Patent Publication Number: US-10768574-B1

Title: Image forming apparatus

Description:
FIELD 
     Embodiments described herein relate generally to an image forming apparatus. 
     BACKGROUND 
     An image forming apparatus is used to form an image on a sheet. The image forming apparatus may include a developing device and a heating element, such as a power supply unit. There is a possibility that a toner stored in the developing device bonds together to become a lump of toner due to a thermal effect of a heating element on the developing device. Accordingly, an image forming apparatus is required to be capable of suppressing the thermal effect of the heating element on the developing device. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a schematic configuration of an image processing apparatus according to an embodiment; 
         FIG. 2  is a front sectional view of a cooling unit; 
         FIG. 3  is a plan sectional view of the cooling unit; 
         FIG. 4  is an enlarged view of the vicinity of a fan in  FIG. 2 ; 
         FIG. 5  is an enlarged view of the vicinity of a fan in  FIG. 3 ; and 
         FIG. 6  is a plan sectional view of the cooling unit according to a modification of the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In accordance with at least one embodiment, an image forming apparatus comprises a developing device; a heating element arranged below the developing device; a case configured to cover the heating element, a first air duct of which an end in a first direction side communicates with the outside being formed at an inner side of the case, and an end of the case in a second direction side opposite to the first direction being blocked by a blocking plate; a duct arranged between the developing device and the case, a second air duct of which an end on the first direction side communicates with the outside and contacting the case being formed at an inner side of the duct; a fan, arranged on the second direction side of both the first air duct and the second air duct, configured to blow out air in the first direction; a cover member configured to cover the second direction side of the first air duct, the second air duct and the fan; and a guide section configured to guide the air blown out of the fan to the first air duct. 
     Hereinafter, an image forming apparatus according to an embodiment are described with reference to the accompanying drawings. 
     In the present application, an X direction, a Y direction, and a Z direction are defined as follows. The X direction is a left and right direction of the image processing apparatus, and is a direction in which a first air duct and a second air duct described below extend. A +X direction (second direction) is a right direction towards the image processing apparatus (with respect to a paper surface of  FIG. 1 ). A −X direction (first direction) is a left direction towards the image processing apparatus. The Y direction is a front and rear direction of the image processing apparatus. The widths of both the first air duct and the second air duct described below are measured in the Y direction. A +Y direction is a back direction of the image processing apparatus (the back side of the paper surface of  FIG. 1 ). The Z direction is a vertical direction, and a +Z direction is the upper direction. 
       FIG. 1  is a diagram illustrating a schematic configuration of an image processing apparatus of the embodiment. The image forming apparatus performs a processing for forming an image on a sheet. An image forming apparatus  1  includes a housing  1   a , a scanner section (a scanner)  2 , an image forming unit (an image former)  3 , a sheet feed section (a sheet feeder)  4 , a conveyance section (a conveyor)  5 , a reversing unit (a reverser or re-router)  6 , a sheet discharge tray  7 , a control panel  8 , a control section (a controller)  9 , and a power supply unit (a power supply) PU. 
     The housing  1   a  forms an external shape of the image forming apparatus  1 . The housing  1   a  accommodates components of the image forming apparatus  1  therein. 
     The scanner section  2  reads image information of an object to be copied as intensity of light in order to generate an image signal. The scanner section  2  outputs the generated image signal to the image forming unit  3 . 
     The image forming unit  3  forms an output image (hereinafter referred to as a toner image) with a developer containing a toner and the like based on an image signal received from the scanner section  2  or an image signal received from an external device. The image forming unit  3  transfers the toner image onto a surface of a sheet S. The image forming unit  3  fixes the toner image to the sheet S. In other words, the image forming unit  3  performs an image forming processing on the sheet. A configuration of the image forming unit  3  is described below. 
     The sheet feed section  4  feeds sheets S one by one to the conveyance section  5  in accordance with a timing at which the image forming unit  3  forms a toner image. The sheet feed section  4  includes a cassette  12  and a pickup roller  14 . The cassette  12  accommodates sheets S of a predetermined size and type. The pickup roller  14  picks up the sheets S one by one from the cassette  12 . The pickup roller  14  feeds the sheet S picked up to the conveyance section  5 . 
     The conveyance section  5  conveys the sheet S fed from the sheet feed section  4  to the image forming unit  3 . The conveyance section  5  includes a conveyance roller  16  and a registration roller  18 . The conveyance roller  16  conveys the sheet S fed from the pickup roller  14  to the registration roller  18 . The conveyance roller  16  enables a tip of the sheet S in a conveyance direction against a nip N of the registration roller  18 . The registration roller  18  aligns the tip position of the sheet S in the conveyance direction by bending the sheet S at the nip N. The registration roller  18  conveys the sheet S in accordance with a timing at which the image forming unit  3  transfers the toner image onto the sheet S. 
     A configuration of the image forming unit  3  is described below. 
     The image forming unit  3  includes a plurality of electrophotographic process units (hereinafter referred to as EPUs or electrophotographic processors)  20 , a toner cartridge  28 , an intermediate transfer belt  30 , a transfer section (a transferor)  32 , and a fixing device (a fixer)  34 . 
       FIG. 2  is a front sectional view of a cooling unit. The EPU  20  forms a toner image corresponding to an image signal from the scanner section  2  or the external device on a photoconductive drum  22 . The plurality of EPUs  20 Y,  20 M,  20 C, and  20 K forms toner images with a yellow toner, a magenta toner, a cyan toner, and a black toner, respectively. The EPU  20  includes the photoconductive drum  22 , an exposure device (exposer)  24  and a developing device (developer)  26 . The photoconductive drum  22  includes a photoconductive layer of which a charge state changes due to exposure on an outer circumferential surface thereof. The exposure device  24  exposes the photoconductive drum  22  with light from a light emitting diode (LED) light source. The exposure device  24  forms an electrostatic latent image corresponding to an image signal on the photoconductive drum  22 . The developing device  26  accommodates the developer containing the toner. The developing device  26  develops the electrostatic latent image on the photoconductive drum  22  with the toner to form a toner image on the photoconductive drum  22 . 
     The image forming apparatus  1  is downsized in the X direction by reducing a distance in the X direction (a distance between the drums) between the photoconductive drums  22  of the adjacent EPUs  20 . The adjacent EPUs  20  are arranged with positions thereof in the Z direction that are shifted from each other. The plurality of EPUs  20 Y,  20 M,  20 C, and  20 K is arranged in such a manner that the EPU  20  in the +X direction is positioned further towards a −Z direction. In this way, interference between the adjacent EPUs  20  is avoided, and the distance between the drums is reduced. 
     The toner cartridge  28  accommodates toner. As shown in  FIG. 1 , the toner cartridge  28  replenishes the toner to the developing device  26 . 
     The intermediate transfer belt  30  is arranged across the plurality of EPUs  20 Y,  20 M,  20 C, and  20 K. The toner image on the photoconductive drum  22  is primarily transferred onto the intermediate transfer belt  30 . 
     The transfer section  32  secondarily transfers the toner image primarily transferred onto the intermediate transfer belt  30  onto the surface of the sheet S. 
     The fixing device  34  applies heat and pressure to the sheet S to fix the toner image to the sheet S. 
     The reversing unit  6  reverses the sheet S to form an image on a back surface of the sheet S. The reversing unit  6  reverses the front and back surfaces of the sheet S discharged from the fixing device  34  through a switchback. The reversing unit  6  conveys the reversed sheet S towards the registration roller  18 . 
     The sheet discharge tray  7  is used to place the sheet S discharged by a sheet discharge roller  36 . The sheet discharge roller  36  discharges the sheet S on which an image is formed in the image forming unit  3  to the sheet discharge tray  7 . 
     The control panel  8  is a part of an input section through which an operator inputs information for operating the image forming apparatus  1 . The control panel  8  includes a touch panel and various hard keys. 
     The control section  9  controls each section of the image forming apparatus  1 . The power supply unit PU transforms a commercial power supply voltage to supply it to the components of the image forming apparatus. 
     Generally, a laser unit that scans a laser beam to expose the photoconductive drum  22  is large. A laser unit may be arranged in the −Z direction side of the plurality of EPUs  20 Y,  20 M,  20 C, and  20 K shown in  FIG. 2 . On the other hand, the exposure device  24  of the embodiment exposes the photoconductive drum  22  with light from the LED light source, as described above. The exposure device  24  is downsized and arranged in the EPU  20 , so as to be smaller than the laser unit. Therefore, a large space is available on the −Z direction side of the plurality of EPUs  20 Y,  20 M,  20 C, and  20 K. The power supply unit PU is arranged in the space on the −Z direction side of the plurality of EPUs  20 Y,  20 M,  20 C, and  20 K. In this way, the image forming apparatus  1  is downsized in the Y direction as compared to the case in which the power supply unit PU is arranged on the +Y direction side of the plurality of EPUs  20 Y,  20 M,  20 C, and  20 K. 
     The power supply unit PU is a heating element (a heater). The developing device  26  is arranged on the +Z direction side of the power supply unit PU. If the temperature of the developing device  26  rises due to the thermal effect of the power supply unit PU, there is a possibility that the toner accommodated in the developing device bonds together to become a lump of toner. If the lump of toner is clogged in the developing device  26 , a development failure occurs in the toner image on the photoconductive drum  22 . In this way, an image defect such as a white streak or a white spot occurs in the image formed on the sheet S. If the image forming apparatus  1  is intermittently operated to suppress the temperature rise of the developing device  26 , the productivity of the image forming apparatus  1  is reduced. 
     In order to suppress the thermal effect of the power supply unit PU on the developing device  26 , the image forming apparatus  1  includes a cooling unit (cooler)  40  for the power supply unit PU. 
     The cooling unit  40  is described below. 
       FIG. 2  is a front sectional view of the cooling unit, and is a cross-sectional view taken along a line II-II of  FIG. 3 .  FIG. 3  is a plan sectional view of the cooling unit, and is a cross-sectional view taken along a line of  FIG. 2 . As shown in  FIG. 2 , the cooling unit  40  is arranged on the +Z direction side of a frame  1   b  of the image forming apparatus  1  together with the power supply unit PU. The cooling unit  40  includes a case  42 , a duct  52 , a fan unit (fan)  60 , a cover member (second cover)  70 , and a shielding portion (shield)  54 . 
     The case  42  is made of a metal material or the like. The case  42  covers the +Z direction side, the +Y direction side, and a −Y direction side of the power supply unit PU while extending in the X direction. In the case  42 , a first air duct  41  is formed. An end on the −X direction side of the case  42  closely contacts an exterior cover (first cover)  80  of the image forming apparatus  1 . An opening  84  is formed in the exterior cover  80 . The end on the −X direction side of the first air duct  41  communicates with the outside of the image forming apparatus  1  through the opening  84 . 
       FIG. 4  is an enlarged view of the vicinity of the fan in  FIG. 2 .  FIG. 5  is an enlarged view of the vicinity of the fan in  FIG. 3 . As shown in  FIG. 4 , an end on the +X direction side of the case  42  (i.e., the first air duct  41 ) is blocked by a blocking plate  44 . The blocking plate  44  is integrally formed with the case  42 . The blocking plate  44  includes an inclined plate  45  arranged on the +Z direction side and a vertical plate  46  arranged on the −Z direction side. The inclined plate  45  is further inclined in the −Z direction towards the +X direction. The vertical plate  46  is parallel to a YZ plane. 
     The duct  52  is made of a resin material or the like. As shown in  FIG. 2 , the duct  52  is arranged between the developing device  26  and the case  42 . A second air duct  51  is formed at the inner side of the duct  52 . The duct  52  covers the +Z direction side, the +Y direction side and the −Y direction side of the second air duct  51  while extending in the X direction. As described above, the plurality of EPUs  20 Y,  20 M,  20 C, and  20 K is arranged in such a manner that the EPU in the +X direction is positioned further towards the −Z direction. A height in the Z direction of the duct  52  (i.e. the second air duct  51 ) becomes lower towards the +X direction. The −Z direction side of the second air duct  51  is covered by the case  42 . Specifically, the second air duct  51  contacts the case  42 . A length of the duct  52  in the X direction is equal to that of the case  42  in the X direction. An end on the −X direction side of the duct  52  closely contacts the exterior cover  80 . An opening  85  is formed in the exterior cover  80 . The end on the −X direction side of the second air duct  51  communicates with the outside of the image forming apparatus  1  through the opening  85 . As shown in  FIG. 3 , an end on the +X direction side of the duct  52  (i.e., the second air duct  51 ) is open except for the shielding portion  54  described below. 
     The fan unit  60  is arranged on the +X direction side of the first air duct  41  and the second air duct  51 , as shown in  FIG. 2 . As shown in  FIG. 3 , the fan unit  60  is arranged at the center of the cooling unit  40  in the Y direction. As shown in  FIG. 4 , the fan unit  60  includes a fan  62  and a fan case  64 . The fan  62  is rotated by a motor (not shown). The fan case  64  is fixed to the frame  1   b . As shown in  FIG. 5 , the fan case  64  includes a back plate  65  and a side plate  66 . The back plate  65  is arranged on the +X direction side of the fan  62  to support the fan  62 . The back plate  65  includes an air suction hole  65   h . The side plate  66  is arranged on the +Y direction side and the −Y direction side of the fan  62 . The side plate  66  closely contacts the surface of the vertical plate  46  on the +X direction side of the blocking plate  44 . The fan case  64  is open on the −X direction side of the fan  62 . The fan  62  rotates to suck the air from the +X direction side through the air suction hole  65   h  and to blow out the air in the −X direction. 
     The cover member  70  is made of a resin material or the like. As shown in  FIG. 2 , the cover member  70  covers the +X direction side of the first air duct  41  (case  42 ), the second air duct  51  and the fan unit  60 . An end on the −X direction side of the cover member  70  closely contacts the ends on the +X direction side of the case  42  and the duct  52 . The outer shape of the end on the −X direction side of the cover member  70  is the same as those of the ends on the +X direction side of the case  42  and the duct  52 . As shown in  FIG. 3 , the cover member  70  includes a back plate  75 , a side plate  76  and a curved plate  78 . The back plate  75  is arranged away from the fan unit  60  in the +X direction. The side plate  76  is arranged away from the fan unit  60  in the +Y direction and the −Y direction. The curved plate  78  is arranged at a corner between the back plate  75  and the side plate  76 . The curved plate  78  smoothly connects the back plate  75  with the side plate  76 . 
     The shielding portion  54  is made of a resin material or the like. As shown in  FIG. 2 , the shielding portion  54  is integrally formed with the duct  52 , and extends from the duct  52  in the −Z direction. The shielding portion  54  is arranged between the fan unit  60  and the second air duct  51  to cover the −X direction side of the fan unit  60 . As shown in  FIG. 5 , the shielding portion  54  includes a main plate  55  and a side plate  56 . The main plate  55  is parallel to the YZ plane. The main plate  55  is arranged away from the fan unit  60  in the −X direction. The main plate  55  is arranged at an end on the −X direction side of the blocking plate  44 . The side plates  56  extend in the +X direction from both ends in the Y direction side of the main plate  55 . The side plate  56  of the shielding portion  54  closely contacts the side plate  66  of the fan unit  60 , such that at least part of the side plate  56  is flush with the side plate  66 . As shown in  FIG. 4 , an end on the −Z direction side of the side plate  56  closely contacts the surface on the +Z direction side of the inclined plate  45 . 
     As shown in  FIG. 4 , the blocking plate  44  includes a first ventilating hole  45   h  formed in the inclined plate  45  and a second ventilating hole  46   h  formed in the vertical plate  46 . 
     As shown in  FIG. 5 , the first ventilating hole  45   h  opens to the inside of the shielding portion  54 . The first ventilating hole  45   h  and the second ventilating hole  46   h  are formed in a portion of the blocking plate  44  facing the fan  62 . The shielding portion  54 , the first ventilating hole  45   h , and the second ventilating hole  46   h  function as a guide section (a guide)  50 G for guiding the air blown out of the fan to the first air duct  41 . 
     An operation of the cooling unit  40  is described below. 
     As shown in  FIG. 2 , if the fan  62  rotates, the air flows from the opening  85  of the exterior cover  80  to the second air duct  51 . The air circulates in the second air duct  51  in the +X direction. The air contacts the surface on the +Z direction side of the case  42  in the process of circulating in the second air duct  51 . In this way, the case  42  is cooled. As shown in  FIG. 3 , the air flows out of the second air duct  51  through both sides in the Y direction of the shielding portion  54 . The air flows into the cover member  70  through both sides in the Y direction of the fan unit  60 . The air changes in a circulating direction thereof along the curved plate  78 . The air flows in the Y direction along the back plate  75  and gathers in an area on the +X direction side of the fan unit  60 . 
     As shown in  FIG. 2 , the fan  62  sucks the air from the +X direction side and blows out the air in the −X direction. The upper half of the air blown out of the fan  62  is received by the shielding portion  54 . As shown in  FIG. 4 , the inclined plate  45  of the blocking plate  44  is arranged on the −Z direction side of the shielding portion  54 . The inclined plate  45  is provided with the first ventilating hole  45   h  opening to the inner side of the shielding portion  54 . The air received by the shielding portion  54  flows into the first air duct  41  through the first ventilating hole  45   h . The lower half of the air blown out of the fan  62  flows into the first air duct  41  through the second ventilating hole  46   h.    
     As shown in  FIG. 2 , the air circulates in the first air duct  41  in the −X direction, which is reverse to the second air duct  51 . The air cools the power supply unit PU in the process of circulating in the first air duct  41 . The air flows out of the opening  84  of the exterior cover  80  to the outside. 
     As described in detail above, the image forming apparatus  1  of the embodiment includes the developing device  26 , the power supply unit PU, the case  42 , the duct  52 , the fan  62 , the cover member  70  and the guide section  50 G. The power supply unit PU is arranged below the developing device  26 . The case  42  covers the power supply unit PU. The first air duct  41  is formed at the inner side of the case  42 . The end on the −X direction side of the first air duct  41  communicates with the outside. The end on the +X direction side of the case  42  is blocked by the blocking plate  44 . The duct  52  is arranged between the developing device  26  and the case  42 . The second air duct  51  is formed at the inner side of the duct  52 . The second air duct  51  contacts the case  42 . The end on the −X direction side of the second air duct  51  communicates with the outside. The fan  62  is arranged on the +X direction side of the first air duct  41  and the second air duct  51 . The fan  62  blows out the air in the −X direction. The cover member  70  covers the +X direction side of the first air duct  41 , the second air duct  51 , and the fan  62 . The guide section  50 G guides the air blown out of the fan  62  to the first air duct  41 . 
     The second air duct  51  is formed between the case  42  covering the power supply unit PU and the developing device  26 . Since the air flowing from the outside circulates in the second air duct  51 , a low temperature air layer is formed in the second air duct  51 . 
     The air layer can suppress the thermal effect of the power supply unit PU on the developing device  26 . Since the temperature rise of the developing device  26  is minimized, the intermittent operation of the image forming apparatus  1  is minimized. Therefore, the decrease in productivity of the image forming apparatus  1  is minimized. 
     The fan  62  is arranged on the +X direction side of the first air duct  41  and the second air duct  51 . A large fan  62  corresponding to the height of the first air duct  41  and the second air duct  51  can be employed. The fan  62  blows out the air in the −X direction towards the power supply unit PU to be cooled. In this way, the power supply unit PU can be cooled efficiently. 
     The guide section  50 G includes the shielding portion  54  and the first ventilating hole  45   h . The shielding portion  54  is arranged between the fan  62  and the second air duct  51  to cover the −X direction side of the fan  62 . The first ventilating hole  45   h  is formed in the blocking plate  44  and opens to the inner side of the shielding portion  54 . 
     The air blown out of the fan  62  is received by the shielding portion  54  arranged on the −X direction side of the fan  62 . The air received by the shielding portion  54  flows into the first air duct  41  through the first ventilating hole  45   h  opening to the inside the shielding portion  54 . Thus, the guide section  50 G guides (i.e., directs) the air blown out of the fan  62  to the first air duct  41 . 
     The blocking plate  44  includes the inclined plate  45  inclined downward towards the +X direction. The first ventilating hole  45   h  is formed in the inclined plate  45 . 
     The shielding portion  54  includes the main plate  55  and the side plate  56 . The main plate  55  is arranged at the end in the −X direction side of the inclined plate  45 . The side plates  56  extend in the +X direction from both ends of the main plate  55  in the Y direction. 
     The side plate  56  prevents the air received by the main plate  55  from escaping in the Y direction. The main plate  55  is arranged at the end on the −X direction side of the inclined plate  45 , and the first ventilating hole  45   h  is formed in the inclined plate  45 . In this way, the air received by the main plate  55  efficiently flows into the first ventilating hole  45   h.    
     The cover member  70  includes the back plate  75 , the side plate  76  and the curved plate  78 . The back plate  75  is arranged away from the fan  62  in the +X direction. The side plate  76  is arranged away from the fan  62  in the Y direction. The curved plate  78  connects the back plate  75  with the side plate  76 . 
     A circulating direction of the air flowing out of the second air duct  51  is changed from the +X direction to the Y direction at the cover member  70 . The air circulates along the curved plate  78 , and in this way, the decrease in the air speed due to the change in the circulating direction is minimized. 
     The first air duct  41  and the second air duct  51  are formed below a plurality of developing devices  26 . 
     In this way, the thermal effect of the power supply unit PU on the plurality of the developing devices  26  is minimized. 
     The height in the vertical direction of the second air duct  51  becomes lower towards the +X direction. 
     The second air duct  51  communicates with the outside at the end on the −X direction side thereof. Since the height on the −X direction side of the second air duct  51  is high, the air tends to flow into the second air duct  51 . 
     The first air duct  41  and the second air duct  51  communicate with the outside through the openings  84  and  85  formed in the exterior cover  80 . 
     Both the opening  84  of the first air duct  41  and the opening  85  of the second air duct  51  are formed in the same exterior cover  80 . Therefore, a manufacturing cost of the openings  84  and  85  is suppressed. 
     As shown in  FIG. 3 , the fan  62  of the embodiment is arranged at the center in the Y direction of the cooling unit  40 . Alternatively, the fan  62  may be arranged at a position other than the center in the Y direction of the cooling unit  40 . 
       FIG. 6  is a plan sectional view of a cooling unit according to a modification of the embodiment.  FIG. 6  is a cross-sectional view of a portion along the line of  FIG. 2 . 
     As described above, the power supply unit PU transforms the commercial power supply voltage to supply it to the components of the image forming apparatus  1 . Therefore, the power supply unit PU includes a primary side circuit PU 1  and a secondary side circuit PU 2 . The primary side circuit PU 1  is connected to a commercial power supply. The secondary side circuit PU 2  is connected to the components of the image forming apparatus  1  and not to the commercial power supply. A heat generation amount of the primary side circuit PU 1  is larger than that of the secondary side circuit PU 2 . Therefore, the fan  62  is arranged closer to the primary side circuit PU 1  with respect to the center of the cooling unit  40  in the Y direction. In this way, the primary side circuit PU 1  of which the heat generation amount is large is efficiently cooled. 
     The cooling unit  40  of the embodiment described above includes one fan  62  and the guide section  50 G. Alternatively, the cooling unit  40  may have a plurality of fans  62  and guide sections  50 G. 
     In the embodiment described above, the duct  52  and the cover member  70  are separately formed. Alternatively, the duct  52  and the cover member  70  may be integrally formed. 
     The shielding portion  54  of the embodiment described above is integrally formed with the duct  52 . Alternatively, the shielding portion  54  may be integrally formed with the cover member  70 . The shielding portion  54  may be formed separately from the duct  52  and the cover member  70 . 
     According to at least one embodiment described above, the second air duct  51  is provided between the case  42  covering the power supply unit PU and the developing device  26 . In this way, the thermal effect of the power supply unit PU on the developing device  26  can be minimized. 
     While certain embodiments have been described these embodiments have been presented by way of example only, and are not intended to limit the scope of the present disclosure. Indeed, the novel embodiments described herein may be embodied in a variety of other forms: furthermore various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the present disclosure. The accompanying claims and there equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the present disclosure.