Image forming apparatus including duct member for cooling

An image forming apparatus includes a housing, a duct member, and a board. The housing has a support plate extending in a vertical direction. The duct member is attached to the support plate and has a first air duct through which air sent by a blower passes. The board has an element that is mounted thereon and generates heat when energized, and has a part supported by the duct member so as to cover an outer surface of the first air duct.

INCORPORATION BY REFERENCE

This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2015-194319 filed on Sep. 30, 2015, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates to an image forming apparatus including an air duct that forms a channel for air to cool an internal device.

An image forming apparatus which forms an image on a sheet member, such as a copy machine and a printer, is known. Within such a type of image forming apparatus, various members that become heat sources are provided. Examples of such members include a heating device for melting toner, and a motor for driving a roller or the like. Due to these heat sources, the temperature within the image forming apparatus increases. The increase in the temperature within the image forming apparatus causes, for example, a decrease in the flowability of a developer such as toner, a decrease in an electric charge amount of the developer, or a variation in a sheet conveyance speed due to expansion of a roller, resulting in an image defect. Thus, hitherto, in the image forming apparatus, a cooling device for sending air to the interior of the image forming apparatus to cool the interior is provided. The conventional cooling device includes an air duct for passing air blown from an air blower, and the air is sent from the air duct toward an object to be cooled, thereby cooling the object.

In addition, the conventional image forming apparatus includes a control board, a power supply board, and the like. The control board has electronic devices such as a CPU to control the image forming apparatus, and the like, mounted thereon, and the power supply board has a power module such as a converter, a transformer, and a transistor, mounted thereon, and each board generates heat when supplied with power. These boards are typically fitted to a support plate provided in the image forming apparatus.

SUMMARY

An image forming apparatus according to one aspect of the present disclosure includes a housing, a duct member, and a board. The housing has a support plate extending in a vertical direction. The duct member is attached to the support plate and has a first air duct through which air sent by a blower passes. The board has an element that is mounted thereon and generates heat when energized, and has a part supported by the duct member so as to cover an outer surface of the first air duct.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings as appropriate. It should be noted that the embodiments described below are merely examples embodying the present disclosure, and do not limit the technical scope of the present disclosure. For the sake of convenience in description, the vertical direction when an image forming apparatus10is in an installed state (a state as illustrated inFIG. 1) in which the image forming apparatus10is ready for use, is defined as an up-down direction7. In addition, a front-rear direction8is defined such that a front side (forward side) is a side on which a sheet feed cassette of a sheet feed conveying portion24illustrated inFIG. 1is inserted and pulled out when the image forming apparatus10is in the installed state. Moreover, a left-right direction9is defined on the basis of the front side of the image forming apparatus10in the installed state.

The image forming apparatus10according to an embodiment of the present disclosure is an apparatus having at least a printing function. The image forming apparatus10is a so-called tandem-type color printer.

As illustrated inFIGS. 1 and 2, the image forming apparatus10includes a housing10A. The housing10A as a whole is substantially in the shape of a rectangular parallelepiped. Various portions of the image forming apparatus10are contained in the housing10A.FIG. 2illustrates the image forming apparatus10when a cover panel10B (seeFIG. 1) forming a left side surface of the housing10A is removed therefrom.

The image forming apparatus10includes four image forming units4, an intermediate transfer belt5, a laser scanning unit13, a secondary transfer roller (not shown), a fixing device16, a sheet tray18, the sheet feed conveying portion24, an operation display portion (not shown), a vertical conveying path26, a belt cleaning device6, a main control board2, and the like.

As illustrated inFIG. 4, the housing10A includes a pair of side frames51and52, each of which extends in the up-down direction7. The side frame51is provided at the left side of the housing10A, and the side frame52is provided at the right side of the housing10A. The side frame51is an example of a support plate according to the present disclosure. Each of the side frames51and52is a plate-shaped member extending in the vertical direction, and is formed by a sheet metal. A duct member100and a secondary control board50, which will be described below, are attached to the side frame51. In addition, various components, such as the image forming units4, the intermediate transfer belt5, the belt cleaning device6, and the main control board2, are provided in a space between the side frames51and52.

The intermediate transfer belt5is provided above the four image forming units4. The belt cleaning device6is provided above the intermediate transfer belt5and at a rearward position in the housing10A.

A manual sheet feed portion45is provided at a front surface side of the image forming apparatus10. The sheet feed portion45feeds a print sheet to the secondary transfer roller (not shown) via a conveying path40and the vertical conveying path26in the image forming apparatus10. The sheet feed portion45includes a sheet receiving portion46and a feeding portion47. The sheet receiving portion46serves also as a front cover of the housing10A of the image forming apparatus10. The sheet receiving portion46is configured to be capable of opening and closing an entrance of the conveying path40with respect to the front surface of the housing10A.FIG. 3illustrates a state in which the sheet receiving portion46is closed with respect to the front surface of the housing10A. If the sheet receiving portion46is opened with respect to the front surface of the housing10A, so that an inner surface of the sheet receiving portion46faces upward, print sheets having a predetermined size can be placed on the inner surface. The print sheets placed on the sheet receiving portion46are fed to the conveying path40by the feeding portion47. A pair of conveying rollers (not shown) are provided at the conveying path40, and each print sheet is conveyed rearward along the conveying path40by the pair of conveying rollers.

An open/close sensor (not shown) is provided at front surface side in the image forming apparatus10. The open/close sensor detects whether the sheet receiving portion46is opened or closed, and is formed by, for example, a mechanical switch such as a limit switch, an optical sensor, or the like. The open/close sensor and the secondary control board50are electrically connected with each other via a signal line. If the sheet receiving portion46is opened with respect to the housing10A, an OFF signal is outputted from the open/close sensor, whereas if the sheet receiving portion46is closed, an ON signal is outputted from the open/close sensor.

As illustrated inFIG. 3, the main control board2is provided above the intermediate transfer belt5. In more detail, the main control board2is provided between the sheet tray18and the intermediate transfer belt5. The sheet tray18forms an upper surface of the image forming apparatus10, and holds a discharged sheet on which an image has been formed. The main control board2controls various portions of the image forming apparatus10. The main control board2is a plate-shaped board on which electronic devices, such as an computing device including a CPU, a ROM, and the like, an electrolytic capacitor, a coil, a converter (e.g., an AC/DC converter), and a transformer that steps up or down a voltage, are mounted. The main control board2is connected to each image forming unit4, the secondary transfer roller (not shown), the fixing device16, the driving roller (not shown), the sheet feed conveying portion24, and the like, and controls these components. If the main control board2is energized, each electronic device generates heat to be a heat source. In addition, if the main control board2is excessively heated by heat from the fixing device16, the main control board2may malfunction. Thus, the main control board2needs to be cooled.

As illustrated inFIG. 2, the image forming apparatus10further includes the secondary control board50, a driving unit60, and a cooling device80. The secondary control board50, the driving unit60, and the cooling device80are provided on the side frame51.

As illustrated inFIGS. 5 and 6, the side frame51is formed by subjecting the sheet metal to a bending process. The side frame51is substantially rectangular, and extends in both the up-down direction7and the front-rear direction8(a horizontal direction). The side frame51includes a rectangular bottom plate54, and a side wall53extending perpendicularly from an outer peripheral end of the bottom plate54. The side wall53extends to the left from the bottom plate54inFIG. 6.

As illustrated inFIGS. 8 and 9, the secondary control board50is attached to the side frame51. In more detail, the secondary control board50is attached at an upper rear position on the left side of the side frame51. The side frame51is provided with bosses51A and brackets51B (seeFIG. 6) for fixing the secondary control board50. Each of the bosses51A and the brackets51B is an example of a fixing portion according to the present disclosure. The two bosses51A are used to fix a lower end portion of the secondary control board50, and are attached to the bottom plate54through welding or the like. Each of the three brackets51B projects from the side wall53in a direction parallel to the bottom plate54. A screw hole is formed in each of the bosses51A and the brackets51B. In addition, the duct member100, which will be described below, is attached to the side frame51. In the present embodiment, the secondary control board50is attached to the bottom plate54of the side frame51through the duct member100, the bosses51A, and the brackets51B.

The secondary control board50converts a commercial voltage to a control voltage and a drive voltage used in the image forming apparatus10, and supplies the control voltage and the drive voltage to various portions of the image forming apparatus10, and receives a signal transmitted through the signal line in accordance with an opening or closing of the sheet receiving portion46, and determines whether the sheet receiving portion46is opened or closed. The secondary control board50is a board on which electronic devices, such as an computing device including a CPU, a ROM, and like, an electrolytic capacitor, a coil, a converter (e.g., an AC/DC converter), and a transformer that steps up or down a voltage, are mounted. Accordingly, if the secondary control board50is energized, each electronic device generates heat to be a heat source, and the secondary control board50therefore needs to be cooled.

As illustrated inFIG. 2, the driving unit60and the cooling device80are attached to the side frame51.

The driving unit60includes a motor62, a drive transmission mechanism such as a gear, and like. The driving unit60is attached to a central portion of the side frame51through a bracket (not shown) using screws or the like. An output shaft of the motor62extends to an opposite side of the side frame51through a through opening (not shown) formed in the side frame51. The drive transmission mechanism is connected to the output shaft. The drive transmission mechanism transmits a rotational driving force of the motor62to portions to be driven, such as a developing roller and a photosensitive drum of each image forming unit4, and a driving roller for driving the intermediate transfer belt5. An electromagnetic clutch or the like is provided between the drive transmission mechanism and each portion to be driven, and the electromagnetic clutch or the like is controlled as appropriate to control drive transmission to each portion to be driven.

As illustrated inFIGS. 4 and 5, the cooling device80is attached to the side frame51. Note that each ofFIGS. 4 and 5illustrates the side frame51with the secondary control board50removed therefrom. The cooling device80includes a resin frame81, a blower fan83(an example of a blower according to the present disclosure), an air duct84(an example of a second air duct according to the present disclosure), and the duct member100. Each of the air duct84and the duct member100guides air sent by the blower fan83.

When the blower fan83is driven, the blower fan83sucks air through a suction port83A and blows the air out through an outlet port, thus sending the air. The blower fan83is, for example, an axial fan. Needless to say, a blower of a type different from the axial fan may alternatively be used as the blower fan83. The blower fan83is attached to the side frame51through the resin frame81. In the present embodiment, the blower fan83is attached at a lower front position on the side frame51.

The resin frame81is obtained by molding a synthetic resin. The resin frame81includes a substantially rectangular fan-mounting portion90. A mounting seat91is provided in the fan-mounting portion90, and the blower fan83is mounted on the mounting seat91. A lower end of the mounting seat91is positioned to the right (i.e., to the far side of the drawing sheet inFIG. 5) relative to an upper end of the mounting seat91. Thus, when the blower fan83is mounted on the mounting seat91, the air blown by the blower fan83is sent obliquely upward.

The air duct84is formed integrally with the resin frame81. The air duct84extends upward from an upper portion of the mounting seat91, and then bends toward the rear of the housing10A (i.e., to the left of the drawing sheet inFIG. 5) to extend in the horizontal direction. An extending end of the air duct84reaches a position near the middle of the side frame51. The extending end of the air duct84is not closed, and forms an opening93facing rearward. The opening93and an air inlet111of an air duct110, which will be described below, are connected to each other. The air duct84is rectangular in cross section, and is formed integrally with the resin frame81. An air inlet of the air duct84is connected to the outlet port of the blower fan83. Thus, the air blown by the blower fan83is guided to the opening93through the air duct84.

In the cooling device80, the blower fan83is driven constantly or at required timing. Since the cooling device80is for cooling the image forming units4, the belt cleaning device6, the main control board2, the secondary control board50, and like, the cooling device80is controlled to be driven, for example, during a period when there is concern for an increase in the temperature of each of these components, specifically, during a period from a start of image formation to an end of the image formation, or during a period from a start of image formation to a predetermined time after an end of the image formation.

As illustrated inFIGS. 5 and 6, the duct member100, which is connected to the opening93of the air duct84, is provided on the side frame51. The duct member100is attached at an upper rear position on the side frame51. The duct member100extends rearward from the opening93. The duct member100includes the air duct110, which will be described below, and the air duct110is connected to the opening93of the air duct84.

Here, in the case where the duct member100is attached to the side frame51, if the duct member100is disposed adjacent to the secondary control board50in the side frame51, a space for attaching the duct member100needs to be secured in the side frame51. In this case, the side frame51should increase in size, which in turn leads to an increase in the size of the image forming apparatus10. Further, it may be difficult to dispose the duct member100so as to allow efficient sending of air because of an interruption of the secondary control board50or another member attached to the side frame51, which may lead to a failure to supply a sufficient volume of air to cool the heat sources. In contrast, the image forming apparatus10according to the present embodiment is able to achieve a sufficient volume of the duct member100while reducing the space for disposing the duct member100.

A communicating opening86(seeFIGS. 11A and 11B) is formed in a surface, of the bottom plate54of the side frame51, on which the duct member100is attached. In a state in which the duct member100is attached to the bottom plate54, the communicating opening86brings an interior of the air duct110and a space on the opposite side of the side frame51into communication with each other. In the present embodiment, the communicating opening86is formed at a position substantially coinciding with the position of the belt cleaning device6in both the up-down direction7and the front-rear direction8, more specifically, at a position slightly forward of the position of the belt cleaning device6. The duct member100guides air sent from the blower fan83through the air duct84to the communicating opening86through the air duct110, and guides the air from the communicating opening86to the space on the opposite side of the side frame51. In more detail, when the blower fan83is driven, air in a space to the left of the side frame51in the housing10A is sucked, and the air then passes through the air duct84, the air duct110, and the communicating opening86to be blown into the space to the right of the side frame51.

As illustrated inFIGS. 7A and 7B, the duct member100includes the air duct110(an example of a first air duct according to the present disclosure) and a wire holding portion120. The duct member100is obtained by molding a synthetic resin, and the air duct110and the wire holding portion120are formed integrally with each other. The duct member100is elongated in one direction, and is attached to the side frame51such that the longitudinal direction of the duct member100(i.e., the left-right direction on the drawing sheet inFIGS. 7A and 7B) coincides with the front-rear direction8of the housing10A.

The air duct110is connected to the opening93of the air duct84, and guides the air sent from the air duct84, toward the rear of the housing10A. The air duct110extends from the air inlet111, which is formed at a front end portion104A of the duct member100, to a position near the middle of the duct member100. In other words, a terminal end portion112of the air duct110is positioned near the middle of the duct member100. The air duct110is rectangular in cross section.

At a rear end portion104B on the other side of the duct member100, a positioning boss102(an example of a boss portion according to the present disclosure) projecting perpendicularly from an outer surface100A of the duct member100is formed. The positioning boss102includes a spacer portion102A and a cross projection102B. The spacer portion102A is columnar, and has an outer diameter greater than that of a positioning hole55A formed in the secondary control board50. The cross projection102B is formed at a projecting end of the spacer portion102A, and has such an outer diameter that the cross projection102B can be inserted through the positioning hole55A.

In addition, the duct member100includes a recessed portion100B, which is recessed from the outer surface100A. The recessed portion100B is formed at a lower portion of the rear end portion104B of the duct member100. The recessed portion100B includes an opening103formed therein.

The wire holding portion120holds a wire, such as the signal line electrically connected to the secondary control board50. The wire holding portion120is adjacent to the air duct110and is formed integrally in the duct member100. The wire holding portion120includes a holding groove121formed in the outer surface100A of the duct member100. The wire is inserted in the holding groove121, and the wire is thus held in the holding groove121. The holding groove121is formed in such a shape as to extend from the front end portion104A rearward above the air duct110, then bend downward along the terminal end portion112, and further bend rearward. A terminal end of the holding groove121reaches the recessed portion100B. In other words, the holding groove121communicates to a recessed space defined by the recessed portion100B. Thus, the wire held in the holding groove121can be guided to the recessed portion100B, and in the recessed portion100B, the wire can be guided to a back side of the duct member100through the opening103.

In addition, engagement projections123which project so as to be opposed to each other are formed in an inner wall of the holding groove121. The wire held in the holding groove121is thus securely held by the engagement projections123.

In addition, the duct member100includes an engagement piece105to fix the duct member100to the bottom plate54of the side frame51. The engagement piece105projects from an upper portion of the duct member100toward the bottom plate54. An engagement hole (not shown) is formed in the bottom plate54. The engagement piece105is inserted through the engagement hole, to be engaged therewith through snap fitting. The duct member100is thus fixed to the bottom plate54. Note that the mechanism of attachment between the duct member100and the side frame51is not limited to the above snap fitting, but a fixing member such as a screw may be used.

In the present embodiment, in a state in which the duct member100is attached to the side frame51, the secondary control board50is attached to the side frame51so as to cover an outer surface110A of the duct member100. Specifically, the positioning hole55A is formed in an upper rear end portion of the secondary control board50. As illustrated inFIG. 10, the positioning boss102of the duct member100is inserted through the positioning hole55A of the secondary control board50. At this time, the spacer portion102A comes into contact with the secondary control board50, and therefore only the cross projection102B passes through the positioning hole55A. As a result, the secondary control board50is positioned with respect to the side frame51.

A plurality of attachment holes55B (seeFIG. 10) are formed in the secondary control board50at positions corresponding to those of the bosses51A and the brackets51B of the side frame51. In a state in which the positioning boss102is inserted through the positioning hole55A of the secondary control board50, each attachment hole55B is aligned with the corresponding boss51A or bracket51B, and then these are fixed to each other by a fixing tool such as a screw56(seeFIG. 8). As a result, the secondary control board50is attached to the side frame51with an upper portion of the secondary control board50covering the outer surface110A of the duct member100. Each ofFIGS. 8 and 9illustrates the secondary control board50attached to the side frame51.

In addition, a first air outlet114is formed in the outer surface110A of the air duct110. The first air outlet114is a through hole formed in the outer surface110A. If air is sent from the blower fan83into the air duct110, the air is blown out through the first air outlet114to flow into a gap between the secondary control board50and the air duct110. The first air outlet114is formed at a position corresponding to an element that generates the most heat on the secondary control board50. Air is thus directly sent to the secondary control board50to cool the secondary control board50.

In addition, the duct member100includes a louver115(an example of an air guide according to the present disclosure) to guide air from the first air outlet114into the gap. As illustrated inFIG. 11A, the louver115extends rearward from a front edge portion of the first air outlet114, and is formed in such a shape as to be slanted outward from the air duct110. The air blown out through the first air outlet114is thus guided along the louver115toward a rear surface of the secondary control board50.

Note that the louver115may be shaped in any manner as long as the louver115is configured to guide the air from the first air outlet114to the gap. For example, as illustrated inFIG. 11B, the louver115may extend forward from a rear edge portion of the first air outlet114, and be formed in such a shape as to be slanted to the interior of the air duct110.

In addition, a second air outlet116is formed in a lower surface110B of the air duct110. The second air outlet116is a through hole formed in the lower surface110B. If air is sent from the blower fan83into the air duct110, the air is blown out through the second air outlet116. The air is thus blown out through the second air outlet116to flow downward along the rear surface of the secondary control board50. As a result, a member provided below the air duct110and an area around the lower end portion of the secondary control board50are cooled.

Here, in the case where the duct member100and the secondary control board50are separately attached to the side frame51, the duct member100is attached adjacently to the secondary control board50on the side frame51. In this case, a space for attaching the duct member100needs to be secured in the side frame51, and this leads to an increase in the size of the side frame51, which in turn leads to an increase in the size of the image forming apparatus10. Further, it may be difficult to dispose the duct member100and the air duct110so as to allow efficient sending of air because of an interruption of the secondary control board50or another member attached to the side frame51, which may lead to a failure to supply a sufficient volume of air to cool the heat sources.

However, as described above, in the image forming apparatus10according to the present embodiment, an upper end portion of the secondary control board50is positioned and supported by the duct member100so as to cover the outer surface110A of the air duct110. This makes it possible to reduce the space in which the air duct110is disposed in the side frame51while securing a sufficient volume of the air duct110without reducing the size of the air duct110.

In addition, since the duct member100integrally includes the wire holding portion120, for example, the signal line connecting the secondary control board50and the open/close sensor that detects whether the sheet receiving portion46is opened or closed can be held in the wire holding portion120. Further, since the signal line is held in the wire holding portion120adjacent to the air duct110, a signal (e.g., a voltage signal) that passes through the signal line is prevented from becoming unstable due to an influence of an ambient temperature.

In the above embodiment, the case where the upper end portion of the secondary control board50is positioned with respect to the duct member100has been shown as an example, but the present disclosure is not limited thereto. For example, the upper end portion of the secondary control board50may be fixed to the duct member100through a screw or the like.