JP2013011797A - Development apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a development apparatus having a structure capable of preventing a defective image such as a void image from being generated.SOLUTION: The development apparatus has a developer supply member 304 capable of supplying a developer to a developing sleeve 302, a developer recovery member 305 for agitating the developer recovered from the developing sleeve 302, and a layer thickness regulation member 303 mounted on the developing sleeve for making the layer thickness of the developer uniform. In a developing container 301 where the developer supply member and the developer recovery member are arranged above and below respectively with respect to the rotation center of the developing sleeve, a partition part 306 for partitioning between the developer supply member 304 and the developer recovery member 305 while having an area C for storing the developer to be delivered from the developer supply member 304 toward the layer thickness regulation member 303. In the inside of the partition part 306, magnetic field generating means 312 for circulating the developer staying between the partition part 306 and the developer supply member 304 opposed to the partition part 306 is rotatably provided.

Description

  The present invention relates to a developing device and an image forming apparatus, and more particularly, to a developing mechanism that uses a two-component developer containing toner and a carrier.

In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a printing machine, an electrostatic latent image formed on a photosensitive member as a latent image carrier is subjected to visible image processing by a developing device, and the visible image is converted into a sheet. A recording output can be obtained by transferring to the above.
As a developer used for development, there is a two-component developer obtained by mixing a toner and a carrier in addition to a one-component developer containing only magnetic or non-magnetic toner.
The two-component developer is composed of a toner and a carrier that carries the toner, and the toner can be electrostatically attracted to the electrostatic latent image on the photosensitive member by charging the toner by a frictional charging effect that occurs during stirring and mixing. It is said.

  In the developing device, a developing sleeve as a developer carrying member for supplying developer toward the electrostatic latent image on the photosensitive member by causing the developer to rise on the peripheral surface by magnetic force, and agitating and mixing the developing sleeve A configuration including a stirring member such as a screw auger for supplying a developer is known.

  On the other hand, the amount of developer supplied to the developing sleeve is set according to the layer thickness of the developer so that the amount carried on the developing sleeve is set. The structure using this is known (for example, Patent Documents 1 and 2).

  In recent years, high image quality and high speed have been demanded, and as one method for realizing this, the use of finer toner toner has been proposed, and the temperature rise during fixing has been proposed. In order to speed up the process, it has also been proposed to use a toner used for fixing, that is, a toner having a low melting point.

  On the other hand, as a configuration for reducing the size of the apparatus, a screw auger as shown in FIG. 10 is arranged in parallel with the screw as shown in FIG. 2 used for explaining the embodiment of the present invention. A configuration has been proposed in which augers are juxtaposed in the vertical direction to reduce the occupied space in the horizontal direction (for example, Patent Document 3).

In a developing device having the above-described configurations, a defective image such as an image may be generated due to the aggregation of the developer as the developer is stirred and conveyed.
That is, among the screw augers arranged side by side in the vertical direction as shown in FIG. 2, in the screw auger which is the side supplying the developer to the developing sleeve, the development is performed from one side in the axial direction to the other side. Although the developer is transported, on the downstream side in the transport direction, the transport amount of the developer decreases due to the fact that it has shifted to the developing sleeve side so far.

  Since such a change in the conveyance amount causes density unevenness, if the rotation speed of the corresponding screw auger is increased to prevent the shortage of the developer, the frictional heat at the rotation support portion of the screw auger due to the increase in the rotation speed is caused. The temperature rises due to the increase, and a new problem arises that the toner caused by wrinkles tends to harden and aggregate.

  In addition to the temperature increase of the screw auger, the toner agglomeration is caused by frictional heat generated in the toner when pushed by the screw blades, thereby causing dead holes such as the inner walls of the containers constituting the screw blades and the developer conveyance path. When vibration or the like acts in the space, it falls off from the inner wall, and as shown by symbol P1 in FIG. B, it is caught in the gap between the developing sleeve and the doctor blade as the layer thickness regulating member, and the developer in this portion A blank image is generated due to insufficient supply.

  An object of the present invention is to provide a developing device and an image forming apparatus having a configuration capable of preventing the occurrence of a defective image such as a blank image in view of the problems in the conventional developing device.

In order to achieve this object, the present invention has the following configuration.
(1) A rotatable developing sleeve that supplies developer to the electrostatic latent image formed on the electrostatic latent image carrier, a developer supply member that can supply developer to the developing sleeve, and A developer collecting member that stirs the developer collected from the developing sleeve and a layer thickness regulating member that is carried on the developing sleeve and that makes the layer thickness of the developer constant are provided, and the developer supplying member and the developing member A developing device including a developer container in which the agent recovery member is disposed above and below the rotation center of the developing sleeve;
The developer container is provided with a partition portion that partitions the developer supply member and the developer recovery member and has a region for storing the developer from the developer supply member toward the layer thickness regulating member, A developing device characterized in that a magnetic field generating means for causing a developer to flow between the partitioning portion and the developer supply member facing the partitioning portion is rotatably provided inside the partitioning portion.

(2) The developing device according to (1), wherein the magnetic field generating means is composed of a member that rotates in the same direction as the developer supplying means.

(3) The developing device according to (1) or (2), wherein the magnetic field generating means has the same rotational speed as that of the developer supply member.

(4) An image forming apparatus comprising the developing device according to any one of (1) to (3).

According to the present invention, the magnetic field generating means causes the developer aggregated due to the temperature rise of the developer supply member or the scraping load from the layer thickness regulating member to stay in the gap between the container inner wall and the developer supply member. This can be prevented by flowing the magnetic field.
As a result, accumulation of the developer to be supplied to the developing sleeve at that portion is prevented by accumulating in the gap, and the occurrence of abnormal images such as blank images due to insufficient supply of the developer is prevented. Is possible.

FIG. 2 is a schematic diagram for explaining an embodiment of an image forming apparatus using a developing device. It is a schematic diagram for demonstrating the principal part structure used for one Embodiment of a developing device. FIG. 3 is a schematic diagram for explaining an operation of a developing sleeve of the developing device shown in FIG. 2. FIG. 4 is a cross-sectional view for explaining the internal configuration of the developing sleeve shown in FIG. 3. FIG. 3 is a perspective view for explaining an installation structure and operation of a developer supply member and a developer recovery member used in the developing device shown in FIG. 2. FIG. 3 is an external view of the developing device shown in FIG. 2. FIG. 6 is a plan view showing a developer supply member and a developer recovery member shown in FIG. 5. FIG. 3 is a schematic view corresponding to FIG. 2 for describing a characteristic portion in an embodiment of the developing device. It is an enlarged view of the characteristic part shown in FIG. It is a schematic diagram which shows one of the prior art examples regarding the arrangement structure of the developer supply member and developer collection member used for a developing device.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the embodiments shown in the drawings.
FIG. 1 is a diagram showing a configuration according to an embodiment of an image forming apparatus using a developing device. In FIG. 1, the image forming apparatus has the following configuration.
The image forming apparatus shown in FIG. 1 includes a plurality of image forming units 17K, 17M, 17Y, and 17C in order from the upstream side in the moving direction (conveying direction) of the conveying belt 15 along the conveying belt 15 that conveys the transfer paper 8. This is a color image forming apparatus that is so-called tandem type that is arranged. 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 color image forming unit is formed of a combination of a plurality of members to form an image. It 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 the 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 a member described later with reference to FIG. Those members having the same configuration function are denoted by the same reference numerals as those in FIG. 2 and subsequent figures, and are denoted by the photosensitive member 1K, the charging device 2K, the developing device 3K, and the like.
A transfer device 5K is arranged on the back side of the upper stretched portion of the conveyor belt 15, and a writing means 16 is provided as means for irradiating the photosensitive member 1 with exposure light L to form an electrostatic latent image. Is provided.

When forming a color image, the image forming unit 17K uniformly charges the peripheral surface of the photoreceptor 1K by the charging device 2K in the dark, and then exposes the exposure light corresponding to the black image from the optical scanning device 16K. L is exposed to form 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 at a position where the photosensitive member 1K and the transfer paper 8 on the transport belt 15 come into contact, that is, a so-called transfer position. A monochromatic (black) image is formed on top. After the transfer, the photosensitive member 1K is freed of unnecessary toner remaining on the peripheral surface of the photosensitive member 1K 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 passes through the image forming portion 17C, is peeled off from the conveying belt 15, and is fixed by the fixing portion 24 while passing between the pair of fixing rollers. The paper is discharged to the paper tray 25.

FIG. 2 is a diagram showing the configuration of the image forming unit. In FIG. 2, the image forming unit 17 (for the sake of convenience, omitting the alphabet for distinguishing colors) is provided with a photosensitive member 1 that is rotatable in the direction of the arrow. Around the photosensitive member 1, there are a charging device 2 used for image forming processing along the rotation direction of the photosensitive member 1, an exposure device (scanning light is indicated by L for convenience), a developing device 3, and a transfer device 5. , A cleaning device 6 is arranged.
The charging device 3 is arranged on the top of the photosensitive member 1 at a position of about 12:00 on the dial of the watch. In this example, the charging device 2 is composed of a rotating body that rotates at the same speed as the photosensitive member. However, the charging device 2 is not limited to the rotating member, and may be a corona discharge type.

  The surface of the photosensitive member 1 is uniformly charged in the dark by the charging device 2, and then an electrostatic latent image is formed by irradiation with exposure light L from writing means (not shown). The electrostatic latent image formed on the photosensitive member 1 by charging moves downstream as the photosensitive member 1 rotates and reaches the developing device 3. The developing device 3 is disposed on the right side of the photoreceptor 1 in FIG.

  The developing device 3 is disposed vertically in the rotation center O-2 of the rotatable developing sleeve 302 in a casing 301 corresponding to a developing container having a space capable of accommodating the developer, and stirs and conveys the developer 320. It corresponds to a supply chamber conveyance member 304 corresponding to a developer supply member capable of pumping the developed developer toward the development sleeve 302 and a developer recovery member that collects the developer after development from the development sleeve 302 and conveys it with stirring. A layer thickness regulating member 303 such as a doctor blade is provided to make the layer thickness of the developer carried on the collection chamber conveying member 305 and the developing sleeve 302 constant.

  A supply chamber conveyance member 304 corresponding to the developer supply member and a collection chamber conveyance member 305 corresponding to the developer recovery member are extended from the inner wall of the container toward the space between both conveyance members in the casing 301 by the supply chamber conveyance member 304. The developer is drawn up and separated from the supply chamber side and the collection chamber side by a partition plate 306 corresponding to a partition portion having a space C for storing the developer toward the layer thickness regulating member 303.

As described above, the developing sleeve 302 is opposed to the photosensitive member 1 at a position between 2 o'clock and 3 o'clock (position of 2:30) when expressed in a clock face, so that the developing nip region A is formed. They are arranged in close proximity so as to constitute.
A portion of the casing 301 corresponding to the portion facing the photoconductor 1 is opened to expose the developing sleeve 302.
The developer 320 in the casing 301 is conveyed to the development nip region A by the development sleeve 302. The toner in the developer 320 adheres to the electrostatic latent image formed on the surface of the photoreceptor 1 in the development nip region A, and is visualized as a toner image. The toner image subjected to the visible image processing by the toner in the developer carried on the developing sleeve 302 moves to the downstream side with the rotation of the photosensitive member 1 and reaches the transfer device 5.

The transfer device 5 is arranged below the photosensitive member 1, that is, at the 6 o'clock position on the dial of the watch as described above.
In this embodiment, 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 photoreceptor 1 and the transfer device 5 face each other is referred to as 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 system in which the toner on the photoconductor is temporarily transferred to an intermediate transfer body (intermediate transfer belt, etc.) and then the color toners are transferred to a transfer paper in a lump. In the region B, the toner on the photosensitive member 1 is transferred to the intermediate transfer member (intermediate transfer belt 15).
After the transfer, the photosensitive member 1 moves downstream as the photosensitive member 1 rotates and reaches the cleaning device 6.

  The cleaning device 6 is arranged at the 10 o'clock position. 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.

  In the developing device 3, the developer transported and stirred by the supply chamber transport member 304 corresponding to the developer supply member is supplied to the developer sleeve 302 after the layer thickness is regulated by the layer thickness regulating member 303. It moves toward the recovery chamber transport member 305 corresponding to the agent recovery member, and is further recirculated to the supply chamber side where the supply chamber transport member is located.

  FIG. 3 is a diagram for explaining the details of the developing device 3. In FIG. 3, the supply chamber transport member 304 and the recovery chamber transport member 305 are provided with helical screws capable of stirring and transporting the developer. A screw blade having an outer diameter of 16 mm or less is used.

In FIG. 3, the developing sleeve 302 has a magnet roller 302 d in which a plurality of magnets MG (only one is indicated by a reference numeral for preventing complication of the drawing) arranged in the circumferential direction, and the periphery thereof is cylindrical. The sleeve 302c is configured to rotate integrally with the rotary 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 sleeve 302, the developing sleeve 302 is mainly composed of a fixed shaft 302a fixed to the stationary member casing 301, a magnet roller 302d having a cylindrical shape integrated with the fixed shaft 302a, and a magnet roller 302d. It comprises a sleeve 302c covering the periphery with a gap and a rotating shaft 302e integral with the sleeve 302c. 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 rotates around these magnets MG.
These magnets MG are for forming a magnetic field so that the developer 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 302d. Here, as shown in FIG. 3, a configuration of a magnet roller having three magnets MG in 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) facing the line connecting the center O-1 of the developing sleeve 302 and the center O-2 of the photosensitive member is referred to as a P1 pole (developing pole). The magnetic poles are referred to as P2 (casing counter pole) and P3 pole (developer regulating member counter pole) in the order of rotation of the developing sleeve 302 indicated by the direction.
The polarity is changed from the P1 pole to the N, S, and S poles, but these poles may have opposite polarities. The P1 pole is a development pole and faces the photoreceptor 1. P2 faces the casing, and P3 faces the developer regulating member.
The developing sleeve 302 and the photosensitive member 1 are not in direct contact with each other in the developing nip region A (see FIG. 1), but are opposed to each other while maintaining a developing gap GP at a constant interval suitable for development.

On the developing sleeve 302, the developer 320 is raised and brought into contact with the photosensitive member 1, so that toner is attached to the electrostatic latent image on the surface of the photosensitive member 1 to be visualized (visualized). )
In the developing device 3, a grounded bias power source is connected to the fixed shaft 302a in FIG. 2 (not shown).
The voltage of the power source VP connected to the fixed shaft 302a is applied to the sleeve 302c via a conductive bearing (not shown) and a conductive rotating shaft 302e in FIG. On the other hand, the lowermost conductive support constituting the photoreceptor 1 is grounded.

In the development nip area A shown in FIG. 2, an electric field for moving the toner separated from the carrier to the photosensitive member 1 side is formed, and the sleeve 302 c and the electrostatic latent image formed on the surface of the photosensitive member 1 are formed. The toner is moved toward the photoreceptor 1 side by the potential difference.
The illustrated developing device is an example in which the developing device is combined with an image forming apparatus of a writing method using exposure light L (see FIG. 1). The charging device 2 uniformly applies negative charges on the photosensitive member 1 and exposes the image portion with the exposure light L in order to reduce the writing amount. A so-called reversal development method is employed in which the latent image is developed with negative polarity toner. This is merely an example, and the polarity of the charged charge placed on the photoreceptor 1 is not a major problem in the development system.

After the development, the P2 pole conveys the developed developer 320 carried on the developing sleeve 302 to the downstream side along with the rotation of the developing sleeve 302 and draws it into the casing 301.
The P2 and P3 poles have the same polarity, and there is no magnetic force to rise between the P2 and P3 poles, so that the ears fall asleep, and the developer 320 that has been drawn around the developing sleeve 302 until then is separated from the developing sleeve 302. The action of “release” works.
The P2-P3 pole corresponding portion (region where the peak of the magnetic distribution curve is extremely low compared to the others) on the developing sleeve where the ears are lying is separated from the developing sleeve 302, and the agent separating region ( In FIG. 2, it is indicated by reference numeral 9).

The developer 320 having the toner adhered to the photosensitive member 1 has a lower toner concentration in the developer. Therefore, the developer having the lowered toner concentration does not leave the developing sleeve 302 and again enters the developing nip region A. When transported and subjected to development, there is a problem that a target image density cannot be obtained.
In order to prevent this, in this example, the developer is separated from the developing sleeve 302 in the agent separation region 9 after development. Thereafter, the developer separated from the developing sleeve 302 is sufficiently agitated and mixed in the casing 301 so as to obtain a target toner concentration and toner charge amount.
Thus, 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. At that time, in order to prevent the developer supplied from the supply chamber conveying member 304 disposed above the developing sleeve 302 from being directly pushed into the developer storage space C, the vehicle overcomes the inflow prevention wall. A measure is taken so that the developer is supplied to the developer storage space C (the flow-in prevention wall 311 is formed in a part of a partition plate 306 constituting a partition portion described later).

  The developer supplied to the storage space C is adjusted to a predetermined thickness by passing through the developer regulating member 303 located immediately downstream of the peak position of the P3 pole, and forms a magnetic brush. It is conveyed to area A. In addition, the P3 pole serves as a transport pole for transporting the developer.

Hereinafter, the arrangement configuration of each member will be described with reference to FIG. 5 showing the internal configuration of the developing device in an assembled state and FIG. 6 showing the disassembled state as necessary.
As shown in FIGS. 2 and 3, the supply chamber conveying member 304 is positioned around the developing sleeve 302 in the direction of 2 o'clock on the clock face with respect to the position of the developing sleeve 302. Has been placed. This position is also on the upstream side of the developer regulating member 303.

  As shown in FIGS. 5 and 6, the supply chamber conveying 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-302 a of the developing sleeve 302. The developer rotates in the clockwise direction indicated by an arrow, and is conveyed while stirring the developer as indicated by an arrow 11 from the back in the longitudinal direction of the center line O-304 toward the front. That is, the supply chamber conveyance member 304 conveys the developer in the axial direction from the near side to the far side by the rotation of the rotation shaft.

  The collection chamber conveyance member 305 is disposed in the vicinity of the agent separation region 9 at a position around the developing sleeve 302 and in the 4 o'clock direction of the developing sleeve 302. As shown in FIG. 5, the recovery chamber transport member 305 has a screw shape with a spiral around the rotation axis, and a center line O- parallel to the center line O-302a (see FIG. 2) of the developing sleeve 302. 5 is rotated counterclockwise as indicated by an arrow about 305 (see FIG. 2), and is indicated by an arrow 12 in FIG. 5 from the long side in the longitudinal direction of the center line O-305 (see FIG. 2) toward the near side. The developer is transported while stirring. That is, the collection chamber transport member 305 transports the developer from the back side to the front side opposite to the transport direction by the supply chamber transport member 304 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.
As shown in FIG. 5, the front end portions of the supply chamber transport member 304 and the collection chamber transport member 305 are set to be slightly in front of the front end portion of the developing sleeve 302 so as to be in front of the developing sleeve 302. The supply of developer at the side end is ensured.
Further, as shown in FIG. 6 and FIG. 7, a toner which will be described later is set so that the back end portions of the supply chamber transport member 304 and the recovery chamber transport member 305 are located on the back side with respect to the back end portion of the developing sleeve 302. Space for replenishment is secured. The developer regulating member 303 is installed according to the length of the developing sleeve 302.

2 and 3, a partition plate used as a partition between the supply chamber transfer member 304 and the recovery chamber transfer member 305 to shield the space around the supply chamber transfer member 304 and the space around the recovery chamber transfer member 305. 306 is supported inside the casing 301. As shown in FIG. 7, communication ports 307 and 308 are provided at both end portions of the partition plate 306.
In FIG. 5, the developer transported in the direction of arrow 12 by the recovery chamber transport member 305 is cut off along the side wall of the casing 301 at the end in the transport direction, and rises along the side wall. 7), the supply chamber transfer member 304 moves the upper transfer path along the supply chamber transfer member 304 along the arrow 14 (movement in the direction indicated by the arrow 11).
Similarly, the developer conveyed in the direction of the arrow 11 by the supply chamber conveying member 304 is lowered along the side wall via the communication port 308 in order to cut off the path at the side wall of the casing 301 at the end in the conveying direction. Then, the recovery chamber transfer member 305 moves along the arrow 13 to the lower transfer path along the recovery chamber transfer member 305 (moves in the direction indicated by the arrow 12).

  2 and 3, the developing device 3 carries the developer and rotates to visualize the electrostatic latent image formed on the photosensitive member 1, and the center line O− of the current developing sleeve 302. A supply chamber transport member 304 that rotates around a center line O-304 parallel to 302a and transports the developer in the longitudinal direction of the center line O-304 while stirring the developer, and a developer release agent that separates the developer from the developing sleeve 302. The developer is agitated in a direction opposite to the direction in which the supply chamber conveying member 304 conveys the developer by rotating around a center line 305 that is disposed in the vicinity of the region 9 and is parallel to the center line 302a of the developing sleeve 302. The recovery chamber transfer member 305 to be transferred while being transported between the supply chamber transfer member 304 and the recovery chamber transfer member 305 at both ends that shield the space around the supply chamber transfer member 304 and the space around the recovery chamber transfer member 305. Open And a structure having a partition plate 306 having a.

In the developing device 3, two developer agitating / conveying members 304 and 305 in the casing 301 that constitute a circulation conveyance path along arrows 11, 14, 12, and 13 in FIG. Therefore, the lateral (horizontal) size of the developing device can be reduced as compared with the prior art shown in FIG. 10 in which the two agitating and conveying members are arranged in the direction away from the developing sleeve (in the horizontal direction). it can.
Further, in the developing device 3 that is compact in the horizontal direction, the space around the supply chamber transport member 304 and the collection chamber transport member 305 is partitioned by the partition plate 306, so that the supply to the developing sleeve 302 is performed. Only the developer 320 in which the toner and the carrier are sufficiently agitated and mixed is supplied by the chamber conveying member 304, and the developer whose toner concentration has decreased immediately after development is merely agitated and conveyed by the recovery chamber conveying member 305, and immediately. Since the toner is not supplied to the developing sleeve 320, only the toner having a target charge amount is used for the developing sleeve 320, and high image quality can be obtained.

On the other hand, toner density management, which is one of developer management in the developing device 3, is performed by toner replenishment control.
The toner supply will be described as follows.
Since the developer 320 (see FIG. 2) 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.
Therefore, in the developing device 3, toner is replenished from the outside from a developer replenishing portion (not shown) provided in the vicinity of the rear end of the developing device 3 in FIG. 6.
In the replenishment at this portion, the replenished toner is not immediately used for development, but passes through the opening 308 shown in FIG. 6 and the collection chamber, that is, the collection chamber conveyance member 305 in FIG. It will be supplied to the space.
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 in which the collection chamber conveyance member 305 is disposed, only the developer 320 separated from the developing sleeve 302 is collected, and the toner is not supplied to the developing sleeve 302. Therefore, a developer having a non-uniform toner concentration that is not sufficiently stirred by the toner 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 sleeve 302, and the toner density is normalized before being conveyed to the front side of the developing device 3. The sheet is lifted up to the upper conveyance path, supplied to the developing sleeve 302 while being conveyed to the back side by the supply chamber conveying member 304, and used for development.

A toner density sensor used for toner replenishment control will be described as follows.
Although the details of the toner density sensor are not shown in the figure, the permeability sensor is provided at the lower part of the unit in FIG. 5 and can detect the mixing ratio of the magnetic carrier and the toner in the developer by the change in the permeability. It is used. Thereby, it can be determined that the toner concentration is insufficient when the carrier concentration of the developer (100-toner concentration), that is, the carrier content in the developer reaches a predetermined value or more. In this way, it is determined from the detected carrier concentration whether the toner concentration on the sensor is insufficiently optimized, and the amount of toner to be replenished is determined. The toner density sensor is disposed at the downstream end of the recovery chamber transport member 305 in the transport direction at the lower part of the unit.

By providing the toner concentration sensor at the downstream end of the collection chamber conveyance member 305 in the conveyance direction, stable carrier concentration detection is possible, that is, as indicated by arrows 11, 14, 12, and 13 in FIG. Since the developer is used for development before being transported to the back side by the supply chamber transport member 304, more developer is returned to the front side by the collection chamber transport member 305, and the developer 320 tends to accumulate on the near side. It is in.
For this reason, since the toner concentration sensor is disposed on the downstream side of the collection chamber conveying member 305, the developer is always filled above the sensor. Therefore, the toner concentration sensor is stably disposed at this position. Carrier concentration can be detected.

  Like the image forming apparatus shown in the figure, for each color of yellow, magenta, cyan, and black, a photosensitive member is arranged in the horizontal direction, and a charging device or a developing device is provided on each photosensitive member to form an electrostatic latent image. In a tandem type color image forming apparatus that obtains a full-color image by sequentially transferring to a transfer sheet after visualizing, developing devices 3K, 3M, and 3Y are respectively applied to the photoconductors 1K, 1M, 1Y, and 1C arranged in the horizontal direction. 3C is provided. For this reason, in order to reduce the size of the image forming apparatus, it is necessary to reduce the interval between the photosensitive members. For this purpose, it is also necessary to reduce the size of each developing device in the horizontal direction (lateral direction).

By using each developing device having the configuration described later, the lateral dimension of each developing device can be made smaller than that of the conventional one shown in FIG. 10, so that the image forming apparatus can be miniaturized.
In addition, as described above, these developing devices 3K, 3M, 3Y, and 3C are configured to include the agent separation region, the agent pumping region, the supply chamber conveyance member, the collection chamber conveyance member, the partition plate, and the like. Toner having a charge amount is used for development, and high image quality can be obtained. In addition, since the deterioration of the toner can be suppressed, it is possible to stably maintain the performance of the developer for a long period of time, and it is possible to provide a developing device having a long life and high durability. Such a benefit is not unique to the tandem full-color image forming apparatus, but can be obtained in a single-color image forming apparatus.

The features of the present embodiment will be described as follows with the image forming apparatus having the above developing device as an object.
FIG. 8 is a diagram showing a configuration of a developing device that is a characteristic part in the present embodiment. The developing device shown in FIG. 8 (using the reference numeral 3 described above for the sake of convenience) prevents inflow. A magnetic field generating means 312 is provided inside the wall.

When the developer is supplied to the developer reservoir C by the supply chamber conveying member 304 disposed above the developing sleeve 302, the casing 301 is pushed directly into the casing 301 after passing through the layer thickness regulating member 303. In order to solve the problem that the amount of the developer is not stable, a flow preventing portion 311 is formed in a part of the partition plate 306.
Since the developer supplied by the supply chamber conveying member passes over the inflow prevention portion 311 and is sent to the developer storage space C, the supply momentum is weakened and the developer amount can be kept constant by the layer thickness regulating member 303. It has a configuration.

The inflow prevention unit 311 is arranged with a certain distance from the supply chamber transfer member 304. If this interval is too large, the developer supplied by the supply chamber conveying member cannot flow over the preventing portion 311. On the other hand, even if it is too small, it is conceivable that the developer is stuck due to frictional heat due to contact of the supply chamber conveying member 304 due to rotational vibration or the like.
In the region indicated by reference numeral D, which is a dead space formed by the inflow prevention portion 311 and the supply chamber conveyance member 304, the developer stays without being replaced, and receives the developer conveyance pressure by the supply chamber conveyance member. As a result, it has been confirmed that it becomes a soft aggregate. Therefore, the region D is a portion where the developer stays.

  When the developer that has become a soft agglomerate leaves the region D for some reason and is supplied to the developer reservoir indicated by C in FIG. 8, the developer is formed in the gap between the layer thickness regulating member 303 and the developing sleeve 302. Since clogging occurs and it becomes impossible to pump up the developer at that portion, a problem such as a white streak image occurs due to the fact that the developer is not carried on a part of the surface of the developing sleeve 302. It was.

In the developing device 3 shown in FIG. 8, a magnetic field generating unit 312 is provided inside the inflow prevention unit 311.
The magnetic field generator 312 has three magnetic poles and is rotatably supported by the developing container.
The rotation direction is the same direction as that of the supply chamber conveyance member 304, and the developer in the D section can be conveyed to the developer storage section C by the rotation.

The three magnetic poles of the magnetic field generating means are the S pole, the N pole, and the N pole, respectively, but a 5-pole configuration is also conceivable. The configuration of the polarity can also be selected in a timely manner from the space where the magnetic field generating means can be arranged and the required magnetic flux density.
Further, the rotation speed is set to be the same as that of the supply chamber transfer member 304. The developer conveyance efficiency by the magnetic field generation means 312 can be increased by synchronizing the movements of the magnetic field generation means 312 and the supply chamber conveyance member 304 with the same rotation speed.

  In the configuration of the embodiment as described above, in the developer retention portion D, which is a dead space formed by the inflow prevention portion 311 and the supply chamber conveyance member 304, the developer flow occurs due to the rotation of the generating means 312. Is done. As a result, the stay of the developer is prevented, so that the stiffening at the time of the stay is eliminated, and it is possible to prevent the developer from becoming a soft aggregate in this portion. As a result, the state where the developer that has become a soft agglomerate is eliminated from reaching the developer reservoir C, so that a part of the developer carried on the developing sleeve 302 is not lost, and a white-out image is obtained. It is possible to obtain a good image in which the occurrence of this is prevented.

In particular, since the conveyance force due to the rotation of the magnetic field generating unit is easily applied to the developer, the flow of the developer in the developer retaining portion is promoted, and the replacement of the developer is promoted, so that the above-described operation can be obtained favorably. be able to.
In addition to fluidizing the developer entering the staying area D, the magnetic field generating means 312 flows in when taking out the developer that has entered the staying area D immediately after the start of the apparatus. It is also possible to arrange at a position other than the prevention unit 311, and it is also possible to arrange at a position where fluidization and scraping for preventing aggregation of the developer that has flowed in are combined.

DESCRIPTION OF SYMBOLS 1 Photoconductor 3 Developing apparatus 302 Developing sleeve 303 Layer thickness regulation member 304 Supply chamber conveyance member 305 Collection chamber conveyance member 306 Partition plate 312 Magnetic field generation means C Developer storage area D Developer retention area

JP 09-325596 A Japanese Patent No. 3944337 JP 2009-92911 A

Claims (4)

A rotatable developing sleeve that supplies developer to the electrostatic latent image formed on the electrostatic latent image carrier, a developer supply member that can supply developer to the developing sleeve, and the developing sleeve A developer collecting member that stirs the collected developer and a layer thickness regulating member that is carried on the developing sleeve and that makes the layer thickness of the developer constant; and the developer supply member and the developer collecting member And a developing device provided with a developing container disposed above and below the rotation center of the developing sleeve,
The developer container is provided with a partition portion that partitions the developer supply member and the developer recovery member and has a region for storing the developer from the developer supply member toward the layer thickness regulating member, A developing device characterized in that a magnetic field generating means for causing a developer to flow between the partitioning portion and the developer supply member facing the partitioning portion is rotatably provided inside the partitioning portion.   The developing device according to claim 1, wherein the magnetic field generating unit rotates in the same direction as the developer supply unit.   The developing device according to claim 1, wherein the magnetic field generating unit has the same rotational speed as that of the developer supply member.   An image forming apparatus comprising the developing device according to claim 1.

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