Patent Publication Number: US-9885456-B2

Title: Ventilation device and vehicular lamp

Description:
TECHNICAL FIELD 
     The present invention relates to a ventilation device forming a ventilation path and a vehicular lamp. 
     BACKGROUND ART 
     For example, in Patent Document 1, a ventilation opening larger than 132 mm 2  is covered with a ventilation unit for reducing condensation provided with at least one water vapor permeable material having an expanded PTFE membrane. It is described that, accordingly, elimination of condensed substances from the vehicular lamp is facilitated, to thereby provide protection not to allow external substances or liquid water to infiltrate. 
     CITATION LIST 
     Patent Literature 
     Patent Document 1: Japanese Patent No. 4276246 
     SUMMARY OF INVENTION 
     Technical Problem 
     An object of the present invention is to improve a defogging property in a housing interior while suppressing infiltration of external substances and liquid water by use of a ventilation path including a bent part. 
     Solution to Problem 
     Under such an object, the present invention provides a ventilation device ( 10 ,  30 ,  50 ,  70 ) for discharging water vapor in an interior ( 8 ) of a housing ( 2 ) of a vehicular lamp ( 1 ) to an outside of the housing, the ventilation device including: a ventilation path support body that forms a ventilation path ( 20 ,  40 ,  60 ,  80 ) that is bent and is in communication with a ventilation opening ( 9 ) in the housing, the ventilation path support body being configured to allow the ventilation path to maintain, up to a terminal end of the ventilation path including a bent part, a minimum cross-sectional area capable of maintaining a fogging reduction rate of 80% or more in a lapse of 5 minutes. 
     Here, the minimum cross-sectional area of the ventilation path ( 20 ,  40 ,  60 ,  80 ) is at least 300 mm 2  or more, and the minimum cross-sectional area of 300 mm 2  or more is maintained up to the terminal end. 
     Moreover, the ventilation path ( 20 ,  40 ,  60 ) of the ventilation path support body has the bent part bending from a first direction (P) to a second direction (Q), and a protruding amount toward the first direction at the bent part is smaller than an opening width of the ventilation opening while maintaining the sum of the cross-sectional area of the ventilation path of 300 mm 2  or more. 
     From another standpoint, the present invention is a ventilation device ( 10 ,  30 ,  50 ,  70 ) for discharging water vapor in an interior ( 8 ) of a housing of a vehicular lamp ( 1 ) to an outside of the housing, the ventilation device including: a ventilation path support body that forms a ventilation path ( 20 ,  40 ,  60 ,  80 ) that is bent and is in communication with a ventilation opening ( 9 ) in the housing ( 2 ), the ventilation path support body being configured to allow the ventilation path to maintain, up to a terminal end of the ventilation path including a bent part, a minimum cross-sectional area of at least 300 mm 2  or more. 
     Here, the ventilation path ( 80 ) of the ventilation path support body includes a branch part from which plural ventilation paths are branched off, and a sum of minimum cross-sectional areas of the plural paths after branching is 300 mm 2  or more, the ventilation path being configured to maintain the sum of the minimum cross-sectional areas of 300 mm 2  or more from the branch part up to the terminal end of the ventilation path. 
     Further, a vehicular lamp ( 1 ), to which the present invention is applied, includes: an electrical component ( 4 ) that emits light; a housing ( 2 ) that forms a space inside thereof including the electrical component; a ventilation opening ( 9 ) provided to the housing to discharge water vapor in an interior ( 8 ) of the housing; and a ventilation path support body ( 10 ,  30 ,  50 ,  70 ) that forms a ventilation path ( 20 ,  40 ,  60 ,  80 ) that is bent and is in communication with the ventilation opening in the housing, wherein the ventilation path of the ventilation path support body is configured to maintain, up to a terminal end of the ventilation path including a bent part, a minimum cross-sectional area capable of maintaining a fogging reduction rate of 80% or more in a lapse of 5 minutes, or is configured to maintain, up to the terminal end of the ventilation path including the bent part, a minimum cross-sectional area of at least 300 mm 2  or more. 
     Note that the above signs in this section are provided for exemplification in describing the present invention, and the present invention is not subjected to limited interpretation by these signs. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to improve the defogging property in the housing interior while suppressing infiltration of the external substances and the liquid water by use of the ventilation path having the bent part. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing an overall configuration of a vehicular lamp to which exemplary embodiments are applied; 
         FIGS. 2A to 2E  are diagrams for illustrating a ventilation member, which is a first exemplary embodiment; 
         FIGS. 3A and 3B  are diagrams for illustrating a ventilation member, which is a second exemplary embodiment; 
         FIGS. 4A to 4C  are diagrams for illustrating a ventilation member, which is a third exemplary embodiment; 
         FIGS. 5A to 5C  are diagrams for illustrating a ventilation member, which is a fourth exemplary embodiment; and 
         FIG. 6  is a diagram showing measurement results of fogging reduction rates in Examples 1 to 3 and Comparative examples 1 to 3. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to attached drawings. 
     [Overall Configuration of Vehicular Lamp] 
       FIG. 1  is a diagram showing an overall configuration of a vehicular lamp  1  to which the exemplary embodiments are applied. 
     The vehicular lamp  1  to which the exemplary embodiments are applied is used as a head lamp, a rear lamp, a brake lamp, a fog lamp, a direction indicator lamp, a taxing lamp, a parking lamp, etc., of various kinds of vehicles typified by, for example, automobiles.  FIG. 1  shows a specific example of these lamps. 
     The vehicular lamp  1  shown in  FIG. 1  includes a housing  2  that protects electrical components of the vehicle and a lens  3  that is attached to the housing  2  to emit light at a proper angle, in such a manner to concentrate light toward the front of the lamp. By the housing  2  and the lens  3 , a closed housing interior  8  of the vehicular lamp  1  is configured, and thereby a waterproofing property or a dust-proofing property for each electrical component in the housing interior  8  is improved. However, the housing interior  8  is not in an absolute sealed state; ventilation is possible via a ventilation opening  9 . The housing interior  8  is provided with, as one of the electrical components, a bulb  4  that emits light and a reflector  5  that reflects light emitted from the bulb  4  in the lateral direction or rear direction toward the front. 
     Moreover, in the exemplary embodiments, the vehicular lamp  1  includes, as one of an aeration unit, a ventilation member  10  that performs transfer of air between interior and exterior of the lamp, and in particular, that is able to quickly discharge water vapor in the housing interior  8  to the exterior of the vehicular lamp  1 . The ventilation member  10  is in communication with the ventilation opening  9  and forms a bending ventilation path, to thereby function as a ventilation path support body that supports the ventilation path. Then, the vehicular lamp  1  provided with the ventilation member  10  can be grasped as a mode of a ventilation device. Around the ventilation opening  9  in the housing  2 , a protruding part  2   a  for attaching the ventilation member  10  is formed. By fitting the ventilation member  10  over the protruding part  2   a , the ventilation member  10  can be attached to the housing  2 . 
     The P-direction shown in  FIG. 1  is a depth direction, which is on an engine room side when the vehicular lamp  1  is used as the head lamp or the fog lamp, or is on a trunk side when the vehicular lamp  1  is used as the rear lamp. If a protruding amount of the ventilation member  10  in the P-direction becomes large, the ventilation member  10  is apt to constitute an obstacle to functional components or the like on the depth side. The water vapor in the housing interior  8 , in the ventilation path, first, heads for a first direction (P-direction) from the ventilation opening  9 . Thereafter, the water vapor is bent at the bent part within the ventilation member  10 , and heads for a second direction (Q-direction) from top to bottom in the figure. 
     In general, an automobile lamp is provided with, as a function of discharging water vapor within the lamp to the outside and a function of canceling pressure difference caused by temperature change, a hole on a lamp housing side, and a ventilation member for dust-proofing and waterproofing is attached to the hole. Compatibility between the function of canceling the pressure difference and the dust-proofing and waterproofing property can be handled by a ventilation member, such as a PTFE (polytetrafluoroethylene) film. However, for the water vapor once infiltrated into the inside of the lamp, it is difficult to be discharged to the outside due to a complicated structure inside the lamp, to thereby cause a problem of condensation inside the lens surface by the temperature change. Moreover, if xenon or halogen is used for the lamp, it is possible to eliminate condensation by heat in lighting; however, for example, when an LED lamp is used, an amount of heat inside the lamp is decreased, and therefore, it becomes difficult to eliminate condensation by heat. Further, in a so-called hybrid vehicle or electric vehicle, electrical components are increased from a safety and environmental standpoint and converge into an engine room, and accordingly, there is a tendency of a shortage of space on the lamp housing side. 
     Here, in a ventilation device disclosed in Patent Document 1 (Japanese Patent No. 4276246), a sum of ventilation opening areas is 132 mm 2  or more, and thereby, a certain functional role in water vapor permeability for eliminating condensation is fulfilled. However, if a PTFE film as the ventilation member is placed at an opening part as in the document for ensuring dust-proofing and waterproofing property, there occurs inferior permeability as compared to a through hole without ventilation material; therefore, it is impossible to respond high demands of defogging property in recent years by an opening of the order of 132 mm 2  shown in the document. Moreover, it is possible to make a ventilation device thinner by placing the ventilation member separately at the opening part; however, if the ventilation member is directly protruded to the outside, there is a possibility that the ventilation member is broken by water pressure, collision of a flying stone or the like. 
     Therefore, in the exemplary embodiments, there is provided a ventilation device capable of discharging water vapor in the housing interior  8  to the outside of the lamp even if a lamp with a low amount of heat, such as an LED, as well as the lamp using xenon or halogen, is used. In other words, the ventilation device is configured such that a ventilation path that is bent and is in communication with the ventilation opening  9  in the housing is formed, and, up to the terminal end of the ventilation path including the bent part, the ventilation path maintains a minimum cross-sectional area capable of maintaining a fogging reduction rate of 80% or higher in a lapse of 5 minutes. Moreover, the ventilation device is configured such that the bent ventilation path maintains a minimum cross-sectional area of at least 300 mm 2  or more to the terminal end of the ventilation path including the bent part. 
     In the past, in recognizing a discharging amount of water vapor in the housing interior  8  of the vehicular lamp  1 , the recognition was remained to the extent of referring to the size of the ventilation opening  9  based on sensory index, such as good/bad or fast/slow, by engineers. Moreover, the reference merely remained on “size of ventilation opening  9 ”; therefore, if a bending ventilation path leading to the ventilation opening  9  was formed, it was impossible to maintain sufficient defogging property by the former techniques. 
     The present inventors found that, by making the indexes of elapsed time and fogging reduction rate more appropriate, the defogging property of various types of lamps including the bending ventilation path became good. Moreover, the present inventors invented that, in various types of lamps including the bending ventilation path, a predetermined cross-sectional area was maintained to the terminal end of the bending ventilation path, and it was ascertained that the defogging property of the various types of lamps became good by actual proof. 
     [First Exemplary Embodiment of Ventilation Member] 
       FIGS. 2A to 2E  are diagrams for illustrating a ventilation member  10 , which is the first exemplary embodiment. Here,  FIG. 2A  is an elevational view in which the ventilation member  10  is viewed from an attaching side to the ventilation opening  9  side shown in  FIG. 1 , and  FIG. 2B  is a bottom view in which the ventilation member  10  is viewed from the lower direction where a discharge port is provided. Moreover,  FIG. 2C  is a diagram showing a IIC-IIC cross section of the ventilation member  10  shown in  FIG. 2A  in the vertical direction (Q-direction) in the figure, and  FIG. 2D  is a diagram showing a IID-IID cross section of the ventilation member  10  shown in  FIG. 2A  in the horizontal direction (P-direction) in the figure. Further,  FIG. 2E  is a diagram for illustrating a cross-sectional area and an opening area of each location of a ventilation path  20 . 
     The ventilation member  10  forms the ventilation path  20  configured with a void (through hole) as an inner tube, and functions as a ventilation device or a ventilation path support body. However, it is possible to define “ventilation device” to include, not only the ventilation member  10 , but also the housing  2 . The ventilation member  10  includes an attaching part  11  for attaching the ventilation member  10  to the ventilation opening  9  (refer to  FIG. 1 ) and for attaching the ventilation member  10  while communicating the ventilation opening  9  and the ventilation path  20 . Moreover, the ventilation member  10  includes a bent-part housing  12  that forms the bent part bending from the first direction (P-direction) to the second direction (Q-direction) in the inner tube used as the ventilation path  20 . Then, the ventilation member  10  forms, by the attaching part  11  and the bent-part housing  12 , the ventilation path  20  configured with an inlet-port side ventilation path  21  that is in communication with the ventilation opening  9 , a bent-part inlet side  22  that follows the inlet-port side ventilation path  21  and is positioned ahead of bending constituting the bent part, the bent-part inlet side  22  having a wide-width cross section, and a bent-part outlet side  23  that follows the bent-part inlet side  22  and is positioned behind bending of the bent part. 
     The material of the ventilation member  10  may be a thermoplastic resin, a thermosetting resin, a metal or the like, and is not limited; however, from a standpoint of improving workability in attaching to the housing  2 , it is preferable to use an elastic body, such as a thermoplastic elastomer or a thermosetting elastomer. Moreover, it is preferable to form the ventilation member  10  with a single material from a standpoint of reducing costs; however, the shape may be formed by injection molding or two-color molding using materials having different hardness. Further, the shape or attaching method of the attaching part  11  of the ventilation member  10  conforms to the structure of the ventilation opening  9  of the housing  2 , but is not limited and may be a circular shape, a rectangular shape, an elliptical shape or the like. 
     Moreover, it is possible to apply oil repellent treatment to the ventilation member  10 . As the oil repellent treatment, specific examples include formation of an oil repellent coating including a polymer having perfluoro-alkyl group. The forming methods of the ventilation member  10  include coating of solution or dispersion of a polymer having perfluoro-alkyl group by an air spray method, an electrostatic spray method, a dip coating method, a spin coating method, a roll coating method, a curtain coating method, an impregnation method or the like, or, a coating forming method by an electrodeposition coating method or a plasma polymerization method. However, the method is not particularly limited as long as a desired coating can be formed. 
     As shown in  FIG. 2E , the cross section of the inlet-port side ventilation path  21  (the surface orthogonal to the first direction (P-direction) on the upstream side of the bent part) has a circular shape with an inner diameter T 1  and has a cross-sectional area S 1 . Moreover, the cross section of the bent-part inlet side  22  (the surface orthogonal to the first direction (P-direction) on the bent-part inlet side) has a semi-circular shape with an inner diameter T 2  and a rectangular shape with a width T 2  continued to the semi-circular shape, the cross-sectional area of the cross section being S 2 . Further, an opening surface of the bent-part outlet side  23  (the surface orthogonal to the second direction (Q-direction) on the downstream side of the bent part) is a rectangle with a width T 2  and a length T 3  in the first direction, which is represented by T 3 ×T 2 , and a cross-sectional area thereof is S 3 . 
     To put the above relation another way, the surface forming the cross-sectional area S 2  (the cross section of the bent-part inlet side  22 ) of the ventilation member  10 , which is the ventilation path support body, is larger than the surface forming the cross sectional area S 1  (the cross section of the inlet-port side ventilation path  21 ), and S 2  includes S 1 . Moreover, the cross-sectional area S 2  is a cross section using a side (T 2 ) constituting the cross-sectional area S 3 . The side (T 2 ) is a length in the direction orthogonal to the first direction (P-direction), and the length thereof is longer than the length (T 1 ) in the cross-sectional area S 1  corresponding thereto. Note that the “the direction orthogonal to” means “the direction intersecting at right angles to” in the exemplary embodiment; however, if the bending is not a right angle and is bent at an obtuse angle or an acute angle, the direction is “the direction obliquely intersecting”. 
     Here, in the exemplary embodiment, all of the cross-sectional areas S 1 , S 2  of the ventilation path  20  and the area S 3  of the opening is 300 mm 2  or more. In other words, the ventilation member  10  forms the ventilation path  20  that is in communication with the ventilation opening  9  and is bent, and is configured to maintain the minimum cross-sectional area of at least 300 mm 2  or more to the terminal end of the ventilation path including the bent part. The significance of the cross-sectional area of 300 mm 2  or more will be described later. 
     Then, in the exemplary embodiment, for smooth movement of the water vapor and quickly discharging thereof to the outside, “the opening area of the ventilation path  20  of the ventilation member  10  connected to the outside of the lamp” is made “not less than the area of the ventilation opening  9  provided on the housing  2  side (the lamp housing side) as a function of discharging the water vapor to the outside and a function of eliminating pressure difference caused by the temperature change”; accordingly, the water vapor moves smoothly and is able to be discharged to the outside in a moment. The relations between respective opening areas are as follows. 
     cross-sectional area S 1 &lt;cross-sectional area S 2   
     cross-sectional area S 1 ≦cross-sectional area S 3   
     In the exemplary embodiment, a through hole is employed as the ventilation path  20  formed in the ventilation member  10 ; however, the ventilation path  20  is not limited to the through hole. Even though the ventilation path  20  is a through hole, a bent ventilation path  20  is formed, and thereby it is possible to make water or dust from the outside harder to enter. Moreover, by setting the cross-sectional area S 2  larger than the cross-sectional area S 1 , it is possible to make T 2  large; accordingly, in the cross-sectional area S 3  determined by T 2 ×T 3 , T 3  can be smaller than T 1 , to thereby make it possible to reduce the protruding amount of the ventilation member  10  in the P-direction. 
     In other words, to maintain smooth movement of the water vapor, the ventilation path  20  is required to maintain the opening area of a certain level or more to the terminal end; however, if the ventilation path  20  is bent while the ventilation path  20  remains to have the cross-sectional area S 1  (if the cross section constituting the cross-sectional area S 1  is rotated 90°), protrusion in the first direction (P-direction) becomes the length in the second direction of the cross-sectional area S 1  (in other words, the protrusion in the first direction (P-direction) becomes the length T 1 ), and thereby, the protruding amount becomes large. Particularly, in recent years, further improvement of the defogging property of a lamp has been required, and as a result, the area of the ventilation opening  9  was increased, and it was also necessary to increase the opening area of the ventilation path  20  of the ventilation member  10 . On the other hand, downsizing of the device has been strongly required. Then, in the exemplary embodiment, the wide-width T 2  was employed in the bent part; therefore, as the protrusion of the bent part in the P-direction, even if T 3 , which was the length smaller than the length of the cross-sectional area S 1  in the second direction or the length in the case where the cross section constituting the cross-sectional area S 1  was rotated 90°, was employed, it was possible to maintain the opening cross section of a certain level or more (for example, 300 mm 2  or more), and thereby, it became possible to provide the ventilation member  10  that is thin in the P-direction while maintaining smooth movement of the water vapor. 
     Note that, as shown in  FIG. 1 , when the ventilation member  10  is fitted over the protruding part  2   a , whether or not the thickness of the housing  2  is taken into consideration or not causes a problem; however, if the thickness is sufficiently small, there is no need for particular consideration. However, if the thickness is large and the ventilation member  10  is fitted over from the outside of the protruding part  2   a , the cross-sectional area of the ventilation path  20  is reduced only at the part. In such a case, regarding the cross-sectional area of the ventilation member  10 , it is necessary to take the thickness into consideration and discuss the size of the inner diameter with the exception of the thickness. However, since description will be complicated, these considerations are summed up in the present specification, and description is given by assuming the inner diameter T 1  in the cross-sectional area S 1 . 
     [Second Exemplary Embodiment of Ventilation Member] 
     Next, a second exemplary embodiment of the ventilation member will be described. 
       FIGS. 3A and 3B  are diagrams for illustrating a ventilation member  30 , which is the second exemplary embodiment. Here,  FIG. 3A  is an elevational view in which the ventilation member  30  is viewed from an attaching side to the ventilation opening  9  side shown in  FIG. 1 , and  FIG. 3B  is a diagram showing a IIIB-IIIB cross section in the vertical direction (Q-direction) in the figure in the ventilation member  30  shown in  FIG. 3A . Note that description of functions, materials, treatments or the like similar to those of the first exemplary embodiment is omitted here. 
     The ventilation member  30  includes an attaching part  31  for attaching the ventilation member  30  to the ventilation opening  9  and for communicating the ventilation opening  9  with the ventilation path  40 . Moreover, the ventilation member  30  includes a bent-part housing  32  that forms the bent part bending from the first direction (P-direction) to the second direction (Q-direction) in the inner tube used as the ventilation path  40 . In the second exemplary embodiment, characteristics are present in further bending from the second direction (Q-direction) to a third direction (R-direction), and the bending to the third direction (R-direction) is also formed by the bent part housing  32 . 
     The ventilation member  30  forms, by the attaching part  31  and the bent-part housing  32 , the ventilation path  40  configured with an inlet-port side ventilation path  41  that is in communication with the ventilation opening  9  shown in  FIG. 1 , a bent-part inlet side  42  that is positioned ahead of bending constituting the bent part and has a wide-width cross section following the inlet-port side ventilation path  41 , a bent-part outlet side  43  that follows the bent-part inlet side  42  and is positioned behind bending of the bent part, and a discharge port  44  further bending toward the R-direction. 
     The cross sections of respective locations of the ventilation path  40  are similar to those of the first exemplary embodiment shown in  FIG. 2E , and therefore, illustration thereof is omitted here. The cross section of the inlet-port side ventilation path  41  (the surface orthogonal to the first direction (P-direction) on the upstream side of the bent part) has, similar to the inlet-port side ventilation path  21  in the first exemplary embodiment, a circular shape with an inner diameter T 1  and has a cross-sectional area S 1 . Moreover, the cross section of the bent-part inlet side  42  (the surface orthogonal to the first direction (P-direction) on the bent-part inlet side) forming the bent part has a semi-circular shape with an inner diameter T 2  and a rectangular shape with a width T 2  continued to the semi-circular shape, which are similar to the bent-part inlet side  22  of the first exemplary embodiment, the cross-sectional area of the cross section being S 2 ′. This S 2 ′ is different from the cross-sectional area S 2  shown in  FIG. 2E  only in the shape of the rectangle added as a cross section, and therefore, hereinafter, S 2  will be described as S 2 . Further, similar to the opening surface of the bent-part outlet side  23  in the first exemplary embodiment, an opening surface of the bent-part outlet side  43  (the surface orthogonal to the second direction (Q-direction) on the downstream side of the bent part) is a rectangle with a width T 2  and a length T 3  in the first direction, and a cross-sectional area thereof is S 3 . Then, the area of the discharge port  44  is S 3 , which is similar to the area of the opening in the bent-part outlet side  43 . Note that it is also preferable to make the discharge port  44  larger than the cross-sectional area of the opening in the bent-part outlet side  43 . 
     Then, in the exemplary embodiment, similar to the first exemplary embodiment, all of the cross-sectional areas S 1 , S 2 , S 3  of the ventilation path  40  and the area S 3  of the opening in the discharge port is 300 mm 2  or more. In other words, the ventilation member  30  forms the ventilation path  40  that is in communication with the ventilation opening  9  and is bent, and is configured to maintain the minimum cross-sectional area of at least 300 mm 2  or more to the terminal end of the ventilation path  40  including the bent part. Further, relations between the opening areas (cross-sectional area S 1 &lt;cross-sectional area S 2 , cross-sectional area S 1 ≦cross-sectional area S 3 ) are similar to those in the first exemplary embodiment. The ventilation path  40  being a through hole is also similar to the first exemplary embodiment. 
     As described above, in the second exemplary embodiment, the ventilation member  30 , which is the ventilation path support body, includes the ventilation path  40  further bending from the second direction (Q-direction) toward the third direction (R-direction). This can reduce infiltration of water or dust from the outside more successfully. Moreover, since the cross section of 300 mm 2  or more is maintained, even if the bending locations are increased, it becomes possible to provide the ventilation member  30  that is thin in the P-direction, which is related to the thickness from the attaching part, while maintaining smooth movement of the water vapor from the housing  2  side of the lamp. Further, since the direction of the discharge port  44  can be selected relatively freely, it becomes possible to select the orientation of the ventilation path  40  or the like; accordingly, degree of freedom in designing the vehicular lamp  1  as a whole can be increased. 
     [Third Exemplary Embodiment of Ventilation Member] 
     Next, a third exemplary embodiment of the ventilation member will be described. 
       FIGS. 4A to 4C  are diagrams for illustrating a ventilation member  50 , which is the third exemplary embodiment. 
     Here,  FIG. 4A  is an elevational view in which the ventilation member  50  is viewed from an attaching side to the ventilation opening  9  side shown in  FIG. 1 , and  FIG. 4B  is a diagram showing a IVB-IVB cross section in the vertical direction (Q-direction) in the figure in the ventilation member  50  shown in  FIG. 4A .  FIG. 4C  is a diagram showing a IVC-IVC cross section of the ventilation member  50  shown in  FIG. 4A  in the horizontal direction (P-direction) in the figure. 
     The third exemplary embodiment shown in  FIGS. 4A to 4C  has characteristics in that the discharge port  44  of the second exemplary embodiment shown in  FIGS. 3A and 3B  is configured with plural discharge ports. Note that description of matters similar to those of the first exemplary embodiment and the second exemplary embodiment is omitted here. 
     The ventilation member  50  includes an attaching part  51  for attaching the ventilation member  50  to the ventilation opening  9  and for communicating the ventilation opening  9  with the ventilation path  60 . Moreover, the ventilation member  50  includes a bent-part housing  52  that forms the bent part bending from the first direction (P-direction) to the second direction (Q-direction) in the inner tube used as the ventilation path  60 . In the third exemplary embodiment, similar to the second exemplary embodiment, the ventilation path  60  is further bent from the second direction (Q-direction) toward the third direction (R-direction). The ventilation member  50  forms, by the attaching part  51  and the bent-part housing  52 , the ventilation path  60  configured with an inlet-port side ventilation path  61  that is in communication with the ventilation opening  9  shown in  FIG. 1 , a bent-part inlet side  62  that follows the inlet-port side ventilation path  61  to be positioned ahead of bending constituting the bent part and has a wide-width cross section, a bent-part outlet side  63  that follows the bent-part inlet side  62  and is positioned behind bending of the bent part, and a discharge port  64  further bending toward the R-direction. The discharge port  64  is configured with plural openings. The specific example shown in  FIG. 4A  includes 18 openings as a whole. However, the number of openings is not limited to that of the exemplary embodiment. Moreover, regarding the orientations of the openings, there is no need for all of the openings to face the third direction (R-direction), and part of the openings may be configured to face the second direction (Q-direction). 
     The cross sections of respective locations of the ventilation path  60  are similar to those of the first and second exemplary embodiments shown in  FIG. 2E , and therefore, illustration thereof is omitted here. The cross section of the inlet-port side ventilation path  61  (the surface orthogonal to the first direction (P-direction) on the upstream side of the bent part) has, similar to the inlet-port side ventilation path  21  in the first exemplary embodiment, a circular shape with an inner diameter T 1  and has a cross-sectional area S 1 . Moreover, the cross section of the bent-part inlet side  42  (the surface orthogonal to the first direction (P-direction) on the bent-part inlet side) has a semi-circular shape with an inner diameter T 2  and a rectangular shape with a width T 2  continued to the semi-circular shape, which are similar to the bent-part inlet side  22  of the first exemplary embodiment, the cross-sectional area of the cross section being S 2 ″. This S 2 ″ is different from the cross-sectional area S 2  shown in  FIG. 2E  and S 2 ′ in the second exemplary embodiment only in the shape of the rectangle added as a cross section, and therefore, hereinafter, S 2 ″ will be described as S 2 . Further, similar to the opening surface of the bent-part outlet side ( 23 ,  43 ) in the first and second exemplary embodiments, an opening surface of the bent-part outlet side  63  (the surface orthogonal to the second direction (Q-direction) on the downstream side of the bent part) is a rectangle with a width T 2  and a length T 3  in the first direction, and a cross-sectional area thereof is S 3 . Then, by summing all of the areas of the  18  opening holes, the area of the discharge port  64  is S 3 , which is similar to the area of the opening in the bent-part outlet side  63 . Note that it is also preferable to make the discharge port  64 , which is the sum of the areas of plural opening holes, larger than the cross-sectional area of the opening in the bent-part outlet side  63 . 
     Then, in the exemplary embodiment, similar to the first and second exemplary embodiments, all of the cross-sectional areas S 1 , S 2 , S 3  of the ventilation path  60  is 300 mm 2  or more. In other words, the ventilation member  50  forms the ventilation path  60  that is in communication with the ventilation opening  9  and is bent, and is configured to maintain the minimum cross-sectional area of at least 300 mm 2  or more to the terminal end of the ventilation path  60  including the bent part. Further, relations between the opening areas (cross-sectional area S 1 &lt;cross-sectional area S 2 , cross-sectional area S 1 ≦cross-sectional area S 3 ) are similar to those in the first and second exemplary embodiments. The ventilation path  60  being a through hole is also similar to the first and second exemplary embodiments. 
     In this manner, in the third exemplary embodiment, the plural opening holes were configured as the discharge port  64 . Then, the sum of the hole areas of the opening holes is 300 mm 2  or more. A multiple number of opening holes may be provided to any locations in the course of the ventilation path. Though each of the opening holes is small, 300 mm2 or more can be ensured by summing thereof; for example, even if opening holes responding to a design request are used, it is possible to highly maintain the defogging property. 
     [Fourth Exemplary Embodiment of Ventilation Member] 
     Next, a fourth exemplary embodiment of the ventilation member will be described. 
       FIGS. 5A to 5C  are diagrams for illustrating a ventilation member  70 , which is the fourth exemplary embodiment. 
     Here,  FIG. 5A  is an elevational view in which the ventilation member  70  is viewed from an attaching side to the ventilation opening  9  side shown in  FIG. 1 , and  FIG. 5B  is a diagram showing a VB-VB cross section of the ventilation member  70  shown in  FIG. 5A . Moreover,  FIG. 5C  is a diagram for illustrating a cross section of each location constituting the ventilation path  80 . 
     The fourth exemplary embodiment shown in  FIGS. 5A to 5C  includes characteristics in that final discharge ports when the water vapor is discharged are provided in many directions, and the ventilation path  80  is bent in plural directions to be branched. Note that description of matters similar to those of the first to third exemplary embodiments is omitted here. 
     The ventilation member  70  includes an attaching part  71  for attaching the ventilation member  70  to the ventilation opening  9  and for communicating the ventilation opening  9  with the ventilation path  80 . Moreover, the ventilation member  70  includes a bent-part housing  72  that forms the bent part bending from the first direction (P-direction) to plural directions (in  FIG. 5B , two directions of V-direction and U-direction) in the inner tube used as the ventilation path  80 . The ventilation member  70  forms, by the attaching part  71  and the bent-part housing  72 , the ventilation path  80  configured with an inlet-port side ventilation path  81  that is in communication with the ventilation opening  9  shown in  FIG. 1 , a bent-part inlet side  82  that follows the inlet-port side ventilation path  81  to be positioned ahead of bending constituting the bent part and has a wide-width cross section, and two discharge ports (a first discharge port  83 , a second discharge port  84 ) that follow the bent-part inlet side  82  and is positioned behind bending of the bent part. Note that the discharge ports may be increased further, to thereby provide a third and a fourth discharge ports. 
     As shown in  FIG. 5C , the cross section of the inlet-port side ventilation path  81  (the surface orthogonal to the first direction (P-direction) on the upstream side of the bent part) has, similar to the inlet-port side ventilation path  21  in the first exemplary embodiment, a circular shape with an inner diameter T 1  and has a cross-sectional area S 1 . Moreover, the cross section of the bent-part inlet side  82  (the surface orthogonal to the first direction (P-direction) on the bent-part inlet side) has a square shape with a side T 5 , which is longer than T 1 , the cross-sectional area of the cross section being S 2 ′″. Hereinafter, for convenience of description, this S 2 ′″ will be described as S 2 . Further, the opening surfaces corresponding to the outlet side of the bent part are surfaces orthogonal to the U-direction and the V-direction on the downstream side of the bent part, namely, the first discharge port  83  and the second discharge port  84 , each of which is T 5 ×T 6  individually. By summing thereof and doubling here, the total cross-sectional area, which is summed cross-sectional areas, is S 3 . Note that, to simplifying the description, the same sign as “S 3 ” used in the first to third exemplary embodiments is also used here. Since the length T 6  related to the thickness in the depth direction (P-direction) can ensure a sufficient cross section due to the plural discharge ports, and therefore, it is possible to make individual T 6  short, as 10 mm or less. 
     Then, in the exemplary embodiment, similar to the first to third exemplary embodiments, all of the cross-sectional areas S 1 , S 2 , and the total cross-sectional area S 3  of the ventilation path  80  is 300 mm 3  or more. In other words, the ventilation member  70  forms the ventilation path that is in communication with the ventilation opening  9  and is bent, and is configured to maintain the minimum cross-sectional area of at least 300 mm 2  or more to the terminal end of the ventilation path including the bent part. Further, relations between the opening areas (cross-sectional area S 1 &lt;cross-sectional area S 2 , cross-sectional area S 1 ≦cross-sectional area S 3 ) are similar to those in the first to third exemplary embodiments. The ventilation path  80  being a through hole is also similar to the first to third exemplary embodiments. 
     In this manner, in the fourth exemplary embodiment, the plural opening holes were configured by providing the first discharge port  83  and the second discharge port  84  as the plural discharge ports. Then, the sum of the hole areas of the plural opening holes is 300 mm 2  or more. In this manner, by forming the discharge port at the terminal end by use of one side (here, T 5 ) of the bent-part inlet side  82  forming the bent part of the ventilation member  70 , and further, by providing the plural discharge ports, even if the length in the depth direction (first direction, P-direction) is made shorter than the length in the first direction when the cross section constituting the cross-sectional area S 1  is rotated 90°, it becomes possible to maintain good defogging property. 
     EXAMPLES 
     Subsequently, the ventilation member  10  ( 30 ,  50 ,  70 ) according to the present invention will be described in more detail by use of examples. Note that the present invention is not limited to the following examples. 
     Example 1 
     After humidity control and water injection are performed as described below to the vehicular lamp  1  including the ventilation opening  9 , the ventilation member  10  was attached to the ventilation opening  9 , and then fogging reduction rate was measured. 
     In this example, as the ventilation member  10 , a ventilation member  10  in a tubular shape including the bent part, with the inner diameter of 40 mm and the cross-sectional area of the ventilation path  20  of 1257 mm 2  was used. In other words, the ventilation member  10  used in this example has the cross-sectional area of 1257 mm 2  from one end of the ventilation path to the other end of the ventilation path including the bent part. 
     Moreover, as the vehicular lamp  1 , a head lamp for a medium-sized vehicle with an internal volume of 6900 cc (HL of a 2011 model Genesis Coupé manufactured by Hyundai Mobis Ltd.) was used. 
     (Humidity Control) 
     The vehicular lamp  1  including the ventilation opening  9  was left in a hot-dry condition (temperature: 80±2° C., relative humidity (RH): 10%) for 2 hours. Subsequently, while the ventilation opening  9  and the like were left open (without attaching the ventilation member  10 ), the vehicular lamp  1  was left in an ordinary temperature and pressure condition (temperature: 15° C. to 35° C., RH: 45% to 75%) for 1 hour. Thereafter, while the ventilation opening  9  was left open, the vehicular lamp  1  was left in a humidity control condition (temperature: 38° C., RH: 70%) for 1 hour, to thereby control the humidity in the housing interior  8  of the vehicular lamp  1 . 
     (Water Injection) 
     To the ventilation opening  9  of the vehicular lamp  1  immediately after the above-described humidity control was performed thereon, the ventilation member  10  was attached. Then, after lighting for 20 minutes, the vehicular lamp  1  was turned off. 
     Thereafter, by use of a hose with an internal diameter of 19 mm, water injection to the vehicular lamp  1  in a turn-off state was conducted from the front side of the lens  3  for 3 minutes. Note that water of 10±2° C. water temperature was used while setting the water pressure at 100±20 kPa. Moreover, water injection was conducted while the tip of the hose was in a state being separated 10 cm from the lens  3  of the vehicular lamp  1  and water injection angle was changed from the vertical direction (90° upward with respect to the horizontal direction) to 30° upward with respect to the horizontal direction. 
     (Measurement of Fogging Reduction Rate) 
     Subsequently, after lighting the vehicular lamp  1  for 10 minutes, the state of the lens  3  was observed until being defogged while the vehicular lamp  1  remained lighted, and thereby the fogging reduction rate of the lens  3  was measured. 
     Note that, in this example, “fogging reduction rate (%)” represents an elimination amount of the fog of the lens  3  after the elapse of a predetermined time after lighting the vehicular lamp  1  for 10 minutes. In this case, the fogging state of the lens  3  at the point of time when the vehicular lamp  1  has been lighted for 10 minutes (elapsed time is 0 minute) is assumed to be the fogging reduction rate of 0%. For example, the fogging reduction rate of 50% refers to the state in which the fog of the lens  3  is eliminated by half as compared to the state at the point of time when the vehicular lamp  1  has been lighted for 10 minutes (elapsed time is 0 minute). Moreover, the fogging reduction rate of 100% indicates the state in which all the fog of the lens  3  is eliminated (the state in which the fog does not occur on the lens  3  at all). 
     Usually, in the lamp, such as the vehicular lamp  1 , it is possible to use the lamp without any concern for influence of the fog of the lens  3  if the fogging reduction rate is 80% or more. 
     In this example, the fogging reduction rate was visually measured by observing the lens  3  of the vehicular lamp  1  from the front side (from the outside of the vehicular lamp  1 ) at predetermined time intervals. 
     Note that, other than the measurement by visual observation, the fogging reduction rate may be calculated by, for example, photographing the lens  3  at predetermined time intervals and applying image processing on the photographed image. 
     Examples 2, 3 and Comparative Examples 1, 2 
     Other than changing the inner diameter of the ventilation member  10  to be attached to the ventilation opening  9  of the vehicular lamp  1  and the cross-sectional area of the ventilation path, measurement of the fogging reduction rate of the lens  3  in the vehicular lamp  1  was conducted in a similar manner as Example 1. 
     Here, in Example 2, a ventilation member  10  in a tubular shape with the inner diameter of 30 mm and the cross-sectional area of 707 mm 2  was used, and, in Example 3, a ventilation member  10  in a tubular shape with the inner diameter of 20 mm and the cross-sectional area of 314 mm 2  was used. Moreover, in Comparative example 1, a ventilation member  10  in a tubular shape with the inner diameter of 15 mm and the cross-sectional area of 177 mm 2  was used, and, in Comparative example 2, a ventilation member  10  in a tubular shape with the inner diameter of 10 mm and the cross-sectional area of 79 mm 2  was used. 
     Comparative Example 3 
     Other than providing three ventilation openings  9  to the vehicular lamp  1  and changing the ventilation member  10  to be attached to each ventilation opening  9 , measurement of the fogging reduction rate of the lens  3  in the vehicular lamp  1  was conducted in a similar manner as Example 1. 
     As each ventilation member  10  to be attached to the ventilation opening  9 , a rubber ventilation member  10  in a tubular shape with the inner diameter of 8.5 mm and the cross-sectional area of 57 mm 2  was used, the ventilation member  10  including a bent part and a ventilation path filled with a porous sponge. Note that, in Comparative example 3, the sum of the cross-sectional areas of the three ventilation members  10  is 171 mm 2 . 
     [Evaluation of Fogging Reduction Rate] 
       FIG. 6  is a diagram showing measurement results of fogging reduction rates in Examples 1 to 3 and Comparative examples 1 to 3, and more specifically, a diagram showing changes over time in the fogging reduction rate measured in Examples 1 to 3 and Comparative examples 1 to 3. 
     As shown in  FIG. 6 , in Examples 1 to 3, the fogging reduction rate of the lens  3  is 80% or more within 5 minutes of elapsed time. 
     In other words, in the vehicular lamp  1  using the ventilation member  10  of Examples 1 to 3, it was confirmed that, even if fogging occurred on the lens  3 , fogging was able to be eliminated to the extent that no influence was exerted on use in a short time, such as within 5 minutes. 
     In contrast thereto, in Comparative examples 1 to 3, it took more than 5 minutes to obtain the fogging reduction rate of lens  3  of 80% or more; therefore, it was confirmed that a longer time was needed to eliminate the fogging of the lens  3  as compared to Examples 1 to 3. 
     The elapsed time of 5 minutes is the time derived by the inventor and the like as a criterion about occurrence of trouble as a lamp used for a vehicle. 
     Moreover, from another standpoint, as shown in  FIG. 6 , in Examples 1 to 3, an increasing rate of the fogging reduction rate (namely, the slope of the graph shown in  FIG. 6 ) in an early stage of elapsed time is significantly large as compared to Comparative examples 1 to 3. 
     In other words, it was confirmed that, by configuring the ventilation member  10  to maintain the minimum cross-sectional area of at least 300 mm 2  or more to the terminal end of including the bent part, the fogging of the lens  3  was able to be quickly eliminated as compared to the case where the minimum cross-sectional area of the ventilation path was less than 300 mm 2 . 
     Subsequently, when Examples 1 to 3 were compared with one another, it was confirmed that, in Examples 1 and 2, the fogging reduction rate was able to be 80% or more in a shorter time as compared to Example 3. Moreover, when Examples 1 and 2 were compared with each other, despite the larger cross-sectional area of the ventilation path  20  in Example 1 as compared to Example 2, there was little difference in the fogging reduction rate. 
     Consequently, for obtaining good defogging property while suppressing infiltration of foreign substances into the housing interior  8  of the vehicular lamp  1  via the ventilation member  10  and suppressing upsizing of the ventilation member  10 , it was confirmed that the minimum cross-sectional area of the ventilation member  10  was preferably of the order of 700 mm 2 . 
     Moreover, though illustration is omitted, when humidity control and water injection were performed and the vehicular lamp  1  was lighted for 10 minutes in a similar manner as Example 1, except for using the ventilation member  10  with the inner diameter of 60 mm and the cross-sectional area of 2826 mm 2 , it was confirmed that the fogging did not occur on the lens  3  (the fogging reduction rate is 100% in the elapsed time of 0 minute). 
     Note that, in the above-described Examples 1 to 3, the ventilation member  10  in a tubular shape including the bent part was used. However, as long as the ventilation member  10  includes the bent part and the minimum cross-sectional area of the ventilation path  20  (if the ventilation path is branched, the sum of the minimum cross-sectional areas of the plural ventilation paths) is at least 300 mm 2  or more, regardless of the shape thereof, for example, even with the shape of the ventilation member  30 ,  50  or  70  shown in  FIGS. 3A and 3B  to  FIGS. 5A to 5C , needless to say, the same result as those shown in  FIG. 6  can be obtained. 
     As described in detail above, according to the exemplary embodiments, by making the indexes of elapsed time and fogging reduction rate appropriate, it was possible to obtain good defogging property of various types of lamps including the bending ventilation path ( 20 ,  40 ,  60 ,  80 ). Particularly, in the exemplary embodiments, as the index of the elapsed time and the fogging reduction rate, the fogging reduction rate of 80% or more within the elapse time of 5 minutes is adopted. Then, by keeping the minimum cross-sectional area capable of maintaining the index to the terminal end of the ventilation path ( 20 ,  40 ,  60 ,  80 ) including the bent part, even in the case where the bending ventilation path ( 20 ,  40 ,  60 ,  80 ) is formed as described above, excellent defogging property can be achieved. 
     Moreover, in the exemplary embodiments, in various types of lamps including the bending ventilation path ( 20 ,  40 ,  60 ,  80 ), a predetermined cross-sectional area is maintained to the terminal end of the bending ventilation path ( 20 ,  40 ,  60 ,  80 ), and thereby, the good defogging property of the vehicular lamp  1  is provided. Particularly, in the exemplary embodiments, as the predetermined cross-sectional area, the minimum cross-sectional area of 300 mm 2  or more is maintained to the terminal end of the ventilation path ( 20 ,  40 ,  60 ,  80 ) including the bent part. Particularly, in recent years, improvement in quality of various kinds of lamps is called for and further improvement of the defogging property is demanded; if the improvements are to be achieved by the hollow ventilation member, there is significance in that the cross-sectional area of the opening is 300 mm 2  or more. 
     While the cross-sectional area of the opening is extended, it is required to bend the hollow ventilation member for ensuring the dust-proofing and waterproofing property. The tubular structure configured with the circular cross section of 300 mm 2  or more has a diameter of about 20 mm; if the tubular structure is directly bent, protrusion by the bent part alone becomes larger than 20 mm. On the depth side of the vehicular lamp  1 , for example, an engine room or the like exists and various kinds of appliances, such as an electronic control unit (ECU), and the like are gathered, and accordingly, it is not preferable that the tubular structure is directly protruded because of space problems. According to the exemplary embodiments, it becomes possible to bend the ventilation path ( 20 ,  40 ,  60 ,  80 ) at a narrow portion thereof while maintaining a sufficient cross-sectional area throughout the ventilation path. 
     REFERENCE SIGNS LIST 
     
         
           1  Vehicular lamp 
           2  Housing 
           3  Lens 
           8  Housing interior 
           9  Ventilation opening 
           10 ,  30 ,  50 ,  70  Ventilation member 
           20 ,  40 ,  60 ,  80  Ventilation path