Fan with silencer

Abstract

To provide a fan with a silencer capable of effectively muffling noise in consideration of characteristics inside a housing that houses the fan and characteristics of noise generated by the rotation of the fan.　The fan with a silencer comprises: a housing provided with an opening; a fan housed in the housing; and a silencer for muffling sound generated by the rotation of the fan. A first portion located near the opening and a second portion which is farther from the opening than the first portion and has a higher acoustic impedance than the first portion are present inside the housing. The silencer has a ventilation part communicating with the opening, and the acoustic impedance of the ventilation part is higher than the acoustic impedance of the first portion.

Description

Fan with silencer

[0001] The present invention relates to a fan with a silencer, which has a fan housed in a housing and a silencer that silences noise generated by the rotation of the fan.

[0002] It is important that a silencer that can efficiently reduce noise generated by the rotation of a fan can do so without reducing the airflow. For this reason, in conventional silencer-equipped fans, the resonant silencer, which has a high ability to absorb sound, is sometimes placed on the outside of the housing so as not to block the air path. An example of such a silencer-equipped fan is the fan described in Patent Document 1.

[0003] The silencer-equipped fan described in Patent Document 1 is used, for example, as an outdoor unit of an air conditioner, and includes a resonance silencer located in a position connected to a space where a sound source (specifically, a fan inside a housing) is located. The resonance silencer is located near an exhaust hole provided in the housing, and has a vent that communicates with the exhaust hole.

[0004] International Publication No. 2021 / 1717110

[0005] In the silencer-equipped fan described in Patent Document 1, a member for restricting the airflow path within the housing, such as a shroud (bell mouth), may be disposed inside the housing that houses the fan. Meanwhile, the airflow path in the space within the housing where the airflow path restricting member is provided is narrower than in the other spaces, resulting in higher acoustic impedance.

[0006] Furthermore, when a fan rotates, it generates noise, specifically narrowband rotational noise and broadband turbulent noise. Because these noises (hereinafter also referred to as fan noise) are emitted from a dipole noise source, they are highly directional, with sound pressure levels particularly high in the direction of the fan's airflow. Taking into account the characteristics of fan noise and the aforementioned characteristics inside the housing, there is a demand for a silencer that can more effectively silence noise.

[0007] The present invention has been made in light of the above circumstances, and aims to solve the problems of the prior art described above and provide a fan with a silencer that can effectively muffle noise by taking into account the characteristics of the interior of the housing that houses the fan and the characteristics of the noise generated by the rotation of the fan.

[0008] As a result of intensive research into achieving the above object, the inventors have found that the above object can be achieved by the following configuration: [1] A fan with a silencer, comprising: a housing with an opening, a fan housed in the housing, and a silencer that silences noise generated by rotation of the fan, wherein the housing has a first portion located on the opening side and a second portion that is farther from the opening than the first portion and has a higher acoustic impedance than the first portion, the silencer has a vent portion that communicates with the opening, and the acoustic impedance of the vent portion is higher than the acoustic impedance of the first portion. [2] The fan with a silencer according to [1], wherein the acoustic impedance of the vent portion is lower than the acoustic impedance of the second portion, and the first portion is located between the second portion and the vent portion in the axial direction of the rotation axis of the fan. [3] The fan with silencer according to [1] or [2], wherein the housing has a first intake hole as an opening provided in a first wall of the housing and an exhaust hole provided in a second wall of the housing, and in the second section, at least a part of a tubular member that regulates the flow of gas from the fan toward the exhaust hole is disposed between the fan and the exhaust hole, and the silencer is disposed with its ventilation part adjacent to the first intake hole. [4] The fan with silencer according to [3], wherein a side wall disposed between the first and second walls of the housing has a communication hole that connects the inside of the housing with an external space of the housing, and within the housing, the first section is located adjacent to the communication hole. [5] The fan with silencer according to [4], wherein the communication hole is a second intake hole, and the fan takes in gas from the external space through the first intake hole and the second intake hole and discharges the gas through the exhaust hole. [6] The silencer-equipped fan according to any one of [1] to [5], wherein a resistance member that provides resistance to the flow of gas passing through the opening is provided at an end of the internal space of the housing on the opening side. [7] The silencer-equipped fan according to [6], wherein the resistance member is a heat exchanger. [8] The silencer-equipped fan according to [6] or [7], wherein the resistance member is adjacent to the opening in the axial direction of the rotation shaft of the fan, and the ventilation part is adjacent to the opening on the side opposite to the resistance member. [9] The silencer-equipped fan according to any one of [1] to [8], wherein the silencer comprises a cylindrical rigid frame that surrounds the ventilation part.

[10] The silencer-equipped fan according to any one of [1] to [8], wherein the silencer comprises an opening-equipped wall surrounding the ventilation section and having a silencer-side opening provided therein, and a back space partitioned by the opening-equipped wall and communicating with the opening via the ventilation section and the silencer-side opening.

[11] The silencer-equipped fan according to

[10] , wherein the silencer muffles sound by resonance of a resonance structure formed by at least the silencer-side opening and the back space.

[12] The silencer-equipped fan according to

[11] , wherein a conversion mechanism that converts sound energy into thermal energy is provided in at least one of the silencer-side opening and the back space.

[13] The silencer-equipped fan according to any one of [1] to

[12] , wherein the silencer has an outer peripheral wall, and a through-hole is provided in a lower end of the outer peripheral wall.

[14] The silencer-equipped fan according to any one of [1] to

[13] , wherein the fan is a fan for an outdoor unit of an air conditioning system.

[0009] According to the present invention, it is possible to provide a fan with a silencer that can effectively muffle noise by taking into consideration the internal structure of the housing in which the fan is housed and the characteristics of the noise generated by the rotation of the fan.

[0010] FIG. 1 is a diagram showing an example of noise silenced by a silencer according to an embodiment of the present invention, showing a noise spectrum. FIG. 2 is a perspective view of a silencer-equipped fan according to an embodiment of the present invention. FIG. 3 is a diagram showing the I-I cross section of FIG. 2. FIG. 4 is a diagram showing the internal structure of a silencer, showing a J-J cross section of FIG. 3. FIG. 5 is a diagram showing the distribution of acoustic impedance inside a housing according to a comparative example. FIG. 6 is a diagram showing the distribution of acoustic impedance in a silencer-equipped fan according to an embodiment of the present invention. FIG. 7 is a perspective view of a silencer-equipped fan according to a modified example of the present invention, showing the silencer-equipped fan from the rear side. FIG. 8 is a diagram showing a silencer provided in a silencer-equipped fan according to a modified example of the present invention, showing the silencer from the rear side. FIG. 9 is a diagram showing measurement results of sound pressure levels in Examples 1 and 3, and Comparative Example 1 (Reference). FIG. 10 is a diagram showing measurement results of sound pressure levels in Examples 2 and 4, and Comparative Example 1 (Reference). FIG. 11 is a diagram showing the sound pressure level measurement results in Examples 2 and 4, and Comparative Example 1 (Reference). FIG. 12 is a diagram showing the sound pressure level measurement results in Examples 1 and 3. FIG. 13 is a diagram showing the sound pressure level measurement results in Examples 2 and 4.

[0011] The present invention will now be described in detail with reference to preferred embodiments shown in the accompanying drawings. The following embodiments are merely examples provided to facilitate understanding of the present invention and are not intended to limit the scope of the present invention. In other words, the configuration of the present invention may be modified or improved from the following embodiments without departing from the spirit of the present invention. Furthermore, unless otherwise specified, the materials and shapes of each component used to implement the present invention may be arbitrarily set depending on the intended use of the present invention and the state of the art at the time of implementing the present invention. Furthermore, the present invention includes equivalents thereof.

[0012] Furthermore, in this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. Furthermore, in this specification, "orthogonal," "vertical," and "parallel" are intended to include the range of error acceptable in the technical field to which the present invention belongs. For example, "orthogonal," "vertical," and "parallel" in this specification mean that they are within a range of less than ±10° from the strict "orthogonal," "vertical," and "parallel." Note that the error from the strict "orthogonal," "vertical," and "parallel" is preferably 5° or less, and more preferably 3° or less. Furthermore, in this specification, the meanings of "same" and "identical" may include the range of error generally acceptable in the technical field to which the present invention belongs. Furthermore, in this specification, "100%" includes 100% in the strict sense, as well as a state in which, although it does not actually reach 100% due to structural constraints, it also includes a state that is as close to 100% as possible.

[0013] In addition, "sound deadening" in the present invention means reducing sound, and is a concept that includes both sound insulation and sound absorption. Sound insulation also includes sound reflection and sound cancellation.

[0014] <<Overview of Silencer-Equipped Fan of the Present Invention>> The silencer-equipped fan of the present invention includes a housing provided with an opening, a fan housed in the housing, and a silencer that silences noise generated by the rotation of the fan. The noise generated by the rotation of the fan (fan noise) is primarily rotational noise such as wind noise and turbulent noise. Using the noise of an air conditioner outdoor unit as an example, as shown in Figure 1, the broadband noise observed between 400 Hz and 1000 Hz is turbulent noise, and the noise with a peak observed below 100 Hz is rotational noise.

[0015] The housing includes a first portion located on the opening side and a second portion located farther from the opening than the first portion and having a higher acoustic impedance than the first portion. The acoustic impedance is defined by the following equation (1): Z = ρ × c / S (1) In the above equation (1), Z is the acoustic impedance (unit: Pa·s / m ３ ) and ρ is the density of air (unit: kg / m ３ ), c represents the speed of sound (unit: m / s), S (unit: m ２ ) indicates the effective area of ​​the target space for which the acoustic impedance is calculated. The target space is the space through which sound travels, and in the present invention, corresponds to the space through which the wind from the fan flows, i.e., the air path. The method for calculating the effective area will be described later.

[0016] The silencer also has a vent that communicates with the opening of the housing, and the acoustic impedance of the vent is higher than the acoustic impedance of the first portion, thereby confining the noise generated when the fan rotates (fan noise) within the housing, and effectively muffling the fan noise by preventing sound loss due to collisions with components within the housing and directional diffusion, etc.

[0017] <<Configuration Example of a Silencer-Equipped Fan According to One Embodiment of the Present Invention>> A configuration example of a silencer-equipped fan according to one embodiment of the present invention (hereinafter, this embodiment) will be described with reference to FIGS. 2 to 4. In the following description, the position, orientation, posture, and state of each device and component refer to the position, orientation, posture, and state when the silencer-equipped fan is in its normal operating position, unless otherwise specified. The silencer-equipped fan according to this embodiment (hereinafter, the silencer-equipped fan 10) has the appearance shown in FIG. 2 and is used, for example, in the outdoor unit of an air conditioning system (more specifically, a building air conditioner). In other words, the silencer-equipped fan 10 is used in an open space, more specifically, an outdoor space. However, the use of the silencer-equipped fan 10 is not particularly limited, and it may be used for purposes other than the outdoor unit of a building air conditioner, such as car air conditioners, air purifiers, ventilation fans, electric fans, circulators, dehumidifiers, humidifiers, jet engines, air-cooling devices for computers and copiers, and other air-cooling devices.

[0018] 2 and 3, the silencer-equipped fan 10 includes a fan 12, a housing 20, a heat exchanger 40, a shroud 42, a grill 44, and a silencer 50. Each of these components will be described below.

[0019] (Fan) The fan 12 is a blower fan, and in this embodiment, it is a fan that blows air in the axial direction of the rotation shaft (hereinafter simply referred to as the axial direction). In this embodiment, as described above, the fan 12 is a fan for an outdoor unit of an air conditioning system, and blows air by expelling gas that has entered the housing 20, more specifically, air, to the outside of the housing 20. Here, wind refers to an artificial flow of air and gas (airflow). The composition of the air or gas that constitutes the wind and the ratio of each gas component are not particularly limited.

[0020] In the following description, the fan 12 is assumed to be an axial fan that blows normal air. However, the fan 12 may be a fan other than an axial fan, such as a centrifugal fan, a backward-curved fan (turbofan), a blade fan, a radial fan, a paddle fan, a multi-blade fan (sirocco fan), a tubular centrifugal fan, a mixed-flow fan, an axial fan, a vane-axial fan, a tube-axial fan, a propeller fan, a counter-rotating axial fan, a line flow fan (registered trademark), a cross-flow fan, or a vortex fan.

[0021] The structure of the fan 12 is the same as that of a known axial flow fan. As shown in FIG. 3 , a plurality of rotor blades 16 extend radially from the outer periphery of a cylindrical central portion 14 (hereinafter simply referred to as the radial direction). A rotor shaft 18 is disposed within the central portion 14 with its axial direction oriented horizontally. The rotor shaft 18 rotates using the torque of a motor (not shown), causing the central portion 14 and the rotor blades 16 to rotate integrally with the rotor shaft 18. As a result, air flows from upwind of the fan 12 to downwind of the fan 12 in the axial direction. Note that, hereinafter, the downwind side of the fan 12 in the axial direction will also be referred to as the "front side," and the upwind side will also be referred to as the "rear side" or "back side."

[0022] When the fan 12 rotates within the housing 20, fan noise, including wind noise, is generated. That is, the rotating blades 16 of the fan 12 correspond to the noise source, which in this embodiment is a dipole noise source. Therefore, the noise generated by the rotation of the fan 12 travels axially inside the housing 20 toward the front and rear, and passes through the first intake hole 30 and the exhaust hole 34 (described later) toward the outside of the housing 20.

[0023] As shown in FIG. 3 , in this embodiment, a small silencer for the fan 12 (hereinafter referred to as a fan silencer 70) is attached to the front end of the central portion 14 in the axial direction. The fan silencer 70 may be a resonance-type silencer or a silencer made of sound-absorbing material. Resonance-type silencers that can be used include membrane-type resonators, air column resonators, Helmholtz resonators, and resonators made of perforated plates. The fan silencer 70 is preferably positioned so as not to overlap with the rotor blades 16 when viewed from the axial direction, i.e., so as not to affect the airflow rate of the fan 12, and is preferably fixed to the front end face of the central portion 14 with adhesive or fasteners such as screws.

[0024] (Housing) The housing 20 is a hollow body having a box or cylindrical shape, and houses the fan 12. The material of the housing 20 is not particularly limited, and examples of materials that can be used include metal materials, wood, resin materials including reinforced plastic materials, and carbon fiber.

[0025] 2 and 3 , the housing 20 has a first wall 22, a second wall 24, and a side wall 26. The first wall 22 is one end of the housing 20 in the axial direction, more specifically, a wall (rear wall) forming the rear end, and a first air intake hole 30 is provided in the first wall 22. The first air intake hole 30 corresponds to an opening of the housing 20 in this embodiment. The second wall 24 is the other end of the housing 20 in the axial direction, more specifically, a wall (front wall) forming the front end, and an exhaust hole 34 is provided in the second wall 24.

[0026] The shapes of the first intake holes 30 and the exhaust holes 34 (more specifically, the shape of the outer edge of each hole) are not particularly limited, and may be circular, elliptical, square, rectangular, other quadrilaterals, polygons other than quadrilaterals, or irregular shapes. Furthermore, the sizes of the first intake holes 30 and the exhaust holes 34 (more specifically, the areas of the holes when viewed in the axial direction) are not particularly limited, and may be the same or different between the first intake holes 30 and the exhaust holes 34. In this embodiment, the rectangular first intake holes 30 are provided over a wide area in the first wall 22, and the circular exhaust hole 34 is provided in the center of the second wall 24.

[0027] The side wall 26 is a generally rectangular cylindrical wall located between the first wall 22 and the second wall 24 in the axial direction. As shown in Figures 2 and 3, the side wall 26 forms the top, bottom, right, and left walls of the housing 20. As shown in Figure 3, one end of the side wall 26 in the lateral width direction of the housing 20 (hereinafter simply referred to as the lateral width direction), specifically the left or right end of the side wall 26, corresponds to the third wall 28. Here, the lateral width direction refers to a direction that intersects both the up-down direction and the axial direction of the silencer-equipped fan 10, or more precisely, a direction that is perpendicular to these directions.

[0028] 3, a second air intake hole 32 is provided in the third wall 28. This second air intake hole 32 corresponds to a communication hole that connects the interior of the housing 20 with the space outside the housing 20. In other words, the side wall 26 of the housing 20 in this embodiment does not have a completely closed cross-sectional structure, and the portion of the third wall 28 where the second air intake hole 32 is provided is missing.

[0029] The shape of the second air intake holes 32 (more specifically, the shape of the outer edge of the second air intake holes 32) is not particularly limited, and may be circular, elliptical, square, rectangular, other quadrilaterals, polygonal shapes other than quadrilaterals, or an irregular shape. Furthermore, the size of the second air intake holes 32, i.e., the opening area (more specifically, the area of ​​the second air intake holes 32 when viewed from a direction penetrating the third wall 28), is not particularly limited. In this embodiment, the rectangular second air intake holes 32 are provided over a wide area in the third wall 28. More specifically, the rear end of the third wall 28 and the rear end of the second air intake holes 32 are located at approximately the same position in the axial direction, and the front end of the second air intake holes 32 is located closer to the front end of the third wall 28 than to the axial center of the third wall 28.

[0030] The second air intake holes 32 also function as side air intakes, and when the fan 12 is rotating, air enters the housing 20 not only through the first air intake holes 30 but also through the second air intake holes 32. In other words, the fan 12 takes in air from the space outside the housing 20 through the first air intake holes 30 and the second air intake holes 32 and expels the air (wind) through the exhaust holes 34. In other words, within the housing 20, there is an air passage through which air that has passed through the first air intake holes 30 flows, and an air passage through which air that has passed through the second air intake holes 32 flows, and these two air passages meet behind the fan 12 in the axial direction.

[0031] 3, in the present embodiment, the range in the width direction in which the first air intake holes 30 are provided overlaps at least a part of the range in which the exhaust holes 34 are provided. On the other hand, the second air intake holes 32 are arranged in a position in the width direction that is different from the first air intake holes 30 and the exhaust holes 34, more specifically, in a position that does not overlap with these holes.

[0032] As shown in Fig. 3, a machine chamber 36 is provided inside the housing 20 and is adjacent to the space housing the fan 12 in the width direction, and a compressor (not shown) is disposed in the machine chamber 36. As such, the interior of the housing 20 is divided into an air passage space in which the fan 12 is disposed and which forms a flow path (air passage) for air passing through the fan 12, and the machine chamber 36, and these two spaces are separated by a partition wall 38 as shown in Fig. 3. The first intake hole 30, the second intake hole 32, and the exhaust hole 34 are all continuous with the air passage space. Hereinafter, unless otherwise specified, the internal space of the housing 20 will refer to the above-mentioned air passage space.

[0033] (Heat Exchanger) The heat exchanger 40 is disposed in the internal space of the housing 20, closer to the rear side than the fan 12, and is disposed within the first air intake vent 30 in the axial direction. The heat exchanger 40 is disposed within the first air intake vent 30 so that its rear end (the end opposite the fan 12) is flush with the rear end surface of the housing 20 in the axial direction. In this embodiment, as shown in FIG. 3 , a heat exchanger 40 is also disposed within the second air intake vent 32. Note that FIG. 2 omits the illustration of the heat exchanger 40 disposed within the second air intake vent 32 in order to explain the internal configuration of the housing 20. The heat exchanger 40 is formed, for example, by a fin coil, a fin tube, or a heat exchange plate, and exchanges heat with air entering the housing 20 through the first air intake vent 30 to heat or cool the air. In other words, the air entering the housing 20 through the first air intake vent 30 passes through the heat exchanger 40 on its way to the fan 12. In other words, the heat exchanger 40 corresponds to a resistance member that provides resistance to the flow of air that passes through the first air intake port 30 and flows toward the fan 12 .

[0034] As described above, the noise generated by the rotation of the fan 12 (fan noise) travels through the housing 20 toward the first air intake vent 30, passes through the first air intake vent 30, and is then released to the outside of the housing 20. In this embodiment, the heat exchanger 40 is disposed adjacent to the first air intake vent 30, so the noise collides with the heat exchanger 40 before passing through the first air intake vent 30. This causes a loss of sound, and it is possible to reduce the noise passing through the first air intake vent 30. Note that the device is not limited to the heat exchanger 40, and may be, for example, a dust filter and its holder, as long as it has resistance to the air flowing toward the fan 12.

[0035] (Shroud) As shown in Fig. 3 , the shroud 42 is a tubular member that is disposed within the housing 20 and adjusts the flow of air (i.e., the wind direction) from the fan 12 toward the exhaust holes 34 inside the housing 20. The shroud 42 extends in the axial direction, and at least a portion of the shroud 42 is disposed axially between the fan 12 and the exhaust holes 34, as shown in Fig. 3 . The air from the fan 12 passes through the shroud 42 toward the exhaust holes 34 and is discharged from the exhaust holes 34. In other words, the shroud 42 defines an air passage within its internal space through which the air from the fan 12 flows.

[0036] Furthermore, the area of ​​the air passage within the shroud 42 is smaller than the area of ​​the air passage on the rear side (first air intake port 30 side) of the shroud 42 inside the housing 20. The area of ​​the air passage is the area when the shroud 42 is viewed in the axial direction, and is the area through which the air passes, i.e., the flow path area.

[0037] 3, in the present embodiment, the rear end of the shroud 42 approaches the area in which the fan 12 is provided in the axial direction. In other words, the rear end of the shroud 42 is located rearward of the front end of the fan 12 in the axial direction (i.e., closer to the first air intake holes 30). In addition, the shroud 42 may approach the area in which the second air intake holes 32 are provided in the axial direction, or may be located forward of the second air intake holes 32 (downstream in the air blowing direction).

[0038] (Grill) The grill 44 corresponds to a breathable member that collides with the flow of air (wind) that flows inside the housing 20 and flows out of the housing 20 through the exhaust holes 34. The grill 44 is formed, for example, of a lattice panel, and the wind passes through the open portions of the grill 44 while collides with the non-open portions (more specifically, the linear portions) of the grill 44. In this embodiment, as shown in FIG. 3 , the grill 44 is disposed adjacent to the exhaust holes 34 in the axial direction. However, the position of the grill 44 is not limited to the position shown in FIG. 3 , and the grill 44 may be disposed adjacent to the first intake holes 30.

[0039] (Muffler) The silencer 50 is disposed adjacent to the housing 20 on the rear side of the housing 20, and silences at least noise generated by the rotation of the fan 12 housed in the housing 20 through resonance, thereby silencing fan noise. The silencer 50 silences noise by resonating with the sound to be silenced in an open space, rather than in a closed space such as the inside of a duct. Note that in this embodiment, the silencer 50 silences noise through resonance and sound absorption. As shown in FIG. 3 , the silencer 50 has a ventilation section 52, an opening-equipped wall 56 having a silencer-side opening 54, a rear space 60 partitioned by the opening-equipped wall 56 and an outer peripheral wall 62, and a conversion mechanism 66.

[0040] The ventilation section 52 is a hollow section that communicates with the first air intake hole 30, and in this embodiment, is adjacent to and continuous with the first air intake hole 30 in the axial direction. In other words, the silencer 50 is disposed in an open space with the ventilation section 52 adjacent to the first air intake hole 30. Air that passes through the first air intake hole 30, i.e., air heading toward the inside of the fan 12, flows through the ventilation section 52. In other words, the ventilation section 52 forms an air path in the silencer 50.

[0041] Furthermore, the shape of the ventilation portion 52 when viewed in the axial direction (more specifically, the shape formed by the outer edge of the space surrounded by the inner circumferential surface 58 of the opening-equipped wall 56) is not particularly limited, but from the perspective of communicating between the ventilation portion 52 and the first air intake hole 30 without blocking the first air intake hole 30, it is preferable that the shape be the same as that of the first air intake hole 30. This ensures good communication between the first air intake hole 30 and the ventilation portion 52, allowing the silencer 50 to be appropriately positioned with respect to the fan 12 and the housing 20 so as not to reduce the airflow rate of the silencer-equipped fan 10. The size (opening area) of the ventilation portion 52 is not particularly limited, but may be the same as or different from the size of the first air intake hole 30.

[0042] Furthermore, the center of the first air intake hole 30 and the center of the ventilation portion 52 may not be on the same straight line, but may be slightly offset.

[0043] The opening wall 56 is an annular or frame-shaped wall that surrounds the ventilation section 52. That is, the opening wall 56 functions as a frame that surrounds the ventilation section 52 and separates the ventilation section 52. The material of the opening wall 56 is not particularly limited, and examples that can be used include metal materials, wood, resin materials including reinforced plastic materials, and carbon fiber.

[0044] 3 and 4, the opening wall 56 is provided with a plurality of silencer-side openings 54. Each of the plurality of silencer-side openings 54 is a hole that penetrates the opening wall 56, with one end thereof contacting the ventilation section 52 and the other end contacting the rear space 60. In other words, by providing each silencer-side opening 54, the ventilation section 52 and the rear space 60 communicate with each other.

[0045] The multiple silencer-side openings 54 are provided at intervals in the circumferential direction (hereinafter simply referred to as the circumferential direction) of the opening-equipped wall 56. Note that, although four silencer-side openings 54 are provided in the configuration shown in Fig. 4, the number of silencer-side openings 54 provided in the opening-equipped wall 56 and the interval (pitch) at which the silencer-side openings 54 are provided in the circumferential direction are not particularly limited and can be determined arbitrarily.

[0046] The shape of each silencer-side opening 54 is not particularly limited, but may be, for example, a polygon, a circle, an ellipse, or an irregular shape.

[0047] Furthermore, as described above, because one end of each silencer-side opening 54 is in contact with the ventilation section 52, there is a possibility that the air (wind) flowing through the ventilation section 52 may enter the rear space 60 through the silencer-side opening 54. In this case, the amount of air passing through the ventilation section 52, i.e., the amount of air blown by the silencer-equipped fan 10, will be reduced by the amount of wind that enters the rear space 60. For this reason, as shown in FIG. 4 , the silencer 50 may further be provided with a suppression member 64 that suppresses the air (wind) flowing through the ventilation section 52 from entering through the silencer-side opening 54.

[0048] The damping member 64 is a flow resistor that resists wind flow while allowing sound to pass through. It is made of, for example, fabric, more specifically, nonwoven fabric, woven fabric, knitted fabric, etc. Examples of nonwoven fabrics that make up the damping member 64 include polymer fibers (e.g., felt, particularly sound-absorbing felt made of various fibers such as polyester, polypropylene, and polyethylene terephthalate, as well as 3M's Thinsulate®, which is made of polypropylene and polyester), metal fibers (e.g., Unix's Poal, which is made of aluminum, and Tommy Firec SS, which is made of stainless steel, etc.), and nonwoven fabrics made of paper fibers. Examples of woven fabrics that make up the damping member 64 include broadcloth (plain woven fabric), non-flammable cloth (manufactured by Istflon Co., Ltd.), metal woven fabric, and metal-polymer composite fiber cloth (e.g., Seiren's conductive cloth). Examples of fibers that can be used for the fabric constituting the suppression member 64 include fibers made of resin materials such as aramid fibers, glass fibers, cellulose fibers, nylon fibers, vinylon fibers, polyester fibers, polyethylene fibers, polypropylene fibers, polyolefin fibers, rayon fibers, low-density polyethylene resin fibers, ethylene vinyl acetate resin fibers, synthetic rubber fibers, copolymer polyamide resin fibers, and copolymer polyester resin fibers; fibers made of metal materials such as stainless steel fibers; fibers of carbon materials; fibers of carbon-containing materials; and fibers of glass materials.

[0049] The material constituting the suppression member 64 may be a material other than cloth, as long as it can suppress the air (wind) flowing through the ventilation section 52 from entering the rear space 60 through the silencer-side opening 54. For example, a finely perforated plate such as a relatively thin expanded metal or punched metal may be used, or a thin porous sheet (film) may be used.

[0050] The rear space 60 is a space formed outside the opening wall 56, and is in communication with the first air intake port 30 (opening) via the ventilation portion 52 and the silencer-side opening 54. The outer peripheral wall 62 is a wall body in the shape of a circular ring or a square frame that separates the rear space 60 on the side opposite the opening wall 56. The material of the outer peripheral wall 62 is not particularly limited, and examples that can be used include metal materials, wood, resin materials including reinforced plastic materials, and carbon fiber.

[0051] The back space 60 forms a resonance structure together with the silencer-side opening 54, and more specifically, forms an air column resonator or a Helmholtz resonator. In other words, the silencer 50 silences fan noise through resonance in the resonance structure formed by the silencer-side opening 54 and the back space 60.

[0052] Furthermore, rainwater or the like may enter the rear space 60 through the ventilation portion 52 and the silencer-side opening 54. In consideration of this, it is preferable that a through-hole 68 for draining water is provided at the lower end of the outer peripheral wall 62, as shown in FIG.

[0053] Furthermore, the length of the opening wall 56 and the outer peripheral wall 62 in the axial direction, i.e., the thickness of the silencer 50, is not particularly limited, but from the viewpoint of making the silencer 50 compact and space-saving, it is preferably, for example, 10 cm to 20 cm.

[0054] The conversion mechanism 66 is a noise reduction mechanism that converts sound energy into thermal energy, and is configured by the viscosity of the fluid near the wall surface of the silencer 50, the unevenness (surface roughness) of the wall surface of the silencer 50, or a sound-absorbing material. Below, a case where the conversion mechanism 66 is configured by a sound-absorbing material will be described.

[0055] Examples of sound-absorbing materials constituting the conversion mechanism 66 include open-cell foam sound-absorbing materials and fiber-based sound-absorbing materials. Examples of foam-based sound-absorbing materials include urethane foam, such as Calmflex (registered trademark) from Inoac Corporation and urethane foam from Hikarisha, soft urethane foam, ceramic particle sintered material, phenolic foam, melamine foam, insulation board, and polyamide foam. Examples of fiber-based sound-absorbing materials include microfiber nonwoven fabrics such as 3M Thinsulate, polyester nonwoven fabrics such as White Quon (registered trademark) from Tokyo Bouon Co., Ltd. and QonPET (registered trademark) from Bridgestone KBG, plastic nonwoven fabrics such as acrylic fiber nonwoven fabrics, natural fiber nonwoven fabrics such as wool and felt, meltblown nonwoven fabrics, metal nonwoven fabrics, glass nonwoven fabrics, floor mats, and carpets. The polyester nonwoven fabrics mentioned above include two-layer products having a high-density, thin nonwoven fabric on the front side and a low-density nonwoven fabric on the back side. Other sound-absorbing materials that can be used include various sound-absorbing materials made of materials containing minute air particles, such as glass wool, rock wool, gypsum board, wood wool cement board, and sound-absorbing materials made of nanofiber fibers, etc. Examples of nanofiber fibers include silica nanofibers and acrylic nanofibers such as XAI manufactured by Mitsubishi Chemical Corporation.

[0056] The conversion mechanism 66 is disposed in at least one of the silencer-side opening 54 and the rear space 60, and in the configuration shown in Fig. 4, it is disposed in the rear space 60. However, without being limited to this, the conversion mechanism 66 may be disposed in the silencer-side opening 54, or may be disposed in both the silencer-side opening 54 and the rear space 60. When the conversion mechanism 66 is disposed in the silencer-side opening 54, it is preferable to dispose the conversion mechanism 66 in the silencer-side opening 54 instead of the suppression member 64 described above, or together with the suppression member 64.

[0057] In this embodiment, the silencer-equipped fan 10 is configured as described above, so that noise generated by the rotation of the fan 12 can be efficiently silenced within the housing 20. This point will be described in detail with reference to FIGS.

[0058] The fan noise generated when the fan 12 rotates has directionality, and in the absence of a silencer 50, the noise travels in the axial direction within the housing 20 and is emitted to the outside of the housing 20 through the first intake hole 30 or the exhaust hole 34, as shown in Figure 5. In other words, the noise source formed by the tip of the rotating blades 16 of the fan 12 is a dipole sound source, and generates strong noise in the forward and backward directions.

[0059] On the other hand, the acoustic impedance is defined in accordance with the above-mentioned formula (1) inside and outside the housing 20. The effective area S required to calculate the acoustic impedance is calculated by the following formula (2): S=S ０ / (1-D ０．５ ) (2)

[0060] In the above formula (2), S ０ is the cross-sectional area of ​​the target space through which sound travels, and in this embodiment, corresponds to the cross-sectional area of ​​the flow path through which the wind passes, i.e., the wind path area S ０ is the area of ​​the region surrounded by the peripheral surface when the peripheral surface surrounding the target space is viewed from the axial direction. The peripheral surfaces surrounding the target space include the inner wall surface of the housing 20, the inner peripheral surface of the shroud 42, and the inner wall surface surrounding the ventilation section 52 of the silencer 50 (for example, the inner peripheral surface 58). In the above formula (2), D is the hole area ratio, which can be calculated by the following formula (3). D=S ｈ / S Ｓ (3) Here, S ｈ is the area of ​​the hole (opening area) when a hole (opening) is provided on the peripheral surface surrounding the target space, and S ｓ is the area of ​​the peripheral surface surrounding the target space, and the peripheral surface area S when the above-mentioned hole (opening) is provided ｓ The area of ​​the hole (opening area S ｈ ) are included.

[0061] The acoustic impedance Zo outside the housing 20 (excluding the space in which the silencer 50 is disposed) can be approximated to 0 because the effective area S is semi-infinite and the hole area ratio D is 1. Furthermore, within the internal space of the housing 20, the acoustic impedance differs between the first portion 46 located on the first air intake hole 30 side (the opening side) and the second portion 48 located farther from the first air intake hole 30 than the first portion 46.

[0062] The first portion 46 is a portion of the internal space of the housing 20 adjacent to the first air intake hole 30 in the axial direction, and more specifically, as shown in FIG. 5 , is a portion from the rear end of the rear surface of the side wall 26 to the rear end of the shroud 42. In other words, the first portion 46 is located adjacent to the second air intake hole 32 in the width direction. Therefore, the effective area S of the first portion 46 is the air passage area S of the first portion 46. ０ The air passage area S of the first portion 46 is calculated by the hole area ratio. ０ is the area of ​​the region surrounded by the side wall 26 when the side wall 26 is viewed from the axial direction. The hole area ratio is calculated from the area of ​​the inner wall surface of the portion of the side wall 26 that surrounds the first portion 46 and the opening area of ​​the second air intake hole 32, and its value is relatively large. As a result, the acoustic impedance Z1 of the first portion 46 is relatively small.

[0063] The second portion 48 is a portion of the internal space of the housing 20 adjacent to the exhaust hole 34 in the axial direction, and more specifically, a portion located inside the shroud 42. In other words, the second portion 48 is partitioned by the shroud 42, and the area S of the air passage formed inside the shroud 42 is ０ is determined according to the inner diameter of the shroud 42. Furthermore, in the second portion 48, the opening area ratio D is 0, and therefore the effective area S in the second portion 48 is significantly smaller than the effective area S in the first portion 46. Therefore, the acoustic impedance Z2 of the second portion 48 is significantly higher than the acoustic impedance Z1 of the first portion 46. Note that, as shown in Figures 5 and 6, in the second portion 48, at least a portion of the shroud 42 is disposed between the fan 12 and the exhaust hole 34 in the axial direction.

[0064] In this embodiment, as shown in Fig. 6, the silencer 50 is disposed on the rear side (first air intake port 30 side) of the housing 20, and the ventilation section 52 of the silencer 50 communicates with the first air intake port 30, and the ventilation section 52 is surrounded by an opening wall 56. The effective area S of the ventilation section 52 is the air passage area S of the ventilation section 52. ０ and the hole area ratio. ０ is the area of ​​the region surrounded by the inner circumferential surface 58 of the opening-equipped wall 56 when the ventilation portion 52 is viewed from the axial direction. The hole area ratio is determined by the area of ​​the inner circumferential surface 58 and the opening area of ​​the silencer-side opening 54 provided in the opening-equipped wall 56. Therefore, the effective area S of the ventilation portion 52 is smaller than the effective area S of the first portion 46, and the acoustic impedance Zr of the ventilation portion 52 is higher than the acoustic impedance Z1 of the first portion 46.

[0065] Furthermore, in this embodiment, the effective area S of the ventilation portion 52 is larger than the effective area S of the second portion 48. Therefore, in this embodiment, the acoustic impedance Zr of the ventilation portion 52 is lower than the acoustic impedance Z2 of the second portion 48. Therefore, the acoustic impedances of the respective portions of the silencer-equipped fan 10 satisfy the magnitude relationship shown in the following equation (4): Zo<Z1<Zr<Z2 (4)

[0066] 6, the ventilation section 52 is located adjacent to the first section 46 in the axial direction with the first intake hole 30 interposed therebetween, and inside the housing 20, the second section 48 is located adjacent to the first section 46 on the opposite side of the first intake hole 30. In other words, the first section 46 is located between the second section 48 and the ventilation section 52 in the axial direction.

[0067] In the above configuration, sound is reflected at the boundary between two spaces with different acoustic impedances, and the greater the difference in acoustic impedance, the greater the amount of reflection at the boundary. Therefore, noise generated when the fan 12 rotates and traveling inside the housing 20 toward the first air intake 30 is reflected at the boundary between the ventilation section 52 and the first section 46. This allows the sound waves of the noise to be trapped inside the housing 20.

[0068] The sound pressure of the sound trapped within the housing 20 is reduced by loss (sound absorption effect) caused by collisions with the rotating blades 16 of the fan 12 and equipment housed within the housing 20, such as the heat exchanger 40. Furthermore, noise that is reflected back toward the fan 12 is diffused by the rotating fan 12, reducing the directionality of the noise. This reduces spatial coherence within the housing 20, thereby reducing the sound pressure of the sound traveling within the housing 20. Due to the above-mentioned effects, in this embodiment, noise generated by the rotation of the fan 12 can be effectively silenced within the housing 20.

[0069] In the embodiments described above, the silencer 50 is configured such that the ventilation portion 52 is surrounded by an opening-equipped wall 56 having a silencer-side opening 54. The silencer 50 silences noise caused by the rotation of the fan 12 by resonance of the resonance structure formed by the silencer-side opening 54 and the rear space 60. However, the silencer 50 is not particularly limited and may have a configuration different from that of the above-described embodiments as long as it can make the acoustic impedance Zr of the ventilation portion 52 higher than the acoustic impedance Z1 of the first portion 46 inside the housing 20. For example, as in the silencer-equipped fan 10x shown in FIG. 7 , the silencer 50x may include a rectangular cylindrical rigid frame 72 surrounding the ventilation portion 52.

[0070] The rigid frame 72 has, for example, the same width and height as the housing 20. The material of the rigid frame 72 is not particularly limited, and may be, for example, a metal material, wood, a resin material including a reinforced plastic material, or carbon fiber.

[0071] The space inside the rigid frame 72 forms the ventilation section 52. As shown in Fig. 8 , a sound-absorbing material 74 may be housed inside the ventilation section 52. The materials exemplified above as the sound-absorbing material constituting the conversion mechanism 66 can be used as the material for the sound-absorbing material 74. The shape of the ventilation section 52 is rectangular or square when viewed from the axial direction of the silencer 50x, and its size (opening area) is smaller than the size of the first air intake hole 30.

[0072] 8 without the sound-absorbing material 74, i.e., a silencer configured solely by the above-described rigid frame 72. In this case, the inner space of the rigid frame 72 forms the ventilation section 52, and the size (opening area) thereof may be approximately the same as the size of the first air intake hole 30, or may be different from the size of the first air intake hole 30.

[0073] Furthermore, the shroud 42 may not be provided inside the housing 20. In other words, the second portion 48 of the internal space of the housing 20 may not be partitioned by the shroud 42. In this case, the effective area S of the second portion 48 is calculated by multiplying the air passage area S of the second portion 48 by 1 / 2. ０ and the air passage area S of the second portion 48 ０ is the area of ​​the region surrounded by the side wall 26 when the side wall 26 is viewed from the axial direction. This area is the air passage area S of the second portion 48 when partitioned by the shroud 42. ０ Therefore, the acoustic impedance of the second portion 48 without the shroud 42 is smaller than that of the second portion 48 with the shroud 42.

[0074] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0075] Example 1 In Example 1, an outdoor unit equipped with a silencer was placed in the center of the test room. The outdoor unit was a Daikin Industries, Ltd. model R22ZES7. During the test, the outdoor unit fan was operated at 1,000 rpm, while the outdoor unit compressor was not operated. The test room was a soundproof room, semi-anechoic room, or anechoic room, with at least the walls and ceiling covered with sound-absorbing material. A second air intake (side air intake) was provided on the side wall of the outdoor unit. A cylindrical shroud (bell mouth) with a diameter of approximately 41 cm was placed inside the outdoor unit adjacent to the exhaust port.

[0076] The silencer has substantially the same configuration as the silencer 50x shown in Figures 7 and 8, and includes a rectangular rigid frame with dimensions of 555 mm high x 675 mm wide x 10 mm thick, and a hollow sound-absorbing material disposed inside the rigid frame. The hollow portion inside the sound-absorbing material forms a vent and communicates with the first air intake port (air intake port on the rear side) of the outdoor unit, more specifically, it is adjacent to and continuous with it.

[0077] Here, the acoustic impedance Zo outside the outdoor unit (excluding the space for arranging the silencer) is approximately 0 Pa·s / m ３ The acoustic impedance Z1 of the portion of the interior space of the outdoor unit adjacent to the first air intake port, i.e., the first portion, is 1148 Pa·s / m ３ Here, among the parameters necessary for calculating Z1, the air passage area S ０、 That is, the area of ​​the region surrounded by the inner wall surfaces of the side walls of the housing surrounding the first portion is 0.239 m ２ and the area of ​​the second intake hole S ｈ is 0.0609m ２ The hole area ratio D calculated from these areas is 0.141 (= 0.0609 / 0.239), and from the above formula (2), the effective area S is 0.382 m ２ In addition, the acoustic impedance Z2 of the portion of the interior space of the outdoor unit adjacent to the exhaust port and where the shroud is arranged, i.e., the second portion, is 3324 Pa·s / m ３ Here, among the parameters necessary for calculating Z2, the air passage area S ０ is the area of ​​the region enclosed by the inner circumferential surface of the shroud, and is 0.132 m ２ In addition, since the hole area ratio D is 0, the effective area S is the air passage area S ０ is equal to 0.132 m ２ is.

[0078] The acoustic impedance Zr at the ventilation part of the silencer in Example 1 is 1991.1 Pa·s / m ３ Here, the air passage area S required to calculate Zr is ０is the area of ​​the region surrounded by the rigid frame. In addition, since the rigid frame has no openings (holes effective for air to pass through) and the hole area ratio D is 0, the effective area S is the air passage area S ０ is equal to.

[0079] Example 2 In Example 2, the thickness of the silencer was set to 20 mm, and the other conditions were the same as those in Example 1. In Example 2, the acoustic impedance of the ventilation portion was the same as in Example 1.

[0080] Example 3 In Example 3, a silencer obtained by removing the sound absorbing material from the silencer of Test 1, i.e., a silencer having only a rigid frame, was used. The other conditions were the same as in Example 1. In Example 3, the acoustic impedance of the ventilation portion was the same as in Example 1.

[0081] In Example 4, the thickness of the silencer used in Example 3 (i.e., the silencer consisting of only a rigid frame) was set to 20 mm, and the other conditions were the same as in Example 1. In addition, in Example 4, the acoustic impedance of the ventilation part was the same as in Example 1.

[0082] (Comparative Example 1) In Comparative Example 1, a silencer was not provided for the outdoor unit. The other conditions were the same as those in Example 1. That is, in Comparative Example 1, an outdoor unit not equipped with the silencer of the present invention was operated alone.

[0083] (Test Results) In Examples 1 to 4 and Comparative Example 1, sound pressure levels during the test were measured using eight microphones installed around the outdoor unit in the test room, and the average value of the sound pressure levels measured by the eight microphones was calculated. The microphones were installed at 45-degree intervals around the outdoor unit, at positions at least 1 m away from the outdoor unit. The measurement results of sound pressure levels in Examples 1 and 3 and Comparative Example 1 (Reference) are shown in FIG. 9. The measurement results of sound pressure levels in Examples 2 and 4 and Comparative Example 1 (Reference) are shown in FIG. 10.

[0084] Furthermore, for each of Examples 1 to 4, the sound deadening spectrum was determined by calculating the difference in sound pressure level at each frequency between each Example and Comparative Example 1. The sound deadening spectrum determined for each of Examples 1 and 3 is shown in Fig. 11. The sound deadening spectrum determined for each of Examples 2 and 4 is shown in Fig. 12.

[0085] As can be seen from Figures 9 to 12, by placing a frame-type silencer adjacent to the first air intake port on the rear side of the outdoor unit, the acoustic impedance of the ventilation section of the silencer is high, and as described above, noise can be confined within the housing of the outdoor unit. This allows for more effective sound absorption during fan rotation than when no silencer is installed, due to loss within the housing and directional diffusion of sound. Furthermore, as is clear from Figures 11 and 12, the sound absorption effect can be enhanced by placing sound-absorbing material around the ventilation section within the rigid frame, and the amount of sound absorption can be increased, particularly around 500 Hz.

[0086] Furthermore, the greater the thickness of the silencer (i.e., the dimensions of the rigid frame and sound-absorbing material in the axial direction), the greater the sound-absorbing effect of the silencer. This is thought to be because the ventilation section, which is a high-impedance space, becomes larger in the axial direction, which is the direction in which the noise travels, and this allows noise to be more effectively contained within the outdoor unit. As described above, the configurations of Examples 1 to 4 described above fall within the scope of the present invention, and the effects of the present invention are clear from the results of Examples 1 to 4.

[0087] 10, 10x Fan with silencer 12 Fan 14 Central portion 16 Rotor 18 Rotating shaft 20 Housing 22 First wall 24 Second wall 26 Side wall 28 Third wall 30 First intake hole (opening) 32 Second intake hole 34 Exhaust hole 36 Machine room 38 Partition wall 40 Heat exchanger 42 Shroud 44 Grill (breathable member) 46 First portion 48 Second portion 50, 50x Silencer 52 Ventilation portion 54 Silencer-side opening 56 Wall with opening 58 Inner peripheral surface 60 Back space 62 Outer peripheral wall 64 Suppression member 66 Conversion mechanism 68 Through hole 70 Fan silencer 72 Rigid frame 74 Sound-absorbing material

Claims

1. A fan with a silencer comprising a housing with an opening, a fan housed in the housing, and a silencer that silences noise generated by the rotation of the fan, wherein the inside of the housing has a first part located on the opening side, and a second part that is farther from the opening than the first part and has a higher acoustic impedance than the first part, and the silencer has a vent part that communicates with the opening, and the acoustic impedance of the vent part is higher than the acoustic impedance of the first part.

2. A silencer-equipped fan as described in claim 1, wherein the acoustic impedance of the ventilation section is lower than the acoustic impedance of the second section, and the first section is disposed between the second section and the ventilation section in the axial direction of the rotation shaft of the fan.

3. A fan with a silencer as described in claim 1, wherein the housing comprises a first intake hole as the opening provided in a first wall of the housing and an exhaust hole provided in a second wall of the housing, and in the second part, at least a part of a tubular member that regulates the flow of gas from the fan toward the exhaust hole is positioned between the fan and the exhaust hole, and the silencer is positioned with the ventilation part adjacent to the first intake hole.

4. A fan with a silencer as described in claim 3, wherein a side wall disposed between the first wall and the second wall in the housing has a communication hole that connects the inside of the housing with the space outside the housing, and within the housing, the first portion is located adjacent to the communication hole.

5. A fan with a silencer as described in claim 4, wherein the communication hole is a second intake hole, and the fan takes in gas from the outer space through the first intake hole and the second intake hole and discharges the gas through the exhaust hole.

6. A fan with a silencer as described in claim 1, wherein a resistance member that provides resistance to the flow of gas passing through the opening is provided at the end of the internal space of the housing on the opening side.

7. A fan with a silencer according to claim 6, wherein said resistance member is a heat exchanger.

8. A fan with a silencer as described in claim 6, wherein the resistance member is adjacent to the opening in the axial direction of the rotation shaft of the fan, and the ventilation section is adjacent to the opening on the opposite side to the resistance member.

9. The fan with a silencer according to claim 1, wherein the silencer comprises a cylindrical rigid frame surrounding the ventilation portion.

10. A fan with a silencer as described in claim 1, wherein the silencer comprises an opening wall surrounding the ventilation section and having a silencer-side opening, and a back space separated by the opening wall and communicating with the opening via the ventilation section and the silencer-side opening.

11. A fan with a silencer according to claim 10, wherein the silencer silences the sound by resonance of a resonance structure formed at least by the silencer-side opening and the back space.

12. A fan with a silencer according to claim 11, wherein a conversion mechanism for converting sound energy into thermal energy is provided in at least one of the silencer-side opening and the rear space.

13. A fan with a silencer according to claim 1, wherein the silencer has an outer peripheral wall, and a through hole is provided at the lower end of the outer peripheral wall.

14. The fan with silencer according to claim 1, wherein the fan is a fan for an outdoor unit of an air conditioning system.

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