Cooling system for an image forming apparatus

An image forming apparatus includes a duct through which air taken in from outside a housing is sent into the housing, a blower fan provided at an upstream end of the duct, a toner bottle provided facing a wall surface of the duct, and a fixing section provided on a downstream side of the toner bottle. A component-facing section facing the toner bottle is formed to be smaller in cross-sectional area than a fan placement section. Therefore, by absorbing heat of air around the toner bottle via a wall of the component-facing section, the component-facing section prevents the toner bottle from becoming hot.

BACKGROUND

The present disclosure relates to an image forming apparatus including a duct through which air taken in from outside a housing is sent into the housing.

2. Description of the Related Art

Conventionally, an electrophotographic image forming apparatus fixes an image onto a sheet of paper by heating, under pressure, a toner image formed on the sheet of paper. During fixation, heat generated by heating a fixing roller holding the sheet of paper may affect surrounding members. Accordingly, there has been proposed a structure that cools down these members by sending air to an area around them (see, for example, Japanese Unexamined Patent Application Publication No. 2010-210729).

An image forming apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2010-210729 includes a fixing section, a paper conveyance path, a blower fan, and a ventilation duct. The blower fan creates a current of air between inside and outside an apparatus body. The ventilation duct includes a plurality of openings for cooling down a unit located near the fixing section, the paper conveyance path, through which a sheet of paper is carried to the fixing section, a sheet of paper being conveyed through the paper conveyance path, a photosensitive drum, and the like. The openings are configured to fan them to cool them down.

A configuration in which a wind is sent into a space before fixation as in the case of the image forming apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2010-210729 causes toner being developed or having already been developed to be scattered by the wind thus blown, so that the scattered toner may cause an image defect by adhering to the photosensitive drum, a transfer roller, a conveyance roller, and a sheet of paper being conveyed, or the like.

Further, doing miniaturization or the like of the image forming apparatus causes easy conduction of heat with internal units densely packed, so that more places are affected by fixing heat. Especially in an area around a developing device, particles of the toner fuse with each other under high temperature to cause an image defect, as the toner is weak against heat. Furthermore, the dense arrangement of components and units makes it difficult to secure a space for the duct. Therefore, there has been a demand for a structure that makes it possible to efficiently cool down a plurality of components and units in a narrow space without scattering toner.

It is desirable to provide an image forming apparatus including a duct that makes it possible not only to provide cooling by blowing out air taken in but also efficiently prevent an internal part from having a temperature rise under fixing heat.

SUMMARY

According to an aspect of the disclosure, there is provided an image forming apparatus including a blower fan that sucks in air from outside a housing and sends the air and a duct though which the air sent by the blower fan is guided into the housing. Assuming that a direction that the air is sent through the duct is a blowing direction and an area of a cross-section of the duct orthogonal to the blowing direction is a duct cross-sectional area, the blower fan is placed in a fan placement section of the duct, the duct has a component-facing section, provided on a downstream side of the fan placement section in the blowing direction, that is smaller in the duct cross-sectional area than the fan placement section, and at least a part of a wall constituting the component-facing section serves as a part of a wall forming an accommodation space of an internal component that is disposed inside the housing.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

An image forming apparatus according to a first embodiment of the present disclosure is described below with reference to the drawings.

FIG. 1is a side view schematically showing an image forming apparatus according to a first embodiment of the present disclosure.

The image forming apparatus1forms an image on a predetermined sheet of paper in accordance with image data transmitted from an outside source. The image forming apparatus1has a housing10in which a photosensitive drum11, an exposure device12, a developing device13, a cleaner device14, a transfer roller15, a charger16, a fixing section17(which is an example of a process unit), a paper conveyance path S, a paper cassette22, a paper output tray26, an auxiliary tray28, a toner bottle30(which is an example of an internal part), a duct40, and an auxiliary duct50are provided.

The photosensitive drum11is disposed along the paper conveyance path S and driven to rotate. The charger16uniformly charges a surface of the photosensitive drum11to a predetermined potential. The exposure device12exposes the surface of the photosensitive drum11to light to form an electrostatic latent image on the surface of the photosensitive drum11. The developing device13develops the electrostatic latent image on the surface of the photosensitive drum11to form a toner image on the surface of the photosensitive drum11.

A nipping region is formed between the transfer roller15and the photosensitive drum11, and the transfer roller15conveys a sheet of paper having been conveyed through the paper conveyance path S and being pinched in the nipping region. The toner image is transferred from the surface of the photosensitive drum11onto the sheet of paper when the sheet of paper passes through the nipping region. The cleaner device14removes and collects residual toner from the surface of the photosensitive drum11after development and image transfer.

The paper cassette22is a cassette in which to store a sheet of paper that is used for image formation, and is provided in a lower part of the housing10. Further, the paper output tray26, located in an upper part of the housing10, is a tray on which to place a sheet of paper subjected to image formation. The auxiliary tray28, located above the paper output tray26, is a tray on which to place a sheet of paper subjected to image formation.

In the image forming apparatus1, a sheet of paper fed from the paper cassette22passes through the paper conveyance path S to be sent to the paper output tray26via the transfer roller15and the fixing section17. The paper conveyance path S, located close to one side wall of the housing10(inFIG. 1, rightward), is provided with a pickup roller23, a registration roller24, a branch guide27, a paper output roller25, and an auxiliary paper output roller29.

The pickup roller23, located near an end of the paper cassette22, feeds sheets of paper one by one from the paper cassette22to the paper conveyance path S. The registration roller24temporarily holds a sheet of paper being conveyed from the paper cassette22and conveys the sheet of paper to the transfer roller15at such a timing that the front end of the toner image on the photosensitive drum11and the front end of the sheet of paper meet.

The fixing section17includes a fixing roller18, a pressure roller19, a heating roller20, and a fixing belt21. The fixing belt21is wound around the fixing roller18and the heating roller20. The pressure roller19is pressed against the fixing roller18via the fixing belt21. The fixing section17receives a sheet of paper with a toner image formed thereon unfixed and conveys the sheet of paper pinched between the fixing belt21and the pressure roller19.

A sheet of paper subjected to fixation is conveyed to pass through the branch guide27. The paper conveyance path S branches at the branch guide27into a path toward the paper output roller25and a path toward the auxiliary paper output roller29located above the paper output tray25. A sheet of paper having passed through the paper output roller25is ejected onto the paper output tray26, and a sheet of paper having passed through the auxiliary paper output roller29is ejected onto the auxiliary tray28. Whether a sheet of paper subjected to image formation is ejected onto the paper output tray26or the auxiliary tray28can be controlled by motion of the branch guide27.

The toner bottle30, located above the exposure device12and near the fixing section17(inFIG. 1, on the left of the fixing section17), has stored therein toner that is fed to the developing device13. The duct40, located between the paper output tray26and the exposure device12, takes in air from outside the housing10and sends the air into the housing10. The positions of the duct40and the toner bottle30will be described in detail later with reference toFIG. 2.

The auxiliary duct50, located below the exposure device12, takes in air from outside the housing10and sends the air into the housing10. Specifically, the auxiliary duct50includes an auxiliary inlet54facing one side wall of the housing10, an auxiliary outlet52facing the developing device13, and an auxiliary fan53located near the auxiliary inlet54. The auxiliary inlet54faces a side wall (inFIG. 1, left) of the housing10opposite to the paper conveyance path S, and the housing10has an auxiliary opening10bprovided in a position corresponding to the auxiliary inlet54. The auxiliary opening10bneeds only be structured such than air can flow in, and may be a hole, such as a long narrow hole like a slit, that is smaller than the auxiliary inlet54. Located near the auxiliary outlet52is an auxiliary duct cross-section reduction section51whose diameter becomes gradually smaller toward the auxiliary outlet52.

Actuating the auxiliary fan53causes air to flow into the auxiliary duct50through the auxiliary inlet54and be blown toward the auxiliary outlet52. The air thus blown becomes higher in flow rate as it passes through the auxiliary duct cross-section reduction section51, whose diameter becomes smaller, thus making it possible to efficiently cool down the developing device13.

FIG. 2is an enlarged view of the main components of a structure in and around the duct40ofFIG. 1.

FIG. 2selectively shows the duct40, the toner bottle30, the fixing section17, the paper output roller25, and the like as the structure in and around the duct40.

The duct40includes a cooling inlet47facing one side wall of the housing10, a cooling outlet45facing an area around the fixing section17, and a blower fan41located near the cooling inlet47. The cooling inlet47faces a side wall (inFIG. 1, left) of the housing10opposite to the paper conveyance path S, and the housing10has a cooling opening10aprovided in a position corresponding to the cooling inlet47. As with the auxiliary opening10b, the cooling opening10amay be a plurality of holes that are smaller than the cooling inlet47.

Actuating the blower fan41causes air to flow into the cooling inlet47of the duct40through the cooling opening10aand be blown toward the cooling outlet45. For illustrative purposes, the following sometimes refers to the direction that air flows through the duct40as “blowing direction A”, refers to a side of the cooling inlet47in the blowing direction A as “upstream side”, and refers to a side of the cooling outlet45in the blowing direction A as “downstream side”.

The blower fan41is placed in a fan placement section42near the cooling inlet47of the duct40. The fan placement section42is configured such that the cross-sectional area of a cross-section perpendicular to the blowing direction A (hereinafter abbreviated as “duct cross-sectional area) becomes larger away from the downstream side for the purpose of sucking in as much air as possible from outside the housing10and attaching as large a blower fan41as possible to the duct40. In the first embodiment, the blower fan41used is an axial-flow fan. In the configuration shown inFIG. 2, a part extending from the cooling inlet47to the fan placement section42is set so that the blower fan41and the duct40are substantially the same in cross-sectional area. In an alternative configuration, however, the duct cross-sectional area may become larger from the fan placement section42toward the upstream side.

Located on the downstream side of the blower fan41is a duct cross-section reduction section43whose duct cross-sectional area becomes gradually smaller toward the downstream side (inFIG. 2, rightward).

Located on the downstream side of the duct cross-section reduction section43is an component-facing section44. The component-facing section44is disposed so that at least a part of a wall thereof faces the toner bottle30. Specifically, the toner bottle30is disposed below the component-facing section44. The wall of the component-facing section44facing the toner bottle30also serves as a wall of a toner bottle accommodation space31(which is an example of an accommodation space) in which the toner bottle30is accommodated.

For illustrative purposes, the following refers to a surface of the wall of the component-facing section44facing the toner bottle30as “facing surface44a”, refers to a surface of the wall of the component-facing section44opposite to the facing surface44aas “covering surface44b” with distinction, and refers to the direction that the facing surface44aand the covering surface44bface each other as “facing direction T”.

Further, the component-facing section44is configured such that the component-facing section44is made smaller in duct cross-sectional area than the fan placement section42by the duct cross-section reduction section43.

The duct cross-sectional area according to the first embodiment is described in detail. For illustrative purposes, a direction orthogonal to the facing direction T and the blowing direction A and parallel to the facing surface44ais sometimes referred to as “wall surface direction H” (seeFIG. 3described below). The distance between inner walls of the fan placement section42in the facing direction T, i.e. the space (duct suction thickness DL1) between an upper surface of the duct40and a lower surface of the duct40, is 80 mm. Further, the distance between inner walls of the fan placement section42in the wall surface direction H, i.e. the space between side surfaces of the duct40(duct suction width WL1, seeFIG. 4described below), is 80 mm. Accordingly, the fan placement section42has a duct cross-sectional area of 64 cm2.

On the other hand, the distance between inner walls of the component-facing section44in the facing direction T, i.e. the space (duct ventilation thickness DL2) between the facing surface44aand the covering surface44b, is 4.5 mm. Further, the distance (duct ventilation width WL2) between inner walls of the component-facing section44in the wall surface direction H is 140 mm. Accordingly, the component-facing section44has a duct cross-sectional area of 6.3 cm2. The component-facing section44has a long narrow rectangular cross-section extending for a long distance in the wall surface direction H with respect to the thickness direction of the wall and has half as large a duct cross-sectional area as the fan placement section42does or smaller.

A wind having passed through the fan placement section42flows directly into the component-facing section44. Note here that since the amount of air per hour that passes through the duct40is constant with respect to a cross-section of the duct40, the reduction in cross-sectional area causes the flow rate of air that flows through the component-facing section44to be higher than the flow rate of air that flows through the fan placement section42. In the first embodiment, since the cross-sectional area is half as large or smaller, the flow rate is twice as high or higher.

Accordingly, even in the event of a rise in temperature of the tone bottle accommodation space31due to conduction of heat of the fixing section17to the interior of the apparatus, the toner bottle accommodation space31can be effectively cooled down by cooling down the facing surface44afacing the toner bottle30at a high flow rate. That is, since a rise in temperature of the toner bottle accommodation space31can be efficiently suppressed, fusion of the toner in the toner bottle30can be prevented.

Further, in making the component-facing section44smaller in duct cross-sectional area, efficient cooling can be achieved by disposing the duct40in a place where the components are densely packed, as the cross-sectional shape of the duct40is a rectangular shape elongated in the wall surface direction H.

The cooling outlet45, which leads to a blowing section10cof the housing10, is provided on the downstream side of the component-facing section44. The blowing section10c, having an empty space inside, includes a fixation downstream blowing hole10dwhose opening faces a space above the fixing section17and an upper blowing hole10ewhose opening faces an area around the paper output roller25. A wind is sent through the fixation downstream blowing hole10dto the paper conveyance path S on the downstream side of fixation. AlthoughFIG. 2distinguishes between the duct40and the blowing section10c, the blowing section10cmay be deemed as a part of the duct40, as the blowing section10cis a ventilation member that guides air.

Thus, on the downstream side of the component-facing section44, a plurality of cooling sections are provided to perform direct cooling by blowing air having passed through the duct40.

The fixing section17is normally controlled at a high temperature of 150° C. in order to fix an unfixed toner image onto a sheet of paper by heating the unfixed toner image under pressure. Given these circumstances, providing the fixation downstream blowing hole10dand the upper blowing hole10emakes it possible to efficiently cool down a sheet of paper heated by passing through the fixing section17, the paper output roller25heated by touching the sheet of paper, the paper conveyance path S, and the like.

Note here that although air blown out of the duct40becomes hotter than air outside the housing10by being subjected to heat of the toner bottle accommodation31when passing through the component-facing section44, such a rise in temperature is at most approximately 10° C. In the first embodiment, a rise in temperature due to the influence of installation environment or continuous operation, if any, results in a temperature barely exceeding 60° C., as the toner bottle accommodation space31is away from the fixing section17. Therefore, even with air subjected to the heat of the toner bottle accommodation space31, a difference in temperature that is needed to cool down a sheet of paper, the paper output roller25, and the like can be secured.

Moreover, in the component-facing section44, direct cooling is not performed by blowing air, but indirect cooling is performed via the facing surface44a. Therefore, air passing through the duct40is not mixed with toner having adhered to the toner bottle30or the like or toner having leaked from the toner bottle30. Accordingly, no toner adheres to a sheet of paper or the paper output roller25. This makes it possible to efficiently cool down a plurality of places (places differing in temperature) while preventing an image defect.

In the first embodiment, the fan placement section42is disposed in a place inside the image forming apparatus1where the components are not densely packed and there is comparatively enough space (inFIG. 1, the left-hand segment of the image forming apparatus1). That is, disposing the blower fan41in a place where there is enough space makes it possible to apply a blower fan41of a larger size. This makes it possible to secure a volume of air that allows sufficient cooling and efficiently make use of space in the image forming apparatus1.

Although the first embodiment is configured such that air taken in from outside the housing10blows out inside the housing10, this does not imply any limitation. In an alternative configuration, air taken in from outside may blow out of the housing10after having cooled down the units inside the housing10through the duct40.

Second Embodiment

Next, an image forming apparatus according to a second embodiment of the present disclosure is described with reference to the drawings. It should be noted that a description and illustration of a structure of the image forming apparatus according to the second embodiment are omitted, as the structure is substantially the same as that of the first embodiment.

FIG. 3is a schematic cross-sectional view of the duct40in a top view.

FIG. 3is a schematic cross-sectional view showing a lower surface side of the duct40, and shows a positional relationship between the duct40and the toner bottle30located therebelow. For illustrative purposes, the following sometimes refers to a direction orthogonal to the facing direction T and the blowing direction A and parallel to the facing surface44aas “wall surface direction H”.

The second embodiment differs from the first embodiment in terms of shape of the duct40. Specifically, the component-facing section44is formed to become larger in width in the wall surface direction H toward the downstream side. That is, the component-facing section44is configured such that the width (duct ventilation width WL2) of an inlet side of the component-facing section44is narrower than the width (duct exhaust width WL3, seeFIG. 4described below) of an outlet side of the component-facing section44.

As shown inFIG. 3, while the toner bottle30is formed to be large in width in the wall surface direction H, the fan placement section42is smaller in width in the wall surface direction H than the toner bottle30. Given these circumstances, the component-facing section44is configured to become wider in width in the wall surface direction H toward the downstream side to have a wider area facing the toner bottle30, thereby being able to efficiently receive heat from the toner bottle30.

Specifically, the duct exhaust width WL3is 260 mm, and the duct ventilation thickness DL2is 4.5 mm. That is, the cross-sectional area of the component-facing section44on the downstream wide is 11.7 cm2, which is smaller than the duct cross-sectional area of the fan placement section42. As a result, the component-facing part44is lower in flow rate on the outlet side than on the inlet side. However, since the component-facing section44is still higher in flow rate than the fan placement section42, the high flow rate, combined with a wider area facing the toner bottle30, can bring about improvement in cooling efficiency. Further, a wider width along the blowing direction A makes it possible to expand the range of cooling while minimizing turbulence of air.

Further, the component-facing section44is provided with a rectifying rib46extended in the blowing direction A. A plurality of the rectifying ribs46are placed at intervals from each other in the wall surface direction H, and a rectifying rib46(first rectifying rib46a) located in the center in the wall surface direction H is extended longer in the blowing direction A than a rectifying rib46(second rectifying rib46b) located at an end in the wall surface direction H. Specifically, the first rectifying rib46aand the second rectifying rib46bhave their downstream ends aligned so as to be located at the cooling outlet45and have their upstream ends differing in position. That is, the first rectifying rib46ahas its upstream end located near the duct cross-section reduction section43, and the second rectifying rib46bhas its upstream end located closer to the cooling outlet45than that of the first rectifying rib46a.

Providing the rectifying ribs46aligns the direction of flow of air with the blowing direction A, thus making it possible to suppress a reduction in flow rate due to turbulence. Further, since the component-facing section44is configured to become larger in width in the wall surface direction H toward the downstream side of the blowing direction A, the arrangement of rectifying ribs46makes it possible to more efficiently rectify the flow of air. Specifically, since air sent from the blower fan41easily concentrates in the center in the wall surface direction H, lengthening a rectifying rib46that is equivalent to a central part increases the conduit resistance of air flowing through a duct space divided by the rectifying ribs46, thus making it hard for the air to flow. Since the air hardly flows through the central part, the air can be dispersed toward the ends, so that a wide area can be cooled down in a balanced manner.

Further, the lengths of the rectifying ribs46in the blowing direction A may be adjusted as appropriate depending on positions in the wall surface direction H. That is, a rectifying rib46located closer to an end of the component-facing section44in the wall surface direction H may be shorter than a rectifying rib46located farther away from the end. In the structure shown inFIG. 3, the lengths of the rectifying ribs46are classified into three levels. Alternatively, the lengths of the rectifying ribs46may be classified into more levels.

Third Embodiment

Next, an image forming apparatus according to a third embodiment of the present disclosure is described with reference to the drawings. It should be noted that a description and illustration of a structure of the image forming apparatus according to the third embodiment are omitted, as the structure is substantially the same as those of the first and second embodiments.

FIG. 4is an exploded perspective view showing a state where members constituting the duct40are separated.

The third embodiment differs from the second embodiment in terms of members constituting the duct40. The duct40is constituted mainly by a fan fixing section61, a toner bottle cooling section62, and a duct cover63.

The fan fixing section61corresponds to lower surface sides of the fan placement section42and the duct cross-section reduction section43, with the blower fan41fixed thereto. The fan fixing section61may be integrally configured as a part of the housing10.

The toner bottle cooling section62corresponds to upper surface sides of the fan placement section42and the duct cross-section reduction section43and to the facing surface44aof the component-facing section44, and is a plate member provided with projections and depressions. This configuration makes it possible to form a duct passageway by collectively sealing ceiling parts of the fan placement section42and the duct cross-section reduction section43and a ceiling part of the toner bottle accommodation space31.

The toner bottle cooling section62has a main part62dcorresponding to the facing surface44a, a suction side upper surface part62b, and an attaching part62e. The main part62ddiffers in height (position) in the facing direction T from the suction side upper surface part62band the attaching part62e. The suction side upper surface part62band the attaching part62eare located above the main part62din the facing direction T.

The toner bottle cooling section62has a standing part62cprovided as a step on a boundary between the main part62dand the suction side upper surface part62band a boundary between the main part62dand the attaching part62e, and a part of the standing part62ccorresponds to a side wall of the duct40in the component-facing section44. That is, the step provided by the standing part62cis equivalent to the distance (duct ventilation thickness DL2) between inner walls of the aforementioned component-facing section44in the facing direction T. The attaching part62eis extended outward from the main part62din the wall surface direction H, and is provided with projections and screw holes for attaching the toner bottle cooling section62to the housing10. When the toner bottle cooling section62has been attached to the housing10via the attaching part62e, the suction side upper surface part62boverlaps the fan fixing section61. A ventilation hole62abored through a boundary between the main part62dand the suction side upper surface part62bin the blowing direction A leads to an upper end of the duct cross-section reduction section43in the fan fixing section61. That is, air having passed through the duct cross-section reduction section43is sent into the component-facing section44via the ventilation hole62a.

The duct cover63corresponds to the covering surface44bof the component-facing section44, is constituted by a thinner sheet material than the toner bottle cooling section62, and has its edge fixed to the standing part62c.

As mentioned above, the duct40may be divided into a plurality of members that are combined to constitute a ventilation member having an empty space inside. Moreover, the fan fixing section61, the toner bottle cooling section62, and the duct cover63may be formed by different members, respectively. That is, of the wall surfaces of the component-facing section44, the facing surface44aand the covering surface44bmay be constituted by different members. The degree of cooling of the facing surface44acan be adjusted according to the member by which it is constituted. Further, the degree of freedom of design of the covering surface44bcan be improved by constituting it as a separate entity without needing to stick to the member of the facing surface44a. That is, since the component-facing section44is configured such that one surface thereof (i.e. an upper surface of the toner bottle cooling section62) is open, it becomes easy to integrally mold rectifying ribs46that are low in height.

In the third embodiment, the toner bottle cooling section62is made of ABS resin, and the duct cover63is made of a PET material. Alternatively, either of the members may be made of metal or the like. That is, when made of a metal having good thermal conductivity, the toner bottle cooling section62can further enhance the efficiency of absorption of heat from the toner bottle accommodation space31. Similarly, the toner bottle cooling section62may be made of a resin material to which carbon has been added, or may have its cooling ability reduced by being formed by a resin material mixed with glass fiber. Further, ABS resin may be replaced by a material mixed with a PET material or by another engineering resin. Thus, as for the material to be applied, it is only necessary to appropriately select an appropriate material in consideration of the thickness and required thermal quality of the toner bottle cooling section62.

It should be noted the embodiments disclosed herein are examples in all respects and are not intended to serve as a basis for limited interpretation. Accordingly, the technical scope of the present disclosure is not intended to be interpreted solely by the embodiments described above, but is defined on the basis of the recitations in the claims. Further, all modifications falling within the meaning and range of the equivalent of the claims are encompassed.

The present disclosure contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2017-230623 filed in the Japan Patent Office on Nov. 30, 2017, the entire contents of which are hereby incorporated by reference.