JP2012233999A - Recording medium conveying device, and image forming apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording medium conveying device that provides stable conveyance force at a low cost, ensures stable behavior of a recording medium in entering the conveying device, and suppresses conveyance skew to stably convey the recording medium.SOLUTION: A recording medium conveying device 400 includes a conveying member 402 that conveys a sheet-like recording medium P carrying a toner image by adsorbing the recording medium P on a surface 402a thereof. In the recording medium conveying device 400, a conveying member 402B at a central part in a width direction W that intersects with the conveying direction X of the recording medium is arranged closer to a contact surface Pd of the recording medium adsorbed by the surface of the conveying member, than conveying members 401A, 401C that are provided adjacent to both-ends of the conveying member 402B.

Description

  The present invention relates to a conveyance device that conveys a recording medium, and an image forming apparatus such as a copying machine, a printer, and a facsimile machine including the recording medium, and a multifunction machine having a plurality of these functions.

In an image forming apparatus provided with a recording medium conveyance device that conveys a recording medium to which a toner image has been transferred to a fixing device, from the viewpoint of stably holding an unfixed toner image on the recording medium, The conveying member cannot be brought into contact with the recording surface. For this reason, there has been proposed a suction type recording medium conveying apparatus that uses a conveying belt as a conveying member and conveys the recording medium while adsorbing the back side opposite to the recording surface of the recording medium to the surface of the conveying belt.
For example, Patent Document 1 uses a conveyance belt provided with an intake hole through which intake air can be passed from the outside to the inside of the conveyance belt to convey a recording medium while adsorbing the belt surface, and according to the paper size. Thus, there is disclosed a recording medium transport apparatus that can selectively switch a region where intake air acts.
Patent Document 2 proposes a recording medium transport apparatus that detects the floating of the recording medium when the recording medium enters the transport apparatus by a sensor and can switch the air volume of the suction fan according to the detection result. .

  In the case of a suction method in which one side (back surface) side of the recording medium is conveyed while being attracted to the conveyance belt, the conveyance direction on the paper entry side is compared with a roller method in which the recording medium is conveyed while pinching the front side and the back side with rollers. The recording medium may cause a so-called conveyance skew such as meandering and shifting due to variations in the positional accuracy of the recording medium in the orthogonal width direction and the wavy state of the recording medium. Such a conveyance skew not only increases the possibility of causing a jam, but also makes the approaching posture of the recording medium into the fixing device unstable, and may cause a wrinkle of the recording medium in the fixing device.

In Japanese Patent Laid-Open No. 2004-260688, since the area where the intake air acts is selectively switched according to the paper size, a stable conveying force can be applied to the recording medium regardless of the paper size, but in the width direction on the paper entry side. It is not considered to eliminate the conveyance skew caused by the variation in the positional accuracy of the recording medium and the wavy state of the paper.
In Patent Document 2, the air volume of the suction fan is changed in accordance with the floating of the recording medium so that the recording medium can be transported with a stable transport force without insufficient suction. Therefore, when the recording medium enters the transport device However, it is not considered to suppress the conveyance skew of the recording medium when the recording medium is adsorbed on the conveyance belt. In addition, it is necessary to provide a sensor for detecting the floating of the recording medium, and there is still room for improvement from the viewpoint of downsizing and cost reduction of the apparatus.
An object of the present invention is to provide a recording medium conveying apparatus that pays attention to the above-mentioned problems and has a stable behavior on a conveying member and can stably convey a recording medium while suppressing a conveying skew.
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can suppress the occurrence of a jam and the generation of wrinkles in a fixing device and obtain a high-quality printed matter.

  In order to achieve the above object, in a recording medium conveying apparatus according to the present invention having a conveying member that adsorbs and conveys a sheet-like recording medium carrying a toner image to the surface thereof, the recording medium conveying apparatus intersects the recording medium conveying direction. The basic configuration is that the central portion of the conveying member in the width direction is arranged closer to the contact surface of the recording medium adsorbed on the surface than both ends of the conveying member.

Specifically, in the recording medium conveying apparatus according to the present invention, a plurality of conveying members are stretched by a plurality of roller members and arranged in the width direction, and the center of the recording medium among the plurality of conveying members is arranged. The outer diameter of the roller member around which the conveying member arranged at the position opposite to the recording medium is wound is made larger than the outer diameter of the roller member around which the other conveying member is wound, so that the contact surface of the recording medium Placed close together.
In the recording medium conveying apparatus according to the present invention, the plurality of roller members around which each conveying member is wound have a driving roller and a driven roller, and at least the driving roller is rotated by a common driving source with the same outer diameter. The outer diameter of the driven roller around which the conveying member arranged at the position facing the central portion of the recording medium is wound is made larger than that of the other driving rollers and driven rollers.
In the recording medium conveying apparatus according to the present invention, the large-diameter roller member is arranged on the downstream side in the medium conveying direction.
In the recording medium conveying apparatus according to the present invention, a plurality of conveying members are stretched by a plurality of roller members and arranged in the width direction, and a position facing a central portion of the recording medium among the plurality of conveying members. The roller member around which the conveying member arranged on the recording medium is wound is arranged closer to the contact surface of the recording medium than the roller member around which the other conveying member is wound.
In the recording medium conveying apparatus according to the present invention, the plurality of roller members around which each conveying member is wound have a driving roller and a driven roller, and the driving roller and the driven roller have the same outer diameter.
In the recording medium conveying apparatus according to the present invention, the driven roller around which the conveying member arranged at a position facing the central portion of the recording medium is wound is disposed close to the contact surface of the recording medium.
In the recording medium conveying apparatus according to the present invention, the driven roller is arranged on the downstream side in the medium conveying direction.
In the recording medium conveying apparatus according to the present invention, a plurality of conveying members are stretched by a plurality of roller members having the same outer diameter and arranged in the width direction, and each conveying member is arranged outwardly from the same surface. The convex portion of the conveying member that has a plurality of convex portions extending in the direction opposite to the central portion of the recording medium is set higher than the convex portions of the other conveying members.
An image carrier, a transfer unit that transfers a toner image formed on the image carrier to a recording medium, a fixing device that fixes the toner image on the recording medium onto which the toner image is transferred, and a transfer unit The image forming apparatus according to the present invention includes a recording medium conveying device according to any one of the above as a conveying unit. The image forming apparatus includes a conveying unit that sucks and conveys the recording medium onto which the toner image is transferred to the fixing device. It is a feature.

According to the present invention, since the recording medium is attracted and conveyed by the surface located at the central portion of the conveying member, the rotational moment of the recording medium due to the variation in the conveying force of the conveying members at both ends is suppressed, and when the recording medium enters or is conveyed The conveyance skew inside can be suppressed.
According to the present invention, the recording medium conveying device that suppresses the conveyance skew when entering the recording medium or during conveyance is used as the conveying means for attracting and conveying the recording medium to the fixing device. It is possible to obtain a high-quality printed matter by suppressing the generation.

1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 3 is a side view illustrating a basic configuration of a recording medium conveyance device. 1 is a perspective view illustrating a first embodiment of a recording medium conveyance device. FIG. 3 is a side view illustrating a characteristic configuration of the recording medium conveyance device according to the first embodiment. FIG. 3 is a cross-sectional view viewed from the downstream side in the transport direction for explaining the operation of the recording medium transport device according to the first embodiment. The perspective view which shows 2nd Embodiment of a recording-medium conveying apparatus. The side view which shows the characteristic structure of the recording-medium conveying apparatus which concerns on 2nd Embodiment. Sectional drawing seen from the conveyance direction downstream explaining the effect | action of the recording-medium conveying apparatus which concerns on 2nd Embodiment. It is a figure which shows the special structure of 3rd Embodiment of a recording medium conveying apparatus, (a) is sectional drawing of the characteristic part of the conveying member arrange | positioned in the center, (b) is the conveying member arrange | positioned at both sides Sectional drawing of a characteristic part. Sectional drawing seen from the conveyance direction downstream explaining the effect | action of the recording-medium conveying apparatus which concerns on 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The image forming apparatus shown in FIG. 1 is a printer capable of full color printing. The printer includes an endless belt-like intermediate transfer belt 11 as an intermediate transfer member inside the image forming unit 100. The intermediate transfer belt 11 is wound around the driving roller 14, the driven rollers 15, 15 ′ and the secondary transfer counter roller 16 in such a posture that the side view is an inverted triangular shape. It is endlessly moved in the clockwise direction in FIG. Between the driven roller 15 ′ and the secondary transfer counter roller 16, a tension roller 18 that presses the intermediate transfer belt 11 from the outside to the inside to apply tension is disposed. Above the intermediate transfer belt 11, four image forming units 18Y, 18M, 18C, and 18K for forming toner images of Y (yellow), M (magenta), C (cyan), and K (black) are provided. Arranged along the belt moving direction.

  The image forming units 18Y, 18M, 18C, and 18K include drum-shaped photoconductors 20Y, 20M, 20C, and 20K as image carriers, developing units 4Y, 4M, 4C, and 4K, and photoconductor cleaning devices 7Y, 7M, and 7C, 7K. The photoreceptors 20Y, 20M, 20C, and 20K are in contact with the intermediate transfer belt 11 to form primary transfer nips for Y, M, C, and K, respectively, and are rotated counterclockwise in the drawing by a driving unit (not shown). It can be driven to rotate. The developing units 4Y, 4M, 4C, and 4K are for developing the electrostatic latent images formed on the photoreceptors 20Y, 20M, 20C, and 20K with toners of Y, M, C, and K. The photoconductor cleaning devices 7Y, 7M, 7C, and 7K clean the transfer residual toner attached to the photoconductors 20Y, 20M, 20C, and 20K after passing through the primary transfer nip. In this printer, a tandem image forming unit is configured by four image forming units 18Y, 18M, 18C, and 18K arranged in the belt moving direction.

  In the printer unit 100, optical writing units 21A and 21B are disposed above the tandem image forming unit. These optical writing units 21A and 21B perform optical writing processing by optical scanning on the surfaces of the photoconductors 20Y, 20M, 20C, and 20K that are rotationally driven in the counterclockwise direction in the drawing to form an electrostatic latent image. To form. Prior to the optical writing process, the surfaces of the photoconductors 20Y, 20M, 20C, and 20K are made uniform by the uniform charging units 3Y, 3M, 3C, and 3K included in the image forming units 18Y, 18M, 18C, and 18K, respectively. It is charged like this.

  The intermediate transfer unit 10 including the intermediate transfer belt 11 has primary transfer rollers 6Y, 6M, 6C, and 6K inside the loop of the intermediate transfer belt 11. These primary transfer rollers 6Y, 6M, 6C, and 6K press the intermediate transfer belt 11 toward the photoreceptors 20Y, 20M, 20C, and 20K behind the primary transfer nips for Y, M, C, and K. Yes.

  A secondary transfer roller 22 is disposed below the intermediate transfer belt 11. The secondary transfer roller 22 is in contact with the secondary transfer counter roller 16 in the loop of the intermediate transfer belt 11 from the belt front surface side to form a secondary transfer nip 29. A sheet-like recording medium P (hereinafter referred to as “recording sheet P”) is fed into the secondary transfer nip 29 at a predetermined timing. Then, the four-color superimposed toner image on the intermediate transfer belt 11 is collectively secondary-transferred onto the recording sheet P at the secondary transfer nip 29.

  An output device such as a personal computer (not shown) is connected to the printer via a signal line such as a printer cable or a network cable, and the control unit 300 receives image information output from the output device. When this image forming apparatus is not a printer but a copying machine, for example, a known scanner that reads image information of a document placed on contact glass with a reading sensor and sends the read image information to the control unit 300 of the printer unit 100. It is good also as a structure provided with the part.

  Based on the received image information, the control unit 300 controls light sources such as laser diodes and LEDs in the optical writing units 21A and 21B of the printer unit 100 to generate laser writing light for Y, M, C, and K. Then, the photoconductors 20Y, 20M, 20C, and 20K are optically scanned. By this optical scanning, electrostatic latent images are formed on the surfaces of the photoreceptors 20Y, 20M, 20C, and 20K, and the latent images are developed into Y, M, C, and K toner images through a predetermined development process.

  The paper feed unit 200 located below the printer unit 100 separates the fed recording sheet P from the paper feed roller 42 that feeds the recording sheet P from the paper feed cassettes 44 arranged in multiple stages in the paper bank 43. A separation roller 45 that leads to the paper feed path 46 and a transport roller 47 that transports the recording sheet P to a paper feed path 48 formed in the printer unit 100 are provided.

  In addition to the paper feed unit 200, manual paper feed is also possible, and the manual feed tray 51 for manual feed and the recording sheet P on the manual feed tray 51 toward the manual feed path 53 one by one. A paper feed separation roller 50 that feeds the paper separately is also provided. In the printer unit 100, the manual paper feed path 53 joins the paper feed path 48.

  Near the end of the paper feed path 48, a registration roller pair 49 is disposed. The registration roller pair 49 is a well-known one having a function of sandwiching the recording sheet P conveyed in the paper feed path 48 between the rollers and then feeding it toward the secondary transfer nip 29 at a predetermined timing.

  In the printer according to the present embodiment, when printing a color image, when the control unit 300 receives color image information, the recording sheet P having a size corresponding to the image information is fed to the paper feed path 48. Along with this, the drive roller 14 is rotationally driven by a drive motor (not shown) to move the intermediate transfer belt 11 endlessly in the clockwise direction in the drawing. At the same time, after starting rotation of the photoconductors 20Y, 20M, 20C, and 20K of the image forming units 18Y, 18M, 18C, and 18K, uniform charging processing, optical writing processing for the photoconductors 20Y, 20M, 20C, and 20K, Perform development processing. The Y, M, C, and K toner images formed on the surfaces of the photoreceptors 20Y, 20M, 20C, and 20K by these processes are sequentially superimposed on the primary transfer nips for Y, M, C, and K. Primary transfer is performed on the intermediate transfer belt 11 to form a four-color superimposed toner image.

  In the paper supply unit 200, one of the paper supply rollers 42 is selectively rotated according to the size of the recording sheet, and the recording sheet P is sent out from one of the three paper supply cassettes 44. The fed recording sheets P are separated one by one by the separation roller 45, introduced into the paper feed path 46, and then sent to the paper feed path 48 in the printer unit 100 via the conveyance roller 47. Further, when the manual feed tray 51 is used, the paper feed separation roller 50 of the manual feed tray 51 is driven to rotate, and is fed into the manual feed path 53 while separating the recording sheets on the tray, so Near the end. In the vicinity of the end of the paper feed path 48, the recording sheet P stops by abutting the leading edge against the registration roller pair 49. Thereafter, when the registration roller pair 49 is rotationally driven at a timing that can synchronize with the four-color superimposed toner image on the intermediate transfer belt 11, the recording sheet P is fed into the secondary transfer nip 29 and 4 on the intermediate transfer belt 11. Adheres closely to the color superimposed toner image. Then, secondary transfer is performed collectively on the recording sheet P by an action such as nip pressure or transfer electric field.

  The recording sheet P on which the four-color superimposed toner image has been transferred at the secondary transfer nip 29 is fed into the fixing device 25 by the recording medium transport unit 400. The four-color superimposed toner image is fixed on the surface of the recording sheet P by being pressed and heated by the fixing device 25 being sandwiched in the fixing nip between the pressure roller 27 and the fixing belt 26. The recording sheet P on which the color image has been formed in this manner is stacked as a one-side printed matter on the discharge tray 57 outside the apparatus via the discharge roller pair 56.

  When an image is also formed on the other surface (back surface) side of the recording sheet P, the recording sheet P is discharged from the fixing device 25, and then the path is switched by a switching claw (not shown). The sheet is fed to the sheet reversing device 58 disposed below the recording medium conveying unit 400. Then, after being turned upside down, it is returned again to the registration roller pair 49 and then passes again through the secondary transfer nip 29 and the fixing device 25, and onto the discharge tray 57 outside the apparatus via the discharge roller pair 56. Stacked as a double-sided print.

  After passing through the secondary transfer nip 29, the surface of the intermediate transfer belt 11 before entering the primary transfer nip for Y where the primary transfer process is the most upstream of the four colors is placed on the surface of the belt cleaning device 17. The cleaning members are in contact with each other, and residual toner adhering to the belt surface is cleaned by these cleaning members.

  Next, an embodiment of a recording medium transport apparatus 400 that is a main part of the present invention will be described. The recording sheet P carries the toner image by passing through the secondary transfer nip 29 and is transported to the fixing device 25, but is transported by the recording medium transport device 400 between the secondary transfer nip 29 and the fixing device 25. Is done. Since the toner image on the recording sheet P being conveyed by the recording medium conveying device 400 is unfixed, when the conveying member included in the recording medium conveying device 400 contacts the surface PA of the recording sheet P on which the toner image is transferred. The toner image is disturbed. For this reason, the recording medium conveying apparatus 400 employs a suction method. As shown in FIG. 2, the recording medium conveying apparatus 400 includes a conveying belt 402 as a conveying member in which a plurality of intake holes 401 are formed, and a driving roller 403 and a driven roller 404 as roller members around which the conveying belt 402 is wound. And a suction means 405 disposed in a loop of the conveying belt 402 wound around the driving roller 403 and the driven roller 404.

  A plurality of air intake holes 401 are formed on the entire surface of the conveyance belt 402, and a conveyance path that connects the belt surface 402 a between the secondary transfer nip 29 and the fixing device 25 when wound around the driving roller 403 and the driven roller 404. It arrange | positions so that 60 conveyance surfaces may be formed. In this embodiment, the driving roller 403 is disposed near the secondary transfer nip 29 on the upstream side in the conveyance direction X of the recording sheet P, and the driven roller 404 is disposed near the fixing device 25 on the downstream side in the conveyance direction X. ing.

  The suction means 405 is disposed in the loop of the conveyor belt 402, and generates a suction force on the belt surface 402a by being rotated by a support plate 406 having a plurality of holes 406a and a drive motor (not shown). The suction fan 407 is provided, and the support plate 406 and the casing 407a of the suction fan 407 are provided with ducts 408 whose both ends are respectively connected. When a drive motor (not shown) is driven to rotate by a drive command from the control unit 300, the suction fan 407 rotates to discharge the air in the duct 408 downward, thereby generating a suction force on the belt surface 402a. . That is, the belt surface 402a constitutes an adsorption surface that adsorbs the back surface Pd serving as the contact surface of the recording sheet P that is in contact with the belt surface.

  Such a recording medium conveying apparatus 400 is configured as one unit. In the case of the conventional suction method, one unit is arranged in the width direction W perpendicular to the recording medium conveying direction, and the conveying belt 402 is arranged. The height of the belt surface 402a was the same in the width direction W. Even when there are a plurality of conveyor belts, the height of the belt surface of each conveyor belt is substantially the same except for attachment errors.

Since the recording sheet P that has passed through the secondary transfer nip 29 is guided from the driving roller 403 side to the belt surface 402A of the conveying belt 402 with respect to the recording medium conveying device 400, the driving roller 403 side is directed to the recording medium conveying device 400. It becomes the entry side of the recording medium. In the case of such a suction-type recording medium conveying apparatus 400, the recording sheet P is inclined on the belt surface 402A of the conveying belt 402 due to the positional accuracy with respect to the recording medium entering position on the driving roller 403 side or the waviness of the recording sheet P. There is a case where a line (conveyance skew) occurs.
(First embodiment)
In order to suppress such a conveyance failure, in this embodiment, the recording medium conveyance device 400 shown in FIG. 2 is replaced with three conveyance units 400A, 400B, and 400C in the width direction W as shown in FIG. The belts 402Aa, 402Ba, and 402Ca of the conveyance belts 402A, 402B, and 403C of the respective conveyance units have different heights while being arranged to constitute the conveyance unit. In addition, the components which comprise each conveyance unit are distinguished by attaching | subjecting the code | symbol of A-C.

  The number of conveying units may be changed as appropriate according to the maximum width of the recording sheet P used in the printer. In this embodiment, three transport units 400A to 400C are arranged, but the number of units is not limited to three, and is configured as one transport unit including transport belts 402A, 402B, and 402C. In short, it is only necessary that a plurality of conveying belts 402 are provided and the height of the belt surface serving as the suction surface is different in the width direction W.

  In this embodiment, among the plurality of transport units 400A to 400C, the height of the belt surface 402Ba of the transport belt 402B of the transport unit 400B disposed at the center in the width direction W is set to the belt surface of the transport belts 402A and 402C located on both sides. Arranged above the positions of 402Aa and 402Ca, the central portion Pa of the recording sheet P is configured to be in close contact with the conveying belt 402B. In the first embodiment, the outer diameters (diameters) of the drive rollers and the driven rollers of the transport units are all the same.

  The drive rollers 403A, 403B, and 403C located on the upstream side in the transport direction X of each transport unit are disposed on a common drive shaft 410, and the drive shaft 410 is rotationally driven by a common drive motor 411. Thus, it is configured to rotate integrally with the drive shaft 410.

  The driven rollers 404A, 404B, and 404C included in each transport unit are rotatably supported by support shafts 412A, 412B, and 412C that are individually supported by a frame (not shown) of each unit. In this embodiment, the heights of the belt surfaces 402Aa, 402Ba, and 402Ca on the driving rollers 403A to 403C are the same, and the heights of the belt surfaces 402Aa, 402Ba, and 402Ca on the driven rollers 404A, 404B, and 404C are different. ing. Specifically, as shown in FIGS. 4 and 5, the support shafts 412A and 412C are arranged on the same axis, the belt surfaces 402Aa and 402Ca have the same height, and the support shaft 412B is supported by the support shafts 412A and 412C. The belt surface 402Ba is positioned higher than the belt surfaces 402Aa and 402Ca.

  With such a configuration, when the central portion Pa of the recording sheet P being conveyed toward the recording medium conveying device 400 reaches the recording medium conveying device 400, the rear surface Pd of the central portion is formed on the conveying belt 402B. Since the sheet is adsorbed, the conveyance force can be dominantly applied to the central portion Pa of the recording sheet P, and the generation of the rotational moment due to the conveyance force variation acting on both ends Pb and Pc of the recording sheet P can be suppressed. In addition, the recording sheet P can be stably conveyed to the fixing device 25 without being skewed when entering the recording medium or during conveyance.

  3 to 5 mainly illustrate the arrangement and height of the conveying belt 402, the driving rollers 403A to 402C, the driven rollers 404A to 404C and the conveying belts 402A to 402C of the conveying units 400A, 400B, and 400C. It is the schematic which showed only.

  By arranging a plurality of the conveyor belts 402 in the width direction W in this way, it is possible to avoid an increase in the size of the mold for molding the conveyor belts 402 compared to the case of using a single conveyor belt, and therefore recording at a low cost. The medium conveyance device 400 can be configured. In addition, by configuring the transport member with a plurality of transport belts 402A to 402C, it is possible to easily configure the surface property, shape, position, and the like of the transport bell 402B located in the center to be different from other belts.

  In this embodiment, since the outer diameters of the driving rollers 403A to 403C and the driven rollers 404A to 404C, which are roller members around which the conveyor belts 402A to 402C are wound, are the same size, the specifications of the roller members can be made common. The component configuration can be simplified and the cost can be reduced.

According to the present embodiment, only the driven roller 404B around which the conveyance belt 402B disposed at a position facing the central portion Pa of the recording sheet P is set higher than the other driven rollers 404A and 404C, so that the recording sheet is obtained. Since it is arranged close to the back surface Pd of P, the drive shaft 410 that rotationally drives the drive rollers 403A to 403C can be the same drive shaft. Further, since the driven roller 404B, which is higher in height than the other driven rollers 404A and 404C, is arranged on the downstream side in the conveyance direction X, it is possible to suppress conveyance failure after the recording sheet P is removed from the secondary transfer nip 29. can do.
(Second Embodiment)
A second embodiment will be described with reference to FIGS. In this embodiment, in order to make the belt surface 402Aa of the conveyance unit 400B arranged in the center in the width direction W described in the first embodiment higher than the belt surfaces 402Aa and 402Ca of the other conveyance units 400A and 400C, The outer diameter (diameter) D1 of the driven roller 404B that stretches the belt 402B is larger than the outer diameter (diameter) D2 of the driven rollers 404A and 404C. Also in this embodiment, the outer diameters (diameters) of the driving rollers 403A to 403C other than the driven roller 404B and the driven rollers 404A and 404C are the same.

  For this reason, in this embodiment, it is not necessary to change the position of the support shaft as in the first embodiment, so that the driven rollers 404A to 404C are rotatably supported by the same support shaft 413. The support shaft 413 is attached to a frame of a unit (not shown).

  In this embodiment, since the plurality of conveyor belts 402A, 402B, and 402C are driven by the same drive shaft 410, the surface speed of the conveyor belt 402B wound around the roller member having an increased diameter is the other conveyor belts 402A, 402C. Therefore, only the diameter of the driven roller 404B is set larger than that of the driven rollers 404A and 404C.

  With such a configuration, when the central portion Pa of the recording sheet P being conveyed toward the recording medium conveying device 400 reaches the recording medium conveying device 400, the rear surface Pd of the central portion is formed on the conveying belt 402B. Since the sheet is adsorbed, the conveyance force can be dominantly applied to the central portion Pa of the recording sheet P, and the generation of the rotational moment due to the conveyance force variation acting on both ends Pb and Pc of the recording sheet P can be suppressed. In addition, the recording sheet P can be stably conveyed to the fixing device 25 without being skewed when entering the recording medium or during conveyance.

  In this way, by making the outer diameter (diameter) D1 of the driven roller 404B larger than the outer diameter (diameter) D2 of the other driven rollers 404A and 404C, the belt surface 402Aa of the central conveying belt 402B is recorded. Since it is close to the back surface Pd of the sheet P, all of the plurality of driven rollers 404A to 404C are supported by a single support shaft 413, and the drive rollers 403A to 402C are also supported by a single drive shaft 410. Therefore, the apparatus configuration can be simplified.

  Since the conveyance of the recording sheet P after the recording sheet P is removed from the secondary transfer nip 29 tends to be more unstable than the state in which the recording sheet P is sandwiched in the secondary transfer nip 29, the diameter is increased. The driven roller 404B is disposed on the downstream side in the transport direction X. 6 to 8 are mainly for explaining that the outer diameter of the driven roller 402B is made larger than that of the other roller members so that the height of the conveyor belt 402 is higher than those of the other conveyor belts 402A and 402C. The schematic diagram shows only the driving rollers 403A to 402C, the driven rollers 404A to 404C and the conveying belts 402A to 402C of the conveying units 400A, 400B and 400C.

  The difference in height of the surface PA of the recording sheet P between both sides and the center is preferably about 1 mm to 3 mm. This is because if the difference between the outer diameters of the driven roller 404B and the driven rollers 404A and 404C is too large, the recording sheet P is warped by the conveying device, which may cause wrinkles during fixing.

  As described above, in the configuration in which the central conveyance belt 402B is brought close to the recording sheet P, it is desirable to make the conveyance belt 402B come close to the back surface Pd of the recording sheet P on the downstream side in the conveyance direction. In the process in which the recording sheet P is transported to each transport belt, the transport of the recording sheet P is less disturbed when the recording sheet P is sandwiched between the secondary transfer nips 29. Rather, the trailing edge of the recording sheet P is After passing through the secondary transfer nip 29, the behavior of the recording sheet P tends to become unstable.

  For the reasons described above, it is desirable that at least the downstream side of the transport unit 400B occupies a position closer to the recording sheet P on the belt surface 402Aa of the transport belt 402B than the upstream side.

  According to this embodiment, only the driven roller 404B at the center disposed on the support shaft 413 is formed to have a larger diameter than the outer diameters of the other driven rollers 404A and 404C and the drive rollers 403A to 403C. Since the outer diameters of the driving rollers 403A to 403C driven by the same are set to the same, the driving speeds of the plurality of conveying belts 402A to 402C can be set to the same, and the central conveying belt 402B and the conveying belts located on both sides thereof can be set. A conveyance failure due to a speed difference with the belts 402A and 402C can be suppressed.

In this embodiment, since the driven roller 404B having a large diameter is disposed on the downstream side in the transport direction X, it is possible to suppress a transport failure after the recording sheet P is removed from the secondary transfer nip 29.
(Third embodiment)
In the above two forms, the position of the belt surface 402Ba that becomes the suction surface of the conveyor belt 402B is changed to a position higher than the other conveyor belts 402A and 402C by changing the position of the driven roller 404B and the outer diameter of the driven roller 404B. In this embodiment, the suction surface is positioned higher than the other transport belts 402A and 402C by the transport belt 402B itself. is there.

  On the belt surface of the conveying belt, ribs serving as a plurality of convex portions are formed for the purpose of preventing the occurrence of fixing unevenness due to the temperature difference of the recording sheet due to the presence / absence region of the intake holes, and between the conveying belt and the recording sheet. There is a case where a recording sheet is sucked and conveyed by providing a space of a certain distance between them.

  Therefore, in the present embodiment, a plurality of ribs 420B extending outward from the belt surface 402Ba are formed on the belt surface 402Ba of the conveying belt 402B located at the center shown in FIG. 9A, and a space 421B is formed between the adjacent ribs 420B. A plurality of ribs 420A and 420C extending outwardly from the belt surfaces 402Aa and 402Ca of the conveyor belts 402A and 402C positioned on both sides of the conveyor belt 402B shown in FIG. Spaces 421A and 421C were formed between the ribs 420A and 420C, respectively. The height h1 of the rib 420B of the conveyor belt 402B is set to be higher than the height h2 of the ribs 420A and 420C of the conveyor belts 402A and 402C. In this embodiment, the recording sheet P is attracted to the upper portions 420Aa to 420Ca of the ribs 420A to 420C of the transport belts 402A to 402C. In this embodiment, the driving rollers 403A to 403C and the driven rollers 404A to 404C as roller members around which the conveyor belts 402A to 402C are wound have the configurations of the second embodiment.

  Even if the conveyance belt itself is configured in this way, as shown in FIG. 10, the recording sheet P is most strongly adsorbed and brought into contact with the conveyance belt 402B located at the center, and the first and second embodiments described above. Similarly, it is possible to obtain the same conveyance stability effect as when the height of the conveyance belt 402B located at the center is increased.

  Further, by using the same drive shaft 410 and driven shaft 413 and a roller member of the same size, the suction surface (contact position) of the transport belt 402B disposed in the center is set to be a recording sheet more than the other transport belts 402A and 402C. Since they are close to P, the driving speeds of the plurality of conveyor belts 402A to 402C can be set to be the same as in the above embodiment, and the central conveyor belt 402B and the conveyors positioned on both sides thereof can be set. The conveyance failure due to the speed difference with the belts 402A and 402C can be suppressed, and the apparatus configuration can be simplified.

  In this embodiment, the height h1 of the rib 420B of the conveyance belt 402B disposed in the center is set to be twice that of the ribs 420A and 420C of the conveyance belts 402A and 401C located on both sides of the conveyance belt 402B. Specifically, the height of the rib 420B at the center is set to 1 mm, and the height h2 of the ribs 420A and 420C of the conveyor belts 402A and 402C is set to about 0.5 mm.

  In each of the above-described embodiments, the case where the three conveying belts 402A, 402B, and 402C are used as the conveying member has been described. However, the application form of the present invention is not limited to the three conveying belts, for example, five But you can. Alternatively, even in the case of one transport belt, the center thereof may be formed thicker than both end sides, and may be disposed so as to be close to the back surface Pd of the recording sheet P.

25 Fixing device 29 Transfer section 40 (Y, M, C, K) Image carrier 400 (A to C) Recording medium conveying device (conveying means)
402 (A to C) Conveying member 402 (Aa to Ca) surface 403 (A to C) Driving roller (roller member)
404 (A to C) driven roller (roller member)
410 Common drive source 420 (A to C) Plural convex portions D1, D2 Outer diameters of roller members h1, h2 Height of convex portion P Sheet-like recording medium Pd Recording medium contact surface X Conveying direction W Width direction

JP 2006-1686 A JP 2006-176265 A

Claims (10)

In a recording medium conveying apparatus provided with a conveying member that adsorbs and conveys a sheet-like recording medium carrying a toner image on its surface,
The central portion of the transport member in the width direction intersecting the transport direction of the recording medium is disposed closer to the contact surface of the recording medium that is attracted to the surface than both ends of the transport member. A recording medium carrying device. The recording medium conveying apparatus according to claim 1,
The conveying member is stretched by a plurality of roller members and arranged in the width direction,
Out of these plural conveying members, the outer diameter of the roller member around which the conveying member arranged at the position facing the central portion of the recording medium is wound, and the outer diameter of the roller member around which the other conveying member is wound. And a recording medium transporting device having a larger diameter than the contact surface of the recording medium. The recording medium conveying apparatus according to claim 2,
The plurality of roller members around which the respective conveying members are wound have a driving roller and a driven roller,
At least the drive roller is rotationally driven by a common drive source with the same outer diameter,
The driven roller on which the conveying member disposed at a position facing the central portion of the recording medium is wound has a larger outer diameter than the driving roller and the driven roller. Conveying device. In the recording medium transport apparatus according to claim 2 or 3,
The recording medium transporting apparatus, wherein the large-diameter roller member is disposed on the downstream side in the medium transporting direction. The recording medium conveying apparatus according to claim 1,
The conveying member is stretched by a plurality of roller members and arranged in the width direction,
Among these plurality of conveying members, a roller member around which a conveying member arranged at a position facing the central portion of the recording medium is wound, and the recording medium is brought into contact with a roller member around which another conveying member is wound. A recording medium transporting apparatus, wherein the recording medium transporting apparatus is disposed close to a surface. The recording medium carrying device according to claim 5,
The plurality of roller members on which the respective conveying members are wound have a driving roller and a driven roller, and the driving roller and the driven roller have the same outer diameter. The recording medium conveying apparatus according to claim 6, wherein
A recording medium conveying apparatus, wherein a driven roller around which a conveying member arranged at a position facing a central portion of the recording medium is wound is arranged close to a contact surface of the recording medium. The recording medium carrying device according to claim 7,
The recording medium transporting apparatus, wherein the driven roller is disposed on the downstream side in the medium transporting direction. The recording medium conveying apparatus according to claim 1,
The conveying member is stretched by a plurality of roller members having the same outer diameter, and a plurality of the conveying members are arranged in the width direction,
Each conveying member has a plurality of convex portions extending outward from the surface on the surface thereof. The convex portion of the conveying member arranged at a position facing the central portion of the recording medium is a convex portion of another conveying member. And a recording medium conveying apparatus, wherein the recording medium conveying apparatus is set higher. An image carrier, a transfer unit that transfers a toner image formed on the image carrier to a recording medium, a fixing device that fixes the toner image on the recording medium onto which the toner image has been transferred, and A conveying unit that sucks and conveys the recording medium onto which the toner image has been transferred in the transfer unit to the fixing device;
An image forming apparatus comprising: the recording medium conveying device according to claim 1 as the conveying unit.

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