JP7073045B2 - Developer - Google Patents

Description

The present invention relates to a developing apparatus provided with a rotatable developer carrier that carries and conveys a developer containing toner and carriers .

An image forming apparatus using an electrophotographic method or an electrostatic recording method has a developing device that develops an electrostatic latent image formed on a photosensitive drum as an image carrier by a developer such as toner. The developing apparatus has a developing sleeve as a developing agent carrier that supports and rotates the developing agent, and supplies the developing agent supported on the developing sleeve to the photosensitive drum.

In the case of such a developing device, there is a risk that air will flow into the developing container constituting the developing device due to the rotation of the developing sleeve, the air pressure inside the developing container will rise, and the developer in the developing container will be scattered outside the container. be. Therefore, an inner cover is provided between the outer cover of the developing container and the developing sleeve, and the air flowing into the developing container from between the developing sleeve and the inner cover is collected between the inner cover and the outer cover. A configuration has been proposed in which the film is discharged to the outside of the developing container from between (see Patent Document 1).

Japanese Patent Application Laid-Open No. 2015-72331

However, in the case of the configuration described in Patent Document 1, there is a possibility that air containing the developing agent is discharged to the outside of the developing container from the inflow path between the developing sleeve that allows air to flow into the developing container and the inner cover. be. In particular, the developer scattered from both ends in the axial direction (rotational axis direction) of the developer carrier of the developing container tends to flow around the developing container, and the scattering of the developing agent may not be sufficiently suppressed.

An object of the present invention is to prevent the developer from scattering to the outside of the developing container from the gap between the developing agent carrier and the developing container at one end and the other end of the developing agent carrier in the direction of the rotation axis. The purpose is to provide a possible developing device .

The developing apparatus of the present invention has a rotatable developer carrier that carries and transports a developer containing a toner and a carrier in order to develop an electrostatic image formed on the image carrier, and inside the developer carrier. It is fixedly arranged non-rotatingly, and is arranged adjacent to the first magnetic pole and adjacent to the first magnetic pole, which is downstream of the first magnetic pole in the rotation direction of the developer carrier and said first. A magnet having a plurality of magnetic poles including a second magnetic pole having the same pole as the magnetic pole of the above, a first frame for accommodating the developer, and a part of the outer peripheral surface of the developer carrier. A developing container composed of a second frame for covering is arranged so as to face the developing agent carrier along the outer peripheral surface of the developing agent carrier, and extends in the direction of the rotation axis of the developing agent carrier. A cover portion provided between the second frame body and the developer carrier is provided between the developer carrier and the cover portion in the radial direction of the developer carrier. A first clearance is formed, and a second clearance is formed between the second frame and the cover portion in the radial direction of the developer carrier. The region in the first region which is a region outside the rotation axis direction of the developer carrier and one end side in the rotation axis direction of the developer carrier than the region where the developer carrier capacity exists. The second clearance is the second region in the second region, which is the region where the developer carrier has the ability to convey the developer and is the central region of the developer carrier in the direction of the rotation axis. It is narrower than the clearance, and is a region outside the rotation axis direction of the developer carrier and is a region outside the region where the developer carrier has the developer transporting capacity, and is the developer carrier. The second clearance in the third region, which is the region on the other end side in the rotation axis direction, is characterized in that it is narrower than the second clearance in the second region .

According to the present invention, it is possible to prevent the developer from scattering to the outside of the developing container from the gap between the developing agent carrier and the developing container at one end and the other end in the rotation axis direction of the developing agent carrier. can.

The schematic block diagram of the image forming apparatus which concerns on 1st Embodiment. The schematic structural sectional view of the image forming part which concerns on 1st Embodiment. The schematic structural cross-sectional view of the developing apparatus which concerns on 1st Embodiment. The schematic structural vertical sectional view of the developing apparatus which concerns on 1st Embodiment. The schematic block diagram of the replenishing apparatus and the developing apparatus which concerns on 1st Embodiment. The cross-sectional view which shows the magnetic flux density around the developing sleeve of the developing apparatus which concerns on 1st Embodiment. The cross-sectional view which shows the air flow around the developing sleeve of the developing apparatus which concerns on 1st Embodiment. It is a figure which shows the air flow of the inflow port of the 2nd gap of the developing apparatus which concerns on 1st Embodiment, (a) is the figure seen from the flow direction, (b) is seen from the direction orthogonal to the flow direction and the width direction. Figure. The cross-sectional view which shows the development sleeve end portion of the developing apparatus which concerns on 1st Embodiment. The cross-sectional view which shows typically the air flow of the developing apparatus which concerns on a comparative example. The cross-sectional view which shows the air flow around the developing sleeve of the developing apparatus which concerns on 2nd Embodiment. It is sectional drawing which shows the modification of the 2nd gap of a developing apparatus, (a) is the height of each of the edge region and the central region is substantially constant, (b) is the height of the edge region is constant. In the case where the central region has a vertex in the central portion.

<First Embodiment>
The first embodiment will be described with reference to FIGS. 1 to 9. First, the schematic configuration of the image forming apparatus of this embodiment will be described with reference to FIGS. 1 and 2.

[Image forming device]
The image forming apparatus 100 of the present embodiment is an electrophotographic tandem full-color printer provided with four image forming units PY, PM, PC, and PK each having a photosensitive drum 1 as an image carrier. The image forming apparatus 100 is a toner image (image) according to an image signal from a document reading device (not shown) connected to the apparatus main body 100A or a host device such as a personal computer communicably connected to the apparatus main body 100A. ) Is formed on the recording material. Examples of the recording material include sheet materials such as paper, plastic film, and cloth. Further, the image forming portions PY, PM, PC, and PK form toner images of yellow, magenta, cyan, and black, respectively.

The four image forming units PY, PM, PC, and PK included in the image forming apparatus 100 have substantially the same configuration except that the developed colors are different. Therefore, the image forming unit PY will be described as a representative, and the description of other image forming units will be omitted.

As shown in FIG. 2, a cylindrical photoconductor, that is, a photosensitive drum 1 is arranged as an image carrier in the image forming portion PY. The photosensitive drum 1 is rotationally driven in the direction of the arrow in the figure. A charging roller 2 as a charging means, a developing device 4, a primary transfer roller 52 as a transfer means, and a cleaning device 7 as a cleaning means are arranged around the photosensitive drum 1. An exposure device (laser scanner in this embodiment) 3 as an exposure means is arranged below the photosensitive drum 1 in the drawing.

A transfer device 5 is arranged above FIG. 1 of each image forming unit. The transfer device 5 is configured such that an endless intermediate transfer belt 51 as an intermediate transfer body is stretched on a plurality of rollers and orbits (rotates) in the direction of an arrow. Then, the intermediate transfer belt 51 carries and conveys the toner image primaryly transferred to the intermediate transfer belt 51 as described later. A secondary transfer outer roller 54 as a secondary transfer means is arranged at a position facing the intermediate transfer inner roller 53 and the intermediate transfer belt 51 among the rollers on which the intermediate transfer belt 51 is stretched, and the intermediate transfer is performed. It constitutes a secondary transfer unit T2 that transfers the toner image on the belt 51 to the recording material. A fixing device 6 is arranged downstream in the recording material transport direction of the secondary transfer unit T2.

A cassette 9 containing the recording material S is arranged in the lower part of the image forming apparatus 100. The recording material S supplied from the cassette 9 is conveyed toward the registration roller 92 by the transfer roller 91. Then, the tip of the recording material S abuts against the registration roller 92 in the stopped state, and a loop is formed to correct the skew of the recording material S. After that, the registration roller 92 is started to rotate in synchronization with the toner image on the intermediate transfer belt 51, and the recording material S is conveyed to the secondary transfer unit T2.

The process of forming, for example, a four-color full-color image by the image forming apparatus 100 configured as described above will be described. First, when the image forming operation starts, the surface of the rotating photosensitive drum 1 is uniformly charged by the charging roller 2. Next, the photosensitive drum 1 is exposed by a laser beam corresponding to an image signal emitted from the exposure apparatus 3. As a result, an electrostatic latent image corresponding to the image signal is formed on the photosensitive drum 1. The electrostatic latent image on the photosensitive drum 1 is visualized by the toner as a developer contained in the developing device 4 and becomes a visible image.

The toner image formed on the photosensitive drum 1 is first-ordered on the intermediate transfer belt 51 by the primary transfer unit T1 (FIG. 2) configured between the primary transfer roller 52 arranged with the intermediate transfer belt 51 interposed therebetween. Transcribed. At this time, a primary transfer bias is applied to the primary transfer roller 52. The toner (transfer residual toner) remaining on the surface of the photosensitive drum 1 after the primary transfer is removed by the cleaning device 7.

Such an operation is sequentially performed in each of the image forming portions of yellow, magenta, cyan, and black, and the toner images of four colors are superimposed on the intermediate transfer belt 51. After that, the recording material S housed in the cassette 9 is conveyed to the secondary transfer unit T2 in accordance with the formation timing of the toner image. Then, by applying the secondary transfer bias to the secondary transfer outer roller 54, the toner images of the four colors on the intermediate transfer belt 51 are collectively secondary transferred onto the recording material S. The toner that cannot be completely transferred by the secondary transfer unit T2 and remains on the intermediate transfer belt 51 is removed by the intermediate transfer belt cleaner 55.

Next, the recording material S is conveyed to the fixing device 6 as the fixing means. The fixing device 6 includes a fixing roller 61 and a pressure roller 62 having a heat source such as a halogen heater inside, and the fixing roller 61 and the pressure roller 62 form a fixing nip portion. The recording material S is heated and pressurized by passing the recording material S on which the toner image is transferred through the fixing nip portion of the fixing device 6. Then, the toner on the recording material S is melted and mixed, and is fixed to the recording material S as a full-color image. After that, the recording material S is discharged to the discharge tray 102 by the discharge roller 101. This completes a series of image formation processes.

The image forming apparatus 100 of the present embodiment forms a monochromatic or multicolored image by using an image forming unit for some of desired monochromatic or four colors, such as a black monochromatic image. Is also possible.

[Developer]
Next, the detailed configuration of the developing device 4 will be described with reference to FIGS. 3 and 4. The developing apparatus 4 includes a developing container 41 (first frame, second frame) containing a developer containing a non-magnetic toner and a magnetic carrier, and a developing container (first frame) . It has a developing sleeve 44 as a developing agent carrier that carries and rotates the agent. In the developing container 41, transfer screws 43a and 43b as a developing agent conveying member that circulates in the developing container while stirring and conveying the developing agent in the developing container are arranged. The developing sleeve 44 can convey the developing agent to the facing region A facing the photosensitive drum 1. Further, inside the developing sleeve 44, a magnet 44a as a magnetic flux generating means having a plurality of magnetic poles in the circumferential direction is arranged so as not to rotate. Further, a developing blade 42 as a regulating member for forming a thin layer of the developing agent is arranged on the surface of the developing sleeve 44. In FIG. 4 and the like, the longitudinal direction of the developing sleeve 44, that is, the rotation axis direction (axial direction) is shown as the width direction W.

The inside of the developing container 41 is divided horizontally into the developing chamber 41a and the stirring chamber 41b by a partition wall 41c whose substantially central portion extends in the direction perpendicular to the paper surface, and the developing agent is divided into the developing chamber 41a and the stirring chamber 41a. It is housed in 41b. Conveying screws 43a and 43b are arranged in the developing chamber 41a and the stirring chamber 41b, respectively. The developer is allowed to pass between the developing chamber 41a and the stirring chamber 41b at both ends in the longitudinal direction of the partition wall 41c (both ends in the rotation axis direction of the developing sleeve 44, both ends in the width direction W in FIG. 4). Delivery units 41d and 41e are provided.

The transport screws 43a and 43b are formed by providing spiral blades as transport portions around the shaft (rotary shaft) of the magnetic material, respectively. Further, in addition to the spiral blade, the transport screw 43b is provided with a stirring rib 43b1 that protrudes from the shaft in the radial direction and has a predetermined width in the transport direction of the developer. The stirring rib 43b1 stirs the developer as the shaft rotates.

The transport screw 43a is arranged at the bottom of the developing chamber 41a along the rotation axis direction of the developing sleeve 44, and the developer in the developing chamber 41a is rotated along the axis direction by rotating the rotating shaft by a motor (not shown). The developer is supplied to the developing sleeve 44 while being conveyed. The developer supported on the developing sleeve 44 and whose toner has been consumed in the developing step is collected in the developing chamber 41a.

Further, the transport screw 43b is arranged at the bottom of the stirring chamber 41b along the rotation axis direction of the developing sleeve 44, and transports the developer in the stirring chamber 41b along the axis direction opposite to the transport screw 43a. The developer is thus conveyed by the transfer screws 43a and 43b and circulates in the developing container 41 via the transfer portions 41d and 41e.

At the upstream end of the transfer screw 43b of the stirring chamber 41b in the transfer direction, a developer supply port 46 for replenishing the developer containing toner is provided in the developing container 41. The developer replenishment port 46 is connected to the replenishment transport unit 83 of the developer replenishment device 80 shown in FIG. 5, which will be described later. Therefore, the developer for replenishment is supplied from the developer replenishing device 80 into the stirring chamber 41b via the replenishment transport unit 83 and the developer replenishment port 46. The transfer screw 43b conveys the developer supplied from the developer supply port 46 and the developer already in the stirring chamber 41b while stirring to make the toner concentration uniform.

Therefore, due to the transporting force of the transport screws 43a and 43b, the developer in the developing chamber 41a in which the toner is consumed in the developing process and the toner concentration is lowered is transferred to one of the transfer portions 41d (left (W1) side in FIG. 4). It moves into the stirring chamber 41b through the stirring chamber 41b. Then, the developer that has moved into the stirring chamber 41b is conveyed while being stirred with the replenished developer, and moves to the developing chamber 41a via the other delivery section 41e (right (W2) side in FIG. 4).

As shown in FIG. 3, in the developing chamber 41a of the developing container 41, there is an opening 41h at a position corresponding to the facing region (development region) A facing the photosensitive drum 1, and the developing sleeve 44 is provided in the opening 41h. The photosensitive drum is rotatably arranged so as to be partially exposed in one direction. On the other hand, the magnet 44a contained in the developing sleeve 44 is fixed in a non-rotating manner. Such a developing sleeve 44 is rotated by a motor (not shown) so that the developing agent can be conveyed to the facing region A, and the developing agent is supplied to the photosensitive drum 1 in the facing region A. In the present embodiment, the developing sleeve 44 is formed in a cylindrical shape by, for example, aluminum or stainless steel as a non-magnetic material. Further, the developing sleeve 44 rotates from the lower side in the direction of gravity to the upper side in the facing region A, that is, in the counterclockwise direction of FIG.

On the upstream side of the developing sleeve 44 in the rotation direction of the opening 41h, a developing blade 42 as a regulating member for regulating the amount of the developing agent carried on the developing sleeve 44 is fixed to the developing container 41. In the present embodiment, since the developing sleeve 44 rotates from the lower side in the gravity direction to the upper side in the facing region A, the developing blade 42 is located below the facing region A in the gravity direction.

The magnet 44a has a total of five poles of a plurality of magnetic poles S1, S2, S3, N1 and N2 in the circumferential direction, and is formed in a roller shape. The developer in the developing chamber 41a is supplied to the developing sleeve 44 by the transport screw 43a, and the developer supplied to the developing sleeve 44 is predetermined on the developing sleeve 44 by the magnetic field generated by the suction magnetic pole S2 of the magnet 44a. Is carried to form a developer pool.

The developer on the developing sleeve 44 passes through the developer pool as the developing sleeve 44 rotates, spikes on the regulating magnetic pole N1, and the layer thickness is increased by the developing blade 42 facing the regulating magnetic pole N1. Be regulated. Then, the developer whose layer thickness is restricted is conveyed to the facing region A facing the photosensitive drum 1, and spikes on the developing magnetic pole S1 to form magnetic spikes. The magnetic spikes come into contact with the photosensitive drum 1 rotating in the same direction as the developing sleeve 44 in the facing region A, and the electrostatic latent image is developed as a toner image by the charged toner.

After that, the developer on the developing sleeve 44 is conveyed into the developing container 41 by the rotation of the developing sleeve 44 while maintaining the adsorption of the developer on the surface of the developing sleeve 44 by the transport magnetic pole N2. Then, the developer carried on the developing sleeve 44 is peeled from the surface of the developing sleeve 44 by the peeling magnetic pole S3 and collected in the developing chamber 41a of the developing container 41.

As shown in FIG. 4, the developing container 41 is provided with an inductance sensor 45 as a toner concentration sensor for detecting the toner concentration in the developing container 41. In the present embodiment, the inductance sensor 45 is provided on the downstream side of the stirring chamber 41b in the developer transport direction.

As shown in FIG. 4, the imageable region of the developing sleeve 44 (the region where the developer can be supported and the region where the developer can be conveyed ) is defined as the coat region B1. Further, the developing sleeve 44 has a central region B2 and an end region B3. The end region B3 is located on both ends of the developing sleeve 44 in the width direction W. The central region B2 is located on the central side of the end region B3 in the width direction W, and is formed to have a length of more than half the length of the coat region B1 including the center of the coat region B1. The end region B3 is a region located on both ends of the developing sleeve 44 including a part of the coat region B1. That is, at least a part of the end region B3 is located outside the coat region B1 in the width direction W.

[Developer replenishment device]
Next, the developer replenishing device 80 will be described with reference to FIG. The developer replenishment device 80 includes a storage container 8 for accommodating a replenishing developer, a replenishment mechanism 81, and a replenishment transport unit 83. The storage container 8 has a structure in which a spiral groove is dug in the inner wall of the cylindrical container, and the storage container 8 itself rotates to generate a carrying force of the developer in the longitudinal direction (rotational axis direction). Let me. A replenishment mechanism 81 is connected to the downstream end of the container 8 in the developer transport direction. The replenishment mechanism 81 has a pump unit 81a for discharging the developer from the discharge port 82 to which the developer is conveyed from the storage container 8. The pump portion 81a is formed in a bellows shape, and when it is rotationally driven, the volume changes to generate air pressure, and the developer conveyed from the storage container 8 is discharged from the discharge port 82.

The upper end of the replenishment transport unit 83 is connected to the discharge port 82, and the lower end of the replenishment transport unit 83 is connected to the developer supply port 46 of the developing device 4. That is, the supply transport unit 83 communicates the discharge port 82 with the developer supply port 46. Therefore, the developer discharged from the discharge port 82 by the pump unit 81a is replenished into the developing container 41 of the developing device 4 through the replenishment transport unit 83.

In the above-mentioned developing apparatus 4, the developing agent supply port 46 is the upstream end of the stirring chamber 41b in the developing agent transport direction, and the developing agent formed by the developing chamber 41a (see FIG. 4) and the stirring chamber 41b. It is provided outside the circulation path of. Specifically, the developer supply port 46 is provided on the upstream side of the stirring chamber 41b in the developer transport direction with respect to one of the transfer portions 41d. Therefore, in the vicinity of the developer supply port 46, there is almost no developer in the circulation path of the developer, and only the developer for replenishment passes through.

Such replenishment by the developer replenishing device 80 is performed by automatic toner replenishment control (hereinafter referred to as ATR (Automatic Toner Replenisher) control). This ATR control operates the developer replenishing device 80 according to the density detection result of the patch image by the image ratio at the time of image formation, the inductance sensor 45, and the density sensor 103 (see FIG. 1) that detects the density of the toner image. The developer is controlled and replenished to the developing device 4.

As shown in FIG. 1, the density sensor 103 faces the surface of the intermediate transfer belt 51 in the rotation direction of the intermediate transfer belt 51, downstream of the most downstream image forming unit PK and upstream of the secondary transfer unit T2. Are arranged. In the control using the density sensor 103, for example, the toner image (patch image) for control is transferred onto the intermediate transfer belt 51 at the start of an image formation job or at the timing of each predetermined number of images to be formed, and the density sensor 103 is used. Detects the density of the patch image. Then, based on this detection result, the developer replenishment device 80 controls the replenishment of the developer.

The configuration for supplying the developer to the developing apparatus 4 is not limited to such a configuration, and a conventionally known configuration may be used.

[Scattering of developer]
Here, the scattering of the developer generated from the developing apparatus will be described. First, in an image forming apparatus, high speed and high image quality of output images are required, and maintenance is required to be simplified. One of the simplifications of this maintenance is the reduction of contamination by the developer inside the image forming apparatus. If the inside of the image forming apparatus is contaminated with a developer, image defects such as stains on the output image may occur, or cleaning work may occur when the developing apparatus or the photosensitive drum unit is replaced. Further, if the developer adheres to each drive system such as a gear, the drive system may slip or the like.

One of the causes of contamination by the developer inside the image forming apparatus is that the developer scatters from the inside of the developing apparatus. For example, in the case of a two-component developer, the toner and the carrier are usually triboelectrically charged inside the developing apparatus, so that the toner and the carrier adhere to each other by electrostatic force. However, there is a risk that this adhesion will be released by some kind of impact, and the toner released from the carrier will be discharged from the inside of the developing device together with the air, causing scattering of the developer.

A specific example of such scattering of the developer will be described using the developer 400 of the comparative example shown in FIG. The developing device 400 is the same as the developing device 4 described above, except that the configuration of the developing container 401 is different. Therefore, the same configuration will be described with the same reference numerals. Further, the developing device 400 is connected to the replenishment transport unit 83 of the developer replenishing device 80, similarly to the developing device 4 described above.

The developing container 401 includes an upper lid 402 that covers the upper part of the developing sleeve 44. Then, between the upper lid 402 and the developing sleeve 44, an air flow path through which air flows into the developing container 401 is formed by the rotation of the developing sleeve 44. This flow path is open at a position facing the photosensitive drum 1, and the scattering of the developer from the inside of the developing container 401 is mainly generated from this flow path. This is because the developing blade 42 is close to and facing the developing sleeve 44 on the opposite side (lower side of FIG. 10) from this flow path. That is, at this position, the layer thickness of the developer supported on the developing sleeve 44 is restricted by the developing blade 42, and air does not easily flow out from the gap between the developing sleeve 44 and the developing blade 42. be.

Here, the scattering of the developer means that the developer such as free toner generated in the developing container 401 by stirring and transporting the developing agent and replenishing the developing agent is discharged to the outside of the developing container 401 through the opening of the flow path. It refers to the things that cannot be collected in the developing container 401.

First, toner release will be described. The toner and carrier contained in the developing container 401 are triboelectrically charged in the stirring chamber 41b and the developing chamber 41a, and adhere to each other due to the electrostatic adhesive force generated by the triboelectric force and the non-electrostatic adhesive force generated by the surface property. There is. When an impact or a shearing force is applied to the toner adhering to the carrier, the toner is peeled off from the carrier and released in the developing container 401. The impact and shear force at this time include the behavior of the developer when the developer is conveyed by the developing sleeve 44.

The developer forms magnetic spikes on the developing sleeve 44, which is a chain-like structure along the magnetic field lines of the internal magnetic poles. Due to the rotation of the developing sleeve 44, the magnetic spike rises forward in the rotation direction just before the magnetic pole, and when it passes over the magnetic pole, it falls forward in the rotation direction. At this time, the rotation direction of the magnetic spike is the same as the rotation direction of the developing sleeve 44. The toner is peeled off from the carrier by the impact and centrifugal force when the magnetic spikes fall, which causes the toner to be released.

The magnetic pole that contributes greatly to the release of toner when the developer is conveyed by the developing sleeve 44 is the peeling magnetic pole S3 that generates a repulsive magnetic field with the adsorption magnetic pole S2. In this peeling magnetic pole S3, in order to peel the developer from the developing sleeve 44, a magnetic force in the direction opposite to the rotation direction of the developing sleeve 44 is applied by the magnetic pole to slow down the speed of the developer to be conveyed and to retain the developer. .. At this time, since the length of the magnetic spikes becomes long, the impact and centrifugal force when the magnetic spikes fall down become large, and the amount of toner released tends to increase.

Further, when the developer is replenished to the developer replenishment port 46 from the developer replenishment device 80, the developer that is blown up before being sufficiently stirred is also a factor of free toner in the developing container 401. .. The toner supplied to the developer supply port 46 is conveyed while being stirred with the developer already in the stirring chamber 41b. At this time, in the mixing region of the supplementary developer and the existing developer, the mixing ratio of the toner and the developer is temporarily increased. When the mixing ratio of the toner and the developer is high, the charge amount of the toner decreases, and the electrostatic adhesion between the toner and the carrier decreases. The toner that cannot be completely mixed with the developer is released as it is or by the impact of stirring and transporting the developer by the transfer screws 43a and 43b, and the free toner is soared in the developing container 401.

Further, when the developer replenishing device 80 discharged by the air pressure generated by the pump unit 81a is used, the air pressure propagates through the replenishment transport unit 83, and air flows into the developing container 401 from the developing agent replenishment port 46. There is. The airflow that has flowed in at this time winds up the free toner in the portion where the mixing ratio of the toner and the developer in the vicinity of the developer supply port 46 is high into the developing container 401. Further, the pneumatic propagation to the developing container 401 causes an unsteady increase in air pressure from the developing agent supply port 46 to the stirring chamber 41b. This increase in atmospheric pressure causes the free toner to flow out of the developing container 401, as will be described later. In particular, the inflow air due to such replenishment of the developing agent is one of the causes of scattering of the developing agent at the end portion on the side including the developing agent replenishing port 46 in the longitudinal direction of the developing container 401 (direction of the rotation axis of the developing sleeve 44). It becomes one.

Next, the airflow inside and in the vicinity of the developing device 400 will be described with reference to FIG. It is the developing sleeve 44 and the photosensitive drum 1 that generate the airflow in the vicinity of the developing device 400. Each will be described here. First, due to the rotation of the developing sleeve 44 and the behavior of the magnetic spikes on the magnetic poles, an air flow is generated in substantially the same direction as the rotation direction of the developing sleeve 44. The airflow generated in the direction substantially the same as the rotation direction of the developing sleeve 44 takes in air into the developing container 401 from the communication port between the inside of the developing container 401 and the outside of the developing container 401. Air also flows into the developing container 401 by replenishing the developing agent.

Assuming that the developing container 401 is a substantially closed space, the continuity equation can be applied because air is a fluid. Assuming that the flow velocity of air is v and the density is ρ, the following equation (1) holds because there is no air springing out in the developing container 401.

Further, considering the steady state, since the density ρ is approximately constant in each region in the developing container 401, the equation (1) can be described as the following equation (2).

From this equation (2), the air flow rate ρv is conserved. In the longitudinal cross section near the developing device 400, the balance of the flow rate ρv becomes 0, and the same amount as the air flow rate flowing in by the developing sleeve 44 and replenishment is discharged to the outside of the developing device 400. Here, the air flow rate that flows into the developing container 401 as the developing sleeve 44 rotates through the communication port composed of the upper lid 402 of the developing container 401 and the developing sleeve 44 is defined as Qa (sleeve inflow). Further, the air flow discharged from the communication port inside the developing container 401 and the outside of the developing container 401 passes through the upper lid 402 side so as to face the flow taken in from this communication port. The air flow rate discharged in this way is referred to as Qb (sleeve discharge). Further, assuming that the air flow rate flowing in with the replenishment to the developing device 400 is Qd (replenishment inflow), the relationship of the following equation (3) is established.
Qa + Qd = Qb ... (3)

The airflow taken in by the developing sleeve 44 and flowing along the developing sleeve 44 is folded back and discharged in the developing container 401. At this time, when the airflow is turned back by containing the developer peeled from the developing sleeve 44 at the developer retaining portion of the peeling magnetic pole S3, the airflow collects the developer such as free toner generated in the developing container 401. It will be included in a large amount and will be directed toward the discharge direction.

There are mainly three steps in which the developer contained in the air (flow rate Qb) discharged from the sleeve is discharged to the outside of the developing container 401. In the first step, the air discharged from the sleeve (flow rate Qb) discharged from the communication port to the outside of the developing device 400 is directly discharged from the gap between the upper lid 402 and the photosensitive drum 1. In the second step, the air discharged from the sleeve (flow rate Qb) is mixed with the developer carried on the developing sleeve 44 in the vicinity of the photosensitive drum 1 and discharged on the air flow g generated by the photosensitive drum 1. Is. In the third step, the free toner contained in the air discharged from the sleeve (flow rate Qb) is transferred to the air flow g generated by the photosensitive drum 1 by inertial force, and is discharged to the outside of the developing container 401.

The scattering of the developing agent is discharged to the outside of the developing container 401 due to at least one of the above three factors. Then, the scattered developer contaminates the periphery of the developing device 400, the outer wall of the developing container 401, the photosensitive drum 1, the exposure device 3, and the transfer device 5.

[Structure of developing container of this embodiment]
In the present embodiment, the development container 41 (first frame body, second frame body) of the developing device 4 is configured as follows. The detailed configuration of the developing container 41 of the present embodiment will be described with reference to FIG. The curve C shown around the developing sleeve 44 in FIG. 6 shows the distribution of the magnetic flux density of each magnetic pole of the magnet 44a. Let R be the rotation direction of the developing sleeve 44. Of the magnetic poles of the magnet 44a, the peeling magnetic pole S3 corresponds to the first magnetic pole, and the suction magnetic pole S2 corresponds to the second magnetic pole. The peeling magnetic pole S3 is arranged on the downstream side of the facing region A with respect to the rotation direction R, and strips the developer carried on the developing sleeve 44. The suction magnetic pole S2 is arranged adjacent to the downstream side of the peeling magnetic pole S3, and has the same pole as the peeling magnetic pole S3, and pumps the developer in the developing container 41 to the developing sleeve 44. In FIG. 6, a straight line indicating the peak position of the magnetic flux density indicates the position of each of the five magnetic poles.

The developing container 41 of the present embodiment has an upper lid 41f that covers the developing sleeve 44 on the downstream side in the rotation direction R of the developing sleeve 44 from the facing region A. The upper lid 41f has an outer cover 47 (second frame body) as a first cover portion and an inner cover 48 (cover portion) as a second cover portion. The outer cover 47 is arranged on the downstream side of the facing region A with respect to the rotation direction R, and covers the developing sleeve 44 through the gap.

The inner cover 48 is arranged between the outer cover 47 and the developing sleeve 44 with a gap between the outer cover 47 and the developing sleeve 44, and covers the developing sleeve 44. The downstream end 48b of the development sleeve 44 of the inner cover 48 in the rotation direction R is a pair of minimum values M1 and M2 on the upstream side of the absolute value rotation direction R of the distribution of the magnetic flux density of the peeling magnetic pole S3. It is located on the downstream side of. Further, it is preferable that the downstream end 48b of the inner cover 48 in the rotation direction R is located on the downstream side of the rotation direction R of the peak position or the peak position of the magnetic flux density of the peeling magnetic pole S3. By arranging the position of the downstream end 48b of the inner cover 48 in the rotation direction R at a position satisfying these conditions, the range of covering the peeling magnetic pole S3 by the inner cover 48 can be further widened.

However, it is preferable that the downstream end 48b of the inner cover 48 in the rotation direction R is located on the horizontal plane H passing through the center O of the developing sleeve 44, or on the upstream side in the rotation direction R than the position of the horizontal plane H. This is because when the downstream end 48b of the inner cover 48 in the rotation direction R is located further downstream than this, it becomes difficult to take in the developer peeled from the developing sleeve 44 into the developing chamber 41a.

[Characteristic configuration in this embodiment]
Next, the characteristic configuration of the developing apparatus 4 of the present embodiment will be described with reference to FIGS. 7 and 8. First, the gap between the inner cover 48 and the developing sleeve 44 is defined as the first gap (gap , first clearance ) F1. The gap between the inner cover 48 and the outer cover 47 is referred to as a second gap (flow path, gap , second clearance ) F2. The gap between the facing end portion 47a of the outer cover 47 facing the photosensitive drum 1 and the photosensitive drum 1 is referred to as a third gap F3. The developing container 41 has a pair of side walls 49 provided at both ends of the developing sleeve 44 in the width direction W between the outer cover 47 and the inner cover 48. Each side wall 49 blocks the space between the outer cover 47 and the inner cover 48 at both sides in the width direction W, and forms a second gap F2 as a flow path along the rotation direction R together with the outer cover 47 and the inner cover 48. do.

The second gap F2 has an inflow port (opening) 11 into which air flows in, and an outflow port 12 in which air flows out. The inflow port 11 is an opening formed by the downstream end portions of the outer cover 47, the inner cover 48, and the pair of side walls 49 in the rotation direction R, respectively. The outlet 12 is an opening formed by the upstream end of each of the outer cover 47, the inner cover 48, and the pair of side walls 49 in the rotation direction R.

In this embodiment, the inflow port 11 has a central region B2 and an end region B3. That is, the second gap F2 has an end region B3 located on both ends of the developing sleeve 44 and a central region located on the center side of the end region B3 in the width direction W at least in a part of the rotation direction R. It has B2 and. The end region B3 is formed so as to be narrower than the central region B2 with respect to the flow direction of the gas flowing in the second gap F2 and the direction orthogonal to the width direction W. That is, when the distance between the outer cover 47 and the inner cover 48 is the height H, the average height H2 of the central region B2 and the average height H3 of the end region B3 are H2>. It becomes a relationship of H3.

Further, the shape of the inflow port 11 and the shape of the outflow port 12 are the same. Further, in the second gap F2, the area of the cross section orthogonal to the flow direction of the flowing gas is made constant. In the present embodiment, the surface of the inner cover 48 on the second gap F2 side is composed of a single curved surface that is linear in the width direction W. Further, the surface of the outer cover 47 on the second gap F2 side is composed of two curved surfaces in which the center of the width direction W projects upward and has an apex 47p, and both ends thereof are inclined downward.

As a result, the height H becomes higher toward the central region B2 of the second gap F2, and the pressure loss of the flowing air becomes smaller. As a result, when the air taken into the developing container 41 by the rotation of the developing sleeve 44 is exhausted from the second gap F2, the air in the end region B3 is concentrated in the central region B2 (FIG. 8 (FIG. 8). b) See). As a result, it is possible to suppress the scattering of the end portion while discharging the air in the developing container 41 due to the air flow taken into the developing container 41.

Further, in the present embodiment, the inflow port 11 is located downstream of the minimum value M1 on the upstream side of the pair of minimum values M1 and M2 with respect to the rotation direction R of the absolute value of the distribution of the magnetic flux density of the peeling magnetic pole S3. To position. Further, the inflow port 11 is located on the downstream side in the rotation direction R from the peak position or the peak position of the magnetic flux density of the peeling magnetic pole S3 and on the upstream side of the suction magnetic pole S2.

The air flow generated by the rotation of the developing sleeve 44 and the photosensitive drum 1 will be described. In the vicinity of the developing sleeve 44, an air flow a is generated as the developing sleeve 44 rotates, and flows through the first gap F1 and flows into the developing container 41. The internal pressure of the developing container 41 increases due to the inflow into the developing container 41, and the air is exhausted from the discharge path. Here, in the configuration without the inner cover 48, the scattered toner generated in the developing container 41 is directly discharged to the outside air through the first gap F1 by the air flow b. As described above, since the amount of toner released increases in the vicinity of the peeling magnetic pole S3, the released toner is scattered outside the developing container 41 by the air flow b.

On the other hand, in the present embodiment, by providing the second gap F2 as an exhaust path between the outer cover 47 and the inner cover 48, an air flow d is generated from the inside of the developing container 41 toward the second gap F2. , An airflow e is generated in the second gap F2 as an exhaust airflow. As a result, since the airflow b, which is an exhaust airflow, is not generated in the first gap F1, the air in the developing container 41 can be discharged without passing near the peeling magnetic pole S3, and the toner scattering can be reduced. A small amount of toner may be discharged from the outlet 12 to the outside of the developing container 41 through the path of the air flow e, but most of the toner adheres to the opposing photosensitive drum 1 and is collected by the cleaning device 7. Does not contaminate the area around the developing device 4.

Here, the toner discharged from both ends in the width direction W at the opening 41h of the developing device 4 is scattered outside the both ends in the width direction W of the photosensitive drum 1 by the air flow in the width direction W of the developing sleeve 44. This may cause contamination around the developing device 4. Further, as described above, the airflow entering the inflow port 11 at both ends of the developing container 41 due to the inflow of air from the replenishment transport section 83 of the developer replenishing device 80 contains more toner than the central portion.

On the other hand, in the present embodiment, the end region B3 of the second gap F2 is formed so as to be narrower than the central region B2 in the flow direction of the gas flowing in the second gap F2 and the direction orthogonal to the width direction W. ing. This makes it difficult for air from both ends of the developing sleeve 44 of the developing container 41 in the width direction W to flow into the second gap F2, and at the same time, the air exhausted from the inside of the developing container 41 is discharged to both ends of the developing sleeve 44. Can be avoided. As a result, it is possible to sufficiently suppress the scattering of the developer from both ends of the developing sleeve 44 of the developing container 41 in the width direction W while discharging the air in the developing container 41 due to the airflow taken into the developing container 41. Contamination around the developing device 4 due to scattered toner can be suppressed.

Further, when the end region B3 is on the center side of the coat region B1 of the developing sleeve 44 and both ends of the inner cover 48 in the width direction W do not face the coat region B1, an air flow b is generated in the coat region B1. It ends up. This causes toner to scatter from the end of the developing container 41. Therefore, it is preferable that at least a part of the end region B3 is wider than the coat region B1 and is located outside.

Here, the central region B2 and the end region B3 will be described with reference to specific examples. Both ends of the developing sleeve 44 are sealed. As a seal configuration for sealing both ends of the developing sleeve 44, a magnetic seal configuration that magnetically shields the outside and the inside of the developing container 41 is used. FIG. 9 shows an example of the magnetic seal configuration. In the magnetic seal configuration shown in FIG. 9, the plate-shaped magnetic plate 13 and the magnet sheet 14 are formed on the sleeve end portion 44b of the developing sleeve 44 which has not been roughened, that is, the width of the developing sleeve 44 is wider than the coat region B1. The configuration is arranged outside the direction W (outside the developer-supporting region).

The magnetic plate 13 as a magnet member can cover the developing sleeve 44 in a non-contact manner along the outer periphery of the developing sleeve 44 to form magnetic spikes. That is, since a magnetic force is generated between the magnetic plate 13 and the magnet 44a in the developing sleeve 44, the developer that has penetrated between the magnetic plate 13 and the developing sleeve 44 forms magnetic spikes. The magnetic spikes close the gap between the magnetic plate 13 and the developing sleeve 44 to prevent the developer from leaking from the sleeve end 44b. Further, the magnet sheet 14 is provided on the outer side of the developing sleeve 44 in the rotation axis direction with respect to the magnetic plate 13. The magnet sheet 14 magnetically holds the developer leaking between the magnetic plate 13 and the developing sleeve 44. By providing the magnetic plate 13 and the magnet sheet 14 in this way, leakage of the developer from the sleeve end portion 44b is suppressed.

The central region B2 is formed so that both ends are located at a position separated from the position of the magnetic plate 13, for example, by 10 mm or more and 30 mm or less on the center side. By doing so, the end region B3 can cover both ends of the coat region B1. In the present embodiment, as an example, the longitudinal length of the central region B2 is set to 290 mm to 310 mm, and the longitudinal length of the end region B3 is set to 20 to 40 mm, respectively. As a result, a part of the end region B3 is wider than the coat region B1 and is located outside.

As described above, according to the developing apparatus 4 of the present embodiment, the end region B3 of the second gap F2 is narrower than the central region B2 in the gas flow direction and the direction orthogonal to the width direction W. Therefore, the pressure loss of the air flowing through the second gap F2 is larger in the end region B3 than in the central region B2, and the air discharged from the developing container 41 through the second gap F2 is at the end. It becomes easier to distribute in the central region B2 than in the region B3. As a result, when the air taken into the developing container 41 by the rotation of the developing sleeve 44 passes through the second gap F2, the air in the end region B3 is concentrated in the central region B2. This makes it difficult for air from both ends of the developing sleeve 44 of the developing container 41 in the width direction W to flow into the second gap F2, and at the same time, the air exhausted from the inside of the developing container 41 is discharged to both ends of the developing sleeve 44. Can be avoided. Therefore, it is possible to sufficiently suppress the scattering of the developer from both ends of the developing sleeve 44 of the developing container 41 in the width direction W. Further, even if the developer is scattered, the amount of scattering is small, so that even if the developer adheres to the image, the amount of adhesion is such that it cannot be visually recognized, and it is possible to suppress deterioration of the image quality.

Further, according to the developing apparatus 4 of the present embodiment, the area of the inflow port 11 and the area of the outflow port 12 are equal to each other, and the area of the cross section orthogonal to the flow direction of the flowing gas in the second gap F2 is constant. .. Therefore, since the pressure loss of the flowing air can be made extremely small as a whole of the second gap F2, the airflow b exhausted from the first gap F1 is not generated, and the contamination around the developing device 4 by the scattered toner is suppressed. can do.

Further, according to the developing apparatus 4 of the present embodiment, at least a part of the end region B3 is located outside the coating region B1 in the width direction W. Therefore, the generation of the air flow b in the coat region B1 can be suppressed as compared with the case where the entire area of the end region B3 is located inside the width direction W with respect to the coat region B1. Can be suppressed.

Further, as described above, since a large amount of toner is released when the magnetic spike falls on the peeling magnetic pole S3, the airflow a of the first gap F1 contains a large amount of the free toner generated in this way. According to the developing apparatus 4 of the present embodiment, the downstream end 48b of the inner cover 48 is positioned on the downstream side of the minimum value M1 on the upstream side of the distribution of the magnetic flux density of the peeling magnetic pole S3, so that at least the peeling magnetic pole S3 A part of the inner cover 48 is used to cover the inner cover 48. In particular, in the present embodiment, since the downstream end 48b of the inner cover 48 is located downstream from the peak position of the peeling magnetic pole S3, the region where free toner is generated when the magnetic spike falls on the peeling magnetic pole S3. Most can be covered by the inner cover 48.

<Second embodiment>
Next, a second embodiment of the present invention will be described in detail with reference to FIG. The present embodiment differs from the first embodiment in that the outlet 12 does not face the photosensitive drum 1 but faces the vicinity of the uppermost portion of the developing sleeve 44. However, since the other configurations are the same as those of the first embodiment, the reference numerals are the same and detailed description thereof will be omitted.

As shown in FIG. 11, the outer cover 47 bends toward the photosensitive drum 1 side so as to cover the developing sleeve 44 from the upper end of the side wall 41g opposite to the photosensitive drum 1 with the developing sleeve 44 of the developing container 41 interposed therebetween. It is formed like this. The outer cover 47 has a first facing portion 47b on the photosensitive drum 1 side, a second facing portion 47c on the side wall 41g side, and a continuous portion 47d that connects the first facing portion 47b and the second facing portion 47c.

The first facing portion 47b faces the developing sleeve 44 on the upstream side in the rotating direction R of the developing sleeve 44 with respect to a part (continuous portion 47d) facing the upstream end 48a in the rotating direction R of the inner cover 48. The second facing portion 47c faces the portion between the upstream end 48a and the downstream end 48b of the inner cover 48 in the rotation direction R.

Since the inner cover 48 is arranged between the second facing portion 47c and the developing sleeve 44, the second facing portion 47c is arranged outside the first facing portion 47b in the radial direction of the developing sleeve 44. For this reason, a continuous portion 47d is provided so that the upstream end of the second facing portion 47c in the rotation direction R and the downstream end of the first facing portion 47b in the rotation direction R are continuous. The continuous portion 47d is formed so as to bend toward the developing sleeve 44 side from the upstream end of the second facing portion 47c in the rotation direction R. Then, the continuous portion 47d faces the upstream end 48a in the rotation direction R of the inner cover 48 and the rotation direction R via the second gap (gap) F22. That is, the inner cover 48 is formed so that the upstream end in the rotation direction R faces a part of the outer cover 47 in the rotation direction R via the second gap F22.

In the vicinity of the developing sleeve 44, airflows a and c are generated in the first gaps (gap) F11 and F12 as the developing sleeve 44 rotates, and flow into the developing container 41. As the air flows into the developing container 41, the internal pressure in the developing container 41 increases, and the air is exhausted from the discharge path. In the present embodiment, as in the first embodiment, an air flow d is generated from the inside of the developing container 41 toward the second gaps (gap, flow path) F21 and F22 between the outer cover 47 and the inner cover 48. , Airflows e and f are generated as exhaust airflows in the second gaps F21 and F22. The airflow f joins the first gap F11 between the developing sleeve 44 and the outer cover 47 near the uppermost portion of the developing sleeve 44, and is discharged from the airflow b to the outside of the developing container 41 via the airflow g.

Also in the developing apparatus 4 of this embodiment, the end regions B3 of the second gaps F21 and F22 are narrower than the central region B2 in the gas flow direction and the direction orthogonal to the width direction W. Therefore, it is possible to prevent air from both ends of the developing sleeve 44 of the developing container 41 in the width direction W from flowing into the second gap F2, and the air exhausted from the inside of the developing container 41 is discharged to both ends of the developing sleeve 44. Can be avoided. Therefore, it is possible to sufficiently suppress the scattering of the developer from both ends of the developing sleeve 44 of the developing container 41 in the width direction W.

Further, according to the developing apparatus 4 of the present embodiment, the upstream end 48a of the inner cover 48 in the rotation direction R faces the continuous portion 47d of the outer cover 47 in the rotation direction R via the second gap F22. Therefore, the airflow e passing through the second gap F21 joins the airflow b of the first gap F11 via the second gap F22. At this time, the airflow f flowing through the second gap F22 becomes an air curtain, and the airflow containing a large amount of free toner is less likely to be discharged from the first gap F12, and the scattering of the developer can be suppressed.

<Other embodiments>
In each of the above-described embodiments, in the cross-sectional shape of the second gap F2, the surface of the outer cover 47 on the second gap F2 side has an apex 47p with the center of the outer cover 47 protruding upward in the width direction and having both ends downward. The case where the two curved surfaces are inclined has been described, but the present invention is not limited to this. For example, as shown in FIG. 12A, the heights of the end region B3 and the center region B2 may be substantially constant. Alternatively, as shown in FIG. 12B, the height of the end region B3 may be constant, and the central region B2 may have a vertex 47p in the center. Further, in each embodiment, the case where the surface of the inner cover 48 on the second gap F2 side is a single curved surface linear in the width direction W has been described, but the present invention is not limited to this. The surface of the inner cover 48 on the second gap F2 side may have various shapes other than the linear shape, similarly to the surface of the outer cover 47 on the second gap F2 side.

Further, in each of the above-described embodiments, a configuration using a two-component developer containing a toner and a carrier as the developing apparatus 4 has been described. However, the present invention can be applied even if a one-component developer containing a magnetic toner is used as long as it has the above-mentioned peeling magnetic pole S3.

Further, in the present invention, in addition to the configuration in which the developing agent is supplied to the developing sleeve 44 and the developing agent is recovered from the developing sleeve 44 in the developing chamber 41a as described above, the functions of supplying and recovering the developing agent are separated. It can also be applied to a so-called function-separated developing device. For example, to explain with reference to FIG. 3, even in a configuration in which the developing agent is supplied from the developing chamber 41a to the developing sleeve 44 and the developing agent peeled off from the developing sleeve 44 is recovered by the stirring chamber 41b, the present invention The invention is applicable.

1 ... Photosensitive drum (image carrier), 4 ... Developer, 11 ... Inlet (opening), 41 ... Development container, 44 ... Development sleeve (developer carrier), 44a ... Magnet (magnetic flux generating means), 47 ... Outer cover (first covering portion), 48 ... Inner cover (second covering portion), 49 ... Side wall, 100 ... Image forming apparatus, A ... Opposing region, B1 ... Coat region (developer-carrying region), B2 ... Center Region, B3 ... end region, F1 ... first gap (gap), F11 ... first gap (gap), F12 ... first gap (gap), F2 ... second gap (gap, flow path), F21 ... first 2 gaps (gap, flow path), F22 ... second gap (gap, flow path), S2 ... suction magnetic pole (second magnetic pole), S3 ... peeling magnetic pole (first magnetic pole), W ... width direction (rotation axis) direction).

Claims (6)

A rotatable developer carrier that carries and transports a developer containing toner and carriers to develop an electrostatic image formed on the image carrier.
It is fixedly arranged inside the developer carrier in a non-rotating manner, and is located downstream of the first magnetic pole and adjacent to the first magnetic pole in the rotation direction of the developer carrier. A magnet having a plurality of magnetic poles including a second magnetic pole arranged together and having the same pole as the first magnetic pole.
A developing container composed of a first frame for accommodating the developer and a second frame for covering a part of the outer peripheral surface of the developer carrier.
It is arranged along the outer peripheral surface of the developer carrier so as to face the developer carrier, and is located between the second frame and the developer carrier along the rotation axis direction of the developer carrier. With the cover part provided in
Equipped with
A first clearance is formed between the developer carrier and the cover portion in the radial direction of the developer carrier, and the second frame and the cover portion are formed in the radial direction of the developer carrier. A second clearance is formed between the cover and the cover.
It is a region outside the developer carrier in the direction of the rotation axis and a region on one end side in the direction of the rotation axis of the developer carrier, rather than a region in which the developer carrier has the ability to convey the developer. The second clearance in the first region is a region in which the developer carrier has the developer transporting capacity and is a region in the center of the developer carrier in the direction of the rotation axis. It is narrower than the second clearance in the region, and is a region outside the rotation axis direction of the developer carrier than the region where the developer carrier has the developer transporting capacity. The second clearance in the third region, which is the region on the other end side in the rotation axis direction of the developer carrier, is narrower than the second clearance in the second region.
A developing device characterized by that. The second clearance becomes narrower from the second region toward the first region with respect to the rotation axis direction of the developer carrier, and the second clearance is narrower with respect to the rotation axis direction of the developer carrier. It becomes narrower from the second region toward the third region.
The developing apparatus according to claim 1. When viewed in a cross section orthogonal to the rotation axis of the developer carrier,
The most downstream end of the cover portion in the rotation direction of the developer carrier is arranged at a position where the magnetic flux density of the first magnetic pole is maximized.
The developing apparatus according to claim 1 or 2. When viewed in a cross section orthogonal to the rotation axis of the developer carrier,
The most downstream end of the cover portion in the rotation direction of the developer carrier is downstream of the position where the magnetic flux density of the first magnetic pole is maximum in the rotation direction of the developer carrier and the developer carrier. It is arranged upstream in the rotation direction of the developer carrier from a position on a horizontal plane passing through the center of rotation of the developer .
The developing apparatus according to claim 1 or 2 . The region of the developer carrier having the developer transporting capacity is a region where the outer peripheral surface of the developer carrier is roughened.
The developing apparatus according to any one of claims 1 to 4 . Further provided with a regulating member arranged to face the developer carrier and to regulate the amount of the developer supported on the developer carrier.
When viewed in a cross section orthogonal to the rotation axis of the developer carrier,
The position where the restricting member is closest to the developer carrier is below the center of rotation of the developer carrier.
The developing apparatus according to any one of claims 1 to 5.

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