JP5929406B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Patent Document 1 discloses a technique for setting the speed of the suction conveyance unit slower than the speed of the fixing device so that the transfer paper is not pulled between the fixing device and the suction conveyance unit. Furthermore, in this prior art, a loop is formed between the fixing device and the suction conveyance unit. When the loop is absorbed by the downward convex guide and the transfer paper detection unit detects the loop size, the control unit controls the speed of the adsorption conveyance unit. Correction is made so that the loop becomes faster and an appropriate loop (see Patent Document 1).

JP 2007-121348 A JP 2003-263051 A Japanese Patent Laid-Open No. 08-087156

  The present invention suppresses the toner image fixed on one side of the recording medium from rubbing against the guide member disposed on one side of the recording medium conveyed with the toner image fixed on one side and the other side of the recording medium. It is the purpose.

According to a first aspect of the present invention, there is provided an image forming unit that forms a toner image on a recording medium, a fixing device that fixes the toner image formed on the recording medium, and the toner image fixed on one surface by the fixing device. A reversal conveyance mechanism that reverses the recording medium so that a toner image is formed on the other surface of the recording medium and conveys the recording medium to the image forming unit, and the reversal on the downstream side in the conveyance direction of the recording medium relative to the fixing device A first conveyance device that conveys the recording medium provided on the one surface side of the recording medium when reversed by a conveyance mechanism; and the inversion on the downstream side in the conveyance direction of the recording medium with respect to the first conveyance device A guide member that is provided on the one surface side of the recording medium when reversed by a transport mechanism and that contacts the leading end of the recording medium and guides the recording medium downstream in the transport direction The recording medium is provided on the downstream side in the conveyance direction of the recording medium with respect to the guide member, and is set so that the conveyance speed is lower than the conveyance speed of the recording medium between the fixing device and the guide member, and before entering. A recording medium conveyance speed VA of the fixing device, wherein the recording medium conveyance direction after entering the recording medium conveyance direction is inclined toward the one surface. When the recording medium conveyance speed VB of the first conveyance apparatus and the recording medium conveyance speed VC of the second conveyance apparatus are set, VA ≧ VB> VC is set .

  In the invention of claim 2, the second conveying device is disposed on the outer peripheral side of the annular first belt and the first belt, and circulates and moves with the recording medium sandwiched between the first belt and the second belt. An annular second belt that conveys the recording medium with the first belt, an inner circumferential side of the first belt or an inner circumferential side of the second belt, and the second belt and the second belt And a cooling means for cooling the recording medium conveyed in the above.

  According to a third aspect of the present invention, the first transport device is disposed on the one surface side of the recording medium, and is set to have a rotational speed higher than the transport speed of the recording medium in the second transport device. And an annular belt member in which a plurality of through holes are formed, and suction means for sucking air from the through holes into the annular belt member.

  According to the first aspect of the present invention, compared to the case where the recording medium transport direction after entering the second transport apparatus is inclined toward the other surface relative to the recording medium transport direction before entering the second transport device, The toner image fixed on one surface of the recording medium is suppressed from rubbing against the guide member.

  According to the invention described in claim 2, the image quality is improved as compared with the case where the cooling means is not provided.

  According to the third aspect of the present invention, as compared with the case where the suction means is not provided, it is possible to effectively form a loop in which the other surface side is convex on the recording medium.

1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to an exemplary embodiment. FIG. 2 is a schematic diagram illustrating a configuration of an image forming unit included in an image forming unit according to the present embodiment. FIG. 3 is a schematic diagram illustrating a configuration of a toner image forming unit included in an image forming unit according to the present embodiment. 1 is a schematic diagram illustrating a configuration of a fixing device employed in an image forming apparatus according to an exemplary embodiment. (A) is a perspective view showing a vacuum conveyance device employed in an image forming apparatus according to an embodiment of the present invention, and (B) is a side view. FIG. 2 is a configuration diagram illustrating a configuration of a recording medium conveyance structure including a fixing device, a vacuum conveyance device, and a medium cooling unit in the image forming apparatus according to the present embodiment. FIG. 7 is an explanatory diagram illustrating a state where a main loop of the conveyance structure of FIG. 6 is shown and a convex loop is formed on the other surface side of the recording medium.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. First, the overall configuration and operation of the image forming apparatus will be described, then the configuration and operation of the fixing device will be described, and then the main part of this embodiment will be described. In the following description, the direction indicated by the arrow H in FIG. 1 is the apparatus height direction, and the apparatus width direction is the direction indicated by the arrow W in FIG. In addition, a direction perpendicular to each of the apparatus height direction and the apparatus width direction (shown by an arrow D as appropriate) is defined as an apparatus depth direction.

[Overall configuration of image forming apparatus]
FIG. 1 is a schematic diagram illustrating an overall configuration of an image forming apparatus 10 according to the present embodiment as viewed from the front side. As shown in this figure, the image forming apparatus 10 includes an image forming unit 12 that forms an image on a recording medium P by an electrophotographic method, a medium conveying unit 50 that conveys the recording medium, and a recording medium P on which an image is formed. And a post-processing unit 60 that performs post-processing and the like. Further, the image forming apparatus 10 includes a control unit 70 that controls the units and the power supply unit 80, and a power supply unit 80 that supplies power to the units including the control unit 70.

<Configuration of image forming unit>
The image forming unit 12 will be described with reference to FIG. 2 which is a schematic view of the image forming unit 12 as viewed from the front side. The image forming unit 12 includes a photosensitive drum 21, which is an example of an image carrier, a charger 22, an exposure device 23, a developing device 24, and a cleaning device 25, and forms a toner image. A toner image forming unit 20, a transfer device 30 for transferring an image formed by the toner image forming unit 20 to the recording medium P, and a fixing device 40 for fixing the toner image transferred to the recording medium P to the recording medium P. It is configured to include.

  A plurality of toner image forming units 20 are provided so as to form a toner image for each color. In this embodiment, a total of six toner image forming portions 20 of the first special color (V), the second special color (W), yellow (Y), magenta (M), cyan (C), and black (K). Is provided. (V), (W), (Y), (M), (C), and (K) shown in FIG. 1 indicate the colors described above. The transfer device 30 is configured to transfer a toner image for six colors onto a recording medium P at a transfer nip NT from a transfer belt 31 on which toner images for six colors are superimposed and transferred primarily.

(Photosensitive drum)
The photosensitive drum 21 is formed in a cylindrical shape and is driven to rotate around its own axis by a driving unit (not shown). As an example, a photosensitive layer having a negative charging polarity is formed on the outer peripheral surface of the photosensitive drum 21. Note that an overcoat layer may be formed on the outer peripheral surface of the photosensitive drum 21. The photosensitive drums of the respective colors are arranged in a straight line along the apparatus width direction when viewed from the front.

(Charger)
The charger 22 charges the outer peripheral surface (photosensitive layer) of the photosensitive drum 21 to a negative polarity. In this embodiment, the charger 22 is a corona discharge type (non-contact charging type) scorotron charger.

(Exposure equipment)
The exposure device 23 is configured to form an electrostatic latent image on the outer peripheral surface of the photosensitive drum 21. Specifically, the exposure light L (see FIG. 3) modulated according to the image data received from the image signal processing unit constituting the control unit 70 is applied to the outer peripheral surface of the photosensitive drum 21 charged by the charger 22. It comes to irradiate. An electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 21 by irradiation of the exposure light L by the exposure device 23. In this embodiment, the exposure device 23 is configured to expose the surface of the photosensitive drum 21 while scanning a light beam emitted from a light source with an optical scanning unit (optical system) including a polygon mirror and an Fθ lens. . In the present embodiment, the exposure device 23 is provided for each color.

(Developer)
The developing device 24 develops the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 21 with the developer G containing toner, thereby forming a toner image on the outer peripheral surface of the photosensitive drum 21. ing. Although not described in detail, the developing device 24 includes at least a container 241 that stores the developer G, and a developing roll 242 that supplies the photosensitive drum 21 while rotating the developer G stored in the container 241. Has been. A toner cartridge 27 for supplying the developer G is connected to the container 241 via a supply path (not shown). The toner cartridges 27 for the respective colors are arranged above the photosensitive drum 21 and the exposure device 23 in the apparatus width direction when viewed from the front, and can be individually replaced.

(Cleaning device)
The cleaning device 25 includes a blade 251 that scrapes off toner remaining on the surface of the photosensitive drum 21 from the surface of the photosensitive drum 21 after the toner image is transferred to the transfer device 30. Although not shown, the cleaning device 25 further includes a housing that collects the toner scraped by the blade 251 and a transport device that transports the toner in the housing to the waste toner box.

(Transfer device)
The transfer device 30 performs primary transfer by superimposing the toner image of the photosensitive drum 21 of each color on the transfer belt 31, and secondarily transferring the superimposed toner image to the recording medium P.

  Specifically, the transfer belt 31 has an endless shape and is wound around a plurality of rolls 32 to determine the posture. In this embodiment, the transfer belt 31 has a reverse obtuse triangular posture that is long in the apparatus width direction when viewed from the front. Among the plurality of rolls 32, the roll 32D shown in FIG. 2 functions as a drive roll that rotates the transfer belt 31 in the arrow A direction by the power of a motor (not shown). Of the plurality of rolls 32, the roll 32 </ b> T illustrated in FIG. 2 functions as a tension applying roll that applies tension to the transfer belt 31. Among the plurality of rolls 32, the roll 32 </ b> B illustrated in FIG. 2 functions as a counter roll of the secondary transfer roll 34.

  The transfer belt 31 is in contact with the photosensitive drum 21 of each color from below at the upper side extending in the apparatus width direction with the above-described posture, and the image on each photosensitive drum 21 is transferred to the transfer bias from the primary transfer roll 33. Transfer is performed upon application of a voltage. The transfer belt 31 is in contact with the secondary transfer roll 34 at the top of the lower end forming an obtuse angle to form a transfer nip NT. The transfer belt 31 receives the transfer bias voltage from the secondary transfer roll 34 and receives the transfer The toner image is transferred to the recording medium P that passes through the nip NT.

(Fixing device)
The fixing device 40 fixes the toner image on the recording medium onto which the toner image has been transferred by the transfer device 30. In this embodiment, the fixing device 40 is configured to fix the toner image to the recording medium P by applying pressure while heating the toner image in the fixing nip NF.

<Medium transport unit>
The medium transport unit 50 includes a medium supply unit 52 that supplies the recording medium P to the image forming unit 12 and a medium discharge unit 54 that discharges the recording medium P on which an image is formed. Further, the medium transport unit 50 includes a medium return unit 56 that is used when images are formed on both sides of the recording medium P, and an intermediate transport unit 58 that transports the recording medium P from the transfer device 30 to the fixing device 40. It is configured.

  The medium supply unit 52 supplies the recording medium P to the transfer nip NT of the image forming unit 12 one by one in accordance with the transfer timing. The medium discharge unit 54 discharges the recording medium P on which the toner image is fixed by the fixing device 40 to the outside of the apparatus. When the medium returning unit 56 forms an image on the other side of the recording medium P having the toner image fixed on one side, the medium returning unit 56 reverses the recording medium to the image forming unit 12 (medium supply unit 52). It comes to return.

<Post-processing section>
The post-processing unit 60 includes a medium cooling unit 62 that cools the recording medium P on which the image is formed by the image forming unit 12, a correction device 64 that corrects the curvature of the recording medium P, and an image formed on the recording medium P. And an image inspection unit 66 to be inspected. Each unit constituting the post-processing unit 60 is disposed in the medium discharge unit 54 of the medium transport unit 50.

  The medium cooling unit 62, the correction device 64, and the image inspection unit 66 constituting the post-processing unit 60 are arranged in this order from the upstream side in the discharge direction of the recording medium P in the medium discharge unit 54, and the medium discharge unit 54. The post-processing is performed on the recording medium P in the discharge process.

[Image forming operation]
An outline of an image forming process on the recording medium P by the image forming apparatus 10 and a subsequent processing process will be described.

  Upon receiving the image formation command, the control unit 70 operates the toner image forming unit 20, the transfer device 30, and the fixing device 40. As a result, the photosensitive drum 21 and the developing roll 242 are rotated, and the transfer belt 31 is rotated. Further, the pressure roll 42 is rotated and the fixing belt 411 is rotated. Further, in synchronization with these operations, the control unit 70 operates the medium conveyance unit 50 and the like.

  As a result, the photosensitive drums 21 of the respective colors are charged by the charger 22 while being rotated. In addition, the control unit 70 sends the image data that has been subjected to image processing by the image signal processing unit to each exposure device 23. Each exposure device 23 emits each exposure light L according to the image data and exposes each charged photosensitive drum 21. Then, an electrostatic latent image is formed on the outer peripheral surface of each photosensitive drum 21. The electrostatic latent image formed on each photoconductor drum 21 is developed by the developer supplied from the developing device 24. As a result, the photosensitive drum 21 of each color has the first special color (V), the second special color (W), yellow (Y), magenta (M), cyan (C), and black (K). A corresponding color toner image is formed.

  The toner images of the respective colors formed on the photosensitive drums 21 of the respective colors are sequentially transferred to the rotating transfer belt 31 by applying a transfer bias voltage through the primary transfer rolls 33 of the respective colors. As a result, a superimposed toner image in which toner images for six colors are superimposed is formed on the transfer belt 31. This superimposed toner image is conveyed to the transfer nip NT by the rotation of the transfer belt 31. A recording medium P is supplied to the transfer nip NT by the medium supply unit 52 in synchronization with the conveyance of the superimposed toner image. The superimposed toner image is transferred from the transfer belt 31 to the recording medium P by applying a transfer bias voltage at the transfer nip NT.

  The recording medium P onto which the toner image has been transferred is conveyed by the intermediate conveyance unit 58 while being sucked with negative pressure from the transfer nip NT of the transfer device 30 toward the fixing nip NF of the fixing device 40. The fixing device 40 applies heat and pressure (fixing energy) to the recording medium P that passes through the fixing nip NF. As a result, the toner image transferred to the recording medium P is fixed to the recording medium.

  The recording medium P discharged from the fixing device 40 is processed by the post-processing unit 60 while being conveyed toward the discharged medium receiving unit outside the apparatus by the medium discharging unit 54. The recording medium P heated in the fixing process is first cooled in the medium cooling unit 62. Next, the curvature of the recording medium P is corrected by the correction device 64. Further, the toner image fixed on the recording medium P is detected by the image inspection unit 66 for the presence and extent of toner density defects, image defects, image position defects, and the like. Then, the recording medium P is discharged to the medium discharge unit 54.

  On the other hand, when an image is formed on a non-image surface on which an image of the recording medium P is not formed (in the case of double-sided printing), the control unit 70 uses the conveyance path of the recording medium P after passing through the image inspection unit 66 as a medium. The discharge unit 54 is switched to the medium return unit 56. As a result, the recording medium P is turned upside down and sent to the medium supply unit 52. An image is formed (fixed) on the back surface of the recording medium in the same process as the image forming process on the front surface. The recording medium P is discharged out of the apparatus by the medium discharge unit 54 through the same process as the post-processing process after image formation on the surface.

[Basic configuration of fixing device]
FIG. 4 is a schematic cross-sectional view showing the main part that performs the fixing operation of the fixing device 40. As shown in this figure, the fixing device 40 includes a fixing belt module 41, an external roll 45 wound around the fixing belt module 41 from the outside, and a pressure roll 42 that forms a fixing nip NF with the fixing belt module 41. It is comprised including. The fixing device 40 includes a halogen lamp 43 that heats the fixing belt module 41 and a peeling pad mechanism 46 for peeling the leading end of the recording medium P that has passed through the fixing nip NF from the fixing belt module 41. Yes.

  The fixing belt module 41 includes a fixing belt 411, a pad member 412 elongated in the apparatus depth direction, and a plurality of rolls 413 each having the apparatus depth direction as the rotation axis direction. The fixing belt 411 has an annular shape (endless shape) that opens on both sides in the apparatus depth direction orthogonal to the conveyance direction of the recording medium P. The fixing belt 411 has a predetermined posture wound around the pad member 412, the plurality of rolls 413, and the external roll 45, and maintains the posture (on a circular orbit along the posture) in FIG. It circulates in the arrow R direction shown.

  The pad member 412 is disposed inside the fixing belt 411, and receives a pressing (nip) load from the pressure roll 42 on the nip forming surface 4121, whereby the fixing nip is interposed between the fixing belt 411 and the pressure roll 42. NF is formed. The pad member 412 is fixed to the apparatus frame and does not follow the rotation of the fixing belt 411.

  The nip forming surface 4121 of the pad member 412 is a curved surface that is concave in an arc shape on the pressure roll 42 side when viewed from the apparatus depth direction. Due to this shape, the pad member 412 has a conveyance direction of the recording medium P as compared with a configuration in which a roll supporting the nip load is provided between the fixing belt 411 and the pressure roll 42 instead of the pad member 412. A long fixing nip NF is formed.

  A sliding sheet 414 is interposed between the fixing belt 411 and the nip forming surface 4121 of the pad member 412. The sliding sheet 414 has at least a surface in contact with the fixing belt 411 made of a low friction material such as a fluorine resin. Thereby, the frictional resistance with respect to the rotation of the fixing belt 411 is reduced.

  A halogen lamp 43 as an example of a heat source is provided in the main body 4122 of the pad member 412. The pad member 412 also functions as a heat transfer member that transfers the heat generated by the halogen lamp 43 to the fixing belt 411 via the nip forming surface 4121.

  Among the plurality of rolls 413, rolls 413C located on both upstream and downstream sides in the circumferential direction of the fixing belt 411 with respect to the pad member 412 function as posture correction rolls. Specifically, each roll 413C suppresses a change in the circumferential direction of the fixing belt 411 before and after the fixing nip NF (the bending angle of the fixing belt 411 at both ends of the fixing nip NF is an obtuse angle). .

  Among the plurality of rolls 413, the roll 413 </ b> H that is located farthest from the pad member 412 functions as an internal heating roll that heats the fixing belt 411 from the inner peripheral side. Specifically, in the roll 413H, the fixing belt 411 is wound from the inner peripheral side, and heat generated by the halogen lamp 43 provided therein is transmitted to the fixing belt 411. In this embodiment, the roll 413H also functions as a steering roll that can adjust the position of the fixing belt 411 in the width direction (apparatus depth direction) by tilting the axis with respect to the apparatus depth direction.

  As an example, the pressure roll 42 is configured by covering an outer periphery of a cylindrical cylindrical roll body 421 with an elastic body layer 422 made of silicone rubber. Although illustration is omitted, on the outer periphery of the elastic layer 422, a release layer made of a fluororesin having a film thickness of 100 μm is formed on the outer periphery. The pressure roll 42 functions as a drive roll that applies a driving force for rotation to the fixing belt 411 by being rotated by a drive source (not shown).

  The fixing device 40 includes an external roll 45 around which the fixing belt 411 is wound from the outer peripheral side. The external roll 45 is disposed between the roll 413C and the roll 413H on the downstream side of the pad member 412 in the circumferential direction of the fixing belt 411. The external roll 45 functions as an external heating roll that heats the fixing belt 411 from the outer peripheral side. Specifically, the external roll 45 transmits heat generated by the halogen lamp 43 provided therein to the fixing belt 411. Further, the external roll 45 functions as a drive roll that applies a driving force for rotation to the fixing belt 411 by being rotated by a drive source (not shown). In this embodiment, the pressure roll 42 is a main drive roll that mainly applies a driving force to the fixing belt 411, and the external roll 45 is positioned as an auxiliary drive roll.

  The fixing belt module 41 includes a pressing roll 415 that presses the fixing belt 411 against the external roll 45 from the inner peripheral side. The pressing roll 415 presses the fixing belt 411 against the external roll 45 with a load determined by the bias of the spring 416. As a result, the frictional force contributing to the transmission of the driving force from the external roll 45 to the fixing belt 411 is increased as compared with the configuration without the pressing roll 415.

  The peeling pad mechanism 46 has a peeling pad 461 disposed downstream of the fixing nip NF in the conveyance direction of the recording medium P, and the tip of the peeling pad 461 is brought close to the fixing nip NF.

  Although not shown, the fixing belt module 41 can be attached to and detached from the apparatus frame as a module composed of a fixing belt 411, a pad member 412, each roll 413, and the like.

[Basic operation of fixing device]
The fixing device 40 is prepared for operation according to a command from the control unit 70 prior to the image forming (transfer) operation to the recording medium P in the image forming unit 12. Specifically, when the pressure roll 42 and the external roll 45 are driven, the fixing belt 411 goes around a predetermined track. Further, the heat generation of each halogen lamp 43 raises the temperature of the fixing belt 411 to a predetermined temperature range and maintains the temperature range. The fixing belt 411 is heated while rotating, so that the temperature of each part is within a predetermined range.

  When the recording medium P onto which the toner image has been transferred by the transfer device 30 is introduced into the fixing nip NF as shown in FIG. 4 by the intermediate conveyance unit 58, the fixing device 40 conveys the recording medium P. While, pressure and heat (fixing energy) are applied to the recording medium P. As a result, the toner image is fixed on the recording medium P.

  Further, the leading edge of the recording medium P that has passed through the fixing nip NF enters between the peeling pad 461 of the peeling pad mechanism 46 and the pressure roll 42. Specifically, the fixing belt 411 has a rounded shape (and a circular orbit formed by the downstream roll 413C) formed at the downstream end in the conveyance direction of the recording medium P on the nip forming surface 4121 of the pad member 412. Along the recording medium P so as to leave the conveyance path. For this reason, the leading edge of the recording medium P is separated from the fixing belt 411 by its waist (restorability) (without following the movement of the fixing belt 411), and the peeling pad 461 and the pressure roll 42 of the peeling pad mechanism 46 Enter between. The recording medium P is peeled off from the fixing belt 411 as it is conveyed. The recording medium P sent out from the fixing device 40 in this way is conveyed to the downstream side (post-processing unit 60 side) by the medium discharge unit 54.

<Medium cooling unit>
As shown in FIG. 6, the medium cooling unit 62 includes a heat absorbing device 621 that absorbs heat of the recording medium P, and a pressing device 623 that presses the recording medium P against the heat absorbing device 621. The heat absorption device 621 is disposed on the upper side, and the pressing device 623 is disposed on the lower side.

  The endothermic device 621 includes an endless endothermic belt 6211, a plurality of rolls 6212 that support the endothermic belt 6211, a heat sink 6213 disposed in the endothermic belt 6211, and a fan 6214 for cooling the heat sink 6213. It is configured. The endothermic belt 6211 is in contact with the recording medium P so that heat exchange is possible on the outer peripheral surface. Among the plurality of rolls 6212, the roll 6212 </ b> D functions as a driving roll that transmits driving force to the heat absorbing belt 6211. The heat sink 6213 is slidably brought into surface contact with the inner peripheral surface of the endothermic belt 6211 within a predetermined range along the medium discharge path of the recording medium P. For example, the heat sink 6213 is made of aluminum or an aluminum alloy. The fan 6214 generates an air flow for heat exchange with the heat sink 6213. Thus, the heat absorbing device 621 is configured to dissipate heat taken from the recording medium P by the heat absorbing belt 6211 to the air flow generated by the fan 6214 via the heat sink 6213.

  The pressing device 623 includes an endless pressing belt 6221 and a plurality of rolls 6222 that support the pressing belt 6221. The pressing device 622 is configured to convey the recording medium P with the heat absorbing belt 6211 while pressing the recording medium P against the heat absorbing belt 6211 (heat sink 6213). The pressing belt 6221 is wound around a plurality of rolls 6222.

<Conveying Structure for Recording Medium Consisting of Fixing Device, Vacuum Conveying Device, and Medium Cooling Unit>
Next, a description will be given of a recording medium conveyance structure including a fixing device, a vacuum conveyance device, which will be described in detail later, and a medium cooling unit. Note that one side PA and the other side PB of the sheet-like recording medium P described below are front and back (one side PA and the other side) at the medium return portion after the toner image is fixed on the one side PA. The surface PA) is reversed and returned to the image forming unit, and the toner image is formed on the other surface PB.

  In the present embodiment, as shown in FIGS. 1 and 6, the medium discharge unit 54 is provided with a vacuum transfer device (suction transfer device) 700 and a guide member 100 as an example of a first transfer device. ing.

(Vacuum transfer device)
As shown in FIGS. 5A and 5B, a vacuum transport device (adsorption transport device) 700 includes a drive roll 72 that is rotationally driven, a driven roll 74 that is rotatably supported, and a drive roll. 72 and a plurality of annular belt members 76 wound around the driven roll 74.

  A plurality of through holes 76A are formed in the belt member 76 over the entire surface, and a suction fan 78 as an example of a suction means is arranged so that air is sucked into the annular belt member 76 from the through holes 76A. Has been.

  With such a configuration, the recording medium P is sucked onto the conveying belt 76, and the driving roll 72 is driven to rotate to rotate the belt member 76, whereby the recording medium P is conveyed toward the downstream side in the conveying direction. ing.

(Guide member)
As shown in FIG. 6, a plate-shaped guide member 100 that guides the recording medium P to the medium cooling unit 62 described later is provided on the downstream side in the transport direction of the vacuum transport device 700.
<Conveying the recording medium>

  As shown in FIG. 6, the fixing device 40 fixes the toner image transferred to the recording medium P. The recording medium P discharged from the fixing device 40 is conveyed to the downstream side in the conveyance direction as the belt member 76 rotates while being sucked by the belt member 76 of the vacuum conveyance device 700. The recording medium P (see FIG. 7) conveyed by the vacuum conveyance device 700 is sent to the downstream side in the conveyance direction while being peeled off from the belt member 76 at the downstream end of the vacuum device 700 in the conveyance direction.

  The leading end PT (see FIG. 7) of the recording medium P peeled off from the belt member 76 is in contact with the guide member 100 disposed on the one surface PA side of the recording medium P. It is guided (guided) by the medium cooling unit 62 as an example. The recording medium P (see FIG. 7) guided by the guide member 100 is sandwiched between an endothermic belt 6211 as an example of a first belt constituting the medium cooling unit 62 and an endothermic belt 6221 as an example of a second belt. And is cooled by a heat sink 6213 as an example of a cooling means disposed in the endothermic belt 6211.

  As shown in FIG. 7, the conveyance direction S <b> 2 of the recording medium P after entering the vacuum conveyance device 700 is different from the conveyance direction S <b> 1 of the recording medium P before the recording medium P enters the vacuum conveyance device 700. It is inclined to the surface PB side. That is, the conveyance path is configured so that the conveyance direction changes before and after the recording medium P enters the vacuum conveyance device 700.

  The conveyance speed of the recording medium P is defined as the conveyance speed VA of the recording medium P of the fixing device 40, the conveyance speed VB of the recording medium P of the vacuum conveyance device 700, and the conveyance speed VC of the recording medium P of the medium cooling unit 62. It is set so that “VA ≧ VB> VC”. That is, the conveyance speed in the vacuum conveyance device 700 is set to be slower than the conveyance speed of the recording medium P between the fixing device 40 and the guide member 100. In the present embodiment, the vacuum conveyance device 700 is set so that the conveyance speed is about 0.5% slower than the fixing device 40.

(Function and effect)
Next, functions and effects of the present embodiment will be described.

  As shown in FIG. 1, after the toner image on one surface PA (see FIG. 7) of the recording medium P is fixed, the other surface PB, which is a non-image surface on which no toner image is formed (at this point). When an image is formed in the case of (see FIG. 7) (in the case of double-sided printing), the front and back are reversed via the reversing path 56P and sent to the medium supply path 52P. Then, the toner image is transferred to the other surface PB of the recording medium P and sent to the fixing device 40, and the toner image is fixed to the other surface PB.

  As shown in FIG. 7, the recording medium P in which the toner images are fixed on both the one side PA and the other side PB in this way is applied to the belt member 76 of the vacuum conveying device 700 as described above. With the surface PA sucked, the belt member 76 is conveyed toward the downstream side in the conveyance direction as the belt member 76 rotates. The recording medium P transported by the vacuum transport device 700 is sent downstream in the transport direction while being peeled off from the belt member 76 at the downstream end in the transport direction. The peeled recording medium P is guided by the medium cooling unit 62 with the leading end PT coming into contact with the guide member 100. The recording medium P is sandwiched between the heat absorbing belt 6211 and the heat absorbing belt 6221 of the medium cooling unit 62 and is conveyed and cooled.

  As described above, the conveyance speed of the recording medium P includes the conveyance speed VA of the recording medium P of the fixing device 40, the conveyance speed VB of the recording medium P of the vacuum conveyance device 700, and the conveyance speed VC of the recording medium P of the medium cooling unit 62. Then, it is set so that “VA ≧ VB> VC”. Therefore, the rear end portion (upstream end portion in the transport direction) of the recording medium P is restrained by the fixing device 40 or the vacuum transport device 700, and the front end portion (downstream flow side end portion in the transport direction) is restrained by the medium cooling portion 62. In this state, the recording medium P is bent at a portion between the vacuum conveyance device 700 and the medium cooling unit 62.

  The conveyance direction S2 of the recording medium P after entering the vacuum conveyance device 700 is inclined to the other surface PB side with respect to the conveyance direction S1 of the recording medium P before the recording medium P enters the vacuum conveyance device 700. ing. Therefore, the loop portion R is formed so that the other surface PB side is convex due to the so-called stiffness of the recording medium P, that is, the direction away from the conveying member 100 is convex. Therefore, the toner image fixed on the one surface PA of the recording medium P is prevented or suppressed from rubbing against the guide member 100.

  Here, the toner image fixed on one surface PA of the recording medium P is softer than the state of being heated and cooled by the fixing device 40. Therefore, if one surface PA of the recording medium P rubs against the guide member 100, the soft toner image may be scratched and the image quality may be deteriorated.

  However, as described above, in the present embodiment, the recording medium P is formed so that the other surface PB side is convex, that is, the direction away from the conveying member 100 is convex. The toner image fixed on the surface PA is prevented or suppressed from rubbing against the guide member 100. Therefore, it is prevented or suppressed that the soft toner image fixed on the one surface PA of the recording medium P on the guide member 100 is scratched and the image quality is deteriorated.

(Other)
The present invention is not limited to the above embodiment.

  For example, in the above-described embodiment, assuming that the conveyance speed VA of the recording medium P of the fixing device 40, the conveyance speed VB of the recording medium P of the vacuum conveyance apparatus 700, and the conveyance speed VC of the recording medium P of the medium cooling unit 62, “VA ≧ The setting is such that “VB> VC”, but the present invention is not limited to this. “VA ≦ VB> VC” may be used. The point is that the medium cooling unit may be set to have a lower conveyance speed than the recording medium conveyance speed between the fixing device and the guide member.

  For example, in the above-described embodiment, the first transport device is the vacuum transport device (suction transport device) 700 that sucks and transports the recording medium P, but is not limited thereto. For example, the first transport device may be a belt transport device that does not have an adsorption function, or may be a transport device configured to transport with a rotating roller.

  Further, for example, in the above-described embodiment, the second transport device is the medium cooling unit 62 that cools the recording medium P after fixing, but is not limited thereto. For example, the second transport device may be the image inspection unit 60 (the transport mechanism portion of the recording medium).

  Further, the configuration of the image forming apparatus is not limited to the configuration of the above-described embodiment, and various configurations can be employed. Furthermore, it cannot be overemphasized that it can implement with a various aspect in the range which does not deviate from the summary of this invention.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming part 40 Fixing apparatus 56 Medium return part (an example of a reverse conveyance mechanism)
62 Medium cooling section (example of second cooling device)
76 Belt member 76A Through hole 78 Suction fan (an example of suction means)
100 Guide member 700 Vacuum transfer device (an example of a first transfer device)
6211 endothermic belt (example of first belt)
6221 endothermic belt (example of second belt 6213 heat sink (example of cooling means)
P Recording medium
PA One side
PB The other side
PT tip

Claims (3)

An image forming unit for forming a toner image on a recording medium;
A fixing device for fixing a toner image formed on the recording medium;
A reversing conveyance mechanism for reversing the recording medium having a toner image fixed on one surface thereof by the fixing device so as to form a toner image on the other surface of the recording medium and conveying the reversal conveyance mechanism to the image forming unit;
A first conveyance device that conveys the recording medium provided on the one surface side of the recording medium when reversed by the reversal conveyance mechanism on the downstream side in the conveyance direction of the recording medium with respect to the fixing device;
Provided on the one surface side of the recording medium when the recording medium is reversed by the reversing conveyance mechanism on the downstream side in the conveyance direction of the recording medium with respect to the first conveyance device; A guide member for guiding the medium downstream in the transport direction;
Provided on the downstream side in the conveyance direction of the recording medium with respect to the guide member, the conveyance speed is set to be lower than the conveyance speed of the recording medium between the fixing device and the guide member, and before the entry. A second transport device in which the transport direction of the recording medium after entering the recording medium transport direction is inclined toward the one surface;
Equipped with a,
A conveyance speed VA of the recording medium of the fixing device;
Transport speed VB of the recording medium of the first transport device,
Transport speed VC of the recording medium of the second transport device,
Then,
An image forming apparatus that is set to satisfy VA ≧ VB> VC . The second transport device is
An annular first belt;
An annular second belt that is disposed on the outer peripheral side of the first belt, circulates and moves the recording medium between the first belt, and conveys the recording medium with the first belt;
A cooling means provided on the inner peripheral side of the first belt or the inner peripheral side of the second belt, for cooling the recording medium conveyed by the second belt and the second belt;
The image forming apparatus according to claim 1, comprising: The first transport device is
An annular belt member disposed on the one surface side of the recording medium, set to have a rotational speed faster than the conveying speed of the recording medium in the second conveying device, and formed with a plurality of through holes; ,
A suction means for sucking air into the inside of the annular belt member from the through hole;
Composed of,
The image forming apparatus according to claim 1.

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