JP2018169574A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device that can sufficiently suppress scattering of developer from both ends in a rotation axis direction of a developer carrier in a developing container.SOLUTION: A developing container has an outer cover 47 that covers a developing sleeve, an inner cover 48 that covers the developing sleeve, and a pair of side walls 49, and forms, with these covers and walls, a second space F2 as a channel in a direction of rotation R of the developing sleeve. The second space F2 has end areas B3 that are located on both ends of the developing sleeve in a width direction W, and a center area B2 that is located toward the center with respect to the end areas B3; the end areas B3 are narrower than the center area B2 in terms of a direction of flow of gas circulating in the second space F2 and a direction orthogonal to a width direction W.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a developing device provided with a developer carrying member that carries and rotates a developer, and a copier, a printer, a facsimile, and a multi-function device equipped with such a function. The present invention relates to an image forming apparatus.

  An image forming apparatus using an electrophotographic system or an electrostatic recording system has a developing device that develops an electrostatic latent image formed on a photosensitive drum as an image carrier with a developer such as toner. The developing device has a developing sleeve as a developer carrying member that carries and rotates the developer, and supplies the developer carried on the developing sleeve to the photosensitive drum.

  In the case of such a developing device, there is a possibility that air flows into the developing container constituting the developing device by rotation of the developing sleeve, the pressure in the developing container increases, and the developer in the developing container is scattered outside the container. is there. For this reason, an inner cover is provided between the outer cover of the developing container and the developing sleeve, and air flowing into the developing container from between the developing sleeve and the inner cover is allowed to flow between the inner cover and the outer cover. There has been proposed a configuration in which the sheet is discharged outside the developing container (see Patent Document 1).

Japanese Patent Laying-Open No. 2015-72331

  However, in the case of the configuration described in Patent Document 1, air containing developer may be discharged out 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. is there. In particular, the developer scattered from both ends in the axial direction (rotation axis direction) of the developer carrying member of the developing container tends to flow around the developing container, and the scattering of the developer may not be sufficiently suppressed.

  An object of the present invention is to provide a developing device and an image forming apparatus that can sufficiently suppress the scattering of the developer from both ends in the rotation axis direction of the developer carrying member of the developing container.

  The developing device according to the present invention includes a developer container in which the developer is accommodated, and a developer that can carry and rotate the developer accommodated in the developer container, and can convey the developer to a facing area facing the image carrier. A first covering portion disposed downstream of the facing region with respect to the rotation direction of the developer carrier, and covering the developer carrier via a gap; and A second cover that is disposed between the first cover part and the developer carrier with a gap between each of the first cover part and the developer carrier and covers the developer carrier. Between the first cover portion and the second cover portion, on both sides in the rotation axis direction of the developer carrier, and a space between the first cover portion and the second cover portion is formed between the first cover portion and the second cover portion. Shielding at both sides in the rotational axis direction, together with the first cover and the second cover A pair of side walls forming a flow path along the rolling direction, and the flow path is positioned at both ends of the developer carrying member with respect to the rotation axis direction at least in part with respect to the rotation direction. An end region, and a central region located closer to the center than the end region, and the end region includes a flow direction of the gas flowing in the flow channel and the rotation axis direction than the central region. It is narrow in the direction orthogonal to

  According to the present invention, the end region of the flow path is narrower than the central region with respect to the gas flow direction and the direction orthogonal to the rotation axis direction. For this reason, the pressure loss of the air flowing through the flow path is larger in the end area than in the central area, and the air discharged from the developing container through the flow path is circulated in the central area rather than the end area. It becomes easy to do. As a result, when the air taken into the developing container by the rotation of the developer carrying member passes through the flow path, the air in the end region is concentrated in the central region. This makes it difficult for air from both ends in the rotation axis direction of the developer carrier of the developer container to flow into the flow path, and discharges air exhausted from the developer container to both ends of the developer carrier. Can be avoided. Therefore, it is possible to sufficiently suppress the developer scattering from both ends in the rotation axis direction of the developer carrying member of the developing container.

1 is a schematic sectional view of an image forming apparatus according to a first embodiment. FIG. 2 is a schematic cross-sectional view of an image forming unit according to the first embodiment. 1 is a schematic cross-sectional view of a developing device according to a first embodiment. 1 is a schematic longitudinal sectional view of a developing device according to a first embodiment. 1 is a schematic cross-sectional view of a replenishing device and a developing device according to a first embodiment. FIG. 3 is a cross-sectional view showing a magnetic flux density around a developing sleeve of the developing device according to the first embodiment. FIG. 3 is a cross-sectional view showing an airflow around the developing sleeve of the developing device according to the first embodiment. 4A and 4B are diagrams illustrating an airflow at an inlet of a second gap of the developing device according to the first exemplary embodiment, where FIG. 5A is a diagram viewed from the flow direction, and FIG. Figure. FIG. 3 is a cross-sectional view illustrating a developing sleeve end portion of the developing device according to the first embodiment. Sectional drawing which shows typically the airflow of the developing device which concerns on a comparative example. Sectional drawing which shows the airflow around the developing sleeve of the developing device which concerns on 2nd Embodiment. FIG. 10 is a cross-sectional view showing a modification of the second gap of the developing device, where (a) shows a case where the heights of the end region and the central region are substantially constant, and (b) shows a case where the height of the end region is constant In this case, the central region has a vertex at the central portion.

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

[Image forming apparatus]
The image forming apparatus 100 of this embodiment is an electrophotographic tandem full-color printer including four image forming units PY, PM, PC, and PK each having a photosensitive drum 1 as an image carrier. The image forming apparatus 100 receives a toner image (image) in response to an image signal from a document reading apparatus (not shown) connected to the apparatus main body 100A or a host device such as a personal computer connected to the apparatus main body 100A. ) On the recording material. Examples of the recording material include sheet materials such as paper, plastic film, and cloth. The image forming units PY, PM, PC, and PK form yellow, magenta, cyan, and black toner images, 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 development colors are different. Therefore, the image forming unit PY will be described as a representative, and description of the other image forming units will be omitted.

  As shown in FIG. 2, the image forming unit PY is provided with a cylindrical photosensitive member, that is, a photosensitive drum 1 as an image carrier. The photosensitive drum 1 is rotationally driven in the arrow direction in the figure. Around the photosensitive drum 1, a charging roller 2 as a charging unit, a developing device 4, a primary transfer roller 52 as a transfer unit, and a cleaning device 7 as a cleaning unit are arranged. Below the photosensitive drum 1 in the figure, an exposure device (laser scanner in the present embodiment) 3 as an exposure means is arranged.

  A transfer device 5 is disposed above each image forming unit in FIG. The transfer device 5 is configured such that an endless intermediate transfer belt 51 as an intermediate transfer member is stretched around a plurality of rollers, and rotates (rotates) in an arrow direction. The intermediate transfer belt 51 carries and conveys the toner image primarily transferred to the intermediate transfer belt 51 as will be described later. Out of the rollers that stretch the intermediate transfer belt 51, a secondary transfer outer roller 54 as a secondary transfer means is disposed at a position facing the secondary transfer inner roller 53 and the intermediate transfer belt 51 across the intermediate transfer belt 51. A secondary transfer portion T2 is configured to transfer the toner image on the belt 51 to the recording material. A fixing device 6 is disposed downstream of the secondary transfer portion T2 in the recording material conveyance direction.

  Under the image forming apparatus 100, a cassette 9 in which the recording material S is accommodated is disposed. The recording material S fed from the cassette 9 is transported toward the registration roller 92 by the transport roller 91. Then, the leading edge of the recording material S comes into contact with the registration roller 92 in the stopped state, and a skew is formed to correct the skew of the recording material S. Thereafter, the registration roller 92 starts 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 portion T2.

  A process for 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 with a laser beam corresponding to an image signal emitted from the exposure device 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 a toner as a developer accommodated in the developing device 4 and becomes a visible image.

  The toner image formed on the photosensitive drum 1 is primarily transferred to the intermediate transfer belt 51 at a primary transfer portion T1 (FIG. 2) configured with the primary transfer roller 52 disposed 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 remaining on the surface of the photosensitive drum 1 after the primary transfer (transfer residual toner) is removed by the cleaning device 7.

  Such an operation is sequentially performed in each of the yellow, magenta, cyan, and black image forming units, and the four color toner images are superimposed on the intermediate transfer belt 51. Thereafter, the recording material S accommodated in the cassette 9 is conveyed to the secondary transfer portion T2 in accordance with the toner image formation timing. Then, by applying a secondary transfer bias to the secondary transfer outer roller 54, the four color toner images on the intermediate transfer belt 51 are secondarily transferred onto the recording material S at once. The toner remaining on the intermediate transfer belt 51 without being completely transferred at the secondary transfer portion T2 is removed by the intermediate transfer belt cleaner 55.

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

  Note that the image forming apparatus 100 according to the present embodiment forms a single-color or multi-color image using an image forming unit for a desired single color or some of four colors, such as a black single-color image. Is also possible.

[Developer]
Next, a detailed configuration of the developing device 4 will be described with reference to FIGS. 3 and 4. The developing device 4 includes a developing container 41 that contains a developer containing non-magnetic toner and a magnetic carrier, and a developing sleeve 44 as a developer carrying member that carries and rotates the developer contained in the developing container. In the developing container 41, conveying screws 43a and 43b are arranged as developer conveying members that circulate in the developing container while stirring and conveying the developer in the developing container. The developing sleeve 44 can transport the developer to a facing area A that faces the photosensitive drum 1. A magnet 44a as a magnetic flux generating means having a plurality of magnetic poles in the circumferential direction is disposed in the developing sleeve 44 so as not to rotate. Further, a developing blade 42 as a regulating member for forming a thin layer of developer is disposed 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 rotational axis direction (axial direction) is shown as the width direction W.

  The inside of the developing container 41 is divided into a developing chamber 41a and a stirring chamber 41b horizontally by a partition wall 41c extending in a direction perpendicular to the paper surface, and the developer is divided into the developing chamber 41a and the stirring chamber. 41b. Conveying screws 43a and 43b are disposed in the developing chamber 41a and the stirring chamber 41b, respectively. The passage of the developer between the developing chamber 41a and the stirring chamber 41b is allowed at both ends in the longitudinal direction of the partition wall 41c (both ends in the rotation axis of the developing sleeve 44 and both ends in the width direction W in FIG. 4). Delivery parts 41d and 41e are provided.

  Each of the conveying screws 43a and 43b is formed by providing a spiral blade as a conveying unit around the axis (rotation axis) of the magnetic body. In addition to the spiral blades, the conveying screw 43b is provided with a stirring rib 43b1 protruding in the radial direction from the shaft and having a predetermined width in the developer conveying direction. The stirring rib 43b1 stirs the developer as the shaft rotates.

  The conveying screw 43a is disposed along the rotational axis direction of the developing sleeve 44 at the bottom of the developing chamber 41a. The developer in the developing chamber 41a is fed along the axial 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 carried on the developing sleeve 44 and having consumed the toner in the developing process is collected in the developing chamber 41a.

  The conveying screw 43b is disposed along the rotational axis direction of the developing sleeve 44 at the bottom of the stirring chamber 41b, and conveys the developer in the stirring chamber 41b along the axial direction opposite to the conveying screw 43a. In this way, the developer is transported by the transport screws 43a and 43b, and circulates in the developing container 41 via the delivery portions 41d and 41e.

  A developer replenishing port 46 for replenishing developer containing toner in the developing container 41 is provided at the upstream end of the agitating chamber 41b in the conveying direction of the conveying screw 43b. The developer replenishing port 46 is connected to a replenishment conveyance unit 83 of a developer replenishing device 80 shown in FIG. Accordingly, the replenishing developer is supplied from the developer replenishing device 80 into the agitating chamber 41 b via the replenishing conveyance unit 83 and the developer replenishing port 46. The conveying screw 43b conveys the developer replenished from the developer replenishing port 46 and the developer already in the agitating chamber 41b while agitating to uniformize the toner density.

  Therefore, the developer in the developing chamber 41a, in which the toner is consumed in the developing process due to the conveying force of the conveying screws 43a and 43b and the toner density is lowered, moves on one delivery portion 41d (left (W1) side in FIG. 4). To move into the stirring chamber 41b. Then, the developer that has moved into the agitating chamber 41b is conveyed while being agitated with the replenished developer, and moves to the developing chamber 41a via the other delivery portion 41e (right (W2) side in FIG. 4).

  As shown in FIG. 3, the developing chamber 41a of the developing container 41 has an opening 41h at a position corresponding to a facing area (developing area) A facing the photosensitive drum 1, and a developing sleeve 44 is formed in the opening 41h. It is rotatably disposed so as to be partially exposed in the direction of the photosensitive drum 1. On the other hand, the magnet 44a included 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 developer can be conveyed to the facing area A, and the developer is supplied to the photosensitive drum 1 in the facing area A. In the present embodiment, the developing sleeve 44 is formed in a cylindrical shape using, for example, aluminum or stainless steel as a nonmagnetic material. Further, the developing sleeve 44 rotates from the lower side to the upper side in the gravity direction in the facing region A, that is, in the counterclockwise direction of FIG.

  A developing blade 42 as a regulating member that regulates the amount of developer carried on the developing sleeve 44 is fixed to the developing container 41 on the upstream side of the opening 41 h in the rotation direction of the developing sleeve 44. In the present embodiment, since the developing sleeve 44 rotates from the lower side to the upper side in the gravitational direction in the facing area A, the developing blade 42 is positioned below the facing area A in the gravitational direction.

  The magnet 44a has a total of five 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 conveying screw 43a, and the developer supplied to the developing sleeve 44 is predetermined on the developing sleeve 44 by a magnetic field generated by the magnetic pole S2 for attracting the magnet 44a. Is carried to form a developer reservoir.

  When the developing sleeve 44 rotates, the developer on the developing sleeve 44 passes through the developer pool, rises at the regulating magnetic pole N1, and has a layer thickness by the developing blade 42 facing the regulating magnetic pole N1. Be regulated. Then, the developer whose layer thickness is regulated is conveyed to the facing area A facing the photosensitive drum 1 and spikes at the developing magnetic pole S1 to form magnetic spikes. The magnetic spike contacts the photosensitive drum 1 that rotates in the same direction as the developing sleeve 44 in the facing area A, and the electrostatic latent image is developed as a toner image by the charged toner.

  Thereafter, 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 to the surface of the developing sleeve 44 by the conveying magnetic pole N2. The developer carried on the developing sleeve 44 is peeled off 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 that detects the toner density 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 conveyance direction.

  As shown in FIG. 4, an imageable area (area where developer can be carried) of the developing sleeve 44 is defined as a coat area B1. 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 center region B2 is located on the center side of the end region B3 in the width direction W, and is formed to have a length that is at least 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 supply device]
Next, the developer supply device 80 will be described with reference to FIG. The developer supply device 80 includes a storage container 8 that stores a developer for supply, a supply mechanism 81, and a supply conveyance unit 83. The container 8 has a structure in which a spiral groove is dug in the inner wall of a cylindrical container, and the container 8 itself rotates to generate a developer conveying force in the longitudinal direction (rotation axis direction). Let A supply mechanism 81 is connected to the downstream end of the container 8 in the developer transport direction. The replenishment mechanism 81 has a pump part 81 a that discharges from a discharge port 82 through which developer is conveyed from the storage container 8. The pump portion 81 a is formed in a bellows shape, and is rotationally driven to change its volume and generate air pressure. The developer conveyed from the storage container 8 is discharged from the discharge port 82.

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

  In the developing device 4 described above, the developer supply port 46 is the upstream end of the stirring chamber 41b in the developer transport direction, and the developer formed by the developing chamber 41a (see FIG. 4) and the stirring chamber 41b. Is provided outside the circulation path. Specifically, the developer supply port 46 is provided on the upstream side in the developer transport direction of the stirring chamber 41b with respect to the one delivery portion 41d. Therefore, in the vicinity of the developer supply port 46, there is almost no developer in the developer circulation path, and only the supply developer passes.

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

  As shown in FIG. 1, the density sensor 103 faces the surface of the intermediate transfer belt 51 downstream of the most downstream image forming unit PK and upstream of the secondary transfer unit T2 in the rotation direction of the intermediate transfer belt 51. Are arranged. In the control using the density sensor 103, for example, a control toner image (patch image) is transferred onto the intermediate transfer belt 51 at the start of an image forming job or every time a predetermined number of images are formed. Thus, the density of the patch image is detected. Based on the detection result, developer replenishment control by the developer replenishing device 80 is performed.

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

[Developer splash]
Here, the scattering of the developer generated from the developing device will be described. First, an image forming apparatus is required to increase the speed and quality of an output image and to simplify maintenance. One of the maintenance simplifications is reduction of contamination due to the developer inside the image forming apparatus. When the inside of the image forming apparatus is contaminated with the developer, an image defect such as a dirty output image may occur, or a cleaning operation may occur when the developing device or the photosensitive drum unit is replaced. Further, when the developer adheres to each drive system such as a gear, there is a possibility that the drive system may slip.

  One cause of such contamination by the developer inside the image forming apparatus is that the developer is scattered from the inside of the developing apparatus. For example, in the case of a two-component developer, since the toner and the carrier are usually frictionally charged inside the developing device, the toner and the carrier are attached by electrostatic force. However, this adhesion is released by some impact, and there is a risk of the developer scattering, in which the toner released from the carrier is discharged together with air from the inside of the developing device.

  A specific example of such scattering of the developer will be described using a developing device 400 of a 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. For this reason, the same code | symbol is attached | subjected and demonstrated to the same structure. Further, similarly to the developing device 4 described above, the replenishing conveyance unit 83 of the developer replenishing device 80 is connected to the developing device 400.

  The developing container 401 includes an upper lid 402 that covers the top of the developing sleeve 44. Between the upper lid 402 and the developing sleeve 44, an air flow path is formed in which air flows into the developing container 401 by the rotation of the developing sleeve 44. This flow path is opened at a position facing the photosensitive drum 1, and the scattering of the developer from the inside of the developing container 401 mainly occurs from this flow path. This is because the developing blade 42 is opposed to the developing sleeve 44 in the vicinity of the flow path (the lower side in FIG. 10). That is, at this position, the developer carried on the developing sleeve 44 is in a state where the layer thickness is regulated 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. is there.

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

  First, toner release will be described. The toner and the carrier stored in the developing container 401 are frictionally charged in the stirring chamber 41b and the developing chamber 41a, and are adhered to each other by the electrostatic adhesion force generated by the frictional charging and the non-electrostatic adhesion force generated by the surface property. Yes. When an impact or shear 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. As the impact and shear force at this time, there is a developer behavior when the developer is conveyed by the developing sleeve 44.

  On the developing sleeve 44, the developer forms a magnetic spike having a chain-like structure along the magnetic field lines of the internal magnetic poles. The magnetic spike rises forward in the rotational direction immediately before the magnetic pole by the rotation of the developing sleeve 44, and falls forward in the rotational direction when passing over the magnetic pole. 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 released due to the toner being peeled off from the carrier by the impact and centrifugal force when the magnetic spike falls.

  The magnetic pole that greatly contributes to the release of the toner when the developer is conveyed by the developing sleeve 44 is a peeling magnetic pole S3 that generates a repulsive magnetic field with the attracting 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, the speed of the conveyed developer is reduced, and the developer is retained. . At this time, since the length of the magnetic spike becomes long, the impact and centrifugal force when the magnetic spike falls down tend to increase, and the amount of released toner tends to increase.

  Further, when the developer is supplied from the developer supply device 80 to the developer supply port 46, the developer that has swollen before being sufficiently agitated also causes free toner in the developer 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 mixed region of the replenishment 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 force between the toner and the carrier decreases. The toner that could not be mixed with the developer is released as it is or by the impact of the developer stirring and transporting by the transport screws 43a and 43b, and the free toner rises 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 developer replenishing port 46. There is. The airflow that flows in at this time winds up the free toner in the developing container 401 at a portion where the mixing ratio of the toner and the developer near the developer supply port 46 is high. The air pressure propagation to the developing container 401 causes an unsteady rise in air pressure from the developer supply port 46 to the stirring chamber 41b. This increase in atmospheric pressure causes free toner to flow out of the developing container 401 as described later. In particular, the inflowing air due to such developer replenishment is one of the causes of the developer scattering at the end including the developer replenishing port 46 in the longitudinal direction of the developing container 401 (the rotational axis direction of the developing sleeve 44). Become one.

  Next, the airflow in and near the developing device 400 will be described with reference to FIG. The developing sleeve 44 and the photosensitive drum 1 generate 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 spike on the magnetic pole, an air flow is generated in substantially the same direction as the rotating direction of the developing sleeve 44. The airflow generated in the substantially same direction as the rotation direction of the developing sleeve 44 takes air into the developing container 401 from the communication port inside the developing container 401 and the developing container 401. Further, air flows into the developing container 401 even when the developer is replenished.

Assuming that the developer container 401 is a substantially closed space, since air is a fluid, a continuous equation can be applied. 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 up in the developing container 401.

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

From this equation (2), the flow rate ρv of air is preserved. In the longitudinal section in the vicinity of the developing device 400, the balance of the flow rate ρv is 0, and the same amount as the flow rate of air flowing in by the replenishment with the developing sleeve 44 is discharged out of the developing device 400. Here, the flow rate of air flowing into the developing container 401 as the developing sleeve 44 rotates through the communication port constituted by 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 defined as Qb (sleeve discharge). Further, when the air flow rate that flows in along with 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 in the developing container 401 and discharged. At this time, when the air flow is folded back at the developer retaining portion of the peeling magnetic pole S3 including the developer peeled from the developing sleeve 44, the air flow causes the developer such as free toner generated in the developing container 401 to flow. It will go in the direction of discharge including many.

  There are mainly three processes in which the developer contained in the sleeve discharge air (flow rate Qb) is discharged out of the developing container 401. In the first step, the sleeve discharge air (flow rate Qb) discharged out of the developing device 400 from the communication port 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. It is. As a third step, the free toner contained in the sleeve discharge air (flow rate Qb) is transferred to the air flow g generated by the photosensitive drum 1 by inertia and discharged to the outside of the developing container 401.

  The scattering of the developer is discharged out of the developing container 401 due to at least one of the above three. 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.

[Configuration of Developer Container of this Embodiment]
In the present embodiment, the configuration of the developing container 41 of the developing device 4 is as follows. A detailed configuration of the developing container 41 of the present embodiment will be described with reference to FIG. A 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. The rotation direction of the developing sleeve 44 is R. Of the magnetic poles of the magnet 44a, the peeling magnetic pole S3 corresponds to the first magnetic pole, and the attracting magnetic pole S2 corresponds to the second magnetic pole. The peeling magnetic pole S <b> 3 is disposed on the downstream side of the facing area A in the rotation direction R, and peels off the developer carried on the developing sleeve 44. The attracting magnetic pole S2 is arranged adjacent to the downstream side of the peeling magnetic pole S3, and has the same polarity as the peeling magnetic pole S3, and pumps the developer in the developing container 41 to the developing sleeve 44. In FIG. 6, the position of each of the five magnetic poles is indicated by a straight line indicating the peak position of the magnetic flux density.

  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 with respect to the facing area A. The upper lid 41f includes an outer cover 47 as a first cover part and an inner cover 48 as a second cover part. The outer cover 47 is disposed on the downstream side of the facing region A with respect to the rotation direction R, and covers the developing sleeve 44 through a gap.

  The inner cover 48 is disposed between the outer cover 47 and the developing sleeve 44 with a gap between each of the outer cover 47 and the developing sleeve 44 and covers the developing sleeve 44. The downstream end 48b in the rotation direction R of the developing sleeve 44 of the inner cover 48 has an upstream minimum value M1 of the pair of minimum values M1 and M2 with respect to the rotation direction R of the absolute value of the magnetic flux density distribution of the peeling magnetic pole S3. It is located on the downstream side. Further, the downstream end 48b in the rotation direction R of the inner cover 48 is preferably located on the downstream side in the rotation direction R from the peak position or peak position of the magnetic flux density of the separation magnetic pole S3. By disposing the position of the downstream end 48b in the rotation direction R of the inner cover 48 at a position that satisfies these conditions, the range in which the peeling magnetic pole S3 is covered by the inner cover 48 can be made wider.

  However, the downstream end 48 b in the rotation direction R of the inner cover 48 is preferably 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 with respect to the horizontal plane H position. This is because if the downstream end 48b in the rotation direction R of the inner cover 48 is located further downstream, it is difficult to take the developer peeled from the developing sleeve 44 into the developing chamber 41a.

[Characteristic configuration in this embodiment]
Next, a characteristic configuration of the developing device 4 of the present embodiment will be described with reference to FIGS. First, the gap between the inner cover 48 and the developing sleeve 44 is defined as a first gap (gap) F1. A gap between the inner cover 48 and the outer cover 47 is defined as a second gap (flow path, gap) F2. A gap between the opposite end 47a of the outer cover 47 facing the photosensitive drum 1 and the photosensitive drum 1 is defined as a third gap F3. The developing container 41 has a pair of side walls 49 provided at both ends in the width direction W of the developing sleeve 44 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. To do.

  The second gap F2 has an inflow port (opening) 11 through which air flows in and an outflow port 12 through 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. The outflow port 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 the center area | region B2 and the edge part area | region B3. That is, the second gap F2 is at least partially in the rotational direction R, with respect to the width direction W, the end region B3 located on both ends of the developing sleeve 44, and the central region located on the center side of the end region B3. B2. And the edge part area | region B3 is formed so that it may be narrower about the direction orthogonal to the flow direction and the width direction W of the gas which distribute | circulates in the 2nd clearance gap F2 rather than center area | region B2. That is, when the distance between the outer cover 47 and the inner cover 48 is a height H, the average height H2 of the central region B2 and the average height H3 of the end region B3 are H2> The relationship is H3.

  The shape of the inlet 11 and the shape of the outlet 12 are the same. Furthermore, in the second gap F2, the area of the cross section perpendicular to the flowing direction of the flowing gas is constant. In the present embodiment, the surface of the inner cover 48 on the second gap F2 side is configured by a single curved surface that is linear in the width direction W. Further, the surface on the second gap F2 side of the outer cover 47 is configured by two curved surfaces with the center in the width direction W protruding upward and having a vertex 47p, and both end portions inclined downward.

  As a result, the height H increases toward the central region B2 of the second gap F2, and the pressure loss of the circulating air decreases. 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 ( b)). Thereby, edge part scattering can be suppressed while discharging the air in the developing container 41 due to the air flow taken into the developing container 41.

  In the present embodiment, the inlet 11 is located downstream of the upstream minimum value M1 of the pair of minimum values M1 and M2 with respect to the rotational direction R of the absolute value of the magnetic flux density distribution of the separation magnetic pole S3. To position. Furthermore, the inflow port 11 is located downstream of the peak direction or peak position of the magnetic flux density of the separation magnetic pole S3 in the rotation direction R and upstream of the adsorption magnetic pole S2.

  The airflow 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 with the rotation of the developing sleeve 44, and flows into the developing container 41 through the first gap F1. The inflow into the developing container 41 increases the internal pressure of the developing container 41, and exhaust is performed from the discharge path. Here, in a configuration that does not have 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, the toner release amount increases in the vicinity of the peeling magnetic pole S3, and thus the released toner is scattered outside the developing container 41 by the air flow b.

  In contrast, 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 air flow e is generated in the second gap F2 as an exhaust air flow. Thereby, since the air flow b which is the exhaust air flow is not generated in the first gap F1, the air in the developing container 41 can be discharged without passing the vicinity of the peeling magnetic pole S3, and the toner scattering can be reduced. A small amount of toner may be discharged out of the developing container 41 through the outlet 12 through the path of the air flow e. However, most of the toner adheres to the opposing photosensitive drum 1 and is collected by the cleaning device 7. The periphery of the developing device 4 is not contaminated.

  Here, the toner discharged from both ends in the width direction W at the opening 41 h of the developing device 4 is scattered outside the both ends in the width direction W of the photosensitive drum 1 by the air current 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 inlet 11 at both ends of the developer container 41 due to the inflow of air from the replenishment conveyance unit 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 to be narrower with respect to the flow direction of the gas flowing in the second gap F2 and the direction orthogonal to the width direction W than the center region B2. ing. This makes it difficult for air from both ends in the width direction W of the developing sleeve 44 of the developing container 41 to flow into the second gap F2, and exhausts air exhausted from the developing container 41 to both ends of the developing sleeve 44. Can be avoided. Thereby, while discharging the air in the developing container 41 due to the air flow taken into the developing container 41, it is possible to sufficiently suppress the scattering of the developer from both ends in the width direction W of the developing sleeve 44 of the developing container 41, Contamination around the developing device 4 due to scattered toner can be suppressed.

  Further, when the end region B3 is closer to the center side than the coating region B1 of the developing sleeve 44 and both end portions in the width direction W of the inner cover 48 do not face the coating region B1, an air flow b is generated in the coating region B1. End up. This causes toner scattering from the end of the developing container 41. Therefore, at least a part of the end region B3 is preferably wider than the coat region B1 and located outside.

  Here, the center region B2 and the end region B3 will be described using specific examples. Both ends of the developing sleeve 44 are sealed. As a seal configuration that seals both ends of the developing sleeve 44, a magnetic seal configuration that magnetically blocks the outside and the inside of the developing container 41 is used. FIG. 9 shows an example of the magnetic seal configuration. The magnetic seal configuration shown in FIG. 9 is such that the plate-like magnetic plate 13 and the magnet sheet 14 are formed at the sleeve end portion 44b of the developing sleeve 44 that has not been subjected to the roughening treatment, that is, the width of the developing sleeve 44 beyond the coating region B1. The configuration is arranged outside the direction W (outside the developer carrying region).

  The magnetic plate 13 as a magnet member can form a magnetic spike by covering the developing sleeve 44 in a non-contact manner along the outer periphery of the developing sleeve 44. 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 entered between the magnetic plate 13 and the developing sleeve 44 forms a magnetic spike. The magnetic spikes block the gap between the magnetic plate 13 and the developing sleeve 44, thereby preventing developer leakage from the sleeve end 44b. Further, the magnet sheet 14 is provided further outside the magnetic plate 13 in the rotation axis direction of the developing sleeve 44. The magnet sheet 14 holds the developer leaking from between the magnetic plate 13 and the developing sleeve 44 by a magnetic force. By providing the magnetic plate 13 and the magnet sheet 14 in this manner, developer leakage from the sleeve end portion 44b is suppressed.

  The central region B2 is formed so that both end portions are positioned at a distance of 10 mm or more and 30 mm or less from the position of the magnetic plate 13 to the center side, for example. 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 290 mm to 310 mm, and the longitudinal length of the end region B3 is 20 to 40 mm. Accordingly, 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 device 4 of the present embodiment, the end region B3 of the second gap F2 is narrower in the gas flow direction and the direction perpendicular to the width direction W than the central region B2. For this reason, the pressure loss of the air flowing through the second gap F2 is larger in the end area B3 than in the central area 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 area B2 than in the area B3. As a result, when the air taken into the developing container 41 due to 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 in the width direction W of the developing sleeve 44 of the developing container 41 to flow into the second gap F2, and exhausts air exhausted from the developing container 41 to both ends of the developing sleeve 44. Can be avoided. Therefore, the scattering of the developer from both ends in the width direction W of the developing sleeve 44 of the developing container 41 can be sufficiently suppressed. Further, even if the developer scatters, the amount of scatter is small, so even if the developer adheres to the image, the amount of adhesion cannot be visually recognized, and it is possible to suppress degradation in image quality.

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

  Further, according to the developing device 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. For this reason, compared with the case where the entire end region B3 is located inside the coating region B1 in the width direction W, the generation of the air flow b in the coating region B1 can be suppressed. Can be suppressed.

  Further, as described above, since a large amount of toner is released when the magnetic spike is tilted by the peeling magnetic pole S3, the air flow a in the first gap F1 includes a large amount of free toner thus generated. According to the developing device 4 of the present embodiment, the downstream end 48b of the inner cover 48 is positioned downstream of the upstream minimum value M1 of the magnetic flux density distribution of the peeling magnetic pole S3, so that at least the peeling magnetic pole S3. Is covered with an inner cover 48. In particular, in this embodiment, since the downstream end 48b of the inner cover 48 is positioned downstream of the peak position of the peeling magnetic pole S3, an area where free toner is generated when the magnetic spike is tilted by the peeling magnetic pole S3. Many 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. This embodiment is different from the first embodiment in that the outflow port 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 configuration is the same as that of the first embodiment, the same reference numerals are used and detailed description thereof is omitted.

  As shown in FIG. 11, the outer cover 47 is bent toward the photosensitive drum 1 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 as follows. The outer cover 47 includes 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 rotational direction R of the developing sleeve 44 with respect to a part (continuous portion 47d) facing the upstream end 48a in the rotational direction R of the inner cover 48. The second facing portion 47 c faces the portion between the upstream end 48 a and the downstream end 48 b of the inner cover 48 in the rotation direction R.

  Since the inner cover 48 is disposed between the second facing portion 47 c and the developing sleeve 44, the second facing portion 47 c is disposed outside the first facing portion 47 b in the radial direction of the developing sleeve 44. For this reason, the continuous part 47d which continues the upstream end of the rotation direction R of the 2nd opposing part 47c and the downstream end of the rotation direction R of the 1st opposing part 47b is provided. The continuous portion 47d is formed to bend toward the developing sleeve 44 from the upstream end in the rotation direction R of the second facing portion 47c. The continuous portion 47d faces the upstream end 48a in the rotation direction R of the inner cover 48 in the rotation direction R via the second gap (gap) F22. That is, the inner cover 48 is formed such that the upstream end in the rotation direction R faces a part of the outer cover 47 in the rotation direction R with the second gap F22 interposed therebetween.

  In the vicinity of the developing sleeve 44, as the developing sleeve 44 rotates, air currents a and c are generated in the first gaps (gap) F11 and F12 and flow into the developing container 41. When air flows into the developing container 41, the internal pressure in the developing container 41 increases, and exhaust is performed 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, 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 air flow f joins the first gap F11 between the developing sleeve 44 and the outer cover 47 in the vicinity of the uppermost portion of the developing sleeve 44, and is discharged out of the developing container 41 from the air flow b through the air flow g.

  Also in the developing device 4 of this embodiment, the end regions B3 of the second gaps F21 and F22 are narrower in the gas flow direction and the direction perpendicular to the width direction W than the central region B2. This makes it difficult for air from both ends in the width direction W of the developing sleeve 44 of the developing container 41 to flow into the second gap F2, and exhausts air exhausted from the developing container 41 to both ends of the developing sleeve 44. Can be avoided. Therefore, the scattering of the developer from both ends in the width direction W of the developing sleeve 44 of the developing container 41 can be sufficiently suppressed.

  Further, according to the developing device 4 of the present embodiment, the upstream end 48a in the rotation direction R of the inner cover 48 faces the continuous portion 47d of the outer cover 47 in the rotation direction R via the second gap F22. For this reason, the airflow e passing through the second gap F21 merges with the airflow b in 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 becomes difficult 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 protrudes upward in the center in the width direction W and has an apex 47p, and both ends are downward. Although the case where it is two inclined curved surfaces was demonstrated, it is not restricted to this. For example, as shown in FIG. 12A, the heights of the end region B3 and the central region B2 may be substantially constant. Alternatively, as shown in FIG. 12B, the end region B3 may have a constant height, and the central region B2 may have a vertex 47p at the center. Moreover, although each embodiment demonstrated the case where the surface at the side of the 2nd clearance gap F2 of the inner cover 48 was one curved surface which is linear in the width direction W, it is not restricted to this. The surface on the second gap F2 side of the inner cover 48 may have various shapes other than the linear shape, similarly to the surface on the second gap F2 side of the outer cover 47.

  In each of the above-described embodiments, the configuration using the two-component developer including toner and carrier as the developing device 4 has been described. However, the present invention can be applied to a configuration having the above-described peeling magnetic pole S3 even if a one-component developer containing a magnetic toner is used.

  Further, the present invention separates the function of supplying and recovering the developer in addition to the configuration in which the developer is supplied to the developing sleeve 44 and the developer is recovered from the developing sleeve 44 in the developing chamber 41a as described above. It is also applicable to a so-called function separation type developing device. For example, referring to FIG. 3, even if the developer is supplied from the developing chamber 41a to the developing sleeve 44 and the developer peeled off from the developing sleeve 44 is collected by the stirring chamber 41b, The invention can be applied.

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum (image carrier), 4 ... Developing apparatus, 11 ... Inlet (opening), 41 ... Developing container, 44 ... Developing sleeve (developer carrier), 44a ... Magnet (magnetic flux generating means), 47 ... outer cover (first covering part), 48 ... inner cover (second covering part), 49 ... side wall, 100 ... image forming apparatus, A ... facing area, B1 ... coat area (developer carrying area), B2 ... center Area, B3 ... end area, 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 ... adsorption magnetic pole (second magnetic pole), S3 ... peeling magnetic pole (first magnetic pole), W ... width direction (rotation axis) direction).

Claims (9)

A developer container in which the developer is accommodated, and a developer carrier that carries and rotates the developer accommodated in the developer container and can transport the developer to a facing region facing the image carrier,
The developer container is
A first cover portion disposed downstream of the facing region with respect to the rotation direction of the developer carrier, and covering the developer carrier via a gap;
A second gap is disposed between the first cover and the developer carrier with a gap between each of the first cover and the developer carrier, and covers the developer carrier. A cover,
A space between the first cover and the second cover is provided on both sides in the rotation axis direction of the developer carrier, and a space between the first cover and the second cover is defined in the rotation axis direction. A pair of side walls that form a flow path along the rotational direction together with the first cover portion and the second cover portion.
The flow path is at least partially related to the rotation direction, with respect to the rotation axis direction, an end region located on both ends of the developer carrier, and a central region located on the center side of the end region. Have
The end region is narrower than the central region with respect to the flow direction of the gas flowing in the flow path and the direction orthogonal to the rotation axis direction,
A developing device. The opening that opens at the downstream end of the flow direction in the flow path includes the end region and the central region.
The developing device according to claim 1. In the flow path, the cross-sectional area perpendicular to the flow direction is constant.
The developing device according to claim 1, wherein At least a part of the end region is located outside of the developer carrying region capable of carrying the developer of the developer carrying body in the rotation axis direction.
The developing device according to claim 1, wherein The central region is formed to have a length that is at least half of the length of the developer carrying region including the center of the developer carrying region capable of carrying the developer of the developer carrying member with respect to the rotation axis direction. ,
The developing device according to claim 1, wherein With respect to the rotation direction, the first magnetic pole is disposed on the downstream side of the opposed region and peels off the developer carried on the developer carrier, and is disposed adjacent to the downstream side of the first magnetic pole, A magnetic flux generating means having a second magnetic pole having the same polarity as the first magnetic pole and pumping up the developer in the developer container onto the developer carrier,
The opening is located downstream of the upstream minimum value of the pair of minimum values related to the rotation direction of the absolute value of the magnetic flux density distribution of the first magnetic pole,
The developing device according to claim 2, wherein: The opening is located at the peak position of the magnetic flux density of the first magnetic pole or at the downstream side of the rotation direction from the peak position.
The developing device according to claim 6. The second cover part is formed such that an upstream end in the rotational direction faces a part of the first cover part in the rotational direction with a gap therebetween.
The developing device according to claim 1, wherein A developing device according to any one of claims 1 to 8,
An image carrier that carries an electrostatic latent image developed by the developing device and rotates in the same direction as the developer carrier in the facing region.
An image forming apparatus.

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