, the pre-fixing conveyance unit 44 includes a suction force generation unit 44A that generates the suction force shown in FIG. FIG. 4 shows a state where the transport belt 90 is removed from the pre-fixing transport unit 44. Here, the suction force generator includes a suction duct 96 inserted inward of the conveyor belt 90 and a suction fan (suction means) 98 that generates a negative pressure of air by rotational driving. A duct opening 95, which is an opening for sucking air, is provided in a range narrower than the belt width of the conveying belt 90 at a position facing the conveying belt 90 of the suction duct 96.

  The other end of the suction duct 96 is connected to an outer suction duct 97 outside the pre-fixing conveyance unit 44, and a suction fan 98 is connected to the other end of the outer suction duct 97. When the suction fan 98 is driven to rotate, negative air pressure is generated in the duct opening 95 via the outer suction duct 97 and the suction duct 96. As a result, air is sucked through the duct opening 95 and the plurality of suction holes 94 of the conveying belt 90 to generate an air flow as shown in FIG. 5, whereby the sheet S is adsorbed to the conveying belt 90. The

  FIG. 6 is a control block diagram of the pre-fixing conveyance unit 44. In FIG. 6, reference numeral 10 denotes a CPU (arithmetic control unit) which is a control unit that controls the sheet suction operation of the pre-fixing conveyance unit 44. The CPU 10 is connected to a path sensor 11 that is provided upstream of the pre-fixing conveyance unit 44 in the sheet conveyance direction and that inputs position information of the sheet. Further, the CPU 10 includes a user setting unit 12 and a job start switch 13 that are provided in an operation unit (not illustrated) and the like for a user to input a setting value (UI input signal), and a fan motor 14 that drives the suction fan 98. It is connected.

  Then, the CPU 10 determines the suction force based on the setting value (UI input signal) input by the user via the user setting unit 12. Then, an output signal from a control unit (not shown) provided in the printer main body 1A indicating a sheet passing (job) start timing associated with the operation of the job start switch 13 and an output signal (sheet position signal) from the path sensor 11 are provided. Originally, the fan motor 14 is driven and controlled. A control unit (not shown) may also serve as the CPU 10.

  Here, in the present embodiment, the CPU 10 switches the magnitude of the suction force according to the basis weight of the sheet S. Next, suction force switching control during sheet conveyance in the present embodiment will be described with reference to the flowchart shown in FIG. In the present embodiment, the suction force is switched between two levels of strong / weak.

  The CPU 10 determines whether the basis weight setting of the sheet S is 160 gsm or more based on the user's paper passing setting (S100). If the basis weight setting of the sheet S is 160 gsm or more (Y in S100), it is next determined whether the sheet length is 200 mm or less (S101). When the sheet length is 200 mm or less (Y in S101), the drive voltage of the fan motor 14 is set to “strong” (S102).

  That is, when it is determined that the basis weight setting of the sheet S is 160 gsm or more and the sheet length is 200 mm or less based on the user's paper passing setting, the CPU 10 switches the suction force setting to strong. When the basis weight setting of the sheet S is not 160 gsm or more (N in S100) and the sheet length is not 200 mm or less (N in S101), the driving voltage of the fan motor 14 is set to “weak” (S103). ).

  Note that the basis weight value and the sheet length of the sheet S, which are threshold values, differ depending on the distance in the conveyance direction and the relative height of the secondary transfer unit 1F, the pre-fixing conveyance unit 44, and the fixing device 45. These values are not limited to this. Further, the switching of the suction force is not limited to two stages.

  Incidentally, as described above, in order to ensure the suction force on the conveyor belt 90, for example, the duct upper end rib 99 of the duct opening 195 shown in FIG. The distance from 200 should be as short as possible to narrow the gap. However, if the duct upper end rib 99 is configured to have the same height as or higher than the belt inner peripheral surface 200, the transport belt 190 and the duct upper end rib 99 during driving are rubbed, resulting in excessive driving torque. And may cause damage to the belt. However, if the height of the duct upper end rib 99 is made too low, rubbing between the belt inner peripheral surface 200 and the duct upper end rib 99 can be avoided, but when the suction force is reduced, the gap becomes wider and sucked. Power loss increases.

  Therefore, in the present embodiment, as shown in FIGS. 8A and 8B, ribs 101 are provided in a lattice shape in the duct opening 95, and the auxiliary rollers 102 are rotatable on the upper surface of the ribs 101. Provided. Here, the auxiliary roller 102 as the roller member rotates in contact with the belt inner peripheral surface 100 of the conveying belt 90 that moves along the duct opening 95 while receiving the suction force of the suction fan 98.

  The auxiliary roller 102 is provided so as to protrude from the upper surface of the rib 101 in the direction of the conveyance belt 90 so as to be able to rotate by contacting the belt inner peripheral surface 100 of the conveyance belt 90 moving along the duct opening 95. ing. In this embodiment, a total of six auxiliary rollers 102 are provided to rotate in two rows along the sheet conveying direction and three rows in the width direction.

  Further, in the present embodiment, as shown in FIGS. 9A and 9B which are enlarged sectional views of the periphery of the auxiliary roller 102, it is supported by the outer peripheral surface 103 of the auxiliary roller 102, the driving roller 91 and the driven roller 92. The distance P with the belt inner peripheral surface 100 in the state of being set is set to 0.2 mm. That is, the auxiliary roller 102 is disposed at a position 0.2 mm lower than the belt inner peripheral surface 100.

  By setting the distance between the outer peripheral surface 103 of the auxiliary roller 102 and the belt inner peripheral surface 100 in this way, a suction force is generated. When the transport belt 90 is sucked downward by this suction force, the auxiliary roller 102 is It abuts on the belt inner peripheral surface 100. That is, the auxiliary roller 102 contacts the conveyor belt 90 only when the conveyor belt 90 is sucked downward by a suction force.

  Further, since the auxiliary roller 102 contacts only when the conveying belt 90 is sucked downward, the resistance in the wide area by the rib 101 with respect to the conveying belt 90 during driving is less than that in the case where the auxiliary roller 102 is not provided. Become. As a result, it is possible to prevent excessive driving torque of the conveyor belt 90 during traveling driving and damage to the belt.

  In the present embodiment, as shown in FIG. 9, the auxiliary roller 102 is not provided on the outer frame rib 104 which is an outer frame provided at the edge of the duct opening 95. Further, the distance between the outer frame rib 104 and the belt inner peripheral surface 100 supported by the driving roller 91 and the driven roller 92 shown by the line A in FIG. 10 is equal to the outer peripheral surface of the auxiliary roller 102 and the belt inner peripheral surface 100. Is set to be almost the same as the distance.

  As a result, when the conveying belt 90 is sucked by the suction force and the conveying belt inner peripheral surface 00 is lowered to the line B in FIG. 10, the upper end of the outer frame rib 104 comes into contact with the belt inner peripheral surface 100. In addition, since the upper end of the outer frame rib 104 is in contact with the belt inner peripheral surface 100 in this way, the gap between the duct opening 95 and the conveyance belt 90 can be narrowed, and air leakage from the gap is prevented. Can do. Thereby, the suction force on the conveyor belt can be efficiently generated.

  As described above, in this embodiment, the auxiliary roller 102 that contacts the conveying belt 90 that moves while receiving the suction force of the suction fan 98 is provided on the rib 101 provided in the duct opening 95. Further, an outer frame rib 104 that comes into contact with the conveyance belt 90 is provided at the edge of the duct opening 95 so as to protrude toward the conveyance belt.

  The friction between the conveyor belt 90 and the rib 101 (suction duct 96) can be reduced by bringing the auxiliary roller 102 into contact with the conveyor belt 90 that moves while receiving the suction force of the suction fan 98. Excessive drive torque and belt damage can be prevented. Further, by providing the outer frame rib 104 at the edge of the duct opening 95, the gap (interval) between the transport belt 90 and the outer frame rib 104 (suction duct 96) can be reduced, and the gap from the gap can be reduced. Loss of suction power can be prevented.

  That is, by providing the auxiliary roller 10 and the outer frame rib 104 in the duct opening 95, even when the suction force increases, the stress on the conveyor belt 90 can be minimized, and on the conveyor belt 90, The maximum suction force can be extracted without loss. Further, by pulling out the suction force on the conveyor belt 90 to the maximum without loss, the suction force can be reduced, so that the friction when the conveyor belt 90 contacts the outer frame rib 104 can be reduced. Can save energy.

DESCRIPTION OF SYMBOLS 1 ... Color laser printer, 1A ... Printer main body, 1B ... Image formation part, 1F ... Secondary transfer part, 10 ... CPU, 44 ... Pre-fixing conveyance unit, 44A ... Suction force generation part, 45 ... Fixing device, 90 ... Conveyance Belt 91 91 drive roller 92 driven roller 94 suction hole 95 duct opening 96 suction duct 98 suction fan 101 rib 102 102 auxiliary roller 104 outer frame rib S Sheet

Claims (6)

While conveying a sheet, an endless conveyance belt having a plurality of suction holes;
A suction duct that is inserted inward of the conveyor belt and provided with an opening for sucking air at a position facing the conveyor belt;
A suction means connected to the suction duct, for sucking air through the openings of the suction duct and the plurality of suction holes of the transport belt to attract the sheet to the transport belt;
A roller member provided in the opening and rotating in contact with the conveyor belt that moves while receiving the suction force of the suction means when the sheet is adsorbed;
A sheet conveying apparatus comprising:   The sheet conveying apparatus according to claim 1, further comprising an outer frame portion provided at an edge of the opening and abutting against the conveying belt.   The sheet conveying apparatus according to claim 2, wherein the outer frame portion is provided to protrude toward the conveying belt.   The sheet conveying apparatus according to claim 2, wherein a rib is provided in the opening, and the roller member is provided on the rib so as to protrude toward the conveying belt.   The sheet conveying apparatus according to claim 4, wherein a distance between the rib and the conveying belt when the sheet is not attracted is wider than a distance between the outer frame portion and the conveying belt.   An image forming apparatus comprising: an image forming unit; and the sheet conveying device according to claim 1.

Images