JP5099022B2 - Image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile machine, and a composite machine thereof, and more particularly, a cylindrical charging member that rotates in contact with the surface of a rotationally driven image carrier In the image forming apparatus in which the surface of the image carrier is charged by a contact-type charging device using a toner, residues such as toner and toner external additives remaining on the surface of the image carrier are It is characterized in that it is possible to appropriately prevent a charging failure such as uneven charging on the surface of the image bearing member from adhering to the outer peripheral surface of the charging member with a simple configuration.

  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, generally, the surface of the image carrier is charged by a charging device and then charged in this manner. The surface of the image is exposed according to the image data by the exposure device to form an electrostatic latent image on the surface of the image carrier, and toner from the developing device is applied to the image carrier on which the electrostatic latent image is formed in this way. The toner image corresponding to the electrostatic latent image is formed on the surface of the image carrier, and the toner image is transferred to a recording paper, an intermediate transfer body, etc., and then remains on the surface of the image carrier after the transfer. Residue such as toner to be removed is removed by a cleaning device, and then the surface of the image carrier is charged again by the charging device as described above.

  Here, in order to charge the image carrier with the charging device as described above, a charging device using corona discharge is generally used. However, in such a charging device, power consumption is large, There was a problem that the amount of generation increased.

  In recent years, in order to suppress power consumption and generation of ozone, a contact-type charging device is used in which the surface of the image carrier is charged by a charging roller that rotates in contact with the surface of the image carrier. Became.

  Here, when the surface of the image carrier is charged by the charging roller rotating in contact with the surface of the image carrier, the image is not removed from the surface of the image carrier by the cleaning device. Residue remaining on the surface of the carrier adheres to the outer peripheral surface of the charging roller, and the residue thus attached causes charging defects such as uneven charging on the surface of the image carrier charged by the charging roller, There is a problem in that unevenness of density occurs in the formed image.

  For this reason, conventionally, a cleaning member made of a blade or a brush is brought into contact with the outer peripheral surface of the charging roller, and the residue adhering to the outer peripheral surface of the charging roller is removed by the cleaning member.

  However, when a cleaning member such as a blade or brush is brought into contact with the outer peripheral surface of the rotating charging roller in this way, a load is applied to the rotating charging roller due to contact with the cleaning member, and the charging roller is appropriately rotated. There was a problem that charging failure such as uneven charging occurred on the surface of the image carrier.

  In recent years, as described in Patent Documents 1 to 3 and the like, the above contact-type charging device has been proposed in which a cylindrical charging member having a cost lower than that of a charging roller is used.

  However, even when such a cylindrical charging member is used, as in the case of the above-described charging roller, a load is applied to the rotating cylindrical charging member due to contact with the cleaning member, and the cylindrical charging member rotates. Is not performed properly, and there is a problem that charging failure such as uneven charging occurs on the surface of the image carrier.

  For this reason, conventionally, as disclosed in Patent Document 4, a charging electrode made of a flexible cylindrical film member is brought into contact with the surface of the image carrier to charge the surface of the image carrier. In such a case, there has been proposed one in which semiconductive fine particles having a particle diameter smaller than that of the toner are adhered to the peripheral surface of the above-described charging electrode to suppress the adhesion of foreign matters such as toner.

  However, when the semiconductive fine particles having a particle size smaller than that of the toner are attached to the peripheral surface of the charging electrode in this way, it is necessary to uniformly attach the semiconductive fine particles to the peripheral surface of the charging electrode, In order to stably attach the semiconductive fine particles to the peripheral surface of the charging electrode, it is necessary to apply an appropriate amount of the semiconductive fine particles from the fine particle applying means, which increases the cost. There was a problem that the control became very troublesome.

  Conventionally, as shown in Patent Document 5, between the cylindrical insulating member in contact with the image carrier and the image carrier, an attraction electric field for attracting the transfer residual toner to the insulating member and the image. There has been proposed a charging and cleaning device that performs cleaning and charging of an image carrier by applying a charging electric field that charges the surface of the carrier.

  However, in this charging and cleaning device, when the image carrier is cleaned and charged, the insulating member is in the opposite direction to the image carrier at the position where the insulating member and the image carrier are in contact with each other. When the insulating member is rotated by the rotating device so as to move to the surface of the image carrier, the transfer residual toner collected from the surface of the image carrier is discharged from the insulating member to the surface of the image carrier and returned to the developing device. The insulating member needs to be rotated in the opposite direction to the above case, and there is a problem that the cost is high and the control becomes very troublesome.

  Further, in this charging and cleaning apparatus, as described above, the suction electric field for attracting the transfer residual toner to the insulating member is applied between the insulating member and the image carrier. Thus, it was not possible to properly recover the external additive of the toner charged to the opposite polarity.

JP-A-5-188733 JP-A-8-240963 JP-A-9-90710 Japanese Patent Laid-Open No. 11-258888 JP-A-9-620655

  The present invention provides the above-described image forming apparatus in which the surface of the image carrier is charged by a contact type charging device using a cylindrical charging member that rotates in contact with the surface of the image carrier to be rotated. The problem is to solve the problem.

  That is, in the present invention, in the image forming apparatus as described above, residues such as toner remaining on the surface of the image carrier and toner external additives adhere to the surface of the cylindrical charging member. An object of the present invention is to appropriately prevent the occurrence of charging defects such as uneven charging when the surface of the image carrier is charged with a simple configuration.

In the image forming apparatus of the present invention, in order to solve the above-described problems, the image bearing member of the image bearing member is contacted by a contact charging device using a cylindrical charging member that rotates in contact with the surface of the image bearing member that is rotationally driven. In the image forming apparatus configured to charge the surface, the holding member that movably holds the cylindrical charging member is in contact with the cylindrical charging member and the charging bias voltage from the charging bias power source is cylindrically charged. In addition to providing a charging bias supply member for supplying to the member, a cleaning member for cleaning the surface of the cylindrical charging member in contact with the cylindrical charging member is provided, and the cylindrical charging member is cylindrical in the holding member. Due to the weight of the charging member, the charging bias supply member and the surface of the image carrier are brought into contact with the surface of the image carrier to move from the position for charging the surface of the image carrier to the position in contact with the cleaning member. By an electrostatic force between the carrier and to move to the position for charging the surface of the image bearing member in contact with a charging bias supply member and the surface of the image bearing member from a position in contact with the cleaning member.

Further, in the image forming apparatus of the present invention, in order to solve the above-described problems, the image carrier is provided by a contact-type charging device using a cylindrical charging member that rotates in contact with the surface of a rotationally driven image carrier. In an image forming apparatus configured to charge the surface of a body, a holding member that movably holds the cylindrical charging member is in contact with the cylindrical charging member, and a charging bias voltage from a charging bias power source is A charging bias supply member that supplies the cylindrical charging member, a cleaning member that contacts the cylindrical charging member and cleans the surface of the cylindrical charging member, and the cylindrical charging member is disposed in the holding member. The weight of the cylindrical charging member moves from a position where it contacts the cleaning member to a position where it contacts the charging bias supply member and the surface of the image carrier to charge the surface of the image carrier, while the cylindrical charging member The electrostatic force between the material and the cleaning member moves from a position where the charging bias supply member and the surface of the image carrier are brought into contact with the surface of the image carrier to a position where the surface is brought into contact with the cleaning member. did.

Further, a cylindrical charging member as described above, causes movably holding the tubular charging member in the holding member, when in the holding member, which Ru is provided a cleaning member and said charging bias supplying member, the holding The member can also be used as a charging bias supply member.

In the image forming apparatus of the present invention, as described above, the holding member that holds the cylindrical charging member movably contacts the cylindrical charging member and supplies the charging bias voltage from the charging bias power source to the cylindrical charging member. And a cleaning member that contacts the cylindrical charging member and cleans the surface of the cylindrical charging member, and the cylindrical charging member is disposed in the holding member in the cylindrical charging member. The above cleaning is performed from the position where the surface of the image carrier is charged by contact with the charging bias supply member and the surface of the image carrier by its own weight or electrostatic force between the cylindrical charging member and the image carrier or the cleaning member. Since it can be moved to the position where it contacts the member or from the position where it contacts the cleaning member to the position where the surface of the image carrier is charged by contacting the charging bias supply member and the surface of the image carrier , it is cylindrical. Charging member When the surface of the image carrier is charged by bringing it into contact with the charging bias supply member and the surface of the image carrier, the cylindrical charging member is rotated without being brought into contact with the cleaning member. The surface of the image carrier is appropriately rotated in contact with the surface of the carrier, so that the surface of the image carrier is appropriately charged. On the other hand, in a state where the surface of the image carrier is not charged, the cylindrical charging member is moved to a position where it comes into contact with the cleaning member, and residues such as toner and toner external additives adhering to the cylindrical charging member are cleaned. It is possible to remove the residue by the member, and the residue charged to the opposite polarity to the image carrier is appropriately removed from the surface of the cylindrical charging member.

  As a result, in the image forming apparatus of the present invention, when the cylindrical charging member is brought into contact with the charging bias supply member and the surface of the image carrier to charge the surface of the image carrier, the cylindrical charging member is The surface of the image carrier rotates appropriately by contacting the surface of the body, and the surface of the image carrier is appropriately charged, and the residue such as toner and toner external additives remaining on the surface of the image carrier When the surface of the image bearing member adheres to the surface of the cylindrical charging member, charging defects such as uneven charging can be easily prevented, and stable image formation can be achieved. You can do it.

In the image forming apparatus according to an embodiment of the present invention, it is a schematic explanatory view showing a state in which a contact charging device is provided on the lower side of the photosensitive drum to perform image formation. In the image forming apparatus according to the above-described embodiment, a state where the surface of the photosensitive drum is charged by bringing the cylindrical charging member rotatably held by the holding member into contact with the surface of the photosensitive drum is shown. FIG. In the image forming apparatus according to the above-described embodiment, a state in which the surface of the cylindrical charging member is cleaned by bringing the cylindrical charging member rotatably held in a movable state on the holding member into contact with the foaming roller of the cleaning member. It is the shown schematic explanatory drawing. In the image forming apparatus of the embodiment, a bias voltage is applied from a cleaning bias power source to the foaming roller of the cleaning member, and the cylindrical charging member is brought into contact with the foaming roller by electrostatic force to clean the surface of the cylindrical charging member. It is the schematic explanatory drawing which showed the example of a change made to do. In the image forming apparatus according to the embodiment, a charging electrode is provided on the inner surface of the holding member on the photosensitive drum side, and a bias voltage is applied to the charging electrode from a charging bias power source. It is the schematic explanatory drawing which showed the example of a change made to charge the surface. FIG. 6 is a schematic explanatory view showing a modification example of a cleaning member for cleaning the surface of a cylindrical charging member in the image forming apparatus of the embodiment. In the image forming apparatus according to another embodiment of the present invention, it is a schematic explanatory view showing a state in which the surface of the photosensitive drum is charged by a contact charging device provided on the upper side of the photosensitive drum.

  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, an image carrier 10 is associated with four developing devices 11 containing toners of different colors of yellow, magenta, cyan, and black. The four photosensitive drums 10 are provided.

  Here, in the image forming apparatus, when full-color image formation is performed, each of the photosensitive drums 10 is rotated, and the lower side of each of the photosensitive drums 10 rotating in this manner is used. The surface of each photosensitive drum 10 is charged by contacting the surface with a cylindrical charging member 122 rotatably held in a holding member 121 in the contact charging device 120.

  Then, each of the charged photosensitive drums 10 is exposed according to the image data by the exposure device 13 to form an electrostatic latent image on the surface of each photosensitive drum 10, respectively. Thus, for each photoconductor drum 10 on which an electrostatic latent image is formed, toner of a predetermined color is supplied from the corresponding developing device 11 to the electrostatic latent image on each photoconductor drum 10, and development is performed. A toner image of each color is formed on the surface of each photosensitive drum 10.

  Next, the toner images of the respective colors formed on the respective photosensitive drums 10 are respectively transferred to the intermediate transfer body 15 in the form of an endless belt that is driven around the roller 14 and transferred in the form of a roller. A primary transfer is sequentially performed by the device 16 to form a full-color toner image on the intermediate transfer member 15. On the other hand, the first cleaning member 17 is brought into pressure contact with the surface of each photosensitive drum 10 after the toner image is transferred in this manner, and remains on the surface of each photosensitive drum 10 without being transferred to the intermediate transfer body 15. Residue such as toner is removed by the first cleaning member 17.

  The full-color toner image formed on the intermediate transfer member 15 as described above is guided to a position facing the secondary transfer device 18 formed into a roller shape by the intermediate transfer member 15, and the image forming apparatus. The recording sheet S accommodated in the lower portion of the sheet is guided between the intermediate transfer member 15 and the secondary transfer device 18 by the feed roller 19, and the full color formed on the intermediate transfer member 15 by the secondary transfer device 18 described above. The toner image is secondarily transferred to the recording sheet S. On the other hand, the second cleaning member 20 is brought into pressure contact with the surface of the intermediate transfer body 15 after the toner image is secondarily transferred in this way, and remains on the surface of the intermediate transfer body 15 without being transferred to the recording sheet S. Residues such as toner are removed by the second cleaning member 20.

  Thereafter, the recording sheet S to which the full-color toner image has been transferred as described above is guided to the fixing device 21, and the full-color toner image transferred by the fixing device 21 is fixed to the recording sheet S. Thus, the full-color toner is obtained. The recording sheet S on which the image is fixed is discharged.

  Here, in the image forming apparatus of this embodiment, in the contact-type charging device 120 that charges the surface of the rotating photosensitive drum 10, the cylindrical charging member 122 is provided as described above as shown in FIG. The holding member 121 that is rotatably held in a movable state is made of a conductive material, and this holding member 121 is used as a charging bias supply member.

  Then, a bias voltage having the same polarity as the charging polarity of the photosensitive drum 10 is applied to the holding member 121 from the charging bias power source 123 and the cylindrical charging member 122 is brought into contact with the holding member 121. The foam roller 124 is provided as a cleaning member for cleaning the surface of the cylindrical charging member 122, and the surface of the photosensitive drum 10 is charged by bringing the cylindrical charging member 122 into contact with the rotating surface of the photosensitive drum 10 as described above. In this state, the cylindrical charging member 122 is prevented from contacting the foaming roller 124.

  When charging the surface of the rotating photosensitive drum 10 by the contact charging device 120, a bias voltage having the same polarity as the charging polarity of the photosensitive drum 10 is applied to the holding member 121 from the charging bias power source 123. Then, the cylindrical charging member 122 is attracted to the photosensitive drum 10 by electrostatic force, the cylindrical charging member 122 is brought into contact with the surface of the photosensitive drum 10 and driven to rotate, and the photosensitive member is driven by the cylindrical charging member 122. The surface of the drum 10 is charged.

  Here, when the surface of the photosensitive drum 10 is charged in this way, the cylindrical charging member 122 is held at a position away from the foaming roller 124, and is cylindrical by contact with the foaming roller 124. The driven rotation of the charging member 122 is not suppressed, and the cylindrical charging member 122 is appropriately driven and rotated as the photosensitive drum 10 rotates, so that the surface of the photosensitive drum 10 is appropriately charged. become.

  On the other hand, in a state where the surface of the photosensitive drum 10 is not charged by the contact-type charging device 120, the foaming roller 124 is rotated, while a bias voltage is not applied from the charging bias power source 123 to the holding member 121. .

  In this way, as shown in FIG. 3, the cylindrical charging member 122 that has been in contact with the surface of the photosensitive drum 10 moves to the lower side of the holding member 121 by its own weight, and the cylindrical charging member 122 rotates. Residues such as toner and toner external additives that are rotated in contact with the foaming roller 124 and adhere to the surface of the cylindrical charging member 122 due to contact with the photosensitive drum 10 are cylindrically formed by the foaming roller 124. It is appropriately removed from the surface of the charging member 122.

  As a result, in the image forming apparatus of this embodiment, the cylindrical charging member 122 is appropriately driven and rotated as the photosensitive drum 10 rotates, so that the surface of the photosensitive drum 10 is appropriately charged. At the same time, the toner remaining on the surface of the photoconductor drum 10 and the residue such as an external additive of the toner adhere to the surface of the cylindrical charging member 122 and the surface of the photoconductor drum 10 has a charging failure such as uneven charging. Is easily prevented, and good image formation can be performed stably.

  In this embodiment, the cylindrical charging member 122 moves to the lower side of the holding member 121 by its own weight and contacts the foaming roller 124 without charging the surface of the photosensitive drum 10. As shown in FIG. 4, a bias voltage is applied to the foaming roller 124 from the cleaning bias power supply 125 so that the cylindrical charging member 122 is attracted to and brought into contact with the foaming roller 124 by an electrostatic force. Thus, the surface of the cylindrical charging member 122 can be cleaned.

  Further, in this embodiment, the holding member 121 is made of a conductive material, and a bias voltage having the same polarity as the charging polarity of the photosensitive drum 10 is applied to the holding member 121 from the charging bias power source 123 to thereby form a cylindrical charging member. 122 is attracted by an electrostatic force to come into contact with the surface of the photosensitive drum 10, but as shown in FIG. 5, the holding member 121 is made of an insulating material, and the holding member 121 on the photosensitive drum 10 side is formed. A charging electrode 126 serving as a charging bias supply member is provided on the inner surface, and a bias voltage having the same polarity as the charging polarity of the photosensitive drum 10 is applied to the charging electrode 126 from the charging bias power source 123 to thereby form the cylindrical charging member 122. It is also possible to make it contact with the surface of the photosensitive drum 10 by being attracted by an electrostatic force.

  In this embodiment, the foam roller 124 is provided as a cleaning member for cleaning the surface of the cylindrical charging member 122. However, the type of the cleaning member is not limited to this, and for example, FIG. As shown, a brush member 126 is provided on the lower side of the holding member 121 and a rotating roller 127 is provided for rotating the cylindrical charging member 122 in contact with the brush member 126, and the rotating roller 127. A bias voltage is applied from the cleaning bias power source 125, the cylindrical charging member 122 is brought into contact with the rotating roller 127 and rotated, and the surface of the cylindrical charging member 122 is cleaned by the brush member 126. It is also possible to do.

  Further, in this embodiment, the contact type charging device 120 for charging the surface of the photosensitive drum 10 is provided on the lower side of the photosensitive drum 10, but the contact type charging device 120 is provided as shown in FIG. It may be provided on the upper side of the photosensitive drum 10.

  In the contact charging device 120 provided on the upper side of the photosensitive drum 10 in this way, a bias voltage having the same polarity as the charging polarity of the photosensitive drum 10 is applied from the charging bias power source 123 to the holding member 121. At the same time, the surface of the photosensitive drum 10 can be charged by bringing the cylindrical charging member 122 into contact with the surface of the photosensitive drum 10 by its own weight. On the other hand, in a state where the surface of the photoconductive drum 10 is not charged, a bias voltage is applied to the foaming roller 124 from the cleaning bias power supply 125, and the cylindrical charging member 122 is attracted to the foaming roller 124 by electrostatic force to come into contact. The surface of the cylindrical charging member 122 can be cleaned by the foaming roller 124.

10 Photosensitive drum (image holding member)
DESCRIPTION OF SYMBOLS 11 Developing device 13 Exposure device 14 Roller 15 Intermediate transfer body 16 Primary transfer device 17 First cleaning member 18 Secondary transfer device 19 Feeding roller 20 Second cleaning member 21 Fixing device 120 Contact-type charging device 121 Holding member (charging bias supply member )
122 Cylindrical charging member 123 Charging bias power supply 124 Foam roller (cleaning member)
125 Bias power supply for cleaning 126 Charging electrode (charging bias supply member)
127 Brush member (cleaning member)
128 Rotating roller S Recording sheet

Claims (3)

In the image forming apparatus in which the surface of the image carrier is charged by a contact type charging device using a cylindrical charging member that rotates in contact with the surface of the image carrier to be rotated, the cylindrical charging member is The holding member that is movably held is provided with a charging bias supply member that contacts the cylindrical charging member and supplies a charging bias voltage from a charging bias power source to the cylindrical charging member, and the cylindrical charging member A cleaning member that cleans the surface of the cylindrical charging member in contact with the cylindrical charging member. In the holding member, the charging member for supplying the charging bias and the surface of the image carrier are separated by the weight of the cylindrical charging member. Is moved from a position for charging the surface of the image carrier to contact with the cleaning member, while being brought into contact with the cleaning member by an electrostatic force between the cylindrical charging member and the image carrier. Image forming apparatus characterized by in contact with the laid et charging bias supply member and the surface of the image carrier is moved to the position for charging the surface of the image bearing member. In the image forming apparatus in which the surface of the image carrier is charged by a contact type charging device using a cylindrical charging member that rotates in contact with the surface of the image carrier to be rotated, the cylindrical charging member is The holding member that is movably held is provided with a charging bias supply member that contacts the cylindrical charging member and supplies a charging bias voltage from a charging bias power source to the cylindrical charging member, and the cylindrical charging member A cleaning member for cleaning the surface of the cylindrical charging member in contact with the charging member, and the charging member from the position where the cylindrical charging member contacts the cleaning member by its own weight in the holding member. The charge bias supply member and the image are moved by the electrostatic force between the cylindrical charging member and the cleaning member while moving to a position where the surface of the image carrier is charged by contacting the supply member and the surface of the image carrier. Image forming apparatus characterized by moving from the position where the contact to the surface of the lifting member to charge the surface of the image bearing member to a position in contact with the cleaning member. 3. The image forming apparatus according to claim 1 , wherein the holding member is used as a charging bias supply member.

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