JP6080784B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus.

  In the electrophotographic image forming apparatus, the photosensitive drum is uniformly charged by the charging roller. Next, laser light is irradiated on the surface of the charged photosensitive drum to form an electrostatic latent image on the surface of the photosensitive drum. Then, the electrostatic latent image on the photosensitive drum is developed using toner. Thereafter, when the toner image on the photosensitive drum is transferred to the sheet or the intermediate transfer belt, the photosensitive drum is neutralized by the neutralizing light emitted from the neutralizing unit, and the surface of the photosensitive drum is cleaned by the cleaning unit (for example, Patent Document 1).

JP 2006-234882 A

  Incidentally, in an image forming apparatus having an intermediate transfer belt to which a toner image on a photosensitive drum is intermediately transferred, an external additive such as a lubricant or an abrasive used together with the toner adheres to the intermediate transfer belt. Here, the external additive adhering to the image forming area corresponding to the width of the maximum printable size in the intermediate transfer belt is transferred from the intermediate transfer belt to the sheet together with the toner. However, the external additive attached to the non-image forming area outside the image forming area in the intermediate transfer belt remains without being transferred to the sheet. Further, when the photosensitive drum is charged by the charging roller, discharge products such as ozone or nitrogen oxide may also adhere to the photosensitive drum due to discharge.

  For this reason, the non-image forming areas of the photosensitive drum and the intermediate transfer belt slide through the external additive or the discharge product, and the non-image forming areas of the photosensitive drum are more easily worn than the image forming area. It should be noted that the non-image forming area to which the external additive or the discharge product is attached is easily scraped by the cleaning unit. When the non-image forming area of the photosensitive drum is worn, a leak current is generated during the charging process of the photosensitive drum by the charging roller, and the image may be disturbed. That is, the wear of the non-image forming area of the photosensitive drum may shorten the life of the photosensitive drum.

  Further, in the image forming apparatus, the photosensitive drum and the charging roller are arranged in pressure contact, and the pressure of the nip portion tends to be stronger on the outside than the inside of the photosensitive drum. one of.

  An object of the present invention is to provide an image forming apparatus capable of suppressing wear of a non-image forming area on a photosensitive drum.

  An image forming apparatus according to an aspect of the present invention includes a photosensitive drum, a housing, a developing roller, a housing, a transfer roller, a first static elimination unit, and a shielding unit. The developing roller develops the electrostatic latent image formed on the photosensitive drum with toner. The housing supports one or both of the photosensitive drum and the developing roller. The transfer roller transfers the toner image of the photosensitive drum developed by the developing roller to a sheet or an intermediate transfer member. The first charge removal unit is disposed in the housing and irradiates a charge removal light for discharging the photosensitive drum to a position between the developing roller and the transfer roller on an outer peripheral surface of the photosensitive drum. The shielding portion is formed in the housing and is a non-image forming area outside a predetermined image forming area in the photosensitive drum among the static eliminating light irradiated from the first static eliminating portion toward the photosensitive drum. The static elimination light irradiated toward is shielded.

  According to the present invention, wear of the non-image forming area on the photosensitive drum is suppressed.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of an image forming unit of the image forming apparatus illustrated in FIG. FIG. 3 is an AA arrow view in FIG. 4 is a diagram showing another example of the image forming unit of the image forming apparatus shown in FIG. FIG. 5 is a BB arrow view in FIG.

  Embodiments of the present invention will be described below with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

[First Embodiment]
First, a schematic configuration of the image forming apparatus 10 according to the first embodiment of the present invention will be described.

[Schematic Configuration of Image Forming Apparatus 10]
As shown in FIG. 1, the image forming apparatus 10 includes a plurality of sets of image forming units 1 to 4, an intermediate transfer belt 5, an optical scanning device 6, a secondary transfer roller 7, a fixing device 8, a paper discharge tray 9, and toner. Containers 21 to 24, a paper feed cassette 31, a transport path 32, and the like are provided. The image forming apparatus 10 forms a color image or a monochrome image based on image data input from an information processing apparatus such as a personal computer on a sheet supplied from the sheet feeding cassette 31 along the conveyance path 32. It is a printer. The transport path 32 is provided with various transport rollers that transport the sheets stacked on the paper feed cassette 31 to the paper discharge tray 9 through the secondary transfer roller 7 and the fixing device 8. . The sheet is a sheet material such as paper, coated paper, postcard, envelope, and OHP sheet. In addition, a facsimile machine, a copier, and a multifunction machine are examples of the image forming apparatus according to the present invention.

  The image forming units 1 to 4 are juxtaposed along the traveling direction of the intermediate transfer belt 5 and constitute a so-called tandem image forming unit. Specifically, the image forming unit 1 corresponds to C (cyan), the image forming unit 2 corresponds to M (magenta), the image forming unit 3 corresponds to Y (yellow), and the image forming unit 4 corresponds to K (black). A toner image is formed.

  FIG. 2 is a diagram showing an example of the configuration of the image forming unit 1. Since each of the image forming units 1 to 4 has the same configuration, only the image forming unit 1 will be described here, and description of the image forming units 2 to 4 will be omitted.

  As shown in FIG. 2, the image forming unit 1 includes an electrophotographic image including a photosensitive drum 11, a charging unit 12, a developing unit 13, a first charge eliminating unit 14, a primary transfer roller 15, and a cleaning unit 16. Forming unit.

  The photosensitive drum 11 is an image carrier that carries an electrostatic latent image and a toner image. More specifically, the photosensitive drum 11 is a positively charged organic photosensitive drum having a single photosensitive layer. The photosensitive drum 11 may be a negatively charged laminated photosensitive drum or an amorphous silicon drum.

  The charging unit 12 includes a charging roller 121 that can rotate while being in contact with the photosensitive drum 11. The charging roller 121 charges the photosensitive drum 11 with electric power supplied from a power source (not shown). The optical scanning device 6 irradiates the photosensitive drum 11 charged by the charging unit 12 with laser light, and forms an electrostatic latent image based on image data on the outer peripheral surface of the photosensitive drum 11. In the configuration in which the photosensitive drum 11 is charged using the charging roller 121, the thinning of the photosensitive drum 11 greatly affects the leak current during the charging process.

  The developing unit 13 includes a developing roller 131 that develops the electrostatic latent image formed on the photosensitive drum 11 with toner (developer). The developing unit 13 includes a housing 132 that rotatably supports the developing roller 131. In addition, an external additive such as a lubricant or an abrasive is used together with the toner for developing the electrostatic latent image by the developing unit 13. Further, the developing unit 13 of each of the image forming units 1 to 4 is supplied with toner from removable toner containers 21 to 24 corresponding to the respective colors.

  The first charge eliminating unit 14 irradiates a position between the developing roller 131 and the primary transfer roller 15 on the outer peripheral surface of the photoconductive drum 11 with a charge removing light for removing the photoconductive drum 11. LED for discharging the photosensitive drum 11 by the above. In other words, the first charge removal unit 14 irradiates the discharge light on the downstream side of the developing roller 13 and the upstream side of the primary transfer roller 15 in the rotation direction of the photosensitive drum 11. As a result, so-called memory images that may occur on the photosensitive drum 11 are suppressed.

  The primary transfer roller 15 transfers the toner image formed on the photosensitive drum 11 to the intermediate transfer belt 5. The intermediate transfer belt 5 runs above the photosensitive drum 11 of each of the image forming units 1 to 4, and an intermediate toner image formed on each of the photosensitive drums 11 is sequentially superimposed and transferred. It is a transfer member. That is, a color image based on the image data is formed on the intermediate transfer belt 5 by superimposing the toner images of the respective colors. An arrangement in which the intermediate transfer belt 5 travels below each of the photosensitive drums 11 is also conceivable as another embodiment.

  Then, the toner image on the intermediate transfer belt 5 is transferred by the secondary transfer roller 7 to a sheet conveyed from the paper feed cassette 31 via the conveyance path 32. Thereafter, the toner image transferred to the sheet is heated and fixed on the sheet by the fixing device 8. The cleaning unit 16 includes a cleaning blade or a cleaning roller for cleaning the photosensitive drum 11 after the toner image is transferred to the intermediate transfer belt 5.

  The image forming apparatus 10 is provided with a separation mechanism (not shown) for bringing the photosensitive drum 11 of each of the image forming units 1 to 3 into contact with and separating from the intermediate transfer belt 5. When the image forming apparatus 10 prints a monochrome image, the photosensitive drum 11 of each of the image forming units 1 to 3 and the intermediate transfer belt 5 are separated by the separation / contact mechanism. As a result, only the black toner image formed by the image forming unit 4 is transferred from the image forming unit 4 to the intermediate transfer belt 5, and a monochrome image is transferred from the intermediate transfer belt 5 to the sheet.

  Incidentally, as shown in FIG. 3, each of the photosensitive drum 11, the charging roller 121, and the intermediate transfer belt 5 includes an image forming area A1 corresponding to the maximum printable size in the main scanning direction D1 and the image forming area. And a non-image forming area A2 outside A1. The image forming apparatus 10 can also form an image in a partial range from the image forming area A1 to the non-image forming area A2, thereby stably performing image formation in the image forming area A1. Is called.

  On the other hand, in the image forming apparatus 10, an external additive used together with toner adheres to the intermediate transfer belt 5. Then, the external additive attached to the image forming area A1 in contact with the sheet in the intermediate transfer belt 5 is transferred to some extent from the intermediate transfer belt 5 to the sheet together with the toner. However, the external additive attached to the non-image forming area A2 that does not contact the sheet in the intermediate transfer belt 5 remains without being transferred. Further, when the photosensitive drum 11 is charged by the charging roller 121, discharge products such as ozone or nitrogen oxide may adhere to the photosensitive drum 11 due to discharge. Therefore, the non-image forming area A2 of the photosensitive drum 11 and the intermediate transfer belt 5 slides through an external additive or a discharge product, and the non-image forming area A2 of the photosensitive drum 11 is slid. It becomes easier to wear than the image forming area A1. It should be noted that the non-image forming area A2 to which the external additive or the discharge product is attached is easily scraped by the cleaning unit 16. When the non-image forming area A2 of the photoconductive drum 11 is worn, a leak current may be generated during the charging process of the photoconductive drum 11 by the charging roller 121, and the image may be disturbed. That is, the wear of the non-image forming area A2 of the photosensitive drum 11 may shorten the life (usable period) of the photosensitive drum 11. In the image forming apparatus 10, since the photosensitive drum 11 and the charging roller 121 are pressed against each other, the pressure at the nip portion is likely to be stronger on the outside than on the inside of the photosensitive drum 11. This is one of the factors that cause the non-image forming area A2 of the body drum 11 to be easily worn.

  In the image forming apparatus 10 according to the present exemplary embodiment, the wear of the non-image forming area A2 in the photosensitive drum 11 is suppressed by the following configuration.

  As shown in FIG. 3, the first static elimination unit 14 is arranged on the upper surface 133 of the housing 132, and a plurality of the first static elimination units 14 are arranged at a predetermined interval in the main scanning direction D <b> 1, toward the photosensitive drum 11. Irradiation light can be irradiated.

  Further, as shown in FIG. 3, shielding parts 134 are formed at both ends of the upper surface 133 of the housing 132 in the main scanning direction D1. More specifically, the shielding part 134 is integrally formed with the housing 132 as a protruding part that protrudes upward from the upper surface 133. The shielding unit 134 removes light that is emitted toward the non-image forming area A2 in the photosensitive drum 11 out of the static elimination light that is emitted from each of the first static elimination units 14 toward the photosensitive drum 11. Shield lightning.

  Here, the formation position of the shielding part 134 on the upper surface 133 of the housing 132 is shielded by the shielding part 134 of the static elimination light emitted from the first static elimination part 14 toward the photosensitive drum 11. The photosensitive drum 11 until the distance between the edge of the neutralizing light reaching the photosensitive drum 11 without any change and the boundary between the image forming area A1 and the non-image forming area A2 is equal to or less than a predetermined allowable value. It is a position close to. Thereby, compared with the case where the shielding part 134 is arranged in the vicinity of the first charge eliminating part 14, the irradiation of the charge eliminating light to the non-image forming area A2 of the photosensitive drum 11 is shielded with high accuracy. be able to.

  As described above, when the neutralization light irradiation to the non-image forming area A2 of the photosensitive drum 11 is suppressed, the charged state of the non-image forming area A2 of the photosensitive drum 11 is maintained. Further, in the image forming apparatus 10, the potential difference between the non-image forming area A2 and the charging roller 121 is reduced, and the discharge in the non-image forming area A2 during the charging process of the photosensitive drum 11 is suppressed. For this reason, adhesion of discharge products or external additives to the non-image forming area A2 of the photosensitive drum 11 is suppressed, and wear of the non-image forming area A2 is suppressed. Further, the occurrence of leakage current during the charging process of the photosensitive drum 11 is also suppressed. Therefore, in the image forming apparatus 10, the life of the photosensitive drum 11 can be extended. In particular, such an effect is obtained in the image forming apparatus 10 that uses a positively charged organic photosensitive drum that is formed of an organic material that is relatively easy to cut like the photosensitive drum 11 and that easily generates a leak current due to a thin film. Appears prominently.

  Furthermore, since the shielding part 134 can be integrally formed on the upper surface 132 of the housing 132, the number of parts for the shielding part 134 does not increase. More specifically, the shielding unit 134 is configured so that the housing 132 faces the photoconductive drum 11 so that the front end of the housing 132 on the photoconductive drum 11 side is positioned in the vicinity of the photoconductive drum 11. The extended structure can be formed in the vicinity of the photosensitive drum 11.

  Further, in the image forming apparatus 10, the positions of the first charge removal unit 14 and the shielding unit 134 are separated from each other in the discharge direction of the charge removal light on the upper surface 133 of the housing 132. More specifically, the arrangement position of the first charge eliminating portion 14 on the upper surface 133 of the housing 132 is a position separated from the photoconductive drum 11 to the extent that toner scattered from the photoconductive drum 11 is difficult to reach. It is. As a result, in the image forming apparatus 10, it is possible to suppress the toner from adhering to the first neutralization unit 14 while suppressing the irradiation of the neutralization light to the non-image forming area A <b> 2, and the neutralization by the first neutralization unit 14. Degradation of performance can be suppressed.

[Second Embodiment]
The image forming apparatus 10 according to the second embodiment of the present invention will be described below. FIG. 4 is a view showing another example of the image forming unit 1. Moreover, FIG. 5 is a BB arrow line view in FIG. In addition, the same code | symbol is used about the structure similar to the said 1st Embodiment, and the description is abbreviate | omitted.

  Specifically, as shown in FIG. 4, the image forming apparatus 10 according to the second embodiment includes a casing 111 that supports the photosensitive drum 11. The housing 111 has a bearing that supports the rotating shaft 112 of the photosensitive drum 11 and supports the photosensitive drum 11 rotatably. The casing 111 supports the cleaning unit 16 together with the photosensitive drum 11. Note that the case 111 or the case 132 may support the photosensitive drum 11 and the developing roller 131 as another embodiment.

  Further, as shown in FIG. 5, shielding portions 114 are formed at both ends of the upper surface 113 of the casing 111 in the main scanning direction D1. More specifically, the shielding portion 114 is integrally formed with the housing 111 as a protruding portion that protrudes upward from the upper surface 113. The shielding portion 114 is a removal that is referred to the non-image forming area A2 in the photosensitive drum 11 out of the neutralizing light emitted from each of the first neutralizing portions 14 toward the photosensitive drum 11. Shield lightning. That is, the image forming apparatus 10 according to the second embodiment includes the shielding unit 114 instead of the shielding unit 134.

  Also in the image forming apparatus 10 configured as described above, irradiation of the static elimination light to the non-image forming area A2 of the photosensitive drum 11 is suppressed by the shielding portion 114, and the non-photosensitive property of the photosensitive drum 11 is reduced. The charged state of the image forming area A2 is maintained. Further, in the image forming apparatus 10, the potential difference between the non-image forming area A2 and the charging roller 121 is reduced, and the discharge in the non-image forming area A2 during the charging process of the photosensitive drum 11 is suppressed. For this reason, adhesion of discharge products or external additives to the non-image forming area A2 of the photosensitive drum 11 is suppressed, and wear of the non-image forming area A2 is suppressed. Further, the occurrence of leakage current during the charging process of the photosensitive drum 11 is also suppressed. Therefore, in the image forming apparatus 10, the life of the photosensitive drum 11 can be extended.

  In particular, since the shielding portion 114 is formed on the upper surface 113 of the casing 111 on which the photosensitive drum 11 is supported, the shielding portion 114 is easily formed at a position as close as possible to the outer peripheral surface of the photosensitive drum 11. Thereby, compared with the case where the shielding part 114 is arranged in the vicinity of the first charge eliminating part 14, the irradiation of the charge eliminating light to the non-image forming area A2 of the photosensitive drum 11 is shielded with high accuracy. be able to.

  Further, as shown in FIG. 4, a configuration in which the image forming apparatus 10 further includes a second static elimination unit 141 and a shielding unit 142 is conceivable. The second charge eliminating unit 141 irradiates a position between the primary transfer roller 15 and the cleaning unit 16 on the outer peripheral surface of the photoconductive drum 11 with a charge eliminating light for eliminating the photoconductive drum 11. In other words, the second static elimination unit 141 irradiates the static elimination light on the downstream side of the primary transfer roller 15 and the upstream side of the cleaning unit 16 in the rotation direction of the photosensitive drum 11. Further, the shielding portion 142 is integrally formed on both ends of the upper surface 113 of the housing 111 in the main scanning direction D1. The shielding unit 142 is similar to the shielding unit 114 in that the non-image forming area in the photosensitive drum 11 out of the neutralizing light emitted from each of the second neutralizing units 141 toward the photosensitive drum 11. The static elimination light referred to A2 is shielded. Thereby, generation | occurrence | production of the said memory image in the said photoconductive drum 11 can be suppressed more effectively.

  Furthermore, the structure which the said 1st static elimination part 14 irradiates with static elimination light to both the direction which goes to the said photoconductive drum 11, and the opposite direction is also considered. That is, the first charge eliminating unit 14 irradiates the discharge light between the developing roller 131 and the transfer roller 15 on the outer peripheral surface of the photosensitive drum 11, and on the outer peripheral surface of the adjacent photosensitive drum 11. Irradiation of static elimination light between the transfer roller 15 and the cleaning unit 16 may be considered as another embodiment. That is, a configuration in which the first static elimination unit 14 also serves as the second static elimination unit 141 can be considered.

  For example, the first charge removal unit 14 of the image forming unit 2 irradiates the discharge light between the developing roller 131 and the transfer roller 15 on the outer peripheral surface of the photosensitive drum 11 of the image forming unit 2. In addition, the first charge removal unit 14 of the image forming unit 2 emits charge removal light between the transfer roller 15 and the cleaning unit 16 on the outer peripheral surface of the photosensitive drum 11 of the adjacent image formation unit 1. It is possible to do. In this case, the first neutralization unit 14 of the image forming unit 2 and the cleaning unit 16 of the image forming unit 1 are in a positional relationship in which the neutralization light from the first neutralization unit 14 is not shielded by the cleaning unit 16. It is arranged with. As a result, the generation of the memory image on the photosensitive drum 11 can be more effectively suppressed using the first charge eliminating unit 14. The image forming unit 4 is provided with the second charge eliminating portion 141 separately from the first charge eliminating portion 14.

  In the image forming apparatus 10, the case where a toner image is transferred from the photosensitive drum 11 to the sheet via the intermediate transfer belt 5 has been described as an example. However, the toner is transferred from the photosensitive drum 11 to the sheet. A configuration in which an image is directly transferred is also conceivable as another embodiment.

1-4: Image forming unit 5: Intermediate transfer belt 6: Optical scanning device 7: Secondary transfer roller 8: Fixing device 9: Paper discharge tray 10: Image forming device 11: Photosensitive drum 111: Housing 112: Rotating shaft 113: Upper surface 114: Shielding unit 12: Charging unit 121: Charging roller 13: Developing unit 131: Developing roller 132: Housing 133: Upper surface 134: Shielding unit 14: First neutralizing unit 15: Primary transfer roller 16: Cleaning unit 21 -24: toner container 31: paper feed cassette 32: transport path

Claims (6)

A photosensitive drum which is a positively charged organic photosensitive drum having a single photosensitive layer ;
A developing roller for developing the electrostatic latent image formed on the photosensitive drum with toner;
A first housing that supports the developing roller;
A second housing that supports a rotating shaft of the photosensitive drum;
A transfer roller for transferring the toner image of the photosensitive drum developed by the developing roller to a sheet or an intermediate transfer member;
The first casing is disposed in the first casing or the second casing, and irradiates a neutralizing light for neutralizing the photosensitive drum on a position between the developing roller and the transfer roller on an outer peripheral surface of the photosensitive drum. A static eliminator,
Of the static elimination light that is formed on the second casing and is emitted from the first static elimination unit toward the photosensitive drum , the non-image forming area outside the predetermined image forming area at both ends of the photosensitive drum. A first shielding unit that shields the static elimination light emitted toward the
A cleaning unit for cleaning the photosensitive drum after the toner image is transferred from the transfer roller to the sheet or the intermediate transfer member;
The second casing is disposed in the first casing or the second casing and irradiates a neutralizing light for neutralizing the photosensitive drum on a position between the transfer roller and the cleaning portion on the outer peripheral surface of the photosensitive drum. A static eliminator,
Of the static elimination light that is formed on the second casing and is emitted from the second static elimination unit toward the photosensitive drum, the static elimination light that is emitted toward the non-image forming regions at both ends of the photosensitive drum. A second shielding part for shielding;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, further comprising a charging roller that is disposed in contact with the photosensitive drum and charges the photosensitive drum. Wherein the first shielding portion, the end portion of the discharging light from the first discharger reaches the photosensitive drum without being shielded by the first shielding portion of the discharging light emitted toward the photosensitive drum 3. The image formation according to claim 1, wherein the image forming region is formed at a position close to the photosensitive drum until a distance between a boundary between the image forming region and the non-image forming region is equal to or less than a predetermined allowable value. apparatus.   The image forming apparatus according to claim 1, wherein the image forming area is an area corresponding to a predetermined maximum printable size in the photosensitive drum.   The first charge removal unit is disposed in the first housing;
  The second charge eliminating portion is disposed in the second casing;
  The first shielding part and the second shielding part are formed in the second housing,
  The image forming apparatus according to claim 1. A plurality of sets of the photosensitive drum, the developing roller, the transfer roller, the first charge eliminating unit, and the cleaning unit are arranged in parallel.
The first neutralizing unit irradiates neutralizing light between the developing roller and the transfer roller on the outer peripheral surface of the photosensitive drum, and the transfer roller and the cleaning unit on the outer peripheral surface of the adjacent photosensitive drum. 5. The image forming apparatus according to claim 1, which also serves as the second charge removal unit capable of emitting charge removal light between the first and second charge removal units.

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