JP2009300755A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of efficiently separating charged-up toner on a rotating sleeve from the sleeve, thereby, capable of achieving stable image formation. <P>SOLUTION: The developing device has the rotating sleeve 37 including a magnet member 36 having a plurality of magnet poles. After regulating the layer thickness of the magnetic developer carried on the rotating sleeve 37 by a bristle cutting plate 33, the magnetic developer is carried on a photoreceptor drum 18, and also, the magnet member 36 is made rotatable independently of the rotating sleeve 37. A magnetic member 34 is disposed at a position facing near a position where magnetic force in the normal direction of the magnet member 36 is nearly zero gauss, and the magnetic pole of the magnet member 36 is rotated so as to face the magnetic member 34, and the magnetic developer is napped. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing device that forms an electrostatic latent image on an image carrier using a magnetic developer, and an image forming apparatus including the developing device.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, printers, facsimiles, or multifunction machines equipped with these functions have been provided with a developing device that realizes a one-component developing thin layer formation using magnetic toner as a magnetic developer. What is installed is well known.

  In addition, since such a developing device uses magnetic toner as the magnetic developer, the developing roller as the toner carrying member disposed opposite to the photosensitive drum as the image carrying member is provided with a plurality of magnetic poles. A developing device using a rotating sleeve containing a fixed magnet member is also known (see, for example, Patent Document 1).

  In such a developing roller, the leading end of a toner layer thickness regulating member such as a blade provided in the developing device has a blade gap (0.2 to 0.4 mm) with respect to the outer peripheral surface of the developing sleeve (rotating sleeve). A system is used in which the gap is disposed opposite to the fixed magnet member in the developing sleeve in a state where the interval is opened.

  FIG. 4 shows an example of such a developing apparatus (developing device). The developing device 100 includes a device case 103 composed of a base 101 and a cover 102, a partition wall 104 partitioning the inside of the device case 103, and a partition wall. A pair of spirals 105, 106 disposed across substantially the entire width of the device case 103 so as to sandwich the 104, a developing roller 107 disposed adjacent to the spiral 106 so as to face the photosensitive drum 18, and a cover 102. And a magnet 110 fixed to the panning plate 109. The panning plate 109 is a toner layer thickness regulating member held via a holder 108.

  The developing roller 107 includes a fixed magnet member 112 fixed to the cored bar 111 and a rotating sleeve 113 that covers the outer periphery of the fixed magnet member 112 and rotates via a driving device (not shown).

  The magnet 110 is disposed on the upstream side in the rotation direction of the developing roller 107 with respect to the cutting plate 109 and has a polarity opposite to that of the fixed magnet member 112.

As a result, the developing roller 107 including the fixed magnet member 112 having a plurality of magnetic poles is used, and the toner accumulated in the device case 103 is carried using the magnetic carrying force formed on the surface of the rotating sleeve 113. However, after the layer thickness is regulated by using the cutting plate 109, the regulated toner layer can be guided to the photosensitive drum 18.
Japanese Patent Laid-Open No. 10-333437

  However, one-component development type toner is generally charged at the blade gap, but it is difficult to efficiently remove the charged toner and supply new toner.

  Therefore, in the technique disclosed in the cited document 1 described above, the toner is replaced by arranging the magnet 110 adjacent to the trimming plate 109 and upstream of the developing roller 107 in the rotation direction.

  However, for example, as shown in FIG. 5 (A), the case where the magnet 110 is arranged adjacent to each other as shown in FIG. Although the toner rises better, if the rotational speed of the rotating sleeve 113 is increased as the image forming process speeds up, the toner will rise too much as shown in FIG. There is a tendency that the electrification becomes too high.

  As described above, if the toner on the rotating sleeve 113 is charged too much, there is a problem that the image formation density is lowered or the charged toner remains attached to the rotating sleeve 113 and an abnormal image is generated.

  As a method for preventing this phenomenon, it is conceivable to increase the magnetic force of the magnet 110 to increase the pressure immediately below the scissor cutting plate 109 to improve the toner exchanging property. The upper toner thin layer becomes thin and the image formation density becomes thin, or agglomerated toner is formed and bites into the blade gap, resulting in a new problem that vertical white stripes are likely to occur in the formed image.

  SUMMARY An advantage of some aspects of the invention is that it provides a developing device and an image forming apparatus capable of efficiently releasing charged toner on a rotating sleeve from the rotating sleeve and realizing stable image formation.

  The developing device according to the present invention includes a rotating sleeve containing a magnet member having a plurality of magnetic poles, and a development in which the magnetic developer is carried on the image carrier after the thickness of the magnetic developer carried on the rotating sleeve is regulated. In the apparatus, the magnet member can be rotated independently of the rotating sleeve, and the magnetic member is disposed at a position where the magnetic force in the normal direction of the magnet member faces approximately zero gauss. Is rotated so as to face the magnetic member, and the magnetic developer is raised.

  At this time, it is preferable that the magnet member is rotated so that the magnetic pole faces the magnetic member at a predetermined timing except during the image forming process.

  Further, it is preferable that the magnetic member is sprinkled with the magnetic developer by rotating the magnetic pole having the maximum magnetic force so as to face the magnetic member.

  Furthermore, the present invention can be an image forming apparatus employing a developing device having any one of the above-described configurations.

  The developing device of the present invention can efficiently remove the charged-up toner on the rotating sleeve from the rotating sleeve and realize stable image formation.

  Next, a developing device according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory view of a printer as an image forming apparatus equipped with a developing device according to an embodiment of the present invention, FIG. 2 is a sectional view of the developing device according to an embodiment of the present invention, and FIG. It is explanatory drawing of the principal part of the developing device which concerns on embodiment.

(Overall configuration of image forming apparatus)
As shown in FIG. 1, a printer 1 as an image forming apparatus according to an embodiment of the present invention includes a paper feed cassette 3 that is slidably stored inside a printer main body 2, and a storage space for the paper feed cassette 3. 4, a paper feed unit 5 for taking out transfer paper (not shown) stored in the paper 4, a manual feed tray 6 arranged in front of the printer main body 2, and a transfer paper (not shown) set in the manual feed tray 6 are taken out. From the manual sheet feeding unit 7, the conveyance path 8 for conveying the transfer paper supplied from each sheet feeding unit 5, 7, and the merging unit of each sheet feeding unit 5, 7 upstream of the conveyance path 8 in the sheet conveyance direction. Also, a pair of registration rollers 9 arranged on the downstream side in the sheet conveyance direction, and a magnetic developer such as toner, which is arranged on the conveyance path 8 downstream of the registration roller pair 9 in the sheet conveyance direction and is supplied from the toner container 10. An image that forms a transfer image on one side A forming unit 11, a fixing device 12 that is disposed downstream of the image forming unit 11 in the sheet conveyance direction of the conveyance path 8 and fixes a toner image formed on one surface of the transfer paper, and a transfer paper that has passed through the fixing device 12 When a transfer image is formed on the other surface, the reverse path 13 is pulled back from the downstream side of the transport path from the fixing device 12 of the transport path 8 to the upstream side of the transport path of the transport path 8 from the registration roller pair 9, and the transport path 8 And a paper discharge section 14 provided at the end of the paper.

(Configuration of toner container 10)
The toner container 10 stores replenishment toner inside the container body 15. Further, the replenishing toner is agitated by a paddle 16 made of a flexible resin material or the like, and is conveyed in the transfer paper width direction (the depth direction in FIG. 1) by the spiral 17, and then forms an image at the predetermined position. To the section 11.

(Configuration of the image forming unit 11)
The image forming unit 11 is arranged around the photosensitive drum 18 as an image carrier in the order of the image forming process along the rotation direction thereof, the charging device 19, the exposure device 20, the developing device 21, the transfer device 22, the cleaning device 23, and the charge eliminating device. A device 24 is provided.

  As a result, in the image forming unit 11, the photosensitive drum 18 is rotationally driven at a predetermined process speed (circumferential speed) by a driving unit (not shown), and the surface thereof is uniformly charged to a predetermined polarity / potential by the charging device 19. .

  An electrostatic latent image is formed on the surface of the charged photosensitive drum 18 by the exposure device 20. Here, the exposure device 20 irradiates the surface of the photosensitive drum 18 with the laser beam P based on the image data included in the print data output from the personal computer or the like, and irradiates the surface of the photosensitive drum 18 with the laser beam. An electrostatic latent image corresponding to the image information is formed by removing the charge of the portion.

  The electrostatic latent image formed on the surface of the photosensitive drum 18 is developed as an unfixed toner image by electrostatically attaching the toner having the charge supplied from the toner container 10 by the developing device 21. Further, the unfixed toner image is transferred onto the transfer paper as a transfer image by the transfer device 22.

  At this time, the photosensitive drum 18 on which the unfixed toner image is transferred onto the transfer paper is subjected to a removal process of residual toner and the like by the cleaning device 23, and then is neutralized by the neutralization device 24 for charging at the next image formation. Processing is performed.

  The charging device 19, the exposure device 20, the transfer device 22, the cleaning device 23, and the charge removal device 24 are known ones, and the configuration is not particularly limited.

(Configuration of developing device 21)
The developing device 21 supplies the toner for replenishment supplied from the toner container 10 to the photosensitive drum 18 of the image forming unit 11 while stirring, and includes a base 25 and a cover 26 as shown in FIG. A device case 27, a partition wall 28 that partitions the inside of the device case 27, and a pair of spirals 29 and 30 that are disposed across substantially the entire width of the device case 27 (the depth direction in FIG. 2) so as to sandwich the partition wall 28. A developing roller 31 disposed adjacent to the spiral 30 so as to face the photoconductive drum 18, a cutting plate 33 held on the cover 26 via a holder 32, and the spiral 30 and the cutting plate 33. And a magnetic member 34 disposed therebetween.

  Both ends of the partition wall 28 (in the depth direction in FIG. 2) are open so that both ends of the spirals 29 and 30 communicate with each other. As a result, the toner replenished from the toner container 10 (spiral 17) via the toner replenishing port 26a formed in the cover 26 is agitated and conveyed (outward) by the spiral 29 toward one side of the developing device 21. Thereafter, the sheet is folded at the open end of the partition wall on one side, stirred and transported (returned) toward the other side of the developing device 21 by the spiral 30, and is further circulated and transported again at the open end of the partition wall on the other side. Yes.

  The developing roller 31 is disposed so that the peripheral surface thereof faces the peripheral surface of the photosensitive drum 18. Therefore, the toner being conveyed to the developing roller 31 is supplied to the peripheral surface of the photosensitive drum 18 via the developing roller 31, and thereby a toner image is formed on the peripheral surface of the photosensitive drum 18. At this time, the developing roller 31 supplies the toner to the photosensitive drum 18 with proper stirring so as not to aggregate.

Specifically, as shown in FIG. 3, the developing roller 31 includes a magnet member 36 fixed to the core metal 35, and a rotating sleeve that covers the outer periphery of the magnet member 36 and rotates via a driving device (not shown). 37, the magnetic pole arrangement of the magnet member 36 is such that the developing pole N1 is located at a position facing the photosensitive drum 18 during the image forming process, and hereinafter, the developing pole N1 is located downstream of the developing pole N in the sleeve rotation direction. The shield pole S1 is located at a position facing the base bottom face 25a that covers the bottom circumferential surface of the rotary sleeve 37 positioned at a predetermined interval, and the blade pole S2, the shield pole S1, and the blade pole S2 near the tip of the cutting plate 33. A four-pole structure in which the transport pole N2 is positioned between the two is employed. Further, the magnet member 36 can be rotated independently of the rotating sleeve 37 by rotating the cored bar 35 through a driving device (not shown), for example. The magnet member 36 may be a magnetic pole arrangement having a five-pole structure, for example.

  On the other hand, in the magnetic member 34, the magnetic force in the normal direction of the magnet member 36 is a substantially zero gauss portion of the magnetic pole arrangement of the magnet member 36 during the image forming process, that is, a substantially four-leaf-shaped normal indicated by a two-dot chain line in FIG. It arrange | positions so that the trough part between the magnetic peak of a direction may be opposed.

  As a result, the magnet member 36 is rotated in a direction opposite to the rotation direction of the rotary sleeve 37 immediately before and immediately after the start of the image forming process, or during standby, and the magnetic member 34 is made to face the maximum magnetic force portion so as to be magnetic. By charging the toner away from the cutting plate 33 (on the downstream side in the rotation direction of the rotating sleeve 37), the charged toner on the rotating sleeve 37 can be replaced.

  Therefore, when the image forming process is actually executed, the magnet member 36 is rotated in the same direction as the rotation direction of the rotary sleeve 37 so that the magnetic pole arrangement of the magnet member 36 becomes the original position. By making the magnetic member 34 face the substantially zero gauss portion, it is possible to execute image formation processing with toner with new ears on the rotating sleeve 37, and thin layer abnormality due to toner charge-up with a simple configuration. Image defects such as white spots due to agglomeration of the magnetic developer near the tip of the cutting plate 33 and a decrease in density can be suppressed.

  In addition, the magnetic member 34 is raised only immediately before and immediately after the start of the image forming process, and at the time of standby, etc., and does not hinder the pumping of the toner during the image forming process, thereby suppressing the deterioration of the toner. Can do.

  In the above embodiment, the developing device of the present invention has been applied to a printer. However, it is needless to say that the present invention can be applied to general image forming apparatuses such as a copying machine and a multifunction peripheral.

  The toner as the magnetic developer is not limited to the one-component magnetic developer, and may be a two-component magnetic developer containing a magnetic carrier.

  Furthermore, the magnet member 36 may have a configuration in which a plurality of magnets are fixed to a core metal in addition to the roller shape described above.

1 is an explanatory diagram of a printer as an image forming apparatus equipped with a developing device according to an embodiment of the present invention. 1 is a cross-sectional view of a developing device according to an embodiment of the present invention. It is explanatory drawing of the principal part of the developing device which concerns on one Embodiment of this invention. It is sectional drawing of the conventional image development apparatus. It is explanatory drawing of the spike in the conventional developing device, (A) is explanatory drawing of the spike when the magnet is not arranged, (B) is the explanatory drawing of the spike at the time of the developing roller low-speed rotation with the magnet arranged (C) is an explanatory view of the heading at the time of high speed rotation of the developing roller provided with a magnet.

Explanation of symbols

18 ... Photosensitive drum (image carrier)
31 ... Developing roller 33 ... Bear cutting plate (toner layer thickness regulating member)
34 ... Magnetic member 35 ... Core metal 36 ... Magnet member 37 ... Rotating sleeve

Claims (4)

In a developing device for carrying a magnetic developer on an image carrier after regulating a layer thickness of a rotating sleeve containing a magnet member having a plurality of magnetic poles and a magnetic developer carried on the rotating sleeve,
The magnet member can be rotated independently of the rotating sleeve, and a magnetic member is disposed at a position where the magnetic force in the normal direction of the magnet member faces approximately zero gauss, and the magnetic pole of the magnet member is made to be magnetic. A developing device characterized in that a magnetic developer is sprinkled by rotating so as to face a member.   The developing device according to claim 1, wherein the magnet member is rotated so that the magnetic pole faces the magnetic member at a predetermined timing except during image forming processing.   The developing device according to claim 1, wherein the magnetic member rotates the magnetic pole having the maximum magnetic force so as to oppose the magnetic member and causes the magnetic developer to stand up.   An image forming apparatus comprising the developing device according to claim 1.

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