JP2005208208A - Developing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing apparatus and an image forming apparatus preventing an adverse effect from having on other components due to accumulation of powder smoke scattered from the developing apparatus. <P>SOLUTION: The developing apparatus 22 is provided with a developing roller 25 rotating by approaching an image carrier and a housing 23 covering the developing roller 25 excluding a developing part to the image carrier and storing toner inside. The housing 23 is provided with a first opening 26 and a second opening 27 corresponding to a non-image forming area 25Y outside an image forming area 25X of the developing roller 25 at the downstream side of the developing part in rotation of the developing roller 25 with respect to the image carrier. Furthermore, in the housing 23, a third opening 28 for returning is provided in a position other than the first opening 26 and the second opening 27. The developing apparatus 22 is also provided with a duct 28 to cover these openings 26, 27 and 28. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer and a copying machine, and a developing device provided in the image forming apparatus. More specifically, the present invention relates to a developing device and an image forming apparatus in which an image carrier and a developing roller are counter-rotated.

  Conventionally, an image forming apparatus that develops an electrostatic latent image on a photosensitive member with toner has a problem that a part of the toner may leak from the gap between the developing device and the photosensitive member and be scattered in the apparatus. It was. When the scattered toner or the like is in a dusty state, it can move to each part in the apparatus by riding on the air flow in the apparatus. Then, for example, it may adhere to and accumulate around the developing device or the photosensitive member and cause the paper, sensor, etc. to become dirty. Therefore, dust accumulation is prevented from being accumulated in each part of the apparatus by providing a dust suction duct or an exhaust fan in the image forming apparatus and collecting it with an air filter. In such a device, the size and cost of the device were inevitably increased by an exhaust fan or the like.

On the other hand, a developing device devised to reduce dust without using a fan has also been devised (see, for example, Patent Document 1 and Patent Document 2). In the developing device described in Patent Document 1, the region surrounded by the photosensitive member and the two developing rollers becomes a substantially closed space and tends to be a high pressure, and there is a vent hole for letting the air in that portion escape. It is provided in the housing. Further, in the developing device described in Patent Document 2, the space surrounded by the developing roller, the developer stirring roller, and the developer flow restriction plate tends to be high pressure, and the developer flow restriction plate is provided with a vent hole. . In these methods, the pressure difference generated in the developing device is reduced. As a result, air blowing from the opening of the developing device that is open so that the developing roller faces the photosensitive member is reduced, and scattering of powder smoke outside the developing device is suppressed.
Japanese Patent No. 3247963 (Fig. 2-3) Japanese Patent No. 3268206 (FIG. 1)

  All of the conventional developing devices described above suppress the generation of a pressure difference inside the developing device, and reduce the blowing of airflow from the opening of the developing device. However, it is difficult to completely suppress the air flow generated with the rotation of the developing roller and the photosensitive member. In particular, in recent years, the rotation speed of each roller has increased due to the higher speed of the apparatus, and in image forming apparatuses that are not equipped with an exhaust fan to reduce the size and weight and reduce costs, the blowout of air from the developing device to the outside is suppressed. It has become even more difficult to do. For this reason, there has been a problem that the dust is scattered outside the developing device and accumulates on the upper surface of the housing or the like in the air stream.

  In particular, two-component toner tends to generate floating toner due to insufficient charging. Furthermore, the floating toner tends to increase as the particle size of the toner is improved to improve the image quality. If these floating toners scatter to the outside of the developing device, there is a possibility that the floating toner may wrap around from the upper end of the housing to the end of the process unit. In that case, there is a problem that the charging performance may be deteriorated due to contamination of the charging charger.

  The present invention has been made to solve the problems of the conventional developing device described above. That is, an object of the present invention is to provide a developing device and an image forming apparatus that prevent other components from being adversely affected by the accumulation of dust smoke scattered from the developing device.

  The developing device of the present invention, which has been made for the purpose of solving this problem, includes a developing roller that rotates in the vicinity of the image carrier, a housing that covers the developing roller except for a developing portion with respect to the image carrier, and stores toner therein. The housing has an opening corresponding to a non-image forming area outside at least one of the image forming areas of the developing roller on the downstream side of the rotation of the developing roller from the developing portion with respect to the image carrier. In addition to being provided, a return opening is provided at a place other than the opening, and has a duct member that covers the opening of the housing and the return opening and communicates the opening with the return opening.

  According to the developing device of the present invention, since the opening is provided on the downstream side of the rotation of the developing roller, the air flow generated by the rotation of the developing roller blows out of the developing roller from the opening. At this time, since the opening is provided in the non-image forming area, the powdery smoke such as the floating toner flows out to the outside in the air current, but the normal toner related to the development does not flow out. Further, since the return opening and the duct member are provided, the air flow blown out from the opening is guided to a desired position by the duct member and returned to the developing device from the return opening. Therefore, it is possible to prevent the other components from being adversely affected by the accumulation of the dust smoke scattered from the developing device without emitting the air current containing the dust smoke to the outside.

Furthermore, in the developing device of the present invention, it is desirable that the duct member is provided with a buffer unit that separates and accumulates toner in the airflow at a position from the opening to the return opening.
In this way, since the airflow returned to the developing device does not contain toner, the amount of dust in the developing device is suppressed.

  The present invention further includes an image carrier, a developing roller that rotates in proximity to the image carrier, a housing that covers the developing roller except for a developing portion for the image carrier, and stores toner therein. In an image forming apparatus that obtains an image by developing a latent image on a carrier with a developing roller, the housing has at least one of the image forming regions of the developing roller on the downstream side of the developing roller relative to the developing portion with respect to the image carrier. The present invention extends to an image forming apparatus in which an opening corresponding to an external non-image forming area is provided.

  Further, in the image forming apparatus of the present invention, it is desirable that the duct member is provided with a buffer unit that separates and accumulates toner in the airflow at a position from the opening to the return opening.

  According to the developing device and the image forming apparatus of the present invention, it is possible to prevent the other components from being adversely affected by the accumulation of powder smoke scattered from the developing device.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a tandem image forming apparatus and a developing device included in the tandem image forming apparatus.

  The image forming apparatus 1 of the present embodiment is a tandem color printer, as schematically shown in FIG. The intermediate transfer belt 11 is rotatably held by a plurality of stretching rollers 12, and image forming units 20Y, 20M, 20C, 20Bk for respective colors and a secondary transfer roller 13 are arranged around the intermediate transfer belt 11. The image forming units 20Y, 20M, 20C, and 20Bk for each color have the same configuration, and include an image carrier 21 and a developing device 22, respectively. The image forming units 20Y, 20M, 20C, and 20Bk for each color include a charging device, an exposure device, a cleaner device, and the like, so that a toner image of each color can be formed on the intermediate transfer belt 11. . Since these are general structures, description is abbreviate | omitted. Each developing device 22 is a cartridge that is detachable from the image forming apparatus 1.

  As shown in FIGS. 2 to 4, the developing device 22 is provided with an opening 24 facing the image carrier 21 in a housing 23 containing toner of each color, from which a part of the developing roller 25 is exposed. ing. The developing roller 25 has a configuration in which a magnetized region 25X is provided at the center in the longitudinal direction, and non-magnetized regions 25Y that are not involved in development are provided at both ends. The housing 23 is provided with a first opening 26 and a second opening 27 on the lower side of the non-magnetized regions 25Y of the developing roller 25 in the drawing, respectively. An opening 28 is provided. Further, a duct 29 is attached to the outside of the housing 23 with these three openings 26, 27, 28 communicating with each other.

  As shown in FIG. 4, the duct 29 is composed of a flange-shaped portion 29a substantially equal to the length of the developing roller 25 and a substantially L-shaped cylindrical portion 29b connected thereto. FIG. 4 shows a state in which the duct 29 is removed from the housing 23. The hook-shaped portion 29 a is provided in parallel to the longitudinal direction of the developing roller 25 so as to cover the first opening 26 and the second opening 27. An opening 30 is provided at a position corresponding to the third opening 28 at the tip of the cylindrical portion 29b. When the duct 29 is attached to the housing 23, the opening 30 overlaps the third opening 28, and the first opening 26, the second opening 27, and the third opening 28 are in communication with each other via the duct 29. When the duct 29 is brought into close contact with the housing 23, the surface of the cylindrical portion 29b on the side in contact with the housing 23 may be omitted.

  Furthermore, as shown in FIG. 5, a plurality of protrusions 31 are formed inside the cylindrical portion 29b. The air flow passing through the inside of the duct 29 becomes a turbulent flow by hitting the protrusion 31. As a result, dust or the like in the air current is accumulated on the wall surface of the duct 29 as shown by the dot hatching in FIG. Therefore, the protrusion 31 functions as a buffer unit that separates and accumulates toner in the airflow.

  In this image forming apparatus 1, the rotation direction of the developing roller 25 is from the top to the bottom in the drawing at the opening 24, and the opening 24 is substantially blocked by the image carrier 21 as shown in FIG. 3. Yes. For this reason, the airflow generated by the rotation of the developing roller 25 is accumulated downstream in the rotation direction of the developing roller 25. Since there is no other way, as shown in FIGS. 3 and 4, the air is blown out of the developing device 22 from the first opening 26 and the second opening 27 and blown into the duct 29. On the other hand, the third opening 28 is provided in a portion not affected by the rotation of the developing roller 25 and the image carrier 21, and compared with the vicinity of the first opening 26 and the second opening 27 in the housing 23 at that position. The atmospheric pressure is low. As a result, an airflow flowing from the first opening 26 and the second opening 27 to the third opening 28 via the duct 29 is generated without using an exhaust fan or the like.

  By the way, in general, powder smoke is often floating toner composed of reversely charged toner or weakly charged toner that is not normally charged. In particular, when two-component toner is used, a lot of floating toner tends to be generated. A large amount of such dust is floating around the non-magnetized region 25Y at both ends of the developing roller 25. On the other hand, no toner that contributes to development exists in the vicinity of the non-magnetized region 25Y. For these reasons, the toner that is carried to the duct 29 in the airflow blown out from the first opening 26 and the second opening 27 is only unnecessary toner that has become dust smoke drifting in the vicinity of the non-magnetized region 25Y. There is no risk of overflowing the toner necessary for development. Further, this air current collides with the wall surface, the projection 31 of the cylindrical portion 29 b, etc. inside the duct 29, and dust is accumulated inside the duct 29. Then, it becomes a clean air flow that does not contain powder smoke, and is returned from the third opening 28 to the inside of the developing device 22.

  In addition, when the installation space is limited, the flange portion 29a of the duct 29 may be formed smaller. Alternatively, as shown in FIG. 6, the first opening 26 may be omitted, and a small duct 32 that allows only the second opening 27 to communicate with the third opening 28 may be provided. Further, a filter may be provided in the middle of the ducts 29 and 32 so as to reliably capture the dust.

  As described in detail above, according to the image forming apparatus 1 of the present invention, the first opening 26, the second opening 27, and the third opening 28 are provided in the housing 23 of the developing device 22, and these are communicated by the duct 29. Has been. Further, the first opening 26 and the second opening 27 are provided in the vicinity of the non-magnetized region 25Y at both ends of the developing roller 25 and on the downstream side in the rotation direction of the developing roller, and the third opening 28 is compared with these. Therefore, an airflow flowing from the first opening 26 and the second opening 27 to the third opening 28 via the duct 29 is generated. Accordingly, the smoke generated around the developing roller 25 is put on this air flow and guided to the duct 29. In addition, since a plurality of protrusions 31 are provided inside the duct 29, turbulence is generated and dust is accumulated in the duct 29. Thus, the image forming apparatus 1 is configured in which the dust smoke scattered along with the blowing of the airflow from the opening facing the photoconductor is induced, and the adverse effect on the other components due to the deposition is prevented.

The best mode is merely an example and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, the shape of the duct 29 is not limited to these, and any shape may be used as long as each opening is connected to guide the airflow. The position of the third opening 28 is not limited to the position shown in the figure, and may be provided at a position slightly away from the developing roller 25.
Further, for example, in the above embodiment, the duct 29 is formed and attached separately from the housing 23, but may be formed integrally with the housing 23.
For example, the present invention can be applied not only to a color printer but also to an image forming apparatus such as a monochrome printer, a copier, and a facsimile.

It is explanatory drawing which shows the outline of the image forming apparatus of this form. It is a perspective view which shows the external appearance of a developing device. It is sectional drawing which shows a developing device. It is explanatory drawing which shows a developing device. It is sectional drawing which shows the inside of a duct. It is explanatory drawing which shows the other example of a developing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 21 Image carrier 22 Developing apparatus 23 Housing 25 Developing roller 26 1st opening (opening)
27 Second opening (opening)
28 3rd opening (return opening)
29 Duct (duct member)
31 Protrusion (buffer part)

Claims (4)

In a developing device comprising: a developing roller that rotates close to an image carrier; and a housing that covers the developing roller except for a developing portion for the image carrier and stores toner therein.
The housing is provided with an opening corresponding to a non-image forming area outside at least one of the image forming areas of the developing roller on the downstream side of the rotation of the developing roller from the developing portion with respect to the image carrier. A return opening is provided at a location other than
A developing device comprising a duct member that covers the opening of the housing and the return opening, and that communicates the opening with the return opening. The developing device according to claim 1,
The developing device according to claim 1, wherein the duct member is provided with a buffer unit that separates and accumulates toner in the airflow at a position between the opening and the return opening. An image bearing member; a developing roller that rotates in proximity to the image bearing member; and a housing that covers the developing roller except for a developing portion for the image bearing member and stores toner therein. In an image forming apparatus for developing a latent image of a body by the developing roller to obtain an image,
The housing is provided with an opening corresponding to a non-image forming area outside at least one of the image forming areas of the developing roller on the downstream side of the rotation of the developing roller from the developing portion with respect to the image carrier. A return opening is provided at a location other than
An image forming apparatus comprising: a duct member that covers the opening of the housing and the return opening, and that communicates the opening with the return opening. The image forming apparatus according to claim 3,
2. An image forming apparatus according to claim 1, wherein the duct member is provided with a buffer unit for separating and accumulating toner in the airflow at a position between the opening and the return opening.

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