Developing device

Abstract

To provide a structure that can suppress an excessive discharge of a developer.SOLUTION: A discharge path 70 is provided outside a circulation route for a developer to connect to a first conveyance path 52, and has a discharge port 100 for discharging an excessive developer in a development container 2. A discharge conveyance unit 71 is provided below a blade 58b of a first conveyance screw 58 and conveys the developer to the discharge port 100. A magnet member 101 is arranged below an upper stream 103 of the discharge port 100 in a direction of conveying the developer in the discharge conveyance unit 71.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a developing device that develops an electrostatic latent image formed on an image carrier with a developer containing toner and carrier. [Background technology]

[0002] In an image forming apparatus using an electrophotographic method or the like, an electrostatic latent image formed on a photosensitive drum is developed into a toner image by a developing device. As such a developing device, one using a two-component developer containing a toner and a carrier has been conventionally used. In a developing device using a two-component developer, a so-called trickle development method is widely used in which, in order to suppress deterioration of carrier particles, excess developer is discharged from a discharge port while a toner containing a small amount of carrier is replenished (for example, Patent Document 1).

[0003] In a developing device, the internal pressure in the developing container may increase due to driving, causing an airflow to blow out from the discharge port, and the developer in the developing container may be discharged excessively by riding on this airflow. Patent Document 1 describes a configuration in which a regulating part is provided to regulate the blowing out of the airflow from the discharge port in order to suppress excessive discharge of developer due to such airflow. In the configuration described in Patent Document 1, the regulating part is partially missing, and developer is discharged through this missing area, while the upper space where no developer exists is blocked by the unmissing part of the regulating part. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-194623 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the case of the configuration described in Patent Document 1, since the regulating portion has a partially missing area, there is a possibility that a small gap may be generated in the path to the discharge port. In order to further increase the speed of the developing device, there is a risk that airflow may flow out from the small gap, leading to excessive discharge of developer.

[0006] The present invention relates to Developing device capable of suppressing excessive discharge of developer through discharge port The purpose is to provide. [Means for solving the problem]

[0007] One aspect of the present invention is a developer carrying member that carries and carries a developer containing toner and a carrier to develop an electrostatic image formed on an image carrying member, a first chamber, and a second chamber that is partitioned from the first chamber by a partition wall, the developer carrying member including: a developing container that contains the developer; a discharge path that is formed with a discharge port for discharging a portion of the developer contained in the developing container; a first communication portion that allows the developer to communicate from the first chamber to the second chamber; a second communication portion that allows the developer to communicate from the second chamber to the first chamber; a first conveying screw portion that is disposed in the first chamber and conveys the developer in a first direction from the second communication portion toward the first communication portion; and a second conveying screw portion that is disposed in the second chamber and conveys the developer in a second direction from the first communication portion toward the second communication portion. A developing device comprising: a second conveying screw section that conveys the developer in two directions; a third conveying screw section that is disposed in the discharge path and conveys the developer in a third direction; and a magnet that is disposed in the discharge path and on the discharge outlet side with respect to the rotation axis of the third conveying screw section, wherein the discharge outlet is disposed downstream of the upstream end of the third conveying screw section in the third direction and is an opening that opens downward in the direction of gravity on a bottom surface of the discharge path, the magnet is disposed downstream of the upstream end of the discharge outlet in the third direction, and a magnetic brush formed by the magnet is disposed so as to overlap the discharge outlet in the third direction. According to one aspect of the present invention, there is provided a developer carrying member that carries and transports a developer containing toner and a carrier to develop an electrostatic image formed on an image carrying member, a first chamber, and a second chamber that is partitioned from the first chamber by a partition wall, the developer carrying member including: a developing container that contains the developer; a discharge path that is formed with a discharge port for discharging a portion of the developer contained in the developing container; a first communication portion that allows the developer to communicate from the first chamber to the second chamber; a second communication portion that allows the developer to communicate from the second chamber to the first chamber; a first transport screw portion that is disposed in the first chamber and transports the developer in a first direction from the second communication portion toward the first communication portion; a second conveying screw portion disposed in a chamber and conveying the developer in a second direction from the first communicating portion toward the second communicating portion; a third conveying screw portion disposed in the discharge path and conveying the developer in a third direction; and a magnet disposed in the discharge path and on the discharge outlet side with respect to a rotation axis of the third conveying screw portion, wherein the discharge outlet is disposed downstream of the upstream end of the third conveying screw portion with respect to the third direction and is an opening provided on a bottom surface of the discharge path that opens downward in the direction of gravity, and the magnet is disposed so as to overlap the discharge outlet with respect to the third direction. Effect of the Invention

[0008] According to the present invention, It is possible to prevent the developer from being excessively discharged through the discharge port. . [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing a schematic configuration of a developing device and a photosensitive drum according to the first embodiment. [Diagram 3] FIG. 2 is a plan view showing the developing device according to the first embodiment, with some parts omitted. [Figure 4] FIG. 2 is a schematic diagram of a developer supply configuration according to the first embodiment. [Diagram 5] FIG. 1A is a schematic diagram showing a state in which the developer surface level is low, and FIG. 1B is a schematic diagram showing a state in which the developer surface level has reached a certain level or higher. [Figure 6] 11 is a graph showing the relationship between the number of images formed and the average residence time of developer when a trickle development method is used and when it is not used. [Figure 7] 5A and 5B are schematic diagrams illustrating the mechanism of excessive discharge of developer when a trickle development method is adopted. [Figure 8] 3 is a schematic diagram showing a part of a first conveying path and a discharge path of the developing device according to the first embodiment. FIG. [Figure 9]FIG. 2 is a plan view of a magnet member according to the first embodiment. [Figure 10] FIG. 4 is a schematic diagram illustrating a developer reservoir region formed by a magnetic field of a magnet member according to the first embodiment. [Figure 11] FIG. 13A is a schematic diagram of a first example of the relationship between the arrangement position of a magnet member and a discharge port, and FIG. 13B is a schematic diagram of a second example of the same. [Figure 12] 6 is a graph showing changes in the amount of developer in a developing device in an example and a comparative example. [Figure 13] 13 is a schematic diagram showing a part of a first conveying path and a discharge path of a developing device according to a second embodiment. FIG. [Figure 14] 13A and 13B are schematic views showing a part of a first conveying path and a discharge path of a developing device according to a third embodiment. [Figure 15] 13A and 13B are schematic views showing a part of a first conveying path and a discharge path of a developing device according to a fourth embodiment. [Figure 16] 13A is a perspective view of a magnet member according to a fourth embodiment in a developed state, and FIG. [Figure 17] FIG. 13 is a perspective view showing the arrangement of magnetic poles of a magnet member according to a fourth embodiment. [Figure 18] FIG. 1A is a schematic diagram showing a state in which the developer surface level is low, and FIG. 1B is a schematic diagram showing a state in which the developer surface level has reached a certain level or higher. [Figure 19] 1A is a perspective view showing a first example of another magnet member, FIG. 1B is a perspective view showing a second example of the same, and FIG. [Figure 20] 13A and 13B are schematic views showing a part of a first conveying path and a discharge path of a developing device according to a fifth embodiment. [Figure 21] FIG. 13 is a cross-sectional view of a brush member according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <First embodiment> The first embodiment will be described with reference to Figures 1 to 12. First, the schematic configuration of an image forming apparatus according to the present embodiment will be described with reference to Figure 1.

[0011] [Image forming device] The image forming apparatus 200 is an electrophotographic full-color printer having four image forming units PY, PM, PC, and PK provided corresponding to the four colors of yellow, magenta, cyan, and black. In this embodiment, the image forming units PY, PM, PC, and PK are of a tandem type arranged along the rotation direction of an intermediate transfer belt 10 described later. The image forming apparatus 200 forms a toner image (image) on a recording material in response to an image signal from a document reading device (not shown) connected to the image forming apparatus main body or a host device such as a personal computer connected to the image forming apparatus main body so as to be able to communicate with the image forming apparatus main body. Examples of the recording material include sheet materials such as paper, plastic film, and cloth.

[0012] To give an overview of such an image forming process, first, each image forming station PY, PM, PC, and PK forms a toner image of each color on the photosensitive drum 13Y, 13M, 13C, and 13K, respectively. The toner image of each color thus formed is transferred onto the intermediate transfer belt 10, and then transferred from the intermediate transfer belt 10 onto a recording material. The recording material onto which the toner image has been transferred is conveyed to a fixing device 11, where the toner image is fixed onto the recording material. A detailed explanation will be given below.

[0013] The four image forming units PY, PM, PC, and PK included in the image forming apparatus 200 have substantially the same configuration, except for the different developing colors. Therefore, hereinafter, the image forming unit PY will be described as a representative, and the configurations of the other image forming units will be shown by replacing the suffix "Y" of the reference numerals attached to the configuration of the image forming unit PY with M, C, and K, respectively, and the description will be omitted.

[0014] In the image forming section PY, a cylindrical photosensitive member, i.e., a photosensitive drum 13Y, is disposed as an image carrier. A charging roller 12Y (charging device), a developing device 1Y, a primary transfer roller 17Y, and a cleaning device 15Y are disposed around the photosensitive drum 13Y. An exposure device (laser scanner) 14Y is disposed below the photosensitive drum 13Y in the figure.

[0015] The charging roller 12Y is rotated by the photosensitive drum 13Y during image formation. The charging roller 12Y is biased toward the photosensitive drum 13Y by a pressure spring (not shown). A charging bias is applied to the charging roller 12Y from a high-voltage power supply. As a result, the photosensitive drum 13Y is almost uniformly charged by the charging roller 12Y.

[0016] In addition, an intermediate transfer belt 10 is disposed facing the photosensitive drums 13Y, 13M, 13C, and 13K. The intermediate transfer belt 10 is tensioned by a plurality of tension rollers, and is rotated by the drive roller, which is one of the plurality of tension rollers. A secondary transfer outer roller 16 is disposed as a secondary transfer member at a position facing a secondary transfer inner roller 18 of the plurality of tension rollers across the intermediate transfer belt 10, and constitutes a secondary transfer portion T2 that transfers a toner image on the intermediate transfer belt 10 to a recording material. A fixing device 11 is disposed downstream of the secondary transfer portion T2 in the recording material conveying direction. In addition, a feeding portion (not shown) is disposed at the bottom of the image forming apparatus 200. The recording material fed from the feeding portion when the image forming operation starts is conveyed to the secondary transfer portion T2 at a predetermined timing.

[0017] The process of forming an image by the image forming apparatus 200 configured as described above will be described. First, when the image forming operation starts, the surface of the rotating photosensitive drum 13Y is uniformly charged by the charging roller 12Y. Next, the photosensitive drum 13Y is exposed to a laser beam corresponding to an image signal emitted from the exposure device 14Y. As a result, an electrostatic latent image corresponding to the image signal is formed on the photosensitive drum 13Y. The electrostatic latent image on the photosensitive drum 13Y is visualized by the toner contained in the development device 1Y, becoming a visible image (toner image).

[0018] The toner image formed on the photosensitive drum 13Y is primarily transferred to the intermediate transfer belt 10 at a primary transfer portion T1Y configured between the photosensitive drum 13Y and a primary transfer roller 17Y arranged with the intermediate transfer belt 10 interposed therebetween. Toner remaining on the surface of the photosensitive drum 13Y after the primary transfer (transfer residual toner) is removed by a cleaning device 15Y.

[0019] This operation is performed in turn in each of the magenta, cyan, and black image forming units, and the four color toner images are superimposed on the intermediate transfer belt 10. Thereafter, in accordance with the timing of the formation of the toner images, the recording material stored in a recording material storage cassette (not shown) in the feeding unit is conveyed to the secondary transfer unit T2, and the four color toner images on the intermediate transfer belt 10 are secondarily transferred all at once onto the recording material. Any toner that was not transferred at the secondary transfer unit T2 and remains on the intermediate transfer belt 10 is removed by an intermediate transfer belt cleaner 19.

[0020] Next, the recording material is conveyed to the fixing device 11. The fixing device 11 includes a fixing roller 20 having a heat source such as a halogen heater inside, and a pressure roller 21, which form a fixing nip portion. The recording material conveyed to the fixing device 11 is passed through the fixing nip portion, whereby the toner image is fixed to the recording material. The recording material is then discharged outside the machine. This completes the series of image forming processes. It is also possible to form a single-color or multi-color image of a desired color using only a desired image forming portion.

[0021] [Developer] Here, the two-component developer used in this embodiment will be described. The developer is a mixture of a non-magnetic toner with a negative charge polarity and a magnetic carrier with a positive charge polarity. The non-magnetic toner is a resin such as polyester or styrene acrylic that contains colorants, wax components, etc., and is pulverized or polymerized to form a powder, to which fine powders such as titanium oxide and silica are added on the surface. The magnetic carrier is a core made of resin particles kneaded with ferrite particles or magnetic powder, and a resin coating is applied to the surface layer.

[0022] [Developing device] Next, the detailed configuration of the developing device 1Y will be described with reference to Figures 2 and 3. The same applies to the developing devices 1M, 1C, and 1K. The developing device 1Y has a developing container 2 that contains a developer consisting of a magnetic carrier and a non-magnetic toner, and a developing sleeve 54 as a developer carrier that carries and transports the developer in the developing container. The developing sleeve 54 has its surface rotatably held, while a magnet roll 54a consisting of multiple magnetic poles (S1, S2, S3, N1, N2) is non-rotatably arranged inside.

[0023] The developing container 2 is divided by a partition wall 51 into a first conveying passage (mixing chamber) 52 as a first chamber and a second conveying passage (developing chamber) 53 as a second chamber. The first conveying passage 52 and the second conveying passage 3 are connected to each other through communication ports at both ends. (First communication section, second communication section) As a result, the first transport path 52 and the second transport path 53 form a circulation path for the developer.

[0024] The developing container 2 is provided with two screw members as transport members for transporting the developer while stirring it. That is, the first transport path 52 is provided with a first transport screw 58, and the second transport path 53 is provided with a second transport screw (second transport section) 59. The first and second transport screws 58 and 59 have rotation shafts 58a and 59a, respectively, and blades 58b and 59b spirally provided around (on) the rotation shafts 58a and 59a.

[0025] When the first conveying screw 58 rotates around the rotation shaft 58a, the spiral blade 58b conveys the developer in the first conveying path 52 in the direction of the arrow α (first direction) which is one side of the longitudinal direction of the developing device 1Y (axial direction of the rotation shaft 58a). When the second conveying screw 59 rotates around the rotation shaft 59a, the spiral blade 59b conveys the developer in the second conveying path 53 in the direction of the arrow β (second direction) which is the other side of the longitudinal direction of the developing device 1Y (axial direction of the rotation shaft 58a). This causes the developer to circulate between the first conveying path 52 and the second conveying path 53.

[0026] The developing device 1Y has a toner concentration sensor (magnetic permeability sensor) 61 as a concentration detection means capable of detecting the toner concentration (the ratio of the weight of toner particles to the total weight of carrier particles and toner particles, T / D ratio) in the developing container 2. The toner concentration sensor 61 is provided at a predetermined position in the first direction of the first conveying path 52, and detects the toner concentration in the first conveying path 52. In this embodiment, an inductance sensor is used as the toner concentration sensor 61, and a sensor surface (detection surface) of the inductance sensor is exposed in the first conveying path 52. The inductance sensor detects the magnetic permeability in a predetermined detection range from the sensor surface. When the toner concentration of the developer changes, the magnetic permeability also changes depending on the mixture ratio of the magnetic carrier and the non-magnetic toner, so the toner concentration can be detected by detecting the change in magnetic permeability with the inductance sensor.

[0027] The developer in the second transport path 53 is pumped up into the magnetic force range of the S2 pole by a second transport screw 59 installed below the developing sleeve 54 inside the second transport path 53, and is carried on the surface of the developing sleeve 54. The carried developer is carried as the surface of the developing sleeve 54 rotates. A regulating blade 55 is disposed near the magnetic pole N1 of the developing sleeve 54, with a predetermined gap therebetween, as a member for forming a thin layer of developer. The gap between the developing sleeve 54 and the regulating blade 55 is generally set to about 200 to 500 μm, and the wider the gap, the greater the amount of developer carried on the developing sleeve 54.

[0028] The transported developer forms a magnetic brush at the N1 pole, and a desired amount of developer is formed into a thin layer on the surface of the developing sleeve 54 by a regulating blade 55 installed at a predetermined interval from the developing sleeve 54. Thereafter, the developer transported to the opposing portion of the photosensitive drum 13Y forms a magnetic brush again at the S1 pole, and a development nip is formed between the photosensitive drum 13Y and the developer.

[0029] As described above, the surface of the photosensitive drum 13Y is charged to a constant potential by the charging roller 12Y, while the image portion is exposed by the exposure device 14Y to form an exposure potential. Meanwhile, a development bias is applied to the developing sleeve 54 through a high-voltage circuit (not shown). The development bias is, for example, a bias in which a rectangular AC waveform is superimposed on a DC waveform of a constant voltage. The toner charged in the developing device 1Y is driven by the potential difference between the development bias and the drum surface in the development nip, and adheres to the exposed portion, completing the development process.

[0030] The carrier and undeveloped toner are further transported downstream in the rotational direction of the developing sleeve 54, where they lose their magnetic binding force in the zero gauss zone (the area where the radial magnetic flux density is zero) formed between the S2 pole and the S3 pole, and are again collected in the second transport path 53.

[0031] When the developing operation is performed, only the toner in the developer is consumed, so the weight ratio of the developer to the toner (T / D ratio) decreases. Therefore, the toner is replenished to control the T / D ratio to a predetermined value. In this embodiment, the predetermined T / D ratio is set to 8%.

[0032] As shown in FIG. 4, a hopper 75 containing a supply developer consisting of toner and a magnetic carrier is installed above the developing device 1Y, and the amount of toner used in image formation can be supplied to the developing device 1Y. The amount of toner supply is controlled by a control unit (not shown) rotating a supply screw 76. Specifically, the control unit calculates the amount of toner consumed in image formation based on the image ratio during image formation and the result of magnetically detecting the T / D ratio in the developing container 2 by the toner concentration sensor 61 (FIGS. 2 and 3), and determines the amount of toner supply. For example, a control toner image (patch image) is formed on the intermediate transfer belt 10 every time a predetermined number of images are formed, and the result of detecting this by a reflection density sensor (not shown) is also used to determine the amount of toner supply.

[0033] Toner is replenished through a toner replenishing port 40 provided in the developing container 2 (see FIG. 3). In this embodiment, the toner replenishing port is provided at the upstream end of the first conveying screw 58 in the first direction, above and outside the conveying path of the first conveying passage 52. However, the position of the replenishing port is not limited to this location and may be set in various locations depending on the main body configuration of the image forming apparatus, etc. The replenished toner circulates through the first conveying passage 52 and the second conveying passage 53 while being stirred and conveyed together with the developer by the first conveying screw 58 and the second conveying screw 59.

[0034] [Trickle development method] The developing device 1Y in this embodiment employs a trickle development method (hereinafter referred to as "trickle") for suppressing deterioration of the carrier in the developer. Trickle is a development method in which, when the volume of the developer in the developing container 2 reaches a certain level or more, excess developer is discharged from a discharge port 100 (see FIG. 8, etc.) provided in the developing container 2, and carrier is replenished using a small amount of carrier contained in the replenishment toner.

[0035] 5(a) and (b) are diagrams for explaining an example of the configuration and mechanism of a typical trickle. Hereinafter, when the terms "upstream" and "downstream" are used, they refer to the upstream (right side of the drawing) and downstream (left side of the drawing) of the conveying direction (first direction) of the blades 58b of the first conveying screw 58.

[0036] The first conveying screw 58 includes a rotating shaft 58a, a blade 58b that conveys the developer in a first direction inside the first conveying path 52, and a reverse conveying portion 58c that serves as a reverse conveying portion that pushes the developer back in the upstream direction at the downstream end of the first conveying screw 58. A discharge path 70 for discharging excess developer is connected downstream of the first conveying path 52, and a discharge port 100 is opened downward in the direction of gravity downstream of the discharge path 70. The discharge path 70 is provided outside the circulation path of the developing container 2, and is connected to the first conveying path 52.

[0037] A discharge conveying section 71 is provided in the discharge path 70. The discharge conveying section 71 is a conveying screw having a spiral blade formed on a rotating shaft 58a, which is the same rotating shaft as the first conveying screw 58, and serves to convey the developer downstream toward the discharge port 100. The inner diameter of the discharge path 70 is smaller than the inner diameter of the first conveying path 52, and the outer diameter of the discharge conveying section 71 is smaller than the blade 58b.

[0038] In Figures 5(a) and (b), the matte part is an imitation of the area where the developer exists. As shown in Figure 5(a), when the volume of the developer in the first conveying path 52 is small and the developer level is low, the developer conveyed by the blade 58b is pushed back by the reverse conveying part 58c. On the other hand, as shown in Figure 5(b), when the volume of the developer in the first conveying path 52 increases and the developer level rises to a certain level or higher, the developer that cannot be pushed back by the reverse conveying part 58c overcomes the reverse conveying part 58c. Then, when the developer that has overcome the step accumulates to exceed the step 60 between the first conveying path 52 and the discharge path 70, it becomes possible to be conveyed by the discharge conveying part 71, and is conveyed to the discharge port 100 and discharged as excess developer.

[0039] It is known that as the developing device 1Y is used, the charging ability of the carrier decreases due to the adhesion of external additives contained in the toner to the carrier surface. Figure 6 is a graph showing the calculation of the average residence time of the carrier in the developing container 2 (representing the degree of deterioration of the carrier) when trickle is not performed (a) and when trickle is performed (b). The conditions for this calculation were an image density of 5%, a developer amount in the developing container 2 of 250 g, a developer T / D ratio of 8%, and a carrier weight ratio in the replenishment toner of 10%.

[0040] In (a) of Figure 6, the average residence time increases in proportion to the period of use (number of images formed). On the other hand, in (b), old carrier is consumed and new carrier is replenished, so the average residence time of the carrier is shorter than in (a) and converges to a certain time (saturation residence time). In other words, the deterioration of the carrier does not progress beyond a certain level, and the toner charging ability of the carrier can be maintained.

[0041] As described above, in the trickle development method, a minute amount of carrier is contained in the replenishment toner. Therefore, the amount of developer in the developing container 2 increases with the replenishment operation, and when the volume exceeds a certain level, a part of the developer spills further into the reverse transport section 58c, and the developer is discharged from the discharge port 100. In this way, the discharge stops when the volume of the developer is small, and is discharged when the volume is large, and the amount of developer in the developing container 2 is kept within a certain range.

[0042] [About excessive developer discharge] As described above, the trickle development method is an effective technique for suppressing the deterioration of the carrier in the developer. However, the trickle development method may result in the discharge of the developer being more than expected. For example, when the driving speed of the developing device 1Y increases with the recent increase in the speed of the image forming apparatus, the amount of air taken into the developing container 2 increases with the rotation of the developing sleeve 54, and the internal pressure of the developing container 2 increases. As a result of the internal pressure of the developing container 2 increasing while the outside of the developing container 2 is at atmospheric pressure, a difference in pressure between the inside and the outside occurs, and an air flow is generated that blows out of the developing container 2 from the discharge port 100 as shown in FIG. 7. Since this air flow contains the developer that has been lifted up by the screw, the developer reaches the discharge path 70 and is transported downstream by the discharge transport section 71. In this way, even when the volume of the developer is such that it should not be discharged, a small amount of developer flows out of the discharge port 100.

[0043] If this "excessive discharge" state continues in which trickle discharge occurs even though the volume of developer is small, the amount of developer in the developing container 2 will gradually decrease, and there is a risk that the developer will not be able to be supplied satisfactorily to the developing sleeve 54.

[0044] [Measures to prevent excessive developer discharge] In this embodiment, as shown in Fig. 8, a ring-shaped magnet member 101, which is a magnetic field generating means, is disposed downstream in the transport direction of the discharge conveyance section 71 from the end of the discharge port 100, thereby preventing the developer in the developing container 2 from being excessively discharged. This will be described in detail below. In the following, "upstream" and "downstream" in the discharge path 70 refer to upstream and downstream in the developer transport direction by the discharge conveyance section 71, respectively.

[0045] First, in the configuration of this embodiment, the first conveying screw 58 that conveys the developer in the first conveying path 52 in the first direction has a rotating shaft 58a and a blade 58b as a first conveying part that is provided in a spiral shape on the rotating shaft. The discharge conveying part 71 is provided downstream of the blade 58b in the first direction and conveys the developer toward the discharge port 100. The discharge conveying part 71 is configured by providing a spiral blade on the rotating shaft 58a and conveys the developer in the same direction as the first direction. Furthermore, in the first direction, a reverse conveying part 58c that conveys the developer in the direction opposite to the first direction is provided between the blade 58b and the discharge conveying part 71. The reverse conveying part 58c is also a blade that is provided in a spiral shape on the rotating shaft 58a.

[0046] Particularly in the case of this embodiment, a magnet member 101 serving as a magnetic field generating means is disposed downstream of an upstream end 103 of the discharge port 100 with respect to the transport direction of the developer in the discharge transport section 71. The magnet member 101 is formed in a ring shape, and is fixed around the entire circumference to an inner wall of the discharge path 70 downstream of the discharge transport section 71. Specifically, the magnet member 101 is disposed at a predetermined interval from the upstream end 103 of the discharge port 100 in the first direction.

[0047] Such a ring-shaped magnet member 101 has a shape as shown in Fig. 9, and in this embodiment, the outer diameter is 14 mm, the inner diameter is 8 mm, and the thickness is 1.5 mm. The rotating shaft 58a passes through the center of the magnet member 101. As a result, the inner peripheral surface 101a of the magnet member 101 faces the outer peripheral surface of the rotating shaft 58a over the entire circumference with a small gap therebetween.

[0048] The magnet member 101 is magnetized with an S pole on one side and an N pole on the other side, and the magnetic flux density of the surface is 50 mT to 60 mT (measured by GX-100 manufactured by Nippon Denji Sokki Co., Ltd.). In this embodiment, the N pole surface is arranged on the discharge port 100 side, but there is no problem whether the pole faces the discharge port 100 side. If the magnetic flux density of the magnet member 101 is too large, the friction between the attached developer and the rotating shaft 58a of the discharge conveying section 71 becomes strong, and the toner may be stuck, and if the magnetic flux density is too small, the effect of this embodiment cannot be obtained. For this reason, in this embodiment, the magnetic flux density is set to the above-mentioned range, but the magnetic flux density can be appropriately set depending on the configuration of the device.

[0049] The developer conveyed by the discharge conveyance section 71 is discharged by dropping from the discharge port 100, but a part of the discharged developer is attracted by the magnetic force of the magnet member 101 and adheres to the surface of the magnet member 101. When the amount of developer adhering to the surface of the magnet member 101 gradually increases, a developer pool area 102 is formed by the adhering developer, as shown in FIG.

[0050] This agent pooling region 102 is formed to extend from the magnet member 101 toward the upstream end 103 of the discharge port 100 (to the right in Fig. 10), so that the discharge port 100 is covered by the agent pooling region 102 formed as shown in Fig. 10. In the illustrated example, a part of the magnet member 101 is exposed to the discharge port 100, and the agent pooling region 102 is formed to protrude below the discharge port 100. Note that the magnet member 101 does not need to be exposed to the discharge port 100, and it is sufficient that the magnet member 101 is arranged so that at least the discharge port 100 is covered by the agent pooling region 102.

[0051] When the discharge port 100 is covered by the agent pooling area 102, the flow path through which the developer is blown out from the discharge port 100 to the outside of the developing container 2 as shown in Fig. 7 is blocked by the agent pooling area 102, so that the flow rate of the airflow flowing out to the outside can be reduced. Therefore, it is possible to prevent the developer from being discharged to the outside from the discharge port 100 by this airflow.

[0052] On the other hand, although the discharge port 100 is covered by the developer pooling region 102, the developer transported by the discharge transport section 71 is pushed toward the developer pooling region 102 by the transporting force of the discharge transport section 71. When the amount of developer exceeds the amount that can be supported by the magnetic force of the magnet member 101, the developer is naturally discharged downward from the discharge port 100 by gravity, so that the developer does not clog in the vicinity of the discharge port 100. In this way, it is possible to achieve both the suppression of excessive developer discharge due to airflow and the normal discharge of developer by the discharge transport section 71.

[0053] In the configuration of this embodiment, the distance A between the upstream end 103 of the discharge port 100 and the magnet member 101 is set to 11.5 mm. It is important to set this distance A appropriately, and the reason for this will be explained below.

[0054] 11(a), if the distance A is set too wide, the formed developer pool area 102 will not be able to adequately cover the discharge port 100. This will result in a gap through which the airflow can flow, making it impossible to adequately prevent the airflow from flowing out and the developer from being discharged by the airflow.

[0055] On the other hand, as shown in Fig. 11(b), if the interval A is set too narrow, the effective opening width of the discharge port 100 becomes small, and the amount of developer that can be discharged per unit time decreases. Therefore, when the amount of developer supplied per unit time is large, such as when images with a high image ratio are continuously printed, if the amount of developer that can be discharged is less than the amount of developer supplied, the amount of developer in the developing container 2 becomes excessive. This causes problems such as developer leakage and poor stirring of the supplied toner.

[0056] For this reason, it is preferable that the distance A is set so that the tip of the agent pooling region 102 supported by the magnet member 101 overlaps with the upstream end 103 of the discharge port 100. For this reason, in this embodiment, the distance A is set to 11.5 mm, but the appropriate value for the distance A varies depending on the configuration in the vicinity of the discharge port 100 and the size and magnetic force of the magnet member 101, and therefore an appropriate value is set depending on the configuration of the developing device.

[0057] In this embodiment, a magnetic material is used as the material of the rotating shaft 58a of the discharge conveying section 71. When the material of the rotating shaft 58a is a magnetic body, the rotating shaft 58a penetrating the center of the ring-shaped magnet member 101 is magnetized by the magnetic force of the magnet member 101, and a magnetic seal is formed between the inner circumferential surface 101a of the magnet member 101 and the rotating shaft 58a. Therefore, this magnetic seal can prevent the developer from slipping through the center of the ring-shaped magnet member 101.

[0058] In addition, since the agent reservoir area 102 formed by the magnet member 101 only needs to cover the upper part of the discharge port 100, it is also possible to use a shape in which the upper part of the ring-shaped magnet member 101 is cut, for example, a semicircular shape. That is, the magnet member 101 only needs to be disposed in a range including at least one end to the other end of the opening width of the discharge port 100 in the circumferential direction of the rotating shaft 58a. In other words, when viewed from the axial direction of the rotating shaft 58a, the magnet member 101 only needs to be located in the same phase as the discharge port 100 in the circumferential direction of the rotating shaft 58a, and have a width equal to or greater than the width of the discharge port 100.

[0059] The magnet member may also be fixed to the rotating shaft 58a. In this case, it is preferable that the magnet member is provided around the entire circumference of the rotating shaft 59a so as to have a small gap between the magnet member and the inner peripheral surface of the discharge passage 70. The magnet member may also be provided on the outer wall of the discharge passage 70. In this case, the discharge passage 70 is made of a non-magnetic material, and a magnetic force acts on the inside of the discharge passage 70 to form a developer reservoir area in the discharge passage 70.

[0060] 10, it is preferable that the discharge conveying portion 71, which is a spiral blade, is disposed so as to extend downstream in the conveying direction beyond the upstream end 103 of the discharge port 100. Of course, the downstream end of the discharge conveying portion 71 is positioned upstream of the magnet member 101. With this configuration, the developer pooling area 102 can be pushed more reliably in the conveying direction by the conveying force of the discharge conveying portion 71, so that the developer can be more reliably discharged even when the developer supply amount is large.

[0061] In addition, in the case of this embodiment, since the magnet member 101 is located downstream of the upstream end 103 of the discharge port 100 and the downstream end of the discharge conveyance section 71, the developer is unlikely to reach the downstream side of the magnet member 101 of the discharge path 70. For this reason, a sealing member such as an oil seal that is usually provided at the downstream end of the discharge path 70 to prevent the developer from leaking may be omitted.

[0062] [Example] Next, an experiment conducted to confirm the effect of this embodiment will be described. In the experiment, a developing device having a magnet member 101 as in this embodiment and a comparative example having no magnet member were used to examine the change in the amount of developer in the developing device when images with an image ratio of 0.5% were continuously formed. The example and comparative example have the same configuration except for the presence or absence of the magnet member 101. The results are shown in FIG. 12.

[0063] In the case of an image with an image ratio of 0.5%, the amount of developer supplied is very small, so if the amount of developer discharged from the developing device is large, the amount of developer in the developing device will gradually decrease. As is clear from Fig. 12, in the developing device having the configuration of the comparative example, the amount of developer gradually decreases as image formation continues, whereas in the developing device having the configuration of this embodiment, the amount of developer in the developing device remains stable even if image formation continues.

[0064] As described above, with the configuration of this embodiment, by covering the discharge port 100 with the developer pool area 102 formed by the magnet member 101, it is possible to suppress the airflow flowing out from the discharge port 100 and suppress the discharge of excessive developer caused by the airflow. Therefore, even if the amount of developer supplied per unit time is small, the amount of developer in the developing device can be properly maintained.

[0065] <Second embodiment> The second embodiment will be described with reference to FIG. 13. In the configuration of the first embodiment described above, a ring-shaped magnet member was used. In contrast, in this embodiment, a flat plate-shaped magnet member 101A is used. Since the other configurations and applications are the same as those of the first embodiment, the same reference numerals are used for the same configurations, and explanations and illustrations are omitted or simplified. The following description will focus on the parts that are different from the first embodiment.

[0066] In this embodiment, a flat plate-shaped magnet member 101A serving as a magnetic field generating means is set at a position spaced apart by an interval A from the upstream end 103 of the discharge port 100. The magnet member 101A is fixed to the inner circumferential surface of the discharge path 70 in a range including at least one end to the other end of the opening width of the discharge port 100 in the circumferential direction of the rotation shaft 58a. Note that, in this embodiment, the magnet member 101A is not disposed over the entire circumference of the discharge path 70, and therefore an oil seal 72 serving as a sealing member for preventing developer leakage is provided downstream of the magnet member 101A of the discharge path 70.

[0067] In the present embodiment, the developer is attracted by the magnetic force of the magnet member 101A and adheres to the surface, forming an agent pooling region 102, which then seals the discharge port 100. Therefore, the flow path through which the developer is blown out from the discharge port 100 to the outside of the developing container 2 is blocked by the agent pooling region 102, thereby reducing the flow rate of the airflow that tends to flow out to the outside. This makes it possible to prevent the developer from being discharged to the outside from the discharge port 100 by this airflow.

[0068] Furthermore, the developer transported by the discharge transport section 71 is pushed downstream in the transport direction by the transport force of the discharge transport section 71, but an oil seal 72, which is a sealing member, is provided further downstream than the magnet member 101A. Therefore, the developer is not transported beyond the oil seal 72, and the developer that exceeds the magnet member 101A is pulled back by the magnetic force of the magnet member 101A and becomes part of the developer pooling area 102.

[0069] When the amount of developer exceeds the amount that can be supported by the magnetic force of the magnet member 101A, the developer is naturally discharged downward from the discharge port 100 by gravity. In this way, it is possible to achieve both the prevention of excessive discharge of developer due to airflow and the normal discharge of developer by the discharge conveyance section 71.

[0070] As described above, the configuration of this embodiment also makes it possible to suppress the discharge of excessive developer due to the airflow flowing out from the discharge port 100, and the amount of developer in the developing device can be properly maintained even when the amount of developer supplied per unit time is small.

[0071] <Third embodiment> The third embodiment will be described with reference to Fig. 14. In the configurations of the first and second embodiments described above, the magnet member is provided in the discharge path 70. In contrast, in this embodiment, the magnet member 101B is provided in the discharge connection path 104 connected to the discharge port 100. Since the other configurations and adoption are similar to those of the first embodiment, the same reference numerals are used for the same configurations, and explanations and illustrations are omitted or simplified. The following description will focus on the parts that are different from the first embodiment.

[0072] First, a discharge connection path 104 serving as a second discharge path is connected to a discharge port 100 of the discharge path 70 serving as a first discharge path. The discharge connection path 104 discharges the developer from the discharge port 100 to the outside. For example, the discharge connection path 104 is connected to a developer recovery container provided outside, and the developer discharged from the discharge port 100 is recovered in the recovery container through the discharge connection path 104. Such a discharge connection path 104 is formed of a non-magnetic material such as resin. For example, it is formed integrally with the developing container 2 from resin. Note that the discharge connection path is usually also provided in the configurations of the first and second embodiments.

[0073] Particularly, in this embodiment, a magnet member 101B is provided as a magnetic field generating means on the outer wall of the discharge connection passage 104. The magnet member 101B is formed in a flat plate shape and is provided on the outer wall of the discharge connection passage 104 on the downstream end side of the discharge port 100. The magnet member 101B may be disposed so as to cover the entire circumference of the outer wall of the discharge connection passage 104, or may be provided on the upstream end side of the discharge port 100. The magnet member 101B may also be provided on the inner wall of the discharge connection passage 104. In any case, it is sufficient that the magnet member 101B is disposed so that the agent reservoir area 102 formed by the magnetic force of the magnet member 101B blocks the discharge connection passage 104.

[0074] In this embodiment, the magnet member 101B is disposed at the upstream end of the discharge connection path 104 in the direction in which the developer passes. In addition, in the vicinity of the discharge port 100, the discharge connection path 104 is closed by the developer pooling area 102.

[0075] In addition, in the present embodiment, unlike the first and second embodiments, no magnet member is provided in the discharge path 70, and therefore a push-back portion 71a is provided to push back the developer downstream of the discharge port 100. The push-back portion 71a is a spiral blade in the opposite direction to the spiral blade of the discharge conveyance portion 71, and conveys the developer in the opposite direction to the developer conveyance direction of the discharge conveyance portion 71. Furthermore, in the present embodiment, an oil seal 72 is provided downstream of the push-back portion 71a (left side of FIG. 14) as in the second embodiment.

[0076] In the present embodiment, the developer is attracted by the magnetic force of the magnet member 101B and adheres to the inner peripheral surface of the discharge connection path 104, forming a developer pool area 102, which seals the discharge connection path 104. Therefore, the flow path from the discharge port 100 to the outside of the developing container 2 is blocked by the developer pool area 102, so that the flow rate of the airflow flowing out to the outside can be reduced. Therefore, it is possible to prevent the developer from being discharged to the outside from the discharge port 100 by this airflow.

[0077] The developer conveyed by the discharge conveying section 71 is pushed to the left in FIG. 14 by the conveying force of the discharge conveying section 71, but the downstream end of the discharge port 100 is provided with an oil seal 72 as a sealing member and a push-back section 71a that pushes back the developer. For this reason, the developer is not conveyed beyond the oil seal 72, but is pushed toward the discharge port 100 located below. When the pushed-in developer exceeds the amount of developer that can be supported by the magnetic force of the magnet member 101B, the developer is naturally discharged downward from the discharge port 100 by gravity. In this way, it is possible to achieve both the suppression of excessive developer discharge due to airflow and the normal discharge of developer by the discharge conveying section 71. The push-back section 71a may be omitted.

[0078] As described above, the configuration of this embodiment also makes it possible to suppress the discharge of excessive developer due to the airflow flowing out from the discharge port 100, and the amount of developer in the developing device can be properly maintained even when the amount of developer supplied per unit time is small.

[0079] <Fourth embodiment> The fourth embodiment will be described with reference to Figures 15 to 19. In the configurations of the first and second embodiments described above, the magnet member is provided downstream of the upstream end 103 of the discharge port 100. In contrast, in this embodiment, the magnet member 101C is provided upstream of the upstream end 103 of the discharge port 100. Since the other configurations and adoption are the same as those of the first embodiment, the same reference numerals are used for the same configurations, and explanations and illustrations are omitted or simplified. The following description will focus on the parts that are different from the first embodiment.

[0080] In this embodiment, as shown in Fig. 15, a part of the blade of the discharge conveying section 71 is cut out, and a magnet member 101C as a magnetic field generating means is fixed around the entire circumference of the rotating shaft 58a. Specifically, the flat plate-shaped magnet member 101C is fixed by attaching it so as to be wrapped around the entire circumference of the rotating shaft 58a. The developer carried on the outer peripheral surface of the magnet member 101C forms a magnetic brush between the inner peripheral surface of the discharge path 70 and the rotating shaft 58a. As a result, the air flow path in the discharge path 70 is blocked by the magnetic brush.

[0081] The attachment position of the magnet member 101C in the longitudinal direction (axial direction of the rotation shaft 58a) is downstream of the reverse transport portion 58c in the first direction. The reason for this is as follows: Even if the magnet member 101C is disposed upstream of the reverse transport portion 58c in the first direction and a magnetic brush is formed at a position upstream of the reverse transport portion 58c, the flow path of the air escaping to the discharge port 100 cannot be sufficiently blocked, and excessive discharge of developer cannot be sufficiently suppressed.

[0082] It is also possible to provide the magnet member 101C by cutting the blade of the reverse conveying section 58c midway. However, since the reverse conveying section 58c is a member that conveys the developer to the upstream side in the first direction, the seal by the magnetic brush cannot be broken even when the volume of the developer increases, and the developer discharge function is impaired. This is the reason why the magnet member 101C is attached downstream of the reverse conveying section 58c in the longitudinal direction. Note that the magnet member 101C may be provided in the first conveying path 52 if it is downstream of the reverse conveying section 58c in the first direction, but it is preferable to place the magnet member 101C in the discharge path as in this embodiment.

[0083] Fig. 16(a) is a perspective view of magnet member 101C, and Fig. 16(b) is a cross-sectional view of magnet member 101C cut in the axial direction of rotating shaft 58a. Magnet member 101C is composed of flexible plate-like magnet member 110 and a sealing surface 111 of double-sided tape attached to one surface of magnet member 110. Magnet member 101C has a length exactly the same as one circumference of rotating shaft 58a, so that there are no gaps when wrapped around the shaft as viewed in cross section.

[0084] 17 shows the magnetization pattern of the magnet member 101C in this embodiment. The plate-shaped magnet member 101C is magnetized on both sides, with the sealing surface 111 side being the S pole and the front surface being the N pole. However, the opposite direction may be reversed.

[0085] The outer diameter of the position on the rotating shaft 58a where the magnet member 101C is attached is preferably designed to an appropriate size according to the magnitude of the magnetic force and thickness of the magnet member 101C. Since the size of the magnetic brush depends on the magnitude of the magnetic force of the magnet member 101C, it is desirable to maintain an appropriate distance between the magnet member 101C and the discharge path 70 in order to block the air flow path with the magnetic brush. If the gap between the magnet member 101C and the discharge path 70 is too close for the strength of the magnetic force, the excess developer cannot be discharged satisfactorily when the volume of the developer increases. Conversely, if the magnetic force is too weak, the sealing property is insufficient and the air flow cannot be blocked. In this embodiment, the gap between the outer peripheral surface of the magnet member 101C and the inner peripheral surface of the discharge path 70 is set to 1 mm or more.

[0086] In this embodiment, the magnet member 101C used had a thickness of 1.0 mm, a width of 3 mm, and a surface magnetic force of 60 mT (measured with GX-100 manufactured by Nippon Denji Sokki Co., Ltd.). The height of the magnetic brush was calculated as the average height of the brush from an image obtained three-dimensionally using a 3D laser microscope (VK-8700 manufactured by Keyence Corporation). The average height of the brush was measured for the above-mentioned magnet member 101C and was 1.2 mm. For this reason, the outer diameter of the position where the magnet member 101C is attached on the rotating shaft 58a was set to 8 mm, and the inner diameter of the discharge path 70 was set to 12 mm, so that the gap between the magnet member 101C and the discharge path 70 was set to 1 mm. The magnetic brush was then contacted with the inner wall of the discharge path 70 to block the air flow.

[0087] Next, the developer discharge mechanism in this embodiment will be described. Figure 18(a) shows the state of the developer surface when the developer bulk is low, and Figure 18(b) shows the state of the developer surface when the developer bulk is high.

[0088] Considering a state in which a certain amount of developer has already been discharged by the trickle development method, a magnetic brush is formed around the magnet member 101C along the magnetic field lines as shown in Figures 18(a) and (b). As shown in Figure 18(a), when the developer is low in bulk, the magnetic brush formed around the magnet member 101C blocks the path through which air escapes toward the discharge port 100, so that the air flow shown in Figure 7 does not occur, or even if it does occur, the air flow rate is reduced. Therefore, the developer rarely reaches the discharge path 70, and excessive discharge of developer is unlikely to occur.

[0089] 18(b), when the volume of developer increases, the developer that is no longer pushed back by the reverse transport portion 58c reaches the discharge path 70 and is transported downstream by the discharge transport portion 71. When the amount of transported developer increases and the developer pressure increases, the developer breaks through the binding force of the magnetic brush and is transported to the most downstream position, where it reaches the discharge port 100 and is discharged as excess developer.

[0090] In the above description, the discharge conveying section 71 is also located downstream of the magnet member 101C, but if the magnet member 101C is close to the discharge port 100, the discharge conveying section 71 does not need to be located downstream of the magnet member 101C. In other words, the discharge conveying section 71 only needs to be located at least upstream of the magnet member 101C.

[0091] As described above, by sealing the area between the discharge path 70 and the rotating shaft 58a with a magnetic brush using the magnet member 101C, excessive discharge of developer carried by the air flow can be effectively suppressed without impairing the developer discharge performance.

[0092] The magnetization pattern of the magnet member 101C is not limited to that shown in FIG. 17, and various forms are assumed. Examples of magnetization patterns are shown in FIGS. 19(a) to 19(c). In the magnet member 101Ca of FIG. 19(a), the magnetization pattern of the magnet member 110A is vertical, not front and back. In the magnet member 101Cb of FIG. 19(b), the magnet member 110B is magnetized on both sides of the magnet member 110B in addition to the magnetization pattern of FIG. 19(a). In the magnet member 101Cc of FIG. 19(c), the N pole and the S pole are alternately magnetized in a diagonal stripe pattern on the surface of the magnet member 110C. Even with these patterns, excessive discharge of the developer carried by the air flow can be effectively suppressed by making the magnetic brush contact with the discharge passage 70.

[0093] 19(a) to (c), there are various possible magnetization patterns. Essentially, it goes without saying that the effect of the present invention can be obtained as long as the magnetic brush contacts the inner wall of the discharge passage 70.

[0094] <Fifth embodiment> The fifth embodiment will be described with reference to Figures 20 and 21. In the configuration of the fourth embodiment described above, a configuration in which a magnetic brush is formed by a magnet member has been described. In contrast, in this embodiment, a brush member 120 is provided instead of a magnetic brush made of a magnet member. Since the other configurations and adoption are the same as those of the fourth embodiment, the same reference numerals are used for the same configurations, and explanations and illustrations are omitted or simplified. The following description will focus on the parts that are different from the fourth embodiment.

[0095] The brush member 120 is provided around the entire circumference between the rotating shaft 58a and the inner wall of the discharge path 70. In this embodiment, as shown in Fig. 20, a part of the blade of the discharge conveying section 71 is cut out, and the brush member 120 is fixed around the entire circumference of the rotating shaft 58a. The fixing position of the brush member 120 is similar to the fixing position of the magnet member 101C in the fourth embodiment.

[0096] As shown in Fig. 21, the brush member 120 is made by implanting fibers 122 on one side of a flexible base material 121 and attaching double-sided tape 123 to the other side as an attachment surface, and is fixed by wrapping it around the rotating shaft 58a. In this embodiment as well, the bristles of the fibers 122 are in contact with the inner wall of the discharge passage 70 as shown in Fig. 20. Note that the brush member 120 may be fixed to the inner wall of the discharge passage 70 and the brush may be in contact with the outer circumferential surface of the rotating shaft 58a.

[0097] This embodiment differs from the fourth embodiment in that the air escape path is sealed by implanted fibers instead of a magnetic brush, but the mechanism for suppressing the excessive discharge of excess developer is the same as that of the fourth embodiment. Also, in the case of this embodiment, as in the fourth embodiment, it is possible to effectively suppress the excessive discharge of developer carried by the air flow.

[0098] <Other embodiments> In the above-mentioned embodiments, the image forming apparatus is a printer. However, the present invention is also applicable to copiers, facsimiles, multifunction machines, and the like. In the above-mentioned embodiments, the developing device is configured to supply developer from the developing chamber (second conveying path 53, second chamber) to the developing sleeve and collect developer from the developing sleeve in the developing chamber. However, the present invention is also applicable to a configuration in which developer is supplied from the developing chamber and collected in a mixing chamber (first conveying path 52, first chamber) arranged with a partition wall between the developing chamber and the mixing chamber. Furthermore, the present invention is also applicable to a configuration in which the first chamber and the second chamber are arranged horizontally side by side, and the first chamber and the second chamber are arranged vertically or inclined with respect to the horizontal direction. The first chamber may be the developing chamber and the second chamber may be the mixing chamber. [Explanation of symbols]

[0099] 1Y, 1M, 1C, 1K...developing device / 2...developing container / 52...first conveying path (first chamber) / 53...second conveying path (second chamber) / 54...developing sleeve / 58...first conveying screw / 58a...rotating shaft / 58b...blade (first conveying section) / 58c...reverse conveying section / 59...second conveying screw (second conveying section) / 70...discharge path (first discharge path) / 71...discharge conveying section / 100...discharge port / 101, 101A, 101B, 101C, 101Ca, 101Cb, 101Cc...magnet member (magnetic field generating means) / 104...discharge connection path (second discharge path) / 120...brush member

Claims

1. A developer carrier that carries and transports a developer containing toner and carrier to develop an electrostatic image formed on an image carrier; a developing container having a first chamber and a second chamber partitioned from the first chamber by a partition wall, the developing container containing the developer; a discharge path having a discharge port for discharging a portion of the developer contained in the developing container; a first communication portion that allows the developer to communicate from the first chamber to the second chamber; a second communication portion that allows the developer to communicate from the second chamber to the first chamber; a first conveying screw portion disposed in the first chamber and configured to convey the developer in a first direction from the second communicating portion toward the first communicating portion; a second conveying screw portion disposed in the second chamber and configured to convey the developer in a second direction from the first communicating portion toward the second communicating portion; a third conveying screw portion disposed in the discharge path and configured to convey the developer in a third direction; a magnet that is disposed in the discharge path and is disposed on the discharge port side with respect to a rotation axis of the third conveying screw portion, the discharge port is disposed downstream of an upstream end of the third conveying screw portion in the third direction, and is an opening provided on a bottom surface of the discharge path and opened downward in a direction of gravity, the magnet is disposed downstream of an upstream end of the discharge port in the third direction, and a magnetic brush formed by the magnet is disposed so as to overlap with the discharge port in the third direction. A developing device characterized by the above.

2. The magnet is disposed downstream of the downstream end of the third conveying screw portion in the third direction.

2. The developing device according to claim 1,

3. The magnet is fixed to an inner wall surface of the discharge passage, 3. The developing device according to claim 1, wherein the developing device is a developing unit.

4. The magnet is a ring-shaped magnet arranged through a gap between the outer peripheral surface of the rotating shaft of the third conveying screw section, 4. The developing device according to claim 3.

5. The third direction further includes an oil seal disposed downstream of the downstream end of the third conveying screw portion and attached to an outer peripheral surface of a rotating shaft of the third conveying screw portion, The magnet is disposed upstream of the oil seal in the third direction.

5. The developing device according to claim 1, wherein the developing device is a developing unit.

6. The discharge path is provided outside a circulation path of the developing container through which the developer circulates between the first chamber and the second chamber, and is connected to the first chamber with respect to the first direction.

6. The developing device according to claim 1, wherein the developing device is a developing unit.

7. The rotation axis of the third conveying screw section is the same as the rotation axis of the first conveying screw section, 7. The developing device according to claim 6.

8. The outer diameter of the third conveying screw portion is smaller than the outer diameter of the first conveying screw portion.

8. The developing device according to claim 6, wherein the developing device is a developing unit.

9. The inner diameter of the discharge passage is smaller than the inner diameter of the first chamber.

9. The developing device according to claim 6, wherein the developing device is a developing unit.

10. The bottom surface of the discharge passage is above the bottom surface of the first chamber.

10. The developing device according to claim 6, wherein the developing device is a developing unit.

11. A developer carrier that carries and transports a developer containing toner and a carrier in order to develop an electrostatic image formed on the image carrier; a developing container having a first chamber and a second chamber partitioned from the first chamber by a partition wall, the developing container containing the developer; a discharge path having a discharge port for discharging a portion of the developer contained in the developing container; a first communication portion that allows the developer to communicate from the first chamber to the second chamber; a second communication portion that allows the developer to communicate from the second chamber to the first chamber; a first conveying screw portion disposed in the first chamber and configured to convey the developer in a first direction from the second communicating portion toward the first communicating portion; a second conveying screw portion disposed in the second chamber and configured to convey the developer in a second direction from the first communicating portion toward the second communicating portion; a third conveying screw portion disposed in the discharge path and configured to convey the developer in a third direction; a magnet that is disposed in the discharge path and is disposed on the discharge port side with respect to a rotation axis of the third conveying screw portion, the discharge port is disposed downstream of an upstream end of the third conveying screw portion in the third direction, and is an opening provided on a bottom surface of the discharge path and opened downward in a direction of gravity, The magnet is disposed so as to overlap with the discharge port in the third direction. A developing device characterized by the above.

12. The magnet is disposed downstream of a downstream end of the third conveying screw portion in the third direction. The developing device according to claim 11 .

13. The magnet is fixed to an inner wall surface of the discharge passage, 13. The developing device according to claim 11 or 12.

14. The magnet is a ring-shaped magnet arranged through a gap between the outer circumferential surface of the rotating shaft of the third conveying screw section, The developing device according to claim 13 .

15. The third direction further includes an oil seal disposed downstream of a downstream end of the third conveying screw portion and attached to an outer peripheral surface of a rotating shaft of the third conveying screw portion, The magnet is disposed upstream of the oil seal in the third direction.

15. The developing device according to claim 11,

16. The discharge path is provided outside a circulation path of the developing container through which the developer circulates between the first chamber and the second chamber, and is connected to the first chamber with respect to the first direction.

16. The developing device according to claim 11,

17. The rotation axis of the third conveying screw section is the same as the rotation axis of the first conveying screw section.

17. The developing device according to claim 16.

18. The outer diameter of the third conveying screw portion is smaller than the outer diameter of the first conveying screw portion.

18. The developing device according to claim 16 or 17.

19. The inner diameter of the discharge passage is smaller than the inner diameter of the first chamber.

19. The developing device according to claim 16, wherein the developing device is a developing unit.

20. The bottom surface of the discharge passage is above the bottom surface of the first chamber.

20. The developing device according to claim 16, wherein the developing device is a developing unit.

Images