Abstract:
The invention provides an image forming apparatus including, for the purpose of removing volatile organic compounds passing through an adsorption filter: a discharge path for discharging air in a main body of the image forming apparatus to an exterior; an adsorption filter provided in the discharge path and capable of removing, by an adsorption, a compound in the air discharged through the discharge path; and a catalyst filter provided in the discharge path and capable of removing, by a catalytic decomposition, a compound in the discharged air; wherein the catalyst filter is provided at a downstream side of the adsorption filter, along a direction of air discharge.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an image forming apparatus of electrophotographic process such as a printer, a copying apparatus or a facsimile apparatus, having an air path for discharging, to the exterior of the apparatus, an emission matter employed in the image forming apparatus.  
         [0003]     2. Related Background Art  
         [0004]     In lithographic printing, a coated paper is often used, in addition to a plain paper, as a recording material. Such coated paper is formed by coating surface of a bond paper with a chemical substance in glossy or matted surface. Such coated paper is advantageously employed in color printing and enables an image presentation of a high definition and a satisfactory color reproducibility.  
         [0005]     On the other hand, in the field of image forming apparatus such as a printer, a copying machine or a facsimile apparatus (but excluding a printing press utilizing ink), a high-definition image (fine-dot image) is requested, and, a faithful color reproducibility is requested by the increase of color documents. For this reason, use of the coated paper is expanding.  
         [0006]     When a coated paper is used in a printer or a copying apparatus, a volatile organic compound (VOC) may be generated by heat from the coated paper. Different from the printing press, the printer or the copying apparatus executes a heating process of about 180° C. in a fixing apparatus for fixing a toner image on the recording material, and such heat induces VOC generation from a chemical substance. It is desirable to remove such VOC.  
         [0007]     In the printer, copying apparatus and the like, the air in the main body of the image forming apparatus is exhausted to the exterior from an exhaust portion such as an air duct, through an adsorption filter. For example, Japanese Patent Application Laid-open No. H02-273764 discloses a configuration of combining a catalyst filter and an adsorption filter, in order to decompose ozone of a high concentration.  
         [0008]     On the other hand, the role of the adsorption filter is becoming more important in recent years, as a VOC removing filter. Such adsorption filter is often based on porous active charcoal. Ozone or VOC generated in the main body of the image forming apparatus is removed by adsorption in the active charcoal.  
         [0009]     Since such adsorption filter achieves a gas removal by a gas adsorption, it is necessary to increase the hermetic nature of the adsorption filter, in order to adsorb VOC gas of a low molecular weight. Such method can improve the efficiency of VOC removal of low molecular weight, but reduces a gas permeation from the interior to the exterior of the image forming apparatus, whereby the temperature within the image forming apparatus may be elevated, eventually giving a detrimental influence on toner image forming means which forms a toner image.  
         [0010]     Also when the VOC concentration becomes high for example by a continuous image formation, an increased removal efficiency for the removal of such VOC lowers the gas permeability of the filter, thereby causing a temperature rise in the image forming apparatus.  
         [0011]     On the other hand, such temperature rise in the apparatus may be reduced by reducing the hermetic property of the adsorption filter in order to increase the gas permeation, but a part of VOC may remain without adsorbed by the adsorption filter.  
         [0012]     It is therefore desirable to increase the gas permeability while removing VOC that may remain unadsorbed without relying on an excessive hermeticity of the adsorption filter.  
       SUMMARY OF THE INVENTION  
       [0013]     An object of the present invention is to remove a volatile organic compound that passes an adsorption filter.  
         [0014]     Another object of the present invention is to provide an image forming apparatus including:  
         [0015]     a discharge path for discharging air in a main body of the image forming apparatus to the exterior;  
         [0016]     an adsorption filter provided in the discharge path and capable of removing, by an adsorption, a compound in the air discharged through the discharge path; and  
         [0017]     a catalyst filter provided in the discharge path and capable of removing, by a catalytic decomposition, a compound in the discharged air;  
         [0018]     wherein the catalyst filter is provided at a downstream side of the adsorption filter, along a direction of air discharge.  
         [0019]     Still other objects of the present invention will become fully apparent from the following detailed description which is to be taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a vertical cross-sectional view showing a schematic configuration of an image forming apparatus in which an air discharge apparatus of the present invention;  
         [0021]      FIG. 2  is a magnified vertical cross-sectional view of the air discharge apparatus of an embodiment  1 ;  
         [0022]      FIG. 3  is a magnified vertical cross-sectional view of the air discharge apparatus of an embodiment  2 ; and  
         [0023]      FIGS. 4A, 4B ,  4 C and  4 D are vertical cross-sectional views showing other air discharge apparatuses. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     In the following, embodiments of the present invention will be explained with reference to the accompanying drawings.  
       Embodiment 1  
       [0025]      FIG. 1  shows an image forming apparatus in which the present invention is applicable. The image forming apparatus shown in  FIG. 1  is an electrophotographic printer, and  FIG. 1  is a vertical cross-sectional view showing a schematic configuration thereof, seen from a front side (operation side).  
         [0026]     The image forming apparatus shown in  FIG. 1  is provided with a reader portion  1  for reading an original, an image forming portion  2  for forming an image (toner image) based on the read original, a feed/conveying portion  3  for supplying the image forming portion  2  with a recording material, a fixing portion  4  for fixing the toner image, formed on the recording material by the image forming portion  2 , a discharge portion  5  for discharging the recording material after the image fixation, a reversing portion  6  for reversing a front side and a back side of the recording material after the image fixation, and an air discharge portion (air discharge apparatus)  10  for discharging air in a main body M of the image forming apparatus. There portions, except for a part of the discharge portion  5 , are provided inside a main body M of a box shape of the image forming apparatus. These portions will be explained in succession, starting from the reader portion  1 .  
         [0027]     [Reader Portion  1 ] 
         [0028]     The reader portion  1  is provided with an original plate  11 , a scanning optical system  12 , a reducing lens  13 , a CCD  14  etc. The scanning optical system  12  includes a light source  12   a  and reflecting mirrors  12   b - 12   f.    
         [0029]     An original (not shown) placed with an image bearing side thereof downwards on the original plate  11  is illuminated by the light source  12   a  and reflecting mirrors  12   b,    12   c.  A reflected light is focused through the reduction lens  13  onto the CCD  14  for photoelectric conversion and is then subjected to an A/D conversion to provide image information, which is transferred to a memory (not shown).  
         [0030]     [Image Forming Portion  2 ] 
         [0031]     The image forming portion  2  is provided with a photosensitive drum  21  as an image bearing member, a corona charger  22  as charging means, an exposure apparatus  23  as exposure means, a developing apparatus  24  as developing means, a transfer charger  25  as transfer means, and a cleaning apparatus  26  as cleaning means. The exposure apparatus  23  is equipped with a laser oscillator  23   a,  a polygon mirror  23   b,  a reflective mirror  23   c  etc. The photosensitive drum  21  is rotated in a direction indicated by an arrow (clockwise in  FIG. 1 ) with a predetermined process speed (peripheral speed), and is surfacially charged uniformly by the corona charger  22  at predetermined polarity and potential. On the photosensitive drum  21  after charging, an electrostatic latent image is formed by the exposure apparatus  23 . The laser oscillator  23   a  emits a laser beam according to the aforementioned image information. The emitted laser beam scans, by the rotation of the polygon mirror  23   b  and the reflection of the mirror  23   c,  the surface of the photosensitive drum  21  in a direction of generating line thereof, whereby an electrostatic latent image is formed on the photosensitive drum  21 . The electrostatic latent image is developed as a toner image by the developing apparatus  24 . The toner image is transferred by the transfer charger  25  onto a recording material S supplied from the feed/conveying portion  3  to be explained in the following. The photosensitive drum  21  after the toner image transfer is subjected to a removal of the toner remaining on the surface (transfer residual toner) by the cleaning apparatus  26 , and is used for a next image formation. Operations of the corona charger  22  and the transfer charger  25  generate ozone by a corona discharge.  
         [0032]     [Feed/Conveying Portion  3 ] 
         [0033]     The feed/conveying portion  3  is provided with sheet cassettes  31 ,  31 , sheet feeding rollers  32 ,  32 , conveying rollers  33 ,  33 , retarding rollers  34 ,  34 , and registration rollers  35 . A recording material S stacked in the sheet cassette  31  is fed by the sheet feed roller  32 , and conveyed after a sheet separation by the conveying roller. 33  and the retarding roller  34 . The conveyed recording material S is once stopped by the registration rollers  35  for correcting a skewing, and is then supplied, in synchronization with the toner image on the photosensitive drum  21 , to a transfer portion between the photosensitive drum  21  and the transfer charger  25 . The recording material S supplied to the transfer portion receives a transfer of the toner image by the transfer charger  25 . The recording material S after the toner image transfer is conveyed by a conveyor belt  36  to the fixing portion  4  to be explained in the following.  
         [0034]     [Fixing Portion  4 ] 
         [0035]     The fixing portion  4  as fixing means is provided with a heating roller  41  serving as image heating member and including therein a halogen heater (not shown) as a heating member, and a pressure roller  42  as a pressure member contacted with the heating roller  41  by a biasing member (not shown) under a predetermined pressure. The recording material S bearing an unfixed toner image passes through a fixing nip between the heating roller  41  rotated clockwise in  FIG. 1  and the pressure roller  42  rotated counterclockwise in  FIG. 1 , whereby the toner image is fixed onto the surface under heat and pressure. The heat applied to the recording material S induces evaporation of moisture in the recording material S and a VOC generation in case the recording material S is a coated paper.  
         [0036]     [Sheet Discharge Portion] 
         [0037]     The sheet discharge portion is provided with sheet discharge rollers  51  and a sheet discharge tray  52 . The recording material S after the toner image fixation is discharged, by the sheet discharge rollers  51 , onto the sheet discharge tray  52  provided outside the main body M of the image forming apparatus. In this manner an image formation is completed on one side (front side) of a recording material S.  
         [0038]     [Reversing Portion  6 ] 
         [0039]     In case of an image formation on both sides of the recording material S, the recording material S, after the toner image fixation thereon, is not discharged but is conveyed to paired switchback rollers  61  in a lower part. The recording material S is reversed by its front side and back side, by the forward and reverse rotations of the paired switchback rollers  61  and is conveyed to a two-side conveying path  62 . Thereafter the recording material S is conveyed, for an image formation on the back side, to the registration rollers  35  by a re-conveying roller  63 . Then an image formation is executed on the back side in a process similar to that on the front side. After the image formation also on the back side, the recording material S is processed in the fixing portion  4  etc. and is discharged onto the tray  52 . Thus, the image formations on both sides (front and back sides) of the recording material S are completed.  
         [0040]     [Air Discharge Apparatus  10 ] 
         [0041]     In the present embodiment, the image forming apparatus is provided with an air discharge apparatus  10  as a discharge path for discharging the air in the main body M of the image forming apparatus, above the aforementioned sheet discharge rollers  51  at a left-side wall M 1  of the main body M.  
         [0042]      FIG. 2  is a magnified cross-sectional view of the air discharge apparatus shown in  FIG. 1 . As shown in these drawings, the air discharge apparatus  10  is provided with a duct (air discharge path)  101 , and, in a successive order from a deeper side (right-hand side in  FIG. 2 ) of the duct  101 , a dust filter  102  for eliminating minute substances such as dusts, an adsorption filter  103 , a motor fan  104  serving as a fan, and a VOC oxidation catalyst filter  105  as the catalyst filter.  
         [0043]     The duct  101  is formed in a tubular form, and is provided with a suction aperture  101   a  which is opened toward the interior of the main body M of the image forming apparatus, and a discharge aperture  101   b  which is opened toward the exterior of the main body M of the image forming apparatus. The duct  101  forms a flow path for air A between the suction aperture  101   a  and the discharge aperture  101   b.  The duct  101  may be formed in a cylindrical shape or a polygonal tubular shape, or an arbitrary shape according to a restriction in design.  
         [0044]     The dust filter  102  is provided in a deepest position (suction aperture  101   a ) in the duct  101 , namely at the most upstream position along the flow of the air A. The dust filter  102  is provided for principally removing flying toner, that is scattered in the air in the main body M of the image forming apparatus.  
         [0045]     The adsorption filter  103  is positioned at the downstream side of the dust filter  102 . The adsorption filter  103  is constituted of active charcoal supported on a cloth, a non-woven cloth or a thin plate, and is provided principally for mechanically eliminating ozone, in the air in the main body M of the image forming apparatus, by adsorption. The adsorption filter  103 , relying on mechanical elimination by adsorption, can also remove VOC by adsorption as in the case of ozone.  
         [0046]     The motor fan  104  is provided at the downstream side of the ozone filter  103 . The motor fan  104  includes a rotatable fan  104   a  and a driving motor (not shown.) and forms a flow of the air A in the duct  101 .  
         [0047]     The VOC oxidation catalyst filter  105  is provided at the downstream side of the motor fan  104 , namely at the discharge aperture  101   b  of the duct  101 . The VOC oxidation catalyst filter  105  is constituted of an oxidation catalyst of precious metal type such as platinum or palladium or base metal type such as manganese or iron, supported by a base material such as a cloth, a non-woven cloth or a thin plate. The VOC oxidation catalyst  105  is provided for chemically removing VOC in the air by oxidation. The VOC oxidation catalyst  105  may be a filter of a honeycomb structure.  
         [0048]     The filter for removing VOC by decomposition in the present invention is different from an ozone filter for decomposing ozone with a catalyst, known in the prior art. Since VOC is more stable than ozone as a compound, an efficiency of decomposition and removal has to be improved in comparison with the prior ozone filter. In order to improve the decomposing efficiency, the filter preferably has, in addition to a catalytic function, for example a function of adsorbing thereon VOC by a material having an adsorbing ability to the compound, such as active charcoal. Specific examples include a filter having a catalyst layer and an adsorption layer, and a structure formed by coating an adsorbing material on a part of a catalyst filter. Thus, a filter configuration having active charcoal in addition to a catalyst decomposes the adsorbed VOC by the catalyst, whereby the VOC itself is made less passable through the filter. Otherwise, there may be employed a filter having a permeability lower than in a prior ozone filter, for example a filter with a finer honeycomb structure or a filter with a thicker catalyst layer. Such lowered permeability increases the passing time for VOC, thereby facilitating decomposition by the catalyst.  
         [0049]     In the aforementioned image forming apparatus, within the conveying path for the recording material P, a portion positioned at the downstream side of the registration rollers  35  is generally formed from the right side to the left side, as shown in  FIG. 1 . The image forming portion  2 , the fixing portion  4  and the air discharge apparatus  10  described above are provided in such portion, from the upstream side to the downstream side. The image forming portion  2  and the fixing portion  4  are provided at approximate same heights, while the air discharge apparatus  10  is positioned diagonally above the fixing portion  4 .  
         [0050]     Also between the corona charger  22  of the image forming portion  2  and the air discharge apparatus  10 , a flow path  7  is provided for guiding the air A in the vicinity of the corona charger  22  to the air discharge apparatus  10 . The flow path  7  is constituted of a horizontally provided upper plate  71 , a lower plate  72  opposed, from a lower side, to the upper plate  71 , and a cover member  73  covering an upper part of the fixing portion  4 . Among these, the upper plate  71  has a right-hand end positioned above the corona charger  22 , and is extended at a left-hand end substantially horizontally to the left to reach a position above the-air discharge apparatus  10 . The upper plate  71  separates the reader portion  1  provided in an upper part of the main body M of the image forming apparatus, from other portions namely the image forming portion  2 , the feed/conveying portion  3 , the fixing portion  4 , the reversing portion  6  etc. Thus the reader portion  1  is protected from entry of ozone and flying toner generated in the image forming portion  2  and of VOC generated in the fixing portion  4 . The lower plate  72  has a right-hand end positioned close to a left-hand end of the corona charger  22 , and is extended, at a left-hand end, to a position above the right-hand side of the fixing portion  4 . The cover member  73  has a horizontal portion.  73   a,  a right bent portion  73   b  bent downwards from the right-hand end of the horizontal portion, and a left bent portion  73   c  bent downwards from the left-hand end of the horizontal portion  73   a.  Between the right-hand end of the horizontal portion  73   a  and the left-hand edge of the lower plate  72 , there is formed an air aperture  74  elongated in a front-back direction. This air aperture  74  is connecting a flow path  8  formed under the lower plate  72  with the flow path  7  formed above the lower plate  72 .  
         [0051]     Another flow path  8 , different from the aforementioned flow path  7 , is formed between the lower plate  72  and the conveyor belt  37  positioned thereunder, and between the image forming portion  2  and the fixing portion  4  positioned to the left. This flow path  8  principally serves to move the ozone generated in the vicinity of the transfer charger  25  and the flying toner generated in the vicinity of the transfer charger  25  and the cleaning apparatus  26 , upwards from the image forming portion  2  to the fixing portion  4  at left, and to further introduce them through the air aperture  74  to the flow path  7  positioned above. In the flow path  8 , the conveyor belt  36  rotates in a direction indicated by an arrow, thereby conveying the recording material P from right to left. In the flow path  8 , therefore, there is easily formed an air flow which moves the air A in the vicinity of the image forming portion  2  toward the fixing portion  4 . Also a flow path  9  is formed between the fixing portion  4  and the air discharge apparatus  10  positioned diagonally above.  
         [0052]     In the image forming apparatus of the aforementioned configuration, ozone is generated by a corona discharge of the corona charger  22  at the primary charging. Ozone is also generated by a corona discharge in the transfer charger  25  at the transfer. Also flying toner is generated in the vicinity of the transfer charger  25  at the transfer operation and of the cleaning apparatus  26  at the cleaning operation. Furthermore, VOC is generated in the fixing portion  4  in case a coated paper is used as the recording material P, by the heating of the coated paper.  
         [0053]     The ozone, flying toner and VOC generated in the aforementioned positions are guided to the air discharge apparatus  10 , by an air flow generated by the rotation of the fan  104  thereof. More specifically, the ozone generated in the vicinity of the corona charger  22  flows from right to left in  FIG. 1  along the flow path  7  and reaches the air discharge apparatus  10 . Also the ozone generated in the vicinity of the transfer charger  25  and the flying toner generated in the vicinity of the transfer charger  25  and in the vicinity of the cleaning apparatus  26  flow from right to left in  FIG. 1  along the flow path  8 , then enters the flow path  7  through the air aperture  74  and reaches the air discharge apparatus  10  through the downstream part of the flow path  7 . Also the VOC generated in the vicinity of the fixing nip of the fixing portion  4  is brought by a rising air flow generated by the heating at the fixing operation and reaches the air discharge apparatus  10  through the flow path  9 .  
         [0054]     As explained above, the air A guided from the main body M of the image forming apparatus to the air discharge apparatus  10  contains ozone, flying toner and VOC. These are sucked from the suction aperture  101   a  of the air discharge apparatus  10  and are satisfactorily removed by the filters before reaching the discharge aperture  101   b.    
         [0055]     The air A, guided to the air discharge apparatus  10  at first passes the dust filter  102 , in which the flying toner is removed. The air A after the removal of the flying toner then passes the adsorption filter  103 . The adsorption filter  103  adsorbs ozone and VOC, but cannot remove the VOC completely. In particular, the VOC of low molecular weight is difficult to adsorb.  
         [0056]     The VOC that cannot be removed completely by the adsorption filter  103  is removed by passing through the VOC oxidation catalyst filter  105 . Thus the air A, from which the flying toner, ozone and VOC are removed, is discharged from the discharge aperture  101   b  of the air discharge apparatus  10  to the exterior of the main body M of the image forming apparatus.  
         [0057]     The VOC oxidation catalyst filter  105  cannot generally decompose VOC of a high concentration because the chemical reaction is time-consuming. Also the durability of the catalyst may be deteriorated-when the VOC of a high concentration is decomposed frequently.  
         [0058]     However the air discharge apparatus  10  of the aforementioned configuration, in which the VOC oxidation catalyst filter  105  passes the air A after the VOC concentration is lowered by the adsorption filter  103 , can securely remove the VOC and can maintain the VOC removing ability over a prolonged period. Also the VOC oxidation catalyst filter  105  can even the VOC of a low molecular weight as the VOC removal is executed by oxidation of VOC.  
       Embodiment 2  
       [0059]      FIG. 3  is a vertical cross-sectional view of an air discharge apparatus  10 A of the present embodiment, in which components equivalent to those in the embodiment  1  will be represented by same symbols and will not be explained further.  
         [0060]     [Air Discharge Apparatus  10 A] 
         [0061]     The air discharge apparatus  10 A of the present embodiment is provided with an ozone decomposition catalyst filter  106 , instead of the VOC oxidation catalyst filter  105  in the aforementioned embodiment  1 . In the present embodiment, the air discharge apparatus  10 A is provided with a duct  101 , and, in a successive order from the upstream side of the air flow A, a dust filter  102 , an adsorption filter  103 , a motor fan  104 , and an ozone decomposition catalyst filter  106 . The image forming apparatus of the present embodiment is same in configuration as that of the embodiment  1 , except for the air discharge apparatus  10 A.  
         [0062]     The ozone decomposition catalyst filter  106  may be constructed by supporting an ozone decomposition catalyst such as manganese dioxide or nickel oxide on a substrate such as a cloth, a non-woven cloth or a thin plate, but such structure is not restrictive.  
         [0063]     Ozone and flying toner generated in the vicinity of the image forming portion  2  in the main body M of the image forming apparatus and VOC generated in the vicinity of the fixing portion  4  are guided, as in the embodiment  1 , by the motor fan  104  to the air discharge apparatus  10  together with the air in the main body M of the image forming apparatus. The air A, guided to the air discharge apparatus  10  at first passes the dust filter  102 , in which the flying toner is removed.  
         [0064]     The air A after the removal of the flying toner then passes the adsorption filter  103 . The adsorption filter  103  adsorbs ozone and VOC, but cannot remove the VOC completely. In particular, the VOC of low molecular weight is difficult to adsorb. The VOC that cannot be removed completely by the adsorption filter  103  is removed by passing through the ozone decomposition catalyst filter  106 , and is discharged to the exterior of the main body M of the image forming apparatus.  
         [0065]     In this operation, the ozone decomposition catalyst filter  106  generates a radical (liberated group) by an ozone decomposition, and such radical oxidizes the VOC, so that a low-molecular VOC such as formaldehyde can be eliminated.  
         [0066]     In the present embodiment, as in the foregoing embodiment  1 , a filter having a VOC adsorbing function (adsorption filter  103  in the present embodiment) is provided at the upstream side of a catalyst filter (ozone decomposition catalyst filter  106  in the present embodiment), so that ozone and VOC are at first removed by the ozone filter  103  and the VOC that cannot be completely removed by the ozone filter  103  is decomposed by the ozone decomposition catalyst filter  106 . Therefore the air discharge apparatus  10  can securely remove VOC and can also maintain the VOC removing ability over a prolonged period.  
       Embodiment 3  
       [0067]     In the air discharge apparatus of the present invention, as long as a filter capable of adsorbing VOC is provided at the upstream side and a filter capable of decomposing VOC is provided at the downstream side, positions of the duct  101 , the dust filter  102 , the motor fan  104  etc. can be selected arbitrarily. Also the dust filter  102  may be dispensed with.  
         [0068]     For example, an air discharge apparatus  10   a  shown in  FIG. 4A  does not have a dust filter, and is provided, in the order from the upstream side of the duct  101  (along the air flow therein), with an adsorption filter  103 , a motor fan  104  and a VOC oxidation catalyst filter  105 .  
         [0069]     An air discharge apparatus  10 b shown in  FIG. 4B  is provided, in the order from the upstream side of the duct  101 , with a dust filter  102 , a motor fan  104 , an adsorption filter  103 , and a VOC oxidation catalyst filter  105 .  
         [0070]     An air discharge apparatus  10   c  shown in  FIG. 4C  is provided, in the order from the upstream side of the duct  101 , with a dust filter  102 , an adsorption filter  103 , a VOC oxidation catalyst filter  105 , and a motor fan  104 .  
         [0071]     Also an air discharge apparatus  10   d  shown in  FIG. 4D  is similar in a filter arrangement to the embodiment  1  shown in  FIG. 2 , having, in the order from the upstream side of the duct  101 , a dust filter  102 , an adsorption filter  103 , a motor fan  104 , and a VOC oxidation catalyst filter  105 . It is different from the air discharge apparatus  10  shown in  FIG. 2 , in having a duct  107  for guiding air A O  principally containing ozone and flying toner, and a duct  108  for guiding air A VOC  principally containing VOC. As explained in the foregoing, the ozone and the flying toner is principally generated in the vicinity of the image forming portion  2 , while the VOC is principally generated in the vicinity of the fixing portion  4 . Therefore, the air A O  containing ozone and flying toner is guided by the duct  107 , and the air A VOC  containing VOC is guided by the duct  107 . These air flows A O , A VOC  are guided individually then united and passed by the ozone filter  103  and the VOC oxidation catalyst filter  105 .  
         [0072]     Also there may be employed an integral filter including an adsorption filter  103  and a VOC oxidation catalyst filter  105  serially at the upstream and downstream sides along the air flow.  
         [0073]     Also in the present embodiment, the VOC oxidation catalyst filter  105  may be replaced by an ozone decomposition catalyst filter  106  (cf.  FIG. 3 ) as in the embodiment 2.  
         [0074]     In the foregoing, there has been explained a case where the main body M of the image forming apparatus is provided with a single air discharge apparatus, but plural air discharge apparatuses may be provided in the main body M of the image forming apparatus. In such case, the ozone and the VOC generated in the main body M of the image forming apparatus can be removed satisfactorily by constructing all the air discharge apparatuses as those of the present invention each including the adsorption filter  103  and the VOC oxidation catalyst filter  105 . Otherwise, an air discharge apparatus provided in a location of VOC generation (vicinity of the fixing portion  4  in the embodiments 1-3) may be constructed as the air discharge apparatus of the present invention including the adsorption filter  103  at the upstream side and the VOC oxidation catalyst filter  105  at the downstream side, and another air discharge apparatus may be constructed without the VOC oxidation catalyst filter  105 . In this manner the air discharge apparatus can be simplified to achieve a cost reduction.  
         [0075]     The present invention has been explained by embodiments thereof, but the present invention is not limited to such embodiment and is subject to any and all modifications within the technical concept of the invention.  
         [0076]     This application claims priority from Japanese Patent Application No. 2004-306262 filed Oct. 20, 2004, which is hereby incorporated by reference herein.