Blower with silencer

Abstract

Provided is a blower with a silencer capable of effectively silencing a sound of a specific frequency resonating in a housing among sounds emitted by the blower.　This blower with a silencer comprises: a blower having a housing in which a fan is disposed; and a silencer for silencing a sound emitted by the blower, wherein the housing has an air intake port and an exhaust port, and the silencer is located outside the housing in an axial direction of a rotating shaft of the fan, and has: a casing having a ventilation portion adjacent to a target ventilation port of the air intake port and the exhaust port, an inner peripheral portion surrounding the ventilation portion, and an outer peripheral portion disposed outside the inner peripheral portion; and an opening formed in the inner peripheral portion and communicating with a casing inner space located between the inner peripheral portion and the outer peripheral portion. The area of a region surrounded by the outer peripheral portion when viewed from the axial direction is larger than the opening area of the target ventilation port.

Description

Blower with silencer

[0001] The present invention relates to a blower with a silencer.

[0002] Technologies for silencing the noise emitted by fans have already been developed, and one example is the technology described in Patent Document 1. In the fan (fan motor) described in Patent Document 1, a silencing section is disposed inside the housing that houses the fan (motor and impeller), thereby making it possible to reduce the noise of the fan without increasing the installation space for the fan.

[0003] Japanese Patent Application Laid-Open No. 2017-141672

[0004] The inventors of the present invention have discovered the following about the above-described blower, particularly a blower for an outdoor unit or the like equipped with a large fan. Specifically, among the sounds emitted by the blower, sounds of a specific frequency are confined within the housing without being radiated (emitted) from the housing. As a result, the sound pressure of the specific frequency increases near the sound source (fan), resulting in amplified (resonated) sounds within the housing. Even if the housing is provided with vents such as an intake vent and an exhaust vent, such sounds of a specific frequency are confined within the housing without being radiated from the vents. This is due to the acoustic characteristics of sound, which reflect at locations where the space suddenly expands toward the outside of the housing, such as vents.

[0005] The object of the present invention is to solve the problems of the conventional technology described above and to provide a blower with a silencer that can effectively silence sounds of specific frequencies that resonate within the housing, among the sounds emitted by the blower.

[0006] To solve this problem, the present invention has the following configuration: [1] A blower with a silencer, comprising: a blower having a fan disposed inside a housing; and a silencer for muffling sound emitted by the blower, wherein the housing has an intake port and an exhaust port, the silencer has a casing having a ventilation section located outside the housing in the axial direction of the rotation shaft of the fan and adjacent to a target vent port of the intake port or the exhaust port, an inner circumferential section surrounding the ventilation section, and an outer circumferential section located outside the inner circumferential section, and an opening formed in the inner circumferential section and communicating with a space inside the casing located between the inner circumferential section and the outer circumferential section, wherein the area of ​​the region surrounded by the outer circumferential section when viewed from the axial direction is larger than the opening area of ​​the target vent port. [2] A blower with a silencer, wherein the wavelength of a first sound corresponding to a resonant frequency inside the housing of the sound emitted by the blower is defined as λ １ When the radius of a virtual circle having the area of ​​the region surrounded by the outer periphery as viewed from the axial direction is a, a>1.1×λ １ [3] The sound emitted by the fan includes a first sound corresponding to a resonance frequency within the housing and a second sound having a higher frequency than the first sound, and the distance between the inner circumferential portion and the outer circumferential portion is set so that the wavelength of the second sound is λ ２ In this case, λ ２ [4] The silencer-equipped fan according to [1] or [2], wherein the interval is 8.5 cm or more. [5] The sound emitted by the fan includes a first sound corresponding to a resonance frequency within the casing and a second sound having a frequency higher than that of the first sound, and the thickness of the casing interior space in the axial direction is such that the wavelength of the second sound is λ ２ In this case, λ ２ [6] The sound emitted by the fan includes a first sound corresponding to a resonance frequency within the housing, and the thickness of the space within the casing in the axial direction is set to λ / 8 or more. １ In this case, λ １

[0014] The silencer-equipped fan according to any one of [1] to [5], wherein the casing further has a cylindrical protrusion protruding from the edge of the target vent opening toward the inside of the casing.

[0015] The silencer-equipped fan according to any one of [1] to [6], wherein a sound-absorbing member is disposed in at least one of the space inside the casing and the opening.

[0016] The silencer-equipped fan according to any one of [1] to [7], wherein a windbreak member is disposed in the opening to prevent wind from entering the space inside the casing.

[0017] The silencer-equipped fan according to any one of [1] to [9], wherein two silencers are provided as the silencers, and both the intake port and the exhaust port are target vents, one of the two silencers is located on the intake port side of the casing, and the other of the two silencers is located on the exhaust port side of the casing.

[0007] According to the present invention, it is possible to provide a fan with a silencer that can effectively silence sounds of specific frequencies that resonate within the housing, among the sounds emitted by the fan.

[0008] 8 is a perspective view showing a state in which the blower and the muffler are disassembled in a blower with a silencer according to one embodiment of the present invention. FIG. 1 is a cross-sectional view taken along the cutting line J-J in FIG. 1. FIG. 2 is a diagram showing the results of calculations of sound pressure distribution inside and around a blower by acoustic simulation, using a blower without a muffler as a calculation model. FIG. 3 is a schematic diagram comparing changes in radiation impedance of a blower without a muffler and changes in radiation impedance of a blower with a muffler. FIG. 4 is a cross-sectional view corresponding to FIG. 2 of a blower with a silencer according to a first modified example of the present invention. FIG. 5 is a cross-sectional view corresponding to FIG. 2 of a blower with a silencer according to a second modified example of the present invention. FIG. 6 is a cross-sectional view corresponding to FIG. 2 of a blower with a silencer according to a third modified example of the present invention. FIG. 7 is a diagram showing the relationship between frequency and silencing volume in Example 1. FIG. 8 is a diagram showing the results of calculations of sound pressure distribution inside and around a blower by acoustic simulation, using the blower with a silencer according to Example 1 as a calculation model, for silencing peak F1 in FIG. 9 is a diagram showing the results of calculations of the sound pressure distribution inside and around the fan by acoustic simulation for the silencing peak F2 in FIG. 8 using the silencer-equipped fan of Example 1 as a calculation model (Part 2); the results of calculations of the sound pressure distribution inside and around the fan by acoustic simulation for the silencing peak F3 in FIG. 8 using the silencer-equipped fan of Example 1 as a calculation model (Part 3); the results of calculations of the sound pressure distribution inside and around the fan by acoustic simulation for the silencing peak F3 in FIG. 8 using the silencer-equipped fan of Example 1 as a calculation model (Part 4); the results of calculations of the sound pressure distribution inside and around the fan by acoustic simulation for Examples 2 and 3; the results of calculations of the frequency and silencing volume in Examples 4 and 5; the results of calculations of the frequency and silencing volume in Examples 6 to 8; the results of calculations of the frequency and silencing volume in Examples 9 to 11; and the results of calculations of the frequency and silencing volume in Examples 12 to 14.

[0009] The silencer-equipped fan of the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings. Note that the following embodiment is merely an example provided to facilitate understanding of the present invention and is not intended to limit the present invention. In other words, the configuration of the present invention may be modified or improved from the following embodiment without departing from the spirit of the present invention. Furthermore, unless otherwise specified, the material and shape of each component used to implement the present invention may be freely 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.

[0010] 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 the difference is within a range of less than ±10° from the strict "orthogonal," "vertical," and "parallel." The difference 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," "identical," and "overall" may include the range of error generally acceptable in the technical field to which the present invention belongs.

[0011] Furthermore, "sound deadening" in the present invention means to muffle sound, and is a concept that includes both sound insulation and sound absorption. Sound insulation means blocking sound, in other words, not allowing sound to pass through. Sound insulation also includes the reflection of sound (acoustics) and the cancellation of sound (acoustics). Sound absorption means converting sound energy into thermal energy, that is, absorbing sound (acoustics).

[0012] <<Configuration of the silencer-equipped blower according to this embodiment>> A silencer-equipped blower (hereinafter referred to as silencer-equipped blower 1) according to one embodiment of the present invention (hereinafter referred to as this embodiment) will be described with reference to Figures 1 and 2. As shown in Figure 1, the silencer-equipped blower 1 includes a blower 10 having a fan 20 disposed inside a housing 30, and a silencer 40 that silences the sound emitted by the blower 10. The silencer-equipped blower 1 is applicable to equipment that includes a blower, and its use is not particularly limited. Examples of the silencer-equipped blower 1 include outdoor units for air conditioners, cooling fans for devices (computers, servers, electronic devices, medical devices, office equipment, home appliances, etc.), axial fans for radiators in mobility vehicles and air conditioning systems, cooling towers in factories and power plants, air exchangers in buildings and shopping malls, etc., air and heat exchangers in agricultural greenhouses, ventilation and dust exhaust systems in factories, and spot cooler systems that use fans. Note that the following description will be given on the assumption that the silencer-equipped blower 1 is used as an outdoor unit for an air conditioner.

[0013] <Blower> The blower 10 is, for example, an outdoor unit disposed in an outdoor space, and more specifically, as shown in FIG. 1 , includes a fan 20 and a housing 30 .

[0014] [Fan] The fan 20 is, for example, an axial flow fan, specifically an axial flow fan (propeller fan). As shown in FIG. 2 , the fan 20 blows air in the axial direction of the rotation axis G of the fan 20, and discharges gas taken in from one axial side of the rotation axis G toward the other axial side. Note that the fan 20 is not limited to an axial flow fan such as an axial flow fan, but may be, for example, a diagonal flow fan (diagonal flow fan, etc.) or a cross-flow fan (line flow fan (registered trademark), cross flow fan, etc.). Note that the following description will be given assuming that the fan 20 is an axial flow fan. The term "wind" is not particularly limited and may refer to, for example, an artificial flow of air and gas (airflow). The composition of the air or gas constituting the wind and the ratio of each component are not particularly limited, but the following description will be given assuming that normal air is being blown.

[0015] In the following description, as shown in FIG. 1 , the axial direction of the rotation axis G of the fan 20 is referred to as the “front-rear direction,” the side that takes in air as viewed from the fan 20 is referred to as the “rear side” or “back side,” and the side that discharges air as viewed from the fan 20 is referred to as the “front side” or “front side.” The following description will be based on the assumption that the blower 10 is positioned so that the rotation axis G is horizontal. For ease of explanation, three mutually orthogonal directions as shown in FIG. 1 will be referred to as the “front-rear direction,” the “up-down direction,” and the “left-right direction.” The left-right direction is defined as viewed from the front, and in the following description, the side of a side air intake port 35 (described later) will be referred to as the “left side,” and the side of a machine room 11 (described later) will be referred to as the “right side,” as shown in FIG. 2 . The “front-rear direction,” “up-down direction,” and “left-right direction” are defined solely based on the arrangement of the blower 10 in this embodiment, and their definitions may differ depending on the arrangement of the blower 10.

[0016] 2, the fan 20 includes a motor 21, a shaft 22, and a plurality of blades 23. The motor 21 may be a known electric motor, and rotates the shaft 22. The motor 21 is, for example, cylindrical, and is supported by a support member (not shown) provided inside the housing 30.

[0017] The shaft portion 22 is, for example, cylindrical and is located in front of the motor 21. The shaft portion 22 is attached to, for example, a shaft of the motor 21 that protrudes toward the shaft portion 22 side, and rotates together with the shaft. The diameter of the shaft portion 22 is, for example, approximately the same as or larger than that of the motor 21. The rotation axis of the shaft portion 22 corresponds to the rotation axis G of the fan 20. As shown in FIG. 1 , the rotation axis G of the fan 20 is located at the center of the fan 20 when viewed from the front-to-rear direction.

[0018] The plurality of blades 23 are attached to the circumferential surface of the shaft portion 22 and each protrude from the circumferential surface toward the outside in the radial direction of the shaft portion 22. The plurality of blades 23 are arranged at intervals along the circumferential direction of the shaft portion 22. Note that, although the example shown in FIG. 1 has three blades 23, this is not limitative and the number of blades 23 may be any number depending on the conditions of use. Furthermore, the shape and angle of the blades 23 may be any shape and angle used in known axial flow fans, etc. The angle of the blades 23 refers to the inclination angle of the blades 23 (or their surfaces) with respect to the rotation axis G. The blades 23 rotate together with the shaft portion 22 and generate wind (airflow) that travels forward.

[0019] [Housing] As shown in Fig. 1, the housing 30 defines the outer edge of the blower 10, and the fan 20 is disposed inside the housing 30. The shape of the housing 30 is not particularly limited, but in this embodiment, for example, the housing 30 has a rectangular parallelepiped shape that is elongated in the left-right direction. Specifically, as shown in Fig. 1, the housing 30 has a plurality of (two) main surface walls 31a-31b, a plurality of (four) side walls 32a-32d, a partition wall 37, an air intake port 33, an exhaust port 34, a side air intake port 35, and a shroud 36 (corresponding to a protrusion, see Fig. 2).

[0020] 1, the two main walls 31a, 31b are each, for example, rectangular, and are arranged apart from each other in the front-to-rear direction across the fan 20. The main wall 31a is located on the front side (front face side) when viewed from the fan 20, and the main wall 31b is located on the rear side (rear face side) when viewed from the fan 20.

[0021] The four side walls 32a, 32b, 32c, and 32d are, for example, rectangular and protrude from four sides of the main surface wall 31a. The four side walls 32a, 32b, 32c, and 32d are connected to each other to form a cylindrical (rectangular) shape surrounding the fan 20. As shown in FIG. 1 , two of the four side walls 32a, 32b, 32c, and 32d are arranged apart from each other in the left-right direction across the fan 20. When viewed from the front, the side wall 32a is located on the left side of the fan 20 (toward the side intake port 35), and the side wall 32b is located on the right side of the fan 20. The remaining two side walls 32c and 32d of the four side walls 32a, 32b, 32c and 32d are arranged apart from each other in the vertical direction across the fan 20, with the side wall 32c located above the fan 20 and the side wall 32d located below the fan 20.

[0022] As shown in FIG. 2 , the partition wall 37 divides the space within the housing 30, defined by the two main walls 31 a, 31 b and the four side walls 32 a, 32 b, 32 c, and 32 d, into two adjacent spaces V1 and V2. The partition wall 37 extends in the front-rear direction from one of the two main walls 31 a, 31 b to the other. Of the two spaces V1 and V2, the fan 20 is located in the left-hand space V1 when viewed from the front, and the machine chamber 11 is located in the right-hand space V2 when viewed from the front. A compressor (not shown) and other components are located in the machine chamber 11. In other words, as shown in FIG. 2 , the housing 30 is composed of a first storage section 38 a and a second storage section 38 b, which are adjacent to each other in the left-right direction. The first storage section 38a is formed by walls that surround the fan 20, and specifically, is formed by the fan 20-side portions of the main surface walls 31a, 31b and the side walls 32c, 32d in the left-right direction, the side wall 32a, and the partition wall 37. The second storage section 38b is formed by walls that surround the machine chamber 11, and specifically, is formed by the machine chamber 11-side portions of the main surface walls 31a, 31b and the side walls 32c, 32d in the left-right direction, the side wall 32b, and the partition wall 37.

[0023] The housing 30 may be constructed by joining adjacent walls among the main surface walls 31a-31b, the side walls 32a-32d, and the partition wall 37 by welding, adhesive, or fastening with screws, or by integrally (seamlessly) forming the main surface walls 31a-31b, the side walls 32a-32d, and the partition wall 37. The material of the housing 30 is not particularly limited, and metal materials, resin materials (including reinforced plastic materials), carbon fiber, and the like can be used. In the above description, the side walls constituting the housing 30 are described as being rectangular tubular with the four side walls 32a, 32b, 32c, and 32d. However, this is not limited thereto. For example, the housing 30 may be cylindrical with one side wall, or may be rectangular with a number of side walls different from the four side walls.

[0024] (Air Intake Port and Exhaust Port) The air intake port 33 and the exhaust port 34 are located apart from each other in the front-rear direction. As shown in FIG. 2 , the air intake port 33 is provided at one end of the housing 30 in the front-rear direction, more specifically, formed in the rear main surface wall 31b. The air intake port 33 is an opening that penetrates the main surface wall 31b in the front-rear direction. On the other hand, the exhaust port 34 is provided at the other end of the housing 30 in the front-rear direction, more specifically, formed in the front main surface wall 31a. The exhaust port 34 is an opening that penetrates the main surface wall 31a in the front-rear direction. Note that in this example, the air intake port 33 and the exhaust port 34 are located apart from each other in the front-rear direction, but this is not limited thereto. For example, the air intake port 33 and the exhaust port 34 may be located at the same position as each other in the front-rear direction, and specifically, may be formed in the same wall (such as the main surface wall 31a) of the housing 30.

[0025] The shapes (edge ​​shapes) of the intake port 33 and the exhaust port 34 are not particularly limited and may be, for example, circular, rectangular (square), quadrilateral other than rectangular, polygonal other than quadrilateral, or irregular. Furthermore, the shapes of the intake port 33 and the exhaust port 34 may be different from each other or the same. In this embodiment, the shape (edge ​​shape) of the intake port 33 is, for example, rectangular, as shown in FIG. 1 , and the center of the intake port 33 is located on a straight line with, for example, the rotation axis G of the fan 20. The lengths of the intake port 33 in the vertical and horizontal directions are, for example, equal to or greater than the diameter of the fan 20. Note that the "diameter of the fan 20" refers to the diameter of an imaginary circle traced by the trajectory of the leading edge of the blades 23 when the fan 20 rotates. The shape (edge ​​shape) of the exhaust port 34 is, for example, circular, as shown in FIG. 1 , and the center of the exhaust port 34 is located on a straight line with, for example, the rotation axis G of the fan 20. The diameter of the exhaust port 34 is, for example, equal to or larger than the diameter of the fan 20 .

[0026] In this embodiment, the opening area of ​​the intake port 33 is smaller than the area of ​​the region surrounded by the first storage section 38a when viewed from the front-rear direction (in other words, the area of ​​the region surrounded by the side walls 32a, 32c, and 32d and the partition wall 37 when viewed from the front-rear direction). In the following description, the "region surrounded by the first storage section 38a when viewed from the front-rear direction" is also referred to as the "specific region within the first storage section 38a." In this embodiment, the specific region within the first storage section 38a is rectangular. Furthermore, the "opening area of ​​the intake port 33" and the "area of ​​the specific region within the first storage section 38a" refer to the maximum area when the area varies depending on the position in the front-rear direction. The same applies to the "opening area of ​​the exhaust port 34" described below. Furthermore, as shown in FIG. 2 , the length U1 of the intake port 33 in the left-right direction is shorter than the length U2 of the specific region within the first storage section 38a in the left-right direction. Although not shown, the vertical length of the intake port 33 is shorter than the vertical length of the specific region in the first storage section 38a. However, this is not limiting, and the opening area of ​​the intake port 33 may be the same as the area of ​​the specific region in the first storage section 38a, or the length of the intake port 33 may be the same as the length of the specific region in the first storage section 38a in at least one of the left-right direction and the up-down direction.

[0027] In this embodiment, the opening area of ​​the exhaust port 34 is smaller than the opening area of ​​the intake port 33 and the area of ​​the specific region within the first storage section 38a. Furthermore, as shown in FIG. 2 , the left-right length U3 of the exhaust port 34 is shorter than the left-right length U1 of the intake port 33 and the left-right length U2 of the specific region within the first storage section 38a. Although not shown, the vertical length of the exhaust port 34 is shorter than the vertical length of the intake port 33 and the vertical length of the specific region within the first storage section 38a. The left-right and vertical lengths of the exhaust port 34 both correspond to the diameter of the circular exhaust port 34. However, this is not limited to this, and the opening area of ​​the exhaust port 34 may be, for example, the same as at least one of the opening area of ​​the intake port 33 and the area of ​​the specific area within the first storage section 38a, and the length of the exhaust port 34 may be, for example, the same as at least one of the length of the intake port 33 and the length of the specific area within the first storage section 38a in at least one of the left-right direction and the up-down direction.

[0028] (Side Air Intake Port) As shown in FIG. 1 , the side air intake port 35 is provided at one end of the housing 30 in the left-right direction. More specifically, it is formed in the left side wall 32a of the housing 30. The side air intake port 35 is an opening that penetrates the side wall 32a in the left-right direction. The side air intake port 35 is located in the center of the housing 30 in the front-to-rear direction. The shape (edge ​​shape) of the side air intake port 35 is not particularly limited and may be, for example, a circle, a rectangle (square), a quadrangle other than a rectangle, a polygon other than a quadrangle, or an irregular shape. In this embodiment, the shape of the side air intake port 35 is, for example, a rectangle that is long in the up-down direction, as shown in FIG. 1 . The center of the side air intake port 35 in the up-down direction is located at the same height as, for example, the rotation axis G of the fan 20.

[0029] A heat exchanger (not shown) is adjacent to the intake port 33 and the side intake port 35 from the inside of the housing 30. The heat exchanger (not shown) extends from the intake port 33 to the side intake port 35. There are no particular limitations on the heat exchanger, and a known heat exchanger may be used, such as a fin-and-tube heat exchanger or a parallel-flow heat exchanger.

[0030] (Shroud) As shown in FIG. 2 , the shroud 36 is provided at one end (main surface wall 31 a) of the housing 30 in the front-to-rear direction and protrudes from the edge of the exhaust port 34 toward the inside of the housing 30 (the rear side in the front-to-rear direction). The shroud 36 is cylindrical, surrounds the fan 20, and functions to smooth the flow of air near the fan 20. The shroud 36 has a cross-sectional area larger at both ends than at the center in the front-to-rear direction. More specifically, the shroud 36 has a shape in which the cross-sectional area increases from the center to each of the ends, specifically a bell-mouth shape. The cross-sectional shape of the shroud 36 is not particularly limited and may be, for example, a circle, a rectangle (square), a quadrangle other than a rectangle, a polygon other than a quadrangle, or an irregular shape. The end of the shroud 36 on the exhaust port 34 side coincides with the edge of the exhaust port 34, or in other words, is a circle with the same size (diameter) as the exhaust port 34. The shroud 36 may be joined to the main surface wall 31 a by welding, adhesive, or fastening with screws, or may be formed integrally (seamlessly) with the main surface wall 31 a. The material of the shroud 36 is not particularly limited, and metal materials, resin materials (including reinforced plastic materials), carbon fiber, etc. may be used.

[0031] <Muffler> As shown in FIG. 1 , the silencer 40 has a ventilation section 41 , a casing 42 , an opening 43 , and a windbreak member 44 .

[0032] 2, the ventilation section 41 is located outside the housing 30 in the front-to-rear direction, adjacent to a target ventilation opening of the intake port 33 and the exhaust port 34, and specifically corresponds to the space H as a ventilation path through which air passes. At least one of the intake port 33 and the exhaust port 34 corresponds to the "target ventilation opening," but in this embodiment, only the intake port 33 corresponds to the target ventilation opening.

[0033] [Casing] As shown in Fig. 1, the casing 42 is annular (frame-shaped) and contacts the main surface wall 31b of the housing 30 from the rear side in the front-to-rear direction as shown in Fig. 2. More specifically, the casing 42 has an inner peripheral portion 45, an outer peripheral portion 46, and two side portions 47, 48 as shown in Fig. 1.

[0034] The inner periphery 45 defines the outer edge of the ventilation section 41 (space H), surrounds the ventilation section 41, and forms a ring shape. The inner periphery 45 is configured by a wall in which an opening 43, which will be described later, is formed. More specifically, as shown in FIG. 2 , the inner periphery 45 is positioned so as to overlap the edge of the air intake port 33 when viewed from the front-to-rear direction, and forms the same rectangular ring shape as the air intake port 33.

[0035] The outer peripheral portion 46 defines the outer edge of the casing 42 and has an annular (frame-like) shape. The outer peripheral portion 46 is disposed outside the inner peripheral portion 45 and surrounds the inner peripheral portion 45 with a gap W therebetween. When viewed from the front-to-rear direction, the outer peripheral portion 46 has the same shape as the inner peripheral portion 45 but is larger than the inner peripheral portion 45. In this embodiment, the outer peripheral portion 46 has a rectangular annular shape that is one size larger than the inner peripheral portion 45. The outer peripheral portion 46 is made of a plate member, and in this embodiment, the rectangular cylindrical shape is formed by connecting multiple (four) flat plate members together.

[0036] The two side portions 47, 48 are, for example, two side plates spaced apart in the front-to-rear direction. As shown in Fig. 2, the side portion 47 is located at the end of the outer peripheral portion 46 opposite the blower 10 in the front-to-rear direction, and the side portion 48 is located at the end of the outer peripheral portion 46 on the blower 10 side in the front-to-rear direction. Note that the side portion 48 may be part of the housing 30, specifically part of the main surface wall 31b.

[0037] The casing 42 configured as described above may be configured by joining adjacent portions of the inner circumferential portion 45, the outer circumferential portion 46, and the side portions 47, 48 together by welding, adhesive, or fastening with screws, or by integrally (seamlessly) forming the inner circumferential portion 45, the outer circumferential portion 46, and the side portions 47, 48. The material of the casing 42 is not particularly limited, and metal materials, resin materials (including reinforced plastic materials), carbon fiber, etc. may be used.

[0038] Between the inner peripheral portion 45 and the outer peripheral portion 46, an internal casing space S is located as a space inside the casing 42. More specifically, the internal casing space S is a space surrounded by the inner peripheral portion 45, the outer peripheral portion 46, and the side portions 47 and 48. Although not specifically shown, columns and walls connecting the side portions 47 and 48 may be arranged in the internal casing space S to ensure the rigidity of the casing 42. However, the internal casing space S is continuous within the casing 42 in the circumferential direction of the casing 42 without being interrupted by such columns and walls. As shown in FIG. 2 , the internal casing space S, together with space H (ventilation portion 41), constitutes a space K surrounded by the outer peripheral portion 46.

[0039] As shown in Fig. 2, the distance W between the inner peripheral portion 45 and the outer peripheral portion 46 is constant over the entire circumferential area (entire circumference) of the casing 42. Furthermore, as shown in Fig. 2, the thickness T of the casing interior space S in the front-to-rear direction is constant over the entire circumferential area (entire circumference) of the casing 42. Note that the thickness T corresponds to the distance between the side portions 47 and 48. However, this is not limiting, and for example, at least one of the distance W and the thickness T may vary depending on the position in the circumferential direction of the casing 42.

[0040] Here, the area of ​​the region surrounded by the outer periphery 46 when viewed from the front-to-rear direction (hereinafter also referred to as the "target region within the outer periphery 46") is larger than the opening area of ​​the air intake 33. Note that, when the area of ​​the target region within the outer periphery 46 varies depending on the position in the front-to-rear direction, the area refers to the maximum area. In this embodiment, the area of ​​the target region within the outer periphery 46 is larger than the area of ​​the specific region within the first storage section 38a. Furthermore, the target region within the outer periphery 46 is rectangular in shape corresponding to the shape of the outer periphery 46 (rectangular ring). Furthermore, as shown in FIG. 2, the horizontal length R of the target region within the outer periphery 46 is longer than the horizontal length U1 of the air intake 33 and the horizontal length U2 of the specific region within the first storage section 38a. Furthermore, although not shown, the vertical length of the target region within the outer periphery 46 is longer than the vertical length of the air intake 33 and the vertical length of the specific region within the first storage section 38a. However, without being limited thereto, the area of ​​the target region within the outer periphery 46 may be equal to or smaller than the area of ​​the specific region within the first storage section 38a, as long as it is larger than the opening area of ​​the intake port 33 (target vent). Furthermore, as long as the area of ​​the target region within the outer periphery 46 is larger than the opening area of ​​the intake port 33 (target vent), the length of the target region within the outer periphery 46 may be equal to or shorter than the length of at least one of the intake port 33 and the specific region within the first storage section 38a in at least one of the left-right and up-down directions.

[0041] In the above description, the inner circumferential portion 45 is positioned to overlap the edge of the intake port 33 when viewed from the front-rear direction and has the same rectangular annular shape as the intake port 33. However, this is not limited thereto. For example, the inner circumferential portion 45 may be positioned outward from the edge of the intake port 33 when viewed from the front-rear direction and may have an annular shape different from that of the intake port 33. In the above description, the outer circumferential portion 46 has the same shape as the inner circumferential portion 45 when viewed from the front-rear direction. However, this is not limited thereto. For example, the outer circumferential portion 46 may have a different shape from the inner circumferential portion 45 when viewed from the front-rear direction. In other words, the shape of the silencer 40 when viewed from the front-rear direction (more specifically, the shapes of the inner circumferential portion 45 and the outer circumferential portion 46 when viewed from the front-rear direction) is not particularly limited and may be, for example, a circle, a rectangle (square), a quadrangle other than a rectangle, a polygon other than a quadrangle, or an irregular shape regardless of the shape of the target air vent. This also applies to the modified examples described below.

[0042] [Opening] The opening 43 is formed in a wall constituting the inner circumferential portion 45 and communicates with the casing interior space S. More specifically, the opening 43 is formed in the inner circumferential portion 45 over the entire circumferential area (entire circumference) of the casing 42, for example, and is an opening that is continuous in the circumferential direction of the casing 42. In the present embodiment, the width of the opening 43 in the front-rear direction is the same as the thickness T of the casing interior space S, as shown in FIG. 2 , and has the same width over the entire circumferential area (entire circumference) of the casing 42. However, this is not limited thereto, and for example, the width of the opening 43 in the front-rear direction may vary depending on the position in the circumferential direction of the casing 42.

[0043] [Windbreak Member] The windbreak member 44 is disposed in the opening 43 (covering the opening 43) or disposed so as to fill the opening 43 and its interior (closer to the casing interior space S than the opening 43) to prevent wind from entering the casing interior space S. The windbreak member 44 is formed, for example, from a member made of an impermeable material, a sound-absorbing material, a woven fabric, or the like. The windbreak member 44 may cover the entire area (entire circumference) of the opening 43 in the circumferential direction of the casing 42, or may cover part of the opening 43 in the circumferential direction of the casing 42.

[0044] Examples of components made of impermeable materials include plates (including punched metal) with one or more openings (holes). Examples of impermeable materials include metal materials, resin materials (including reinforced plastic materials), carbon fiber, and closed-cell foam materials. Sound-absorbing materials are made of porous materials that absorb sound by converting sound energy into thermal energy. Examples of sound-absorbing materials include open-cell foam sound-absorbing materials and fiber-based sound-absorbing materials. Examples of foam 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, phenolic foam, melamine foam, insulation board, and polyamide foam. Examples of fibrous sound-absorbing materials include microfiber nonwoven fabrics such as Micromat manufactured by Taihei Felt Co., Ltd. and Thinsulate manufactured by 3M Corporation; polyester nonwoven fabrics (including those with a two-layer structure having a thin, high-density nonwoven fabric on the front side and a low-density nonwoven fabric on the back side) such as White Qion (registered trademark) manufactured by Tokyo Bouon Co., Ltd. and QonPET (registered trademark) manufactured by Bridgestone KBG Corporation; 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. Furthermore, nonwoven fabrics and woven fabrics can also be used as fibrous sound-absorbing materials, covering only the opening 43. Examples of such nonwoven fabrics and woven fabrics include high-density surface nonwoven fabrics such as QonPET (registered trademark) and Precise (registered trademark) manufactured by M.A. Life Materials Co., Ltd. Other fibrous sound-absorbing materials include fabrics and recycled products used in clothing, automobile and residential interiors, etc.

[0045] <<Operation and Effects of the Silencer-Equipped Fan of the Present Embodiment>> Generally, it is not easy to silence low-frequency sounds below 1 kHz. On the other hand, in fans such as outdoor units equipped with large fans, the sounds they emit span a wide frequency range, from low frequencies below 1 kHz to high frequencies above 1 kHz, making it difficult to silence them. Silencing of such low-frequency sounds is particularly required. The inventors focused on peak sounds generated at specific frequencies, specifically peak sounds near 260 Hz, among the sounds emitted by fans, and investigated the mechanism by which these peak sounds are generated. In this specification, the "sound source" of the sound emitted by the fan 10 is defined as the leading edge of the blades 23 of the fan 20, unless otherwise specified.

[0046] FIG. 3 shows the results of an acoustic simulation of the sound pressure distribution inside and around the blower 10, using a blower 10 without a silencer 40 as a calculation model. FIG. 3 shows the sound pressure distribution of sounds emitted from a sound source at frequencies of 220 Hz, 260 Hz, and 300 Hz. Specifically, the sound pressure intensity distribution is shown in dB, with brighter colors indicating greater sound pressure intensity. Note that in FIG. 3 , the bottom side of the drawing corresponds to the intake port 33 side of the blower 10 (the rear side in the front-to-rear direction), and the top side of the drawing corresponds to the exhaust port 34 side of the blower 10 (the front side in the front-to-rear direction). It can be seen from FIG. 3 that the sound pressure inside the blower 10 is higher under the 260 Hz condition than under the 220 Hz and 300 Hz conditions.

[0047] Based on the above results, the inventors discovered the following. Specifically, among the sounds emitted by the blower 10, a small proportion, particularly for low-frequency sounds, propagates directly outward from the housing 30. Instead, a certain amount is reflected in response to the sudden change in acoustic impedance at the target vents (the intake vent 33 and the exhaust vent 34). The reflected sound returns to the housing 30 and is then re-radiated. A specific frequency (260 Hz in the structure of the blower 10 of this embodiment) coincides with the resonant frequency determined by the volume of the housing 30 and the size (opening area) of the target vent. Therefore, at this specific frequency, the sound radiated from the sound source and the reflected sound are aligned in phase, resulting in particularly strong sound pressure within the housing 30 and making it difficult for the sound to radiate outward from the housing 30. At this time, sound pressure increases particularly near the sound source (the fan 20), increasing the volume of sound radiated within the housing 30. Ultimately, the sound is radiated outward from the housing 30 through the target vent, resulting in particularly strong sound radiated at frequencies where resonance occurs. Among the sounds emitted by blower 10, sounds of a specific frequency that resonate within housing 30, that is, sounds corresponding to the resonant frequency within housing 30, are referred to as "enclosure resonance sounds (corresponding to first sounds)." Enclosure resonance sounds are determined according to the volume of housing 30 and the opening area of ​​the target air vent, and in the case of a typical housing such as an outdoor unit, the frequency corresponds to around 200 Hz to 300 Hz.

[0048] Here, the ease of radiation from inside the housing 30 to the outside is determined by the radiation impedance, which is defined based on the opening area of ​​the target air vent (the air intake 33 in this embodiment) and the wavelength of the housing resonance sound. While the spread of sound is limited at the target air vent, the sound spreads virtually without limit outside the housing 30. For this reason, the radiation impedances of the two are significantly different, and as a result, the housing resonance sound is reflected at the target air vent and is trapped within the housing 30 without being radiated from the target air vent.

[0049] In contrast to this, in this embodiment, the silencer-equipped blower 1 is provided with the silencer 40, and as shown in Fig. 2, the area of ​​the target region within the outer periphery 46 is larger than the opening area of ​​the air intake 33 serving as the target air opening. As a result, a space K surrounded by the outer periphery 46 that is larger than the space surrounded by the air intake 33 is located between the space surrounded by the air intake 33 and the external space of the housing 30, and the radiation impedance from the air intake 33 to the outside of the housing 30 can be changed stepwise in the front-to-rear direction.

[0050] This will be described in more detail with reference to FIG. 4 . FIG. 4 is a schematic diagram comparing the change in radiation impedance in the front-to-rear direction of the fan 10 without the silencer 40 with the change in radiation impedance in the front-to-rear direction of the fan 10 with the silencer 40 according to this embodiment. As can be seen from FIG. 4 , the fan 1 with the silencer according to this embodiment includes the silencer 40, and thus the change in radiation impedance in the front-to-rear direction is more gradual than the fan 10 without the silencer 40, and abrupt changes in impedance in the front-to-rear direction are suppressed. As such, in this embodiment, at the frequency of the housing resonance noise, the reflection coefficient at the target air vent is reduced, thereby reducing the sound returning to the interior of the housing 30, and the resonance effect is reduced, thereby suppressing an increase in sound pressure near the sound source. As a result, the amplification (resonance) of the housing resonance noise within the housing 30 can be suppressed, and the housing resonance noise can be effectively silenced.

[0051] However, it is conceivable that making the target vent larger than a predetermined size would facilitate the enclosure resonance noise being emitted from the enclosure 30. For example, if the enclosure resonance noise has a frequency of 260 Hz, it is conceivable to set the diameter of a virtual circle having the opening area of ​​the target vent (i.e., the equivalent diameter of a circle) to approximately the same as the enclosure resonance noise wavelength of 1.32 m. However, making the target vent larger than a predetermined size would result in an increase in the size of the fan 10 (particularly the size of the enclosure 30), which is undesirable. Furthermore, for example, providing an exhaust port 34 that is larger than necessary relative to the size of the fan 20 disposed inside the enclosure 30 would not have a favorable effect on the exhaust volume. In contrast, the silencer-equipped fan 1 can effectively silence enclosure resonance noise, eliminating the need to increase the size of the target vent, thereby preventing the fan 10 from becoming larger.

[0052] Furthermore, in this embodiment, even when the side intake port 35 is provided in the center of the housing 30 in the front-to-rear direction, housing resonance noise can be effectively silenced. More specifically, the silencer-equipped blower 1 effectively silences housing resonance noise based on the relationship between the area of ​​the target region within the outer circumferential portion 46 and the opening area of ​​the intake port 33 serving as the target air opening. In other words, the silencer-equipped blower 1 exerts its silencer effect based on the configuration of the end of the housing 30 in the front-to-rear direction, more specifically, based on the opening area of ​​the intake port 33. Therefore, even when the side intake port 35 is located in the center of the housing 30 in the front-to-rear direction, housing resonance noise can be effectively silenced.

[0053] In this embodiment, as shown in FIG. 2, when the radius of a virtual circle having the area of ​​the target region within the outer periphery 46 (i.e., the circle equivalent radius) is a, a>c×λ １ / (2π), the housing resonance noise can be more effectively silenced. "c" corresponds to the normalization constant of the radiation impedance, which will be described later, and takes any of the values ​​"1.1", "1.3", "1.5", "1.8", and "2.0", with the larger value being more preferable. １ " represents the wavelength of the housing resonance sound, and "π" represents the constant pi.

[0054] Regarding radiation impedance, an example is known in which a disk of radius a is used as a radiation source. In this example, the ease of radiation is determined by the normalization constant c of radiation impedance = 2π × a / λ. １ In this embodiment, a>c×λ is set as follows: １ / (2π). Note that when the value of the normalization constant c is 2.0 or less, the larger c is, the greater the sound radiation efficiency becomes, and the more effective it is at silencing housing resonance noise. On the other hand, when the value of the normalization constant c is greater than 2.0, the radiation efficiency remains almost unchanged. In other words, when c = 1.1 to 2.0, the closer c is to 2.0, the more effective it is at silencing housing resonance noise. When c > 2.0, the more effective it is at silencing housing resonance noise. On the other hand, from the perspective of the size of the silencer 40, the larger the value of the normalization constant c is, the larger the area of ​​the target region within the outer peripheral portion 46 becomes, and the larger the silencer 40 becomes. Therefore, a smaller value of the normalization constant c is preferable. From the above perspectives, it is most preferable for the normalization constant c to be around 2.0 from the perspectives of both the effective silencing of housing resonance noise and preventing the silencer 40 from becoming larger.

[0055] In this embodiment, as shown in FIG. 2, the thickness T of the casing space S in the front-rear direction is λ １ / 4.5 or less (λ １ = 260 Hz), the thickness T may be approximately 29 cm or less. As will be described later in the [Example], according to the blower with silencer 1, as shown in Figs. 8 and 13, the dependency (contribution) of the thickness T on the silencing effect of the housing resonance noise is small. １ By setting the thickness T of the casing space S to λ / 4.5 or less, it is possible to effectively muffle the housing resonance noise while suppressing an increase in the size of the device in the front-rear direction. １ / 6 or less (λ １ λ = 260 Hz), and １ / 10 or less (λ １ = approximately 13 cm or less at 260 Hz).

[0056] The sound emitted by the blower 10 includes housing resonance noise and target noise (corresponding to a second noise) with a higher frequency than the housing resonance noise. The silencer-equipped blower 1 according to this embodiment can effectively muffle the target noise as well as the housing resonance noise. When the housing resonance noise is 260 Hz, the "target noise" refers to any component of the sound with a frequency greater than 260 Hz and up to approximately 1 kHz. In particular, by targeting other peak noises, such as the NZ noise of the fan 20, and sounds with frequencies at which the sound pressure reaches a maximum in the noise spectrum, as the target noise, a high noise suppression effect can be achieved. Note that the "N" in "NZ noise" refers to the fan rotation speed, and the "Z" refers to the number of blades. Specifically, as shown in FIG. 2 , the silencer 40 can muffle the target noise by utilizing the resonance phenomenon by adjusting the distance W between the inner peripheral portion 45 and the outer peripheral portion 46 to achieve the same resonant frequency as the frequency of the target noise. Furthermore, when the windbreak member 44 and a sound-absorbing member 49C (see FIG. 7) described later are arranged inside the silencer 40, these members have the effect of lowering the resonant frequency of the silencer 40, and by utilizing this effect in combination, the resonant frequency of the silencer 40 can be appropriately adjusted to the frequency of the desired target sound.

[0057] In this embodiment, the distance W between the inner peripheral portion 45 and the outer peripheral portion 46 is set to λ ２ In this case, approximately λ ２ More specifically, when the frequency of the target sound is 1 kHz (i.e., wavelength λ ２When the width of the opening 43 is 34 cm, the distance W is preferably 8.5 cm or more, and more preferably 8.5 cm. Adjusting the distance W requires consideration of an opening edge correction according to the opening area of ​​the opening 43. Furthermore, when the windshield member 44 and a sound-absorbing member 49C (see FIG. 7 ), which will be described later, are disposed within the silencer 40, as described above, these elements have the effect of lowering the resonant frequency of the silencer 40. Therefore, this effect must be taken into account when adjusting the distance W. This allows the target sound to be effectively silenced by utilizing the resonance phenomenon (so-called λ / 4 resonance) caused by the silencer 40, along with the housing resonance noise. Furthermore, by disposing sound-absorbing materials (such as the windshield member 44 and the member 49C) within the silencer 40, the resonant frequency band of the silencer 40 can be broadened. This makes it possible to accommodate a relatively wide band of target sound.

[0058] In this embodiment, the thickness T of the casing space S is set to λ ２ In this case, λ ２ As mentioned above, the silencer 40 silences the target sound by utilizing the resonance phenomenon, and the greater the thickness T of the casing internal space S, the greater the silencing effect. For example, if the target sound is a sound with a frequency of 500 Hz or less, the wavelength λ of the target sound is ２ Since the thickness T of the casing internal space S is 68 cm or more, it is preferable that the thickness T of the casing internal space S is, for example, 8.5 cm or more. ２ / 6 or more is more preferable, and λ ２ It is more preferable that the ratio is 1 / 4 or more.

[0059] <<Regarding Other Embodiments>> Below, a silencer-equipped blower according to a modified example of the present invention will be described. In the following description, the configuration, operation, and effects of the silencer-equipped blower according to the modified example of the present invention that are different from the silencer-equipped blower 1 according to the above embodiment will be mainly described, and a description of the configuration, operation, and effects that are common to the silencer-equipped blower 1 will be omitted. Furthermore, in the silencer-equipped blower according to the modified example of the present invention, components that have the same functions as the components of the silencer-equipped blower 1 according to the above embodiment will be denoted by the same reference numerals for convenience.

[0060] <Modification 1> In the above embodiment, as shown in FIG. 2 , only the intake port 33 corresponds to the target vent port. However, this is not limited thereto. For example, as in a silencer-equipped blower 1A shown in FIG. 5 , only the exhaust port 34 may correspond to the target vent port, and a silencer 40A may be located on the exhaust port 34 side. The silencer 40A has a ventilation section 41, a casing 42, an opening 43, and a windbreak member 44. The detailed configuration of each section is similar to that of the silencer 40, and therefore description thereof will be omitted. Meanwhile, unlike the rectangular inner periphery 45 of the above embodiment, the inner periphery 45 of this modification overlaps with the edge of the circular exhaust port 34 when viewed from the front-to-rear direction, and has a circular shape of the same size (diameter) as the exhaust port 34. Furthermore, unlike the rectangular outer periphery 46 of the above embodiment, the outer periphery 46 of this modification has a circular shape that is slightly larger than the circular inner periphery 45 of this modification when viewed from the front-to-rear direction, for example. In the silencer-equipped fan 1A configured as described above, as shown in Fig. 5, the area of ​​the target region within the outer circumferential portion 46 is larger than the opening area of ​​the exhaust port 34, which serves as the target air vent. In this modification, the target region within the outer circumferential portion 46 is circular. As a result, a space K surrounded by the outer circumferential portion 46 that is larger than the space surrounded by the exhaust port 34 is located between the space surrounded by the exhaust port 34 and the space outside the housing 30, so that the radiation impedance from the exhaust port 34 to the outside of the housing 30 can be changed in stages in the front-to-rear direction. As a result, the silencer-equipped fan 1A can effectively muffle housing resonance noise.

[0061] Furthermore, the silencer-equipped blower 1A of this modified example has a cylindrical shroud 36 that protrudes from the edge of the exhaust port 34, which serves as the target vent, toward the inside of the housing 30. Because the shroud 36 protrudes from the edge of the exhaust port 34, the opening area of ​​the exhaust port 34 tends to be smaller than the opening area of ​​the intake port 33. For this reason, the change in radiation impedance in the front-to-rear direction from the exhaust port 34 to the outside of the housing 30 tends to be larger than the change in radiation impedance in the front-to-rear direction from the intake port 33 to the outside of the housing 30. As a result, sound is less likely to be radiated from the exhaust port 34, which tends to intensify housing resonance noise. In response to this, in the silencer-equipped blower 1A, by positioning the silencer 40A on the exhaust port 34 side, housing resonance noise is more likely to be radiated from the exhaust port 34. In other words, in the silencer-equipped blower 1A, by positioning the silencer 40A on the exhaust port 34 side, which tends to intensify housing resonance noise compared to the intake port 33, the effect of the present invention can be further enhanced. The protruding portion corresponding to the shroud 36 is not limited to protruding from the edge of the exhaust port 34, but may protrude from the edge of the intake port 33 toward the inside of the housing 30, for example. In such a case, by positioning the silencer on the intake port 33 side, the effect of the present invention can be further enhanced for the same reason as above.

[0062] <Modification 2> In the above embodiment, as shown in FIG. 2 , only the intake port 33 corresponds to the target vent port. However, this is not limited to this. For example, as shown in FIG. 6 , a silencer-equipped blower 1B may include two silencers 40, 40A as mufflers, and both the intake port 33 and the exhaust port 34 may be target vent ports. In this case, one of the two silencers 40, 40A (the silencer 40) may be located on the intake port 33 side of the housing 30, and the other (the silencer 40A) may be located on the exhaust port 34 side of the housing 30. In the example shown in FIG. 6 , the silencer 40 has a configuration similar to the silencer 40 in the above embodiment, and the silencer 40A has a configuration similar to that of the above modification 1. With this silencer-equipped blower 1B, similar to the above embodiment, housing resonance noise can be effectively silenced.

[0063] <Modification 3> Furthermore, as in the silencer-equipped fan 1C shown in FIG. 7 , a sound-absorbing member 49C may be disposed in the casing interior space S of each of the two silencers 40, 40A of the silencer-equipped fan 1B shown in FIG. 6 . The member 49C may be disposed throughout the entire casing interior space S in the circumferential direction of the casing 42, or may be disposed partially in the circumferential direction of the casing 42. Furthermore, when viewed in a cross section perpendicular to the circumferential direction of the casing 42, the member 49C may fill the casing interior space S, or may line at least one of the inner peripheral portion 45, the outer peripheral portion 46, and the side portions 47, 48. The member 49C may be, for example, a member made of an impermeable material, a sound-absorbing material, or a cloth, as described in the description of the windbreak member 44. With this silencer-equipped fan 1C, similar to the above embodiment, housing resonance noise can be effectively silenced. 15 and 16, by arranging member 49C in casing internal space S, it is possible to improve the deterioration of the sound emitted by blower 10 due to the arrangement of silencer 40 in a wide band of 1 kHz or less (see region E in FIGS. 15 and 16). Note that, although member 49C has been described above as being arranged in casing internal space S, this is not limitative and member 49C may be arranged in at least one of casing internal space S and opening 43, for example.

[0064] 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.

[0065] Example 1 In Example 1, the silencer-equipped blower 1 shown in FIGS. 1 and 2 was used. The fan 20 was a three-blade axial fan with a diameter of 40 cm. The interior dimensions of the first storage section 38a were 50 cm in the vertical direction, 50 cm in the horizontal direction (corresponding to length U2), and 29 cm in the front-to-back direction. The rectangular (strictly speaking, square) air intake 33 had dimensions of 48 cm in the vertical direction and 48 mm in the horizontal direction. The circular exhaust port 34 had a diameter of 43 cm. The cylindrical shroud 36 had dimensions such that the end on the exhaust port 34 side in the front-to-back direction had a diameter of 43 cm, similar to the exhaust port 34, and protruded 5 cm inward from the housing 30. The rectangular (strictly speaking, square) inner peripheral portion 45 had interior dimensions of 48 cm in the vertical direction and 48 mm in the horizontal direction, similar to the air intake 33. The target area within the outer peripheral portion 46 had dimensions of 70 cm in the vertical direction and 70 cm in the horizontal direction. The thickness T of the casing interior space S was 10 cm. The casing 42 was fabricated by preparing an acrylic resin plate (5 mm thick) and cutting the plate to a predetermined shape and size, then joining the edges of multiple plates. A known fabric was used for the windbreak member 44, and the entire area (entire periphery) of the opening 43 in the circumferential direction of the casing 42 was covered with the windbreak member 44.

[0066] In Example 1, the sound deadening level was evaluated. To evaluate the sound deadening level, the silencer-equipped blower 1 was placed in the center of a soundproof room (which may be a semi-anechoic or anechoic room) whose walls and ceiling were covered with sound-absorbing material. The sound pressure around the silencer-equipped blower 1 was measured using a microphone placed 1 m above the floor and 1 m away from the wall (main surface wall 31b) on the air intake 33 side of the housing 30. FIG. 8 is a diagram showing the relationship between frequency and sound deadening level in Example 1. The sound deadening level corresponds to the difference in sound pressure from the blower 10 without the silencer 40. As can be seen from FIG. 8, three sound deadening peaks F1 to F3 appeared in Example 1. The sound deadening peak F1 was at 260 Hz, and the sound deadening level was 5.6 dB. The sound deadening peak F2 was at 580 Hz, and the sound deadening level was 12.2 dB. The sound deadening peak F3 was at 980 Hz, and the sound deadening level was 10.6 dB.

[0067] For the three sound attenuation peaks F1 to F3, as shown in Figures 9 to 11, acoustic simulations were performed using the silencer-equipped fan of Example 1 as a calculation model, and the spatial distribution of sound pressure inside and around the fan 10 was visualized. The acoustic simulations were performed using the finite element method COMSOL MultiPhysics. As shown in Figure 9, at sound attenuation peak F1 (260 Hz), there were no sound pressure antinodes or nodes within the housing 30. This is thought to be because sound is radiated from the housing 30, rather than sound attenuation due to a resonance phenomenon. On the other hand, as shown in Figures 10 and 11, sound pressure nodes were present at sound attenuation peaks F2 and F3. This is thought to be because sound attenuation occurs due to a resonance phenomenon (specifically, air column resonance) in the silencer 40, resulting in sound interference.

[0068] Example 2 Example 2 differs from Example 1 in that the dimensions of the target area within the outer periphery 46 are 80 cm in the vertical direction by 80 cm in the horizontal direction, but is otherwise common to Example 1. Example 3 Example 3 differs from Example 1 in that the dimensions of the target area within the outer periphery 46 are 90 cm in the vertical direction by 90 cm in the horizontal direction, but is otherwise common to Example 1.

[0069] FIG. 12 is a diagram showing the relationship between frequency and silencing level in Examples 2 and 3. As can be seen from FIG. 12 , multiple silencing peaks appeared in each of Examples 2 and 3. Specifically, the silencing level in Example 2 was 7.9 dB at 260 Hz, 14.3 dB at 440 Hz, and 3.5 dB at 840 Hz. The silencing level in Example 3 was 12.1 dB at 260 Hz, 11.8 dB at 320 Hz, and 2.0 dB at 820 Hz. The silencing effect at 260 Hz was exhibited in all Examples 1 to 3, and in particular, the silencing level increased as the area of ​​the target region within the outer peripheral portion 46 increased. This is thought to be because the normalized constant of the radiation impedance approached "2" as the area of ​​the target region within the outer peripheral portion 46 increased.

[0070] <Example 4> Example 4 differs from Example 1 in that the thickness T of the casing internal space S is set to 20 cm, but is otherwise common to Example 1. <Example 5> Example 5 differs from Example 1 in that the thickness T of the casing internal space S is set to 30 cm, but is otherwise common to Example 1.

[0071] Fig. 13 is a diagram showing the relationship between frequency and silencing level in Examples 4 and 5. As can be seen from Fig. 13, multiple silencing peaks appeared in each of Examples 4 and 5. Specifically, the silencing levels in Example 4 were 9.5 dB at 260 Hz, 13.9 dB at 580 Hz, and 4.7 dB at 860 Hz. The silencing levels in Example 5 were 10.0 dB at 260 Hz, 7.9 dB at 720 Hz, and 12.7 dB at 980 Hz. The silencing effect at 260 Hz was exhibited in both Examples 4 and 5. Furthermore, Example 4 exhibited a large silencing level for the 580 Hz sound (primary resonance), while Example 5 exhibited a large silencing level for the 980 Hz sound (higher-order resonance). This is thought to be because, as the thickness T of the casing internal space S increases, the sound entering the casing internal space S travels obliquely with respect to the direction in which the inner circumferential portion 45 and the outer circumferential portion 46 oppose each other, reducing the amount of silencing of primary resonance sounds while increasing the amount of silencing of higher-order resonance sounds. Note that, in order to suppress the reduction in the amount of silencing of primary resonance sounds, it is conceivable to make the sound entering the casing internal space S parallel to the direction in which the inner circumferential portion 45 and the outer circumferential portion 46 oppose each other. To achieve this, for example, a partition wall that divides the casing internal space S into two or more spaces in the front-to-rear direction may be provided within the casing internal space S, or two or more silencers may be arranged adjacent to each other in the front-to-rear direction for a common target air vent.

[0072] Example 6 Example 6 used the silencer-equipped blower 1A shown in FIG. 5 . Example 6 differs from Example 1 in that the silencer 40 is not located on the intake port 33 side, but the silencer 40A is located on the exhaust port 34 side. The inner dimensions of the inner circumferential portion 45 are circular and have a diameter of 43 cm, similar to the exhaust port 34. The target area within the outer circumferential portion 46 is circular and has a diameter of 70 cm. The thickness T of the casing interior space S was 10 cm. The sound pressure around the silencer-equipped blower 1A was measured using a microphone positioned 1 m above the floor and 1 m away from the wall (main surface wall 31 a) on the exhaust port 34 side of the housing 30, which is different from Example 1; however, Example 6 is otherwise the same as Example 1.

[0073] <Example 7> Example 7 differs from Example 6 in that the diameter of the target region within the outer circumferential portion 46 is set to 90 cm, but is otherwise common to Example 6. <Example 8> Example 8 differs from Example 6 in that the thickness T of the casing internal space S is set to 20 cm, but is otherwise common to Example 6.

[0074] FIG. 14 is a graph showing the relationship between frequency and silencing level in Examples 6 to 8. As can be seen from FIG. 14, multiple silencing peaks appeared in each of Examples 6 to 8. Specifically, the silencing levels in Example 6 were 2.6 dB at 260 Hz, 16.2 dB at 540 Hz, and 3.3 dB at 960 Hz. The silencing levels in Example 7 were 11.4 dB at 260 Hz, 23.5 dB at 320 Hz, and 3.8 dB at 1020 Hz. The silencing levels in Example 8 were 6.5 dB at 260 Hz, 18.9 dB at 560 Hz, and 3.0 dB at 1020 Hz. The silencing effects in Examples 6 to 8 tended to be similar to those in Examples 1 to 5, in which the silencer 40 was located on the intake port 33 side. The 260 Hz noise reduction effect was exhibited in all of Examples 6 to 8, and the effect was particularly large in Example 7, in which the diameter of the target area within the outer periphery 46 was large.

[0075] Example 9 used the silencer-equipped blower 1B shown in FIG. 6 . Example 9 differs from Example 1 in that the silencer 40 is located on the intake port 33 side and the silencer 40A is located on the exhaust port 34 side. The conditions for the silencer 40 were the same as those for Example 1. The conditions for the silencer 40A were the same as those for Example 6. Regarding the evaluation of the silencing sound volume, a microphone was placed 1 m away from the wall (main surface wall 31 b) on the intake port 33 side of the housing 30 at a height of 1 m from the floor, and a microphone was placed 1 m away from the wall (main surface wall 31 a) on the exhaust port 34 side of the housing 30 at a height of 1 m from the floor, and the sound pressure was measured. This is different from Example 1, but the other points are the same as those of Example 1.

[0076] <Example 10> Example 10 is common to Example 9 except that the conditions of the silencer 40 are the same as those of Example 3 and the conditions of the silencer 40A are the same as those of Example 7. <Example 11> Example 11 is common to Example 9 except that the conditions of the silencer 40 are the same as those of Example 4 and the conditions of the silencer 40A are the same as those of Example 8.

[0077] FIG. 15 is a diagram showing the relationship between frequency and silencing level in Examples 9 to 11. As can be seen from FIG. 15, multiple silencing peaks appeared in each of Examples 9 to 11. Specifically, the silencing levels in Example 9 were 5.3 dB at 260 Hz, 15.4 dB at 560 Hz, and 9.4 dB at 980 Hz. The silencing levels in Example 10 were 15.7 dB at 320 Hz, 3.9 dB at 480 Hz, and 5.0 dB at 1060 Hz. The silencing levels in Example 11 were 6.2 dB at 340 Hz, 20.1 dB at 560 Hz, and 3.1 dB at 920 Hz. In Example 10, the silencing peaks of the housing resonance sound and the primary resonance sound corresponding to the target sound overlapped, and a larger silencing peak appeared midway between these silencing peaks.

[0078] Example 12 Example 12 used the silencer-equipped blower 1C shown in FIG. 7 . Example 12 differs from Example 9 in that a member 49C is disposed within the casing internal space S, but is otherwise common to Example 9. A micromat (flow resistivity approximately 1000 Rayls / m) manufactured by Taihei Felt Co., Ltd. was used as the member 49C. The member 49C was filled throughout the entire casing internal space S in the circumferential direction of the casing 42. Example 13 Example 13 differs from Example 10 in that a member 49C is disposed within the casing internal space S, but is otherwise common to Example 10. Example 14 Example 14 differs from Example 11 in that a member 49C is disposed within the casing internal space S, but is otherwise common to Example 11.

[0079] FIG. 16 is a graph showing the relationship between frequency and silencing level in Examples 12 to 14. As can be seen from FIG. 16, multiple silencing peaks appeared for each of Examples 12 to 14. Specifically, the silencing level for Example 12 was 5.6 dB at 260 Hz, 2.5 dB at 360 Hz, 9.5 dB at 540 Hz, and 6.1 dB at 960 Hz. The silencing level for Example 13 was 11.7 dB at 260 Hz, 7.4 dB at 300 Hz, 3.2 dB at 480 Hz, and 4.6 dB at 1020 Hz. The silencing level for Example 14 was 3.0 dB at 260 Hz, 6.9 dB at 340 Hz, 16.2 dB at 540 Hz, and 5.5 dB at 980 Hz. The silencing effect at 260 Hz was demonstrated in all of Examples 12 to 14. Furthermore, with respect to the frequency sound that worsened noise in Examples 9 to 11 (see region E in FIG. 15 ), in Examples 12 to 14, by placing member 49C in casing internal space S, the worsening noise was improved over a wide frequency band (see region E in FIG. 16 ). The effects of the present invention are clear from the evaluation results described above.

[0080] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C Blower with silencer 10 Blower 11 Machine room 20 Fan 21 Motor 22 Shaft 23 Blade 30 Housing 31a, 31b Main surface wall 32a, 32b, 32c, 32d Side wall 33 Air intake port 34 Exhaust port 35 Side air intake port 36 Shroud (corresponding to protrusion) 37 Partition wall 38a First storage section 38b Second storage section 40, 40A Silencer 41 Ventilation section 42 Casing 43 Opening 44 Windbreak member 45 Inner peripheral portion 46 Outer peripheral portion 47, 48 Side portion 49C Member (corresponding to sound-absorbing member) E Area G Rotating shaft H, K, V1, V2 Space R, U1, U2, U3 Length S Internal space T Thickness W Spacing

Claims

1. A blower with a silencer, comprising: a blower having a fan disposed within a housing; and a silencer for silencing noise emitted by the blower, wherein the housing has an intake port and an exhaust port, and the silencer has: a ventilation section located outside the housing in the axial direction of the rotation axis of the fan and adjacent to a target vent port of the intake port or the exhaust port, a casing having an inner circumferential section surrounding the ventilation section and an outer circumferential section located outside the inner circumferential section, and an opening formed in the inner circumferential section and communicating with a space inside the casing located between the inner circumferential section and the outer circumferential section, and wherein the area of ​​the region surrounded by the outer circumferential section when viewed in the axial direction is larger than the opening area of ​​the target vent port.

2. Among the sounds emitted by the fan, the wavelength of a first sound corresponding to the resonant frequency within the housing is defined as λ １ and a>1.1×λ where a is the radius of a virtual circle having the area of ​​the region surrounded by the outer periphery when viewed from the axial direction. １ 2. The blower with a silencer according to claim 1, wherein the following relationship is satisfied:

3. The sound emitted by the fan includes a first sound corresponding to a resonance frequency within the housing and a second sound having a higher frequency than the first sound, and the distance between the inner circumferential portion and the outer circumferential portion is set so that the wavelength of the second sound is λ ２ In this case, λ ２ 2. The blower with silencer according to claim 1, wherein the muffler-equipped fan has a muffler ratio of 1 / 4 or more.

4. A blower with a silencer according to claim 3, wherein the distance is 8.5 cm or more.

5. The sound emitted by the blower includes a first sound corresponding to a resonance frequency within the casing and a second sound having a higher frequency than the first sound, and the thickness of the space within the casing in the axial direction is set to λ, where λ is the wavelength of the second sound. ２ In this case, λ ２ 2. The blower with silencer according to claim 1, wherein the muffler has a diameter of 1 / 8 or more.

6. The sound emitted by the blower includes a first sound corresponding to a resonance frequency within the casing, and the thickness of the space within the casing in the axial direction is set to λ, where λ is the wavelength of the first sound. １ In this case, λ １ 2. The blower with silencer according to claim 1, wherein the muffler has a muffler ratio of 1 / 4.5 or less.

7. The blower with silencer according to claim 1, wherein the housing further has a cylindrical protrusion that protrudes from the edge of the target vent toward the inside of the housing.

8. A blower with a silencer according to claim 1, wherein a sound-absorbing member is disposed in at least one of the space within the casing and the opening.

9. A blower with a silencer according to claim 1, wherein a windbreak member is disposed in the opening to prevent wind from entering the space within the casing.

10. A blower with silencer as described in claim 1, wherein two silencers are provided as the silencers, both the intake port and the exhaust port are the target air vents, one of the two silencers is located on the intake port side of the housing, and the other of the two silencers is located on the exhaust port side of the housing.

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