JP2012203006A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problems of an image forming device using an intermediate transfer system: when a tip of a recording medium to be conveyed to a transfer position curls, the curling part comes in contact with an intermediate transfer belt during transfer, thereby deteriorating an image transferred on the intermediate transfer belt and degrading the quality of the printed image.SOLUTION: The image forming device includes: an intermediate transfer belt 51 on which a toner image is primarily transferred from an image carrier; a secondary transfer counter roller arranged inside the intermediate transfer belt 51 to guide it; a secondary transfer belt unit 70 that forms a secondary transfer nip part 78 together with the secondary transfer counter roller 54 to secondarily transfer the toner image primarily transferred on the intermediate transfer belt 51 onto a recording medium at the secondary transfer nip part 78; and a pre-transfer guide member 60 located upstream the secondary transfer nip part 78 in a conveyance direction of the recording medium and between the recording medium and the intermediate transfer belt 51, to guide the conveyed recording medium to the secondary transfer nip part 78 and press it toward the secondary transfer belt 71.

Description

  The present invention relates to an image forming apparatus that forms an image on a recording medium, and more particularly to an intermediate transfer type image forming apparatus.

  Conventionally, in this type of image forming apparatus, a toner image is temporarily transferred from an image forming unit to an intermediate transfer belt, and further, a toner image on the intermediate transfer belt is transferred to a recording medium by a secondary transfer unit (for example, Patent Document 1).

JP 2010-277038 A (page 4, FIG. 1)

  However, in the image forming apparatus having the above configuration, when the leading end portion of the recording medium is curled, the leading end portion of the recording medium conveyed to the transfer position and the intermediate transfer belt are rubbed, and the image transferred to the intermediate transfer belt is deteriorated, and printing is performed. There was a problem that the quality of the image deteriorated.

An image forming apparatus according to the present invention includes:
An endless intermediate transfer belt on which a toner image is primarily transferred from an image carrier, a secondary transfer facing portion that is disposed inside the intermediate transfer belt and guides the intermediate transfer belt, and the secondary transfer facing portion And a secondary transfer nip portion, and a secondary transfer portion that secondary-transfers the toner image primarily transferred to the intermediate transfer belt to the recording medium at the secondary transfer nip portion, and a conveyance direction of the recording medium Upstream of the secondary transfer nip portion, between the recording medium and the intermediate transfer belt, and guides the conveyed recording medium to the secondary transfer nip portion and the secondary transfer portion. And a pre-transfer guide portion that is biased toward the surface.

  According to the present invention, since the recording medium does not contact the intermediate transfer belt on the upstream side from the secondary transfer nip portion, the toner image transferred to the intermediate transfer belt is not deteriorated due to rubbing or the like. A quality print image can be provided.

1 is a main part configuration diagram showing a main part configuration of a first embodiment of an image forming apparatus according to the present invention; FIG. 3 is a schematic configuration diagram illustrating a positional relationship among an intermediate transfer belt unit, a secondary transfer belt unit, a first conveyance guide and a second conveyance roller pair, and a second conveyance guide in the first embodiment. FIG. 3 is an external perspective view of an intermediate transfer belt unit and a pre-transfer guide member attached thereto in Embodiment 1. (A) is an external appearance perspective view of the guide member before transfer of Embodiment 1, (b) is the side view. In Embodiment 1, it is a figure which shows the positional relationship of the guide film of the guide member before transfer, and the secondary transfer belt unit which is a secondary transfer part. In Embodiment 1, it is explanatory drawing which shows typically each width W1, W2, W3, W4 of a secondary transfer belt, an intermediate transfer belt, a guide film, and a recording medium, and the relative positional relationship in the width direction. . (A), (b), and (c) are operation | movement explanatory drawings for demonstrating the process in which the recording medium which the front-end | tip part curled convexly passes a conveyance path to a secondary transfer nip part. (A), (b), and (c) are operation | movement explanatory drawings for demonstrating the process in which the recording medium which the front-end | tip part curled concavely passes a conveyance path to a secondary transfer nip part. It is a block diagram of an intermediate transfer belt unit employed in the image forming apparatus of Embodiment 2 based on the present invention and a pre-transfer guide member attached thereto. FIG. 6 is a cross-sectional view at a central portion in a longitudinal direction of a pre-transfer guide member according to Embodiment 2. (A) is an external appearance perspective view of the guide member before transfer of Embodiment 3, (b) is the side view. FIG. 6 is a side view of a guide film according to a third embodiment. In Embodiment 3, it is a figure which shows the positional relationship of the guide film of the guide member before transfer, and the secondary transfer belt unit as a secondary transfer part. FIG. 10 is a diagram illustrating a positional relationship between a guide film and a secondary transfer belt unit as a secondary transfer unit in the image forming apparatus according to the fourth embodiment. FIG. 10 is a diagram showing a modification example in the fourth embodiment. FIG. 10 is a diagram illustrating a positional relationship between a guide film and a secondary transfer roller as a secondary transfer unit in the image forming apparatus according to the fifth embodiment. (A), (b) is a side view which shows the shape of the guide film of the pre-transfer guide member of Embodiment 6, (c) is a figure which shows another example. (A), (b) is a side view which shows the modification of the guide film of the pre-transfer guide member of Embodiment 6. FIG.

Embodiment 1 FIG.
FIG. 1 is a main part configuration diagram showing the main part configuration of Embodiment 1 of an image forming apparatus according to the present invention. As shown in FIG. 1, the image forming apparatus 1 forms an image on a recording medium 10 by an electrophotographic method based on image data transmitted from an external computer or the like.

  The image forming apparatus 1 has a configuration as an indirect transfer type tandem color electrophotographic printer, and includes a paper feed tray 11, a paper feed unit 13, a transport unit 16, four toner image forming units 39C, 39M, 39Y, and 39K ( If there is no need to distinguish between them, they may be simply referred to as toner image forming unit 39), intermediate transfer belt unit 50, secondary transfer belt unit 70, fixing unit 25, paper discharge unit 26, and image forming apparatus main body 40. A medium stacking section 41 is provided for stacking the recording medium 10 with the image forming surface facing down at the top.

  Each toner image forming unit 39 includes a photosensitive member 34 as an image carrier, a charging roller 35 for uniformly charging the surface of the photosensitive member 34, and development for developing an electrostatic latent image formed on the photosensitive member 34 with toner. The roller 38 is held. The optical unit 36 disposed above the photoconductor 34 includes LED elements arranged in the axial direction of the photoconductor 34, and forms an electrostatic latent image corresponding to image data on the surface of the charged photoconductor 34. To do. Thus, the toner image forming unit 39C forms a cyan (C) toner image, the toner image forming unit 39M forms a magenta (M) toner image, and the toner image forming unit 39Y uses a yellow (Y) toner image. The toner image forming unit 39K forms a black (K) toner image. The optical unit 36 may be a laser scanning unit including a laser irradiation unit and a polygon mirror.

  FIG. 2 is a schematic configuration diagram showing the positional relationship between the intermediate transfer belt unit 50, the secondary transfer belt unit 70, the first conveyance guide 19, the second conveyance roller pair 18, and the second conveyance guide 20 belonging to the conveyance unit 16. 3 is an external perspective view of the intermediate transfer belt unit 50 and the pre-transfer guide member 60 attached to the intermediate transfer belt unit 50, and FIG. 4A is an external perspective view of the pre-transfer guide member 60. 4 (b) is a side view of the pre-transfer guide member 60. FIG. The configuration of the image forming apparatus 1 will be described in more detail with reference to FIG. 2, FIG. 3, and FIG.

  The intermediate transfer belt unit 50 shown in FIG. 3 is detachably attached to the image forming apparatus main body 40 (FIG. 1), and as shown in the figure, the endless intermediate transfer belt 51 includes left and right intermediate transfer belt unit frames. It is stretched by an intermediate transfer belt driving roller 53, a secondary transfer counter roller 54, and an intermediate transfer belt stretching roller 55 supported by 58 (only one (left side) shown in FIG. 3). The intermediate transfer belt drive roller 53 is driven by a drive motor (not shown) and rotationally drives the intermediate transfer belt 51 in the direction of the arrow in the drawing. In addition, as in the case of the intermediate transfer belt unit 50 of the image forming apparatus 1, a portion excluding the detachable or movable component is referred to as an image forming apparatus main body 40 (FIG. 1). There is.

  A secondary transfer counter roller 54 as a secondary transfer counter portion is a metallic roller that is disposed inside the intermediate transfer belt 51 and guides the inner surface of the intermediate transfer belt 51. The intermediate transfer belt unit 50 is connected to the image forming apparatus main body. By being attached to 40, it is disposed at a position facing the secondary transfer roller 72 (FIG. 2) via the secondary transfer belt 71 and the intermediate transfer belt 51, and is electrically grounded.

  The intermediate transfer belt stretching roller 55 has shaft portions 55a at both ends (only one is shown in FIG. 3) of the intermediate transfer belt 51 by left and right intermediate transfer belt unit frames 58 (only the left side is shown in FIG. 3). It is rotatably held by left and right holder members 56 (only the left side is shown in FIG. 3) held so as to be slidable in a predetermined direction enabling stretching. Between the holder member 56 and the intermediate transfer belt unit frame 58, an intermediate transfer belt tension spring 57 is installed in a direction in which the secondary transfer belt 71 is stretched. The above-described configuration using the intermediate transfer belt unit frame 58, the intermediate transfer belt stretching roller 55 holder member 56, and the intermediate transfer belt stretching spring 57 is configured similarly on the right side (not shown).

  Further, a position 1 in contact with the photoreceptors 34 (FIG. 1) of the toner image forming units 39C, 39M, 39Y, and 39K inside the intermediate transfer belt 51 is supported by the left and right intermediate transfer belt unit frames 58. Secondary transfer rollers 52C, 52M, 52Y, and 52K (which may be simply referred to as primary transfer roller 52 if they do not need to be distinguished) are installed.

  A pre-transfer guide member 60 as a pre-transfer guide portion is fixedly attached to the intermediate transfer belt unit frame 58 with a fixing screw 64 on the upstream side of the secondary transfer counter roller 54 in the belt conveyance direction.

  The pre-transfer guide member 60 includes a metal sheet metal guide 61 as a guide portion, a fixing member 63 fixed to the sheet metal guide 61, and a guide film 62 as a sheet-like member attached to the fixing member 63. Is done. The sheet metal guide 61 is continuously connected to the bottom 61d by being bent in a “U” shape from both ends in the longitudinal direction of the bottom 61d. The left and right mounting side surfaces 61a and 61b are opposed to each other and the upper side from the side of the bottom 61d. It is comprised from the introduction guide part 61c which inclines and extends.

  The fixing member 63 is formed in a wedge shape in cross section, and is fixedly disposed with an adhesive tape on the upper surface opposite to the lower surface serving as the guide surface of the bottom portion 61 d of the sheet metal guide 61. On the inclined upper surface of the fixing member 63, a guide film 62, which is a second guide portion inclined downward from the sheet metal guide 61 toward the opposite side to the introduction guide portion 61c, is adhered. It is attached by tape. The pre-transfer guide member 60 is fixed and attached to the left and right intermediate transfer belt unit frames 58 by fixing screws 64 and 64 penetrating through attachment holes formed in the left and right side surfaces 61a and 61b of the sheet metal guide 61. . Here, the fixing member 63 and the guide film 62 correspond to the urging portion.

  Here, because there is a space limitation due to the positional relationship between the medium conveyance path and the intermediate transfer belt unit 50 in the image forming apparatus 1, each member is fixed with an adhesive tape, but the positions of the sheet metal guide 61 and the guide film 62 are fixed. Other fixing methods may be used if possible. The guide film 62 is, for example, a polyester film. Here, Lumirror S10 # 350 manufactured by Toray Industries, Inc. was used.

  The sheet metal guide 61 prevents the secondary transfer current from leaking through the recording medium, and further prevents jamming due to the sheet metal guide 61 being electrostatically charged and sticking the recording medium. Is grounded. For example, as shown in FIG. 3, the load resistor 45 is fixed to a connection terminal that is fastened together with the sheet metal guide 61 by a fixing screw 45 and is electrically connected to the other end, and the other end is fixed to the image forming apparatus main body 40 (FIG. 1). Is electrically connected. Here, the resistance value of the load resistor 45 is set to 100 MΩ.

  The secondary transfer belt unit 70 corresponding to the secondary transfer unit is fixedly disposed on the image forming apparatus main body 40. As shown in FIG. 2, the secondary transfer belt unit 70 includes a secondary transfer belt 71, a secondary transfer roller 72, a secondary transfer belt stretching roller 73 as a stretching roller, and a secondary as a driving roller. A transfer belt driving roller 74, a cleaning blade 75, a cleaning counter roller 76, and a secondary transfer belt unit frame 77 are included.

  The secondary transfer belt 71 is stretched by a secondary transfer belt driving roller 74 and a secondary transfer belt stretching roller 73 that are rotatably held by a secondary transfer belt unit frame 77. The secondary transfer belt drive roller 74 is driven by a drive motor (not shown) and rotationally drives the secondary transfer belt 71 in the direction of arrow A in the drawing. A secondary transfer roller 72 is installed inside the secondary transfer belt 71 at a position facing the secondary transfer counter roller 54 via the intermediate transfer belt 51 and the secondary transfer belt 71. The secondary transfer roller 72 is rotatably held by the secondary transfer belt unit frame 77 and has a structure in which the periphery of the metallic shaft is wound with a conductive sponge, and the end of the metallic shaft is illustrated in FIG. It is connected to a power supply (not shown).

  The shaft portion of the secondary transfer roller 72 is urged toward the center of the secondary transfer counter roller 54 by an urging means (not shown). Due to this urging, the sponge portion of the contact portion of the secondary transfer roller 72 is crushed and the secondary transfer nip portion is nipped with the secondary transfer counter roller 54 via the secondary transfer belt 71 and the intermediate transfer belt 51. 78 (formed around the dotted line) is formed. A cleaning blade 75 is installed as a cleaning unit at a position in contact with the surface of the secondary transfer belt 71 on the downstream side of the secondary transfer nip portion 78 of the secondary transfer belt unit 70. A cleaning counter roller 76 is installed at a position opposite to the secondary transfer belt 71 via the secondary transfer belt 71.

  FIG. 5 shows the guide film 62 of the pre-transfer guide member 60 and the secondary transfer belt unit as the secondary transfer portion when the intermediate transfer belt unit 50 to which the pre-transfer guide member 60 is attached is mounted on the image forming apparatus main body 40. It is a figure which shows the positional relationship of 70. FIG.

  As shown in the figure, the leading edge of the guide film 62 is 2 upstream of the secondary transfer nip portion 78 and downstream of the secondary transfer belt drive roller 74 in the medium transport direction (the direction of arrow A in the figure). It is in contact with the next transfer belt 71. The second transport guide 20 is disposed at a position facing the sheet metal guide 61 of the pre-transfer guide 60 on the upstream side of the secondary transfer belt unit 70 in the medium transport direction from the contact position, as shown in FIG. Further, a second conveyance roller pair 18 and a first conveyance guide 19 are arranged on the upstream side thereof, and convey and guide the recording medium, respectively. Here, it is assumed that the image forming apparatus is placed so that the medium conveyance direction by the secondary transfer belt unit 70 is the horizontal direction.

  As shown in FIG. 5, the guide film 62 is fixed so that the angle θ formed with the recording medium conveyance surface of the secondary transfer belt 71 is 9.5 °, and the leading end of the guide film 62 is attached to the secondary transfer belt 71. They are brought into contact and deformed by elasticity, and are attached so that the deformation amount α is 0.5 mm. Here, the deformation amount α is a moving amount at a height at which the tip portion is displaced by deformation.

  Here, a pressing force by the guide film 62 of about 30 gf is generated at the contact portion. With this pressing force, the recording medium 10 passing between the secondary transfer belt 71 is urged toward the secondary transfer belt 71. Therefore, if the pressing force is too small, the contact between the guide film 62 and the secondary transfer belt 71 cannot be secured, and if it is too strong, it becomes a load for conveying the medium and causes paper clogging. According to the experiments by the inventors, it is preferable to set a range of 10 gf to 100 gf, for example. Also, the deformation amount α is appropriately set according to the characteristics of the guide film 62.

  FIG. 6 is an explanatory view schematically showing the relative positions in the width direction and the widths W1, W2, W3, and W4 of the secondary transfer belt 71, the intermediate transfer belt 51, the guide film 62, and the recording medium 10. It is. As shown in the figure, the widths are in a relationship of W1> W2> W3> W4 here, and the positions of the members in the width direction are arranged so as to be within the region of the wider member.

With the above configuration, the overall operation of the image forming apparatus 1 will be described with reference mainly to FIG.
In each toner image forming unit 39, a toner image is formed by a procedure of charging the surface of the photoreceptor 34 by the charging roller 35, forming an electrostatic latent image by the optical unit 36, and developing the toner image by the developing roller 38. The toner images formed by the respective toner image forming units 39 form an electric field between the photosensitive member 34 and the primary transfer roller 52, so that the intermediate transfer belt 51 is sequentially arranged from the upstream side in the moving direction of the intermediate transfer belt 51. It is transferred on top of it.

  On the other hand, the recording medium 10 is picked up one by one by the pickup roller 12 of the paper feeding unit 13 and sent out downstream in the medium transport direction by the paper feeding roller pair 15. The recording medium 10 sent out in this way passes through the pre-transfer guide member 60 and the second conveyance guide 20 by the first conveyance roller pair 17, the first conveyance guide 19, and the second conveyance roller pair 18 of the conveyance unit 16. It is sent to the secondary transfer nip portion 78. At the secondary transfer nip portion 78, while the recording medium 10 is being conveyed, a predetermined voltage is applied to the secondary transfer nip portion 78 to form a predetermined electric field between the secondary transfer counter rollers 54 and onto the intermediate transfer belt 51. The formed toner image is transferred to the recording medium 10.

  Thereafter, the unfixed toner on the recording medium 10 is fixed on the recording medium 10 by being thermocompression-bonded by the heat roller 24 and the pressure roller 23 that are controlled to have a predetermined temperature in the fixing unit 25. The The recording medium 10 on which the toner image is fixed is conveyed by the paper discharge unit 26 and discharged by the paper discharge roller pair 27 onto the medium stacking portion 41 formed on the apparatus main body 40 with the image forming surface facing down. As a result, the image forming apparatus 1 ends the image formation on the recording medium 10.

  7 and 8, the leading end portion of the recording medium 10 passes through the conveyance path formed by the second conveyance guide 20 and the introduction guide portion 61 c and the bottom portion 61 d of the sheet metal guide 61, and enters the secondary transfer nip portion 78. It is operation | movement explanatory drawing for demonstrating the process to reach. Next, the movement process of the recording medium 10 will be further described with reference to these drawings. Here, it is assumed that borderless printing is performed in which the toner image transferred onto the intermediate transfer belt 51 is formed larger than the recording medium 10.

  First, the case where the leading end of the recording medium 10 is curled in a convex shape will be described with reference to FIG.

  The recording medium 10 is guided by the first conveyance guide 19 and reaches the second conveyance roller 18 in the conveyance unit 16 (FIG. 1). The leading end of the recording medium 10 conveyed by the second conveying roller 18 is guided by the pre-transfer guide member 60 and the second conveying guide 20, and eventually, as shown in FIG. And the guide film 62 come into contact with each other.

  The guide film 62 has its tip abutted against the secondary transfer belt 71 with the above-mentioned predetermined pressing force, and thus prevents the recording medium 10 from proceeding. The next transfer belt 71 passes through the contact position by the driving force in the direction of arrow A. At this time, as shown in FIG. 7B, the convex curled portion at the tip is conveyed while being leveled by the guide film 62 and reaches the secondary transfer nip portion 78. The secondary transfer nip portion 78 transfers the toner image formed on the intermediate transfer belt 51 to the recording medium 10 while conveying the nipped recording medium 10 in the direction of arrow A.

  As described above, the guide film 62 is urged against the secondary transfer belt 71 so that the front end portion thereof is deformed by the deformation amount α and a pressing force of about 30 gf is generated. Therefore, as shown in FIG. In addition, the curl of the recording medium 10 can be smoothed smoothly from the front end to the rear end of the recording medium 10.

  The toner image in a region larger than the size of the recording medium 10 is not transferred to the recording medium 10 but is transferred from the intermediate transfer belt 51 to the secondary transfer belt 71 and conveyed to the position of the cleaning blade 75 by the secondary transfer belt 71. Then, it is scraped off by the cleaning blade 75. As a result, the remaining toner does not adversely affect the printing results of the next page and subsequent pages.

  Next, a case where the leading end of the recording medium 10 is curled in a concave shape will be described with reference to FIG.

  At this time, the leading end of the recording medium 10 is guided and moved by the pre-transfer guide member 60 and the second transport guide 20, and eventually the concave curled portion at the leading end and the guide film 62 come into contact as shown in FIG. .

  The guide film 62 has its tip abutted against the secondary transfer belt 71 with the above-mentioned predetermined pressing force, and thus prevents the recording medium 10 from proceeding. The next transfer belt 71 passes through the contact position by the driving force in the direction of arrow A. At this time, as shown in FIG. 8B, the concave curled portion at the tip is conveyed while being leveled by the guide film 62 and reaches the secondary transfer nip portion 78. The secondary transfer nip portion 78 transfers the toner image formed on the intermediate transfer belt 51 to the recording medium 10 while conveying the nipped recording medium 10 in the direction of arrow A.

  In the case of a concave curl, even after the leading edge of the recording medium 10 passes through the guide film 62, the leading edge contacts the intermediate transfer belt 10 side due to the restoring force of the recording medium 10. Since it is only on the straight line at the tip and immediately reaches the secondary transfer nip portion 78 while moving with the intermediate transfer belt 10, image abnormality due to rubbing or the like is unlikely to occur.

  Further, when the recording medium 10 is not curled, the recording medium 10 passes through the guide film 62 as it is without going through the process of curling, and reaches the secondary transfer nip portion 78.

  As described above, according to the image forming apparatus of the present embodiment, even when the recording medium is curled, the tip of the recording medium does not rub the toner image on the intermediate transfer belt. Good print results can be obtained without degrading the print quality. In addition, even in borderless printing in which there is a high probability of rubbing due to the presence of a toner image on the intermediate transfer belt corresponding to the edge of the recording medium, a good printing result can be obtained in the same manner, so there is no border. This is particularly effective during printing.

Embodiment 2. FIG.
FIG. 9 is a configuration diagram of the intermediate transfer belt unit 50 employed in the image forming apparatus according to the second embodiment of the present invention and a pre-transfer guide member 160 attached thereto, and FIG. 10 is a pre-transfer guide member. It is sectional drawing in the longitudinal direction center part of 160. FIG.

  The image forming apparatus employing the intermediate transfer belt unit 50 and the pre-transfer guide member 160 is mainly different from the intermediate transfer belt unit 50 and the pre-transfer guide member 60 of the first embodiment shown in FIGS. These are the configurations of the pre-transfer guide member 160. Therefore, in the image forming apparatus employing the pre-transfer guide member 160, the same reference numerals are given to the parts common to the image forming apparatus 1 (FIG. 1) of the first embodiment described above, or the drawings are omitted. Is omitted and the differences will be explained with emphasis. The main configuration of the image forming apparatus according to the present embodiment is the same as the main configuration of the image forming apparatus 1 according to the first embodiment shown in FIG. 1 except for the pre-transfer guide member 160. 1 is referred to.

  The pre-transfer guide member 160 in the present embodiment is a fixing screw that penetrates through the mounting holes formed in the left and right side surface portions 61a and 61b of the sheet metal guide 61, like the pre-transfer guide member 60 of the first embodiment. 64 and 64 are fixedly attached to the left and right intermediate transfer belt unit frames 58.

  A plate-like rotation member 166 formed of sheet metal is connected to a guide film placement portion 166c extending in the same direction as the bottom portion 61d of the sheet metal guide 61, and is bent in a “U” shape from both ends thereof. , Opposite side portions 166a and 166b (only 166b is shown in FIG. 10), and held by a sheet metal guide 61 so as to be rotatable in the directions of arrows C and D at the shaft portion 167. As shown in FIG. 10, the plate-like rotating member 166 is held near the bottom 61d of the end of the sheet metal guide 61 opposite to the introduction guide 61c. For this reason, the side portions 166a and 166b of the plate-like rotating member 166 are also formed at the end opposite to the introduction guide portion 61c.

  A guide film 62 extending from the sheet metal guide 61 toward the opposite side of the introduction guide portion 61c is attached to the guide film placement portion 166c of the plate-like rotating member 166 with an adhesive tape. A compression spring 165 as an elastic member is attached between the guide film placement portion 166c of the plate-like rotation member 166 and the bottom portion 61d of the plate-like rotation member 166 on the side close to the introduction guide portion 61c. The moving member 166 is urged in the direction of the arrow C in the rotation direction. As a result, the leading end portion of the guide film 62 extending from the sheet metal guide 61 extends obliquely downward from the sheet metal guide 61 and is urged downward in a rotational position where the compression spring 165 compresses. Here, the plate-like rotating member 166, the guide film 62, and the compression spring 165 correspond to the urging portion.

  When the intermediate transfer belt unit 50 in which the pre-transfer guide member 160 configured as described above is fixed at a predetermined position as shown in FIG. 9 is attached to the image forming apparatus main body 40 (FIG. 1), the above-described case shown in FIG. As in the first embodiment, the leading edge of the guide film 62 is upstream of the secondary transfer nip portion 78 and downstream of the secondary transfer belt drive roller 74 in the medium transport direction (the direction of arrow A in the figure). Abuts on the secondary transfer belt 71.

  The contact portion of the guide film 62 is deformed by a predetermined amount as shown in FIG. 5 due to this contact, and the compression spring 165 and each mounting position are adjusted so that a pressing force by the guide film 62 of about 30 gf is generated in the contact portion Has been. With this pressing force, the recording medium 10 passing between the secondary transfer belt 71 is urged toward the secondary transfer belt 71. If the pressing force is too small, the contact between the guide film 62 and the secondary transfer belt 71 cannot be secured, and if it is too strong, it becomes a load for conveying the medium and causes paper clogging. According to the experiments by the inventors, it is preferable to set a range of 10 gf to 100 gf, for example. Also, the deformation amount α is appropriately set according to the characteristics of the guide film 62.

  The operation of the entire apparatus by the image forming apparatus of the present embodiment having the above configuration and the process leading to the secondary transfer nip portion 78 when the leading end of the recording medium 10 is curled are the same as those of the first embodiment. Since the operation is the same as that described in the image forming apparatus 1, a description thereof is omitted here.

  As described above, according to the image forming apparatus of the present embodiment, the same effects as those of the image forming apparatus of the first embodiment can be obtained. Further, since the guide film 62 is pressed against the secondary transfer belt 71 by the force of the compression spring 165 and the recording medium 10 is urged, a stable urging force is maintained even when the guide film 62 creeps over time. It becomes possible to give to.

Embodiment 3 FIG.
FIG. 11A is an external perspective view of the pre-transfer guide member 260 employed in the image forming apparatus according to the third embodiment of the present invention, and FIG. 11B is a side view of the pre-transfer guide member 260. FIG. 12 is a side view of the guide film 262.

  The image forming apparatus employing the pre-transfer guide member 260 is mainly different from the pre-transfer guide member 60 of the first embodiment shown in FIG. 4 described above in the shape of the guide film 262. Therefore, in the image forming apparatus that employs the pre-transfer guide member 260, parts common to the image forming apparatus 1 (FIG. 1) of Embodiment 1 described above are denoted by the same reference numerals or omitted from the drawings. Is omitted and the differences will be explained with emphasis. The main part configuration of the image forming apparatus according to the present embodiment is the same as that of the main part of the image forming apparatus 1 according to the first embodiment shown in FIG. 1 except for the pre-transfer guide member 260. 1 is referred to.

  The pre-transfer guide member 260 in the present embodiment has the same configuration as the pre-transfer guide member 60 of the first embodiment except for the shape of the guide film 262. The guide film 262 as a sheet member here is fixedly disposed with an adhesive tape on the inclined upper surface of the fixing member 63, and is inclined downward toward the opposite side to the introduction guide portion 61 c, and obliquely downward from the sheet metal guide 61. A base portion 262a extending in front of the base portion 262a, and a tip end portion 262b that is connected to the tip of the base portion 262a and is bent in a cross-section “<” shape and inclined upward.

  The contact portion 262c, which corresponds to the outer ridge portion of the bent portion and contacts the secondary transfer belt 71 as will be described later, is stretched by this bending because the polyester that is the material of the guide film 262 has elasticity. R shape.

  When the intermediate transfer belt unit 50 in which the pre-transfer guide member 260 configured as described above is fixed at a predetermined position so as to correspond to the pre-transfer guide member 60 of FIG. 3 is attached to the image forming apparatus main body 40, FIG. As shown, the contact portion 262c of the guide film 262 is 2 on the upstream side of the secondary transfer nip portion 78 and on the downstream side of the secondary transfer belt driving roller 74 in the medium transport direction (the direction of arrow A in the figure). It contacts the next transfer belt 71. FIG. 13 is a view showing the positional relationship between the guide film 262 of the pre-transfer guide member 260 and the secondary transfer belt unit 70 as the secondary transfer portion.

  As shown in FIG. 13, the guide film 262 is fixed so that the angle θ formed with the recording medium conveyance surface of the secondary transfer belt 71 is 9.5 °, and the tip thereof is attached to the secondary transfer belt 71. They are brought into contact and deformed by elasticity, and are attached so that the deformation amount α is 0.5 mm. In addition, the shape and the mounting position of the guide film 262 are taken into consideration so that the contact portion 262c contacts the secondary transfer belt 71 even in a deformed state.

  Here, a pressing force by the guide film 262 of about 30 gf is generated at the contact portion. With this pressing force, the recording medium 10 passing between the secondary transfer belt 71 is urged toward the secondary transfer belt 71. Therefore, if this pressing force is too small, the contact between the guide film 262 and the secondary transfer belt 71 cannot be secured, and if it is too strong, it becomes a load for transporting the medium and causes paper clogging. According to the experiments by the inventors, it is preferable to set a range of 10 gf to 100 gf, for example. Also, the deformation amount α is appropriately set according to the characteristics of the guide film 262.

  The operation of the entire apparatus by the image forming apparatus of the present embodiment having the above configuration and the process leading to the secondary transfer nip portion 78 when the leading end of the recording medium 10 is curled are the same as those of the first embodiment. Since the operation is the same as that described in the image forming apparatus 1, a description thereof is omitted here.

  As described above, according to the image forming apparatus of the present embodiment, the same effects as those of the image forming apparatus of the first embodiment can be obtained. Furthermore, according to the image forming apparatus of the present embodiment, the guide film 262 contacts the secondary transfer belt 71 at the R-shaped contact portion 262c, and therefore the secondary transfer belt 71 is moved at the edge portion of the guide film 262. There is no risk of injury. As a result, it is possible to suppress the occurrence of poor cleaning caused by the scratches on the surface of the secondary transfer belt 71 damaged.

Embodiment 4 FIG.
FIG. 14 is a diagram showing the positional relationship between the guide film 262 of the pre-transfer guide member 260 and the secondary transfer belt unit 70 as the secondary transfer unit in the image forming apparatus according to the fourth embodiment of the present invention. The image forming apparatus according to the present embodiment is different from the image forming apparatus according to the third embodiment described above in that an auxiliary roller 267 is added. Therefore, the description of the parts common to the image forming apparatus of Embodiment 3 is omitted here.

  In the image forming apparatus according to the present embodiment, as shown in FIG. 14, the auxiliary member is formed of a non-conductive resin at a position facing the contact portion 262c of the guide film 262 with the secondary transfer belt 71 interposed therebetween. The auxiliary roller 267 is disposed in contact with the guide roller 262 so that the moving path of the secondary transfer belt 71 is not changed by the pressing force of the guide film 262.

  As described above, the auxiliary transfer roller 267 is opposed to the contact portion 262c of the guide film 262 via the secondary transfer belt 71, so that when the guide film 262 biases the secondary transfer belt 71, the secondary transfer belt 71 is moved. There is no escape. This makes it possible to make the conveyance path of the recording medium constant and improve the accuracy of the leading edge writing position.

  FIG. 15 is a diagram showing a modification of the present embodiment. Here, the contact portion 262c of the guide film 262 is configured to contact the secondary transfer belt 71 at or near the position where the secondary transfer belt 71 is in contact with the secondary transfer belt drive roller 74. Yes. Also in this case, the recording medium conveyance path can be maintained constant, and the accuracy of the leading edge writing position can be improved. Here, the secondary transfer belt drive roller 74 is positioned closer to the secondary transfer nip portion 78, and the distance between the contact portion 262c of the guide film 262 and the secondary transfer nip portion 78 is separated. Is preventing.

  In the above example, the pre-transfer guide member 260 according to the third embodiment is used. However, the pre-transfer guide member 60 according to the first embodiment or the pre-transfer guide member 160 according to the second embodiment is used. However, the same effect can be obtained.

Embodiment 5 FIG.
FIG. 16 is a diagram showing the positional relationship between the guide film 62 of the pre-transfer guide member 60 and the secondary transfer roller 290 as the secondary transfer unit in the image forming apparatus according to the fifth embodiment of the present invention. The image forming apparatus according to the present embodiment is different from the image forming apparatus according to the first embodiment described above in that the secondary transfer unit includes only the secondary transfer roller 290. Therefore, the description of the parts common to the image forming apparatus of Embodiment 1 is omitted here.

  In the present embodiment, as shown in FIG. 16, the recording medium 10 that has passed through the conveyance path formed by the second conveyance guide 20 and the introduction guide portion 61c and the bottom portion 61d of the sheet metal guide 61 is transferred to the secondary transfer belt 71 ( 5), the sheet is directly conveyed to the secondary transfer nip portion 78 formed by the secondary transfer counter roller 54 and the secondary transfer roller 290, and the secondary transfer is performed at the secondary transfer nip portion 78. It has a configuration. In this case, the secondary transfer roller 290 may be configured to be directly driven to rotate in the direction of the arrow by the driving unit, and the secondary transfer roller 290 is provided on the surface downstream of the secondary transfer nip portion 78 in the rotation direction. A cleaning blade 75 for scraping off the toner transferred to the roller 290 is provided.

  The guide film 62 of the pre-transfer guide member 60 directly contacts the secondary transfer roller 290 and presses the surface of the secondary transfer roller 290 with a pressing force of about 30 gf, for example. As a result, the recording medium 10 that has passed through the conveyance path formed by the introduction guide portion 61c and the bottom portion 61d of the second conveyance guide 20 and the sheet metal guide 61 is, for example, when the leading end is curled convexly or concavely. Even in such a case, the contact force between the guide film 62 and the secondary transfer roller 290 is reached without contacting the intermediate transfer belt 51 on which the toner image is formed, and the conveying force by the secondary transfer roller 290 obtained at this contact portion. As a result, the toner image formed on the intermediate transfer belt 51 is further transferred to the recording medium 10 by being guided to the secondary transfer nip portion 78.

  As described above, according to the image forming apparatus of the present embodiment, the same effects as those of the first embodiment can be obtained. Furthermore, according to the image forming apparatus of the present embodiment, the conveyance path of the recording medium is not changed by the guide film 62, so that it is possible to improve the accuracy of the leading edge writing position.

Embodiment 6 FIG.
FIG. 17 is a side view showing the shape of the guide film of the pre-transfer guide member of the image forming apparatus according to the sixth embodiment of the present invention. The image forming apparatus according to the present embodiment is different from the image forming apparatus according to the first embodiment described above only in the shape of the front end portion of the guide film (62 in the first embodiment) of the pre-transfer guide member 60 (FIG. 4). It is. Therefore, the description of the parts common to the image forming apparatus of Embodiment 1 is omitted here.

  In the present embodiment, as shown in FIG. 17A, a cut surface 362a that forms an obtuse angle θ2 with the flat surface portion 362b is formed on the side of the front end portion of the guide film 362 as a sheet member that faces the secondary transfer belt 71. Forming. The cut surface 362a is formed by a blade (knife). At this time, a smooth ridge portion 362c having no burr can be formed by inserting the blade from the flat surface portion 362b toward the distal end.

  FIG. 17B is an operation explanatory diagram illustrating a use state in which the guide film 362 contacts the secondary transfer belt 71 with a pressing force of, for example, about 30 gf. In this state of use, the ridge 362c contacts the secondary transfer belt 71 as shown in FIG.

  As described above, the ridge portion 362c that is in contact with the secondary transfer belt 71 has a smooth surface and is formed at an obtuse angle, so that damage to the sliding secondary transfer belt 71 can be suppressed. it can.

  Here, the cut surface 362a is formed so as to form a part of the tip of the guide film 362. However, the present invention is not limited to this. For example, as shown in FIG. You may form so that it may become the cut surface 362c.

  FIG. 18 is a side view of a guide film showing a modification of the present embodiment. Here, as shown in FIG. 18 (a), a chamfered portion 462a having an arcuate cross section from the flat surface portion 462b to the front end portion is formed on the side of the front end portion of the guide film 462 as a sheet member that comes into contact with the secondary transfer belt 71. Forming. The chamfered portion 462a can be formed by cutting with a grinder.

  FIG. 18B is an operation explanatory diagram illustrating a use state in which the guide film 462 contacts the secondary transfer belt 71 with a pressing force of, for example, about 30 gf. In this state of use, a chamfered portion 462 a having an arcuate cross section comes into contact with the secondary transfer belt 71 as shown in FIG.

  As described above, since the chamfered portion 462a having a smooth surface comes into contact with the secondary transfer belt 71, damage to the sliding secondary transfer belt 712 can be suppressed.

  Here, an example is shown in which the guide film whose tip is cut or chamfered is brought into contact with the secondary transfer belt 71, but the present invention is not limited to this, and FIGS. 14 and 15 in the above-described fourth embodiment. As shown in FIG. 16, the front end portion may be arranged corresponding to the auxiliary roller or the secondary transfer belt drive roller. Further, as shown in FIG. 16 in the fifth embodiment, the secondary transfer roller It is also possible to arrange them corresponding to.

  In each of the above-described embodiments, a polyester guide film is used as the sheet-like member. However, the present invention is not limited to this, and various materials such as a plastic film material such as polycarbonate or nylon may be used. It can take the form.

  In each of the above-described embodiments, the example applied to the belt driving device of the electrophotographic printer has been described. However, the present invention is not limited to this, and an image on a recording material using an electrophotographic system is used. Can be used for image forming apparatuses such as facsimile machines, copiers, and MFPs (Multifunction Peripherals).

  DESCRIPTION OF SYMBOLS 1 Image forming apparatus, 10 Recording medium, 11 Paper feed tray, 12 Pickup roller, 13 Paper feed unit, 15 Paper feed roller pair, 16 Transport unit, 17 First transport roller pair, 18 Second transport roller pair, 19 First Conveyance Guide, 20 Second Conveyance Guide, 23 Pressure Roller, 24 Heat Roller, 25 Fixing Unit, 26 Discharge Unit, 27 Discharge Roller Pair, 34 Photoconductor, 35 Charging Roller, 36 Optical Unit, 38 Development Roller, 39 Toner image forming unit, 40 apparatus main body, 41 medium stacking unit, 50 intermediate transfer belt unit, 51 intermediate transfer belt, 52 primary transfer roller, 53 intermediate transfer belt drive roller, 54 secondary transfer counter roller, 55 intermediate transfer belt tension Roller, 55a Shaft, 56E 57 intermediate transfer belt tension spring, 58 intermediate transfer belt unit frame, 60 pre-transfer guide member, 61 sheet metal guide, 61a, 61b side surface part, 61c introduction guide part, 61d bottom part, 62 guide film, 63 fixing member, 64 fixing screws, 70 secondary transfer belt unit, 71 secondary transfer belt, 72 secondary transfer roller, 73 secondary transfer belt stretching roller, 74 secondary transfer belt drive roller, 75 cleaning blade, 76 cleaning counter roller, 77 Secondary transfer belt unit frame, 78 Secondary transfer nip portion, 80 Pre-transfer guide member, 160 Pre-transfer guide member, 165 Compression spring, 166 Plate-like rotating member, 166a side portion, 166b side portion, 166c Guide film Placement part, 167 shaft part, 260 guide member before transfer, 262 guide film, 262a base part, 262b tip part, 262c contact part, 267 auxiliary roller, 290 secondary transfer roller, 362 guide film, 362a cut surface, 362b plane Part, 362c ridge part, 462 guide film, 462a chamfered part.

Claims (14)

An endless intermediate transfer belt on which a toner image is primarily transferred from an image carrier;
A secondary transfer facing portion that is disposed inside the intermediate transfer belt and guides the intermediate transfer belt;
Forming a secondary transfer nip portion together with the secondary transfer facing portion, and at the secondary transfer nip portion, a secondary transfer portion that secondary-transfers the toner image primarily transferred onto the intermediate transfer belt to a recording medium;
An upstream side of the secondary transfer nip portion in the conveyance direction of the recording medium is positioned between the recording medium and the intermediate transfer belt and guides the conveyed recording medium to the secondary transfer nip portion. An image forming apparatus comprising: a pre-transfer guide portion that urges the secondary transfer portion. The pre-transfer guide portion is
A guide portion having a guide surface for guiding the recording medium;
The image forming apparatus according to claim 1, further comprising: an urging unit that guides the recording medium and urges the recording medium to the secondary transfer unit. The biasing part is
A sheet-like member;
And a fixing member configured to incline the sheet-like member with respect to the transport direction and hold the front end portion of the sheet-like member in contact with the secondary transfer portion with a predetermined pressing force. Item 3. The image forming apparatus according to Item 2. The biasing part is
A plate-like rotating member rotatably held by the guide member;
A sheet-like member held by the plate-like rotating member;
And an elastic member disposed between the guide member and the plate-like rotating member and abutting a front end portion of the sheet-like member against the secondary transfer portion with a predetermined pressing force. 2. The image forming apparatus according to 2.   5. The image according to claim 3, wherein the leading end portion of the sheet-like member is bent into a “<” shape in cross section to form a ridge portion, and the ridge portion is brought into contact with the secondary transfer portion. Forming equipment.   A cut surface that forms an obtuse angle with the flat surface portion is formed at a tip portion of the sheet member that faces the secondary transfer portion, and a ridge portion where the flat surface portion and the cut surface intersect is formed in the secondary transfer portion. The image forming apparatus according to claim 3, wherein the image forming apparatus is brought into contact with the image forming apparatus.   4. A chamfered portion having an arcuate cross section is formed at a front end portion of the sheet member facing the secondary transfer portion, and the chamfered portion is brought into contact with the secondary transfer portion. 5. The image forming apparatus according to 4. The secondary transfer portion is
A driving roller;
A tension roller,
A secondary transfer belt which is stretched between the driving roller and the stretching roller and conveys the recording medium;
A secondary transfer roller that forms the secondary transfer nip portion together with the intermediate transfer belt and the secondary transfer belt together with the secondary transfer facing portion;
The image forming apparatus according to claim 3, wherein the sheet-like member is in contact with the secondary transfer belt.   9. The auxiliary member in contact with the secondary transfer belt is disposed at a position facing the contact position between the sheet-like member and the secondary transfer belt via the secondary transfer belt. The image forming apparatus described.   9. The image forming apparatus according to claim 8, wherein a contact position between the sheet-like member and the secondary transfer belt is provided at a contact portion between the drive roller and the secondary transfer belt. The secondary transfer portion is
A secondary transfer roller that forms the secondary transfer nip portion together with the secondary transfer facing portion with the intermediate transfer belt interposed therebetween,
The image forming apparatus according to claim 3, wherein the sheet-like member is in contact with the secondary transfer roller.   The image forming apparatus according to claim 1, wherein the sheet-like member is formed of a polyester film.   13. The image formation according to claim 1, wherein the toner image can be set to a size larger than the recording medium, and borderless printing without a margin portion of the recording medium is possible. apparatus.   14. The intermediate transfer belt constitutes an intermediate transfer belt unit that can be attached to and detached from an image forming apparatus main body, and the pre-transfer guide portion is attached to the intermediate transfer belt unit. The image forming apparatus described.

Images