Image forming apparatus

An image forming apparatus includes a development device, an airflow generating device which generates an airflow, and a support member which supports a lower surface of the development device. An inner door is openable and closable so as to detachably attach the development device, an outer door covers the inner door, and a first duct portion is formed by the inner door and a lateral surface of the development device. The first duct portion guides the airflow along the lateral surface in a vertical direction, and a second duct portion guides the airflow along a longitudinal direction of the development device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming apparatus having a cooling mechanism which cools a developing unit.

2. Description of the Related Art

Japanese Patent Laid-Open No. 2008-170853 discloses that an imaging unit is disposed below an intermediate transfer belt and a writing unit is disposed below the imaging unit. Further, an airflow duct is formed between the imaging unit and the writing unit to pass cooling air. The cooling air is adapted to cool the imaging unit through a slit formed in the airflow duct.

In Japanese Patent Laid-Open No. 2008-170853, however, since airflow is formed to cool a bottom surface of the imaging unit from a short-side direction of the imaging unit, the slit is required for exposure to the airflow duct. Thus, there is a risk that a toner scattered from a development device through the slit contaminates an exposure unit or other members inside the apparatus body.

It is desirable to provide an image forming apparatus having a cooling mechanism capable of cooling a bottom of a developing unit while suppressing the contamination of the inside of the apparatus body due to scattering of a developer.

SUMMARY OF THE INVENTION

An image forming apparatus includes: a development device which is provided so as to be detachably attachable to an apparatus body to develop an electrostatic image on a surface of an image bearing member with a developer; an airflow generating device which generates an airflow; a duct which induces the airflow generated by the airflow generating device into the apparatus body; and a support member which supports a lower surface of the development device along a longitudinal direction of the development device; wherein a tubular flow path is formed between the support member and a bottom of the development device such that air flows along the longitudinal direction, and the flow path is connected to the duct.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an exemplary embodiment of the invention will be illustratively described in detail with reference to the accompanying drawings. However, the dimensions, materials, shapes, and relative arrangements of the components that are described in this embodiment are appropriately modified according to a configuration of an apparatus to which the invention is applied, and various conditions, therefore, unless otherwise specifically described, the embodiment is not intended to limit the scope of the invention only thereto.

FIG. 1is a perspective view of an image forming apparatus100in a state where a front cover1is opened. The image forming apparatus100includes an apparatus body100A and the front cover1which is rotatably attached with respect to the apparatus body100A. When a user opens the front cover1in a direction of an arrow J, an inner cover2will appear on the inside. Openings2aare formed in parallel with each other on the inner cover2. Four cartridges221(seeFIG. 2) are inserted into the openings2ain parallel with each other in a horizontal direction. In addition, an opening3kis formed on the inner cover2. A developing unit220as a development device is inserted into the opening3k. A small cover3is attached to the developing unit220.FIG. 1illustrates a state where the small cover3is removed from one developing unit220.

FIG. 2is a perspective view of the image forming apparatus100in a state where the inner cover2ofFIG. 1is transparent. Inside the apparatus body100A, a duct20is disposed above the developing unit220, and the cartridge221is disposed above the duct20. A fan21as an “airflow generating device” is attached to the duct20to generate the airflow. The duct20induces the airflow, which is generated by the fan21, into the inside of the apparatus body100A. The developing unit220extends in a direction perpendicular to an extending direction of the duct20. The above-described small cover3as a “door member” faces one end in a longitudinal direction of a developer container209of the developing unit220to freely open and close the opening (opening portion)3k.

FIG. 3is a perspective view of the image forming apparatus100in a state where the small cover3, the duct20, and the fan21ofFIG. 2are transparent. Inside the apparatus body100A, four image forming units200are disposed in parallel with each other in a horizontal direction. Each of the four image forming units200includes a drum unit270and the developing unit220and is used to form images which are different from each other in color.

An intermediate transfer belt260is disposed above four image forming units200. The intermediate transfer belt260is stretched by various rollers such as a secondary transfer roller, an idle roller, or a tension roller, which are not illustrated in the drawing. The secondary transfer roller is disposed along a conveying path of an image-transferred material so that a nip portion is formed between the secondary transfer roller and a roller opposite thereto.

Four cartridges221are disposed in parallel with each other above the intermediate transfer belt260. Thus, the cartridge221is disposed above the developing unit220, as a “replenishing portion” which replenishes the developer to the developing unit220. A replenishing unit (not illustrated) is disposed at an inner side of the apparatus body100A to deliver the toner supplied from the cartridge221to the developing unit220.

A laser unit70is disposed below four image forming unit200. In other words, the laser unit70as an “exposure portion” is disposed below the developing unit220. The laser unit70is configured to expose a photosensitive drum210as an “image bearing member”.

A cassette75is disposed below the laser unit70. A sheet conveying path, a secondary transfer roller, and a fixing device are disposed on a right side of the apparatus body100A. In addition, a discharge tray312is formed at an upper part of the apparatus body100A.

The surface of the photosensitive drum210is uniformly charged by a charge roller and is formed with an electrostatic image through the exposure by the laser unit70to form a developer image using the developing unit220. Then the developer image is transferred onto a recording material at the nip portion between the intermediate transfer belt260and the secondary transfer roller. Meanwhile, the recording material accommodated in the cassette75is discharged to the discharge tray312through the conveying roller, the nip portion between the intermediate transfer belt260and the secondary transfer roller, and the fixing device.

FIG. 4is a perspective view of the image forming unit200. In the image forming apparatus100, the image forming unit200is freely detachable (detachably attachable) to the apparatus body100A. As illustrated inFIG. 4, the image forming unit200includes the developing unit220and the drum unit270. The developing unit220has a developing roller211, and the drum unit270has the photosensitive drum210. The developing unit220as a “development device” develops the electrostatic image on the surface of the photosensitive drum210with the developer.

FIG. 5is a cross-sectional view of the image forming unit200. As illustrated inFIG. 5, the image forming unit200includes the developing unit220and the drum unit270. The developing unit220employs a system for using two-component developer and has a developer container209. Inside the developer container209, the developing roller211is disposed at an upper part and conveying screws212and213are disposed at a lower part. A regulating member214faces the surface of the developing roller211to regulate the amount of coating of the toner on the surface of the developing roller211. The developer is filled up to a position of a developer-surface level216inside the developer container209.

The replenished toner circulates inside the developer container209by the conveying screws212and213and is then conveyed to the developing roller211. The developing roller211and the photosensitive drum210are disposed in proximity to each other so as to have a predetermined distance.

FIG. 6Ais a perspective view of the developing unit220as viewed from a front side. As illustrated inFIG. 6A, the developing unit220has the developing roller211.

FIG. 6Bis a perspective view of the developing unit220as viewed from a rear side. As illustrated inFIG. 6B, a replenishing port300for receiving the toner, a replenishing shutter301, and a seal302are disposed immediately above the conveying screw212at the rear of the developing unit220. The developing unit220is considered as a unit which can be detachably attachable to the apparatus body100A and be replaced in the apparatus body100A. When the developing unit220is detached from the apparatus body100A, the replenishing shutter301shields the replenishing port300such that the developer inside the developing unit220is sealed.

Further, the developing unit220immediately after shipment is configured such that a gap inside the developing unit is completely covered by a film member (not illustrated) to completely seal the developer and a winding shaft215winds up the film member as soon as a driving input is received.

In addition, the developer inside the developing unit is sealed by the seal302as described above so as to prevent it from leaking into the outside of the developing unit220even during the driving input, but the developer attached to the seal may be scratched off by an opening/closing operation of the replenishing shutter301, and thus being dropped or scattered into the inside of the apparatus.

A driving coupling76is provided beside the replenishing port300to drive the developing roller211and the conveying screws212and213. The driving coupling76receives the driving input from a driving source inside the apparatus to rotate and drive the developing roller211. Further, a high-voltage contact77is provided immediately above the driving coupling76so as to add an electrical polarity to the developer.

As described above, function members such as the shutters, the driving coupling76, or the high-voltage contact77are collectively disposed at the rear of the developing unit220to receive various types of input from the apparatus body100A, and thus it is difficult to dispose other functions at the rear of the developing unit220. Further, for example, a space can be created by bringing the high-voltage contact77to the front of the developing unit220, but it is necessary to pull a high-voltage line from the inside of the apparatus body100A to the front, resulting in causing problems such as unit arrangement or cost increase.

In the above configuration, when the developing unit220receives the driving input, the developing roller211, the conveying screws212and213, and the winding shaft215(seeFIG. 5) receive a rotation driving.

FIG. 7is a cross-sectional view of the developing unit220at the front in a longitudinal direction. InFIG. 7, a gear for driving the conveying screws212and213and the winding shaft215is illustrated. The developing unit220has the conveying screws212and213as a “conveyance member” which conveys the developer. The conveying screw213has a penetrating shaft213a. The penetrating shaft213ais axially supported by a bearing440. A gear430is fittingly engaged with an end of the penetrating shaft213a. The driving force of the gear430is transmitted to gears431and432.

The gear432drives to rotate the winding shaft215(further, the developing roller211directly receives the driving force from the driving coupling76) (seeFIG. 6). The bearing440for axially supporting the conveying screw213and shafts441and442for supporting the gears are supported and covered by a driving support plate445and the developer container209.

The gear430, the shaft441, the gear431, the shaft442, and the gear432as a “driving transmitting member” are members which transmit the driving force to the conveying screws212and213. The driving support plate445as a “cover member” is a member which covers the gear430, the shaft441, the gear431, the shaft442, and the gear432. The developer container209holds the conveying screws212and213, the gear430, the shaft441, the gear431, the shaft442, the gear432, and the driving support plate445.

When the conveying screws212and213rotate, the developer circulates inside the developer container209while being agitated. At this time, since a composition of the developer can contain iron, driving energy caused by the agitation is converted into heat in the form of a self-heating of the developer. That is, when the driving input is transmitted to the conveying screws212and213, the developer stores heat. Accordingly, the higher the agitating speed and the conveying speed, the more heat storage quantity of the developer increases.

In addition, friction heat is generated by a sliding friction in the bearing440and the like for axially supporting the conveying screws212and213and the shafts441and442for supporting the gears, and such heat is propagated to the developer container209and thus is further applied to the developer.

As described above, the developer is weak to the heat. As the heat is applied to the developer, quality characteristics of the image are reduced. For example, variation in the amount of developer coating, change in electrical polarity, and damage of the developer occur on the surface of the developing roller211, resulting in reducing the image quality such as density unevenness and low density of the image formed by the image forming apparatus100. Therefore, a structure for cooling the developer is essential for the image forming apparatus100, and a future image forming apparatus strongly requires cooling performance which is more improved.

FIG. 8Ais a perspective view of a surface of the small cover3, andFIG. 8Bis a perspective view of a back side of the small cover3. As illustrated inFIGS. 8A and 8B, a rotating shaft3ais fixed to the bottom of the small cover3. The rotating shaft3ais rotatably supported on the apparatus body100A. When mounting the developing unit220to the apparatus body100A, a user sequentially opens the front cover1and the small cover3. By this, an insertion space of the developing unit220, which is partitioned in the apparatus body100A, is exposed to the outside. The user pushes the developing unit220up to a predetermined position while guiding it to a developing tray500fixed in the apparatus body100A. Thus, the developing unit220is positioned inside the apparatus body100A.

In addition, as illustrated inFIG. 8B, two (a pair) ribs (first walls) (rib members)3care protruded along a vertical direction. An inclined surface3bas an “inclined portion” is formed between the ribs3cto guide airflow with a first flow path J1 to a second flow path J2. The small cover3illustrated inFIG. 8Blooks like an approximate U-shape by the inclined surface3band the rib3cwhen viewed in plane from above.

FIG. 9is a perspective view of the developing tray500. The developing tray500as a “support member” illustrated inFIG. 9supports a lower surface of the developer container209of the developing unit220along the longitudinal direction of the developer container209. The developing tray500is a member which guides the developing unit220while supporting the developing unit220. The developing tray500includes two ribs500awhich protrudes upward at both ends in the width direction. Accordingly, the developing tray500is formed in a section of an upward U-shape when viewed in a cross section. The developing tray500is adapted to guide insertion/extraction of the developing unit220by two ribs500aand to receive the dropping and scattering toner by a plane portion500bduring the insertion/extraction of the developing unit220.

FIG. 10is a perspective view illustrating the configuration of the duct20, the fan21, the small cover3, the developing unit220, and the developing tray500. After the developing unit220is mounted in the apparatus body100A, the small cover3is closed, and the cooling mechanism of the developer is completed by the fan21, the duct20, the small cover3, the developing tray500, and the developing unit220.

First, the fan21rotates to suck the air into the inside of the duct20. The air flows along the direction of an arrow E in the inside of the duct20. The inside of the duct20is formed in a smooth tubular shape and the airflow is formed along the duct20without causing nearly loss.

A plurality of opening portions20ato be opened downward is formed at the duct20, and the opening portion20acorresponds to the opening (place surrounded by the rib3c, the inclined surface3b, and the driving support plate445) formed on the small cover3and the driving support plate445. The air is branched by changing the flow to the direction of an arrow F through the opening portion20a.

FIG. 11is a cross-sectional view of a cooling mechanism700. As illustrated inFIG. 11, the cooling mechanism700is mainly formed by the small cover3, the developing tray500, and the developer container209at a downstream side of the opening portion20a. The opening portion20aof the duct20and the driving support plate445of the developer container209and the small cover3ensure a predetermined amount of overlap, and the opening portion20aof the duct20is communicated with the driving support plate445of the developer container209and the small cover3. For this reason, the first flow path J1 is mutually overlapped therewith. The first flow path J1 of a substantially tubular shape, which is connected to the duct20, is formed between the driving support plate445of the developer container209and the small cover3to pass the airflow generated by the fan21. The second flow path J2 of a substantially tubular shape, which is connected to the first flow path J1, is formed between the developing tray500and the developer container209to pass the airflow generated by the fan21. The airflow generated by the fan21passes through the first flow path J1 and the second flow path J2. The airflow flows from the front part toward the rear part of the apparatus body100A by the fan21.

In addition, an airflow path of a tubular shape is formed by the driving support plate445of the developer container209and the inclined surface3bof the small cover3at a lower part of the cooling mechanism. Since the airflow path is formed in a tubular shape of a small gap, the minimum airflow is leaked from the gap and the loss of air volume is small.

When the air flows in the direction of an arrow F, the shaft, the bearing and the developer container, which are covered by the driving support plate445, are cooled.

The air flows in the direction of an arrow G by the inclined surface3bof the small cover3. The small cover3faces the driving support plate445of each developing unit220. The inclined surface3bof the small cover3is smoothly formed such that the air volume of the airflow is maximized and the loss of the airflow is minimized together with the driving support plate445. Thus, the loss of the air volume is minimized even in a case of changing the direction of the airflow.

When the air flows in the direction of the arrow G, the air flows into a space formed by the developer container209and the developing tray500to be exhausted to the back from an opening hole602awhich is formed at a rear-side plate602. Moreover, as illustrated inFIG. 5, the developer container209includes two (a pair) legs220a,220a(second walls) (rib members) formed downward at the bottom. The leg220ais formed along the second flow path J2 (seeFIG. 11). The developer container209is formed in a downward U-shape by a bottom220bthereof and the legs220aand220adescribed above. In addition, the developing tray500is formed in an upward U-shape by the plane portion500band the ribs500aand500a.

The legs220aand220aof the developer container209are disposed so as to be overlapped with the ribs500aand500aof the developing tray500in the vertical direction, and a state similar to a closed space is ensured between the developer container209and the developing tray500. That is, the pair of legs220aare provided on the developing tray500and are formed along the second flow path J2, and lateral surfaces thereof face those of the pair of ribs (rib members)500aprovided in the developing tray500. For this reason, the air can flow along the bottom of the developer container209while keeping the small loss of the air volume. As a result, as the air flows in the direction of the arrow G, the bottom of the developer container209having the maximum area, which comes in contact with the developer, is cooled.

According to the configuration of the embodiment, the air is sucked in the duct20by the fan21and is introduced into the space between the small cover3or the developing tray500and the developing unit220to efficiently cool the developer inside the developing unit220. Then the air evacuates to the rear-side plate602of the apparatus body100A.

In addition, a space sandwiched between a front-side plate601and the rear-side plate602is formed immediately below the developing tray500, and the laser unit70is formed in this space. The laser unit70is separated from the space, in which the air flows, by the developing tray500. Accordingly, dropping and scattering developer is received by the developing tray500and is exhausted to the back of the apparatus body100A by the air flow. Consequently, the developer is not diffused at the inside of the apparatus body100A or the front of apparatus body100A, which is directed toward the user, and is not adhered onto the laser unit70.

When inserting and extracting the developing unit220into/from the apparatus body100A, the user is accessible to the developing unit220only by opening the small cover3corresponding to each the developing unit220, and thus insertion/extraction properties and detachability of the developing unit220are not impaired.

According to the configuration of the embodiment, it is possible to cool the developing unit220by avoiding the sacrifice of the arrangement or detachability of the developing unit220inside the apparatus body100A while suppressing the contamination of the inside of the apparatus body100A due to the dropping or scattering of the developer. For details, an airflow duct is formed by the developing unit220, the small cover3, and the developing tray500such that cooling air passes through a space between the small cover3and the developing unit220and a space between the developing tray500and the developing unit220. Consequently, the lateral surfaces and the lower surface of the developing unit220are efficiently cooled, the detachability of the developing unit220is not impaired, and the scattering of the toner is suppressed inside the apparatus body100A.

Moreover, the invention may not be limited to the configuration of the embodiment. For example, the fan21is disposed at the right end on the near side of the front-side plate601, but may be disposed between the front-side plate601and the rear-side plate602according to the arrangement of the duct20. As the arrangement advantageous to the dropping and scattering of the developer, the replenishing unit is arranged at the rear of the apparatus body100A, but may be configured to replenish the developer to the developing unit220from the front of the apparatus body100A. Like the configuration of the embodiment, however, as the developing tray500is provided, the scattering of the developer is suppressed to the minimum even in the inside of the apparatus body100A.

Further, the driving coupling76as an “input member” to input the driving force to the gear430, the shaft441, the gear431, the shaft442, and the gear432may be configured in such a manner that a part is disposed at the rear of the apparatus body100A and the other part is disposed at the front of the apparatus body100A.

According to the invention, it is possible to cool the developing unit by avoiding the sacrifice of the arrangement or detachability of the developing unit inside the apparatus body while suppressing the contamination of the inside of the apparatus body due to the dropping or scattering of the developer.

This application claims the benefit of Japanese Patent Application No. 2013-010476, filed Jan. 23, 2013, which is hereby incorporated by reference herein in its entirety.