WO2026018549A1 - Fan with silencer - Google Patents

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

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

It is important that a silencer that can efficiently reduce noise generated by fan rotation without reducing airflow. For this reason, in conventional silencer-equipped fans, a resonance-type silencer with 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 a silencer-equipped fan with such a configuration is the fan described in Patent Document 1.

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

International Publication No. 2021/1717110

In the silencer-equipped fan described in Patent Document 1, a member that regulates the airflow path within the housing, such as a shroud (bell mouth), may be placed inside the housing that houses the fan. However, in the space inside the housing where the airflow path regulating member is installed, the airflow path becomes narrower than in other spaces, resulting in higher acoustic impedance.

Fan rotation also generates noise, specifically narrowband rotational noise and broadband turbulent noise. Because this noise (hereinafter referred to as fan noise) is emitted from a dipole noise source, it is 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 internal characteristics of the housing, there is a demand for a silencer that can more effectively muffle noise.

The present invention was made in light of the above circumstances, and aims to solve the problems of the prior art mentioned 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.

As a result of extensive research into achieving the above object, the present 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, and 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] A silencer-equipped fan according to [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] The fan with silencer described in [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 part, at least a part of a cylindrical member that regulates the flow of gas from the fan toward the exhaust hole is arranged between the fan and the exhaust hole, and the silencer is arranged with its ventilation part adjacent to the first intake hole.
[4] A fan with a silencer according to [3], wherein the side wall arranged 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 the first part is located inside the housing adjacent to the communication hole.
[5] The silencer-equipped fan according to [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 expels the gas through the exhaust hole.
[6] A 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 the end of the internal space of the housing on the opening side.
[7] The fan with a silencer 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 section is adjacent to the opening on the opposite side of the resistance member.
[9] The fan with a silencer according to any one of [1] to [8], wherein the silencer includes a cylindrical rigid frame that surrounds the ventilation section.
[10] The silencer-equipped fan according to any one of [1] to [8], wherein the silencer comprises an opening wall that surrounds the ventilation section and has a silencer-side opening provided therein, and a back space that is partitioned by the opening wall and communicates with the opening via the ventilation section and the silencer-side opening.
[11] The fan with a silencer according to [10], wherein the silencer silences 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 for converting sound energy into thermal energy is provided in at least one of the silencer-side opening and the rear 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 at the lower end of the outer peripheral wall.
[14] The fan with a silencer according to any one of [1] to [13], wherein the fan is a fan for an outdoor unit of an air conditioning system.

The present invention provides a fan with a silencer that can effectively muffle noise by taking into account the internal structure of the housing that houses the fan and the characteristics of the noise generated by the rotation of the fan.

FIG. 1 is a diagram showing an example of noise that is silenced by a silencer according to an embodiment of the present invention, illustrating a noise spectrum. 1 is a perspective view of a fan with a silencer according to an embodiment of the present invention; FIG. 3 is a view showing a cross section taken along line II of FIG. 2. 4 is a diagram showing the internal structure of the silencer, and is a cross-sectional view taken along the line JJ in FIG. 3. FIG. 10 is a diagram showing the distribution of acoustic impedance inside a housing according to a comparative example. FIG. 2 is a diagram showing the distribution of acoustic impedance in a silencer-equipped fan according to one embodiment of the present invention. FIG. 10 is a perspective view of a silencer-equipped fan according to a modified example of the present invention, as viewed from the rear side. 10 is a diagram showing a muffler provided in a muffler-equipped fan according to a modified example of the present invention, the muffler being viewed from the rear side. FIG. FIG. 10 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 the measurement results of sound pressure levels in Examples 2 and 4 and Comparative Example 1 (reference). FIG. 1 is a diagram showing the silencing spectra of Examples 1 and 3. FIG. 10 is a diagram showing the silencing spectra of Examples 2 and 4.

The present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings. Note that the following embodiments are merely examples given to facilitate understanding of the present invention and are not intended to limit 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 material and shape of each member used to implement the present invention can be arbitrarily set depending on the application 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.

In addition, 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.
In addition, in this specification, "orthogonal,""vertical," and "parallel" include the range of error acceptable in the technical field to which the present invention pertains. For example, "orthogonal,""vertical," and "parallel" in this specification mean that the deviation is within a range of less than ±10° from the strict "orthogonal,""vertical," and "parallel." The deviation from the strict "orthogonal,""vertical," and "parallel" is preferably 5° or less, and more preferably 3° or less.
In addition, in this specification, the meanings of "same" and "identical" may include a range of error generally accepted 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 100% is not actually reached due to structural constraints, but is as close to 100% as possible.

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

<<Outline of the silencer-equipped fan of the present invention>>
The silencer-equipped fan of the present invention includes a housing 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's 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.

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. Here, the acoustic impedance is defined by the following equation (1):
Z=ρ×c/S (1)
In the above formula (1), Z represents acoustic impedance (unit: Pa·s/m ³ ), ρ represents air density (unit: kg/m ³ ), c represents sound speed (unit: m/s), and S (unit: m ² ) represents 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.

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 section. This allows the noise generated when the fan rotates (fan noise) to be contained within the housing, and the fan noise can be effectively silenced by sound loss due to collisions with components inside the housing and directional diffusion, etc.

<<Configuration example of a silencer-equipped fan according to one embodiment of the present invention>>
An example of the configuration of a silencer-equipped fan according to one embodiment of the present invention (hereinafter referred to as this embodiment) will be described with reference to FIGS.
In the following description, the position, orientation, posture, and state of each device and component represent 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 referred to as 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, an air conditioner for a building). 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.

As shown in Figures 2 and 3, the silencer-equipped fan 10 comprises a fan 12, a housing 20, a heat exchanger 40, a shroud 42, a grill 44, and a silencer 50. Each component will be described below.

(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.

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

The structure of the fan 12 is the same as that of a known axial flow fan, and as shown in Fig. 3, a plurality of rotor blades 16 extend radially from the outer circumferential surface of a cylindrical central portion 14 (hereinafter simply referred to as the radial direction) of the central portion 14. A rotor shaft 18 is disposed inside 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.
In the following description, the leeward side as viewed from the fan 12 in the axial direction will also be referred to as the "front side," and the windward side will also be referred to as the "rear side" or "back side."

When the fan 12 rotates within the housing 20, fan noise, including wind noise, is generated. In other words, 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 within the housing 20 toward the front and rear, passing through the first intake hole 30 and exhaust hole 34 (described below) and heading outside the housing 20.

Furthermore, as shown in FIG. 3, in this embodiment, a small silencer for the fan 12 (hereinafter referred to as 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. Furthermore, the fan silencer 70 is preferably positioned so that it does not overlap with the rotor blades 16 when viewed from the axial direction, that is, so that it does not 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.

(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.

As shown in Figures 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 the 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.

The shape of each of the first intake holes 30 and the exhaust holes 34 (more specifically, the shape of the outer edge of each hole) is not particularly limited, and may be circular, elliptical, square, rectangular, other quadrilateral, polygonal other than quadrilateral, or irregular. Furthermore, the size of each of the first intake holes 30 and the exhaust holes 34 (more specifically, the area of each hole when viewed from the axial direction) is not particularly limited, and may be the same for the first intake holes 30 and the exhaust holes 34 or may be different.
In this embodiment, the rectangular first intake holes 30 are provided over a wide area in the first wall 22, and the second wall 24 has a circular exhaust hole 34 provided in the center thereof.

The side wall 26 is a roughly 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. Here, as shown in Figure 3, one end of the side wall 26 in the width direction of the housing 20 (hereinafter simply referred to as the width direction), specifically the left or right end of the side wall 26, corresponds to the third wall 28. Here, the width direction refers to the direction that intersects both the up-down direction and the axial direction of the silencer-equipped fan 10, or more precisely, the direction that is perpendicular to these directions.

As shown in Figure 3, the third wall 28 is provided with a second air intake hole 32. 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.

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. To explain in more detail, 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.

Furthermore, the second air intake hole 32 functions as a side air intake, and when the fan 12 rotates, air enters the housing 20 not only through the first air intake hole 30 but also through the second air intake hole 32. In other words, the fan 12 takes in air from the space outside the housing 20 through the first air intake hole 30 and the second air intake hole 32, and expels the air (wind) through the exhaust hole 34. In other words, within the housing 20, there is an air passage through which air that has passed through the first air intake hole 30 flows, and an air passage through which air that has passed through the second air intake hole 32 flows, and these two air passages converge axially behind the fan 12.

In this embodiment, as shown in FIG. 3, the range in the width direction in which the first air intake holes 30 are provided overlaps with at least a portion of the range in which the exhaust holes 34 are provided. On the other hand, the second air intake holes 32 are located in a different position in the width direction from the first air intake holes 30 and the exhaust holes 34, more specifically, in a position that does not overlap with these holes.

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 described above, 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 air intake hole 30, the second air intake hole 32, and the exhaust hole 34 are all continuous with the air passage space.
In the following description, unless otherwise specified, the internal space of the housing 20 refers to the air passage space described above.

(heat exchanger)
The heat exchanger 40 is disposed rearward of the fan 12 in the internal space of the housing 20, and is disposed within the first air intake hole 30 in the axial direction. The heat exchanger 40 is disposed within the first air intake hole 30 so that its rear end (the end opposite the fan 12) in the axial direction reaches the same position as the rear end surface of the housing 20. In this embodiment, as shown in Fig. 3, a heat exchanger 40 is also disposed within the second air intake hole 32. Note that in Fig. 2, the heat exchanger 40 disposed within the second air intake hole 32 is not shown in order to explain the internal configuration of the housing 20.
The heat exchanger 40 is configured by, for example, a fin coil, a fin tube, or a heat exchange plate, and exchanges heat with the air that has entered the housing 20 through the first air intake holes 30, heating or cooling the air. In other words, the air that has entered the housing 20 through the first air intake holes 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 holes 30 and flows toward the fan 12.

As described above, the noise generated by the rotation of the fan 12 (fan noise) travels inside 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 the noise passing through the first air intake vent 30 can be reduced.
It should be noted 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.

(Shroud)
As shown in Fig. 3 , the shroud 42 is a cylindrical 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 in its internal space through which the air from the fan 12 flows.

Furthermore, the area of the air passage within the shroud 42 is smaller than the area of the air passage inside the housing 20 behind the shroud 42 (towards the first air intake port 30). The area of the air passage is the area when looking at the shroud 42 in the axial direction, and is the area through which the air passes, i.e., the flow path area.

In this embodiment, as shown in FIG. 3, 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 axially rearward of the front end of the fan 12 (i.e., closer to the first air intake hole 30). Also, the shroud 42 may approach the area in which the aforementioned second air intake hole 32 is provided, or may be positioned axially forward of the second air intake hole 32 (downstream in the air blowing direction).

(grill)
The grill 44 corresponds to a breathable member that collides with the air flow (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.

(silencer)
The silencer 50 is disposed adjacent to the housing 20 on the rear side thereof, and silences at least the noise generated by the rotation of the fan 12 housed in the housing 20 through resonance, thereby silencing the noise of the fan. 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. 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 wall 56 in which a silencer-side opening 54 is provided, a back space 60 partitioned by the opening wall 56 and an outer peripheral wall 62, and a conversion mechanism 66.

The ventilation section 52 is a hollow portion 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 placed 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., wind 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.

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

Furthermore, the center of the first air intake vent 30 and the center of the ventilation section 52 may not be on the same straight line, but may be slightly offset.

The opening wall 56 is a ring-shaped or frame-shaped wall that surrounds the ventilation section 52. In other words, the opening wall 56 functions as a frame that surrounds the ventilation section 52 and separates it. There are no particular restrictions on the material of the opening wall 56, and examples that can be used include metal materials, wood, resin materials including reinforced plastic materials, and carbon fiber.

Furthermore, as shown in Figures 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 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 are connected to each other.

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

Furthermore, the opening shape of each silencer-side opening 54 is not particularly limited, but may be, for example, polygonal, circular, elliptical, or irregular.

Furthermore, as mentioned 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.

The suppression member 64 is a flow resistor that resists wind flow while allowing sound to pass through, and is made of, for example, fabric, more specifically, nonwoven fabric, woven fabric, knitted fabric, or the like.
Examples of nonwoven fabrics that make up the suppression member 64 include nonwoven fabrics made of polymer fibers (e.g., felt, particularly sound-absorbing felt made from various fibers such as polyester, polypropylene, and polyethylene terephthalate, as well as 3M's Thinsulate (registered trademark) made from polypropylene and polyester fibers), metal fibers (e.g., Unix's Poal made from aluminum fibers, and Tommy Firec SS made from stainless steel fibers), and paper fibers.
Examples of the woven fabric that may be used for the suppression member 64 include broadcloth (plain woven fabric), non-flammable cloth (manufactured by Istflon Co., Ltd.), metal woven fabric, and composite fiber fabric of metal and polymer (such as conductive cloth manufactured by Seiren Co., Ltd.).
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.

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

The rear space 60 is a space formed outside the opening wall 56, and is connected to the first air intake hole 30 (opening) via the ventilation section 52 and the silencer-side opening 54. The outer peripheral wall 62 is a circular or rectangular frame-shaped wall that separates the rear space 60 on the side opposite the opening wall 56. There are no particular restrictions on the material of the outer peripheral wall 62, and examples that can be used include metal materials, wood, resin materials including reinforced plastic materials, and carbon fiber.

The rear space 60, together with the silencer-side opening 54, forms a resonance structure; specifically, it 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 rear space 60.

Furthermore, rainwater and other liquids may enter the rear space 60 through the ventilation section 52 and the silencer-side opening 54. Taking this into consideration, it is recommended that a through-hole 68 for draining water be provided at the lower end of the outer wall 62, as shown in Figure 4.

Furthermore, the axial length of the opening wall 56 and the outer peripheral wall 62, i.e., the thickness of the silencer 50, is not particularly limited, but from the perspective of making the silencer 50 compact and space-saving, a value of, for example, 10 cm to 20 cm is preferable.

The conversion mechanism 66 is a sound-absorbing mechanism that converts sound energy into thermal energy, and is formed 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 sound-absorbing material. The following describes the case where the conversion mechanism 66 is formed from sound-absorbing material.

Examples of the sound absorbing material that constitutes the conversion mechanism 66 include open-cell foam sound absorbing materials and fiber sound absorbing materials.
Examples of foam-based sound-absorbing materials include foamed urethane foam such as Calmflex (registered trademark) from Inoac Corporation and urethane foam from Hikarisha, soft urethane foam, sintered ceramic particles, phenol foam, melamine foam, insulation board, and polyamide foam.
Examples of fiber-based sound-absorbing materials include microfiber nonwoven fabrics such as Thinsulate from 3M, polyester nonwoven fabrics such as White Qion (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, carpets, etc. The above polyester nonwoven fabrics include products with a two-layer structure 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.

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, this is not limited to this, and the conversion mechanism 66 may be disposed in the silencer-side opening 54, or 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.

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 explained in detail with reference to Figures 5 and 6.

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

On the other hand, the acoustic impedance is defined according to 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)

In the above formula (2), _S0 is the cross-sectional area of the target space through which sound travels, and in this embodiment, it corresponds to the cross-sectional area of the flow path through which wind passes, i.e., the air duct area. The air duct area _S0 is the area of the region surrounded by the peripheral surface surrounding the target space when the peripheral surface 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 (e.g., inner peripheral surface 58) surrounding the ventilation section 52 of the silencer 50.
In the above formula (2), D is the pore area ratio, which is calculated by the following formula (3).
D=S _h /S _S (3)
Here, S _h is the area of a hole (opening area) when a hole (opening) is provided in the peripheral surface surrounding the target space, S _s is the area of the peripheral surface surrounding the target space, and the peripheral surface area S _s when the hole (opening) is provided includes the area of the hole (opening area S _h ).

The acoustic impedance Zo outside the housing 20 (excluding the space in which the silencer 50 is located) can be approximated to 0 because the effective area S is semi-infinite due to the hole area ratio D being 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 30 side (opening side) and the second portion 48 located farther from the first air intake 30 than the first portion 46.

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. Specifically, as shown in FIG. 5 , it is a portion extending from the rear end of the rear surface of the side wall 26 to the rear end of the shroud 42. That is, 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 calculated from the air passage area _S0 of the first portion 46 and the opening area ratio. The air passage area _S0 of the first portion 46 is the area of the region surrounded by the side wall 26 when viewed from the axial direction. The opening area ratio is calculated from the area of the inner wall surface of the portion of the side wall 26 surrounding the first portion 46 and the opening area of the second air intake hole 32, and this value is relatively large. As a result, the acoustic impedance Z1 of the first portion 46 is relatively small.

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, specifically, a portion located inside the shroud 42. In other words, the second portion 48 is partitioned by the shroud 42, and the area _S0 of the air passage formed inside the shroud 42 is determined by the inner diameter of the shroud 42. Furthermore, since the opening area ratio D is 0 in the second portion 48, 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 FIGS. 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.

In this embodiment, as shown in FIG. 6 , a silencer 50 is disposed on the rear side (first air intake port 30 side) of the housing 20. The vent 52 of the silencer 50 is in communication with the first air intake port 30 and is surrounded by an opening-equipped wall 56. The effective area S of the vent 52 is determined by the air passage area _S0 of the vent 52 and the hole area ratio. The air passage area _S0 of the vent 52 is the area of the region surrounded by the inner circumferential surface 58 of the opening-equipped wall 56 when the vent 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 vent 52 is smaller than the effective area S of the first portion 46, and the acoustic impedance Zr of the vent 52 is higher than the acoustic impedance Z1 of the first portion 46.

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 various portions of the silencer-equipped fan 10 satisfy the magnitude relationship shown in the following equation (4).
Zo<Z1<Zr<Z2 (4)

Furthermore, as shown in FIG. 6, the ventilation section 52 is located adjacent to the first section 46 in the axial direction, with the first air intake hole 30 interposed between them, and inside the housing 20, the second section 48 is located adjacent to the first section 46 on the opposite side of the first air 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.

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 vent 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 within the housing 20.

The sound pressure of the sound trapped inside the housing 20 is reduced by loss (sound absorption effect) caused by collisions with the rotating blades 16 of the fan 12 and the equipment housed inside 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, and therefore reduces the sound pressure of the sound traveling inside the housing 20.
Due to the above-described effects, in this embodiment, noise generated by the rotation of the fan 12 can be effectively silenced within the housing 20 .

In the embodiments described above, the silencer 50 is configured such that the ventilation section 52 is surrounded by an opening wall 56 having a silencer-side opening 54. The silencer 50 silences noise caused by the rotation of the fan 12 through 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 section 52 higher than the acoustic impedance Z1 of the first portion 46 within 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 section 52.

The rigid frame 72 has, for example, the same width and height as the housing 20. There are no particular restrictions on the material of the rigid frame 72, and examples that can be used include metal materials, wood, resin materials including reinforced plastic materials, and carbon fiber.

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

It is also possible to use a silencer with the configuration shown in Figure 8 excluding the sound-absorbing material 74, that is, a silencer constructed solely from the rigid frame 72 described above. In this case, the inner space of the rigid frame 72 forms the ventilation section 52, and its size (opening area) 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.

Furthermore, the shroud 42 does not have to be provided inside the housing 20. In other words, the second portion 48 of the internal space of the housing 20 does not have to be partitioned by the shroud 42. In this case, the effective area S of the second portion 48 is the air passage area _S0 of the second portion 48, _which 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 larger than the air passage area _S0 of the second portion 48 when partitioned by the shroud 42. 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.

The present invention will now be explained in more detail using examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be modified 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.

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 outdoor unit. During the test, the fan of the outdoor unit was operated at a rotation speed of 1000 rpm, while the compressor of the outdoor unit was not operated. The test room had a structure in which at least the walls and ceiling were covered with sound-absorbing material, i.e., it was a soundproof room, semi-anechoic room, or anechoic room.
A second air intake hole (side air intake port) was provided on the side wall of the outdoor unit. A cylindrical shroud (bell mouth) with a diameter of approximately 41 cm was disposed inside the outdoor unit adjacent to the exhaust hole.

The silencer has approximately the same configuration as silencer 50x shown in Figures 7 and 8, and comprises a rectangular rigid frame measuring 555 mm high x 675 mm wide x 10 mm thick, and hollow sound-absorbing material placed inside the rigid frame. The hollow portion inside the sound-absorbing material forms a vent and communicates with the outdoor unit's first air intake (air intake on the rear side), specifically, it is adjacent and continuous.

Here, the acoustic impedance Zo outside the outdoor unit (excluding the space for arranging the silencer) can be considered to be approximately 0 Pa·s/m ³ .
Furthermore, 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, was 1148 Pa·s/ ^m3 . Among the parameters required to calculate Z1, the air passage area S0 of the first portion _, i.e., the area of the region enclosed by the inner wall surfaces of the side walls of the housing surrounding the first portion, is 0.239 ^m2 , and the area _Sh of the second air intake port is 0.0609 ^m2 . 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 ^m2 .
Furthermore, 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 located, i.e., the second portion, was 3324 Pa·s/ ^m3 . Among the parameters required to calculate Z2, the air passage area _S0 of the second portion is the area of the region surrounded by the inner circumferential surface of the shroud, and is 0.132 ^m2 . Furthermore, since the hole area ratio D is 0, the effective area S is equal to the air passage area _S0 , i.e., 0.132 ^m2 .

The acoustic impedance Zr at the ventilation portion of the silencer in Example 1 was 1991.1 Pa·s/ ^m³ . Here, the air passage area _S0 required to calculate Zr is 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 equal to the air passage area _S0 .

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.

Example 3
In Example 3, a silencer made of only a rigid frame was used, which was the silencer of Test 1 without the sound-absorbing material. Other conditions were the same as in Example 1. In addition, in Example 3, the acoustic impedance of the ventilation part was the same as in Example 1.

Example 4
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.

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

(Regarding test results)
In Examples 1 to 4 and Comparative Example 1, the sound pressure level during the test was 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 a distance of at least 1 m from the outdoor unit. The measurement results of the sound pressure levels in Examples 1 and 3 and Comparative Example 1 (reference) are shown in Figure 9. The measurement results of the sound pressure levels in Examples 2 and 4 and Comparative Example 1 (reference) are shown in Figure 10.

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 Figure 11. The sound deadening spectrum determined for each of Examples 2 and 4 is shown in Figure 12.

As can be seen from Figures 9 to 12, by placing a frame-type silencer adjacent to the first air intake port located on the rear side of the outdoor unit, the acoustic impedance of the ventilation section of the silencer is high, and as mentioned above, noise can be contained within the outdoor unit's housing. This allows for loss within the housing and directional diffusion of sound, making it possible to more effectively muffle noise when the fan is rotating than when a silencer is not installed. Furthermore, as is clear from Figures 11 and 12, the noise-muffling effect can be enhanced by placing sound-absorbing material around the ventilation section within the rigid frame, and the amount of silencing can be increased, particularly around 500 Hz.

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 noise travels, and this allows noise to be more effectively contained within the outdoor unit.
As described above, the configurations of the above-mentioned Examples 1 to 4 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.

10, 10x Fan with silencer 12 Fan 14 Center portion 16 Rotor 18 Rotor shaft 20 Housing 22 First wall 24 Second wall 26 Side wall 28 Third wall 30 First intake hole (opening)
32 Second intake port 34 Exhaust port 36 Machine room 38 Partition wall 40 Heat exchanger 42 Shroud 44 Grill (breathable member)
46 First portion 48 Second portion 50, 50x Muffler 52 Ventilation portion 54 Muffler-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 (14)

A fan with a silencer, the fan including a housing having an opening, a fan housed in the housing, and a silencer that silences noise generated by rotation of the fan,
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 are present inside the housing;
the silencer has a vent portion communicating with the opening,
A fan with a silencer, wherein the acoustic impedance of the vent portion is higher than the acoustic impedance of the first portion. the acoustic impedance of the ventilation portion is lower than the acoustic impedance of the second portion;
The silencer-equipped fan according to claim 1 , wherein the first portion is disposed between the second portion and the ventilation portion in the axial direction of the rotation shaft of the fan. the housing includes 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,
In the second portion, 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,
The silencer-equipped fan according to claim 1 , wherein the silencer is disposed with the vent portion adjacent to the first intake hole. a side wall disposed between the first wall and the second wall of the housing has a communication hole that communicates the inside of the housing with an external space of the housing;
The silencer-equipped fan according to claim 3 , wherein the first portion is located adjacent to the communication hole inside the housing. the communication hole is a second intake hole,
The silencer-equipped fan according to claim 4 , wherein 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. A fan with a silencer as described in claim 1, wherein a resistance member that provides resistance to the flow of gas through the opening is provided at the end of the internal space of the housing on the opening side. The silencer-equipped fan of claim 6, wherein the resistance member is a heat exchanger. 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 fan's rotation shaft, and the ventilation section is adjacent to the opening on the side opposite the resistance member. The fan with silencer according to claim 1, wherein the silencer comprises a cylindrical rigid frame surrounding the ventilation section. The silencer-equipped fan of claim 1, wherein the silencer comprises an opening wall surrounding the ventilation section and having a silencer-side opening, and a rear space separated by the opening wall and communicating with the opening via the ventilation section and the silencer-side opening. The silencer-equipped fan according to claim 10, wherein the silencer silences the sound by at least resonating a resonance structure formed by the silencer-side opening and the rear space. The silencer-equipped fan 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. The silencer has an outer circumferential wall,
The silencer-equipped fan according to claim 1 , wherein a through-hole is provided in a lower end portion of the outer peripheral wall. The fan with silencer according to claim 1, wherein the fan is a fan for an outdoor unit of an air conditioning system.