JP2011186213A - Developing device for electrophotographic-system image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent developer from entering a shaft sealing part. <P>SOLUTION: A developing device for an electrophotographic-system image forming apparatus has: screws for stirring and conveying the developer containing toner and magnetic carrier; a housing surrounding the screws; and a bearing part adjacent to a screw end and comprising the shaft sealing part and a bearing. The shaft sealing part has a G seal located on the screw side and a G seal located on the bearing side, and a grease is charged to a space between the G seal located on the screw side and the G seal located on the bearing side. The developing device for the electrophotographic-system image forming apparatus includes a disc-like flange, between the screw end and the shaft sealing part, in a screw shaft. The flange is disposed so that the screw shaft passes through the center of the flange, and a sheet-like magnet is provided on a surface of the flange, perpendicular to the direction of the screw shaft. And a magnetic-body ring as a magnet ring is provided on the inner surface of the housing while facing the outer periphery of the radial side surface of the flange. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a developing device of an electrophotographic image forming apparatus, and more specifically to a bearing portion of a screw that stirs and conveys a developer, and includes a shaft seal made up of a plurality of seal members and grease. In order to effectively reduce the developer entering and aggregating into the seal member of the shaft seal portion, the developer enters the vicinity of the seal member of the shaft seal portion. It is effective to prevent this.

  A developing method in a developing machine of an electrophotographic image forming apparatus, in which a latent image on a photosensitive member is developed with a developer containing a carrier made of a magnetic material and toner, and developing in the developing machine. A plurality of screws are provided in the developing machine for transporting and stirring the agent. These screws need to have the ability to supply, transport and agitate the required amount of developer into the developing machine according to the printing speed of the image forming apparatus and the size of the printing area. As the print area becomes larger, the required development area increases, and accordingly, the necessary developer supply amount increases. Further, as the printing speed increases, the supply amount per unit time to the developing roller in the development area increases, and accordingly, the developer supply amount, the conveyance amount, and the stirring amount by the screw increase. Become.

In order to improve the stability of the screw conveyance / stirring performance, the developer does not enter the bearing, the toner aggregates, and the toner does not stick to increase the driving resistance of the developing machine. In addition, a bearing portion in which two seal members are combined and grease is enclosed between them to improve the sealing performance against penetration of the developer into the bearing is known (Patent Document 1). This is shown in FIG. 5 and FIG. FIG. 8 is an enlarged view of the bearing portion of FIG.
The seal member is specifically a G seal (a lip seal having a G-shaped cross section), but a lip seal having a U-shaped cross section or a V-shaped cross section can also be used as an equivalent (hereinafter referred to as a G seal). .

The structure of the bearing portion of the above-described bearing and the shaft seal portion of Patent Document 1 is as shown in FIG. 7, and is based on the bearing (specifically, rolling bearing) 18 of the paddle shaft 23 and the shaft seal portion 16. The shaft seal portion 16 includes two G seals 19 and 20. The lip 19a of the first G seal 19 on the conveying screw (also simply referred to as “screw”) side, the lip 20a of the second G seal 20 on the bearing 18 side, the inner peripheral surface of the bearing case 17, and the paddle shaft 23 Grease 26 is sealed in a space 25a formed by the base portion 23a of the second G seal 20, and the lip 20a of the second G seal 20, the bearing 18, the inner peripheral surface of the bearing case 17, and the base portion of the paddle shaft 23 Grease 26 is sealed in a space 25b formed by 23a. The space 25 a is between the first G seal 19 and the second G seal 20, and the space 25 b is between the second G seal 20 provided at a position close to the bearing 18 and the bearing 18.
The right side with respect to the side plate 10a of the developing device is the inside of the developing device and the left side is the outside of the developing device. Then, a geared joint (not shown) is attached to the tip of the tip portion 23b of the paddle shaft 23, and the developing drive motor is connected via the joint.

  The grease 26 enclosed in the space 25a between the first G seal 19 and the second G seal 20 includes the first G seal 19, the base 23a of the paddle shaft 23, the second G seal 20, The sliding surface of the base 23a with the lip is lubricated to reduce the generation of frictional heat, and the developer that has entered through the first G seal 19 is captured. Further, grease 26 is also sealed in the space 25b between the second G seal 20 and the bearing 18, and the same lubricating action and sealing action are produced.

  In the shaft seal portion 16 of the conventional example described above, when the developer enters the first G seal 19, toner agglomerates are minutely generated at the sliding portion between the G seal 19 and the paddle shaft 23. This may be mixed in the developer and supplied to the developing roller, and there is a problem that the image quality is impaired as follows. That is, in a printing pattern having a high image density, when the aggregate adheres to the developing roller during transfer in the developed area, the aggregate inhibits the transfer of toner in the surrounding area. The toner adhesion amount around the aggregate is reduced, and the print density is reduced in a minute region around the aggregate, so that the print image quality is impaired.

  Also, recent image forming apparatuses have become very fast and highly functional, and for this reason, the amount of developer required in the developing machine becomes very large depending on the printing speed and the area of the printing area, Therefore, a large screw conveying ability and stirring ability are required. In addition, the development area increases as the printing area increases, and therefore, the necessary developer supply amount increases. As the developer supply amount per unit time increases, the flow rate of the developer flowing through the developing machine increases, and as a result, a large amount of developer is piled up in the vicinity of the G seal 19 of the shaft seal portion 16. Thus, there is a problem that the pressure on the G seal increases.

Therefore, it is necessary to make the configuration in which the developer does not easily enter the shaft seal portion. For example, Patent Document 2 describes a buffer plate that reduces the pressure of the developer, and Patent Document 3 includes a magnetic plate that prevents movement of a two-component developer that attempts to enter the bearing portion. Are listed. This also describes a magnet ring, which describes that magnetic lines of force are densely formed between both members by disposing a magnetic ring facing a sheet-like magnet.
Patent Documents 4 and 5 describe that a magnetic ring (magnet member) is provided to prevent the developer from entering the bearing. And in patent document 5, the reverse winding screw is described.

However, with the configurations of Patent Document 2 and Patent Document 3, it is difficult to sufficiently prevent the developer from entering the bearings with the configurations described in the related art as the image forming apparatus becomes faster.
Moreover, in the structure of patent document 4 and patent document 5, since the magnet ring seals a developer with a screw and a magnetic force line, there exists a subject that the influence by frictional heat cannot be avoided.

〔Task〕
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a developing device that can effectively prevent the developer from entering the shaft seal portion and obtain good image quality.

[Solution 1]
A screw that conveys the developer containing toner and a magnetic carrier while stirring; a housing that surrounds the screw; a bearing portion that includes a shaft seal portion and a bearing adjacent to the screw end portion; An electrophotographic image forming apparatus in which a portion has a G seal on the screw side and a G seal on the bearing side, and the space between the G seal on the screw side and the G seal on the bearing side is filled with grease In the developing device, a disk-shaped flange is provided on the screw shaft between the screw end portion and the shaft seal portion, and the flange is disposed so that the screw shaft passes through the center of the flange. A sheet-like magnet is provided on a surface orthogonal to the axial direction of the screw, and a magnet ring is provided on the inner surface of the housing so as to face the outer periphery of the radial side surface of the flange It is characterized in that it comprises a sexual member ring.

  According to the present invention, it is possible to provide a developing device capable of effectively preventing the developer from entering the shaft seal portion and obtaining a good image quality.

FIG. 1 is an overall configuration diagram of an electrophotographic image forming apparatus. These are explanatory drawings which show the flow of the developer of a developing machine. These are sectional drawings of the composition of Example 1. FIG. These are sectional drawings of the structure of Example 2. FIG. These are sectional drawings of the prior art example which employ | adopted the conventional shaft sealing part for the bearing of a screw edge part. These are figures which show the comparison result of the effect with respect to the structure of FIG. 5 of the Example of FIG. These are the figures which show the test result which confirmed the presence or absence of the aggregation of the developer in Example 1 of FIG. These are sectional drawings of the conventional bearing device.

An embodiment of the present invention will be described. The present invention is characterized by a configuration relating to protection of a bearing in a developing device used in an electrophotographic image forming apparatus, that is, a bearing at an end portion of a screw shaft that conveys a developer containing magnetic toner.
In short, a flange provided at the end of the screw, a sheet magnet attached to the flange, a housing surrounding the bearing, flange, screw, etc., and a magnetic ring on the inner surface of the housing facing the outer periphery of the flange ing. Then, the developer is captured by a magnetic force in the gap between the flange and the magnetic ring, a strong seal is formed by the captured developer, and the flow of the developer in the vicinity of the G seal is prevented, and the G seal On the other hand, it is a feature that the pressure from the developer is effectively avoided.

[Entire image forming apparatus]
Before describing an embodiment of the present invention, the configuration of the entire image forming apparatus as the background will be described.
In FIG. 1, 50 is a printer as an image forming apparatus, 51y is an image forming unit that forms a yellow image, 51m is an image forming unit that forms a magenta image, and 51c is a image forming unit that forms a cyan image. An image portion, 51k is an image forming portion for forming a black image, 52 is an intermediate transfer member to which the above-described four color images are temporarily transferred, and each color image forming portion has the same configuration for all four colors. . As a representative example, the yellow color image forming unit 51y will be described. An exposure unit 53 irradiates the photosensitive drum 54 with exposure light L based on image information, 54 is a photosensitive drum as an image carrier, and 56 is a photosensitive member. A developing device that develops the electrostatic latent image formed on the drum 54, 58 is a primary transfer unit that transfers the toner image formed on the photosensitive drum 54 to the transfer material P, and 59 is on the photosensitive drum 54. A cleaning unit that collects the untransferred toner, 61 to 63 are a paper feeding unit that stores a transfer material P such as transfer paper, and 64 is a fixing unit that fixes the unfixed toner on the transfer material (printing paper) P. , 90 is a waste toner bottle for storing waste toner collected by the cleaning unit 59 and the secondary transfer unit 60, and 1 is a toner bottle.

Next, an operation during normal image formation in the printer 50 will be described.
First, image information is converted into an electrical signal by the image forming unit 51y, and then transmitted to the exposure unit 53 (writing unit). Then, the exposure unit 53 emits exposure light L such as laser light based on the image information of the electrical signal toward the photosensitive drum 54.
On the other hand, the photosensitive drum 54 rotates counterclockwise in the drawing, and first, the surface thereof is uniformly charged at a position facing the charging unit 55. Then, the surface of the photosensitive drum 54 charged by the charging unit 55 reaches the irradiation position of the exposure light L. An electrostatic latent image corresponding to the image information is formed at this position.
Thereafter, the surface of the photosensitive drum 54 on which the latent image is formed reaches a portion facing the developing device 56. Then, the latent image on the photosensitive drum 54 is developed by the developing device 56. Specifically, the toner in the developing device 56 is mixed with a carrier by a stirring roller together with toner supplied from a toner hopper (not shown in the drawing). The frictionally charged toner is supplied onto the developing roller together with the carrier. Thereafter, the toner carried on the developing roller reaches the position facing the photosensitive drum 54 after passing through the position of the doctor blade. The toner adheres to the electrostatic latent image formed on the surface of the photosensitive drum 54 at the facing position.

The toner supplied from the toner hopper is appropriately supplied into the developing device 56 as the toner in the developing device 56 is consumed. Consumption of toner in the developing device 56 is indirectly detected by an optical sensor (toner concentration sensor, not shown) facing the photosensitive drum 54.
Thereafter, the surface of the photosensitive drum 54 developed by the developing device 56 reaches a portion facing the primary transfer portion 58. At this position, the toner image on the photosensitive drum 54 is transferred onto the intermediate transfer member 52. At this time, a small amount of untransferred toner that is not transferred to the intermediate transfer member 52 remains on the photosensitive drum 54. Then, the surface of the photosensitive drum 54 having untransferred toner that has passed through the primary transfer portion 58 reaches a portion facing the cleaning portion 59, and the untransferred toner is cleaned by the cleaning portion 59 by a cleaning blade that contacts the photosensitive drum 54. Collected in. The toner collected by the cleaning unit 59 is transported as waste toner toward the waste toner bottle 90 via a waste toner transport path (not shown).

  The surface of the photosensitive drum 54 that has passed through the cleaning unit 59 reaches a charge eliminating unit (not shown), where the potential on the surface of the photosensitive drum 54 is removed, and a series of image forming processes is completed. Then, the toner image formed by the yellow color image forming unit 51 y is transferred to the intermediate transfer member 52.

  Similarly, in order to form a color image composed of a plurality of colors, the intermediate transfer body 52 transfers the toner images of the respective colors from the magenta image forming unit 51m, the cyan image forming unit 51c, and the black image forming unit 51k. Is done. After a color toner image having a plurality of colors is formed on the intermediate transfer member 52, the toner image is conveyed to the secondary transfer unit 60 by the intermediate transfer member 52.

On the other hand, the transfer material P conveyed to the secondary transfer unit 60 operates as follows.
First, one of the plurality of paper feeding units 61, 62, and 63 of the printer 50 is automatically or manually selected. For example, when the upper paper supply unit 61 is selected, one of the transfer materials P stored in the paper supply unit 61 is conveyed toward the position of the conveyance path K. Thereafter, the material to be transferred P that has passed through the conveyance path K reaches the position of the registration roller, and the material to be transferred P is subjected to the secondary transfer at a timing in order to align with the toner image on the intermediate transfer member 52. It is conveyed toward the part 60.
After the transfer process, the transfer material P passes through the position of the secondary transfer unit 60 and then reaches the fixing unit 64 through the conveyance path. At this position, the unfixed toner image on the transfer material P is fixed by heat and pressure. Thereafter, the transfer material P after the fixing process is discharged from the printer 50 as an output image. In this way, a series of image forming processes is completed.

[Developer flow]
Next, the flow of the developer in the developing device 56 will be described with reference to FIG.
Inside the developing device 56, a conveying member (screw) that conveys and stirs a developer composed of toner and a carrier, and a developing unit that has a function of developing the fresh latent image by supplying the developer to the image forming area. ing. The arrow in the figure indicates the developer conveyance path, that is, the flow.
The developer in the supply screw 71 is conveyed from the A end side to the B end side shown in FIG. 2 and is supplied from the supply screw 71 to the developing roller 74. Most of the developer in the supply screw 71 is supplied to the developing roller 74, but the excess part is not supplied to the developing roller 74 but is conveyed to the recovery screw 72.

The developing roller 74 has a ferromagnetic magnetic body therein, and a sleeve formed of a nonmagnetic material that is not in contact with the magnetic body. The sleeve has minute irregularities on the surface, and conveys the developer to the developing unit by rotating. The developer used for development in the developing unit is collected in the collection screw 72. The collection screw 72 collects excess developer from the developing roller 74 while conveying the developer from the A end side to the B end side in FIG. 2 and delivers it to the stirring screw 73 at the B end.
In consideration of the circulation of the developer, the stirring screw 73 always transports all the developer from the B end to the A end at regular intervals, and is provided with toner replenishment and toner concentration detection means. ing.

Since the supply screw 71, the recovery screw 72, and the stirring screw 73 are all rotating and transport the developer in the axial direction, the internal developer flows.
In a printer that requires a large amount of printing per unit time, when the amount of development per unit time by the developing device 52 is large, the rotational speed of the screw rotation shaft (screw shaft), which is a conveying member, inevitably increases.
The end of the rotating shaft of the screw is supported by a rolling bearing, but the bearing and its shaft seal are devised so that there is no problem even if it rotates at high speed (heat generation due to frictional heat, increased rotational resistance, etc.) There is a need.

Next, with reference to FIG. 3, a first embodiment of the bearing surrounding structure at the end of the screw will be described. In the first embodiment, the developer is conveyed toward the bearing portion 76 by the screw 80 and discharged from the discharge port near the bearing portion 76 (arrow D). The developer conveyed by the screw 80 is the bearing. This is an example in which the present invention is applied to a structure that is pushed toward the portion 76.
The bearing portion 76 according to the first embodiment includes a bearing 78 and a shaft seal portion 85 (a shaft seal portion formed by G seals 83a and 83b).
At the end of each of the supply screw 71, the recovery screw 72, and the stirring screw 73 of the developing device shown in FIG. 2, an auxiliary screw (reverse conveying screw in the first embodiment) 81 is provided at the end of the screw 80, and a flange ( Disc) 75. The flange 75 is arranged so that the shaft of the screw 80 passes through the center of the flange 75. The flange 75 is a shielding plate against the developer flow toward the shaft seal portion 85, and there is a gap g between the outer periphery thereof and the inner surface of the housing 82. The flange 75 is a non-contact type sealing plate with respect to the housing 82.

  The developer conveyance direction at the screw end shown in FIG. 3 is the direction of arrow C. In this case, the developer is delivered to the adjacent screw through the conveyance path direction of arrow D. The conveying direction of the auxiliary screw 81 is the direction of arrow E, thereby pushing back the developer flow in the direction of arrow C by the screw 80 in the opposite direction, thereby avoiding the developer colliding with the flange 75 vigorously, It is prevented from flowing into the shaft seal part vigorously.

Further, the flange 75 is provided with a sheet-like magnet 77 on a surface orthogonal to the screw axis. There is a small gap g between the sheet magnet 77 and the outer periphery of the flange 75.
The flange 75 rotates at the same speed as the screw 80, and the developer is conveyed in the direction of arrow C by the screw 80 and discharged in the direction of arrow D. In this state, the developer flow from the screw 80 side to the shaft seal portion 85 is stopped by colliding with the flange 75 and further captured by the magnetic force between the sheet-like magnet 77 and the magnetic ring 79. Even if the developer collides with the flange 75, the developer is pulled by the magnetic force of the sheet magnet 77 and the magnetic ring 79, and the movement thereof is suppressed, resulting in a movement like a fluid having a high viscosity. Therefore, the developer can be sealed, and the developer can be prevented from flowing into the bearing portion 76 side.
In FIG. 3, the sheet-like magnet 77 is provided on the back side (shaft seal portion 85 side) of the flange 75 when viewed from the main developer flow direction (arrow C direction). Is obtained.

  The developer contains a carrier and a toner, and when these are subjected to a large load, their properties tend to deteriorate. In order to prevent such deterioration, the gap between the rotating object (for example, the screw 80 and the flange portion 75) and the stationary object (for example, the housing 82) should be large. On the other hand, in order to prevent the developer from entering the vicinity of the first G seal 83a of the shaft seal portion 85, the gap g is preferably narrow. In view of the above, the size of the gap is preferably about 0.8 to 2 mm.

In Example 1, the peripheral speed of the outer periphery of the flange 75 is 650 to 850 mm / sec.
The size ga of the gap g between the magnetic body ring 79 and the flange 75 is appropriately set in the range of 1.2 to 0.9 mm.

  Further, when the developer held on the sheet-shaped magnet 77 rubs against a portion other than the magnetic ring 79, the toner that is not held by the magnetic force is separated, and only the toner is separated and attached to the rubbed surface. This is a phenomenon that occurs particularly in places with a large sliding load. From this point of view, it is desirable that the width of the magnetic ring 79 is larger than the width of the developer formed by the sheet magnet 77.

If the magnetic force of the sheet-like magnet 77 is too weak, the capturing force for the developer is insufficient, and therefore the sealing performance by the developer captured in the gap g is insufficient. On the other hand, if the magnetic force is too strong, there will be no seal deficiency due to insufficient capture force, but the captured developer is compressed with strong magnetic force or the like, and its internal pressure increases, so the developer layer in the gap g There arises a problem that an internal shear resistance (a shear resistance in the rotational direction generated with the rotation of the flange 75) is generated, resulting in a rotational resistance of the screw shaft.
Therefore, it is preferable that the sealing performance by the developer trapped in the gap g is not insufficient.

[Confirmation test for developer aggregation]
In Example 1, the size ga of the gap g on the outer periphery of the flange 75 was set in several steps within a range of 0.4 to 2.0 mm. As a result, “whether there is an aggregate in the developer? And “whether the developer flows in the vicinity of the toner seal (near the center of the sheet magnet 77)”. The result is as shown in FIG. The presence or absence of agglomerates is confirmed by checking whether defects occur as white spots during printing, and the seal effect on the developer is actually disassembled after the operation is completed, and the developer accumulates. We investigated whether or not. What was judged to be good by this investigation was a state in which the background portion of the screw shaft end could be confirmed even if there was some contamination of the screw shaft end due to the scattering of the developer.

  Further, when the developer captured by the sheet magnet 77 rubs against a portion other than the magnetic ring 79, the toner that adheres to the rubbing surface but is not strongly captured by the magnetic force is separated from the adhering surface. End up. This is a phenomenon that occurs at a location where the rubbing force against the developer trapped by the magnetic force of the sheet magnet 77 is particularly large. From this point of view, the magnetic ring 79 has a width larger than the width of the developer formed by the sheet magnet 77.

Next, Example 2 will be described with reference to FIG.
In the second embodiment, the developer is introduced in the vicinity of the bearing portion 76 (arrow D ′), and this is conveyed in the direction away from the bearing portion 76 by the screw 80 ′ (arrow F). This is an example in which the present invention is applied to a structure in which the agent is piled up and may be pushed toward the bearing portion 76, and the flow direction of the developer is opposite to that in Example 1, in which the screw conveyance direction is opposite. The route is different. And in Example 2, the conveyance direction by auxiliary screw 81 and the conveyance direction by screw 80 'correspond.
Before describing the second embodiment, a description will be given with reference to the technical background of the second embodiment.
FIG. 5 shows an example in which the bearing portion of Patent Document 1 is simply applied to a conventional screw.
The bearing portion 76 in this conventional example includes a bearing 78 and a shaft seal portion 85 (a shaft seal portion formed by the first G seal 83a and the second G seal 83b), and is inserted into the housing 82 from the direction of the arrow D ′. The developed developer is conveyed in the direction of arrow F by the screw 80 ′ and pushed away from the G seal 83 of the bearing portion 76.
If the input amount per unit time is increased due to a high printing speed or the like, the conveyance speed in the F direction by the screw 80 'becomes high. In this case, the rotational speed of the screw shaft becomes high, and the generation of frictional heat due to the friction with the lips of the first and second G seals 83a and 83b is significant. Therefore, the first G seal 83a When the developer enters the sliding portion between the screw 80 and the shaft end portion of the screw 80, there is a high possibility that the toner will be aggregated, and there is a high possibility that the print image quality will be deteriorated due to the mixing of the aggregated toner.

  On the other hand, in FIG. 5, when a large amount of developer flows from the direction of the arrow D ′, the developer piles up at the end of the screw 80 ′, and the possibility that the developer enters the first G seal 83 a increases. And such penetration | invasion of a developer is accelerated | stimulated because a developing agent exists in high density around. Therefore, it is necessary to prevent the above-described adverse effects caused by the developer entering and aggregating into the sliding portion between the first G seal 83a and the shaft end portion of the screw 80 '. Therefore, it is necessary to prevent a high-density developer from being present on the first G seal 83a. Example 2 is for this purpose.

In Example 2 of FIG. 4, a flange 75 having a sheet magnet 77 is provided adjacent to the bearing portion 76 of FIG. 5, and a magnetic ring is provided on the inner surface of the housing 82 so as to face the outer periphery of the flange 75. In this example, there is an auxiliary screw between the flange 75 and the screw 80 '.
The conveyance direction of the auxiliary screw 81 is the same as the conveyance direction of the main screw 80 ′. That is, the spiral direction of the screw 80 ′ of the second embodiment is the opposite direction to the screw 80 of the first embodiment, and the transport direction (arrow F direction) by the screw 80 ′ coincides with the transport direction of the auxiliary screw 81. . Even if a large amount of developer flows in from the adjacent screw so as to overflow from the direction of the arrow D ′, it is pushed from the flange 75 by the auxiliary screw 81 even if the developer is piled up at the end of the screw 80 ′. Since they are separated, it is avoided to enter the gap g between the outer periphery of the flange 75 and the magnetic ring 79. For this reason, the sealing effect by the seal | sticker by the developer trapped with the magnetic force between the flange 75 and the magnetic body ring is high, and the penetration | invasion of the developer to the 1st G seal 83a is prevented reliably.

For example, a flange 75 and a circular sheet shape for blocking the flow path of the developer and preventing the developer from flowing into the configuration of FIG. 5 (that is, the configuration described in Patent Document 1). However, it is still impossible to prevent the developer from sufficiently entering the bearing. Further, in the configuration of FIG. 5 (configuration described in Patent Document 1), a flange 75 for blocking the flow path of the developer and preventing the developer from flowing vigorously and a sheet shape that is a circular sheet shape. In addition to the configuration in which the magnet 77 is provided, the pitch of the portion near the bearing portion of the conveying screw 80 is narrowed (for example, as shown by reference numeral 81 in FIG. Even in the configuration in which the pitch is reduced), it cannot be said that the developer can be sufficiently sealed. In contrast, by providing a magnetic ring 79 on the outer periphery of the flange 75 to form a strong magnetic force, the effect of sealing the developer can be enhanced, and as a result, the developer enters the bearing. This can be prevented sufficiently.
Further, in the configuration of FIG. 5 (configuration described in Patent Document 1), a flange 75 for blocking the flow path of the developer and preventing the developer from flowing vigorously and a sheet shape that is a circular sheet shape. In addition to the configuration in which the magnet 77 is provided, the pitch of a part of the screw is made narrower than the pitch of the other screws, and the magnetic ring is provided on the outer periphery of the flange (for example, the magnetic ring in the configuration of FIG. 3). 79), the effect of sealing the developer is further enhanced.

In summary, the developer is transported between the flange provided at the screw end, the sheet magnet provided at the flange, and the screw end in the direction of the magnet sheet provided further on the end side than the flange. And a housing surrounding the screw, and a magnetic ring is provided on the inner surface of the housing so as to face the outer periphery of the flange, so that the flow of developer toward the shaft seal portion is stagnated by the flange. It causes the effect of weakening. Further, a minute annular gap is formed between the sheet-like magnet and the magnetic ring, and the developer is captured in the annular gap by the circumferential magnetic force formed by the sheet-like magnet and the magnetic ring, A developer seal is formed. That is, the developer is adsorbed on the outer periphery of the sheet magnet, and the magnetic ring is magnetized by the influence of the sheet magnet and adsorbs the developer itself, so that it is trapped in the annular gap. Since the developer is firmly fixed by both the inner and outer peripheral surfaces of the gap, the developer is not pulled away from the gap by the rotation of the flange and is strongly held. Therefore, the sealing effect by the developer is extremely high.
Therefore, it is possible to prevent the developer from entering the bearing portion.

  The above-mentioned seal with developer means a seal means in which the developer is captured by a magnetic force in a minute annular gap between the outer periphery of the flange provided with the magnet and the inner surface of the housing, and the gap is sealed by the captured developer. To do.

56: developing device 71: supply screw 72: recovery screw 73: stirring screw 74: developing roller 75: flange 76: bearing portion 77: sheet-shaped magnet 78: bearing
79: Magnetic body ring 80: Screw 81: Auxiliary screw 82: Housing 83: G seal 83a: First G seal 83b: Second G seal 85: Shaft seal

JP 2004-226695 A JP 2003-91157 A Japanese Patent Laid-Open No. 5-134540 Japanese Patent Laid-Open No. 11-7195 JP 2003-162146 A Japanese Patent Laid-Open No. 3-251882

Claims (5)

It has a screw that conveys the developer containing toner and magnetic carrier while stirring,
A housing surrounding the screw;
A bearing portion including a shaft seal portion and a bearing is provided adjacent to the screw end portion,
In the electrophotographic system, the shaft seal portion has a G seal on the screw side and a G seal on the bearing side, and the space between the G seal on the screw side and the G seal on the bearing side is filled with grease. In the developing device in the image forming apparatus,
A screw-shaped flange is provided on the screw shaft between the screw end and the shaft seal portion, and the flange is disposed so that the screw shaft passes through the center of the flange,
A sheet magnet is provided on the surface of the flange perpendicular to the direction of the axis of the screw;
A developing device in an electrophotographic image forming apparatus, comprising a magnetic ring, which is a ring of a magnet, on an inner surface of a housing facing an outer periphery of a radial side surface of the flange.   2. The screw includes an auxiliary screw that generates a conveying force in a direction toward the bearing portion and generates a conveying force in a direction opposite to the screw between the screw and the flange. The developing device according to 1.   2. The screw includes an auxiliary screw that generates a conveying force in a direction away from the bearing portion and generates a conveying force in the same direction as the screw between the screw and the flange. The developing device according to 1.   The developing device according to any one of claims 1 to 3, wherein the sheet magnet is magnetized so that the magnetic poles on the front surface and the back surface are different from each other.   5. The developing device according to claim 1, wherein different magnetic poles are alternately magnetized in the same plane of the sheet-like magnet. 6.

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