JP5773243B2 - Developing device, process cartridge and image forming apparatus having the same - Google Patents

Description

  The present invention circulates and conveys a two-component developer containing toner and a carrier (hereinafter simply referred to as “developer”) along the developer circulation path, and the developer being circulated and transported as a developer carrier. The present invention relates to a developing device that supplies the toner to the surface and conveys the developing region, and a process cartridge and an image forming apparatus including the developing device.

  In recent years, along with a demand for miniaturization of an image forming apparatus using electrophotographic technology such as a copying machine, a printer, a facsimile, etc., the development apparatus mounted thereon has been miniaturized. However, in the downsized developing device, the developer conveyance path constituting the developer circulation path is inevitably shortened, and the conveyance path until the toner replenished to the developer in the circulation path is conveyed to the development region. The length is short. Therefore, the stirring time for rubbing the replenished toner and the magnetic carrier tends to be insufficient, and the toner with insufficient charge tends to contribute to development. As a result, floating toner is likely to be generated, causing problems such as background contamination and toner scattering. Such a problem becomes conspicuous when the amount of toner replenishment increases, particularly when a document having a high image area ratio is continuously printed.

  Even when the developer agitation time is insufficient, when the developer transport amount to the developing region is regulated by the gap (doctor gap) between the developing sleeve (developer carrying member) and the developing doctor (developer regulating member) In addition, if the toner and the magnetic carrier can be rubbed strongly, the occurrence of a situation in which the toner with insufficient charge contributes to development can be suppressed. However, in the downsized developing device, the developing sleeve is reduced, and as a result, the magnet (magnetic field generating means) disposed therein is also downsized. As the magnet becomes smaller, the magnetic flux density on the outer peripheral surface of the developing sleeve becomes smaller, so that the force for magnetically restraining the developer passing through the doctor gap becomes weaker. As a result, the force for sliding the toner and the magnetic carrier when passing through the doctor gap is weakened, and the toner with insufficient charge amount tends to contribute to development. Therefore, in a downsized developing device, a configuration that can sufficiently charge the toner in the developer on the circulation conveyance path in the developing device is desired.

  In the developing device described in Patent Document 1, both the replenishment-side agitating chamber (developer agitating and conveying path) in which the toner replenishing port is opened and the developing-side agitating chamber (developer supplying and conveying path) adjacent to the developing sleeve are developed. It extends in parallel along the sleeve axial direction and is arranged side by side in the horizontal direction. These agitating chambers are configured such that the upstream end and the downstream end in the developer transport direction communicate with each other through the opening, and the developer is circulated and transported. In this developing device, a shutter member is provided in an opening portion that leads from the replenishing side stirring chamber to the developing side stirring chamber, and the sectional area of the opening portion can be changed by moving the shutter member up and down by a driving device. . In this developing device, when the shutter member is driven in a direction in which the cross-sectional area of the opening is reduced, the developer moves slowly on the upstream side of the opening in the developer transport direction (hereinafter referred to as “developer moving slowly part”). ") Is expanded to the upstream side in the developer conveyance direction. As a result, the moving distance from when the developer enters the developer movement slow spot until it passes through the developer movement slow spot and moves from the opening to the development side stirring chamber is larger than when the opening cross-sectional area is large. become longer. In the place where the developer movement is slow, the developer moves little by little while receiving the compressive force of the developer conveyed later, so that the toner and the magnetic carrier are rubbed strongly. Therefore, the toner can be charged efficiently in such a portion where the developer movement is slow. In the developing apparatus described in Patent Document 1, the sectional area of the opening is reduced by the shutter member, and the developer moving distance in the developer moving slow portion where the toner can be charged efficiently can be increased. The developed developing device can sufficiently charge the toner.

However, the developing device described in Patent Document 1 has a configuration in which the replenishment side stirring chamber (developer stirring conveyance path) and the development side stirring chamber (developer supply conveyance path) are arranged side by side in the horizontal direction. The movement of the developer from the downstream end of the developer stirring conveyance path to the upstream end of the developer supply conveyance path is a movement in the horizontal direction, and does not move against gravity.
On the other hand, there has been conventionally known a developing device in which the developer agitation transport path is arranged vertically below the developer supply transport path. In this developing device, the developer conveyed to the downstream end of the developer agitating / conveying path is pushed into the developer conveyed later, so that the developer is conveyed on the developer supply / conveying path through the opening at the downstream end of the developer agitating / conveying path. Raised to the stream end. In this case, at the downstream end of the developer agitating / conveying path, the developer moving direction is suddenly changed from the developer conveying direction in the developer agitating / conveying path, and the developer is supplied against the gravity. It is necessary to move to the upstream end of the conveyance path. Therefore, as in the developing device described in Patent Document 1, the developer moves from the downstream end of the developer agitation transport path to the upstream end of the developer supply transport path and does not move against gravity. Then, the developer receives a strong compressive force when passing through the developer moving slow portion at the downstream end of the developer stirring and conveying path. Therefore, the toner and the carrier can be rubbed more strongly at the developer movement slow portion at the downstream end of the developer stirring and conveying path, and the toner has a high triboelectric charging efficiency.

  However, even in the conventional apparatus in which the movement of the developer from the downstream end of the developer agitating / conveying path to the upstream end of the developer supplying / conveying path moves against the gravity, the developer movement is slow at the downstream end of the developer agitating / conveying path. In this case, there is a problem that the triboelectric charge amount of the toner in the toner is still insufficient and the toner having the insufficient charge amount may contribute to the development. Therefore, further improvement with respect to insufficient charge amount of toner is desired.

  The present invention has been made in view of the above problems, and an object of the present invention is to improve the charge amount of the toner passing through the portion where the developer moves slowly, so that the toner with insufficient charge amount contributes to development. It is an object of the present invention to provide a developing device capable of suppressing the occurrence of a situation, and a process cartridge and an image forming apparatus including the developing device.

In order to achieve the above object, the invention of claim 1 circulates and conveys a two-component developer containing a toner and a carrier along a developer circulation path and develops a part of the developer circulation path. The two-component developer conveyed in the developer supply conveyance path is supplied to the outer peripheral surface of the developer carrying member, and the two-component developer carried on the outer peripheral surface of the developer carrying member is rotated by the developer carrying member. In the developing device for developing the latent image by transporting the toner to the developing area and attaching the toner in the two-component developer to the latent image on the surface of the latent image carrier in the developing area. A developer agitation transport path serving as at least a part of the developer circulation path from the toner replenishment point where the toner is replenished to the component developer to the upstream end in the developer transport direction of the developer supply transport path is the developer supply path. Located below the transport path in the vertical direction, The two-component developer conveyed to the downstream end in the developer conveyance direction of the developer agitation conveyance path by the member is pushed into the two-component developer conveyed later in the developer agitation conveyance path, thereby The developer agitating and conveying path is lifted to the developer conveying direction upstream end of the developer supplying and conveying path through an opening communicating the downstream end of the developer conveying direction and the developer supplying and conveying path upstream of the developer conveying direction. the configuration has been provided, the developer the developer the developer conveyance direction upstream side portion than the opening in the developer conveyance direction downstream side portion than the developer carrying region on the carrier in an agitation compartment, a developing Constructing a cross-sectional area enlargement part that enlarges the upper space than the upstream part of the developer transport direction in which the upper end wall and the lower end wall of the agent stirring transport path are parallel to increase the cross-sectional area perpendicular to the developer transport direction , The developer stirring and conveying path It is characterized in that the movement of the developer transport direction downstream end near a two-component developer is provided with a portion which becomes slow.
Also, the invention of claim 2, in the developing device according to claim 1, said developer stirring and conveying member is a screw-shaped blade on a rotation axis parallel to the developer carrying direction of the developer agitation conveyance path parts are provided, a conveying screw for conveying the two-component developer of the developer agitation conveyance path by rotationally driving the rotary shaft in a direction along the rotational axis, the cross-sectional area expanding portion, said The blade portion is formed on the side that moves upward in the vertical direction across the rotating shaft of the conveying screw .
Also, the invention of claim 3, in the developing device according to claim 1 or 2, the cross-sectional area expanding portion, characterized in that it is configured to the cross-sectional area as the developer conveyance direction downstream side is larger It is what.
According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the developer agitating and conveying member is a rotating shaft parallel to the developer conveying direction of the developer agitating and conveying path. A screw that is provided with a screw-like blade portion and that rotates the rotation shaft to convey the two-component developer in the developer agitating and conveying path in a direction along the rotation shaft; The screw is configured such that the side on which the blade portion moves toward the upper side in the vertical direction across the rotation shaft is further away from the outer peripheral surface of the developer carrier than the opposite side. It is what.
According to a fifth aspect of the present invention, there is provided a process in which the latent image carrier and the developing device for developing the latent image on the latent image carrier are integrally supported and detachably attached to the image forming apparatus main body. In the cartridge, the developing device according to any one of claims 1 to 4 is used as the developing device.
According to a sixth aspect of the present invention, a latent image carrier, latent image forming means for forming a latent image on the latent image carrier, and a two-component developer containing toner and carrier are used on the latent image carrier. An image forming apparatus including: a developing device that develops a latent image; and a toner image formed on the latent image carrier by the developing device is finally transferred to a recording material to form an image on the recording material In the apparatus, the developing device according to any one of claims 1 to 4 is used as the developing device.

In the present invention, the downstream portion in the developer stirring and conveying path is configured to have a larger cross-sectional area than the upstream portion. As a result, compared with the configuration in which the downstream side portion in the developer stirring and conveying path has the same cross-sectional area as the upstream side portion thereof, the toner has entered the developer moving slow portion at the downstream end of the developer stirring and conveying path. It is possible to increase the moving distance until the developer passes through the portion and is lifted to the upstream end of the developer supply conveyance path. This is for the reason explained below.
The developer conveyed in the upstream portion of the developer agitating / conveying path receives a conveying force from the developer agitating / conveying member, so that the developer moves away from the developer conveying direction on the inner wall of the developer agitating / conveying path. In the state restricted by the above, the entire device behaves so as to translate in the developer transport direction. In this case, the moving distance of the developer transported in the upstream portion is approximately equal to the length of the upstream portion along the developer transport direction of the developer stirring transport path, and the entire developer is efficiently handled. This is because it can be conveyed downstream. When the downstream portion in the developer agitating / conveying path has the same cross-sectional area as the upstream side portion, the movement in the direction away from the developer conveying direction is also restricted to the inner wall of the developer agitating / conveying path. In this state, the entire device behaves so as to translate along the developer transport direction. In the downstream portion, a developer movement slow spot is generated, but the same behavior occurs in the developer movement slow spot. Therefore, the moving distance of the toner passing through the developer movement slow spot is approximately equal to the length of the developer movement slow spot along the developer transport direction of the developer stirring transport path.
On the other hand, when the downstream side portion in the developer stirring and conveying path is configured to have a larger cross-sectional area than the upstream side portion as in the present invention, the developer in the slow-moving portion of the developer is When pushed in by the developer conveyed later, it is possible to move in a direction away from the developer conveying direction. The developer that has moved in the direction away from the developer transport direction is taken into the developer portion that is moving in the developer transport direction on the upstream side from this, and from this developer portion by this incorporation. Developer that moves in a direction deviating from the developer transport direction appears, and this developer is eventually taken into the upstream developer portion. The developer in the portion where the developer movement is slow is gradually conveyed downstream while taking such behavior. Therefore, the average moving distance of the toner passing through the developer movement slow portion is approximately longer than the length of the developer movement slow portion along the developer transport direction of the developer stirring transport path.
In addition, when the upper space of the downstream portion in the developer stirring and conveying path is enlarged to increase the cross-sectional area, the developer that has entered the downstream portion can move to the opening through the upper enlarged space. The shortest distance to the opening is short. Therefore, in this case, at first glance, it seems that the moving distance of the toner passing through the portion where the developer moves slowly is shortened. However, the developer at the downstream end of the developer agitating / conveying path is pushed into the opening by the developer conveyed later and rises up to the inside of the opening. Therefore, even if the developer that has entered the downstream portion in the developer agitating and conveying path tries to go to the opening through the upper enlarged space, the opening entrance is blocked by the raised developer. Therefore, entry into the opening is prevented. Therefore, even if an upper enlarged space in the downstream portion in the developer agitating and conveying path is provided, there is almost no developer sent to the opening via the shortest route passing through the upper enlarged space, and the developer movement slow position is not present. As described above, the average moving distance of the toner passing therethrough is longer than the length of the developer moving slow portion.
Therefore, according to the present invention, the average moving distance until the toner passes through the portion where the developer moves more slowly than when the downstream portion in the developer agitating / conveying path has the same cross-sectional area as the upstream portion. Can be increased, and the charge amount of the toner that has passed through the portion where the developer moves slowly can be increased.
In addition, according to the present invention, since the developer in the developer movement slow portion is taken out of the developer transport direction and taken into the upstream developer portion, the relative movement between the toner and the carrier is reduced. There are more opportunities for friction between the toner and the carrier and the triboelectrification efficiency of the toner is higher than in the case where the developer is activated and behaves so that the entire developer moves in parallel along the developer transport direction.

  As described above, according to the present invention, by improving the charge amount of the toner passing through the portion where the developer movement is slow, it is possible to obtain an excellent effect that it is possible to suppress the occurrence of a situation where the toner with insufficient charge amount contributes to development. .

FIG. 3 is an explanatory diagram illustrating a main part of the image forming apparatus according to the embodiment. FIG. 3 is an explanatory diagram for explaining a configuration of a developing device provided in the image forming apparatus. It is sectional drawing which shows the structure of the developing roller provided in the developing device. It is a perspective view which shows the structure of the supply chamber conveyance member and recovery chamber conveyance member which are arrange | positioned inside the casing of the developing device. FIG. 3 is a perspective view when the developing device is viewed from a developing region side. It is explanatory drawing when the supply chamber inside where the supply chamber conveyance member is arrange | positioned is seen from upper direction. FIG. 2 is an explanatory diagram illustrating a schematic configuration of the entire image forming apparatus. It is explanatory drawing when the structure of the collection | recovery chamber downstream end in the developing device is seen from a substantially horizontal direction. It is explanatory drawing when the structure of the collection chamber downstream end in the conventional developing device is seen from a substantially horizontal direction. It is explanatory drawing which shows the example in which a corner | angular part exists in a cross-sectional area expansion part. It is explanatory drawing which shows the example which eliminated the corner | angular part in a cross-sectional area enlarged part, and was set as the rounded round corner part. (A) is explanatory drawing which shows the cross section of the collection | recovery chamber downstream part in the developing device of embodiment. (B) is explanatory drawing which shows the cross section of the collection chamber upstream part in the developing device. 6 is a graph showing a change in toner charge amount over time when a developer containing toner having a reduced charge amount is circulated and conveyed into a developing device to raise the toner charge amount. It is explanatory drawing which shows the cross section of the said duplication location when it comprises so that the longitudinal direction position of the same cross-sectional area expansion part may overlap with the position which opposes the developer holding area | region of a developing roller.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram illustrating a main part of the image forming apparatus according to the present exemplary embodiment.
The photoreceptor 1 as a latent image carrier is rotated in the clockwise direction in the figure as indicated by the arrow in the figure. A charging device 2 is disposed around the photoreceptor 1. In the present embodiment, the charging device 2 charges the surface of the photosensitive member with a charging roller made of a rotating member that is driven to rotate at the same linear velocity as the surface of the photosensitive member 1, but may be of a corona discharge type. . The charging device 2 charges the surface of the photoreceptor 1 uniformly in the dark. An electrostatic latent image is formed on the surface of the photoreceptor 1 that has been charged by the charging device 2 by receiving light L from an optical writing device (not shown) as a latent image forming unit. The electrostatic latent image moves to the downstream side in the rotation direction of the photosensitive member as the photosensitive member 1 rotates, and reaches a developing region facing the developing device 3.

  The developing device 3 includes a supply chamber conveying member 304 for agitating and conveying the developer 320, a recovery chamber conveying member 305 as a developer agitating and conveying member, a developing roller 302 as a developer carrying member, and the like in the casing 301. I have. The casing 301 has an opening at a position facing the photoreceptor 1, and a part of the developing roller 302 is exposed from this opening. A development area A is a position where the developing roller 302 and the photosensitive member 1 are close to each other and face each other. The developer 320 in the casing 301 is carried on the outer peripheral surface of the developing roller 302, so that the developer 320 is conveyed to the developing area A as the developing roller 302 rotates. Then, the toner in the developer 320 adheres to the electrostatic latent image formed on the surface of the photoreceptor 1 in the development area A, and is visualized as a toner image.

  The toner image formed in this way moves to the downstream side in the rotation direction of the photosensitive member as the photosensitive member 1 rotates, and reaches a transfer region facing the transfer device 5. In the present embodiment, the transfer device 5 is constituted by a transfer roller which is a rotating body, but may be of a corona discharge type. A region where the photoconductor 1 and the transfer device 5 face each other is a transfer region B. The toner image on the photoreceptor 1 is transferred to the transfer paper 8 in the transfer region B, and becomes an image on the transfer paper 8. It can also be applied to an intermediate transfer belt method in which the toner on the photosensitive member is temporarily transferred to an intermediate transfer member (such as an intermediate transfer belt) and then the toner on the intermediate transfer member is transferred to transfer paper. In the transfer area B, the toner on the photosensitive member is transferred to an intermediate transfer member (intermediate transfer belt).

  The surface portion of the photoconductor 1 after the transfer moves to the downstream side in the photoconductor rotation direction with the rotation of the photoconductor 1 and reaches the cleaning area facing the cleaning device 6. The cleaning device 6 uses a cleaning blade 601 to remove toner remaining on the surface of the photoreceptor 1 without being completely transferred onto the transfer paper. The surface of the photoreceptor 1 that has passed through the cleaning device 6 is then uniformly charged by the charging device 2 and the next image forming process is repeated.

Next, the configuration of the developing device 3 will be described in detail.
FIG. 2 is an explanatory diagram for explaining the configuration of the developing device 3.
The developing device 3 includes a developing roller 302, a supply chamber conveying member 304, a collection chamber conveying member 305, and a developer regulating member 303 inside the casing 301, and the developer 320 is agitated and conveyed to circulate. The conveying member of this embodiment is a conveying screw in which a screw-like blade portion is provided on a rotating shaft extending in parallel to the developer conveying direction, and the blade member has an outer diameter of 16 mm or less. Yes.

  As shown in FIG. 2, the developing roller 302 has a magnet roller 302d in which three magnets MG as magnetic field generating means are arranged in the circumferential direction, and a cylindrical sleeve 302c is integrated with the rotating shaft 302e around the periphery. It is the structure which rotates automatically. The sleeve 302c is made of a nonmagnetic metal such as aluminum. The magnet roller 302d is fixed to an immovable member, for example, the casing 301, so that each magnet MG faces a predetermined direction, and the sleeve 302c rotates around the periphery thereof so that the developer 320 attracted by the magnet MG is attracted to the sleeve surface. It is carried by the carrier.

FIG. 3 is a cross-sectional view showing the structure of the developing roller 302.
The developing roller 302 mainly includes a fixed shaft 302a fixed to the casing 301, a columnar magnet roller 302d integrated with the fixed shaft 302a, and a sleeve 302c covering the periphery of the magnet roller 302d with a predetermined gap. The sleeve 302c and the rotation shaft 302e are integrated. The rotation shaft 302e is rotatable with respect to the fixed shaft 302a via a bearing 302f, and the rotation shaft 302e is driven to rotate by receiving power from a rotation driving means (not shown). A plurality of magnets MG are fixed to the outer periphery of the magnet roller 302d at a predetermined interval as shown in FIG. The sleeve 302c is rotated around these magnets MG. These magnets MG are for forming a magnetic field so that the developer can be spiked on the outer peripheral surface of the sleeve 302c, and can be cut off. A magnetic brush is formed by gathering magnetic carriers along magnetic lines of force emitted from these magnets MG.

  Although there are many configurations of the magnet roller, here, as shown in FIG. 2, a configuration of the magnet roller having three magnets MG inside the sleeve 302c and generating three magnetic poles will be described. The magnetic pole closest to the portion (area corresponding to the development area A) facing the line connecting the center O-1 of the developing roller 302 and the center O-2 of the photoreceptor is the P1 pole (development pole), and is counterclockwise in the figure. The magnetic poles P2 (casing facing pole) and P3 pole (developer regulating member facing pole) are set in order of the rotation direction of the developing roller 302 shown in the surrounding direction. As for the polarities, the P1 pole is the N pole, the P2 pole is the S pole, and the P3 pole is the S pole, but these poles may have opposite polarities. The P3 pole is disposed at a position facing the developer regulating member 303.

  The developing roller 302 and the photosensitive member 1 are opposed to each other while maintaining a certain distance (development gap GP) suitable for development. The developer 320 is spiked on the developing roller 302, and the developer 320 is brought into contact with the photoreceptor 1. In the developing device 3, a grounded bias power source (not shown) is connected to the fixed shaft 302a. The voltage of the power source VP connected to the fixed shaft 302a is applied to the sleeve 302c through the conductive bearing and the conductive rotating shaft 302e. On the other hand, the lowermost conductive support constituting the photoreceptor 1 is grounded. Therefore, when a voltage is applied from the power source VP, a developing electric field that moves the toner in the developer 320 to the electrostatic latent image on the photoreceptor 1 is formed in the developing area A, and the toner becomes an electrostatic latent image. A toner image is formed by adhesion.

  In the present embodiment, the charging device 2 uniformly applies negative charges on the photoconductor 1 and exposes the image portion with the exposure light L in order to reduce the writing amount. By adopting a reversal development method in which negative potential toner is electrostatically adsorbed to the image portion by lowering the potential. This is merely an example, and the polarity of the charged charges placed on the photoreceptor 1 is set as appropriate.

  After the development, the P2 pole transports the developed developer 320 carried on the developing roller 302 to the downstream side in the developing roller rotation direction as the developing roller 302 rotates, and draws it into the casing 301. Since the P2 pole and the P3 pole have the same polarity, a repulsive magnetic field is formed on the outer peripheral surface of the developing roller from the P2 pole to the P3 pole, and the developer 320 that has been attracted to the outer peripheral surface of the developing roller 302 until then. The action of “agent removal” that separates the toner from the developing roller 302 works. The region where this action works is the agent separation region, which is indicated by reference numeral 9 in FIG. Since the developer 320 that has undergone development processing in the development area A has a reduced toner density, the developer having the lowered toner density is transported to the development area A again without being separated from the development roller 302 and used for development. If this is done, the target image density cannot be obtained. In order to prevent this, in this embodiment, the developer is separated from the developing roller 302 in the agent separation region 9 after development. After that, the developer separated from the developing roller 302 is sufficiently stirred and mixed in the casing 301 so as to contribute to the development again so that the target toner concentration and the target toner charge amount are obtained.

  The developer having the target toner concentration and charge amount is supplied to the developer storage space C by the supply chamber conveying member 304. The developer supplied to the developer storage space C passes through a gap between the developer regulating member 303 located immediately downstream of the peak position of the P3 pole and the outer peripheral surface of the developing roller 302, thereby having a predetermined thickness. And is conveyed to the development area A. The P3 pole also functions as a transport pole for transporting the developer.

FIG. 4 is a perspective view showing the configuration of the supply chamber transfer member 304 and the recovery chamber transfer member 305 disposed inside the casing 301.
FIG. 5 is a perspective view of the developing device 3 when viewed from the developing region side.
As shown in FIG. 4, the supply chamber conveyance member 304 has a screw shape with a spiral around the rotation axis, and is centered on a center line O-304 parallel to the center line O-302a of the developing roller 302. 1 rotates in the clockwise direction indicated by the arrow in FIG. 1, and conveys the developer while stirring the developer as indicated by the arrow 11 in FIG. 4 from the front side in the longitudinal direction of the center line O-304 toward the back side. To do. That is, the supply chamber conveyance member 304 conveys the developer from the near side to the back side along the rotation axis direction by the rotation of the rotation axis.

  As shown in FIG. 4, the collection chamber transport member 305 has a screw shape with a spiral around the rotation axis, and is centered on a center line O-305 that is parallel to the center line O-302a of the developing roller 302. 1 is rotated counterclockwise in FIG. 1 as indicated by an arrow in FIG. 1, and is conveyed while stirring the developer as indicated by an arrow 12 in FIG. 4 from the long side in the longitudinal direction of the center line O-305 toward the near side. To do. That is, the collection chamber transport member 305 transports the developer from the back side to the front side in the direction opposite to the transport direction by the supply chamber transport member 304 along the rotation axis direction by the rotation of the rotation shaft.

  In this embodiment, the recovery chamber, which is a developer agitation transport path in which the recovery chamber transport member 305 is disposed, is positioned below the supply chamber, which is the developer supply transport path in which the supply chamber transport member 304 is disposed. It is configured as follows. The front end of the supply chamber and the collection chamber is set to be slightly in front of the front end of the developing roller 302 so that the supply of the developer at the front end of the developing roller 302 is stabilized. Can be secured. Further, the back end of the supply chamber and the collection chamber are set to be located on the back side of the back end of the developing roller 302, and a space for toner replenishment described later is secured. The developer regulating member 303 is installed according to the length of the developing roller 302.

FIG. 6 is an explanatory view when the inside of the supply chamber in which the supply chamber transfer member 304 is disposed is viewed from above.
A partition plate 306 between the supply chamber transfer member 304 and the recovery chamber transfer member 305 and partitioning the supply chamber and the recovery chamber is supported on the inner wall of the casing 301. A communication port 307 and a communication port 308 are provided at both ends in the longitudinal direction of the partition plate 306. The developer conveyed in the collection chamber in the direction of arrow 12 in FIG. 4 (from the back side to the near side) by the collection chamber conveyance member 305 moves in the longitudinal direction on the inner side wall of the casing 301 that forms the downstream end of the collection chamber. Since the progress is blocked, the swell rises along the inner side wall and moves to the upstream end of the supply chamber along the arrow 14 in FIG. On the other hand, the developer conveyed by the supply chamber conveyance member 304 in the direction of arrow 11 in FIG. 4 (from the front side to the rear side) is shown in FIG. 4 from the communication port 308 of the partition plate 306 constituting the bottom surface of the supply chamber. It descends along the arrow 13 to the upper end of the recovery chamber. Then, the collection chamber is conveyed by the collection chamber conveyance member 305. In this way, in the present embodiment, the developer is circulated and conveyed in the casing 301 along the circulation conveyance path along the arrows 11, 13, 12, and 14 in FIG.

  In the present embodiment, the developer in the supply chamber is supplied to the developing roller 302, and the developer that has passed through the developing area A as the developing roller 302 rotates is recovered in a recovery chamber separate from the supply chamber. As a result, the developer used in the development process in the development region A and having the lowered toner concentration is not returned to the supply chamber, so that the developer reduces the toner concentration of the developer in the supply chamber. The toner density can be maintained at a substantially constant level.

  Since the developer 320 in the developing device 3 consumes toner while repeating the developing operation, it is necessary to supply toner to the developer in the device from the outside of the developing device. In this embodiment, toner is replenished from the outside through a toner replenishing port provided in the vicinity of the end on the far side of the developing device 3. Since the rear end of the developing device 3 is the downstream end of the supply chamber in the developer transport direction or the upstream end of the recovery chamber in the developer transport direction, the toner replenished in this portion is the upstream end of the recovery chamber. Then, the developer is conveyed while being stirred with the developer from the downstream end to the downstream end and then fed to the upstream end of the supply chamber. Therefore, the replenished toner is not immediately used for development, but is used for development after being sufficiently agitated and mixed with the developer by the collection chamber transport member 305.

  In the collection chamber, the developer 320 having a reduced toner density away from the developing roller 302 and the replenishing toner are conveyed to the front side of the developing device 3 while being agitated and mixed. As a result, the developer conveyed to the downstream end (the front side of the developing device 3) in the collection chamber is normalized in toner concentration, lifted to the upstream end of the supply chamber through the communication port 307, and supplied. While being conveyed from the near side to the far side in the supply chamber by the chamber conveying member 304, it is supplied to the developing roller 302 and used for development.

  In this embodiment, a toner concentration sensor (not shown) is disposed at the bottom near the downstream end of the collection chamber. This toner concentration sensor is a sensor for measuring magnetic permeability, and can detect the carrier concentration (= 100−toner concentration) of the developer. It is determined from the detected carrier concentration whether the toner concentration of the developer in the detection region of the toner concentration sensor is appropriate or insufficient, and the amount of toner to be replenished is determined.

  In the present embodiment, as described above, the developer in the supply chamber is supplied to the developing roller 302, and the developer that has passed through the developing region A as the developing roller 302 rotates does not return to the supply chamber. Collect with. Therefore, the amount (bulk) of the developer in the supply chamber decreases toward the downstream side, and the amount (bulk) of the developer in the collection chamber increases toward the downstream side. Since the developer needs to be lifted and moved to the upstream end of the supply chamber at the downstream end of the recovery chamber, a large amount of developer is always present at the downstream end of the recovery chamber in the developer circulation conveyance path in the casing 301. It is unevenly distributed. Therefore, by disposing the toner concentration sensor near the downstream end of the collection chamber, it is possible to make the developer always filled in the detection region of the toner concentration sensor, and stable carrier concentration detection is possible.

FIG. 7 is an explanatory diagram showing a schematic configuration of the entire image forming apparatus in the present embodiment.
This image forming apparatus is a so-called tandem type image forming device in which four image forming units 17K, 17M, 17Y, and 17C are arranged in order from the upstream side in the conveying belt moving direction along the conveying belt 15 that conveys the transfer paper 8. Device. The order of colors is not limited to this. For example, the black image forming unit 17K may be arranged on the most downstream side in the transport belt moving direction, and magenta (M), cyan (C), yellow (Y), and black (K) may be formed in this order. Each of these image forming units 17K, 17M, 17Y, and 17C is composed of a combination of a plurality of members, and is not necessarily configured as a unit.

  The image forming unit 17K forms black images, the image forming unit 17M forms magenta, the image forming unit 17Y forms yellow images, and the image forming unit 17C forms cyan images. The only difference is the internal configuration of each image forming unit. Therefore, in the following description, the outline of the image forming unit 17K will be described. For the other image forming units, K added to the end of the reference numeral of each member in the image forming unit 17K, M for the image forming unit 17M, and the image The forming unit 17Y is replaced with Y, and the image forming unit 17C is replaced with C, and the description thereof is omitted.

  The conveyor belt 15 is composed of an endless belt that is rotatably supported by two conveyor rollers 18 and 19, one of which is a driving roller that is driven to rotate and the other is a driven roller that is driven to rotate. Accordingly, it can be rotated in the direction of the arrow in the figure. Below the transport belt 15, paper feed trays 20, 21, and 22 that store transfer paper 8 are provided. For example, the transfer paper 8 at the uppermost position among the transfer papers 8 stored in the paper feed tray 20 is sent out at the time of image formation and is temporarily kept on standby by the registration roller 23, and the image formation and timing in the image forming unit 17K are set. They are fed together and attracted to the conveyor belt 15 by electrostatic attraction. In this way, the transfer paper 8 adsorbed to the conveyance belt 15 is conveyed to the first image forming unit 17K, where a black image is transferred.

  The image forming unit 17K includes a member having the same configuration function as the member described with reference to FIG. The members having the same configuration functions are denoted by the same reference numerals as those in FIG. 1 with K added to the end of the photosensitive member 1K, the charging device 2K, the developing device 3K, and the like. Although the conveyance belt 15 is omitted in FIG. 1, actually, as shown in FIG. 7, a transfer device 5K is disposed on the back side of the upper stretched portion of the conveyance belt 15, and the photosensitive member is also provided. An optical writing device 16 is provided as means for forming an electrostatic latent image by irradiating the exposure light L to 1.

  When forming a color image, in the image forming unit 17K, the peripheral surface of the photosensitive member 1K is uniformly charged by the charging device 2K in the dark, and then the image forming unit 17K performs exposure corresponding to the black image from the optical writing device 16K. Exposure with light L forms an electrostatic latent image. This electrostatic latent image is visualized with black toner in the developing device 3K, and a black toner image is formed on the photoreceptor 1K. This toner image is transferred onto the transfer paper 8 by the action of the transfer device 5K in alignment with the transfer paper 8 in the area where the photoreceptor 1K and the transfer paper 8 on the conveyor belt 15 contact, that is, the transfer area. A black image is formed. After the transfer, the photosensitive member 1K has unnecessary toner remaining on the peripheral surface thereof removed by the cleaning device 6K, and is prepared for the next image formation.

  In this way, the transfer paper 8 on which the single color (black) is transferred by the image forming unit 17K is transported to the next image forming unit 17M by the transport belt 15. In the image forming unit 17M, the magenta toner image formed on the photoconductor 1M by the same process as in the image forming unit 17K is superimposed and transferred onto the black toner image on the transfer paper 8. The transfer paper 8 is further conveyed to the next image forming unit 17Y, and the yellow toner image formed on the photoconductor 1Y in the same manner is overlaid on the black and magenta toner images already formed on the transfer paper 8. Is done. Similarly, in the next image forming unit 17C, a cyan toner image is transferred and overlapped to obtain a full color image. The transfer paper 8 on which the full-color superimposed image is formed in this way passes through the image forming unit 17C, is peeled off from the conveyance belt 15, and then fixed by the fixing unit 24 while passing between the pair of fixing rollers. The paper is discharged to the paper discharge tray 25.

  In the tandem type image forming apparatus as in the present embodiment, the photoconductors 1K, 1M, 1Y, and 1C are arranged close to each other in a direction (lateral direction) orthogonal to the photoconductor rotation axis direction. In order to reduce the size of the image forming apparatus in the horizontal direction, it is necessary to reduce the interval between the photoconductors. For this purpose, it is necessary to reduce the lateral dimensions of the developing devices 3M, 3Y, and 3C disposed between the photosensitive members. As described above, in the developing device 3 of the present embodiment, the supply chamber and the recovery chamber, which are developer transport paths for circulating and transporting the developer, are arranged side by side in the vertical direction. Can be made smaller in the size of the developing device in the horizontal direction.

Moreover, in the configuration in which the collection chamber is disposed below the supply chamber as in this embodiment, the developer conveyed to the downstream end of the collection chamber is lifted against gravity and moved to the upstream end of the supply chamber. It will be. In this case, as compared with the configuration in which the supply chamber and the recovery chamber are arranged side by side, the compressive force acting on the developer in the developer movement slow position where the developer moves slowly at the downstream end of the recovery chamber. The toner becomes strong, and the toner can rub against the carrier strongly before passing through the portion where the developer moves slowly. Therefore, before the replenished toner replenished at the upstream end of the recovery chamber moves to the upstream end of the supply chamber, the toner charge amount that can be charged at the developer movement slow position is the horizontal direction between the supply chamber and the recovery chamber. Increased compared to the configuration arranged side by side.
The above-described effective effects in the present embodiment are not unique to the tandem type full-color image forming apparatus, and can of course be obtained in a single-color image forming apparatus.

Next, the configuration at the downstream end of the recovery chamber, which is a characteristic part of the present invention, will be described.
FIG. 8 is an explanatory diagram when the configuration of the downstream end of the collection chamber in the developing device 3 of the present embodiment is viewed from a substantially horizontal direction.
FIG. 9 is an explanatory diagram of the configuration of the downstream end of the recovery chamber in the conventional developing device viewed from a substantially horizontal direction.
The developer transported to the downstream end of the recovery chamber by the recovery chamber transport member 305 as indicated by an arrow 12 in the figure is rapidly changed in its moving direction as indicated by an arrow 14 in the figure, and the gravity is changed. It is necessary to move to the upper end side of the supply chamber against this. Therefore, the movement of the developer in the downstream portion of the recovery chamber becomes slow, and the developer is clogged in the downstream portion of the recovery chamber as shown in the figure. The developing device of the present embodiment has a recovery chamber downstream side portion including such a developer movement slowing portion with a cross-sectional area (a cross section perpendicular to the developer transport direction of the recovery chamber) than the recovery chamber upstream side portion. (Area) is configured to be large. Specifically, a part of the partition plate 306 facing the downstream portion of the recovery chamber is recessed to provide a cross-sectional area enlarged portion 310.

By providing such a cross-sectional area enlarged portion 310 in the downstream portion of the recovery chamber, the developer movement is compared with the conventional configuration shown in FIG. 9 where the downstream portion of the recovery chamber has the same cross-sectional area as the upstream portion. It is possible to lengthen the moving distance until the toner that has entered the slow spot passes through the spot and is lifted to the upstream end of the supply chamber.
In the case of this embodiment shown in FIG. 8, the developer in the developer movement slow portion is only pushed in the developer transport direction (the direction of arrow 12 in the figure) when pushed in by the developer transported later. In addition, it is possible to move in a direction deviating from the developer conveying direction, that is, in a direction toward the cross-sectional area enlarged portion 310. The developer that has moved toward the cross-sectional area enlargement section 310 is taken into the developer portion that is subsequently conveyed along the developer conveyance direction (the direction of arrow 12 in the figure). Then, from the developer portion in which the developer in the cross-sectional area enlarged portion 310 is taken in in this way, the developer toward the cross-sectional area enlarged portion 310 correspondingly appears, and this developer is further conveyed later. It will be taken in by the developer part which comes. According to this embodiment, the developer in the developer movement slow portion is gradually conveyed while taking such a behavior, and finally moves to the upstream end of the supply chamber through the communication port 307. In the conventional configuration in which the cross-sectional area enlargement portion 310 does not exist as shown in FIG. 9, the developer in the developer movement slow portion moves in parallel along the developer transport direction (the direction of arrow 12 in the figure). Thus, the movement in the direction away from the developer transport direction hardly occurs. Therefore, according to the present embodiment, compared to the conventional configuration in which the cross-sectional area enlarged portion 310 does not exist, the moving distance of the toner passing through the portion where the developer moves slowly is long. In the portion where the developer movement is slow, the developer moves little by little while receiving a strong compressive force, and the toner and the magnetic carrier are rubbed strongly, so that the triboelectric charging efficiency of the toner is high. Since the developer moving distance when passing through such a developer moving slow portion becomes long, the toner sent to the upstream end of the supply chamber can be sufficiently charged.

  Here, if the developer moved into the cross-sectional area enlarged portion 310 is configured to be difficult to move, a developer (immobilizer) that cannot be removed from the cross-sectional area enlarged portion 310 appears. Such an immobilizing agent may be solidified particularly in a high temperature and high humidity environment. When the developer thus solidified comes out of the cross-sectional area enlargement unit 310 and is conveyed to the supply chamber at any moment, it is caught in the gap between the developer regulating member 303 and the outer peripheral surface of the developing roller 302. Causes abnormal images. Therefore, it is desirable that the cross-sectional area enlarged portion 310 has a shape in which the developer inside thereof can easily move. When the corner portion 310a is present in the cross-sectional area enlarged portion 310 as in the example shown in FIG. 10, it is difficult to move the developer pushed into the corner portion 310a from the corner portion 310a. Is likely to occur. Therefore, it is preferable that the corner portion 310a in the example shown in FIG. 10 is eliminated and the rounded corner portion 310b is rounded as in the example shown in FIG.

FIG. 12A is an explanatory diagram showing a cross section of the downstream portion of the recovery chamber in the developing device 3 of the present embodiment.
FIG. 12B is an explanatory view showing a cross section of the upstream portion of the recovery chamber in the developing device 3 of the present embodiment.
As described above, the recovery chamber transport member 305 in the recovery chamber is a transport screw. By rotating counterclockwise in the drawing, the screw-shaped blade portion rotates on the rotation shaft, and the surface of the blade portion (transport) The developer is transported in the direction of the rotation axis. The conveyance surface of the blade portion that imparts a conveyance force to the developer imparts not only a conveyance force in the rotation axis direction but also a conveyance force in the rotation direction of the rotation shaft to the developer. For this reason, the developer positioned in the collection chamber portion on the right side in the drawing with respect to the rotation axis is given not only a conveyance force in the rotation axis direction but also a conveyance force in the vertical direction upward.

  In the present embodiment, as shown in FIG. 12A, with respect to the rotation axis of the recovery chamber transport member 305, on the upper side of the recovery chamber on the side (right side in the figure) on which the blade portion moves upward in the vertical direction, A cross-sectional area enlarged portion 310 is provided. By providing the cross-sectional area enlarging unit 310 here, the developer that moves to the upper side in the vertical direction in response to the conveying force from the collection chamber conveying member 305 can be sent to the cross-sectional area enlarging unit 310. As a result, a compressive force can be applied to the developer in the cross-sectional area enlargement unit 310 to promote frictional charging of the toner, and a force for moving the developer in the cross-sectional area enlargement unit 310 can be applied. The agent can be made difficult to appear.

FIG. 13 is a graph showing the change in toner charge amount over time when a developer containing toner having a reduced charge amount is circulated and conveyed into the developing device to raise the toner charge amount.
In this graph, time is taken on the horizontal axis, and the time when the driving of the developing device is started is 0 second. In this graph, the toner charge amount rising using the developing device 3 of the present embodiment is plotted with “◯”, and the development of the conventional configuration shown in FIG. The toner charge amount rising using the apparatus is plotted with “x”. As can be seen from this graph, the developing device 3 of the present embodiment in which the cross-sectional area enlargement unit 310 is provided in the downstream portion of the collection chamber is more charged than the toner of the conventional configuration without the cross-sectional area enlargement unit 310. It was confirmed that the amount rose quickly. The fact that the rise time of the toner charge amount is fast in this way indicates that the toner charging capability of the developing device is high. If the toner charging capability is high, the charge amount of the replenishment toner can be quickly raised to a desired charge amount, and occurrence of problems such as toner scattering and background contamination is suppressed.

Next, a problem will be described when the longitudinal position of the cross-sectional area enlarged portion 310 provided in the collection chamber downstream side portion is configured to overlap with the position of the developing roller 302 facing the developer carrying region.
FIG. 14 is a diagram illustrating a cross-section of the overlapping portion in the case where the longitudinal position of the cross-sectional area enlarged portion 310 provided in the downstream portion of the recovery chamber is configured to overlap the position facing the developer carrying region of the developing roller 302. FIG.
The collection chamber portion of the developing roller 302 that faces the developer carrying area is in communication with the outer peripheral surface of the developing roller 302 in order to receive the developer separated from the agent separating area 9 of the developing roller 302. When the bulk of the developer present in such a collection chamber portion increases, the upper surface of the developer in the collection chamber portion approaches the agent separation area 9 of the developing roller 302. For this reason, when the bulk of the developer present in the collection chamber increases, the developer detached in the agent separation area 9 of the developing roller 302 immediately adheres to the outer peripheral surface of the developing roller 302 and is conveyed to the developer storage space C. A phenomenon called re-pumping occurs, in which the developer that has been transported through the collection chamber adheres to the outer peripheral surface of the developing roller 302 and is transported to the developer storage space C. When such re-pumping occurs, the developer whose toner concentration has decreased due to the development is not collected in the collection chamber and contributes to the development again, and image formation with an appropriate image density cannot be performed. Problems and replenished toner that has not yet been sufficiently frictionally charged contribute to development, causing problems such as toner scattering and background contamination. In the cross-sectional area enlarged portion 310 provided in the downstream portion of the recovery chamber, there is a portion where the developer moves slowly, so that the bulk of the developer is high as shown in FIG. Therefore, when the cross-sectional area enlarged portion 310 is provided so as to face the developer carrying area of the developing roller 302, the upper surface of the developer is brought close to the agent separation area 9 of the developing roller 302 as shown in FIG. Re-pumping is likely to occur.

  Therefore, in the present embodiment, the developer conveyance area in the collection chamber is more transported than the developer carrying region so that the cross-sectional area enlarged portion 310 provided in the downstream portion of the collection chamber does not face the developer carrying region of the developing roller 302. It is arranged downstream in the direction (outside in the developing roller axial direction). As a result, at least a part of the developer movement slow portion near the downstream end of the recovery chamber does not face the developer carrying area of the developing roller 302, and the occurrence of re-pumping is suppressed.

Note that the recovery chamber in the present embodiment has a portion from the developer carrying area of the developing roller 302 to 20 mm in the developer transport direction, and the developer carrying area of the developing roller 302 as shown in FIG. As shown in FIG. 12B, the developer carrying area of the developing roller 302 is not provided as shown in FIG. 12 (b), and thereafter the structure is arranged so as to face the communication port 307. May be.
Further, in this embodiment, the configuration in which the developer circulation path is formed by the supply chamber and the collection chamber arranged above and below has been described. However, the development from the toner replenishment point on the developer circulation path to the upstream end of the supply chamber is described. The present invention can be applied as long as the developer circulation path has a portion where the developer is lifted and conveyed.

As described above, the image forming apparatus according to this embodiment includes the photosensitive member 1 as a latent image carrier, the optical writing device 16 as a latent image forming unit that forms a latent image on the photosensitive member 1, and the toner and the carrier. A developing device 3 that develops the latent image on the photoreceptor 1 with a two-component developer, and the toner image formed on the photoreceptor 1 by the developing device 3 is finally transferred to a transfer paper 8 as a recording material. The image forming apparatus forms an image on the transfer paper 8. The developing device 3 circulates and conveys the developer 320 along the developer circulation path, and the developer 320 that is conveyed in a supply chamber that is a developer supply and conveyance path that bears a part of the developer circulation path. The developer 320 is supplied to the outer peripheral surface of the developing roller 302 as a developer carrying member, and the developer 320 carried on the outer peripheral surface of the developing roller 302 is conveyed to the developing area A by the rotation of the developing roller 302. The toner in 320 is attached to the latent image on the surface of the photoreceptor to develop the latent image. In the developing device 3, the developer agitating and conveying path serving as at least a part of the developer circulation path from the toner replenishment point where the toner is replenished to the developer 320 on the developer circulation path to the upstream end of the supply chamber. The developer 320 is disposed below the supply chamber in the vertical direction, and the developer 320 transported to the downstream end of the recovery chamber by the recovery chamber transport member 305, which is a developer stirring transport member, is transported later through the recovery chamber. By being pushed into 320, it is configured to be lifted to the upstream end of the supply chamber through a communication port 307 that is an opening that connects the downstream end of the recovery chamber and the upstream end of the supply chamber. Then, in the vicinity of the downstream end of the recovery chamber, the section of the downstream side of the recovery chamber including the developer movement slow spot where the movement of the developer 320 slows down is larger than the upstream side of the recovery chamber. An area enlargement unit 310 is provided. Thereby, since the developer moving distance when passing through the developer moving slow portion can be increased, the toner sent to the upstream end of the supply chamber can be sufficiently charged.
In the present embodiment, the cross-sectional area expanding portion 310 is provided at the upper part of the recovery chamber downstream portion so that the upper space of the recovery chamber downstream portion is wider than the recovery chamber upstream portion. As a result, the force moved from the cross-sectional area enlargement unit 310 due to gravity acts on the developer moved to the cross-sectional area enlargement unit 310. Therefore, the developer enters and exits the cross-sectional area enlargement unit 310 and the developer in the cross-sectional area enlargement unit 310. Can be activated, and the triboelectric charging of the toner can be further promoted.
In particular, in the present embodiment, the recovery chamber transport member 305 is provided with a screw-like blade portion on a rotation shaft parallel to the developer transport direction of the recovery chamber, and the rotation shaft is driven to rotate to rotate the rotation chamber. The conveying screw is a conveying screw that conveys the developer 320 in a direction along the rotation axis, and the cross-sectional area enlarged portion 310 is formed on the side where the blade portion moves upward in the vertical direction across the rotation axis of the conveying screw. Yes. As a result, the developer that moves in the vertical direction in response to the transport force from the collection chamber transport member 305 can be sent to the cross-sectional area enlargement unit 310, and compressive force is applied to the developer in the cross-sectional area enlargement unit 310. Thus, triboelectric charging of the toner can be promoted. In addition, since a force for moving the developer in the cross-sectional area enlarged portion 310 can be applied, the immobilizing agent hardly appears.
Further, in the present embodiment, the developer movement slow portion near the downstream end of the collection chamber is configured to be located downstream of the developer carrying region on the developing roller 302 in the developer conveyance direction by the collection chamber. . Thereby, generation | occurrence | production of re-pumping can be suppressed.
Moreover, in this embodiment, you may comprise a collection chamber downstream part so that a cross-sectional area may become large toward the downstream. In this case, an immobilizing agent is hardly generated in the cross-sectional area enlarged portion 310.
In the present embodiment, the recovery chamber transport member 305 is provided with a screw-like blade portion on a rotation shaft parallel to the developer transport direction of the recovery chamber, and the development in the recovery chamber is performed by rotating the rotation shaft. The conveying screw conveys the agent 320 in a direction along the rotation axis, and the conveying screw has a side where the blade part moves upward in the vertical direction across the rotation axis, and the side of the developing roller 302 that is opposite to the opposite side. It is comprised so that it may become away from an outer peripheral surface. The developer on the side where the blade portion moves upward in the vertical direction across the rotating shaft receives an upward conveying force due to the rotation of the conveying screw, and as a result, the upper surface of the developer is raised. In this way, if the side where the developer upper surface rises is close to the developing roller 302, re-pumping is likely to occur. However, in this embodiment, the side where the developer upper surface rises is the side far from the developing roller 302. Hard to occur.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 3 Developing device 5 Transfer device 6 Cleaning device 8 Transfer paper 9 Agent separation area 11, 13, 12, 14 Developer conveying direction 15 Conveying belt 16 Optical writing device 17 Image forming unit 301 Casing 302 Developing roller 302c Sleeve 302d Magnet roller 303 Developer regulating member 304 Supply chamber conveying member 305 Collection chamber conveying member 306 Partition plate 307 Communication port 308 Communication port 310 Cross-sectional area enlarged portion 320 Developer

JP 2007-25638 A

Claims (6)

A two-component developer containing toner and a carrier is circulated and conveyed along the developer circulation path, and a two-component developer conveyed in a developer supply and conveyance path serving as a part of the developer circulation path. The two-component developer supplied to the outer peripheral surface of the developer carrying member and transported to the developing region by the rotation of the developer carrying member is transported to the developing region, and the two-component developer is developed in the developing region. In the developing device for developing the latent image by attaching the toner therein to the latent image on the surface of the latent image carrier,
Developer agitation serving as at least part of the developer circulation path from the toner replenishment point where toner is replenished to the two-component developer on the developer circulation path to the upstream end in the developer conveyance direction of the developer supply conveyance path A transport path is disposed vertically below the developer supply transport path;
The two-component developer conveyed to the downstream end in the developer conveyance direction of the developer agitation conveyance path by the developer agitation conveyance member is pushed into the two-component developer conveyed later in the developer agitation conveyance path. In this manner, the developer supply conveyance path upstream end in the developer supply conveyance path passes through an opening that communicates the developer conveyance direction downstream end of the developer stirring conveyance path and the developer supply conveyance path upstream end in the developer conveyance direction. Configured to be lifted to
The developer conveyance direction upstream side portion than the opening in the developer conveyance direction downstream side portion than the developer carrying region on the developer carrier in the developer stirring and conveying path, upper end of the developer agitation path The developer agitating / conveying path is configured by forming a cross-sectional area enlarging portion in which the upper space is enlarged from the upstream side portion in the developer conveying direction in which the wall and the lower end wall are parallel to increase the cross-sectional area perpendicular to the developer conveying direction. A developing device characterized in that a portion where the movement of the two-component developer is slow is provided near the downstream end in the developer transport direction . The developing device according to claim 1 ,
The developer agitating and conveying member is provided with a screw-like blade portion on a rotating shaft parallel to the developer conveying direction of the developer agitating and conveying path, and the developer agitating and conveying path is driven by rotating the rotating shaft. A conveying screw for conveying the two-component developer in the direction along the rotation axis,
The developing device according to claim 1, wherein the cross-sectional area enlarging portion is formed on a side where the blade portion moves upward in the vertical direction across the rotation shaft of the conveying screw. The developing device according to claim 1 or 2 ,
The developing device according to claim 1, wherein the cross-sectional area enlarging portion is configured such that the cross-sectional area increases toward the downstream side in the developer transport direction. The developing device according to any one of claims 1 to 3 ,
The developer agitating and conveying member is provided with a screw-like blade portion on a rotating shaft parallel to the developer conveying direction of the developer agitating and conveying path, and the developer agitating and conveying path is driven by rotating the rotating shaft. A conveying screw for conveying the two-component developer in the direction along the rotation axis,
The conveying screw is configured such that the side on which the blade portion moves toward the upper side in the vertical direction across the rotation shaft is further away from the outer peripheral surface of the developer carrier than the opposite side. A developing device. In a process cartridge that integrally supports a latent image carrier and a developing device that develops a latent image on the latent image carrier and is configured to be detachable from the image forming apparatus main body,
As the developing apparatus, process cartridge characterized by using a developing apparatus according to any one of claims 1 to 4. A latent image carrier, a latent image forming unit that forms a latent image on the latent image carrier, and a developing device that develops the latent image on the latent image carrier using a two-component developer containing toner and a carrier. An image forming apparatus for forming an image on the recording material by finally transferring the toner image formed on the latent image carrier by the developing device to the recording material,
As the developing device, an image forming apparatus characterized by using the developing apparatus according to any one of claims 1 to 4.

Images