Patent Publication Number: US-2021187152-A1

Title: Photocatalytic device

Description:
TECHNICAL FIELD 
     The present invention relates to a photocatalytic device including: a photocatalytic filter on which a photocatalyst is carried; and a light irradiation unit which irradiates a surface of the photocatalytic filter with ultraviolet light or visible light. 
     BACKGROUND ART 
     As for this type of photocatalytic device, Patent Literature 1, for example, has proposed a photocatalytic device including: a housing that allows a gas to circulate therein; a photocatalytic filter disposed in the housing; and a light irradiation unit including first and second irradiation parts that are alternately arranged in parallel, have a plurality of photodiodes mounted on a substrate, and irradiate the surface of the photocatalytic filter with light. 
     Thus, the conventional photocatalytic device is generally configured to allow a gas to pass through vent holes of a photocatalytic filter while irradiating a filter surface of the photocatalytic filter with light, thereby decomposing and eliminating a harmful substance, an odor, etc., in the gas by the photocatalyst during the circulation of the gas. This configuration of the conventional photocatalytic device requires an inlet-side flow channel and an outlet-side flow channel to be provided for allowing the gas to smoothly pass through the vent holes on both sides of the photocatalytic filter so as to face the entire filter surfaces. Such flow channels result in the increase in device dimensions in the filter thickness direction. 
     In the inlet-side or outlet-side flow channel, it is also necessary to provide an irradiation unit for irradiating the fitter surface with light. Since this irradiation unit should not prevent smooth circulation of gas, the structure for irradiating the filter surface with light without increasing gas circulation resistance tends to be complicated as in Patent Literature 1, which may cause an increase in cost and impede improvement of light irradiation efficiency. Consequently, power consumption will be increased for ensuring an amount of light irradiation, and heat generation is also increased. 
     CITATION LIST 
     Patent Literature 
     [PTL 1] Japanese Unexamined Patent Application Publication No. 2013-169502 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a photocatalytic device which realizes miniaturization such as reduction in its thickness or diameter without increasing gas circulation resistance, improves light irradiation efficiency, has a simple structure, realizes energy saving and cost reduction, and solves the problem of heat generation. 
     Solution to the Problems 
     The inventors of the present invention have conducted thorough research in view of the above circumstances, and found the facts as follows. A photocatalytic filter includes a corrugated member and a gas is allowed to flow over front and rear surfaces of the filter from one end toward the other end along a direction in which ridges and valleys extend, instead of adopting the conventional configuration in which a gas is allowed to pass through a photocatalytic filter from one surface to the other surface through vent holes so as to penetrate a filter surface. According to the configuration of the present invention, a contact area between the gas and the filter surfaces can be maintained. In addition, a gas inflow part and a gas outflow part are provided at both end positions of a photocatalytic filter instead of providing a gas inlet-side flow channel and a gas output-side flow channel at positions facing filter surfaces. Accordingly, it is possible to allow the gas to flow as described above, and device dimensions in the filter thickness direction can be significantly reduced. The inventors have further found that the above configuration increases the degree of freedom in designing a light irradiation unit, realizes a novel light irradiation mode having higher efficiency with a simple structure, and realizes energy saving and cost reduction. Thus, the present invention has been completed. 
     That is, the present invention includes the following inventions. 
     (1) A photocatalytic device includes: a photocatalytic filter having a surface on which a photocatalyst is supported, the photocatalytic filter being formed of a corrugated member having a plurality of ridges and a plurality of valleys alternately arranged, the photocatalytic filter having light-passing holes that allow ultraviolet light or visible light to pass therethrough, at top portions of the ridges and bottom portions of the valleys; a light irradiation unit configured to irradiate one of front and rear surfaces of the photocatalytic filter with ultraviolet light or visible light; a reflection wall facing the other one of the front and rear surfaces of the photocatalytic filter, the reflection wall reflecting light that has been emitted from the light irradiation unit and has passed through the light-passing holes of the ridges and the valleys of the photocatalytic filter, toward the other surface; and a gas inflow part and a gas outflow part respectively provided at one end and the other end of the photocatalytic filter, the gas inflow part and the gas outflow part allowing a gas to flow in a space between the light irradiation unit and the photocatalytic filter and a space between the reflection wall and the photocatalytic filter, over the front and rear surfaces of the photocatalytic filter from the one end toward the other end along a direction in which the ridges and the valleys extend. 
     (2) The photocatalytic device according to above (1) further includes a metallic support member configured to support the photocatalytic filter at the one end or the other end, wherein the support member supports the light irradiation unit. 
     (3) In the photocatalytic device according to above (1) or (2), the light irradiation unit includes: a light source disposed at a position corresponding to the one end or the other end of the photocatalytic filter; and a light guide member having a light emitting surface facing the one of the surfaces of the photocatalytic filter, the light guide member taking light emitted from the light source therein, and applying the light to the one of the surfaces of the photocatalytic filter through the light emitting surface. 
     (4) In the photocatalytic device according to any one of above (1) to (3), the light-passing holes of the photocatalytic filter are through-grooves elongated in the direction in which the ridges and the valleys extend, and upright pieces are formed at paired opening edges which extend along a longitudinal direction of each through-groove and are opposed each other, the upright pieces being cut and raised for forming the through-groove and being erected at a projecting surface of the ridge or the valley. 
     Advantageous Effects of the Invention 
     The photocatalytic device according to the present invention configured as described above allows a gas to flow in the direction in which the ridges and the valleys extend, along the filter surfaces on both sides of the photocatalytic filter that is corrugated and therefore has a sufficient surface area, while irradiating the filter surfaces with light. Thus, a harmful substance, an odor, etc., in the gas can be efficiently decomposed and/or eliminated by the photocatalyst. 
     Furthermore, the gas inlet-side flow channel and outlet-side flow channel which have conventionally been required at the positions facing the filter surfaces are omitted, and the gas-inflow part and the gas outflow part are provided instead of the flow channels, at the both ends of the filter, to circulate the gas as described above. Thus, the device dimensions in the filter thickness direction are significantly reduced, and the degree of freedom in designing the light irradiation unit is increased. 
     Furthermore, the light-passing holes that allow ultraviolet light or visible light to pass therethrough are formed at the top portions of the ridges and the bottom portions of the valleys, and the photocatalytic device is provided with: the light irradiation unit that irradiates one of the front and rear surfaces of the photocatalytic filter with ultraviolet light or visible light; and the reflection wall that is provided on a side facing the other one of the front and rear surfaces of the photocatalytic filter, and reflects light, which has been emitted from the light irradiation unit and has passed through the light-passing holes, toward the other surface. Therefore, the both filter surfaces can be efficiently irradiated with light, and a light irradiation configuration having high light irradiation efficiency can be realized with the simple structure. Moreover, energy saving and cost reduction can be realized, and heat generation can be reduced. The light-passing holes also allow air to pass therethrough. However, the light-passing holes are not provided as flow channels mainly for gas as in the conventional devices but are provided as holes mainly for light to pass therethrough. 
     The highly efficient light irradiation configuration realized by the light irradiation unit and the reflection wall is realized by omitting the gas inlet-side flow channel and outlet-side flow channel having been required at the positions facing the filter surfaces as described above. Since the gas flows along the direction in which the ridges and the valleys of the corrugated filter extend, the light irradiation unit and the reflection wall do not impede the gas flow. Therefore, the device dimensions in the filter thickness direction can be reduced by bringing the light irradiation unit and/or the reflection wall close to the filter surface. Therefore, the photocatalytic device can be configured to be suitable for: deodorizing a refrigerating compartment or decomposing VOC in a vegetable compartment in a refrigerator; deodorizing/sterilizing the interior of a vehicle by being fitted in a beverage holder; or deodorizing/sterilizing a small space by being placed at a bedside, in a shoe cabinet, in a closet, on a desk, etc., in a house. 
     The photocatalytic device is provided with the metallic support member that supports the photocatalytic filter at the one end or the other end, and the support member supports the light irradiation unit. In this configuration, heat generated by the light irradiation unit can be transferred to the metallic photocatalytic filter through the support member, and efficiently dissipated by the gas flowing at the surface of the photocatalytic filter that serves as a heatsink. 
     Meanwhile, the light irradiation unit includes: the light source disposed at a position corresponding to the one end or the other end of the photocatalytic filter; and the light guide member that has the light emitting surface facing the one of the surfaces of the photocatalytic filter, and that takes light emitted from the light source therein and applies the light to the one of the surfaces of the photocatalytic filter through the light emitting surface. In this configuration, reduction in the thickness of the light irradiation unit can be achieved, whereby the device dimensions in the filter thickness direction can be further reduced. This light guide member can be efficiently used when the gas inlet-side flow channel and outlet-side flow channel having been required at the positions facing the filter surfaces as described above are omitted. 
     Meanwhile, the light-passing holes of the photocatalytic filter are through-grooves elongated in the direction in which the ridges and the valleys extend, and the upright pieces are formed at the paired opening edges which extend along the longitudinal direction of each through-groove and are opposed each other. The upright pieces are cut and raised for forming the through-groove and are erected at a projecting surface of the ridge or the valley. In this configuration, the photocatalytic filter has a large surface area due to the corrugated surfaces having the ridges and the valleys, and the surface area is further increased by the upright pieces at the opening edges of the through-grooves formed at the ridges or the valleys. Thus, a sufficient content area between the gas and the photocatalytic filter surface can be ensured, whereby a catalytic reaction is performed more efficiently, and more photocatalyst layers can be provided, thereby realizing an excellent purification effect. 
     Furthermore, since the photocatalytic filter having the through-grooves and the upright pieces formed in the corrugated member can be manufactured through machine work such as pressing, the manufacturing cost can be reduced as compared with a conventional ceramic filter and a filter that requires etching treatment. In addition, since the through-grooves are formed at the top portions of the ridges and the bottom portions of the valleys, the photocatalytic filter is easily deformable, thereby increasing the degree of freedom in shape. Furthermore, since the upright pieces are cut and raised pieces, the maximum contact area can be maintained without wasting the base material. Moreover, the upright pieces can be efficiently and inexpensively formed through machine work. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a photocatalytic device with a lid member being separated, according to the first embodiment of the present invention. 
         FIG. 2  is an exploded perspective view of the photocatalytic device. 
         FIG. 3  is a vertical cross-sectional view of a photocatalytic device unit constituting the photocatalytic device. 
         FIG. 4  is a horizontal cross-sectional view of the unit. 
         FIG. 5  is a perspective view showing a photocatalytic filter provided in the unit. 
         FIG. 6A  is a perspective view showing the photocatalytic filter in its flat state before being formed in a cylindrical shape, and  FIG. 6B  is a planar view thereof. 
         FIG. 7  is a side view of the photocatalytic filter. 
         FIG. 8  is a perspective view of a major part of the photocatalytic filter. 
         FIG. 9  is a perspective view showing a state where the unit constituting the photocatalytic device is separated from a power supply case. 
         FIG. 10  shows a unit including two photocatalytic filters, as a modification of the above unit. 
         FIG. 11  is a perspective view showing a photocatalytic device with an upper housing being separated, according to the second embodiment of the present invention. 
         FIG. 12  is an exploded perspective view of the photocatalytic device. 
         FIG. 13  is a vertical cross-sectional view of a photocatalytic device unit constituting the photocatalytic device. 
         FIG. 14  is a perspective view showing a state where the unit constituting the photocatalytic device is separated from a power supply case. 
         FIG. 15  is an exploded perspective view showing a lower housing and an internal structure thereof. 
         FIG. 16  is an exploded perspective view showing the structure of an upper case. 
         FIG. 17  is a vertical cross-sectional view of a photocatalytic device according to the third embodiment of the present invention, taken along the direction in which ridges or valleys extend. 
         FIG. 18  is a vertical cross-sectional view of the photocatalytic device, taken along the direction orthogonal to the direction in which the ridges or the valleys extend. 
         FIG. 19  is a vertical cross-sectional view showing a photocatalytic device according to the fourth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, the first embodiment will be described with reference to  FIGS. 1 to 10 . 
     As shown in  FIGS. 1 to 4 , a photocatalytic device  1  of the present invention includes a photocatalytic filter  2 , a light irradiation unit  3 , a reflection wall  4 , a gas inflow part  11 , and a gas outflow part  12 . The photocatalytic filter  2  is formed of a corrugated member  20  having a plurality of ridges  21  and a plurality of valleys  22  alternately arranged. Light-passing holes  23 , through which ultraviolet light or visible light passes, are provided at top portions of the ridges  21  and the bottom portions of the valleys  22 . A photocatalyst is carried on the surface of the photocatalytic filter  2 . The light irradiation unit  3  irradiates one surface  2   a  of front and rear surfaces of the photocatalytic filter  2  with ultraviolet light or visible light. The reflection wall  4  is provided on a side facing the other surface  2   b  of the photocatalytic filter  2 . The reflection wall  4  reflects the light, which has been emitted from the light irradiation unit  3  and has passed through the light-passing holes  23  of the photocatalytic filter  2 , toward the other surface  2   b.  The gas inflow part  11  and the gas outflow part  12  are respectively provided at one end  2   c  side and the other end  2   d  side with respect to the photocatalytic filter  2 . These parts  11  and  12  allow a gas to flow through a space s 1  between the light irradiation unit  3  and the photocatalytic filter  2  and a space s 2  between the photocatalytic filter  2  and the reflection wall  4 , over the front and rear surfaces of the photocatalytic filter  2  from the one end toward the other end along the direction in which the ridges and the valleys extend. 
     With reference to  FIGS. 6 to 8 , the photocatalytic filter  2  is manufactured as follows. Through a press work, the member  20  is formed into a flat corrugated shape in which all the top portions of the plurality of ridges  21  are positioned on the same plane and all the bottom portions of the plurality of valleys  22  are positioned on the same plane. After being coated with a photocatalyst layer over the entire surface, the corrugated member  20  is rounded in a cylindrical shape around an axis parallel to the direction in which the ridges  21  and the valleys  22  extend, with the one surface  2   a,  of the front and rear surfaces, facing inward. Then, the ridges  21  or the valleys  22  at the opposed ends are overlapped and connected to each other. Thus, the cylindrical photocatalytic filter  2  shown in  FIG. 5  is obtained. This cylindrical photocatalytic filter  2  is housed in a housing  6  having a cylindrical peripheral wall  61 , in a manner of being coaxial with the housing  6 . 
     In the present embodiment, the ridges  21  and the valleys  22  each have an angular shape, so that the photocatalytic filter  2  has an angular corrugated shape as a whole. However, the photocatalytic filter  2  may have a non-angular corrugated shape in which ridges and valleys are smoothly continued. As for “ridges” and “valleys”, when one of the both surfaces of the corrugated member is an upper surface while the other surface is a lower surface, portions projecting at the upper surface are regarded as “ridges” while portions projecting at the lower surface are regarded as “valleys”. Examples of the material of the member may include, but are not limited to, various metal materials such as aluminum and stainless steel. 
     Not all the ridges  21  and the valleys  22  need to have the light-passing holes  23 . For example, the light-passing holes  23  may be provided while skipping every other or every two or more ridges  21  or valleys  22 . The dimensions, number, layout, etc., of the light-passing holes  23  can be appropriately determined to attain shape retainability according to the intended use, size, etc., of the device. In this embodiment, for each ridge  21  or valley  22 , two light-passing holes  23 , being through-grooves elongated in the extending direction of the ridge  21  or valley  22 , are continuously formed at an interval, and shape retainability as a whole is maintained by a bridge portion  25  (remaining portion of the ridge  21  or valley  22  between the light-passing holes  23 ). However, the length, interval, etc., of the light-passing holes  23  can be appropriately determined according to the plate thickness, other dimensions, and the degree of desired shape retainability. For example, three or more light-passing holes  23  may be continuously formed in the column direction, or only one light-passing hole  23  may be formed. 
     At paired and opposing opening edges extending along the longitudinal direction of each light-passing hole  23 , upright pieces  24  are provided so as to erect from the projecting surface of the ridge  21  or the valley  22 . The upright pieces  24  are cut and raised for forming the light-passing holes  23 . The photocatalytic filter  2  having the upright pieces  24  thus formed has a large surface area contacting the gas due to the surfaces of the corrugated member having the ridges  21  and the valleys  22 , and simultaneously, the contact area with the gas and light is increased by the inner surfaces of the light-passing holes  23  formed in the ridges  21  or the valleys  22 , and the upright pieces  24  at the opening edges. This allows catalytic reaction to be efficiently performed. As mentioned above, the upright pieces  24  are erected from the projecting surface of the ridge  21  or the valley  22 , whereby the upright pieces  24  do not impede incoming light. Accordingly, the catalyst layer formed on the corrugated surfaces, the inner surfaces of the through-grooves, and the surfaces of the upright pieces  24  are efficiently irradiated with the light. 
     The upright pieces  24  can be efficiently formed through cutting and raising work using punching, simultaneously with or immediately after the press work to form the corrugated shape. Although the upright pieces  24  formed at the opposing opening edges are long pieces extending over almost the entire lengths of the respective opening edges, a plurality of upright pieces  24  may be provided at intervals. In this case, upright pieces  24  having a long projection length may be formed alternately (zigzag) at the opposing opening edges through cutting and raising work. The cut pieces are raised toward the both sides from the center, so that the upright pieces  24  provided at the opposing opening edges have the same height, specifically, about half the dimension of the through-groove in the width direction orthogonal to the column direction thereof. The cutting and raising work is adopted, whereby the upright pieces  24  can be formed without wasting the base material, and the contact area can be increased to the maximum. 
     The photocatalyst layer is obtained by carrying photocatalyst particles, such as particles of an ultraviolet-excitation type photocatalyst such as titanium oxide or particles of a visible-light-excitation type photocatalyst mainly composed of tungsten trioxide, on the surface of the member. The base member into the corrugated shape having the ridges  21  and the valleys  22  may be formed through press work. In such a case, if the photocatalyst layer has been formed on the surface of the member in advance, the photocatalyst layer may be peeled off or may cause degradation of shape accuracy. In order to avoid this, the photocatalyst layer should be formed after the press work to form the corrugated shape. The method for carrying the photocatalyst particles (photocatalyst layer formation method) is not particularly limited. Preferably, a slurry dipping method, which is relatively low in cost, is adopted. Other dipping methods, vacuum impregnation, a sol-gel method, etc., may also be adopted. 
     As shown in  FIG. 3  and  FIG. 4 , the light irradiation unit  3  is disposed at the center position in the housing  6 . The light irradiation unit  3  emits light outward to irradiate, with the light, the one surface  2   a,  facing inward, of the cylindrical photocatalytic filter  2  facing the light irradiation unit  3 . The light irradiation unit  3  is provided over an area of almost the same length as the photocatalytic filter  2  in the axial direction so as to irradiate the entire surface  2   a  of the photocatalytic filter  2  almost uniformly with the light. In this embodiment, the light irradiation unit  3  includes a columnar light guide member  31  that has the aforementioned length and has a light emitting surface at an outer peripheral surface  31   b  facing the filter surface  2   a.  The light irradiation unit  3  further includes a light source  30  disposed at one end  31   c  side of the light guide member  31 . Thus, light emitted from the light source  30  is taken into the light guide member  31 , and the light is applied to the filter surface  2   a  through the light emitting surface (outer peripheral surface  31   b ). 
     Instead of using the light guide member  31 , a plurality of LED substrates, each having the aforementioned length and including LED elements as light sources disposed at predetermined intervals along the axial direction, may preferably be arranged in different directions so as to irradiate the entire surface of the surrounding filter surface  2   a  with light. However, the light emission unit having the light guide member and the light source disposed at one end side of the light guide member as in the present embodiment can emit light more uniformly to the surroundings and allow the light source that generates heat to be locally disposed. Moreover, generated heat can be efficiently dissipated through a support member  5  and the like described later. Therefore, the configuration according to the present embodiment is more preferable. 
     The light guide member  31  has a cylindrical shape, and includes a light shielding layer  32  whose inner surface serves as a reflection surface, at the other end  31   d  opposite to the one end that faces the light source  30 . As for the light source  30 , an LED element that emits ultraviolet light or visible light having a wavelength suitable for the photocatalyst of the photocatalytic filter  2  is adopted, and an LED substrate  33  having the LED element is disposed facing the one end of the light guide member  31 . 
     As shown in  FIG. 2  and  FIG. 3 , the photocatalytic filter  2  and the light irradiation unit  3  are coaxially supported by a common support member  5  made of metal. Specifically, the support member  5  has: first holding pieces  51  provided at an outer position and projecting so as to hold the outer peripheral surface of a portion at the one end  2   c  (lower end in the drawings) of the photocatalytic filter  2 ; and second holding pieces  52  provided at an inner position and projecting so as to hold the outer peripheral surface of a portion at the one end  31   c  (lower end in the drawings) of the light guide member  31  of the light irradiation unit  3 . In a center area surrounded by the second holding pieces  52 , a mounting surface  53  on which the LED substrate  33  is mounted is provided. 
     The light emitted from the light emitting surface (outer peripheral surface  31   b ) of the light guide member  31  and applied to the filter surface  2   a  activates the photocatalyst on the fitter surface  2   a,  passes through the light-passing holes  23  of the filter  2  to reach the other surface  2   b,  is reflected by the reflection wall  4  that is the inner peripheral surface of the peripheral wall  61  of the housing, is applied to the entirety of the other surface  2   b  of the photocatalytic filter  2 , and activates the photocatalyst on the surface  2   b.  As for the reflection wall  4 , the surface of the metal material of the housing may be used as it is or after being subjected to mirror finishing, or a mirror sheet may be adhered to the inner surface of the peripheral wall  61 . 
     Since the photocatalytic filter  2  and the light irradiation unit  3  are supported by the metallic support member  5 , heat generated in the light irradiation unit  3  is transferred to the metallic photocatalytic filter  2  through the support member  5 , and is efficiently discharged from the surface of the photocatalytic filter  2  into the gas. That is, according to the present embodiment, the support member and the photocatalytic filter  2  can efficiently function as heatsinks. In particular, in this embodiment, since the heat of the light irradiation unit  3  is generated from the LED substrate  33 , the heat is efficiently transferred to the support member  5  to which the LED substrate  33  is directly mounted. 
     A vent hole  54  is provided in an area between the outer position where the first holding pieces  51  of the support member  5  are provided and the inner position where the second holding pieces  52  of the support member  5  are provided. The vent hole  54  allows the gas to flow into a space s 1  between the inner surface  2   a  of the supported photocatalytic filter  2  and the outer peripheral surface  31   b  of the light guide member  31 . In this embodiment, the support member  5  is mounted on a bottom plate  62  of the housing  6  via a fan  7  that forcibly feeds the gas into the vent hole  54 . 
     The fan  7  is provided with a plurality of cylindrical leg members  70  disposed spaced apart from each other. The fan  7  and the support member  5  disposed above the fan  7  are screwed onto the housing bottom plate  62  by means of mounting screws  71  via the leg members  70 . In an end portion of the peripheral wall  61  of the housing connected to the bottom plate  62 , a plurality of ventilation windows  63  penetrating through the housing  6  are formed at intervals in the housing circumferential direction, whereby the gas can be taken into a housing bottom space from the outside of the housing. The fan  7  draws the external gas into the housing  6  through the ventilation windows  63 , and further takes the gas through the space between the leg members  70  to feed the gas into the space s 1 . A space s 2  is provided between the outer surface  2   b  of the photocatalytic filter  2  supported by the support member  5  and the inner surface of the peripheral wall  61  of the housing, and part of the external gas taken through the ventilation windows  63  flows into the space s 2 . 
     A lid member  64  is mounted to an end portion of the peripheral wall  61  of the housing opposite to the bottom plate  62  (upper side in the drawings). The lid member  64  has penetrating ventilation windows  65  that allow the spaces s 1 , s 2  to communicate with the outside of the housing. Thus, the gas, which has entered the housing through the ventilation windows  63  and has flowed into the spaces s 1 , s 2  from the housing bottom side, i.e., the one end  2   c  side of the photocatalytic filter  2 , flows in the spaces s 1 , s 2  toward the other end  2   d  along the direction in which the ridges  21  and the valleys  22  of the photocatalytic filter  2  extend, and thereafter, the gas is discharged to the outside of the housing through the ventilation windows  65 . 
     While flowing in the spaces s 1 , s 2 , the gas efficiently contacts the corrugated front and rear surfaces  2   a,    2   b  of the photocatalytic filter  2 , and is efficiently purified by the photocatalyst on the front and rear surfaces  2   a,    2   b  which is activated while being irradiated with light. The ventilation windows  63  that allow the gas to flow into the housing, and a space s 3  between the ventilation windows  63  and the one end  2   c  of the photocatalytic filter function as gas inflow parts  11 , while a space s 4  between the other end  2   d  of the photocatalytic filter and the lid member  64 , the ventilation windows  65  of the lid member, and the like function as gas outflow parts  12 . 
     Thus, in the housing  6 , light is radially applied to the photocatalytic filter  2  that is rounded in a cylindrical shape and disposed coaxially with the housing  6 , from the inner side toward the outer side, and the inner and outer surfaces of the photocatalytic filter  2  are irradiated with the light through the light-passing holes  23 . Meanwhile, the gas flows through the spaces s 1 , s 2  serving as flow channels at both the front and rear surfaces along the axial direction (direction in which the ridges  21  and the valleys  22  extend) intersecting the radial direction, and the gas is efficiently purified by the activated photocatalyst while the gas flows. In the present invention, this intersecting configuration allows the spaces s 1 , s 2  to be set small, whereby the whole device can be miniaturized. 
     The light-passing holes  23  are through-holes, and not only the light but also the gas is allowed to come and go between the space s 1  and the space s 2  through the holes. A transparent film may be adhered to the holes to allow only the light to pass therethrough while preventing the gas from passing therethrough. The ventilation windows  63 ,  65  are preferably provided with dust collecting filters having light shielding property to prevent ultraviolet light or the like from leaking outside, and the dust collecting filters preferably support the photocatalyst. 
     The fan  7  is a means for forcing the gas to flow into the flow channels formed by the spaces s 1 , s 2  in the housing  6 . The fan  7  may be omitted, or placed at the other end side in the housing  6  or outside the housing  6 . A through-hole  66  at the center of the bottom plate  62  is a hole through which wires for supplying power to the LED substrate  33  of the light irradiation unit  3  and the fan  7  pass. 
     in the present embodiment, the housing  6  having the photocatalytic filter  2  and the light irradiation unit  3  disposed therein constitutes a single photocatalytic device unit U 1  that functions as a photocatalytic device when externally supplied with power. 
     Reference numeral  8  denotes a power supply case in which a control board  80 , a battery  81 , etc., are provided. The power supply case  8  is coaxially and detachably connected to the bottom plate  62  of the photocatalytic device unit U 1  constituted by the aforementioned housing  6 . A power supply switch  85  and a USB connector  86  are exposed at the outer peripheral surface of the power supply case  8 , so that the battery  81  being housed in the case  8  can be charged through a USB cable. Preferably, the power supply case  8  is further provided with an odor sensor, and on-off control may be performed based on an output from the sensor to save power. Thus, the unit U 1  and the power supply case  8  configured to be detachable from each other enables a user to replace the power supply case  8  with an auxiliary one and continue to use the unit U 1  when the battery power has been consumed. Thus, convenience is improved. 
     As shown in  FIG. 2 , on a connection-side upper plate  82  of the power supply case  8 , engagement projections  83 , which are heads of connection bolts, are provided so as to be detachably engaged with hook slots  67  formed at corresponding positions on the unit U 1  side bottom plate  62 . Thus, the unit U 1  and the power supply case  8  are rotated and connected to each other. Likewise, a through-hole  84  is formed in the upper plate  82  at a position corresponding to the through-hole  66  of the bottom plate  62 . Through the through-hole  84 , wires (not shown) of the light source  30  and the fan  7  on the unit U 1  side can be drawn into the power supply case  8  and detachably connected to the corresponding wires (not shown) with connectors or the like. 
     Electrical connection of the light source  30  and the fan  7  on the unit U 1  side with the power supply case  8  side is not limited to the connection through the wires as described above. For example, as shown in  FIG. 9 , connection terminals  68 ,  69  are preferably provided on the lower surface of the bottom plate  62  and the upper surface of the upper plate  82 , which face each other, so that the corresponding terminals are electrically connected to each other when the unit U 1  and the power supply case  8  are rotated and connected as described above. Thus, the work of connecting wires with connectors becomes unnecessary, and mounting/dismounting of the unit U 1  on/from the power supply case  8  is facilitated. In this embodiment, one of the two types of connection terminals (connection terminal  69  on the upper plate  82 ) is a spring pin type connector while the other connection terminal (connection terminal  68  on the bottom plate  62 ) is a terminal plate having a slope on which the spring pin type connector climbs and presses the terminal plate due to the rotation/connection described above. However, the present invention is not particularly limited to this combination. 
     When the connection terminals  68 ,  69  are electrically connected to each other as shown in  FIG. 9 , positive/negative terminals for the light source  30  and positive/negative terminals for the fan  7  need to be matched in a one-to-one correspondence. Therefore, combinations of the hook slots  67  with the corresponding engagement projections  83  need to be fixed. For this purpose, preferably, the hook slots  67  and the engagement projections  83  are not disposed at equal intervals but are disposed at positions shifted in the circumferential direction or the radial direction. Thus, combinations of the hook slots  67  with the corresponding engagement projections  83  can be fixed while using the hook slots  67  having the same shape and structure and the engagement projections  83  having the same shape and structure. 
       FIG. 10  shows a photocatalytic device  1 A according to a modification in which a plurality of (two in this modification) photocatalytic filters  2  are provided along the axial direction in a unit U 1 . In this modification, a plurality of light emission units  3  are provided so as to correspond to the photocatalytic filters  2 . However, only one light irradiation unit  3  may be provided for two or more photocatalytic filters  2  by elongating a light guide member  31  so as to penetrate the two or more photocatalytic filters  2 . Alternatively, although not illustrated, a plurality of cylindrical photocatalytic filters having different diameters may be stacked coaxially in the radial direction. 
     Next, the second embodiment of the present invention will be described with reference to  FIG. 11  to  FIG. 16 . 
     In a photocatalytic device  1 A according to the second embodiment, a housing  6 A having a photocatalytic filter  2  and a light irradiation unit  3  disposed therein constitutes a photocatalytic device unit U 2  that functions as a photocatalytic device when externally supplied with power. In contrast to the unit U 1  of the first embodiment, the unit U 2  is configured such that the housing  6 A is separable into an upper housing  601  and a lower housing  602 . The upper housing  601  includes: an upper peripheral wall  611  having an inner reflection wall  4  that faces the photocatalytic filter  2  and the light guide member  31 ; and a lid part  641  having ventilation windows  65 A at an upper end thereof. The wall  611  and the lid part  641  are integrally formed. The lower housing  602  includes: a lower peripheral wall  612  that has ventilation windows  63 A, and surrounds a fan  7 , a light source  30 , and a support member  5 A that supports one ends  2   c.    31   c  (lower ends in the drawings) of the photocatalytic filter  2  and the light guide member  31 , and the light source  30 ; and a bottom plate  62  having hook slots  67  and connection terminals  68 A to be electrically connected to connection terminals  69 A in a power supply case  8 A. The wall  612  and the bottom plate  62  are integrally formed. 
     The housing  6 A being vertically separable as described above facilitates assembly, disassembly, and cleaning, partial reuse, replacement, etc., of the photocatalytic filter  2 , the light irradiation unit  3 , the fan  7 , etc., thereby reducing manufacturing cost and improving convenience. Joint portions of the upper housing  601  and the lower housing  602  are provided with projections  613  and recesses  614  that catch and hold the projections  613 , 
     An activated carbon filter  72  is attached over the entire inner surface of the lid part  641  of the upper housing  601  so as to cover the ventilation windows  65 A. This filter  72  purifies the gas discharged from the housing  6 A, and prevents the light emitted from the light irradiation unit  3  from leaking to the outside through the ventilation windows. As shown in  FIG. 13 , this filter  72  is interposed to be held between the lid part  641  of the upper housing  601 , and the photocatalytic filter  2  and the light guide member  31 , and is replaceable when the upper housing  601  is separated from the lower housing  602 . More preferably, the activated carbon filter  72  is obtained by knitting activated carbon fibers. 
     A dust collecting filter  73  is attached to each of the ventilation windows  63 A of the lower housing  602  so as to cover the ventilation window  63 A. In this embodiment, the dust collecting filter  73  is pasted to the inner edge of each ventilation window  63 A. Alternatively, a sheet of the dust collecting filter  73  may be made annular and pasted over the entire inner surface. Still alternatively, each dust collecting filter  73  may be detachably attached to the ventilation window  63 A by using, for example, guide pieces for insertion of the filter  73 . 
     The support member  5 A that supports the photocatalytic filter  2  and the light irradiation unit  3  is configured to be separable into a planar metallic first support member  501  and a stereoscopic metallic second support member  502 . The first support member  501  has, in the center thereof, a mounting part  55  having a mounting surface  53  on which an LED substrate  33  is mounted, and has a plurality of vent holes  541  formed around the mounting part  55 . The second support member  502  is mountable to the upper surface of the first support member  501 . The second support member  502  has, at an outer position, first holding pieces  51 A, projecting in the axial direction, for holding the outer peripheral surface of a portion at the one end  2   c  (lower end in the drawings) of the photocatalytic filter  2 , and has, at an inner position, second holding pieces  52 A, projecting in the axial direction, for holding the outer peripheral surface of a portion at the one end  31   c  (lower end in the drawings) of the light guide member  31  of the light irradiation unit  3 . Vent holes  542  are provided in an area between the first holding pieces  51 A and the second holding pieces  52 A. A through-hole  56  that allows light emitted from the light source  30  to reach the light guide member  31  is provided in an area surrounded by the second holding pieces  52 A. 
     The support member  5 A being separable as described above facilitates setting of an appropriate gap (distance) between the light source  30  and the end portion of the light guide member  31 , and also facilitates manufacturing, thereby achieving cost reduction. Projections and recesses  55   a  are formed at a peripheral edge, facing the vent holes  541 , of the mounting part  55  of the first support member  501 , so that heat generated from the light source  30  can be efficiently discharged into the gas passing through the vent holes  541 . The first support member  501  can be easily manufactured through punching of a raw member, for example. 
     The second support member  502  has a plurality of holding pieces  51 A along the circumferential direction, and a plurality of holding pieces  52 A along the circumferential direction. The second support member  502  may have a single annular holding piece  51 A and/or a single annular holding piece  52 A. The second support member  502  has a plurality of vent holes  542  corresponding to the respective vent holes  541  of the first support member  501 . The holding pieces  52 A are offset upward in the axial direction with respect to the holding pieces  51 A, so that a gap is maintained between the light source  30  mounted to the first support member  501  and the end portion of the light guide member  31 . This offset in the axial direction is realized by tilting, in the axial direction, a plurality of connection parts  57  that connect the outer area where the holding pieces  51 A are provided with the inner area where the holding pieces  52 A are provided. The second support member  502  can be easily and efficiently manufactured through punching and pressing. 
     The fan  7 , the first support member  501 , and the second support member  502  have a plurality of sets of through-holes  7   a,    58 , and  59  formed at corresponding communication positions in the outer areas thereof, and are fixed in the lower housing  602  by mounting screws  71  that penetrate these through-holes and are fitted into screw holes  62   b  formed at corresponding positions in the bottom plate  62  of the lower housing  602 . 
     The power supply case  8 A of this embodiment is configured to be separable into an upper case  801  and a lower case  802 , like the housing  6 A. The upper case  801  accommodates a control board  80 , and has a switch  85 , a USB connector  86 , etc., exposed at the outer peripheral surface thereof. The lower case  802  accommodates a battery  81 . The power supply case  8 A being vertically separable as described above facilitates assembly, disassembly and cleaning, partial reuse, replacement, etc., of the control board, the battery, etc., inside the power supply case  8 A, thereby reducing manufacturing cost and improving convenience. Joint portions of the upper case  801  and the lower case  802  are provided with projections  813  and recesses  814  that catch and hold the projections  813 . 
     The configuration for assembling the unit U 2  to the power supply case  8 A and the configuration for electrical connection therebetween are basically identical to those of the first embodiment shown in  FIG. 9 . In this second embodiment, however, as a lock mechanism in the assembled state, a plate spring  87  that is bent to almost have the shape of “&lt;” is disposed on the upper plate  82  of the power supply case  8 A, and a locking projection  74  is disposed on the bottom plate  62  of the unit U 2  at a position corresponding to the plate spring  87 . When the engagement projections  83  on the power supply case side are inserted in the hook slots  67  on the unit U 2  side and are relatively rotated, an end of the plate spring  87  climbs over the locking projection  74 , thereby locking the unit U 2  with the case  8 A in a reversely rotatable manner. An operation piece  87   a  is provided at an end portion of the plate spring  87  so as to penetrate a through-hole  88  of the upper case  801  and project from the outer peripheral surface in a mariner of forming an L-shape. When the projecting operation piece  87   a  is pushed down with a finger toward the lower case  802 , engagement of the plate spring  87  with the locking projection  74  is released, which enables the aforementioned reverse rotation, and thus the unit U 2  can be separated from the power supply case  8 A. This lock mechanism prevents the unit U 2  and the power supply case  8 A from being unnecessarily separated from each other. 
     Since other components, modifications, effects, and the like of the second embodiment are basically identical to those of the first embodiment, the same components are denoted by the same reference characters, and description thereof is omitted. 
     The third embodiment of the present invention will be described with reference to  FIG. 17  and  FIG. 18 . 
     In a photocatalytic device  1 B according to the third embodiment, a photocatalytic filter  29  is used in a flat state as shown in  FIG. 6 , without being rounded in a cylindrical shape as in the first and second embodiments. Also, instead of the cylindrical light guide member  31 , a flat light guide member  31 B is adopted and arranged in parallel to the photocatalytic filter  2 B. 
     A housing  6 C has a box shape. The flat photocatalytic filter  2 B is disposed in an internal area on the upper side in  FIG. 17 , and the flat light guide member  31 B is disposed in parallel to and away from the photocatalytic filter  2 B in the internal area on the upper side. Instead of using the light guide member  31 B, a plate-shaped LED substrate on which LED elements as light sources are disposed at predetermined intervals may also be preferably used. 
     The light guide member  31 B has an end surface  310  on the same side as one end  2   c  of the photocatalytic filter  2 B in the direction in which ridges and valleys extend, and this end surface  310  serves as an incident surface on which light from the opposed light source  30  enters. The light guide member  31 B is provided with a light shielding layer  32  whose inner surface serves as a reflection surface, on the surface excluding the end surface  310  and a light radiation surface  311  facing the photocatalytic filter  2 B. 
     Light emitted from a light emitting surface (light radiation surface  311 ) of the light guide member  31 B and applied to the filter surface  2   a  activates the photocatalyst on the surface  2   a,  passes through the light-passing holes of the filter  2 B to reach the other surface side, is reflected by the reflection wall  4  that is the inner surface of an upper wall  615  of the housing  6 C, is applied to the entirety of the other surface  2   b  of the photocatalytic filter  2 B, and activates the photocatalyst on the surface  2   b.  As for the reflection wall  4 , the surface of the metal material of the housing may be used as is, or after being subjected to mirror finishing, or a mirror sheet may be adhered to the inner surface of the upper wall  615 . 
     Since the end portions of the photocatalytic filter  2  and the light irradiation unit  3 , on the one end  2   c  side, are supported by a metallic support member  5 B in the housing  6 C, heat generated in the light irradiation unit  3  is transferred to the metallic photocatalytic filter  2 B through the support member  5 B, and is efficiently discharged from the surface of the photocatalytic filter  2 B into the gas. That is, according to the present embodiment, the support member  5 B and the photocatalytic filter  2 B can efficiently function as heatsinks. 
     The support member  5 B is provided with a vent hole (not shown) communicating with upper and lower spaces s 2 , s 1  of the photocatalytic filter  2 B. In an area, inside the housing, on the side opposite to the photocatalytic filter  2 B with respect to the support member  5 B, a fan  7  that forcibly feeds the gas into the vent hole is provided. In addition, on upper, lower, left, and right walls of the housing on the side opposite to the support member  5 B with respect to the fan  7 , a plurality of ventilation windows  63 B penetrating the housing are provided, whereby the gas can be taken into the housing from the outside. The fan  7  draws the external gas into the housing through the ventilation windows  63 B, and feeds the gas into the spaces s 1 , s 2  through the vent hole. 
     A ventilation window  65 B that allows the spaces s 1 , s 2  to communicate with the outside of the housing is formed penetrating a wall  616  of an end portion, of the housing  6 B, facing the other end  2   d  of the photocatalytic filter  2 B. Thus, the gas, which has entered the housing through the ventilation windows  63 B and flowed into the spaces s 1 , s 2 , flows in the spaces s 1 , s 2  toward the other end  2   d  along the direction in which the ridges  21  and the valleys  22  of the photocatalytic filter  2 B extend, and thereafter is discharged from the housing through the ventilation window  65 B. 
     While flowing in the spaces s 1 , s 2 , the gas efficiently contacts the corrugated front and rear surfaces  2   a,    2   b  of the photocatalytic filter  2 B, and is efficiently purified by the photocatalyst on the front and rear surfaces  2   a,    2   b,  which is activated while being irradiated with light. The ventilation windows  63 B that allow the gas to flow into the housing, and a space s 3  between the ventilation windows  63 B and the one end  2   c  of the photocatalytic filter function as gas inflow parts  11 , while the ventilation window  65 B and a space s 4  between the other end  2   d  of the photocatalytic filter and the end wall  616  function as gas outflow parts  12 . 
     Thus, in the housing  6 B, light is applied to the photocatalytic filter  2 B from the lower side toward the upper side, so that the inner and outer surfaces of the filter  2 B are irradiated with the light through the light-passing holes. Meanwhile, the gas flows through the spaces s 1 , s 2  serving as flow channels at both the front and rear surfaces along the axial direction (direction in which the ridges  21  and the valleys  22  extend) intersecting the light emission direction, and the gas is efficiently purified by the activated photocatalyst while the gas flows. In the present invention, this intersecting configuration allows the spaces s 1 , s 2  to be set small, whereby the whole device can be miniaturized. 
     In this embodiment, the housing  6 B having the photocatalytic filter  2 B and the light irradiation unit  3  disposed therein constitutes a single photocatalytic device unit U 3  that functions as a photocatalytic device when being supplied with power from the outside. When a power supply case having a box shape similar to the photocatalytic device unit U 3  is connected to the unit U 3  as in the first and second embodiments, the unit U 3  can be driven with power from a battery inside the power supply case. 
     Since other components, modifications, effects, and the like of the third embodiment are basically identical to those of the first and second embodiments, the same components are denoted by the same reference characters, and description thereof is omitted. 
     Next, the third embodiment of the present invention will be described with reference to  FIG. 19 . 
     As shown in  FIG. 19 , a photocatalytic device  1 C according to the present embodiment is configured as a photocatalytic device that functions as a lighting device (lamp) by using a unit U 4  having almost the same structure as the unit U 1  of the first embodiment. 
     As for power to be supplied, power of the lighting device (lamp) can be used. In this embodiment, for example, a portion of the peripheral wall  61  of the housing  6  of the unit U 4  is cut and raised to form a placement piece  75  that projects from the outer peripheral surface of the housing  6 , so as to allow a light source  90  for lighting to be placed. A transparent lens body is provided around the unit U 4 . Inlet ports  92  for introducing external air and exhaust ports  93  for discharging the air are provided through the lens housing  91  at positions corresponding to the ventilation windows  63  and  65  of the unit U 4 , respectively. These inlet ports  92  and the exhaust ports  93  are preferably provided with a dust protection filter and/or a light protection net. 
     The light source  90  for lighting need not be disposed on the peripheral wall  61  of the housing as in the present embodiment, and may be disposed on a center portion, of the wall at the upper end of the housing, which is surrounded by the ventilation windows  65 , or on other parts. It is also preferable to provide a human sensor, and control the photocatalytic device such that, when the sensor does not detect any human, only lighting is turned off while continuing the operation as the photocatalytic device. The photocatalytic device configured as a lighting device according to the present embodiment is suitable to be used in a small space such as a toilet. 
     Since other components, modifications, effects, and the like of the fourth embodiment are basically identical to those of the first and second embodiments, the same components are denoted by the same reference characters, and description thereof is omitted. 
     The embodiments of the present invention have been described above. However, the present invention is by no means limited to the embodiments, and can be incorporated in various kinds of equipment as well as lighting equipment by using a common unit. Thus, the present invention can be implemented, as a matter of course, in various forms without departing from the gist of the present invention. 
     DESCRIPTION OF THE REFERENCE CHARACTERS 
     
         
         
           
               1 ,  1 A,  1 B,  1 C photocatalytic device 
               2 ,  2 B photocatalytic filter 
               2   a,    2   b  filter surface 
               2   c  one end 
               2   d  the other end 
               3  light irradiation unit 
               4  reflection wall 
               5 ,  5 A,  5 B support member 
               6 ,  6 A,  6 B,  6 C housing 
               7  fan 
               7   a  through-hole 
               8 ,  8 A power supply case 
               11  inflow part 
               12  outflow part 
               20  member 
               21  ridge 
               22  valley 
               23  light-passing hole 
               24  upright piece 
               25  bridge 
               30  light source 
               31 ,  31 B light guide member 
               31   b  outer peripheral surface 
               31   c  one end 
               31   d  the other end 
               32  light shielding layer 
               33  substrate 
               51 ,  51 A holding piece 
               52 ,  52 A holding piece 
               53  mounting surface 
               54  vent hole 
               55  mounting part 
               55   a  projections and recesses 
               56  through-hole 
               57  connection part 
               61  peripheral wall 
               62  bottom plate 
               62   b  screw hole 
               63 ,  63 A,  63 B ventilation window 
               64  lid member 
               65 ,  65 A,  65 B ventilation window 
               66  through-hole 
               67  hook slot 
               68 ,  68 A connection terminal 
               69 ,  69 A connection terminal 
               70  leg member 
               71  mounting screw 
               72  activated carbon filter 
               73  dust collecting filter 
               74  locking projection 
               75  placement piece 
               80  control board 
               81  battery 
               82  upper plate 
               83  engagement projection 
               84  through-hole 
               85  switch 
               86  connector 
               87  plate spring 
               87   a  operation piece 
               88  through-hole 
               90  light source 
               91  lens housing 
               92  inlet port 
               93  exhaust port 
               310  end surface 
               311  light radiation surface 
               501  first support member 
               502  second support member 
               541  vent hole 
               542  vent hole 
               601  upper housing 
               602  lower housing 
               611  upper peripheral wall 
               612  lower peripheral wall 
               613  projection 
               614  locking recess 
               615  wall 
               616  wall 
               616  wall 
               641  lid part 
               801  upper case 
               802  lower case 
               813  projection 
               814  locking recess 
             s 1 , s 2  space 
             s 3 , s 4  space 
             U 1 , U 2 , U 3 , U 4  unit