Developing unit and image formation device

Abstract

To suppress occurrence of toner accumulation unlike the situation of not employing a structure for avoiding difficulty in maintaining a contact state between a film and a developer holding body.SOLUTION: Provided is a developing unit comprising: a developer holding body that holds developer, which contains toner and carrier, to be supplied to an image holding body that forms an electrostatic latent image; a covering member 51 that covers part of the developer holding body; and a film 52 where end portions 52a and 52b of the developer holding body in a circumferential direction S thereof are attached to the covering member 51, and which is brought into contact with the developer held by the developer holding body. The film 52 is also attached to the covering member 51 even at an intermediate position 52c in the circumferential direction S.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] For example, Patent Document 1 discloses a developing device including a developer carrier arranged opposite a latent image carrier, a developer regulating member, and a casing member, the developing device including a first seal member having one end held by the casing member and the other end contacting the surface of the latent image carrier at a position upstream of the development area in the surface movement direction of the latent image carrier, a second seal member having one end held on the surface of the casing member facing the developer carrier and the other end contacting the first seal member at a position upstream of the development area in the surface movement direction of the developer carrier, and a third seal member having one end held on the surface of the casing member facing the developer carrier and the other end hanging down under its own weight and contacting the developer on the developer carrier that has passed the regulating position by the developer regulating member at a position upstream of the development area in the surface movement direction of the developer carrier. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-139111 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, consider a case where a cover member is provided to cover a part of the developer carrier to prevent toner from floating around and contaminating the developer carrier that holds the developer containing toner and carrier. If toner accumulates and forms a mass on the side of the cover member facing the developer carrier, the mass may fall off the cover member and cause image defects. If the generation of such a mass is suppressed by providing the cover member with a film that comes into contact with the developer held by the developer carrier, care must be taken to ensure that the film does not become difficult to maintain in contact with the developer layer, otherwise toner accumulation may occur. An object of the present invention is to suppress the occurrence of toner accumulation, compared to a case in which a configuration is not adopted that prevents a situation in which it becomes difficult to maintain a state of contact between the film and the developer layer on the developer carrier. [Means for solving the problem]

[0005] The invention described in claim 1 is a developing unit comprising: a developer holder that holds a developer containing toner and a carrier and that is supplied to an image holder that forms an electrostatic latent image; a cover member that covers a part of the developer holder; and a film whose circumferential end portion of the developer holder is attached to the cover member and comes into contact with the developer held by the developer holder, the film also being attached to the cover member at an intermediate position in the circumferential direction. The invention described in claim 2 is the developing device described in claim 1, characterized in that the intermediate position on the film is set based on the height of the layer of developer formed by a magnet for attracting the developer that the developer holder has. The invention described in claim 3 is the developing device described in claim 2, characterized in that the intermediate position set by the setting includes a position corresponding to the position of the attracting magnet where the height of the developer layer is high. The invention described in claim 4 is the developing device described in claim 3, characterized in that the intermediate position set by the setting does not include a position between the attraction magnets where the height of the developer layer is lower than the position of the attraction magnet. The invention described in claim 5 is the developing device described in claim 1, characterized in that the film attached to the covering member is bent into a shape that conforms to the change in height of the developer layer in the circumferential direction of the developer holder. The invention described in claim 6 is the developing device described in claim 1, characterized in that the intermediate position of the film is a central position of the film in the circumferential direction, and the film is attached to the central position of the cover member in the circumferential direction. The invention described in claim 7 is the developing device described in claim 1, characterized in that the covering member has a mark indicating the intermediate position of the film on a surface facing the developer holder. An eighth aspect of the present invention is the developing unit according to the seventh aspect, wherein the mark is a linear mark extending along the longitudinal direction of the cover member. The invention described in claim 9 is the developing device described in claim 8, characterized in that the linear mark is not formed in an area of ​​the cover member corresponding to an end of the developer holder where a magnet for attracting the developer is not provided on the developer holder. The invention described in claim 10 is an image forming apparatus including an image holder that forms an electrostatic latent image, a developing means that develops the electrostatic latent image formed on the image holder into a toner image, a transfer means that transfers the toner image by the developing means onto a recording material, and a fixing means that fixes the toner image transferred onto the recording material to the recording material, wherein the developing means is a developer holder that holds a developer containing toner and a carrier and is supplied to the image holder that forms an electrostatic latent image, a cover member that covers a part of the developer holder, and a film whose circumferential ends are attached to the cover member and come into contact with the developer held by the developer holder, and which is also attached to the cover member at an intermediate position in the circumferential direction. Effect of the Invention

[0006] According to the invention of claim 1, the occurrence of toner accumulation can be suppressed compared to a case in which a configuration is not adopted that prevents a situation in which it becomes difficult to maintain contact between the film and the developer layer on the developer holder. According to the invention of claim 2, the occurrence of toner accumulation can be suppressed compared to a case in which the intermediate position of the film is not provided with a configuration in which it is set based on the height of the developer layer formed by the developer attracting magnet held by the developer holder. According to the invention of claim 3, the intermediate position set can suppress the occurrence of toner accumulation compared to a case in which the configuration does not include a position corresponding to the position of the attracting magnet where the developer layer is high. According to the invention of claim 4, the occurrence of toner accumulation can be suppressed compared to a case in which the intermediate position set does not include positions between the attracting magnets where the height of the developer layer is lower than the position of the attracting magnets. According to the invention of claim 5, the film attached to the covering member can suppress the occurrence of toner accumulation compared to a case in which the film does not have a configuration in which it bends to a shape that follows the change in height of the developer layer around the circumferential direction of the developer holder. According to the invention of claim 6, a film whose intermediate position is the central position in the circumferential direction of the film can be applied regardless of the rotational direction of the developer holder, compared to a film that does not have a configuration in which it is attached to the central position in the circumferential direction of the covering member. According to the invention of claim 7, the covering member can improve the ease of assembly compared to a case in which the covering member does not have a configuration in which a mark indicating the middle position of the film is provided on the surface facing the developer holder. According to the invention of claim 8, the marker can be made easier to assemble than when not provided with a configuration in which the marker is a linear marker extending along the longitudinal direction of the covering member. According to the invention of claim 9, the linear markings are not formed in the area of ​​the cover member corresponding to the end of the developer holder where the developer attracting magnet on the developer holder is not provided, thereby improving assembly workability compared to a case in which the linear markings are not formed in the area of ​​the cover member corresponding to the end of the developer holder where the developer attracting magnet is not provided. According to the invention of claim 10, the occurrence of toner accumulation can be suppressed compared to a case in which a configuration is not adopted that prevents a situation in which it becomes difficult to maintain contact between the film and the developer layer on the developer holder. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an image forming apparatus. [Diagram 2] FIG. 2 is a diagram illustrating a developing device of the image forming apparatus. [Diagram 3] FIG. 2 is a perspective view illustrating a more specific configuration of the developing device. [Figure 4] FIG. 4 is a diagram illustrating the magnetic poles of the magnet roll of the developing roll. [Diagram 5] 13A and 13B are diagrams illustrating a film provided on the inner surface of the cover member. [Figure 6] 5A and 5B are diagrams for explaining the attachment position of the film to the cover member, in which (a) shows a case where the attachment position is a predetermined position, and (b) shows a case where the attachment position is shifted from the predetermined position. [Figure 7] FIG. 4 is a perspective view showing an inner surface of a cover member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram illustrating an image forming apparatus 1. As shown in FIG. The image forming apparatus 1 according to this embodiment includes a paper feed unit 1A, a printing unit 1B, and a paper discharge unit 1C. The paper feed unit 1A includes a first paper storage section 11 to a fourth paper storage section 14 for storing paper P as an example of a recording medium. The paper feed unit 1A also has feed rolls 15-18 that correspond to the first paper storage section 11 to the fourth paper storage section 14, respectively, and feed the paper P stored in each paper storage section to a transport path connected to the printing unit 1B.

[0009] The printing unit 1B includes an image forming section 20 that forms an image on a sheet P. The printing unit 1B also includes a control section 21 that controls each section of the image forming apparatus 1. The printing unit 1B also includes an image processing section 22. The image processing section 22 performs image processing on image data transmitted from the image reading device 4 and the personal computer (PC) 5. The printing unit 1B is also provided with a UI (User Interface) 23, which is configured with a touch panel or the like and notifies the user of information and receives information input from the user.

[0010] Image forming section 20, as an example of an image forming means, is provided with six image forming units 30T, 30P, 30Y, 30M, 30C, and 30K (hereinafter, sometimes simply referred to as "image forming units 30") arranged in parallel at regular intervals. Each image forming unit 30 includes a photosensitive drum 31 on which an electrostatic latent image is formed while rotating in the direction of arrow A, a charging roll 32 which charges the surface of the photosensitive drum 31, a developing device 33 which develops the electrostatic latent image formed on the photosensitive drum 31, and a drum cleaner 34 which removes toner and the like from the surface of the photosensitive drum 31. The photoconductor drum 31 is an example of an image carrier.

[0011] The image forming section 20 is also provided with a laser exposure device 26 that exposes the photoconductor drum 31 of each image forming unit 30 to laser light. The exposure of the photoconductor drum 31 by the laser exposure device 26 is not limited to using laser light. For example, a light source such as an LED (Light Emitting Diode) may be provided for each image forming unit 30, and the photoconductor drum 31 may be exposed to light emitted from the light source.

[0012] Each image forming unit 30 is configured similarly, except for the toner contained in the developer 33. The image forming units 30Y, 30M, 30C, and 30K form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Further, the image forming units 30T and 30P form toner images using toner corresponding to a corporate color, foaming toner for Braille, fluorescent color toner, toner for improving gloss, etc. In other words, the image forming units 30T and 30P form toner images using toner of a special color.

[0013] The image forming section 20 is also provided with an intermediate transfer belt 41 onto which the toner images of each color formed on the photosensitive drums 31 of the image forming units 30 are transferred. The image forming section 20 is also provided with a primary transfer roll 42 that transfers the respective color toner images of the respective image forming units 30 onto the intermediate transfer belt 41 at a primary transfer portion T1. The image forming unit 20 is also provided with a secondary transfer roll 40 that transfers the toner image transferred onto the intermediate transfer belt 41 onto the paper P at a secondary transfer portion T2. Furthermore, the image forming section 20 is provided with a belt cleaner 45 that removes toner and the like from the surface of the intermediate transfer belt 41, and a fixing device 80 that fixes the secondarily transferred image onto the paper P.

[0014] The image forming unit 20 performs an image forming operation based on a control signal from the control unit 21 . Specifically, in the image forming unit 20, first, image processing is performed on the image data input from the image reading device 4 or the PC 5 by the image processing unit 22, and the image data after image processing is supplied to the laser exposure device 26. Then, for example, in a magenta (M) image forming unit 30M, the surface of the photosensitive drum 31 is charged by the charging roll 32, and then the laser exposure device 26 irradiates the photosensitive drum 31 with laser light modulated by image data obtained from the image processing unit 22.

[0015] As a result, an electrostatic latent image is formed on the photoconductor drum 31 . The formed electrostatic latent image is developed by the developing unit 33, and a magenta toner image is formed on the photosensitive drum 31. Similarly, yellow, cyan and black toner images are formed in the image forming units 30Y, 30C and 30K, and special color toner images are formed in the image forming units 30T and 30P.

[0016] The respective color toner images formed in each image forming unit 30 are electrostatically transferred sequentially by a primary transfer roll 42 onto an intermediate transfer belt 41 rotating in the direction of arrow C in Figure 1, and superimposed toner images are formed on the intermediate transfer belt 41. The superimposed toner image formed on the intermediate transfer belt 41 is transported to a secondary transfer portion T2 constituted by a secondary transfer roll 40 and a backup roll 49 as the intermediate transfer belt 41 moves.

[0017] On the other hand, the paper P is taken out from the first paper storage unit 11 by, for example, the delivery roll 15, and then transported to the position of the registration roll 74 via the transport path. When the superimposed toner image is transported to the secondary transfer portion T2, a sheet of paper P is supplied from the registration roll 74 to the secondary transfer portion T2 in accordance with the transport timing. Then, in the secondary transfer portion T2, the superimposed toner images are electrostatically transferred onto the paper P all at once by the action of a transfer electric field formed between the secondary transfer roll 40 and the backup roll 49.

[0018] Thereafter, the paper P onto which the superimposed toner images have been electrostatically transferred is transported to a fixing device 80. In the fixing device 80, pressure and heat are applied to the paper P on which the unfixed toner image has been formed, and the toner image is fixed to the paper P. Then, the sheet P on which the fixing process has been performed passes through a curl correction section 81 provided in the sheet discharge unit 1C, and is then conveyed to a sheet stacking section (not shown).

[0019] Fig. 2 is a diagram illustrating the developing unit 33 of the image forming apparatus 1. The developing unit 33 shown in Fig. 2 is viewed from the rear side. The developing unit 33 includes a container 331 that contains a developer (not shown). The container 331 is configured with a container housing 332 made of resin. The housing 332 of the developing unit 33 is arranged to extend along a direction perpendicular to the paper surface of FIG. 2, which is the direction from the front side to the rear side of the image forming apparatus 1 (see FIG. 1), and has a rear end (not shown) on the rear side and a front end (not shown) on the front side.

[0020] An opening 333 is provided in the housing 332 at a location facing the photoconductor drum 31 (see FIG. 1). A developing roll 334 that adheres a developer to the surface of the photoconductor drum 31 is provided in the opening 333. The developing roll 334, which is an example of a developer holder, is formed in a cylindrical shape and is arranged so as to extend along a direction from the front side to the rear side of the image forming apparatus 1. In addition, the developing roll 334 is arranged so as to extend along the longitudinal direction of the developing unit 33.

[0021] The developing roll 334 is provided with a developing sleeve 334A that is formed of a cylindrical body and that is driven to rotate, and a magnet roll 334B that is disposed inside the developing sleeve 334A. The developing sleeve 334A is made of a metal such as SUS, etc. The developing sleeve 334A rotates in the direction of the arrow D in the figure. The developing roll 334 is an example of a developer carrier.

[0022] Furthermore, in this embodiment, at the primary transfer portion T1 (see FIG. 1) between the developing roll 334 and the photosensitive drum 31, the developing sleeve 334A and the photosensitive drum 31 rotate so that they move in the same direction. The developing unit 33 is provided with a layer regulating member 335 that regulates the layer thickness of the developer held on the developing roll 334 .

[0023] As shown in FIG. 2, the developing device 33 is provided with a first transport member 336 and a second transport member 337 for transporting the developer. The first transport member 336 and the second transport member 337 are provided on the opposite side to the side on which the photoconductor drum 31 (see FIG. 1) is installed, with the developing roll 334 interposed therebetween. The first transport member 336 has a rotation axis aligned with the rotation axis of the developing sleeve 334A that is driven to rotate, and rotates around this rotation axis to transport the developer in the container 331.

[0024] In the developing device 33 configured in this manner, new toner or toner to which a very small amount of carrier has been added is stirred and transported between the first transport member 336 and the second transport member 337, and thus circulated and transported. More specifically, by transferring the developer through connection ports formed at both ends of a partition wall extending in the axial direction, the developer stirred by the first transport member 336 is stirred by the second transport member 337, and can also be stirred by the first transport member 336. In the developing device 33, a circulation path is formed, which is a path that circulates in the axial direction by the rotation of each of the first transport member 336 and the second transport member 337.

[0025] The developing unit 33 is provided with a third transport member 338 adjacent to the second transport member 337. In addition, the developing unit 33 is provided with a pick-up roll 339 located above the third transport member 338. The transport path formed by the rotation of the third transport member 338 is connected to the circulation path described above, and receives the developer from the circulation path. The third transport member 338 supplies the developer to a pickup roll 339. The pickup roll 339 supplies the developer to the developing roll 334. For example, the first transport member 336 transports toward the front side of the paper, the second transport member 337 transports toward the back side of the paper, and the third transport member 338 transports toward the front side of the paper.

[0026] The developing roll 334, the layer regulating member 335, the first transport member 336, the second transport member 337, the third transport member 338 and the pickup roll 339 are disposed substantially parallel to the photoconductor drum 31 (see FIG. 1).

[0027] Next, a more specific configuration of the developing unit 33 will be described. Fig. 3 is a perspective view for explaining a more specific configuration of the developing unit 33. In Fig. 3, explanations of parts that are the same as those in Fig. 2 may be omitted. 3, the developing unit 33 includes a cover member 51 having an arc-shaped cross-sectional portion 51a that covers a part of the pickup roll 339. The cover member 51 is a member for preventing toner from floating and contaminating the toner, and is an example of a covering member.

[0028] FIG. 4 is a diagram for explaining the magnetic poles of the magnet roll 334B of the developing roll 334. As shown in FIG. As shown in Fig. 4, the magnet roll 334B is provided with a plurality of magnetic poles arranged along the circumferential direction. More specifically, the magnet roll 334B is provided with seven magnetic poles 61a to 67a. The arrangement of the magnetic poles is as shown in Fig. 4 by a line segment 61 indicating the position of the first magnetic pole 61a, a line segment 62 indicating the position of the second magnetic pole 62a, a line segment 63 indicating the position of the third magnetic pole 63a, a line segment 64 indicating the position of the fourth magnetic pole 64a, a line segment 65 indicating the position of the fifth magnetic pole 65a, a line segment 66 indicating the position of the sixth magnetic pole 66a, and a line segment 67 indicating the position of the seventh magnetic pole 67a.

[0029] The arrangement of the magnetic poles 61a to 67a sets a magnetic attraction force distribution 60 in the normal direction indicated by the thick line. The magnetic attraction force distribution 60 indicates that the thickness of the developer layer, i.e., the height of the layer from the surface of the developing roll 334, changes depending on the position in the circumferential direction S of the developing roll 334. As shown in Fig. 4, the magnetic attraction force distribution 60 is such that the developer layer is high at the positions of line segments 64 and 65 where the magnetic poles 64a and 65a are located, and the developer layer is low between the adjacent magnetic poles 64a and 65a, for example, between the line segments 64 and 65. In this manner, the height of the developer layer on the developing roll 334 varies in the circumferential direction S. The magnetic poles 64a and 65a are an example of an attracting magnet.

[0030] FIG. 5 is a diagram illustrating the film 52 provided on the inner surface 51b of the cover member 51. As shown in FIG. As shown in FIG. 5, a film 52 is provided on an inner surface 51b of the cover member 51. The film 52 is provided on the inner surface 51b of the cover member 51 by attaching an adhesive tape 53 to an end 52a of the film 52 and an adhesive tape 54 to an end 52b. The film 52 is preferably a soft and flexible material. For example, a urethane-based material can be used for the film 52, and the thickness is, for example, 50 to 200 μm.

[0031] Moreover, in the film 52, an adhesive tape 55 is attached to an intermediate portion 52c located between the end portion 52a and the end portion 52b in the circumferential direction S of the developing roll 334. The position of the intermediate portion 52c is an example of a middle position in the circumferential direction. The adhesive tapes 53 to 55 are double-sided adhesive tapes having adhesive surfaces on both sides, and each of them is located between the inner surface 51b of the cover member 51 and the film 52. Therefore, the film 52 is located between the cover member 51 in the circumferential direction of the developing roll 334, and no gap is formed between the film 52 and the cover member 51 through which the toner can enter.

[0032] More specifically, end portion 52b to which adhesive tape 54 is attached is located at line segment 64, and middle portion 52c to which adhesive tape 55 is attached is located at line segment 65. The height between developing roll 334 and film 52 is high at the positions where adhesive tapes 54 and 55 are attached, and low at the intermediate position.

[0033] In this way, the adhesive tapes 54, 55 are attached at a position where the developer layer is high, thereby ensuring the height between the developing roll 334 and the film 52. More specifically, by attaching the adhesive tape 55 to the middle portion 52c, which is the same position as the line segment 65, in addition to the adhesive tapes 53, 54 to the ends 52a, 52b of the film 52, the film 52 comes into light contact with the developer layer even if the height of the developer layer changes in the circumferential direction. This prevents the toner accumulated on the inner surface 51b side of the cover member 51 from forming a mass and dropping onto the developing roll 334 (see FIG. 3) to cause image defects.

[0034] In this embodiment, the adhesive tape 55 is attached to one intermediate portion 52c, but the present invention is not limited to this and may be attached to a plurality of intermediate portions.

[0035] Here, the intermediate portion 52c of the film 52 refers to a portion of the film 52 when attached to the cover member 51 at a position corresponding to the line segment 65 (the fifth magnetic pole 65a shown in FIG. 4) where the developer layer becomes high, and may be located at the center of the film 52 or may be shifted from the center. The center position here refers to the center position of the film 52 in the same direction as the circumferential direction S of the cross-sectional arc portion 51a of the cover member 51. In addition, the position of intermediate portion 52c of film 52 is set based on magnetic attraction force distribution 60 (see FIG. 4), and it is determined whether intermediate portion 52c is to be the center position of film 52. If intermediate portion 52c is located at the center position of film 52, it is possible to set film 52 so that the deflection shape is the same on the upstream side and downstream side in the direction of arrow D from intermediate portion 52c.

[0036] More specifically, the intermediate portion 52c of the film 52 is provided at a position where the film 52 is in light contact with the developer layer. Therefore, it is possible to avoid including a position where the height of the developer layer is lower than that of the fourth magnetic pole 64a or the fifth magnetic pole 65a, for example, between the fourth magnetic pole 64a and the fifth magnetic pole 65a. It is also possible to position the intermediate portion 52c at a position shifted from the above-mentioned high position of the developer layer, and to include the above-mentioned low position of the developer layer. Furthermore, when there are a plurality of intermediate portions 52c, it is also possible to include positions where the developer layer is lower than the positions where the developer layer is higher, in addition to the positions where the developer layer is higher.

[0037] 6 is a diagram for explaining the attachment position of film 52 to cover member 51, where (a) shows a case where the attachment position is a predetermined position, and (b) shows a case where the attachment position is shifted from the predetermined position. Note that in FIG. 6, the developer layer is shown in an elliptical shape. 6(a), when the film 52 is attached to the above-mentioned end portions 52a and 52b with adhesive tapes 53 and 54 and to a predetermined intermediate portion 52c with adhesive tape 55, the film 52 is bent to match the height of the developer layer. That is, the film 52 is bent to a shape that follows the change in the height of the developer layer in the circumferential direction of the developing roll 334. The predetermined position here refers to the position of intermediate portion 52c of film 52, and also to the center position in circumferential direction S of the arc-shaped cross-section of cover member 51 corresponding to the position of line segment 65 (see, for example, FIG. 6(a)).

[0038] On the other hand, as shown in Fig. 6(b), when the film 52 is attached with the adhesive tape 55 at a position 52d near the end 52a, instead of at the intermediate portion 52c, which is a position that is predetermined in accordance with the line segment 65, the warped shape of the film 52 does not match the height of the developer layer. For this reason, the film 52 does not come into contact with the developer layer, and the toner accumulates higher than the magnetic attraction force distribution 60 (see Fig. 4) set by the arrangement of the magnetic poles 61a to 67a, and the toner may fall into the developing roll 334 (see Fig. 3) in the form of lumps, causing a defective image.

[0039] In this way, when attaching film 52 to cover member 51, if adhesive tape 55 is attached to ends 52a, 52b and at a position shifted from the predetermined position, there is a risk of image defects occurring compared to when adhesive tape 55 is attached at a predetermined position, but the risk of image defects occurring is reduced compared to when film 52 is not provided.

[0040] The position of intermediate portion 52c of film 52 on cover member 51 when attached to cover member 51 may be the center position in circumferential direction S of cover member 51, or may be shifted from the center position.

[0041] In this specification, light contact refers to the film 52 contacting the developer layer in such a manner that the film 52 does not affect the height of the developer layer on the developing roll 334, and that no space is formed between the film 52 and the developer layer in which toner can accumulate.

[0042] FIG. 7 is a perspective view showing the inner surface 51b of the cover member 51. As shown in FIG. As shown in FIG. 7, an inner surface 51b of the cover member 51 is provided with linear marks 51c that indicate the position where the middle portion 52c (see FIG. 5) of the film 52 is attached with adhesive tape 55 (see FIG. 5). The mark 51c is formed to extend in the longitudinal direction n of the cover member 51. This improves the workability when attaching the film 52 to the cover member 51. The longitudinal direction n is the same as the axial direction of the developing roll 334. The mark 51c is an example of a mark that indicates the middle position of the film.

[0043] Also, a mark 51e is formed on the inner surface 51b of the cover member 51, which corresponds to the position of an axial end 51d of the film 52 in the axial direction of the developing roll 334. The magnetic poles 64a, 65a (see FIG. 4, for example) are not provided on the end side of the mark 51e. Therefore, the above-mentioned mark 51c is not formed on the end side of the mark 51e. This improves the workability of pasting. The axial end 51d is an example of a region of the cover member that corresponds to the end of the developer carrier.

[0044] <Additional Notes> (((1))) a developer carrier for holding a developer containing a toner and a carrier and supplied to an image carrier for forming an electrostatic latent image; a cover member for covering a part of the developer carrier; a film having an end portion in a circumferential direction of the developer carrier attached to the cover member and contacting the developer held by the developer carrier, the film also being attached to the cover member at an intermediate position in the circumferential direction; A developing device comprising: (((2))) the intermediate position on the film is set based on the height of a layer of the developer formed by a magnet for attracting the developer that is provided on the developer holder; The developing device according to (((1))) above. (((3))) the intermediate position according to the setting includes a position corresponding to a position of the attracting magnet where the height of the developer layer is high; The developing device according to (((2))) above. (((4))) the intermediate position set by the setting does not include a position between the attracting magnets where the height of the developer layer is lower than the position of the attracting magnets; The developing device according to (((3))) above. (((5))) the film attached to the cover member is bent into a shape conforming to a change in height of the developer layer in the circumferential direction of the developer carrier; The developing device according to (((1))) or (((2))) above. (((6))) The intermediate position of the film is a central position of the film in the circumferential direction, and the film is attached to the covering member at a central position in the circumferential direction. The developing device according to any one of ((1))) to (((5))) above. (((7))) the cover member has a mark indicating the intermediate position of the film on a surface facing the developer carrier; The developing device according to any one of ((1))) to (((6))) above. (((8))) The mark is a linear mark extending along the longitudinal direction of the covering member. The developing device according to (((7))) above. (((9))) the linear mark is not formed in an area of ​​the cover member corresponding to an end of the developer carrier where a magnet for attracting the developer is not provided; The developing device according to (((8))) above. (((10))) an image carrier for forming an electrostatic latent image; a developing means for developing the electrostatic latent image formed on the image carrier into a toner image; a transfer means for transferring the toner image produced by the developing means onto a recording material; a fixing unit for fixing the toner image transferred onto the recording material onto the recording material; Including, The developing means is a developer carrier for holding a developer containing a toner and a carrier and supplied to an image carrier for forming an electrostatic latent image; a cover member for covering a part of the developer carrier; a film having an end portion in a circumferential direction of the developer carrier attached to the cover member and contacting the developer held by the developer carrier, the film also being attached to the cover member at an intermediate position in the circumferential direction; An image forming apparatus comprising:

[0045] According to the invention of (((1))), the occurrence of toner accumulation can be suppressed compared to a case in which a configuration for preventing a situation in which it is difficult to maintain contact between the film and the developer layer on the developer holder is not adopted. According to the invention of (((2))), the occurrence of toner accumulation can be suppressed compared to a case in which the intermediate position in the film is not provided with a configuration in which it is set based on the height of the developer layer formed by the developer attracting magnet possessed by the developer holder. According to the invention (((3))), the intermediate position set can suppress the occurrence of toner accumulation compared to a case in which the configuration does not include a position corresponding to the position of the attracting magnet where the developer layer is high. According to the invention (((4))), the occurrence of toner accumulation can be suppressed compared to a case in which the intermediate position set does not include positions between the attracting magnets where the height of the developer layer is lower than the position of the attracting magnets. According to the invention (((5))), the film attached to the covering member can suppress the occurrence of toner accumulation compared to a case in which the film does not have a configuration in which it bends to a shape that follows the change in height of the developer layer around the circumferential direction of the developer holder. According to the invention of (((6))), a film whose intermediate position is the central position in the circumferential direction of the film can be applied regardless of the rotational direction of the developer holder, compared to a film that does not have a configuration for being attached to the central position in the circumferential direction of the covering member. According to the invention (((7))), the covering member can improve assembly workability compared to a case in which the covering member does not have a mark indicating the intermediate position of the film on the surface facing the developer holder. According to the invention (((8))), the marker is a linear marker extending along the longitudinal direction of the covering member, and compared to a case in which the marker is not provided, the ease of assembly can be improved. According to the invention (((9))), the linear markings are not formed in the area of ​​the cover member corresponding to the end of the developer holder that is not provided with a magnet for attracting developer, which the developer holder has, thereby improving assembly workability compared to a case in which the linear markings are not formed in the area of ​​the cover member corresponding to the end of the developer holder that is not provided with a magnet for attracting developer. According to the invention (((10))), the occurrence of toner accumulation can be suppressed compared to a case in which a configuration for preventing a situation in which it is difficult to maintain contact between the film and the developer layer on the developer holder is not adopted. [Explanation of symbols]

[0046] 1...image forming apparatus, 31...photosensitive drum, 33...developing unit, 334...developing roll, 51...cover member, 51a...cross-sectional arc-shaped portion, 51c...mark, 51d...axial end portion, 51e...mark, 52...film, 52a, 52b...end portion, 52c...middle portion, 60...magnetic attraction force distribution, 64a...fourth magnetic pole, 65a...fifth magnetic pole, n...longitudinal direction, S...circumferential direction

Claims

1. a developer carrier for holding a developer containing a toner and a carrier and supplied to an image carrier for forming an electrostatic latent image; a cover member for covering a part of the developer carrier; a film having an end portion in a circumferential direction of the developer carrier attached to the cover member and contacting the developer held by the developer carrier, the film also being attached to the cover member at an intermediate position in the circumferential direction; A developing device comprising:

2. the intermediate position on the film is set based on the height of a layer of the developer formed by a magnet for attracting the developer that is provided on the developer holder; 2. The developing device according to claim 1,

3. the intermediate position according to the setting includes a position corresponding to a position of the attracting magnet where the height of the developer layer is high; 3. The developing device according to claim 2.

4. the intermediate position set by the setting does not include a position between the attracting magnets where the height of the developer layer is lower than the position of the attracting magnets; 4. The developing device according to claim 3.

5. the film attached to the cover member is bent into a shape conforming to a change in height of the developer layer in the circumferential direction of the developer carrier; 2. The developing device according to claim 1,

6. The intermediate position of the film is a central position of the film in the circumferential direction, and the film is attached to the covering member at a central position in the circumferential direction.

2. The developing device according to claim 1,

7. the cover member has a mark indicating the intermediate position of the film on a surface facing the developer carrier; 2. The developing device according to claim 1,

8. The mark is a linear mark extending along the longitudinal direction of the covering member.

8. The developing device according to claim 7.

9. the linear mark is not formed in an area of ​​the cover member corresponding to an end of the developer carrier where a magnet for attracting the developer is not provided; 9. The developing device according to claim 8.

10. an image carrier for forming an electrostatic latent image; a developing means for developing the electrostatic latent image formed on the image carrier into a toner image; a transfer means for transferring the toner image produced by the developing means onto a recording material; a fixing unit for fixing the toner image transferred onto the recording material onto the recording material; Including, The developing means is a developer carrier for holding a developer containing a toner and a carrier and supplied to an image carrier for forming an electrostatic latent image; a cover member for covering a part of the developer carrier; a film having an end portion in a circumferential direction of the developer carrier attached to the cover member and contacting the developer held by the developer carrier, the film also being attached to the cover member at an intermediate position in the circumferential direction; An image forming apparatus comprising:

Images