JP4903551B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus, and more particularly to a developer mixing and stirring system for an image forming apparatus.

  An electrophotographic image forming apparatus is an apparatus that forms an electrostatic latent image on the outer peripheral surface of a uniformly charged photosensitive drum, and forms the image by visualizing the electrostatic latent image with toner. Therefore, it is used in digital printers and copiers. In such an image forming apparatus, a two-component magnetic brush developing method has been mainly employed in recent years in order to satisfy the demand for higher image quality and higher speed.

  In the two-component development method, a two-component developer composed of a carrier that is a magnetic material and a non-magnetic or weakly magnetic toner is used. The two-component developer is mixed so that the carrier and the toner become uniform by a stirrer of the developing unit, and is stirred so that the toner is frictionally charged.

  A conventional stirrer is configured so that, for example, two screws each provided with a stirring blade on a shaft are arranged in parallel in a stirring tank, and the developer is circulated between the screws by rotating these screws. (For example, patent document 1). In such a stirrer, the developer is conveyed by flowing on a stirring blade provided on the shaft by rotation of the screw.

Japanese Patent No. 3508104

  In the conventional stirrer, since the screw is provided in the stirring vessel, the developer flows into the bearing portion of the shaft and wears the bearing portion. In order to prevent this, for example, as shown in FIG. 7, for example, an oil is provided between the end portion of the portion of the shaft 12 provided in the stirring vessel 11 where the stirring blade 13 is formed and the bearing portion 14. A seal member 15 such as a seal is provided. However, even if such a seal member 15 is provided, the developer wraps around the seal member 15 and wears the seal member 15, and the bearing portion 14 also wears. For this reason, the lifetime of the seal member 15 and the bearing portion 14 is short, and it is necessary to replace an expensive developing unit in a short period of time.

  Further, in the vicinity of both ends of the two screws, a developer delivery region in which the developer is conveyed from one conveyance path to another conveyance path is formed. When the stirring blade is provided up to the developer delivery area, the developer is compressed in the delivery area. For this reason, the developer deteriorates, for example, the surface coating agent of the carrier is peeled off or the toner is worn.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved image formation capable of preventing wear of a stirrer for stirring a developer. To provide an apparatus.

In order to solve the above-described problems, according to one aspect of the present invention, a developer carrying member having a magnet roller made up of a plurality of magnetic poles inside and carrying a developer made up of a carrier and toner on the peripheral surface, and development An image forming apparatus is provided that includes a developer agitator that agitates the agent and supplies the developer to the developer carrying member. The developer agitator of the image forming apparatus is inserted into the developer tank, a cylindrical member fixed in the developer tank by communicating the hollow portion and the outside of the developer tank, and rotatably inserted into the cylindrical member. A magnet shaft formed by alternately arranging different magnetic poles in the circumferential direction, and a stirring blade provided on the outer circumferential surface of the cylindrical member and having a spiral inclined surface with respect to the axial direction of the magnet shaft. Prepare. The developer stirrer rotates the developer in the direction of rotation of the magnet shaft on the outer peripheral surface of the cylindrical member by the magnetic force of the magnet shaft as the magnet shaft rotates, and the developer is swollen by the inclination of the stirring blade. The stirring blade is conveyed in the longitudinal direction of the shaped member, and the stirring blade is not formed in a region facing the developer carrier.

  The developer stirrer of the present invention conveys the developer while stirring it in a space surrounded by the inner surface of the developer tank and the outer peripheral portion of the cylindrical member that does not rotate. A magnet shaft is rotatably provided inside the cylindrical member, and the magnetic field on the outer peripheral surface of the cylindrical member changes by rotating a magnet shaft formed by alternately arranging different magnetic poles in the circumferential direction. Due to the change in the magnetic field, the developer receives a force that moves in the rotation direction of the magnet shaft. The developer is pressed by the inclination of the helical stirring blade formed on the outer peripheral surface of the cylindrical member, and is conveyed in the longitudinal direction of the cylindrical member. In this way, the developer can be moved by using the magnetic force acting on the developer from the magnet roller not in contact with the developer via the cylindrical member.

  Here, an opening is formed in the developer tank in a region facing the developer carrier. Thereby, the outer peripheral surface of the cylindrical member provided in the developer tank and the outer peripheral surface of the developer carrying member come to face each other. As a result, the developer moving on the outer peripheral surface of the cylindrical member provided inside the developer tank can be transferred to the peripheral surface of the developer carrier.

  At this time, a magnetic shielding member may be provided between the developer carrier and the cylindrical member on the downstream side in the rotation direction of the developer carrier in the region where the developer carrier and the cylindrical member face each other. Good.

  The developer stirrer can also be provided with at least two agitation transport units composed of a cylindrical member and a magnet shaft, and a partition wall provided between adjacent agitation transport units. That is, the agitation transport unit is inserted into, for example, a cylindrical transport path constituted by the developer tank and the partition wall. At this time, each stirring conveyance part is arrange | positioned so that the longitudinal direction of the cylindrical member of each stirring conveyance part may become parallel. Further, the developer conveying directions by the adjacent agitating and conveying units are configured to be different.

  Further, at both ends of the agitating and conveying unit, a developer moving region in which the developer can move from one agitating and conveying unit to another agitating and conveying unit by opening a partition and communicating adjacent agitating and conveying units. It can also be formed. As a result, each conveyance path provided with each agitation conveyance unit communicates with each other via the developer movement area, so that the area where the developer is agitated increases, and the toner and the carrier can be mixed uniformly. At this time, in at least one developer movement region, the magnetic force on the outer peripheral surface of the cylindrical member from which the developer is moved is configured to be smaller than the magnetic force on the outer peripheral surface of the cylindrical member to which the developer is moved. The Thereby, in the developer movement region, a force that draws the developer from the movement source to the movement destination acts on the developer, and thus the movement between the conveyance paths can be performed smoothly.

  In addition, the two magnet shafts of the adjacent agitating / conveying units are rotated with each other so that different magnetic poles face each other at least in the developer moving region. By causing different magnetic poles to face each other, an attractive force acts between the magnetic poles, so that the developer can be smoothly moved between the conveyance paths. Further, a developer guide plate may be provided in the developer movement area to connect the outer peripheral surface of the cylindrical member from which the developer is moved and the inner surface of the developer tank to which the developer is moved. Thereby, the developer can be smoothly moved from the movement source to the movement destination.

  On the other hand, in order to improve the stirring efficiency, the cylindrical member may be provided with an inhibiting member that inhibits the flow of the developer in the rotation direction of the magnet shaft. Alternatively, at least one hole may be formed in the stirring blade. Thereby, a turbulent flow is generated in the flow of the developer conveyed in the conveyance path by the agitation conveyance unit, and the developer can be further agitated.

  Further, the stirring blade is preferably provided so that the outer edge portion thereof does not contact the inner surface of the developer tank. When a partition wall is provided inside the developer tank, the partition wall should not be in contact with the partition wall. If the developer conveyed by the agitation conveyance unit stays at one end of the conveyance path, pressure is applied to the developer, leading to deterioration of the developer. By forming a gap without bringing the outer edge portion of the stirring blade into contact with the developer tank, the pressure applied to the developer can be released.

  As described above, according to the present invention, it is possible to provide an image forming apparatus capable of preventing wear of a stirrer that stirs a developer.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<Schematic configuration of image forming apparatus>
First, an image forming apparatus 1 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic side view showing a schematic configuration of the image forming apparatus 1 according to the present embodiment.

  As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment includes a photosensitive drum 10, a developing roller 20, and a stirring unit 30.

  The photosensitive drum 10 is an electrostatic latent image carrier on which an image is formed on the peripheral surface, and is made of, for example, OPC (Organic PhotoConductor). Around the photosensitive drum 10, a charging unit (not shown) for charging the photosensitive drum 10 and an exposure unit (not shown) for exposing the peripheral surface of the charged photosensitive drum 10 to form an electrostatic latent image. 1), a stirring unit 30 for stirring the developer, a developing roller 20 for developing the electrostatic latent image formed on the photosensitive drum 10, and a cleaning unit (not shown) for cleaning the peripheral surface of the photosensitive drum 10. ) And a static elimination lamp (not shown) for resetting the potential of the photosensitive drum 10 is disposed.

  The developing roller 20 is a developer carrier that supplies toner to the electrostatic latent image formed on the photosensitive drum 10. The developing roller 20 includes a magnet roller 210 and a developing sleeve 220. As shown in FIG. 1, the magnet roller 210 has, for example, five magnetic poles (magnetic poles S 1, S 2, N 3, S 3, N 1), Different magnetic poles are alternately arranged in the development area for developing the formed electrostatic latent image. On the other hand, the same magnetic pole is arranged adjacent to the position facing the stirring unit 30. The developing sleeve 220 is a cylindrical member made of a nonmagnetic metal. In the developing roller 20 according to the present embodiment, only the developing sleeve 220 rotates, and the magnet roller 210 disposed in the developing sleeve 220 is fixed to the housing 5. Further, the developing roller 20 is provided with a developing bias applying unit (not shown) for applying a developing bias.

  The agitation unit 30 is a unit that agitates a magnetic carrier and a non-magnetic or weak magnetic toner constituting the developer to charge the carrier and the toner. For example, as shown in FIG. 1, the agitation unit 30 includes a first agitation conveyance unit 310 and a second agitation conveyance unit 320. The developer conveyed while being agitated by the second agitating and conveying unit 320 moves to the peripheral surface of the developing roller 20 while being agitated and conveyed by the first agitating and conveying unit 310. In this embodiment, the carrier is positively charged and the toner is negatively charged. The second agitating and conveying unit 320 is provided with a toner concentration sensor 340 for detecting the toner concentration. When the toner concentration in the conveying path decreases, the developer is supplied from the developer supplying unit 50 into the conveying path. Is done. The detailed configuration of the stirring unit 30 will be described later.

  In such an image forming apparatus 1, first, the peripheral surface of the photosensitive drum 10 is charged by the charging unit, and the potential of the peripheral surface of the photosensitive drum 10 becomes about −600 V, for example. Next, the peripheral surface of the charged photosensitive drum 10 is exposed by an exposure unit to form an electrostatic latent image. The exposed portion of the peripheral surface of the photosensitive drum 10 has a low potential, for example, about -100V. Further, the electrostatic latent image formed on the photosensitive drum 10 is developed in the development area. At this time, a developing bias of about −500 V is applied to the developing roller 20, and the negatively charged toner is transferred from the developing roller 20 to the exposed portion of the photosensitive drum 10 due to the potential difference with the photosensitive drum 10. As a result, a toner image is formed.

  When the toner image is formed, the photosensitive drum 10 is rotated to convey the toner image to a region where the transfer roller (not shown) and the photosensitive drum 10 face each other. A transfer bias is applied to the transfer roller, and the toner image is transferred to the transfer belt by the potential difference between the transfer roller and the photosensitive drum 10. Thereafter, the developer remaining on the photoconductor drum 10 is collected by the cleaning unit, and the electric potential of the photoconductor drum 10 is reset by the charge eliminating lamp.

  The schematic configuration of the image forming apparatus 1 according to the present embodiment has been described above. Next, based on FIGS. 2 to 5, the configuration of the stirring unit 30, which is a characteristic part of the present embodiment, in the image forming apparatus 1 according to the present embodiment will be described in detail. FIG. 2 is a partial cross-sectional view of the image forming apparatus 1 according to the present embodiment. 3 is a cross-sectional view taken along the line AA in FIG. 4 is a cross-sectional view taken along the line BB of FIG. 5 is a cross-sectional view taken along the line CC of FIG.

<Configuration of stirring unit>
As shown in FIG. 2, the stirring unit 30 of the image forming apparatus 1 according to the present embodiment includes a developer tank 331, a first stirring and conveying unit 310 provided in the developer tank 331, and a second stirring unit. Conveying unit 320. The developer tank 331 is a container for storing the developer to be stirred, and the developer tank 331 according to the present embodiment is connected to the housing 5 of the image forming apparatus 1 and provided integrally therewith. To do. In the present embodiment, the first agitation transport unit 310 and the second agitation transport unit 320 are arranged up and down so that the support shafts 314 and 324 of the agitation transport units 310 and 320 are parallel to each other. Further, in the first agitation transport unit 310, the first agitation transport unit 310 and the support shaft 211 that supports the magnet roller 210 of the developing roller 20 are parallel to each other on the substantially opposite side of the second agitation transport unit 320. Further, it is disposed adjacent to the developing roller 20.

  The first agitation transport unit 310 includes a first cylindrical member 311, a first agitation blade 312, a first agitation magnet 313, and a first support shaft 314. Both ends of the first tubular member 311 are fixed to the inner wall of the developer tank 331 and the hollow part is provided so as to communicate with the outside of the developer tank 331.

The first stirring blade 312 is provided on the outer peripheral surface of the first cylindrical member 311 and has a spiral inclined surface with respect to the longitudinal direction of the first stirring magnet 313. The first stirring blade 312 is not formed in a region facing the developing roller 20 so as not to hinder the transfer of the developer performed between the first stirring and conveying unit 310 and the developing roller 20. In the present embodiment, as shown in FIG. 3, for example, the outer periphery of the first cylindrical member 311 located on the opposite side of the center C _{2 of} the first stirring magnet 313 from the rotation center C ₁ of the developing roller 20. A first stirring blade 312 is formed in a region of the surface at a predetermined angle θ (for example, about 200 ° to 215 °). Further, as shown in FIG. 2, the first stirring blade 312 may not be provided at a position where the developer supplied from the developer supply unit 50 falls.

  The first stirring magnet 313 is a substantially columnar magnet formed by alternately arranging different magnetic poles in the circumferential direction. For example, as shown in FIG. 3, the four magnetic poles are centered on the first support shaft 314. (Magnetic poles S1a, N1a, S1a, N2a) are arranged. The first stirring magnet 313 is inserted into the first cylindrical member 311. The first support shaft 314 is rotatably supported by the first bearing portion 316 and is connected to an external drive unit (not shown) via a connecting portion 317. That is, the first stirring magnet 313 is rotationally driven by the external driving unit inside the first cylindrical member 311.

As described above, the first agitation transport unit 310 is disposed to face the developing sleeve 220 of the developing roller 20. Here, a magnetic shielding member 335 that shields magnetism is provided between the first cylindrical member 311 and the developing roller 20. The magnetic shielding member 335 is a member that prevents the developer from moving from the first agitating and conveying unit 310 to the developing roller 20, and is, for example, a nonmagnetic member such as aluminum or SUS or a member that shields magnetism such as resin. Become. The magnetic shielding member 335 is a region where the first cylindrical member 311 and the developing roller 20 face each other, and is a line connecting the rotation center C ₁ of the developing roller 20 and the center C _{2 of} the first stirring magnet 313. Is provided further downstream in the rotation direction of the developing roller.

  The second agitating and conveying unit 320 is configured in substantially the same manner as the first agitating and conveying unit 310, and includes a second cylindrical member 321, a second agitating blade 322, a second agitating magnet 323, And a second support shaft 324. The second cylindrical member 321 is provided so that both ends are fixed to the inner wall of the developer tank 331 and the hollow part communicates with the outside of the developer tank 331.

  The second stirring blade 322 is provided on the outer peripheral surface of the second cylindrical member 321 and has a spiral inclined surface with respect to the longitudinal direction of the second stirring magnet 323. The second stirring blade 322 is formed so as to make a round around the second cylindrical member 321.

  The second stirring magnet 323 is a substantially cylindrical magnet formed by alternately arranging different magnetic poles in the circumferential direction. For example, as shown in FIG. 3, the four magnetic poles are centered on the second support shaft 324. (Magnetic poles S1b, N1b, S1b, N2b) are arranged. The second stirring magnet 323 is inserted into the second cylindrical member 321. The second support shaft 324 is rotatably supported by the second bearing portion 326 and is connected to an external drive unit (not shown) via a connecting portion 327. That is, the second stirring magnet 323 is driven to rotate inside the second cylindrical member 321 by an external driving unit.

  In the second agitation transport unit 320 according to the present embodiment, a protrusion 328 is formed on the outer peripheral surface of the second cylindrical member 321 in order to increase the developer agitation efficiency. Providing the protrusions 328 prevents the developer from moving in the circumferential direction of the second cylindrical member, so that the developer can be further stirred. In the present embodiment, one protrusion 328 is provided on the second stirring and conveying unit 320 as an obstructing member that hinders the flow of the developer. However, the present invention is not limited to this example. An inhibiting member may be provided. The shape of the inhibition member is not limited to the substantially plate-like protrusion as shown in FIG. Moreover, you may provide an obstruction member in the 1st stirring conveyance part 310. FIG.

  As shown in FIGS. 2 and 3, a partition wall 332 is provided between the first agitation transport unit 310 and the second agitation transport unit 320 to partition the agitation transport units 310 and 320. Accordingly, the space (path P3) surrounded by the developer tank 331, the partition 332, and the first cylindrical member 311 in which the developer is conveyed, the developer tank 331, the partition 332, and the second cylinder. A space (path P1) surrounded by the shaped member 321 is formed. In addition, the partition 332 is not formed on both ends in the longitudinal direction, and a space (path P3) in which the first agitation transport unit 310 is provided and a space (path P1) in which the second agitation transport unit 320 is provided. Communicates with both ends. Thus, paths P2 and P4 are formed that connect the space in which the first agitation transport unit 310 is provided and the space in which the second agitation transport unit 320 is provided.

  The path P2 functions as a developer moving area that moves the developer from the path P1 to the path P3, and the path P4 moves the developer from the path P3 to the path P1. In the present embodiment, developer guide plates 333 and 334 for guiding the developer are provided so that the developer is smoothly moved in the developer movement region.

  As shown in FIG. 4, the developer guide plate 333 is provided so as to connect the outer peripheral surface of the second cylindrical member 321 and the inner wall of the developer tank 331 on the first stirring and conveying unit 310 side. At this time, in order to guide the developer along the flow of the developer, the developer guide plate 333 extends upward along the rotational direction of the second stirring magnet 323 from the second cylindrical member 321 side. (Inclined leftward and upward in FIG. 4). On the other hand, as shown in FIG. 5, the developer guide plate 334 is provided so as to connect the outer peripheral surface of the first tubular member 311 and the inner wall of the developer tank 331 on the second stirring and conveying unit 320 side. . The developer guide plate 334 is provided so as to extend downward from the first cylindrical member 311 along the rotational direction of the first stirring magnet 313 (inclined diagonally to the left in FIG. 5). In addition, with this configuration, when the developer is moved from the moving source agitating and conveying unit to the moving destination agitating and conveying unit, the developer can be prevented from returning to the moving source agitating and conveying unit.

  Further, as described above, the second agitation transport unit 320 is provided with the toner concentration sensor 340 that detects the toner concentration in the space (path P1) in which the second agitation transport unit 320 is provided. When the toner concentration in the path P1 decreases, the developer is supplied into the transport path from the developer supply unit 50 provided above one end of the first agitation transport unit 310. The developer supplied from the developer supply unit 50 is supplied to the first agitation transport unit 310 via a developer supply pipe 510 in which a supply screw 520 is provided.

<Operation of stirring unit>
Next, based on FIG. 6, the developer stirring and conveying action by the stirring unit 30 according to the present embodiment will be described. In addition, FIG. 6 is explanatory drawing for demonstrating the effect | action of the stirring unit 30 concerning this embodiment.

  The agitation unit 30 according to the present embodiment moves the developer in a space in which the first agitation transport unit 310 and the second agitation transport unit 320 are provided. First, the developer located in the space (path P1) in which the second stirring and conveying unit 320 is provided is conveyed from right to left in FIG. When the second stirring magnet 323 provided inside the second cylindrical member 321 is rotated, for example, to the back side in FIG. 6, the developer that is offset downward by gravity is caused by the magnetic force of the second stirring magnet 323. The second stirring magnet 323 rotates on the outer peripheral surface of the second cylindrical member 321 in the rotational direction. As a result, the developer is offset from the bottom surface of the developer tank 331 to the side surface downstream of the second stirring magnet 323 in the rotation direction. The developer offset to the side surface side is pushed by the second stirring blade 322 and moves in the axial direction of the second support shaft 324 (longitudinal direction of the second stirring and conveying unit 320).

  In this manner, the force that rotates the developer in the circumferential direction of the second cylindrical member 321 is converted into the moving force in the axial direction of the second support shaft 324 by the second stirring blade 322, thereby developing the developer. The agent moves along the path P2 from the right to the left in FIG. Here, in the present embodiment, the first agitating and conveying unit 310 is located above the second agitating and conveying unit 320, and therefore the developer conveyed from the right to the left in FIG. 6 by the second agitating and conveying unit 320. Stays at the left end and becomes clogged. When the developer is clogged, pressure is applied to the developer and the developer deteriorates. Further, the developer moved to the left end portion of the second agitating / conveying section 320 moves to a space (path P3) in which the first agitating / conveying section 310 is provided via a path P2 which is a developer moving area. However, the developer must be moved against gravity.

  Therefore, in the present embodiment, by making the magnetic force of the first agitation transport unit 310 that is the movement source larger than the magnetic force of the second agitation conveyance unit 320 that is the movement destination in the developer movement region (path P2), Move the developer upward. In order to make the magnetic force of the first agitation transport unit 310 in the developer movement region (path P2) larger than the magnetic force of the second agitation transport unit 320, for example, the second agitation in the developer movement region (path P2). The diameter of the magnet 323 is made smaller than the diameter of the first stirring magnet 313, the diameter of the second cylindrical member 321 is made larger than the diameter of the first cylindrical member 311, or the second cylindrical member It can be set by providing a magnetic shielding member on the inner peripheral surface of 321. By forming the state in which the magnetic force acts in this way, the developer can be moved to the space where the first agitation transport unit 310 is provided via the developer moving area.

  In addition, as described above, in this embodiment, the developer guide plate 333 is provided that couples the outer peripheral surface of the second cylindrical member 321 and the inner surface of the developer tank 331 provided with the first agitating and conveying unit 310. Thus, the developer can be moved upward along the flow of the developer formed by the rotation of the second stirring magnet 323 and the first stirring magnet 313.

  Further, in the stirring unit 30 according to the present embodiment, a gap is formed between the outer edge portion of the second stirring blade 322 and the inner surface of the developer tank 331 and the partition wall 332. This is formed to release the pressure applied to the developer when the developer is moved from the right to the left by the second agitating and conveying unit 320 and stays at the left end. Thereby, deterioration of the developer can be reduced. A gap is similarly formed between the first stirring blade 312 and the partition wall 332.

  Next, the developer conveyed to the space in which the first agitation conveyance unit 310 is provided via the developer movement region (path P2) is the first agitation provided in the first cylindrical member 311. By the magnetic force of the magnet 313, the path P3 is conveyed from left to right in FIG. Similarly to the developer conveyance in the path P1, the developer conveyance in the path P3 is caused by the first developer magnet 313 rotating toward the front side of FIG. The magnetic force of the stirring magnet 313 causes the first stirring magnet 313 to rotate in the rotation direction on the outer peripheral surface of the first cylindrical member 311. As a result, the developer is shifted to the inner surface of the developer tank 331 on the downstream side in the rotation direction of the first stirring magnet 313 from the wall surface 332. The developer offset to the inner side is pushed by the first stirring blade 312 and moves in the axial direction of the first support shaft 314 (longitudinal direction of the first stirring and conveying unit 310).

  The developer conveyed along the path P3 moves to the developing roller 20 side and adheres to the peripheral surface of the developing sleeve 220 in a region facing the developing roller 20. At this time, the pitch of the first stirring blades 312 (the length in the axial direction when the stirring blade rotates once in the circumferential direction of the cylindrical member) so that sufficient developer is supplied to the developing roller 20 is: The pitch may be larger than the pitch of the second stirring blades 322. By increasing the pitch of the stirring blades, the developer transport amount can be increased.

  The developer conveyed to the right end portion of the path P3 by the first agitating / conveying section 310 passes to the space (path P1) where the second agitating / conveying section 320 is provided via the path P4 which is a developer moving area. Moved. Since the developer moves from the first stirring and conveying unit 310 to the second stirring and conveying unit 320 from the top to the bottom, the developer may be dropped according to gravity. At this time, by making the magnetic force of the first stirring magnet 313 in the developer moving area (path P4) zero or small, the developer is released from the restriction by the magnetic field at the movement source, and the developer can be made easier. Can be moved to the space (path P1) in which the second agitating and conveying unit 320 is provided. In this case, the diameter of the first stirring magnet 313 in the developer movement region (path P4) is reduced, the diameter of the first cylindrical member 311 is increased, or the inner peripheral surface of the first cylindrical member 311 is used. What is necessary is just to provide a magnetic shielding member in this.

  In addition, as described above, in the present embodiment, the developer guide plate 334 that couples the outer peripheral surface of the first cylindrical member 311 and the inner surface of the developer tank 331 provided with the second stirring and conveying unit 320 is provided. Thus, the developer can be moved downward along the flow of the developer formed by the rotation of the first stirring magnet 313 and the second stirring magnet 323.

  A developer supply pipe 510 that conveys the developer supplied from the developer supply unit 50 to the stirring unit 30 is provided above the right end portion of the first agitation transport unit 310. The developer supplied from the developer supply unit 50 according to the toner density in the path P1 detected by the toner density sensor 340 is supplied from the developer supply pipe 510 to the developer tank from above the developer moving area (path P4). 331. Therefore, the developer conveyed by the first agitation conveyance unit 310 and the developer put in from the developer supply unit 50 are both in the second agitation conveyance unit 320 via the developer movement region (path P4). Is transported from the right to the left while being agitated by the second agitating and conveying unit 320 in the path P1.

  As described above, in the stirring unit 30 according to the present embodiment, the space (path P3) formed by the developer tank 331, the partition 332, and the first cylindrical member 311, the developer tank 331, the partition 332, and the second A space (path P1) formed by the cylindrical member 321 and a developer movement area (paths P2, P4) formed by communicating both ends of the paths P1, P3 are formed. Then, the toner and the carrier are charged and uniformly stirred by transporting the developer while stirring the path P1, the path P2, the path P3, the path P4, the path P1,. And provided to the developing roller 20.

  In the stirring unit 30, the magnetic force of the stirring magnets 313 and 323 inserted into the cylindrical members 311 and 321 acts on the developer on the outer peripheral surface of the cylindrical members 311 and 321, thereby moving the developer. . That is, the developer moves on the outer peripheral surfaces of the non-rotating cylindrical members 311 and 321 and is not in contact with the agitating magnets 313 and 323 for applying a moving force to the developer. Therefore, the developer does not flow into the bearing portions 316 and 326 that rotatably support the support shafts 314 and 324 to which the stirring magnets 313 and 323 are fixed. For this reason, the bearing portions 316 and 326 are not worn by the inflow of the developer, and the life of the bearing portions 316 and 236 can be extended.

  Furthermore, the movement of the developer can be easily controlled by changing the magnitude of the magnetic force of the stirring magnet according to the position where the stirring magnet is disposed. In this embodiment, in the developer movement region, the developer is moved to a destination by making the magnetic force of the stirring magnet 313 (323) to which the developer is moved larger than the magnetic force of the stirring magnet 323 (313) that is the movement source. It is comprised so that it may be attracted | sucked to the stirring magnet side. Thereby, it is possible to smoothly deliver the developer in the developer moving area.

  The image forming apparatus 1 according to the embodiment of the present invention has been described above. In the image forming apparatus 1 of the present invention, the agitating magnets 313 and 323 are inserted in the cylindrical members 311 and 321 so that the developer in the space provided with the agitating and conveying units 310 and 320 is not in contact with the developer. It is characterized in that it is transported while stirring by rotating. With this configuration, the developer moves on the outer peripheral surfaces of the fixed cylindrical members 311 and 321, and therefore does not contact the rotating stirring magnets 313 and 323, and the support shaft on which the stirring magnets 313 and 323 are fixed. It does not flow into the bearing portions 316 and 326 that support 314 and 324. As a result, wear of the bearing portions 316 and 326 can be prevented, and the life of the stirring unit 30 can be extended, and further, the life of the entire image forming apparatus 1 can be extended.

  Further, the magnetic force of the stirring magnet 313 (323) to which the developer is moved is configured to be larger than the magnetic force of the moving stirring magnet 323 (313). Thereby, it is possible to smoothly deliver the developer in the developer moving area. In particular, even when the agitating / conveying units 310 and 320 are arranged vertically, the developer can be delivered without any problem, so that the agitating unit layout can be made flexible.

  In the image forming apparatus 1 of the present embodiment, a developer layer is formed on the developing roller 20 using the developer supplied from the stirring unit 30, and a magnetic brush is formed between the developing roller 20 and the photosensitive drum 10. And the toner is supplied to the electrostatic latent image on the photosensitive drum 10 by a magnetic brush. However, the present invention is not limited to this example. For example, a toner supply roller is provided between the developer agitator and the development roller, a developer layer is formed on the toner supply roller using the toner supply roller as a developer carrier, and the developer on the toner supply roller. The stirrer according to this embodiment is also applied to an image forming apparatus configured to supply toner from a layer to a developing roller to form a toner layer on the developing roller to develop an electrostatic latent image on the photosensitive drum. Can be applied.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the above-described embodiment, two agitation transport units are provided in the developer tank. However, the present invention is not limited to such an example, and one or three or more agitation transport units may be provided. .

  In the above-described embodiment, one or two or more agitation transport units are provided inside the developer tank, and a partition wall is provided between adjacent agitation transport units. However, the present invention is limited to this example. For example, a stirring unit is configured by connecting a plurality of units each provided with one agitation transport unit inside one cylindrical developer tank and opening the connected surfaces of the units at both ends. You can also.

1 is a schematic side view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a partial cross-sectional view of the image forming apparatus according to the embodiment. FIG. It is sectional drawing in the AA cutting line of FIG. It is sectional drawing in the BB cutting line of FIG. It is sectional drawing in the CC cut line of FIG. It is explanatory drawing for demonstrating the effect | action of the stirring unit concerning the embodiment. It is a fragmentary sectional view which shows the bearing part of the shaft in the conventional stirrer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Photosensitive drum 20 Developing roller 210 Magnet roller 220 Developing sleeve 30 Stirring unit 310 1st stirring conveyance part 311 1st cylindrical member 312 1st stirring blade 313 1st stirring magnet 314 1st Support shaft 320 Second agitating and conveying unit 321 Second cylindrical member 322 Second agitating blade 323 Second agitating magnet 324 Second supporting shaft 328 Protruding portion 331 Developer tank 340 Toner concentration sensor 50 Developer supplying portion

Claims (11)

A developer carrying body having a magnet roller composed of a plurality of magnetic poles inside and carrying a developer composed of carrier and toner on the peripheral surface;
A developer agitator that agitates the developer and supplies the developer to the developer carrier;
An image forming apparatus comprising:
The developer stirrer
A developer tank;
A cylindrical member that communicates between the hollow portion and the outside of the developer tank and is fixed in the developer tank;
A magnet shaft that is rotatably inserted into the cylindrical member and is formed by alternately arranging different magnetic poles in the circumferential direction;
A stirring blade provided on the outer peripheral surface of the cylindrical member and having a spiral inclined surface with respect to the axial direction of the magnet shaft,
Along with the rotation of the magnet shaft, the magnetic force of the magnet shaft rotates the developer on the outer peripheral surface of the cylindrical member in the rotation direction of the magnet shaft, and the developer is removed by the inclination of the stirring blade. Transport in the longitudinal direction of
The image forming apparatus, wherein the stirring blade is not formed in a region facing the developer carrying member.   The image forming apparatus according to claim 1, wherein the developer tank has an opening formed in a region facing the developer carrier. The image forming apparatus according to claim 1 , wherein a magnetic shielding member is provided between the developer carrier and the cylindrical member. Comprising at least two agitating and conveying parts composed of the cylindrical member and the magnet shaft, and a partition wall provided between the adjacent agitating and conveying parts,
Each agitating and conveying part is arranged so that the longitudinal direction of the cylindrical member of each agitating and conveying part is parallel,
The image forming apparatus according to claim 1, wherein the developer conveying directions by the agitating and conveying units adjacent to each other are different. The image forming apparatus according to claim 4 , wherein the agitation conveyance unit is inserted into a cylindrical conveyance path constituted by the developer tank and the partition wall. The developer can move from one stirring and transporting unit to the other stirring and transporting unit by connecting the stirring transporting unit adjacent to each other by opening the partition at both ends of the stirring and transporting unit. A developer transfer area is formed,
In at least one developer movement region, the magnetic force on the outer peripheral surface of the cylindrical member from which the developer moves is smaller than the magnetic force on the outer peripheral surface of the cylindrical member to which the developer moves. The image forming apparatus according to claim 4 or 5 . The image forming apparatus according to claim 4 , wherein the two magnet shafts of the agitating and conveying units adjacent to each other rotate so that different magnetic poles face each other. The developer moving region is provided with a developer guide plate that couples an outer peripheral surface of the cylindrical member from which the developer moves and an inner surface of the developer tank to which the developer moves. An image forming apparatus according to claim 6 or 7 . The image forming apparatus according to claim 1 , wherein the cylindrical member is provided with an obstruction member that obstructs the flow of the developer in the rotation direction of the magnet shaft. The image forming apparatus according to claim 1, wherein at least one hole is formed in the stirring blade. The image forming apparatus according to claim 1 , wherein the stirring blade is provided so as not to contact an inner surface of the developer tank.

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