JP5206593B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming unit using an electrophotographic system such as a copying machine, a printer, a facsimile machine, and a composite machine of these, and includes a photosensitive member and a charging member for charging the surface of the photosensitive member. The present invention relates to an image forming apparatus in which a plurality are mounted. In particular, as the above-described image forming unit, a short-life image forming unit with a short life of the photoconductor and a long-life image forming unit with a long photoconductor life are used, and two or more image forming units are used. When a charging bias voltage is applied to the charging member from the common power supply for charging, an appropriate charging bias voltage is applied to the charging member in two or more image forming units so that good image formation can be performed. It has the characteristics in the point.

  In an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile machine, and a composite machine of these, in general, a photosensitive member is charged by a charging device, and then the charged photosensitive member is exposed by an exposure device. Exposure is performed according to the image data to form an electrostatic latent image on the surface of the photoconductor, and toner is supplied from the developing device to the photoconductor on which the electrostatic latent image is formed in this way, A toner image corresponding to the electrostatic latent image is formed.

  Here, when charging the photosensitive member with the charging device as described above, the amount of ozone generated increases when a charging device using corona discharge is used. The charging member is charged by applying a charging bias voltage from a charging power source to the charging member in contact with or close to the surface of the photosensitive member.

  In recent years, in order to perform full-color image formation, an image forming apparatus is provided with a plurality of image forming units each including a photosensitive member and a charging member that charges the surface of the photosensitive member. Toners of different colors are supplied to the photoreceptor from each developing device to form toner images of each color on the surface of each photoreceptor, and thus toner images of each color formed on the surface of each photoreceptor. Is transferred to a recording medium via an intermediate transfer belt or the like to form a full-color image on the recording medium.

  Here, in the image forming apparatus provided with a plurality of image forming units including the photosensitive member and the charging member for charging the surface of the photosensitive member in this way, the surface of each photosensitive member is charged by the charging member. Conventionally, an appropriate charging bias voltage is generally applied to each charging member from a separate charging power source so that the surface of each photoconductor is charged to an appropriate potential.

  However, providing a plurality of charging power sources corresponding to each charging member that charges the surface of the photoreceptor in this way increases the cost and requires a space for accommodating these, resulting in an increase in the size of the apparatus. It is also necessary to appropriately control the charging bias voltage applied to each charging member from each charging power source, which causes problems such as troublesome control.

  Conventionally, as disclosed in Japanese Patent Application Laid-Open No. 2004-133620, a charging common power source in which a charging power source for applying a charging bias voltage to each charging member is used in common has been proposed.

  Here, in the device disclosed in Patent Document 1, a charging bias voltage is applied to each charging member from a charging common power source as described above, while a supporting substrate bias power source is applied to each photoconductor. The surface potential of each photoconductor is adjusted by applying an appropriate bias voltage to each photoconductor from each supporting substrate bias power source.

  However, if the support base bias power source is provided for each photoconductor in this manner, the cost is high and a space for housing these is required as in the case of providing a plurality of charging power sources. However, it is necessary to appropriately control the bias voltage to be applied to each photoconductor from each supporting substrate bias power source, which causes troublesome control.

JP 2004-62016 A

  An object of the present invention is to solve the above-described problems in an image forming apparatus in which a plurality of image forming units each including a photoconductor and a charging member for charging the surface of the photoconductor are mounted. It is.

  In the image forming apparatus of the present invention, as the above-described image forming unit, a short-life image forming unit with a short life of the photoreceptor and a long-life image forming unit with a long life of the photoreceptor are used. The charging bias voltage is applied from one common charging power source to the charging members in the two or more image forming units to charge the surface of the photoreceptor in each image forming unit. To appropriately control the charging bias voltage applied to the charging member in two or more image forming units to appropriately charge the surface of the photoreceptor in each image forming unit so that good image formation can be performed. It is to be an issue.

  In the present invention, in order to solve the above-described problems, an image forming apparatus including a plurality of image forming units each including a photosensitive member and a charging member that charges the surface of the photosensitive member. When a short-life image forming unit with a short photoconductor life and a long-life image forming unit with a long photoconductor life are used as the unit for image formation, the short-life image forming unit and long life Identifying means for identifying the image forming unit for charging, a charging common power source for applying a charging bias voltage to the charging member in two or more image forming units, and a charging bias voltage for applying the charging member from the charging common power source to the charging member Means for switching between a first bias voltage corresponding to the image forming unit for short life and a second bias voltage corresponding to the image forming unit for long life. Therefore, when the identification unit identifies two or more image forming units to which the charging bias voltage is applied to the charging member by the charging common power source, and the short-life image forming unit is included, the control unit The charging bias voltage to be applied to each charging member from the charging common power source is set to the first bias voltage, while when only the long-life image forming unit is used, the charging means supplies the charging member to each charging member. The charging bias voltage applied to is set to the second bias voltage.

  In the image forming apparatus of the present invention, the charging member can be provided in contact with or close to the surface of the photoreceptor.

  Further, in the image forming apparatus of the present invention, as the above-mentioned photoreceptor, one having an organic photosensitive layer on the surface can be used. When such a photoreceptor is used, the layer thickness of the organic photosensitive layer in the photoreceptor used for the long-life image forming unit is larger than the layer thickness of the organic photosensitive layer in the photoreceptor used for the short-life image forming unit. Is also thicker.

  The image forming apparatus of the present invention is suitably used when the short-life image forming unit is replaced with the long-life image forming unit after use.

  In the image forming apparatus of the present invention, the charging bias voltage is applied to the charging member by the charging common power source by the identification unit when the charging bias voltage is applied to the charging member in the two or more image forming units from the charging common power source. In the case where two or more image forming units are identified and a short-life image forming unit is included, a first common unit corresponding to the short-life image forming unit is connected to each charging member from the charging common power source by the control means. On the other hand, when only the long-life image forming unit is applied, the control means applies a second bias voltage corresponding to the long-life image forming unit to each charging member from the charging common power source by the control means. I did it.

  This eliminates the need for providing a separate charging power source for each charging member provided in each image forming unit, thereby reducing costs and increasing the size of the apparatus.

  In addition, when the short-life image forming unit is included as described above, the first bias voltage corresponding to the short-life image forming unit is applied to the charging member in each image forming unit from the common power source for charging. The surface potential of the long-life photoreceptor used in the long-life image forming unit deviates from an appropriate surface potential when the second bias voltage corresponding to the long-life image forming unit is applied. A long-life image forming unit using a long-life photoconductor has a wider tolerance of the surface potential of the photoconductor than a short-life image forming unit using a short-life photoconductor. Therefore, the image is hardly adversely affected and good image formation can be performed.

  On the other hand, when only the long-life image forming unit is used as described above, the second bias voltage corresponding to the long-life image forming unit is applied from the charging common power source to the charging member in each image forming unit. By doing so, the surface of each photoconductor in the long-life image forming unit is charged to an appropriate potential by the charging member, so that better image formation can be performed.

1 is a schematic explanatory view showing an image forming apparatus according to an embodiment of the present invention. 2 is a partial explanatory view of a photoconductor used in the image forming apparatus of the embodiment. FIG. In the image forming apparatus of the embodiment, a state in which a first bias voltage is applied to each charging roller from a common charging power source when all the image forming units mounted are short-life image forming units is shown. FIG. In the image forming apparatus of the embodiment, when a part of the short-life image forming unit is replaced with the long-life image forming unit, the first bias voltage is applied to each charging roller from the common power supply for charging. It is the partial explanatory view showing the state. In the image forming apparatus of the embodiment, when all of the mounted image forming units are replaced with long-life image forming units, the second bias voltage is applied to each charging roller from the common power supply for charging. FIG. When the surface of the photosensitive member is charged by bringing the charging roller into contact with the surface of the photosensitive member provided with the organic photosensitive layer as in the image forming apparatus of the embodiment, the thickness of the organic photosensitive layer is charged. FIG. 6 is a diagram showing a relationship with a surface potential of a photoreceptor.

  Next, an image forming apparatus according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. Note that the image forming apparatus according to the present invention is not limited to those shown in the following embodiments, and can be implemented with appropriate modifications within a range not changing the gist thereof.

  In the image forming apparatus of this embodiment, as shown in FIG. 1, four image forming units 10 </ b> A to 10 </ b> D are mounted in the apparatus main body 1.

  Here, in each of the image forming units 10 </ b> A to 10 </ b> D, the drum-shaped photoconductor 11 is rotatably provided, and the charging roller 12 that contacts the surface of the photoconductor 11 and charges the surface of the photoconductor 11. A charging member comprising: an exposure device 13 that performs exposure according to image information on the surface of the charged photoconductor 11 to form an electrostatic latent image on the surface of the photoconductor 11, and the surface of the photoconductor 11 described above. A developing device 14 that supplies toner to the formed electrostatic latent image to form a toner image, and the photoconductor 11 after the toner image formed on the surface of the photoconductor 11 is transferred to the intermediate transfer belt 21. A neutralization device 15 that neutralizes the surface of the photosensitive member 11 by irradiating light on the surface and a first cleaning device 16 that removes residual toner and the like remaining on the surface of the photoreceptor 11 after the neutralization are provided.

  In addition, each developing device 14 in each of the image forming units 10A to 10D stores toners of different colors such as black, yellow, magenta, and cyan.

  Here, in the image forming apparatus according to this embodiment, when full color image formation is performed, a charging bias voltage is applied from the charging common power supply 30 to each charging roller 12 in each of the image forming units 10A to 10D. Then, the surface of each photoconductor 11 in each of the image forming units 10A to 10D is charged, and the surface of each photoconductor 11 thus charged is exposed according to the image information by the exposure device 13, respectively. An electrostatic latent image is formed on the surface of the body 11.

  Then, toner of each color is supplied from the corresponding developing device 14 to each photoconductor 11 on which the electrostatic latent image is formed in this way, and each photoconductor 11 in each of the image forming units 10A to 10D. A toner image of each color is formed on the surface.

  Next, the toner images of the respective colors formed on the surfaces of the photoreceptors 11 in the image forming units 10 </ b> A to 10 </ b> D in this way are placed on the surface of the intermediate transfer belt 21 that is stretched around the rotation roller 22. Then, the toner images are sequentially transferred by the primary transfer rollers 23 provided on the back side of the intermediate transfer belt 21 so as to face the photoconductors 11 to form a full-color toner image on the surface of the intermediate transfer belt 21. Like to do.

  Then, after the full-color toner image is transferred to the intermediate transfer belt 21 in this way, the surface of each photoconductor 11 is irradiated with light from the static eliminator 15 to neutralize the surface of each photoconductor 11, Residues such as toner remaining on the surface of the photoreceptor 11 are removed from the surface of each photoreceptor 11 by the first cleaning device 16.

  On the other hand, the full-color toner image formed on the surface of the intermediate transfer belt 21 as described above is guided to the transfer portion where the rotation roller 22 and the transfer roller 2 face each other, and the recording medium S is fed by the paper feed roller 3. The recording medium S is fed to the transfer section where the rotating roller 22 and the transfer roller 2 face each other by the timing roller 4 at an appropriate timing, and a full-color toner image on the surface of the intermediate transfer belt 21 is recorded on the recording medium S. I try to make it transfer.

  Next, the recording medium S on which the full-color toner image is transferred in this way is guided to a fixing unit provided with a pair of fixing rollers 6 and 6, and the above-described full-color toner image is interposed between the pair of fixing rollers 6 and 6. Is fixed to the recording medium S, and then the recording medium S is discharged by the discharge roller 7.

  Further, after the full-color toner image formed on the surface of the intermediate transfer belt 21 as described above is transferred to the recording medium S, the residue such as toner remaining on the surface of the intermediate transfer belt 21 is removed by the second cleaning device. 8 is removed from the intermediate transfer belt 21.

  Here, in the image forming apparatus of this embodiment, as each of the image forming units 10A to 10D, the short life image forming units 10AS to 10DS to which the photoconductor 11 having a short life is attached are long. The long-life image forming units 10AL to 10DL to which the photoconductor 11 is attached are used.

  As shown in FIG. 2, the photosensitive member 11 is provided with an organic photosensitive layer 11b having a charge generation layer 11b1 and a charge transport layer 11b2 on the surface of a conductive substrate 11a such as an aluminum tube. The photoconductor 11 having a longer life is thicker than the photoconductor 11 having a short life.

  In the image forming apparatus of this embodiment, as shown in FIG. 3, the image forming unit for short life, in which the photoconductor 11 having a short life is mounted, is initially prepared as each of the image forming units 10A to 10D. 10AS to 10DS are mounted, and after using the short-life image forming units 10AS to 10DS, the long-life image forming units 10AL to 10DL to which the long-life photoconductor 11 is mounted are appropriately attached. In the example shown in FIG. 4, one short-life image forming unit 10AS is changed to a long-life image forming unit 10AL.

  Finally, as shown in FIG. 5, all the short-life image forming units 10AS to 10DS are replaced with long-life image forming units 10AL to 10DL.

  Further, in the image forming apparatus of this embodiment, as shown in FIGS. 3 to 5, identification for identifying the short-life image forming units 10AS to 10DS and the long-life image forming units 10AL to 10DL is performed. In addition to providing the means 31, the charging bias voltage applied to each charging roller 12 from the charging common power supply 30 is set to the first bias voltage Vb1 corresponding to the short-life image forming units 10AS to 10DS and the long-life image formation. Control means 32 for switching to the second bias voltage Vb2 corresponding to the units 10AL to 10DL is provided.

  Here, in identifying the short-life image forming units 10AS to 10DS and the long-life image forming units 10AL to 10DL by the identification means 31, the short-life image forming units 10AS to 10DS and the long-life image forming units 10AS to 10DS are used. Different projections (not shown) are provided on the image forming units 10AL to 10DL, and the image forming units 10AS to 10DS for short life and the image forming units 10AL to 10DL for long life are provided. Information for identification can be stored in a memory (not shown), and these can be detected by the identification means 31 described above.

  Further, as described above, the photosensitive member 11 having the organic photosensitive layer 11b provided on the surface of the conductive substrate 11a is used, and the charging roller 12 is brought into contact with the surface of the photosensitive member 11 to charge the surface of the photosensitive member 11. In this case, as shown in FIG. 6, as the layer thickness of the organic photosensitive layer 11b increases, the surface potential of the charged photoreceptor 11 decreases.

  For this reason, in the image forming apparatus of this embodiment, the charging bias voltage applied to each charging roller 12 from the charging common power supply 30 by the control unit 32 corresponds to the short-life image forming units 10AS to 10DS. When switching between the 1 bias voltage Vb1 and the second bias voltage Vb2 corresponding to the long-life image forming units 10AL to 10DL, the short-life image forming unit using the photoconductor 11 having a small layer thickness of the organic photosensitive layer 11b. The absolute value | Vb1 | of the first bias voltage Vb1 corresponding to 10AS to 10DS and the second bias corresponding to the long-life image forming units 10AL to 10DL using the photoconductor 11 having the large organic photosensitive layer 11b. The absolute value | Vb2 | of the voltage Vb2 is in a relationship of | Vb1 | <| Vb2 |.

  In the image forming apparatus according to this embodiment, the mounted image forming units 10A to 10D are identified by the above-described identifying means 31, and as shown in FIG. 3 and FIG. 4, the short-life image forming unit. When it is detected that at least one 10AS to 10DS is present, the above-mentioned charging means is used by the control means 32 even when any of the long-life image forming units 10AL to 10DL is mounted. The first bias voltage Vb1 corresponding to the short-life image forming units 10AS to 10DS is applied from the common power supply 30 to the charging rollers 12 in all the image forming units 10A to 10D.

  Here, when there is at least one short-life image forming unit 10AS to 10DS as described above, the short-life image is transferred from the charging common power supply 30 to each charging roller 12 in each of the image forming units 10A to 10D. When the first bias voltage Vb1 corresponding to the forming units 10AS to 10DS is applied, the surface potential of the photoconductor 11 having a large layer thickness of the organic photosensitive layer 11b in the mounted long-life image forming units 10AL to 10DL is It becomes lower than a suitable surface potential when the second bias voltage Vb2 is applied.

  However, in the long-life image forming units 10AL to 10DL using the photoconductor 11 having a large layer thickness of the organic photoconductive layer 11b, the allowable range of the surface potential of the photoconductor 11 is wide, and therefore the organic photoconductive layer 11b. Compared to the case where the photoconductor 11 is charged by applying the second bias voltage Vb2 to the charging rollers 12 of the short-life image forming units 10AS to 10DS using the photoconductor 11 having a small layer thickness. The image is hardly adversely affected and good image formation can be performed.

  As shown in FIG. 5, when the identification means 31 detects that all the short-life image forming units 10AS to 10DS have been replaced with the long-life image forming units 10AL to 10DL, The control means 32 switches the charging bias voltage applied to each charging roller 12 from the charging common power supply 30 to the second bias voltage Vb2 corresponding to the long-life image forming units 10AL to 10DL.

  In this way, each photoconductor 11 in each of the long-life image forming units 10AL to 10DL is charged to have an appropriate surface potential by each charging roller 12 to which the second bias voltage Vb2 is applied. Good image formation can be performed.

  It should be noted that each charging roller from the above-mentioned charging common power source 30 is changed according to variations in timing for switching the short-life image forming units 10AS to 10DS to the long-life image forming units 10AL to 10DL, changes in environmental conditions, and the like. It is also possible to correct the first bias voltage Vb1 and the second bias voltage Vb2 applied to 12.

DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Transfer roller 3 Paper feed roller 4 Timing roller 6 Fixing roller 7 Paper discharge roller 8 Second cleaning device 10A to 10D Image forming unit 10AS to 10DS Image forming unit for short life 10AL to 10DL Image formation for long life Unit 11 photoreceptor 11a conductive substrate 11b organic photosensitive layer 11b1 charge generation layer 11b2 charge transport layer 12 charging roller (charging member)
DESCRIPTION OF SYMBOLS 13 Exposure apparatus 14 Developing apparatus 15 Static elimination apparatus 16 1st cleaning apparatus 21 Intermediate transfer belt 22 Rotating roller 23 Primary transfer roller 30 Charging common power supply 31 Identification means 32 Control means S Recording medium Vb1 First bias voltage Vb2 Second bias voltage

Claims (4)

  In an image forming apparatus in which a plurality of image forming units each equipped with a photoconductor and a charging member for charging the surface of the photoconductor are mounted, the above-mentioned image forming unit can be used for short-life image formation with a short photoconductor lifetime. And a long-life image forming unit with a long life of the photosensitive member, and an identification means for identifying the short-life image forming unit and the long-life image forming unit are provided. In the image forming unit, a charging common power source for applying a charging bias voltage to the charging member is provided, and the charging bias voltage to be applied to the charging member from the charging common power source corresponds to the short-life image forming unit. Control means for switching between one bias voltage and a second bias voltage corresponding to the long-life image forming unit is provided. When two or more image forming units to which the charging bias voltage is applied to the charging member are identified by the charging common power source, and the image forming unit for short life is included, While the charging bias voltage to be applied to the charging member is the first bias voltage, the charging bias voltage to be applied to each charging member from the charging common power source by the above control means when only the long-life image forming unit is used. An image forming apparatus having a second bias voltage.   2. The image forming apparatus according to claim 1, wherein the charging member is provided in contact with or close to the surface of the photosensitive member.   3. The image forming apparatus according to claim 1, wherein the photosensitive member is provided with an organic photosensitive layer on a surface thereof, and the layer of the organic photosensitive layer in the photosensitive member used in the long-life image forming unit. An image forming apparatus characterized in that the thickness is larger than the layer thickness of an organic photosensitive layer in a photoreceptor used for an image forming unit for short life.   4. The image forming apparatus according to claim 1, wherein the image forming unit is replaced with the long-life image forming unit after the short-life image forming unit is used. Image forming apparatus.

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