JP3989422B2 - Developing device, image forming apparatus, and process cartridge - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and a developing device and a process cartridge mounted on the image forming apparatus.

  As this type of developing device, there is known a developing device that carries a developer on a developing sleeve that is a developer carrying member, and that conveys the developer regulated to a certain amount to a photosensitive member that is an image carrying member facing the developing sleeve. ing. When a two-component developer composed of a magnetic carrier and toner is used as a developer, a developing sleeve having a magnetic field generating means is used, and the developer contained in the developing device is carried on the developing sleeve. The developer carried on the developing sleeve passes through a gap between the developing sleeve surface and the developer regulating member arranged to face the developing sleeve surface with a certain distance (doctor gap). As a result, the developer on the developing sleeve is regulated so as to have a constant amount (for example, Patent Document 1), and the developer is supplied to the latent image formed on the photoconductor to be visualized.

  However, such a developing apparatus has a problem that the developer stays and the developer immobile layer is easily formed immediately upstream of the developer regulating member in the moving direction of the developing sleeve surface as shown in FIG. The developer immovable layer refers to a layer that stays at a certain place without being conveyed with the rotation of the developing sleeve.

  In Patent Document 2, in order to prevent the formation of a developer immovable layer, a cylindrical toner conveying member that constantly rotates at a constant interval from the developing sleeve is provided immediately upstream of the developer regulating member. is suggesting.

However, in Patent Document 2, it is possible to prevent the occurrence of a developer immovable layer, but a bearing and a driving unit that support the toner conveying member are required, so that the configuration is complicated and the cost is unavoidable. In addition, since the toner conveying member is driven in the opposite direction at a position facing the developer carrying member, a strong stress is applied to the developer, and there is a concern about early deterioration of the developer. Further, when rotating at a high speed, there is a concern that the developer is dissolved or fixed due to the generation of heat.
Japanese Patent Publication No. 06-064396 JP 05-35067 A

  When the developer non-moving layer is formed, the developer moving layer as a developer conveyed along with the surface movement of the developing sleeve is rubbed against the developer non-moving layer. As a result, frictional heat is generated, and the developer adheres to the developer immovable layer to form a layer (hereinafter referred to as “developer fixed layer”). With the formation of the developer immovable layer and the developer fixing layer, the developer movable space where the developer is conveyed is reduced, and the amount of the developer fed to the developer regulating member is reduced. For this reason, the layer thickness of the developer conveyed to the development area varies, and an abnormal image is generated. For example, in the case of a black solid image, an image defect such as a white belt-like density drop occurs.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide the following image forming apparatus, a developing device mounted on the image forming apparatus, and a process cartridge. . That is, an image forming apparatus or the like that can stably maintain the layer thickness of the developer conveyed to the developing region.

To achieve the above object, a first aspect of the invention, the developer carrying a two-component developer comprising a magnetic carrier and a toner, the magnet roller body inside is responsible lifting the surface of the non-magnetic sleeve fixedly disposed And a developer regulating member that regulates the thickness of the two-component developer on the developer carrier, the developer regulation in the moving direction of the surface of the non-magnetic sleeve of the developer carrier with the surface and gaps from immediately upstream member provided opposed developer accumulation restriction member, and the developer residence regulating member and said developer carrying member is configured to be the same potential, the developer residence regulations The gap between the member and the surface of the nonmagnetic sleeve is not less than the gap between the developer regulating member and the surface of the nonmagnetic sleeve and is not more than 1.8 mm .
According to a second aspect of the present invention, in the developing device of the first aspect, the developer regulating member is also configured to have the same potential as the developer retention regulating member.
Further, according to the invention of claim 3, the two-component developer comprising a magnetic carrier and a toner, a developer carrying member and developer carrying the magnet roller body inside is lifting responsible to the surface of the non-magnetic sleeve fixedly disposed A developing device including a developer regulating member that regulates the thickness of the two-component developer on the body, and an image carrier that is provided to face the developer carrier and carries a latent image on the surface. In the image forming apparatus having the above, the developing device according to claim 1 or 2 is used as the developing device.
Further, according to the invention of claim 4, the two-component developer comprising a magnetic carrier and a toner, a developer carrying member and developer carrying the magnet roller body inside is lifting responsible to the surface of the non-magnetic sleeve fixedly disposed A developing device including a developer regulating member that regulates the thickness of the two-component developer on the body, an image carrier that is provided to face the developer carrier and carries a latent image on the surface, An image having a charging device for uniformly charging the image carrier, and a cleaning device for cleaning toner remaining on the image carrier after the toner image is transferred from the image carrier to the transfer member by the developing device. 3. A process cartridge used in a forming apparatus and configured to be detachable from an image forming apparatus main body and including at least the image carrier and the developing device. And it is characterized in the use of the.

  According to these inventions, there is an excellent effect that the layer thickness of the developer conveyed to the development area can be stably maintained.

The reason why such an effect is obtained will be described below.
By providing the developer retention regulating member at a position where the developer stays and the developer immobile layer is easily formed, the formation of the developer immovable layer can be suppressed to a very small region. The position of the very small region where the developer immobile layer is formed is a corner portion immediately below the surface where the developer regulating member and the developer retention regulating member are in contact with each other. As a result of extensive studies by the inventor, it has been clarified that the developer fixing layer described above is not formed on the surface of the developer immobile layer formed in a very small region. The present inventor considers the reason why the developer fixing layer is not formed as follows. That is, since the developer immovable layer in the very small area is formed at the corner portion, the moving speed of the developer moving layer that is rubbed against the surface of the immovable layer is smaller than that in the other portions. For this reason, the frictional heat generated by the rubbing with the developer moving layer is smaller than that in other portions. Further, as will be described later, since the staying restriction member is made of a conductive material, this frictional heat is dissipated through the staying restriction member. Therefore, it is considered that the developer fixing layer due to frictional heat is not formed. As described above, since the developer fixing layer is not formed on the developer non-moving layer, the amount of the developer fed to the developer regulating member is reduced due to the developer fixing layer formed on the surface of the developer non-moving layer. There is no.

Further, since the bias having the same potential is applied to the developer carrying member and the developer retention regulating member, there is no potential difference between these members. The reason for the above configuration in the present invention will be described first from the problem when no voltage is applied to the developer retention regulating member.
In general, a DC voltage or a voltage in which AC and DC are superimposed is applied as a developing bias to the developer carrying member. Therefore, when no voltage is applied to the developer retention regulating member, a potential difference is generated between the developer retention regulating member and the developer carrier.
When the developer retention regulating member is made of, for example, metal and grounded, in reverse development, a potential difference (in this case, 500 [V]) corresponding to a developing bias voltage (for example, −500 [V]) applied to the developer carrying member. ) Occurs. As a result, the developer adheres to the developer retention regulating member. Then, a developer fixing layer is formed by applying mechanical stress or heat. With the same configuration, in the case of regular development, toner adheres to the developer carrying member with a potential difference (in this case, 300 [V]) corresponding to a voltage (for example, −300 [V]) applied to the development bias ( Adsorb). The developer fixing layer is formed by applying mechanical stress or heat.
On the other hand, if the developer retention regulating member and the developer carrying member are set to the same potential, the developer adheres (adsorbs) to the developer carrying member and the developer retention regulating member, and mechanical stress and heat are applied to this. The occurrence of the developer fixing layer formed by the above can be prevented. Since a developer fixing layer does not occur in these members, the developer movable space is not reduced, and the amount of developer fed to the developer regulating member is not reduced.
As described above, since the developer fixing layer is not formed on the developer immovable layer, the developer retention regulating member, and the developer carrier, the layer thickness of the developer conveyed to the development region can be stably maintained. is there.

  Japanese Patent Application Laid-Open No. H10-260260 discloses that a toner supply amount regulating wall that faces the developing sleeve with a gap is provided immediately upstream of the developer regulating member in order to prevent formation of the developer immovable layer. . However, it is described that the toner supply amount regulation wall has a bad effect that the conveyed toner clogs and aggregates on the back of the blade, and an image and white streaks are generated due to insufficient coating of the toner layer. The inventor does not form a developer immovable layer other than a very small area in the corner portion directly below the surface where the developer regulating member and the developer retention regulating member are in contact with each other, and the developer fixing layer does not form this developer. The present invention has been completed by finding an interval and a configuration that are not formed on the surface of the passive layer.

Hereinafter, an embodiment in which the present invention is applied to a printer which is an image forming apparatus will be described. FIG. 1 is a schematic configuration diagram of a main part of the printer according to the present embodiment.
A latent image is formed on the uniformly charged surface of the photosensitive drum 1 with a charging device 2 for charging the surface of the photosensitive drum 1 with a charging roller or the like, a laser beam or the like around the photosensitive drum 1 as an image carrier. An exposure device 3 is provided. Further, a developing device 4 is provided on the photosensitive drum 1 to form a toner image by attaching charged toner to the latent image. Further, a transfer device 5 that transfers the toner image formed on the photosensitive drum 1 to the recording paper 6 by a transfer belt, a transfer roller, a charger, or the like, and a cleaning device 7 that removes the toner remaining on the photosensitive drum 1 after the transfer. Is arranged. Further, a static eliminating device 8 for removing the residual potential on the photosensitive drum 1 is disposed in order.

In the printer configured as described above, the photosensitive drum 1 whose surface is uniformly charged by the charging roller of the charging device 2 forms an electrostatic latent image by the exposure device 3 and forms a toner image by the developing device 4.
The toner image is transferred from the surface of the photosensitive drum 1 by the transfer device 5 to the recording paper conveyed from a paper supply tray (not shown). Thereafter, the toner image on the recording paper is fixed on the recording paper by a fixing device (not shown). On the other hand, the toner remaining on the photosensitive drum without being transferred is collected by the cleaning device 7. The photosensitive drum 1 from which the residual toner has been removed is initialized by the charge eliminating lamp 8 and used for the next image forming process.

  Next, the configuration of the developing device 4 will be described with reference to FIG. The developing device 4 includes a developing container 4A and a toner supply unit 4B. Among them, a developing roller 41 as a developer carrying member is disposed in the developing container 4A so as to face the photosensitive drum 1 as an image carrying member in the vicinity thereof, and a developing region D is formed in a portion facing both of them. It has come to be.

  The developing roller 41 is provided with a developing sleeve 43 formed of a nonmagnetic material such as aluminum, brass, stainless steel, or conductive resin in a cylindrical shape. The developing sleeve 43 is rotated in the direction of the arrow, that is, in the counterclockwise direction in the drawing by a rotation driving mechanism (not shown). In the developing sleeve 43, a magnet roller body 44 that forms a magnetic field is provided in a fixed state so as to cause the developer to stand on the surface of the developing sleeve 43. At this time, the carrier constituting the developer is spiked in the form of a chain on the developing sleeve 43 along the magnetic lines of force generated from the magnet roller body 44. The charged toner is attached to the carrier spiked in a chain shape to form a magnetic brush. The formed magnetic brush is transferred in the same direction as the developing sleeve 43, that is, in the counterclockwise direction as the developing sleeve 43 rotates. A doctor blade 45 that regulates the height of the spikes of the developer chain, that is, the amount of the developer, is installed on the upstream side of the development region D in the developer conveyance direction, that is, in the counterclockwise direction. In the present embodiment, the gap between the developing sleeve 43 and the doctor blade 45 is set to 0.5 [mm].

  A developer retention regulating member 52b integrally formed with a stay 52 as a structural support is provided immediately upstream of the rotation direction of the developing sleeve 43 with respect to the doctor blade 45 so as to face the developing sleeve 43. The developer retention regulating member plays a role of regulating the amount of the developer and minimizing the formation of the developer immovable layer. Further, the developer carrying member and the developer retention regulating member are opposed to each other with a gap that prevents the developer from staying in the opposite direction. The stay 52 integrally including the developer retention regulating member 52b can be made of, for example, a conductive resin material in which a metal material such as aluminum, iron, or stainless steel, carbon particles, or the like is dispersed. The gap between the developer retention regulating member 52 b and the developing sleeve 43 is set to be equal to or larger than the gap with the doctor blade 45. This is because the excessive layer thickness is regulated by the tip portion 52a of the developer retention regulating member described later, and the layer thickness is finally regulated by the doctor blade 45.

By providing the developer retention regulating member 52b at a position where the developer stays and the developer immobile layer is easily formed, the formation of the developer immovable layer can be suppressed to a very small region. Here, the position where the developer non-moving layer is formed is a corner portion immediately below the surface where the doctor blade 45 and the developer retention regulating member 52b are in contact with each other. As a result of extensive studies by the inventor, it has been clarified that the developer fixing layer is not formed on the surface of the developer immobile layer formed in a very small region.
Therefore, the amount of the developer fed to the doctor blade 45 is not reduced due to the developer fixed layer fixed to the developer non-moving layer.

The developer retention restricting member 52 b is connected to a developing bias power source connected to the developing sleeve 43. As a result, the developer retention regulating member 52b has the same potential as the developing sleeve 43, and the potential difference between these members is eliminated. Therefore, the developer adheres (adsorbs) to the developing sleeve 43 and the developer retention regulating member 52b, and it is possible to prevent the occurrence of the developer fixing layer formed by applying mechanical stress or heat thereto. . Since the developer fixing layer is not generated, the developer movable space is not reduced, and the amount of the developer fed to the developer regulating member is not lowered.
According to this embodiment, since the developer fixing layer is not formed on the developer immovable layer, the developer retention regulating member, or the developer carrying member, the layer thickness of the developer conveyed to the development region can be stably maintained. Can do.

  The gap between the developing sleeve 43 and the developer retention regulating member 52b is preferably 1.8 [mm] or less. This is because if the gap is set to 1.8 [mm] or less, retention of the developer can be more effectively prevented. Furthermore, even when the developing sleeve is rotated at a high speed, the developer can be prevented from staying effectively, so that the gap is more preferably set to 1.4 [mm] or less. In the present embodiment, the length in the transport direction of the developing sleeve 43 facing the developing sleeve 43 of the developer retention regulating member 52b is set to 6.5 [mm].

  In the present embodiment, the doctor blade 45 is also connected to a developing bias power source connected to the developing sleeve 43. As a result, in addition to the developer retention regulating member 52b, the doctor blade 45 has the same potential as the developing sleeve 43, and the potential difference between these members is eliminated. Therefore, the developer adheres (adsorbs) to the developing sleeve 43, the developer retention regulating member 52b, and the doctor blade 45, and the occurrence of a developer fixing layer formed by applying mechanical stress or heat to the developer sleeve 43 is prevented. can do. Since the developer fixing layer does not occur, the developer movable space is not reduced, and the layer thickness of the developer conveyed to the development region can be stably maintained.

  A stirring roller 46 and a paddle wheel 47 are provided in the rear area of the developing roller 41, and the developer is stirred and mixed by the stirring roller 46 so that the developer is pumped up by the paddle wheel 47. A developer case 51 as a developer storage member is disposed on the lower side so as to enclose the developing roller 41, the paddle wheel 47, and the stirring roller 46.

  Further, for example, when the toner concentration sensor 48 detects that the density of the toner supplied to the photosensitive drum 1 has decreased, the toner replenishing unit 4B feeds the toner T toward the stirring roller 46 by the rotation of the toner replenishing roller 4B. It is like that. In the vicinity of the doctor blade 45 described above, a separator 49 is disposed in which one end in the extending direction is positioned in the vicinity of the doctor blade 45 and the other end in the extending direction is positioned on the stirring roller 46. A rotatable conveying screw 50 is disposed at the other end of the separator 49 in the extending direction.

  In the developing container 4A having the above configuration, the developer is pumped up by the rotation of the paddle wheel 47, discharged toward the developing roller 41, and carried on the surface of the developing roller 41 by the magnetic force of the magnet roller body 44. Then, the developer carried on the developing roller 41 moves on the surface with the rotation of the developing sleeve 43, the excess layer thickness is regulated by the tip end portion 52 a of the developer retention regulating member, and then the doctor blade 45. Finally, after the layer thickness is regulated, the developing roller 41 and the photosensitive drum 1 pass through the developing region D facing each other. Thereafter, it passes through the gap with the developer case 51, falls to the bottom of the developer case 51 at a position where the magnetic force of the magnet roller body 44 does not act, and is again stirred by the paddle wheel 47. Further, as shown in FIG. 2, the excess developer scraped off by the tip end portion 52a of the developer retention restriction member 52b is a right side surface 52c in the drawing of the stay 52 that is integrally formed with the developer retention restriction member 52b. And are sequentially conveyed to the back side of the image forming apparatus by a plurality of inclined fins 49 a arranged on the separator 49. A developer guide path is disposed at the innermost end of the separator 49 and is guided toward the conveying screw 50 located at the other end in the extension direction. It is conveyed to the front side of the image forming apparatus by the conveying screw 50 and falls through a slit (not shown) facing the agitation roller 46 disposed at the foremost end. The developer is transported by the fins 49a and the screws 50 so that the toner density is uniform in the front-rear direction of the image forming apparatus, and at the same time, the developer transport amount is set equal to each other in the front-rear direction. Can be maintained at a constant level.

(Modification)
FIG. 3 is a schematic configuration diagram of a printer showing a modification of the present embodiment. This printer is an example in which a process cartridge 80 is mounted on a printer body. In this figure, a process cartridge 80 integrally supports a photosensitive drum 1, a developing device 4, a charging device 2, a static eliminating device 8, and a cleaning device 7. These units are detachable from the printer body. Thereby, it becomes detachable collectively with respect to a printer, and maintainability and exchangeability can be improved.
The process cartridge 80 in this modified example integrally supports the photosensitive drum 1, the developing device 4, the charging device 2, the charge eliminating device 8, and the cleaning device 7. However, the present invention is not limited to this. Other process cartridges may be used as long as at least the photosensitive drum 1 and the developing device 4 are integrally supported and are detachable from the printer main body.

The printer used in the above embodiment is an example of an apparatus to which the present invention can be applied, and is not limited to this apparatus. Further, as an example of the shape of the developer regulating member, the example has been described in which the developing sleeve 43 is opposed to the developing sleeve 43 with a predetermined gap, but is not limited thereto. For example, the gap with the developing sleeve 43 may be separated on the slope or step by step toward the upstream side in the moving direction of the surface of the developing sleeve 43. On the contrary, you may comprise so that it may approach.
Further, although the example in which the developer retention regulating member 52b is configured integrally with the stay 52 has been described, the present invention is not limited to this.

1 is a schematic configuration diagram of a main part of a printer according to an embodiment. FIG. 2 is a configuration diagram of a developing device according to the present embodiment. FIG. 10 is a configuration diagram of a developing device according to a modification. FIG. 6 is a partially enlarged view showing a configuration of a conventional developing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging apparatus 3 Exposure apparatus 4 Developing apparatus 5 Transfer apparatus 7 Cleaning apparatus 8 Static elimination apparatus 43 Developing sleeve 45 Doctor blade 52b Developer retention control member

Claims (4)

The two-component developer comprising a magnetic carrier and a toner, a developer carrying member for responsible lifting the surface of the non-magnetic sleeve to the magnet roller body is fixedly disposed in the interior of the two-component developer on the developer carrying member In a developing device including a developer regulating member that regulates the thickness,
The developer accumulation restriction member facing with the surface gap just upstream from the developer regulating member in the moving direction of the non-magnetic sleeve surface of the developer carrying member is provided,
Developer residence regulating member and said developer carrying member and is configured to be the same potential,
A developing device characterized in that a gap between the developer retention regulating member and the surface of the nonmagnetic sleeve is not less than a gap between the developer regulating member and the surface of the nonmagnetic sleeve and not more than 1.8 mm . The developing device according to claim 1.
The developing device according to claim 1, wherein the developer regulating member is also configured to have the same potential as the developer carrying member. The two-component developer comprising a magnetic carrier and a toner, the thickness of the developer carrying member and the developer carrying member of the two-component developer in which the magnet roller body is responsible lifting the surface of the non-magnetic sleeve which is fixedly disposed in the interior A developing device comprising a developer regulating member that regulates the thickness;
In an image forming apparatus having an image carrier that is provided to face the developer carrier and bears a latent image on the surface thereof,
3. An image forming apparatus according to claim 1, wherein the developing device is the one of claim 1 or 2. The two-component developer comprising a magnetic carrier and a toner, the thickness of the developer carrying member and the developer carrying member of the two-component developer magnet roller body is responsible lifting the surface of the non-magnetic sleeve which is fixedly disposed in the interior A developing device comprising a developer regulating member that regulates the thickness;
An image carrier that is provided to face the developer carrier and carries a latent image on the surface;
A charging device for uniformly charging the image carrier;
The image forming apparatus includes a cleaning device that cleans toner remaining on the image carrier after the toner image is transferred from the image carrier to the transfer body by the developing device. In a process cartridge configured to be detachable and including at least the image carrier and the developing device,
3. A process cartridge according to claim 1, wherein the developing device is the one of claim 1 or 2.

Images