JP4546403B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus configured such that a developer including a toner and a magnetic carrier is supplied to a photoreceptor.

  2. Description of the Related Art Conventionally, as an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine using an electrophotographic system, an image forming apparatus configured such that a developer containing toner and a magnetic carrier is supplied to a photosensitive member. It has been known.

  FIG. 5 is a cross-sectional view showing a configuration of a conventional image forming apparatus provided with such a developing device. As shown in FIG. 5, a developing device 80 of a conventional image forming apparatus is generally provided with an agitation paddle 81 for agitating a developer, and adjacent to the agitation paddle 81. The agitation paddle rotates around a roller shaft. A magnetic roller 82 for supplying developer 3 agitated by 81 to the photosensitive member, and five suction magnets N1 to N3, S1 to S2 provided on the magnetic roller 82 and attracting the developer 3 to the cylindrical outer wall of the magnetic roller 82 And.

  Then, a repulsive magnetic field is created in the portion where the same poles are arranged side by side, that is, the portion where the N2 pole and the N3 pole are formed, and the developer 3 is separated, and the separated developer 3 is applied to the developing stirring unit 83 by gravity and centrifugal force. Moving. Therefore, in such an image forming apparatus 80, the central axis height of the stirring paddle 81 of the developer 3 is lower than the roller axis height of the magnetic roller 82 in consideration of separation of the developer from the magnetic roller 82. Is arranged.

  Further, for example, Patent Document 1 has at least two stirring paddles for transporting a developer composed of toner and a carrier in the axial direction, and a magnet is provided in the vicinity of the stirring paddle on the side where the toner is replenished. In addition, a technique of a developing device for an electrophotographic apparatus that reduces the occurrence of toner flying and toner fog is disclosed.

  In the developing device for an electrophotographic apparatus disclosed in the above-mentioned Patent Document 1 and the conventional developing device shown in FIG. 5, it is necessary to separate the developed developer into a developing agitation unit in which an agitation paddle is arranged. Gravity plays a big role as stress for separation. Therefore, it is desirable that the layout of the developing system is arranged such that the central axis height of the developer agitation paddle is lower than the horizontal with respect to the central axis height of the magnetic roller.

  Therefore, in the conventional developing device shown in FIG. 5 and the developing device for an electrophotographic apparatus disclosed in Patent Document 1, the stirring paddle must be disposed substantially horizontally with respect to the magnetic roller. There was a limit to reducing the space in the horizontal direction and making it compact. In particular, a color image forming apparatus often has a tandem configuration in which three color developing devices of yellow, cyan, and magenta or four color developing devices in which a black developing device is added to the three colors are arranged. For this reason, there has been a problem that the number of photoconductors and developing devices increases and the size of the image forming apparatus increases.

  Therefore, in order to reduce the space in the horizontal direction of the image forming apparatus and make it compact, in recent years, various layouts have been studied, and a structure in which the magnetic roller 92 and the stirring paddle 91 are arranged obliquely as shown in FIG. 6 is considered. ing.

FIG. 6 is a cross-sectional view showing a configuration of the image forming apparatus 90 in which the stirring paddle 91 is disposed at a position above the magnetic roller 92. With such a configuration, it is possible to arrange the adjacent photoconductor under the developing stirring unit 93, and to realize space saving of the image forming apparatus.
JP 2004-85687 A

  However, in the image forming apparatus 90 as shown in FIG. 6 described above, the stirring paddle 91 is disposed at a position above the magnetic roller 92, which is disadvantageous for separating the developer 3. As a result of the decrease in the amount of developer 3 circulating to the stirring paddle 91, the stirring of the developer 3 and the re-supply to the magnetic roller 92 become insufficient, and it is likely that printing defects and image density reduction are likely to occur on the photoreceptor. There was a problem.

  Also, in order to solve this problem, the developer pressure difference is increased by changing the size of the transport path on the developer feeding side and the return side, or by increasing the rotation speed of the stirring paddle, so that the pressure difference of the developer is increased upward from the magnetic roller. When trying to return the developer, pressure and stress are applied to the developer, which causes a new problem of deteriorating the developer.

  The present invention has been made in view of the above problems, and even when the stirring paddle is arranged at a position above the magnetic roller, the amount of the developer that deteriorates the developer or circulates from the magnetic roller to the stirring paddle. A compact image forming apparatus with a small installation area that can sufficiently prevent the occurrence of printing defects and image density reduction by sufficiently stirring the developer and re-supplying the magnetic roller without reducing The issue is to provide.

In order to solve the above problems, one image forming apparatus according to the present invention is configured to agitate a developer containing toner and a magnetic carrier and to supply the agitated developer to the photoreceptor. An image forming apparatus, comprising: a stirring paddle for stirring the developer; a developer stirring chamber for storing the developer; and a developer stirring chamber for storing the stirring paddle; A cylindrical magnetic roller rotatable about a substantially horizontal roller shaft, a plurality of suction magnets arranged inside the hollow of the magnetic roller and attracting the developer stirred by the stirring paddle to the cylindrical outer wall of the magnetic roller; and An agitation magnet provided on the agitation paddle for attracting the developer and rotating the attracted developer as the agitation paddle rotates; and a magnetic roller about the agitation paddle; A rear magnet provided in the vicinity of the stirring paddle in the opposite direction, and the magnetic roller rotates about the roller shaft while rotating and circulating the developer attracted to the outer wall of the cylinder by the attraction magnet The developer is supplied to the photosensitive member, and the stirring paddle supplies the developer attracted by the stirring magnet to the magnetic roller from the developer stirring chamber with the rotation, and from the magnetic roller, The developer that has not been supplied to the photosensitive member is attracted by the stirring magnet and conveyed to the developer stirring chamber, and the stirring magnet and the rear magnet are in close proximity to each other so that the same poles face each other. The image forming apparatus is characterized in that the directions of each N pole and S pole are oriented.

According to engagement Ru images forming apparatus to the present invention, magnetic stirring of agitation paddles, because the attracted developer is rotated with rotation of the stirring paddles along with attract developer, the developer agitating paddle As a result of being able to pump upward, even if the stirring paddle is arranged further upward, stirring is not insufficient.

  In addition, since the directions of the N pole and the S pole are oriented so that the same poles face each other in the state where the stirrer magnet and the rear magnet are closest to each other, between the stirrer magnet and the rear magnet As a result, the magnetic field is weakened at the place where the same poles face each other. As a result, the developer pumped up by the stirring magnet of the stirring paddle can be easily separated and stirred again by the stirring paddle.

  In these image forming apparatuses, it is preferable that the magnetic roller is provided obliquely below the stirring paddle.

  In this case, since the magnetic roller is provided obliquely below the stirring paddle, the lateral dimension can be shortened, so that the installation area of the image forming apparatus can be reduced. become.

  Here, it is preferable that the plurality of attracting magnets are arranged inside the hollow of the magnetic roller so that the directions of the N pole and the S pole are substantially radial around the roller axis of the magnetic roller.

  In this way, since the plurality of attracting magnets are arranged in the hollow interior of the magnetic roller so that the direction of the N pole and the S pole is substantially radial about the roller axis of the magnetic roller, the cylindrical outer wall of the magnetic roller As a result, the developer can be supplied from the stirring paddle to the photosensitive member effectively and reliably.

  Further, the magnetic field formed by the plurality of attraction magnets is formed on the cylindrical outer wall of the magnetic roller on the stirring paddle side, and the same-polarity magnetic field region in which the directions of the N poles and S poles of the adjacent attraction magnets on both sides are the same. It is preferable that a different polar magnetic field region formed on the cylindrical outer wall of the magnetic roller outside the homopolar magnetic field region and having different N-pole and S-pole directions of adjacent attracting magnets on both sides is preferably provided.

  In this way, in the different magnetic field regions in which the directions of the N and S poles of the adjacent attracting magnets on both sides are different, the magnetic field is strengthened, so that the developer attracted to the cylindrical outer wall of the magnetic roller is effectively used. In addition, it can be reliably conveyed.

  Further, in the same magnetic field region where the directions of the N and S poles of the adjacent attracting magnets on both sides are the same, the magnetic field is weakened, so that the developer attracted to the cylindrical outer wall of the magnetic roller can be easily separated. Then, it becomes possible to stir again with the stirring paddle.

  As described above, according to the present invention, the developer is deteriorated even when the layout of the developing device is limited, such as the stirring paddle being disposed at a position higher than the magnetic roller in accordance with space saving. Without reducing the amount of developer circulating from the magnetic roller to the agitation paddle, the developer should be sufficiently agitated, re-supplied to the magnetic roller, and separated from the magnetic roller. As a result, it is possible to obtain a good image that does not cause a printing defect or a decrease in image density. Therefore, there is a remarkable effect that a compact image forming apparatus with a small installation area can be realized.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a conceptual view of an image forming apparatus 1 according to an embodiment of the present invention as viewed from the side, and FIG. 2 is a cross-sectional view of the developing device 2 of the image forming apparatus 1 as viewed from the side. FIG. 3 is a conceptual diagram showing the arrangement of the magnets in the developing device 2, and FIG. 4 is a perspective view showing the configuration of the stirring paddle 5.

  Referring to FIG. 1, the illustrated image forming apparatus 1 according to the embodiment of the present invention is a tandem developing type color image forming apparatus. In the image forming apparatus main body 1a, four developing devices 2 and The photosensitive member 21 includes an OPC photosensitive member, an a-Si photosensitive member, and the like, and can hold an electrostatic latent image by being charged, and an exposure unit 27.

  The image forming apparatus 1 also charges the paper feed cassette 24 that stores the paper 23 that is a recording medium, the transport belt 25 that transports the paper 23 from the paper feed cassette 24, the developer container 26, and the photosensitive member 21. A charging device 22 for transferring the toner image, a transfer device 28 for transferring the toner image on the photosensitive member 21 to a recording medium by a transfer bias, and fixing the transferred toner image on the paper 23 onto which the toner images of the respective colors are sequentially transferred. And a fixing device 29.

  The image forming apparatus 1 sequentially transfers the toner images of the respective colors onto the paper 23 via the developing device 2, the photosensitive member 21, the exposure unit 22, and the transfer device 28, and fixes the toner images. The apparatus 29 is configured to fix and discharge the paper.

  Here, the developing device 2 is a device configured to form an image on the surface of the photosensitive member 2 by stirring the developer 3 and supplying it to the photosensitive member 2, as shown in FIG. In the housing 4 configured to accommodate the developer 3, the stirring paddle 5 for stirring the developer 3, the stirring mixer 6 for stirring and mixing the developer 3 in the stirring paddle 5, and the stirring paddle 5 are adjacent to each other. And a developing roller 8 for supplying the developer 3 to the photosensitive member.

  Further, as shown in FIG. 3, the developing device 2 is provided between a plurality of attracting magnets N1 to N3 and S1 to S2 provided inside the hollow of the magnetic roller 7, and between the stirring paddle 5 and the magnetic roller 7. The intermediate magnet 9 is provided. The developing device 2 further includes a stirring magnet 10 provided in the stirring paddle 5 and a rear magnet 11 provided in the vicinity of the stirring paddle 5 in the direction substantially opposite to the magnetic roller 7 with the stirring paddle 5 as a center. I have.

  The developer 3 is a developer called a so-called two-component developer containing a toner and a magnetic carrier. In this embodiment, the magnetic carrier is 106 Ωcm to 109 Ωcm, the saturation magnetization is 70 emu / g, the average A ferrite carrier having a particle size of 35 μm is employed. Further, the mixing ratio of the toner and the carrier of the developer 3 is about 2 to 40% by weight of the toner with respect to the total amount of the toner and the carrier.

  The housing 4 is a container capable of holding the developer 3 provided facing the photoconductor 21, and the housing 4 is a first developer containing a stirring paddle 5 at a position adjacent to the magnetic roller 7. There is a stirring chamber 4a and a second developer stirring chamber 4b that is partitioned by the first developer stirring chamber 4a and the partition wall 4c and contains the stirring mixer 6, and the first developer stirring chamber 4a The second developer stirring chamber 4b communicates with both ends of the magnetic roller 7 in the axial direction. Further, the housing 4 is provided with a spike cutting blade 4e for regulating the amount of the developer 3 adsorbed on the magnetic roller 7.

  The stirring paddle 5 stirs the developer 3 and transports the developer 3 in the axial direction. As shown in FIG. 4, the screw-like paddle portion 5a capable of stirring and transporting the developer and the stirring paddle 5 and a stirring magnet 10 provided along the longitudinal direction. The stirring paddle 5 is configured to be rotationally driven in the direction indicated by the arrow around the stirring paddle shaft 5b by a driving means (not shown).

  Although not shown in detail, the agitating mixer 6 agitates the developer 3 and conveys the developer 3 in the axial direction, similarly to the agitating paddle 5. The stirring mixer 6 is also configured to be driven to rotate around the stirring paddle shaft 5b in the direction indicated by the arrow by a driving means (not shown). In the case of the stirring mixer 6, however, the stirring mixer 6 is opposite to the stirring paddle 5. The direction of rotation is set so as to convey the developer 3 in the direction, so that the developer 3 circulates between the first developer agitating chamber 4a and the second developer agitating chamber 4b. Yes.

  The magnetic roller 7 is a cylindrical member that is provided adjacent to the stirring paddle 5 and is rotatable about a substantially horizontal roller shaft. By rotating about the roller shaft, the magnetic roller 7 is disposed inside the magnetic roller 7. The developer 3 is supplied from the stirring paddle 5 to the developing roller 8 while rotating and circulating the developer 3 attracted to the outer wall of the cylinder by the suction magnets N1 to N3 and S1 to S2 arranged to be stationary.

  A DC bias voltage can be applied to the magnetic roller 7.

  In these image forming apparatuses 1, the magnetic roller 7 is provided obliquely below the stirring paddle 5.

  As the developing roller 8, a cylindrical body made of anodized aluminum, a cylindrical body made of phenol resin, or a resin layer formed on the surface of an aluminum cylindrical body is used, and a bias voltage is applied. The developer 3 can be supplied from the developing roller 8 to the photoconductor 21.

  The developing roller 8 is disposed so as to be close to the magnetic roller 7 and the photosensitive member 21 at different portions, and a DC bias voltage applied to the magnetic roller 7 and a DC bias applied to the developing roller 8. A thin layer of toner only is formed on the developing roller 8 by a potential difference from the voltage.

  The plurality of attraction magnets N1 to N3 and S1 to S2 are disposed so as to be stationary inside the hollow of the magnetic roller 7, and attract the developer 3 stirred by the stirring paddle 5 to the cylindrical outer wall of the magnetic roller 7. The magnetic roller 7 is disposed in the hollow interior of the magnetic roller 7 and fixed to the developing device 2 so that the direction of the N pole and the S pole is substantially radial about the roller axis of the magnetic roller 7.

  These attraction magnets N1 to N3 and S1 to S2 have a five-pole structure, and a magnetic field to be formed is formed on the cylindrical outer wall of the magnetic roller 7 on the stirring paddle 5 side, and adjacent attraction magnets N1 to N3 and S1 on both sides. Are formed on the cylindrical outer wall of the magnetic roller 7 on the outer side of the homopolar magnetic field region where the directions of the N and S poles of S2 to S2 are the same, and adjacent magnets N1 to N3 and S1 on both sides. To S2 are different polar magnetic field regions in which the directions of the N and S poles are different.

  The developer 3 can be separated from the magnetic roller 7 by generating a repulsive magnetic field in the same magnetic field region in which the same poles are arranged side by side, in this case, the portions that are the N2 and N3 poles.

  The intermediate magnet 9 is a magnet disposed between the stirring paddle 5 and the magnetic roller 7, and the intermediate magnet 9 is attracted to the stirring paddle 5 side among the plurality of suction magnets N1 to N3 and S1 to S2. The directions of the north and south poles are oriented so that the same poles as the magnets N2 and N3 face each other.

  Since the intermediate magnet 9 repels between the N2 pole, the N3 pole, and the intermediate magnet 9 in this way, it has the effect of preventing the developer 3 pumped up from the N2 pole from going to the N3 pole. .

  The stirring magnet 10 attracts the developer 3 and rotates the attracted developer 3 as the stirring paddle 5 rotates. The stirring magnet 10 is in a state closest to the intermediate magnet 9. The directions of the N pole and the S pole are oriented so that the same poles as the intermediate magnet 9 face each other. The stirring magnet 10 is provided on the entire length of the stirring paddle 5 with respect to the stirring paddle 5 using a double-sided tape, an adhesive, or the like.

  The rear magnet 11 is provided in the vicinity of the stirring paddle 5 in a direction substantially opposite to the magnetic roller 7 with the stirring paddle 5 as the center. The rear magnet 11 is provided with the stirring magnet 10 provided in the stirring paddle 5. In the state closest to the rear magnet 11, the directions of the north and south poles are oriented so that the same poles as the stirring magnet 10 face each other.

  Thus, by arranging the rear magnet 11 so as to face the stirring magnet 10 and have the same polarity, the developer 3 attracted by the stirring magnet 10 is not transported to the intermediate magnet 9 by the rear magnet 11. It is configured so that it can be peeled off.

  The agitating magnet 10, the intermediate magnet 9, and the rear magnet 11 increase the rotational torque of the magnetic roller 7 and the agitating paddle 5 or hinder the flow and agitating of the developer 3 if the magnetic force is increased too much. The magnetic force is normally set to about 50 to 300 gauss. When it is required to increase the speed of the developing device, it is set to around 500 gauss.

  Next, with reference to FIG. 2 and FIG. 3, the operation of the image forming apparatus 1 according to the embodiment of the present invention will be described.

  First, the procedure for stirring in a single unit of the developing device 2 is as follows. That is, the developer 3 is conveyed and agitated in the first developer agitating chamber 4a and the second developer agitating chamber 4b, the toner distribution in the developer 3 is maintained uniformly, and the toner and A predetermined charge is imparted to the toner by frictional charging with the carrier.

  The stirred developer 3 is supplied to the magnetic roller 7 by the stirring paddle 5, and the magnetic roller 7 magnetically attracts the developer 3 to form a magnetic brush of the developer 3 composed of toner and carrier, The developer 3 is conveyed to a position facing the developing roller 8 by rotation.

  An electric field is formed between the developing roller 8 and the magnetic roller 7 by the DC voltage to the developing roller 8 and the DC voltage of the magnetic roller 7, and the positively charged toner is transferred to the developing roller 8. A toner layer is formed on the surface. On the other hand, the carrier remains magnetically attracted to the magnetic roller 7 without being transferred.

  Here, the toner layer formed on the developing roller 8 is conveyed to the developing region by the rotation of the developing roller 8, and the direct current voltage applied to the developing roller 8 and the alternating current due to the rectangular wave applied at the time of development are superimposed. The bias flies within the electrostatic field between the photosensitive member 21 and the developing roller 8 and adheres to the surface of the photosensitive member 21 for development.

  In the image forming apparatus 1 according to the embodiment of the present invention, by performing such a development process corresponding to each color such as yellow, cyan, magenta, and black, it is possible to form a color image. Yes.

  Here, the action of each magnet in the developing device 2 is as follows.

  That is, first, in the stirring paddle 5, the stirring magnet 10 attracts the developer 3 and rotates the attracted developer 3 as the stirring paddle 5 rotates. In contrast, the developer 3 is easily separated when it comes near the intermediate magnet 9 because it is disposed in the same pole.

  Further, when the stirring paddle 5 is further rotated thereafter, the stirring magnet 10 passes through the intermediate magnet 9 and approaches the region where the developer 3 separated from the N2 pole of the magnetic roller 7 stays. Since the stirring magnet 10 has already separated the developer 3 by the intermediate magnet 9, the developer 3 can be easily attracted again.

  Since the rear magnet 11 is also arranged so as to face the stirring magnet 10 and have the same polarity, the stirring magnet 10 does not carry the attracted developer 3 to the intermediate magnet 9 and moves the rear magnet 11. Are separated in the vicinity of After that, if the stirring magnet 10 passes the rear magnet 11 by the rotation of the stirring paddle 5, the developer 3 that has been sufficiently stirred with the toner in the developing stirring section is again sucked, and development sufficient for development is performed. The agent 3 can be supplied to the magnetic roller 7.

  In the magnetic roller 7, a plurality of attracting magnets N <b> 1 to N <b> 3, S <b> 1 to S <b> 2 attract the developer 3 to the cylindrical outer wall of the magnetic roller 7 and convey it to the developing roller 8. The developer 3 is separated from the magnetic roller 7 in the magnetic field region, that is, the portion where the N2 pole and the N3 pole are here.

  At this time, the intermediate magnet 9 repels the N2 pole and the N3 pole so that the developer 3 pumped up from the N2 pole does not go to the N3 pole.

  As described above, according to the image forming apparatus 1 according to the embodiment of the present invention, the attracting magnets N1 to N3 and S1 to S2 attract the developer 3 to the cylindrical outer wall of the magnetic roller 7, and the magnetic roller 7 is While the attracted developer 3 is rotated and circulated, the developer 3 is supplied from the stirring paddle 5 to the photoconductor. At this time, the same polarity of the intermediate magnet 9 and the attracting magnets N1 to N3 and S1 to S2 are provided. Since the magnetic field is weakened at a location where the developer 3 faces, the developer 3 is easily separated from the cylindrical outer wall of the magnetic roller 7. As a result, the developer 3 pumped upward by the magnetic roller 7 can be easily refluxed to the upper stirring paddle 5. Then, the separated developer 3 is stirred again by the stirring paddle 5 and can be supplied again to the magnetic roller 7.

  Further, since the developer 3 pumped upward by the magnetic roller 7 can be easily refluxed to the upper stirring paddle 5, even when the stirring paddle 5 is disposed at a position higher than the magnetic roller 7, The developer 3 can be sufficiently stirred and re-supplied to the magnetic roller 7 without deteriorating the developer or reducing the amount of the developer 3 circulating from the magnetic roller 7 to the stirring paddle 5. As a result, it is possible to prevent printing failure and image density reduction. Therefore, a compact image forming apparatus 1 with a small installation area can be realized.

  Further, according to the image forming apparatus 1, the stirring magnet 10 of the stirring paddle 5 attracts the developer 3 and rotates the attracted developer 3 as the stirring paddle 5 rotates. As a result of being able to pump up above the stirring paddle 5, even if the stirring paddle 5 is arranged further upward, the amount of the developer 3 circulating from the magnetic roller 7 to the stirring paddle 5 does not decrease, and the developer 3 Stirring can be sufficiently performed.

  Also, since the stirring magnet 10 of the stirring paddle 5 is closest to the intermediate magnet 9, the direction of the N pole S pole is oriented so that the same polarity as the intermediate magnet 9 faces each other. In the place where the same poles between the magnet 10 and the intermediate magnet 9 face each other, the magnetic field is weakened. As a result, the developer 3 pumped upward by the stirring magnet 10 of the stirring paddle 5 is easily separated and the cylinder of the magnetic roller 7 is separated. It can be moved to the outer wall.

  Further, according to the image forming apparatus 1, the agitating magnet 10 provided in the agitating paddle 5 is in the state of being closest to the aft magnet 11 so that the same polarity as the agitating magnet 10 faces N. Since the direction of the pole S-pole is oriented, the magnetic field is weakened in the place where the same poles between the stirring magnet 10 and the rear magnet 11 face each other. As a result, the stirring magnet 10 of the stirring paddle 5 is pumped upward. The developer 3 can be easily separated and stirred again with the stirring paddle 5.

  Further, since the magnetic roller 7 is provided obliquely below the stirring paddle 5, the lateral dimension can be shortened, so that the installation area of the image forming apparatus 1 can be reduced. Become.

  In addition, since the plurality of attracting magnets N1 to N3 and S1 to S2 are arranged in the hollow interior of the magnetic roller 7 so that the direction of the N pole S pole is substantially radial around the roller axis of the magnetic roller 7, The magnetic field that attracts the developer 3 can be formed over the entire circumference of the cylindrical outer wall of the magnetic roller 7, and as a result, the developer 3 can be effectively and reliably supplied from the stirring paddle 5 to the photosensitive member. .

  Further, in the different magnetic field regions in which the directions of the north and south poles of the adjacent attracting magnets N1 to N3 and S1 to S2 on both sides are different, the magnetic field is strengthened, and as a result, the development attracted to the cylindrical outer wall of the magnetic roller 7 The agent 3 can be conveyed effectively and reliably.

  Further, in the same magnetic field region where the directions of the N poles and S poles of the adjacent attracting magnets N1 to N3 and S1 to S2 on both sides are the same, the magnetic field is weakened, so that it is attracted to the cylindrical outer wall of the magnetic roller 7. The developer 3 can be easily separated and stirred again with the stirring paddle 5.

  The above-described embodiment is merely a preferred specific example of the present invention, and the present invention is not limited to the above-described embodiment.

  For example, the image forming apparatus 1 according to the embodiment of the present invention includes a photoconductor 21, a paper feed cassette 24, a transport belt 25, a developer container 26, a charger 27, a transfer device 28, and a fixing device 29 as shown in FIG. It is not limited to the configuration. Further, the developer 3 is not limited to one using a ferrite carrier having 106 Ωcm to 109 Ωcm, a saturation magnetization of 70 emu / g, and an average particle size of 35 μm. Any image forming apparatus of a tandem development type that employs a developer containing toner and a magnetic carrier can be applied to various image forming apparatuses.

  Further, the developing device 2 is not necessarily limited to the one provided with the developing roller 8. The present invention can also be applied to a system in which the developer 3 is directly supplied from the magnetic roller 7 to the photoreceptor 21.

  Further, the plurality of attracting magnets do not necessarily have five poles, and the number is arbitrary.

  Moreover, the stirring mixer 6 is not necessarily required, and the design of the stirring unit can be changed in various ways.

  In addition, it goes without saying that various design changes are possible within the scope of the claims of the present invention.

1 is a conceptual view of an image forming apparatus according to an embodiment of the present invention as viewed from the side. 1 is a conceptual view of a developing device of an image forming apparatus according to an embodiment of the present invention as viewed from the side. It is a conceptual diagram which shows arrangement | positioning of each magnet in a developing device. It is a perspective view which shows the structure of a stirring paddle. It is sectional drawing which shows the structure of the image development apparatus of the conventional image forming apparatus. It is sectional drawing which shows the structure of the image development apparatus which has arrange | positioned the stirring paddle in the position above a magnetic roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Developer 5 Agitation paddle 7 Magnetic roller 9 Intermediate magnet 10 Agitation magnet 11 Back magnet 21 Photosensitive body N1-N3, S1-S2 Attraction magnet

Claims (5)

An image forming apparatus configured to stir a developer containing toner and a magnetic carrier, and to feed the stirred developer to a photoreceptor,
A stirring paddle for stirring the developer;
A developer stirring chamber for storing the developer and the stirring paddle;
A cylindrical magnetic roller provided obliquely below the stirring paddle and rotatable about a substantially horizontal roller shaft;
A plurality of attracting magnets arranged inside the hollow of the magnetic roller and attracting the developer stirred by the stirring paddle to the cylindrical outer wall of the magnetic roller;
An agitation magnet provided in the agitation paddle for attracting the developer and rotating the attracted developer with the rotation of the agitation paddle;
A rear magnet provided in the vicinity of the stirring paddle in the direction substantially opposite to the magnetic roller around the stirring paddle;
With
The magnetic roller rotates around a roller shaft to supply developer to the photoreceptor while rotating and circulating the developer attracted to the outer wall of the cylinder by the attraction magnet.
As the stirring paddle rotates, the developer attracted by the stirring magnet is supplied from the developer stirring chamber to the magnetic roller, and the developer that has not been supplied from the magnetic roller to the photosensitive member is supplied to the stirring paddle. Attracted by a stirring magnet and conveyed into the developer stirring chamber,
An image forming apparatus, wherein the stirrer magnet and the rear magnet are oriented closest to each other so that the same poles face each other in the state of being closest to each other. The plurality of attraction magnets are arranged in a hollow interior of the magnetic roller so that the directions of the N pole and the S pole are substantially radial about the roller axis of the magnetic roller. The image forming apparatus described. The magnetic field formed by the plurality of attracting magnets is
A homopolar magnetic field region formed on the cylindrical outer wall of the magnetic roller on the stirring paddle side and in which the directions of the north and south poles of the adjacent attracting magnets on both sides are the same,
A different-polarity magnetic field region formed on the cylindrical outer wall of the magnetic roller outside the same-polarity magnetic field region and having different N-pole and S-pole directions of adjacent attracting magnets on both sides,
The image forming apparatus according to claim 1, further comprising: In addition, an intermediate magnet disposed between the stirring paddle and the magnetic roller,
The stirrer magnet and the intermediate magnet are oriented in the direction of the north and south poles so that the same poles face each other in the state of being closest to each other as the stir paddle rotates. The image forming apparatus according to claim 1. When the stirring magnet enters the range of the magnetic field of the intermediate magnet with the rotation of the stirring paddle, the attracted developer is separated obliquely downward toward the magnetic roller, and the rotation of the stirring paddle If the developer passes through the intermediate magnet, the developer that has not been supplied from the magnetic roller to the photosensitive member is attracted.If the developer enters the magnetic field range of the rear magnet as the stirring paddle rotates, the developer is attracted. The image forming apparatus according to claim 4, wherein the developer is separated in the developer stirring chamber.

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