Ventilated silencer

Abstract

A ventilated silencer is provided which can suppress the occurrence of wind noise and which has excellent silencing effect in the low-frequency band and high ventilation performance. The ventilated silencer has an opening structure that has an inlet-side air duct, an extension part which communicates with the inlet-side air duct and has a larger cross-sectional area than the inlet-side air duct, and an outlet-side air duct which communicates with the extension part and which has a smaller cross-sectional area than the extension part, wherein the cross-sectional area of the opening structure gradually decreases from the extension part towards the connection between the extension part and the outlet-side air duct. The ventilated silencer has a back space, which is surrounded by the opening structure, the side surface of the extension part facing the outlet-side air duct and the peripheral surface of the extension part, and has a porous sound absorption member, which is arranged at least in the opening of the back space.

Description

[Technical field]

[0001] The present invention relates to a ventilation type silencer. [Background technology]

[0002] In an air pipe that transports gas, an expansion type silencer is known as a silencer that silences noise from a gas supply source, etc., midway through the air pipe. The expansion type silencer is installed midway through the air pipe and has an expansion section with a larger cross-sectional area than the air pipe.

[0003] In a ventilation type muffler, when the wind speed passing through the inside increases, wind noise occurs, and the muffling performance decreases. To address this issue, in order to muffle the noise while suppressing the generation of wind noise, the inlet pipe and tail pipe communicating with the expansion section are made tapered.

[0004] For example, Patent Document 1 describes an expansion-type silencer in which an inlet pipe and tail pipe (outlet pipe) are inserted into an expansion section, the insides of the inlet pipe and tail pipe inserted into the expansion section are tapered, bellmouths are formed at the openings of the inlet pipe and tail pipe, and the bellmouths are arranged so that they face each other. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Jpn. Jpn. Published No. 61-184808 Summary of the Invention [Problem to be solved by the invention]

[0006] When using an expansion silencer for noise control in equipment with ventilation pipes, such as various equipment equipped with fans, there is a size restriction for mounting on the equipment. However, there is a problem that the noise silencing performance at low frequencies decreases when the expansion silencer is made small.

[0007] Furthermore, when the tail pipe in the extension is tapered, a space (hereinafter referred to as the back space) is formed between the tail pipe and the housing of the extension. In a ventilation type silencer, when wind passes through the silencer, the wind flows into this back space, and there is a risk that the airflow will be disturbed, such as the wind flowing backward, resulting in a decrease in the amount of ventilation. In addition, there is a risk that the disturbance of the airflow will generate vortices and pressure fluctuations, which will increase wind noise.

[0008] The object of the present invention is to solve the problems of the above-mentioned conventional technology, and to provide a ventilation type silencer that can suppress the generation of wind noise, has a high noise reduction effect in the low frequency band, and has high ventilation performance. [Means for solving the problem]

[0009] In order to solve this problem, the present invention has the following configuration. [1] An inlet side ventilation pipe, an expansion part communicating with the inlet side ventilation pipe and having a larger cross-sectional area than the inlet side ventilation pipe, and an outlet side ventilation pipe communicating with the expansion part and having a smaller cross-sectional area than the expansion part, The opening structure has a cross-sectional area that gradually decreases from within the expansion section toward a connection section between the expansion section and the outlet-side vent pipe, a rear space surrounded by the opening structure, a side surface of the extension part on the outlet side vent pipe side, and a peripheral surface of the extension part; A ventilation type silencer having a porous sound absorbing material disposed at least at an opening of a back space. [2] If the resonance frequency in the back space when no porous sound-absorbing material is placed is F, the first resonance frequency of the ventilation type silencer when no porous sound-absorbing material is placed is f1, and the cut-off frequency determined by the cross-sectional area of ​​the opening of the outlet side ventilation pipe is fc, then: f1×(1-0.2) <F<fc The ventilation type silencer according to [1] satisfies the above. [3] The opening structure has a rectangular cross-sectional shape perpendicular to the central axis of the outlet side vent pipe, and the distance between a pair of opposing sides gradually becomes shorter from within the expansion section toward the connection section between the expansion section and the outlet side vent pipe, while the distance between the other pair of opposing sides is constant. A ventilated silencer as described in [1] or [2]. [4] The ventilation type silencer described in [1] or [2], wherein the opening structure has a structure in which two plate-shaped members face each other and the distance between the two plate-shaped members gradually becomes shorter from within the extension portion toward the connection portion between the extension portion and the outlet side ventilation pipe. [5] The ventilation type silencer according to any one of [1] to [4], wherein the extension portion has a rectangular cross-sectional shape perpendicular to the central axis of the outlet side ventilation pipe. [6] The ventilation type silencer according to any one of [1] to [5], wherein the central axis of the outlet side ventilation pipe and the central axis of the inlet side ventilation pipe are aligned in a straight line. [7] A ventilation type silencer according to any one of [1] to [6], wherein the porous sound-absorbing material is arranged in the region from the side surface of the extension portion on the inlet side vent pipe side to the side surface of the outlet side vent pipe side. [8] The ventilation type silencer according to any one of [1] to [7], wherein the central axis of the outlet side ventilation pipe is offset from the center of the side surface of the extension portion. [9] The ventilation type silencer according to any one of [1] to [8], wherein the opening structure has a region in which the thickness becomes thinner toward the inlet side ventilation pipe.

[10] The ventilation type silencer according to any one of [1] to [9], wherein the opening structure is detachable from the extension portion. Effect of the Invention

[0010] According to the present invention, it is possible to provide a ventilation type silencer that can suppress the generation of wind noise, has a high noise absorbing effect in the low frequency band, and has high ventilation performance. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view conceptually showing an example of a ventilation type silencer of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line BB in FIG. [Diagram 3] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Figure 4] FIG. 11 is a cross-sectional view conceptually showing another example of an opening structure. [Diagram 5]FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Figure 6] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Figure 7] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Figure 8] FIG. 11 is a cross-sectional view conceptually showing another example of an opening structure. [Figure 9] FIG. 11 is a cross-sectional view conceptually showing another example of an opening structure. [Figure 10] FIG. 11 is a cross-sectional view conceptually showing another example of an opening structure. [Figure 11] FIG. 11 is a cross-sectional view conceptually showing another example of an opening structure. [Figure 12] FIG. 11 is a cross-sectional view conceptually showing another example of an opening structure. [Figure 13] FIG. 11 is a cross-sectional view conceptually showing another example of an opening structure. [Figure 14] FIG. 11 is a cross-sectional view conceptually showing another example of an opening structure. [Figure 15] FIG. 11 is a cross-sectional view conceptually showing another example of an opening structure. [Figure 16] FIG. 11 is a cross-sectional view conceptually showing another example of an opening structure. [Figure 17] FIG. 2 is a diagram showing a schematic configuration of a ventilation type silencer of Comparative Example 1. [Figure 18] FIG. 11 is a diagram showing a schematic configuration of a ventilation type silencer of Comparative Example 2. [Figure 19] FIG. 11 is a diagram showing a schematic configuration of a ventilation type silencer of Comparative Example 3. [Figure 20] FIG. 13 is a diagram for explaining a method for measuring the sound level of noise. [Figure 21] 1 is a graph showing the relationship between frequency and sound pressure level. [Figure 22] 1 is a graph showing the relationship between frequency and sound pressure level. [Figure 23] 1 is a graph showing the relationship between frequency and muffling volume. [Figure 24] 1 is a graph showing the relationship between frequency and muffling volume. [Diagram 25] 1 is a graph showing the relationship between frequency and muffling volume. [Figure 26] 13 is a graph comparing the total sound level. [Figure 27] 1 is a graph showing the relationship between frequency and transmission loss. [Figure 28] 1 is a graph showing the relationship between frequency and transmission loss. [Figure 29] FIG. 13 is a diagram for explaining a method for measuring wind speed. [Diagram 30] 1 is a graph comparing wind speeds. [Diagram 31] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Diagram 32] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Diagram 33] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Diagram 34] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Diagram 35] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Diagram 36] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Figure 37] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Figure 38] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Figure 39] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Diagram 40] FIG. 40 is a view of the ventilation type silencer shown in FIG. 39 with the opening structure removed. [Diagram 41] FIG. 40 is a front view of an opening structure of the ventilation type silencer shown in FIG. 39. [Diagram 42] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Diagram 43] FIG. 4 is a cross-sectional view conceptually showing another example of a ventilation type silencer of the present invention. [Diagram 44]FIG. 4 is a front view conceptually showing another example of a ventilation type silencer of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described in detail below. The following description of the components will be given based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In this specification, "vertical" and "parallel" include the range of error permitted in the technical field to which the present invention pertains. For example, "vertical" and "parallel" mean within a range of less than ±10° from strictly vertical or parallel, and the error from strictly vertical or parallel is preferably 5° or less, and more preferably 3° or less. In this specification, the terms "same" and "identical" are intended to include a generally acceptable margin of error in the technical field.

[0013] [Ventilated silencer] The ventilation type silencer of the present invention is The device has an inlet side ventilation pipe, an expansion part communicating with the inlet side ventilation pipe and having a larger cross-sectional area than the inlet side ventilation pipe, and an outlet side ventilation pipe communicating with the expansion part and having a smaller cross-sectional area than the expansion part, The opening structure has a cross-sectional area that gradually decreases from within the expansion section toward a connection section between the expansion section and the outlet-side vent pipe, a rear space surrounded by the opening structure, a side surface of the extension part on the outlet side vent pipe side, and a peripheral surface of the extension part; The ventilation type silencer has a porous sound absorbing material disposed at least at the opening of the back space.

[0014] The configuration of the ventilation type silencer of the present invention will be described with reference to the drawings. Fig. 1 is a schematic cross-sectional view showing an example of an embodiment of the ventilation type silencer of the present invention, and Fig. 2 is a cross-sectional view taken along line BB in Fig. 1.

[0015] As shown in FIG. 1, the ventilation type silencer 10 has a cylindrical inlet side ventilation pipe 12, an extension section 14 connected to one open end face of the inlet side ventilation pipe 12, a cylindrical outlet side ventilation pipe 16 connected to the end face of the extension section 14 opposite to the face on the inlet side ventilation pipe 12 side, an opening structure 24, and a porous sound-absorbing material 30.

[0016] The inlet side vent pipe 12 is a cylindrical member that transports gas flowing in from one open end face to an expansion section 14 connected to the other open end face.

[0017] The outlet side vent pipe 16 is a cylindrical member, and transports gas flowing in from one open end face connected to the expansion portion 14 to the other open end face.

[0018] The cross-sectional shape of the inlet side vent pipe 12 and the outlet side vent pipe 16 (hereinafter collectively referred to as vent pipes) may be various shapes such as circular, rectangular, triangular, etc. In addition, the cross-sectional shape of the vent pipe does not have to be constant in the axial direction of the central axis of the vent pipe (hereinafter simply referred to as the central axis). For example, the diameter of the vent pipe may change in the axial direction.

[0019] The inlet side vent pipe 12 and the outlet side vent pipe 16 may have the same cross-sectional shape and cross-sectional area, or may have different shapes and / or cross-sectional areas. In the example shown in Fig. 1, the inlet side vent pipe 12 and the outlet side vent pipe 16 are arranged so that their central axes coincide with each other, i.e., they are arranged on a straight line, but this is not limited thereto, and the central axis of the inlet side vent pipe 12 and the central axis of the outlet side vent pipe 16 may be misaligned.

[0020] In the following description, the direction in which the inlet vent pipe 12, the expansion portion 14 and the outlet vent pipe 16 are arranged is also referred to as the flow path direction.

[0021] The expansion section 14 is disposed between the inlet side vent pipe 12 and the outlet side vent pipe 16, and transports the gas flowing in from the inlet side vent pipe 12 to the outlet side vent pipe 16. In the example shown in Fig. 1 and Fig. 2, the expansion section 14 is a hollow, approximately rectangular parallelepiped shape, with the inlet side vent pipe 12 connected to one side and the outlet side vent pipe 16 connected to the side opposite to this side.

[0022] The cross-sectional area of ​​the expansion section 14 perpendicular to the flow path direction is larger than that of the inlet side vent pipe 12 and is also larger than that of the outlet side vent pipe 16. That is, for example, when the cross-sectional shapes of the inlet side vent pipe 12, the outlet side vent pipe 16, and the expansion section 14 are circular, the diameter of the cross section of the expansion section 14 is larger than the diameters of the inlet side vent pipe 12 and the outlet side vent pipe 16.

[0023] The cross-sectional shape of the extension section 14 perpendicular to the flow path direction may be various shapes such as a circle, a rectangle, a triangle, etc. Furthermore, the cross-sectional shape of the extension section 14 does not have to be constant in the axial direction of the central axis of the extension section 14. For example, the diameter of the extension section 14 may change in the axial direction. In the example shown in Fig. 2, the cross-sectional shape of the extension section is approximately square.

[0024] An opening structure 24 is disposed at the connection point of the extension 14 with the outlet vent pipe 16 .

[0025] The opening structure 24 is arranged adjacent to the connection with the outlet side vent pipe 16 within the expansion section 14, and is a tapered tubular member whose opening area gradually decreases from the inlet side vent pipe 12 side toward the outlet side vent pipe 16 side.

[0026] 2, the cross-sectional shape perpendicular to the central axis of the outlet side vent pipe 16 is circular. The shape and area of ​​the end face of the opening structure 24 on the outlet side vent pipe 16 side are approximately the same as the cross-sectional shape and cross-sectional area of ​​the outlet side vent pipe 16. On the other hand, the end face of the opening structure 24 on the inlet side vent pipe 12 side is approximately square and has a larger area than the end face on the outlet side vent pipe 16 side.

[0027] The end face of the opening structure 24 on the inlet side vent pipe 12 side does not contact the inner peripheral surface of the expansion section 14. Therefore, a back space 26 is formed which is surrounded by the opening structure 24, the side face of the expansion section 14 on the outlet side vent pipe 16 side, and the inner peripheral surface of the expansion section 14 and is open on the inlet side vent pipe 12 side.

[0028] 1, a porous sound-absorbing material 30 is disposed at the opening of the back space 26. That is, the porous sound-absorbing material 30 is disposed at a position in contact with the end face of the opening structure 24 on the inlet side ventilation pipe 12 side.

[0029] As shown in Fig. 2, the porous sound-absorbing material 30 is substantially square-shaped when viewed from the flow path direction, and has a substantially square-shaped opening. The porous sound-absorbing material 30 is disposed along the inner peripheral surface of the extension section 14. In the example shown in Fig. 1, the length of the porous sound-absorbing material 30 in the flow path direction is shorter than the length of the extension section 14, and is the length from a midpoint between the inlet side air duct 12 of the extension section 14 and the opening of the back space 26 to a midpoint inside the back space 26. The thickness of the porous sound-absorbing material 30 in the direction perpendicular to the flow path direction is substantially equal to the width of the opening of the back space 26.

[0030] The porous sound absorbing material 30 is disposed within the extension portion 14 and serves to absorb and deaden sound.

[0031] As described above, in a ventilation type silencer having an extension section, when the wind speed of the wind passing through the inside increases, there is a problem that wind noise occurs and the sound silencing performance decreases. In response to this, in order to mute the sound while suppressing the generation of wind noise, the outlet side ventilation pipe communicating with the extension section is made into a tapered shape. Also, by arranging a tapered outlet side ventilation pipe in the extension section, ventilation is improved. However, when a tapered outlet side ventilation pipe is arranged in the extension section, a back space surrounded by the outlet side ventilation pipe and the housing of the extension section is formed, and when wind passes through the silencer (extension section), the wind flows into this back space, and the airflow is disturbed, such as the wind flowing backward, and the effect of improving the ventilation volume may not be fully obtained. Also, the disturbance of the airflow may cause vortexes and pressure fluctuations, which may cause wind noise. In addition, when installing a ventilation type silencer having an expansion section in various devices, there are size restrictions depending on the device, but there was a problem that if the expansion type silencer was made smaller, the noise silencing performance at low frequencies would decrease.

[0032] In contrast, the ventilation type silencer of the present invention has a tapered opening structure at the connection between the extension part and the outlet side ventilation pipe, and has a configuration in which a porous sound absorbing material is arranged at the opening of the back space surrounded by the opening structure and the extension part. In this back space, resonance occurs due to the vibration of the air due to the three-dimensional tapered structure, so low-frequency resonance can be expressed with a smaller size than air column resonance that resonates with a linear structure. At this time, the particle speed becomes high due to resonance at the opening of the back space, so by arranging a porous sound absorbing material at this position, the sound absorption effect can be made broadband and the sound absorbing performance can be improved. Therefore, even if the expansion type silencer is made small, the sound absorbing performance at low frequencies can be improved.

[0033] In addition, by placing a porous sound-absorbing material at the opening of the rear space, it becomes difficult for wind to flow into the rear space, which suppresses airflow disturbances such as backflow, and suppresses a decrease in the ventilation volume as an expansion type silencer.

[0034] In addition, by placing porous sound-absorbing material at the opening of the rear space, it is possible to suppress the occurrence of vortexes and pressure fluctuations caused by turbulent airflow, and to suppress the deterioration of soundproofing performance due to the generation of wind noise.

[0035] In addition, the ventilation type silencer of the present invention forms a back space between the opening structure and the expansion part. Since the size of the opening communicating with the expansion part is small, the back space acts as a resonator with a lower resonance frequency than a normal air column resonator, and the sound deadening effect in the low frequency band can be improved.

[0036] 1, the porous sound-absorbing material 30 is arranged near the position of the opening of the rear space 26 in the flow path direction, but the present invention is not limited to this, and as in the example shown in Fig. 3, the porous sound-absorbing material 30 may be arranged over the entire area of ​​the extension section 14 in the flow path direction from the side surface on the inlet side ventilation pipe 12 side to the side surface on the outlet side ventilation pipe 16 side. By arranging the porous sound-absorbing material 30 over the entire area of ​​the extension section 14 in the flow path direction, it is possible to more suitably suppress turbulence of the air flow in the extension section 14, and suppress a decrease in the amount of ventilation. In addition, in FIG. 3, the porous sound-absorbing material 30 is configured to be placed in a portion of the rear space 26, but this is not limited to this, and the porous sound-absorbing material 30 may fill the entire rear space 26.

[0037] In the example shown in FIG. 1, the shape of the cross-sectional portion of the opening structure 24 in a cross section parallel to the flow path direction (the central axis direction of the outlet side ventilation pipe 16) is a so-called trumpet shape that is convex toward the central axis side, but is not limited thereto. For example, the shape of the cross-sectional portion of the opening structure 24 in a cross section parallel to the flow path direction may be linear. Alternatively, as in the example shown in FIG. 4, the shape of the cross-sectional portion of the opening structure 24 in a cross section parallel to the flow path direction may have a portion that is concave toward the central axis side. Alternatively, for example, the shape of the cross-sectional portion of the opening structure 24 in a cross section parallel to the flow path direction may be a shape that gradually increases in diameter along the central axis, having a portion where the diameter increases monotonically, a constant portion, and a portion where the diameter increases monotonically in sequence.

[0038] 2, the porous sound-absorbing material 30 is configured to be disposed over the entire circumferential area of ​​the expansion section 14 when viewed from the flow path direction, but this is not limited thereto, and the porous sound-absorbing material 30 may be disposed over at least a portion of the circumferential area of ​​the expansion section 14. By disposing the porous sound-absorbing material 30 over the entire circumferential area of ​​the expansion section 14, it is possible to more suitably suppress turbulence of the airflow within the expansion section 14, suppress a decrease in the amount of ventilation, and furthermore, since the area of ​​the porous sound-absorbing material is increased when viewed from the flow path direction, the sound absorbing effect can be improved.

[0039] In addition, in the example shown in Figure 2, the shape of the extension portion 14 when viewed from the flow path direction is approximately square, the shape of the end face of the opening structure 24 on the inlet side air pipe 12 side is approximately square, and the shape of the porous sound-absorbing material 30 when viewed from the flow path direction is approximately square with an approximately square opening, but this is not limited to this.

[0040] For example, as shown in the example of Figure 5, the shape of the expansion section 14 when viewed from the flow path direction may be approximately square, the shape of the end face of the opening structure 24 on the inlet side air pipe 12 side may be approximately circular, and the shape of the porous sound-absorbing material 30 when viewed from the flow path direction may be approximately square with an approximately circular opening.

[0041] Alternatively, as in the example shown in Figure 6, the shape of the expansion section 14 when viewed from the flow path direction may be approximately circular, the shape of the end face of the opening structure 24 on the inlet side air pipe 12 side may be approximately circular, and the shape of the porous sound-absorbing material 30 when viewed from the flow path direction may be approximately circular with a substantially circular opening.

[0042] It is preferable that the cross-sectional shape of the expansion portion 14 and the cross-sectional shape of the opening structure 24 (the shape of the end face on the inlet side ventilation pipe 12 side) are similar to each other.

[0043] 2 and 5 to 6, the opening structure 24 has an end face on the inlet side vent pipe 12 side that is square or circular, and the diameter (the diameter of the inscribed circle in the case of a polygon such as a square) decreases from the inlet side vent pipe 12 side toward the outlet side vent pipe 16 side, but is not limited to this. For example, the opening structure may have a rectangular cross section perpendicular to the central axis of the outlet side vent pipe, and the distance between a pair of opposing sides gradually decreases from within the expansion section toward the connection section between the expansion section and the outlet side vent pipe, and the distance between the other pair of opposing sides is constant.

[0044] As an example, in the example shown in FIG. 7, the opening structure 24 has a rectangular cross-sectional shape perpendicular to the central axis of the outlet side ventilation pipe 16 (shape seen from a direction perpendicular to the paper surface of FIG. 7), and the distance between the sides facing each other horizontally is constant in FIG. 7, while the distance between the sides facing each other vertically is gradually shortened from inside the extension portion 14 toward the connection portion between the extension portion 14 and the outlet side ventilation pipe 16 (from the inlet side ventilation pipe 12 side toward the outlet side ventilation pipe 16 side). In other words, the opening structure 24 shown in FIG. 7 is composed of two plate-shaped parts of a substantially trapezoid shape (the legs of the trapezoid (opposite sides other than the upper and lower bases) are curved) facing each other in parallel, and two plate-shaped parts arranged at the positions of the legs of the trapezoid between these two plate-shaped parts. In this way, by making the opening structure flat, it is possible to increase the volume of the porous sound-absorbing material arranged at the opening of the back space, and the sound absorption effect can be improved.

[0045] In addition, when the opening structure 24 has a flat shape, the cross-sectional shape of the extension portion 14 perpendicular to the flow path direction may be rectangular as shown in Fig. 8. That is, the cross-sectional shape of the extension portion 14 and the shape of the end face of the opening structure 24 on the inlet side ventilation pipe 12 side may be similar. By making the cross-sectional shape of the extension portion 14 rectangular, the extension portion 14 can be made thinner, and the ventilation type silencer can be made thinner.

[0046] In addition, in each of the above examples, the opening structure is a cylindrical shape, but is not limited thereto. The opening structure may be a structure in which two plate-like members face each other and the distance between the two plate-like members gradually decreases from inside the expansion section toward the connection section between the expansion section and the outlet side vent pipe (from the inlet side vent pipe side toward the outlet side vent pipe side).

[0047] The opening structure 24 shown in Fig. 9 has two curved plate-like members, which are arranged facing each other non-parallel, and the distance between the two plate-like members gradually decreases from the inlet side ventilation pipe 12 side toward the outlet side ventilation pipe 16 side. Also, the opening structure 24 shown in Fig. 9 is open in the direction perpendicular to the paper surface of Fig. 9.

[0048] When the opening structure 24 is made of two plate-like members as in the example shown in Fig. 9, it is preferable to arrange the porous sound-absorbing material 30 so as to be in contact with the side surfaces of the plate-like members, as in the example shown in Fig. 7. This increases the area of ​​the porous sound-absorbing material 30 exposed to the flow path, thereby improving the sound absorbing effect.

[0049] Furthermore, as in the example shown in Fig. 9, when the opening structure 24 is made of two plate-like members, the cross-sectional shape of the extension section 14 perpendicular to the flow path direction may be rectangular, as in the example shown in Fig. 8. In the example shown in Fig. 8, two plate-like members are arranged in the longitudinal direction of the long side in the cross section of the extension section 14.

[0050] In addition, in the examples shown in Figures 1 and 2, the central axis of the outlet side ventilation pipe coincides with the center of the side surface of the expansion section, but the central axis of the outlet side ventilation pipe may be offset from the center of the side surface of the expansion section.

[0051] For example, in the example shown in Fig. 10, the outlet side ventilation pipe 16 is connected to a position shifted downward in the figure from the center of the side surface of the expansion section 14. In addition, since the outlet side ventilation pipe 16 is connected to a position shifted from the center of the side surface of the expansion section 14, the opening structure 24 is also disposed at a position shifted from the center of the side surface of the expansion section 14. Note that Fig. 10 is a cross-sectional view parallel to the flow path direction.

[0052] In the example shown in FIG. 10, the opening structure 24 has two plate-like members that are substantially opposed to each other, and the plate-like member on the side closer to the housing of the extension part 14 (lower side in FIG. 10) is arranged parallel to the central axis of the outlet side ventilation pipe 16, and the other plate-like member is arranged non-parallel to the central axis of the outlet side ventilation pipe 16. That is, the two plate-like members are arranged non-parallel to each other, and the distance between the two plate-like members gradually decreases from the inlet side ventilation pipe 12 side to the outlet side ventilation pipe 16 side. In addition, the opening structure 24 shown in FIG. 10 is open in a direction perpendicular to the paper surface of FIG. 10. In addition, in the example shown in FIG. 10, the two plate-like members are integrally formed on the outlet side ventilation pipe 16 side. In addition, when viewed from the left side of FIG. 10, each plate-like member is curved concavely toward the central axis side.

[0053] The opening structure may be only one curved plate-like member among those shown in Fig. 10. For example, it may be a gradually larger opening structure with one side being a wall or porous sound-absorbing material and the other side being a curved plate-like member. In this way, the opening structure may be configured such that the cross section at the end on the inlet side vent pipe side is not closed.

[0054] By disposing the outlet side vent pipe and the opening structure at a position offset from the center of the side of the extension section, the distance between the end face of the opening structure on the inlet side vent pipe side and the inner wall of the extension section changes depending on the position, and the size of the opening of the back space changes depending on the position. This makes the resonance frequency in the back space different depending on the position, so the frequency range to be silenced can be made lower and wider. In addition, the ventilation type silencer can be installed in accordance with the spatial restrictions inside the device in which it is installed.

[0055] Also, even when the outlet side vent pipe and the opening structure are disposed at a position offset from the center of the side surface of the extension part as shown in Fig. 10, the shape of the extension part as viewed from the flow path direction may be substantially square as shown in Fig. 11, or substantially rectangular as shown in Fig. 12. Figs. 11 and 12 are cross-sectional views perpendicular to the flow path direction.

[0056] In the example shown in Fig. 10, the opening structure 24 has two plate-like members that are approximately facing each other, and the plate-like member on the side closer to the housing of the extension part 14 is arranged parallel to the central axis of the outlet side ventilation pipe 16, and the other plate-like member is arranged non-parallel to the central axis of the outlet side ventilation pipe 16, but this is not limited to the configuration. As in the examples shown in Figs. 13 and 14, the opening structure 24 may have two plate-like members that are approximately facing each other, and the plate-like member on the side farther from the housing of the extension part 14 is arranged parallel to the central axis of the outlet side ventilation pipe 16, and the plate-like member on the side closer to the housing may be arranged non-parallel to the central axis of the outlet side ventilation pipe 16. Note that Fig. 13 is a cross-sectional view parallel to the flow path direction, and Fig. 14 is a cross-sectional view perpendicular to the flow path direction.

[0057] 13 and 14, two plate-like members are arranged in the longitudinal direction of the long side of the cross section of the extension section 14, but the present invention is not limited to this. As in the example shown in Fig. 15 and 16, two plate-like members may be arranged in the longitudinal direction of the short side of the cross section of the extension section 14. Fig. 15 is a cross-sectional view parallel to the flow path direction, and Fig. 16 is a cross-sectional view perpendicular to the flow path direction.

[0058] 31, for example, in an extension section 14 having a rectangular cross-sectional shape, the porous sound-absorbing material 30 may be disposed so as to be in contact with the opening structure 24, and a space 14a may be formed on the rear side of the porous sound-absorbing material 30 (the side opposite the opening structure 24). In this configuration, the wind flowing through the ventilation type silencer does not easily pass through the porous sound-absorbing material 30, so the wind flow path smoothly connects from the porous sound-absorbing material 30 to the opening structure 24, resulting in a structure in which wind noise is unlikely to occur. This configuration can reduce the amount of porous sound-absorbing material 30 used compared to when the porous sound-absorbing material 30 is disposed throughout the extension section 14.

[0059] 32 to 34 show several examples of the shape of the example shown in FIG. 31 as viewed from the flow path direction. In the example shown in Fig. 32, the width of the extension section 14 in the left-right direction (direction perpendicular to the paper surface of Fig. 31) is approximately the same as the diameter of the outlet-side ventilation pipe 16, and the side surfaces of the two plate-like members constituting the opening structure 24 are approximately in contact with two wall surfaces existing in the width direction (left-right direction) of the extension section 14. In the case of this configuration, the porous sound-absorbing material 30 is arranged on the upper and lower sides of the opening structure 24 in Fig. 32.

[0060] In the example shown in Fig. 33, the width of the extension section 14 in the left-right direction (direction perpendicular to the paper surface of Fig. 31) is larger than the diameter of the outlet-side ventilation pipe 16. In this configuration, the porous sound-absorbing material 30 is arranged so as to surround the periphery of the opening structure 24, and the side surfaces of the two plate-like members constituting the opening structure 24 are approximately in contact with the porous sound-absorbing material 30 arranged on the left and right. Also, in the example shown in Fig. 33, the porous sound-absorbing material 30 is filled between the opening structure 24 and the two wall surfaces in the width direction (left-right direction) of the extension section 14.

[0061] In the example shown in Fig. 34, the width of the extension portion 14 in the left-right direction (direction perpendicular to the paper surface of Fig. 31) is larger than the diameter of the outlet-side ventilation pipe 16. In the configuration of Fig. 34, the porous sound-absorbing material 30 is arranged so as to surround the periphery of the opening structure 24, and the side surfaces of the two plate-like members constituting the opening structure 24 are approximately in contact with the porous sound-absorbing materials 30 arranged on the left and right. Also, in the example shown in Fig. 34, a space 14a is formed on the opposite side of the porous sound-absorbing material 30 to the opening structure 24 in the width direction (left-right direction).

[0062] The opening structure is not limited to a shape in which the cross-sectional shape expands as in the above-mentioned examples, and may be configured such that the thickness of the opening structure 24b at the end gradually becomes thinner as in the example shown in Fig. 35. That is, the opening structure 24b has the same cross-sectional shape as the outlet side vent pipe 16, and the thickness of the end on the inlet side vent pipe 12 side gradually becomes thinner toward the inlet side vent pipe 12. The opening structure 24b and the outlet side vent pipe 16 may be formed integrally.

[0063] For example, in the example shown in FIG. 35, when the inner diameter of the outlet side ventilation pipe 16 is 30 mm and the wall thickness is 2 mm, the ratio of the area of ​​the inner diameter (diameter 34 mm) of the tip end (inlet side ventilation pipe 12 side) to the area of ​​the inner diameter of the base end (outlet side ventilation pipe 16 side) of the opening structure 24b is 1.28 times, and when the wall thickness is 3 mm, the ratio of the area of ​​the inner diameter of the tip end to the area of ​​the inner diameter of the base end is 1.44 times, and the opening structure 24b has a configuration in which the cross-sectional area gradually changes. As in the example shown in FIG. 35, by configuring the opening structure 24b to have a region where the wall thickness gradually becomes thinner, the change in the cross-sectional area can be made gentle and wind noise can be reduced. In addition, it is preferable to keep the outer shape of the opening structure constant and gradually widen the inside, but it is also possible to configure the tip to be thin and pointed.

[0064] Furthermore, as in the example shown in FIG. 35, the opening structure 24b may have a region of constant thickness over a certain length and a region of gradually thinner thickness toward the tip, or may be composed only of a region of gradually thinner thickness. Also, a configuration may be used in which the thickness of the end portion of an opening structure having an expanding cross-sectional shape (outer shape) such as the examples shown in Figs. 1 to 16 is gradually reduced.

[0065] Here, in the present invention, the length and diameter of the inlet side vent pipe and the outlet side vent pipe, the size of the expansion part, the length of the opening structure, the size and shape of the end face on the inlet side vent pipe side, as well as the size of the back space, the area of ​​the opening of the back space, the size and flow resistance of the porous sound-absorbing material, etc. may be appropriately set according to the sound-absorbing performance (silencing frequency, silencing volume) and ventilation volume required for the ventilation type silencer.

[0066] In addition, in the present invention, if the resonance frequency in the back space when no porous sound-absorbing material is arranged is F, the first resonance frequency of the ventilation type silencer when no porous sound-absorbing material is arranged is f1, and the cutoff frequency determined by the cross-sectional area of ​​the opening of the outlet side ventilation pipe is fc, f1×(1-0.2) <F<fc It is preferable that the following is satisfied.

[0067] Here, the first resonance frequency f1 of the ventilation type silencer in a state where no porous sound absorbing material is arranged is the lowest frequency resonance that occurs in the flow path direction with the inlet and outlet of the ventilation type silencer as the node of sound pressure, and when the length of the ventilation type silencer is L, f1=2×(sound speed) / L is the frequency.

[0068] The cutoff frequency fc is a frequency determined by the cross-sectional dimensions of the flow path, and at frequencies below fc, the propagating sound waves can be approximated as plane waves and are easy to propagate. Generally, fc is When the cross-sectional shape of the outlet side of the vent pipe is circular fc=0.586×(speed of sound) / (diameter of circle) When the cross section of the outlet side of the vent pipe is rectangular fc=0.5×(speed of sound) / (long side of rectangle) It is.

[0069] In a typical expansion type ventilation silencer, resonance with the entrance and exit as nodes of sound pressure amplifies the transmitted sound waves and reduces the sound silencing performance. Improving the sound silencing performance of the first resonance frequency, which is the lowest frequency, is often a problem.

[0070] By lowering the resonance frequency F in the back space, the low-frequency sound deadening performance can be improved. However, there is a tendency for the sound deadening performance to deteriorate at higher frequencies than the resonance frequency F in the back space, and when this deterioration frequency and the deterioration frequency due to the first resonance are in a region close to each other, the sound deadening performance deteriorates significantly, so it is preferable that the resonance frequency F is 0.8 times or more the first resonance frequency f1 of the ventilation type silencer. It is more preferable that the resonance frequency F is 0.9 times or more.

[0071] Furthermore, at frequencies higher than the cutoff frequency fc of the outlet side vent pipe, sound is less likely to propagate through the vent pipe, and sound is silenced in the vent pipe section even without a silencer. Therefore, the resonant frequency F in the back space should be set to be equal to or lower than the cutoff frequency fc of the outlet side vent pipe.

[0072] The resonant frequency F in the back space can be measured by a normal incidence sound transmission loss measurement in accordance with ASTM E 2611, or by an acoustic simulation (not including fluid calculations) using the finite element method.

[0073] In addition, in each of the above-mentioned examples, the ventilation type silencer has an opening structure only on the outlet side vent pipe side, but this is not limited thereto, and an opening structure may be provided at the connection part between the expansion part and the inlet side vent pipe in the expansion part. The opening structure on the inlet side vent pipe side has the same structure as the opening structure on the outlet side vent pipe side, except that the cross-sectional area is gradually increased from the inlet side vent pipe side to the outlet side vent pipe side.

[0074] In the example shown in Fig. 1, the inlet side ventilation pipe 12 and the outlet side ventilation pipe 16 are configured so that their central axes are aligned in the same straight line, but this is not limiting. For example, as in the examples shown in Fig. 36 and Fig. 37, the inlet side ventilation pipe 12 and the outlet side ventilation pipe 16 may be configured so that their central axes are not aligned in the same straight line. Even in such a configuration, the opening structure can be disposed.

[0075] In the example shown in FIG. 36, a bent vent pipe 32 is disposed at the connection part of the extension part 14 with the inlet side vent pipe 12 to bend the flow path from the flow direction of the inlet side vent pipe 16 to the direction connecting the inlet side vent pipe 12 and the outlet side vent pipe 16. An opening structure 24 is disposed at the connection part of the extension part 14 with the outlet side vent pipe 16. The opening structure 24 is configured with two plate-like members disposed facing each other, and the two plate-like members are disposed so as to bend the flow path from the direction connecting the inlet side vent pipe 12 and the outlet side vent pipe 16 to the flow direction of the outlet side vent pipe 16. In addition, in the opening structure 24, one plate-like member is curved in a direction away from the other plate-like member in the direction from the outlet side vent pipe 16 toward the inlet side vent pipe 12. As a result, the opening structure 24 has a configuration in which the cross-sectional area gradually changes. In the example shown in FIG. 36, the opening structure 24 is configured such that one of the plate-like members has a curved structure, but it may be configured such that both plate-like members have a curved structure.

[0076] 37, the opening structure 24 has two plate-like members arranged facing each other, and the two plate-like members are curved. The two plate-like members are curved in the same direction, but with different radii of curvature, resulting in a configuration in which the cross-sectional area changes gradually.

[0077] Furthermore, even if the inlet side ventilation pipe 12 and the outlet side ventilation pipe 16 are configured such that their central axes are not collinear, the opening structure may have an area where the wall thickness gradually becomes thinner, so that the cross-sectional area gradually changes. 38, the opening structure 24b is made of two plate-like members, and the two plate-like members are curved so as to bend the flow path from the direction connecting the inlet side ventilation pipe 12 and the outlet side ventilation pipe 16 to the flow direction of the outlet side ventilation pipe 16. In addition, the tip side of the plate-like members (the inlet side ventilation pipe 12 side) has a region where the thickness gradually becomes thinner.

[0078] Furthermore, the average roughness Ra of the inner surface (the surface on the central axis side) of the aperture structure is preferably 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.1 mm or less. By reducing the average roughness Ra of the inner surface of the aperture structure, it is possible to suppress the wind flowing over the surface of the aperture structure from separating to generate vortices, thereby preventing wind noise.

[0079] In addition, when it is assumed that the ventilation type silencer of the present invention is used by connecting it to a hose, it is desirable that the inlet side ventilation pipe and the outlet side ventilation pipe of the ventilation type silencer have an uneven shape and / or a bellows shape on the outer circumferential surface. When connected to a hose, it is tightly fastened, so that wind leakage, sound leakage, sound reflection, etc. can be prevented.

[0080] In addition, in the ventilation type silencer of the present invention, the opening structure may be configured to be detachable from the expansion part. In this case, in order to make the opening structure shaped to be easily inserted into the opening formed in the expansion part, it is preferable that the outer shape of the cross section of the opening structure perpendicular to the central axis of the ventilation pipe is constant regardless of the position in the central axis direction.

[0081] Fig. 39 is a cross-sectional view conceptually showing another example of the ventilation type silencer of the present invention. Fig. 40 shows a view of the ventilation type silencer shown in Fig. 39 with the opening structure removed. Fig. 41 shows a front view (viewed from the central axis direction) of the opening structure of the ventilation type silencer shown in Fig. 39. The opening structure 24c shown in Fig. 40 can be said to be a cross-sectional view of line CC in Fig. 41.

[0082] The ventilation type silencer shown in Figure 39 has a cylindrical inlet side ventilation pipe 12, an extension section 14b connected to one open end face of the inlet side ventilation pipe 12, a cylindrical outlet side ventilation pipe 16 connected to the end face of the extension section 14b opposite to the face on the inlet side ventilation pipe 12 side, an opening structure 24c, and a porous sound-absorbing material 30. In the ventilation type silencer shown in FIG. 39, the inlet side ventilation pipe 12, the outlet side ventilation pipe 16, and the porous sound absorbing material 30 have the same configuration as the ventilation type silencer shown in FIG. 1, so the description thereof will be omitted. In addition, although the outlet side vent pipe 16 is not shown in FIG. 40, the opening structure 24c is detachable from the outlet side vent pipe 16.

[0083] The extension portion 14b of the ventilation type silencer shown in Fig. 39 has an opening 15 on the surface of the outlet side ventilation pipe 16 as shown in Fig. 40. The opening 15 has approximately the same size and shape as the outer shape of the opening structure 24c when viewed from the axial direction of the central axis of the ventilation pipe (hereinafter also referred to as the front view), so that the opening structure 24c can be inserted and installed in the extension portion 14b. In the illustrated example, the outer shape of the opening structure 24c in the front view is rectangular, so the shape of the opening 15 of the extension portion 14b is also rectangular.

[0084] In the illustrated example, the cross-sectional shape of the extension portion 14b perpendicular to the central axis of the ventilation pipe is substantially rectangular, and the porous sound-absorbing material 30 is disposed along each of the four inner surfaces of the extension portion 14b. Therefore, the cross-sectional shape perpendicular to the central axis of the space that becomes the ventilation passage surrounded by the porous sound-absorbing material 30 is substantially rectangular. The cross-sectional shape of the space that becomes the ventilation passage substantially coincides with the shape of the opening 15. In other words, the cross-sectional shape of the space that becomes the ventilation passage substantially coincides with the outer shape of the opening structure 24c in the front view.

[0085] As shown in Figures 40 and 41, the opening structure 24c has a cross-sectional shape perpendicular to the central axis of the vent pipe that is constant regardless of the position in the central axis direction, has a through hole penetrating two faces facing in the central axis direction, and is formed so that the cross-sectional area of ​​this through hole decreases from one face side (the inlet side vent pipe 12 side when installed in the expansion section 14b) to the other face side (the outlet side vent pipe 16 side when installed in the expansion section 14b). In other words, the opening structure 24c is substantially rectangular parallelepiped-shaped, has a through hole penetrating two opposing faces, and has a shape (tapered shape) in which the cross-sectional area of ​​this through hole decreases from one face to the other face.

[0086] In the illustrated example, on one surface side (the inlet side ventilation pipe 12 side) of the opening structure 24c, the cross-sectional shape perpendicular to the central axis of the through-holes approximately matches the cross-sectional shape of the space that becomes the ventilation passage surrounded by the porous sound-absorbing material 30. On the other hand, on the other surface side (the outlet side ventilation pipe 16 side) of the opening structure 24c, the cross-sectional shape perpendicular to the central axis of the through-holes approximately matches the cross-sectional shape of the outlet side ventilation pipe 16.

[0087] In this way, the opening structure 24c is shaped so that the outer shape of the cross section perpendicular to the central axis of the ventilation pipe is constant regardless of the position in the central axis direction, so that the opening structure 24c can be detached from the opening 15 provided in the extension part 14b. In addition, by making the opening structure 24c and the extension part 14b separate members, the design of each member is facilitated, and the manufacture by injection molding is also facilitated. In addition, by making the opening structure 24c a separate member, it is possible to easily change the opening structure 24c, so that, for example, the resonance frequency in the back space 26 surrounded by the opening structure 24c, the side of the extension part 14b on the outlet side ventilation pipe 16 side, and the inner peripheral surface of the extension part 14b can be easily set.

[0088] 1 and the like, the ventilation type silencer composed of the extension part 14b and the opening structure 24c can smoothly connect the space in the extension part 14b to the outlet side ventilation pipe 16 by the opening structure 24c, and can widen the sound absorbing effect by disposing the porous sound absorbing material 30 in the back space 26. Also, disposing the porous sound absorbing material 30 in the back space 26 makes it difficult for wind to flow into the back space 26, so that the decrease in the ventilation amount can be suppressed and the generation of wind noise can be suppressed.

[0089] In the example shown in Fig. 39, the cross-sectional shape of the extension portion 14b is rectangular, the cross-sectional shape of the space serving as the ventilation passage surrounded by the porous sound-absorbing material 30 is rectangular, and the outer shape of the opening structure 24c in the front view is rectangular, but this is not limited to this, and these shapes can be various shapes such as circles, ellipses, triangles, hexagons, and other polygonal shapes. Fig. 44 shows a front view of another example of the opening structure 24c. Furthermore, the cross-sectional shape of the extension portion 14b and the outer shape of the opening structure 24c in a front view do not have to be similar to each other.

[0090] 39, the porous sound-absorbing material 30 is arranged along the entire inner circumferential surface of the extension portion 14b, i.e., along each of the four inner surfaces of the rectangular extension portion 14b, but the present invention is not limited to this. For example, as in the example shown in FIG. 42, the porous sound-absorbing material 30 may not be arranged on one of the four inner surfaces of the rectangular extension portion 14b, and the opening structure 24c may be detachably attached so as to contact this inner surface.

[0091] 39 and 42, the porous sound-absorbing material 30 is arranged over the entire area of ​​the extension section 14b in the central axis direction, but this is not limited to this. The porous sound-absorbing material 30 only needs to be arranged at least at the entrance (opening) of the back space 26, and may be arranged not to be arranged in part of the back space 26, as in the example shown in Fig. 43. By reducing the amount of porous sound-absorbing material 30 arranged in the back space 26, the effect of resonance occurring in the back space 26 can be increased.

[0092] Materials for forming the vent pipe, the extension portion, and the opening structure include metal materials, resin materials, reinforced plastic materials, carbon fiber, etc. Metal materials include, for example, aluminum, titanium, magnesium, tungsten, iron, steel, chromium, chromium molybdenum, nichrome molybdenum, and alloys thereof. Examples of the resin material include acrylic resin (PMMA), polymethylmethacrylate, polycarbonate, polyamide, polyarylate, polyetherimide, polyacetal, polyetheretherketone, polyphenylene sulfide, polysulfone, polyethylene terephthalate, polybutylene terephthalate (PET), polyimide, triacetylcellulose (TAC), polypropylene (PP), polyethylene (PE), polystyrene (PS), ABS resin (acrylonitrile, butadiene, styrene copolymer synthetic resin), flame-retardant ABS resin, ASA resin (acrylonitrile, styrene, acrylate copolymer synthetic resin), PVC (polyvinyl chloride) resin, and PLA (polylactic acid) resin. Examples of the reinforced plastic material include carbon fiber reinforced plastics (CFRP: Carbon Fiber Reinforced Plastics) and glass fiber reinforced plastics (GFRP: Glass Fiber Reinforced Plastics).

[0093] From the viewpoints of weight reduction and ease of molding, it is preferable to use a resin material as the material for the ventilation type silencer. Also, from the viewpoint of sound insulation in the low frequency range, it is preferable to use a material with high rigidity. From the viewpoints of weight reduction and sound insulation, the density of the members constituting the ventilation type silencer is 0.5 g / cm 3 ~2.5g / cm 3 It is preferable that:

[0094] There are no particular limitations on the porous sound-absorbing material, and any conventionally known sound-absorbing material can be used as appropriate. For example, various known sound absorbing materials can be used, such as foams, foaming materials (urethane foam (e.g., Calmflex F by Inoac Corporation, urethane foam by Hikari Corporation, etc.), soft urethane foam, ceramic particle sintered material, phenol foam, melamine foam, polyamide foam, etc.), and nonwoven fabric sound absorbing materials (microfiber nonwoven fabric (e.g., Thinsulate by 3M Corporation), polyester nonwoven fabric (e.g., White Qion by Tokyo Soundproofing Co., Ltd., QonPET by Bridgestone KBG Corporation, and these products are also provided in a two-layer structure of a thin, high-density surface nonwoven fabric and a low-density back nonwoven fabric), and plastic nonwoven fabrics such as acrylic fiber nonwoven fabric, natural fiber nonwoven fabrics such as wool and felt, metal nonwoven fabrics, and glass nonwoven fabrics), as well as materials containing tiny air bubbles (glass wool, rock wool, nanofiber sound absorbing materials (silica nanofiber, acrylic nanofiber (e.g., XAI by Mitsubishi Chemical Corporation))).

[0095] It is desirable that these materials have non-combustible, flame retardant and self-extinguishing properties. It is also desirable that the entire ventilation type silencer has non-combustible, flame retardant and self-extinguishing properties. EXAMPLES

[0096] The present invention will be described in more detail below based on examples. The materials, amounts, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples.

[0097] [Comparative Example 1] Acrylic plates were combined to form a rectangular parallelepiped cylindrical member with an opening of 80 mm x 80 mm and a length of 200 mm. Two acrylic plate members with a hole of 28 mm diameter in the center and the same size as the opening surface of the cylindrical member were prepared, and the plate members were attached to both opening surfaces of the cylindrical member and acoustically blocked with tape to prepare an extension part. A cylindrical inlet side ventilation pipe and an outlet side ventilation pipe with an inner diameter of 28 mm and a length of 50 mm were prepared, and the center of the hole on the end surface of the extension part was aligned with the center of the cylinder and connected. In this way, a ventilation type silencer 100a having an inlet side ventilation pipe 112, an extension part 114, and an outlet side ventilation pipe 116 as shown in FIG. 17 was produced. The ventilation pipe was produced from ABS resin using a 3D printer (manufactured by XYZ Printing Co., Ltd.). The thickness of the ABS resin was 3 mm. The inner wall was polished.

[0098] [Comparative Example 2] A ventilation type silencer 100b as shown in FIG. 18 was produced in the same manner as in Comparative Example 1, except that a 15 mm-thick porous sound-absorbing material (QonPET, manufactured by Bridgestone KBG Corporation) 130 was arranged along the inner circumferential surface of the extension portion 114.

[0099] [Comparative Example 3] A horn-shaped tube (narrow side inner diameter 28 mm, wide side opening 50 mm x 50 mm, flow path direction length 45 mm, thickness 1.5 mm, made of ABS) with openings on both sides was produced using a 3D printer. The horn diameter was expanded in an exponential manner. This horn-shaped tube was used as the opening structure 124, and the opening on the narrow side (28 mm diameter side) was aligned and attached to the connection part of the extension part 114 with the outlet side ventilation pipe 116. A ventilation type silencer 100c as shown in FIG. 19 was produced in the same manner as in Comparative Example 1. A back space 126 is formed between the peripheral surface and side surface of the extension part 114 and the opening structure 124.

[0100] [Example 1] A 15 mm thick porous sound absorbing material (QonPET, manufactured by Bridgestone KBG Corporation) 30 was arranged along the inner peripheral surface of the extension portion 14, and an opening structure 24 similar to the opening structure made in Comparative Example 3 was attached to the connection portion of the extension portion 14 with the outlet side ventilation pipe 16, with the opening on the narrow side (28 mm diameter side) aligned, and the ventilation type silencer 10 was produced in the same manner as in Comparative Example 1. A back space 26 is formed between the peripheral surface and side surface of the extension portion 14 and the opening structure 24. The porous sound absorbing material 30 is arranged at the opening of the back space 26.

[0101] [evaluation] The noise absorbing performance of the produced ventilation type silencer during ventilation was measured using a measuring device as shown in FIG.

[0102] As shown in FIG. 20, a 2 m inlet hose (transparent vinyl hose (inner diameter 28 mm) manufactured by Chubu Vinyl Industries Co., Ltd.) 208 was connected to the inlet vent pipe of the ventilation type silencer, and two blower fans (San Ace DC blower (model number 9BMC24P2G001) manufactured by Sanyo Denki Co., Ltd.) 204 were arranged on the tip side of the inlet hose 208. A straightening plate 206 was connected so that the air blown from the blower fan 204 driven by a voltage of 24 V flows into the inlet hose 208. In addition, a 3 m outlet hose 210 was connected to the outlet vent pipe, and the tip of the outlet hose 210 was arranged in the reverberation chamber 202. Four measurement microphones were installed in the reverberation chamber 202.

[0103] The two blower fans 204 were driven to blow air, and measurements were taken with four measurement microphones. The frequency range of 62.5 Hz to 5000 Hz was analyzed in 1 / 3 octave bands to determine the sound pressure level (average value of the four microphones).

[0104] In addition, the sound pressure level was obtained using a state where the ventilation type silencer was not provided and the inlet side hose 208 and the outlet side hose 210 were directly connected as a reference (ref). The measurement results of the sound pressure levels in the example, comparative example, and reference are shown in the graphs of Fig. 21 and Fig. 22. Further, the difference in sound pressure level between the Example and Comparative Example and the Reference was determined as the amount of attenuation. Comparisons between Example 1 and Comparative Examples 1 to 3 are shown in Figs. 23, 24, and 25, respectively.

[0105] FIG. 26 shows the results of determining the total amount of muffling in the frequency range of 62.5 Hz to 5000 Hz for each of Example 1 and Comparative Examples 1 to 3.

[0106] Next, the transmission loss of each ventilation type silencer in the non-ventilated state was evaluated by the normal incidence transmission loss measurement method specified in ASTM E2611-09. Comparisons between Example 1 and Comparative Examples 2 and 3 are shown in Figures 27 and 28, respectively.

[0107] Next, the ventilation volume (wind speed) was measured using a measuring device as shown in FIG.

[0108] As shown in Fig. 29, an inlet hose 208, a straightening plate 206, and two blower fans 204 were arranged on the inlet vent pipe side of the ventilation type silencer, similar to the measurement device shown in Fig. 20. A 30 cm outlet hose 212 was connected to the outlet vent pipe of the ventilation type silencer, and an anemometer (Tenmars wind speed / volume meter TM-413) 214 was connected to the tip of the outlet hose 212.

[0109] The two blower fans 204 were driven to blow air, and the wind speed passing through the ventilation type silencer was measured by an anemometer 214. The wind speed inside the hose was calculated from the wind speed measured by the anemometer using the following formula. The results are shown in FIG. (Air speed inside the hose) = (Air speed on the anemometer) x (Wind receiving area on the anemometer) / (Cross-sectional area of ​​the hose)

[0110] 23, 24, 25 and 26 show that the examples of the present invention have higher sound deadening performance than the comparative examples. Comparative example 3, which has an opening structure, has the same sound deadening volume as example 1 at the peak around 1200 Hz, but there is a frequency band between 700 Hz and 1200 Hz where the sound deadening volume becomes small, and it is found that good sound deadening performance cannot be obtained in the low frequency range.

[0111] Also, from Fig. 27, it can be seen that the acoustic sound deadening performance (when there is no wind) in the vicinity of 500 Hz is improved by having an opening structure in Example 1. Also, from Fig. 28, it can be seen that while the sound deadening performance deteriorates in Comparative Example 3 at the first resonance (850 Hz), Example 1 has a porous sound-absorbing material and can widen the frequency band of the rear resonance, improving the sound deadening performance in this frequency band and improving the total sound deadening volume.

[0112] Also, from FIG. 30, it can be seen that the embodiment of the present invention has higher ventilation performance than the comparative example. The above results clearly show the effects of the present invention. [Explanation of symbols]

[0113] 10, 100a~100c ventilation type silencer 12, 112 Inlet ventilation pipe 14, 14b, 114 Extension 16, 116 Outlet side ventilation pipe 24, 24b, 24c, 124 opening structure 26, 126 back space 30, 130 Porous sound absorbing material 32 Bent vent pipe

Claims

1. an inlet side ventilation pipe; an expansion part communicating with the inlet side ventilation pipe and having a larger cross-sectional area than the inlet side ventilation pipe; and an outlet side ventilation pipe communicating with the expansion part and having a smaller cross-sectional area than the expansion part, The opening structure has a cross-sectional area that gradually decreases from within the expansion portion toward a connection portion between the expansion portion and the outlet-side ventilation pipe, a rear space surrounded by the opening structure, a side surface of the extension portion on the outlet-side vent pipe side, and a peripheral surface of the extension portion, A ventilation type silencer having a porous sound absorbing material disposed at least at an opening of the back space.

2. The resonance frequency in the back space when the porous sound-absorbing material is not disposed is F, and the first resonance frequency of the ventilation type silencer when the porous sound-absorbing material is not disposed is f 1 and the cutoff frequency determined by the cross-sectional area of ​​the opening of the outlet side vent pipe is f c , f 1 ×(1-0.2)<F<f� The ventilation type silencer according to claim 1, which satisfies the above.

3. The opening structure has a rectangular cross-sectional shape perpendicular to the central axis of the outlet side ventilation pipe, and the distance between a pair of opposing sides gradually decreases from inside the extension portion toward the connection portion between the extension portion and the outlet side ventilation pipe, and the distance between the other pair of opposing sides is constant.

4. 3. The ventilation type silencer according to claim 1 or 2, wherein the opening structure has a structure in which two plate-shaped members face each other, and the distance between the two plate-shaped members gradually becomes shorter from inside the extension portion toward the connection portion between the extension portion and the outlet side ventilation pipe.

5. 3. The ventilation type silencer according to claim 1, wherein the extension portion has a rectangular cross section perpendicular to a central axis of the outlet side ventilation pipe.

6. 3. The ventilation type silencer according to claim 1, wherein a central axis of the outlet side vent pipe and a central axis of the inlet side vent pipe are aligned on a straight line.

7. 3. The ventilation type silencer according to claim 1, wherein the porous sound absorbing material is disposed in a region from a side surface of the extension portion on the inlet side vent pipe side to a side surface of the extension portion on the outlet side vent pipe side.

8. 3. The ventilation type silencer according to claim 1, wherein a central axis of the outlet side ventilation pipe is offset from a center of the side surface of the extension portion.

9. 3. The ventilation type silencer according to claim 1, wherein the opening structure has a region in which the thickness decreases toward the inlet side ventilation pipe.

10. The ventilation type silencer according to claim 1 or 2, wherein the opening structure is detachable from the extension portion.

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