Patent Document

TECHNICAL FIELD 
     The present disclosure relates to an image forming apparatus and a duct. 
     BACKGROUND ART 
     Conventionally, there is known an image forming apparatus in which an exhaust fan is stored in a space between a side wall of a housing of the image forming apparatus and an external cover (see, for example, Patent Literature 1). The housing stores an image forming portion for forming an image on a paper sheet. The image forming portion includes, for example, a fixing unit for fixing toner onto a recording sheet by heat, and the like. The exhaust fan is attached to the side wall of the housing. The exhaust fan discharges a high-temperature air warmed by the heat of the image forming portion (in particular, the fixing unit) to the outside from an exhaust outlet formed in the external cover. Heat generating equipments such as an electric board and the like, as well as the exhaust fan, are stored in the space between the side wall of the housing and the external cover. 
     CITATION LIST 
     Patent Literature 
     [PTL 1] Japanese Laid-Open Patent Publication No. 2004-272089 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     Meanwhile, to prevent occurrence of failures, it is desirable to cool the heat generating equipments, which include a motor, an electromagnetic clutch and the like, as well as the electric board. 
     However, according to the conventional image forming apparatus disclosed in Patent Literature 1, after the high-temperature air warmed by the heat of the image forming portion (in particular, the fixing unit) is sucked out from the inside of the housing by the exhaust fan, a part of the high-temperature air does not flow toward the exhaust outlet, but flows toward the heat generating equipments. As a result, far from being cooled, the heat generating equipments are further heated by the high-temperature air warmed by the heat of the image forming portion. As a result, the duct of the conventional image forming apparatus has a problem that it makes the heat generating equipments easily fail. 
     As a countermeasure for this problem, an additional exhaust fan may be disposed in the vicinity of the heat generating equipments such that the high-temperature air does not remain around the heat generating equipments. However, this configuration has a problem that as the number of exhaust fans increases, it increases the cost as well. 
     The present invention has been made in view of such conventional circumstances, and it is an object of the present invention to provide an inexpensive configuration for discharging heat from the inside of the housing, and preventing high-temperature air from remaining around the heat generating equipments. 
     Solution to the Problems 
     An image forming apparatus according to an aspect of the present invention includes a housing, an external cover, an equipment storage space, an opening, an exhaust fan, a heat generating equipment, and a duct. The housing stores an image forming portion configured to form an image on a recording medium. The external cover covers an outer side of a side wall of the housing. The external cover has an exhaust outlet formed therein. The equipment storage space is formed between the side wall of the housing and the external cover. The opening is formed in the side wall and allows inside of the housing to communicate with the equipment storage space. The exhaust fan is disposed in the equipment storage space and takes in air from the housing via the opening and exhausts the air from the exhaust outlet formed in the external cover. The heat generating equipment is disposed in the equipment storage space. The duct connects an air outlet of the exhaust fan and the exhaust outlet formed in the external cover. A communicating portion, which allows inside and outside of the duct to communicate with each other, is formed in a wall of the duct, the wall being located on the heat generating equipment side. 
     A duct according to another aspect of the present invention is provided in an equipment storage space that is provided between a side wall of a housing and an external cover and stores a heat generating equipment, the housing storing an image forming portion configured to form an image on a recording medium, the external cover covering an outer side of the side wall of the housing and having an exhaust outlet formed therein. The side wall has an opening that allows inside of the housing to communicate with the equipment storage space. An exhaust fan, which is configured to take in air from the housing via the opening and exhaust the air from the exhaust outlet formed in the external cover, is disposed in the equipment storage space. The duct includes a duct main body connecting an air outlet of the exhaust fan and the exhaust outlet formed in the external cover. A communicating portion, which allows inside and outside of the duct to communicate with each other, is formed in a wall of the duct main body, the wall being located on the heat generating equipment side. 
     Advantageous Effects of the Invention 
     According to the present invention, it is possible to provide an inexpensive configuration for discharging heat from the inside of the housing, while preventing high-temperature air from remaining around the heat generating equipments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a printer, viewed from the front side thereof, as an image forming apparatus in Embodiment 1 of the present invention. 
         FIG. 2  is a perspective view of the printer in Embodiment 1 of the present invention, viewed diagonally from the upper right of rear side thereof. 
         FIG. 3  is a schematic cross-sectional view taken along the III-III line of  FIG. 2 . 
         FIG. 4  is an enlarged view of a peripheral part of an exhaust fan in the equipment storage space of the printer in Embodiment 1 of the present invention. 
         FIG. 5  is a perspective view of an external cover covering the rear side of the printer in Embodiment 1 of the present invention, viewed diagonally from the right of the front side of the printer. 
         FIG. 6  is a schematic plan view, viewed from below, of a cut formed as a communicating portion in the duct in Embodiment 1 of the present invention. 
         FIG. 7  shows Embodiment 2 of the present invention, corresponding to  FIG. 2 . 
         FIG. 8  shows Embodiment 3 of the present invention, corresponding to  FIG. 2 . 
         FIG. 9  is a side view, viewed from the rear side, of a printer in Embodiment 4 of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the following embodiments. 
     Embodiment 1 
       FIG. 1  shows a laser printer  1  (hereinafter, merely referred to as “printer  1 ”) as the image forming apparatus in the present embodiment. The printer  1  includes a sheet feed portion  10 , an image forming portion  20 , a sheet discharge portion  50 , and a housing  60 . A plurality of pairs of conveying rollers  11 - 13  for nipping and conveying a paper sheet P are provided in a sheet conveyance path extending from the sheet feed portion  10  to the sheet discharge portion  50 . It is noted that in the following description, the front and depth sides of the paper surface in  FIG. 1  are referred to as “front side” and “rear side”, respectively, and the left and right sides of the paper surface in  FIG. 1  are referred to as “left side” and “right side”, respectively. 
     The sheet feed portion  10  is disposed in the housing  60  at a lower position. The sheet feed portion  10  includes a sheet feed cassette  10   a  and a pick-up roller  10   b . The sheet feed cassette  10   a  stores paper sheets P. The pick-up roller  10   b  picks up a paper sheet P from the sheet feed cassette  10   a  and feeds it to the outside of the sheet feed cassette  10   a . The paper sheet P fed to the outside of the sheet feed cassette  10   a  is supplied to the image forming portion  20  via a pair of conveying rollers  11 . 
     The image forming portion  20  includes a photoconductor drum  21 , a charging unit  23 , an exposure device  25 , a developing device  27 , a transfer unit  28 , a fixing unit  29 , and a toner container (not shown), wherein the photoconductor drum  21  is an example of the image carrying member. The image forming portion  20  causes the charging unit  23  to charge the circumferential surface of the photoconductor drum  21 , then causes the exposure device  25  to form an electrostatic latent image on the photoconductor drum  21  by irradiating the surface of the photoconductor drum  21  with laser light based on the document sheet image data (for example, image data of a document sheet image received from an external terminal). The electrostatic latent image formed (carried) on the surface of the photoconductor drum  21  is developed by the developing device  27  as a toner image. Subsequently, the image forming portion  20  causes the transfer unit  28  to transfer the toner image to the paper sheet P supplied from the sheet feed portion  10 , and supplies the paper sheet P after the transfer to the fixing unit  29 . 
     The fixing unit  29  includes a fixing roller  29   a  and a pressure roller  29   b  that are disposed to face each other. A heater is embedded in the fixing roller  29   a . In the fixing unit  29 , the paper sheet P supplied from the image forming portion  20  is pressed between the fixing roller  29   a  and the pressure roller  29   b , thereby the toner image is thermally fixed to the paper sheet P. The paper sheet P, to which the toner image has been thermally fixed by the fixing unit  29 , is conveyed by the rollers  29   a  and  29   b  toward the downstream side. The paper sheet P output from the fixing unit  29  is discharged to the sheet discharge portion  50  via the plurality of pairs of conveying rollers  12 ,  13 . 
     As shown in  FIG. 2 , the housing  60  includes a frame  61  and sheet metals  62 . In the whole view, the housing  60  has an approximate rectangular parallelepiped shape, and the frame  61  constitutes the framework of the housing  60 . Six sheet metals  62  are provided in total, and the sheet metals  62  form the front and rear, left and right, and upper and lower walls respectively.  FIG. 2  shows only a sheet metal  62   a  which forms the rear wall of the housing  60  (hereinafter this sheet metal is referred to as “rear sheet metal”). 
     As shown in  FIG. 3 , the rear sheet metal  62   a  is disposed at a position close to the fixing unit  29  which is a component of the image forming portion  20 . The rear sheet metal  62   a  is covered with an external cover  63  provided in the outside of the printer  1 . The external cover  63  is fixed to the frame  61  (see  FIG. 2 ) by bolts (not shown). A rectangular-shaped exhaust outlet  63   f  is provided in an upper-left part of the external cover  63 . The exhaust outlet  63   f  is covered with a louver  64 . The external cover  63  is disposed in rear of the rear sheet metal  62   a , separated by a predetermined distance therefrom. In addition, there is formed, between the external cover  63  and the rear sheet metal  62   a , an equipment storage space S having a thickness in the front-rear direction. 
     Back to  FIG. 2 , in the equipment storage space S, an exhaust fan  100 , a drum driving motor  30 , a conveyance clutch  72 , a sheet feed conveyance motor  71 , a board box  80 , and the like are disposed. These equipments are fixed to a surface of the rear sheet metal  62   a  on the external cover  63  side, by bolts or the like. 
     The board box  80  is attached to an upper-left (upper-right, in  FIG. 2 ) part of the rear sheet metal  62   a . The board box  80  stores various boards such as a power board, an engine board, a main board, and the like. 
     The exhaust fan  100  is attached to an upper-right (upper-left, in  FIG. 2 ) part of the rear sheet metal  62   a . The exhaust fan  100  includes a fan casing  101  and an impeller  102  stored in the fan casing  101 . The fan casing  101  is composed of a case in the shape of a rectangular box. An air inlet  101   a  (see  FIG. 3 ) is provided in the front surface of the fan casing  101 , and an air outlet  101   b  is provided in the rear surface of the fan casing  101 . The exhaust fan  100  is configured to generate, with the rotation of the impeller  102 , an airflow that mainly flows from the front side to the rear side. The fan casing  101  is attached to the rear sheet metal  62   a  such that the air inlet  101   a  overlaps (mates) with an opening  62   f  formed in the rear sheet metal  62   a . The opening  62   f  is formed in the rear sheet metal  62   a  at a position close to the fixing roller  29   a . The space of the inside of the housing  60  communicates with the equipment storage space S via the opening  62   f.    
     The drum driving motor  30  is a motor for driving the photoconductor drum  21 . The drum driving motor  30  includes an output shaft  30   a  (see  FIG. 2 ), a rotor  30   b , and a starter (not shown). The rotor  30   b  is cylindrical and integrally rotatably coupled with the output shaft  30   a  in the equipment storage space S. The starter is disposed coaxially with the rotor  30   b . The output shaft  30   a  penetrates through the rear sheet metal  62   a , and an end of the output shaft  30   a  is integrally rotatably coupled with the photoconductor drum  21 . When the drum driving motor  30  is activated, it is heated since a coil thereof is electrically conducted. In addition, when the drum driving motor  30  is activated, it is heated due to the friction of the bearing. 
     The conveyance clutch  72  is configured to switch between a power transmission state and a power interruption state. In the power transmission state, the conveyance clutch  72  transmits the power of a conveyance motor (not shown) to the pairs of conveying rollers  12 ,  13 . In the power interruption state, the conveyance clutch  72  interrupts the transmission of the power. The conveyance clutch  72  is composed of an electromagnetic clutch. A controller (not shown) controls the conductive state and non-conductive state of an excitation coil of the conveyance clutch  72 . When the excitation coil is in the conductive state, the power of the conveyance motor is transmitted to the pairs of conveying rollers  12 ,  13  via the conveyance clutch  72 . On the other hand, when the excitation coil is in the non-conductive state, the transmission of the power is interrupted. The conveyance clutch  72  is heated when the excitation coil is electrically conducted by the controller. 
     The sheet feed conveyance motor  71  is a motor for driving the pick-up roller  10   b . The sheet feed conveyance motor  71  is activated and controlled by the controller. When the sheet feed conveyance motor  71  is activated, it is heated since a coil thereof is electrically conducted. In addition, when the sheet feed conveyance motor  71  is activated, it is heated due to the friction of the bearing. 
     The above-described drum driving motor  30 , conveyance clutch  72 , and sheet feed conveyance motor  71  are heat generating equipments  70  stored in the equipment storage space S, and these heat generating equipments  70  are disposed below a duct  90  which is described below. 
     As shown in  FIGS. 3 to 5 , the air outlet  101   b  of the exhaust fan  100  and the exhaust outlet  63   f  formed in the external cover  62  are connected with each other via the duct  90 . The duct  90  is formed in a shape of a rectangular frame extending in the front-rear direction. A rear end of the duct  90  is fixed to the peripheral edge of the exhaust outlet  63   f  formed in the external cover  63  (see  FIG. 5 ). It is noted that, with the attachment of the external cover  62  to the housing  60 , the whole part of a front end of the duct  90 , except for a cut  90   f  (described below), abuts the peripheral edge of the air outlet  101   b  of the exhaust fan  100  (see  FIG. 3 ). 
     The duct  90  includes a top wall  90   a , a bottom wall  90   b , a left wall  90   c , and a right wall  90   d . The top wall  90   a  and the bottom wall  90   b  face each other in the up-down direction. The left wall  90   c  and the right wall  90   d  face each other in the left-right direction. The cut  90   f  is formed in, among the walls of the duct  90 , the bottom wall  90   b  which is located on the heat generating equipments (in the present embodiment, the drum driving motor  30 , conveyance clutch  72 , and sheet feed conveyance motor  71 ) side. As shown enlarged in  FIG. 6 , the cut  90   f  is formed at the center of a front end of the bottom wall  90  in the left-right direction. In a plan view, the cut  90   f  is opened toward the front side, and is elongated in the left-right direction. The cut  90   f  functions as a communicating portion  97  that allows the inside and outside of the duct  90  to communicate with each other. 
     In the printer  1  configured as described above, when the exhaust fan  100  is activated, high-temperature air in the housing  60  heated by the heat of the fixing roller  29   a  is guided through the opening  61   d  formed in the rear wall  62   a  to the air inlet  101   a  of the fan casing  101  (see  FIG. 3 ). The air then flows into the fan casing  101  from the air inlet  101   a , flows into the duct  90  from the air outlet  101   b  of the fan casing  101 , and then after flowing through the duct  90 , is discharged to the outside of the printer  1  from the exhaust outlet  63   f  formed in the external cover  63 . During this operation, in the duct  90 , an airflow flowing from the housing  60  side to the exhaust outlet  63   f  side (from the front side to the rear side) at a relatively high speed is formed. As a result, high-temperature air that remains around the heat generating equipments  70  (in the present embodiment, the drum driving motor  30 , conveyance clutch  72 , and sheet feed conveyance motor  71 ) is dragged by the high-speed airflow and caused to flow into the duct  90  from the cut  90   f  formed in the bottom wall  90   b  of the duct  90 . The high-temperature air that has flown into the duct  90  is discharged from the exhaust outlet  63   f , together with the high-speed airflow. As a result, it is possible to prevent the high-temperature air from remaining around the heat generating equipments  70 , and prevent the heat generating equipments  70  from failing. In this configuration, since the exhaust fan  100 , which is originally aimed to exhaust heat from the housing  60 , is used to prevent air from remaining around the heat generating equipments  70 , there is no need to install an additional exhaust fan. As a result, it is possible to reduce the product cost by restricting increase in the number of parts. 
     Embodiment 2 
       FIG. 7  shows Embodiment 2. Embodiment 2 is different from Embodiment 1 in that it includes guide plates  91 ,  92  for guiding an airflow into the duct  90 . It is noted that the same component elements as those shown in  FIG. 5  are assigned the same reference numbers, and description thereof is omitted. 
     That is, in the present embodiment, a first guide plate  91  and a second guide plate  92  are attached to the bottom wall  90   b  of the duct  90 . The first guide plate  91  includes an inclined plate  91   a  and a vertical plate  91   b . The inclined plate  91   a  is inclined from a right end of the bottom wall  90   b  to a lower right. The vertical plate  91   b  extends from a lower end of the inclined plate  91   a  downward. The second guide plate  92  projects forward from a left end of the bottom wall  90   b.    
     In the state where the external cover  63  is attached to the housing  60 , a flow guide passage  95  is formed by the external cover  63 , the first guide plate  91 , the second guide plate  92 , the rear sheet metal  62   a , and a right wall  80   a  of the board box  80 . The flow guide passage  95  communicates with the inside of the duct  90  via the cut  90   f . The flow guide passage  95  guides air around the heat generating equipments  70  to the cut  90   f , and causes the air to flow into the duct  90  from the cut  90   f.    
     As described above, in Embodiment 2, the guide plates  91 ,  92  are configured to guide high-temperature air around the heat generating equipments  70  to the cut  90   f . As a result, it is further possible to prevent high-temperature air from remaining around the heat generating equipments. 
     Embodiment 3 
       FIG. 8  shows Embodiment 3. Embodiment 3 is different from the above-described embodiments in that the external cover  63  includes an intake opening  63   g . It is noted that the same component elements as those shown in  FIGS. 5 and 7  are assigned the same reference numbers, and description thereof is omitted. 
     That is, in the present embodiment, the external cover  63  is provided with the intake opening  63   g  in addition to the exhaust outlet  63   f . The intake opening  63   g  is provided to take in air from the outside of the printer  1  into the equipment storage space S. The intake opening  63   g  is formed in a lower-right part of the external cover  63 , below the exhaust outlet  63   f . The intake opening  63   g  is formed in the external cover  63  at a position close to the sheet feed conveyance motor  71  (a heat generating equipment). 
     As a result, in Embodiment 3, driving the exhaust fan  100  causes the outside air to flow into the equipment storage space S from the intake opening  63   g  formed in the external cover  63 . The outside air that has flown into the equipment storage space S passes the circumference of the heat generating equipments  70 , flows into the duct  90  from the cut  90   f  formed in the duct  90 , and is discharged to the outside of the printer  1  from the exhaust outlet  63   f . Accordingly, by providing the intake opening  63   g , an airflow flowing from the heat generating equipments  70  side to the duct  90  side (from below to above) is formed. It is thus possible to prevent high-temperature air from remaining around the heat generating equipments  70 . 
     In addition, in Embodiment 3, the duct  90  is disposed above the heat generating equipments  70  by paying attention to the fact that the high-temperature air around the heat generating equipments  70  easily rises due to the density difference from the surrounding air. With this configuration, the high-temperature air around the heat generating equipments  70  is easily guided into the duct  90  disposed above the heat generating equipments  70 . 
     Embodiment 4 
       FIG. 9  shows Embodiment 4. The present embodiment is different from the above-described embodiments in the configuration of the drum driving motor  30 . That is, in the present embodiment, a plurality of impellers  30   c  are formed on the circumferential surface of the rotor  30   b  of the drum driving motor  30 . The plurality of impellers  30   c  are formed at equal intervals in the circumferential direction. 
     With this configuration, the impellers  30   c  rotate together with the rotor  30   b , thereby airflows are forcibly generated around the drum driving motor  30 . As a result, it is possible to further prevent high-temperature air, which has been warmed by the heat of the drum driving motor  30  (a heat generating equipment  70 ), from remaining around the drum driving motor  30 . 
     Other Embodiments 
     In the above-described embodiments, as an example of the heat generating equipments  70 , the drum driving motor  30 , sheet feed conveyance motor  71 , and conveyance clutch  72  are explained. However, not limited to this, the heat generating equipments  70  may be composed of, for example, an electric board and the like. 
     In the above-described embodiments, the communicating portion  97  is composed of the cut  90   f . However, not limited to this, the communicating portion  97  may be composed of a through hole. 
     In the above-described embodiments, the duct  93  is fixed to the external cover  63 . However, not limited to this, the duct  93  may be fixed to, for example, the rear sheet metal  62   a.    
     In the above-described embodiments, the guide plates  91 ,  92  are fixed to the duct  93 . However, not limited to this, the guide plates  91 ,  92  may be fixed to, for example, the rear sheet metal  62   a.    
     In the above-described embodiments, only one exhaust fan  100  is provided However, not limited to this, a plurality of exhaust fans  100  may be provided. 
     In the above-described embodiments, the laser printer  1  of the electrophotography is explained as an example of the image forming apparatus. However, the present invention is not limited to this. That is, the image forming apparatus may be, for example, an image forming apparatus of the inkjet method. In that case, the image forming portion may include one or more ink heads for ejecting ink onto a paper sheet, and the like. 
     The present invention is not limited to the above-described Embodiments 1 to 4. The present invention includes configurations made by appropriately combining Embodiments 1 to 4.

Technology Category: b