Ventilation system

Abstract

Provided is a ventilation system in which a muffler is given a compact structure, sound muffling is ensured, and pressure loss in the muffler is minimized.　This ventilation system has a muffler placed partway along a ventilation path, and in the muffler, a sound-absorbing member surrounds a housing having a housing internal ventilation path extending from an entrance opening to an exit opening. The ventilation system is also provided with an upstream cylinder forming an upstream ventilation path on the upstream side of the entrance opening, a downstream cylinder forming a downstream ventilation path on the downstream side of the exit opening, a cylindrical first connecting section that is connected to the upstream cylinder and that links the upstream ventilation path and the entrance opening, and a cylindrical second connecting section that is connected to the downstream cylinder and that links the downstream ventilation path and the exit opening. The first connecting section and the second connecting section each have an opening part in the interior, and the cross-sectional size of the opening part in at least one section becomes smaller toward the housing internal ventilation path.

Description

Technical Field

[0001] The present invention relates to a ventilation system in which a muffler is arranged at an intermediate position in a ventilation path.

Background Art

[0002] In a configuration where a muffler is arranged at an intermediate position in a ventilation path, while ensuring the air permeability inside the muffler, it is required to sufficiently reduce the noise propagating in the ventilation path by the muffler.

[0003] In the ventilation system described in Patent Document 1, a box-shaped expansion part is provided in the middle of the ventilation path, and this expansion part constitutes a muffler (see FIG. 5). Specifically, inside the expansion part, a ventilation path (hereinafter, inner ventilation path) extending from the inlet to the outlet of the expansion part and a sound-absorbing member surrounding the inner ventilation path are arranged. Thereby, while ensuring the air permeability inside the expansion part, noise can be reduced inside the expansion part.

[0004] Further, in the muffler described in Patent Document 1, the ventilation path narrows at an intermediate position in the inner ventilation path and widens on the downstream side thereof (see FIG. 5). As a result, the flow velocity of the wind (airflow) flowing through the ventilation path becomes faster inside the inner ventilation path, making it easier for the effect of the sound-absorbing member to be exerted, and as a result, the noise reduction performance is improved.

[0005] Furthermore, when the size of the cross-section of the ventilation path suddenly changes at an intermediate position in the inner ventilation path, turbulent flow is generated at that location, and as a result, the pressure loss becomes relatively large. In view of this, in the muffler described in Patent Document 1, in order to suppress the pressure loss, the cross-sectional area of the inner ventilation path is gradually changed at the inlet-side end and the outlet-side end of the inner ventilation path. Specifically, the cross-sectional area is reduced as it moves away from the inlet or the outlet. In other words, the cross-sectional area of the inner ventilation path gradually increases as it approaches the inlet or the outlet.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, when the cross-sectional area of the inner ventilation passage is changed, the thickness of the sound-absorbing member surrounding the inner ventilation passage changes accordingly. Therefore, in the muffler described in Patent Document 1, the thickness of the sound-absorbing member is reduced near the inlet and the outlet of the expansion portion. Reducing the thickness of the sound-absorbing member in this way can reduce the sound absorption effect in the muffler. However, in the muffler described in Patent Document 1, if an attempt is made to ensure the thickness of the sound-absorbing member near the inlet and the outlet of the expansion portion, the entire muffler becomes larger. As a result, it is necessary to secure a wider installation space for the muffler.

[0008] The present invention has been made in view of the above circumstances, and solves the problems of the above prior art. Specifically, an object of the present invention is to provide a ventilation system that can ensure sound absorption while making the muffler have a compact structure and suppressing pressure loss in the ventilation passage.

MEANS FOR SOLVING THE PROBLEMS

[0009] To achieve the above object, the ventilation system of the present invention has the following configuration. [1] A ventilation system having a ventilation passage and a muffler disposed at an intermediate position of the ventilation passage, the muffler having an inlet opening and an outlet opening, the ventilation passage including a housing provided therein with a housing ventilation passage extending from the inlet opening to the outlet opening, and a sound-absorbing member disposed in the housing so as to surround the housing ventilation passage, the ventilation passage including an upstream cylindrical body forming an upstream ventilation passage on the upstream side of the inlet opening, a downstream cylindrical body forming a downstream ventilation passage on the downstream side of the outlet opening, a cylindrical first connection portion connected to the upstream cylindrical body to connect the upstream ventilation passage and the inlet opening, and a cylindrical second connection portion connected to the downstream cylindrical body to connect the downstream ventilation passage and the outlet opening, each of the first connection portion and the second connection portion having an opening therein, and the size of the cross section of the opening in at least one of the first connection portion and the second connection portion becoming smaller as it approaches the housing ventilation passage. [2] The ventilation system according to [1], wherein the size of the cross section of the opening in each of the first connection portion and the second connection portion becomes smaller as it approaches the housing ventilation passage. [3] The first connection portion is connected to the upstream cylindrical body by being inserted into the upstream cylindrical body, the second connection portion is connected to the downstream cylindrical body by being inserted into the downstream cylindrical body, each of the first connection portion and the second connection portion having an outer peripheral portion surrounding the opening, and at the tip portion of at least one of the connection portions, the wall thickness of the outer peripheral portion becoming smaller as it moves away from the housing. The ventilation system according to [1] or [2]. [4] The ventilation system according to [3], wherein at the tip portion of each of the first connection portion and the second connection portion, the wall thickness of the outer peripheral portion becomes smaller as it moves away from the housing. [5] The housing ventilation passage extends along a first direction, the inner peripheral surface of at least one of the connection portions being inclined with respect to the first direction, the inclination angle of the inner peripheral surface with respect to the first direction being 0.1 degrees or more and 45 degrees or less. The ventilation system according to any one of [1] to [4]. [6] The housing ventilation passage extends along a first direction, the first connection portion protruding from one end of the housing in the first direction, the second connection portion protruding from the other end of the housing in the first direction, each of the first connection portion and the second connection portion having an outer peripheral surface formed with irregularities along the first direction. The ventilation system according to any one of [1] to [5]. [7] The ventilation system according to [6], wherein in each of the first connection part and the second connection part, the outer diameter of the portion where the outer peripheral surface is convex becomes smaller as it moves away from the housing. [8] The ventilation system according to any one of [1] to [7], wherein the ventilation passage inside the housing extends along a first direction, and in a second direction intersecting the first direction and a third direction intersecting both the first direction and the second direction, the range where the inlet opening exists is different from the range where the outlet opening exists. [9] The ventilation system according to [8], wherein among the openings in at least one of the connection parts, the size of the cross section of the end on the side of the ventilation passage inside the housing is the same as the size of the opening adjacent to the end among the inlet opening and the outlet opening.

[10] The ventilation system according to any one of [1] to [9], wherein the first connection part and the second connection part are constituted by resin molded products.

[11] The ventilation system according to any one of [1] to

[10] , wherein the inner diameter of the end on the side of the ventilation passage inside the housing of the opening in each of the first connection part and the second connection part is 150 mm or less. [Effect of the Invention]

[0010] According to the present invention, among the first connection part and the second connection part, the size of the cross section of the opening in at least one of the connection parts becomes smaller as it approaches the ventilation passage inside the housing. As a result, without reducing the thickness of the sound absorption member inside the housing, the sound insulation performance is improved and the pressure loss in the ventilation passage is reduced. As a result, it is possible to secure sound insulation performance while making the silencer have a compact structure, and it is possible to suppress the pressure loss in the ventilation passage. [Brief Description of the Drawings]

[0011]

Figure 1

Figure 2

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Figure 14

Mode for Carrying Out the Invention

[0012] The ventilation system of the present invention will be described in detail below with reference to the preferred embodiments shown in the accompanying drawings. However, the following embodiments are merely examples given for the purpose of facilitating the understanding of the present invention and do not limit the present invention. That is, the present invention can be modified or improved from the following embodiments without departing from its gist.

[0013] In addition, the materials, shapes, etc. of each member used to implement the present invention can be arbitrarily determined according to the use of the present invention, the technical level at the time of implementing the present invention, etc. The present invention also includes equivalents thereof.

[0014] In addition, in this specification, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In addition, in this specification, "orthogonal", "perpendicular", and "parallel" shall include the range of errors allowed in the technical field to which the present invention pertains. For example, "orthogonal", "perpendicular", and "parallel" in this specification mean within a range of less than ±10° with respect to strict orthogonality, perpendicularity, or parallelism. The error from strict orthogonality or parallelism is preferably 5° or less, and more preferably 3° or less. In addition, in this specification, the meanings of "the same", "identical", "equal", and "uniform" may include the range of errors generally allowed in the technical field to which the present invention pertains. In addition, in this specification, the meanings of "all", "any", and "every" include not only the case of 100%, but also the range of errors generally allowed in the technical field to which the present invention pertains. For example, cases where it is 99% or more, 95% or more, or 90% or more may be included.

[0015] In addition, "noise reduction" in the present invention is a concept including both the meanings of sound insulation and sound absorption. Sound insulation means shielding sound, in other words, not allowing sound to pass through. Sound absorption means reducing reflected sound, and more simply put, absorbing sound (acoustics).

[0016] Also, hereinafter, three mutually orthogonal directions shall be referred to as the "XYZ directions". The X direction is the extending direction of the internal ventilation passage 26 described later and corresponds to the first direction of the present invention. The Z direction corresponds to the second direction of the present invention, and the Y direction corresponds to the third direction of the present invention. Also, hereinafter, the side closer to the exhaust port in the ventilation passage shall be referred to as the "downstream side", and the opposite side shall be referred to as the "upstream side".

[0017] [Configuration Example of the Ventilation System of the Present Invention] The configuration of the ventilation system 10 according to an embodiment of the present invention (hereinafter referred to as the present embodiment) will be described with reference to the drawings. Note that FIG. 3 is a view showing the upstream end face of the housing 20 provided in the muffler 14, and in the figure, an outlet opening 24 that does not appear on the upstream end face is shown by a dashed line.

[0018] The ventilation system 10 according to the present embodiment silences noise in the system while flowing an air current (wind) along a predetermined path. As shown in FIGS. 1 and 2, the ventilation system 10 includes a ventilation passage 12 and a muffler 14 disposed at an intermediate position in the ventilation passage 12.

[0019] The ventilation passage 12, excluding the expansion part described later, is constituted by a cylindrical body such as a hose or a duct. The cylindrical body may be a circular cylinder or a rectangular cylinder. Inside the ventilation passage 12, the air current (wind) sent from the non-air supply source flows toward the exhaust port located at the end of the ventilation passage 12.

[0020] The muffler 14 forms an expansion part in the ventilation passage 12. The expansion part is a part where the cross-sectional area of the internal space is enlarged compared to the part other than the expansion part of the ventilation passage 12 (hereinafter also referred to as the normal part). Here, the "cross-sectional area" corresponds to the size of the cross-section, and the cross-section is a cross-section with the direction in which the ventilation passage 12 extends, in other words, the first direction as the normal direction.

[0021] As shown in FIGS. 1 to 3, the silencer 14 includes a housing 20, a sound-absorbing member 30, a first connecting portion 40, and a second connecting portion 50. The silencer 14 silences the sound entering the housing 20 by resonance (acoustic resonance) in the housing 20 and sound absorption by the sound-absorbing member 30.

[0022] The housing 20 is a box-shaped or cylindrical hollow body having an outer wall. The outer wall of the housing 20 is a plate material with a relatively thin thickness, forming both ends in each of the XYZ directions of the housing 20. The material of the outer wall is not particularly limited, and for example, metal materials, resin materials, reinforced plastic materials, carbon fiber, etc. can be used.

[0023] Examples of the metal material include metal materials such as alloys such as aluminum, titanium, magnesium, tungsten, iron, steel, chromium, chromium molybdenum, nickel chromium molybdenum, copper, hot-dip galvanized steel sheet (Steel Galvanized Cold Commercial: SGCC), and stainless steel. Examples of the resin material include acrylic resin, polymethyl methacrylate, polycarbonate, polyamideimide, polyarylate, polyetherimide, polyacetal, polyether ether ketone, polyphenylene sulfide, polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyimide, ABS resin (acrylonitrile, flame-retardant ABS resin, butadiene, styrene copolymer synthetic resin), polypropylene, triacetyl cellulose (TAC: Triacetylcellulose), polypropylene (PP: Polypropylene), polyethylene (PE: Polyethylene), polystyrene (PS: Polystyrene), ASA (Acrylate Sthrene Acrylonitrile) resin, polyvinyl chloride (PVC: Polyvinyl Chloride) resin, and PLA (Polylactic Acid) resin. Examples of the reinforced plastic material include carbon fiber reinforced plastics (CFRP) and glass fiber reinforced plastics (GFRP). In addition, as the material of the outer wall of the housing 20, natural rubber, chloroprene rubber, butyl rubber, EPDM (ethylene propylene diene rubber), silicone rubber, and rubbers including cross-linked structures thereof can be further used.

[0024] Moreover, each part of the outer wall of the housing 20 may be made of the same material, or a part of the housing 20 may be made of a material different from that of its peripheral part. Alternatively, a part of the housing 20 may be made of the same type of material as its peripheral part, but have a different thickness (plate thickness) from the peripheral part.

[0025] As shown in FIG. 2, an inlet opening 22 is provided at the upstream end of the housing 20 in the X direction, and an outlet opening 24 is provided at the downstream end. The inlet opening 22 and the outlet opening 24 are circular holes penetrating the outer wall of the housing 20 in the X direction and communicating with the internal space of the housing 20. The contour shape of each of the inlet opening 22 and the outlet opening 24 is not limited to a circle, and may be, for example, a quadrilateral or a polygon with five or more sides.

[0026] The airflow in the ventilation passage 12 flows into the housing 20 from the upstream side of the housing 20 through the inlet opening 22 and flows out of the housing 20 through the outlet opening 24. That is, an internal ventilation passage 26 of the housing extending from the inlet opening 22 to the outlet opening 24 is formed inside the housing 20, and the internal ventilation passage 26 of the housing constitutes a part of the ventilation passage 12. The internal ventilation passage 26 of the housing extends linearly along the X direction (the first direction). Therefore, the airflow (wind) flows in the X direction inside the housing 20. In other words, the X direction corresponds to the ventilation direction inside the housing 20.

[0027] Note that the inlet opening 22 and the outlet opening 24 each extend perpendicularly to the outer wall of the housing 20 and are formed through the outer wall, having a length (depth) corresponding to the thickness of the outer wall. Also, in each of the inlet opening 22 and the outlet opening 24, the diameter (opening size) is uniform over the range from the upstream end to the downstream other end of each opening.

[0028] Also, in the present embodiment, as can be seen from FIGS. 2 and 3, the existence ranges of the inlet opening 22 and the outlet opening 24 in the Y direction and the Z direction overlap. Here, the existence range of each opening in the Y direction and the Z direction is the range in which each opening exists in the virtual plane (YZ plane) when each opening is projected onto the virtual plane having the X direction as the normal direction. By overlapping the existence ranges of the inlet opening 22 and the outlet opening 24 in this way, the ventilation in the housing 20 is improved, and air (wind) flows smoothly from the inlet opening 22 toward the outlet opening 24.

[0029] Note that in order to improve the ventilation in the housing 20, it is preferable that the inlet opening 22 and the outlet opening 24 have the same size and the existence ranges of the inlet opening 22 and the outlet opening 24 completely coincide. Here, the size of the opening means the area of the opening.

[0030] On the other hand, the sizes of the inlet opening 22 and the outlet opening 24 may be different from each other. In this case, it is preferable that the existence range of the smaller-sized opening is contained inside the existence range of the larger-sized opening. Also, the existence range of the inlet opening 22 and the existence range of the outlet opening 24 may partially overlap. Alternatively, due to design constraints of the ventilation path or the like, in the Y direction and the Z direction, the existence range of the inlet opening 22 and the existence range of the outlet opening 24 may not overlap and may be separated (shifted) from each other. In this case, the ventilation path 26 in the housing is not limited to extending linearly and may be bent at an intermediate position.

[0031] Further, each of the inlet opening 22 and the outlet opening 24 is provided in the Z direction at the central portion of the housing 20 or at a portion closer to the end of the housing 20. That is, in the direction intersecting the housing internal ventilation passage 26, the inlet opening 22 and the outlet opening 24 may be provided at the central portion of the housing 20, or may be provided at a position offset toward the end side of the housing 20.

[0032] As shown in FIG. 2, the sound absorbing member 30 is disposed in the housing 20 while surrounding the housing internal ventilation passage 26. It absorbs the sound that has entered the housing 20, particularly high-frequency sound. As the sound absorbing member 30, a sound absorbing material that converts sound energy into heat energy for sound absorption can be appropriately used. The sound absorbing material is formed into a cylindrical or rectangular tube shape surrounding the entire circumference of the housing internal ventilation passage 26 and is disposed in the housing 20.

[0033] Examples of the sound absorbing material include porous sound absorbing materials such as foams, foam materials, and non-woven fabric-based sound absorbing materials. Specific examples of the foam and the foam material include foam urethane foams such as Carmflex of Inoac Corporation and urethane foam manufactured by Kousha Co., Ltd., soft urethane foam, ceramic particle sintered materials, phenol foam, melamine foam, and polyamide foam. Specific examples of the non-woven fabric-based sound absorbing material include microfiber non-woven fabrics such as Sinsulate of 3M Company, polyester non-woven fabrics such as White Cuon of Tokyo Soundproofing Company and QonPET of Bridgestone C.B. Company (including those having a two-layer structure with a thin non-woven fabric on the surface with a high density and a non-woven fabric on the back side with a low density) and plastic non-woven fabrics such as acrylic fiber non-woven fabrics, natural fiber non-woven fabrics such as wool and felt, metal non-woven fabrics, and glass non-woven fabrics.

[0034] In addition to the above, the sound absorbing material forming the sound absorbing member 30 may be a sound absorbing material made of a material containing minute air, specifically, various sound absorbing materials such as glass wool, rock wool, and sound absorbing materials made of nanofiber-based fibers. Examples of the nanofiber-based fibers include silica nanofibers and acrylic nanofibers such as XAI manufactured by Mitsubishi Chemical Corporation.

[0035] Also, when using a sound-absorbing material as the sound-absorbing member 30, the flow resistivity of the sound-absorbing material is preferably 1000 (Pa×s / m 2 ) to 100000 (Pa×s / m 2 ). When the sound-absorbing member 30 has a laminated structure in which a plurality of layers are stacked, the flow resistance of the entire structure can be measured, and the flow resistivity can be calculated from the thickness of the entire structure.

[0036] Furthermore, as the sound-absorbing member 30, a sound absorber made of a plate or film in which innumerable through-holes with a diameter of about 100 μm are formed, such as a fine perforated plate, can be used. In this case, sound can be absorbed by the sound absorber and the back space formed on the back side of the sound absorber. Examples of the fine perforated plate include an aluminum fine perforated plate such as Souno manufactured by Daiken Kogyo Co., Ltd., and a vinyl chloride resin fine perforated plate such as Dynock manufactured by 3M Company. Also, another sound-absorbing material may be arranged in these back spaces, and a plurality of sound-absorbing members 30 may be used in combination.

[0037] Other sound-absorbing members 30 are also conceivable. For example, it may be composed of a plate-like body or a film-like body that resonates when sound with a frequency close to the resonance frequency is incident, and converts sound energy into heat energy by internal loss of the plate or film to absorb sound. Also, the sound-absorbing member 30 may be a resonator-type sound-absorbing structure composed of a perforated plate. When sound with the same frequency as the resonance frequency hits, the air in the hole part vibrates, and the sound energy is converted into heat energy by the viscous loss at that time. Also, these sound-absorbing structures and another sound-absorbing material may be arranged respectively, and a plurality of sound-absorbing members 30 may be used in combination.

[0038] Note that a part of the sound-absorbing member 30 may enter the housing ventilation path 26 at an intermediate position in the housing ventilation path 26. However, from the viewpoint of improving the air permeability in the housing 20, it is preferable that the sound-absorbing member 30 is arranged in a state avoiding the housing ventilation path 26, that is, so as not to enter the housing ventilation path 26.

[0039] In addition, in order to ensure the air permeability within the housing 20 while maintaining the sound absorption performance in the high-frequency band, the occupancy rate of the sound absorption member 30 is preferably 80% or more, more preferably 90% or more, and particularly preferably 95%. The occupancy rate of the sound absorption member 30 refers to the ratio (volume ratio) of the area occupied by the sound absorption member 30 to the volume of the space in the internal space of the housing 20 excluding the internal housing ventilation passage 26. Note that the sound absorption member 30 is filled from one end (the upstream end) in the X direction to the other end (the downstream end) of the internal space of the housing 20. On the other hand, in the Y direction or the Z direction, a gap may be provided between the inner wall surface of the housing 20 and the sound absorption member 30, or the sound absorption member 30 may be filled without a gap.

[0040] As shown in FIG. 2, the first connection portion 40 is a cylindrical portion protruding from the edge of the inlet opening 22 at one end (specifically, the upstream end face) of the housing 20 in the X direction, and functions as a joint for the ventilation passage 12. Inside the first connection portion 40, an opening 42 formed by a hole in a substantially frustum of a cone shape or a substantially frustum of a pyramid shape is provided. The opening 42 is adjacent to the inlet opening 22 and communicates with the internal housing ventilation passage 26.

[0041] Then, as shown in FIG. 2, the first connection portion 40 is connected to the upstream cylindrical body 15 to connect the upstream ventilation passage 16 and the inlet opening 22. The upstream ventilation passage 16 is the portion of the ventilation passage 12 located upstream of the inlet opening 22. The upstream cylindrical body 15 is a cylindrical body such as a hose or a duct forming the upstream ventilation passage 16. In the present embodiment, by connecting the first connection portion 40 to the upstream cylindrical body 15, the upstream ventilation passage 16, the opening 42, and the internal housing ventilation passage 26 are arranged in a straight line and are continuous.

[0042] As shown in FIG. 2, the second connection portion 50 is a cylindrical portion protruding from the edge of the outlet opening 24 at the other end (specifically, the downstream end face) of the housing 20 in the X direction, and functions as a joint for the ventilation passage 12. Inside the second connection portion 50, an opening 52 formed by a hole in a substantially frustum of a cone shape or a substantially frustum of a pyramid shape is provided. The opening 52 is adjacent to the outlet opening 24 and communicates with the internal housing ventilation passage 26.

[0043] And, as shown in FIG. 2, the second connection portion 50 is connected to the downstream-side cylindrical body 17, thereby connecting the downstream-side ventilation passage 18 and the outlet opening 24. The downstream-side ventilation passage 18 is a portion of the ventilation passage 12 that is located on the downstream side of the outlet opening 24. The downstream-side cylindrical body 17 is a cylindrical body such as a hose or a duct that forms the downstream-side ventilation passage 18. In the present embodiment, by connecting the second connection portion 50 to the downstream-side cylindrical body 17, the downstream-side ventilation passage 18, the opening 52, and the ventilation passage 26 inside the housing are aligned and continuous in a straight line.

[0044] In the present embodiment, as shown in FIG. 2, the first connection portion 40 is connected to the upstream-side cylindrical body 15 (a hose in the configuration shown in FIG. 2) by being inserted into the upstream-side cylindrical body 15. Similarly, the second connection portion 50 is connected to the downstream-side cylindrical body 17 by being inserted into the downstream-side cylindrical body 17 (a hose in the configuration shown in FIG. 2).

[0045] Further, in the present embodiment, each of the first connection portion 40 and the second connection portion 50 is constituted by a resin molded product, more specifically, a resin molded product produced by injection molding or the like. Examples of the resin material constituting each connection portion are the same as the examples of the resin material constituting the housing 20 described above. Also, when the housing 20, the first connection portion 40, and the second connection portion 50 are each constituted by the same type of resin material, the housing 20, the first connection portion 40, and the second connection portion 50 may be integrally molded, that is, they may be a single component.

[0046] Note that the first connection portion 40 and the second connection portion 50 may be separate from the housing 20. In this case, the means for attaching the first connection portion 40 and the second connection portion 50 to the housing 20 is not particularly limited. For example, flanges may be provided at the base end portions of the first connection portion 40 and the second connection portion 50, and these flanges may be fixed to the housing 20 with screws or the like. Alternatively, the first connection portion 40 and the second connection portion 50 may be fixed to the end faces of the housing 20 with an adhesive or the like.

[0047] Further, the first connecting portion 40 and the second connecting portion 50 may be made of a material different from that of the housing 20. For example, the housing 20 may be made of a resin material, and the first connecting portion 40 and the second connecting portion 50 may be made of a metal material. Alternatively, the housing 20 may be made of a metal material, and the first connecting portion 40 and the second connecting portion 50 may be made of a resin material.

[0048] Also, in the present embodiment, as shown in FIGS. 2, 4A, and 4B, the openings 42 and 52 in each of the first connecting portion 40 and the second connecting portion 50 are gradually reduced in diameter as they approach the housing internal ventilation passage 26 in the X direction. More specifically, in the ventilation passage 12, at the portion adjacent to the housing internal ventilation passage 26 (that is, the openings 42 and 52), the cross-sectional area of the ventilation passage 12 gradually decreases as it approaches the housing internal ventilation passage 26. In the present embodiment, the cross-sectional area of the openings 42 and 52 changes linearly in proportion to the distance from the housing internal ventilation passage 26.

[0049] With such a configuration, it is possible to suppress the generation of pressure loss and wind noise at the inlet opening 22 or the outlet opening 24 while enhancing the sound absorption effect in the muffler 14. More specifically, by increasing the flow velocity (wind speed) of the air flow in the housing 20, the sound absorption performance of the sound absorption member 30 is effectively exerted, and the sound absorption performance of the muffler 14 is improved. Therefore, in the present embodiment, the cross-sectional area of the portion provided in the housing 20 in the ventilation passage 12, that is, the housing internal ventilation passage 26, is made smaller than the cross-sectional area of the normal portion.

[0050] On the other hand, when the cross-sectional area of the ventilation passage 12 changes abruptly (discontinuously), a step perpendicular to the location where the cross-sectional area changes is formed, and turbulent flow occurs around the step. As a result, the pressure loss at that location becomes relatively large. In addition, wind noise is generated when the air flow (wind) flowing in the ventilation passage 12 passes through the above step, and this may be propagated downstream as noise.

[0051] In the present embodiment, in order to suppress a sudden change in the cross-sectional area of the ventilation passage 12, the cross-sectional area of the ventilation passage 12 is gradually changed. Specifically, on the inlet opening 22 side, the cross-sectional area is gradually decreased toward the downstream side, and on the outlet opening 24 side, the cross-sectional area is gradually decreased toward the upstream side. Thereby, the pressure loss at the location where the cross-sectional area changes in the ventilation passage 12 can be reduced, and the generation of the wind noise can be suppressed.

[0052] Here, in the muffler 100 described in Patent Document 1, for the above reasons, as shown in FIG. 5, among the inner ventilation passages 120 surrounded by the sound-absorbing material 110 in the muffler 100, the cross-sectional area of the central portion 126 is smaller. Therefore, at the upstream end portion 122, the inner diameter is reduced toward the downstream side, and at the downstream end portion 124, the inner diameter is reduced toward the upstream side.

[0053] However, in the configuration of the muffler 100, the thickness of the sound-absorbing material 110 becomes thin near the inlet opening 102 and the outlet opening 104 of the muffler 100, and there is a possibility that the sound absorption effect in the muffler 100 may be reduced due to the decrease in the thickness of the sound-absorbing material 110. In the configuration of the muffler 100, if the thickness of the sound-absorbing material 110 is to be ensured at each of the inlet opening 102 and the outlet opening 104, the thickness of the sound-absorbing material 110 will be increased as a whole, so that the muffler 100 will be enlarged. In this case, it is necessary to secure a wider installation space for the muffler 100, and the installation location of the muffler 100 may be limited.

[0054] On the other hand, in the muffler 14 of the present embodiment, in the first connection portion 40 and the second connection portion 50 outside the housing 20 that houses the sound-absorbing member 30, the cross-sectional area of the ventilation passage 12 becomes smaller as it approaches the ventilation passage 26 inside the housing. Thereby, the ventilation passage 26 inside the housing can be made narrower than the normal portion without reducing the thickness of the sound-absorbing member 30 inside the housing 20. As a result, the pressure loss in the ventilation passage 12 can be reduced without impairing the sound absorption property, and the generation of the wind noise can be suppressed.

[0055] As described above, the muffler 14 of the present embodiment has a compact structure, can exhibit good sound attenuation performance, and can reduce the pressure loss in the ventilation passage 12.

[0056] Regarding the configurations of each of the first connection portion 40 and the second connection portion 50 in more detail, each of the first connection portion 40 and the second connection portion 50 has an outer peripheral portion 44, 54 surrounding the openings 42, 52 as shown in FIGS. 4A and 4B. The outer peripheral portions 44, 54 have an inner peripheral surface 46, 56 facing the openings 42, 52 and an outer peripheral surface 48, 58 located on the side opposite to the inner peripheral surface 46, 56.

[0057] The inner peripheral surfaces 46, 56 of each of the first connection portion 40 and the second connection portion 50 are tapered surfaces as shown in FIGS. 4A and 4B and are inclined with respect to the X direction (the first direction). In the present embodiment, the above-mentioned tapered surface is a surface in which the size of the cross section having the X direction as the normal direction changes concentrically.

[0058] And the inclination angle of each part of the inner peripheral surfaces 46, 56 with respect to the X direction is 0.1 degree or more and 45 degrees or less. The inclination angle of each part of the inner peripheral surface 46, 56 is the angle (strictly speaking, an acute angle) at which the generatrix of each part of the inner peripheral surface 46, 56 in the circumferential direction of the inner peripheral surface 46, 56 inclines with respect to the X direction, and is indicated by the symbol θ in FIGS. 4A and 4B. The generatrix of each part of the inner peripheral surface 46, 56 is the intersection line between the cross section orthogonal to the inner peripheral surface 46, 56 at each part and the inner peripheral surface 46, 56.

[0059] Note that the above inclination angle θ may be uniform in the circumferential direction of the inner peripheral surface 46, 56, or may change according to the position in the circumferential direction. Further, the magnitude of the above inclination angle θ is preferably 0.1 degree to 30 degrees, more preferably 0.1 degree to 20 degrees, and particularly preferably 0.1 degree to 10 degrees.

[0060] In addition, in the present embodiment, as shown in FIG. 2, among the openings 42 in the first connection portion 40, the cross-sectional area of the downstream end (i.e., the end on the housing internal ventilation path 26 side) is the same as the opening area of the inlet opening 22 adjacent to the downstream end. Similarly, among the openings 52 in the second connection portion 50, the cross-sectional area of the upstream end (i.e., the end on the housing internal ventilation path 26 side) is the same as the opening area of the outlet opening 24 adjacent to the upstream end. Here, the opening area of each of the inlet opening 22 and the outlet opening 24 is the size of each opening, that is, the area surrounded by the edge of the opening.

[0061] According to the above configuration, no step is formed at the boundary position between the opening 42 and the inlet opening 22 in the first connection portion 40, and at the boundary position between the opening 52 and the outlet opening 24 in the second connection portion 50. As a result, problems caused by the step, specifically, pressure loss and wind noise due to the generation of turbulent flow near the step, can be suppressed.

[0062] Each of the first connection portion 40 and the second connection portion 50 is configured by a hose nipple type joint as shown in FIGS. 4A and 4B. In other words, unevenness is formed along the X direction on the outer peripheral surfaces 48, 58 of each connection portion.

[0063] Specifically, on the outer peripheral portions 44, 54 of each of the first connection portion 40 and the second connection portion 50, portions where the outer peripheral surfaces 48, 58 are convex (hereinafter referred to as convex portions 60) are provided in a plurality of series in the X direction. In each convex portion 60, the outer peripheral surface 48, 58 bulges outward at the end closest to the housing 20, and the outer diameter of the convex portion 60 gradually decreases as it moves away from the housing 20. That is, each convex portion 60 has a tapered shape.

[0064] According to the above configuration, the first connection part 40 inserted into the upstream cylindrical body 15 made of a hose or the like can be prevented from coming off from the upstream cylindrical body 15, and the connection state between the upstream cylindrical body 15 and the first connection part 40 can be maintained well. Similarly, the second connection part 50 inserted into the downstream cylindrical body 17 made of a hose or the like can be prevented from coming off from the downstream cylindrical body 17, and the connection state between the downstream cylindrical body 17 and the second connection part 50 can be maintained well.

[0065] Further, due to the tapered shape of the convex part 60 described above, the adhesion between the upstream cylindrical body 15 and the first connection part 40, and the adhesion between the downstream cylindrical body 17 and the second connection part 50 can be enhanced. Thereby, the airtightness of the air passage 12, particularly the upstream air passage 16 and the downstream air passage 18, can be enhanced.

[0066] Also, in the present embodiment, as shown in FIGS. 4A and 4B, at the tip portions (the ends on the side opposite to the housing 20) of each of the first connection part 40 and the second connection part 50, the thickness of the outer peripheral portions 44, 54 becomes smaller as it is farther from the housing 20. Here, the thickness corresponds to the distance between the inner peripheral surfaces 46, 56 and the outer peripheral surfaces 48, 58 in the outer peripheral portions 44, 54.

[0067] In addition, when the outer peripheral portions 44, 54 have an uneven structure and include a plurality of convex portions 60 arranged in the X direction, as shown in FIG. 4C, a virtual plane (shown by a broken line in FIG. 4C) passing through the outermost protruding portion of each convex portion 60 is defined as the outer peripheral surface 48, 58 to define the thickness.

[0068] With the above configuration, when the first connection part 40 is inserted into the upstream cylindrical body 15 made of a hose or the like, as shown in FIG. 4A, the end portion (the portion overlapping the first connection part 40) of the upstream cylindrical body 15 gently bends along the outer peripheral surface 48 of the first connection part 40. Thereby, the inner peripheral surface 46 of the first connection part 40 and the inner surface of the upstream cylindrical body 15 are smoothly continuous, and it is possible to suppress the formation of a step between these surfaces. As a result, at the connection portion between the upstream cylindrical body 15 and the first connection part 40, the pressure loss and the wind noise due to the formation of a step can be suppressed.

[0069] Similarly, when the second connection part 50 is inserted into the downstream cylindrical body 17 made of a hose or the like, as shown in FIG. 4B, the end part of the downstream cylindrical body 17 (the part overlapping the second connection part 50) gently bends along the outer peripheral surface 58 of the second connection part 50. Thereby, the inner peripheral surface 56 of the second connection part 50 and the inner surface of the downstream cylindrical body 17 are smoothly continuous, and it is possible to suppress the formation of a step between these surfaces. As a result, at the connection portion between the downstream cylindrical body 17 and the second connection part 50, it is possible to suppress the pressure loss and the wind noise due to the formation of a step.

[0070] In addition, in the configuration shown in FIGS. 4A and 4B, at the tip portions of each of the first connection part 40 and the second connection part 50, the thickness of the outer peripheral portions 44, 54 becomes smaller as it is farther from the housing 20. However, the present invention is not limited to this, and the thickness of the outer peripheral portions 44, 54 may become smaller as it is farther from the housing 20 over the entire range from the tip to the base end of each connection part.

[0071] Further, in the present embodiment, the inner diameter of the downstream end (the end on the housing internal ventilation path 26 side) of the opening 42 in the first connection part 40, that is, the minimum value of the inner diameter of the opening 42 is 150 mm or less. Similarly, the inner diameter of the upstream end (the end on the housing internal ventilation path 26 side) of the opening 52 in the second connection part 50, that is, the minimum value of the inner diameter of the opening 52 is 150 mm or less. Generally, in a ventilation path with an inner diameter of 150 mm or less, the flow velocity of the airflow (wind) in the ventilation path becomes relatively fast. Under a situation where the flow velocity is fast, the effect of the ventilation system 10 of the present embodiment becomes significant. That is, as the flow velocity increases, the pressure loss increases, and the wind noise is likely to occur. However, with the above-described configuration, the pressure loss and the wind noise in the muffler 14 can be effectively suppressed.

[0072] In addition, in the present embodiment, since the inner diameter of the end on the housing internal ventilation path 26 side of each of the openings 42, 52 is 150 mm or less, under a general ventilation volume, the flow velocity of the housing internal ventilation path 26 becomes, for example, 10 m / s or more. Under such a situation, the effect of suppressing the pressure loss and the wind noise in the muffler 14 is favorably exhibited.

[0073] Also, the inner diameter of the end on the housing ventilation path 26 side at each of the openings 42, 52 is preferably 150 mm or less, more preferably 100 mm or less, and particularly preferably 50 mm or less. Further, from the viewpoint of molding accuracy, the above inner diameter is preferably 1 mm or more.

[0074] [Other Embodiments] The specific examples of the configuration of the ventilation system 10 described above are merely examples, and other configuration examples are also conceivable.

[0075] In the above-described embodiment, the cross-sectional areas (sizes of the cross-sections) of the openings 42, 52 of the first connection portion 40 and the second connection portion 50 become smaller as they approach the housing ventilation path 26, but it is not limited thereto. The cross-sectional area of either one of the openings 42, 52 may become smaller as it approaches the housing ventilation path 26.

[0076] In the above-described embodiment, the wall thicknesses of the outer peripheral portions 44, 54 at the tip portions of the first connection portion 40 and the second connection portion 50 become smaller as they are farther from the housing 20, but it is not limited thereto. The wall thickness of the outer peripheral portion 44, 54 may become smaller as it is farther from the housing 20 at either one of the tip portions.

[0077] In the above-described embodiment, the cross-sectional areas of the openings 42, 52 in each of the first connection portion 40 and the second connection portion 50 change linearly in proportion to the distance from the housing ventilation path 26 in the X direction. However, it is not limited thereto, and as shown in FIG. 6A, the cross-sectional areas of the openings 42, 52 may change non-linearly, for example, exponentially, with respect to the distance from the housing ventilation path 26. That is, the inner peripheral surfaces 46, 56 of the first connection portion 40 and the second connection portion 50, which are tapered surfaces, may be curved surfaces with respect to the X direction.

[0078] Also, in the above-described embodiment, the inner peripheral surfaces 46, 56 are surfaces in which the sizes of the cross-sections having the X direction as the normal direction change concentrically, but it is not limited thereto, and as shown in FIG. 6B, the surfaces in which the sizes of the cross-sections change eccentrically may also be used.

[0079] In the above-described embodiment, the outer peripheral surfaces 48 and 58 of each of the first connection portion 40 and the second connection portion 50 are surfaces with unevenness formed along the X direction, but the present invention is not limited thereto. For example, as shown in FIG. 6C, the outer peripheral surfaces 48 and 58 may be smooth surfaces without unevenness.

[0080] In the above-described embodiment, the first connection portion 40 is inserted inside the upstream-side cylinder 15 and connected to the upstream-side cylinder 15, and the second connection portion 50 is inserted inside the downstream-side cylinder 17 and connected to the downstream-side cylinder 17. However, the connection mode of each connection portion is not particularly limited, and the tip of the first connection portion 40 and the tip of the upstream-side cylinder 15 may be butted against each other and the two may be connected. Similarly, the tip of the second connection portion 50 and the tip of the downstream-side cylinder 17 may be butted against each other and the two may be connected. Alternatively, as shown in FIG. 7, the tip portion of the upstream-side cylinder 15 may be inserted inside the first connection portion 40, and the first connection portion 40 and the tip portion of the upstream-side cylinder 15 may be connected in a state where they overlap. Similarly, the tip portion of the downstream-side cylinder 17 may be inserted inside the second connection portion 50, and the second connection portion 50 and the tip portion of the downstream-side cylinder 17 may be connected in a state where they overlap.

Example

[0081] Hereinafter, the present invention will be described more specifically by way of examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0082] [Calculation Example Regarding Pressure Loss] In the ventilation system of the present invention, in each of the first connection portion and the second connection portion, the cross-sectional area of the opening gradually decreases as it approaches the ventilation path inside the housing, so that the pressure loss in the ventilation path can be reduced. Regarding this point, the relationship between the degree of change in the cross-sectional area of the opening and the pressure loss was obtained by calculation. Hereinafter, the conditions and calculation results of each calculation example will be described.

[0083] (Calculation Example 1) In Calculation Example 1, for each of the case where the cross-sectional area of the opening 42 in the first connection portion 40 changes (hereinafter, Case 1A), and the case where the cross-sectional area does not change (hereinafter, Case 1B), the pressure loss when passing through the opening 42 was obtained. In Case 1A, a calculation model was adopted in which the upstream ventilation passage 16, the opening 42, and the in-housing ventilation passage 26 were configured as shown in FIG. 8A. Further, the inclination angle of the tapered surface forming the inner peripheral surface 46 of the first connection portion 40 (indicated by the symbol θ in FIG. 8A) was defined as the degree of change in the cross-sectional area of the opening. The inclination angle θ was set to 50 degrees, 45 degrees, 27 degrees, 15 degrees, and 9 degrees. In Case 1B, a calculation model was adopted in which the upstream ventilation passage 16, the opening 42, and the in-housing ventilation passage 26 were configured as shown in FIG. 8B. In this model, a perpendicular step was formed between the opening 42 and the upstream ventilation passage 16. In other words, it was assumed that the above inclination angle θ was 90 degrees.

[0084] In each case, the inner diameter of the upstream ventilation passage 16 (denoted as D1 in FIGS. 8A and 8B) was set to 30 mm, and the inner diameter of the in-housing ventilation passage 26 (denoted as D2 in FIGS. 8A and 8B) was set to 24 mm. In Case 1A, the minimum value of the inner diameter of the opening 42 was set to the inner diameter D2 of the in-housing ventilation passage 26.

[0085] Then, in each case, the relationship between the pressure at a predetermined position of the upstream ventilation passage 16 (the position denoted as x1 in FIGS. 8A and 8B) and the flow velocity at a predetermined position of the in-housing ventilation passage 26 (the position denoted as x2 in FIGS. 8A and 8B) was obtained. Specifically, the value of the flow velocity at position x2 was set, and the pressure required at position x1 to achieve the set flow velocity was obtained. Also, for each inclination angle θ, the set value of the flow velocity at position x2 was changed, and the pressure at position x1 was obtained for each set value. The flow velocities were set to approximately 10 m / s, approximately 15 m / s, and approximately 23 m / s. Note that Flowsquare 4.0, which is fluid calculation software, was used for the calculation.

[0086] The calculation results in Calculation Example 1 are shown in FIG. 9. Further, from the calculation results shown in FIG. 9, for each inclination angle θ, an approximate curve showing the relationship between the pressure at position x1 and the flow velocity (wind velocity) at position x2 was obtained. Furthermore, for each inclination angle θ, from the above approximate curve, the pressure at position x1 when the flow velocity at position x2 reaches a predetermined value (specifically, 20 m / s) was obtained. The relationship between the inclination angle θ and the pressure at position x1 thus obtained is shown in FIG. 10.

[0087] As can be seen from FIG. 10, when the inclination angle θ is 45 degrees or less, the pressure at position x1 decreases. From this, it was found that by setting the inclination angle θ to 45 degrees or less, the resistance between the opening 42 of the first connection portion 40 and the upstream ventilation passage 16 is greatly reduced, and the pressure loss at that position can be suppressed. Also, from FIG. 10, it was found that the degree of decrease in pressure loss increases as the inclination angle θ decreases. From this, it is considered that the inclination angle θ is preferably 30 degrees or less, more preferably 20 degrees or less, and particularly preferably 10 degrees or less.

[0088] (Calculation Example 2) In Calculation Example 2, for each of the case where the cross-sectional area of the opening 52 in the second connection portion 50 changes (hereinafter, Case 2A) and the case where the cross-sectional area does not change (hereinafter, Case 2B), the pressure loss when passing through the opening 52 was obtained. In Case 2A, a calculation model was used in which the housing ventilation passage 26, the opening 52, and the downstream ventilation passage 18 were configured by horizontally inverting FIG. 8A. Also, the inclination angle θ of the tapered surface forming the inner peripheral surface 56 of the second connection portion 50 was set as the degree of change in the cross-sectional area of the opening. The inclination angle θ was set to 45 degrees, 27 degrees, 15 degrees, and 9 degrees. In Case 2B, a calculation model was used in which the housing ventilation passage 26, the opening 52, and the downstream ventilation passage 18 were configured by horizontally inverting FIG. 8B. In this model, a vertical step was formed between the opening 52 and the downstream ventilation passage 18. In other words, it was assumed that the above inclination angle θ was 90 degrees.

[0089] In each case, the inner diameter of the downstream ventilation passage 18 was set to 30 mm, and the inner diameter of the ventilation passage 26 inside the housing was set to 24 mm. Further, in Case 2A, the minimum value of the inner diameter of the opening 52 was set to the inner diameter of the ventilation passage 26 inside the housing. Then, for each case, in the same manner as in Calculation Example 1, the relationship between the pressure at the predetermined position x1 of the ventilation passage 26 inside the housing and the flow velocity (wind velocity) at the predetermined position x2 of the downstream ventilation passage 18 was obtained. The calculation results in Calculation Example 2 are shown in FIG. 11.

[0090] Further, from the calculation results shown in FIG. 11, for each inclination angle θ, an approximate curve showing the relationship between the pressure at the predetermined position x1 of the ventilation passage 26 inside the housing and the flow velocity at the predetermined position x2 of the downstream ventilation passage 18 was obtained. Furthermore, for each inclination angle θ, from the above approximate curve, the pressure at the predetermined position x1 of the ventilation passage 26 inside the housing when the flow velocity at the predetermined position x2 of the downstream ventilation passage 18 reaches 20 m / s was obtained. The relationship between the inclination angle θ thus obtained and the pressure at the predetermined position x1 of the ventilation passage 26 inside the housing is shown in FIG. 12.

[0091] As can be seen from FIG. 12, when the inclination angle θ is 45 degrees or less, the pressure at the predetermined position x1 of the ventilation passage 26 inside the housing decreases. From this, it was found that by setting the inclination angle θ to 45 degrees or less, the resistance between the opening 52 of the second connection portion 50 and the downstream ventilation passage 18 is greatly reduced, and the pressure loss at that position can be suppressed. Also, from FIG. 12, it can be seen that the degree of decrease in pressure loss increases as the inclination angle θ decreases. From this, it is considered that the inclination angle θ is preferably 30 degrees or less, more preferably 20 degrees or less, and particularly preferably 10 degrees or less.

[0092] [Example 1] In Example 1, the ventilation system 10 shown in FIG. 13A was fabricated. In Example 1, a polyvinyl chloride (PVC) pipe having an inner diameter of 70 mm and a length in the X direction of 250 mm was used as the housing 20 of the silencer 14. Also, inside the housing 20, a sound-absorbing member 30 made of a cylindrical sound-absorbing material with a hole having an inner diameter of 24 mm was arranged. In addition, a first connection part 40 was provided at the upstream end of the housing 20, and a second connection part 50 was provided at the downstream end. The length (projection length) in the X direction of each of the first connection part 40 and the second connection part 50 is 50 mm. In addition, the cross-sectional areas of the openings 42 and 52 in each of the first connection part 40 and the second connection part 50 become smaller as they approach the housing 20. Further, among the openings 42 and 52, the inner diameter of the end closest to the housing 20, that is, the minimum value of the inner diameter is 24 mm. In addition, the inclination angles of the inner peripheral surfaces 46 and 56 of each of the first connection part 40 and the second connection part 50 were set to 3 degrees. In addition, by connecting a resin hose forming the upstream-side cylinder 15 or the downstream-side cylinder 17 to each of the first connection part 40 and the second connection part 50, the muffler 14 was arranged at an intermediate position in the ventilation passage 12.

[0093] In Example 1, for the ventilation system 10 configured as described above, the soundproofing characteristics of the muffler 14 were measured. Specifically, a resin hose connected to one connection part was connected to a speaker as a sound source, and white noise was passed through the speaker. Further, a resin hose connected to the other connection part was placed in a reverberation chamber, and in the reverberation chamber, the sound pressure when white noise was passed through was measured. The sound pressure was measured both when the muffler 14 was present and when the muffler 14 was absent, and the sound volume reduction by the muffler 14 was calculated from the difference between the measurement results of both.

[0094] In addition, in Example 1, a resin hose connected to one connection part was connected to a fan (not shown), and an anemometer was attached to the resin hose connected to the other connection part. Then, the fan was driven while changing the applied voltage to the fan (in other words, the rotation speed of the fan), and the wind speed when using the muffler 14 was measured by the anemometer at the end of the hose. [Comparative Example] In the comparative example, a ventilation system 10X shown in FIG. 13B was fabricated. In the comparative example, the cross-sectional areas of the openings 42X and 52X in each of the first connection part 40X and the second connection part 50X are constant. More specifically described, in the comparative example, the inner diameters of the respective openings 42X and 52X do not change over the range from one end to the other end of the opening, and specifically, they are constant at 24 mm. In other respects, the configuration of the ventilation system 10X in the comparative example is common to the configuration of the ventilation system 10 in Example 1.

[0095] In the comparative example, in the same procedure as in Example 1, with and without the muffler 14X respectively, the sound pressure in the reverberation chamber was measured, and the noise reduction amount by the muffler 14X was calculated from the difference between the measurement results of both. Also, in the comparative example, in the same procedure as in Example 1, while changing the applied voltage (rotation speed) to the fan, the fan was driven, and the wind speed when using the muffler 14X was measured.

[0096] [Measurement Results of Example 1 and Comparative Example] Regarding each of Example 1 and the comparative example, the measurement results of the noise reduction amount by the muffler are shown in FIG. 14. The horizontal axis in FIG. 14 indicates the frequency of the sound (unit: Hz), and the vertical axis indicates the noise reduction amount (unit: dB). As can be seen from FIG. 14, in Example 1 and the comparative example, similar noise reduction amounts were obtained. From this, it was found that the influence of the inclination angle of the inner peripheral surface (taper surface) of each of the first connection part and the second connection part on the noise reduction amount is relatively small.

[0097] Also, regarding each of Example 1 and the comparative example, the measurement results of the wind speed when using the muffler are shown in Table 1.

[0098] [Table 1]

[0099] As can be seen from Table 1, when the voltage applied to the fan was adjusted to each set value in Table 1, the wind speed in Example 1 was greater than that in the comparative example. From this, it was found that in Example 1, the pressure loss in the ventilation passage was smaller than that in the comparative example, and the ventilation performance was improved. Case 1A of Calculation Example 1, Case 2A of Calculation Example 2, and Example 1 described above are within the scope of the present invention, and the effects of the present invention are clear from the calculation results or measurement results in these examples.

Explanation of Signs

[0100] 10, 10X Ventilation System 12 Ventilation Passage 14, 14X Silencer 15 Upstream Cylinder 16 Upstream Ventilation Passage 17 Downstream Cylinder 18 Downstream Ventilation Passage 20 Housing 22 Inlet Opening 24 Outlet Opening 26 Internal Ventilation Passage in Housing 30 Sound Absorbing Member 40, 40X First Connection Port 42, 42X Opening 44 Outer Periphery 46 Inner Peripheral Surface 48 Outer Peripheral Surface 50, 50X Second Connection Port 52, 52X Opening 54 Outer Periphery 56 Inner Peripheral Surface 58 Outer Peripheral Surface 60 Convex Portion 100 Silencer 102 Inlet Opening 104 Outlet Opening 110 Sound Absorbing Material 120 Inner Ventilation Passage 122 Upstream End 124 Downstream End 126 Central Portion

Claims

1. It has a ventilation passage and a muffler disposed at an intermediate position in the ventilation passage, The muffler is a housing having an inlet opening and an outlet opening, and a housing ventilation passage extending from the inlet opening to the outlet opening in the ventilation passage is provided inside; a sound-absorbing member disposed inside the housing so as to surround the housing ventilation passage; an upstream-side cylindrical body forming an upstream-side ventilation passage on the upstream side of the inlet opening in the ventilation passage; a downstream-side cylindrical body forming a downstream-side ventilation passage on the downstream side of the outlet opening in the ventilation passage; a cylindrical first connection portion disposed outside the muffler and connected to the upstream-side cylindrical body to connect the upstream-side ventilation passage and the inlet opening; a cylindrical second connection portion disposed outside the muffler and connected to the downstream-side cylindrical body to connect the downstream-side ventilation passage and the outlet opening; each of the first connection portion and the second connection portion has an opening inside; in at least one of the first connection portion and the second connection portion, the size of the cross section of the opening becomes smaller as it approaches the housing ventilation passage; the first connection portion is connected to the upstream-side cylindrical body by being inserted into the upstream-side cylindrical body, or the second connection portion is connected to the downstream-side cylindrical body by being inserted into the downstream-side cylindrical body; each of the first connection portion and the second connection portion has an outer peripheral portion surrounding the opening; A ventilation system in which, at the tip portion of at least one of the connection portions, the wall thickness of the outer peripheral portion becomes smaller as it moves away from the housing.

2. The ventilation system according to claim 1, wherein the size of the cross section of the opening in each of the first connection portion and the second connection portion becomes smaller as it approaches the housing ventilation passage.

3. The ventilation system according to claim 1, wherein at the tip portion of each of the first connection portion and the second connection portion, the wall thickness of the outer peripheral portion becomes smaller as it moves away from the housing.

4. The housing ventilation passage extends along a first direction, the inner peripheral surface of at least one of the connection portions is inclined with respect to the first direction, The ventilation system according to claim 1, wherein the inclination angle of the inner peripheral surface with respect to the first direction is 0.1 degrees or more and 45 degrees or less.

5. The housing ventilation passage extends along a first direction, the first connection portion projects from one end of the housing in the first direction, the second connection portion projects from the other end of the housing in the first direction, The ventilation system according to claim 1, wherein each of the first connection part and the second connection part has an outer peripheral surface with unevenness formed along the first direction.

6. The ventilation system according to claim 5, wherein in each of the first connection part and the second connection part, the outer diameter of the portion where the outer peripheral surface is convex becomes smaller as it moves away from the housing.

7. The ventilation passage in the housing extends along the first direction, The ventilation system according to claim 1, wherein in a second direction intersecting the first direction and a third direction intersecting both the first direction and the second direction, the range where the inlet opening exists is different from the range where the outlet opening exists.

8. The ventilation system according to claim 7, wherein the size of the cross section of the end on the side of the ventilation passage in the housing among the openings in at least one of the connection parts is the same as the size of the opening adjacent to the end among the inlet opening and the outlet opening.

9. The ventilation system according to claim 1, wherein the first connection part and the second connection part are constituted by resin molded products.

10. The ventilation system according to claim 1, wherein the inner diameter of the end on the side of the ventilation passage in the housing of the opening in each of the first connection part and the second connection part is 150 mm or less.

11. It has a ventilation passage and a muffler arranged at an intermediate position of the ventilation passage, The muffler is A housing having an inlet opening and an outlet opening, and a ventilation passage in the housing extending from the inlet opening to the outlet opening in the ventilation passage is provided inside; An acoustic absorption member arranged in the housing in a state of surrounding the ventilation passage in the housing, and An upstream cylindrical body forming an upstream ventilation passage on the upstream side of the inlet opening in the ventilation passage; A downstream cylindrical body forming a downstream ventilation passage on the downstream side of the outlet opening in the ventilation passage; A cylindrical first connection part arranged outside the muffler and connected to the upstream cylindrical body to connect the upstream ventilation passage and the inlet opening; A cylindrical second connection part arranged outside the muffler and connected to the downstream cylindrical body to connect the downstream ventilation passage and the outlet opening are provided, Each of the first connection part and the second connection part is provided with an opening inside, Among the first connection part and the second connection part, the size of the cross section of the opening in at least one of the connection parts becomes smaller as it approaches the ventilation passage in the housing. The size of the cross-section of each part of the ventilation passage in the housing is smaller than the size of the cross-section of the end portion on the side opposite to the ventilation passage in the housing among the openings in the at least one connection portion. The first connection portion is connected to the upstream cylindrical body by being inserted into the inside of the upstream cylindrical body, or the second connection portion is connected to the downstream cylindrical body by being inserted into the inside of the downstream cylindrical body. Each of the first connection portion and the second connection portion has an outer peripheral portion surrounding the opening. A ventilation system in which, at the tip portion of the at least one connection portion, the wall thickness of the outer peripheral portion becomes smaller as it is farther from the housing.

Images