Developing device and image forming apparatus

Abstract

To reduce dimension in the gravity direction, of a development device which has: a first and a second conveyance paths arranged adjacent to each other vertically in the gravity direction; and a third conveyance path for recovering a developer having become excessive in a development member and conveying the excessive developer to the second conveyance path, as compared with configuration in which the third conveyance path is arranged above the second conveyance path in the gravity direction.SOLUTION: This development device comprises: a first and a second conveyance member arranged in a first and a second conveyance path which is formed vertically adjacent to each other in the gravity direction, and is used for conveying a developer in such a manner that the developer circulates between the first and second conveyance paths; a development member which is arranged facing the first conveyance path and is supplied with a developer; and a third conveyance member arranged in a third conveyance path for recovering a developer having become excessive in the development member and conveying the excess developer to the second conveyance path, the axial center of the second conveyance member is arranged above the axial center of the third conveyance member in the gravidity direction.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] The following Patent Document 1 discloses a developing container having a developing roll that transports toner to a developing area where an electrostatic latent image is developed into a toner image, a developing roll housing section that houses the developing roll, a first stirring chamber arranged diagonally below the developing roll housing section, and a second stirring chamber adjacent to the developing roll housing section and arranged above the first stirring chamber, a first stirring member that is housed in the first stirring chamber and transports the toner in the first stirring chamber while stirring it in a predetermined first transport direction, and a second stirring member that is housed in the second stirring chamber and transports the toner in the second stirring chamber in a second transport direction opposite to the first transport direction. and a communication passage that communicates the downstream end of the first stirring chamber in the first transport direction with the upstream end of the second stirring chamber in the second transport direction in order to transport the toner from the downstream end of the first stirring chamber in the first transport direction to the upstream end of the second stirring chamber in the second transport direction, the communication passage being on the side farther from the developing roll with respect to the rotation axis of the first stirring member, and the portion of the communication passage that contacts the second stirring chamber and is located closest to the developing roll is formed vertically below the axis of the developing roll. This developing device further includes a retained developer transport member for stirring and transporting the developer retained between the developing roll and the first stirring member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-175768 A Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to provide a developing device and an image forming apparatus having a first transport path and a second transport path arranged adjacent to each other above and below in the direction of gravity, and a third transport path that collects and transports excess developer in the developing member to the second transport path, which can reduce the dimension in the direction of gravity compared to a configuration in which the third transport path is arranged above the second transport path in the direction of gravity. [Means for solving the problem]

[0005] The developing device according to the first aspect of the present invention comprises: a first transport member and a second transport member that are disposed in a first transport path and a second transport path that are formed vertically in a gravity direction, and that transport the developer so as to circulate the developer between the first transport path and the second transport path; a developing member disposed opposite to the first transport path and receiving a developer from the first transport path; a third transport member provided in a third transport path for recovering and transporting the developer surplus in the developing member to the second transport path, The axial center of the second conveying member is disposed higher in the direction of gravity than the axial center of the third conveying member.

[0006] A developing device according to a second aspect of the present invention is the developing device according to the first aspect, further comprising a partition member having a predetermined height between the second transport path and the third transport path.

[0007] A third aspect of the developing device of the present invention is the developing device of the second aspect, wherein the upper end of the partition member is located above the direction of gravity in a virtual line connecting the axial center of the second conveying member and the axial center of the third conveying member.

[0008] A fourth aspect of the developing device of the present invention is the developing device of the first aspect, wherein a return prevention member is formed between the second transport path and the third transport path to prevent developer transported from the third transport path to the second transport path from returning to the third transport path.

[0009] A fifth aspect of the developing device of the present invention is the developing device of the fourth aspect, wherein the return prevention member allows developer to move from the third transport path to the second transport path but prevents developer from moving from the second transport path to the third transport path.

[0010] An image forming apparatus according to a sixth aspect of the present invention comprises the developing device according to any one of the first to fifth aspects, and a latent image carrier disposed opposite the developing device. Effect of the Invention

[0011] According to the first aspect of the developing device of the present invention, in a developing device having a first transport path and a second transport path arranged adjacent to each other above and below in the direction of gravity, and a third transport path that collects and transports excess developer in the developing member to the second transport path, the dimension in the direction of gravity can be made smaller than in a configuration in which the third transport path is arranged above the second transport path in the direction of gravity.

[0012] According to the developing device of the second aspect of the present invention, it is possible to prevent the developer collected in the second transport path from returning back to the third transport path.

[0013] According to the developing device of the third aspect of the present invention, it is possible to allow the developer to be collected from the third transport path to the second transport path, and to prevent the developer from returning from the third transport path to the second transport path.

[0014] According to the developing device of the fourth aspect of the present invention, it is possible to always transport the developer in one direction, from the third transport path to the second transport path.

[0015] According to the developing device of the fifth aspect of the present invention, it is possible to prevent the developer from accumulating between the third transport path and the second transport path.

[0016] Furthermore, according to one aspect of the present invention, in a developing device having a first transport path and a second transport path arranged adjacent to each other above and below in the direction of gravity, and a third transport path that collects and transports excess developer in the developing member to the second transport path, it is possible to provide an image forming device that can reduce the dimension in the direction of gravity compared to a configuration in which the third transport path is arranged above the second transport path in the direction of gravity. [Brief description of the drawings]

[0017] [Figure 1] 1 is a side view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] 1 is a cross-sectional view of a developing device according to an embodiment of the present invention, as viewed from a direction in which the developing device extends. [Diagram 3] 1 is a cross-sectional view of a developing device according to an embodiment of the present invention, as viewed from the front side. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Next, a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows an image forming apparatus 10 according to the first embodiment of the present invention. The image forming apparatus 10 has an image forming apparatus main body 12 in which an image forming section 14, a transfer device 16, a fixing device 18, and a paper feeder 20 are arranged. Also, a recording medium transport path 22 for transporting a recording medium such as paper is formed in the image forming apparatus main body 12.

[0019] The image forming section 14 employs an electrophotographic method and forms an image on a recording medium. The image forming section 14 has, for example, a plurality of, for example, four, image forming units 24. The four image forming units 24 form toner images of different colors, for example, yellow, magenta, cyan, and black.

[0020] Each image forming unit 24 has a photoconductor drum 26. The photoconductor drum 26 is an example of an image carrier, and rotates while carrying a toner image to be transferred to a recording medium on its outer circumferential surface. The image forming unit 24 is also provided with a charging device 28 that charges the photoconductor drum 26, a developing device 30 that develops the charged latent image with a developer, and a cleaning device 32 that cleans the photoconductor drum 26 after transfer. An optical writing device 48 that forms a latent image on the charged photoconductor drum 26 is also provided.

[0021] The transfer device 16 has an intermediate transfer belt 34. The toner images are primarily transferred from the photoconductor drums 26 onto the intermediate transfer belt 34 by a primary transfer member 36, and the primarily transferred toner images are secondarily transferred onto a recording medium by a secondary transfer member 38.

[0022] The intermediate transfer belt 34 is supported so as to be rotatable by a plurality of support members 40. In addition, a backup member 42 is provided opposite the secondary transfer member 38.

[0023] The fixing device 18 fixes the toner image transferred onto the recording medium onto the recording medium using, for example, heat and pressure.

[0024] The paper feeder 20 has a storage section 44 that stores recording media in a stacked state, and a delivery member 46 that delivers the recording media stored in the storage section 44 toward the recording medium transport path 22 .

[0025] The recording medium transport path 22 transports the recording medium from the paper feed device 20 to between the secondary transfer member 38 and the backup member 42, then transports the recording medium to the fixing device 18, and further transports the recording medium so that it is discharged outside the image forming device main body 12.

[0026] In the image forming apparatus 10 configured as described above, the toner images formed on the outer peripheral surfaces of the photosensitive drums 26 are primarily transferred to the intermediate transfer belt 34, the toner images primarily transferred to the intermediate transfer belt 34 are secondarily transferred to a recording medium, and the toner images secondarily transferred to the recording medium are fixed to the recording medium by the fixing device 18.

[0027] Next, the developing device 30 of this embodiment will be described with reference to FIG. 2. This is a two-component developing device that stirs developer consisting of a carrier and a toner, charges the toner, and develops the toner. In the following description, the upper side in the direction of gravity is called the upper side, the lower side in the direction of gravity is called the lower side, and when there is no distinction between upper and lower, the upper and lower sides in the direction of gravity are called the upper and lower sides in the direction of gravity, or simply the upper and lower sides. In addition, the direction perpendicular to the upper and lower sides in the direction of gravity and along which the developing roll 52, the first transport member 82, the second transport member 84, and the like described later extend is called the axial direction. Furthermore, the side on which the developer supply port 70 of the first transport path 62 described later is formed, that is, the left side of the paper in FIG. 3, is called the supply end side for convenience, and the side on which the lower discharge port 80 of the second transport path 64 described later is formed, that is, the right side of the paper, is called the discharge end side.

[0028] The developing device 30 is disposed facing the photosensitive drum 26 as an image carrier. The developing device 30 has a developing device main body 50 in the form of a developing device housing. In the developing device main body 50, a developing roll 52 as a developing member is disposed facing the photosensitive drum 26. The developing roll 52 includes a magnet roll 54 for forming a uniform magnetic field in the axial direction, and a developing sleeve 56 rotatably mounted on the outer periphery of the magnet roll 54. The magnet roll 54 is fixed to the developing device main body 50 within the developing sleeve 56. The developing sleeve 56 is supported rotatably by a cylindrical member made of a non-magnetic material to the developing device main body 50. A layer thickness regulating member 58 for regulating the layer thickness of the developer is fixed to the developing device main body 50 above the developing roll 52 and facing the developing sleeve 56. The layer thickness regulating member 58 is formed of sheet metal. The toner adhering to the periphery of the developing sleeve 56 is adapted to be moved to the latent image formed on the photosensitive drum 26 after the layer thickness is regulated by a layer thickness regulating member 58 .

[0029] The developing device main body 50 is divided by a partition wall 60 that divides the inside of the developing device main body 50 into upper and lower parts in the direction of gravity, and a first transport path 62 and a second transport path 64 are provided, which are formed on the upper and lower parts in the direction of gravity. The upper surface of the partition wall 60, which has an arc-shaped cross section, constitutes the lower surface of the first transport path 62. The lower surface of the partition wall 60, which has an arc-shaped cross section, constitutes the upper surface of the second transport path 64. The first transport path 62 and the second transport path 64 have the same axial length and extend in the axial direction. The developing roll 52 is disposed opposite a developer supply port 66 formed in the first transport path 62 along the axial direction, and developer is supplied from the first transport path 62.

[0030] As shown in FIG. 3, the upper surface 68 of the developing device main body 50 is also the upper surface of the first transport path 62, and a developer supply port 70 is provided on the supply end side of a portion corresponding to the upper portion of the first transport path 62. A first communication port 72 is formed in a portion of the partition wall 60 below the developer supply port 70 in the direction of gravity. The partition wall 60 is further provided with a second communication port 74 on the discharge end side of the first communication port 72. The partition wall 60 is also provided with an upper discharge port 76 in a portion close to the discharge end side. The bottom surface 78 of the developing device main body 50 is also the bottom surface of the second transport path 64, and a lower discharge port 80 is formed in a portion closest to the discharge end side.

[0031] A first transport member 82 and a second transport member 84 are rotatably arranged in the first transport path 62 and the second transport path 64, respectively, for agitating and circulating the developer between the first transport path 62 and the second transport path 64.

[0032] 2, a third transport path 86 is provided obliquely below the developing roll 52 in the direction of gravity to return and collect the surplus developer on the developing roll 52 to the second transport path 64. A third transport member 88 is rotatably disposed on the third transport path 86.

[0033] As shown in FIG. 3, the first conveying member 82, the second conveying member 84, and the third conveying member 88 have axial centers 90, 92, and 94, respectively. The supply end side of the axial center 90 of the first conveying member 82 is journaled by a first upper stage bearing B1 at the upper part of the supply end side of the developing device main body 50, and the discharge end side is journaled by a second upper stage bearing B2 at the upper part of the discharge end side of the developing device main body 50. Similarly, the supply end side of the axial center 92 of the second conveying member 84 is journaled by a first lower stage bearing B3 at the lower part of the supply end side of the developing device main body 50, and the discharge end side is journaled by a second lower stage bearing B4 at the lower part of the supply end side of the developing device main body 50. Here, the axial positions of the second upper stage bearing B2 supporting the discharge end side of the axial center 90 of the first conveying member 82 and the second lower stage bearing B4 supporting the discharge end side of the axial center 92 of the second conveying member 84 are the same.

[0034] The first conveying member 82, the second conveying member 84 and the third conveying member 88 are provided with conveying blades 96, 98 and 100 which are spirally shaped around axial centers 90, 92 and 94 and are inclined in the same direction.

[0035] The conveying blades 96 of the first conveying member 82 are formed about an axial center 90 between the first communication port 72 and the second communication port 74. The conveying blades 98 of the second conveying member 84 are also formed about an axial center 92 between the first communication port 72 and the second communication port 74.

[0036] Furthermore, the first conveying member 82 is provided, in a portion between the second communication opening 74 and the upper discharge opening 76, with a discharge conveying blade 102 whose blade inclination direction is opposite to that of the conveying blade 96, an adjustment blade 104 whose blade inclination direction is the same as that of the conveying blade 96, and an upper discharge blade 106 whose blade inclination direction is the same as that of the discharge conveying blade 102 and whose blade length in the radial direction is short. The discharge conveying blade 102 is formed so that a part of the blade overlaps the second communication opening 74. The upper discharge blade 106 is disposed in an upper discharge space 108 whose diameter in the vertical direction and width direction is smaller than that of the first conveying path 62, which is formed between the protruding portion of the partition wall 60 protruding upward and the protruding portion of the upper surface of the first conveying path 62 protruding downward.

[0037] Further, the second transport member 84 is provided, in a portion between the second communication port 74 and the lower discharge port 80, with a developer return blade 110 whose blade is inclined in the opposite direction to the transport blade 98, and a lower discharge blade 112 whose blade is inclined in the same direction as the transport blade 98. The lower discharge blade 112 is disposed in a lower discharge space 114 whose diameter in the vertical and width directions is smaller than that of the second transport path 64, and which is formed between a protruding portion of the partition wall 60 protruding downward and a protruding portion of the bottom surface of the second transport path 64 protruding upward.

[0038] With the above-mentioned configuration, the developer supplied from the developer supply port 70 falls downward in the direction of gravity through the first transport path 62, is supplied to the second transport path 64 through the first communication port 72, and is transported by the second transport member 84 through the second transport path 64 toward the discharge end to a position near the lower side of the second communication port 74. The developer transported to the position near the lower side of the second communication port 74 is prevented from being transported toward the discharge end by the developer return blade 110, and collides with developer transported further from the supply end side of the second transport path 64. As a result, the developer near the lower side of the second communication port 74 is pushed upward in the direction of gravity and is sent into the first transport path 62 through the second communication port 74.

[0039] The developer sent into the first transport path 62 is transported by the transport blades 96 of the first transport member 82 in the direction of the first communication port 72, i.e., toward the supply end, and is supplied from the developer supply port 66 onto the developing roll 52. The developer remaining in the first transport path 62 without being supplied to the developing roll 52 is transported by the first transport member 82 in the direction of the supply end to the first communication port 74, then falls downward in the direction of gravity at the first communication port 74 and is supplied again to the second transport path 64, repeating the circulation described above.

[0040] A part of the developer sent from the second transport path 64 into the first transport path 62 through the second communication port 74 is transported toward the discharge end by the discharge transport blade 102, and is further pushed back toward the supply end by the adjustment blade 104 so that more than a predetermined amount of developer is not discharged. The excess developer that is not returned toward the supply end by the adjustment blade 104 is transported in the upper discharge space 108 toward the discharge end by the upper discharge blade 106, falls downward in the direction of gravity through the upper discharge port 76, and is discharged into the lower discharge space 114 of the second transport path 64. The excess developer discharged into the lower discharge space 114 is further transported toward the discharge end by the lower discharge blade 112, and is finally discharged from the lower discharge port 80 to the outside of the developing device main body 50.

[0041] In this way, the upper discharge outlet 76, the lower discharge outlet 80, the discharge transport blade 102, the adjustment blade 104, the upper discharge blade 106, the upper discharge space 108, and the lower discharge blade 112 constitute a developer discharge structure that discharges excess developer discharged from the first transport path 62 to the outside through the second transport path 64.

[0042] On the other hand, of the developer supplied from the first transport path 62 onto the developing roll 52, any excess developer that remains after development is completed is peeled off from the developing roll 52 toward the third transport path 86, then recovered and transported from the third transport path 86 to the second transport path 64, where it is mixed and stirred by the second transport member 84 together with new developer supplied from a developer replenishing device (not shown), and as shown by the arrow in Figure 3, is pushed up from the second communication port 74 to the first transport path 62 at the discharge end of the developing device main body 50, and is again supplied onto the developing roll 52 by the first transport member 82, creating a flow of developer.

[0043] Here, the positional relationship between the developing roll 52, the second transport member 84, and the third transport member 88 will be described. As shown in Fig. 2, an axial center 92 of the second transport member 84 is disposed above the third transport member 88 in the direction of gravity. Note that the axial center 92 of the second transport member 84 and the axial center 94 of the third transport member 88 are both disposed below the axial center of the developing roll 52 in the direction of gravity. Also, an axial center 90 of the first transport member 82 is disposed above the axial center of the developing roll 52 in the direction of gravity.

[0044] Therefore, the positional relationship between the bottom surface 78 of the second conveying path 64 and the bottom surface of the third conveying path 86 is either at the same height in the direction of gravity, or the bottom surface of the second conveying path 64 is slightly higher or slightly lower than the bottom surface of the third conveying path 86, since the diameter of the third conveying member 88 is smaller than the diameter of the second conveying member 84. Note that, in this embodiment, an example is described in which the axis center 92 of the second conveying member 84 is disposed above the axis center 94 of the third conveying member 88 in the direction of gravity, but by appropriately selecting the diameters of the second conveying member 84 and the third conveying member 88, the axis center 92 of the second conveying member 84 may be at the same height as the axis center of the third conveying member 88 or slightly lower in the direction of gravity, as long as the bottom surfaces of the second conveying path 64 and the third conveying path 86 are in a vertical relationship that is approximately the same.

[0045] Furthermore, a partition member 116 having a predetermined height is formed between the second transport path 64 and the third transport path 86. This partition member 116 is a plate-shaped wall surface protruding upward in the direction of gravity from near the gap between the bottom surface of the second transport path 64 and the bottom surface of the third transport path 86, and extends along the axial direction. An upper end 118 of this partition member 116 is located above the imaginary line connecting the axial center 92 of the second transport member 84 and the axial center 94 of the third transport member 88 in the direction of gravity. The height of this partition member 116 in the direction of gravity may be any height as long as it is a height that allows the developer to be transported from the third transport path 86 to the second transport path 64 by the third transport member 88, and is a height that prevents the developer transported from the third transport path 86 to the second transport path 64 from returning to the third transport path 86 again.

[0046] In addition, the partition member 116 between the second transport path 64 and the third transport path 86 allows the developer to be transported from the third transport path 86 to the second transport path 64 by the third transport member 88, while functioning as a return prevention member that prevents or blocks the developer transported from the third transport path 86 to the second transport path 64 from returning to the third transport path 86 again. Any member that allows the developer to flow in one direction, such as a plate body with a free end above in the direction of gravity or an opening formed in the partition member 116, can be used. [Explanation of symbols]

[0047] 10 Image forming device 12 Image forming device main body 14 Image forming section 16 Transcription device 18 Fixing device 20 Paper feeder 22 Recording medium transport path 24 Image forming unit 26 Photoconductor drum 28 Charging device 30 Developing device 32 Cleaning equipment 34 Intermediate transfer belt 36 Primary transfer member 38 Secondary transfer member 40 Support member 42 Backup parts 44 Storage area 46 Delivery member 48 Equipment 50 Developing device body 52 Developing roll 54 Magnet Roll 56 Developing sleeve 58 Layer thickness control member 60 Partition Wall 62 First conveyor path 64 Second conveyor 66 Developer supply port 68 Top 70 Developer supply port 72 First communication port 74 Second communication port 76 Upper discharge port 78 Bottom 80 Lower discharge port 82 First conveying member 84 second conveying member 86 Third Transport Path 88 Third conveying member 90, 92, 94 96, 98 Conveying blade 102 Discharge conveying blade 104 Adjustable blade 106 Upper discharge blade 108 Upper discharge space 110 Developer return blade 112 Lower discharge blade 114 Lower discharge space 116 Partition material 118 Top B1, B2 Upper bearing B3, B4 Lower bearing

Claims

1. a first transport member and a second transport member that are disposed in a first transport path and a second transport path that are formed so as to overlap each other in the vertical direction of gravity, and that transport the developer so as to circulate the developer between the first transport path and the second transport path via a first communication port and a second communication port; a developing member disposed opposite to the first transport path and receiving developer from the first transport path; a third transport member provided in a third transport path for recovering and transporting the developer surplus in the developing member to the second transport path, a developing device, wherein an axial center of the second conveying member is disposed higher in a gravitational direction than an axial center of the third conveying member.

2. 2. The developing device according to claim 1, further comprising a partition member having a predetermined height formed between said second transport path and said third transport path.

3. 3. The developing device according to claim 2, wherein an upper end of said partition member is located above, in the direction of gravity, an imaginary line connecting an axial center of said second conveying member and an axial center of said third conveying member.

4. 2. The developing device according to claim 1, further comprising a return prevention member formed between the second transport path and the third transport path for preventing developer transported from the third transport path to the second transport path from returning to the third transport path.

5. 5. The developing device according to claim 4, wherein the anti-return member is configured to permit the developer to move from the third transport path to the second transport path, but to prevent the developer from moving from the second transport path to the third transport path.

6. 6. An image forming apparatus comprising: the developing device according to claim 1; and a latent image carrier disposed opposite the developing device.

Images