JP2014095835A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus including a guide member for guiding a sheet to an intermediate transfer belt.
An image carrier that carries a toner image to be printed on a sheet, a transfer member that transfers the toner image on the image carrier to the sheet, and a sheet that faces the transfer position where the toner image is transferred to the sheet by the transfer member. An image forming apparatus including a guide member that guides a sheet and a conveyance unit that conveys a sheet to the guide member, wherein the guide member is located at a downstream end portion in the sheet conveyance direction of the guide member and is downstream from the upstream in the sheet conveyance direction. As a result, the inclined portion that is inclined away from the sheet conveying direction and the inclined portion of the guide member are positioned upstream of the sheet conveying direction, and the print surface of the sheet conveyed from the conveying portion is rubbed to rub the sheet. And a polarity adjusting surface for adjusting the polarity.
[Selection] Figure 2

Description

  The embodiment described in this specification relates to a technique of an image forming apparatus that prints a toner image on a sheet.

  2. Description of the Related Art Conventionally, there is an upper transfer guide that is positioned upstream of a transfer position in a transfer unit where a toner image is transferred to a sheet, and that guides the sheet to a good position in the transfer unit by rubbing the sheet. In some cases, a conductive polyester film is adhered to the surface of the upper transfer guide that rubs the sheet to prevent frictional charging that occurs when the sheet is rubbed, and to prevent whiteout of the image transferred to the sheet. (Patent Document 1).

JP 2010-85491 A

  However, since the transfer upper guide of Patent Document 1 is formed of a polyester film at the downstream end in the sheet conveying direction, the polyester film needs to be thicker than a predetermined thickness to ensure strength. Therefore, the manufacturing cost for manufacturing the guide member has increased.

  An image forming apparatus according to an embodiment described in the present specification includes an image carrier that carries a toner image to be printed on a sheet, a transfer member that transfers the toner image on the image carrier to the sheet, and a transfer member on the sheet. An image forming apparatus comprising: a guide member that guides a sheet toward a transfer position for transferring a toner image; and a conveyance unit that conveys the sheet to the guide member, wherein the guide member is a downstream end of the guide member in the sheet conveyance direction. A sheet that is positioned at the upstream side of the sheet conveyance direction and that is inclined away from the sheet conveyance direction, and a sheet that is positioned on the upstream side in the sheet conveyance direction of the inclined portion of the guide member and is conveyed from the conveyance unit And a polarity adjusting surface for adjusting the polarity of the sheet.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment. The figure which expanded the A section in FIG. The perspective view which shows the guide member of FIG. The figure which expanded the B section in FIG. The figure which expanded the C section in FIG. The figure which expands the D section in FIG. 5, and shows the inclination-angle of an inclination part. FIG. 6 is an enlarged view of a portion D in FIG. 5, illustrating a distance between a downstream end portion in the sheet conveyance direction on the first inclined surface and a virtual plane extending along a transfer plane including a transfer position on the intermediate transfer belt. The figure which shows the guide member by a prior art example.

  Hereinafter, an image forming apparatus 1 according to an embodiment will be described with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus 1 according to the embodiment, and FIG. 2 is an enlarged view of a portion A in FIG. It is assumed that the width direction of the image forming apparatus 1 is the x axis, the depth direction is the y axis, and the height direction is the z axis.

  As shown in FIG. 1, an MFP (Multi Function Peripheral) which is an image forming apparatus 1 according to the embodiment takes a sheet 4 accommodated in a sheet feeding unit 11 located at an inner bottom portion of an image forming apparatus main body 10. The sheet 4 is sent one by one to the conveyance path 12 (conveyance unit), and the sheet 4 is conveyed upward by the conveyance roller 121 (conveyance unit), and the sheet discharge receiving unit provided in the middle part of the image forming apparatus body 10 from the sheet discharge roller 131 13 is discharged. Further, an image reading unit 14 that reads an image printed on the sheet 4 is provided on the upper portion of the image forming apparatus main body 10.

  An image forming unit 20 (a portion indicated by a one-dot chain line in FIG. 1) is arranged in the middle of the conveyance path 12. As shown in FIG. 1, the image forming unit 20 includes a plurality of printing units that primarily transfer a plurality of colors (Yellow, Cyan, Magenta, Black) toner images (toner images) to an intermediate transfer belt 200 (transfer member). (Image carrier) (printing unit Y201, printing unit M202, printing unit C203, printing unit Bk204) and the toner images carried on the printing units Y, M, C, Bk, 201, 202, 203, 204 respectively. An intermediate transfer belt 200 that performs primary transfer in an overlapping manner, and a secondary transfer roller 26 that secondary-transfers the toner image superimposed and primary transferred onto the intermediate transfer belt 200 to the sheet 4 at a secondary transfer position.

  As shown in FIG. 1, each of the printing units Y, M, C, Bk, 201, 202, 203, and 204 is provided with a photosensitive layer on the surface and rotates in the counterclockwise direction. Bk, 211, 212, 213, 214, chargers Y, M, C, Bk, 221, 222, 223, 224 for uniformly charging the surface of the photosensitive member, and photosensitive layer uniformly charged by the charger. The exposure portions Y, M, C, Bk, 231, 232, 233, and 234 that form an electrostatic latent image by exposing the toner and the electrostatic latent images formed by the exposure by the exposure portion are developed with toner and are visualized. The developing portions Y, M, C, Bk, 241, 242, 243, and 244 to be converted and the toner image that has been visualized by the developing portions are transferred to the intermediate transfer belt 200 and the toner remaining on the photosensitive member is collected. Cleaning units Y, M, C, Bk, 251, 252 253 and 254 are provided.

  A fixing device 27 is disposed downstream of the image forming unit 20 in the sheet conveyance direction. The fixing device 27 heat-fixes the toner image transferred to the sheet 4 by the secondary transfer roller 26 and conveys the sheet 4 to the paper discharge roller 131.

  As shown in FIG. 2, a guide member 30 is disposed upstream of the image forming unit 20 in the sheet conveyance direction. The guide member 30 slides and rubs the sheet 4 conveyed by the conveying roller 121 to transfer the toner image on the intermediate transfer belt 200 (point P in FIG. 2) (transfer position for transferring the toner image). ) Toward the sheet 4.

  The configuration of the guide member 30 will be described. 3 is a perspective view showing the guide member 30 of FIG. 1, and FIG. 4 is an enlarged view of a portion B in FIG.

  The guide member 30 is a member extending in the width direction (y-axis direction), and has a sheet detection mechanism 31 that detects the passage of the sheet 4 at the center. As shown in FIG. 4, the guide member 30 includes an inclined portion 32 located at the downstream end portion in the sheet conveying direction, and a polarity adjusting surface 33 located on the print surface side of the sheet 4 upstream of the inclined portion 32 in the sheet conveying direction. Have

  As shown in FIG. 4, the inclined portion 32 has a shape that is inclined in a direction away from the sheet conveying direction, and is formed of a material having higher rigidity than the polarity adjusting surface 33, for example, an ABS resin. The polarity adjustment surface 33 adjusts the polarity on the printing surface of the sheet 4 to a plus polarity, and is formed of a conductive material, such as a polyester film.

  As shown in FIG. 4, the inclined portion 32 includes a first inclined surface 321 positioned on the downstream end side of the polarity adjusting surface 33 of the guide member 30 in the sheet conveying direction, and a first inclined surface 321 of the guide member 30. And a second inclined surface 322 located on the downstream end side in the sheet conveying direction. The first inclined surface 321 guides the rear end of the sheet 4 guided to the secondary transfer position of the intermediate transfer belt 200, and the angle with respect to the polarity adjustment surface 33 is set smaller than that of the second inclined surface 322. ing. Since the sheet 4 is guided by the second inclined surface 322, the amount of deflection of the sheet 4 guided to the secondary transfer position of the intermediate transfer belt 200 is gradually relaxed, and the intermediate transfer belt 200 is moved behind the sheet 4. Avoid collisions at the edges.

  Next, the characteristics of the polarity adjustment surface 33 of the guide member 30 will be described.

  The guide member 30 rubs the sheet 4 conveyed from the conveyance roller 121 and guides it to the secondary transfer position of the image forming unit 20. At this time, when the surface of the guide member 30 that rubs against the sheet 4 is formed of a non-conductive material such as ABS resin, the surface of the sheet 4 is frictionally charged when the guide member 30 rubs against the sheet 4 and is minus. Is charged. When a negative charge is charged on the surface of the sheet 4, the charge polarity of the sheet 4 (negative charge polarity) and the charge polarity of the toner transferred onto the intermediate transfer belt 200 become the same. resist. For this reason, the toner image carried on the intermediate transfer belt 200 is not completely transferred to the sheet 4, and whiteout occurs in the image transferred to the sheet 4.

  On the other hand, when the surface of the guide member 30 that rubs the sheet 4 is formed of a conductive material such as a polyester film, even if the guide member 30 rubs the sheet 4, the electric charge remains inside the guide member 30. There is no frictional charge on the surface that is discharged and rubbed. Therefore, the charging polarity of the sheet 4 remains a positive charging polarity, and no white spots occur in the image transferred to the sheet 4.

  Since the polarity adjustment surface 33 of the guide member 30 in the present embodiment is formed of a conductive member having such characteristics, the polarity adjustment surface 33 relates to the print surface of the sheet 4 immediately before being guided to the secondary transfer position of the image forming unit 20. The charging polarity can be adjusted to a positive polarity. Thereby, the image forming apparatus 1 according to the present embodiment can prevent white spots from occurring in an image transferred to the sheet 4 by the secondary transfer roller 26.

  Next, the characteristic of the inclined part 32 in the guide member 30 of this embodiment is demonstrated. FIG. 5 is an enlarged view of a portion C in FIG.

  The printing surface of the sheet 4 is rubbed by the polarity adjustment surface 33 and is guided to the secondary transfer position of the intermediate transfer belt 200 without contacting the inclined portion 32. Then, as shown in FIG. 5, only when the rear end of the sheet 4 passes, it is guided by the first inclined surface 321 and guided to the intermediate transfer belt 200. Thus, only the rear end of the sheet 4 is rubbed against the inclined portion 32 because the inclined portion 32 of the present embodiment is inclined so as to be separated from the sheet conveying direction as it proceeds from the upstream to the downstream in the sheet conveying direction. It is because it has been. Specifically, while the sheet 4 is in contact with both the polarity adjustment surface 33 and the intermediate transfer belt 200, the inclined portion 32 that is positioned between them and separated from the conveyance path 12 is particularly on the surface of the sheet 4. There is no contact. When the sheet 4 is in contact with only the intermediate transfer belt 200, the downstream end of the sheet 4 in the sheet conveyance direction is a free end, and is guided by the inclined portion 32 and conveyed to the secondary transfer position. Is done.

  With this configuration, even if the image forming apparatus 1 of the present embodiment has a configuration in which the downstream end portion of the guide member 30 in the sheet conveyance direction is formed of a material other than the conductive material, this downstream end portion is the secondary of the intermediate transfer belt 200. Since there is no contact with the printing surface of the sheet 4 guided to the transfer position, no white spots occur in the image transferred to the sheet 4 by the secondary transfer roller 26.

  Further, the downstream end portion of the sheet 4 in the sheet conveying direction is rubbed against the inclined portion 32 made of a non-conductive material. The downstream end portion is a toner image transferred by the secondary transfer roller 26. Since this is not an area to be transferred, even if this area is negatively charged, it does not cause white spots in the image.

  Next, the configuration of the first inclined surface 321 in the inclined portion 32 will be described in detail. FIG. 6 is a diagram illustrating an inclination angle of the inclined portion 32 by enlarging the D portion in FIG. 5.

  The first inclined surface 321 of the guide member 30 of the present embodiment is made of a material having higher rigidity than the polarity adjustment surface 33 and is inclined by 20 ° to 45 °, more preferably 25 ° with respect to the polarity adjustment surface 33. ing.

  Generally, since the inclination angle of the transfer plane including the secondary transfer position of the intermediate transfer belt 200 is different from the inclination angle of the guide surface of the guide member 30, the sheet 4 is conveyed through the conveyance path 12 having different inclination angles. Then, the sheet 4 conveyed in the conveyance path 12 bends. When the sheet 4 is bent in this manner, for example, when the sheet 4 is a strong (high rigidity) thick paper or a high density paper such as a postcard, the sheet 4 is guided to the secondary transfer position of the intermediate transfer belt 200. After the sheet 4 passes through the guide surface of the guide member 30, the deflection of the sheet 4 returns vigorously, contacts the toner image transferred onto the intermediate transfer belt 200, and is transferred onto the intermediate transfer belt 200. A white streak is formed on the toner image.

  For this reason, by tilting the first inclined surface 321 of this embodiment by 20 ° or more with respect to the polarity adjusting surface 33, even the strong sheet 4 is guided to the secondary transfer surface of the intermediate transfer belt 200. The trailing end of the bent sheet 4 is guided by the first inclined surface 321, and the amount of deflection of the trailing end of the sheet 4 is gradually reduced to generate white stripes in the toner image transferred onto the intermediate transfer belt 200. prevent.

  Further, if the inclination angle of the first inclined surface 321 is inclined more than 45 °, the printing surface of the sheet 4 is soiled when the toner that forms the toner image primarily transferred onto the intermediate transfer belt 200 falls. End up. Therefore, the inclination angle of the first inclined surface 321 is set to 45 ° or less with respect to the polarity adjusting surface 33.

  Next, the positional relationship of the inclined portion 32 with respect to the intermediate transfer belt 200 will be described in detail. FIG. 7 is an enlarged view of a portion D in FIG. 5, where the first inclined surface 321 has a downstream end in the sheet conveyance direction and a virtual plane extending along the transfer plane including the secondary transfer position on the intermediate transfer belt 200. It is a figure which shows distance.

  As shown in FIG. 7, the guide member 30 according to the present embodiment extends along the transfer plane including the secondary transfer position on the intermediate transfer belt 200 from the downstream end portion in the sheet conveyance direction on the first inclined surface 321 of the inclined portion 32. The distance to the imaginary plane extending in this manner (the dashed line portion in FIG. 7) (hereinafter referred to as the imaginary plane of the intermediate transfer belt 200) is preferably 1.5 mm or less, more preferably 1.0 mm or less. As will be described later, by setting the guide member 30 to this position, it is possible to prevent white streaks from being formed on the toner image transferred to the intermediate transfer belt 200.

  In general, the amount of deflection of the sheet 4 guided to the secondary transfer position of the intermediate transfer belt 200 is the distance from the downstream end of the first inclined surface 321 in the sheet conveyance direction to the virtual plane of the intermediate transfer belt 200. The bigger it gets, the bigger it gets. This is because the sheet 4 is greatly bent because it contacts the sheet 4 on two planes that are separated from the transfer plane including the secondary transfer position of the intermediate transfer belt 200 and the virtual plane of the intermediate transfer belt 200. Therefore, the amount of deflection of the sheet 4 guided to the secondary transfer position of the intermediate transfer belt 200 is shortened by shortening the distance from the virtual plane of the intermediate transfer belt 200 to the downstream end of the first inclined surface 321 in the sheet conveyance direction. And the formation of white stripes on the toner image transferred to the intermediate transfer belt 200 can be prevented.

  In order to achieve the effect that white stripes are not formed on the toner image transferred to the intermediate transfer belt 200, the optimum distance from the virtual plane of the intermediate transfer belt 200 to the downstream end portion of the first inclined surface 321 in the sheet conveying direction. About the following, the installation position verification test of the guide member 30 was done.

In the installation position verification test of the guide member 30, only the distance from the virtual plane of the intermediate transfer belt 200 to the downstream end of the first inclined surface 321 in the sheet conveyance direction is changed in the image forming apparatus 1 of the present embodiment. The image forming process under each condition was performed. Then, the image that has been subjected to the image formation processing is confirmed. When white streaks are not formed, ◯, when slightly white streaks are formed on the image, Δ when the streak is not noticeable, clearly white streaks The case where it formed in the image was evaluated as x. The conditions regarding the distance from the virtual plane of the intermediate transfer belt 200 to the downstream end portion in the sheet conveying direction on the first inclined surface 321 were 0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm. Further, a sheet 4 having a density of 280 g / m ³ was used.

Table 1 summarizes the test results.
Table 1 Calculation result of fixed position of guide member 30

  As can be seen from Table 1, when the distance from the virtual plane of the intermediate transfer belt 200 to the downstream end of the first inclined surface 321 in the sheet conveying direction is 1.5 mm, white streaks appear on the image printed on the sheet 4. Although it was slightly formed, it was not noticeable visually. When the distance from the virtual plane of the intermediate transfer belt 200 to the downstream end of the first inclined surface 321 in the sheet conveyance direction is set to 0.5 mm and 1.0 mm, white stripes appear on the image printed on the sheet 4. It was confirmed that it was not formed at all.

  From this test result, the distance from the virtual plane of the intermediate transfer belt 200 to the downstream end portion of the first inclined surface 321 in the sheet conveyance direction is 1.5 mm or less, and more preferably 1.0 mm or less. It was confirmed that white streaks could be prevented from being formed on the image printed on.

  Next, the features of the guide member 30 of the present embodiment will be described in comparison with the conventional transfer upper guide. FIG. 8 is a view showing a guide member 30 according to a conventional example.

  As shown in FIG. 8, in the conventional transfer upper guide, a sheet member made of a polyester film is bonded to a guide surface for guiding a sheet (not shown). The polarity of the sheet printed surface of the sheet conveyed to the intermediate transfer belt (not shown) is adjusted by this sheet member, and the toner image transferred on the intermediate transfer belt is transferred to the sheet.

  However, as can be seen from FIG. 8, the downstream end portion of the sheet member in the sheet conveyance direction is a free end portion in order to smoothly convey the sheet to the intermediate transfer belt. Thus, since the transfer upper guide of the conventional example is formed with a free end portion made of a polyester film at the downstream end portion in the sheet conveying direction, it is necessary to give the end portion a predetermined strength, and the sheet member It was necessary to increase the thickness. Further, since the polyester film is an elastic material, when a large amount of sheets are conveyed, the shape of the free end made of the polyester film is deformed and sometimes damaged.

  On the other hand, the guide member 30 of the present embodiment is made of a material having rigidity higher than that of the polarity adjusting surface 33 at the downstream end in the sheet conveying direction even if the polarity adjusting surface 33 is formed of a polyester film. Since the inclined portion 32 is used, the shape of the downstream end portion of the guide member 30 in the sheet conveying direction is not deformed and is not damaged even when the sheet 4 is conveyed in a large amount.

  In addition, the guide member 30 of the present embodiment is not configured to have the end portion of the polarity adjustment surface 33 as a free end portion like the conventional transfer upper guide, and therefore the thickness of the polarity adjustment surface 33 is set to 0.1 mm, for example. It can be made thinner. Thus, by reducing the thickness of the polarity adjusting surface 33, the amount of the polyester film used can be reduced, and the cost for manufacturing the guide member 30 can be reduced as compared with the conventional transfer guide.

  In the above-described embodiment, the inclined portion 32 has been described as a material having rigidity higher than that of the polarity adjusting surface 33, but any inelastic material may be used. That is, the inclined portion 32 of the embodiment may be any as long as the shape of the inclined portion 32 is not deformed when the sheet 4 is guided by the guide member 30.

  The above-described embodiments are merely examples, and can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-mentioned embodiment is only a mere illustration in all points, and should not be interpreted limitedly. The interpretation of the technical matters indicated by the claims is not limited to the text of the specification. Further, all modifications, various improvements, alternatives and modifications belonging to the equivalent scope of the claims are all within the scope of the present invention.

  As described in detail above, according to the technique described in this specification, the manufacturing cost of the guide member 30 that guides the sheet 4 to the intermediate transfer belt 200 can be reduced.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image forming apparatus main body 11 Paper feed part 12 Conveyance path (conveyance part) 121 Conveyance roller (conveyance part) 13 Paper discharge receiving part 131 Paper discharge roller 14 Image reading part 20 Image formation part 200 Intermediate transfer belt (transfer) Element)
201 Printing unit Y (image carrier) 202 Printing unit M (image carrier) 203 Printing unit C (image carrier) 204 Printing unit Bk (image carrier) 211 Photoconductor Y 212 Photoconductor M213 Photoconductor C 214 Photosensitive Body Bk 221 Charger Y 222 Charger M 223 Charger C 224 Charger Bk 231 Exposure unit Y 232 Exposure unit M 233 Exposure unit C 234 Exposure unit Bk 241 Development unit Y 242 Development unit M 243 Development unit C 244 Development unit Bk 251 Cleaning unit Y 252 Cleaning unit M 253 Cleaning unit C 254 Cleaning unit Bk
26 Secondary transfer roller 27 Fixing device 30 Guide member 31 Sheet detection mechanism 32 Inclined portion 321 First inclined surface 322 Second inclined surface 33 Polarity adjusting surface 4 Sheet

Claims (5)

An image carrier for carrying a toner image to be printed on the sheet, a transfer member for transferring the toner image on the image carrier to the sheet, and guiding the sheet toward a transfer position for transferring the toner image onto the sheet by the transfer member An image forming apparatus comprising: a guide member configured to perform transport; and a transport unit configured to transport a sheet to the guide member.
The guide member is
An inclined portion that is located at the downstream end portion in the sheet conveying direction of the guide member and is inclined away from the sheet conveying direction as it proceeds from the upstream side to the downstream side in the sheet conveying direction;
An image forming apparatus having a polarity adjusting surface positioned on the upstream side of the inclined portion of the guide member in the sheet conveying direction and rubbing the print surface of the sheet conveyed from the conveying portion to adjust the polarity of the sheet. The apparatus of claim 1, comprising:
The inclined part is an image forming apparatus formed of a material having higher rigidity than the polarity adjusting surface. The apparatus according to claim 1 or 2, comprising:
The image forming apparatus in which the inclined portion of the guide member is inclined by 20 ° to 45 ° with respect to the polarity adjustment surface. The apparatus according to any one of claims 1 to 3,
The inclined portion includes a first inclined surface located on the downstream end side in the sheet conveying direction on the polarity adjusting surface, and a second inclined surface adjacent to the downstream end portion in the sheet conveying direction on the first inclined surface. And
An image forming apparatus, wherein a distance from a virtual plane extending along a transfer plane including a transfer position of the transfer member to a downstream end portion in the sheet conveying direction on the first inclined surface is 1.5 mm or less. An apparatus according to any one of claims 1 to 4, wherein
The polarity adjusting surface is an image forming apparatus formed of a polyester film.

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