Developing device and image forming apparatus

Abstract

To adjust axial lengths of first and second conveyance paths arranged adjacent to each other in a gravity direction, in a development device which has the first and second conveyance paths and discharges an excess developer from the end of the first conveyance path arranged above the second conveyance path.SOLUTION: A development device 30 comprises: a first conveyance member 82 and a second conveyance member 84 which are arranged in a first conveyance path 62 and a second conveyance path 64 formed vertically adjacent to each other in the gravity direction, and convey a developer in such a manner that the developer circulates between the first conveyance path 62 and the second conveyance path 64; a development device body 50 in which the first conveyance path 62 and the second conveyance path 64 are formed; and developer discharge structure in which an excess developer discharged from the first conveyance path 62 is discharged to the outside through the second conveyance path 64, or through between an end of the second conveyance path 64 and the development device body 50.SELECTED DRAWING: Figure 4

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 which have a first transport path and a second transport path arranged adjacent to each other above and below in the direction of gravity, and discharge excess developer from the end of the first transport path arranged on the upper side, and which are capable of adjusting the axial lengths of the first transport path and the second transport path. [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 device main body having the first transport path and the second transport path formed therein; The developing device has a developer discharge structure, in which excess developer discharged from the first transport path is discharged to the outside through the second transport path or through a gap between an end of the second transport path and the developing device main body.

[0006] A second aspect of the developing device of the present invention is the developing device of the first aspect, wherein the first transport path and the second transport path have the same axial length and are separated from each other by a partition wall, and the developer discharge structure includes an upper discharge outlet formed in a part of the partition wall and a lower discharge outlet formed below the end side of the second transport path.

[0007] A third aspect of the developing device of the present invention is the developing device of the first aspect, wherein the first transport path and the second transport path have the same axial length and are separated from each other by a partition wall, and the developer discharge structure includes an upper discharge outlet formed on the end side of the partition wall and a lower discharge outlet formed below the end side of the second transport path, and the axial positions of the upper discharge outlet and the lower discharge outlet are consistent.

[0008] A developing device according to a fourth aspect of the present invention is the developing device according to the third aspect, further comprising a developer adhesion prevention member disposed on the shaft of the second transport member below the upper discharge port.

[0009] A developing device of a fifth aspect of the present invention is the developing device of any one of the second to fourth aspects, in which a transport blade is arranged on the shaft of the second transport member below the upper discharge outlet, for sending developer to the end side of the second transport path.

[0010] A sixth aspect of the developing device of the present invention is the developing device of the first aspect, wherein the second transport path has an axial length shorter than that of the first transport path, and the developer discharge structure includes an upper discharge outlet formed below an end of the first transport path, and a communicating space formed between the end of the second transport path and a wall surface of the developing device main body, and excess developer discharged from the upper discharge outlet is discharged to the outside through the communicating space.

[0011] An image forming apparatus according to a seventh aspect of the present invention includes the developing device according to any one of the first to sixth aspects, and a latent image carrier disposed opposite the developing device. Effect of the Invention

[0012] According to the first aspect of the developing device of the present invention, a developing device can be provided which has a first transport path and a second transport path arranged adjacent to each other above and below in the direction of gravity, and in which excess developer is discharged from the end of the first transport path arranged on the upper side, and which makes it possible to adjust the axial lengths of the first transport path and the second transport path.

[0013] According to the developing device of the second aspect of the present invention, the excess developer can be discharged from the first transport path through the second transport path to the outside of the developing device main body.

[0014] According to the developing device of the third aspect of the present invention, the excess developer can be made to fall downward in the direction of gravity from the first transport path through the second transport path and discharged to the outside of the developing device main body.

[0015] According to the developing device of the fourth aspect of the present invention, it is possible to prevent excess developer discharged from the first transport path from adhering to the shaft of the second transport member.

[0016] According to the developing device of the fifth aspect of the present invention, it is possible to prevent the excess developer discharged from the first transport path to the second transport path from remaining in the second transport path.

[0017] According to the developing device of the sixth aspect of the present invention, it is possible to prevent the excess developer discharged from the first transport path from entering the second transport path.

[0018] Furthermore, according to one aspect of the present invention, an image forming apparatus can be provided 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 in which excess developer is discharged from the end of the first transport path arranged on the upper side, wherein the axial lengths of the first transport path and the second transport path can be adjusted. [Brief description of the drawings]

[0019] [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. [Figure 4] 4 is a cross-sectional view showing an example of a developer discharging structure of a developing device according to an embodiment of the present invention. [Diagram 5] FIG. 6 is a cross-sectional view showing a configuration of a developing device according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a cross-sectional view showing the configuration of a developing device according to a third embodiment of the present invention. [Figure 7] FIG. 11 is a cross-sectional view showing a configuration of a developing device according to a fourth embodiment of the present invention. [Figure 8] FIG. 13 is a cross-sectional view showing a configuration of a developing device according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] The fixing device 18 fixes the toner image transferred onto the recording medium onto the recording medium using, for example, heat and pressure.

[0026] 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 .

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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 .

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] Next, the configuration of a developing device 30A according to a second embodiment of the present invention will be described with reference to Fig. 5. Note that most of the configuration of the developing device 30A of the second embodiment is the same as the configuration of the developing device 30 of the first embodiment, so the same components are given the same reference numerals and detailed descriptions are omitted, and only different components are given different reference numerals and described.

[0050] In the developing device 30A of the second embodiment, similarly to the above-mentioned embodiment, a first transport member 82 is disposed in the first transport path 62, and a second transport member 84 is disposed in the second transport path 64. The discharge end side of the shaft center 90 of the first transport member 82 is journaled on an upper portion of the discharge end side wall 120 of the developing device main body 50 by a second upper bearing B2.

[0051] On the other hand, the second transport path 64 has a shorter axial length than the first transport path 62, and a communication space 124 partitioned by a developer stirring chamber side wall 122, which is an end of the second transport path 64, is provided between the second transport path 64 and a discharge end side wall 120 of the developing device main body 50. Therefore, the discharge end side of the shaft center 90 of the second transport member 84 arranged in the second transport path 64 is located at the side of the developing device main body 50. The shaft center 92 of the second transport member 84 is journaled on the developer stirring chamber side wall 122 by the lower bearing B4, and is shorter than the length of the shaft center 90 of the first transport member 82. The communicating space 124 is surrounded by the discharge end side wall 120, the developer stirring chamber side wall 122, the partition wall thick portion 126 where the partition wall 60 is thickened above and below in the direction of gravity, and the bottom surface of the developing device main body 50, which is a bottom thick portion 128 that is thicker than the bottom surface of the second conveying path 64.

[0052] An upper discharge port 130 is formed at the discharge end of the partition thick portion 126, and a lower discharge port 132 is formed at the discharge end of the bottom thick portion 128. The axial positions of the upper discharge port 130 and the lower discharge port 132 are approximately the same.

[0053] The first conveying member 82 has upper discharge blades 106A similar to the above embodiment, but differs in that the upper discharge blades 106A are formed over a long axial distance up to near the discharge end side wall 120, i.e., above the upper discharge port 130.

[0054] A portion of the developer sent from the second transport path 64 into the first transport path 62 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 106A, falls downward in the direction of gravity through the upper discharge port 130, falls freely through the communication space 124, and is discharged from the lower discharge port 132 to the outside of the developing device main body 50.

[0055] The discharge transport blade 102, the adjustment blade 104, the upper discharge blade 106A, the upper discharge space 108, the upper discharge outlet 130, the communicating space 124, and the lower discharge outlet 132 constitute a developer discharge structure that discharges excess developer discharged from the first transport path 62 through the upper discharge outlet 130 to the outside of the developing device main body 50 through the communicating space 124.

[0056] Next, the configuration of a developing device 30B according to a third embodiment of the present invention will be described with reference to Fig. 6. Note that most of the configuration of the developing device 30B of the third embodiment is the same as the configuration of the developing devices 30 and 30A of the first and second embodiments, so the same components are given the same reference numerals and detailed descriptions are omitted, and only different components are given different reference numerals and described.

[0057] In the developing device 30B of the third embodiment, as in the second embodiment, the second transport path 64 has a shorter axial length than the first transport path 62, and a communication space 124 is provided between the second transport path 64 and the discharge end side wall 120 of the developing device main body 50, which is partitioned by the developer stirring chamber side wall 122, which is the end of the second transport path 64. An upper discharge port 130 is formed at the discharge end of a partition wall thick portion 126 where the partition wall 60 is thickened vertically in the gravity direction, and a lower discharge port 132 is formed at the discharge end side of a bottom thick portion 128 where the bottom surface of the developing device main body 50 is thick. The axial positions of the upper discharge port 130 and the lower discharge port 132 are substantially the same.

[0058] The discharge end side of the shaft center 90 of the first transport member 82 disposed in the first transport path 62 is journaled by the second upper bearing B2 on the upper part of the discharge end sidewall 120 of the developing device main body 50, as in the first and second embodiments. On the other hand, the shaft center 92 of the second transport member 84 disposed in the second transport path 64 penetrates the developer stirring chamber sidewall 122, crosses the communication space 124 in the axial direction, reaches the discharge end sidewall 120 of the developing device main body 50, and is journaled by the second lower bearing B4 fixed to the lower part of the discharge end sidewall 120. The blade structure formed on the first transport member 82 is the same as that of the second embodiment described above, and therefore a detailed description thereof will be omitted.

[0059] A part of the developer sent from the second transport path 64 into the first transport path 62 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 106A, and falls downward in the direction of gravity through the upper discharge port 130. In the communication space 124, the excess developer falls around the axial center 92 of the second transport member 84 that crosses the communication space 124 in the axial direction, and is finally discharged from the lower discharge port 132 to the outside of the developing device main body 50.

[0060] The discharge transport blade 102, the adjustment blade 104, the upper discharge blade 106A, the upper discharge space 108, the upper discharge outlet 130, the communicating space 124, and the lower discharge outlet 132 constitute a developer discharge structure that discharges excess developer discharged from the first transport path 62 through the upper discharge outlet 130 to the outside of the developing device main body 50 through the communicating space 124.

[0061] Next, the configuration of a developing device 30C according to a fourth embodiment of the present invention will be described with reference to Fig. 7. The configuration of the developing device 30C according to the fourth embodiment is substantially the same as that of the developing device 30B according to the third embodiment, except that a developer adhesion prevention member 134 is attached to the axial center 92 of the second transport member 84. Therefore, the same components are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0062] The developer adhesion prevention member 134 is disposed at a portion where the axial center 92 of the second transport member 84 crosses the communication space 124 in the axial direction, particularly below the upper discharge port 130. The developer adhesion prevention member 134 is in the form of an elastic member such as a spiral spring loosely wound around the axial center 92 of the second transport member 84. This elastic member may be provided with a wing-like member that extends radially outward from the axial center 92 side and contacts the wall surface of the developing device main body 50 as shown in FIG. 6(B). As the axial center 92 of the second transport member 84 rotates, the developer adhesion prevention member 134 and the wing-like member rotate relatively around the axial center 92, but do not rotate with respect to the developing device main body 50. This prevents the developer falling from above from adhering to the axial center 92 of the second transport member 84 or from accumulating around the axial center 92.

[0063] Next, the configuration of a developing device 30D according to a fifth embodiment of the present invention will be described with reference to Fig. 8. The configuration of the developing device 30D of the fifth embodiment is substantially the same as that of the developing device 30 of the first embodiment, except that the upper discharge port 76 is provided closer to the discharge end side of the upper discharge space 108 and the upper discharge blade 106 is extended to the discharge end side of the upper discharge space 108. Therefore, the same components are denoted by the same reference numerals and detailed description will be omitted.

[0064] As in the first embodiment, a part of the developer sent from the second transport path 64 into the first transport path 62 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 the developer is not discharged in an amount greater than a predetermined amount. 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, and falls downward in the direction of gravity through the upper discharge port 76. The excess developer that falls closest to the discharge end side of the lower discharge space 114 of the second transport path 64 falls around the axial center 92 of the second transport member 84, and is finally discharged from the lower discharge port 80 to the outside of the developing device main body 50.

[0065] Since the lower discharge blade 112 is provided in the lower discharge space 114 up to the vicinity of the discharge end side wall 120, the excess developer discharged into the lower discharge space 114 is always pushed toward the discharge end and discharged to the outside of the developing device main body 50 through the lower discharge port 80. [Explanation of symbols]

[0066] 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 30-30D Developer 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 Optical writing device 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 Transporting parts 90, 92, 94 axis center 96, 98 Conveying blade 102 Discharge conveying blade 104 Adjustable blade 106, 106A Upper discharge vane 108 Upper discharge space 110 Developer return blade 112 Lower discharge blade 114 Lower discharge space 116 Partition member 116 118 Top 120 Discharge end side wall 122 Developer mixing chamber side wall 124 Communication space 126 Partition wall thick part 128 Thick bottom part 130 Upper discharge port 132 Lower discharge port 134 Developer adhesion prevention member 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 at least partially in the vertical direction in the 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 device main body having the first transport path and the second transport path formed therein; a developer discharge structure in which excess developer discharged from the first transport path is discharged to the outside through the second transport path or through a gap between an end of the second transport path and the developing device main body, The developer discharge structure includes an upper discharge outlet formed on the end side of a partition wall separating the first transport path and the second transport path, and a lower discharge outlet formed below the end side of the second transport path, and the axial positions of the upper discharge outlet and the lower discharge outlet are consistent.

2. 2. The developing device according to claim 1, wherein the first transport path and the second transport path have the same axial length.

3. 2. The developing device according to claim 1, wherein a developer adhesion prevention member is disposed on the shaft of said second transport member below said upper discharge port.

4. 3. The developing device according to claim 1, wherein a transport blade for sending out the developer to an end side of the second transport path is disposed on a shaft of the second transport member below the upper discharge port.

5. A first transport member and a second transport member are disposed in a first transport path and a second transport path formed so as to overlap each other in the vertical direction of gravity, and transport a developer so as to circulate the developer between the first transport path and the second transport path; a developing device main body having the first transport path and the second transport path formed therein; a developer discharge structure in which excess developer discharged from the first transport path is discharged to the outside through the second transport path or through a gap between an end of the second transport path and the developing device main body, The developer discharging structure includes: an upper discharge port formed below an end of the first transport path; a communication space formed between an end of the second transport path and a wall surface of the developing device body, The excess developer discharged from the upper discharge port is discharged to the outside through the communicating space.

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