JP5780449B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device using a two-component developer composed of a toner and a carrier, a process cartridge including the developing device, and an image forming apparatus including any one of these.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer, or a multi-function machine, development using a two-component developing method containing a two-component developer (hereinafter referred to as a developer) composed of toner and a magnetic carrier (hereinafter referred to as a carrier) Many devices are used. In such a developing device, the following configuration of the developing device is known for the purpose of downsizing the developing device and the image forming apparatus.

  The developing device is provided with two parallel conveying paths whose both end portions are communicated with each other through a communicating portion, and the conveying screws which are conveying members in the respective conveying paths are reversed along the longitudinal direction of the developing device. The developer is conveyed in the direction and is circulated through the communication portion. In this configuration, the developer is supplied from one transport path to the developer carrying member (hereinafter referred to as a developing roller) while being circulated.

  In the developing device having such a configuration, according to the consumption of toner in the developing device, toner is appropriately supplied into the device from a toner supply port provided at one end of the developing device. The replenished toner is transported along the longitudinal direction in each transport path by the two transport screws together with the developer in the developing device, and mixed while circulating through the communication portion. Then, a part of the mixed developer is supplied and carried on the developing roller facing from one conveying screw. After the developer carried on the developing roller is regulated to an appropriate amount at the doctor blade position with the rotation of the developing roller, the toner in the developer is at a position facing the photosensitive drum, which is a latent image carrier, It adheres to the latent image on the photosensitive drum.

  Thus, the developing device in which the transport screw is mounted in each transport path does not require much installation space in the short direction (direction orthogonal to the longitudinal direction). Therefore, the developing device and the image forming apparatus can be reduced in size.

  As such a biaxial agitation type developing device, for example, Patent Document 1 describes the following developing device configuration. On the inner wall that separates the first conveyance path that faces the developing roller and the second conveyance path to which toner is replenished, it opens and closes at the approximate center in the longitudinal direction of each conveyance path, separately from the communication portions provided at both ends of each conveyance path. An opening with a possible shutter member is provided. The shutter member has a substantially vertical rotation axis at the center in the longitudinal direction of the opening so that the shutter member that is parallel to the inner wall is rotated and opened in the same direction as the developer circulation direction in each conveyance path. It is rotatably provided at the center. When the shutter member rotates and the angle with the inner wall increases, a part of the developer on the upstream side of the second transport path supplied with toner is transported to the downstream side of the first transport path, and the development on the upstream side of the first transport path is performed. The developer circulation path through which a part of the developer is transported downstream of the second transport path is increased. By increasing the developer circulation path, a part of the developer having a high toner concentration on the upstream side of the second transport path is passed through the opening without greatly changing the developer amount in each transport path. The toner density on the downstream side of the first conveyance path can be increased. When the toner density decreases on the downstream side of the first transport path, the developer transport speed in each transport path is increased, and the angle with the inner wall of the shutter member is increased, so that the toner density on the downstream side of the first transport path is increased. Part of the developer on the upstream side of the second conveyance path having a high value is conveyed. With this configuration, when the toner density is lowered on the downstream side of the first transport path, the toner density is quickly increased to an appropriate toner density, and the developer density in the longitudinal direction of the first transport path supplied to the developing roller is increased. Unevenness can be suppressed.

  In addition, two transport paths having transport members for transporting the developer along the longitudinal direction of the developing device are provided instead of two, and the developer is supplied to the developing roller and the developer is circulated in the device. A developing device having a configuration is also known. For example, Patent Document 2 describes the configuration of a triaxial agitation type developing device having a developer discharge port as follows. The developer discharge port is disposed downstream of the supply conveyance path, which is a conveyance path for supplying the developer to the developing roller, in which the bulk of the developer increases or decreases according to the increase or decrease of the developer amount in the entire conveyance path. Provide. Further, when the developer bulk in the supply conveyance path is larger than the normal developer bulk, a portion higher than the normal developer bulk is provided at a predetermined height that can be discharged from the developer discharge port. Here, the developer discharge port is connected to a developer discharge conveyance path having a discharge conveyance screw, and conveys the discharged developer to the outside of the developing device. The developer discharge port is provided on a side wall that forms a supply conveyance path in a direction other than the flying direction of the developer flying by the operation of a supply screw that is a conveyance member in the supply conveyance path. By providing the developer discharge port in this way, the developer in the supply conveyance path that has not reached the height of the developer discharge port can be prevented from flying and being discharged from the developer discharge port. It is possible to prevent the developer in the supply conveyance path from falling below the required amount. By preventing the developer in the supply conveyance path from falling below the required amount, it is possible to suppress the occurrence of an abnormal image due to unstable supply of the developer to the latent image carrier.

  However, in the configuration of the developing device of the biaxial stirring system described in Patent Document 1 and the developing device of the triaxial stirring system described in Patent Document 2, each developer in the developing device is always in the middle of image formation. Continue to circulate on the transport path and the developing roller. The developer is subjected to stress and deteriorates by repeating the circulation in each conveyance path and the passage of the developer regulating member. Furthermore, with the recent increase in the speed of image forming apparatuses, the stress received by the developer tends to increase. Further, the toner has been lowered in melting point due to the demand for energy saving of the image forming apparatus, and the toner easily deteriorates due to stress or heat and easily forms an aggregate. Further, when the developer is stressed, the toner additive is detached, and the fluidity of the developer is deteriorated due to the removal of the additive from the toner, so that the developer staying in each conveyance path is likely to be generated. When the developer retention occurs, the developer further deteriorates, further promoting the formation of toner aggregates and the occurrence of developer retention.

  When the toner deteriorates to form an aggregate or the developer stays, the developer that has deteriorated in each transport path forms a stay layer, and the formed stay layer adheres to the inner wall of the transport path. The staying layer adhering to the inner wall of the conveyance path repeats generation / detachment, but when it grows to a certain level, it collapses at a stroke by some impact (vibration of equipment in the image forming apparatus, etc.). Then, when the deteriorated developer of the collapsed staying layer is supplied onto the developing roller, an abnormal image such as a black spot image or a toner drop image is generated on the image due to insufficient stirring, and is stable over a long period of time. This causes a problem that development cannot be performed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device capable of suppressing the occurrence of abnormal images due to a staying layer of developer in the transport path and performing stable development over a long period of time. Is to provide.

In order to achieve the above object, a developing device according to claim 1 includes a developer carrying member for carrying and conveying a developer composed of toner and a carrier to a region facing the latent image carrying member, and the developer carrying member. And a first transport path having a first transport member for transporting the developer in the longitudinal direction and supplying the developer to the developer carrier, and in parallel with the first transport path. One or more transport paths having transport members for transporting the developer in the longitudinal direction, and through communication portions provided at both ends in the longitudinal direction of the first transport path and the one or more transport paths. In the developing device that forms the developer circulation path, the amount of developer in the transport path having the transport member is reduced so that most of the transport member in the vertical height direction is exposed, in order to increase the total amount of the developer in the conveying path, those Which is characterized in that it is possible to separately drive controlling the movable member of the conveying member or the like having a movable member and the one or more transport path of the first conveying member or the like provided in the apparatus It is.
According to a second aspect of the present invention, the process cartridge includes a latent image carrier, a charging device that charges the latent image carrier, a cleaning device that cleans the surface of the latent image carrier, and a developing device. A process cartridge used in an image forming apparatus includes the developing device according to claim 1 as the developing device.
An image forming apparatus according to a third aspect includes the developing device according to the first aspect as a developing device.
According to a fourth aspect of the present invention, there is provided an image forming apparatus including the process cartridge according to the second aspect as a process cartridge.
The present invention can drive and control a movable member such as a conveying member in the developing device to reduce the amount of developer in the conveying path so that most of the conveying member in the vertical height direction is exposed. Once the amount is reduced in this way, the developer amount is returned to the normal developer amount, so that the developer flow when returning to the normal developer amount can collide with the exposed developer staying layer. . Then, the developer stagnant layer in an exposed state can be broken by the impact of the collision.
Therefore, before the staying layer of the developer grows to a state where an abnormal image occurs, the amount of the developer in the transport path is increased or decreased so that the growth of the staying layer of the developer does not occur. Can be maintained.

  The present invention can maintain the growth of the staying layer of the developer in the transport path in a state where no abnormal image is generated, so that the occurrence of the abnormal image due to the staying layer of the developer is suppressed and stable over a long period of time. A developing device capable of developing can be provided.

1 is an overall configuration diagram of a printer according to an embodiment. FIG. 3 is an enlarged explanatory diagram of an image forming unit of the printer according to the embodiment. FIG. 6 is a perspective explanatory view of a developer flow in each conveyance path. Cross-sectional explanatory drawing of the staying layer in a conveyance path | route. Cross-sectional explanatory drawing at the time of exposing the 1st conveyance member in a 1st conveyance path | route. Cross-sectional explanatory drawing after breaking the staying layer in a 1st conveyance path | route. Explanatory drawing of the structural example which changes the opening width ratio of a communication part.

  Hereinafter, as an example of an embodiment in which the present invention is applied to an image forming apparatus, an example in which the present invention is applied to an intermediate transfer tandem type full color printer (hereinafter referred to as a printer) will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a printer according to the present embodiment, FIG. 2 is an explanatory diagram of an image forming unit of the printer according to the present embodiment, and FIG. 3 is a perspective explanatory diagram of a developer flow in each conveyance path. FIG. 4 is a cross-sectional explanatory view of the staying layer in the transport path. 5 is a cross-sectional explanatory diagram when the first conveying member in the first conveying path is exposed, FIG. 6 is a cross-sectional explanatory diagram after breaking the staying layer in the first conveying path, and FIG. It is explanatory drawing of the example of a structure which changes the opening width ratio of a communication part.

  First, the outline of this printer will be described with reference to FIG. In the toner supply device 31 of the printer main body 100, four toner cartridges (toner containers) 32Y, 32M, 32C, and 32K corresponding to each color (yellow, magenta, cyan, and black) are detachably (replaceable). Has been. A portion other than the toner cartridge in the toner replenishing device 31 is a toner conveying device that conveys toner, which is a powdery image forming agent discharged from the toner cartridge, to a developing device, which will be described later. An intermediate transfer unit 15 is disposed below the toner supply device 31. Image forming portions 6Y, 6M, 6C, and 6K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 8 as an intermediate transfer member of the intermediate transfer unit 15. Here, the configuration of each image forming unit is the same except for the color of the toner used, and therefore, in the following description, reference numerals Y, M, C, and K are omitted as appropriate.

  As shown in FIG. 2, the image forming unit 6 corresponding to each color includes a photosensitive drum 1 as a latent image carrier, a charging device 4 as a charging unit disposed around the photosensitive drum 1, and a developing unit. A developing device 5 and a cleaning device 2 as a cleaning unit. Moreover, the static elimination apparatus (not shown) which is a static elimination part is also provided. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1, and a yellow image is formed on the photosensitive drum 1. The image forming unit 6 includes a process cartridge including any one of the photosensitive drum 1, the charging device 4, and the cleaning device 2, and the developing device 5, and the other devices described above.

  The photosensitive drum 1 is rotationally driven in a clockwise direction in the drawing by a drive motor (not shown). Then, the surface of the photosensitive drum 1 is uniformly charged at the charging position by the charging device 4 (“charging process”). Thereafter, the surface of the photosensitive drum 1 reaches the irradiation position of the laser beam L emitted from the exposure unit 7 (see FIG. 1), and an electrostatic latent image corresponding to each color is formed by exposure scanning at this position. ("Exposure process"). After that, the electrostatic latent image is visualized by reaching the development area and attaching the toner (“development process”).

  Thereafter, the surface of the photosensitive drum 1 reaches a position facing the cleaning device 2. At this position, the untransferred toner remaining on the photosensitive drum 1 is mechanically scraped and collected by the cleaning blade 2a (“cleaning process”). Further, after that, the surface of the photosensitive drum 1 reaches a position facing a static eliminating portion (not shown), and the residual potential on the photosensitive drum 1 is removed at this position. Thus, a series of image forming processes performed on the photosensitive drum 1 is completed.

  The exposure unit 7 emits laser light L from a light source and scans the laser light L on the photosensitive drum 1 through a plurality of optical elements while scanning with a polygon mirror which is a rotationally driven rotary polygon mirror. Irradiate.

  Then, the toner images of the respective colors formed on the photosensitive drums 1 that have undergone the development process are transferred onto the intermediate transfer belt 8 in an overlapping manner (“primary transfer process”). In this way, a color toner image is formed on the intermediate transfer belt 8.

  Here, the intermediate transfer unit 15 includes an intermediate transfer belt 8, four primary transfer bias rollers 9Y, 9M, 9C, and 9K, a secondary transfer backup roller 12, a cleaning backup roller 13, a tension roller 14, and the like. An intermediate transfer cleaning unit 10 for cleaning the intermediate transfer belt 8 is also provided. The intermediate transfer belt 8 is stretched and supported by the three rollers 12 to 14 and is endlessly moved in the direction of the arrow in FIG. The four primary transfer bias rollers 9Y, 9M, 9C, and 9K respectively sandwich the intermediate transfer belt 8 with the photosensitive drums 1Y, 1M, 1C, and 1K to form a primary transfer nip. A transfer bias having a polarity opposite to the polarity of the toner is applied to the primary transfer bias rollers 9Y, 9M, 9C, and 9K. The intermediate transfer belt 8 travels in the direction of the arrow, and sequentially passes through the primary transfer nips of the primary transfer bias rollers 9Y, 9M, 9C, and 9K. In this way, the toner images of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred while being superimposed on the intermediate transfer belt 8.

  Thereafter, the four-color toner images primarily transferred onto the intermediate transfer belt 8 reach the position facing the secondary transfer roller 19. At this position, the secondary transfer backup roller 12 sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19 to form a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 8 are transferred onto a transfer material P such as transfer paper conveyed to the position of the secondary transfer nip (“secondary transfer process”). . At this time, the untransferred toner that has not been transferred to the transfer material P remains on the intermediate transfer belt 8.

  Thereafter, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning unit 10. At this position, the untransferred toner on the intermediate transfer belt 8 is collected. In this way, a series of transfer processes performed on the intermediate transfer belt 8 is completed.

  Here, the transfer material P transported to the position of the secondary transfer nip is transported from a paper feed unit 26 disposed below the apparatus main body 100 via a paper feed roller 27, a registration roller pair 28, and the like. It has been done. Specifically, a plurality of transfer materials P are stored in the paper supply unit 26 in a stacked manner. When the paper feed roller 27 is rotated in the counterclockwise direction in FIG. 1, the uppermost transfer material P is fed between the rollers of the registration roller pair 28.

  The transfer material P conveyed to the registration roller pair 28 is temporarily stopped at the position of the roller nip of the registration roller pair 28 that has stopped rotating. Then, the registry roller pair 28 is rotationally driven in synchronization with the color image on the intermediate transfer belt 8, and the transfer material P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the transfer material P.

  Thereafter, the transfer material P on which the color image has been transferred at the position of the secondary transfer nip is conveyed to the position of the fixing unit 20. At this position, the color image transferred to the surface is fixed on the transfer material P by heat and pressure generated by the fixing roller and the pressure roller. Thereafter, the transfer material P is discharged out of the apparatus through the rollers of the discharge roller pair 29. The transfer material P discharged from the apparatus by the discharge roller pair 29 is sequentially stacked on the stack unit 30 as an output image. In this way, a series of image forming processes in the printer is completed.

  Next, the configuration and operation of the developing device 5 that is a characteristic part of the present embodiment will be described. As shown in FIG. 2, the developing device 5 includes a developing roller 51 that is a developer carrying member facing the photosensitive drum 1, a doctor blade 52 that faces the developing roller 51, and two developer storage portions separated by an inner wall. It consists of a developer transport path. A first transport screw 55 that is a first transport member is provided in a first developer transport path 53 that is a first transport path closer to the developing roller 51. A second transport screw 56 that is a second transport member is provided in the second developer transport path 54 that is the second transport path on the side far from the developing roller 51. A toner concentration detection sensor 58 for detecting the toner concentration in the developer is also provided in the second developer conveyance path 54. The developing roller 51 includes a magnet (not shown) fixed inside, a sleeve (not shown) that rotates around the magnet, and the like. In each developer conveyance path, a two-component developer (hereinafter referred to as developer G) containing a carrier and toner is accommodated. The second developer transport path 54 communicates with a toner transport pipe 43 that is a toner replenishment path through an opening formed thereabove.

  The developing device 5 having such a configuration operates as follows. The sleeve of the developing roller 51 rotates in the direction of the arrow that is counterclockwise in FIG. The developer G carried on the developing roller 51 by the magnetic field formed by the magnet moves on the developing roller 51 as the sleeve rotates. Here, the developer G in the developing device 5 is adjusted such that the toner concentration (toner concentration) in the developer is detected by the toner concentration detection sensor 58 and the toner concentration falls within a predetermined range. Specifically, the toner contained in the toner cartridge 32 corresponding to each color is replenished into the second developer transport path 54 via the toner transport pipe 43 according to the toner consumption in the developing device 5.

  Thereafter, the toner replenished in the second developer transport path 54 circulates in each developer transport path while being mixed and stirred together with the developer G by each transport screw (perpendicular to the paper surface in FIG. 2). Move in any direction). The toner in the developer G is attracted to the carrier by frictional charging with the carrier, and is carried on the developing roller 51 together with the carrier by the magnetic force formed on the developing roller 51.

  The developer G carried on the developing roller 51 is conveyed in the direction of the arrow in FIG. 2 and reaches the position of the doctor blade 52. The developer G on the developing roller 51 is conveyed to a developing area that is a position facing the photosensitive drum 1 after the developer amount is made appropriate at this position. The toner is attracted to the latent image formed on the photosensitive drum 1 by the electric field formed in the development area. Thereafter, the developer G remaining on the developing roller 51 reaches the upper side of the first developer conveying path 53 as the sleeve rotates, and is separated from the developing roller 51 at this position.

  Next, the flow of developer G and toner will be described. As shown in FIG. 3, the developing roller 51 and the first conveying screw 55 are driven by a driving device A (not shown) through gear trains 61, 62, and 63, respectively. Further, the second conveying screw 56 is also driven by the driving device B (not shown) through the gear 64. Further, the toner replenished in the second developer transport path 54 falls onto the developer G and is transported in the direction of the arrow while being taken into the developer G by the second transport screw. Then, the circulation in the second developer transport path 54 and the first developer transport path 53 is repeated through the communication portions Z provided at both ends of each developer transport path.

  The state of each developer transport path, each transport screw, and developer G will be described with reference to FIGS. Each developer conveyance path and each conveyance screw are provided with a certain amount of gaps and operate. As shown in FIG. 2, the developer has good fluidity in the initial state, and the developer G existing in the gap between each developer transport path and each transport screw is also positively transported. However, as shown in FIG. 4, when the fluidity deteriorates due to the deterioration of the developer, the developer G present in the voids stays and becomes a passivating agent G 'to form a staying layer. The stagnant layer of the immobilizing agent G ′ adheres to the inner wall of each developer transport path and repeats generation / removal. However, when the immobilizing agent G ′ grows to a certain level, it collapses at once due to mechanical operation vibrations and is taken into the developer G. If the toner is supplied to the developing roller 51 in this state, problems such as a black spot image, a toner drop image, and toner scattering are caused by insufficient stirring.

  Therefore, in the developing device 5 of this embodiment, the developer in each developer transport path is increased or decreased so that most of the transport screw in any developer transport path is exposed in the vertical height direction. Then, drive control of a movable member such as a transport screw in the apparatus is performed. Specifically, the drive amount ratio of each conveyance screw or each communication portion that decreases the amount of developer in one developer conveyance path and increases the total amount of developer in another developer conveyance path. The drive control is performed to change the opening width ratio of Z or the driving degree ratio of each conveying screw and the opening width ratio of each communicating portion Z. When one of the conveying screws is exposed to the most part in the vertical height direction and returned to the normal developer amount, the developer G that is conveyed increases in amount and collides with the stagnant layer of the immobilizing agent G ′. By doing so, the staying layer of the passivating agent G ′ can be broken. By performing such drive control before the stagnant layer of the immobilizing agent G ′ grows up to a state that causes a defect such as a black spot image, a toner drop image, or toner scattering due to insufficient stirring, such a problem occurs. Can be suppressed.

Next, for more specific drive control of the movable member, as shown in FIG. 5, the first transport screw 55, which is the first transport member provided in the first developer transport path 53, which is the first transport path, is shown. The drive control for exposing most of the vertical height direction will be described as an example. The increase or decrease of the developer G in the first developer transport path 53 that is the first transport path and the second developer transport path 54 that is the second transport path can be performed, for example, as follows. Changes to the drive speed ratio of each transport screw (each transport member) as shown in Table 1 and the opening width ratio of the two communicating portions Z connecting the developer transport paths as shown in Table 2 It is a change to become.

  Increasing the driving speed of the first conveying screw 55 to be exposed, or widening the opening of the communication portion Z on the downstream side in the developer conveying direction of the first developer conveying path 53 provided with the first conveying screw 55 to be exposed. Thus, the developer in the first developer transport path 53 decreases. Then, the developer on the second developer transport path 54 side facing the first developer transport path 53 increases. By controlling the driving of the movable member in the developing device 5 as described above, the developer G in the first developer transport path 53 that is the first transport path is reduced, and the first transport screw 55 that is the first transport member. Most of the vertical height direction can be exposed. That is, the developer G in the first developer conveyance path 53 is reduced so as to expose most of the first conveyance screw 55, and the immobilizing agent G ′ in the first developer conveyance path 53 is removed as shown in FIG. The stagnant layer can be exposed. Then, when returning to the normal driving speed ratio and opening width ratio from this state and transporting the developer G, the developer G collides with the staying layer of the passivating agent G ′, and the staying layer of the passivating agent G ′ is It is removed as shown in FIG.

  An example of the drive control described above is a case where the stagnant layer of the immobilizing agent G ′ in the first developer transport path 53 is removed. Here, as shown in Table 1 or Table 2, the movable member in the developing device 5 is moved so that the developer G in the second developer conveying path 54 which is the second conveying path exposes the second conveying screw 56. By controlling the driving, the stagnant layer of the immobilizing agent G ′ in the second developer conveying path 54 can be removed in the same manner. Moreover, the removal efficiency of the stagnant layer of passivating agent G 'can be made favorable by exposing each conveyance screw 2/3 or more of the vertical height direction.

  The change of the drive speed ratio of each conveyance screw can be implemented as follows, for example. The drive control between the driving device A that drives the developing roller 51 and the first conveying screw 55 and the driving device B that drives the second conveying screw 56 described with reference to FIG. Is to do so. Further, for example, as shown in FIG. 7A, the opening width ratio of the communication portion Z connecting the developer transport paths is changed by opening the communication portions Z provided at both ends of the inner wall separating the developer transport paths. The portion sandwiched between the two is defined as a movable inner wall 57 that can slide. Then, the movable inner wall 57 is connected to the longitudinal direction of each developer transport path by using an actuator or the like (not shown) from the side of the communicating portion Z where the opening width is to be increased by 1/3 of the width of the communicating portion Z at the normal time. And slide to the other communication part Z side. In this way, by sliding the movable inner wall 57, the ratio of the opening width between the communicating portion Z where the opening width is desired to be increased and the other communicating portion Z can be set to 2: 1.

  Here, the change in the drive speed ratio of each conveyance screw and the change in the opening width ratio of the communication portion Z connecting the developer conveyance paths are merely examples. About change of the drive speed ratio of each conveyance screw, you may comprise as follows, for example. Only the driving device A is used as the driving device, and two idler gears having different gear ratios are selectively engaged with the gear 64 that drives the conveying screw 56 from the gear trains 61, 62, and 63 that drive the developing roller 51 and the conveying screw 55. In combination, the driving force is transmitted. In other words, any configuration is possible as long as the drive speed ratio between the first transport screw 55 as the first transport member and the second transport screw 56 as the second transport member can be a ratio as shown in Table 1. As for the change in the opening width ratio of the communicating portions Z connecting the developer transport paths, for example, the two communicating portions Z may be provided with a shutter for changing the opening width, respectively, or one of them. That is, the communication part Z (first → 2) from the first developer conveyance path 53 to the second developer conveyance path 54 and the communication part Z from the second developer conveyance path 54 to the first developer conveyance path 53. Any configuration can be used as long as the ratio of the opening width to (second → 1) can be as shown in Table 2.

  By repeating the drive control of the movable member in the developing device 5 as described above in a state where the stagnant layer of the immobilizing agent G ′ does not generate an abnormal image, the stagnant layer of the immobilizing agent G ′ that generates the abnormal image is repeated. Generation can be prevented, and a stable image can be provided over a long period of time. That is, by repeating such drive control before the stagnant layer of the immobilizing agent G ′ grows to a state where an abnormal image is generated, the generation of the stagnant layer of the immobile agent G ′ that generates the abnormal image is prevented. This makes it possible to provide stable images over a long period of time. It is effective to carry out such drive control at a fixed interval, for example, at the end of image formation every several hundred sheets.

Further, as shown in Table 3, when the change in the driving speed ratio of each developer conveying member and the change in the opening width ratio of the communicating portion Z connecting the developer conveying paths are performed in combination, either one is performed. Rather than changing, the desired developer amount can be increased or decreased in a short time.

  In this embodiment, the example in which the present invention is applied to the developing device 5 having two developer conveyance paths has been described, but the present invention is similarly applied to a developing device having three developer conveyance paths. Applicable.

The developing device 5 of the printer that is the image forming apparatus of the present embodiment can exhibit the following operations and effects. In the developing device 5, drive control for changing the drive speed ratio of each conveyance screw or drive control for changing the opening width ratio of the two communicating portions Z connecting the developer conveyance paths can be performed. Further, it is possible to perform drive control that combines a change in the drive speed ratio of each conveyance screw and a change in the opening width ratio of the two communicating portions Z connecting the developer conveyance paths. By performing drive control like these, the amount of developer in the developer transport path having the transport screw to be exposed can be reduced so that most of the transport screw in the vertical height direction is exposed. . Once the amount of developer G has been reduced in this manner and then returned to the normal developer amount, the amount of developer G in the developer transport path where the transport screw is exposed is returned to the normal developer amount. The flow can be impinged on a stagnant layer of immobile agent G ′ in an exposed state. And the staying layer of the immobilizing agent G ′ in an exposed state can be broken by the impact of this collision.
Therefore, the drive control as described above is repeated in a state where the stagnant layer of the immobilizing agent G ′ does not generate an abnormal image (for example, at the end of image formation every several hundred sheets), thereby generating an abnormal image. Generation of a stagnant layer of the passivating agent G ′ in a state can be prevented. That is, before the stagnant layer of the immobilizing agent G ′ grows until an abnormal image is generated, the stagnant layer of the immobilizing agent G ′ is grown by increasing or decreasing the amount of the developer in each developer transport path. It is possible to maintain a state where no abnormal image occurs.
Therefore, since the growth of the stagnant layer of the immobilizing agent G ′ in each developer conveyance path can be maintained in a state where no abnormal image occurs, the occurrence of the abnormal image due to the stagnant layer of the immobilizing agent G ′ is suppressed. Thus, it is possible to provide the developing device 5 that can perform stable development over a long period of time.
Further, the process cartridge of the printer that is the image forming apparatus of the present embodiment includes any one of the photosensitive drum 1, the charging device 4, and the cleaning device 2, and the developing device 5 described above. Thus, the same operation and effect as the developing device 5 described above can be obtained.
In addition, since the printer that is the image forming apparatus of the present embodiment includes the developing device 5 described above, the same operations and effects as those of the developing device 5 described above can be achieved.
In addition, since the printer that is the image forming apparatus of the present embodiment includes the process cartridge described above, the same operations and effects as the process cartridge described above can be achieved.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Cleaning apparatus 4 Charging apparatus 5 Developing apparatus 6 Image forming part 7 Exposure part 8 Intermediate transfer belt 10 Intermediate transfer cleaning part 15 Intermediate transfer unit 20 Fixing part 26 Paper feed part 30 Stack part 31 Toner replenishing apparatus 51 Developing roller 52 Doctor blade 53 First developer transport path 54 Second developer transport path 55 First transport screw 56 Second transport screw 56 Developer transport path 57 Movable inner wall 58 Toner concentration sensor 61, 62, 63 Gear train 64 Gear (first gear) 2 conveying screw 56)
100 Device main body A, B Drive device G Developer G 'Immobilizer Z Communication part

JP 2007-148182 A JP 2009-063710 A

Claims (4)

A developer carrier that carries and conveys a developer composed of toner and a carrier to a region facing the latent image carrier;
A first conveying path having a first conveying member that faces the developer carrying member and conveys the developer in the longitudinal direction and supplies the developer to the developer carrying member;
One or more transport paths provided in parallel with the first transport path and having a transport member for transporting the developer in the longitudinal direction,
In a developing device that forms a developer circulation path through communication portions provided at both longitudinal ends of the first transport path and the one or more transport paths ,
The amount of developer in the transport path having the transport member is decreased and the total amount of developer in other transport paths is increased so that most of the transport member in the vertical height direction is exposed. Therefore, it is possible to separately drive and control a movable member such as the first transport member provided in the apparatus and a movable member such as the transport member provided in the one or more transport paths. A developing device. In a process cartridge used in an image forming apparatus including a latent image carrier, a charging device that charges the latent image carrier, a cleaning device that cleans the surface of the latent image carrier, and a developing device.
A process cartridge comprising the developing device according to claim 1 as the developing device.   An image forming apparatus comprising the developing device according to claim 1 as a developing device.   An image forming apparatus comprising the process cartridge according to claim 2 as a process cartridge.

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