具体实施方式：
[0060]A ventilation housing of a first aspect of the present disclosure is a ventilation housing including:
[0061]a housing; and
[0062]a ventilation assembly, wherein
[0063]the housing includes a tubular projection extending to project from an outer surface of the housing and internally having a first space communicating the inside and the outside of the housing,
[0064]the ventilation assembly includes:[0065]an internal member being a tubular body having an opening at a first end portion and an opening at a second end portion;[0066]a gas-permeable membrane covering the opening at the first end portion of the internal member; and[0067]an external member being a tubular body having a bottom, the external member being joined to the internal member with the internal member inserted in the interior of the external member from the first end portion side,
[0068]the ventilation assembly is fixed to the projection with the projection inserted in the opening at the second end portion of the internal member to make an inner peripheral surface of the internal member and an outer peripheral surface of the projection abut each other,
[0069]the ventilation assembly has a second space serving as a ventilation path connecting the gas-permeable membrane and the outside of the ventilation assembly in at least one selected from the inside of the internal member, the inside of the external member, and an interspace between the internal member and the external member joined together,
[0070]a height H1 of the internal member is 6.0 mm or more and 10 mm or less, and
[0071]a ratio H1/H2 of the height H1 of the internal member to a height H2 of the projection is 1.00 or more and 1.70 or less.
[0072]According to a second aspect of the present disclosure, in the ventilation housing of the first aspect,
[0073]a ratio S2min/S1 between an area S1 of a cross-section of the first space taken along a plane perpendicular to a central axis of the projection and a smallest total area S2min determined by comparison of values of different total areas determined at different distances from the gas-permeable membrane is 1.0 or more, the total areas each being determined for a cross-section(s) of the second space taken along a plane perpendicular to a ventilation direction in the ventilation path, the cross-section(s) being located at a certain distance from the gas-permeable membrane.
[0074]According to a third aspect of the present disclosure, in the ventilation housing of the first or second aspect, a ratio S2out/S1 between an area S1 of a cross-section of the first space taken along a plane perpendicular to a central axis of the projection and a total area S2out of a plane consisting of a cross-section(s) of the second space taken at a position(s) where the second space is the narrowest when the second space is observed from the second end portion side along a central axis of the ventilation assembly is 1.0 or more.
[0075]According to a fourth aspect of the present disclosure, in the ventilation housing of any one of the first to third aspects, when the ventilation assembly is observed in a direction perpendicular to a central axis of the ventilation assembly, a length of a portion of the internal member in a direction along the central axis is 6.0 mm or more and 8.0 mm or less, the portion being covered by the external member.
[0076]According to a fifth aspect of the present disclosure, in the ventilation housing of any one of the first to fourth aspects,
[0077]the external member and/or the internal member has a locking mechanism detachably joining the external member and the internal member together.
[0078]Embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. The following description is not intended to limit the present invention to particular embodiments.
First Embodiment
[0079]FIGS. 1A and 1B show a ventilation assembly 1A of a first embodiment. FIG. 1B shows a cross-section B-B of the ventilation assembly 1A shown in FIG. 1A. FIG. 1A shows a cross-section A-O-A of the ventilation assembly 1A shown in FIG. 1B. “O” in FIG. 1B indicates the central axis of the ventilation assembly 1A. FIGS. 1A and 1B show a state where the ventilation assembly 1A is fixed to a projection 52 of a housing 51, in other words, the vicinity of the projection 52 of the housing 51 in a ventilation housing including the ventilation assembly 1A fixed to the projection 52. FIG. 2 shows an exploded perspective view of the ventilation assembly 1A shown in FIGS. 1A and 1B. As shown in FIGS. 1A, 1B, and 2, the ventilation assembly 1A is fixed to the tubular projection 52 extending to project from an outer surface 53 of the housing 51 and internally having a first space 59 communicating the inside and the outside of the housing 51.
[0080]The ventilation assembly 1A includes an internal member 2, a gas-permeable membrane 3, and an external member 4. The internal member 2 is a tubular body having an opening 12A at an end portion 11A and an opening 12B at an end portion 11B that is opposite to the end portion 11A. The internal member 2 has an open tubular structure in which both end portions have openings. The gas-permeable membrane 3 is disposed at the one end portion 11A of the internal member 2 so as to cover the opening 12A at the end portion 11A. The external member 4 is a tubular body having a bottom. The external member 4 has a closed tubular structure in which one end portion 42 has an opening and the other end portion has a closed opening closed by a bottom portion 32. The external member 4 is joined to the internal member 2 with the internal member 2 inserted in the interior of the external member 4 from the end portion 11A side where the gas-permeable membrane 3 is disposed. Here, the interior of the external member 4 refers to a space surrounded by the opening of the external member 4 and an inner peripheral surface 31. The external member 4 covers the gas-permeable membrane 3 so as to function as a cover that protects the gas-permeable membrane 3 from foreign matters such as dust and water coming from the outside.
[0081]The ventilation assembly 1A has a second space 5 serving as a ventilation path connecting the gas-permeable membrane 3 and the outside of the ventilation assembly 1A. The ventilation assembly 1A has a space 5a, which is a part of the second space 5, between an outer peripheral surface 40 of the external member 4 joined to the internal member 2 and an inner peripheral surface 13 of the internal member 2. The ventilation assembly 1A also has the space 5a between the internal member 2 and the external member 4 joined together, more specifically, between the inner peripheral surface 31 of the external member 4 and an outer peripheral surface 19 of the internal member 2. In the ventilation assembly 1A, an inner side 33 of the bottom portion 32 of the external member 4 and the gas-permeable membrane 3 are spaced apart from each other. The ventilation assembly 1A has a space 5b, which is a part of the second space 5, between the inner side 33 and the gas-permeable membrane 3 spaced apart from each other. The term “ventilation path” refers to a route through which gas can move between the gas-permeable membrane and the outside of the ventilation assembly. The term “ventilation path” refers to, for example, a gas flow route allowing air having permeated through the gas-permeable membrane 3 and reached the space 5b to pass through the space 5b and then the space 5a and eventually reach the outside of the ventilation assembly 1A. Therefore, such a space as the space 5a can be a “ventilation path” not only when located between the internal member 2 and the external member 4 joined together but also when located inside the internal member 2 or the external member 4. It should be noted that the ventilation path is determined for the ventilation assembly obtained when the internal member 2 is inserted as deep in the external member 4 as possible.
[0082]The ventilation assembly 1A is fixed to the projection 52 of the housing 51 with the projection 52 inserted in the internal member 2 through the opening 12B at the other end portion 11B of the internal member 2 to make the inner peripheral surface 13 of the internal member 2 and an outer peripheral surface 58 of the projection 52 abut each other. The projection 52 is inserted in a through hole 14 of the internal member 2 to fix the ventilation assembly 1A. The through hole 14 is a space connecting the end portions 11A and 11B and surrounded by the inner peripheral surface 13 of the internal member 2. In a ventilation housing including the ventilation assembly 1A fixed to the projection 52, ventilation between the inside and the outside of the housing 51 can be ensured through the first space 59 in the interior of the projection 52, the through hole 14 of the internal member 2, the gas-permeable membrane 3, and the second space 5.
[0083]A thickness T1 of the internal member 2 may be 1.0 mm or more and 3.0 mm or less, the thickness T1 being the distance between the inner peripheral surface 13 and the outer peripheral surface 19. The lower limit of the thickness T1 may be 1.1 mm or more, 1.2 mm or more, or even 1.3 mm or more. The upper limit of the thickness T1 may be 2.9 mm or less, 2.8 mm or less, or even 2.7 mm or less. The internal member 2 having a thickness T1 within these ranges ensures sufficient strength of the internal member 2 while allowing a reduction in the height of the ventilation assembly 1A. For example, breaking, tearing, and the like of the internal member 2 can be prevented at the time of joining the external member 4 to the internal member 2. It should be noted that the thickness T1 is determined for the internal member 2 in which the projection 52 has not been inserted.
[0084]The internal member 2 of the first embodiment has a thin portion 15 having a decreased thickness T1 and extending from the end portion 11B from which the projection 52 is inserted at the time of fixation of the ventilation assembly 1A to a given height in the direction along the central axis O. Moreover, the internal member 2 has a step 16 at the boundary between the thin portion 15 and the rest of the internal member 2. The step 16 is located farther from the outer surface 53 of the housing 51 than the end portion 42 of the external member 4 on the opening side is (the step 16 is located on the upper side of the ventilation assembly 1A with respect to the end portion 42). However, the position of the step 16 is not limited to this example. When the internal member 2 has the thin portion 15, it is easier to insert the projection 52 of the housing 51 in the ventilation assembly 1A. This effect is particularly advantageous when the internal member 2 has a small inner diameter, for example, due to a reduction in height, in other words, when it is difficult for the end portion 11B of the internal member 2 to stretch at the time of insertion of the projection 52. The internal member 2 does not have the thin portion 15 on the end portion 11A side where the gas-permeable membrane 3 is disposed, and that can prevent an inclination of the external member 4 and the internal member 2 to each other at the time of joining the members 2 and 4 together and an inclination of the internal member 2 at the time of inserting the projection 52 of the housing 51. This effect is particularly advantageous when the internal member 2 has a small thickness T1. In the example shown in FIGS. 1A, 1B, and 2, the peripheral surface of the thin portion 15 and the outer peripheral surface 19 are connected at the step 16 by a plane perpendicular to the central axis O. The plane connecting the peripheral surface of the thin portion 15 and the outer peripheral surface 19 at the step 16 may be inclined to the direction perpendicular to the central axis O.
[0085]A height H1 of the internal member 2 is 6.0 mm or more and 10 mm or less, the height H1 being the distance between the end portions 11A and 11B of the internal member 2 in the direction along the central axis O. The upper limit of the height H1 may be 9.5 mm or less, 9.0 mm or less, or even 8.5 mm or less. The lower limit of the height H1 may be 6.5 mm or more, 7.0 mm or more, or even 7.5 mm or more. Because the height H1 is in these ranges, the housing 51 exhibits excellent moisture permeation performance, compared to conventional ones. The central axis O of the ventilation assembly 1A is, more specifically, the central axis of the internal member 2. The central axis of the projection 52 commonly coincides with the central axis O of the ventilation assembly 1A.
[0086]The internal member 2 and the projection 52 of the first embodiment are each in the shape of a cylinder. Because the material of the internal member 2 is commonly an elastic body, the inner peripheral surface 13 of the internal member 2 commonly has a diameter equal to or smaller than the diameter of the outer peripheral surface 58 of the projection 52. It should be noted that the elastic modulus of the elastic body forming the internal member 2 and/or the diameter of the inner peripheral surface 13 of the internal member 2 can be controlled, for example, in consideration of ease of insertion of the projection 52 into the internal member 2, sealing properties between the housing 51 and the ventilation assembly 1A, and the like. The shape of the internal member 2 which is a tubular body and the shape of the tubular projection 52 are not limited to a cylinder.
[0087]The inner diameter of the cylindrical internal member 2 is, for example, 6.0 to 8.0 mm. Half the value obtained by subtracting the inner diameter of the cylindrical internal member 2 from the outer diameter thereof corresponds to the thickness T1.
[0088]The external member 4 is in the shape of a cylinder having a bottom. When the external member 4 is observed along the central axis O, a portion of a peripheral wall 37 of the external member 4 projects toward the interior of the external member 4, more specifically, toward the central axis O. As the peripheral wall 37 projects in the above manner, the external member 4 includes, on the outer peripheral surface 40, a plurality of grooves 41 (41A, 41B, 41C, and 41D) extending along the central axis O. In the example shown in FIGS. 1A, 1B, and 2, the grooves 41 are provided at regular intervals in the peripheral direction of the external member 4 when observed along the central axis O, and the grooves 41 extend from the end portion 42 of the external member 4 on the opening side to the bottom portion 32. In the external member 4, the thickness of the peripheral wall 37 at each of groove 41 portions and that at each of portions other than the groove 41 portions are substantially uniform. However, the positions which are on the outer peripheral surface 40 and where the grooves 41 are provided, the intervals between the adjacent grooves 41, the directions in which the grooves 41 extend, and zones where the grooves 41 extend and which are present between the end portion 42 and the bottom portion 32 of the external member 4 are not limited to those in the above example. The thickness of the peripheral wall 37 at each groove 41 portion and that at each portion other than the groove 41 portions may be different.
[0089]At the groove 41 portions, the inner peripheral surface 31 of the external member 4 coincides with the peripheral surface of a virtual column A having the central axis O as its central axis. The internal member 2 and the external member 4 are joined to each other by making the outer peripheral surface 19 and the inner peripheral surface 31 at the groove 41 portions abut each other. Because the material of the internal member 2 is commonly an elastic body, the virtual column A commonly has a diameter equal to or smaller than the diameter of the outer peripheral surface 19. Gaps 6A between the inner peripheral surface 31 of the external member 4 at the portions other than the groove 41 portions and the outer peripheral surface 19 of the internal member 2 are each a part of the space 5a. In the example shown in FIGS. 1A, 1B, and 2, the outer peripheral surface 19 of the internal member 2 does not have a protruding portion projecting from the surface 19. The outer peripheral surface 19 forms the entire peripheral surface of the column in the peripheral direction of the surface 19. In the example shown in FIGS. 1A, 1B, and 2, the number of the gaps 6A is four. In the first embodiment, the number of the gaps 6A is required to be one or two or more and may be two to eight or even three to six.
[0090]When the ventilation assembly 1A is observed in the direction perpendicular to the central axis O, a length D8 of a portion of the internal member 2 in the direction along the central axis O, the portion being covered by the external member 4, may be, for example, 3.5 mm or more and 9.5 mm or less or may be 6.0 mm or more and 8.0 mm or less. The lower limit of the length D8 may be 4.0 mm or more, 4.5 mm or more, or even 5.0 mm or more. The upper limit of the length D8 may be 9.0 mm or less, 8.5 mm or less, or even 8.0 mm or less. When the length D8 is in these ranges, the internal member 2 and the external member 4 are more reliably joined together and the external member 4 is unlikely to drop from the internal member 2, for example, at the time of fixation of the ventilation assembly 1A to the projection 52 of the housing 51. Moreover, sufficient moisture permeation performance can be ensured. Furthermore, entry of foreign matters such as dust and water from the outside of the ventilation assembly 1A into the second space 5 can be reduced. It should be noted that the length D8 is determined when the internal member 2 is inserted as deep in the external member 4 as possible.
[0091]For the internal member 2 and the external member 4 joined by making them abut each other, a length (inside-outside contact length) D4 in the direction along the central axis O is, for example, 4.0 to 8.0 mm, the length D4 of a portion where the internal member 2 and the external member 4 abut each other, more specifically, the length D4 of a portion where the outer peripheral surface 19 of the internal member 2 and the inner peripheral surface 31 of the external member 4 at the groove 41 portion abut each other. When the length D4 is in these ranges, the internal member 2 and the external member 4 are more reliably joined together and the external member 4 is unlikely to drop from the internal member 2, for example, at the time of fixation of the ventilation assembly 1A to the projection 52 of the housing 51. In the example shown in FIGS. 1A, 1B, and 2, a portion of the internal member 2, the portion abutting the inner peripheral surface 31 of the external member 4, extends in the direction along the central axis O from the end portion 11A where the gas-permeable membrane 3 is disposed to the step 16, in other words, to the lower end of the portion other than the thin portion 15. The portion of the internal member 2, the portion abutting the inner peripheral surface 31, spans the entire outer peripheral surface 19 in the peripheral direction.
[0092]A distance D6 in the direction along the central axis O and between the end portion (lower end) 42 on the opening side of the external member 4 and the end portion 11B of the internal member 2 is, for example, 0 to 3.0 mm, and may be 0.2 to 2.0 mm or even 0.4 to 1.0 mm. When the distance D6 is in these ranges, the internal member 2 and the external member 4 are more firmly joined together. It should be noted that the distance D6 is determined when the internal member 2 is inserted as deep in the external member 4 as possible.
[0093]The external member 4 includes two or more second projecting portions 34 projecting from the inner side 33 of the bottom portion 32 in the direction along the central axis O. Each of the second projecting portions 34 also projects from the inner peripheral surface 31 of the external member 4 toward the central axis O when observed along the central axis O. In a state where the external member 4 and the internal member 2 are joined together, the inner side 33 of the bottom portion 32 of the external member 4 and the gas-permeable membrane 3 are kept spaced apart from each other by making the second projecting portions 34 and the end portion 11A of the internal member 2 abut each other. The second projecting portions 34 may be provided in such a manner that in a state where the external member 4 and the internal member 2 are joined together, the second projecting portions 34 abut the gas-permeable membrane 3 or abut both the internal member 2 and the gas-permeable membrane 3.
[0094]A height H3 of the ventilation assembly 1A is, for example, 6.0 mm or more and 12 mm or less, the height H3 being the distance between a virtual plane being perpendicular to the central axis O and passing through the lowermost point in the ventilation assembly 1A and a virtual plane being perpendicular to the central axis O and passing through the uppermost point in the ventilation assembly 1A. The upper limit of the height H3 may be 11 mm or less, 10.5 mm or less, or even 10 mm or less. The lower limit of the height H3 may be 6.5 mm or more, 7.0 mm or more, or even 7.5 mm or more. It should be noted that the height H3 is determined when the internal member 2 is inserted as deep in the external member 4 as possible. In the example shown in FIGS. 1A, 1B, and 2, the lowermost point is located at the end portion 11B of the internal member 2, and the uppermost point is located at an outer side 35 of the bottom portion 32 of the external member 4.
[0095]An area S1 of a cross-section of the first space 59 taken along a plane perpendicular to the central axis of the projection 52 may be 5 mm2 or more and 60 mm2 or less. The lower limit of the area S1 may be 10 mm2 or more, 12 mm2 or more, 14 mm2 or more, or even 16 mm2 or more. The upper limit of the area S1 may be 50 mm2 or less, 40 mm2 or less, 30 mm2 or less, or even 20 mm2 or less. The central axis of the projection 52 commonly coincides with the central axis O of the ventilation assembly 1A.
[0096]In a state where the ventilation assembly 1A is fixed to the projection 52 of the housing 51, a ratio S2min/S1 of an area S2min of a cross-section(s) of the second space 5 to the area S1 of the cross-section of the first space 59 is, for example, 0.8 or more. The lower limit of the ratio S2min/S1 may be 1.0 or more, 1.1 or more, 1.2 or more, 1.3 or more, or even 1.4 or more. The upper limit of the ratio S2min/S1 is, for example, 3.0 or less and may be 2.5 or less or even 2.0 or less. The ventilation assembly and the ventilation housing having a ratio S2min/S1 in the above range are excellent in ventilation properties and/or moisture permeation performance. The area S1 is the area of the cross-section of the first space 59 taken along a plane perpendicular to the central axis of the projection 52. The area S2min is a smallest total area determined by comparison of values of different total areas determined at different distances from the gas-permeable membrane is 1.0 or more, the total areas each being determined for a cross-section(s) of the second space 5 taken along a plane perpendicular to a ventilation direction in the ventilation path, the cross-section(s) being located at a certain distance from the gas-permeable membrane. The term “ventilation path” refers to a path through which gas can move between the gas-permeable membrane and the outside of the ventilation assembly. The term “ventilation direction” refers to the direction in which gas should go at a particular position in the second space regarded as the ventilation path. Thus, the ventilation direction varies depending on the position in the second space. The expression “total area determined for cross-sections located at a certain distance from the gas-permeable membrane” is based on the viewpoint that the sum of areas of cross-sections of the second space 5 taken at a group of positions to which the distance (in the case of a point-symmetric gas-permeable membrane, the distance from the center of the gas-permeable membrane) from the gas-permeable membrane is the same is regarded as a total area. Of different total areas determined at different distances in such a manner, a total area of a cross-section(s) taken at a position(s) where the total area value is the smallest is the area S2min. The area S2min is determined when the internal member 2 is inserted as deep in the external member 4 as possible. In the example shown in FIGS. 1A, 1B, and 2, the cross-sections whose areas compose the area S2min are each surrounded by the second projecting portion 34, a peripherally end portion 46 of a portion which is included in the groove 41 and where the internal member 2 and the external member 4 abut each other, the inner side 33 of the bottom portion 32 of the external member 4, and the end portion 11A of the internal member 2 (refer to a cross-section 47 in FIG. 2). FIG. 2 shows a part of the cross-sections whose areas compose the area S2min (only the cross-section 47 located between one second projecting portion 34 and one end portion 46). Because the cross-sections whose areas compose the area S2min are present between four second projecting portions 34 and eight end portions 46, eight times the area of the cross-section 47 corresponds to the area S2min. The area S2min can be evaluated, for example, by a method described in EXAMPLES.
[0097]In a state where the ventilation assembly 1A is fixed to the projection 52 of the housing 51, a ratio S2out/S1 of an area S2out of a cross-section(s) of the second space 5 to the area S1 of the cross-section of the first space 59 is, for example, 0.8 or more, and may be 1.0 or more, 1.2 or more, 1.3 or more, 1.5 or more, 1.8 or more, 2.0 or more, or even 2.2 or more. The upper limit of the ratio S2out/S1 is, for example, 4.0 or less and may be 3.0 or less. The ventilation assembly and the ventilation housing having a ratio S2out/S1 in the above range are excellent in ventilation properties and/or moisture permeation performance. The area S2out is a total area of a plane consisting of a cross-section(s) of the second space 5 taken at a position(s) where the second space 5 within the observable range is the narrowest when the second space 5 is observed from the other end portion 11B side along the central axis of the ventilation assembly 1A. The area S2out is determined when the internal member 2 is inserted as deep in the external member 4 as possible. In the example shown in FIGS. 1A, 1B, and 2, the cross-sections whose areas compose the area S2out are each surrounded by the inner peripheral surface 31 of the external member 4 and the outer peripheral surface 19 of the internal member 2 (refer to a cross-section 48 in FIG. 1B). FIG. 1B shows a part of the cross-sections whose areas compose the area S2out (only the cross-section 48 located between a pair of the adjacent grooves 41C and 41D). Because the cross-sections whose areas compose the area S2out are located between the four grooves 41, four times the area of the cross-section 48 corresponds to the area S2out. The area S2out can be evaluated, for example, by a method described in EXAMPLES.
[0098]Resins, such as polyamide, polycarbonate, and polybutylene terephthalate, having a relatively high hygroscopicity are sometimes included in housings of electrical components and electronic devices. A housing including any of such resins absorbs surrounding water vapor. The absorbed water vapor is emitted by heat from a heat source inside the housing or heat from the outside, such as sunlight, and a portion of the emitted water vapor remains inside the housing. It is desirable that the water vapor remaining inside the housing be immediately discharged to the outside of the housing through the projection 52 and the ventilation assembly 1A in order to prevent fogging inside the housing. The ventilation assembly and/or ventilation housing having excellent moisture permeation performance, for example, can reduce fogging inside the housing and promote removal of fogging inside the housing.
[0099]A height H2 of the projection 52 being the distance in the direction along the central axis O from the outer surface 53 of the housing 51 to the front end 54 of the projection 52 is, for example, 5.0 to 12 mm and may be 4.0 mm or more and 8.0 mm or less.
[0100]A ratio H1/H2 of the height H1 of the internal member 2 to the height H2 of the projection 52 is 1.00 or more and 1.70 or less. The lower limit of the ratio H1/H2 may be more than 1.00, 1.02 or more, 1.04 or more, 1.06 or more, 1.08 or more, or even 1.10 or more. The upper limit of the ratio H1/H2 may be 1.60 or less, 1.50 or less, 1.40 or less, 1.30 or less, 1.25 or less, 1.22 or less, 1.20 or less, 1.18 or less, 1.16 or less, or even 1.14 or less. The ventilation assembly and the ventilation housing having a ratio H1/H2 in the above range can effectively reduce dropping of the ventilation assembly from the projection of the housing. When the ventilation assembly 1A is used, the projection 52 is inserted in the ventilation assembly 1A through the opening 12B at the other end portion 11B of the internal member 2. The ratio H1/H2 is determined for the ventilation assembly 1A obtained when the projection 52 is inserted as deep in the internal member 2 as possible.
[0101]In the case where the internal member 2 is fixed to the projection 52, a distance D9 between the outer surface 53 of the housing 51 and the end portion 42 of the external member 4 on the opening side is, for example, 0.5 mm or more and 4.0 mm or less. In the case where the distance D9 is in this range, an appropriate gas permeation amount can be ensured while dropping of the ventilation assembly 1A from the projection 52 of the housing 51 is prevented. It should be noted that the distance D9 is determined when the internal member 2 is inserted as deep in the external member 4 as possible.
[0102]The gas-permeable membrane 3 is a membrane that allows gas (typically air) to permeate therethrough in its thickness direction and that prevents foreign matters from permeating therethrough. Therefore, the ventilation assembly 1A ensures ventilation between the inside and the outside of the housing 51 and can prevent entry of foreign matters such as dust, water, oil, and salt into the inside of the housing 51. In the first embodiment, the shape of the gas-permeable membrane 3 is a circle. However, the shape of the gas-permeable membrane 3 is not limited to a circle and can be selected according to the shape of a portion which is included in the internal member 2 and where the gas-permeable membrane 3 is disposed. The shape of the gas-permeable membrane 3 may be, for example, a polygon.
[0103]In the first embodiment, the gas-permeable membrane 3 is disposed on the end face of the end portion 11A of the internal member 2. However, in the ventilation assembly and the ventilation housing of the present invention, the position where the gas-permeable membrane 3 is disposed is not limited to the end face of the end portion 11A as long as the gas-permeable membrane 3 covers the opening 12A at the end portion 11A.
[0104]A woven fabric, non-woven fabric, mesh, or net formed of a resin or metal or a porous resin membrane can be used as the gas-permeable membrane 3. However, the gas-permeable membrane 3 is not limited as long as the gas-permeable membrane 3 allows gas to permeate therethrough and can prevent foreign matters such as liquid from permeating therethrough. In the first embodiment, the gas-permeable membrane 3 used is a laminate of a porous resin membrane and a gas-permeable reinforcing layer. The reinforcing layer can improve the strength of the gas-permeable membrane 3. The porous resin membrane is, for example, a porous body which is formed of a fluorine resin or polyolefin and which can be manufactured by a commonly-known stretching or extraction technique. Examples of the fluorine resin include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-ethylene copolymer. Examples of the monomer forming the polyolefin include ethylene, propylene, 4-methylpentene-1,1-butene, and a polyolefin that is a homopolymer or copolymer of any of these monomers can be used as the gas-permeable membrane 3. A porous nanofiber film including polyacrylonitrile, nylon, or polylactic acid may be used as the gas-permeable memb