JP2014032340A - Developing device, process cartridge, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device that prevents toner scattering as well as increase in size of the device.SOLUTION: A developing device includes: a developer carrier which faces an image carrier and carries developer; a first conveyance member that faces the developer carrier and supplies the developer to the developer carrier while conveying the developer in a longitudinal direction; a second conveyance member that faces a developer carrier and conveys the developer separated from the developer carrier in a longitudinal direction; a first relay part where the developer having reached the downstream side of the first conveyance path of the first conveyance member flows to the upstream of the second conveyance path of the second conveyance member; a second relay part where the developer having reached the downstream of the second conveyance path flows to the upstream of the first conveyance path; and a ventilation path formed between the first and second relay parts and leading from the second conveyance path to the first conveyance path. The ventilation path is located below the first conveyance member, and has a mesh for supplying air from the second conveyance path to the first conveyance path.

Description

  The present invention relates to a developing device, a process cartridge, and an image forming apparatus that form a color image.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, a developing device that contains a two-component developer composed of a toner and a carrier (including a case where an additive or the like is added), the developer being long A technique is known in which two transport members that are transported in a direction to form a circulation path are installed in the vertical direction.

  In a developing device using a two-component developer, toner is appropriately replenished into the developing device from a toner replenishing port provided in a part of the developing device according to toner consumption in the developing device. The replenished toner is agitated and mixed together with the developer in the developing device by a conveying member (agitating and conveying member) such as a conveying screw. Part of the stirred and mixed developer is supplied to a developing roller (developer carrier).

  After the developer carried on the developing roller is regulated to an appropriate amount by a doctor blade (developer regulating member), the toner in the two-component developer is a latent image on the photosensitive drum at a position facing the photosensitive drum. Adhere to. A magnet is fixed inside the developing roller, and a plurality of magnetic poles are formed around the developing roller by the magnet.

  In Patent Document 1, a developer that reaches the downstream side of the first conveyance path by the first conveyance member flows to the upstream side of the second conveyance path by the second conveyance member; And a second relay part in which the developer that has reached the downstream side flows to the upstream side of the first transport path, and the second transport path (toner collection path) to the second relay part between the first relay part and the second relay part. There is disclosed a developing device that suppresses toner scattering by providing an air passage that leads to one conveyance path (toner supply path) to create an air flow from the toner recovery path to the toner supply path.

  However, in the developing device described in Patent Document 1, a ventilation path must be provided to avoid the first conveyance screw that conveys toner in the first conveyance path and the second conveyance screw that conveys toner in the second conveyance path. In other words, there is a problem that the developing device becomes larger correspondingly.

  SUMMARY An advantage of some aspects of the invention is that it provides a developing device that prevents the apparatus from becoming large and prevents toner scattering.

  In order to solve the above problems, a developing device of the present invention is a developing device that contains a developer having a carrier and a toner and develops a latent image formed on the image bearing member. A developer carrying body that carries the developer, a first carrying member that faces the developer carrying body and that supplies the developer to the developer carrying body while carrying the developer in the longitudinal direction; The second conveying member that faces the developer carrying member and conveys the developer separated from the developer carrying member in the longitudinal direction, and the developer that reaches the downstream side of the first conveying path by the first conveying member is the first conveying member. A first relay part that flows upstream of the second transport path by the two transport members, a second relay part that flows downstream of the second transport path, and a developer that flows upstream of the first transport path; Between the first relay unit and the second relay unit from the second transport path to the second And a ventilation path leading to the conveying path, the vent path is positioned below the first transport member, characterized in that it comprises a mesh venting from the second transport path to the first transport path.

  According to the present invention, it is possible to prevent enlargement of the apparatus and toner scattering.

1 is a schematic configuration diagram of an image forming apparatus including a developing device according to an embodiment of the present invention. 1 is a schematic cross-sectional configuration diagram of a developing device according to an embodiment of the present invention. It is a figure which shows magnetic force distribution of the magnetic pole formed on the developing roller of embodiment of this invention. FIG. 3 is a longitudinal sectional view of the developing roller according to the embodiment of the present invention. FIG. 2 is a cross-sectional perspective view of a main part of the developing device according to the embodiment of the present invention. 1 is a perspective view of a main part of a developing device according to an embodiment of the present invention. FIG. 3 is a half sectional view of the developing device according to the embodiment of the present invention as viewed from above. FIG. 2 is a schematic cross-sectional configuration diagram (with an air passage) of the developing device according to the embodiment of the present invention. FIG. 4 is a diagram illustrating a developer transport surface and a back surface of the transport surface of the toner transport screw according to the embodiment of the present invention. FIG. 5 is a schematic diagram illustrating a flow of airflow through a ventilation path in the developing device according to the embodiment of the present invention. FIG. 6 is a graph showing a toner scattering effect when an air passage is provided in the developing device according to the embodiment of the present invention.

  An image forming apparatus including a developing device according to an embodiment of the present invention will be described below with reference to FIG. Here, the uniformly charged image carrier is irradiated with light from the optical writing means to form an electrostatic latent image, and this electrostatic latent image is visualized by the developing device according to the present embodiment, and further recorded. An image forming apparatus 1 that forms a color image will be described as an example of an image forming apparatus that obtains a recorded image by transferring it to the image.

  In the image forming apparatus 1, a plurality of image forming units 17K, 17M, 17Y, and 17C are arranged in order from the upstream side in the moving direction (conveying direction) of the conveying belt along the conveying belt 15 that conveys the transfer paper 8. The so-called tandem type. The order of colors is not limited to this. For example, it is possible to arrange black at the most downstream side and form an image in the order of MCYK.

  Each of these image forming units is formed of a combination of a plurality of members and forms an image. The image forming unit is not necessarily configured as a unit. The image forming unit 17K forms black, the image forming unit 17M forms magenta, the image forming unit 17Y forms yellow, and the image forming unit 17C forms cyan. The image forming units have different colors. However, the internal configuration is the same for 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 a driving roller, one of which is driven to rotate, and an endless belt that is rotatably supported by the conveying rollers 18, 19 that are driven rollers, the other of which is driven to rotate. , Can be rotated in the direction of the arrow. Below the transport belt 15, paper feed trays 20, 21, and 22 that store transfer papers 8 a to 8 c are provided.

  For example, the transfer paper 8a at the uppermost position 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 sent out at the same timing as the image formation in the image forming unit 17K. It is attracted to the conveyor belt 15 by electroadsorption. 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 charging device 2K, a developing device 3K, a photoconductor (image carrier) 7K, and a cleaning device 6K. As shown in FIG. 1, a transfer device 5K is arranged on the back side of the upper stretched portion of the conveyor belt 15, and an electrostatic latent image is formed by irradiating the photoconductor 7K with exposure light L. An optical scanning device 16K is provided as means for forming.

  When forming a color image, in the image forming unit 17K, the peripheral surface of the photoreceptor 7K is uniformly charged by the charging device 2K in the dark, and then the exposure light corresponding to the black image from the optical scanning device 16K. L is exposed to form an electrostatic latent image. The electrostatic latent image is visualized with black toner in the developing device 3K, and a black toner image is formed on the photoreceptor 7K.

  This toner image coincides with the transfer paper 8 at a so-called transfer position, which is a position where the photoconductor 7K and the transfer paper 8 on the conveyor belt 15 are in contact, and is transferred onto the transfer paper 8 by the action of the transfer device 5K. A monochrome (black) image is formed on the transfer paper 8. After the transfer, the photoreceptor 7K is prepared for the next image formation after unnecessary toner remaining on the peripheral surface of the photoreceptor 7K is removed by the cleaning device 6K.

  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 7M by the same process as in the image forming unit 17K is transferred onto the black toner image on the transfer paper 8 in an overlapping manner.

  The transfer paper 8 is further conveyed to the next image forming unit 17Y, and the yellow toner image formed on the photoconductor 7Y in the same manner is superimposed on the black and magenta toner images already formed on the transfer paper 8. Transcribed. Similarly, in the next image forming unit 17C, the cyan toner image formed on the photoreceptor 7C is transferred onto the black, magenta, and yellow toner images already formed on the transfer paper 8. A full color image can be obtained.

  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 this embodiment, for example, at least one of the charging device 2K, the developing device 3K, and the cleaning device 6K constituting the image forming unit 17K described above is integrated with the photoconductor 7K. The process cartridge may be detachably installed on the image forming apparatus main body.

  Next, an outline of image formation in the present embodiment will be described below with reference to FIG. FIG. 2 is an arrangement configuration diagram of each member showing an outline around the photoconductor 7 using the developing device 3 of the present embodiment. The photoconductor 7 is rotated in a clockwise direction as indicated by an arrow by a driving means (not shown). The charging device 2 is disposed at the top of the photoconductor 7 and at approximately 11 o'clock in terms of a clock face. The charging device 2 includes a rotating body that is rotated at the same speed as the photoconductor 7 by a driving unit (not shown), but is not limited to the rotating body and may be a corona discharge type.

  After the surface of the photoconductor 7 is uniformly charged in the dark by the charging device 2, an electrostatic latent image is formed by receiving exposure light L from a light scanning unit (not shown). The electrostatic latent image moves downstream as the photoconductor 7 rotates and reaches the developing device 3. The developing device 3 is disposed on the right side of the photoreceptor 7.

  The developing device 3 includes a supply chamber conveyance member 304 and a collection chamber conveyance member 305 for agitating and conveying the developer 320 in the casing 301, and other members such as a developing roller 302 and other members.

  When the photosensitive member 7 is expressed by a clock face, the developing roller 302 is opposed to the photosensitive member 7 in the direction between 2 o'clock and 3 o'clock on the photosensitive member 7 (direction of 2:30), thereby developing nip region. A are arranged close to each other so as to constitute A. A portion of the casing 301 corresponding to the portion facing the photoconductor 7 is open to expose the developing roller 302.

  The developer 320 in the casing 301 is conveyed to the development nip region A by the developing roller 302. The toner in the developer 320 adheres to the electrostatic latent image formed on the surface of the photoreceptor 7 in the development nip region A, and is visualized as a toner image.

  The toner image moves downstream as the photoconductor 7 rotates and reaches the opposite side of the transfer device 5. The transfer device 5 is arranged at the bottom of the photoconductor 7 at the 6 o'clock direction. In this example, the transfer device 5 is composed of a rotating body, but is not limited to a rotating body, and may be a corona discharge type. A region where the photoconductor 7 and the transfer device 5 face each other is referred to as a transfer region B.

  The toner image on the photoconductor 7 is transferred to the transfer paper 8 in the transfer region B and becomes an image on the transfer paper 8. In addition, the present invention can be applied to an intermediate transfer belt system in which the toner on the photosensitive member 7 is once transferred to an intermediate transfer member (intermediate transfer belt or the like), and then the multicolor toners are collectively transferred to a transfer sheet. In the transfer area B, the toner on the photoconductor 7 is transferred to an intermediate transfer body (intermediate transfer belt).

  The surface of the photoconductor 7 after the transfer moves to the downstream side with the rotation of the photoconductor 7 and reaches the cleaning device 6. The cleaning device 6 is arranged in the direction of 10:00 on the photoconductor 7. The cleaning device 6 uses a cleaning blade 601 to remove toner remaining on the surface of the photoconductor 7 without being completely transferred onto the transfer paper. The surface of the photoreceptor 7 that has passed the cleaning device 6 is then uniformly charged by the charging device 2 and the next image forming process is repeated.

  Next, the developing device 3 of the present embodiment will be described below with reference to FIGS. The developing device 3 includes a developing roller (developer carrying member) 302, a supply chamber conveying member 304 (first conveying member), a recovery chamber conveying member 305 (second conveying member), a developer regulation, and a casing 301. The developer 303 is circulated while being stirred and conveyed. In this embodiment, for example, a spiral screw is used as a member for stirring the developer, and a screw blade having an outer diameter of 16 mm or less is used.

  As shown in FIG. 3, the developing roller 302 has a magnet roller 302 d in which a plurality of magnets MG (only one is indicated by a symbol for preventing complication of the drawing) arranged in the circumferential direction. A cylindrical sleeve 302c is configured to rotate integrally with the rotating shaft 302e.

  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 a sleeve 302c rotates around the magnet roller MG to convey the developer 320 attracted by the magnet MG. To go.

  In FIG. 4 showing the structure of the developing roller 302, the developing roller 302 is mainly composed of a fixed shaft 302a fixed to the casing 301 as a stationary member, a magnet roller 302d having a cylindrical shape integrated with the fixed shaft 302a, and a magnet roller. A sleeve 302c covering the periphery of 302d via a gap, a rotating shaft 302e integrated with the sleeve 302c, and the like. 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 320 can be spiked on the peripheral surface of the sleeve 302c, and can be cut off. Magnetic carriers are gathered to form a magnetic brush along the normal magnetic field lines emitted from these magnets MG.

  There are many configurations of the magnet roller. First, as shown in FIG. 3, the configuration of the magnet roller having three magnets MG inside the sleeve 302c and generating three magnetic poles (magnetic force distribution) will be described. The magnetic pole of the part (area corresponding to the development nip area A shown in FIG. 2) opposed on the line connecting the center O-1 of the developing roller 302 and the center O-2 of the photoreceptor 7 is referred to as a P1 pole (developing pole). Hereinafter, the magnetic poles are referred to as a P2 pole (casing counter pole) and a P3 pole (developer regulating member counter pole) in the rotation direction of the developing roller 302 shown in the counterclockwise direction.

  The polarities are the N, S, and S poles in the order from the P1 pole to the P3 pole, but these poles may have opposite polarities. The P1 pole is a development pole and faces the photoreceptor 7. The P2 pole faces the casing, and the P3 pole faces the developer regulating member 303.

  The developing roller 302 and the photosensitive member 7 are not in direct contact with each other in the developing nip region A (see FIG. 2), and are opposed to each other while maintaining a developing gap GP at a constant interval suitable for development. Then, on the developing roller 302, the developer 320 is made to rise, and the developer 320 is brought into contact with the photoconductor 7, whereby toner is attached to the electrostatic latent image on the surface of the photoconductor 7 to be visualized.

  In the developing device 3 of the present embodiment, a grounding 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 a conductive bearing (not shown) and a conductive rotating shaft 302e. On the other hand, the lowermost conductive support constituting the photoconductor 7 is grounded.

  Thus, an electric field for moving the toner separated from the carrier to the photosensitive member 7 side is formed in the developing nip region A, and the toner is generated by the potential difference between the sleeve 302c and the electrostatic latent image formed on the surface of the photosensitive member 7. Is moved toward the photosensitive member 7 side.

  Note that the developing device 3 of the present embodiment is an example in which the developing device 3 is combined with an image forming apparatus of a writing method using exposure light L (see FIG. 2). The charging device 2 uniformly applies negative charges on the photoconductor 7 and exposes the image portion with the exposure light L in order to reduce the writing amount. A reversal development method is used in which a latent image is developed with negative polarity toner. However, this is only an example, and the polarity of the charged charge placed on the photoconductor 7 is not a big problem in the developing method of this embodiment.

  After the development, the P2 pole conveys the developed developer 320 carried on the developing roller 302 to the downstream side along with the rotation of the developing roller 302 and draws it into the casing 301.

  The P2 and P3 poles have the same polarity, and the P2 and P3 poles do not have a magnetic force to rise, and the ears fall asleep, and the developer 320 that has been attracted around the developing roller 302 until then is separated from the developing roller 302. The action of “separation” works. The portion corresponding to the P2 to P3 poles on the developing roller 302 where the ears are lying (region where the peak of the mountain shape of the magnetic force distribution curve is extremely low compared to other regions) separates the developer 320 from the developing roller 302. (Indicated by symbol C in FIG. 2).

  The developer 320 having the toner adhered to the photosensitive member 7 has a lower toner concentration in the developer 320. Therefore, the developer 320 having the lowered toner concentration is not separated from the developing roller 302 and again in the development nip region. If it is transported to A and used for development, there is a problem that a target image density cannot be obtained.

  In order to prevent this, in the present embodiment, the developer 320 is separated from the developing roller 302 in the agent separation region C after development. Thereafter, the developer 320 separated from the developing roller 302 is sufficiently agitated and mixed in the casing 301 so as to obtain a target toner concentration and toner charge amount.

  In this way, the developer 320 having the target toner concentration and charge amount is supplied to the developer storage space D by the supply chamber conveying member 304. The developer 320 supplied to the storage space D is adjusted to a predetermined thickness by passing through the developer regulating member 303 located immediately downstream of the P3 pole peak position, and forms the magnetic brush as described above. Is conveyed to the developed nip region A. Further, the P3 pole serves as a transport pole for transporting the developer 320.

  Hereinafter, the arrangement configuration of each member and the like of the developing device 3 will be described with reference to FIGS. 5 and 6 as necessary. As shown in FIGS. 2 and 3, the supply chamber conveying member 304 is disposed around the developing roller 302 and in the 2 o'clock direction of the developing roller 302. This position is also on the upstream side of the developer regulating member 303.

  As shown in FIGS. 5 and 6, the supply chamber conveyance member 304 has a screw shape with a spiral around the rotation axis, and a center line O-3 parallel to the center line O-1 of the developing roller 302 is formed. The developer 320 is rotated in the clockwise direction indicated by an arrow at the center, and the developer 320 is conveyed while stirring as indicated by an arrow W from the front side in the longitudinal direction of the center line O-3 toward the back side. That is, the supply chamber conveyance member 304 conveys the developer 320 in the axial direction from the near side to the back side by the rotation of the rotation shaft.

  The collection chamber conveying member 305 is disposed in the vicinity of the agent separation region C at a position around the developing roller 302 and in the 4 o'clock direction of the developing roller 302. As shown in FIG. 5, the collection chamber transport member 305 has a screw shape with a spiral around the rotation axis, and an arrow centering on a center line O-4 parallel to the center line O-1 of the developing roller 302. The developer 320 is conveyed while being agitated as indicated by an arrow Y from the back side in the longitudinal direction of the center line O-4 toward the front side as indicated by an arrow Y. That is, the collection chamber transport member 305 transports the developer 320 from the back side opposite to the transport direction by the supply chamber transport member 304 toward the front side by the rotation of the rotation shaft.

  The supply chamber transfer member 304 is positioned above the recovery chamber transfer member 305, and the space around the supply chamber transfer member 304 and the space around the recovery chamber transfer member 305 are adjacent to each other in the casing 301. Yes.

  The front side ends of the supply chamber transport member 304 and the collection chamber transport member 305 are set so as to be located slightly in front of the front end of the developing roller 302, and the developer at the front end of the developing roller 302 is set. The supply of 320 is secured. Further, the back end portions of the supply chamber transport member 304 and the collection chamber transport member 305 are located on the back side with respect to the back end portion of the developing roller 302 to secure a space for toner replenishment described later. . The developer regulating member 303 is installed according to the length of the developing roller 302.

  A partition plate 306 between the supply chamber transfer member 304 and the recovery chamber transfer member 305 that shields the space around the supply chamber transfer member 304 and the space around the recovery chamber transfer member 305 is supported inside the casing 301. Yes. As shown in FIG. 7, communication ports 307 (second relay portion) and 308 (first relay portion) are provided at both end portions in the longitudinal direction of the partition plate 306.

  The developer 320 transported in the direction of arrow Y by the collection chamber transport member 305 is cut off at the end in the transport direction at the side wall of the casing 301 and thus rises along the side wall, and the communication port 307 (second relay) described above. The supply chamber transfer member 304 moves the upper transfer path (first transfer path or supply chamber) along the supply chamber transfer member 304 along the arrow Z.

  Similarly, the developer 320 conveyed in the direction of the arrow W by the supply chamber conveying member 304 is disconnected through the communication port 308 (first relay unit) in order to cut off the course at the end of the conveyance direction at the side wall of the casing 301. It descends along the side wall, and moves along the arrow X to the lower conveyance path (second conveyance path or collection chamber) along the collection chamber conveyance member 305 by the collection chamber conveyance member 305.

  Thus, the developing device 3 of the present embodiment carries the developer 320 and rotates to visualize the electrostatic latent image formed on the photoreceptor 7 and the center line O− of the developing roller 302. The developer 320 is separated from the developing roller 302 and the supply chamber transport member 304 that rotates around the center line O-3 parallel to 1 and transports the developer 320 in the longitudinal direction of the center line O-3 while stirring. It is arranged in the vicinity of the agent separation area C, rotates around a center line O-4 parallel to the center line O-1 of the developing roller 302, and is opposite to the direction in which the supply chamber transport member 304 transports the developer 320. The recovery chamber transport member 305 that transports the developer 320 while stirring the developer 320 between the supply chamber transport member 304 and the recovery chamber transport member 305, and the space around the supply chamber transport member 304 and the recovery chamber transport member 305. Open at both ends to shield the space A configuration having a partition plate 306 having a.

  As a result, two supply chamber conveyance members 304 and recovery chamber conveyance members 305 in 301 that constitute a circulation conveyance path along the arrows W, X, Y, and Z are arranged side by side above and below the developing roller 302. Compared to the configuration in which two conveying members are arranged in the direction away from the developing roller 302 (in the horizontal direction), the horizontal size (in the horizontal direction) of the developing device can be reduced.

  Further, in the developing device 3 which is thus made compact in the horizontal direction, the space around the supply chamber conveyance member 304 and the collection chamber conveyance member 305 is partitioned by the partition plate 306. In this case, only the developer 320 in which the toner and the carrier are sufficiently agitated and mixed is supplied by the supply chamber conveyance member 304, and the developer 320 whose toner concentration immediately after development is reduced is exclusively agitated and conveyed by the recovery chamber conveyance member 305. Since the toner is not immediately supplied to the developing roller 302, only toner having a target charge amount is used for the developing roller 302, and high image quality can be obtained.

  Next, toner supply in the present embodiment will be described. Since the developer 320 of the developing device 3 consumes the toner every time the developing operation is repeated, it is necessary to supply the toner to the developer 320 in the device from the outside of the developing device 3. In this embodiment, toner is replenished from the outside through a replenishment opening 309 for the developer 320 provided in the vicinity of the back end of the developing device 3. In this replenishment, the replenished toner is not immediately used for development, but is supplied to the collection chamber through the communication port 308. The toner supplied to the recovery chamber is agitated by the recovery chamber transport member 305 and is subjected to development at a stable predetermined toner concentration.

  In the lower conveyance path by the collection chamber conveyance member 305, only the developer 320 separated from the developing roller 302 is collected, and the toner is not supplied to the developing roller 302. Therefore, the newly replenished toner from the replenishment opening 309 is used. A developer that is not sufficiently stirred and has a non-uniform toner concentration is not subjected to development.

  The replenished toner is agitated and mixed in the developer 320 having a lowered toner density away from the developing roller 302, and the toner density is normalized before being conveyed to the front side of the developing device 3. It is lifted up to the upper conveyance path, supplied to the developing roller 302 while being conveyed to the back side by the supply chamber conveying member 304, and used for development.

  Next, the toner concentration sensor in the present embodiment will be described. In the present embodiment, the toner concentration sensor is disposed at the downstream end of the collection chamber transport member 305 in the transport direction (not shown). This sensor is a sensor for measuring magnetic permeability, and can detect the carrier concentration of the developer [= 100−toner concentration (%)]. Further, it is determined from the detected carrier concentration whether the toner concentration on the sensor is appropriate or insufficient, and the amount of toner to be replenished is determined.

  As already described above, since the developer 320 is used for development before being transported to the back side of the upper transport path by the supply chamber transport member 304, the developer 320 is returned to the near side by the collection chamber transport member 305. There is a tendency that the amount of developer 320 to be increased increases and the developer 320 accumulates on the near side. Therefore, by disposing the toner concentration sensor on the downstream side of the collection chamber transport member 305, the developer 320 is always filled above the sensor, and stable carrier concentration detection is possible.

  Next, the configuration of the air passage 310 (mesh) in the developing device 3 of the present embodiment will be described below with reference to FIG. The air passage 310 is provided closer to the developing roller 302 than the line connecting the screw shafts of the upper and lower conveying members. This is because the collection chamber transport member 305 (screw) rotates in the counterclockwise direction and the developer 320 is transported while being biased to the right side. This is because the ventilation efficiency is improved.

  Further, the mesh is disposed near (below) the supply chamber conveying member 304 (screw). If the mesh is disposed on the collection chamber conveying member 305 side, the developer 320 accumulates on the mesh and cannot be vented. Therefore, it is necessary to arrange the mesh on the supply chamber transfer member 304 side.

  Note that the developer 320 is transported to the supply chamber, and the airflow that has passed through the ventilation path 310 strikes the developer 320. However, when the supply chamber conveying member 304 (screw) rotates, the developer conveying surface is clogged with the developer 320, but there is air on the surface opposite to the developer conveying surface, and the faster the screw rotation speed, the opposite the This will increase the amount of air. For this reason, airflow is not always generated through the air passage 310, but airflow is generated after the screw conveying surface passes over the air passage 310.

  FIG. 9 shows the developer conveying surface S of the screw and the reverse side T of the conveying surface. When the screw rotates in the illustrated rotation direction V, the developer 320 is conveyed in the left direction in FIG. The conveying force is due to the generation of a force U that pushes the developer 320 toward the conveying surface S due to the rotation of the screw blades. On the contrary, the developer conveying surface S and the opposite side surface T have no force to pull the developer 320, become an air layer, and have a negative pressure. This phenomenon of negative pressure becomes larger as the screw rotation speed becomes faster.

  As described above, the lower side of the supply chamber conveying member 304 (screw) is not always filled with the developer 320, and when the screw conveying surface passes through the mesh portion, a force for sucking an airflow is generated. Therefore, the air flow in the recovery chamber passes through the mesh and flows into the supply chamber.

  Next, the position of the ventilation path 310 will be described below with reference to FIG. This is a delivery section R where the developer 320 is lifted up at the right end of the figure. An air passage 310 is provided on the left side. This is a place where the developer 320 may come into contact, but as already described, an air layer exists on the back side of the screw. Since the air before the developer 320 is lifted has no destination and tends to stay, the air easily passes through the ventilation path 310 to the supply chamber I side.

  As the pressure in the developing device, the most downstream part of the recovery chamber Q is the highest, and the most upstream part of the supply chamber I is the lowest (negative pressure). Therefore, since there is a pressure difference between the most downstream of the recovery chamber Q and the most upstream of the supply chamber I, air flows through the air passage.

  Next, FIG. 11 shows the toner scattering reduction effect by providing the air passage 310 (mesh). In the graph, “no air passage” and “with air passage” are plotted on the horizontal axis, and “toner scattering amount” is plotted on the vertical axis of the graph. Since the air passage 310 is provided, airflow from the developing device is reduced, and toner scattering is also reduced.

  In the graph of FIG. 11, for example, in the developing device 3, the toner density is set to 10%, the configuration is such that the toner scattered around the developing roller 302 is not leaked to the outside, and single idling is performed for 1 hour. Then, the results of measuring the amount of scattered toner adhering to the film and the developing device are shown. As a result, the toner scattering amount was reduced by providing the air passage 310. In this embodiment, as described above, since the size of the developing device 3 does not change even if the air passage 310 is provided, it can be seen that the configuration is excellent in reducing the size.

  Next, the size of the mesh hole of the mesh in the ventilation path 310 of this embodiment is demonstrated. The purpose of arranging the mesh is to prevent the developer (particularly the carrier) from passing through, but to allow the air to pass through the air passage. In the present embodiment, for example, if the average particle diameter of the carrier is 35 μm, it is preferable that a 35 μm carrier is not passed as a mesh hole.

  Therefore, in the present embodiment, for example, a mesh having a mesh size of 500 mesh or more and an aperture of 0.026 mm or less is used. With this mesh, a carrier having an average particle diameter of 35 μm does not pass, and an air passage through which only air passes can be formed. However, if the mesh hole is too small, it will not serve as a ventilation path. Therefore, in the present embodiment, for example, a mesh of 500 mesh is used.

  This mesh needs to be electrically floating. “Electrically floating” means that the mesh is not connected to ground or the like. In the present invention, the toner in the developer is negatively charged by frictional charging. If the mesh is grounded, a positive charge is induced in the mesh, and the toner separates from the carrier and adheres to the mesh. Therefore, it is necessary to float electrically in order to prevent charge from being induced in the mesh.

  As described above, the developing device of the present embodiment described above is a developing device that stores a developer having a carrier and toner and develops a latent image formed on the image bearing member. A developer carrying body that carries the developer, a first carrying member that faces the developer carrying body and that supplies the developer to the developer carrying body while carrying the developer in the longitudinal direction; The second conveying member that faces the developer carrying member and conveys the developer separated from the developer carrying member in the longitudinal direction, and the developer that reaches the downstream side of the first conveying path by the first conveying member is the first conveying member. A first relay part that flows upstream of the second transport path by the two transport members, a second relay part that flows downstream of the second transport path, and a developer that flows upstream of the first transport path; Between the first relay unit and the second relay unit from the second transport path to the second And a ventilation path leading to the conveying path, the vent path comprises a mesh positioned below the first transport member, to vent from the second transport path to the first transport path.

  As a result, the apparatus can be prevented from being enlarged, and toner scattering can be prevented by reducing the internal pressure by aeration from the toner recovery chamber (second transport path) to the toner supply chamber (first transport path).

  In the developing device of the present embodiment described above, the mesh hole in the mesh is smaller than the average particle size of the carrier in the developing device described above. Thereby, it is possible to prevent the developer from dropping from the supply unit.

  Further, in the developing device of the present embodiment described above, in the above-described developing device, the air passage is located on the developer carrier side. Accordingly, the air passage can be smoothly performed without the air passage coming into contact with the developer in the toner recovery chamber (second transport route).

  Further, in the developing device of the present embodiment described above, the mesh is electrically floating in the above-described developing device. Thereby, adhesion of toner to the mesh can be prevented.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Charging apparatus 3 Developing apparatus 5 Transfer apparatus 6 Cleaning apparatus 7 Photoconductor 8 Transfer paper 301 Casing 302 Developing roller 303 Developer control member 304 Supply chamber conveyance member 305 Collection chamber conveyance member 306 Partition plate 307, 308 Communication port 309 Replenishment opening 310 Air passage 320 Developer

JP 2010-204506 A

Claims (6)

A developing device that contains a developer having a carrier and toner and that develops a latent image formed on an image carrier,
A developer carrying body facing the image carrying body and carrying a developer;
A first conveying member facing the developer carrying member and supplying the developer to the developer carrying member while conveying the developer in the longitudinal direction;
A second conveying member that faces the developer carrying member and conveys the developer detached from the developer carrying member in the longitudinal direction;
A first relay portion in which the developer that has reached the downstream side of the first transport path by the first transport member flows to the upstream side of the second transport path by the second transport member;
A second relay unit in which the developer that has reached the downstream side of the second transport path flows to the upstream side of the first transport path;
Between the first relay unit and the second relay unit, a ventilation path that leads from the second transport path to the first transport path,
The developing device according to claim 1, wherein the ventilation path includes a mesh that is located below the first conveyance member and vents from the second conveyance path to the first conveyance path.   The developing device according to claim 1, wherein the mesh hole in the mesh has a smaller diameter than an average particle diameter of the carrier.   The developing device according to claim 1, wherein the air passage is located on the developer carrying member side.   The developing device according to claim 1, wherein the mesh is electrically floating.   A process cartridge comprising the developing device according to claim 1.   An image forming apparatus comprising the process cartridge according to claim 5.

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