Sound reduction device

Abstract

To provide a sound reduction device which can reduce a volume of sound caused by an air flow without increasing pressure loss.SOLUTION: A sound reduction device for reducing sound caused by an air flow includes: an air flow passage part 42 having an inner wall face 421 forming an air passage in which air flows; and a plurality of grooves 60, 61 and 62 which are formed on the inner wall face of the air passage part in a recessed manner and are arranged side by side on the inner wall face. In the plurality of grooves, at least one of arrangements, shapes and quantities vary along an air flow direction.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to sound reduction devices. [Background technology]

[0002] Conventionally, there is known an aerodynamic noise reduction device that is provided with multiple protrusions that protrude from the wall surface of the air flow path toward the air flow path (see, for example, Patent Document 1). In this aerodynamic noise reduction device, the multiple protrusions have non-uniform shapes or are installed in non-uniform positions, so that the protrusions suppress turbulence in the airflow near the wall surface and also reduce new turbulence in the airflow that is generated by the protrusions, thereby enhancing the aerodynamic noise reduction effect. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-052808 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the protrusions provided in the air flow path create resistance to the air flowing through the air flow path. Therefore, the protrusions cause an increase in pressure loss when the air flows through the air flow path compared to when the protrusions are not present in the air flow path. Furthermore, the protrusions provided in the air flow path cause a new noise to be generated when the air collides with the protrusions as it flows through the air flow path.

[0005] An object of the present disclosure is to provide a sound reduction device that can reduce the volume of sound caused by air flow without increasing pressure loss. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, A sound reduction device that reduces noise caused by air flow is an air flow path portion (30, 37, 42, 114) having an inner wall surface (36, 373, 421, 1141) that forms an air flow path (30a, 42a, 114a) through which air flows; a plurality of grooves (60, 61, 62, 63, 64, 65, 66, 67, 68) formed in a recess relative to the inner wall surface of the air flow path portion and arranged side by side on the inner wall surface; When the air flow direction is defined as the direction from the upstream side to the downstream side in the air flow direction, at least one of the arrangement, shape and number of the plurality of grooves changes along the air flow direction.

[0007] According to the inventors' intensive research, when air flows through an air flow path, if the air flowing along the inner wall surface separates from the inner wall surface, multiple vortices may be generated, which can cause noise due to the air flow. When the multiple vortices generated combine, the resulting noise increases. However, by providing multiple grooves on the inner wall surface, it is possible to break up the vortices generated when air separates from the inner wall surface and suppress the growth of the combined vortices. This reduces the volume of noise caused by the air flow. Furthermore, by using grooves on the inner wall surface to reduce the volume of noise, the grooves are less likely to create resistance when the air flows through the air flow path. This reduces the increase in pressure loss when the air flows through the air flow path compared to a configuration in which sound caused by the air flow is reduced by using members protruding into the air flow path.

[0008] However, when air flows along a portion where the surface shape changes due to the formation of grooves, there is a risk of generating a sound different from the sound caused by the generation of vortices. In response to this, by changing at least one of the arrangement, shape, and quantity of multiple grooves along the air flow direction, the surface shape of the portion of the inner wall surface where the grooves are formed can be gradually changed along the air flow direction. This makes it possible to suppress sudden changes in the surface shape of the portion of the inner wall surface where the grooves are formed. Therefore, it is possible to suppress the volume of the sound generated by air flowing along the portion of the inner wall surface where the grooves are formed. Therefore, it is possible to reduce the volume of the sound caused by the air flow without increasing pressure loss.

[0009] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a vehicle air conditioner to which a sound reduction device according to a first embodiment is applied. [Figure 2] FIG. 2 is a cross-sectional view of the blower unit according to the first embodiment. [Figure 3] 3 is a diagram showing a state in which the air outlet mode of the vehicle air conditioner according to the first embodiment is set to a face outlet mode. FIG. [Figure 4] 3 is a diagram showing a state in which the air outlet mode of the vehicle air conditioner according to the first embodiment is set to a foot / defroster air outlet mode. FIG. [Figure 5] 10A and 10B are diagrams illustrating vortices that occur when air flows through a face duct. [Figure 6] 10A and 10B are diagrams for explaining the positions of grooves provided in a face duct. [Figure 7] FIG. 3 is a diagram illustrating the shape of a groove according to the first embodiment. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. [Figure 9]9 is a cross-sectional view taken along the line IX-IX in FIG. 7. [Figure 10] XX cross-sectional view of FIG. 7. [Figure 11] FIG. 4 is a graph illustrating the effect of the grooves according to the first embodiment. [Figure 12] FIG. 10 is a diagram for explaining the shape of a groove according to a modified example of the first embodiment. [Figure 13] FIG. 10 is a diagram for explaining the shape of a groove according to a modified example of the first embodiment. [Figure 14] FIG. 10 is a diagram for explaining the shape of a groove according to a modified example of the first embodiment. [Figure 15] FIG. 10 is a diagram illustrating the shape of a groove according to the second embodiment. [Figure 16] FIG. 10 is a diagram illustrating the shape of a groove according to a third embodiment. [Figure 17] FIG. 10 is a diagram illustrating the shape of a groove according to a fourth embodiment. [Figure 18] 18 is a cross-sectional view taken along the line XVIII-XVIII in FIG. 17. [Figure 19] FIG. 10 is a diagram for explaining the depth of a second groove according to a fourth embodiment. [Figure 20] FIG. 13 is a diagram for explaining the depth of a second groove according to a modified example of the fourth embodiment. [Figure 21] FIG. 13 is a diagram for explaining the depth of a second groove according to a modified example of the fourth embodiment. [Figure 22] FIG. 13 is a diagram for explaining the depth of a second groove according to a modified example of the fourth embodiment. [Figure 23] FIG. 10 is a diagram illustrating the shape of a groove according to a fifth embodiment. [Figure 24] FIG. 13 is a diagram illustrating the shape of a groove according to a sixth embodiment. [Figure 25] FIG. 13 is a diagram illustrating the shape of a groove according to the seventh embodiment. [Figure 26] 26 is a cross-sectional view taken along line XXVI-XXVI of FIG. 25. [Figure 27] FIG. 13 is a diagram illustrating the depth of a first groove according to the seventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same as or equivalent to those described in the preceding embodiments will be given the same reference numerals, and their description may be omitted. Furthermore, in the embodiments, when only some of the components are described, the components described in the preceding embodiments can be applied to the remaining components. The following embodiments can be partially combined with each other, even if not specifically stated, as long as there is no particular problem with the combination.

[0012] (First embodiment) A noise reduction device according to this embodiment will be described with reference to FIGS. 1 to 11. In this embodiment, an example will be described in which the noise reduction device is applied to a vehicle air conditioner 1 shown in FIG. 1 that is mounted on a vehicle. The vehicle air conditioner 1 shown in FIG. 1 adjusts the air temperature inside the vehicle cabin by blowing conditioned air adjusted to a desired temperature into the vehicle cabin. As shown in FIGS. 1 to 3, the vehicle air conditioner 1 includes an air blower unit 10 and an air conditioning unit 20. The vehicle air conditioner 1 also includes an air conditioning case 30 that houses the air conditioning unit 20 and forms the outer shell of the vehicle air conditioner 1, thereby forming an air supply passage 30a through which air to be supplied into the vehicle cabin flows. The vehicle air conditioner 1 houses various components of the air conditioning unit 20 in the air conditioning case 30. As shown in FIG. 3, the vehicle air conditioner 1 is disposed behind an instrument panel 5 that is disposed at the front end of the vehicle cabin.

[0013] 1 and other figures indicates the left-right direction when the vehicle air conditioner 1 is installed in a vehicle, i.e., the vehicle width direction, and the arrow DRfr indicates the front-rear direction when the vehicle air conditioner 1 is installed in a vehicle. Also, the arrow DRud shown in Fig. 2 and other figures indicates the up-down direction when the vehicle air conditioner 1 is installed in a vehicle, i.e., the top-bottom direction.

[0014] The blower 10 introduces air into the air conditioning case 30 and generates an air current that guides the air introduced into the air conditioning case 30 into the vehicle interior. The blower 10 is provided with a blower 11 that blows air to the air conditioning unit 20.

[0015] As shown in FIGS. 1 and 2 , the blower 11 is a centrifugal blower that draws in air along an axial direction, which is the direction in which the fan axis CL of the blower 11 extends, and blows the drawn-in air from the inside to the outside in a radial direction perpendicular to the axial direction. The blower 11 of this embodiment includes a centrifugal multi-blade fan 111 composed of multiple blades 111a, a motor 112 that drives the centrifugal multi-blade fan 111, a scroll casing 113 that surrounds the centrifugal multi-blade fan 111, and a blower duct 114. The blower 11 generates an airflow within the scroll casing 113 by rotating the centrifugal multi-blade fan 111 around the fan axis CL using rotational torque generated by the motor 112 as a drive source. The rotation speed of the motor 112 is controlled by a control device (not shown). The blower 11 is not limited to a centrifugal blower and may be, for example, a sirocco fan or a turbo fan.

[0016] The centrifugal multi-blade fan 111 has an air inlet 111b for drawing in air on one side in the axial direction of the blower 11. The centrifugal multi-blade fan 111 also has an air outlet 111c on the radially outer side centered on the fan axis CL, which blows out the air drawn in through the air inlet 111b in a direction away from the fan axis CL. The air blown out from the air outlet 111c flows through the scroll casing 113.

[0017] The scroll casing 113 is a spiral member that houses the centrifugal multi-blade fan 111 and forms a passage through which air flows that is blown out from the air outlet 111c of the centrifugal multi-blade fan 111. The scroll casing 113 is formed in a hollow shape and is made of a material that has a certain degree of elasticity and excellent strength, for example, a resin member such as polypropylene.

[0018] The scroll casing 113 has a scroll wall surface 113a that forms a passage through which air flows. The scroll wall surface 113a extends from a nose portion 113b to a winding end portion 113c such that the distance from the fan axis CL increases clockwise in Fig. 1 according to a logarithmic spiral function with respect to the winding angle about the fan axis CL. Therefore, the scroll wall surface 113a extends in a curved shape that surrounds the fan axis CL.

[0019] The nose portion 113b is the portion of the scroll wall surface 113a located on the most upstream side in the air flow. The spiral end portion 113c is the portion of the scroll wall surface 113a located on the most downstream side in the air flow. The nose portion 113b faces the spiral end portion 113c. That is, the nose portion 113b faces the most downstream part of the air flow in the scroll casing 113. In the nose portion 113b, the upstream side of the air flow and the downstream side of the air flow communicate with each other via a small gap. A blower duct 114 is connected to the most downstream side of the air flow in the scroll casing 113.

[0020] The air blower duct 114 guides the air blown out from the scroll casing 113 to the air conditioning unit 20. The upstream side of the air flow of the air blower duct 114 is connected to the scroll casing 113, and the downstream side of the air flow is connected to the air conditioning case 30. The air blower duct 114 is formed integrally with the scroll casing 113 and extends in the centrifugal direction of the centrifugal multi-blade fan 111, with the opening area increasing from the upstream side of the air flow to the downstream side of the air flow. In addition, the portion of the air blower duct 114 that connects to the nose portion 113b is bent in an arc shape.

[0021] The air blower duct 114 of this embodiment has an air blower inner wall surface 1141 that forms an air blower duct flow path 114a that guides air blown out from the blower 11 to the air conditioning unit 20, and an air blower duct bent portion 1142 that is connected to the nose portion 113b and is formed by bending. The air blower duct bent portion 1142 is a bent portion of the air blower duct 114 and is bent in an arc shape. In this embodiment, a sound reduction unit 50 (described below) that is a sound reduction device is provided on a part of the inner wall surface of the air blower duct bent portion 1142 of the air blower inner wall surface 1141. The air blower inner wall surface 1141 functions as an air flow path that guides air blown out from the blower 11 to the air conditioning unit 20. The air blower duct 114 functions as an air flow path portion. Note that in FIG. 1 and other figures, the portion where the sound reduction unit 50 is provided is indicated by hatching.

[0022] The air conditioning unit 20 adjusts the temperature of the air introduced from the blower unit 10 to a desired temperature. Specifically, as shown in FIG. 1, the air conditioning unit 20 includes an evaporator 21 that cools the air, and a heater core 22 that heats the air that has passed through the evaporator 21. As shown in FIG. 3, the air conditioning unit 20 also includes a defroster door 23, a face door 24, a foot door 25, a rear door 26, a differential mix door 27, and an air mix door 28. These components of the air conditioning unit 20 are housed in an air conditioning case 30 that forms an air passage 30a.

[0023] The air conditioning case 30 is hollow and made of a material that has a certain degree of elasticity and excellent strength, such as a resin material such as polypropylene. The air conditioning case 30 is made up of multiple case members that are integrally joined together by fastening means such as metal springs and screws.

[0024] 1, the air conditioning case 30 has an air duct 114 of the blower unit 10 connected to its most upstream airflow portion. Also, as shown in FIGS. 2 and 3, the air conditioning case 30 has a defroster outlet 31, a face outlet 32, a foot outlet 33, a first rear outlet 34, and a second rear outlet 35 formed on its most downstream airflow portion. The air conditioning case 30 has a passage inner wall surface 36 that forms an air passage 30a, which is an air flow path, and a mounting portion 37 where the evaporator 21 is disposed.

[0025] The defroster outlet 31 is an opening for blowing conditioned air, the temperature of which has been adjusted by the air conditioning unit 20, toward the windshield 7 at the front of the vehicle. The defroster outlet 31 opens toward the upper side of the DRud in the up-down direction near the windshield 7. The defroster outlet 31 is controlled to open and close by a defroster door 23 provided upstream of the defroster outlet 31 in the air flow direction. The defroster outlet 31 is connected to a defroster interior outlet 5a in the instrument panel 5 that opens on the surface near the windshield 7 of the vehicle.

[0026] The defroster interior air outlet 5a is formed along the front windshield 7 etc. so that conditioned air can be blown out along the interior side surface of the front windshield 7 etc. to reduce the degree of fogging. The defroster interior air outlet 5a is connected to the defroster air outlet 31 by a defroster duct 41. The defroster duct 41 is formed to extend linearly above the defroster air outlet 31 in the up-down direction DRud toward the front windshield 7. The defroster duct 41 guides the air blown out from the defroster air outlet 31 to the defroster interior air outlet 5a.

[0027] The face air outlet 32 ​​is an opening for blowing conditioned air, temperature-adjusted by the air conditioning unit 20, toward the upper bodies of occupants seated in the front seats inside the vehicle interior. The face air outlet 32 ​​opens upward in the up-down direction DRud on a surface of the air conditioning case 30 that is rearward in the front-rear direction DRfr from the position where the defroster air outlet 31 is formed. The face air outlet 32 ​​is controlled to open and close by a face door 24 provided upstream of the face air outlet 32 ​​in the air flow direction. The face air outlet 32 ​​is connected to a face interior air outlet 5b that opens in the instrument panel 5 at a position facing the front seats.

[0028] The face interior air outlets 5b are provided on the right and left sides of the surface of the instrument panel 5 in the left-right direction DRw so that conditioned air can be blown out to both the occupant seated on the driver's seat and the occupant seated on the passenger seat of the vehicle. The face interior air outlets 5b are connected to the face air outlet 32 ​​by a face duct 42.

[0029] The face duct 42 guides the air blown out from the face outlet 32 ​​to the face indoor outlet 5b. The face duct 42 is hollow and, like the air conditioning case 30, is made of a material that has a certain degree of elasticity and excellent strength, such as a resin member such as polypropylene. The face duct 42 has a face duct inner wall surface 421 that forms a face duct flow path 42a through which the air flows.

[0030] The face duct 42 extends linearly upward in the up-down direction DRud from the face air outlet 32 ​​toward the face indoor air outlet 5b, then gently bends midway and extends linearly rearward in the front-rear direction DRfr. The face duct 42 of this embodiment includes a bent face duct bent portion 422 and a straight face duct straight portion 423 located upstream of the face duct bent portion 422 in the air flow. The face duct bent portion 422 is a bent portion of the face duct 42 and bent in an arc shape. In this embodiment, a sound reduction portion 50 (described later) is provided on a portion of the face duct inner wall surface 421, which is the inner wall surface of each of the face duct bent portion 422 and the face duct straight portion 423. The face duct 42 functions as an air flow path that guides air blown out from the face air outlet 32 ​​to the face indoor air outlet 5b.

[0031] The foot air outlet 33 is an opening for blowing conditioned air, the temperature of which has been adjusted by the air conditioning unit 20, toward the lower bodies of occupants seated in the front seats inside the vehicle interior. The foot air outlet 33 opens to the inside of the instrument panel 5. The opening area of ​​the foot air outlet 33 is controlled to open and close by a foot door 25 provided upstream of the foot air outlet 33 in the air flow direction. The foot air outlet 33 is connected to a foot interior air outlet (not shown) provided at the feet of the occupant by a foot duct (not shown).

[0032] The first rear air outlet 34 and the second rear air outlet 35 are openings for blowing conditioned air, temperature-adjusted by the air conditioning unit 20, toward the lower bodies of occupants seated in the rear seats inside the vehicle interior. The first rear air outlet 34 and the second rear air outlet 35 are provided in the air conditioning case 30 below the foot air outlet 33 in the up-down direction DRud. The opening areas of the first rear air outlet 34 and the second rear air outlet 35 are controlled to open and close by the rear door 26, which is provided upstream of the first rear air outlet 34 and the second rear air outlet 35 in the air flow. The first rear air outlet 34 and the second rear air outlet 35 are connected to a rear interior air outlet (not shown) that opens to the rear seats by a rear duct 43, shown in FIG. 1 .

[0033] When the first rear air outlet 34 is opened by the rear door 26, air heated by the heater core 22 flows through the rear duct 43. On the other hand, when the second rear air outlet 35 is opened by the rear door 26, air cooled by the evaporator 21 flows through the rear duct 43. The rear duct 43 guides the air blown out from the first rear air outlet 34 and the second rear air outlet 35 to a rear interior air outlet (not shown). The conditioned air blown out from each of these air outlets 31 to 35 is supplied to the predetermined air outlets 31 to 35 in the vehicle cabin through the connected defroster duct 41, face duct 42, rear duct 43, etc.

[0034] 1, an intermediate partition plate 14 is provided inside the air conditioning case 30 to divide the air passage 30a into a driver's seat side and a passenger seat side in the left-right direction DRw. The air passage 30a formed inside the air conditioning case 30 is divided into two in the left-right direction DRw by the intermediate partition plate 14. Therefore, separately temperature-adjusted conditioned air can flow in each of the two air passages 30a divided into two in the left-right direction of the vehicle without mixing.

[0035] As a result, the vehicle air conditioning system 1 blows temperature-adjusted air into the vehicle cabin from the right and left outlets in the left-right direction DRw, thereby enabling independent left-right temperature control, which allows the air conditioning settings to be adjusted independently for the driver's seat and the passenger seat. The defroster door 23, face door 24, foot door 25, and rear door 26 are each a one-sided, plate-shaped door having a rotating shaft and a flat door plate. The operation of the defroster door 23, face door 24, foot door 25, and rear door 26 is controlled by a control device (not shown).

[0036] As shown in FIG. 1 , the air conditioning case 30 is formed in a stepped shape upstream of the evaporator 21 in the air flow. Specifically, the passage inner wall surface 36 is formed in a stepped shape in the portion upstream of the evaporator 21 in the air flow such that the air passage 30a becomes narrower from the upstream side of the air flow toward the downstream side of the air flow. The air conditioning case 30 of this embodiment has two step-like bends 361 that are gently bent in a stepped shape. The two step-like bends 361 are bent portions upstream of the portion where the evaporator 21 is provided in the air flow, and each bends in an arc shape. In this embodiment, a sound reduction unit 50, which will be described later, is provided on the inner wall surface of each of the two step-like bends 361 of the passage inner wall surface 36.

[0037] 3, the air conditioning case 30 has a portion that is opened and closed by the rear door 26 recessed toward the inside of the air passage 30a. Specifically, the air conditioning case 30 has a bottom portion, which is the lower end portion in the up-down direction DRud, that faces the rear door 26 and protrudes gently upward in the up-down direction DRud. The air conditioning case 30 of this embodiment has a gently bent bottom bend portion 362. The bottom bend portion 362 is a portion that is bent at the bottom of the passage inner wall surface 36 so as to protrude upward in the up-down direction DRud and is bent in an arc shape. In this embodiment, a sound reduction portion 50, which will be described later, is provided on the inner wall surface of the bottom bend portion 362 of the passage inner wall surface 36.

[0038] The air conditioning case 30 has a rear outlet bend 363 formed downstream in the air flow direction from the bottom bend 362, which is bent so that the air passage 30a narrows after passing through the first rear air outlet 34 and the second rear air outlet 35. The rear outlet bend 363 is bent gently in an arc shape toward the rear in the front-to-rear direction DRfr at the most downstream part of the air flow in the air conditioning case 30. In this embodiment, a sound reduction section 50, which will be described later, is provided on the inner wall surface 36 of the passage inner wall surface 36 at the inner wall surface of the rear outlet bend 363.

[0039] Furthermore, the air conditioning case 30 has a defroster outlet bend 364 formed upstream in the air flow direction of the defroster outlet 31 and bent so as to guide air to the defroster outlet 31. The defroster outlet bend 364 is a portion continuous with the portion of the air conditioning case 30 where the face outlet 32 ​​is formed, and is bent gently in an arc upward in the up-down direction DRud. In this embodiment, a sound reduction unit 50, which will be described later, is provided on the inner wall surface of the defroster outlet bend 364.

[0040] The arrangement portion 37 extends in the left-right direction DRw and is formed in a flat shape that extends downward in the up-down direction DRud as it extends rearward in the front-rear direction DRfr. The arrangement portion 37 also has a recess 371 in which the evaporator 21 is arranged. The recess 371 is formed to be recessed downward in the up-down direction DRud so that the evaporator 21 can be arranged therein. The front end of the recess 371 in the front-rear direction DRfr and the rear end of the recess 371 in the front-rear direction DRfr are gently bent upward in the up-down direction DRud. The recess 371 in this embodiment has a bent arrangement bend portion 372.

[0041] The arrangement bend portion 372 is a bent portion at each end of the arrangement portion 37 in the front-rear direction DRfr, and is bent in an arc shape. In this embodiment, a sound reduction portion 50, which will be described later, is provided on an arrangement surface 373, which is the lower wall surface of the arrangement bend portion 372 in the up-down direction DRud. The arrangement surface 373, together with the passage inner wall surface 36, forms the air passage 30a, which is an air flow path that guides air that has passed through the evaporator 21 toward the downstream side of the air flow. The arrangement portion 37 functions as an air flow path portion.

[0042] The evaporator 21 is located, for example, on the vehicle front side of the air conditioning case 30, and is a heat exchanger that, together with a compressor, a condenser, and a pressure reduction mechanism (not shown), constitutes a vapor compression refrigeration cycle. Specifically, the evaporator 21 is a cooling heat exchanger that cools the air being blown by absorbing the latent heat of evaporation of the low-temperature refrigerant flowing inside the evaporator 21 from the air in the air passage 30a. The evaporator 21 is provided to crosswise block the entire air passage 30a, cools the air passing through the evaporator 21, and supplies the cooled air to the cooled air passage 30b, which is the air passage 30a downstream of the evaporator 21 in the air flow direction.

[0043] The heater core 22 is located below the evaporator 21 and toward the rear of the vehicle, and is a heating heat exchanger that exchanges heat between the high-temperature coolant of the running engine and the blown air, using the high-temperature coolant as a heat source, to heat the air passing through the heater core 22. The heater core 22 is arranged so as to partially block the air passage 30a downstream of the evaporator 21 in the air flow. The heater core 22 heats the air passing through the heater core 22 and supplies warm air to the warm air passage 30c, which is the air passage 30a downstream of the heater core 22 in the air flow.

[0044] The differential mix door 27 is positioned rearward of the vehicle relative to the evaporator 21. The differential mix door 27 is an air volume adjustment unit that adjusts the volume of the cold air that flows toward the defroster outlet 31 among the cold air that has passed through the evaporator 21 and been introduced into the cold air passage 30b. The differential mix door 27 is a one-side supported plate-like door having a rotating shaft and a flat door plate. The differential mix door 27 rotates the door plate to adjust the flow length of the air that is guided to the defroster door 23.

[0045] The air mix door 28 is positioned rearward of the evaporator 21. The air mix door 28 is an air volume adjustment unit that adjusts the volume of cold air that flows into the heater core 22 from among the cold air that has passed through the evaporator 21 and been introduced into the cold air passage 30b. The air mix door 28 is a one-sided support plate-like door that has a rotating shaft and a flat door panel. The air mix door 28 adjusts the temperature of the air blown into the passenger compartment by rotating the door panel to adjust the ratio of the volume of cold air that flows into the heater core 22 and the volume of cold air that bypasses the heater core 22.

[0046] For example, when the differential mix door 27 and the air mix door 28 are positioned as shown by the solid lines in Fig. 3, the hot air passage 30c is fully closed. Then, the cold air that has passed through the evaporator 21 and been introduced into the cold air passage 30b is completely blocked from flowing to the heater core 22. This maximizes the cooling capacity of the vehicle air conditioner 1, providing cool air into the passenger compartment.

[0047] 3 indicates the state of the defroster mix door 27 and the air mix door 28 when the air outlet mode of the vehicle air conditioner 1 is set to the face outlet mode. In this case, the defroster door 23, the face door 24, the foot door 25, and the rear door 26 are also set to opening positions that implement the face outlet mode. Then, air introduced into the interior of the vehicle air conditioner 1 is blown out from the face outlet 32, the first rear outlet 34, and the second rear outlet 35.

[0048] 4, the warm air passage 30c is fully opened. That is, all of the cool air that has passed through the evaporator 21 and been introduced into the cool air passage 30b is introduced into the heater core 22. This maximizes the heating capacity of the vehicle air conditioner 1, providing heated air into the passenger compartment.

[0049] 4 indicates the state of the defroster mix door 27 and the air mix door 28 when the foot / defroster blowout mode is set as the blowout mode of the vehicle air conditioner 1. In this case, the defroster door 23, the face door 24, the foot door 25, and the rear door 26 are also set to opening positions that implement the foot / defroster blowout mode. Then, air introduced into the vehicle air conditioner 1 is blown out from the defroster outlet 31, the foot outlet 33, the first rear outlet 34, and the second rear outlet 35.

[0050] 3 and 4, the cold air passage 30b and the hot air passage 30c are each partially opened. In this case, the cold air that has passed through the evaporator 21 and been introduced into the cold air passage 30b partly bypasses the heater core 22, and the rest is introduced into the heater core 22.

[0051] The air passage 30a has an air mix chamber 30d, located downstream of the heater core 22 in the air flow direction, that mixes the cool air that bypasses the heater core 22 with the warm air that has passed through the heater core 22. The cool air that bypasses the heater core 22 and the cool air that has passed through the heater core 22 are mixed in the air mix chamber 30d and their temperature is adjusted. As a result, when the air mix door 28 is positioned at a position intermediate between the positions shown in Figures 3 and 4, the temperature-adjusted conditioned air is blown out from the open air outlet, passes through the duct, and is sent into the vehicle cabin.

[0052] The first rear air outlet 34 is an opening facing the warm air passage 30c. The second rear air outlet 35 faces a passage extending from the downstream side of the evaporator 21 to a position below the heater core 22, and is an opening through which cool air that does not pass through the heater core 22 is blown out. Therefore, when the rear door 26 is in the position shown by the solid line in FIG. 3, the first rear air outlet 34 is closed. In this case, cool air that has passed through the evaporator 21 is blown out from the second rear air outlet 35. Furthermore, when the rear door 26 is in the position shown by the solid line in FIG. 4, the second rear air outlet 35 is closed. In this case, warm air that has passed through the heater core 22 is blown out from the first rear air outlet 34. The rear door 26, the differential mix door 27, and the air mix door 28 are controlled in operation by a control device (not shown).

[0053] In the vehicle air conditioner 1 configured as described above, noise due to the air flow may be generated when air flows through the air duct flow path 114a in the air duct 114, the air passage 30a in the air conditioning case 30, and the face duct flow path 42a in the face duct 42. Specifically, in the air duct flow path 114a, noise due to the air flow may be generated when air flows along the inner wall surface of the air duct bend 1142 of the air-blowing inner wall surface 1141. In the air passage 30a, noise due to the air flow may be generated when air flows along the inner wall surfaces of the step bend 361, the bottom bend 362, the rear outlet bend 363, and the defroster outlet bend 364 of the passage inner wall surface 36. Furthermore, in the face duct flow path 42a, noise due to the air flow may be generated when air flows along the inner wall surface of the face duct bend 422 of the face duct inner wall surface 421.

[0054] For this reason, the vehicle air conditioner 1 of this embodiment is provided with a sound reduction unit 50 at a location where sound caused by these air flows is generated. In explaining the sound reduction unit 50, first, the generation of sound caused by air flows will be explained using the diagram of the face duct 42 shown in Fig. 5. Note that the sound reduction unit 50 is omitted from Fig. 5.

[0055] As described above, the face duct 42 has a face duct inner wall surface 421 that forms the face duct flow path 42a, as well as a face duct bent portion 422 that bends in an arc and a face duct straight portion 423 that extends linearly. When air flows through the face duct flow path 42a formed inside the face duct 42, the air flows along the shape of the face duct 42, as shown by arrow F1 in Figure 5. Therefore, part of the air flowing through the face duct flow path 42a flows along the face duct inner wall surface 421.

[0056] When air flows through the face duct bend 422, the air flowing along the inside of the face duct bend 422, part of the face duct inner wall surface 421, separates from the inner wall surface. This separation generates multiple vortices V, each with a vortex axis in a direction perpendicular to the plane of FIG. 5 (in this embodiment, the left-right direction DRw). The multiple vortices V generated by the separation of air can grow into larger vortices V due to the combination of vortices V as they move downstream in the air flow. The generation of multiple vortices V due to this separation of air can cause noise when air flows through the face duct flow path 42a. The larger the generated vortices V, the louder the generated noise.

[0057] In contrast, in the face duct 42 of this embodiment, as shown in Fig. 6, a sound reduction section 50 is provided on the face duct inner wall surface 421. Specifically, the sound reduction section 50 is provided along the inside of the inner wall surface of the face duct bending section 422 of the face duct inner wall surface 421. The portion of the face duct inner wall surface 421 where the sound reduction section 50 is provided is a portion on the radially inner side when the direction extending radially from the center of an imaginary circle that forms the arc of the arc-shaped face duct bending section 422 is taken as the radial direction. In other words, the portion of the face duct inner wall surface 421 that forms the face duct bending section 422 where the sound reduction section 50 is provided is a portion closer to the center of the arc that forms the arc-shaped face duct bending section 422.

[0058] Hereinafter, of the face duct inner wall surface 421 that forms the face duct bending portion 422, the portion closer to the center of the arc that forms the arc-shaped face duct bending portion 422 will also be referred to as the inner bending surface 424. In this embodiment, as shown in Fig. 6, the sound reduction section 50 is provided on the inner bending surface 424 from the portion where the bending starts to the portion where the bending ends, that is, from the portion of the inner bending surface 424 that extends from the most upstream portion to the most downstream portion of the air flow.

[0059] In this embodiment, a sound reduction section 50 is also provided on the face duct straight section 423, which is located upstream of the face duct bent section 422 in the air flow. Specifically, a sound reduction section 50 is also provided on the inner straight surface 425, which is a section of the face duct inner wall surface 421 that forms the face duct straight section 423 and is continuous with the inner curved surface 424. In this embodiment, the sound reduction section 50 is provided in the section from the inner straight surface 425 to the inner curved surface 424. In this embodiment, when the size of the inner curved surface 424 from the most upstream portion to the most downstream portion of the air flow is defined as the inner curved surface length, the sound reduction section 50 is provided on the inner straight surface 425 in a range that is approximately 20% of the length of the inner curved surface along the extension direction of the inner straight surface 425. Hereinafter, the range in which the sound reduction section 50 is formed on the inner curved surface 424 and the inner straight surface 425 is also referred to as the sound reduction range.

[0060] Next, the shape of sound reduction section 50 will be described with reference to Fig. 7. Fig. 7 is a plan view of part of inner curved surface 424 and inner straight surface 425 on which sound reduction section 50 is formed. Sound reduction section 50 is provided so that the sound reduction range is substantially rectangular when inner curved surface 424 and inner straight surface 425 are shown in plan view.

[0061] The sound reduction section 50 is formed on each of the inner curved surface 424 and the inner straight surface 425 without protruding from these wall surfaces toward the face duct flow path 42a. Specifically, as shown in FIG. 7, the sound reduction section 50 is configured by a plurality of grooves 60 formed on the inner curved surface 424 and the inner straight surface 425. The grooves 60 formed on the inner curved surface 424 are recessed from the inner curved surface 424 toward the outside of the face duct flow path 42a. The grooves 60 formed on the inner straight surface 425 are recessed from the inner straight surface 425 toward the outside of the face duct flow path 42a. For convenience, in FIG. 7 and FIG. 12 (described later), reference numerals are assigned to the plurality of grooves 60 and representative grooves in a section S (described later), and reference numerals for other grooves are omitted.

[0062] The grooves 60 formed in each of the inner curved surface 424 and the inner straight surface 425 are formed to have a depth smaller than the thickness of the face duct 42. The groove depth of the grooves 60 formed in each of the inner curved surface 424 and the inner straight surface 425 is set to be within a range of 0.05 mm to 1 mm. The reason for setting the groove depth of the grooves 60 within this range is that, when the face duct 42 is molded by resin molding, the deeper the groove, the more difficult it is for the resin to flow to the back of the groove 60 and the resin is more difficult to remove from the mold after molding. Therefore, by setting the groove depth of the grooves 60 within a range of 0.05 mm to 1 mm, it becomes easier for the resin to flow to the back of the groove 60 and the resin is more easily removed from the mold after molding.

[0063] As shown in Fig. 7, the direction from upstream to downstream in the flow direction of air flowing through the face duct flow path 42a is referred to as the air flow direction DRf, and the direction perpendicular to the air flow direction DRf is referred to as the air flow perpendicular direction DRfc. The sound reduction section 50 of this embodiment is composed of a plurality of first grooves 61 formed along the air flow direction DRf and a plurality of second grooves 62 formed along a direction intersecting the air flow direction DRf. Each of the plurality of second grooves 62 is formed along the air flow perpendicular direction DRfc that is perpendicular to the air flow direction DRf. Note that the arrow F1 in Fig. 7 indicates the flow of air flowing through the face duct flow path 42a.

[0064] The multiple first grooves 61 are formed in a line at unequal intervals along the airflow orthogonal direction DRfc. The first grooves 61 separate the inner curved surface 424 and the inner straight surface 425 in the airflow orthogonal direction DRfc. The first grooves 61 have a first groove width L1, which is the dimension in the airflow orthogonal direction DRfc, that is significantly smaller than a first interval S1, which is the interval between the first grooves 61 in the airflow orthogonal direction DRfc.

[0065] By making the first groove width L1 smaller than the first interval S1, when air flows along the face duct inner wall surface 421 in the air flow direction DRf, the air is less likely to flow into the first grooves 61. This makes it easier to avoid new pressure loss occurring when the air flows through the face duct flow path 42a, which is caused by the air flowing into the first grooves 61.

[0066] Furthermore, the arrangement of the multiple first grooves 61 varies within a predetermined range within the sound reduction range. Specifically, as shown in FIGS. 7 to 9, the first spacing S1 between the multiple first grooves 61 gradually decreases in stages from the upstream side to the downstream side in the air flow direction DRf within the predetermined range. As a result, the number of first grooves 61 gradually increases in stages from the upstream side to the downstream side in the air flow direction DRf within the predetermined range. For this reason, as shown in FIGS. 8 and 9, the first spacing S1 between the first grooves 61 formed on the inner curved surface 424 is smaller than the first spacing S1 between the first grooves 61 formed on the inner linear surface 425. Hereinafter, the predetermined range in which the number of first grooves 61 gradually increases from the upstream side to the downstream side in the air flow direction DRf is also referred to as a variation range CR.

[0067] In this embodiment, the first spacing S1 of the multiple first grooves 61 decreases by three stages from the most upstream portion to the most downstream portion in the air flow direction DRf of the change range CR within the sound reduction range. The number of first grooves 61 in the change range CR increases by three stages, from six at the most upstream portion of the air flow direction DRf to eight, nine, and eleven, toward the most downstream portion. However, the multiple first grooves 61 formed side by side along the direction perpendicular to the air flow DRfc have the same first spacing S1.

[0068] Furthermore, the first groove depths D1 of the plurality of first grooves 61 formed on the inner curved surface 424 and the inner linear surface 425 are equal to each other. That is, throughout the entire sound reduction range, the first groove depths D1 of the plurality of first grooves 61 are equal to each other. Furthermore, throughout the entire sound reduction range, the first groove widths L1 of the plurality of first grooves 61 are equal to each other.

[0069] The second grooves 62 are arranged at irregular intervals along the air flow direction DRf. The second grooves 62 separate the inner curved surface 424 and the inner straight surface 425 in the air flow direction DRf. The second grooves 62 have a second groove width L2, which is the size in the air flow direction DRf, that is significantly smaller than the second interval S2, which is the interval between the second grooves 62 in the air flow direction DRf.

[0070] By making the second groove width L2 smaller than the second interval S2, when air flows along the face duct inner wall surface 421 in the air flow direction DRf, the air is less likely to flow into the second grooves 62. This makes it easier to avoid new pressure loss occurring when the air flows through the face duct flow path 42a, which is caused by the air flowing into the second grooves 62.

[0071] The arrangement of the second grooves 62 varies within a predetermined range of the sound reduction range. Specifically, as shown in FIGS. 7 and 10 , the second spacing S2 of the second grooves 62 gradually decreases in stages from the upstream side to the downstream side in the air flow direction DRf within the change range CR of the sound reduction range. In other words, the dimension of the second grooves 62 from one side to the other side of two adjacent second grooves 62 in the air flow direction DRf gradually decreases from the upstream side to the downstream side in the air flow direction DRf within the change range CR. Therefore, the second spacing S2 of the second grooves 62 formed on the inner curved surface 424 is smaller than the second spacing S2 of the second grooves 62 formed on the inner linear surface 425. The second spacing S2 of the second grooves 62 of this embodiment decreases in three stages from the most upstream portion to the most downstream portion in the air flow direction DRf within the change range CR.

[0072] Furthermore, the second groove depths D2 of the plurality of second grooves 62 formed on the inner curved surface 424 and the inner linear surface 425 are equal to each other. That is, throughout the entire sound reduction range, the second groove depths D2 of the plurality of second grooves 62 are equal to each other. Furthermore, throughout the entire sound reduction range, the second groove widths L2 of the plurality of second grooves 62 are equal to each other. The first groove depths D1 and second groove depths D2 of the plurality of first grooves 61 and the plurality of second grooves 62 are equal to each other, and the first groove widths L1 and second groove widths L2 are equal to each other.

[0073] By forming a plurality of first grooves 61 and a plurality of second grooves 62 in the inner curved surface 424 and the inner straight surface 425 in this manner, the inner curved surface 424 and the inner straight surface 425 are partitioned into a plurality of sections S, as shown in Fig. 7. The plurality of sections S are surrounded by the plurality of first grooves 61 and the plurality of second grooves 62 formed in the inner curved surface 424 and the inner straight surface 425. As shown in Fig. 7, the sections S in this embodiment partitioned by the first grooves 61 and the second grooves 62 are substantially square-shaped.

[0074] The areas of the sections S, which are areas when viewed in a direction perpendicular to the air flow direction DRf and the air flow orthogonal direction DRfc, gradually become smaller in stages from the upstream side to the downstream side in the air flow direction DRf. In other words, the first grooves 61 and the second grooves 62 are arranged to include a change range CR in which the areas of the sections S become smaller from the upstream side to the downstream side in the air flow direction DRf.

[0075] 7, the partition area of ​​the sections S on the inner curved surface 424 is smaller than the partition area of ​​the sections S on the inner straight surface 425. In this embodiment, the partition area of ​​the sections S decreases in three stages from the most upstream part to the most downstream part of the air flow direction DRf in the change range CR. The partition area of ​​the sections S is smallest at the most downstream part of the air flow direction DRf in the sound reduction range. Furthermore, the sizes of the multiple sections S are constant upstream of the change range CR in the air flow direction DRf in the sound reduction range.

[0076] As a result, the number of sections S increases stepwise from the upstream side to the downstream side in the air flow direction DRf within the change range CR. In this embodiment, the number of sections S increases in three steps from the most upstream part to the most downstream part in the air flow direction DRf within the change range CR, from six at the most upstream part to seven, eight, and ten at the most downstream part. However, the sections S aligned in the direction perpendicular to the air flow DRfc have the same section area.

[0077] As a result, the sound reduction range on the inner curved surface 424 and the inner straight surface 425 has an uneven shape in the direction along the air flow DRf, with sections S that protrude relative to the first grooves 61 and second grooves 62 and first grooves 61 and second grooves 62 that are recessed relative to the sections S arranged alternately. The surface height of the sections S is the same as the surface height of the face duct inner wall surface 421 at a portion where the sound reduction section 50 is not provided.

[0078] Next, the effect of forming the first grooves 61 and the second grooves 62 in the sound reduction range will be described. As described above, the vortex V, which is a factor in generating sound when air flows, is generated when air flowing along the face duct inner wall surface 421 separates from the face duct inner wall surface 421. The larger the generated vortex V grows, the louder the generated sound. In response to this, by forming the first grooves 61 and the second grooves 62 in the sound reduction range, the growth of the vortex V can be suppressed.

[0079] Specifically, by forming the first grooves 61 and the second grooves 62 in the sound reduction range, it is possible to break up the multiple vortices V that are generated when air flows along the face duct inner wall surface 421. Therefore, even if the multiple vortices V that are generated by air separating from the face duct inner wall surface 421 when air flows along the face duct inner wall surface 421 combine on the air flow downstream side of the face duct bend section 422, it is possible to suppress the growth of the combined vortices V. Therefore, it is possible to reduce the volume of the sound caused by the generation of vortices V compared to a configuration in which the first grooves 61 and the second grooves 62 are not formed in the sound reduction range.

[0080] When the first grooves 61 and the second grooves 62 break up the multiple vortices V, the air flowing along the face duct inner wall surface 421 passes through the sound reduction range in which the multiple first grooves 61 and the multiple second grooves 62 are formed. Therefore, the air flows from the area where the multiple first grooves 61 and the multiple second grooves 62 are not formed to the area where the multiple first grooves 61 and the multiple second grooves 62 are formed. In other words, the air flows from outside the sound reduction range to within the sound reduction range. This sound reduction range has an uneven shape in which sections S and the first grooves 61 and the second grooves 62 are alternately arranged. In contrast, the area outside the sound reduction range is a flat area in which the first grooves 61 and the second grooves 62 are not formed.

[0081] The inventors' careful investigation revealed that when air flows through a portion of the face duct inner wall surface 421 where the surface shape changes, which is the boundary between the sound reduction range and the outside of the sound reduction range, a sound different from the sound caused by the generation of vortices V may be generated. Such a sound different from the sound caused by the generation of vortices V is, for example, sound caused by the first grooves 61 and the second grooves 62, which is generated when air collides with the first grooves 61 and the second grooves 62 or when the vortex V is broken up. The sound caused by the first grooves 61 and the second grooves 62 tends to become louder the more abruptly the surface shape of the face duct inner wall surface 421 changes. Although the sound caused by the first grooves 61 and the second grooves 62 is small compared to the sound caused by the generation of vortices V, it is desirable to keep it as small as possible.

[0082] In contrast, the arrangement of the multiple first grooves 61 and multiple second grooves 62 constituting the groove 60 of this embodiment changes along the air flow direction DRf within the change range CR. As a result, the surface shape of the change range CR on the face duct inner wall surface 421 gradually changes along the air flow direction DRf. This makes it possible to suppress sudden changes in the surface shape of the change range CR on the face duct inner wall surface 421. This makes it possible to suppress the volume of sound caused by the first grooves 61 and the second grooves 62 when air flows through the sound reduction range.

[0083] In this embodiment, the first grooves 61 and the second grooves 62 are arranged so that the first spacing S1 and the second spacing S2 gradually decrease along the air flow direction DRf within the change range CR. As a result, the area of ​​the section S surrounded by the first grooves 61 and the second grooves 62 gradually decreases in stages from the upstream side to the downstream side in the air flow direction DRf within the change range CR. As a result, the number of first grooves 61 and second grooves 62 gradually increases as air flows along the face duct inner wall surface 421.

[0084] According to this, when the multiple vortices V are broken up by the first grooves 61 and the second grooves 62, the vortices V can be gradually broken up. That is, by configuring the partition area of ​​the sections S to become smaller from the upstream side to the downstream side in the air flow direction DRf, the air vortices V can be gradually made finer from the upstream side to the downstream side in the air flow direction DRf. Therefore, within the sound reduction range, the volume of the sound generated when the vortices V are broken up can be reduced compared to a configuration in which the partition area of ​​the sections S is constant from the most upstream part to the most downstream part in the air flow direction DRf.

[0085] Next, the difference in loudness of sound generated when air flows through the face duct flow path 42a between when the partition area of ​​the section S decreases from the upstream side to the downstream side in the air flow direction DRf and when it is constant will be described with reference to FIG. 11 . The graph in FIG. 11 shows the experimental results of FFT analysis of the sound generated when air flows through the face duct flow path 42a. The dashed line in FIG. 11 indicates the loudness of sound at each frequency obtained by FFT analysis of the sound generated when air flows through the face duct flow path 42a of this embodiment, in which the partition area of ​​the section S decreases from the upstream side to the downstream side in the air flow direction DRf. In contrast, the solid line in FIG. 11 indicates the loudness of sound at each frequency obtained by FFT analysis of the sound generated when air flows through the face duct flow path 42a in an embodiment in which the partition area of ​​the section S is constant from the most upstream to the most downstream side in the air flow direction DRf.

[0086] As shown in Fig. 11, in this embodiment, the volume of sound generated when air flows through the face duct flow path 42a can be reduced across most frequency bands compared to a configuration in which the partition area is constant. Thus, the sound reduction device of this embodiment can suppress the sound generated when air collides with the first grooves 61 and the second grooves 62 by varying the arrangement of the multiple first grooves 61 and the multiple second grooves 62 from the upstream side to the downstream side in the air flow direction DRf within the sound reduction range. Furthermore, by configuring the partition area to gradually decrease from the upstream side to the downstream side in the air flow direction DRf, the multiple vortices V can be gradually separated by the first grooves 61 and the second grooves 62. Therefore, the volume of sound caused by the generation of the vortices V can be reduced.

[0087] The above description has been given of the first grooves 61 and the second grooves 62, which are formed to gradually break up the vortex V that is generated when air flows along the inner wall surface of the face duct bend 422 in the face duct 42. However, in the vehicle air conditioner 1 of this embodiment, the vortex V that is generated when air separates from the inner wall surface of the air supply duct bend 1142 may grow, which may increase the noise caused by the air flow in the air supply duct flow path 114a. Furthermore, the vortex V that is generated when air separates from the inner wall surfaces of the step bend 361, the bottom bend 362, the rear outlet bend 363, and the differential outlet bend 364 may grow, which may increase the noise caused by the air flow in the air supply passage 30a.

[0088] For this reason, in this embodiment, similar first grooves 61 and second grooves 62 are formed on the inner wall surfaces of the air supply duct bend 1142, the staircase bend 361, the bottom bend 362, the rear air supply bend 363, and the differential air supply bend 364. Specifically, the first grooves 61 and the second grooves 62 are formed on the inner wall surface of the air supply inner wall surface 1141 that forms the air supply duct bend 1142, from the portion where the bend starts to the portion where the bend ends. Also, the first grooves 61 and the second grooves 62 are formed on the inner wall surfaces of the passage inner wall surface 36 that form the air supply duct bend 1142, the staircase bend 361, the bottom bend 362, the rear air supply bend 363, and the differential air supply bend 364, from the portion where the bend starts to the portion where the bend ends.

[0089] Furthermore, when the air supply duct bend 1142, the step bend 361, the bottom bend 362, the rear outlet bend 363, and the differential outlet bend 364 each have a linearly extending portion on the upstream side of the air flow, the first groove 61 and the second groove 62 may be formed in that portion. This makes it possible to suppress noise generated when air collides with the first groove 61 and the second groove 62 as it flows through the air supply duct flow path 114a and the air supply passage 30a. Furthermore, vortices V generated when air flows through the air supply duct flow path 114a and the air supply passage 30a can be gradually broken up, thereby reducing the volume of the sound caused by the vortices V.

[0090] As described above, the sound reduction device of this embodiment includes an air conditioning case 30 having a passage inner wall surface 36 and an arrangement surface 373 that form an air flow passage 30a through which air flows, a face duct 42 having a face duct inner wall surface 421 that forms a face duct flow path 42a through which air flows, an air flow duct 114 having an air flow inner wall surface 1141 that forms an air flow duct flow path 114a through which air flows, and a plurality of first grooves 61 and a plurality of second grooves 62 that are recessed and arranged side by side in the passage inner wall surface 36, the arrangement surface 373, the face duct inner wall surface 421, and the air flow inner wall surface 1141. The arrangement of the plurality of first grooves 61 and the plurality of second grooves 62 varies along the air flow direction DRf.

[0091] As described above, when air flows through air passage 30a, face duct flow path 42a, and air duct flow path 114a, multiple vortices V that cause sound are generated when the air separates from passage inner wall surface 36, arrangement surface 373, face duct inner wall surface 421, and air blow inner wall surface 1141. When the multiple vortices V that are generated combine with each other, the sound caused by the generation of vortices V becomes louder.

[0092] However, by providing multiple first grooves 61 and multiple second grooves 62 on passage inner wall surface 36, arrangement surface 373, face duct inner wall surface 421, and airflow inner wall surface 1141, it is possible to break up multiple vortices V that are generated when air separates from passage inner wall surface 36, arrangement surface 373, face duct inner wall surface 421, and airflow inner wall surface 1141, thereby suppressing the growth of the combined vortices V. As a result, the volume of the sound caused by the generation of vortices V can be reduced.

[0093] Furthermore, by using a configuration in which sound volume is reduced by the multiple first grooves 61 and multiple second grooves 62 provided on the passage inner wall surface 36, the arrangement surface 373, the face duct inner wall surface 421, and the airflow inner wall surface 1141, the first grooves 61 and second grooves 62 are less likely to provide resistance to air flow through the airflow passage 30a, the face duct flow path 42a, and the airflow duct flow path 114a. Therefore, compared to a configuration in which sound caused by airflow is reduced by using members protruding into the airflow passage 30a, the face duct flow path 42a, and the airflow duct flow path 114a, an increase in pressure loss when air flows through the airflow passage 30a, the face duct flow path 42a, and the airflow duct flow path 114a can be suppressed.

[0094] However, when air flowing along the passage inner wall surface 36, the placement surface 373, the face duct inner wall surface 421 and the air blower inner wall surface 1141 passes through the sound reduction range, there is a risk that a sound caused by the first groove 61 and the second groove 62 will be generated, which is different from the sound caused by the generation of the vortex V.

[0095] In contrast, by varying the arrangement of the multiple first grooves 61 and the multiple second grooves 62 along the air flow direction DRf, the surface shape of the change range CR on each of the passage inner wall surface 36, the arrangement surface 373, the face duct inner wall surface 421, and the airflow inner wall surface 1141 can be gradually changed along the airflow direction DRf. This makes it possible to suppress sudden changes in the surface shape of the sound reduction range on each of the passage inner wall surface 36, the arrangement surface 373, the face duct inner wall surface 421, and the airflow inner wall surface 1141 when air passes through the sound reduction range. This makes it possible to suppress the volume of sound caused by the first grooves 61 and the second grooves 62 when air flows through the sound reduction range. This therefore makes it possible to reduce the volume of sound caused by the air flow without increasing pressure loss.

[0096] Furthermore, according to the above embodiment, the following effects can be obtained.

[0097] (1) In the above embodiment, the multiple first grooves 61 and the multiple second grooves 62 are arranged to include a change range CR in which the partition area of ​​the multiple sections S becomes smaller as one moves from the upstream side to the downstream side of the air flow direction DRf.

[0098] By configuring the first grooves 61 and the second grooves 62 in this way, the number of the first grooves 61 and the second grooves 62 gradually increases along the air flow direction DRf within the change range CR. This allows the vortices V to be gradually divided when the multiple vortices V are divided by the first grooves 61 and the second grooves 62. Therefore, within the sound reduction range, the volume of the sound generated when dividing the vortices V can be reduced compared to a configuration in which the partition area of ​​the section S is constant from the most upstream portion to the most downstream portion in the air flow direction DRf.

[0099] (First modified example of the first embodiment) In the above-described first embodiment, an example was described in which the multiple first grooves 61 and the multiple second grooves 62 are arranged to include a change range CR in which the partition area of ​​the multiple sections S becomes smaller as one moves from the upstream side to the downstream side of the air flow direction DRf, but this is not limited to this.

[0100] 12, the multiple first grooves 61 and the multiple second grooves 62 may be arranged to include a narrowing range in which the partitioned areas of the multiple sections S gradually decrease in stages from the most upstream portion of the air flow direction DRf toward the downstream side in the change range CR in the air flow direction DRf, and an enlarging range in which the partitioned areas of the multiple sections S gradually increase in stages toward the most downstream portion of the air flow direction DRf downstream of the narrowing range in the change range CR in the air flow direction DRf. That is, the partitioned areas of the sections S may be largest at the most downstream portion of the air flow direction DRf in the sound reduction range.

[0101] The reason why the partition area of ​​the section S may gradually decrease in stages from the most upstream portion toward the downstream side in the air flow direction DRf, and then gradually increase in stages toward the most downstream portion will be explained.

[0102] When air passes through the sound reduction range and flows from a portion where the plurality of first grooves 61 and the plurality of second grooves 62 are formed to a portion where the plurality of first grooves 61 and the plurality of second grooves 62 are not formed, there is a risk of generating a sound different from the sound caused by the generation of the vortex V. In other words, when air flows from the sound reduction range to outside the sound reduction range, the air flows from an uneven portion to a flat portion, and there is a risk of generating a sound different from the sound caused by the generation of the vortex V.

[0103] In contrast to this, by gradually increasing the partition area in stages toward the downstream side in the air flow direction DRf within the sound reduction range, the number of first grooves 61 and second grooves 62 gradually decreases. This makes it possible to reduce the volume of sound that is different from the sound caused by the generation of vortices V, which is generated when air passes from a portion where the first grooves 61 and second grooves 62 are formed to a portion where they are not formed. Therefore, if the sound generated when air flows from the sound reduction range to outside the sound reduction range is relatively loud, it is effective to arrange the first grooves 61 and second grooves 62 so that the partition area at the most downstream part of the sound reduction range is largest.

[0104] 13, the first grooves 61 and the second grooves 62 may be arranged to include a change range CR in which the partitioned areas of the multiple sections S increase from the most upstream portion toward the downstream side in the air flow direction DRf. Alternatively, as shown in Fig. 14, the first grooves 61 and the second grooves 62 may be arranged to include an expansion range in which the partitioned areas of the multiple sections S gradually increase in stages from the most upstream portion toward the downstream side in the air flow direction DRf in the change range CR, and a contraction range downstream of the expansion range in the air flow direction DRf in the change range CR in which the partitioned areas of the multiple sections S gradually decrease in stages toward the most downstream portion in the air flow direction DRf.

[0105] (Second modified example of the first embodiment) In the first embodiment described above, an example has been described in which the multiple first grooves 61 and the multiple second grooves 62 are arranged so as to include a change range CR in which the multiple sections S become smaller and a range in which the size of the multiple sections S is constant within the sound reduction range, but this is not limiting. For example, the multiple first grooves 61 and the multiple second grooves 62 may be arranged so that the change range CR extends from the most upstream part to the most downstream part within the sound reduction range, and the multiple sections S become smaller from the most upstream part to the most downstream part.

[0106] (Third modified example of the first embodiment) In the first embodiment described above, an example has been described in which the first groove widths L1 of the plurality of first grooves 61 are equal to one another over the entire sound reduction range, but this is not limiting. Also, an example has been described in which the second groove widths L2 of the plurality of second grooves 62 are equal to one another over the entire sound reduction range, but this is not limiting.

[0107] For example, throughout the entire sound reduction range, the first groove widths L1 of the plurality of first grooves 61 may be different from one another or may be only partially equal. Furthermore, throughout the entire sound reduction range, the second groove widths L2 of the plurality of second grooves 62 may be different from one another or may be only partially equal.

[0108] (Fourth Modification of the First Embodiment) In the first embodiment described above, an example has been described in which the sections S separated by the first grooves 61 and the second grooves 62 have a substantially square shape, but this is not limiting. For example, the sections S separated by the first grooves 61 and the second grooves 62 may have a rectangular shape extending along the flow direction DRf or a rectangular shape extending along the cross-flow direction DRfc.

[0109] (Second embodiment) Next, a second embodiment will be described with reference to FIG. 15. In this embodiment, the shape of the groove 60 is different from that of the first embodiment. Other than this, the second embodiment is similar to the first embodiment. Therefore, in this embodiment, differences from the first embodiment will be mainly described, and descriptions of similar parts to the first embodiment may be omitted. Note that in this embodiment, as in the first embodiment, details of the groove 60 will be described using the groove 60 formed in the face duct 42.

[0110] As shown in Fig. 15, the grooves 60 of this embodiment are composed of a plurality of grooves 60 formed in a polygonal shape. Specifically, the grooves 60 of this embodiment include a first triangular groove 63 formed along the direction orthogonal to the air flow DRfc. The grooves 60 also include a second triangular groove 64 formed along a direction intersecting the direction orthogonal to the air flow DRfc, and a third triangular groove 65 formed along a direction intersecting both the direction orthogonal to the air flow DRfc and the direction in which the second triangular groove 64 extends. The arrangements of the first triangular grooves 63, the second triangular grooves 64, and the third triangular grooves 65 vary within a predetermined range of the sound reduction range.

[0111] The multiple first triangular grooves 63 are formed in a line at unequal intervals along the air flow direction DRf. Specifically, as shown in FIG. 15 , the spacing between the multiple first triangular grooves 63 in the air flow direction DRf decreases every two rows as the multiple first triangular grooves 63 move from the upstream side to the downstream side of the air flow direction DRf. Here, the predetermined range in which the spacing between the first triangular grooves 63 decreases as the multiple first triangular grooves 63 move from the upstream side to the downstream side of the air flow direction DRf is also referred to as a change range CR. In this embodiment, as shown in FIG. 15 , the arrangement of the multiple first triangular grooves 63 changes for each change range CR. Specifically, for the multiple first triangular grooves 63, the first triangular spacing S3, which is the spacing between the first triangular grooves 63 in the air flow direction DRf, gradually decreases in stages as the multiple first triangular grooves 63 move from the upstream side to the downstream side of the air flow direction DRf for each change range CR.

[0112] In other words, the dimension between two adjacent first triangular grooves 63 gradually decreases from the upstream side to the downstream side in the air flow direction DRf for each change range CR in the air flow direction DRf. Therefore, the first triangular spacing S3 of the first triangular grooves 63 formed on the inner curved surface 424 is smaller than the first triangular spacing S3 of the first triangular grooves 63 formed on the inner linear surface 425.

[0113] The second triangular grooves 64 are arranged at irregular intervals along the direction orthogonal to the air flow DRfc. The arrangement of the second triangular grooves 64 varies for each change range CR. Specifically, the second triangular grooves 64 have second triangular spacings S4, which are the spacings between the second triangular grooves 64 in the direction orthogonal to the air flow DRfc, that gradually decrease in stages from the upstream side to the downstream side in the air flow direction DRf for each change range CR. Therefore, the second triangular spacings S4 of the second triangular grooves 64 formed on the inner curved surface 424 are smaller than the second triangular spacings S4 of the second triangular grooves 64 formed on the inner linear surface 425. As a result, the number of second triangular grooves 64 gradually increases from the upstream side to the downstream side in the air flow direction DRf.

[0114] The third triangular grooves 65 are formed in a line at irregular intervals along the direction orthogonal to the air flow DRfc. The arrangement of the third triangular grooves 65 varies for each change range CR. Specifically, for each change range CR, the third triangular grooves 65 have third triangular spacings S5, which are the spacings between the third triangular grooves 65 in the direction orthogonal to the air flow DRfc, that gradually decrease in stages from the upstream side to the downstream side in the air flow direction DRf. Therefore, the third triangular spacings S5 of the third triangular grooves 65 formed on the inner curved surface 424 are smaller than the third triangular spacings S5 of the third triangular grooves 65 formed on the inner linear surface 425. As a result, the number of third triangular grooves 65 gradually increases from the upstream side to the downstream side in the air flow direction DRf.

[0115] By forming a plurality of first triangular grooves 63, second triangular grooves 64, and third triangular grooves 65 in the inner curved surface 424 and the inner linear surface 425 in this manner, the inner curved surface 424 and the inner linear surface 425 are partitioned into a plurality of sections S, as shown in FIG. 15 . The plurality of sections S are surrounded by the plurality of first triangular grooves 63, second triangular grooves 64, and third triangular grooves 65 formed in the inner curved surface 424 and the inner linear surface 425. As shown in FIG. 15 , the sections S in this embodiment, which are partitioned by the first triangular groove 63, second triangular groove 64, and third triangular groove 65, have a triangular shape. In this embodiment, the first triangular groove 63, second triangular groove 64, and third triangular groove 65 are formed so that the shape of each section S surrounded by the first triangular groove 63, second triangular groove 64, and third triangular groove 65 is a substantially equilateral triangle.

[0116] The areas of the multiple sections S gradually decrease for each change range CR from the upstream side to the downstream side in the air flow direction DRf. In other words, the multiple first triangular grooves 63, the multiple second triangular grooves 64, and the multiple third triangular grooves 65 are arranged to include change ranges CR in which the areas of the multiple sections S decrease from the upstream side to the downstream side in the air flow direction DRf. Therefore, the area of ​​the sections S on the inner curved surface 424 is smaller than the area of ​​the sections S on the inner straight surface 425. However, the areas of the multiple sections S aligned in the direction perpendicular to the air flow DRfc are equal to each other.

[0117] The triangular shape of each section S formed by the first triangular groove 63, the second triangular groove 64, and the third triangular groove 65 may be a shape other than an equilateral triangle, such as a right-angled triangle or an isosceles triangle. The directions in which the first triangular groove 63, the second triangular groove 64, and the third triangular groove 65 are formed may be directions other than those described above. For example, the first triangular groove 63 may be formed along the air flow direction DRf. The second triangular groove 64 may be formed along a direction intersecting the air flow direction DRf, and the third triangular groove 65 may be formed along a direction intersecting the air flow direction DRf and the direction in which the second triangular groove 64 extends.

[0118] As described above, by varying the arrangement of the multiple first triangular grooves 63, the multiple second triangular grooves 64, and the multiple third triangular grooves 65 along the air flow direction DRf, the surface shape of the change range CR on the face duct inner wall surface 421 can be gradually changed along the air flow direction DRf. This makes it possible to suppress abrupt changes in the surface shape of the sound reduction range on the face duct inner wall surface 421 when air passes through the sound reduction range. This makes it possible to suppress the volume of sound caused by the first triangular grooves 63, the second triangular grooves 64, and the third triangular grooves 65, which is generated when air flows through the sound reduction range. This makes it possible to reduce the volume of sound caused by the air flow without increasing pressure loss.

[0119] Furthermore, according to the above embodiment, the following effects can be obtained.

[0120] (1) In the above embodiment, the multiple first triangular grooves 63, the multiple second triangular grooves 64, and the multiple third triangular grooves 65 are arranged to include a change range CR in which the partition area of ​​the multiple sections S becomes smaller as you move from the upstream side to the downstream side of the air flow direction DRf.

[0121] By configuring the first triangular grooves 63, the second triangular grooves 64, and the third triangular grooves 65 in this way, the numbers of the first triangular grooves 63, the second triangular grooves 64, and the third triangular grooves 65 gradually increase along the air flow direction DRf in the change range CR. This allows the vortices V to be gradually divided when the multiple vortices V are divided by the first triangular grooves 63, the second triangular grooves 64, and the third triangular grooves 65. Therefore, in the sound reduction range, the volume of the sound generated when dividing the vortices V can be reduced compared to a configuration in which the partition area of ​​the section S is constant from the most upstream portion to the most downstream portion in the air flow direction DRf.

[0122] (First modified example of the second embodiment) In the second embodiment described above, an example has been described in which each of the sections S formed by the first triangular groove 63, the second triangular groove 64, and the third triangular groove 65 has a triangular shape, but this is not limiting. For example, each of the sections S formed by the first triangular groove 63, the second triangular groove 64, and the third triangular groove 65 may have a shape other than a triangle, such as a pentagonal shape or a hexagonal shape.

[0123] (Second Modification of the Second Embodiment) In the above-described second embodiment, an example was described in which the multiple first triangular grooves 63, the multiple second triangular grooves 64, and the multiple third triangular grooves 65 are arranged to include a change range CR in which the partition area of ​​the multiple sections S becomes smaller as one moves from the upstream side to the downstream side of the air flow direction DRf, but this is not limited to this.

[0124] For example, the multiple first triangular grooves 63, the multiple second triangular grooves 64, and the multiple third triangular grooves 65 may be arranged to include a contraction range in which the partition area of ​​the multiple sections S gradually decreases in stages from the most upstream part of the air flow direction DRf in the change range CR toward the downstream side, and an expansion range downstream of the contraction range in the air flow direction DRf in the change range CR, in which the partition area of ​​the multiple sections S gradually increases in stages toward the most downstream part of the air flow direction DRf.

[0125] Alternatively, the multiple first triangular grooves 63, the multiple second triangular grooves 64, and the multiple third triangular grooves 65 may be arranged to include a change range CR in which the partitioned areas of the multiple sections S increase from the most upstream portion toward the downstream side of the air flow direction DRf. Alternatively, the multiple first triangular grooves 63, the multiple second triangular grooves 64, and the multiple third triangular grooves 65 may be arranged to include an expansion range in which the partitioned areas of the multiple sections S gradually increase in stages from the most upstream portion toward the downstream side of the air flow direction DRf in the change range CR, and a contraction range downstream of the expansion range in the air flow direction DRf in the change range CR in which the partitioned areas of the multiple sections S gradually decrease in stages toward the most downstream portion of the air flow direction DRf.

[0126] (Third embodiment) Next, a third embodiment will be described with reference to FIG. 16. In this embodiment, the shape of the groove 60 is different from that of the first embodiment. Other than this, the third embodiment is similar to the first embodiment. Therefore, in this embodiment, differences from the first embodiment will be mainly described, and descriptions of similar parts to the first embodiment may be omitted. Note that in this embodiment, as in the first embodiment, details of the groove 60 will be described using the groove 60 formed in the face duct 42.

[0127] As shown in Fig. 16, the sound reduction section 50 of this embodiment is composed of a plurality of circular grooves 66 formed in an annular shape. The circular grooves 66 are lined up at equal intervals along the air flow orthogonal direction DRfc to form a group of circular grooves 660. The plurality of circular grooves 66 that make up the circular groove group 660 are spaced equally apart in the air flow orthogonal direction DRfc. Furthermore, the plurality of circular grooves 66 that make up the circular groove group 660 that are lined up along the air flow orthogonal direction DRfc have the same outer diameters and inner diameters. The sound reduction section 50 of this embodiment is composed of a plurality of circular groove groups 660 that are lined up along the air flow direction DRfc.

[0128] However, the arrangement of the multiple circular grooves 66 constituting the circular groove group 660 varies along the air flow direction DRf. Specifically, the multiple circular grooves 66 constituting the circular groove group 660 have smaller outer and inner diameters for each of the two rows of the circular groove group 660 as they move from the upstream side to the downstream side of the air flow direction DRf. That is, in the two rows of the circular groove group 660, the outer diameters of the multiple circular grooves 66 constituting the circular groove group 660 formed downstream in the air flow direction DRf are smaller than the outer diameters of the multiple circular grooves 66 constituting the circular groove group 660 formed upstream in the air flow direction DRf. Furthermore, in the two rows of the circular groove group 660, the inner diameters of the multiple circular grooves 66 constituting the circular groove group 660 formed downstream in the air flow direction DRf are smaller than the inner diameters of the multiple circular grooves 66 constituting the circular groove group 660 formed upstream in the air flow direction DRf.

[0129] Here, the predetermined range in which the outer diameter and inner diameter of the circular grooves 66 decrease from the upstream side to the downstream side in the air flow direction DRf is also referred to as a change range CR. In this embodiment, the arrangement of the multiple circular grooves 66 changes for each change range CR, as shown in Fig. 16. Specifically, the outer diameter and inner diameter of the multiple circular grooves 66 decrease for each change range CR.

[0130] As a result, the number of circular grooves 66 constituting one circular groove group 660 gradually increases from the upstream side to the downstream side in the air flow direction DRf for each change range CR. Therefore, the number of circular grooves 66 constituting one circular groove group 660 formed on the inner curved surface 424 is greater than the number of circular grooves 66 constituting one circular groove group 660 formed on the inner straight surface 425. Note that the intervals in the air flow direction DRf between the circular grooves 66 formed on each of the inner curved surface 424 and the inner straight surface 425 are equal. That is, throughout the entire sound reduction range, the intervals between the circular grooves 66 constituting each of the circular groove groups 660 arranged along the air flow direction DRf are equal.

[0131] By forming a plurality of circular grooves 66 in the inner curved surface 424 and the inner straight surface 425 in this manner, the inner curved surface 424 and the inner straight surface 425 are divided into a plurality of sections S as shown in Fig. 16. The plurality of sections S are surrounded by the plurality of circular grooves 66 formed in the inner curved surface 424 and the inner straight surface 425. As shown in Fig. 16, the sections S in this embodiment that are divided by the circular grooves 66 have a circular shape. In this embodiment, the circular grooves 66 are formed so that the shape of each section S surrounded by the circular grooves 66 is approximately a perfect circle.

[0132] The areas of the sections S gradually become smaller for each change range CR from the most upstream portion to the most downstream portion in the air flow direction DRf. In other words, the circular grooves 66 are arranged to include a change range CR in which the areas of the sections S become smaller from the upstream side to the downstream side in the air flow direction DRf. Therefore, the area of ​​the sections S on the inner curved surface 424 is smaller than the area of ​​the sections S on the inner straight surface 425. However, the areas of the sections S aligned in the direction perpendicular to the air flow DRfc are equal to each other. Note that the circular shape of each section S formed by the circular grooves 66 may be a shape other than a perfect circle, and may be, for example, an ellipse.

[0133] As described above, by varying the arrangement of the multiple circular grooves 66 along the air flow direction DRf, the surface shape of the change range CR on the face duct inner wall surface 421 can be gradually changed along the air flow direction DRf. This makes it possible to suppress sudden changes in the surface shape of the sound reduction range on the face duct inner wall surface 421 when air passes through the sound reduction range. This makes it possible to suppress the volume of sound caused by the circular grooves 66 when air flows through the sound reduction range. Therefore, it is possible to reduce the volume of sound caused by the air flow without increasing pressure loss.

[0134] Furthermore, according to the above embodiment, the following effects can be obtained.

[0135] (1) In the above embodiment, the circular grooves 66 are arranged to include a change range CR in which the partition area of ​​the multiple sections S decreases from the upstream side to the downstream side in the air flow direction DRf.

[0136] By configuring the circular grooves 66 in this way, the number of circular grooves 66 gradually increases along the air flow direction DRf within the change range CR. This allows the vortices V to be gradually divided when the multiple vortices V are divided by the circular grooves 66. Therefore, within the sound reduction range, the volume of the sound generated when dividing the vortices V can be reduced compared to a configuration in which the partition area of ​​the section S is constant from the most upstream portion to the most downstream portion in the air flow direction DRf.

[0137] (Modification of the third embodiment) In the above-described third embodiment, an example was described in which the multiple circular grooves 66 are arranged to include a change range CR in which the partition area of ​​the multiple sections S becomes smaller as one moves from the upstream side to the downstream side of the air flow direction DRf, but this is not limited to this.

[0138] For example, the multiple circular grooves 66 may be arranged to include a contraction range in which the partition area of ​​the multiple sections S gradually decreases in stages from the most upstream part of the air flow direction DRf in the change range CR toward the downstream side, and an expansion range downstream of the contraction range in the air flow direction DRf in the change range CR in which the partition area of ​​the multiple sections S gradually increases in stages toward the most downstream part of the air flow direction DRf.

[0139] Alternatively, the multiple circular grooves 66 may be arranged to include a change range CR in which the partitioned areas of the multiple sections S increase from the most upstream portion toward the downstream side in the air flow direction DRf. Alternatively, the multiple circular grooves 66 may be arranged to include an expansion range in which the partitioned areas of the multiple sections S gradually increase in stages from the most upstream portion toward the downstream side in the air flow direction DRf in the change range CR, and a contraction range downstream of the expansion range in the air flow direction DRf in the change range CR in which the partitioned areas of the multiple sections S gradually decrease in stages toward the most downstream portion in the air flow direction DRf.

[0140] (Fourth embodiment) Next, a fourth embodiment will be described with reference to FIGS. 17 to 19. This embodiment differs from the first embodiment in that the sound reduction section 50 does not have the first groove 61. Furthermore, this embodiment differs from the first embodiment in the shape of the second groove 62. Other than this, this embodiment is similar to the first embodiment. Therefore, in this embodiment, differences from the first embodiment will be mainly described, and descriptions of similar portions to the first embodiment may be omitted. Note that in this embodiment, as in the first embodiment, details of the groove 60 will be described using the groove 60 formed in the face duct 42.

[0141] 17, the plurality of grooves 60 constituting the sound reduction section 50 of this embodiment do not have first grooves 61 formed along the air flow direction DRf, and are composed only of a plurality of second grooves 62 formed along the direction perpendicular to the air flow DRfc. The plurality of second grooves 62 are formed on each of the inner curved surface 424 and the inner linear surface 425. The plurality of second grooves 62 are formed side by side at equal intervals along the air flow direction DRf.

[0142] 18 and 19, the second grooves 62 have a change range CR within the sound reduction range in which the second groove depth D2 increases from the upstream side to the downstream side in the air flow direction DRf. In the change range CR, the second groove depth D2 of the second grooves 62 gradually increases in a step-like manner from the upstream side to the downstream side in the air flow direction DRf. In the second grooves 62 of this embodiment, the second groove depth D2 increases in two steps from the most upstream part to the most downstream part in the air flow direction DRf within the change range CR.

[0143] Furthermore, in this embodiment, of the sound reduction range in which the second grooves 62 are formed, the range in which the second grooves 62 are formed on the inner linear surface 425 is the change range CR. That is, the second groove depth D2 of the second grooves 62 formed on the inner linear surface 425 gradually increases from the upstream side to the downstream side in the air flow direction DRf. The second groove depth D2 of the second grooves 62 formed on the inner curved surface 424 is constant. Therefore, the second groove depth D2 of the second grooves 62 formed on the inner curved surface 424 is greater than the second groove depth D2 of the second grooves 62 formed on the inner linear surface 425.

[0144] The change range CR is not limited to this, and may be configured to extend from the inner straight surface 425 to the inner curved surface 424. In other words, the second groove depth D2 of the second grooves 62 formed in the inner straight surface 425 and the inner curved surface 424 may gradually become deeper from the upstream side toward the downstream side in the air flow direction DRf.

[0145] As described above, by gradually increasing the depth of the second grooves 62 from the upstream side to the downstream side in the air flow direction DRf, the surface shape of the change range CR on the face duct inner wall surface 421 can be gradually changed along the air flow direction DRf. This makes it possible to suppress abrupt changes in the surface shape of the sound reduction range on the face duct inner wall surface 421 when air passes through the sound reduction range. This makes it possible to suppress the volume of sound caused by the second grooves 62 when air flows through the sound reduction range. Therefore, it is possible to reduce the volume of sound caused by the air flow without increasing pressure loss.

[0146] Furthermore, when the multiple vortices V are broken up by the second grooves 62, the vortices V can be broken up gradually. Therefore, within the sound reduction range, the volume of the sound generated when the vortices V are broken up can be reduced compared to a configuration in which the second groove depth D2 is constant from the most upstream part to the most downstream part in the air flow direction DRf.

[0147] (Modification of the fourth embodiment) In the above-described fourth embodiment, an example was described in which the second groove depth D2 of the multiple second grooves 62 includes a change range CR in which the second groove depth D2 gradually increases from the upstream side to the downstream side in the air flow direction DRf, but this is not limited to this.

[0148] For example, as shown in FIG. 20, the plurality of second grooves 62 may be configured to include an expanding range in the change range CR in which the second groove depth D2 gradually increases from the most upstream side to the downstream side in the air flow direction DRf, and a contracting range downstream of the expanding range in the change range CR in the air flow direction DRf in which the depth decreases toward the most downstream part of the air flow direction DRf.

[0149] Alternatively, as shown in Fig. 21, the plurality of second grooves 62 may be configured to include a change range CR in which the second groove depth D2 gradually decreases from the most upstream portion toward the downstream side in the air flow direction DRf. Alternatively, as shown in Fig. 22, the plurality of second grooves 62 may be configured to include, in the change range CR, a narrowing range in which the second groove depth D2 gradually decreases from the most upstream side toward the downstream side in the air flow direction DRf, and an enlarging range in which the depth increases toward the most downstream portion in the air flow direction DRf, downstream of the narrowing range in the change range CR in the air flow direction DRf.

[0150] (Fifth embodiment) Next, a fifth embodiment will be described with reference to FIG. 23. This embodiment differs from the first embodiment in that the grooves 60 constituting the sound reduction section 50 have a rectangular recessed portion 67 in addition to the first grooves 61 and the second grooves 62. The arrangement of the first grooves 61 and the second grooves 62 is also different from that of the first embodiment. Other than this, the fifth embodiment is similar to the first embodiment. Therefore, in this embodiment, differences from the first embodiment will be mainly described, and descriptions of similar portions to the first embodiment may be omitted. Note that in this embodiment, as in the first embodiment, details of the grooves 60 will be described using the grooves 60 formed in the face duct 42.

[0151] The first grooves 61 of this embodiment are formed on the inner curved surface 424 and the inner straight surface 425 at equal intervals along the direction perpendicular to the air flow DRfc. The second grooves 62 of this embodiment are formed on the inner curved surface 424 and the inner straight surface 425 at equal intervals along the air flow direction DRf.

[0152] By forming a plurality of first grooves 61 and a plurality of second grooves 62 in the inner curved surface 424 and the inner straight surface 425 in this manner, the inner curved surface 424 and the inner straight surface 425 are partitioned into a plurality of substantially square sections S, as shown in Fig. 23. The plurality of sections S in this embodiment have a constant section area throughout the entire sound reduction range. Therefore, as shown in Fig. 23, the sections S on the inner curved surface 424 and the sections S on the inner straight surface 425 have the same section area. The plurality of sections S are formed on the inner curved surface 424 and the inner straight surface 425, lined up at equal intervals at predetermined intervals along the direction orthogonal to the air flow DRfc and the air flow direction DRf, respectively.

[0153] Here, among the multiple sections S surrounded by the first groove 61 and the second groove 62 in this embodiment, some of the sections S have multiple rectangular recesses 67 formed by recessing. The rectangular recesses 67 are formed on the inner curved surface 424 and the inner straight surface 425. The rectangular recess 67 formed on the inner curved surface 424 is recessed from the inner curved surface 424 toward the outside of the face duct flow path 42a. The rectangular recess 67 formed on the inner straight surface 425 is recessed from the inner straight surface 425 toward the outside of the face duct flow path 42a. Note that in FIG. 23, the rectangular recesses 67 are indicated by dashed lines for ease of understanding. Also, in FIG. 23, reference numerals are assigned to representative ones of the multiple rectangular recesses 67, and reference numerals for other ones are omitted.

[0154] The plurality of rectangular recesses 67 formed on each of the inner curved surface 424 and the inner linear surface 425 are formed to have the same depth. That is, the plurality of rectangular recesses 67 have the same depth throughout the entire sound reduction range. The depths of the plurality of rectangular recesses 67 are also equal to the first groove depth D1 and the second groove depth D2. The rectangular recesses 67 communicate with the adjacent first grooves 61 and second grooves 62. Therefore, of the plurality of first grooves 61 and the plurality of second grooves 62, the first grooves 61 and second grooves 62 adjacent to the rectangular recesses 67 communicate with each other via the rectangular recesses 67.

[0155] The rectangular recesses 67 are formed so that the number of them gradually changes in stages from the upstream side to the downstream side in the air flow direction DRf. Here, the sections S aligned along the direction perpendicular to the air flow DRfc are considered to be a group of sections SG. In this embodiment, the number of sections S in which the rectangular recesses 67 are formed gradually decreases from the upstream side to the downstream side in the air flow direction DRf for each of the two rows of sections groups SG. In other words, as shown in FIG. 23 , the rectangular recesses 67 include a change range CR in which the number decreases from the upstream side to the downstream side in the air flow direction DRf.

[0156] Specifically, the number of sections S in which rectangular recesses 67 are formed decreases by one from three at the most upstream position in the air flow direction DRf to two and then one toward the most downstream position in each of the two rows of section groups SG. The positions of the sections S in which rectangular recesses 67 are formed in each of the two rows of section groups SG are irregular. Some of the rectangular recesses 67 in each of the two rows of section groups SG are aligned in the air flow direction DRf, while others are not. The rectangular recesses 67 in each of the two rows of section groups SG may also be aligned in a regular pattern.

[0157] By forming rectangular recessed portions 67 in some of the sections S among the multiple sections S surrounded by the first groove 61 and the second groove 62 in this way, it is possible to make the areas where the first groove 61 and the second groove 62 are formed have an uneven shape. In this case, among the multiple sections S surrounded by the first groove 61 and the second groove 62 in this way, the areas where the rectangular recessed portions 67 are not formed correspond to convex portions that protrude relative to the rectangular recessed portions 67, and the areas where the rectangular recessed portions 67 are formed correspond to concave portions that are recessed relative to the areas where the rectangular recessed portions 67 are not formed.

[0158] Furthermore, by configuring the number of multiple rectangular recesses 67 to gradually decrease from the upstream side to the downstream side in the air flow direction DRf, the proportion of the area in which the rectangular recesses 67, which are recessed portions, are formed can be gradually reduced from the upstream side to the downstream side in the air flow direction DRf.

[0159] As described above, by gradually reducing the number of rectangular recesses 67 from the upstream side to the downstream side in the air flow direction DRf, the surface shape of the change range CR on the face duct inner wall surface 421 can be gradually changed along the air flow direction DRf. This makes it possible to suppress abrupt changes in the surface shape of the sound reduction range on the face duct inner wall surface 421 when air passes through the sound reduction range. This makes it possible to suppress the volume of sound caused by the first grooves 61 and the second grooves 62 when air flows through the sound reduction range. Therefore, it is possible to reduce the volume of sound caused by the air flow without increasing pressure loss.

[0160] Furthermore, when the multiple vortices V are split by the first grooves 61 and the second grooves 62, the vortices V can be split gradually. Therefore, in the sound reduction range, the volume of the sound generated when the vortices V are split can be reduced compared to a configuration in which the rectangular recessed portions 67 are not formed.

[0161] (Modification of the fifth embodiment) In the above-described fifth embodiment, an example has been described in which the plurality of rectangular recesses 67 include a change range CR in which the number decreases from the upstream side to the downstream side in the air flow direction DRf, but the present invention is not limited to this.

[0162] For example, the multiple rectangular recesses 67 may be configured to include an increase range in the change range CR in which the quantity gradually increases from the most upstream side to the downstream side in the air flow direction DRf, and a decrease range in which the quantity decreases downstream of the increase range in the change range CR in the air flow direction DRf toward the most downstream part of the air flow direction DRf.

[0163] Alternatively, the plurality of rectangular recesses 67 may be configured to include a change range CR in which the quantity increases from the most upstream portion toward the downstream side in the air flow direction DRf. Alternatively, the plurality of rectangular recesses 67 may be configured to include, in the change range CR, a decrease range in which the quantity decreases from the most upstream side toward the downstream side in the air flow direction DRf, and an increase range in which the quantity gradually increases toward the most downstream portion in the air flow direction DRf, downstream of the decrease range in the change range CR in the air flow direction DRf.

[0164] (Sixth embodiment) Next, a sixth embodiment will be described with reference to FIG. 24 . This embodiment differs from the second embodiment in that the groove 60 constituting the sound reduction section 50 has a triangular recessed portion 68 in addition to a first triangular groove 63, a second triangular groove 64, and a third triangular groove 65. Furthermore, the arrangement of the first triangular groove 63, the second triangular groove 64, and the third triangular groove 65 differs from that of the second embodiment. Other than this, this embodiment is similar to the second embodiment. Therefore, in this embodiment, differences from the second embodiment will be mainly described, and descriptions of similar portions to the second embodiment may be omitted. Note that, in this embodiment, as in the first and second embodiments, details of the groove 60 will be described using the groove 60 formed in the face duct 42.

[0165] The first triangular grooves 63 of this embodiment are formed in a line at predetermined intervals along the air flow direction DRf on the inner curved surface 424 and the inner straight surface 425. The second triangular grooves 64 and the third triangular grooves 65 of this embodiment are formed in a line at predetermined intervals along the direction orthogonal to the air flow DRfc on the inner curved surface 424 and the inner straight surface 425.

[0166] By forming a plurality of first triangular grooves 63, second triangular grooves 64, and third triangular grooves 65 in the inner curved surface 424 and the inner straight surface 425 in this manner, the inner curved surface 424 and the inner straight surface 425 are partitioned into a plurality of approximately triangular sections S, as shown in Fig. 24. The plurality of sections S in this embodiment have a constant section area throughout the entire sound reduction range. Therefore, as shown in Fig. 24, the sections S on the inner curved surface 424 and the sections S on the inner straight surface 425 have the same section area. The plurality of sections S are formed on the inner curved surface 424 and the inner straight surface 425, lined up at equal intervals at predetermined intervals along the direction orthogonal to the air flow DRfc and the air flow direction DRf, respectively.

[0167] Here, among the multiple sections S surrounded by the first triangular groove 63, the second triangular groove 64, and the third triangular groove 65 in this embodiment, some of the sections S have multiple triangular recesses 68 formed by recessing. The triangular recesses 68 are formed on the inner curved surface 424 and the inner straight surface 425. The triangular recess 68 formed on the inner curved surface 424 is recessed from the inner curved surface 424 toward the outside of the face duct flow path 42a. The triangular recess 68 formed on the inner straight surface 425 is recessed from the inner straight surface 425 toward the outside of the face duct flow path 42a. Note that in Figure 24, the triangular recesses 68 are indicated by dashed lines for ease of understanding. Also, in Figure 24, reference numerals are assigned to representative ones of the multiple triangular recesses 68, and reference numerals for other ones are omitted.

[0168] The plurality of triangular recesses 68 formed on each of the inner curved surface 424 and the inner linear surface 425 are formed to have the same depth. That is, the plurality of triangular recesses 68 have the same depth throughout the entire sound reduction range. The depth of the plurality of triangular recesses 68 is also the same as the depth of the first triangular groove 63, the second triangular groove 64, and the third triangular groove 65. Each triangular recess 68 communicates with the adjacent first triangular groove 63, the second triangular groove 64, and the third triangular groove 65. Therefore, among the plurality of first triangular grooves 63, the plurality of second triangular grooves 64, and the plurality of third triangular grooves 65, the first triangular groove 63, the second triangular groove 64, and the third triangular groove 65 that are adjacent to a triangular recess 68 communicate with each other via the triangular recess 68.

[0169] The number of triangular recesses 68 gradually decreases in stages from the upstream side to the downstream side in the air flow direction DRf. Here, the sections S aligned along the direction perpendicular to the air flow DRfc are considered to be a group of sections SG. In this embodiment, the number of sections S in which the triangular recesses 68 are formed gradually decreases from the upstream side to the downstream side in the air flow direction DRf for each of the two rows of sections groups SG. In other words, as shown in FIG. 24, the triangular recesses 68 include a change range CR in which the number decreases from the upstream side to the downstream side in the air flow direction DRf.

[0170] The positions of the sections S in which the triangular recesses 68 are formed in each of the two rows of section groups SG are irregular. Some of the triangular recesses 68 in each of the two rows of section groups SG are formed in alignment with the air flow direction DRf, while other parts are not. Note that the triangular recesses 68 in each of the two rows of section groups SG may also be formed in a regular arrangement.

[0171] By forming triangular recesses 68 in some of the sections S among the plurality of sections S surrounded by the first triangular groove 63, the second triangular groove 64, and the third triangular groove 65 in this way, it is possible to make the areas where the first triangular groove 63, the second triangular groove 64, and the third triangular groove 65 are formed have an uneven shape. In this case, among the plurality of sections S surrounded by the first triangular groove 63, the second triangular groove 64, and the third triangular groove 65 in this way, the areas where the triangular recesses 68 are not formed correspond to convex portions that protrude relative to the triangular recesses 68, and the areas where the triangular recesses 68 are formed correspond to concave portions that are recessed relative to the areas where the triangular recesses 68 are not formed.

[0172] Furthermore, by configuring the number of multiple triangular depressions 68 to gradually decrease from the upstream side to the downstream side in the air flow direction DRf, the proportion of the area in which the triangular depressions 68, which are recessed portions, are formed can be gradually reduced from the upstream side to the downstream side in the air flow direction DRf.

[0173] As described above, by gradually reducing the number of triangular recesses 68 from the upstream side to the downstream side in the air flow direction DRf, the surface shape of the change range CR on the face duct inner wall surface 421 can be gradually changed along the air flow direction DRf. This makes it possible to suppress abrupt changes in the surface shape of the sound reduction range on the face duct inner wall surface 421 when air passes through the sound reduction range. This makes it possible to suppress the volume of sound caused by the first grooves 61 and the second grooves 62 when air flows through the sound reduction range. Therefore, it is possible to reduce the volume of sound caused by the air flow without increasing pressure loss.

[0174] Furthermore, when the multiple vortices V are split by the first grooves 61 and the second grooves 62, the vortices V can be split gradually. Therefore, in the sound reduction range, the volume of the sound generated when the vortices V are split can be reduced compared to a configuration in which the triangular recessed portions 68 are not formed.

[0175] (Modification of the sixth embodiment) In the sixth embodiment described above, an example has been described in which the plurality of triangular recesses 68 include a change range CR in which the number decreases from the upstream side to the downstream side in the air flow direction DRf, but the present invention is not limited to this.

[0176] For example, the multiple triangular depressions 68 may be configured to include an increase range in the change range CR in which the quantity gradually increases from the most upstream side to the downstream side in the air flow direction DRf, and a decrease range in which the quantity decreases downstream of the increase range in the change range CR in the air flow direction DRf toward the most downstream part of the air flow direction DRf.

[0177] Alternatively, the plurality of triangular recesses 68 may be configured to include a change range CR in which the quantity increases from the most upstream portion toward the downstream side in the air flow direction DRf. Alternatively, the plurality of triangular recesses 68 may be configured to include, within the change range CR, a decrease range in which the quantity decreases from the most upstream side toward the downstream side in the air flow direction DRf, and an increase range in which the quantity gradually increases toward the most downstream portion in the air flow direction DRf, downstream of the decrease range in the change range CR in the air flow direction DRf.

[0178] Seventh embodiment Next, a seventh embodiment will be described with reference to FIGS. 25 to 27. This embodiment differs from the first embodiment in that the sound reduction section 50 does not have the second groove 62. Furthermore, this embodiment differs from the first embodiment in the shape of the first groove 61. Other than this, this embodiment is similar to the first embodiment. Therefore, in this embodiment, differences from the first embodiment will be mainly described, and descriptions of similar parts to the first embodiment may be omitted. Note that in this embodiment, as in the first embodiment, details of the groove 60 will be described using the groove 60 formed in the face duct 42.

[0179] 25, the plurality of grooves 60 constituting the sound reduction section 50 of this embodiment do not have second grooves 62 formed along the direction orthogonal to the air flow DRfc, and are composed only of a plurality of first grooves 61 formed along the direction orthogonal to the air flow DRf. The plurality of first grooves 61 are formed on each of the inner curved surface 424 and the inner linear surface 425. The plurality of first grooves 61 are formed side by side at equal intervals along the direction orthogonal to the air flow DRfc.

[0180] 26 and 27, the first grooves 61 have a change range CR within the sound reduction range in which the first groove depth D1 changes from the upstream side to the downstream side in the air flow direction DRf. In the change range CR, the first groove depth D1 of the first grooves 61 continuously and gradually increases from the upstream side to the downstream side in the air flow direction DRf.

[0181] In this embodiment, the first groove depth D1 of the first grooves 61 formed in the range from the inner straight surface 425 to the inner curved surface 424 increases from the upstream side to the downstream side in the air flow direction DRf. Therefore, within the sound reduction range, the range in which the first grooves 61 formed on the inner straight surface 425 and the inner curved surface 424 are formed is the change range CR. In other words, the first grooves 61 formed on the inner straight surface 425 and the inner curved surface 424 include the change range CR in which the first groove depth D1 gradually increases from the upstream side to the downstream side in the air flow direction DRf.

[0182] The first groove depth D1 of the first grooves 61 formed in the inner curved surface 424 is larger than the first groove depth D1 of the first grooves 61 formed in the inner straight surface 425. Note that the change range CR is not limited to this, and may be only in the inner straight surface 425. That is, the range in which the first groove depth D1 of the first grooves 61 gradually deepens from the upstream side to the downstream side in the air flow direction DRf may be formed only in the inner straight surface 425.

[0183] As described above, by gradually increasing the first groove depth D1 of the first grooves 61 from the upstream side to the downstream side in the air flow direction DRf within the change range CR, the surface shape of the change range CR on the face duct inner wall surface 421 can be gradually changed along the air flow direction DRf. This makes it possible to suppress abrupt changes in the surface shape of the sound reduction range on the face duct inner wall surface 421 when air passes through the sound reduction range. This makes it possible to suppress the volume of sound caused by the first grooves 61 due to air flowing through the sound reduction range. Therefore, it is possible to reduce the volume of sound caused by the air flow without increasing pressure loss.

[0184] Furthermore, when the multiple vortices V are broken up by the first grooves 61, the vortices V can be broken up gradually. Therefore, within the sound reduction range, the volume of the sound generated when the vortices V are broken up can be reduced compared to a configuration in which the first groove depth D1 of the first grooves 61 is constant.

[0185] (Modification of the seventh embodiment) In the above-described seventh embodiment, an example was described in which the first groove depth D1 of the multiple first grooves 61 includes a change range CR in which the first groove depth D1 gradually increases from the most upstream side to the most downstream side in the air flow direction DRf, but this is not limited to this.

[0186] For example, the multiple first grooves 61 may be configured to include an expanding range in the change range CR in which the first groove depth D1 gradually increases from the most upstream side to the downstream side in the air flow direction DRf, and a contracting range in which the depth decreases toward the most downstream part of the air flow direction DRf downstream of the expanding range in the change range CR in the air flow direction DRf.

[0187] Alternatively, the plurality of first grooves 61 may be configured to include a change range CR in which the first groove depth D1 gradually decreases from the most upstream portion toward the downstream side in the air flow direction DRf. Alternatively, the plurality of first grooves 61 may be configured to include, in the change range CR, a narrowing range in which the first groove depth D1 gradually decreases from the most upstream side toward the downstream side in the air flow direction DRf, and an enlarging range in which the depth increases toward the most downstream portion in the air flow direction DRf, downstream of the narrowing range in the change range CR in the air flow direction DRf.

[0188] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as follows.

[0189] In the above embodiment, an example has been described in which the noise reduction device is applied to a vehicle air conditioner 1, but the invention is not limited to this. For example, the noise reduction device may be applied to an air conditioner used in a device other than a vehicle, or may be applied to a device other than an air conditioner, as long as it has a flow path through which air flows.

[0190] In the above-described embodiment, the grooves 60 vary in only one of the arrangement, shape, and quantity along the air flow direction DRf. However, this is not limiting. For example, the grooves 60 may be configured by combining two or more of the configurations described in the first to seventh embodiments. For example, the first grooves 61 and the second grooves 62 may be arranged to include a change range CR in which the partition area of ​​the sections S decreases from the upstream side to the downstream side in the air flow direction DRf. In this case, the first grooves 61 in the change range CR may have a first groove depth D1 that gradually increases from the upstream side to the downstream side in the air flow direction DRf, as described in the seventh embodiment. Furthermore, the second groove depth D2 of the second grooves 62 in the change range CR may gradually increase from the upstream side to the downstream side in the air flow direction DRf, as described in the fourth embodiment. As described in the fifth embodiment, the configuration may have multiple rectangular recesses 67, and the number of the multiple rectangular recesses 67 in the change range CR may decrease as you move from the upstream side to the downstream side of the air flow direction DRf.

[0191] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle.

[0192] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless they are expressly stated as being essential or are clearly limited to a specific number in principle.

[0193] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., the shapes, positional relationships, etc. are not limited to those unless otherwise specified or when they are limited in principle to specific shapes, positional relationships, etc. [Explanation of symbols]

[0194] 30, 37, 42, 114 Air flow path section 30a, 42a, 114a Air flow passage 36, 373, 421, 1141 Inner wall surface 60, 61, 62, 63, 64, 65, 66, 67, 68 groove

Claims

1. A sound reduction device that reduces sound caused by air flow, an air flow path portion (30, 37, 42, 114) having an inner wall surface (36, 373, 421, 1141) that forms an air flow path (30a, 42a, 114a) through which the air flows; a plurality of grooves (60, 61, 62, 63, 64, 65, 66, 67, 68) recessed into the inner wall surface of the air flow path portion and arranged side by side on the inner wall surface, A noise reduction device in which at least one of the arrangement, shape, and quantity of the plurality of grooves changes along the air flow direction, when the air flow direction is defined as the direction from upstream to downstream in the air flow direction.

2. The inner wall surface has a plurality of compartments (S) surrounded by the plurality of grooves, The sound reduction device according to claim 1 , wherein the plurality of grooves are arranged to include a change range (CR) in which the sizes of the plurality of compartments change along the air flow direction.

3. The sound reduction device according to claim 2 , wherein the plurality of grooves are arranged such that the change range includes a range in which the plurality of compartments become smaller from the upstream side to the downstream side in the air flow direction.

4. 3. The noise reduction device according to claim 2, wherein the plurality of grooves are arranged to include a contracting range in which the plurality of compartments become smaller from the most upstream part of the air flow direction in the change range toward the downstream side, and an expanding range downstream of the contracting range in the air flow direction in which the plurality of compartments become larger toward the most downstream part of the air flow direction.

5. The sound reduction device according to claim 2 , wherein the plurality of grooves are arranged such that the change range includes a range in which the plurality of compartments become larger from the upstream side to the downstream side in the air flow direction.

6. 3. The noise reduction device according to claim 2, wherein the plurality of grooves are arranged to include an expanding range in which the plurality of sections become larger from the most upstream part of the air flow direction in the change range toward the downstream side, and a contracting range in which the plurality of sections become smaller toward the most downstream part of the air flow direction downstream of the expanding range in the change range.

7. The plurality of grooves include a plurality of second grooves (62) extending along a direction intersecting the air flow direction and arranged side by side in the air flow direction, The sound reduction device according to claim 1 , wherein the plurality of second grooves include a change range (CR) in which the depth of each of the plurality of second grooves aligned along a direction intersecting the air flow direction changes along the air flow direction.

8. The noise reduction device according to claim 7 , wherein the range of depth change of the plurality of second grooves includes a range in which the depth increases from the upstream side to the downstream side in the air flow direction.

9. 8. The sound reduction device according to claim 7, wherein the plurality of second grooves include an expanding range in which the depth increases from the most upstream portion of the air flow direction in the change range toward the downstream side, and a contracting range in the change range downstream of the expanding range in the air flow direction in which the depth decreases toward the most downstream portion of the air flow direction.

10. The noise reduction device according to claim 7 , wherein the varying range of depth of the plurality of second grooves includes a range in which the depth decreases from the upstream side to the downstream side in the air flow direction.

11. 8. The noise reduction device according to claim 7, wherein the plurality of second grooves include a contraction range in which the depth decreases from the most upstream portion of the air flow direction in the change range toward the downstream side, and an expansion range in which the depth increases toward the most downstream portion of the air flow direction downstream of the contraction range in the change range.

12. The inner wall surface has a plurality of compartments (S) surrounded by the plurality of grooves, The plurality of grooves include recessed portions (67, 68) formed in the plurality of sections, The sound reduction device according to claim 1 , wherein the recessed portion includes a change range (CR) whose quantity changes along the air flow direction.

13. The noise reduction device according to claim 12 , wherein the changing range of the recessed portions includes a range in which the number of the recessed portions decreases from the upstream side to the downstream side in the air flow direction.

14. 13. The sound reduction device according to claim 12, wherein the recessed portions are formed to include a decreasing range in which the number decreases from the most upstream portion of the air flow direction in the change range toward the downstream side, and an increasing range in which the number increases toward the most downstream portion of the air flow direction downstream of the decreasing range in the change range in the air flow direction.

15. The noise reduction device according to claim 12 , wherein the changing range of the recessed portions includes a range in which the number of the recessed portions increases from the upstream side to the downstream side in the air flow direction.

16. 13. The sound reduction device according to claim 12, wherein the recessed portions are formed to include an increasing range in which the number increases from the most upstream portion of the air flow direction in the change range toward the downstream side, and a decreasing range in which the number decreases toward the most downstream portion of the air flow direction downstream of the increasing range in the change range.

17. The plurality of grooves are formed along the air flow direction and include a plurality of first grooves (61) arranged side by side along a direction intersecting the air flow direction, The sound reduction device according to claim 1 , wherein each of the plurality of first grooves includes a change range (CR) in which the depth of each groove changes along the air flow direction.

18. The sound reduction device according to claim 17 , wherein the varying range of depth of the plurality of first grooves includes a range in which the depth increases from the upstream side to the downstream side in the air flow direction.

19. 18. The sound reduction device according to claim 17, wherein the plurality of first grooves include an expanding range in which the depth increases from a most upstream portion of the air flow direction in the change range toward a downstream side, and a contracting range in the change range downstream of the expanding range in the air flow direction in which the depth decreases toward a most downstream portion of the air flow direction.

20. The noise reduction device according to claim 17 , wherein the varying range of depth of the plurality of first grooves includes a range in which the depth decreases from the upstream side to the downstream side in the air flow direction.

21. 18. The sound reduction device according to claim 17, wherein the plurality of first grooves include a contraction range in which the depth decreases from the most upstream portion of the air flow direction in the change range toward the downstream side, and an expansion range in which the depth increases toward the most downstream portion of the air flow direction downstream of the contraction range in the change range in the air flow direction.

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