Medium guiding device and image forming apparatus

Abstract

To reduce the occurrence of an image quality defect due to an impact when a rear end of a medium with high rigidity is brought into contact with an endless belt supported on a rotating body, compared with a case where a medium guiding device does not comprise second and third guiding units.SOLUTION: A medium guiding device comprises: a first guiding unit that guides a medium toward a transfer unit that transfers an image on an endless belt to the medium, in which its downstream-side end along a direction to guide the medium is arranged to face a rotating body that supports the endless belt; a second guide unit that is elastically deformable and arranged on the first guide unit, in which its downstream-side end along the direction to guide the medium is arranged to project from the first guide unit; and a third guide unit that is elastically deformable and arranged on the second guide unit, in which its downstream-side end along the direction to guide the medium is arranged to project from the second guide unit.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a medium guide device and an image forming apparatus. [Background technology]

[0002] Conventionally, techniques relating to a medium guide device have already been proposed, for example, as disclosed in Patent Documents 1 to 3.

[0003] Patent Document 1 discloses a device configured to include a transfer section that transfers an image onto a recording material, a guide section that guides the recording material toward the transfer section, and a plate-like member that is provided in the guide section and is more easily elastically deformable than the guide section, and that guides the conveyed recording material along the plate surface and is thinner on the downstream side in the conveying direction than on the upstream side.

[0004] Patent document 2 discloses a transfer material guide member that includes a main guide section that is positioned forward in the direction of movement of the transfer material and that guides the image transfer surface side of the transfer material, and a sub-guide section that is positioned behind the main guide section in the direction of movement; the sub-guide section is cantilevered by the main guide member and is configured to vary the separation timing of the rear end of the transfer material in the direction of movement between one end and the other end in the width direction, which corresponds to the direction perpendicular to the direction of movement of the transfer material; and the configuration that varies the separation timing is configured so that the tip of the sub-guide section that is positioned forward in the direction of movement of the transfer material is inclined along the width direction of the transfer material.

[0005] In Patent Document 3, the contact portion of the guide member that comes into contact with the transfer material is made of a conductive material, and the contact portion is configured to be grounded. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-054649 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-089925 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-172083 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of this invention is to suppress the occurrence of image quality defects caused by the impact when the rear end of a highly rigid medium comes into contact with an endless belt supported by a rotating body, compared to when the second and third guide sections are not provided. [Means for solving the problem]

[0008] The invention described in claim 1 provides a first guide section that guides a medium toward a transfer section that transfers an image on the endless belt to a medium, and that is arranged so that a downstream end of the medium along the guiding direction faces a rotating body that supports the endless belt; a second guide portion that is disposed in the first guide portion and is capable of elastic deformation such that a downstream end portion along a guiding direction of the medium protrudes from the first guide portion; a third guide section that is disposed in the second guide section and is capable of elastic deformation such that a downstream end portion along the guiding direction of the medium protrudes from the second guide section; The media guide device includes:

[0009] The invention described in claim 2 is the medium guide device according to claim 1, wherein the third guide portion is disposed on the endless belt side of the second guide portion.

[0010] The invention described in claim 3 is the medium guide device according to claim 2, wherein the second guide portion has a protruding amount set to be larger than the protruding amount of the third guide portion.

[0011] The invention described in claim 4 is the medium guide device according to claim 3, wherein the second and third guide portions have the same thickness.

[0012] The invention described in claim 5 is a media guide device described in claim 2, in which a portion of the third guide portion, excluding the protruding portion protruding from the second guide portion, is not adhered to the second guide portion.

[0013] The invention described in claim 6 is a media guide device described in claim 1, wherein the downstream end of the third guide section along the guiding direction of the media is away from the opposing position of the first guide section and the rotating body by a predetermined distance or more.

[0014] The invention described in claim 7 is a media guide device described in claim 6, wherein the gap between the downstream end of the third guide section along the guide direction of the media and the endless belt is greater than or equal to a predetermined threshold value.

[0015] The invention described in claim 8 is a media guide device described in claim 1, in which a portion of the second guide portion, excluding the protruding portion protruding from the first guide portion, is not adhered to the first guide portion.

[0016] The invention described in claim 9 is a media guide device described in claim 8, wherein the third guide portion is adhered to the second guide portion at a protruding portion where the second guide portion protrudes from the first guide portion.

[0017] The invention described in claim 10 comprises an endless belt for holding an image; a transfer means for transferring the image to a medium in a transfer section; a guide means for guiding a surface of the medium transported to the transfer unit on the side of the endless belt; Equipped with The image forming apparatus uses the medium guide device according to any one of claims 1 to 9 as the guide means. [Effects of the Invention]

[0018] According to the invention described in claim 1, compared to when the second and third guide sections are not provided, it is possible to suppress the occurrence of image quality defects caused by the impact when the rear end of a highly rigid medium comes into contact with the endless belt supported by a rotating body.

[0019] According to the invention described in claim 2, the third guide section can further suppress the occurrence of image quality defects caused by the impact when the rear end of the highly rigid medium comes into contact with the endless belt supported by the rotating body, compared to when it is positioned on the opposite side of the endless belt of the second guide section.

[0020] According to the invention described in claim 3, compared to when the protrusion amount of the third guide portion is greater than the protrusion amount of the second guide portion, it is possible to suppress the occurrence of image quality defects called trailing end smudges, which occur when the tip of the third guide portion comes close to the endless belt.

[0021] According to the invention as set forth in claim 4, it is possible to reduce component costs compared to when the second and third guide portions have different thicknesses.

[0022] According to the invention described in claim 5, the third guide section can smoothly transfer the medium to the third guide section compared to when its entire surface is bonded to the second guide section.

[0023] According to the invention described in claim 6, the third guide section can suppress the occurrence of an image quality defect called trailing edge bleeding, compared to when the downstream end along the guide direction of the medium is close to the opposing position of the first guide section and the rotating body.

[0024] According to the invention described in claim 7, the third guide section can reliably suppress the occurrence of image quality defects called trailing end smudges, compared to when the gap between the downstream end of the medium along the guiding direction and the endless belt is less than a predetermined threshold value.

[0025] According to the invention described in claim 8, the second guide portion can be easily deformed compared to when the entire surface of the second guide portion is bonded to the first guide portion.

[0026] According to the invention as set forth in claim 9, the third guide portion is more easily deformed than when the third guide portion is bonded to a portion other than the protruding portion of the second guide portion.

[0027] According to the invention described in claim 10, compared to when a media guide device described in any of claims 1 to 9 is not used as a guide means, it is possible to suppress the occurrence of image quality defects caused by the impact when the rear end of a highly rigid medium comes into contact with an endless belt supported by a rotating body. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus to which a medium guiding device in accordance with Embodiment 1 of the present invention is applied. [Figure 2] 1 is a configuration diagram showing a medium guide device of an image forming apparatus in accordance with Embodiment 1 of the present invention. [Figure 3] 1 is a plan view showing the configuration of a guide member of a medium guide device in accordance with Embodiment 1 of the present invention. [Figure 4] FIG. 10 is a configuration diagram showing a medium guide device of a conventional image forming apparatus. [Figure 5] 10A and 10B are explanatory diagrams showing the mechanism of image quality defects that occur in a conventional media guide device. [Figure 6] FIG. 10 is an explanatory diagram showing trailing edge bleeding as an image quality defect. [Figure 7] 10A and 10B are explanatory diagrams showing the mechanism of image quality defects that occur in a conventional media guide device. [Figure 8] FIG. 10 is an explanatory diagram showing rear end dirt as an image quality defect. [Figure 9] FIG. 10 is an explanatory diagram showing a trailing edge smudge as an image quality defect. [Figure 10] 1 is a cross-sectional view showing the configuration of a guide member of a medium guide device in accordance with Embodiment 1 of the present invention. [Figure 11] 1 is a cross-sectional configuration diagram showing a guide section of a medium guide device in accordance with Embodiment 1 of the present invention. [Figure 12] FIG. 10 is a plan view showing the configuration of a guide member in which second and third plate-shaped members are arranged. [Figure 13] FIG. 4 is a plan view showing second and third plate-shaped members. [Figure 14]3 is a configuration diagram showing the operation of the medium guide device in accordance with Embodiment 1 of the present invention. FIG. [Figure 15] 4 is an explanatory diagram showing the operation of the medium guide device in accordance with Embodiment 1 of the present invention; FIG. [Figure 16] FIG. 10 is a schematic diagram showing conditions of an experimental example. [Figure 17] 6 is a table showing the results of an experiment example of the medium guide device in accordance with Embodiment 1 of the present invention. [Figure 18] 6 is a table showing the results of an experiment example of the medium guide device in accordance with Embodiment 1 of the present invention. [Figure 19] 10 is a cross-sectional configuration diagram showing a guide section of a medium guide device in accordance with Embodiment 2 of the present invention. FIG. [Figure 20] 11 is a cross-sectional configuration diagram showing a guide section of a medium guide device in accordance with Embodiment 3 of the present invention. FIG. [Figure 21] FIG. 10 is a cross-sectional configuration diagram showing a guide section of a medium guide device in accordance with Embodiment 4 of the present invention. [Figure 22] FIG. 11 is a plan view showing the configuration of a guide section of a medium guide device in accordance with Embodiment 5 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0030] [Embodiment 1] 1 is a schematic diagram showing the overall configuration of an image forming apparatus to which a media guide device according to embodiment 1 of the present invention is applied. In the figure, the symbol X indicates the width direction of the image forming apparatus, Y indicates the depth direction of the image forming apparatus, and Z indicates the vertical direction of the image forming apparatus.

[0031] <Overall configuration of image forming apparatus> The image forming apparatus 1 according to the first embodiment is configured as, for example, a color printer. As shown in FIG. 1, the image forming apparatus 1 includes multiple image forming devices 10, an intermediate transfer device 20, a paper feeder 50, a fixing device 40, and the like. The multiple image forming devices 10 form toner images developed with toner constituting a developer. The intermediate transfer device 20 holds each toner image formed by the image forming device 10 and transports it to a secondary transfer position T2 where the toner image is finally transferred to a recording sheet 5 (an example of a medium). The paper feeder 50 stores and supplies the required recording sheet 5 to the secondary transfer position T2 of the intermediate transfer device 20. The fixing device 40 fixes the toner image on the recording sheet 5 that has been secondary transferred by the intermediate transfer device 20. Reference numeral 1a in the figure denotes the main body of the image forming apparatus 1. The main body 1a is formed by supporting structural members, an exterior cover, and the like. The dashed-dotted lines in the figure indicate the main transport path along which the recording sheet 5 is transported within the main body 1a of the image forming apparatus 1. In this first embodiment, a plurality of image forming devices 10 and an intermediate transfer device 20 constitute an image forming means.

[0032] The image forming device 10 is composed of four image forming devices 10Y, 10M, 10C, and 10K that are dedicated to forming toner images of four colors, yellow (Y), magenta (M), cyan (C), and black (K), respectively. These four image forming devices 10 (Y, M, C, K) are arranged at an angle in the internal space of the device body 1a of the image forming device 1 so that the yellow (Y) image forming device 10Y is located above along the vertical direction Z, and the black (K) image forming device 10K is located below along the vertical direction Z.

[0033] Each image forming device 10 (Y, M, C, K) includes a rotating photosensitive drum 11. Around the photosensitive drum 11, a charging device 12, an exposure device 13, a developing device 14, a primary transfer device 15, a drum cleaning device 16, and other components are arranged. The charging device 12 charges the image-forming peripheral surface (image bearing surface) of the photosensitive drum 11 to a desired potential. The exposure device 13 irradiates the charged peripheral surface of the photosensitive drum 11 with light based on image information (signals), forming electrostatic latent images for each color with a potential difference. The developing device 14 develops the electrostatic latent images with developer toner of the corresponding color (Y, M, C, K) to form toner images. The primary transfer device 15 transfers each toner image to the intermediate transfer device 20 at the primary transfer position T1. The drum cleaning device 16 cleans and removes any toner or other debris remaining on the image bearing surface of the photosensitive drum 11 after the primary transfer.

[0034] The photoreceptor drum 11 has an image bearing surface formed on the circumferential surface of a grounded cylindrical or columnar substrate, the peripheral surface of which has a photoconductive layer (photosensitive layer) made of a photosensitive material. The photoreceptor drum 11 is supported so that it rotates in the direction indicated by arrow A by a driving force transmitted from a driving means (not shown).

[0035] The charging device 12 is composed of a contact-type charging roll that is placed in contact with the photosensitive drum 11. A charging voltage is applied to the charging device 12. When the developing device 14 performs reversal development, the charging voltage applied is a voltage or current of the same polarity as the charging polarity of the toner supplied from the developing device 14. Note that the charging device 12 may also be a non-contact charging device such as a scorotron that is placed in a non-contact state on the surface of the photosensitive drum 11.

[0036] The exposure device 13 consists of an LED print head that forms an electrostatic latent image by irradiating the photosensitive drum 11 with light corresponding to image information using LEDs (Light Emitting Diodes) as light-emitting elements arranged along the axial direction of the photosensitive drum 11.

[0037] Each developing device 14 is configured by arranging a developing roll 141, an agitation supply member 142, an agitation transport member 143, a layer thickness regulating member (not shown), and the like inside a housing 140. The housing 140 has an opening facing the photosensitive drum 11 and a developer storage chamber formed inside. The developing roll 141 holds the developer and transports it to a development area facing the photosensitive drum 11. The agitation supply member 142 is made of a screw auger or the like that agitates the developer while supplying it to pass through the developing roll 141. The agitation transport member 143 is made of a screw auger or the like that agitates the developer while transporting it to the agitation supply member 142. The layer thickness regulating member regulates the amount (layer thickness) of developer held on the developing roll 141. A power supply device (not shown) supplies a development voltage between the developing roll 141 and the photosensitive drum 11 in this developing device 14. As the four-color developer, for example, a two-component developer containing non-magnetic toner and magnetic carrier is used.

[0038] The primary transfer device 15 is a contact type transfer device that includes a primary transfer roll that rotates in contact with the periphery of the photosensitive drum 11 via the intermediate transfer belt 21. A primary transfer voltage is supplied to the primary transfer device 15. As the primary transfer voltage, a DC voltage having a polarity opposite to the charge polarity of the toner is supplied from a power supply device (not shown).

[0039] Drum cleaning device 16 is configured with a cleaning plate and the like disposed inside a housing (not shown). The cleaning plate is disposed so as to contact the peripheral surface of photosensitive drum 11 after primary transfer with a required pressure, and scrapes off and cleans residual toner and other adhering matter. Drum cleaning device 16 may also be equipped with a sending member (not shown) formed of a screw auger or the like that collects the toner and other adhering matter removed by the cleaning plate and transports it to a collection system (not shown).

[0040] As shown in FIG. 1, the intermediate transfer device 20 is disposed above each of the image forming devices 10 (Y, M, C, K) in the vertical direction Z. The intermediate transfer device 20 is mainly composed of an intermediate transfer belt 21, multiple belt support rolls 22-25, a secondary transfer device 30, and a belt cleaning device 26. The intermediate transfer belt 21 is an example of an endless belt that holds a toner image, which is an example of an image. The secondary transfer device 30 is an example of a transfer means. The intermediate transfer belt 21 rotates in the direction indicated by arrow B while passing through a primary transfer position T1 between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roll). The multiple belt support rolls 22-25 rotatably support the intermediate transfer belt 21 from its inner surface while maintaining it in a desired state.

[0041] The intermediate transfer belt 21 is an endless belt made of a material in which a resistance adjuster such as carbon black is dispersed in a synthetic resin such as polyimide resin or polyamide resin. The belt support roll 25 is configured as a drive roll that is rotationally driven by a drive device (not shown). The belt support roll 25 also serves as a back support roll for secondary transfer. The belt support roll 22 also serves as an opposing roll that faces the belt cleaning device 26. The belt support roll 23 is configured as a surface adjustment roll that forms the image formation surface of the intermediate transfer belt 21. The belt support roll 24 is configured as a sensor roll that faces an optical sensor (not shown) that detects the density and position of a toner image for adjusting image quality formed on the intermediate transfer belt 21.

[0042] 1, the secondary transfer device 30 is a contact-type transfer device equipped with a secondary transfer roll 31. The secondary transfer roll 31 rotates in contact with the circumferential surface of the intermediate transfer belt 21 at a secondary transfer position T2, which is an example of a transfer section and is the outer circumferential surface of the intermediate transfer belt 21 supported by a belt support roll 25 in the intermediate transfer device 20. A DC voltage having the same polarity as or opposite to the charge polarity of the toner is supplied as a secondary transfer voltage from a power supply device (not shown) to the secondary transfer roll 31 or the belt support roll 25 of the intermediate transfer device 20.

[0043] The belt cleaning device 26 is composed of, for example, a main body 260, a cleaning brush 261, a cleaning plate 262, and a delivery member 263. The main body 260 is formed in the shape of a container with a portion open. The cleaning brush 261 is arranged to rotate while contacting the circumferential surface of the intermediate transfer belt 21 after the secondary transfer with a required pressure, and scrapes off and cleans off any remaining toner or other adhering matter. The cleaning plate 262 is arranged to contact the circumferential surface of the intermediate transfer belt 21 after the secondary transfer with a required pressure, and removes and cleans any remaining toner or other adhering matter. The delivery member 263 is composed of, for example, a screw auger that collects the toner and other adhering matter removed by the cleaning brush 261 and cleaning plate 262 and transports them to a collection system (not shown).

[0044] The fixing device 40 is configured by arranging a heating rotor 42, a pressure rotor 43, and other components inside a housing 41. The housing 41 is formed with an inlet and outlet for the recording paper 5. The heating rotor 42 is formed in the form of a belt or roll that rotates in the direction indicated by the arrow and is heated by a heating means so that the surface temperature is maintained at a predetermined temperature. The pressure rotor 43 is formed in the form of a roll or belt that rotates in contact with the heating rotor 42 at a predetermined pressure and rotates substantially along the axial direction of the heating rotor 42. In this fixing device 40, the contact area between the heating rotor 42 and the pressure rotor 43 forms the fixing nip N where the required fixing process (heating and pressure) is performed.

[0045] The paper feeder 50 is disposed below each of the imaging devices 10 (Y, M, C, K) in the vertical direction Z. The paper feeder 50 is mainly composed of one (or more) paper containers 51 and feeders 52 and 53. The paper container 51 stores recording paper 5 of a desired size, type, etc., stacked on a bottom plate 54. The feeders 52 and 53 feed the recording paper 5 one sheet at a time from the paper container 51. The paper container 51 is arranged so that it can be pulled out, for example, from the front side of the device main body 1a (the side that the user faces during operation).

[0046] Examples of recording paper 5 include thin paper such as plain paper or tracing paper used in electrophotographic copiers and printers, or overhead projector sheets. To further improve the smoothness of the image surface after fixing, it is preferable that the surface of recording paper 5 is as smooth as possible. For example, coated paper in which the surface of plain paper is coated with a resin or the like, or so-called thick paper with a relatively high basis weight such as art paper for printing can be suitably used. Also usable as recording paper 5 is thick paper such as postcards with a thickness of about 0.2 to 0.22 mm.

[0047] A paper feed conveying path 56 including one or more paper feed roll pairs 55 and the like is provided between the paper feed device 50 and the secondary transfer device 30. The paper feed roll pair 55 conveys the recording paper 5 sent out from the paper feed device 50 to the secondary transfer position T2. ​​The paper feed roll pair 55, which is arranged in the paper feed conveying path 56 at a position immediately before the secondary transfer position T2, is configured as, for example, a roll (registration roll) that adjusts the conveyance timing of the recording paper 5. A medium guiding device 60 according to this embodiment 1 is arranged in the paper feed conveying path 56 that conveys the recording paper 5 from the paper transport roll pair 55 to the secondary transfer position T2. ​​The medium guiding device 60 will be described in detail later.

[0048] Further, a paper transport path 57 is provided between the secondary transfer device 30 and the fixing device 40, which transports the recording paper 5 after secondary transfer sent from the secondary transfer device 30 to the fixing device 40. Above the fixing device 40, a paper discharge roll pair 59 is provided which discharges the recording paper 5 that has been subjected to the fixing process by the fixing device 40 to a paper discharge section 58 provided at the top of the device main body 1a.

[0049] The image forming apparatus 1 may be provided with a double-sided paper transport path (not shown) for forming images on both sides of the recording paper 5.

[0050] 1, reference numeral 100 indicates a control device that comprehensively controls the operation of the image forming apparatus 1. The control device 100 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), which are not shown, as well as buses and communication interfaces that connect the CPU, ROM, etc.

[0051] <Operation of image forming device> The basic image forming operation of the image forming apparatus 1 will be described below.

[0052] Here, we will explain the operation in full-color mode, in which the four image forming devices 10 (Y, M, C, K) are used to form a full-color image composed of a combination of toner images of four colors (Y, M, C, K).

[0053] When the image forming apparatus 1 receives image information and command information requesting a full-color image forming operation (printing) from a personal computer or image reading device (not shown), the control device 100 starts the four image forming devices 10 (Y, M, C, K), the intermediate transfer device 20, the secondary transfer device 30, the fixing device 40, etc.

[0054] In each imaging device 10 (Y, M, C, K), as shown in FIG. 1, first, each photosensitive drum 11 rotates in the direction indicated by arrow A, and each charging device 12 charges the surface of each photosensitive drum 11 to a required polarity (negative polarity in the first embodiment) and potential. Next, exposure device 13 irradiates the charged surface of photosensitive drum 11 with light emitted based on image signals obtained by converting the light into each color component (Y, M, C, K). Then, an electrostatic latent image of each color component, configured with a required potential difference, is formed on the surface of each photosensitive drum 11.

[0055] Next, the developing device 14 of each image forming device 10 (Y, M, C, K) performs development. Development is performed by supplying toner of the corresponding color (Y, M, C, K) charged to the required polarity (negative polarity) from the developing roll 141 and electrostatically attaching it to the electrostatic latent image of each color component formed on the photosensitive drum 11. Through this development, the electrostatic latent image of each color component formed on each photosensitive drum 11 is visualized as a toner image of four colors (Y, M, C, K) developed with the toner of the corresponding color.

[0056] Next, the toner images of each color formed on the photosensitive drum 11 of each image forming device 10 (Y, M, C, K) are transported to the primary transfer position T1. Then, the primary transfer devices 15 (Y, M, C, K) perform primary transfer of the toner images of each color in a superimposed order onto the intermediate transfer belt 21 of the intermediate transfer device 20, which rotates in the direction indicated by arrow B.

[0057] Furthermore, in each imaging device 10 (Y, M, C, K) where the primary transfer has been completed, the drum cleaning device 16 scrapes off any adhering matter to clean the surface of the photosensitive drum 11. This makes each imaging device 10 (Y, M, C, K) ready for the next image formation operation.

[0058] Next, the intermediate transfer device 20 holds the primarily transferred toner image by the rotation of the intermediate transfer belt 21 and transports it to the secondary transfer position T2. ​​Meanwhile, the paper feeder 50 sends out the required recording paper 5 to a paper feed path 56 in accordance with the image creation operation. In the paper feed path 56, a pair of paper transport rolls 55, which serve as registration rolls, feeds and supplies the recording paper 5 to the secondary transfer position T2 in accordance with the transfer timing.

[0059] At the secondary transfer position T2, the secondary transfer device 30 performs secondary transfer of the toner images on the intermediate transfer belt 21 all at once onto the recording paper 5. After the secondary transfer is completed in the intermediate transfer device 20, the belt cleaning device 26 removes and cleans the surface of the intermediate transfer belt 21 to remove any toner or other adhering matter remaining thereon after the secondary transfer.

[0060] Next, the recording paper 5 onto which the toner image has been secondarily transferred is peeled off from the intermediate transfer belt 21 and transported to the fixing device 40 via a paper transport path 57. In the fixing device 40, the recording paper 5 after the second transfer is introduced into and passes through a fixing nip N between a rotating heating rotor 42 and a pressure rotor 43. This performs the necessary fixing process (heating and pressurizing) to fix the unfixed toner image onto the recording paper 5. Finally, the recording paper 5 after fixing is discharged by a paper discharge roll pair 59 to a paper discharge section 58 located at the top of the device main body 1a.

[0061] By the above operation, the recording paper 5 is outputted on which a full color image formed by combining four color toner images is formed.

[0062] <Configuration of the media guide device> 1 and 2, the image forming apparatus 1 according to the first embodiment includes a medium guide device 60 as an example of a guide means. The medium guide device 60 includes first to third guide units that guide at least the surface of the recording paper 5 that faces the intermediate transfer belt 21 and is transported to the secondary transfer position T2 in the paper feed transport path 56. For convenience, the second and third guide units are not shown in FIG.

[0063] The medium guide device 60 includes a pair of guide members 61, 62 that respectively guide both the front and back sides of the recording paper 5 transported by the paper transport roll pair 55 to the secondary transfer position T2. ​​Of the pair of guide members 61, 62, the guide member 61 located on the intermediate transfer belt 21 side is an example of a first guide section.

[0064] The pair of guide members 61, 62 are formed, for example, by bending a metal plate having a required thickness. The guide member 61 guides the front side (image side) of the recording paper 5 to the secondary transfer position T2. ​​The guide member 62 guides the back side of the recording paper 5 to the secondary transfer position T2.

[0065] As shown in FIGS. 2 and 3 , the guide member 61 has a guide portion 611, a base end portion 612, and an attachment portion 614. The guide portion 611 of the guide member 61 is formed as a flat rectangular plate having a required width along the depth direction Y, for example, a width wider than the length along the longitudinal direction of an A4-size recording sheet 5. The guide portion 611 of the guide member 61 is attached to a frame (not shown) of the device main body 1a via the attachment portion 614. As shown in FIG. 2 , the guide portion 611 of the guide member 61 is disposed so as to be inclined at a required approach angle with respect to the intermediate transfer belt 21, which is stretched between the belt support roll 24 and the belt support roll 25 (each of which serves as an example of a rotating body). The base end portion 612 of the guide member 61 is bent slightly in a substantially L-shape toward the outside of the paper feed conveyance path 56, above the paper conveyance roll 55a of the paper conveyance roll pair 55 located at the lower end of the guide portion 611. As shown in FIG. 3, the attachment portions 614 of the guide member 61 are provided on both ends of the guide portion 611 along the longitudinal direction.

[0066] 2, a downstream end 613 of the guide member 61 along the guide direction C, which is also the conveying direction of the recording paper 5, is located in a position facing the belt support roll 24 that supports the back surface of the intermediate transfer belt 21. The downstream end 613 of the guide member 61 is arranged linearly without inclining along a direction that intersects with the guide direction C of the recording paper 5 guided by the guide member 61.

[0067] The intermediate transfer belt 21 is wound around the outer periphery of the belt support roll 24 toward the secondary transfer position T2 where the belt support roll 25 and the secondary transfer roll 31 come into contact with each other. A downstream end 613 of the guide member 61 is located at a position facing the belt support roll 24 that supports the intermediate transfer belt 21.

[0068] Here, the opposing position where the downstream end 613 of the guide member 61 faces the belt support roll 24 refers to a positional relationship where the downstream end 613 of the guide member 61 and the intermediate transfer belt 21 are closest to each other, and the belt support roll 24 is located on the back surface of the intermediate transfer belt 21. Therefore, the rear end 5b of the recording paper 5 that has passed the downstream end 613 of the guide member 61 directly contacts the belt support roll 24 via the intermediate transfer belt 21 in this state. In FIG. 10, H indicates a perpendicular line at the position where the intermediate transfer belt 21 separates from the belt support roll 24.

[0069] Below the guide member 61, a transport guide 63 is provided to guide the recording paper 5 supplied from the paper feeder 50 to the paper transport roll pair 55. The transport guide 63 is located on the paper transport roll 55a side of the nip position of the paper transport roll pair 55.

[0070] On the other hand, the guide member 62 has a guide portion 621, an intermediate portion 622, and a base end portion 623. The guide portion 621 of the guide member 62 is disposed at an angle relative to the guide portion 611 of the guide member 61 so that the distance between the lower end and the guide portion 621 is slightly wider than when the guide portion 621 is parallel to the guide portion 611 of the guide member 61. Like the guide portion 611 of the guide member 61, the guide portion 621 of the guide member 62 is formed in a flat rectangular shape with a required width along the depth direction Y perpendicular to the drawing, for example, a width wider than that of an A4-sized recording paper 5. The intermediate portion 622 of the guide member 62 is disposed so as to bend from the lower end of the guide portion 621 toward one paper transport roll 55b of the paper transport roll pair 55. The base end portion 623 of the guide member 62 is disposed so that a portion of one paper transport roll 55b protrudes from the lower end of the intermediate portion 622 into the paper transport path 56. The nip portion where the paper transport rolls 55 a and 55 b that make up the paper transport roll pair 55 come into contact is located between the transport guide 63 and the base end portion 623 of the guide member 62 .

[0071] Unlike the guide member 61, the downstream end 624 of the guide member 62 along the guiding direction C of the recording paper 5 does not face the belt support roll 24 that supports the back surface of the intermediate transfer belt 21. The downstream end 624 of the guide member 62 is located at a position closer to the secondary transfer position T2 than the opposing position where it faces the belt support roll 24.

[0072] 14, the leading edge 5a of the recording paper 5 supplied from the paper feeder 50 is guided by the transport guide 63 and the base end 623 of the guide member 62, and the recording paper 5 is transported toward one of the paper transport rolls 55a from the nip position of the paper transport roll pair 55. The recording paper 5 is then nipped by the paper transport roll pair 55 and transported through the middle part 622 of the guide member 62 located above in the vertical direction Z to an area where the guide part 611 of the guide member 61 and the guide part 621 of the guide member 62 face each other.

[0073] Incidentally, in the image forming apparatus 1 according to the first embodiment, the intermediate transfer device 20 is made smaller than that of conventional image forming apparatuses, and accordingly the image forming apparatus 1 is also made smaller.

[0074] 4 shows a part of the intermediate transfer device 20 and the medium guiding device 60 in the conventional image forming apparatus 1. Note that FIG. 4 is illustrated at the same scale as the part of the intermediate transfer device 20 and the medium guiding device 60 according to the first embodiment shown in FIG.

[0075] 2 and 4, in the image forming apparatus 1 according to this embodiment, the outer diameters of the belt support rolls 24, 25 (including other belt support rolls) that support the intermediate transfer belt 21 of the intermediate transfer device 20 are set smaller than those of the conventional device, thereby achieving a reduction in diameter. However, the outer diameter of the secondary transfer roll 31 is the same. Furthermore, in the image forming apparatus 1 according to this embodiment, the belt support roll 24 is positioned higher and closer to the belt support roll 25 than in the conventional device. In other words, in the image forming apparatus 1 according to this embodiment, the distance between the belt support roll 24 and the belt support roll 25 is set shorter than in the conventional device.

[0076] Accordingly, in the image forming apparatus 1 according to this embodiment 1, as shown in FIG. 2, the downstream end 613 of the guide member 61 in the media guide device 60 along the guide direction C of the recording paper 5 is positioned opposite the belt support roll 24, unlike conventional devices.

[0077] 4, in the conventional image forming apparatus 1, the downstream end 613 of the guide member 61 of the media guiding device 60 along the guiding direction C of the recording paper 5 is not positioned in an opposing position facing the belt support roll 24. In other words, the downstream end 613 of the guide member 61 of the conventional media guiding device 60 along the guiding direction C of the recording paper 5 is positioned in an opposing position facing only the intermediate transfer belt 21, which is spaced from the belt support roll 24 above the position where the intermediate transfer belt 21 is stretched by the belt support roll 24.

[0078] The present inventors have conducted extensive research into the effect that a change in the positional relationship of the medium guiding device 60 due to the miniaturization of the intermediate transfer device 20 has on the quality of the image transferred onto the recording paper 5 at the secondary transfer position T2.

[0079] As a result, the inventors have found that in the image forming apparatus 1 according to the first embodiment, the downstream end 613 of the guide member 61 along the guide direction C of the recording paper 5 is located in a position facing the belt support roll 24 that supports the intermediate transfer belt 21. Therefore, when the recording paper 5 is cardboard that is relatively thicker and more rigid than plain paper, particularly a postcard, image quality defects occur due to the impact when the trailing end 5b of the highly rigid recording paper 5 leaves the guide member 61 and comes into contact with the intermediate transfer belt 21 supported by the belt support roll 24, as shown in FIG.

[0080] 5(a), when the leading edge 5a of the recording paper 5 passes the secondary transfer position T2, the conveyance direction of the recording paper 5 changes to the left in the figure so as to move away from the intermediate transfer belt 21. At this time, the recording paper 5 is folded into a substantially V-shape before and after the secondary transfer position T2. ​​Therefore, when the trailing edge 5b of the recording paper 5, such as a postcard, passes the end 613 of the guide member 61, the recording paper 5 is bounced up by its own rigidity and comes into contact with the intermediate transfer belt 21, as shown in FIG.

[0081] 4, in a conventional image forming apparatus, there is no belt support roll 24 on the back surface of the intermediate transfer belt 21 corresponding to the end 613 of the guide member 61. As a result, when the rear end of the highly rigid recording paper 5 passes the end 613 of the guide member 61 and is bounced up by the rigidity of the recording paper 5 itself to come into contact with the intermediate transfer belt 21, the contact force of the recording paper 5 is absorbed to some extent by the intermediate transfer belt 21.

[0082] In contrast, in the image forming apparatus 1 according to the first embodiment, as shown in FIG. 2, a rigid belt support roll 24 is provided on the back surface of the intermediate transfer belt 21 corresponding to the end 613 of the guide member 61. As a result, when the trailing edge 5b of the highly rigid recording sheet 5 passes the leading edge of the guide member 61 and is raised by the rigidity of the recording sheet 5 to contact the intermediate transfer belt 21, as shown in FIG. 5B, the back surface of the intermediate transfer belt 21 is supported by the rigid belt support roll 24. Therefore, the contact force of the trailing edge 5b of the recording sheet 5 against the intermediate transfer belt 21 is not absorbed by the intermediate transfer belt 21 but is transmitted to the secondary transfer position T2 via the recording sheet 5 itself. As a result, the contact force of the trailing edge 5b of the recording sheet 5 is transmitted as vibrations to the image being transferred to the recording sheet 5 at the secondary transfer position T2 of the intermediate transfer belt 21. It has been found that the image transferred to the trailing edge of the recording sheet 5 suffers from an image quality defect called trailing edge bleeding due to the effects of vibrations, as shown in FIG. 6.

[0083] As shown in FIG. 4, this trailing edge bleeding that occurs at the trailing edge of the recording paper 5 does not occur in conventional image forming apparatuses, or even if it does occur, it is at a level that is not problematic.

[0084] Therefore, the present inventors have devised the following countermeasure to prevent or suppress the occurrence of an image defect known as trailing edge bleeding. As shown in FIG. 7 , this countermeasure involves attaching a Mylar 200 to the surface of the guide member 61, with the leading edge of the Mylar 200 protruding beyond the end 613 of the guide member 61. This ensures that the trailing edge 5b of the flipped-up recording paper 5 does not contact the surface of the intermediate transfer belt 21 supported by the belt support roll 24, but rather contacts the intermediate transfer belt 21 away from the belt support roll 24. This makes it possible to prevent or suppress the occurrence of trailing edge bleeding caused by the trailing edge 5b of the flipped-up recording paper 5 contacting the intermediate transfer belt 21 supported by the belt support roll 24. Note that FIG. 7 only illustrates the Mylar 200, and does not illustrate the guide member 61.

[0085] Furthermore, the inventors have conducted various studies to confirm the quality of the image transferred onto the recording paper 5 in the image forming apparatus 1 in which the above-mentioned countermeasures have been taken.

[0086] As a result, the inventors discovered that the occurrence of so-called trailing edge bleeding can be prevented or suppressed by attaching mylar 200 to the surface of guide member 61 and having the tip of mylar 200 protrude beyond end 613 of guide member 61. However, it became clear that a new image quality defect called trailing edge staining or trailing edge smudge occurs at the trailing edge of recording paper 5.

[0087] Here, as shown in Fig. 7, when the trailing edge 5b of the recording paper 5 passes through the Mylar 200 attached to the surface of the guide member 61, the Mylar 200 becomes frictionally charged to a positive polarity or the like due to the friction between the trailing edge 5b of the recording paper 5 and the Mylar 200, in accordance with its charging tendency. As a result, negatively charged toner t on the intermediate transfer belt 21 is electrostatically attracted and adheres to the back surface and leading edge of the Mylar 200. Therefore, when the trailing edge 5b of the recording paper 5 separates from the Mylar 200, the toner t that has adhered to the back surface and leading edge of the Mylar 200 adheres to the surface of the trailing edge of the recording paper 5, and appears as trailing edge dirt on the recording paper 5 as shown in Fig. 8.

[0088] Furthermore, when the leading edge of the Mylar 200 provided on the guide member 61 approaches the intermediate transfer belt 21, the leading edge of the Mylar 200 may come into contact with the toner image on the intermediate transfer belt 21. In this case, as shown in FIG. 9, if a high-density toner image is present on the intermediate transfer belt 21, it has been found to cause an image quality defect called trailing edge smudge, in which the high-density toner image that should be transferred to the trailing edge 5b of the recording paper 5 is disturbed.

[0089] Therefore, the media guide device of the image forming device according to this embodiment 1 not only prevents or suppresses the occurrence of trailing edge bleeding, but also prevents or suppresses the occurrence of secondary trailing edge dirt and trailing edge smudges even when a configuration is adopted that prevents or suppresses the occurrence of trailing edge bleeding.

[0090] The media guide device 60 of the image forming apparatus 1 according to this embodiment 1 is configured to include a second guide section that is arranged in the first guide section and is capable of elastic deformation so that its downstream end along the guide direction of the media protrudes from the first guide section, and a third guide section that is arranged in the second guide section and is capable of elastic deformation so that its downstream end along the guide direction of the media protrudes from the second guide section.

[0091] That is, as shown in FIG. 10, the media guide device 60 according to the first embodiment is configured such that a first plate-shaped member 71, which is an example of a second guide section, is laminated on the surface of the guide member 61 on the paper-passing side through which the recording paper 5 passes. The first plate-shaped member 71 is made of, for example, a Mylar film, which is a PET (polyethylene terephthalate) film having a thickness of approximately 0.10 to 0.75 mm. The thickness of the first plate-shaped member 71 is not limited to the above-mentioned range and may be thinner or thicker than the above-mentioned value. The first plate-shaped member 71 is laminated on the surface of the guide member 61 by an adhesive layer 73 made of an adhesive or glue such as double-sided tape. Here, the term "adhesion" includes both adhesion and bonding. In the first embodiment, an adhesive made of double-sided tape is used as the adhesive layer 73.

[0092] 11 and 12, the first plate-shaped member 71 has a base end 711 formed in a horizontally elongated rectangular shape in plan view corresponding to the guide portion 611 of the guide member 61. The base end 711 of the first plate-shaped member 71 is provided with its back surface 71b adhered to the guide portion 611 of the guide member 61 via an adhesive layer 73 made of double-sided tape. Also, as shown in FIG. 13, the first plate-shaped member 71 has a protruding portion 712 at its tip, the protruding portion 712 being slightly wider than the maximum paper passing width of the recording paper 5 (for example, the longitudinal direction of A4 size). The corners of the protruding portion 712 are formed in a rounded shape.

[0093] As shown in Figures 11 to 13, the first plate-like member 71 is not entirely adhered to the surface 61a of the guide member 61 by an adhesive layer 73, but rather the base end side excluding a required width W1 (see Figure 11) located at the tip end along the conveying direction of the recording paper 5 is adhered to the surface 61a of the guide member 61.

[0094] Therefore, the first plate-shaped member 71 has a non-adhesive region over a required width W1 at its tip end along the guiding direction C, excluding the protruding portion 712, that is not adhered to the surface 61a of the guide member 61. As shown in Fig. 11, a minute gap G1 corresponding to the thickness of the adhesive layer 73 is interposed between the first plate-shaped member 71 and the surface 61a of the guide member 61 in the non-adhesive region.

[0095] 10, the first plate-shaped member 71 is disposed so that a base end 711 on the downstream side along the guide direction C of the recording paper 5 protrudes a required protrusion amount (length) L1 from the end 613 of the guide member 61. The protrusion amount L1 of the first plate-shaped member 71 is set to, for example, about 1 to 10 mm. In this first embodiment, the protrusion amount L1 of the first plate-shaped member 71 is set to about 2 to 5 mm. However, the protrusion amount L1 of the first plate-shaped member 71 is not limited to this and may be smaller or larger than this range.

[0096] As shown in FIG. 10 , a second plate-shaped member 72, which serves as an example of a third guide section, is laminated on the back surface 71b of the first plate-shaped member 71 facing the intermediate transfer belt 21. Like the first plate-shaped member 71, the second plate-shaped member 72 is made of a Mylar film, which is a PET (polyethylene terephthalate) film with a thickness of approximately 0.10 to 0.75 mm. The thickness of the second plate-shaped member 72 is not limited to the above-described range and may be thinner or thicker than the above-described value. In this first embodiment, the thickness of the second plate-shaped member 72 is set equal to the thickness of the first plate-shaped member 71. Setting the thickness of the second plate-shaped member 72 equal to the thickness of the first plate-shaped member 71 reduces component costs. However, the second plate-shaped member 72 may be thicker or thinner than the first plate-shaped member 71.

[0097] The second plate-like member 72 is laminated on the back surface 71b of the first plate-like member 71, which is the surface facing the intermediate transfer belt 21, by an adhesive layer 74 made of a pressure sensitive adhesive or adhesive such as double-sided tape.

[0098] 12 and 13, the second plate-shaped member 72 is formed in the shape of an elongated rectangle in plan view having the same width as the protruding portion 712 of the first plate-shaped member 71. A surface 72a of the second plate-shaped member 72 is provided in a state of being adhered to the protruding portion 712 of the first plate-shaped member 71 via an adhesive layer 74 made of double-sided tape. The adhesive layer 74 made of double-sided tape is slightly narrower in width and shorter in length than the second plate-shaped member 72.

[0099] As shown in Figure 11, the second plate-shaped member 72 is not entirely adhered to the back surface 71b of the first plate-shaped member 71 by an adhesive layer 74, but rather has its base end side, excluding a required width W2 located at the tip end along the guide direction C of the recording paper 5, adhered to the back surface 71b of the first plate-shaped member 71.

[0100] Furthermore, the base end of the second plate-shaped member 72 is located on the back surface 71b of the first plate-shaped member 71 at a position spaced a minute distance L4 from the end 613 of the guide member 61. As a result, the second plate-shaped member 72 is not located in a position that overlaps with the guide member 61 along the guiding direction C of the recording paper 5. This position of the second plate-shaped member 72 spaced a distance L4 is continuous with the non-adhesive region of the first plate-shaped member 71. Therefore, the first plate-shaped member 71 is not adhered to the guide member 61 or the second plate-shaped member 72 for a length of the distance L4 in addition to the non-adhesive region, and this region allows free elastic deformation although it is restricted by the minute gap G1.

[0101] Therefore, the second plate-shaped member 72, excluding its protruding portion, has a non-adhesive region over a required width W2 at its tip end along the guide direction C that is not adhered to the back surface 71b of the first plate-shaped member 71. A minute gap G2 corresponding to the thickness of the adhesive layer 74 is interposed between the second plate-shaped member 72 and the back surface 71b of the first plate-shaped member 71 in the non-adhesive region.

[0102] 10, the second plate-shaped member 72 is disposed so that its downstream end 721 in the guide direction C of the recording paper 5 protrudes a required protrusion amount (length) L2 from the leading end 713 of the first plate-shaped member 71. The protrusion amount L2 of the second plate-shaped member 72 is set to, for example, about 1 to 10 mm. However, the protrusion amount L2 of the second plate-shaped member 72 is not limited to this and may be smaller or larger than this range.

[0103] In this first embodiment, the second plate-shaped member 72 has a protrusion amount L2 of about 1 to 3 mm, which is set to a value smaller than the protrusion amount L1 of the first plate-shaped member 71. However, the protrusion amount L2 of the second plate-shaped member 72 may be set to be equal to or larger than the protrusion amount L1 of the first plate-shaped member 71.

[0104] When the protrusion amount L2 of the second plate-shaped member 72 is set to a value smaller than the protrusion amount L1 of the first plate-shaped member 71, the downstream end 721 of the second plate-shaped member 72 along the guide direction C can be prevented from coming close to the surface of the intermediate transfer belt 21, which is desirable in terms of preventing or suppressing the occurrence of trailing end smudges.

[0105] <Action of the media guide device> In the media guide device of this embodiment 1, it is possible to suppress the occurrence of image quality defects caused by the impact when the rear end of the highly rigid media comes into contact with the endless belt supported by the rotating body, compared to when the second and third guide sections are not provided, in the following manner.

[0106] That is, in the image forming apparatus 1 to which the media guide device 60 according to this embodiment 1 is applied, as shown in Figures 1 and 2, in conjunction with the image forming operation, the recording paper 5 supplied from the paper feed device 50 is transported along the paper feed transport path 56 via the media guide device 60 to the secondary transfer position T2 of the intermediate transfer device 20.

[0107] 14, the recording paper 5 is transported by the paper transport roll pair 55 to the secondary transfer position T2 of the intermediate transfer device 20. At this time, the leading edge 5a of the recording paper 5 is guided along the guide portion 611 of the guide member 61 with its front surface in contact with the first plate-like member 71 stacked on the surface 61a of the guide member 61. The first plate-like member 71 is arranged in a stacked state on the surface of the guide portion 611 of the guide member 61.

[0108] The recording paper 5 guided along the guide portion 611 of the guide member 61 on which the first plate-like member 71 is stacked is transported to the secondary transfer position T2 of the intermediate transfer device 20 via the second plate-like member 72, and the toner image on the intermediate transfer belt 21 is secondarily transferred onto the recording paper 5. The recording paper 5 on which the toner image has been transferred is separated from the intermediate transfer belt 21 by its own rigidity according to the curvature of the secondary transfer roll 31, and is transported to the fixing device 40 along the paper transport path 57 (see FIG. 1).

[0109] At this time, the recording paper 5 passes through the secondary transfer roll 31 of the intermediate transfer device 20 and is conveyed so that the leading edge 5 a side of the recording paper 5 is bent along the outer peripheral surface of the secondary transfer roll 31 .

[0110] Furthermore, the rear end 5b of the recording paper 5 is guided downstream along the guide direction C, which is the conveying direction, by the guide member 61 and the first and second plate-like members 71, 72 stacked on the surface of the guide member 61. When the rear end 5b of the recording paper 5 is guided by the first and second plate-like members 71, 72 stacked on the surface of the guide member 61, the leading end 5a of the recording paper 5 is conveyed so as to bend along the outer circumferential surface of the secondary transfer roll 31, and as a reaction force, an elastic restoring force acts on the rear end 5b of the recording paper 5 toward the intermediate transfer belt 21.

[0111] As a result, as shown in Figure 15(a), conventionally, the rear end 5b of the recording paper 5 moves while being pressed against the surface of the Mylar 200 by the elastic restoring force of the recording paper 5. Therefore, the Mylar 200, which is made of a synthetic resin film such as PET (polyethylene terephthalate), becomes frictionally charged to a positive polarity or the like due to rubbing against the rear end 5b of the recording paper 5.

[0112] When the Mylar 200 is frictionally charged to a positive polarity, a portion of the toner t that constitutes the toner image on the intermediate transfer belt 21 adheres to the back surfaces of the first and second plate-like members 71, 72, particularly the back surfaces near the tips, due to electrostatic adsorption.

[0113] Then, when the trailing edge 5b of the recording paper 5 leaves the Mylar 200 and moves to the secondary transfer position T2, the toner t that has adhered to the back surface of the Mylar 200 adheres to the front surface of the recording paper 5. As a result, as described above, this causes an image quality defect called trailing edge dirt, as shown in Figure 15(a). Here, N1 represents the friction force between the trailing edge 5b of the recording paper 5 and the Mylar 200, L10 represents the friction length between the trailing edge 5b of the recording paper 5 and the Mylar 200, and Q1 represents the amount of charge due to friction between the trailing edge 5b of the recording paper 5 and the Mylar 200.

[0114] However, in the medium guide device 60 according to the first embodiment, as shown in FIG. 10 , a first plate-shaped member 71 and a second plate-shaped member 72 are arranged in a stacked state on the surface of the guide member 61. Moreover, the second plate-shaped member 72 is stacked on the side of the first plate-shaped member 71 facing the intermediate transfer belt 21. As a result, as shown in FIG. 15( b), when the trailing end 5 b of the recording paper 5 passes through the guide member 61, the protrusion amount L20 by which the trailing end 5 b of the recording paper 5 moves from the first plate-shaped member 71 to the second plate-shaped member 72 and rubs against it is relatively short. Moreover, because the second plate-shaped member 72 is stacked on the side of the first plate-shaped member 71 facing the intermediate transfer belt 21, the restoring force generated by the bending deformation of the trailing end 5 b of the recording paper 5 when the trailing end 5 b of the recording paper 5 moves from the first plate-shaped member 71 to the second plate-shaped member 72 is also reduced, and the frictional force N2 with the second plate-shaped member 72 is reduced. Furthermore, the protrusion amount of the second plate-shaped member 72 is set to be smaller than that of the first plate-shaped member 71. Therefore, the protrusion amount L20 of the second plate-shaped member 72, which the trailing edge 5b of the recording paper 5 rubs against, is also shorter than that of the first plate-shaped member 71.

[0115] As described above, in the medium guiding device 60 according to the first embodiment, the first and second plate-shaped members 71 and 72 are stacked on the surface 61a of the guide member 61. Therefore, even when the end 613 of the guide member 61 is positioned opposite the belt support roll 24, the trailing end 5b of the recording paper 5 guided by the guide member 61 is guided by the first and second plate-shaped members 71 and 72. The trailing end 5b of the recording paper 5 comes into contact with the surface of the intermediate transfer belt 21 spaced apart from the belt support roll 24.

[0116] Therefore, even when the recording paper 5 is highly rigid, such as a postcard, the contact force is relatively small when the rear end 5b of the recording paper 5 that is bounced up comes into contact with the surface of the intermediate transfer belt 21 that is separated from the belt support roll 24. This makes it possible to reduce or prevent the impact at the secondary transfer position T2 that is caused by the contact force when the rear end 5b of the recording paper 5 comes into contact with the surface of the intermediate transfer belt 21, and to prevent or suppress the occurrence of trailing end bleeding.

[0117] Furthermore, in the medium guiding device 60 according to the first embodiment, the plate members stacked on the front surface 61a of the guide member 61 are made up of first and second plate members 71, 72, and the second plate member 72 is stacked on the back surface 71b of the first plate member 71. Therefore, the amount of charge Q2 caused by frictional electrification of the first and second plate members 71, 72 is small, and it is possible to prevent or suppress the occurrence of rear end contamination.

[0118] Furthermore, in the medium guide device 60 according to the first embodiment, the plate members stacked on the surface 61a of the guide member 61 are made up of first and second plate members 71, 72, and the protrusion amount of the second plate member 72 is set to be smaller than that of the first plate member 71. Therefore, it is possible to prevent the end 721 of the second plate member 72 stacked on the surface 61a of the guide member 61 from coming close to the surface of the intermediate transfer belt 21, and it is possible to prevent or suppress the occurrence of trailing edge smudges.

[0119] Experimental example Next, in order to confirm the effect of the media guide device 60 according to the above-mentioned embodiment 1, the inventors produced a prototype image forming device 1 incorporating the media guide device 60 configured as shown in Figures 1 and 10, and conducted experiments to confirm the occurrence of image quality defects such as trailing edge bleeding, trailing edge dirt, and trailing edge smudge.

[0120] 16, the experiment was carried out by changing the gap g between the intermediate transfer belt 21 and the tips of the first and second plate-like members 71 and 72 stacked on the surface 61a of the guide member 61, and the distance d from the opposing position of the belt support roll 24 to the tips of the first and second plate-like members 71 and 72. Note that the guide member 61 is arranged with its end 613 facing the belt support roll 24. In the experimental example, the position of the guide member 61 remains the same.

[0121] 17 and 18 are charts showing the results of the above-mentioned experimental example. In each chart, a circle indicates a case where the occurrence of any of the problematic levels of trailing-edge bleeding, trailing-edge soiling, and trailing-edge smudge was prevented. An x indicates a case where any of the problematic levels of trailing-edge bleeding, trailing-edge soiling, and trailing-edge smudge occurred.

[0122] As is clear from Figure 17, it has been found that the occurrence of trailing edge bleeding can be prevented when the distance along the guiding direction C of the recording paper 5 from the opposing position where the end 613 of the guide member 61 and the belt support roll 24 face each other is 2.0 mm or more, which is an example of a predetermined distance.

[0123] In contrast, when the distance along the guiding direction C of the recording paper 5 from the opposing position where the end 613 of the guide member 61 faces the belt support roll 24 is less than 2.0 mm, the end 613 of the guide member 61 is close to the opposing position with the belt support roll 24, causing trailing edge bleeding.

[0124] Furthermore, as is clear from Figure 17, if the gap g between the tip of the second plate-shaped member 72 and the intermediate transfer belt 21 is 1.40 mm or more, which is an example of a predetermined gap, a sufficient gap can be set between the tip of the second plate-shaped member 72 and the intermediate transfer belt 21, and it has been found that the occurrence of trailing edge smudge can be prevented.

[0125] On the other hand, when the gap g between the leading edge of the second plate-shaped member 72 and the intermediate transfer belt 21 was less than 1.40 mm, the leading edge of the second plate-shaped member 72 was close to the intermediate transfer belt 21, causing trailing edge smudges.

[0126] Furthermore, as is clear from FIG. 18, it has been found that by providing the second plate-like member 72 so that it protrudes from the leading end of the first plate-like member 71, it is possible to prevent the occurrence of rear end contamination.

[0127] On the other hand, as is clear from Figure 18, when the second plate-shaped member 72 was not protruded from the tip of the first plate-shaped member 71, and as a result only the first plate-shaped member 71 was provided, rear end contamination occurred.

[0128] [Embodiment 2] 19 is a configuration diagram showing a medium guide device according to embodiment 2 of the present invention. The medium guide device according to embodiment 2 is configured so that the second guide unit is located on the endless belt side rather than on the opposite side to the endless belt side of the first guide unit, and the third guide unit is located on the opposite side of the endless belt of the second guide unit.

[0129] 19, the medium guide device 60 according to the second embodiment has a first plate-shaped member 71 as an example of a second guide section stacked on a back surface 61b of the guide member 61, rather than on a front surface 61a of the guide member 61. Also, a second plate-shaped member 72 as an example of a third guide section is configured to be placed on a front surface 71a of the first plate-shaped member 71, rather than on a back surface 71b of the first plate-shaped member 71.

[0130] In the case of the media guide device 60 according to this embodiment 2, the first plate-shaped member 71 is arranged on the back surface 61b of the guide member 61, so that while it is close to the intermediate transfer belt 21, frictional charging caused by the rear end 5b of the recording paper 5 rubbing against the first plate-shaped member 71 can be prevented.

[0131] The other configurations and operations are the same as those of the first embodiment, and therefore the description thereof will be omitted.

[0132] [Embodiment 3] 20 is a configuration diagram showing a medium guide device according to embodiment 3 of the present invention. In the medium guide device according to embodiment 3, the third guide section is not flat, but the tip of the third guide section is curved or bent.

[0133] That is, the media guide device 60 according to this embodiment 3 is configured so that the tip portion 720 of the second plate-shaped member 72, which is an example of the third guide portion, is curved or bent toward the intermediate transfer belt 21, as shown in FIG.

[0134] In the case of the media guide device 60 according to this embodiment 3, by curving or bending the tip portion 720 of the second plate-shaped member 72, it is possible to more effectively prevent or suppress the trailing edge bleeding that occurs when the trailing edge 5b of the recording paper 5 abuts against the intermediate transfer belt 21.

[0135] Furthermore, in the case of the medium guiding device 60 according to the third embodiment, it is possible to shorten the protrusion amounts L1 and L2 of the first and second plate-shaped members 71 and 72 by curving or bending the tip 720 of the second plate-shaped member 72. This makes it possible to effectively prevent or suppress the occurrence of stains on the trailing edge 5b of the recording paper 5 caused by the trailing edge 5b rubbing against the second plate-shaped member 72.

[0136] The other configurations and operations are the same as those of the first embodiment, and therefore the description thereof will be omitted.

[0137] [Embodiment 4] 21 is a structural diagram showing a medium guide device according to embodiment 4 of the present invention. The medium guide device according to embodiment 4 is configured to include, in addition to a third guide section, a fourth guide section that is arranged to protrude from an end of the third guide section.

[0138] 21, the medium guide device 60 according to the fourth embodiment is configured such that a third plate-shaped member 80 as an example of a fourth guide section is laminated on the back surface of a second plate-shaped member 72 as an example of a third guide section via an adhesive layer 81. The third plate-shaped member 80 is configured similarly to the second plate-shaped member 72.

[0139] In the case of the media guide device 60 of this embodiment 4, a third plate-shaped member 80 is provided at the tip of the second plate-shaped member 72, so that the occurrence of trailing edge bleeding and trailing edge dirt can be further prevented or suppressed.

[0140] The other configurations and operations are the same as those of the first embodiment, and therefore the description thereof will be omitted.

[0141] [Embodiment 5] 22 is a configuration diagram showing a medium guide device according to embodiment 5 of the present invention. In the medium guide device according to embodiment 5, the second guide section is not simply formed in a flat plate shape, but is configured so that a dashed slit is provided at the base end of the second guide section along a direction intersecting the medium transport direction.

[0142] That is, as shown in Figure 22, the media guide device 60 of this embodiment 5 is configured so that the first plate-shaped member 71, which is an example of a second guide section, is not simply formed flat, but has a dashed slit 90 near the tip of the base end of the first plate-shaped member along a direction intersecting the conveying direction of the recording paper 5.

[0143] In the case of the media guide device 60 according to this embodiment 5, by providing a dashed slit 90 in the first plate-shaped member 71 along a direction intersecting the conveying direction of the recording paper 5, the elastic deformation of the first plate-shaped member 71 becomes easier, and it becomes possible to further prevent or suppress the occurrence of trailing end bleeding caused by the trailing end 5b of the recording paper 5 abutting against the intermediate transfer belt 21.

[0144] The other configurations and operations are the same as those of the first embodiment, and therefore the description thereof will be omitted.

[0145] (Addendum) (((1))) a first guide section that guides the medium toward a transfer section that transfers an image on the endless belt to the medium, and that is disposed so that a downstream end of the medium along the guiding direction faces a rotating body that supports the endless belt; a second guide portion that is disposed in the first guide portion and is capable of elastic deformation such that a downstream end portion along a guiding direction of the medium protrudes from the first guide portion; a third guide section that is disposed in the second guide section and is capable of elastic deformation such that a downstream end portion along the guiding direction of the medium protrudes from the second guide section; A media guide device comprising: (((2))) The medium guide device according to (((1))), wherein the third guide section is disposed on the endless belt side of the second guide section. (((3))) The medium guide device according to (((2))), wherein the second guide portion is set to have a larger protrusion amount than the third guide portion. (((4))) The medium guide device according to (((3))), wherein the second and third guide portions are set to have the same thickness. (((5))) The medium guide device according to (((2))), wherein a part of the third guide portion excluding a protruding portion protruding from the second guide portion is not adhered to the second guide portion. (((6))) The third guide section has a downstream end along the guide direction of the medium that is at least a predetermined distance away from the opposing position of the first guide section and the rotating body (((1))). (((7))) The medium guiding device according to (((6))), wherein the third guiding section has a gap between the downstream end of the medium in the guiding direction and the endless belt that is equal to or greater than a predetermined threshold value. (((8))) The medium guide device according to (((1))), wherein a part of the second guide portion excluding a protruding portion protruding from the first guide portion is not adhered to the first guide portion. (((9))) The medium guide device according to (((8))), wherein the third guide portion is bonded to the second guide portion at a protruding portion where the second guide portion protrudes from the first guide portion. (((10))) an endless belt for holding the image; a transfer means for transferring the image to a medium in a transfer section; a guide means for guiding a surface of the medium transported to the transfer unit on the side of the endless belt; Equipped with An image forming apparatus using the medium guide device according to any one of (((1))) to (((9))) as the guide means.

[0146] The media guide device according to (((1))) can suppress the occurrence of image quality defects caused by the impact when the rear end of the highly rigid media comes into contact with the endless belt supported by the rotating body, compared to a case where the second and third guide sections are not provided. According to the media guide device of (((2))), the third guide section can further suppress the occurrence of image quality defects caused by the impact when the rear end of the highly rigid media comes into contact with the endless belt supported by the rotating body, compared to when it is positioned on the opposite side of the endless belt of the second guide section. According to the media guide device of (((3))), it is possible to suppress the occurrence of image quality defects called trailing end smudges, which occur when the tip of the third guide section comes close to the endless belt, compared to when the protrusion amount of the third guide section is greater than the protrusion amount of the second guide section. According to the medium guiding device of (((4))), it is possible to reduce component costs compared to when the second and third guiding parts have different thicknesses. According to the medium guide device of (((5))), the third guide section can smoothly transfer the medium to the third guide section compared to when its entire surface is bonded to the second guide section. According to the media guide device of (((6))), the third guide section can suppress the occurrence of an image quality defect called trailing edge bleeding, compared to when the downstream end along the media guide direction is close to the opposing position of the first guide section and the rotating body. According to the media guiding device of (((7))), the third guiding section can reliably suppress the occurrence of image quality defects called trailing end smudges, compared to when the gap between the downstream end along the guiding direction of the media and the endless belt is less than a predetermined threshold value. According to the medium guide device of (((8))), the second guide section is more easily deformed than when the entire surface of the second guide section is bonded to the first guide section. According to the medium guide device of (((9))), the third guide portion is more easily deformed than when it is bonded to a portion other than the protruding portion of the second guide portion. According to the image forming apparatus of (((10))), compared to when the media guide device described in any of (((1))) to (((9))) is not used as the guide means, it is possible to suppress the occurrence of image quality defects caused by the impact when the rear end of the highly rigid media comes into contact with the endless belt supported by the rotating body. [Explanation of symbols]

[0147] 1...Image forming device 5...Recording paper (medium) 20...Intermediate transfer device 21...Intermediate transfer belt 24...Belt support roll 25...Belt support roll 30...Secondary transfer device 60...Media guide device 61...Guide member 62...Guide member 71...first plate-shaped member 72...Second plate-shaped member T2: Secondary transfer position

Claims

1. a first guide section that guides the medium toward a transfer section that transfers an image on the endless belt to the medium, and that is disposed so that a downstream end of the medium along the guiding direction faces a rotating body that supports the endless belt; a second guide portion that is disposed in the first guide portion and is capable of elastic deformation such that a downstream end portion along a guiding direction of the medium protrudes from the first guide portion; a third guide portion that is disposed in the second guide portion and is capable of elastic deformation such that a downstream end portion along a guiding direction of the medium protrudes from the second guide portion; A media guide device comprising:

2. The medium guide device according to claim 1 , wherein the third guide portion is disposed on a side of the second guide portion facing the endless belt.

3. The medium guide device according to claim 2 , wherein the second guide portion has a protruding amount set to be larger than the protruding amount of the third guide portion.

4. The media guide device according to claim 3 , wherein the second and third guide portions have the same thickness.

5. The medium guide device according to claim 2 , wherein a part of the third guide portion excluding a protruding portion protruding from the second guide portion is not adhered to the second guide portion.

6. The medium guide device according to claim 1 , wherein the downstream end of the third guide section along the guide direction of the medium is spaced a predetermined distance or more from the opposing position of the first guide section and the rotating body.

7. The medium guide device according to claim 6 , wherein the third guide section has a gap between the downstream end of the medium in the guide direction and the endless belt that is equal to or greater than a predetermined threshold value.

8. The medium guide device according to claim 1 , wherein a portion of the second guide portion excluding a protruding portion protruding from the first guide portion is not adhered to the first guide portion.

9. The medium guide device according to claim 8 , wherein the third guide portion is bonded to the second guide portion at a protruding portion where the second guide portion protrudes from the first guide portion.

10. an endless belt for holding the image; a transfer means for transferring the image to a medium in a transfer section; a guide means for guiding a surface of the medium transported to the transfer unit on the side of the endless belt; Equipped with 10. An image forming apparatus using the medium guide device according to claim 1 as the guide means.

Images