Developing device and image forming apparatus

Abstract

To provide a developing device that, even if developer enters both end areas of a developing roller, can effectively prevent the developer that enters from flowing (scattering) to the outside of the developing device.SOLUTION: A developer tank has, at both end positions of an opening in an axial direction of a developing roller, a wall part (side face part) 57b to which a bearing of the developing roller is attached, and a curved surface part 58 that is formed to extend along a surface of the developing roller over the length of a predetermined distance in the axial direction from the wall part (side face part) 57b. In an area of the curved surface part 58 below the developing roller and on a side of the wall part (side face part) 57b, a developer recovery part 60 is further formed which has a space wider than a space formed between the surface of the developing roller 53 and the curved surface part 58. A regulation member 55 is attached to an edge of the opening on a side where the developer recovery part is provided.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a developing device provided in an image forming apparatus and an image forming apparatus including the developing device.

Background Art

[0002] An image forming apparatus develops a toner image on a photoreceptor drum by a developing device, transfers the toner image formed on the photoreceptor drum to an intermediate transfer member once by a transfer device, and then transfers it to printing paper, or directly transfers it to printing paper, and a fixing device fixes the printing paper on which the toner image is transferred to form an image.

[0003] Patent Document 1 discloses a developing device 234 including a developing roller 502 and a developing case 503. The developing roller 502 carries and conveys a developer and visualizes an electrostatic latent image formed on a photoreceptor drum 31. Note that the names and reference numerals of the respective components in the description of the background art are those in Patent Document 1.

[0004] The developing case 503 has a shaft hole 531 that pivotally supports the developing roller 502 and a shielding portion 534 that prevents leakage of the developer from the shaft hole 531.

[0005] By attaching a seal member 504 made of a nonwoven fabric or a rocket material to the surface of the shielding portion 534 on the side of the developing roller 502, a gap with the developing roller 502 is eliminated. Further, an elastic member 505 is attached to the lower end 342 using a double-sided tape or the like to prevent intrusion of a developer (not shown).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the above-described developing device, since the gap between the developing roller 502 and the shielding portion 534 is narrow, the developer accumulated in the gap may be discharged toward the photosensitive drum side due to the rotation of the developing roller, which may contaminate the inside of the developing device or cause defects in the formed image.

[0008] The present disclosure has been made in view of the above problems, and an object thereof is to provide a developing device that can effectively prevent the developer that has entered the both end regions of the developing roller from ejecting (scattering) to the outside of the developing device.

Means for Solving the Problems

[0009] The developing device according to the present disclosure for achieving the above object includes a developing tank having an opening facing the image carrier and accommodating a developer therein, a developing roller rotatably provided in a predetermined direction at the opening of the developing tank and carrying the developer on its surface, a supply member supported rotatably in the developing tank below the developing roller and supplying the developer to the surface of the developing roller, and a regulating member disposed to face the developing roller and regulating the layer thickness of the developer supplied to the surface of the developing roller. The developing tank has, at both axial end positions of the developing roller at the opening, wall portions to which bearings of the developing roller are attached, and curved surface portions formed along the surface of the developing roller over a length of a predetermined distance in the axial direction from the wall portions. In a region below the developing roller of the curved surface portion and on the side of the wall portion, a developer recovery portion having a space wider than the space formed between the surface of the developing roller and the curved surface portion is further formed, and the regulating member is attached to an edge portion of the opening on the side where the developer recovery portion is provided.

[0010] According to the above configuration, the developing tank has a wall portion to which the bearings of the developing roller are attached at positions corresponding to both longitudinal ends of the developing roller, and a curved surface portion formed along the surface of the developing roller over a length of a predetermined distance in the axial direction from the wall portion. In a region below the developing roller of the front curved surface portion and on the wall portion side, a developer recovery portion having a space wider than the space formed between the surface of the developing roller and the curved surface portion is further formed. Since the regulating member is attached to the edge of the opening on the side where the developer recovery portion is provided, the developer that has entered between the surface of the developing roller and the curved surface portion can be recovered in the developer recovery portion. Therefore, even if the developer enters the both end regions of the developing roller, it is possible to effectively prevent the entered developer from ejecting (scattering) to the outside of the developing device.

[0011] In the developing device according to the present disclosure, it may be characterized in that a sealing elastic member that contacts the surface of the developing roller is provided in a region of the curved surface portion where the developer recovery portion is not provided.

[0012] According to the above configuration, since a sealing elastic member that contacts the surface of the developing roller is provided, it is possible to suppress the discharged developer from being discharged through a region of the curved surface portion where the developer recovery portion is not provided while making it difficult for the developer to be recovered into the developer recovery portion.

[0013] In the developing device according to the present disclosure, the developer is a two-component developer containing toner made of a non-magnetic material and carrier made of a magnetic material. The developing roller is a magnet roller in which a plurality of magnets extending in the axial direction are arranged in the circumferential direction around the rotation axis inside, and a sleeve made of a non-magnetic material and longer than the axial length of the plurality of magnets is rotatably arranged outside the plurality of magnets. The curved surface portion may be provided so as to face a region where the magnets are not arranged inside the sleeve.

[0014] In the developing roller, in the region where a magnet is disposed inside the sleeve, the developer adheres to the surface of the sleeve by magnetic force. On the other hand, in the region where no magnet is disposed inside the sleeve, the developer can be separated from the surface of the sleeve. By providing a curved surface portion in such a region, the developer can be efficiently recovered.

[0015] In the development according to the present disclosure, the developer recovery portion may have a drop port communicating with a space in which the supply member provided below the curved surface portion is disposed.

[0016] According to the above configuration, the developer recovered by the developer recovery portion can be returned to the developing tank by its own weight through the drop port without providing a complicated mechanism or an expensive member for returning the developer to the developing tank. Even if the developer enters the end portion of the developing roller due to the rotation of the developing roller, it can be returned to the developing tank, so that the developer can be effectively prevented from blowing out from the end portion of the developing roller.

[0017] In the developing device according to the present disclosure, the supply member is a screw having spiral blades formed on the outside, and the drop port is provided above a region that conveys the developer in the axial direction while pushing the developer downward by the rotation of the supply member.

[0018] When the drop port is configured to drop into a region that conveys the developer in the axial direction while pushing the developer upward, the developer returned to the developing tank through the drop port may be lifted by an air flow generated from below to above by the screw, and there is a risk that the developer blows out from the developing tank.

[0019] On the other hand, when the drop port is configured to drop into a region that conveys the developer in the axial direction while pushing the developer downward, the developer dropped through the drop port is drawn into an air flow generated by the screw so as to be drawn in from above to below and returned to the developing tank, so that the risk of the developer blowing out from the developing tank can be suppressed.

[0020] In the developing device according to the present disclosure, the developer recovery unit may have a first inclined portion that extends from the downstream side to the upstream side in the rotation direction of the developing roller in the predetermined direction as it approaches the dropping port, or from the upstream side to the downstream side in the rotation direction of the developing roller in the predetermined direction as it approaches the dropping port.

[0021] According to the above configuration, the developer that has entered the curved surface portion is guided to the dropping port by sliding down the first inclined portion.

[0022] In the developing device according to the present disclosure, the developer recovery unit may have a second inclined portion that approaches the wall portion side as it approaches the dropping port.

[0023] According to the above configuration, the developer that has entered the curved surface portion is guided to the dropping port by sliding down the second inclined portion.

[0024] The image forming apparatus according to the present disclosure for achieving the above object is characterized by including a developing device having any of the above-described characteristic configurations.

[0025] According to the above configuration, since the developing device suppresses the developer that has entered both end portions in the longitudinal direction of the developing roller from being discharged to the photosensitive drum side, it is possible to provide an image forming apparatus that does not cause contamination inside the main body of the image forming apparatus or defects in the formed image.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 8A

Figure 8B

Figure 9

Figure 10A

Figure 10B

Mode for Carrying Out the Invention

[0027] [Embodiment 1] Hereinafter, a tandem type color image forming apparatus including a developing device according to the present disclosure will be described.

[0028] As shown in FIG. 1, a color image forming apparatus 1 (hereinafter referred to as the image forming apparatus 1) includes four image forming units 2 (2K, 2C, 2M, 2Y) that form toner images of respective colors of black (K), cyan (C), magenta (M), and yellow (Y), an intermediate transfer device 3 to which the toner images formed by each image forming unit 2 are intermediate-transferred, a transfer device 4, a fixing device 5, a paper feeding device 6, a conveying device 7, a paper discharge tray 8, and a control unit (not shown) that controls the color image forming apparatus 1. P is printing paper. The image forming apparatus 1 is the "image forming apparatus" in the claims.

[0029] In the figure, arrow X indicates the left-right direction when the image forming apparatus 1 is viewed from the front. The arrow direction is the right side, and the side opposite to the arrow is the left side. Also, arrow Y in the figure indicates the depth direction when the image forming apparatus 1 is viewed from the front. The front side (front side) where an operation unit (not shown) is provided perpendicular to the paper surface is the front side, and the back side (rear side) perpendicular to the paper surface is the back side. Also, arrow Z in the figure indicates the up-down direction when the image forming apparatus 1 is viewed from the front. The arrow direction is the upper side, and the side opposite to the arrow is the lower side.

[0030] Note that the letters K, C, M, and Y of the image forming units 2K, 2C, 2M, and 2Y are used to distinguish the respective image forming units corresponding to black (K), cyan (C), magenta (M), and yellow (Y), and may be omitted when distinction is not necessary. The same applies to the configurations of the following parts.

[0031] Since the image forming units 2K, 2C, 2M, and 2Y have basically the same configuration, the image forming unit 2K that forms a black (K) toner image will be described.

[0032] As shown in FIG. 1, the image forming unit 2 includes a photosensitive drum 20, a charger 21 that charges the photosensitive drum 20, an exposure device 22 that exposes the charged photosensitive drum 20, a developing device 23 that develops a toner image on the exposed photosensitive drum 20, and a cleaning device 9 that cleans the surface of the photosensitive drum 20.

[0033] The photoreceptor drum 20 has a photosensitive layer (photoconductor) formed on the surface of a grounded conductive drum, which becomes an insulator in the dark and a conductor when exposed to light. The surface of the photoreceptor drum 20 is charged to a negative predetermined potential (e.g., -550V) by a charger 21. The surface of the photoreceptor drum 20 charged to the predetermined potential is exposed by an exposure device 22 based on the image data to be printed. The exposure device 22 of the present disclosure is a scanning type exposure device that irradiates a beam emitted from one light source onto a rotating polygon mirror or the like to scan in the rotational axis direction of the photoreceptor drum 20. When the surface of the photoreceptor drum 20 charged to the predetermined potential is exposed by the exposure device 22, the portion irradiated with light becomes a conductor due to the property of the photoconductor and the charge decreases, and an electrostatic latent image having a potential distribution corresponding to the image data is formed.

[0034] The electrostatic latent image formed on the surface of the photoreceptor drum 20 is developed by the developing device 23 to form a toner image. As shown in FIGS. 2 to 8B, the developing device 23 has an opening 50 that opens toward the photoreceptor drum 20, and a developing tank 51 that houses a developer containing toner therein. At the opening 50 of the developing tank 51, a developing roller 53 is rotatably provided in a predetermined direction R and carries the developer on its surface 53a. A supply member (first screw) 61 is rotatably supported by the developing tank 51 below the developing roller 53 in the vertical direction (up and down direction) and supplies the developer to the surface 53a of the developing roller 53. A replenishing member (second screw) 72 is arranged adjacent to the supply member (first screw) 61 and replenishes the supply member (first screw) 61 with the developer. The conveying device 52 includes a regulating member 55 and the like that are arranged at the opening 50 with a predetermined interval (for example, 0.7 mm) from the surface 53a of the developing roller 53, that is, arranged to face the developing roller 53, and regulate the film thickness of the developer supplied from the supply member (first screw) 61 to the surface 53a of the developing roller 53. That is, when the developing roller 53 rotates in the predetermined direction R, the developer supplied to the surface of the developing roller 53 is regulated so that the layer thickness in the rotational axis direction of the developing roller 53 becomes constant when passing through the regulating member 55, and is sent to the facing portion with the photoreceptor drum 20. A power source (not shown) is connected to the developing roller 53, and a developing bias (for example, -400 V), which is a predetermined voltage, is applied thereto. Due to the potential difference between the developing roller 53 and the electrostatic latent image generated thereby, toner is supplied from the developer on the surface of the developing roller 53.

[0035] In the present disclosure, a so-called two-component developer containing a non-magnetic toner and a magnetic carrier is used as the developer, but a one-component magnetic developer made of a magnetic toner may also be used. The particle diameter of the toner is about 5 to 8 μm, and the particle diameter of the carrier is about 40 μm. The ratio of the toner contained in the developer (toner / developer) is controlled to about 7% by a toner concentration sensor 74 described later.

[0036] The toner image formed on the surface 20a of the photosensitive drum 20 developed by the developing device 23 is transferred to the intermediate transfer belt 42 of the intermediate transfer device 3. Here, the intermediate transfer device 3 includes an intermediate transfer roller 41, an intermediate transfer belt 42, a driving roller 43, and a driven roller 44. The transfer device 4 includes a transfer roller 45. Also, a transfer power source (not shown) that supplies a bias, which is a predetermined voltage or current, is connected to the intermediate transfer roller 41 and the transfer roller 45, respectively.

[0037] The intermediate transfer roller 41 is disposed at a position corresponding to the photosensitive drums 20 of the respective image forming units 2K, 2C, 2M, 2Y, and brings the intermediate transfer belt 42 into contact with the surface of each photosensitive drum 20. The intermediate transfer belt 42 is stretched by the driving roller 43 and the driven roller 44, and when the driving roller 43 is rotated by a driving source (not shown), it rotates in the direction of arrow R (FIG. 1). On the intermediate transfer belt 42 rotated by a driving source (not shown), at the contact positions with the respective photosensitive drums 20 by the intermediate transfer roller 41, the toner images formed on the photosensitive drums 20 of the respective image forming units 2K, 2C, 2M, 2Y are sequentially intermediate-transferred to form a color toner image. The color toner image formed on the surface of the intermediate transfer belt 42 is transferred to the printing paper P conveyed from the paper feeding device 6 described later at the contact portion with the transfer roller 45.

[0038] The printing paper P onto which the color image is transferred at the contact portion between the intermediate transfer belt 42 and the transfer roller 45 is sent to the fixing device 5. The fixing device 5 is configured such that a fixing belt 5a heated to a predetermined temperature by a heat source and a pressure roller 5b having a heat-resistant elastic layer on its surface are in contact with each other and rotate. The color toner image transferred to the printing paper P is melted by the heat of the fixing belt 5a and fixed to the printing paper P by the pressing force of the pressure roller 5b.

[0039] Further, the image forming apparatus 1 is capable of stacking a plurality of sheets of printing paper P on which a toner image is fixed, and a paper feeding device 6 that feeds out the stacked plurality of sheets of printing paper P one by one, and the printing paper P fed out from the paper feeding device 6 is conveyed to the contact portion between the intermediate transfer belt 42 and the transfer roller 45, and the contact portion between the fixing belt 5a and the pressure roller 5b. And a paper discharge tray 8 for stacking the printing paper P that has passed through the contact portion between the fixing belt 5a and the pressure roller 5b by the conveying device 7. The paper discharge tray 8 is a tray on which the printing paper P with the toner image fixed thereon is sequentially stacked.

[0040] In addition, the cleaning device 9 provided in each image forming unit 2K, 2C, 2M, 2Y removes the transfer residual toner remaining on the photosensitive drum 20 without being intermediate transferred to the intermediate transfer belt 42 from the photosensitive drum 20 among the toner images formed on the photosensitive drum 20. The surface of the photosensitive drum cleaned by the cleaning device 9 has the electrostatic latent image formed by receiving light irradiation from a light source (not shown) erased. The surface of the photosensitive drum 20 with the electrostatic latent image erased is charged to a predetermined potential again by the charger 21. The image forming apparatus 1 including the developing device 23 of the present disclosure continuously forms an image on the printing paper P by repeating the above cycle.

[0041] Next, the developing device 23 of the present disclosure will be described in detail. FIG. 2 is a cross-sectional view of the developing device 23 viewed at the central position in the Y direction, which is the depth direction, and is a diagram for explaining the positional relationship between the photosensitive drum 20 and the developing roller 53 and the internal structure of the developing device 23. FIG. 3 is a perspective view of the developing tank 51 with the upper cover removed as viewed from the back side so that the positional relationship between the developing roller 53, the supply member (first screw) 61, and the replenishing member (second screw) 72 can be understood. FIG. 4 is a perspective view of the developing device 23 as viewed from the front side. FIG. 5 is a perspective view of the developing tank 51 with the developing roller 53 removed from the developing device 23 as viewed from the back side. FIG. 6 is a perspective view of the developer recovery unit 60, which will be described later, as viewed obliquely. FIG. 7A is a cross-sectional view of the developing device 23 as viewed from the A-A direction of FIG. 2 showing the cross-section, and FIG. 7B is a cross-sectional view as viewed from the B-B direction of FIG. 7A. FIG. 8A is a cross-sectional view showing a cross-section of the developer recovery unit 60 included in the developing device 23 according to Embodiment 1 in a direction orthogonal to the axial direction of the developing roller 53. FIG. 8B is a cross-sectional view taken along the C-C line in FIG. 8A.

[0042] As shown in FIGS. 2 and 3, the developing device 23 includes a developing tank 51, a developing roller 53, a conveying device 52 including a supply member (first screw) 61 and a replenishing member (second screw) 72, and a regulating member 55.

[0043] The developing roller 53, the first screw 61, and the second screw 72 are rotatably supported in a developing tank 51 in which a developer is accommodated. The first screw 61 and the second screw 72 are arranged so as to be adjacent to each other horizontally below the developing roller 53 in the vertical direction, and are screws having spiral blades on the outer periphery of the rotation shaft. The developing tank 51 has a first chamber 56 and a second chamber 57 in which the first screw 61 and the second screw 72 are respectively accommodated, and the first chamber 56 and the second chamber 57 are partitioned by a partition wall 71. The partition wall 71 has a first communication port 75 and a second communication port 76 that communicate the first chamber 56 and the second chamber 57 at both axial ends of the developing roller 53, respectively. A density sensor 74 for detecting the density of the toner is provided below the second chamber 57.

[0044] The developing tank 51 stores the above-described developer. When the density sensor 74 detects that toner has been consumed during image formation, new toner is supplied from a toner container (not shown) through the inlet 73. As described above, when the toner stored in the developing tank 51 or replenished from the inlet 73 is rotated by a drive source (not shown) for the replenishing member (second screw) 72, it is conveyed in the direction of arrow F1 in FIG. 3 (front side) (the second screw 72 rotates clockwise when viewed from the front side with respect to the rotation axis. See FIG. 2). The developer conveyed to the front side by the replenishing member (second screw) 72 is conveyed to the first chamber 56 through the first communication port 75 provided at the front side end of the partition wall 71. The developer conveyed to the first chamber 56 through the first communication port 75 is conveyed in the direction of arrow F2 in FIG. 3 (rear side) by the first screw 61 rotated by a drive source (not shown). As shown in FIG. 2, the first screw 61 rotates counterclockwise when viewed from the front side with respect to the rotation axis.

[0045] A part of the developer conveyed in the direction of arrow F2 by the first screw 61 is supplied to the developing roller 53 provided above the first screw 61. The developer not supplied to the developing roller 53 is sent to the rear side by the first screw 61 and then conveyed to the second chamber 57 through the second communication port 76 provided in the partition wall 71. The developer conveyed to the second chamber 57 through the second communication port 76 is conveyed again to the F1 side by the second screw 72. In this way, the developer is conveyed by the first screw 61 and the second screw 72 so as to circulate between the first chamber 56 and the second chamber 57. At this time, the toner is triboelectrically charged to a carrier and charged to a predetermined potential.

[0046] As shown in FIGS. 2 and 4, the developing roller 53 is provided at the opening 50 of the developing tank 51. The developing roller 53 includes a shaft portion 65, a sleeve 66 disposed around the shaft portion 65 and rotated by a driving force from a drive source (not shown), and a plurality of magnets 67 (non-rotating) fixed inside the sleeve 66 at predetermined intervals in the circumferential direction so that the surface magnetic poles change alternately. It is composed of a magnetic roller having

[0047] The magnet 67 disposed inside the rotatable sleeve 66 (developing roller 53) is arranged over a region slightly longer than the image forming region (see FIG. 3) and excluding both end portions in the longitudinal direction (axial direction) of the developing roller 53. Since the sleeve 66 (developing roller 53) is longer than the length of the region where the magnet 67 is disposed, the developer is not supplied from the first screw 61 to both end regions where the magnet 67 is not disposed at both ends of the sleeve 66.

[0048] The regulating member 55 is provided below the developing roller 53 in the vertical direction Z of the opening 50 so that the gap with the surface 53a of the developing roller 53 is a predetermined interval, and regulates so that the layer thickness of the developer supplied to the image forming region of the surface 53b of the developing roller 53 becomes constant.

[0049] A developing bias of a predetermined voltage value from a developing power source is applied to the sleeve 66 of the developing roller 53. At the opposing portion of the developing roller 53 and the photosensitive drum 20, the toner is developed on the photosensitive drum 20 by receiving the repulsive force from the developing roller 53.

[0050] Here, in the both end regions of the developing roller 53, since the carrier having magnetism by the magnet 67 is not attracted to the surface 53a of the developing roller 53 together with the surrounding toner, the developer is not supplied from the first screw 61 to the surface 53a (sleeve 66) of the developing roller 53. That is, originally, the developer is not supplied to both end portions of the surface 53a of the developing roller 53 where the magnet 67 is not provided. However, when continuously forming an image (when the developing roller 53 is continuously rotating), under low humidity conditions where the charge amount of the toner becomes low, even in such both end regions, the toner and the carrier may be extruded from the image forming region and enter due to the rotation of the developing roller 53 (sleeve 66).

[0051] When the developer enters these both-end regions, since there are no magnets inside, the entering developer cannot be maintained on the surface 53a of the developing roller 53, and may be ejected outside the developing device 23, which may contaminate the inside of the image forming apparatus 1. In particular, when it is ejected toward the photosensitive drum 20, it causes image defects. Therefore, the developing device 23 of the present embodiment is provided with a developer recovery unit 60 so that even if the developer enters these both-end regions, the developer can be recovered.

[0052] This developer recovery unit 60 is provided in the region of the developing tank 51 facing the both-end regions of the developing roller 53. Thereby, even if the developer enters the both-end regions, it is possible to effectively prevent the entering developer from being ejected (scattered) outside the developing device 23. Hereinafter, the developing device 23 of the present embodiment will be described in detail.

[0053] As shown in FIGS. 5, 6, 7A, and 7B, the developing tank 51 has a wall portion (side surface portion) 57b to which the bearings of the developing roller 53 are attached at both axial ends of the developing roller 53 of the opening portion 50, and from the wall portion (side surface portion) 57b over a predetermined length in the rotational axis direction of the developing roller 53, a curved surface portion 58 formed along the both-end regions of the developing roller 53 is provided. Here, the curved surface portion 58 is provided above the first chamber 56, in other words, above the first screw 61.

[0054] The wall portion (side surface portion) 57b provided at the opening 50 is parallel to the axial end surface of the developing roller 53 and has an insertion portion 57a through which the bearing of the developing roller 53 is inserted. The curved surface portion 58 is formed along the surface 53a of the developing roller 53 (see FIGS. 7A and 8B) over a length of a predetermined distance (for example, 10 mm) in the axial direction of the developing roller 53 from the wall portion (side surface portion) 57b. The curved surface portion 58 is formed along the surface 53a of the developing roller 53 so as to form a predetermined gap, for example, a gap of about 0.7 mm, between the curved surface portion 58 and the surface 53a of the developing roller 53. In other words, the developing tank 51 has, at both axial end positions of the developing roller 53 at the opening 50, a wall portion (side surface portion) 57b to which the bearing of the developing roller 53 is attached, and a curved surface portion 58 formed along the surface of the surface 53a of the developing roller 53 over a length of a predetermined distance in the axial direction of the wall portion (side surface portion) 57b.

[0055] And at the boundary portion of the curved surface portion 58 with the wall portion (side surface portion) 57b (the side of the wall portion (side surface portion) 57b in the curved surface portion 58), a developer recovery portion 60 having a space wider than the space between the surface 53a of the developing roller 53 and the curved surface portion 58 is provided. Here, the developer recovery portion 60 is a region below the developing roller 53 in the curved surface portion 58, and in the region on the wall portion (side surface portion) 57b side, it has a space wider than the space formed between the surface 53a of the developing roller 53 and the curved surface portion 58.

[0056] Note that the developer recovery portion 60 is provided upstream in the rotation direction (predetermined direction R) of the developing roller 53 of the regulating member 55 in the developing tank 51 (see FIG. 8A). Thereby, the developer that has entered between the surface 53a of the developing roller 53 and the curved surface portion 58 can be recovered in the developer recovery portion 60.

[0057] Furthermore, the developer recovery portion 60 has a drop port 62 communicating with the upper space where the first screw 61 is disposed, a first inclined portion 63 inclined toward the drop port 62 on the downstream side in the rotation direction (predetermined direction R) of the developing roller 53 of the drop port 62, and a second inclined portion 64 inclined from the curved surface portion 58 toward the drop port 62 in the axial direction of the developing roller 53 of the drop port 62 (see FIGS. 8A and 8B).

[0058] As described above, by providing the first inclined portion 63 and the second inclined portion 64, even if the developer enters the curved surface portion 58, the first inclined portion 63 and the second inclined portion 64 slide down by their own weights and are guided to the drop port 62 and recovered into the first chamber 56, so that it is possible to prevent the developer from blowing out to the outside of the developing device 23.

[0059] That is, the developer recovered by the developer recovery unit 60 returns to the developing tank 51 by its own weight through the drop port 62 without relying on a complicated mechanism or expensive members for returning the developer to the developing tank 51. In this way, even if the developer enters the end portions (both end regions) of the developing roller 53 due to the rotation of the developing roller 53, it can be returned to the developing tank 51 (the first chamber 56), so that the developer is effectively prevented from blowing out from the end portion of the developing roller 53.

[0060] Furthermore, the drop port 62 of the developer recovery unit 60 is configured to drop the developer to the left side of the rotation axis of the first screw 61. This is because the rotation direction of the first screw 61 is counterclockwise (see FIG. A). The reason will be described in detail below.

[0061] If the drop port 62 is configured such that the developer drops to the right side of the rotation axis of the first screw 61, the developer returned to the developing tank 51 through the drop port 62 may be lifted by the air flow generated from below to above by the first screw 61, and there is a risk that the developer blows out from the developing tank 51.

[0062] On the other hand, if the drop port 62 is configured such that the developer drops to the other side of the rotation axis of the first screw 61, the developer dropped through the drop port 62 is drawn into the air flow generated so as to be drawn in from above to below by the first screw 61 and returned to the developing tank 51, so that the risk of the developer blowing out from the developing tank 51 can be suppressed.

[0063] As described above, by providing the dropping port 62, the first inclined portion 63, and the second inclined portion 64 on the wall portion (side surface portion) 57b side of the curved surface portion 58, even if the developer wraps around the end portions (both end regions) of the developing roller 53, it can be effectively prevented from blowing out of the developing device 23.

[0064] As described above, in the developing device 23, since the developer that has entered both end portions in the longitudinal direction of the developing roller 53 is suppressed from being discharged toward the photosensitive drum 20 side, there is no possibility that the inside of the main body of the image forming apparatus 1 is contaminated or that defects occur in the formed image. [Embodiment 2] Next, Embodiment 2 of the present disclosure will be described with reference to FIGS. 9, 10A, and 10B. Here, a configuration different from that of the above-described Embodiment 1 will be described, and the above description will be incorporated for the same configuration.

[0065] The developing device according to Embodiment 2 is provided with a sealing elastic member 59 that abuts on the surface 53a of the developing roller 53 in a region of the curved surface portion 58 where the developer recovery portion 60 is not provided. In the present Embodiment 2, a silicon sponge having a thickness of 1.5 mm is attached as the sealing elastic member 59.

[0066] Since the sealing elastic member 59 that abuts on the surface 53a of the developing roller 53 is provided, it becomes difficult for the developer on the image forming region of the surface 53a of the developing roller 53 to enter the developer recovery portion 60. As a result, the amount of the developer that moves to the developer recovery portion 60 side beyond the curved surface portion 58 can be reduced. Therefore, it is possible to prevent the dropping port 62 provided in the developer recovery portion 60 from being clogged with the developer that has passed through the curved surface portion 58 where the sealing elastic member 59 is attached and has entered the developer recovery portion 60 side, and it can be effectively recovered into the first chamber 56.

[0067] Note that, like the developing device according to Embodiment 2, the developer recovery portion 60 may be configured not to include the second inclined portion 64. [Embodiment 3] Next, Embodiment 3 of the present disclosure will be described. Here, a configuration different from that of Embodiment 1 or Embodiment 2 described above will be described, and the above description will be incorporated by reference for the same configuration.

[0068] The developing device according to Embodiment 3 does not include the dropping port 62, the first inclined portion 63, and the second inclined portion 64 in the developer recovery unit 60. Even without the dropping port 62, the developer can be recovered and stored.

[0069] The configurations disclosed in any of the above-described embodiments can be applied in combination with the configurations disclosed in other embodiments as long as there is no contradiction. Also, the embodiments disclosed in this specification are illustrative, and the embodiments of the present disclosure are not limited thereto, and can be appropriately modified within the scope not departing from the object of the present disclosure.

Explanation of Reference Numerals

[0070] 1: Color image forming apparatus (image forming apparatus) 20: Photoconductor drum 23: Developing device 42: Intermediate transfer belt 50: Opening 51: Developing tank 52: Conveying device 53: Developing roller 53a: Surface 55: Regulation member 57b: Wall portion (side surface portion) 58: Curved surface portion 59: Sealing elastic member 60: Developer recovery unit 61: First screw (supply member) 62: Dropping port 63: First inclined portion 64: Second inclined portion 65: Shaft portion 66: Sleeve 67: Magnet P: Printing paper

Claims

1. A developing tank having an opening facing the image carrier and containing a developer therein, A developing roller rotatably provided in a predetermined direction at the opening of the developing tank and carrying the developer on its surface, A supply member rotatably supported by the developing tank below the developing roller and supplying the developer to the surface of the developing roller, A regulating member arranged to face the developing roller and regulating the layer thickness of the developer supplied to the surface of the developing roller, and comprising: The developing tank is At both axial end positions of the developing roller at the opening, a wall portion to which a bearing of the developing roller is attached, and a curved surface portion formed along the surface of the developing roller over a length of a predetermined distance in the axial direction from the wall portion, respectively, In a region below the developing roller of the curved surface portion and on the wall portion side, a developer recovery portion having a space wider than a space formed between the surface of the developing roller and the curved surface portion is further formed, The regulating member is attached to an edge of the opening on the side where the developer recovery portion is provided. A developing apparatus characterized by this.

2. In a region of the curved surface portion where the developer recovery portion is not provided, a sealing elastic member that contacts the surface of the developing roller is provided. The developing apparatus according to claim 1, characterized by this.

3. The developer is a two-component developer containing toner made of a non-magnetic material and carrier made of a magnetic material, The developing roller is A plurality of magnets extending in the axial direction are arranged in the circumferential direction around the rotation axis inside, A magnet roller in which a sleeve made of a non-magnetic material and longer than the axial length of the plurality of magnets is rotatably arranged outside the plurality of magnets, The curved surface portion is provided so as to face a region inside the sleeve where the magnet is not disposed. The developing device according to claim 1, characterized in that.

4. The developer recovery unit has a drop port communicating with a space where the supply member provided below the curved surface portion is disposed. The developing device according to claim 3, characterized in that.

5. The supply member is a screw having spiral blades formed on the outside, The drop port is provided above a region that conveys the developer in the axial direction while pushing the developer downward as the supply member rotates. The developing device according to claim 4, characterized in that.

6. The developer recovery unit has a first inclined portion that goes from the downstream side to the upstream side in the rotation direction of the developing roller in the predetermined direction as it approaches the drop port, or goes from the upstream side to the downstream side in the rotation direction of the developing roller in the predetermined direction as it approaches the drop port. The developing device according to claim 4, characterized in that.

7. The developer recovery unit has a second inclined portion that approaches the wall portion side as it approaches the drop port. The developing device according to claim 4, characterized in that.

8. An image forming apparatus, characterized in that it includes the developing device according to any one of claims 1 to 7.

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