JP4199822B2 - Development device - Google Patents

Description

  The present invention relates to a developing device, and more particularly to a developing device having a magnetic seal member that is used in an image forming apparatus such as a digital copying machine, a facsimile machine, and a printer and is disposed in a non-contact manner with a developing sleeve.

In an image forming apparatus typified by a digital copying machine, a facsimile machine, a printer, etc., the surface of the photosensitive drum is uniformly charged, and light based on the original image is irradiated onto the surface of the photosensitive drum, thereby staticizing the original image. An electrostatic latent image is formed, and then a developer (or toner) is attached to the electrostatic latent image by a developing device to form a toner image.
Next, the toner image is attracted and transferred from the photosensitive drum by the transfer device.
Thereafter, the sheet on which the toner image has been transferred is separated from the photosensitive drum, conveyed to a fixing device, and the toner image is fixed on the transfer sheet by heat, pressure, or the like.

In an image forming apparatus that performs such toner development, a one-component magnetic developer composed of magnetic toner or a two-component magnetic developer composed of a mixture of magnetic carrier and toner is generally used as a developer. Has been.
In addition, a developing device for performing development using such a magnetic developer is provided so as to face the surface of the photosensitive drum, and toner charged to a predetermined polarity on the surface of the photosensitive drum. A developing sleeve for transporting the developer containing it is accommodated.

Here, in such a developing device using magnetic toner, a configuration is proposed in which magnetic seal members are provided at both ends of the developing sleeve in order to prevent the developer from flowing out of the developing region.
The magnetic seal member is formed of a magnet, and NS poles are magnetized by a predetermined magnetic pole pattern to form multiple magnetic poles, and a magnetic brush is formed by toner spikes along the lines of magnetic force generated by the magnetic pole pattern. This improves the sealing performance of the toner.
However, in the magnetic seal member having such a configuration, the above-described developing sleeve has a structure including a magnet (fixed magnet) having a plurality of magnetic poles in a non-magnetic sleeve such as aluminum. When the magnetic poles having the same polarity are opposed to each other in parallel between the magnetic poles magnetized on the magnetic seal member by rotation, for example, the magnetic seal member 50 is magnetized as shown in FIG. When the N pole of the magnet 51 and the N pole of the magnet 51 face each other in parallel, an NN repulsive magnetic field is formed, so that the magnetic force lines of the magnetic seal are bent in the longitudinal direction (axial direction) of the developing sleeve. End up.
Further, since the toner is arranged along the magnetic field lines, the developer is likely to slip through toward the end of the developing sleeve, and as a result, the developer is likely to flow out of the developing region, and a good sealing property is obtained. It becomes impossible to demonstrate.
Therefore, a configuration has been proposed in which a magnetic member having a high transmittance is disposed outside the magnetic seal member (outside in the rotation axis direction of the developing sleeve) (see, for example, Patent Document 1).

That is, as shown in FIG. 10, by disposing the magnetic member 52 at the end of the magnetic seal member 50, the N pole and magnet magnetized on the magnetic seal member 50 as shown in FIG. 9B. Even when the N poles of 51 are opposed in parallel and an N-N repulsive magnetic field is formed, the magnetic lines of force radiated from the magnetic seal member 50 are at the boundary between the magnetic seal member 50 and the magnetic member 52. Since it enters the magnetic member 52 having a high transmittance, it is possible to suppress the generation of magnetic lines of force that extend to the outside of the magnetic member 52.
JP-A-11-133750 (pages 4-6, 6-11)

However, in the magnetic seal member in the conventional developing device, although the spread of the magnetic lines of force to the outside of the magnetic member 52 can be suppressed, the N pole magnetized by the magnetic seal member 50 and the N pole possessed by the magnet 51 are still present. Since the N-N repulsive magnetic field is formed in parallel with each other, the magnetic field lines radiated from the magnetic seal member 50 are guided to the magnetic member 52 having high transmittance at the boundary between the magnetic seal member 50 and the magnetic member 52. Strong magnetic force (1000 to 2200 gauss in magnetic flux density) is required.
As a result, there is a disadvantage that the cost of the magnetic seal member 50 increases.
Further, since it is necessary to separately provide the magnetic member 52 at the end of the magnetic seal member 50, there are disadvantages that the manufacturing process of the magnetic seal member 50 is complicated and the cost is increased.

  The present invention solves the above-mentioned problems, and can suppress and prevent the developer from slipping in the direction of the end of the developing sleeve with a low cost and simple configuration, and can exhibit a good sealing property. An object of the present invention is to provide a developing device including a member.

In order to achieve the above object, the present invention provides a developer container for containing a developer,
A developing sleeve that incorporates a magnet and is rotatably attached to the opening of the developer container and conveys the developer to the electrostatic latent image formed on the photoreceptor, and a predetermined distance from the developing sleeve And a magnetic seal member disposed at both ends of the developing sleeve in a separated state. A plurality of N poles are provided on the inner peripheral surface of the magnetic seal member facing the outer peripheral surface of the developing sleeve. And the S poles are alternately magnetized at predetermined intervals, and the arrangement direction of the magnetic poles is parallel to the longitudinal direction of the developing sleeve, and the developing sleeve of the magnetic seal member And the magnetic pole of the magnet facing the downstream end of the magnetic seal member in the rotation direction of the developing sleeve is different in polarity.

  According to this configuration, in the magnetic pole magnetized in the multi-pole, the magnetic pole having the same polarity as the magnetic pole of the magnet facing the inner peripheral surface of the magnetic seal member does not face in parallel. While being able to prevent slipping in the end direction, it is possible to exhibit good sealing properties.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a front view illustrating a configuration of a main part of an image forming apparatus main body including a developing device according to an embodiment of the present invention.
The main part is a photosensitive drum 1 that rotates in one direction (in the direction of the arrow in the drawing), the charging device 2 that faces the photosensitive drum 1 and is disposed along the rotational direction of the photosensitive drum 1. The developing device 3, the transfer device 4, the separation device 5, and the cleaning device 6.

Under such a configuration, a copy original image is read by a document reading unit (not shown), and the surface of the photosensitive drum 1 rotating in the direction of the arrow in the drawing is uniformly charged by the charging device 2. Be made.
Next, light based on the image read by the document reading unit is irradiated onto the surface of the photosensitive drum 1 by the exposure device 7 to form an electrostatic latent image of the image.
A toner thin film is formed on the developing sleeve 9 containing a magnet therein, and a toner image is formed by transporting and adhering the toner to the electrostatic latent image by the developing sleeve 9.

Further, the toner image is drawn from the photosensitive drum 1 by the transfer device 4 and transferred onto the paper (not shown) supplied between the photosensitive drum 1 and the transfer device 4 via the paper supply path 8. The
Thereafter, the sheet onto which the toner image has been transferred is separated from the photosensitive drum 1 by the separating device 5 and conveyed to a fixing device (not shown), and the toner image is fixed on the transfer paper by the fixing device.

On the other hand, after the toner image is transferred by the transfer device 4, the toner remaining on the surface of the photosensitive drum 1 is completely removed by the cleaning device 6.
The photosensitive drum 1 from which the residual toner has been removed is subjected to removal of residual charges on the surface by a neutralization unit (not shown) constituted by a plurality of LEDs and the like, and reaches the charging device 2.

FIG. 2 is a cross-sectional view of the developing device according to the embodiment of the present invention.
The developing device 3 includes a developing housing 13 that is a developer container filled with a magnetic developer (or magnetic toner). In the developing housing 13, a spiral first stirring and conveying member 10 is provided. Similarly, a spiral second stirring / conveying member 11 is provided.
A developing sleeve 9 in which a magnet (or magnet roller) 9b having a plurality of magnetic poles is incorporated in a nonmagnetic sleeve 9a made of aluminum or the like is rotatably attached to an opening 13a of the developing housing 13. The magnet 9b built in the developing sleeve 9 includes two N poles (N1 and N2) and two S poles (S1 and S2).
Above the developing sleeve 9, a developing blade 12 that regulates the amount (or toner amount) of the developer conveyed to the photosensitive drum 1 is disposed at a predetermined distance from the developing sleeve 9. Yes.

  Here, in the developing sleeve 9 in this embodiment, the built-in magnet 9b is fixed and the cylindrical sleeve 9a is rotated in the direction of the arrow shown in FIG. 2 (that is, counterclockwise). However, the magnet 9b may be rotated and the sleeve 9a may be fixed, or both the magnet 9b and the sleeve 9a may be rotated (the rotation direction may be the same direction or the opposite direction).

When an insufficient toner amount in the developing device 3 is detected by a toner sensor (not shown), toner T is supplied to the developing device 3 from a toner hopper (not shown).
In this embodiment, the toner T is a magnetic toner, and a one-component magnetic developer (one-component magnetic toner) made of the magnetic toner is used as a developer.
Further, the toner T is first conveyed while being agitated from the front of the figure to the back by rotating the first agitating and conveying member 10 in the direction of the arrow in the figure, and the first agitating and conveying member 10 at the far side end. To the second stirring and conveying member 11.
Then, when the second agitating and conveying member 11 rotates in the direction of the arrow in the figure, the toner T is conveyed while being agitated in the near direction from the back side in the figure, while receiving the magnetic force of the magnet 9b, the developing sleeve 9 receives the magnetic force. It is the structure which adheres suitably to the surrounding surface (conveyance surface).

The toner T adhering to the peripheral surface of the developing sleeve 9 is conveyed to a position facing the photosensitive drum 1 (developing unit) by counterclockwise rotation by the developing sleeve 9.
At this time, the thickness of the toner layer carried by the developing sleeve 9 to the developing portion is regulated by the developing blade 12 disposed at a predetermined distance from the developing sleeve 9, and the amount of toner conveyed to the developing portion is reduced. Be controlled.

The method for developing the electrostatic latent image on the photosensitive member (electrostatic latent image carrier) may be either the normal development method or the reversal development method. Either the contact development method or the jumping development method in which the two are not in contact may be used, but from the viewpoint of suppressing fogging, a combination of the reverse development method and the jumping development method is recommended.
In this case, the photosensitive member is charged with the same polarity as the toner, and the charge in the latent image portion is removed by exposure.
Then, by applying an alternating voltage in which an alternating current is superimposed on a direct current as a developing bias between the developing sleeve and the photosensitive member in the developing unit, the toner on the developing sleeve removes the electrostatic latent charge from which the charge on the photosensitive member has been removed. The toner is transferred to an image, and the toner is attached to the electrostatic latent image to be visualized as a toner image.

There is no limitation on the material of the photoreceptor that can be used here, and conventionally known materials can be used.
For example, a photoconductor such as an amorphous silicon photoconductor, an organic photoconductor, a Se photoconductor, a ZnO photoconductor, or a CdS photoconductor can be used.
In this embodiment, the drum-shaped photoconductor, that is, the photoconductor drum 1 is used. However, the shape of the photoconductor is not limited, and a known shape other than the drum shape can be used. .
Examples of the shape include a sheet shape, a belt shape, and a web shape.

Further, as shown in FIG. 3, magnetic seal members 14 having NS poles magnetized in multiple magnetic poles on the inner peripheral surface 15 are disposed at both ends of the developing sleeve 9.
For these magnetic seal members 14, for example, anisotropic rubber magnets magnetized with a magnetic flux density of 400 to 500 G (Gauss) or neodymium magnets are used.
As shown in FIG. 2, the magnetic seal member 14 is not in contact with the developing sleeve 9, that is, in a state where it is separated from the outer peripheral surface of the developing sleeve 9 (or the outer peripheral surface of the sleeve 9a) by a predetermined distance d. It is disposed at both ends of the developing sleeve 9 and is disposed on the opposite side of the photosensitive drum 1 via the developing sleeve 9.
The magnetic seal member 14 is attached to the developing housing 13.

Here, in this embodiment, as shown in FIGS. 3 to 5, three N poles Na, Nb, Nc are formed on the inner peripheral surface 15 of the magnetic seal member 14 (that is, the surface facing the developing sleeve 9). And two S poles Sa and Sb are magnetized substantially perpendicularly to the longitudinal direction (or axial direction) X of the developing sleeve 9.
In these three N poles Na, Nb, Nc and the two S poles Sa, Sb, adjacent magnetic poles are magnetized on the inner peripheral surface 15 at a predetermined interval w.
Here, the predetermined interval w means a pitch interval between the center lines C of adjacent magnetic poles (see FIG. 5), and if the interval w is narrowed, the number of magnetic poles that can be magnetized on the inner peripheral surface 15 increases. The magnetic force (or magnetic flux density) of the magnetic seal member 14 at a position facing the surface of the developing sleeve 9 is increased, and better sealing performance can be exhibited.

In other words, in the present embodiment, with the above-described configuration, it is possible to increase the number of magnetic poles that can be magnetized on the inner peripheral surface 15 facing the surface of the developing sleeve 9 by narrowing the interval w between adjacent magnetic poles. .
Accordingly, the magnetic force (or magnetic flux density) of the magnetic seal member 14 at a position facing the surface of the developing sleeve 9 is increased, and the rubber magnetized to a smaller magnetic flux density (400 to 500 G) than that of the conventional magnetic seal member. A magnet can be used, and a rubber magnet having such a small magnetic force can exhibit good sealing performance.
Moreover, the cost of the magnetic seal member 14 can be reduced by using a low-cost rubber magnet.

  In order to exhibit such a good sealing property, it is preferable that the predetermined interval w is 1 to 5 mm. In the present embodiment, as described above, the magnetic flux density is 400 to 500 G (Gauss). Therefore, the predetermined interval w is set to 2 mm.

  As described above, when the magnetic poles magnetized on the magnetic seal member 14 are magnetized substantially perpendicularly to the longitudinal direction X of the developing sleeve 9, the lines of magnetic force on the inner peripheral surface 15 of the magnetic seal member 14 are as shown in FIG. As shown in FIG. 8, the magnetic toner T is arranged on the two south poles Sa and Sb along the magnetic field lines.

Further, by rotation of the magnet 9b having a plurality of magnetic poles, for example, as shown in FIG. 6, the N pole (see FIG. 6) that the magnet 9b has on the inner peripheral surface 15 of the magnetic seal member 14 magnetized with the plurality of magnetic poles. In this case, the three N poles Na, Nb, Nc and the two S poles Sa, Sb are attached substantially perpendicularly to the longitudinal direction X of the developing sleeve 9 as described above. Unlike the prior art described above, the magnetic poles having the same polarity as the magnetic poles of the magnet 9b facing the inner peripheral surface 15 of the magnetic seal member 14 (that is, N poles) may face each other in parallel. Disappear.
Therefore, as shown in FIG. 6, the lines of magnetic force generated by the opposing magnetic poles of the magnetic seal member 14 and the developing sleeve 9 are formed in accordance with the NS forward magnetic field and no NN repulsive magnetic field is formed. Magnetic field lines are not bent in the longitudinal direction X (or axial direction) of the developing sleeve 9, and as a result, it is possible to prevent the developer from slipping in the direction of the end of the developing sleeve 9 and to exhibit good sealing performance. Is possible.

In the present embodiment, as described above, the magnetic pole having the same polarity as the magnetic pole of the magnet 9b facing the inner peripheral surface 15 of the magnetic seal member 14 is not opposed in parallel. A repulsive magnetic field is not formed in the magnetic field lines generated by the opposing magnetic poles with the sleeve 9.
Therefore, it is not necessary to separately provide a magnetic member at the end of the magnetic seal member 14, and as a result, the manufacturing process of the magnetic seal member 14 is facilitated and the cost can be reduced.
In addition, since a strong magnetic force at the boundary between the magnetic seal member 14 and the magnetic member is not required, the cost of the magnetic seal member can be further reduced.

  In addition, this invention is not limited to the said embodiment, Based on the meaning of this invention, it is possible to change suitably the structure of each part, a shape, etc., and excludes them from the scope of the present invention. is not.

For example, in the above embodiment, the configuration is such that three N poles Na, Nb, Nc and two S poles Sa, Sb are magnetized on the inner peripheral surface 15 of the magnetic seal member 14. The number of N poles and S poles is not particularly limited as long as a plurality of N poles and a plurality of S poles are alternately magnetized.
For example, five N poles and five S poles may be alternately magnetized at a predetermined interval w.

  In the above-described embodiment, a one-component magnetic developer composed of magnetic toner is used as the developer. However, the present invention is, for example, a two-component system in which a magnetic carrier and toner are mixed as the developer. Needless to say, the present invention can also be applied when a magnetic developer is used.

As described above, in the present invention, the plurality of magnetic poles are magnetized on the inner peripheral surface of the magnetic seal member (that is, the surface facing the developing sleeve) substantially perpendicularly to the longitudinal direction of the developing sleeve. Therefore, in the plurality of magnetic poles, the magnetic poles having the same polarity as the magnetic poles of the magnets facing the inner peripheral surface of the magnetic seal member do not face each other in parallel.
Accordingly, it is possible to prevent the developer from slipping toward the end portion of the developing sleeve and to exhibit good sealing performance.
In addition, since it is not necessary to separately provide a magnetic member at the end of the magnetic seal member, the manufacturing process of the magnetic seal member is facilitated and the cost can be reduced.
In addition, since a strong magnetic force is not required at the boundary between the magnetic seal member and the magnetic member, the cost of the magnetic seal member can be further reduced.

FIG. 3 is a front view illustrating a configuration of a main part of an image forming apparatus main body including a developing device according to an embodiment of the present invention. These are sectional views of the developing device according to the embodiment of the present invention. These are the perspective views for demonstrating the seal structure in the developing device which concerns on embodiment of this invention. These are perspective views of the magnetic seal member in the developing device according to the embodiment of the present invention. These are front views of the magnetic seal member in the developing device according to the embodiment of the present invention. These are the perspective views for demonstrating the magnetic force line by the opposing magnetic pole of the magnetic seal member and developing sleeve in the developing device which concerns on embodiment of this invention. These are the front views for demonstrating the magnetic force line on the internal peripheral surface of the magnetic seal member in the developing device which concerns on embodiment of this invention. These are front views for explaining the arrangement of magnetic toners in the developing device according to the embodiment of the present invention. These are the figures for demonstrating the line of magnetic force in the case of forming the NN repulsive magnetic field in the conventional developing apparatus. These are the perspective views of the magnetic seal member in the conventional developing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging device 3 Developing device 4 Transfer device 5 Separating device 6 Cleaning device 7 Exposure device 8 Paper supply path 9 Developing sleeve 9a Sleeve 9b Magnet 10 First stirring and conveying member 11 Second stirring and conveying member 12 Developing blade 13 Developing Housing 13a Opening 14 Magnetic seal member 15 Inner peripheral surface

Claims (1)

A developer container containing the developer;
A developing sleeve that incorporates a magnet and is rotatably attached to the opening of the developer container, and conveys the developer to an electrostatic latent image formed on a photoreceptor;
A developing device having a magnetic seal member disposed at both ends of the developing sleeve at a predetermined interval from the developing sleeve;
A plurality of N poles and S poles are alternately magnetized at predetermined intervals on the inner peripheral surface of the magnetic seal member facing the outer peripheral surface of the developing sleeve, and the arrangement direction of the magnetic poles is Configured to be parallel to the longitudinal direction of the developing sleeve,
The magnetic seal member is configured such that the magnetic pole on the inner side in the longitudinal direction of the developing sleeve and the magnetic pole of the magnet facing the downstream end in the rotation direction of the developing sleeve of the magnetic seal member are different from each other. A developing device.

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