Abstract:
An image forming apparatus has an image supporting body that supports a toner image and an exposure part that exposes the image supporting body. The image forming apparatus also has a transfer part for transferring the toner image formed on the image supporting body onto a recording medium and a fixing device that fixes the toner image transferred onto the recording medium to the recording medium. Moreover a control part and a power supply part and a blowing unit are held by the image forming apparatus and the blowing unit generates an air flow. The control part, the power supply part, and the exposure part are disposed at an upstream side of the air flow generated by the blowing unit, and the fixing device is disposed at a downstream side.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an image forming apparatus of an electrophotographic system or the like.  
           [0003]    2. Description of the Related Art  
           [0004]    In an image forming apparatus of an electrophotographic system, a toner image is transferred to a sheet, and this toner image is fixed to the sheet. With respect to the fixation of the toner image, a heat pressure fixing device using heat and pressure is generally used. There is a fear that radiation heat or the like generated from this kind of fixing device has a bad influence on other structural elements.  
           [0005]    Thus, it is conventionally well known to provide a blowing unit for exhausting the heat of the fixing device to the outside (see patent documents 1 to 3).  
           [0006]    [Patent document 1] JP-A-2-50169  
           [0007]    [Patent document 2] JP-A-5-224476  
           [0008]    [Patent document 3] JP-A-6-230617  
           [0009]    However, when an image forming apparatus is miniaturized, respective structural elements must be put together and arranged, and there is increased fear that the heat generated from the fixing device has a bad influence on other structural elements. Especially, when the heat enters an exposure part, the temperature of a component (for example, a plastic lens or a scanner motor) constituting the exposure part becomes high, and there is a problem that the refractivity is changed by the thermal expansion of the plastic lens, or the lifetime of bearings of the scanner motor becomes short. Besides, when a cooling unit is provided in the respective structural elements, the number of parts is increased, and this causes the cost to become high and may hinder the miniaturization of the image forming apparatus.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention has been made in view of the above circumstances and provides an image forming apparatus in which even if it is miniaturized, heat from a fixing device is efficiently exhausted to the outside, and the influence of the heat on other structural elements including an exposure part can be reduced.  
           [0011]    In order to solve the above problems, according to an aspect of the present invention, an image forming apparatus includes an image supporting body for supporting a toner image, an exposure part for exposing the image supporting body, a transfer part for transferring the toner image formed on the image supporting body onto a recording medium, a fixing device for fixing the toner image transferred onto the recording medium to the recording medium, a control part, a power supply part, and a blowing unit for generating an air flow, in which the control part, the power supply part, and the exposure part are disposed at an upstream side of the air flow generated by the blowing unit, and the fixing device is disposed at a downstream side. Accordingly, since the control part, the power supply part and the exposure part, which are apt to be influenced by heat, are disposed at the upstream side of the air flow generated by the blowing unit, it is possible to reduce the influence of radiation heat or the like, which is generated by the fixing device, upon the control part, the power supply part and the exposure part.  
           [0012]    Preferably, the blowing unit includes an air inlet, an air outlet, and a blowing fan disposed between the air outlet and the air inlet, at least one of the control part, the power supply part and the exposure part is disposed at an upstream side of the blowing fan, and the fixing device is provided at a downstream side of the blowing fan. Accordingly, since the control part, the power supply part and the exposure part are provided between the air inlet and the blowing fan, they can receive the outer air in flowing from the air inlet, so that they are effectively cooled. Besides, since the fixing device is provided between the blowing fan and the air outlet, the radiation heat or the like generated by the fixing device is directly exhausted to the outside through the air outlet, so that it is possible to effectively reduce the influence of the radiant heat, which is generated by the fixing device, upon the control part, the power supply part and the exposure part.  
           [0013]    Preferably, the blowing unit further includes an exhaust fan, and this exhaust fan is disposed between the fixing device and the air outlet. By this, the radiant heat or the like generated by the fixing device can be effectively exhausted, and the air flow generated by the blowing fan can be intensified, so that it is possible to reduce the influence of the radiant heat or the like, which is generated by the fixing device, upon other structural elements.  
           [0014]    Preferably, there is provided an image forming apparatus main body which houses the image supporting body, the exposure part, the transfer part, the fixing device, the control part and the power supply part, and the blowing fan is disposed apart from the contour of the image forming apparatus main body. Accordingly, it is possible to reduce the leak of noise, which is generated by the blowing fan, out of the image forming apparatus main body.  
           [0015]    Preferably, the control part, the power supply part, and the exposure part are disposed in parallel to the air flow generated by the blowing fan. By this, the control part, the power supply part and the exposure part can mutually reduce the influence of heat upon the other structural elements. Besides, it is preferable that at least one of the control part and the power supply part is provided above the exposure part. By this, it is possible to reduce the bad influence of heat, which is generated by at least one of the control part and the power supply part, upon the exposure part. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    Preferred embodiments of the present invention will be described in detail based on the following figures, wherein:  
         [0017]    [0017]FIG. 1 is a sectional view showing an image forming apparatus of an embodiment of the invention;  
         [0018]    [0018]FIG. 2 is a perspective view showing a process cartridge used for the image forming apparatus of the embodiment of the invention;  
         [0019]    [0019]FIG. 3 is a perspective view showing the arrangement of an optical writing device, a power supply device and a control device of the image forming apparatus of the embodiment of the invention;  
         [0020]    [0020]FIG. 4 is a perspective view showing the image forming apparatus of the embodiment of the invention;  
         [0021]    [0021]FIG. 5 is a perspective view showing a first duct used for the image forming apparatus of the embodiment of the invention and viewed from the front side;  
         [0022]    [0022]FIG. 6 is a perspective view showing the first duct used for the image forming apparatus of the embodiment of the invention and viewed from the back side;  
         [0023]    [0023]FIG. 7 is a perspective view showing a second duct used for the image forming apparatus of the embodiment of the invention and viewed from the back side;  
         [0024]    [0024]FIG. 8 is a perspective view showing a state where the optical writing device, the first duct, and the second duct used for the image forming apparatus of the embodiment of the invention are assembled and viewed from the back side; and  
         [0025]    [0025]FIG. 9 is view schematically exemplifying the arrangement of the power supply device, the control device, the optical writing device, and a fixing device with respect to an air flow by a blowing fan of the image forming apparatus of the embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    Embodiments of the invention will be described with reference to the drawings.  
         [0027]    [0027]FIG. 1 shows the outline of an image forming apparatus  10  according to an embodiment of the invention. The image forming apparatus  10  includes an image forming apparatus main body  12 , an exhaust part  14  is provided at an upper part of the image forming apparatus main body  12 , and for example, two stage sheet feeding cassettes  16   a  and  16   b  are disposed at a lower part of the image forming apparatus main body  12 .  
         [0028]    Pickup rolls  18   a  and  18   b  are disposed in the vicinities of the upper parts of innermost ends of the respective sheet feeding cassettes  16   a  and  16   b , and retarder rolls  20   a  and  20   b  and feed rolls  22   a  and  22   b  are disposed in front of the pickup rolls  18   a  and  18   b.    
         [0029]    A transporting passage  24  is a sheet passage from the pickup roll  18   b  of the lower end sheet feeding cassette  16   b  to an exhaust port  26 , and this transporting passage  24  includes a portion located in the vicinity of the back surface (right side of FIG. 1) of the image forming apparatus main body  12  and substantially vertically formed from the feed roll  22   b  of the lower end sheet feeding cassette  16   b  to an after-mentioned fixing device  28 . An after-mentioned transfer device  32  and an image supporting body  34  are disposed through a sheet transporting guide  30  at the upstream side of this transporting passage  24  with respect to the fixing device  28 , and a resist roll  36  is disposed at the upstream side of the transfer device  32  and the image supporting body  34 . Incidentally, the sheet transporting guide  30  has many vent holes, and air can pass through them. Besides, an exhaust roll  38  is disposed in the vicinity of the exhaust port  26  of the transporting passage  24 .  
         [0030]    Accordingly, a sheet selectively sent out from one of the sheet feeding cassettes  16   a  and  16   b  by the pickup roll  18   a  or  18   b  is handled by the retarder roll  20   a  or  20   b  and the feed roll  22   a  or  22   b , is guided to the transporting passage  24 , is temporarily stopped by the resist roll  36 , and passes through the transfer device  32  and the image supporting body  34  described later at a suitable timing so that a toner image is transferred, this transferred toner image is fixed by the fixing device  28 , and the sheet is exhausted to the exhaust part  14  from the exhaust port  26  by the exhaust roll  38 .  
         [0031]    The exhaust part  14  is inclined so that a portion of the exhaust port is low, and gradually becomes high toward the front direction (left direction of FIG. 1). This exhaust part  14  is supported by the image forming apparatus main body  12  so that it can be freely rotated around a lower end. This exhaust part  14  is rotated upward and is opened, so that an after-mentioned process cartridge  44  can be detached and attached.  
         [0032]    The fixing device  28  is constituted by, for example, a heat roll  40  and a pressure roll  42 , the heat roll  40  and the pressure roll  42  are brought into pressure contact with each other to form a nip part, and the sheet passes through this nip part so that the toner image is fixed to the sheet.  
         [0033]    The process cartridge  44  includes a process cartridge main body  46 , and the image supporting body  34 , a charging device  48 , a developing device  50  and a cleaning device  52  are contained in the process cartridge main body  46  and are integrated. The image supporting body  34  is made of, for example, a photoreceptor, and a latent image is formed by an after-mentioned optical writing device  54 . Besides, the transfer device  32  made of, for example, a transfer roll is disposed so as to be opposite to the image supporting body  34 . The charging device  48  is formed of, for example, a charging roll, comes in contact with the image supporting body  34  and rotates, and uniformly charges the image supporting body  34 .  
         [0034]    The developing device  50  makes the latent image formed on the image supporting body  34  a visible image by toner, and includes a first toner storage chamber  56 , a second toner storage chamber  58 , and a developing chamber  60 . The first toner storage chamber  56  and the second toner storage chamber  58  are disposed above and below an opening part  62 , a first toner agitating and transporting member  64  is disposed in the first toner storage chamber  56 , second to fourth toner agitating and transporting members  66 ,  68  and  70  are disposed in the second toner storage chamber  58 , and toner is transported to the developing chamber  60 . The opening part  62  is formed so that scanning light from the after-mentioned optical writing device  54  passes through, the first toner storage chamber  56  and the second toner storage chamber  58  communicate with each other through the opening part  62 , and the toner of the first toner storage chamber  56  is transported to the second toner storage chamber  58 . A developing roll  72  is disposed in the developing chamber  60 , and this developing roll  72  causes the latent image of the image supporting body  34  to support the toner image.  
         [0035]    A cleaning device  52  includes, for example, a cleaning blade  74  and a toner recovery chamber  76 , and the toner scraped off by this cleaning blade  74  is recovered into the toner recovery chamber  76 .  
         [0036]    The optical writing device  54  is located in the image forming apparatus main body  12  and is disposed in the vicinity (vicinity of the left end of FIG. 1) of the front of the image forming apparatus main body  12  in parallel to the sheet feeding cassettes  16   a  and  16   b . This optical writing device  54  includes an optical writing device main body  78 , and plural vent holes  79  for allowing the passage of air are provided in the upper surface and the lower surface of the optical writing device main body  78 , respectively. This optical writing device main body  78  contains therein a polygon unit  80  composed of a polygon mirror and a motor for rotating the polygon mirror, a semiconductor laser (not shown), and other optical parts (not shown) such as a plastic lens. Scanning light is emitted from an outgoing window  82  formed in the optical writing device main body  78  at the process cartridge side, and the scanning light is irradiated to the image supporting body  34  through the opening part  62  of the process cartridge  44 .  
         [0037]    Further, the process cartridge  44  includes a shutter  84  for opening and closing the side face of the image supporting body  34  at the transfer device  32  side. As shown in FIG. 2, this shutter  84  includes a support part  86  rotatably and movably supported to the process cartridge main body  46 , and a shield part  88  extending from this support part  86 . This shutter  84  is guided by a guide (not shown) provided in the image forming apparatus main body  12  so that it is opened and closed in synchronization with the attachment and detachment of the process cartridge  44 . That is, before the process cartridge  44  is mounted, the shutter  84  closes the side portion of the image supporting body  34  by a not-shown elastic body to protect the image supporting body  34 , and after the process cartridge  44  is mounted, as shown in FIG. 1, it is moved against the not-shown elastic body to a retract position where the side portion of the image supporting body  34  is opened. In this retract position, the shield part  88  faces the heat roll  40  of the fixing device  28 , shuts off the radiant heat or the like from the heat roll  40 , and prevents the process cartridge  44  from being heated.  
         [0038]    In the shutter  84 , many vent holes  90  are formed in parallel to the support part  86  and in the vicinity of the support part of the shield part  88 . In the case where the shutter  84  is in the retract position, a first gap  92  is formed between the shutter  84  and the process cartridge main body  46 . The vent holes  90  communicates with the first gap  92 , the first gap  92  constitutes a part of an after-mentioned air passage  94 , and an air flow is generated in the first gap  92  by the air introduced through the vent holes  90  to cool the process cartridge  44 . Further, the air having passed through the first gap  92  cools the air around the fixing device  28 , and passes through the sheet transporting guide  30 .  
         [0039]    A blowing fan  96  is located in the image forming apparatus main body  12 , is disposed above the optical writing device  54 , and feeds the air from the front side of the image forming apparatus main body  12  to the back side (from the left to the right of FIG. 1). A first duct  98  is provided at the upstream side of the blowing fan  96 . The first duct  98  covers the upper part of the optical writing device  54  and the upstream side of the blowing fan  96 , and an inlet part  100  for receiving the air is provided at the left side (back side of the paper plane of FIG. 1) of the image forming apparatus main body  12 . Incidentally, the blowing fan  96  is disposed to be separated from the contour of the image forming apparatus main body  12 , so that the leakage of noise, which is generated by the blowing fan  96 , into the outside of the image forming apparatus main body  12  is reduced.  
         [0040]    [0040]FIG. 3 is a perspective view showing the arrangement of the optical writing device  54 , the power supply device  102 , and the control device  104 . The image forming apparatus main body  12  includes, as an enclosure, a back surface part  106  (right side of FIG. 1), a left surface part  108  (back side of the paper plane of FIG. 1), and a right surface part  110 . The power supply device  102  and the control device  104  are provided in parallel in the left surface part  108 . The power supply device  102  and the control device  104  are positioned above the optical writing device  54  and is opposed to the inlet part  100 . The power supply device  102  receives external electric power and supplies the electric power to the respective parts constituting the image forming apparatus  10 . The control device  104  controls the respective parts constituting the image forming apparatus  10 .  
         [0041]    A second duct  114  is provided at the downstream side of the blowing fan  96 . The second duct  114  constitutes a part of the after-mentioned air passage  94 . Further, at the downstream side of the second duct  114 , a second gap  116  is formed at the upper part of the foregoing first toner storage chamber  56  and between the process cartridge main body  46  and the exhaust part  14 . In the exhaust part  14 , many air guide ribs  118  protruding toward the second gap  116  are formed in parallel to the direction of the air flow.  
         [0042]    In the image forming apparatus  10 , as shown in FIG. 4, a first air inlet  120  is provided at the upper part of the left side, a second air inlet  122  is provided at the lower part of the left side, and an air exhaust outlet  124  is provided at the back surface (right side of FIG. 1). The first air inlet  120  is disposed to be substantially opposite to the power supply device  102  and the control device  104 . Besides, the first air inlet  120  takes the outside air (outer air) into the image forming apparatus  10  by the rotation of the blowing fan  96 . The second air inlet  122  is disposed below the optical writing device  54 . Besides, the second air inlet  122  takes the outer air into the lower part of the optical writing device  54  by the rotation of the blowing fan  96 . The air outlet  124  is disposed substantially at the center of the back surface of the image forming apparatus  10 . Further, an exhaust fan  126  is located in the image forming apparatus main body  12 , is provided to be opposite to the air outlet  124 , and exhausts the air in the image forming apparatus main body  12  through the air outlet  124 . Besides, a vent hole  128  for allowing the passage of air between the inside and the outside of the image forming apparatus main body  12  is provided above the fixing device  28  and at the upper surface (upper side of FIG. 1) of the image forming apparatus main body  12 .  
         [0043]    Incidentally, as shown in FIG. 1, it is not always necessary to cause the front of the blowing fan  96  to be opposite to the process cartridge  44 , and it may be disposed at an arbitrary angle in accordance with the intensity of the air flow and cooling places. For example, the blowing fan  96  may be disposed to be opposite to the foregoing power supply device  102  and the control device  104 .  
         [0044]    Next, the details of the air passage  94  will be described.  
         [0045]    The air passage  94  is an air flow passage from the foregoing first air inlet  120  and the second air inlet  122  to the air outlet  124 . Besides, it is preferable that the blowing unit recited in the claims is constituted by the first air inlet  120 , the second air inlet  122 , the blowing fan  96 , the exhaust fan  1 - 26 , the air outlet  124  and the like, and further, the foregoing vent hole  128  may be provided.  
         [0046]    The first air inlet  120  is connected to the inlet part  100  through the power supply device  102  and the control device  104 . That is, when the blowing fan  96  is rotated and the outer air is taken in through the first air inlet  120 , the power supply device  102  and the control device  104  are respectively cooled by the air. The second air inlet  122  is located at the left side of the image forming apparatus  10 , is provided below the optical writing device  54 , and is connected to the lower part of the first duct  98  through the plural vent holes  79  provided in the upper surface and the lower surface of the optical writing device main body  78 . Besides, this first duct  98  extends from the inlet part  100  to substantially the center of the optical writing device  54 , and as shown in FIGS. 5, 6 and  8 , a projection  130  is formed at the front side (left side of FIG. 1) of the extending portion. This projection  130  is made opposite to the polygon unit  80  of the optical writing device  54 . That is, the outer air taken from the second air inlet  122  into the lower part of the optical writing device  54  cools the polygon unit  80  and the like of the optical writing device  54 , and is received by the projection  130  into the first duct  98 . As stated above, the first duct  98  is connected to the first air inlet  120  through the power supply device  102  and the control device  104 , and is connected to the second air inlet  122  through the optical writing device  54 . Incidentally, the first air inlet  120  and the second air inlet  122  may be an integrally formed air inlet.  
         [0047]    Besides, a blowing fan receiving part  132  is formed at the back side (right side of FIG. 1) of the first duct  98 , and the blowing fan  96  is inserted and disposed in this blowing fan receiving part  132 .  
         [0048]    The second duct  114  is connected to the first duct  98  at the blowing fan receiving part  132  of the first duct  98 , and is, together with the first duct  98 , attached to the upper part of the optical writing device  54 . As shown in FIG. 7, in this second duct  114 , a blowing fan attachment part  134  is provided substantially at the center front side of the second duct  114 , and the blowing fan  96  is attached to the blowing fan attachment part  134 . Besides, the second duct  114  includes first air guide surfaces  136   a  and  136   b  extending from the blowing fan attachment part  134  to both sides. Further, a second air guide surface  138  is provided to be opposite to the first air guide surfaces  136   a  and  136   b . Accordingly, the air flow from the blowing fan  96  is guided by the first air guide surfaces  136   a  and  136   b  and the second air guide surface  138  to expand to both sides, passes through the upper part of the second air guide surface  138 , and is sent to the process cartridge  44  side.  
         [0049]    As described above, the second gap  116  is formed above the first toner storage chamber  56  and between the process cartridge main body  46  and the exhaust part  14 . Besides, in the exhaust part  14 , the many air guide ribs  118  projecting toward the second gap  116  are formed in parallel to the direction of the air flow. The air is made to flow toward the sheet transporting guide  30  through the second gap  116  and the foregoing first gap  92 .  
         [0050]    In the sheet transporting guide  30 , as described before, the many vent holes are formed, and the air can smoothly pass through. The air outlet  124  is formed at the outside of the exhaust fan  126 , and the air is exhausted through this air outlet  124 .  
         [0051]    Next, the function of an air cooling system by the blowing fan  96  and the exhaust fan  126  will be described. When the blowing fan  96  and the exhaust fan  126  are rotated, the outer air is sucked from the first air inlet  120  and the second air inlet  122  formed in the image forming apparatus  10 . The outer air sucked from the first air inlet  120  enters the first duct  98  through the power supply device  102  and the control device  104 . At this time, heat of the power supply device  102  and the control device  104  is lost by the sucked outer air, and the power supply device  102  and the control device  104  are respectively cooled. The air having cooled the power supply device  102  and the control device  104  is guided to the blowing fan  96  by the first duct  98 . The outer air sucked from the second air inlet  122  enters the first duct  98  through the optical writing device  54 . At this time, the heat of the optical writing device  54  is lost by the sucked outer air, and the optical writing device  54  is cooled. The air having cooled the optical writing device  54  is guided to the blowing fan  96  by the first duct  98 .  
         [0052]    The air guided to the blowing fan  96  is sent to the second duct  114  by the blowing fan  96 . In this second duct  114 , the air is expanded to both sides by the first air guide surfaces  136   a  and  136   b  and the second air guide surface  138 , passes through the upper part of the second duct  114 , and flows toward the process cartridge  44 . Since the second gap  116  is formed between the process cartridge  44  and the exhaust part  14 , the air passes through this second gap  116 . Further, since the vent holes  90  are formed in the shutter  84 , and the first gap  92  is formed between the process cartridge main body  46  of the process cartridge  44  and the shutter  84 , the air passes through the first gap  92 . Although radiant heat or the like from the fixing device  28  is shut off by the shield part  88  of the shutter  84  to a certain degree, heat of the process cartridge  44  is further lost by the air flow passing through the first gap  92 , and the process cartridge  44  is cooled. Besides, the temperature of the fixing device  28  is higher than that of the other parts constituting the image forming apparatus  10 , the air flow having passed through the process cartridge  44  and the like cools the heated air around the fixing device  28 , and is sent to the sheet transporting guide  30  side. The air sent to the sheet transporting guide  30  side passes through the vent holes formed in the sheet transporting guide  30 , and is exhausted to the outside of the image forming apparatus  10  through the exhaust fan  126  and the air outlet  124 .  
         [0053]    Next, a description will be given to the arrangement of the power supply device  102 , the control device  104 , the optical writing device  54  and the fixing device  28  with respect to the air flow by the blowing fan  96 . FIG. 9 schematically shows the arrangement of the power supply device  102 , the control device  104 , the optical writing device  54  and the fixing device  28  with respect to the air flow by the blowing fan  96  of the image forming apparatus  10 . The power supply device  102  and the control device  104  are provided between, for example, the first air inlet  120  and the blowing fan  96 , and the optical writing device  54  is provided between, for example, the second air inlet  122  and the blowing fan  96 . The fixing device  28  is provided between, for example, the blowing fan  96  and the air outlet  124 . Thus, the power supply device  102 , the control device  104  and the optical writing device  54  are respectively cooled by the outer air. Then, the air having cooled these is guided to the blowing fan  96 . That is, the power supply device  102 , the control device  104  and the optical writing device  54  can be cooled in parallel by the outer air, and the influence of the air heated by the other devices is mutually reduced.  
         [0054]    The blowing fan  96  receives the air having cooled the power supply device  102 , the control device  104  and the optical writing device  54 , and sends the air, as an air flow, to a peripheral space  140  positioned around (mainly at the lower part) the fixing device  28 . By this air flow, the blowing fan  96  cools the air of the peripheral space  140  and the like, and sends it to the air outlet  124 . Besides, the exhaust fan  126  is provided between the fixing device  28  and the air outlet  124 , so that the air flow is increased, and the power supply device  102 , the control device  104 , the optical writing device  54 , the air of the peripheral space  140  and the like are efficiently cooled. Besides, although the outer air guided to the peripheral space  140  through the vent hole  128  is heated by the fixing device  28 , it is exhausted by the blowing fan  126  and the like through the air outlet  124 .  
         [0055]    Thus, it is possible to prevent the heat generated by the fixing device  28  from having an influence on the control device  104 , the power supply device  102 , and the optical writing device  54  which are susceptible to heat. Besides, since the power supply device  102  and the control device  104  are disposed above the optical writing device  54 , it is possible to reduce the degree that the heat generated by the power supply device  102  and the control device  104  ascends and goes around the optical writing device  54 .  
         [0056]    Incidentally, in the foregoing embodiment, although the blowing fan  96  is provided between the fixing device  28  and the power supply device  102 , the control device  104 , and the optical writing device  54 , the invention is not limited to this, and as long as the fixing device  28  is disposed at the downstream side of the power supply device  102 , the control device  104  and the optical writing device  54 , the blowing fan may be provided at another place. Besides, the blowing unit may include three or more fans.  
         [0057]    As described above, according to the invention, the power supply device, the control device and the optical writing device are provided at the upstream side of the air flow, and the fixing device is provided at the downstream side, so that even if the image forming apparatus is miniaturized, the heat from the fixing device is efficiently exhausted to the outside, and the influence of the heat upon the other structural elements including the exposure part can be reduced.  
         [0058]    The entire disclosure of Japanese Patent Application No. 2003-139810 filed on May 19, 2003 including specification, claims, drawings and abstract is incorporated herein by reference in its entirety.