Abstract:
In the present invention, in order to efficiently cool circuit boards such as an image formation section ( 20 ) and a power source board ( 71 ) accommodated in a main body housing ( 60 ), the power source board ( 71 ) and a cooling fan ( 100 ) are attached to a lateral wall part ( 62   a ) adjacent to the image formation section ( 20 ) in the main body housing ( 60 ), and the cooling fan ( 100 ) cools the image formation section ( 20 ) and the power source board ( 71 ) by utilizing air flow generated by rotation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage of International Application No. PCT/JP2014/063438, filed May 21, 2014, which claims the benefit of priority of Japanese Application No. 2013-175052, filed Aug. 26, 2013, in the Japanese Patent Office, the disclosures of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an image forming device. 
     BACKGROUND ART 
     Conventionally, an image forming device is known, in which air is inhaled into an image forming device main body by means of a cooling fan; and the inhaled air cools portions to be cooled such as an image forming portion, a power source board and the like that are housed in the device main body (e.g., see a patent document 1). In this device, a right wall portion of the image forming device main body is provided with an air inhaling opening. The air inhaling opening is connected to a duct in which cooling air flows, and the cooling fan is disposed in the duct. The image forming portion is disposed near a left wall portion in the image forming device main body and a downstream-side end portion of the duct is opened near the image forming portion. And, the image forming portion is cooled by an airflow blown out from the downstream-side end portion of the duct. On the other hand, the power source board is disposed below the duct. And, the power source board is cooled by an airflow blown out from a branch opening formed through a portion of the duct. 
     CITATION LIST 
     Patent Literature 
     PLT1: JP-A-2003-316237 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the conventional image forming device disclosed in the above patent document 1, it is necessary to guide the air flow from the air inhaling opening formed through the right wall portion of the device main body to the image forming portion disposed near the left wall portion. Accordingly, the total length of the duct becomes long. Because of this, there is a problem that the air flow inhaled from the air inhaling opening becomes warm during a time the air flow flows in the duct; and it is impossible to efficiently cool the portions to be cooled such as the image forming portion, the power source board and the like. Besides, there is a problem that the material cost used for the duct becomes high because the total length of the duct is long. 
     Accordingly, it is conceivable that a cooling fan for cooling the power source board is further disposed besides the cooling fan for cooling the image forming portion. In this way, it is possible to shorten the duct length extending from each cooling fan to the portions (image forming portion, power source board) to be cooled and thereby improve cooling efficiency. 
     However, in this case, there is a problem that the production cost increases all the more because the number of cooling fans increases. Besides, there is also a problem that because the number of fans increases, the fan noise becomes loud. 
     The present disclosure has been made in light of the above points, and it is an object of the present disclosure to efficiently cool the image forming portion and the boards by means of an inexpensive structure. 
     Solution to Problem 
     An image forming device according to the present disclosure includes: a main body housing portion that houses an image forming portion which records an image onto a sheet; a board; and a cooling fan for cooling the image forming portion and the board. 
     And, both the board and the cooling fan are mounted on a side wall portion of the main body housing portion adjacent to the image forming portion, and the cooling fan is configured to cool the image forming portion and the board by means of an airflow generated by rotation of the cooling fan. 
     According to this structure, because the cooling fan is mounted on the side wall portion adjacent to the image forming portion, it is possible to remove the duct for guiding the airflow generated by the rotation of the cooling fan or to shorten the duct length. Therefore, it is possible to improve the cooling efficiency for the image forming portion. Besides, because the board is mounted on the side wall portion, it is possible remove the duct for supplying the airflow generated by the rotation of the cooling fan to the board or to shorten the duct length. Therefore, it is possible to improve the cooling efficiency for the board. Besides, according to the above structure, because it is unnecessary to increase the number of cooling fans, it is possible to curb the production cost and the fan noise. 
     It is preferable that the cooling fan includes a fan casing mounted on the side wall portion and an impeller that is housed in the fan casing and rotates to make the airflow flow into the casing from outside the main body housing portion, and the fan casing includes: an air inflow opening; a first blow-out opening for blowing out part of the airflow flowing into the casing from the air inflow opening to the image forming portion; and a second blow-out opening for blowing out part of the airflow flowing into the casing from the air inflow opening to the board. 
     According to this structure, when the impeller rotates, the airflow flows into the casing from outside the main body housing portion through the air inflow opening of the fan casing. Part of the airflow flowing into the casing is blown out from the first blow-out opening to the above image forming portion. And, the image forming portion is cooled by the blown-out airflow. Besides, part of the airflow flowing into the casing is blown out from the second blow-out opening to the above power source board. And, the power source board is cooled by the blown-out airflow. 
     It is preferable that the image forming portion includes a photosensitive drum that carries an electrostatic latent image; the side wall portion is located in one side in a shaft direction of the photosensitive drum in the main body housing portion; and the first blow-out opening of the fan casing is configured to blow out part of the airflow flowing into the casing from the air inflow opening to one end portion in the shaft direction of the photosensitive drum or to a portion near the one end portion. 
     According to this structure, the impeller rotates, whereby part of the airflow flowing into the fan casing is blown out through the first blow-out opening to the one end portion in the shaft direction of the above photosensitive drum or to the portion near the one end portion. The blown-out airflow flows from one side to the other side in the shaft direction along a surface of the photosensitive drum. Accordingly, unlike the conventional, it is possible to efficiently cool the entire image forming portion including the photosensitive drum without using the long duct. 
     Further, it is preferable that the one end portion in the shaft direction of the photosensitive drum is connected to a drive mechanism for driving the photosensitive drum. 
     According to this structure, it is possible to cool the drive mechanism for the photosensitive drum by means of the airflow that is blown out through the first blow-out opening of the fan casing to the one end portion in the shaft direction of the photosensitive drum. Therefore, it is unnecessary to additionally dispose a cooling fan for cooling the drive mechanism and dispose a long duct for guiding the airflow to the drive mechanism. Therefore, it is possible to improve the cooling efficiency and achieve the low cost. 
     The image forming device includes an outer cover that covers the side wall portion from outside the image forming device and is provided with an air inhaling portion. And, it is preferable that a gap is formed between the side wall portion and the outer cover; and the board and the cooling fan are mounted on a surface of the side wall portion near the outer cover. 
     According to this structure, an operator can gain access to the above board and the cooling fan by only removing the outer cover. Therefore, it is possible to improve maintenance characteristics of the image forming device. 
     It is preferable that the image forming device further includes another board for supplying a high voltage to the image forming portion; wherein the another board is mounted on the side wall portion; the cooling fan includes a fan casing mounted on the side wall portion and an impeller that is housed in the fan casing and rotates to make an airflow flow into the casing from outside the main body housing portion; and the fan casing includes: an air inflow opening; a first blow-out opening for blowing out part of the airflow flowing into the casing from the air inflow opening to the image forming portion; a second blow-out opening for blowing out part of the airflow flowing into the casing from the air inflow opening to the board; and a third blow-out opening for blowing out part of the airflow flowing into the casing from the air inflow opening to the another board. 
     According to this structure, it is possible to cool a high-voltage board by means of the airflow blown out from the third blow-out opening of the fan casing. Therefore, it is unnecessary to additionally dispose a cooling fan for cooling the high-voltage board and dispose a long duct for guiding the airflow to the high-voltage board. Therefore, it is possible to improve the cooling efficiency and achieve the low cost. 
     It is preferable that the board is a power source board and the another board is a high-voltage board. 
     According to this structure, it is possible to efficiently cool the high-voltage board and the power source board. 
     The above board is the power source board, and the image forming device further includes: the high-voltage board for supplying a high voltage to the image forming portion; a main board that controls operation of the image forming device; and an engine board that controls operation of an actuator which includes the cooling fan. And, it is preferable that the power source board, the high-voltage board, the main board, and the engine board are all mounted on the side wall portion; and the cooling fan is configured to cool the image forming portion, the power source board as the board, the high-voltage board, the main board, and the engine board by means of an airflow generated by rotation of the cooling fan. 
     According to this structure, it is possible to dispose the cooling fan near heat source devices (portions to be cooled) such as the boards, the image forming portion and the like that need to be cooled. Accordingly, it is unnecessary to dispose the conventional long duct for cooling each board and the image forming portion. Therefore, it is possible to improve the cooling efficiency and achieve the low cost. 
     The cooling fan includes a fan casing mounted on the side wall portion and an impeller that is housed in the fan casing and rotates to make an airflow flow into the casing from outside the main body housing portion, and the fan casing includes: an air inflow opening; a first blow-out opening for blowing out part of the airflow flowing into the casing from the air inflow opening to the image forming portion; a second blow-out opening for blowing out part of the airflow flowing into the casing from the air inflow opening to the power source board, the main board and the engine board; and a third blow-out opening for blowing out part of the airflow flowing into the casing from the air inflow opening to the high-voltage board. In this way, it is possible to improve the cooling efficiency for the boards, the image forming portion and the like as soon as possible. 
     Advantageous Effects of Invention 
     According to the present disclosure, it is possible to efficiently cool the image forming portion ad the boards by means of an inexpensive structure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic cross-sectional view when seeing, from a front side, a laser printer as an image forming device according to an embodiment. 
         FIG. 2  is a perspective view when seeing a frame of a housing from a diagonally front right side. 
         FIG. 3  is a perspective view when seeing an image forming portion housed in a housing from a diagonally front right side. 
         FIG. 4  is a perspective view when seeing a housing from a rear side. 
         FIG. 5  is a schematic cross-sectional view cut along a V-V line of  FIG. 4 . 
         FIG. 6  is a perspective view when seeing a cooling fan from a front side (air inflow side). 
         FIG. 7  is a perspective view when seeing a cooling fan from a rear side. 
         FIG. 8  is a schematic cross-sectional view cut along a VIII-VIII line of  FIG. 5 . 
         FIG. 9  is a schematic cross-sectional view cut along a IX-IX line of  FIG. 4 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 
       FIG. 1  shows a laser printer  1  (hereinafter, simply called a printer) as an image forming device according to the present embodiment. This printer  1  has a paper sheet feeding portion  10 , an image forming portion  20 , a fixing portion  40 , a sheet delivery portion  50 , and a housing  60 . A sheet conveyance route extending from the sheet feeding portion  10  to the sheet delivery portion  50  is provided with a plurality of conveyance roller pairs  11 - 13  that sandwich and convey a sheet P. In the meantime, in the description performed below, a side before the paper surface of  FIG. 1  and a side behind the paper surface of  FIG. 1  are respectively called a “front side” and a “rear side,” and a left side of the paper surface of  FIG. 1  and a right side of the paper surface of  FIG. 1  are respectively called a “left side” and a “right side.” 
     The sheet feeding portion  10  is disposed in a lower portion in the housing  60 . The sheet feeding portion  10  has a sheet feeding cassette  10   a  in which the sheets P are housed and a pick-up roller  10   b  that takes out the sheet P in the sheet feeding cassette  10   a  and sends the sheet P to outside the cassette. The sheet P sent out from the sheet feeding cassette  10   a  to outside the cassette is supplied to the image forming portion  20  via the conveyance roller pair  11 . 
     The image forming portion  20  includes a photosensitive drum  21 , a charging device  23 , a light exposure device  25 , a developing device  27 , a transfer device  29 , and a toner container (not shown). After a circumferential surface of the photosensitive drum  21  is electrified by the charging device  23 , laser light based on document image data (e.g., image data of document image received from an external terminal) is directed to a surface of the photosensitive drum  21  by the light exposure device  25 , so that the image forming portion  20  forms an electrostatic latent image. The electrostatic latent image formed (carried) on the surface of the photosensitive drum  21  is developed as a toner image by the developing device  27 . And, the image forming portion  20  uses the transfer device  29  to transfer the toner image onto the sheet P supplied from the sheet feeding portion  10  and supplies the sheet P after the transfer to the fixing portion  40 . 
     At the fixing portion  40 , the sheet P supplied from the image forming portion  20  is pressed between a fixing roller  40   a  and a pressure roller  40   b , whereby the toner image is fixed onto the sheet P. And, the sheet P, on which the toner image is fixed by the fixing portion  40 , is sent out to a downstream side by both rollers  40   a ,  40   b . The sheet P sent out by the fixing portion  40  is delivered to the sheet delivery portion  50  via the plurality of conveyance roller pairs  12 ,  13 . The sheet delivery portion  50  is formed by recessing an upper surface portion of the housing  60  in to a recessed shape. 
     The housing  60  has a frame  61  (see  FIG. 2 - FIG. 4 ) and a sheet metal  62 . The housing  60  has a substantially rectangular-parallelepiped shape as a whole, and the frame  61  forms a skeleton. The sheet metals  62  are disposed to the number of 6 in all, and each sheet metal  62  forms one of a front wall portion, rear wall portion, left wall portion, right wall portion, upper wall portion, and lower wall portion of the housing  60 .  FIG. 2 - FIG. 4  show only a sheet metal (hereinafter, called a rear sheet metal)  62   a  that forms the rear wall portion of the housing  60 . 
     As shown in  FIG. 5 , the rear sheet metal  62   a  is disposed adjacently to the photosensitive drum  21  that is a constituent element of the image forming portion  20 . The rear sheet metal  62   a  is located near one side in a shaft center direction of the photosensitive drum  21 . One end portion in the shaft center direction of the photosensitive drum  21  is connected to a drive mechanism  150  for driving the drum  21 . The drive mechanism  150  has a drive gear  151  connected to the photosensitive drum  21  in an integrally rotatable manner and a driven gear  152  connected to a transfer roller  29   a  of the transfer device  29  in an integrally rotatable manner. The driven gear  152  meshes with the drive gear  151 . And, when the driven pear  152  is driven by a not-shown motor, the photosensitive drum  21  rotates together with the drive gear  151 , and the transfer roller  29   a  rotates together with the driven gear  151 . 
     The rear sheet metal  62   a  is covered by the outer cover  63  from outside the printer  1 . The outer cover  63  is fixed to the frame  61  by a not-shown bolt. The outer cover  63  is disposed backward from the rear sheet metal  62   a  a predetermined distance away from the rear sheet metal  62   a . In this way, a space (gap) S having a thickness in a front-rear direction is formed between the outer cover  63  and the rear sheet metal  62   a . The outer cover  63  is provided with an air inhaling opening  63   f . The air inhaling opening  63   f  is formed through a portion of the outer cover  63  near a rear side of a cooling fan  100  (described later). The left wall portion of the housing  60  is provided with an air exhaust opening  60   f  for discharging air in the housing  60  to outside. The air exhaust opening  60   f  is formed through a front lower end portion of the left wall portion of the housing  60 . 
     Back to  FIG. 4 , the rear sheet metal  62   a  is provided thereon with a power source board  71 , an engine            main board  72 , a high-voltage board  73  (see  FIG. 9 ), and the cooling fan  100 .
     The cooling fan  100  is disposed at a position of the rear sheet metal  62   a  located slightly left from an extended position in the shaft center direction of the photosensitive drum  21 . The cooling fan  100  is configured to cool the image forming portion  20  and each of the boards  71 - 73  by means of an airflow generated by rotation of the cooling fan  100 . Details of the cooling fan  100  are described later. 
     The power source board  71  is mounted on a portion of a rear surface of the rear sheet metal  62   a  on the left side of the cooling fan  100 . The power source board  71  supplies necessary electric power to each of devices of the printer  1  such as a heater incorporated in the fixing roller  40   a , a motor for driving the photosensitive drum  21  and the like. 
     The engine            main board  72  is mounted above the power source board  71  on the rear surface of the rear sheet metal  62   a . The engine          main board  72  has both a function as an engine board that controls an actuator (in detail, a drive motor for the cooling fan  100 , a drive motor for a conveyance system and the like) which includes the cooling fan  100  and a function as a main board that controls operation of the image forming portion  20 .
     The high-voltage board  73  is mounted on a front surface of the rear sheet metal  62   a . The high-voltage board  73  is located slightly above a height position of an upper end surface of the cooling fan  100 . The high-voltage board  73  supplies a high voltage to the transfer device  29 , the developing device  27 , the photosensitive drum  21  and the like. 
     As shown in  FIG. 5 - FIG. 7 , the cooling fan  100  has a fan casing  101  and an impeller  110 . In the meantime, in the description performed below, unless otherwise specified, the description is performed on condition that the cooling fan  100  is mounted on the rear sheet metal  62   a  (in the state of  FIG. 5 ). 
     The fan casing  101  has a rectangular main body casing  102  for housing the impeller  110 , and a duct portion  103  integrally formed with the main body casing  102 . The impeller  110  is rotatably supported on the main body casing  102  by four support portions  104  that extend outward in a radial direction from an outer circumferential portion of the impeller  110 . The impeller  110  is driven to rotate by a not-shown motor. 
     An upper surface and lower surface of the main body casing  102  are each provided with a fixing bracket portion  105  (see  FIG. 7 ). Each fixing bracket portion  105  is provided with a through-hole  105   f  that penetrates in a thickness direction of the fixing bracket portion  105 . The main body casing  102  is fixed to the rear sheet metal  62   a  by a not-shown bolt inserted in the through-hole  105   f.    
     A rear wall portion  102   a  of the main body casing  102  is provided with a through-hole  102   f  (see  FIG. 6 ). The through-hole  102   f  is formed through an entirety except for four corners of the rear wall portion  102   a . The through-hole  102   f  composes an air inflow opening  200  for allowing an airflow to flow into the fan casing  101 . A left wall portion  102   d  of the main body casing  102  is provided with a rectangular opening portion  102   r  that penetrates in a thickness direction. The opening portion  102   r  composes a second blow-out opening  202  for blowing out part of the airflow, which flows from the air inflow opening  200  into the fan casing  101 , to the power source board  71  and the engine            main board  72 .
     The duct portion  103  is connected to a front side of the main body casing  102  and penetrates the rear sheet metal  62   a  (see  FIG. 5 ). The duct portion  103  has an inclination wall portion  103   a  that inclines rightward (toward the photosensitive drum  21 ) from a front portion to a rear portion (see  FIG. 7 ). An upper end edge of the inclination wall portion  103   a  is connected to an upper wall portion  103   b  and a lower end edge of the inclination wall portion  103   a  is connected to a lower wall portion  103   c . The upper wall portion  103   b  and the lower wall portion  103   c  are horizontally disposed to oppose each other. The upper wall portion  103   b  and the lower wall portion  103   c  are respectively connected to an upper vertical wall portion  102   b  and a lower vertical wall portion  102   c  that compose a portion of the main body casing  102 . 
     A downstream-side opening portion  103   f  of the duct portion  103  is opened near one end portion in the shaft center direction of the photosensitive drum  21 . And, the opening portion  103   f  composes a first blow-out opening  201  that blows out part of the airflow, which flows from the air inflow opening  200  into the fan casing  101 , to the one end portion in the shaft center direction of the photosensitive drum  21 . 
     The upper vertical wall portion  102   b  is provided with a substantially square-shaped opening portion  102   s  that penetrates in a thickness direction. The opening portion  102   s  is connected to a through-hole  62   f  (see  FIG. 9 ) that is formed near a lower side of the high-voltage board  73  on the rear sheet metal  62   a . And, the opening portion  102   s  composes a third blow-out opening  203  for blowing out part of the airflow, which flows from the air inflow opening  200  into the fan casing  101 , to the high-voltage board  73 . 
     In the printer  1  composed as described above, when the cooling fan  100  is driven, air outside the printer  1  is guided into the cooling fan  100  via the air inhaling opening  63   f  formed through the outer cover  63  (see  FIG. 5 ). And, an airflow flows into the casing  101  via the air inflow opening  200  formed through the fan casing  101 . The airflow flowing into the fan casing  101  roughly separates into three airflows of: an airflow blown out from the first blow-out opening  201 ; an airflow blown out from the second blow-out opening  202 ; and an airflow blown out from the third blow-out opening  203  (see  FIG. 9 ). 
     As indicated by an outline arrow in  FIG. 5  and  FIG. 8 , the airflow blown out from the first blow-out opening  201  is blown out to the one end portion in the shaft center direction of the photosensitive drum  21 . Thereafter, the airflow flows from the one end to the other end (from the rear side to the front side) in the shaft center direction along a boundary portion between the photosensitive drum  21  and the developing roller  27   a  (see  FIG. 8 ), thereafter, flows from the right side to the left side along the front wall portion of the housing  60  to be discharged from the exhaust opening  60   f . In this way, the entire image forming portion  20  including the photosensitive drum  21  is cooled by the airflow discharged from the first blow-out opening  201 . Accordingly, it is possible to prevent the image forming portion  20  from being excessively heated by heat from the fixing portion  40  adjacent to the image forming portion  20  and prevent the image forming portion  20  from being excessively heated by operation of the light exposure device  25 . 
     As indicated by an outline arrow in  FIG. 5 , the airflow blown out from the second blow-out opening  202  flows from the right side to the left side along the rear sheet metal  62   a , passes the power source board  71 , thereafter, is discharged from a not-shown exhaust opening to outside the printer  1 . Because the engine            main board  72  is disposed above the power source board  71 , besides the power source board  71 , the engine          main board  72  is cooled by the airflow. Accordingly, it is possible to prevent the power source board  71  and the engine main board  72  from excessively generating heat to malfunction.
     As indicated by an outline arrow in  FIG. 9 , the airflow blown out from the third blow-out opening  203  flows from the lower side to the upper side along the rear sheet metal  62   a , passes the high-voltage board  73 , thereafter, is discharged from the exhaust opening  60   f  to outside the printer  1 . In this way, the high-voltage board  73  is cooled by the airflow. Accordingly, it is possible to prevent the high-voltage board  73  from malfunctioning because of excessive heat generation. 
     As described above, in the above embodiment, all the boards  71 - 73  are mounted on the rear sheet metal  62   a  adjacent to the image forming portion  20 , and the cooling fan  100  is mounted on the rear sheet metal  62   a . Besides, the drive mechanism  150  of the photosensitive drum  21 , which is a constituent element of the image forming portion  20 , is disposed near the rear sheet metal  62   a . In this way, it is possible to gather and dispose the heat sources such as the boards  71 - 73 , the image forming portion  20 , the drive mechanism  150  and the like in a rear portion of the printer  1  and to dispose the cooling fan  100  at the place near the heat sources. 
     Accordingly, it is unnecessary to dispose a long duct to cool the heat sources such as the boards  71 - 73 , the image forming portion  20 , the drive mechanism  150  and the like. Therefore, it is possible to efficiently cool the heat sources (places to be cooled) by means of an inexpensive structure. Besides, it is also unnecessary to increase the number of cooling fans  100  to cool each board  71 - 73 , the image forming portion and the drive mechanism  150 . Accordingly, it is possible to reduce the fan noise and the production cost. 
     Besides, in the above embodiment, the cooling fan  100 , the power source board  71 , and the engine            main board  72  are mounted on the surface (rear side) of the rear sheet metal  62   a  near the outer cover  63 .
     Accordingly, an operator can easily gain access to the cooling fan  100 , the power source board  71 , and the engine            main board  72  by only removing the outer cover  63 . Therefore, it is possible to improve maintenance characteristics of these devices.
     Other Embodiments 
     The present disclosure is not limited to the above embodiment. 
     In other words, in the above embodiment, the engine board and the main board are unified as the engine            main board  72 . However, this is not limiting, but both boards may be separated.
     In the above embodiment, as an example of the image forming device, the laser printer  1  of electro-photographic type is described. However, this is not limiting. In other words, the image forming device may be an image forming device of ink jet type, for example. 
     In the above embodiment, only one cooling fan  100  is disposed. However, this is not limiting, but a plurality of the cooling fans  100  may be disposed. 
     INDUSTRIAL APPLICABILITY 
     As described above, the present disclosure is useful for an image forming device, especially useful for an image forming device that includes: a main body housing portion which houses an image forming portion that records an image onto a sheet; a power source board; and a cooling fan for cooling the image forming portion and the power source board. 
     REFERENCE SIGNS LIST 
     
         
           1  laser printer (image forming device) 
           20  image forming portion 
           21  photosensitive drum 
           60  housing (main body housing portion) 
           62   a  rear sheet metal (side wall portion) 
           63  outer cover 
           63   f  air inhaling opening 
           71  power source board (one board) 
           72  engine          main board (engine board, main board) 
           73  high-voltage board (another board) 
           100  cooling fan 
           101  fan casing 
           110  impeller 
           150  drive mechanism 
           200  air inflow opening 
           201  first blow-out opening 
           202  second blow-out opening 
           203  third blow-out opening