JP2008164684A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily supply developer to a rotatable sleeve from a supply magnet, and to easily remove the developer on the rotatable sleeve side by using a supply magnet. <P>SOLUTION: The developing unit 22 using magnetic developer includes a developing roller 31 and a supply roller 33. The developing roller 31 includes a developing magnet 36 and the rotatable developing sleeve 34. The developing magnet 36 has around a center shaft: a first pole 31a disposed opposite a photoreceptor drum 21; a second pole 31b and a third pole 31c, which are different from each other in magnetism and disposed on both sides of the first pole 31a; a fourth pole 31d and fifth pole 31e, which are the same as the first pole 31a in magnetism and disposed opposite the first pole and between the second and third poles 31b and 31c. The supply roller 33 is disposed opposite the developing roller 31, and has the supply magnet 37 and a supply sleeve 35. The supply magnet 37 has a sixth pole 33a disposed opposite the fourth pole 31d and fifth pole 31e and is the same as the first pole 31a in magnetism. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device, and more particularly to a developing device that is used in an image forming apparatus and forms an image on an electrostatic latent image carrier using a magnetic developer.

  The image forming apparatus includes an electrostatic latent image carrier and a developing device that supplies toner to the electrostatic latent image carrier. An image forming apparatus is known that supplies toner in a developing device to an electrostatic latent image carrier by a magnetic brush. As shown in FIG. 4, the developing device used in such an image forming apparatus has a developing roller 51 that faces the electrostatic latent image carrier 41 and a supply roller 53 that supplies developer to the developing roller 51. is doing. In the developing roller 51, the sleeve on the surface rotates in a direction opposite to the direction in which the electrostatic latent image carrier 41 rotates, and the developing roller 51 is moved from a position facing the electrostatic latent image carrier 41 as shown in FIG. A first S pole 51a, a second N pole 51b, a third S pole 51c, a fourth N pole 51d, and a fifth N pole 51e are arranged in this order in the direction opposite to the rotation direction. Here, FIG. 4 is a schematic view showing the configuration of the conventional supply roller 53 and developing roller 51. The supply roller 53 includes a sixth S pole 53a and a seventh S pole 53b at positions facing the fourth N pole 51d and the fifth N pole 51e, respectively, and the surface sleeve rotates in the same direction as the developing roller ( Patent Document 1).

In the developing device described in Patent Document 1, the developer attached to the sleeve on the surface of the supply roller 53 is transferred from the sixth S pole 53a to the fourth N pole 51d side. Then, the third S pole 51c, the second N pole 51b, and the first S pole 51a are conveyed in this order on the developing roller 51, and the toner is supplied to the electrostatic latent image carrier 41. When toner is supplied from the developing roller 51 onto the electrostatic latent image carrier 41 by the first S pole 51a, the developer that has not been supplied to the electrostatic latent image carrier 41 is conveyed to the fifth N pole 51e. The developer conveyed to the fifth N pole 51e is peeled off from the developing roller by the seventh S pole 53b.
JP 07-325477 A

  In the developing device described in Patent Document 1, since the sixth S pole 53a and the seventh S pole 53b having the same magnetism are arranged side by side, the eighth N pole is provided between the sixth S pole 53a and the seventh S pole 53b. Will occur naturally. For this reason, a part of the developer does not move from the fourth N pole 51d to the sixth S pole 53a, but moves from the sixth S pole to the eighth N pole. The developer conveyed from the sixth south pole to the eighth north pole moves from the eighth north pole to the seventh south pole 53b and rotates on the supply roller 53 again. In this case, since the amount of the developer supplied from the supply roller 53 to the developing roller 51 decreases, the supply amount of the developer to the electrostatic latent image carrier 41 decreases. Further, since the developer moving from the sixth south pole 53a to the eighth north pole is not peeled off from the supply roller 53, the same developer exists on the supply roller 53, and the developer may be deteriorated. .

  Further, since the fourth N pole 51d and the fifth N pole 51e having the same magnetism are arranged side by side, the ninth S pole may naturally occur between the fourth N pole 51d and the fifth N pole 51e. . In this case, the developer on the fourth N pole 51d side is not peeled off by the sixth pole 53a and is conveyed to the ninth S pole side. At this time, the same developer rotates again on the developing roller 51, and the developer may be deteriorated.

  An object of the present invention is to facilitate the supply of developer from a supply roller to a developing roller. In addition, the developer on the developing roller side is easily peeled off by the supply roller.

  A developing device according to a first aspect is a developing device that is used in an image forming apparatus and forms an image on an electrostatic latent image carrier using a magnetic developer, and a container main body that stores the magnetic developer therein. A developing roller provided in the container main body for supplying the electrostatic developer to the electrostatic latent image carrier for development, and a supply roller provided inside the container main body for supplying the magnetic developer to the developing roller. ing. The developing roller is a member that is non-rotatably supported by the container body and has a magnetic pole disposed around the central axis, and is at least on both sides of a position where the magnetic pole facing the electrostatic latent image carrier and the facing roller are opposed to each other. A developing magnet having a polar magnetic pole is disposed, and a developing sleeve that is rotatable around the central axis in a first direction around the developing magnet. The supply roller is a member that is disposed on the container main body so as not to rotate and is opposed to the developing sleeve, and a magnetic pole is disposed around the central axis, and is different from the magnetic pole on the developing roller side at a position facing the developing roller. A supply magnet in which the opposite polarity is arranged, and a supply sleeve that is rotatable around the central axis in the first direction on the outer periphery of the supply magnet.

  In this developing device, the developer attached to the supply sleeve is transported to a position corresponding to the opposite polarity different from the magnetic pole on the development roller side as the supply sleeve rotates, and the developer is moved to the development roller side. Then, as the developing sleeve rotates, the developer is conveyed to a position facing the electrostatic latent image carrier, and the developer is supplied to the electrostatic latent image carrier.

  Here, since the opposite polarity different from the magnetic pole on the developing roller side is arranged at the position facing the developing roller, the developer easily moves from the supply roller side to the developing roller side.

  A developing device according to a second aspect is the developing device according to the first aspect, wherein the supply magnet has a pumping magnetic pole having a polarity different from the opposite polarity arranged on the side opposite to the side where the developing roller is arranged. Also have.

  Here, the developer in the container body can be easily pumped by the pumping magnetic pole having a polarity different from the opposite polarity.

  A developing device according to a third aspect is the developing device according to the first or second aspect, wherein the opposed magnetic pole disposed at a position facing the developing roller of the supply magnet is located at a position facing the developing roller of the developing magnet. Of the arranged magnetic poles of the same polarity, the magnetic force is stronger than the upstream magnetic pole arranged upstream, and the magnetic force is weaker than the downstream magnetic pole arranged downstream of the opposing position.

  Here, the developer is easily conveyed from the downstream side to the upstream side of the opposed magnetic pole disposed at the position facing the developing roller of the supply magnet.

  A developing device according to a fourth aspect is the developing device according to any one of the first to third aspects, wherein the opposing magnetic pole of the supply magnet has a stronger magnetic force than the pumping magnetic pole.

  Here, it becomes easy to convey the developer from the pumping magnetic pole side to the opposing magnetic pole side of the supply magnet.

  The present invention can facilitate the supply of the developer from the supply roller to the developing roller. Further, the developer on the developing roller side can be easily peeled off by the supply roller.

[Constitution]
FIG. 1 shows a color printer 1 which is an image forming apparatus in which an embodiment of the present invention is adopted. FIG. 1 is a schematic diagram for showing the arrangement of each component, and details of each part are omitted.

  The color printer 1 is connected to a computer (not shown) or the like, and is a device that can print a color image on paper based on image information sent from the computer or the like.

  The color printer 1 includes an image forming unit 2 that forms a color image based on image information, a fixing unit 3 that fixes a toner image formed by the image forming unit 2 on a sheet, and an image forming unit 2 and a fixing unit 3. And a paper feed cassette (not shown) for feeding the paper to the paper transport unit 4 and a discharge unit 7 for discharging the paper on which the toner image is fixed.

  The image forming unit 2 is a part for forming a toner image, and includes a photosensitive drum 21 on which an electrostatic latent image is formed, four developing units 22 for forming a toner image, and image information. A laser unit 23 that scans and exposes the surface of the photosensitive drum 21, a charging device 24 that uniformly charges the surface of the photosensitive drum 21, and an intermediate transfer member 25 to which an image of the photosensitive drum 21 is transferred. And a secondary transfer roller 27 for transferring the image of the intermediate transfer member 25 onto the paper.

  The photosensitive drum 21 is disposed at the approximate center of the apparatus, and its rotation axis is provided so as to extend perpendicular to the paper surface of FIG.

  FIG. 2 shows an enlarged part of the developing unit 22. As shown in this figure, the developing device 22 is disposed around the photosensitive drum 21 and includes a developing device main body 22 a, a developing roller 31, and a supply roller 33.

  The four developing device bodies 22a are arranged around the photosensitive drum 21, and store toners of different colors of yellow, cyan, magenta, and black, respectively.

  The developing roller 31 is disposed so as to face the photoconductive drum 21 and rotates in a direction opposite to the direction in which the photoconductive drum 21 rotates (the same direction at the facing position). Further, the developing roller 31 has a hollow cylindrical developing sleeve 34 that can rotate about its axis on the surface, and two S-pole permanent magnets and three N-pole permanent magnets are provided inside the developing sleeve 34. A developing magnet 36 having

  Specifically, as shown in FIG. 3, the developing magnet 36 has a first pole 31 a (N pole) facing the photosensitive drum 21 and a first pole 31 a (on the rotation direction of the developing roller 31) on the downstream side. A second pole 31b (S pole), a third pole 31c (S pole) upstream of the first pole 31a (N pole), a fourth pole 31d (N pole) upstream of the third pole 31c, A fifth pole 31e (N pole) is provided downstream of the two poles 31b. Here, FIG. 3 is a schematic view showing the configuration of the developing roller 31 and the supply roller 33. The first pole 31 a is a portion for supplying toner to the photosensitive drum 21. The second pole 31b has a polarity (S pole) opposite to that of the first pole 31a so that toner and carrier are conveyed from the first pole 31a side. The fifth pole 31e is disposed at a position facing the supply roller 33, and has a polarity (N pole) opposite to that of the second pole 31b so that toner and carrier are conveyed from the second pole 31b side. ing. The fifth pole 31e is a part that delivers toner and carrier to the supply roller 33 side. The fourth pole 31d is disposed so as to face the supply roller 33, and has the same polarity (N pole) as the fifth pole 31e. Further, since a repulsive force acts between the fourth pole 31d and the fifth pole 31e, the toner and carrier on the fifth pole 31e side are not easily conveyed to the fourth pole 31d side. The third pole 31c is disposed between the fourth pole 31d and the first pole 31a, and has a polarity (S pole) opposite to that of the first pole 31a and the fourth pole 31d. For this purpose, the toner and carrier are conveyed from the fourth pole 31d side, and the toner and carrier are conveyed to the first pole 31a.

  The supply roller 33 is a member for supplying the toner and carrier in the developing device 22 to the developing roller 31 and rotates in the same direction as the developing roller 31 (opposite direction at the opposite position). The supply roller 33 is provided with a hollow cylindrical supply sleeve 35 that rotates about an axis on the surface, and the supply sleeve 35 includes two magnetic poles (sixth pole 33a and seventh pole 33b). A magnet 37 is arranged. The sixth pole 33a is disposed at a position facing the developing roller 31, and has a polarity (S pole) different from that of the fourth pole 31d and the fifth pole 31e. The sixth pole 33a has a lower magnetic force than the fourth pole 31d, but has a stronger magnetic force than the fifth pole 31e. Therefore, the toner and the carrier are easily transferred from the sixth pole side to the fourth pole side, and the toner and the carrier are easily separated from the fifth pole 31e side to the sixth pole 33a side. The seventh pole 33b is disposed on the substantially opposite side of the sixth pole 33a with respect to the axis and is opposed to the stirring member, and has a polarity opposite to that of the sixth pole 33a. The seventh pole 33b is a member having a weaker magnetic force than the sixth pole 33a. The toner and carrier in the developing device 22 are pumped up by the seventh pole 33b, and the toner and carrier are conveyed from the seventh pole 33b side to the sixth pole 33a side.

  The laser unit 23 scans and exposes the photosensitive drum 21 based on image information sent from an external computer or the like, and is disposed above the photosensitive drum 21. Specifically, the front end of the laser unit 23 (the end on the side from which the laser beam is emitted) is positioned almost directly above the rotation axis of the photosensitive drum 21 and is disposed along the outer frame of the color printer 1. ing. The internal configuration of the laser unit 23 is the same as the conventional configuration, and includes a laser light source, a polygon mirror, a polygon mirror driving motor, and the like. In addition, a reflection mirror 26 is provided in front of the laser beam path of the laser unit 23. Therefore, as indicated by a one-dot chain line in FIG. 1, the laser light emitted from the laser unit 23 is bent by the reflection mirror 26 and irradiated onto the surface of the photosensitive drum 21.

  The intermediate transfer body 25 is one to which the toner images of the respective colors formed on the photosensitive drum 21 are sequentially transferred. The intermediate transfer body 25 is downstream of the four developing devices 22 in the rotation direction of the photosensitive drum 21 and upstream of the cleaning mechanism 38. Is arranged. The intermediate transfer member 25 is a cylindrical member having a larger cross-sectional area than the photosensitive drum, and has a rotation axis parallel to the rotation axis of the photosensitive drum 21.

  The secondary transfer roller 27 is for transferring the image transferred to the intermediate transfer member 25 onto the conveyed paper, and is disposed below the intermediate transfer member 25. The secondary transfer roller 27 is applied with a bias voltage for image transfer to the paper by a voltage application device (not shown).

  The fixing unit 3 is a part for fixing the image formed by the image forming unit 2 on a sheet, and includes a pressure roller and a heating roller.

  The paper transport unit 4 is a part for transporting paper in a paper feed cassette (not shown) to the image forming unit 2 and the fixing unit 3, and is continuous from the paper feed cassette to the discharge unit 7.

  The paper feed cassette is a portion in which paper for printing is stored.

  The discharge unit 7 is a portion where the paper on which the image is fixed is discharged through the paper transport unit 4, and is disposed on the upper surface of the color printer 1.

[Operation]
An image forming operation will be described.

  When image data is transmitted from an externally connected computer, the surface of the photosensitive drum 21 is charged, and the laser unit 23 irradiates the surface of the photosensitive drum 21 with laser light based on the image data. Then, the toner in the developing device 22 is supplied to the surface of the photosensitive drum 21, and a toner image is formed on the surface of the photosensitive drum 21. The toner image on the surface of the photosensitive drum 21 is transferred to a sheet via the intermediate transfer member 25. The sheet on which the toner image is transferred is conveyed to the fixing unit 3 by the sheet conveying unit 4, and the image is fixed by the fixing unit 3. The sheet on which the toner image is fixed is discharged from the discharge unit 7.

  Next, an operation for supplying the developer in the developing unit 22 onto the photosensitive drum 21 will be described.

  When toner and carrier are attracted to the seventh pole 33b, the sixth pole 33a has a different polarity from the seventh pole 33b having a stronger magnetic force than the seventh pole 33b. Accordingly, the toner and the carrier are conveyed from the seventh pole 33b side to the sixth pole 33a side. Since the magnetic force of the fourth pole 31d is stronger than that of the fifth pole 31e and the sixth pole 33a, the toner and carrier conveyed to the sixth pole 33a side are transferred to the fourth pole 31d side. The toner and carrier on the sixth pole 33a side are conveyed to the first pole 31a side via the third pole 31c as the developing sleeve 34 rotates. Then, the toner on the first pole 31 a side is supplied to the photosensitive drum 21. Thereafter, the toner that has not been supplied to the carrier and the photosensitive drum 21 is conveyed to the fifth pole 31e via the second pole 31b. The toner and carrier conveyed to the fifth pole 31e side are peeled off to the sixth pole 33a side.

  Here, only the sixth pole 33a having the opposite polarity (S pole) to the fourth pole 31d and the fifth pole 31e is arranged at a position facing the fourth pole 31d and the fifth pole 31e, and the first Since the magnetic force of the sixth pole 33a is weaker than that of the fourth pole 31d and stronger than that of the fifth pole 31e, the developer on the sixth pole 33a side is easily transferred to the fourth pole 31d side. Easy to peel off developer. Furthermore, since the sixth pole 33a has a stronger magnetic force than the seventh pole 33b, the developer adsorbed on the seventh pole 33b is easily transported to the sixth pole 33a side.

[Other Embodiments]
In the above embodiment, the color printer 1 has been described. However, the present invention is not limited to this, and may be a copying machine or a multifunction machine.

1 is an overall schematic diagram of a color printer 1. FIG. FIG. 3 is an enlarged schematic cross-sectional view of the developing device 22. FIG. 3 is a diagram illustrating a configuration of a developing roller 31 and a supply roller 33 used in the color printer 1. FIG. 4 is a diagram illustrating a configuration of a developing roller 31 and a supply roller 33 used in a conventional image forming apparatus.

Explanation of symbols

1 Color printer (image forming device)
21 Photosensitive drum (electrostatic latent image carrier)
22 Developer (Developer)
22a Developer body (container body)
31 Developing roller 31a 1st pole 31b 2nd pole 31c 3rd pole 31d 4th pole 31e 5th pole 33 Supply roller 33a 6th pole 33b 7th pole 34 Developing sleeve 35 Supply sleeve 36 Developing magnet 37 Supply magnet

Claims (4)

A developing device that is used in an image forming apparatus and forms an image on an electrostatic latent image carrier using a magnetic developer,
A container body for storing the magnetic developer inside;
A developing roller that is provided in the container main body and supplies the magnetic developer to the electrostatic latent image carrier to perform development;
A supply roller that is provided inside the container body and supplies a magnetic developer to the developing roller;
With
The developing roller is
A member that is non-rotatably supported by the container body and has a magnetic pole arranged around a central axis, and at least the same polarity on both sides of the opposing position of the magnetic pole facing the electrostatic latent image carrier and the supply roller A developing magnet on which magnetic poles of
A developing sleeve that is rotatable around the central axis in a first direction on the outer periphery of the developing magnet;
The supply roller is
A member that is disposed on the container main body so as not to rotate and is opposed to the developing sleeve, and is provided with a magnetic pole around a central axis, and is different from the magnetic pole on the developing roller side at a position facing the developing roller. A supply magnet with opposing magnetic poles disposed thereon;
A supply sleeve rotatable on the outer periphery of the supply magnet in the first direction around the central axis;
Development device   2. The developing device according to claim 1, wherein the supply magnet further includes a pumping magnetic pole having a polarity different from a counter magnetic pole disposed on a side opposite to the side on which the developing roller is disposed. The opposed magnetic pole arranged at the position of the supply magnet facing the developing roller is more than the upstream magnetic pole arranged at the upstream side of the same polarity magnetic pole arranged at the opposed position of the developing magnet to the supply roller. Also has a strong magnetic force, which is weaker than the downstream magnetic pole located downstream of the opposing position,
The developing device according to claim 1 or 2. The developing device according to claim 1, wherein the opposing magnetic pole of the supply magnet has a stronger magnetic force than the pumping magnetic pole.

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