Developing apparatus and image forming apparatus

Abstract

Compared to a configuration in which magnetic members are positioned opposite each other at magnetic poles located inside a cylindrical rotating member, this configuration makes it less likely that the developer adhering to the outer surface of the rotating member will be in a manner different from the originally intended adhesion manner. [Solution] The rotating member is rotatably mounted and has one end and the other end, and comprises a plurality of magnetic poles arranged in the direction of rotation on the inside of the rotating member to which the developer adheres to the outer surface. The rotating member is located on the outside of the rotating member and opposite to one end, and has a downstream end located on the downstream side in the direction of rotation, and forms a magnetic field with the magnetic poles. The rotating member is located on the outside of the rotating member and opposite to one end, and is located on the other end side of the first magnetic member, and forms a magnetic field with the magnetic poles, and has an opposing portion. The opposing portion of the second magnetic member is located upstream in the direction of rotation from the first magnetic pole located counting from the downstream end side of the first magnetic member toward the upstream side in the direction of rotation.

Description

Technical Field

[0001] The present invention relates to a developing device and an image forming apparatus.

Background Art

[0002] Patent Document 1 discloses a developing device in which, with respect to the axial direction of a developer carrier, an outer peripheral surface of the developer carrier has a first region including a developing region and a second region that is outside the first region, adjacent to the first region, and has a lower developer conveyance ability or substantially no conveyance ability than the first region, and boundaries between the first region and the second region of the outer peripheral surface of the developer carrier at both axial ends of the developer carrier are located between a magnetic seal member and a magnetic member in the axial direction of the developer carrier.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a developing device used for development, a magnetic pole may be arranged inside a cylindrical rotating member, and a developer may be attached to an outer peripheral surface of the rotating member. Here, in a configuration where a magnetic member is arranged outside the rotating member, the developer on the outer peripheral surface of the rotating member may move due to this magnetic member. In this case, the attachment mode of the developer attached to the outer peripheral surface of the rotating member may become different from the originally planned attachment mode. An object of the present invention is to make it less likely that the attachment mode of the developer attached to the outer peripheral surface of the rotating member becomes different from the originally planned attachment mode as compared with a configuration in which a magnetic member is arranged at a location facing a magnetic pole located inside the cylindrical rotating member.

Means for Solving the Problems

[0005] The invention described in claim 1 is a developing apparatus comprising: a rotating member formed in a cylindrical shape, rotatably mounted, having one end and the other end, to which a developer adheres to its outer surface; a plurality of magnetic poles disposed inside the rotating member and arranged in line in the rotational direction of the rotating member; a first magnetic member disposed outside the rotating member and positioned opposite to one end of the rotating member, having a downstream end which is the end located downstream in the rotational direction of the rotating member, and forming a magnetic field with the magnetic poles; and a second magnetic member disposed outside the rotating member and positioned opposite to one end of the rotating member, and positioned further toward the other end of the rotating member than the first magnetic member, forming a magnetic field with the magnetic poles, having a facing portion which is the portion facing the rotating member, wherein the facing portion of the second magnetic member is located upstream in the rotational direction from the first magnetic pole which is located upstream in the rotational direction from the downstream end of the first magnetic member. The invention described in claim 2 is a developing apparatus according to claim 1, wherein the opposing portion of the second magnetic member has a downstream end which is the end located downstream in the rotational direction of the rotating member, and the downstream end of the opposing portion of the second magnetic member is located downstream in the rotational direction of the magnetic pole which is the second magnetic pole located upstream in the rotational direction from the downstream end of the first magnetic member. The invention described in claim 3 is a developing apparatus according to claim 2, wherein the downstream end of the opposing portion of the second magnetic member is located downstream in the rotational direction from an intermediate position located between the first magnetic pole and the second magnetic pole. The invention described in claim 4 is a developing apparatus according to claim 1, wherein the second magnetic member is provided upstream in the rotational direction of a virtual plane that extends along the radial direction of the rotating member and is directed from the rotation center of the rotating member toward the first magnetic pole. The invention described in claim 5 is a developing apparatus according to claim 4, wherein the opposing portion of the second magnetic member has a downstream end which is the end located downstream in the rotational direction of the rotating member, the second magnetic member has a downstream edge which is located downstream in the rotational direction of the rotating member and is connected to the downstream end it has and extends toward a direction toward away from the rotating member, and all portions of the downstream edge of the second magnetic member are provided upstream in the rotational direction of the virtual plane, and the second magnetic member is provided such that the virtual plane and the second magnetic member do not intersect. The invention described in claim 6 is an image forming apparatus comprising an image holder for holding an image and a developing apparatus for applying a developer to the image holder, wherein the developing apparatus has the configuration of the developing apparatus described in any one of claims 1 to 5. [Effects of the Invention]

[0006] According to the invention of claim 1, compared to a configuration in which magnetic members are arranged at opposing locations of magnetic poles located inside a cylindrical rotating member, it is possible to make it less likely that the manner in which the developer adheres to the outer surface of the rotating member will differ from the originally intended manner of adhesion. According to the invention of claim 2, compared to a configuration in which the downstream end of the opposing portion of the second magnetic member is positioned upstream in the rotational direction from the second magnetic pole located upstream in the rotational direction from the downstream end of the first magnetic member, the range in which the movement of the developer attempting to move in the axial direction of the rotating member can be restricted can be expanded in the circumferential direction of the rotating member. According to the invention of claim 3, compared to a configuration in which the downstream end of the opposing portion of the second magnetic member is located upstream in the rotational direction from an intermediate position located between the first and second magnetic poles, the range in which the movement of the developer attempting to move in the axial direction of the rotating member can be restricted can be expanded in the circumferential direction of the rotating member. According to the invention of claim 4, compared to a configuration in which a part of the second magnetic member is located downstream in the direction of rotation from a virtual plane directed toward the first magnetic pole located from the rotation center of the rotating member, it is possible to make it less likely that the manner in which the developer adheres to the outer surface of the rotating member will be different from the originally intended manner of adhesion. According to the invention of claim 5, compared to a configuration in which a part of the second magnetic member is located downstream in the direction of rotation from a virtual plane directed toward the first magnetic pole located from the rotation center of the rotating member, it is possible to make it less likely that the manner in which the developer adheres to the outer surface of the rotating member will be different from the originally intended manner of adhesion. According to the invention of claim 6, compared to a configuration in which magnetic members are arranged at opposing locations of magnetic poles located inside a cylindrical rotating member, it is possible to make it less likely that the manner in which the developer adheres to the outer surface of the rotating member will differ from the originally intended manner of adhesion. [Brief explanation of the drawing]

[0007] [Figure 1] This is a diagram showing an image forming apparatus. [Figure 2] This is a diagram showing the developing apparatus viewed from above. [Figure 3] Figure 2 shows a cross-sectional view of the developing apparatus along line III-III. [Figure 4] Figure 2 is a cross-sectional view of the developing apparatus in the IV-IV line. [Figure 5] Figure 2 is a cross-sectional view of the developing apparatus in the VV line. [Figure 6] This is an explanatory diagram illustrating the developer suction mechanism in a developing device. [Figure 7] This figure shows the state of one end of the developing apparatus as viewed from the direction indicated by arrow VII in Figure 2. [Figure 8] This is a perspective view of the developing device, looking from the other end towards one end. [Figure 9] This is a perspective view of one end of the developing apparatus from the direction indicated by arrow IX in Figure 7. [Figure 10]It is a view of the developing device seen from below. [Figure 11] It is a perspective view of a cross section of the developing device taken along line XI-XI of FIG. 7. [Figure 12] It is a diagram for comparing the sizes of the first opening and the second opening. FIG. 12(a) is a diagram showing the first opening, and FIG. 12(b) is a diagram showing the second opening. [Figure 13] It is an explanatory diagram for explaining a mechanism for preventing scattering of the developer in the developing device. [Figure 14] It is a view when looking at the first magnetic member, the second magnetic member, etc. from the direction indicated by arrow XIV in FIG. 13. [Figure 15] It is a view when looking at one end of the opposing member obliquely upward and from the side of the other end. [Figure 16] It is a cross-sectional view of the developing device taken along line XVI-XVI of FIG. 15. [Figure 17] It is a diagram showing a comparative example of the second magnetic member, etc.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing an image forming apparatus 100 according to the present embodiment. FIG. 1 shows a state when the image forming apparatus 100 is viewed from the front side of the image forming apparatus 100. The image forming apparatus 100 is an image forming apparatus 100 of an intermediate transfer type called a tandem type. This image forming apparatus 100 is provided with a plurality of image forming units 200 that form an image to be transferred onto a sheet P, which is an example of a recording medium.

[0009] Each of the image forming units 200 includes a photosensitive drum 11 as an example of an image carrier, uses a developer containing toner, and forms a toner image, which is an image to be transferred onto the sheet P, on this photosensitive drum 11. In other words, each of the image forming units 200 forms a toner image to be transferred onto the sheet P on this photosensitive drum 11 using a powdery developer. The developer in this embodiment consists of a dry carrier and a dry toner. Each of the image forming units 200 uses the carrier and toner to form a toner image on the photoreceptor drum 11.

[0010] The six image forming units 200 use different types of developers to form toner images on the photoreceptor drum 11. Specifically, in this embodiment, four of the six image forming units 200 form toner images using yellow, magenta, cyan, and black developer. Furthermore, the remaining two image forming units 200 use developers other than basic colors, such as clear, white, gold, silver, pink, green, and orange, to form toner images.

[0011] In addition to the basic colors, other examples of developers include those containing magnetic toners and those containing conductive toners. Furthermore, developers containing toners that emit light when exposed to ultraviolet or infrared light are also examples of developers other than the basic colors. In this embodiment, a so-called two-component developer, which is a mixture of carrier and toner, is used as the developer. However, the developer is not limited to this, and a so-called one-component developer, which is composed only of toner, may also be used.

[0012] Furthermore, the image forming apparatus 100 is provided with an intermediate transfer belt 15 and a primary transfer unit 10 for transferring the toner images formed in each of the image forming units 200 to the intermediate transfer belt 15. Furthermore, the image forming apparatus 100 is provided with a secondary transfer unit 20 for transferring the toner image transferred onto the intermediate transfer belt 15 to the paper P.

[0013] Furthermore, the image forming apparatus 100 is equipped with a fixing device 60 for fixing the toner image transferred to the paper P onto the paper P. Furthermore, the image forming apparatus 100 is equipped with a CPU that executes programs and a control unit 40 that controls each part within the image forming apparatus 100. Furthermore, the image forming apparatus 100 is equipped with a UI (User Interface) 45, which consists of a display panel and the like, that receives instructions from the user and displays information to the user.

[0014] Each of the image forming units 200 is provided with a developing device 14. Each of the image forming units 200 is also provided with a developing agent supply device 70 for supplying developing agent to the developing device 14. The developing device 14 makes the electrostatic latent image on the photoreceptor drum 11 visible using toner. In other words, the developing device 14 develops the photoreceptor drum 11, which is the image holder, and forms an image on the photoreceptor drum 11 using toner. The developer supply device 70 supplies developer to the developing device 14. As described above, the developer consists of a carrier and a toner, and the developer supply device 70 supplies the carrier and toner to the developing device 14 as the developer. In this embodiment, the carrier has a positive charge polarity, and the toner has a negative charge polarity.

[0015] In each of the image forming units 200, a photosensitive drum 11, which is an example of an image holder, rotates in the direction of arrow A. Furthermore, each of the image forming units 200 is provided with a charger 12 for charging the photoreceptor drum 11, and a laser exposure unit 13 as an example of an exposure device for forming an electrostatic latent image on the photoreceptor drum 11. In Figure 1, the exposure beam from the laser exposure unit 13 is indicated by the symbol Bm. Note that the exposure device may be configured with a device equipped with a light source such as an LED.

[0016] Furthermore, each image forming unit 200 is provided with a primary transfer roll 16 that transfers the toner image formed on the photoreceptor drum 11 to the intermediate transfer belt 15 via the primary transfer unit 10. Additionally, each image forming unit 200 is provided with a drum cleaner 17 that removes any remaining developer on the photoreceptor drum 11. The intermediate transfer belt 15 moves in a predetermined speed in the direction of arrow B shown in Figure 1 by a drive roll 31 driven by a motor (not shown). The primary transfer unit 10 includes a primary transfer roll 16 positioned opposite the photoreceptor drum 11, with an intermediate transfer belt 15 in between. Then, the toner images on each photoreceptor drum 11 are sequentially electrostatically attracted to the intermediate transfer belt 15, and superimposed toner images are formed on the intermediate transfer belt 15.

[0017] A secondary transfer section 20, as an example of a transfer section, is composed of a secondary transfer roll 22 positioned on the outer surface side of the intermediate transfer belt 15 and a backup roll 25 positioned on the inner surface side of the intermediate transfer belt 15. In this embodiment, the toner image formed by the image forming unit 200 and transferred onto the intermediate transfer belt 15 is transferred to the paper P that has been transported to the secondary transfer unit 20 in the secondary transfer unit 20.

[0018] Furthermore, in this embodiment, a reversal mechanism 900 is provided for reversing the paper P. The reversal mechanism 900 reverses the front and back sides of the paper P, on which the toner image has been transferred to one side in the secondary transfer unit 20, and then supplies the paper P to the secondary transfer unit 20 again. This allows for the formation of toner images on both sides of the paper P in this embodiment.

[0019] Specifically, in this embodiment, the reversal mechanism 900 reverses the front and back sides of the paper P by feeding the paper P, which has passed through the fixing device 60, to the branch path R2, which branches off from the paper transport path R1. Specifically, after the paper P has passed through the branch section BP, the reversal mechanism 900 transports the paper P in the reverse direction and then feeds the paper P into the branch path R2. This branching path R2 merges with the paper transport path R1 upstream of the secondary transfer unit 20. As a result, in this embodiment, the paper P, with its front and back sides reversed, is supplied to the secondary transfer unit 20 again. In this case, a toner image is formed not only on one side of the paper P but also on the other side, so that a toner image is formed on both sides of the paper P.

[0020] The processing flow performed by the image forming apparatus 100 will be explained. The image forming apparatus 100 receives image data output from, for example, an image reading device or a computer (not shown). Image processing is then performed on this image data. As a result, image data corresponding to each of the multiple image forming units 200 is generated. Specifically, for example, image data is generated that is used to form images using basic color developers such as yellow, magenta, cyan, and black, and image data is generated that is used to form images using developers other than the basic colors. The generated image data is output to the laser exposure unit 13 provided in the image forming unit 200.

[0021] The laser exposure unit 13 irradiates the photoreceptor drum 11 with an exposure beam Bm emitted from, for example, a semiconductor laser, according to the input image data. In this embodiment, after the surface of each photoreceptor drum 11 is charged by the charger 12, scanning exposure is performed on this surface by the laser exposure unit 13. As a result, an electrostatic latent image is formed on the surface of the photoreceptor drum 11. Next, the developing device 14 performs a developing process, and a toner image is formed on the photoreceptor drum 11. This toner image is then transferred to the intermediate transfer belt 15 in the primary transfer unit 10.

[0022] After the toner image is transferred onto the intermediate transfer belt 15, the movement of the intermediate transfer belt 15 moves the toner image to the secondary transfer section 20. At the same time, the paper P from the first paper storage section 53 and the second paper storage section 54 is transported to the secondary transfer section 20 by the transport roll 52, etc. Then, the toner image on the intermediate transfer belt 15 is electrostatically transferred all at once onto the paper P in the secondary transfer unit 20.

[0023] Subsequently, the paper P onto which the toner image has been transferred is peeled off the intermediate transfer belt 15 and transported to the transport belt 55. The transport belt 55 transports the paper P to the fuser unit 60. The paper P, transported to the fuser 60, is heated and pressurized in the fuser 60. This fixes the toner image on the paper P to the paper P. Then, the paper P is discharged from the image forming apparatus 100.

[0024] Furthermore, if a toner image is formed on both sides of the paper P, after the paper P passes through the fuser 60, it is supplied again to the secondary transfer unit 20 via the branch path R2. Then, in the secondary transfer unit 20, the toner image is transferred to the other side of the paper P. After that, the paper P passes through the fuser unit 60 again, and the toner image transferred to the other side is fixed to the paper P.

[0025] The developing device 14 will now be described. Figure 2 shows the developing apparatus 14 as viewed from above. When the developing device 14 is installed in the image forming apparatus 100, it is positioned along the depth direction of the image forming apparatus 100. The developing device 14 has one end 141 and the other end 142 which are located at different positions in the longitudinal direction. When the developing device 14 is installed on the image forming apparatus 100, the developing device 14 is installed relative to the image forming apparatus 100 such that one end 141 is located on the rear side of the image forming apparatus 100 and the other end 142 is located on the front side of the image forming apparatus 100.

[0026] A driving force receiving part 143 is provided at one end 141 of the developing device 14 to receive driving force. In this embodiment, the driving force from a drive source (not shown), such as a motor, provided on the main body side of the image forming apparatus 100, is transmitted to this driving force receiving section 143. The drive force receiving unit 143 is linked to a transport member (described later) provided inside the developing device 14. In this embodiment, the drive force from the drive source is transmitted to this drive force receiving unit 143, causing the transport member to rotate.

[0027] In this embodiment, as will be described later, four members are provided as members that rotate in response to a driving force from a drive source: a one-way conveying member, a counter-direction conveying member, an opposing member, and a downward conveying member. A driving force receiving part 143 may be provided corresponding to each of these four members. Furthermore, the driving force from the drive source may be transmitted to each of these four driving force receiving parts 143. In addition, a smaller number of drive force receiving parts 143 than the four components described above may be provided, such as one drive force receiving part 143. The drive force transmitted from the drive source to this drive force receiving part 143 may then be transmitted to each of the four components through a transmission mechanism (not shown) provided in the developing device 14.

[0028] Figure 3 is a cross-sectional view of the developing apparatus 14 along the line III-III in Figure 2. Figure 3 shows the cross-sectional state of the central part in the longitudinal direction of the developing apparatus 14. The developing device 14 is provided with a one-way movement path 191 through which the developer moves in one direction. Furthermore, the developing device 14 is provided with a reverse direction movement path 192 through which the developer travels when moving in the opposite direction to the one direction. The reverse direction movement path 192 is located below the one-way movement path 191.

[0029] In the one-way movement path 191, the developer moves perpendicular to the plane of the paper in Figure 3 and towards the back of the paper. In the opposite-way movement path 192, the developer moves perpendicular to the plane of the paper in Figure 3 and towards the front of the paper. A one-way transport member 410 for transporting the developer is provided in the one-way movement path 191. In this embodiment, the developer moves in the inward direction as the one-way transport member 410 rotates around a rotation axis 411 that extends along the one-way movement path 191.

[0030] More specifically, in this embodiment, the unidirectional transport member 410 rotates upon receiving the driving force transmitted from the driving force receiving part 143 (see Figure 2), causing the developer to move in the rearward direction. In this embodiment, the developer is transported in one direction, towards the back, by the unidirectional transport member 410. The unidirectional transport member 410 is a rotating member that rotates around an axis center 410A along this unidirectional direction.

[0031] The opposite direction movement path 192 is provided with an opposite direction transport member 420 for transporting the developer. The opposite direction transport member 420 is positioned below the one-way transport member 410. In this embodiment, the opposite-direction transport member 420 rotates around a rotation axis 421 that extends along the opposite-direction movement path 192, causing the developer to move toward the front. More specifically, the opposite-direction transport member 420 rotates upon receiving the driving force transmitted from the driving force receiving section 143, causing the developer to move toward the front. In this embodiment, the developer is transported in the opposite direction to the one described above by the opposite-direction transport member 420.

[0032] On the left side of the unidirectional transport member 410, there is an opposing member 430 which is positioned opposite the photoreceptor drum 11, which is an example of an image holder. The opposing member 430 supplies the developer supplied from the unidirectional transport member 410 to the photoreceptor drum 11. The opposing member 430 receives the developer supplied from the unidirectional transport member 410 and supplies this developer to the photoreceptor drum 11. The opposing member 430 is made of a cylindrical body. The opposing member 430 is made of a metal such as SUS (stainless steel).

[0033] The opposing member 430 receives the driving force transmitted from the driving force receiving section 143 and rotates counterclockwise around its axis 431 as the center of rotation, moving the developer supplied from the unidirectional transport member 410 and adhering to its outer surface to the photoreceptor drum 11. As a result, developer is supplied to the photoreceptor drum 11, and the toner contained in the developer adheres to the surface of the photoreceptor drum 11.

[0034] The opposing member 430 is a rotating member that rotates around an axis center 431 along the aforementioned one direction. Similarly, the one-way conveying member 410 is also a rotating member that rotates around an axis center 410A along the aforementioned one direction. In this embodiment, the opposing member 430 and the unidirectional conveying member 410 are arranged such that the axis center 410A of the unidirectional conveying member 410 is located above the axis center 431 of the opposing member 430.

[0035] Furthermore, in this embodiment, a first movement restricting unit 450 is provided, which is positioned between the opposing member 430 and the unidirectional transport member 410, and which restricts the movement of a portion of the developer that is attempting to move from the unidirectional transport member 410 to the opposing member 430. In this embodiment, the developer that has passed over the first movement restricting section 450 from the developer on the one-way movement path 191 is supplied to the opposing member 430.

[0036] Furthermore, in this embodiment, a downward conveying member 440 is provided, which is positioned below the opposing member 430. The downward conveying member 440 is a rotating member that rotates around an axis center 440A along the one direction described above. The downward transport member 440 is positioned closer to the photoreceptor drum 11 than the opposite-direction transport member 420. The downward conveying member 440 and the opposite direction conveying member 420 are arranged along the aforementioned one direction, and their positions in the horizontal direction are offset from each other.

[0037] The downward transport member 440 transports the developer that has separated from the opposing member 430 in a direction perpendicular to the paper surface in Figure 3 and towards the back of the paper surface. The downward transport member 440 transports the developer that has separated from the opposing member 430 in the aforementioned one direction, so that this developer is supplied to one end of the opposite-direction transport member 420 (details will be described later).

[0038] The downward transport member 440 rotates due to the driving force transmitted from the driving force receiving section 143, and transports the developer that has detached from the opposing member 430 in a direction perpendicular to the paper surface in Figure 3 and towards the back of the paper surface. The downward transport member 440 is provided on the downward movement path 193, which is located closer to the photoreceptor drum 11 than the opposite direction movement path 192. The downward movement path 193 is arranged to extend perpendicular to the plane of the paper in Figure 3 and is located below the opposing member 430. In this embodiment, the developer that has detached from the opposing member 430 travels along this downward movement path 193.

[0039] Furthermore, in this embodiment, a second movement restricting unit 452 is provided, which is positioned between the downward conveying member 440 and the opposite-direction conveying member 420, and which restricts the movement of the developer from the opposite-direction conveying member 420 to the downward conveying member 440. Furthermore, in this embodiment, a third movement restricting unit 453 is provided, which is positioned between the opposing member 430 and the opposite direction conveying member 420, and which restricts the movement of the developer from the opposite direction conveying member 420 to the opposing member 430.

[0040] Furthermore, in this embodiment, a fourth movement restricting section 454 is provided between the one-way conveying member 410 and the opposite-way conveying member 420. The fourth movement restricting unit 454 restricts the movement of the developer from the one-way transport member 410 to the opposite-way transport member 420. Furthermore, the fourth movement restricting unit 454 restricts the movement of the developer from the opposite-way transport member 420 to the one-way transport member 410. In this embodiment, the second movement restricting section 452 to the fourth movement restricting section 454 are integrated. The second movement restricting section 452 to the fourth movement restricting section 454 are composed of a single common part. Furthermore, in this embodiment, a fifth movement restricting unit 455 is provided, which is positioned between the opposing member 430 and the downward transport member 440, and restricts the movement of the developer from the downward transport member 440 to the opposing member 430.

[0041] Furthermore, in this embodiment, a magnetic roll 145B is provided inside the opposing member 430. The magnetic roll 145B is provided with five magnetic poles 121 to 125 arranged along the circumferential direction of the magnetic roll 145B. The magnetic pole 121 is a pickup pole that attracts the developer supplied from the unidirectional movement path 191. As a result, the developer adheres to the surface of the opposing member 430.

[0042] The magnetic poles 122-124 act as transport poles, moving the developer on the surface of the opposing member 430 downstream in the rotational direction of the opposing member 430. In the rotational direction of the opposing member 430, an opposing restricting portion 127 is provided downstream of the magnetic pole 122 and upstream of the magnetic pole 123. The opposing restricting portion 127 is positioned opposite each other on the outer circumferential surface of the opposing member 430.

[0043] The opposing restricting portion 127 is positioned with a gap between it and the opposing member 430. The opposing restricting section 127 restricts the movement of a portion of the developer adhering to the surface of the opposing member 430, thereby setting the thickness of the developer adhering to the surface of the opposing member 430 to a predetermined thickness. In other words, the opposing restricting portion 127 restricts the movement of a portion of the developer that adheres to the outer surface of the opposing member 430 and moves toward the photoreceptor drum 11 as the opposing member 430 rotates.

[0044] As the developer on the surface of the opposing member 430 moves downstream in the rotational direction of the opposing member 430, this developer moves to the surface of the photoreceptor drum 11, which is an example of an image holder, and the toner contained in this developer adheres to the photoreceptor drum 11. This causes development to occur, and an image made of toner is formed on the surface of the photosensitive drum 11. This image is temporarily held by the photoreceptor drum 11 and moved to the primary transfer section 10 (see Figure 1) by the rotating photoreceptor drum 11. Then, this image is transferred to the intermediate transfer belt 15.

[0045] The magnetic pole 125 acts as a pick-off pole, forming a repulsive magnetic field that detaches the developer adhering to the surface of the opposing member 430 from the opposing member 430. The magnetic pole 125 detaches the developer remaining on the surface of the opposing member 430 that was not transferred to the photoreceptor drum 11 from the opposing member 430. In this embodiment, the developer is detached at the detachment point 296. In this embodiment, the detachment point 296 is located in front of the magnetic pole 121, which acts as a pickup pole, and in this embodiment, the developer detachment occurs on the side in front of the magnetic pole 121. The developer that has detached from the opposing member 430 moves downward and reaches the downward movement path 193. The developer that reaches the downward movement path 193 is moved by the downward transport member 440 toward one end 141 (see Figure 2) of the developing device 14, and then moves toward the opposite direction movement path 192 (see Figure 3) (details will be described later).

[0046] The one-way conveying member 410 (see Figure 3), the opposite-way conveying member 420, the opposing member 430, the magnetic roll 145B, and the downward conveying member 440 extend in a direction perpendicular to the plane of the paper in Figure 3 and are arranged in a relationship where they are parallel to each other. The unidirectional transport member 410 includes a rotating shaft 411 that extends along the longitudinal direction of the developing device 14, and a protruding portion 412 that protrudes from the outer circumferential surface of the rotating shaft 411. The projection 412 is provided from one end to the other in the axial direction of the rotating shaft 411 and is spirally arranged. In other words, the projection 412 is screw-shaped.

[0047] In this embodiment, when the rotating shaft 411 provided on the unidirectional transport member 410 rotates, the protruding portion 412 presses the developer in the axial direction of the rotating shaft 411, thereby causing the developer to move in the direction in which the rotating shaft 411 extends. The opposite-direction conveying member 420 and the downward conveying member 440 have the same configuration as the one-direction conveying member 410, and the opposite-direction conveying member 420 and the downward conveying member 440 are also provided with a rotating shaft that extends along the longitudinal direction of the developing device 14 and a helical projection.

[0048] The unidirectional conveying member 410, the opposite-direction conveying member 420, the opposing member 430, and the downward conveying member 440 are rotating members that rotate around an axis center along the aforementioned unidirectional direction. In this embodiment, when comparing the positions in the horizontal direction, the axis center 420A of the opposite-direction conveying member 420 is located further away from the opposing member 430 than the axis center 410A of the one-direction conveying member 410. Furthermore, in this embodiment, the axis center 420A of the opposite-direction conveying member 420 is located at a point offset from directly below the axis center 410A of the unidirectional conveying member 410.

[0049] Furthermore, in this embodiment, the axial center 440A of the downward conveying member 440 is located at a point offset from directly below the axial center 431 of the opposing member 430. More specifically, in this embodiment, when comparing the positions in the horizontal direction, the axis center 440A of the downward conveying member 440 is located closer to the opposite conveying member 420 than the axis center 431 of the opposing member 430. Furthermore, in this embodiment, when comparing the positions in the vertical direction, the axial center 440A of the downward conveying member 440 is located below the axial center 420A of the opposite direction conveying member 420.

[0050] Figure 4 is a cross-sectional view of the developing apparatus 14 along line IV-IV in Figure 2. Figure 4 shows the cross-sectional state at the other end 142 of the developing apparatus 14. In this embodiment, as shown in Figure 4, an upward movement path 196 is provided at the other end 142 of the developing apparatus 14, arranged in the vertical direction. In this embodiment, the developer that has moved through the opposite direction movement path 192 moves through this upward movement path 196 towards the one-way movement path 191.

[0051] In the developing apparatus 14 of this embodiment, an upward movement path 196 is provided as an example of a second movement path through which the developer passes from the opposite-direction transport member 420 to the one-direction transport member 410. Here, "arranged along the vertical direction" is not limited to a state in which the upward movement path 196 is aligned along the vertical direction, but also includes a state in which the upward movement path 196 is arranged at an inclination with respect to the vertical direction.

[0052] In this embodiment, when the developer is transported to the other end 142 of the developing device 14 by the opposite-direction transport member 420, the developer accumulates below the upward movement path 196, and the developer gradually moves upward within the upward movement path 196. This supplies the developer to the unidirectional transport member 410. The unidirectional transport member 410 transports the developer, which has moved through the upward movement path 196, along the unidirectional movement path 191 toward one end 141 (see Figure 2) of the developing device 14.

[0053] Figure 5 is a cross-sectional view of the developing apparatus 14 on the VV line shown in Figure 2. In this embodiment, as shown in Figure 5, a downward movement path 197 arranged along the vertical direction is provided at one end 141 of the developing apparatus 14. Similarly, "arranged along the vertical direction" is not limited to the state in which the downward movement path 197 is aligned vertically, but also includes the state in which the downward movement path 197 is inclined with respect to the vertical direction.

[0054] In this embodiment, the developer that has moved through the unidirectional movement path 191 moves through the downward movement path 197 to the opposite direction movement path 192. In this embodiment, a downward movement path 197 is provided as an example of a first movement path through which the developer passes from the one-way transport member 410 to the opposite-way transport member 420.

[0055] In this embodiment, the developer that has traveled along the one-way movement path 191 travels along the downward movement path 197 to the opposite-way movement path 192. Then, the developer travels along this opposite-way movement path 192 to the other end 142 (see Figure 2) of the developing device 14. In the developing apparatus 14 of this embodiment, a developer transport path 198 is provided, which is formed in an annular shape by four paths: a one-way transport path 191, a downward transport path 197, a reverse-direction transport path 192, and an upward transport path 196 (see Figure 4). In this embodiment, the developer circulates along this annular developer transfer path 198.

[0056] Furthermore, in this embodiment, as shown in Figure 5, a connecting path 190 is provided that extends laterally and connects the downward movement path 193 and the opposite direction movement path 192. In this embodiment, a connecting path 190 is provided as a path for the developer to move from the downward transport member 440 to the opposite direction transport member 420. The connection path 190 is positioned at an angle, sloping upwards. In other words, the connection path 190 is positioned at an angle, sloping both horizontally and vertically.

[0057] In this embodiment, the developer that has moved along the downward movement path 193 by the downward transport member 440 moves to the opposite direction movement path 192 via the connecting path 190. In this embodiment, the developer accumulated at the downstream end of the downward movement path 193 in the direction of developer movement is pressed by the developer being transported sequentially from the upstream side, and moves through the connecting path 190 to the opposite direction movement path 192.

[0058] In the developing apparatus 14 of this embodiment, as described above, an annular developer transfer path 198 is provided, and the developer is agitated as it moves along this annular developer transfer path 198. Furthermore, in this embodiment, as the agitated developer passes through the unidirectional movement path 191 (see Figure 3), a portion of the developer is supplied to the opposing member 430 beyond the first movement restricting section 450, and the developer adheres to the surface of the opposing member 430. As the opposing member 430 rotates, the developer adhering to the surface of the opposing member 430 moves to the position opposite the photoreceptor drum 11, thereby supplying the developer to the photoreceptor drum 11.

[0059] Of the developer adhering to the surface of the opposing member 430, the developer that was not supplied to the photoreceptor drum 11 passes the position opposite the magnetic pole 125 (see Figure 3), which acts as a pick-off pole, and when it reaches the detachment point 296, it detaches from the opposing member 430 and moves downward. The developer that has moved downwards reaches the downward transport path 193, which is equipped with a downward transport member 440.

[0060] The developer that has reached the downward movement path 193 travels through the downward movement path 193 to the downstream end 193A of the downward movement path 193, which is located on the downstream side in the direction of movement of the developer. Subsequently, this developer is pressed by the developer being transported sequentially from the upstream side, and moves through the connection path 190 to the opposite direction movement path 192. When the developer moves to the opposite direction movement path 192, it moves again along the annular developer movement path 198.

[0061] Let me explain the developing device 14 further. Figure 6 is an explanatory diagram illustrating the developer suction mechanism in the developing apparatus 14. Figure 6 shows a cross-section of the developing apparatus 14 along the line VI-VI in Figure 2. In this embodiment, as shown in Figure 6, the developing apparatus 14 is provided with an opening 150 facing the photoreceptor drum 11. In this embodiment, a portion of the opposing member 430 is exposed through this opening 150. In this embodiment, the opening 150 is located between the photoreceptor drum 11 and the radial center of the opposing member 430. The opposing member 430 supplies developer to the photosensitive drum 11. The opposing member 430 can also be considered as a supply member. The opening 150 is provided to extend in the longitudinal direction of the developing apparatus 14. The opening 150 is provided to extend along the axial direction of the opposing member 430.

[0062] In the image forming apparatus 100 of this embodiment, a suction unit for drawing in air is provided on the main body side of the image forming apparatus 100. In this embodiment, the suction from this suction unit creates an airflow in the developing apparatus 14, as shown by arrow 6A in Figure 6. This causes the developer floating around the developing apparatus 14 to move towards the suction unit.

[0063] Figure 7 shows the state when one end 141 of the developing apparatus 14 is viewed from the direction indicated by arrow VII in Figure 2. In Figure 7, the developing apparatus 14 is viewed from the side of the opening 150. The opening 150 of the developing apparatus 14 is provided with an upper opening 151 that forms the upper edge of the opening 150 and a lower opening 152 that forms the lower edge of the opening 150. Furthermore, the opening 150 is provided with a left opening portion 153 that forms the left edge of the opening 150, and a right opening portion that forms the right edge of the opening 150. The right opening portion is not shown in the illustration. The portion of the outer circumferential surface of the opposing member 430 that is exposed through the opening 150 is located between the upper part 151 of the opening and the lower part 152 of the opening.

[0064] Furthermore, in this embodiment, a blocking member 160 is provided that closes a portion of the opening 150. This blocking member 160 restricts the movement of the developer. In this embodiment, the developer moves from the opposing member 430 side toward the photoreceptor drum 11 side shown in Figure 1. The blocking member 160 restricts the movement of the developer from the opposing member 430 towards the photoreceptor drum 11. The blocking member 160 can also be considered as a restricting member that restricts the movement of the developer.

[0065] In the developing device 14, when the developer adhering to the outer surface of the opposing member 430 returns to the developing device 14, air is drawn into the developing device 14. Consequently, the internal pressure of the developing device 14 increases. This increase in internal pressure causes the developer inside the developing device 14 to attempt to move out of the developing device 14 through the opening 150. In this case, the developer moves from the opposing member 430 side toward the photoreceptor drum 11 side. The blocking member 160 restricts the movement of the developer from the opposing member 430 side toward the photoreceptor drum 11 side.

[0066] The blocking member 160 is provided in the shape of a plate. This plate-shaped blocking member 160 is provided along the axial direction of the opposing member 430. Furthermore, this plate-shaped blocking member 160 is provided along the circumferential direction of the opposing member 430. The sealing member 160 is made of, for example, a resin material. Examples of resin materials include polyethylene terephthalate and polyurethane.

[0067] The blocking member 160 has a left end portion 161 as an example of an axial end portion that is at a different position in the axial direction from the opposing member 430, and a right end portion 162 as an example of the other axial end portion. The rightmost end 162 is located closer to the central part 430C in the axial direction of the opposing member 430 than the leftmost end 161. The rightmost end 162 can be considered as the central end, which is the end located on the central part 430C side in the axial direction of the opposing member 430. The leftmost end 161 is located on the opposite side from the rightmost end 162, which is the central end. The leftmost end 161 can be considered as the opposite end, located on the opposite side from the rightmost end 162. Furthermore, the blocking member 160 has an upper end portion 163 located on the upstream side in the rotational direction of the opposing member 430. Also, the blocking member 160 has a lower end portion 164 located on the downstream side in the rotational direction of the opposing member 430.

[0068] The blocking member 160 is positioned opposite the axial end of the opposing member 430. The upper end portion 163 of the sealing member 160 is attached, for example, to a bearing member provided at the end of the opposing member 430. This bearing member is a member that supports the opposing member 430 in a rotatable state. The upper end portion 163 of the sealing member 160 may be attached to a housing or other part other than the bearing member. Furthermore, the lower end portion 164 of the sealing member 160 is attached to the lower part 152 of the opening. The lower end portion 164 is attached to the surface of the lower opening 152, that is, the surface on the photoreceptor drum 11 side. Alternatively, the lower end portion 164 may be attached to the back surface of the lower opening 152, that is, the surface on the opposing member 430 side.

[0069] The sealing member 160 is provided so as to cover the left side of the opening 150 in the diagram. Although not explained here, a sealing member 160 is also provided on the right side of the opening 150. Another sealing member 160 is provided at the opposite position of the other end 433 of the opposing member 430. The other end 433 of the opposing member 430 is shown in Figure 10.

[0070] Figure 8 is a perspective view of the developing device 14 from the other end 142 to the one end 141. The blocking member 160 is positioned between the photoreceptor drum 11 shown in Figure 6 and the opposing member 430 which is positioned opposite the photoreceptor drum 11. In this embodiment, as described above, the upper end portion 163 of the sealing member 160 is attached to a bearing member provided at the end of the opposing member 430. The lower end portion 164 is attached to the lower part of the opening 152.

[0071] In this embodiment, the sealing member 160 is positioned with a gap G between it and a plurality of components constituting the developing apparatus 14. The sealing member 160 is positioned with a gap G between it and the opposing member 430, which is an example of a component. In this embodiment, the blocking member 160 and the opposing member 430 are not in contact. A gap G is provided between the blocking member 160 and the opposing member 430. A first opening 250 is provided between the right end portion 162 of the sealing member 160 and the opposing member 430, allowing air from outside the gap G to flow into the gap G.

[0072] The first opening 250 is provided in a manner that extends in the vertical direction. The width of the first opening 250 differs in the vertical direction. Specifically, the widths of the portion 260 located below the central portion 265 and the portion 270 located above the central portion 265 in the vertical direction of the first opening 250 are smaller than the width of the central portion 265 of the first opening 250. The first opening 250 is formed so that its width widens from the portion 260 located below the central portion 265 towards the central portion 265. Furthermore, the first opening 250 is formed so that its width widens from the portion 270 located above the central portion 265 towards the central portion 265.

[0073] Figure 9 is a perspective view of one end 141 of the developing apparatus 14, taken from the direction indicated by arrow IX in Figure 7. In this embodiment, a second opening 300 is provided between the left end portion 161 of the sealing member 160 and the opposing member 430. In this embodiment, air from outside the gap G flows into the gap G through this second opening 300.

[0074] In this embodiment, as shown in Figure 9, the second opening 300 is provided in a manner that extends in the vertical direction. Furthermore, the second opening 300 is formed so that its width differs in the vertical direction. Specifically, the width of the portion 310 located below the central portion 315 in the vertical direction of the second opening 300 is different from the width of the portion 320 located above the central portion 315.

[0075] The width of the lower portion 310 of the second opening 300 in the vertical direction is greater than the width of the upper portion 320. In the second opening 300, the width of the second opening 300 widens from the upper part 320 to the lower part 310.

[0076] Figure 10 is a view of the developing apparatus 14 from below. Figure 10 shows the state when the developing apparatus 14 is viewed from the direction indicated by arrow X in Figure 7. Figure 11 is a perspective view of the cross-section of the developing apparatus 14 along the XI-XI line in Figure 7. Note that Figure 10 shows the outer cover 700, located at the bottom of the developing apparatus 14, removed in order to illustrate the airflow within the developing apparatus 14. In this embodiment, as shown in Figure 11, an outer cover 700 is provided. Figure 10 shows the outer cover 700 removed.

[0077] In this embodiment, as shown in Figure 10, a discharge section 400 for discharging air from inside the developing apparatus 14 is provided at one end 141 of the developing apparatus 14. This discharge section 400 is a so-called duct and is composed of an annular member. In this embodiment, the air inside the developing apparatus 14 passes through the discharge section 400 and heads toward a suction section (not shown) provided on the main body side of the image forming apparatus 100.

[0078] As shown in Figure 11, one end 141 of the developing apparatus 14 is provided with an inlet 350 into which air flows toward the discharge section 400. Furthermore, as shown in Figure 10, a flow path 330 is provided along the axial direction of the opposing member 430. The developer floating at opposing positions such as the central part 430C of the opposing member 430 passes through this channel 330 and heads toward the inlet part 350.

[0079] Now, referring to Figure 11, we compare the positions of the opposing members 430 in the rotational direction. In this embodiment, the position of the inlet 350 in this rotational direction is different from the positions of the first opening 250 and the second opening 300 in this rotational direction. The inlet portion 350 is located downstream of the first opening 250 and the second opening 300 in the rotational direction of the opposing member 430.

[0080] Also, refer to Figure 10 to compare the axial positions of the opposing members 430. In this embodiment, the position of the inlet 350 in the axial direction is different from the position of the second opening 300 in the axial direction. The inlet portion 350 is located closer to the central portion 430C in the axial direction of the opposing member 430 than to the central portion 160C of the blocking member 160. The entrance portion 350 has a central portion 350C located at an intermediate position in the width direction. The central portion 350C of the inlet portion 350 is located closer to the central portion 430C in the axial direction of the opposing member 430 than the central portion 160C of the blocking member 160. The inlet portion 350 is positioned relative to the blocking member 160, and is positioned towards the central portion 430C in the axial direction of the opposing member 430.

[0081] Furthermore, the developing apparatus 14 is provided with a connecting channel 332 that connects the discharge section 400 and the inlet section 350. This connecting channel 332 is provided so as to extend in the rotational direction of the opposing member 430. In addition, this connecting channel 332 is provided so as to extend in the axial direction of the opposing member 430. The connecting channel 332 is provided in a manner that is inclined with respect to both the rotational and axial directions of the opposing member 430. The air that passes through the inlet section 350 then goes through this connecting passage 332 and heads towards the discharge section 400. If the connecting channel 332 is provided at an angle, outside the inlet 350 shown in Figure 11, an airflow directed diagonally downward, as indicated by arrow 11A in the figure, is likely to occur. In this case, the air that is trying to go towards the inlet 350 is more likely to pass through the location of the first opening 250, but less likely to pass through the second opening 300.

[0082] In this case, if the second opening 300 is not provided and is blocked, developer is more likely to accumulate at the location where the second opening 300 is installed. In this case, clumps of developer are more likely to form at the location where the second opening 300 is installed. In this case, the solidified developer falls into the inlet 350 or the connecting channel 332 located downstream of the inlet 350. This narrows the airflow path. When the airflow path is narrowed, it becomes difficult for exhaust to be released from the developing device 14. This can easily lead to problems such as poor developing. In contrast, in the configuration of this embodiment, an airflow is generated from the second opening 300 toward the inlet 350. This makes it less likely for developer to accumulate at the location where the second opening 300 is installed. In this case, the above-mentioned problems are less likely to occur.

[0083] In this embodiment, as described above, the air inside the developing apparatus 14 is directed toward the discharge section 400. At this point, some of this air enters the gap G through the first opening 250 shown in Figure 11. This air then heads towards the inlet 350. Furthermore, air enters the gap G through the second opening 300. This air also heads towards the inlet 350.

[0084] Thus, in this embodiment, air is supplied to the gap G formed between the sealing member 160 and the opposing member 430 from multiple directions. In this embodiment, air can be supplied from outside the gap G into the gap G from multiple directions. In this embodiment, air is supplied to the gap G from the right end 162 side of the sealing member 160. Also, in this embodiment, air is supplied to the gap G from the left end 161 side of the sealing member 160. In this embodiment, air can be supplied to the gap G from both the first opening 250 side and the second opening 300 side.

[0085] In this embodiment, as shown in Figure 10, a separate passage 334 is provided for air heading toward the discharge section 400, in addition to the passage 330 and the connecting passage 332. A portion of the air heading toward the discharge section 400 from the right side in the axial direction of the opposing member 430 passes through this passage 334 to the discharge section 400.

[0086] Figure 12 is a diagram for comparing the size of the first opening 250 and the size of the second opening 300. Figure 12(a) shows the first opening 250, and Figure 12(b) shows the second opening 300. In this embodiment, the first opening 250 and the second opening 300 are of different sizes. In this embodiment, the area of ​​the second opening 300 is smaller than the area of ​​the first opening 250. This prevents the developer inside the gap G from moving out of the gap G through the second opening 300.

[0087] In this embodiment, as indicated by arrow 11A in Figure 11, air mainly enters the gap G from the first opening 250 side. In this case, some of the air that enters the gap G from the first opening 250 may move to the outside of the gap G through the second opening 300. In this case, the developer inside the gap G will be more likely to move out of the gap G through the second opening 300. In contrast, in this embodiment, as described above, the area of ​​the second opening 300 is smaller than the area of ​​the first opening 250. In this case, compared to the case where the area of ​​the second opening 300 is larger than the area of ​​the first opening 250, it becomes less likely for the developer in the gap G to move out of the gap G through the second opening 300.

[0088] Furthermore, in this embodiment, as described above and as shown in Figure 12(b), the width of the lower portion 310 of the second opening 300 is greater than the width of the upper portion 320. In this case, the amount of air supplied to the lower side where the developer tends to accumulate increases, reducing the buildup of the developer. In the second opening 300, the developer tends to accumulate in the lower portion 310 of the second opening 300. In this embodiment, the airflow is improved in this area where the developer tends to accumulate, making it less likely for the developer to accumulate in this area.

[0089] Next, the mechanism for preventing the scattering of developer in the developing apparatus 14 will be described. The following describes the scattering prevention mechanism located on one end 432 side in the axial direction of the opposing member 430. A similar scattering prevention mechanism is also provided on the other end 433 side in the axial direction of the opposing member 430. Figure 13 is an explanatory diagram illustrating the mechanism for preventing the scattering of developer in the developing apparatus 14. Figure 13 is the same as Figure 11.

[0090] In this embodiment, as described above, a magnetic roll 145B is provided inside the opposing member 430. The magnetic roll 145B is provided with multiple magnetic poles. In this embodiment, five magnetic poles 121 to 125 are provided as multiple magnetic poles. The five magnetic poles 121 to 125 are arranged in a line along the circumferential direction of the magnetic roll 145B. The five magnetic poles 121 to 125 are arranged in a line along the rotational direction of the opposing member 430. Hereinafter, in this specification, when referring to each of the five magnetic poles 121 to 125 without special distinction, they will be referred to as "magnetic pole 120". Furthermore, in this specification, when referring to each of the five magnetic poles 121 to 125 separately, they will be referred to as "the first magnetic pole 121 to the fifth magnetic pole 125".

[0091] A first magnetic member 170 is provided on the outside of the opposing member 430 to form a magnetic field between it and the multiple magnetic poles 120. The first magnetic member 170 is provided at a position opposite to one end 432 in the axial direction of the opposing member 430. The first magnetic member 170 is provided on the outside of the opposing member 430. The first magnetic member 170 is composed of a plate-shaped member having curvature. Furthermore, the first magnetic member 170 is provided with a gap H between it and the opposing member 430. Also, the first magnetic member 170 is provided along the outer circumferential surface of the opposing member 430.

[0092] The first magnetic member 170 has a downstream end 171 which is the end located on the downstream side in the rotational direction of the opposing member 430. Furthermore, the first magnetic member 170 has an upstream end 172 which is the end located on the upstream side in the rotational direction of the opposing member 430. In the figure, the rotation direction of the opposing member 430 is indicated by arrow 13A.

[0093] Furthermore, in this embodiment, a second magnetic member 180 is provided on the outside of the opposing member 430 to form a magnetic field between it and the plurality of magnetic poles 120. The second magnetic member 180 is also provided at a position opposite to one end 432 in the axial direction of the opposing member 430. The second magnetic member 180 is also positioned with a gap K between it and the opposing member 430.

[0094] The second magnetic member 180 is located on the other end 433 side of the opposing member 430, relative to the first magnetic member 170. The other end 433 of the opposing member 430 is shown in Figure 10. Furthermore, the second magnetic member 180 is located closer to the central portion 430C in the axial direction of the opposing member 430 than the first magnetic member 170. The central portion 430C is also shown in Figure 10. The second magnetic member 180 is formed in the shape of a plate. This plate-shaped second magnetic member 180 is provided along the radial direction of the opposing member 430.

[0095] The second magnetic member 180 has an opposing portion 185 that faces the opposing member 430. The opposing portion 185 is provided along the outer circumferential surface of the opposing member 430. The opposing portion 185 is positioned opposite to the multiple magnetic poles 120 provided inside the opposing member 430. Specifically, the opposing portion 185 is positioned opposite the first magnetic pole 121 and the fifth magnetic pole 125.

[0096] The opposing portion 185 has a downstream end 181, which is the end located on the downstream side in the rotational direction of the opposing member 430. The opposing portion 185 also has an upstream end 182, which is the end located on the upstream side in the rotational direction of the opposing member 430.

[0097] Figure 14 shows the first magnetic member 170, the second magnetic member 180, etc., viewed from the direction indicated by arrow XIV in Figure 13. Here, we will explain the positional relationship of the opposing member 430 in the direction of rotation. In Figure 14, the direction of rotation of the opposing member 430 is indicated by arrow 13A. Figure 14 shows the downstream end 171 of the first magnetic member 170, the second magnetic pole 122, the downstream end 181 of the opposing portion 185, and the first magnetic pole 121. These are arranged in the following order from downstream to upstream in the rotational direction of the opposing member 430: the downstream end 171 of the first magnetic member 170, the second magnetic pole 122, the downstream end 181 of the opposing portion 185, and the first magnetic pole 121.

[0098] The second magnetic pole 122 is located upstream of the downstream end 171 of the first magnetic member 170 in the rotational direction of the opposing member 430. The second magnetic pole 122 is the first magnetic pole among the multiple magnetic poles 120, counting from the downstream end 171 toward the upstream side. Furthermore, the first magnetic pole 121 is located upstream of the downstream end 171 of the first magnetic member 170 in the rotational direction of the opposing member 430. The first magnetic pole 121 is the second magnetic pole to be located when counting upstream from the downstream end 171.

[0099] The downstream end 181 of the opposing portion 185 is located upstream of the second magnetic pole 122 in the rotational direction of the opposing member 430. Furthermore, the downstream end 181 of the opposing portion 185 is located downstream of the first magnetic pole 121 in the rotational direction of the opposing member 430.

[0100] The downstream end 181 of the opposing portion 185 is located upstream of the second magnetic pole 122 in the rotational direction of the opposing member 430, and downstream of the first magnetic pole 121 in the rotational direction of the opposing member 430. In other words, the downstream end 181 of the second magnetic member 180 is located between the second magnetic pole 122 and the first magnetic pole 121 in the rotational direction of the opposing member 430.

[0101] Here, we assume an intermediate position M between the second magnetic pole 122 and the first magnetic pole 121. This intermediate position M is the position between the second magnetic pole 122 and the first magnetic pole 121 in the rotational direction of the opposing member 430. The distance between this intermediate position M and the second magnetic pole 122 is equal to the distance between this intermediate position M and the first magnetic pole 121. Here, "distance" refers to the distance measured along the circumferential direction of the opposing member 430. In this embodiment, the downstream end 181 of the opposing portion 185 is located downstream of the intermediate position M in the rotational direction of the opposing member 430. The downstream end 181 of the opposing portion 185 is positioned so as to be closer to the second magnetic pole 122 than to the first magnetic pole 121 in the rotational direction of the opposing member 430.

[0102] Here, we assume a virtual plane Y that extends along the radial direction of the opposing member 430 and points from the rotation center 435 of the opposing member 430 toward the second magnetic pole 122. In this embodiment, the downstream edge 183 of the second magnetic member 180 is located upstream of the virtual plane Y in the rotational direction of the opposing member 430.

[0103] Although not explained above, the second magnetic member 180 has a downstream edge 183. This downstream edge 183 is the edge of the second magnetic member 180 that is located furthest downstream in the rotational direction of the opposing member 430, among the multiple edges that the second magnetic member 180 has. This downstream edge 183 is connected to the opposing portion 185 at the downstream end 181 of the opposing portion 185. The downstream edge 183 extends away from the opposing member 430, starting from the connection point with the opposing portion 185. Furthermore, this downstream edge 183 is formed in a straight line.

[0104] The downstream edge 183 is inclined toward the downstream side in the rotational direction of the opposing member 430. Here, we assume a virtual plane Z that passes through the rotation center 435 and the downstream end 181 of the opposing member 430, and is aligned with the radial direction of the opposing member 430. In this embodiment, the downstream edge 183 is inclined with respect to this virtual plane Z. The downstream edge 183 of the second magnetic member 180 is provided in such a way that it is tilted downstream of this virtual plane Z in the rotational direction of the opposing member 430.

[0105] In this embodiment, as described above, the downstream edge 183 is provided on the upstream side of the rotational direction of the opposing member 430 relative to the virtual plane Y. Furthermore, in this embodiment, the entire portion of the downstream edge 183 is located upstream of the virtual plane Y in the rotational direction of the opposing member 430.

[0106] Furthermore, we assume a virtual plane X extending from the rotation center 435 of the opposing member 430 to the downstream end 171 of the first magnetic member 170. Also, as described above, we assume a virtual plane Z extending from the rotation center 435 of the opposing member 430 to the downstream end 181 of the second magnetic member 180. Furthermore, here we assume a reference plane W that passes through the rotation center 435 of the opposing member 430 and extends horizontally. Furthermore, we assume the angles θ1 between plane X and reference plane W, θ2 between plane Y and reference plane W, and θ3 between plane Z and reference plane W. In this embodiment, the downstream end 171 of the first magnetic member 170 is provided such that angle θ1 is greater than angle θ2. Furthermore, the downstream end 181 of the second magnetic member 180 is provided such that angle θ2 is greater than angle θ3.

[0107] In this embodiment, angle θ1 is approximately 70°. Angle θ2 is approximately 61°. Furthermore, angle θ3 is approximately 48°. In this case, the value obtained by subtracting angle θ2 from angle θ1 is smaller than the value obtained by subtracting angle θ3 from angle θ2. In a configuration with this kind of angular relationship, the virtual plane Y is positioned to be closer to the virtual plane X. In this case, the second magnetic pole 122 is positioned closer to the downstream end 171 of the first magnetic member 170 than to the downstream end 181 of the opposing portion 185. The angles shown above are just examples, and the range of angles is not limited to these values.

[0108] Figure 15 shows one end 432 of the opposing member 430 viewed from diagonally above and from the other end 433 side. In Figure 15, the second magnetic pole 122 is shown on the outside of the opposing member 430 to make it easier to understand the positional relationship of each component. In reality, the second magnetic pole 122 is located inside the opposing member 430.

[0109] In this embodiment, as described above, the second magnetic pole 122 is located upstream of the downstream end 171 of the first magnetic member 170 in the rotational direction of the opposing member 430. Furthermore, the second magnetic pole 122 is located downstream of the downstream end 181 of the opposing portion 185 in the rotational direction of the opposing member 430.

[0110] The roles of the first magnetic member 170 and the second magnetic member 180 will now be explained. The second magnetic member 180 restricts the movement of the developer in the direction indicated by 15A in the figure. In this embodiment, a magnetic field is formed between the opposing portion 185 of the second magnetic member 180 and the plurality of magnetic poles 120 provided inside the opposing member 430. As a result, a layer of developer is formed between the opposing portion 185 and the opposing member 430, extending along the rotational direction of the opposing member 430. This layer will be referred to hereafter as the "rotational direction layer".

[0111] The developer moving in the direction indicated by 15A in the diagram is restricted from moving by this rotational layer. The developer moving along the axial direction of the opposing member 430, and from the central part 430C of the opposing member 430 toward one end 432, is restricted from moving by this rotational layer. The central portion 430C of the opposing member 430 is shown in Figure 7. As a result, in this embodiment, scattering of the developer caused by the movement of the developer in the axial direction of the opposing member 430 is suppressed.

[0112] On the other hand, the first magnetic member 170 restricts the movement of the developer downstream in the rotational direction of the opposing member 430. This suppresses the scattering of the developer caused by its movement downstream in the rotational direction of the opposing member 430.

[0113] Figure 16 is a cross-sectional view of the developing apparatus 14 along the line XVI-XVI in Figure 15. In this embodiment, as indicated by reference numeral 16Y in the figure, the developer accumulates at the location where the magnetic field is generated due to the magnetic field formed between the first magnetic member 170 and the second magnetic pole 122. Hereinafter, the developer that accumulates at the location indicated by reference numeral 16Y will be referred to as the "developer aggregate". Although not explained above, in this embodiment, the first magnetic member 170 and the magnetic pole 120 are arranged in a state where they are offset from each other in the axial direction of the opposing member 430. In this embodiment, the developer assembly restricts the movement of the developer toward the downstream side in the rotational direction of the opposing member 430.

[0114] In this embodiment, the developer adhering to the outer surface of the opposing member 430 moves from the back to the front of the page in Figure 16 as the opposing member 430 rotates. This movement of the developer is restricted by the developer assembly. Furthermore, a strip-shaped developer layer is formed next to the developer assembly by the second magnetic pole 122, as indicated by reference numeral 16X. In this embodiment, this strip-shaped developer layer also restricts the movement of the developer toward the downstream side in the rotational direction of the opposing member 430. This suppresses the scattering of developer caused by the developer moving downstream in the rotational direction of the opposing member 430.

[0115] In this embodiment, as described above, the second magnetic member 180 shown in Figure 15 restricts the movement of the developer moving in the axial direction of the opposing member 430. However, this regulation is not complete, and as indicated by the reference numeral 15X in Figure 15, some of the developer passes between the second magnetic member 180 and the opposing member 430. More specifically, for example, at the locations indicated by reference numerals 13E and 13F in Figure 13, the passage of the developer is more likely to occur, as shown by reference numeral 15X in Figure 15. In the locations indicated by reference numerals 13E and 13F in Figure 13, there is no magnetic pole 120 near these locations. In this case, the magnetic field generated between the second magnetic member 180 and the magnetic pole 120 becomes smaller in the locations indicated by reference numerals 13E and 13F. In this case, the passage of the developer, as shown by reference numeral 15X in Figure 15, is more likely to occur in the locations indicated by reference numerals 13E and 13F.

[0116] The developer that has passed between the second magnetic member 180 and the opposing member 430 reaches the location indicated by reference numeral 16X in Figure 16 as the opposing member 430 rotates. The area indicated by the symbol 16X contains a developer. In this case, the developer that has reached the area indicated by the symbol 16X is restricted from moving at that location.

[0117] Figure 17 shows a comparative example of the second magnetic member 180, etc. In this comparative example, as shown in Figure 17(a), in the rotational direction of the opposing member 430, the downstream end 181 of the opposing portion 185 is located downstream of the second magnetic pole 122. In this case, the cross-sectional state along the line XVIIb-XVIIb in Figure 17(a) becomes the state shown in Figure 17(b). In the state shown in Figure 17(b), the magnetic field formed between the opposing portion 185 and the second magnetic pole 122 causes the surrounding developer to be attracted to the area between the opposing portion 185 and the second magnetic pole 122.

[0118] In this case, the developer runs out at the location indicated by symbol 17Y, resulting in a missing portion of the strip-shaped developer layer. In this case, the developer moves downstream in the rotational direction of the opposing member 430 through this missing portion. In this case, the developer attempting to move from the back to the front of the paper in Figure 17(b) passes through the strip-shaped developer layer. In other words, in this case, the developer adhering to the outer surface of the opposing member 430 and moving downstream in the rotational direction of the opposing member 430 passes through the band-shaped developer layer. In this case, it is likely to cause the developer to scatter. In contrast, the configuration of this embodiment shown in Figures 13-16 suppresses the occurrence of developer loss and reduces developer scattering.

[0119] In this embodiment, as shown in Figure 14, in the rotational direction of the opposing member 430, the downstream end 181 of the opposing portion 185 is located downstream of the intermediate position M. This makes it easier to suppress the movement of the developer in the axial direction of the opposing member 430 compared to the case where the downstream end 181 is located upstream of the intermediate position M. In this embodiment, as described above, the second magnetic member 180 restricts the movement of the developer in the axial direction. When the downstream end 181 of the opposing portion 185 is located upstream of the intermediate position M, the area subject to this restriction becomes smaller compared to when it is located downstream. In contrast, if the downstream end 181 of the opposing portion 185 is located downstream of the intermediate position M, the area subject to this restriction becomes larger.

[0120] Although embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the embodiments described above. Various other modifications and substitutions of configurations that do not depart from the technical concept of the present invention are included in the present invention.

[0121] (Note) (((1))) A developing apparatus comprising: a rotating member formed in a cylindrical shape, rotatably mounted, having one end and the other end, to which developer adheres to the outer surface; a plurality of magnetic poles disposed inside the rotating member and arranged in line in the rotational direction of the rotating member; a first magnetic member disposed outside the rotating member and positioned opposite to one end of the rotating member, having a downstream end which is the end located downstream in the rotational direction of the rotating member, and forming a magnetic field with the magnetic poles; and a second magnetic member disposed outside the rotating member and positioned opposite to one end of the rotating member, and positioned further toward the other end of the rotating member than the first magnetic member, forming a magnetic field with the magnetic poles, having a facing portion which is the portion facing the rotating member, wherein the facing portion of the second magnetic member is located upstream in the rotational direction from the first magnetic pole which is located upstream in the rotational direction from the downstream end of the first magnetic member among the plurality of magnetic poles. (((2))) The developing apparatus according to (((1))), wherein the opposing portion of the second magnetic member has a downstream end which is the end located downstream in the rotational direction of the rotating member, and the downstream end of the opposing portion of the second magnetic member is located downstream in the rotational direction of the magnetic pole which is the second magnetic pole located upstream in the rotational direction from the downstream end of the first magnetic member. (((3))) The developing apparatus according to (((2))), wherein the downstream end of the opposing portion of the second magnetic member is located downstream in the rotational direction from the intermediate position located between the first magnetic pole and the second magnetic pole. (((4))) The developing apparatus according to any one of (((1)) to (((3))), wherein the second magnetic member is provided upstream in the rotational direction of a virtual plane that extends along the radial direction of the rotating member and is directed from the rotation center of the rotating member toward the first magnetic pole. (((5))) The developing apparatus according to (((4))), wherein the opposing portion of the second magnetic member has a downstream end which is the end located downstream in the rotational direction of the rotating member, the second magnetic member has a downstream edge which is located downstream in the rotational direction of the rotating member and is connected to the downstream end it has and extends toward a direction toward away from the rotating member, and all of the downstream edge of the second magnetic member is provided upstream in the rotational direction of the virtual plane, and the second magnetic member is provided such that the virtual plane and the second magnetic member do not intersect. (((6))) An image forming apparatus comprising an image holder for holding an image and a developing device for applying a developer to the image holder, wherein the developing device has the configuration of the developing device described in any of (((1))) to (((5))).

[0122] According to the developing apparatus described in (((1))), compared to a configuration in which magnetic members are arranged at opposing locations of magnetic poles located inside a cylindrical rotating member, it is possible to make it less likely that the manner in which the developer adheres to the outer surface of the rotating member will differ from the originally intended manner of adhesion. In the developing apparatus according to (((2))), compared to a configuration in which the downstream end of the opposing portion of the second magnetic member is positioned upstream in the rotational direction from the second magnetic pole located upstream in the rotational direction from the downstream end of the first magnetic member, the range in which the movement of the developer attempting to move in the axial direction of the rotating member can be restricted can be expanded in the circumferential direction of the rotating member. In the developing apparatus according to (((3))), compared to a configuration in which the downstream end of the opposing portion of the second magnetic member is located upstream in the rotational direction from the intermediate position located between the first and second magnetic poles, the range in which the movement of the developer attempting to move in the axial direction of the rotating member can be restricted can be expanded in the circumferential direction of the rotating member. With the developing apparatus according to (((4))), compared to a configuration in which a part of the second magnetic member is located downstream in the direction of rotation from a hypothetical plane toward the first magnetic pole located from the rotation center of the rotating member, it is possible to make it less likely that the manner in which the developer adheres to the outer surface of the rotating member will be different from the originally intended manner of adhesion. With the developing apparatus according to (((5))), compared to a configuration in which a part of the second magnetic member is located downstream in the direction of rotation from a hypothetical plane toward the first magnetic pole located from the rotation center of the rotating member, it is possible to make it less likely that the manner in which the developer adheres to the outer surface of the rotating member will be different from the originally intended manner of adhesion. According to the developing apparatus described in (((6))), compared to a configuration in which magnetic members are arranged at opposing locations of magnetic poles located inside a cylindrical rotating member, it is possible to make it less likely that the manner in which the developer adheres to the outer surface of the rotating member will differ from the originally intended manner of adhesion. [Explanation of Symbols]

[0123] 11...Photoreceptor drum, 14...Developing device, 100...Image forming device, 121...First magnetic pole, 122...Second magnetic pole, 127...Opposite restricting section, 150...Opening, 160...Blocking member, 170...First magnetic member, 180...Second magnetic member, 190...Connection path, 191...One-way movement path, 192...Opposite-way movement path, 196...Upward movement path, 197...Downward movement path, 250...First opening, 300...Second opening, 350...Inlet section, 410...One-way transport member, 420...Opposite-way transport member, 430...Opposite member, 431...Axis center, 440...Downward transport member, 452...Second movement restricting section, 453...Third movement restricting section, 455...Fifth movement restricting section

Claims

1. A rotating member formed in a cylindrical shape, rotatably mounted, having one end and the other end, with developer adhering to its outer surface, A plurality of magnetic poles are arranged inside the rotating member and aligned in the direction of rotation of the rotating member, A first magnetic member is positioned on the outside of the rotating member and opposite to one end of the rotating member, and has a downstream end which is the end located downstream in the rotational direction of the rotating member, and forms a magnetic field with the magnetic pole, A second magnetic member is positioned on the outside of the rotating member, opposite to one end of the rotating member, and positioned on the other end side of the rotating member than the first magnetic member, and forms a magnetic field with the magnetic pole, the second magnetic member having a facing portion which is the portion facing the rotating member, Equipped with, Of the plurality of magnetic poles, the opposing portion of the second magnetic member is located upstream in the rotational direction from the first magnetic pole, which is located upstream of the downstream end of the first magnetic member and counted from the downstream end. Developing device.

2. The opposing portion of the second magnetic member has a downstream end which is the end located downstream in the rotational direction of the rotating member, The developing apparatus according to claim 1, wherein the downstream end of the opposing portion of the second magnetic member is located downstream in the rotational direction of the magnetic pole that is the second to be located upstream in the rotational direction from the downstream end of the first magnetic member.

3. The developing apparatus according to claim 2, wherein the downstream end of the opposing portion of the second magnetic member is located downstream in the rotational direction from the intermediate position located between the first magnetic pole and the second magnetic pole.

4. The developing apparatus according to claim 1, wherein the second magnetic member is provided upstream in the rotational direction of a virtual plane that extends along the radial direction of the rotating member and is directed from the rotation center of the rotating member toward the first magnetic pole.

5. The opposing portion of the second magnetic member has a downstream end which is the end located downstream in the rotational direction of the rotating member, The second magnetic member is located downstream of the rotating member in the rotational direction and has a downstream edge that is connected to its own downstream end and extends away from the rotating member. The developing apparatus according to claim 4, wherein all portions of the downstream edge of the second magnetic member are provided upstream of the virtual plane in the rotational direction, and the second magnetic member is provided in such a manner that the virtual plane and the second magnetic member do not intersect.

6. An image forming apparatus comprising an image holder for holding an image, and a developing device for applying a developer to the image holder, wherein the developing device has the configuration of the developing device described in any one of claims 1 to 5.

Images