JP2006284889A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of preventing toner accumulation or agglomeration by relieving high concentrations of toner near the ends of the rotating sleeve. <P>SOLUTION: Magnets 10 that repulse a magnet roller 22 are disposed on a layer thickness regulating blade 15 on the longitudinal end sides of the rotating sleeve 21, namely, only in prescribed positions at both ends of the layer thickness regulating blade 15. For example, the magnets 10 are disposed opposite the layer thickness regulating blade 15 in the vicinity of the corresponding ends of a developing area. Alternatively, each magnet 10 is disposed opposite the layer thickness regulating blade 15 near the boundary between a sealed part and a non-sealed part. This causes a repulsion electric field to be generated between each magnet 10 and the magnet roller 22, with the result that magnetic developer passing between them is dispersed by the repulsion magnetic field. Accordingly, high concentrations of toner at the ends of the rotating sleeve 21 are relieved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine, and in particular, a layer thickness regulating member that regulates a layer thickness of a magnetic developer carried on a rotating sleeve of a developing roller substantially uniformly, and the rotation A so-called toner fattening phenomenon at the end of the rotating sleeve in a developing device including a seal member that seals the magnetic developer carried on the sleeve at the end of the rotating sleeve (the developer layer is thicker than other portions). This relates to a technology that prevents the phenomenon).

2. Description of the Related Art Image forming apparatuses such as copying machines, printers, and facsimile machines are provided with a developing device that develops an electrostatic latent image on an image carrier such as a photosensitive drum or a photosensitive belt.
The developing device is generally provided with a layer thickness regulating blade (corresponding to a layer thickness regulating member) for making the developer carried on the surface of the rotating sleeve uniform. When the developer on the surface of the rotating sleeve is leveled by the layer thickness regulating blade, excess developer scraped off by the layer thickness regulating blade moves toward the end of the rotating sleeve (axially outward). However, at this time, it is necessary to prevent developer leakage (spilling) at the end of the rotating sleeve.
As a technique for preventing such leakage of the developer, a technique for sealing the developer by bringing an elastic member such as felt or sponge into pressure contact with the end surface of the rotating sleeve is described in Patent Document 1. As described above, there is a method of sealing the developer by forming a magnetic brush with an internal magnet roller by disposing a magnetic member with a predetermined gap along the outer peripheral surface of both ends of the rotating sleeve. Are known.

Here, a schematic configuration of the developing device Y to which the latter method, that is, the method of sealing the developer with a magnetic brush, is applied will be described with reference to FIGS. 6 is a schematic configuration diagram of the developing device Y, and FIG. 7 is a detailed diagram of an end structure of the developing roller 20.
As shown in FIGS. 6 and 7, the developing device Y includes a developing roller 20 that includes a magnet roller 22 included in a rotating sleeve 21, a toner storage unit 18 that stores toner having a predetermined charge, and the like. The toner in the toner container 18 is agitated to be charged to a predetermined charge, and the agitation roller 13 for feeding the charged toner to the supply roller 12 described later, and the toner fed from the agitation roller 13 are A supply roller 12 for feeding to the developing roller 20, a layer thickness regulating blade 15 (an example of a layer thickness regulating means) for making the layer thickness of the toner layer on the rotating sleeve 21 substantially uniform, and a toner on the rotating sleeve 21. A magnetic seal member 14 (an example of sealing means) that seals at both ends in the axial direction (longitudinal direction) of the rotary sleeve 21 and a housing 17 that accommodates or supports these members are provided. Composed of Te.

In the developing device Y configured as described above, the toner supplied from the supply roller 12 is pumped up by the magnetic force of the magnet roller 22 and is carried on the surface of the rotating sleeve 21 that rotates counterclockwise. . The carried toner is conveyed to the downstream side in the rotational direction from the location where the toner is pumped up by the rotation of the rotating sleeve 21, and is arranged at a predetermined interval from the rotating sleeve 21 vertically above the rotating sleeve 21. It is carried to the layer thickness regulation raid 15. When the toner reaches the layer thickness regulating blade 15, the layer thickness of the toner is regulated substantially uniformly by the layer thickness regulating blade 15. At this time, the toner on the rotating sleeve 21 is pushed toward both end portions of the rotating sleeve 21 by the restriction by the layer thickness restricting blade 15, but since the magnetic seal member 14 is provided in the developing device Y, Toner leakage from the end of the rotating sleeve 21 is prevented.
JP-A-10-26884

However, in the developing device Y, although the toner leakage described above is prevented by providing the magnetic seal member 14, the escape sleeve for the toner that has moved to both ends of the rotating sleeve 21 is eliminated. In the vicinity of both end portions of the toner 21, the toner density is increased. Such high density of the toner is remarkable at the boundary between the seal portion by the magnetic seal member 14 and the non-seal portion (region on the center side from the position where the magnetic seal member is disposed).
The toner having such a high density is not easily leveled by the layer thickness regulating blade 15 but is pressed and compressed, but is restored to its original thickness after passing through the layer thickness regulating blade 15. As a result, as shown in FIG. 8, a so-called toner fattening phenomenon occurs in which the toner layer in the vicinity of the end portion of the rotating sleeve 21 becomes thicker than the toner layer in other portions (for example, in the vicinity of the central portion) (see symbol P in FIG. 8). ). In particular, when a stainless steel rotating sleeve is used, its surface roughness is smaller than that of aluminum, and the surface roughness is further reduced at the blasted end. Tends to cause toner thickening. When such toner fattening develops and expands to the developing area on the rotating sleeve 21 (the area on the rotating sleeve 21 corresponding to the image forming area on the photosensitive drum; the hatched area in FIG. 8), More than the necessary amount of toner adheres to the image forming area, or the toner adheres to the non-image forming area and appears as noise (black dots) on the paper. Further, there is a problem that the toner aggregates due to the high density of the toner. These problems may also occur when an elastic member such as felt is pressed against the rotary sleeve 21 for sealing instead of the magnetic seal member 14.
Further, when the magnetic seal member 14 is used as a toner leakage prevention measure, the toner interposed in the gap between the rotating sleeve 21 and the magnetic seal member 14 is overcharged as compared with the toner in other regions. A phenomenon occurs in which the toner that has moved to the magnetic seal member 14 is pushed back, and toner fattening occurs near the development area, which is a problem.
Each of the above-mentioned problems is noticeable as the rotational speed of the rotary sleeve 21 is increased in response to the recent demand for higher speed printing.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to prevent toner thickening and toner aggregation by reducing the density of toner in the vicinity of the end of the rotating sleeve. It is an object of the present invention to provide a developing device capable of achieving the above.

In order to achieve the above object, the present invention provides a developing roller comprising a fixed magnet enclosed by a rotating sleeve, and a magnetic developer carried on the rotating sleeve, the thickness of the magnetic developer disposed on the rotating sleeve so as to face the surface of the rotating sleeve. The present invention is applied to a developing device comprising a layer thickness regulating member that regulates substantially uniformly and a seal member that seals the magnetic developer carried on the rotating sleeve at the end of the rotating sleeve. The developing device is characterized in that a magnet that repels the fixed magnet is disposed only at a predetermined position on the end side in the longitudinal direction of the rotating sleeve. Note that the magnetic developer used in the developing device corresponds to a one-component developer containing magnetic toner, a two-component developer containing non-magnetic toner and a carrier, or a liquid developer containing one of these. .
As a result, the magnetic developer at the end of the rotating sleeve is repelled by the magnet when passing through the repulsive magnetic field formed by the fixed magnet and the magnet so that the magnetic field (magnetic field) by the magnet does not reach. Since it is dispersed, toner fattening and toner aggregation at the end of the rotating sleeve can be prevented. As a result, it is possible to prevent adhesion of more toner than necessary to the image forming area on the photosensitive drum and noise such as black spots.
In this case, if the magnet has the same polarity as the fixed magnet opposed to the magnet, a repulsive magnetic field is generated between the magnet and the fixed magnet, so that dispersion of the magnetic developer is promoted.
In addition, the magnet is disposed upstream of the layer thickness regulating member in the rotating sleeve rotation direction so that the toner on the rotating sleeve is made uniform by the layer thickness regulating member after the toner is dispersed by the magnet. Is preferred.
Further, as a specific example of the predetermined position where the magnet is disposed, a position facing the vicinity of the end of the developing area on the rotating sleeve, that is, the vicinity of the end of the developing area in the layer thickness regulating member Opposing positions are conceivable. As a result, the magnetic pole of the magnet is directed to the vicinity of the end portion of the developing region, so that the toner dispersion efficiency in this portion can be improved.
Further, the predetermined position where the magnet is disposed is a position facing the vicinity of the boundary between the seal part and the non-seal part on the rotating sleeve sealed by the seal member, that is, the layer thickness regulating member. The position which opposes the boundary vicinity of a seal part and the said non-seal part may be sufficient. Since the density of the toner is increased near the boundary between the seal part and the non-seal part, if a magnet is provided at the position, the toner is efficiently dispersed, and the toner is favorably prevented and toner aggregation is preferably prevented. It becomes possible. In this case, if the magnet is disposed from the seal part to the non-seal part, the magnetic pole of the magnet is directed near the boundary between the seal part and the non-seal part. Increases the dispersion efficiency.

  According to the present invention, in the developing device, a magnetic field repelling the magnetic field of the fixed magnet is generated only at a predetermined position of the layer thickness regulating member on the end side in the longitudinal direction of the rotary sleeve, and the repulsion is generated at the end of the rotary sleeve. A magnetic field is formed. As a result, the magnetic developer passing through the repulsive magnetic field is dispersed, so that toner fertilization and toner agglomeration at the end of the rotating sleeve are prevented, and an amount of toner exceeding the required amount on the image forming area on the photosensitive drum is prevented. It is possible to reduce or prevent the occurrence of noise such as adhesion and black spots.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a schematic configuration diagram of the developing device X according to the embodiment of the present invention, and FIG. 2 is a main configuration when the developing device X is viewed from the developing roller side (arrow AA in FIG. 1). 3 is a diagram for explaining the mounting position of the magnet attached to the layer thickness regulating blade, FIG. 4 is a diagram for explaining the arrangement position of the layer thickness regulating blade, and FIG. 5 is a diagram showing the layer thickness regulating blade. FIG. 6 is a schematic configuration diagram of a conventional developing device Y, FIG. 7 is a detailed diagram of the end structure of the developing roller, and FIG. 8 is a diagram illustrating the toner fattening phenomenon. It is a figure to do. In FIG. 1, components common to those of the conventional developing device Y are denoted by the same reference numerals.

As shown in FIG. 1, a developing device X according to an embodiment of the present invention is formed on an image carrier such as a photosensitive drum or a photosensitive belt in an image forming apparatus such as a copying machine, a facsimile machine, or a printer. The developed electrostatic latent image is developed by attaching toner, and rotates a magnet roller 22 (corresponding to a fixed magnet) having four magnetic poles in substantially the same manner as the conventional developing device Y (FIG. 6). A developing roller 20 including a sleeve 21, a toner container 18 containing a one-component developer containing magnetic toner (hereinafter referred to as “toner”), and the toner in the toner container 18 are agitated to stir the toner. The toner is charged to a predetermined charge (in this embodiment, the negative electrode), and a stirring roller 13 for feeding the charged toner to a supply roller 12 described later, and the fed toner is fed to the rotating sleeve 2. A supply roller 12 that feeds the toner, a layer thickness regulating blade 15 (an example of a layer thickness regulating means) that regulates and substantially equalizes the layer thickness of the toner layer carried on the rotating sleeve 21, and toner on the rotating sleeve 21. A magnetic seal member 14 (an example of a sealing means) that seals at both ends of the rotating sleeve 21 and a housing 17 that accommodates or supports each of these components are configured.
Further, in the developing device X, unlike the developing device Y, a magnet 10 having a polarity S that repels the magnet roller 22 is attached to the layer thickness regulating blade 15. The mounting position of the magnet 10 will be described later.
The developing device X is a dry developing device, and will be described as a one-component developing type developing device that develops using a one-component developer containing magnetic toner charged on the negative electrode. A developing device of a two-component developing system that develops using a two-component developer containing a carrier, or a wet developing device using a liquid developer containing either the one-component developer or the two-component developer. Also, the present invention can be applied.

The developing roller 20 includes a magnet roller 22 including four magnetic poles 22a (N pole), 22b (S pole), 22c (N pole), and 22d (S pole) provided therein, and the magnet roller. 22 and a non-magnetic cylindrical rotating sleeve 21 provided on the outer periphery of 22. The magnet roller 22 is a block type in which a plurality of magnets are bonded so that adjacent magnetic poles are different, and is fixedly supported by the housing 17 so as not to rotate. On the other hand, the rotating sleeve 21 is pivotally supported by the housing 17 so as to be rotatable counterclockwise in the outer circumferential direction of the magnet roller 22.
Each of the four magnetic poles constituting the magnet roller 22 has an individual role, and the magnetic pole 22a (pumping pole) pumps up the toner charged on the negative electrode supplied from the supply roller 12 to the surface of the rotating sleeve 21. The magnetic pole 22b (conveying pole) serves to convey the toner on the rotating sleeve 21, and the magnetic pole 22c (developing pole) causes the electrostatic latent image on the photosensitive drum 4 to rise by raising the toner. The magnetic pole 22d (collection pole) plays a role of developing (conveying) the toner remaining after development into the developing device X. The magnet roller 22 is not limited to the block type, and may be formed integrally with, for example, four magnetic pole areas. Further, the number of magnetic poles is not limited to four.

At both ends of the developing roller 20, the magnetic seal member 14 made of a magnetic material is provided so as to face the outer peripheral surface of the inner side of the housing 17 of the rotating sleeve 21 with a predetermined gap therebetween. The magnetic seal member 14 forms a concentrated magnetic field with the magnet roller 22 included in the rotary sleeve 21 and forms a magnetic brush with the toner interposed in the predetermined gap, so that the toner rotates. Outflow from both ends of the sleeve 21 is prevented.
In the present embodiment, the magnetic seal member 14 is illustrated as an example of the sealing means. However, instead of the magnetic seal member 14, an elastic member such as felt or sponge is used, and this elastic member is attached to the surface of the rotating sleeve 21. The outflow (leakage) of the toner may be prevented by press contact. In this case, the elastic member is an example of a sealing means.

The layer thickness regulating blade 15 is downstream in the rotational direction of the rotary sleeve 21 from the location where the toner is pumped up by the pumping pole 22a (N pole), and upstream of the surface facing the photosensitive drum 4 in the rotational direction. On the side, the surface of the rotating sleeve 21 is opposed to the surface.
The magnet 10 is attached to the layer thickness regulating blade 15 as described above. Specifically, as shown in FIG. 2 (a), the magnet 10 is located on the end side in the longitudinal direction of the rotary sleeve 21 in the layer thickness regulating blade 15 and adjacent to the magnetic seal member 14. (Corresponding to a predetermined position), that is, only at the adjacent positions at both ends of the layer thickness regulating blade 15. Here, FIG. 2A is a diagram of the developing device X of FIG.

  Here, as shown in FIG. 4B, the layer thickness regulating blade 15 is a plate-like magnetic member having a thickness of 2 mm, a height of 20 mm, and a width that is longer than at least the entire width of the rotating sleeve 21. The magnet 10 is a plate magnet having a thickness of 2 mm, a height of 10 mm, and a width of 10 mm. Further, the magnet 10 is mounted so that the lower surface of the layer thickness regulating blade 15 and the magnet 10 are flush with each other, and the gap between the lower surface and the surface of the rotating sleeve 21 is set to about 0.3 mm. ing. Of course, the size and dimensions are not limited to these, and it is needless to say that sizes and dimensions appropriately designed according to the specifications of the developing device and the specifications of the toner to be used can be adopted. In this embodiment, the layer thickness regulating blade 15 of the magnetic member is used, but a layer thickness regulating blade made of a nonmagnetic member may be used.

  As described above, since the developing device X is provided with the magnet 10 at both ends of the layer thickness regulating blade 15, the magnetic seal member 14 is provided so that toner is present in the vicinity of the magnetic seal member 14. Even if the toner particles are collected, the toner is dispersed by passing through a repulsive magnetic field generated between the magnet 10 and the conveyance pole 22b of the magnet roller 22. Therefore, the density of toner does not increase near the magnetic seal member 14 at the end of the rotating sleeve 21, and as a result, toner fattening and toner aggregation are prevented.

The arrangement position of the layer thickness regulating blade 15 is within a range in which toner is conveyed by the magnet roller 22. Therefore, the layer thickness regulating blade 15 and the magnet 10 attached thereto are arranged in a range where the magnetic field of the transport pole 22b (S pole) is affected, as shown in FIG. Become.
As described above, in order to generate a repulsive magnetic field between the magnet 10 and the magnet roller 22, the magnet 10 has the same polarity as that of the transport pole 22b (S pole). Therefore, a repulsive magnetic field that draws curved lines of magnetic force is formed between the magnet 10 and the transport pole 22b as shown in FIG. For this reason, the negative toner present in the magnetic field is affected by both magnetic fields, and is dispersed in a wide range in a direction in which the magnetic field is less affected, that is, in a direction away from the magnet 10. Specifically, it is dispersed toward the center of the rotating sleeve 21. Since the magnetic seal member 14 is disposed at the end of the rotating sleeve 21, the rotating sleeve 21 is not dispersed toward the end of the rotating sleeve 21.
The magnet 10 may be provided on any surface of the layer thickness regulating blade 15, but as shown in FIG. 2A, in the present embodiment, the layer thickness regulating blade 15 has the above-mentioned. The rotating sleeve 21 is provided on the upstream surface 15a in the rotation direction. As a result, the toner layer after the toner is dispersed by the magnet 10 is made uniform by the layer thickness regulating blade 15, and the toner layer leveled to a uniform height is used for development.

By the way, the reason why the toner in the vicinity of the magnetic seal member 14 is increased in density is that the magnetic seal member 14 is provided to eliminate the escape place of the toner that has moved to both ends of the rotary sleeve 21. In view of such factors, it can be said that the region where the toner density is the highest is the point where the toner that has moved in the direction of the end due to the regulation by the layer thickness regulating blade 15 collides with the magnetic seal member 14. That is, as shown in FIG. 3A, a region 33 in the vicinity of the boundary between the sealing portion 31 (horizontal stripe portion) and the non-sealing portion 32 (shaded portion) on the rotating sleeve 21 sealed by the magnetic seal member 14. Is the most dense area. As a matter of fact, it is obvious that the rate of occurrence of toner fattening and toner aggregation in this region 33 is high.
Therefore, in order to efficiently eliminate the increase in density of the toner, it is preferable to attach the magnet 10 at a position facing the region 33 in the layer thickness regulating blade 15. In this case, as shown in FIG. 2 (b), the magnet 10 is disposed from the seal portion 31 to the non-seal portion 32, and the center of the magnet 10 is located between the seal portion 31 and the non-seal portion. If it is arranged so as to be located at the boundary with the portion 32, the magnetic pole of the magnet 10 is directed near the boundary, that is, the strongest magnetic field is applied near the boundary, which is preferable. At this time, the magnet 10 and the magnetic seal member 14 are overlapped to cause positional interference. However, a notch or the like that can accommodate the magnet 10 is formed on the side surface of the magnetic seal member 14 and then there. The position interference can be eliminated by fitting the magnet 10 or the like.

Further, if importance is attached to preventing the adhesion of an excessive amount of toner to the image forming area (especially the end of the image forming area) on the photosensitive drum 4 and unnecessary adhesion of the toner to the non-image forming area. For example, the magnet 10 is attached to the layer thickness regulating blade 15 facing the region 35 in the vicinity of the widthwise end of the developing region 34 (shaded portion) on the rotating sleeve 21 shown in FIG. You can do it.
Of course, magnets may be provided separately in both of the regions 33 and 34, or a single magnet covering the regions 33 and 34 may be provided.

1 is a schematic configuration diagram of a developing device X according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of main components when the developing device X according to the embodiment of the present invention is viewed from the developing roller side (the arrow AA in FIG. 1). The figure explaining the detail of the attachment position of the magnet attached to the layer thickness control blade. The figure explaining the arrangement position of a layer thickness regulation blade. The direction of the magnetic field between the magnet and magnet roller attached to the layer thickness regulating blade is shown. 1 is a schematic configuration diagram of a conventional developing device Y. FIG. FIG. 3 is a detailed view of an end portion structure of the developing roller. The figure explaining a toner fattening phenomenon.

Explanation of symbols

4 ... photosensitive drum 10 ... magnet 12 ... supply roller 13 ... stirring roller 14 ... magnetic seal member 15 ... layer thickness regulating blade (layer thickness regulating member)
17 ... Housing 18 ... Toner container 20 ... Developing roller 21 ... Rotating sleeve 22 ... Magnet roller

Claims (6)

A developing roller comprising a fixed magnet enclosed by a rotating sleeve;
A layer thickness regulating member which is disposed opposite to the surface of the rotating sleeve and regulates the layer thickness of the magnetic developer carried on the rotating sleeve substantially uniformly;
A seal member that seals the magnetic developer carried on the rotating sleeve at an end of the rotating sleeve;
A developing device comprising:
A developing device comprising: a magnet that repels the fixed magnet only at a predetermined position on the end side in the longitudinal direction of the rotary sleeve in the layer thickness regulating member.   The developing device according to claim 1, wherein the magnet has the same polarity as the fixed magnet facing the magnet.   The developing device according to claim 1, wherein the magnet is disposed upstream of the layer thickness regulating member in the rotating sleeve rotation direction.   The developing device according to claim 1, wherein the predetermined position where the magnet is disposed is a position facing the vicinity of the end of the developing region on the rotating sleeve.   The said predetermined position where the said magnet is arrange | positioned is a position which opposes the boundary vicinity of the seal part on the said rotation sleeve sealed by the said seal member, and a non-seal part. Development device.   The developing device according to claim 5, wherein the magnet is disposed from the sealing portion to the non-sealing portion.

Images