JP2010276696A - Developing device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove a developer after development properly from the surface of a developer carrier, in a developing device for developing by allowing the developer carrier for conveying the developer including a toner and a carrier to an image carrier. <P>SOLUTION: When the developer, after development, is removed from the developer carrier and returned to a device body 20a, between adjacent magnetic poles S1, S2 having the same polarity of a magnet member 21a provided on the inner peripheral side of the developer carrier, after performing development by introducing a developer D containing the toner and the carrier to the image carrier 10 by the developer carrier 21; a developer guidance section 28 facing the developer carrier at an interval is provided on the magnetic pole S1 section on the rotation direction upstream side of the developer carrier; and an interval with the developer carrier on a position where a magnetic force Bθ toward the tangential direction of the developer carrier by the magnetic pole S1 becomes a maximum is set smaller than an interval with the developer carrier on a position, where a magnetic force Br toward a normal direction of the developer carrier becomes maximum. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a developing device used to develop an electrostatic latent image formed on an image carrier in an image forming apparatus such as a copying machine, a printer, a facsimile, and a composite machine thereof, and to such an image forming apparatus. It is. In particular, a developer containing toner and a magnetic carrier contained in the apparatus main body is held on the lower surface of a developer carrier provided with a magnet member having a plurality of magnetic poles fixed on the inner peripheral side. The developer carrying member is rotated, the developer is guided to the developing area facing the image carrier, and development is performed. The developer after development is returned into the device main body by the developer carrying member, The developed developer returned to the inside is separated from the surface of the developer carrier between adjacent magnetic poles of the same polarity provided on the magnet member, and is guided below the developer carrier. In the developing device, the developed developer returned into the apparatus main body is appropriately separated from the surface of the developer carrier between adjacent magnetic poles of the same polarity provided on the magnet member, and accommodated in the apparatus main body. Suitable for used developer And it has a feature that was to be returned to.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, printers, facsimiles, and composite machines thereof have used various developing devices to develop an electrostatic latent image formed on an image carrier. As such a developing device, in addition to a one-component developing type developing device using only toner as a developer, a two-component developing type developing device using a developer containing toner and a magnetic carrier is known.

  As such a two-component developing system developing device, there is a magnet member having a plurality of magnetic poles on the inner peripheral side by a rotating supply member for developer containing toner and magnetic carrier housed in the apparatus main body. This is supplied to the surface of a fixed developer carrier, and this developer carrier is rotated to guide the developer to a development area facing the image carrier, and the toner in the developer is transferred to the image carrier. While supplying and developing, a developer that returns the developer after development into the apparatus main body is widely used.

  Here, in such a developing apparatus, the developed developer supplied with the toner as described above is guided to the developing region facing the image carrier while being held on the surface of the developer carrier. When used again for development, there is a problem in that sufficient toner is not supplied to the image carrier and density unevenness occurs in the formed image.

  For this reason, in such a developing device, a pair of magnetic poles having the same polarity are provided adjacent to the magnet member, and the magnet member is returned to the apparatus main body by a repulsive magnetic force between the adjacent magnetic poles of the same polarity. Further, the developer after development is separated from the surface of the developer carrying member between the adjacent magnetic poles of the same polarity.

  However, even when the developer after development is separated from the surface of the developer carrying member between adjacent magnetic poles of the same polarity provided on the magnet member in this way, the developer after development remains the developer. It is said that the developer after development is left without being sufficiently detached from the surface of the carrier, or the developer after development is supplied again to the surface of the developer carrier, and the developer after development is used again for development. The problem still existed.

  In particular, when the developing device is downsized and the developer contained in the apparatus main body is supplied to the lower surface of the developer carrier by a supply member provided below the developer carrier, The position where the developer is supplied to the developer carrier and the position where the developer after development is released from the developer carrier are close to each other, and the developer after development is not sufficiently released from the surface of the developer carrier. In addition, the developed developer that has been separated is supplied again to the surface of the developer carrying member, and the developed developer is often used again for development.

  Conventionally, as shown in Patent Document 1, a magnetic material is provided between the adjacent magnetic poles of the same polarity and the supply member so as to face the developer carrier, and The magnetic material is induced to be magnetized by the magnetic poles so that the developer after development is sufficiently separated from the surface of the developer carrying member.

  However, when a magnetic material is provided between the adjacent magnetic poles of the same polarity and the above supply member so as to face the developer carrier, the developer flows against the magnetic material and the flow of the developer is obstructed. Or the magnetic material may be deformed, and it is difficult to sufficiently remove the developer after development from the surface of the developer carrier only by inductively magnetizing the magnetic material as described above. There was a problem of becoming.

Japanese Patent Laid-Open No. 6-19462

  The present invention provides a developer containing toner and a magnetic carrier contained in an apparatus main body on a surface on the lower side of a developer carrier provided with a magnet member having a plurality of magnetic poles fixed on the inner peripheral side. Then, the developer carrying member is rotated, the developer is guided to a developing area facing the image carrier, and the toner in the developer is supplied to the latent image formed on the image carrier for development. The developer after the development is returned into the apparatus main body, and the developer after the development returned into the apparatus main body is separated from the surface of the developer carrier between the adjacent magnetic poles of the same polarity provided in the magnet member. It is an object of the present invention to solve the above-described problems in the developing device that is guided below the developer carrier.

  That is, in the present invention, in the above developing device, the developed developer returned into the main body of the device is exposed from the surface of the developer carrying member between adjacent magnetic poles of the same polarity provided in the magnet member. A developer that has been properly detached and thus has been separated so that the developer after the development is appropriately guided below the developer carrier and is not supplied again to the developer carrier. Therefore, it is an object of the present invention to stably form a good image with no unevenness of density and the like supplied appropriately.

  In the developing device of the present invention, in order to solve the above-described problems, a developer containing toner and a magnetic carrier housed in the device main body is fixed to the inner peripheral side by a magnet member having a plurality of magnetic poles. The developer carrying member is supplied to the lower surface of the developer carrying member, and the developer carrying member is rotated, and the developer is guided to the developing region facing the image carrying member to perform development. The developer is returned to the apparatus main body, and the developed developer returned to the apparatus main body is separated from the surface of the developer carrying member between the adjacent magnetic poles of the same polarity provided on the magnet member and developed. In the developing device that leads to the lower side of the developer carrier, a developer guide is provided so as to face the developer carrier in the magnetic pole portion on the upstream side in the rotation direction of the developer carrier with a gap of the same polarity. In this developer guide Thus, the distance from the developer carrier at the position where the magnetic force Bθ in the tangential direction of the developer carrier by the magnetic pole on the upstream side in the rotation direction of the developer carrier is the maximum in the normal direction of the developer carrier The distance from the developer carrier at the position where the magnetic force Br toward the maximum is smaller than that of the developer carrier.

  Here, in the developer guide portion, the distance from the developer carrier at the position where the magnetic force Bθ in the tangential direction of the developer carrier by the magnetic pole upstream in the rotation direction of the developer carrier is maximized. The position at which the magnetic force Bθ in the tangential direction of the developer carrier is maximized when the distance between the developer carrier and the developer carrier is smaller than the distance between the developer carrier and the magnetic force Br in the normal direction of the developer carrier. In the developer guide portion facing the developer carrier, a protrusion protruding toward the developer carrier can be provided in the axial direction of the developer carrier. In addition, the shape of this protruding item | line is not specifically limited, For example, it can be set as various shapes, such as a quadratic prism shape and a triangular prism shape.

  Further, as described above, between the adjacent magnetic poles of the same polarity provided on the magnet member, the developed developer is appropriately separated from the surface of the developer carrying member and guided below the developer carrying member. In order to achieve this, the magnetic force Bθmax at the position where the magnetic force Bθ in the tangential direction of the developer carrying member is maximized is the magnetic force Br in the normal direction of the developer carrying member at the position where the magnetic force Bθ is maximized. It is preferable to make it larger.

  In the image forming apparatus of the present invention, the developing device as described above is used when the electrostatic latent image formed on the image carrier is developed by the developing device.

  In the developing device of the present invention, when the developer after development is separated from the surface of the developer carrying member between adjacent magnetic poles of the same polarity provided on the magnet member as described above, the magnetic poles of the same polarity described above are used. In the developer guide, a developer guide portion is provided so as to face the developer carrier in the magnetic pole portion upstream in the rotation direction of the developer carrier, with the developer guide portion rotating in the rotation direction of the developer carrier. Development at a position where the magnetic force Br in the normal direction of the developer carrying member is maximized is the distance from the developer carrying member at the position where the magnetic force Bθ in the tangential direction of the developer carrying member is maximized by the magnetic pole on the upstream side. Since the distance between the developer carrier and the developer carrier is smaller, the developer after development conveyed by the developer carrier is suppressed at the position where the magnetic force Bθ in the tangential direction of the developer carrier is maximized. Become.

  For this reason, at the position where the magnetic force Bθ directed in the tangential direction of the developer carrying member is maximized, the force with which the developer after development is conveyed in the tangential direction of the developer carrying member is reduced and is conveyed by the developer carrying member. The developed developer is prevented from being guided to the magnetic pole of the same polarity on the downstream side in the rotation direction of the developer carrier, and the magnetic force Br toward the normal direction of the developer carrier is also reduced. The force for holding the developer after development on the surface of the developer carrier is also reduced, and the developer after development is appropriately detached from the surface of the developer carrier between the magnetic poles of the same polarity. The developer after the development is prevented from being supplied again to the developer carrying member.

  As a result, in the above developing device, the developer after development is appropriately detached from the surface of the developer carrying member, and a new developer is appropriately supplied to the developer carrying member. In an image forming apparatus using the apparatus, a good image without occurrence of density unevenness can be stably obtained.

1 is a schematic explanatory diagram of an image forming apparatus using a developing device according to an embodiment of the present invention. FIG. 2 is a schematic explanatory view showing a developing device according to an embodiment of the present invention used in the image forming apparatus. In the developing device according to the above-described embodiment, the magnetic force Bθ in the tangential direction of the developer carrier and the magnetic force in the normal direction of the developer carrier by the magnetic poles of the magnet member provided on the inner peripheral side of the developer carrier. FIG. 5 is a partial explanatory view showing a state in which Br changes and a relationship with a position where a protrusion is provided on a developer guide that faces the developer carrying member with a gap. In the developing device according to the above-described embodiment, it is a schematic explanatory diagram of a modified example in which the shape of the ridge provided in the developer guide is changed.

  Next, an image forming apparatus and a developing apparatus according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. Note that the image forming apparatus and the developing apparatus according to the present invention are not limited to those shown in the following embodiments, and can be appropriately modified and implemented without departing from the scope of the invention.

  In the image forming apparatus according to this embodiment, as shown in FIG. 1, four developments containing a developer containing toner and a magnetic carrier corresponding to four photosensitive drums (image carriers) 10 are accommodated. A device 20 is provided.

  In each developing device 20, a roller-shaped developer carrier 21 that conveys the developer to the photosensitive drum 10 is provided so as to face the corresponding photosensitive drum 10, and each developing device 20. , Black, yellow, magenta, and cyan toners are used by changing the color of the toner in each developer.

  Then, when full-color image formation is performed by this image forming apparatus, each of the photosensitive drums 10 is rotated, and the surface of each of the photosensitive drums 10 is charged by the charging device 11, respectively. Each of the photosensitive drums 10 is exposed according to the image formation information by the latent image forming device 12 so that an electrostatic latent image is formed on the surface of each of the photosensitive drums 10.

  Next, with respect to each photosensitive drum 10 on which the electrostatic latent image is formed in this way, the developer is guided to a position facing the photosensitive drum 10 by the developer carrying member 21 in the corresponding developing device 20, and is predetermined. The toners of the colors are supplied to the electrostatic latent images on the photosensitive drums 10 for development, and toner images of the respective colors are formed on the surfaces of the photosensitive drums 10.

  Then, the toner images of the respective colors formed on the respective photosensitive drums 10 in this manner are respectively transferred to the intermediate transfer body 13 in the form of an endless belt that is driven across the roller 13a. A primary image is sequentially transferred by the transfer device 14 to form a full-color toner image on the intermediate transfer member 13. On the other hand, residues such as toner remaining on the surface of each photoreceptor drum 10 without being transferred to the intermediate transfer body 13 are removed by the first cleaning device 15.

  Next, the full-color toner image formed on the intermediate transfer member 13 as described above is guided to a position facing the secondary transfer device 16 formed into a roller shape by the intermediate transfer member 13 and the image forming apparatus. The recording sheet 19 accommodated in the lower portion of the sheet is guided between the intermediate transfer member 13 and the secondary transfer device 16, and a full-color toner image formed on the intermediate transfer member 13 by the secondary transfer device 16 is transferred to the recording sheet 19. Secondary transfer is performed on the recording sheet 19.

  Thereafter, the recording sheet 19 to which the full-color toner image has been transferred is guided to the fixing device 17, and the transferred full-color toner image is fixed to the recording sheet 19. The sheet 19 is discharged. On the other hand, toner and other residues that are not transferred to the recording sheet 19 and remain on the intermediate transfer member 13 are removed from the intermediate transfer member 13 by the second cleaning device 18.

  Here, in the developing device 20 in this embodiment, as shown in FIG. 2, a developer carrying member 21 is disposed on the upper portion of the device main body 20a so as to face the photosensitive drum 10 with a required interval. A magnet member 21 a provided with a plurality of magnetic poles N, S,... Is fixedly provided on the inner peripheral side of the developer carrier 21.

  Further, a partition wall 27 along the axial direction of the developer carrier 21 is provided in the apparatus main body 20a in which the developer D containing toner and magnetic carrier is accommodated. The first transport unit 22 that supplies the developer D to the developer carrier 21 and the second transport unit 23 that circulates and transports the developer D between the first transport unit 22 and the second transport unit 23. And separated.

  Further, a first screw member 24 that rotates and conveys the developer D and supplies the developer D to the developer carrier 21 is provided in the first conveyance unit 22, and the first A second screw member 25 that rotates and conveys the developer D is provided in the second conveying section 23.

  And the 1st screw member 24 and the 2nd screw member 25 which were provided in the 1st conveyance part 22 and the 2nd conveyance part 23 are rotated, and the developer D is made into the 1st conveyance part 22 and The developer D is transported in the opposite direction by the second transport unit 23, and the developer D is transported from the first transport unit 22 and the second transport through circulation ports (not shown) provided at both ends of the partition wall 13. The developer D in the first transport unit 22 is caused to circulate between the developer carrier 21 and the lower surface of the developer carrier 21 positioned on the upper side by the first screw member 24. I am trying to supply.

  The developer D thus supplied to the lower surface of the developer carrier 21 is held on the surface of the developer carrier 21 by the magnetic force of the magnet member 21a.

  Next, the developer carrying member 21 holding the developer D on the surface in this way is rotated, and the developer carrying member 21 is in the middle of transporting the developer D to the developing region facing the photosensitive drum 10. At the position, a regulating member 26 is provided so as to face the developer carrying member 21 with a necessary interval, and the amount of the developer D held on the surface of the developer carrying member 21 and conveyed to the developing region is regulated. The member 26 is used for regulation.

  The developer D thus regulated by the regulating member 26 is guided to the developing region facing the photosensitive drum 10 by the developer carrying member 21, and the toner in the developer D is formed on the photosensitive drum 10. The electrostatic latent image formed on the photosensitive drum 10 is developed and supplied to the portion of the electrostatic latent image.

  Further, after developing the electrostatic latent image formed on the photosensitive drum 10 in this manner, the developed developer D held on the surface of the developer carrier 21 is transferred to the apparatus by the developer carrier 21. It returns to the inside of the main body 20a.

  Here, in the developing device 20 of this embodiment, a pair of magnetic poles S1 and S2 having the same polarity adjacent to the magnet member 21a are provided, and the developed developer D returned into the device main body 20a is supplied to the pair. Are separated from the surface of the developer carrier 21 between the magnetic poles S1 and S2 of the same polarity, and at the magnetic pole S1 portion on the upstream side in the rotation direction of the developer carrier 21, the developer carrier 21 is provided. And a developer guide 28 for guiding the developer D after development into the apparatus main body 20a.

  Further, in the developing device 20, as shown in FIGS. 2 and 3, the developer carrier is provided at the magnetic pole S1 upstream of the developer carrier 21 in the rotation direction of the pair of magnetic poles S1 and S2 having the same polarity. At the portion of the developer guide portion 28 that faces the position where the magnetic force Bθ toward the tangential direction of 21 is the maximum, a convex ridge 28 a that is a square column shape protruding toward the developer carrier 21 is formed on the developer carrier 21. The distance between the developer carrier 21 and the developer guide portion 28 provided with the protrusions 28a at the position where the magnetic force Bθ that is provided along the axial direction and that extends in the tangential direction of the developer carrier 21 is maximized is as described above. The distance between the developer carrier 21 and the developer guide portion 28 at a position where the magnetic force Br in the normal direction of the developer carrier 21 due to the magnetic pole S1 is maximized is made smaller.

  In this way, at the position where the magnetic force Bθ in the tangential direction of the developer carrier 21 by the magnetic pole S1 is maximized, the developer D after development conveyed by the developer carrier 21 is the ridge 28a. Therefore, the force that the developer D after development is conveyed in the tangential direction of the developer carrier 21 decreases, and the developer D after development conveyed by the developer carrier 21 becomes the developer carrier 21. Is prevented from being guided to the magnetic pole S2 having the same polarity on the downstream side in the rotation direction.

  Further, in the developing device 20, the developer carrying at the position where the magnetic force Bθ is maximum than the magnetic force Bθmax at the position where the magnetic force Bθ toward the tangential direction of the developer carrier 21 by the magnetic pole S1 is maximum. The magnetic force Br toward the normal direction of the body 21 is reduced, and the force for holding the developer D after development on the surface of the developer carrying body 21 is also weakened.

  As a result, the developed developer D released from the surface of the developer carrier 21 between the magnetic poles S1 and S2 of the same polarity is the same polarity magnetic pole S2 on the downstream side in the rotation direction of the developer carrier 21. The developer D after development that has been released without being guided to the developer is guided to the lower side of the developer carrier 21 by gravity and is taken into the developer D accommodated in the apparatus main body 20a. The subsequent developer D is prevented from being supplied again to the developer carrier 21.

  Then, a new developer D is supplied by the first screw member 24 to the surface of the developer carrier 21 from which the developer D after development has been detached in this way, and is used for development. Thus, it is possible to stably obtain a good image without occurrence of uneven density.

  In the developing device 20 of this embodiment, the portion of the developer guide portion 28 that opposes the position where the magnetic force Bθ in the tangential direction of the developer carrier 21 by the magnetic pole S1 is maximized has a rectangular column shape. The protrusions 28a are provided along the axial direction of the developer carrier 21, but the shape of the protrusions 28a is not limited to this. For example, as shown in FIG. 4, it is also possible to provide a ridge 28a having a triangular prism shape.

  Further, when providing such a ridge 28a, the developer guide 28 itself can be formed in such a shape in addition to attaching the ridge 28a to the developer guide 28.

10 Photosensitive drum (image carrier)
DESCRIPTION OF SYMBOLS 11 Charging device 12 Latent image forming device 13 Intermediate transfer member 13a Roller 14 Primary transfer device 15 First cleaning device 16 Secondary transfer device 17 Fixing device 18 Second cleaning device 19 Recording sheet 20 Developing device 20a Device main body 21 Developer carrier 21a Magnet member 22 1st conveyance part 23 2nd conveyance part 24 1st screw member 25 2nd screw member 26 Control member 27 Partition 28 Developer guide part 28a Convex strip D Developer S1, S2 Adjacent same polarity Magnetic field Bθ Magnetic force in the tangential direction of the developer carrier Bθmax Maximum magnetic force in the tangential direction of the developer carrier due to the magnetic pole S1 Br Magnetic force in the normal direction of the developer carrier

Claims (4)

  A developer containing toner and a magnetic carrier housed in the apparatus main body is supplied to the lower surface of a developer carrier provided with a magnet member having a plurality of magnetic poles fixed to the inner peripheral side. The developer carrying member is rotated, the developer is guided to the developing area facing the image carrier, and development is performed. The developed developer is returned to the apparatus main body, and after the development is returned to the apparatus main body. In the developing device for separating the developer from the surface of the developer carrier between the adjacent magnetic poles of the same polarity provided on the magnet member and guiding the developer to the lower side of the developer carrier, A developer guide is provided in the magnetic pole portion on the upstream side in the rotation direction of the developer carrier so as to face the developer carrier with a space therebetween, and in the developer guide, the developer carrier is upstream in the rotation direction of the developer carrier. Developer bearing by magnetic pole on the side The distance from the developer carrier at the position where the magnetic force Bθ toward the tangential direction of the body is maximum is smaller than the distance from the developer carrier at the position where the magnetic force Br toward the normal direction of the developer carrier is maximum. A developing device characterized by that.   2. The developing device according to claim 1, wherein the developer carrying member protrudes toward the developer carrying member at a portion of the developer guide that faces the developer carrying member at a position where the magnetic force Bθ in the tangential direction of the developer carrying member is maximized. A developing device characterized in that the projected ridges are provided in the axial direction of the developer carrier.   3. The developing device according to claim 1, wherein a magnetic force Bθmax at a position where the magnetic force Bθ in the tangential direction of the developer carrying member is maximized is a developer carrying at a position where the magnetic force Bθ is maximized. A developing device characterized by being larger than a magnetic force Br directed in a normal direction of the body.   An image forming apparatus for developing an electrostatic latent image formed on an image carrier by a developing device, wherein the developing device according to any one of claims 1 to 3 is used. Forming equipment.

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