JPH07281528A - Developing device for image forming device - Google Patents

Abstract

PURPOSE:To make magnetic flux density high on a part where a seal is formed by restraining toner and to surely prevent the toner from leaking at a low cost without especially enhancing accuracy on process and assembling by magnetically connecting a magnetic sealing member to a magnet roller and forming a magnetic circuit. CONSTITUTION:Since the magnet roller 7 extends outside the toner carrying part of a sleeve 4, the toner leaking toward a side part enters a gap part between the end edge of the magnet roller and the annular part 10a of the seal member 10. The magnetic flux exists on the gap part between the end edge of the roller 7 and the annular part 10a of the member 10 with high density, the toner reaching the part is controlled to be accumulated. In this case, the magnetic flux generated from the roller 7 is converged on the annular part 10a of the member 10, then is returned to the roller 7 through a connecting part, the annular part, and a shaft part 7a. Consequently, magnetic resistance can be made small by adequately setting saturated magnetic flux amount on the connecting part and the annular part.

Description

Detailed Description of the Invention

[0001]

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus utilizing an electrostatic transfer process, such as an electrostatic copying machine and a printer, and more particularly to a developing apparatus therefor.

[0002]

2. Description of the Related Art A developing device in a known image forming apparatus including a step of applying a magnetic toner to an electrostatic latent image formed on an image carrier to form a toner image includes a developing container and a magnetic toner. An image in which a latent image is formed on a part of the toner chamber containing a toner chamber and a non-magnetic sleeve which is adjacent to the toner chamber and includes a magnet roller and is axially supported on the side wall of the developing container. It is provided with a structure facing the carrier.

With this structure, the magnetic toner attracted to the sleeve by the action of the magnet roller is brought to the developing portion where the sleeve and the image carrier face each other by rotating the sleeve, and the action of the developing bias is exerted. In general, the toner on the sleeve side is applied to the latent image on the image carrier side to form a toner image.

In the developing device having such a structure, there is a possibility that toner may leak from the bearing portions of the side walls of the developing container at both ends of the magnet roller and the sleeve, and therefore a sealing mechanism is required to prevent this. However, as a sealing mechanism, there is provided a magnetic seal in which a seal member made of a magnetic material is disposed so as to surround the sleeve at a position near the end of the magnet roller and further outside the surface of the end of the sleeve surrounding the magnet roller. Are known.

That is, the magnetic seal has a structure in which an annular seal member is arranged outside the sleeve end so as to sandwich and surround the sleeve with the inner magnet roller end.

With such a structure, the magnetic toner that moves so as to leak from the sleeve end portion to the outside is restrained by the magnetic field formed between the magnet roller end portion and the seal member and stays at this position. However, eventually, a toner layer is firmly formed on this portion, and the toner that subsequently leaks is blocked and a sealing action is performed.

In the case of the seal mechanism as described above, in order to firmly hold the toner at a predetermined position, the distance between the magnet end and the seal member and the distance between the sleeve and the seal member outside the sleeve should be as small as possible. It is necessary to narrow the width to increase the magnetic flux density, and to reduce the thickness of the formed toner layer to strengthen the coupling force between the toners.

As described above, in the known magnetic seal mechanism,
Since the improvement of the sealing function depends on narrowing the distance between the magnet roller and the sealing member and the distance between the sleeve and the sealing member, it is necessary to improve the processing and assembling accuracy of each member. I can not escape up.

The present invention has been made to cope with such a situation, and in a developing device equipped with the magnetic seal as described above, the toner is restrained and sealed without particularly improving the processing and assembly precision. SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing device capable of increasing the magnetic flux density at the portion where the toner is formed, and more reliably preventing toner leakage at low cost.

[0010]

[Constitution of the invention]

In order to achieve the above object, the present invention has a developing sleeve rotatably supported to convey the stored magnetic toner, and a developing sleeve included in the developing sleeve. In a developing device of an image forming apparatus including a magnet roller, an annular magnetic seal member is provided outside the developing sleeve at a position of an end portion of the magnet roller included in the developing sleeve and spaced from the outer peripheral surface of the sleeve. Then, the magnetic seal member is magnetically connected to the magnet roller to form a magnetic circuit, or in the above, the magnetic seal member includes a developing sleeve and a support member for supporting the magnet roller. And a developing device.

With this structure, the toner restraining action of the magnetic seal mechanism formed at the end portion of the developing sleeve where the magnetic toner leaks can be strengthened, and the toner leakage can be reliably prevented.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS "FIG. 1" shows an embodiment of the present invention, and is a sectional view showing one of the portions of a developing device for supporting a magnet roller and a sleeve on the side wall of the developing device, FIG.
FIG. 4 is a perspective view of a seal member.

Both ends of the magnet roller 7 (only one of which is shown in the drawing) are supported at appropriate places on the side wall of the developing container. The magnet roller 7 may be an integral member such as a plastic magnet, but the bearing portion 7a may be made of a ferromagnetic material such as iron and the magnet main body 7b portion may be formed of a magnet.

Reference numeral 4 is a sleeve, the end portion of which is axially supported by a bearing 5 arranged on the developing device container side. A drive gear 9 is provided at the end of the sleeve, and the sleeve 4 is rotated via the gear 9 by a drive source (not shown).

A magnetic toner 2a is housed inside a container 2 inside the side wall 3 of the developing device (on the right side in the drawing) and abuts against the sleeve 4 to form a toner carrying portion 6. Reference numeral 8 is a spacer roller that contacts the surface of an image carrier (not shown) to set the distance between the surface and the surface of the sleeve 4.

With such a structure, the magnetic toner in the developing container adheres to the surface of the sleeve 4 by the action of the magnet roller, and is conveyed along the surface by the rotation of the sleeve, so that the sleeve comes close to the image carrier. It is assumed that the toner is transported to the part and further transferred to the image carrier side by the action of the developing bias.

Reference numeral 10 is a magnetic seal member,
The magnet roller 7 is provided with an annular portion 10a arranged near the end portion 7c of the magnet roller 7 so as to surround the magnet roller, and the sleeve 4 end portion is present between the outer periphery of the magnet roller and the annular portion 10a of the magnetic seal member 10. It is configured to do.

FIG. 2 is a perspective view showing only the magnetic seal member 10. As described above, when this is arranged in the developing device, the portion located outside the end portion 7c of the magnet roller is the portion indicated by reference numeral 10a, and at this time, the portion surrounding the bearing portion 7a of the magnet roller 7 is located. It is an annular portion indicated by reference numeral 10b. Both of them are connected by a connecting portion 10c to be integrally formed as a whole and are made of a ferromagnetic material.

As shown in FIG. 1, since the magnet roller 7 extends to the outside of the toner carrying portion of the sleeve 4, the toner leaking to the side is provided with the end portion of the magnet roller and the annular portion of the magnetic seal member 10. It enters the gap part between 10a.

In this gap portion, since a magnetic flux exists at a high density between the end edge of the magnet roller 7 and the annular portion 10a of the magnetic seal member 10, the toner reaching this portion is confined there and stagnates. .

In this case, the magnetic flux generated from the magnet roller 7 is concentrated on the annular portion 10a of the magnetic seal member and then returned to the magnet roller 7 via the connecting portion 10c, the annular portion 10b and the shaft portion 7a. Connection part 10c, annular part 1
By appropriately setting the saturation magnetic flux amount of 0b, the magnetic resistance in this portion can be made as small as possible.

Therefore, with the above-described structure, the magnetic flux density in the gap between the sleeve 4 and the inner surface of the annular portion 10a of the magnetic seal member 10 is increased, and the toner arriving at this portion is more reliably stagnated. Can perform a sealing action. Further, when the magnetic flux density between the sleeve 4 and the annular portion 10a of the magnetic seal member 10 is equal to or higher than a predetermined value, the gap between them can be adjusted appropriately.

As described above, since the magnetic flux density of the magnetic seal portion is improved at the position where the magnetic toner leaks from the sleeve end portion to the outside, the dimensional accuracy of each member having the relevant portion can be improved. Assembly accuracy can be roughened, which contributes to cost reduction.

FIG. 3 is an axial sectional view of a developing sleeve showing another embodiment. For illustration, a magnetic seal member 20 made of a magnetic material such as iron supports a bearing 5 that axially supports the sleeve 4. The magnetic seal member 20 is located at a position facing the end portion 7c of the magnet roller 7 with the sleeve 4 interposed therebetween, and its inner peripheral surface 20a is equidistant from the outer peripheral surface of the sleeve.

The other end 20 of the magnetic seal member 20.
The reference character b supports an end shaft portion of the magnet roller 7, and the inner peripheral surface 20a and the end portion 20b are integrally connected by a connecting portion 20c.

With the operation of the developing device, the magnetic toner in the developing device leaks to the outside of the toner carrying portion 6 of the sleeve 4, and the space between the surface of the sleeve 4 and the inner peripheral surface 20a of the magnetic seal member 20. To the gap 12. In the gap portion 12, since magnetic flux exists from the end portion of the magnet roller in the direction of the inner peripheral surface 20a of the magnetic seal member 20, the magnetic flux density in this gap portion is higher than that in other portions, and the magnetic flux density has entered there. The toner is restrained and stagnates at this position.

The magnetic circuit having this configuration will be briefly described. After the magnetic flux generated from the magnetronie 7 is concentrated on the inner peripheral surface 20a of the magnetic seal member 20, the magnetic coupling member 20c
The magnet roller is replaced via the end 20b. In this case, according to the configuration shown in the figure, since the magnetic seal member 20 also serves as a support member for the bearing 5, it is not necessary to provide a means for supporting the bearing on the side wall of the developing device.

Therefore, the connecting portion 2 of the magnetic seal member 20 is
Since the magnetic flux passage cross section of 0c can be made sufficiently large and the magnetic resistance of this portion can be reduced, the coupling force between the magnetic toner, the magnetic seal member, and the magnetic toner can also be increased. The restraint action becomes great, and the leakage of toner can be prevented more reliably.

If the magnetic flux density between the sleeve 4 and the magnetic seal member 20 is a predetermined value or more, it is easy to increase the gap between the sleeve and the magnetic seal member. The accuracy and mounting accuracy can be roughened, which also contributes to cost reduction.

In the case of the illustrated apparatus, the example in which the end portion of the magnet roller is fixed to the magnetic seal member has been described, but it goes without saying that the present invention can be applied to a developing device in which the magnet roller is rotated. Absent. In addition,
In this case, the magnetic seal member is composed of an iron-based sintered material,
It is preferable that the magnet roller be axially supported by this.

[0031]

As described above, according to the present invention,
In a developing device for developing a magnetic developer stored in a developing device through a developing sleeve having a magnet roller, the end of the sleeve is sandwiched and the outer side of the sleeve is opposed to the inner end of the magnet roller. Since the magnetic seal member is positioned and a magnetic circuit is formed between the magnetic seal member and the magnet roller, it is possible to increase the magnetic flux density of the gap between the developing sleeve surface and the seal member located similar to the outer circumference thereof. Therefore, it is possible to securely restrain the magnetic developer leaking from the inside of the developing device to this portion and reliably prevent the developer from leaking.

Further, since the magnetic flux density in the gap is large, the allowable range for processing and assembling accuracy of each member at the relevant portion is widened, which greatly contributes to cost reduction.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a sealing mechanism showing an embodiment of the present invention.

FIG. 2 is a perspective view of a seal member used in the same mechanism.

FIG. 3 is a sectional view of a main part of a seal mechanism showing another embodiment.

[Explanation of symbols]

 4 Developing Sleeve 5 Bearing 6 Toner Conveying Section 7 Magnet Rollers 10 and 20 Magnetic Seal Member 12 Gap

Claims (2)

[Claims] 1. A developing device of an image forming apparatus, comprising: a developing sleeve rotatably supported to convey a stored magnetic toner; and a magnet roller contained in the developing sleeve. An annular magnetic seal member is disposed outside the developing sleeve at a position of the end of the enclosed magnet roller and spaced from the outer peripheral surface of the sleeve, and the magnetic seal member is magnetically connected to the magnet roller to magnetically A developing device that forms a circuit. 2. The developing device according to claim 1, wherein the magnetic seal member comprises a supporting member for supporting the developing sleeve and the magnet roller.