JP2017075708A - Sound absorbing structure and air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound absorbing structure capable of reducing noise despite of frequency while maintaining an air flow controlling function.SOLUTION: A sound absorbing structure 20 is provided in a stabilizer 10 for receiving the air flow generated by a centrifugal impeller, and comprises: a wind shield 21 that blocks an air flow from passing through while allowing the pressure fluctuation based on the air flow to pass through; an entrance 23A located at the rear of the wind shield 21; a passage 23E extending from the entrance 23A; a depth wall 23D that is a dead-end of the passage 23E; and an acoustic absorption chamber 23 in which the pressure fluctuation, which is approaching from the entrance 23A after passing through the wind shield 21, attenuates by repeating the reflection in the passage 23E.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a structure that is provided, for example, in the vicinity of a blower and reduces noise generated by the blowing.

A cross flow fan is used as a blower for an indoor unit of an air conditioner. This crossflow fan can be easily increased in air volume by increasing the size of the impeller in the rotation axis direction. However, the increase in noise generated from the fan as the air volume increases is regarded as a problem.
Therefore, Patent Document 1 proposes a cross flow fan that can reduce noise at a low cost. This cross flow fan is provided with a sound absorbing structure only at a specific position of a tongue portion (stabilizer) disposed on the radially outer side of the impeller with a gap between the impeller and the sound absorbing structure. It has been proposed to provide a sound absorbing material made of a porous material and an air chamber provided at the back of the sound absorbing material.

JP 2014-62465 A

Patent document 1 makes an air chamber provided in the back part of a sound-absorbing material function as a resonance chamber, and aims at reducing noise of a specific frequency effectively by setting the volume appropriately. This suggests that the sound absorption structure of Patent Document 1 is effective only for a specific frequency, and when the noise frequency has a width, noise based on frequencies other than the specific frequency still remains. .
On the other hand, when providing a sound absorbing structure in the stabilizer, it is necessary to maintain the function of controlling the air flow as the stabilizer. If the assumed air flow is damaged by providing the sound absorbing structure, the function as a stabilizer cannot be maintained.
In view of the above, an object of the present invention is to provide a sound absorbing structure capable of reducing noise regardless of frequency while maintaining the function of controlling the flow of air.

The present invention is a sound absorbing structure provided in a member that receives an air flow generated by a blower source and blocks the passage of the air flow, but the windshield through which the air flow changes passes, and behind the windshield. A sound absorption chamber that has an entrance located at the entrance, a back wall that is a dead end of the passage, and a pressure change that passes through the windshield and enters from the entrance is attenuated by repeated reflection in the passage, It is characterized by comprising.
Since the windshield in the present invention allows pressure fluctuations to pass through, the pressure fluctuations that have passed through the windshield are guided to the sound absorption chamber, and are reflected by the wall surfaces that define the sound absorption chamber to be converted into thermal energy, thereby reducing noise. Since the sound absorption chamber is a space closed by the wall surface except for the entrance, the pressure fluctuation introduced into the sound absorption chamber is not released from the sound absorption chamber.
A windshield is provided at the entrance of the sound absorption chamber, and the function of controlling the air flow can be maintained by forming the surface of the windshield against which the air flow abuts in a desired shape.
Thus, the sound absorbing structure of the present invention reduces the noise introduced into the sound absorbing chamber while maintaining the function of controlling the air flow by the windshield. In addition, since the sound absorbing chamber employs a mechanism for absorbing sound by attenuation due to repeated reflection, it can be said to be a sound absorbing structure corresponding to pressure fluctuations in a wide frequency band.

The sound absorbing chamber in the present invention preferably includes a portion where the passage is reversed, and the passage is preferably reversed in a U shape from the entrance toward the back wall.
Although the sound absorbing chamber can be formed as a linear space, there may be no space for providing the linear sound absorbing chamber. In this case, by setting the sound absorption chamber including a portion where the passage is reversed, the number of times of reflection can be increased even when there is no linear space. A typical example is a sound absorption chamber in which the passage is reversed in a U shape from the entrance toward the back wall.

It is preferable that the windshield in this invention is provided in the area | region including the point with the largest pressure fluctuation by the flow of the received air among members.
As described above, the noise introduced into the sound absorption chamber can be reduced while maintaining the function of controlling the air flow by the windshield at the point where the pressure fluctuation is the largest and may cause a large noise.

The present invention is typically applied to a stabilizer of an air conditioner. That is, the air conditioner according to the present invention is an impeller in which a plurality of blades are arranged in the circumferential direction and a stabilizer that is disposed with a space between the impeller, and has any of the sound absorbing structures described above, A cross flow fan. And when the stabilizer includes a facing portion that faces the impeller, a guide portion that guides the airflow flowing out from the impeller to the air outlet, and a connecting portion that connects the facing portion and the guiding portion, the sound absorbing structure is , Provided at the connecting portion.
Since the sound absorbing structure of the present invention is provided in the connecting portion of the stabilizer having the largest pressure fluctuation due to the rotation of the impeller, it is possible to reduce the generation of noise due to the pressure fluctuation colliding with the connecting portion while maintaining the function as a stabilizer.

The stabilizer of the present invention has a main body segment including a facing portion, a guide portion, and a part of a connecting portion, and a tip segment forming another portion of the connecting portion, and the sound absorbing chamber is between the main body segment and the tip segment. It is preferable to form.
As described above, since the present invention is divided into two segments, the main body segment and the tip segment, the stabilizer of the present invention can be used without difficulty even if the sound absorption chamber is a relatively complicated embodiment such as a U-shape. Can be manufactured.

  According to the present invention, the noise introduced into the sound absorption chamber is reduced while maintaining the function of controlling the air flow by the windshield. In addition, the sound absorbing chamber employs a mechanism that absorbs sound by attenuation due to repeated reflection, and therefore can cope with pressure fluctuations in a wide frequency band.

It is sectional drawing which shows the indoor unit of an air conditioning apparatus provided with the crossflow fan which concerns on embodiment of this invention. (A) is sectional drawing which shows the sound absorption structure provided in the front-end | tip part of the stabilizer of the crossflow fan of FIG. 1, (b) is a figure which shows the element which identifies this front-end | tip part. It is a figure explaining the sound absorption effect | action in the sound absorption structure of FIG. It is a figure which shows the assembly | attachment method of the sound absorption structure of FIG. (A) shows the site | part which measured the pressure fluctuation level about the stabilizer, (b) is a graph which shows the measurement result of a pressure fluctuation level.

Hereinafter, an indoor unit 1 of an air conditioner including a sound absorbing structure 20 according to an embodiment of the present invention will be described with reference to the accompanying drawings.
The indoor unit 1 shown in FIG. 1 includes a casing 2, a cross flow fan 6 housed inside the casing 2, and a heat exchanger 8 that covers the upper half of the cross flow fan 6 as main components. ing.

As shown in FIG. 1, the casing 2 includes a gap 9 that houses the cross flow fan 6 and the heat exchanger 8, and includes a guide surface 3 on the side facing the heat exchanger 8.
The guide surface 3 is formed of a curved surface that is recessed outward in the radial direction of the impeller 7 that is a blower source, and extends to the air outlet 5 so that a part of the outlet flow passage on the downstream side of the cross flow fan 6 is formed together with the stabilizer 10. Form. The guide surface 3 extends along the direction of the rotation shaft 7X of the impeller 7.

As shown in FIG. 1, the cross flow fan 6 includes an impeller 7 and a stabilizer 10.
The impeller 7 is rotated by a rotating electric machine (not shown) to suck air from the outside of the casing 2, and the sucked air passes through the heat exchanger 8 and is then discharged to the outside of the casing 2. The impeller 7 has a substantially cylindrical shape extending along the width direction of the casing 2 (direction of the rotation shaft 7X), and a plurality of blades 7A are provided on the outer peripheral portion thereof. In the present embodiment, the impeller 7 is disposed on the downstream side in the air flow direction with respect to the heat exchanger 8, but is not limited thereto, and is disposed on the upstream side of the heat exchanger 8. Also good.

The stabilizer 10 is in the vicinity of the impeller 7, and forms a flow path of the air flow by the rotation of the impeller 7, particularly a flow path related to discharge from the casing 2.
As shown in FIGS. 1 and 2, the stabilizer 10 is arranged around the impeller 7 with a gap between the stabilizer 10 and the impeller 7. The stabilizer 10 includes a facing portion 11 that faces the impeller 7, a guide portion 13 that guides the airflow flowing out from the impeller 7 to the air outlet 5, and a connecting portion 12 that is provided between the facing portion 11 and the guiding portion 13. The opposing portion 11 and the guide portion 13 are connected so as to bend at an acute angle at the connecting portion 12 and change the direction of the bending. The stabilizer 10 is characterized in that the connecting portion 12 is provided with a sound absorbing structure 20 (not shown in FIG. 1). The stabilizer 10 will be described in detail later.

  When the impeller 7 is rotated in the rotation direction C shown in FIG. 1 by a rotating electric machine (not shown), the indoor air passes through the air suction port 4 provided in the casing 2 as indicated by the one-dot chain line arrow. Sucked into. The sucked air undergoes heat exchange with the refrigerant when passing through the heat exchanger 8, and the temperature is adjusted. The temperature-adjusted air passes through the impeller 7 of the cross flow fan 6 and is blown into the room from an air outlet 5 provided in the casing 2.

As shown in FIG. 1, the impeller 7 has a plurality of blades 7 </ b> A arranged in the circumferential direction around the rotation shaft 7 </ b> X of the impeller 7, and each blade 7 </ b> A rotates as it goes radially outward. A forward vane that curves in direction C. Both ends of the rotating shaft 7X are directly or indirectly supported by the casing 2.
Each blade 7A is located on the opposite side of the impeller 7 in the rotational direction C, the negative pressure surface 7B protruding to the opposite side, the pressure surface located on the back side of the negative pressure surface 7B, and recessed on the opposite side 7C.

Hereinafter, the sound absorbing structure 20 included in the stabilizer 10 of the present embodiment will be described with reference to FIGS.
The sound absorbing structure 20 is provided in the connecting portion 12 which is a region including the tip portion of the stabilizer 10 in order to reduce noise generated in the connecting portion 12 of the stabilizer 10 based on the rotation of the impeller 7. The sound absorbing structure 20 has a configuration that can realize noise reduction at a low cost.

Here, the reason why the sound absorbing structure 20 is provided at the tip portion of the stabilizer 10 in the present embodiment is that when the pressure fluctuation level at the tip portion of the stabilizer 10 is measured, the tip portion becomes the point where the pressure fluctuation is the largest. .
That is, while rotating the impeller 7, the pressure is measured continuously at five positions A to E in FIG. 5A, and the pressure fluctuation level based on the measurement result is shown in FIG. 5B. Asked to show. As shown in FIG. 5B, it was confirmed that the pressure fluctuation level at the position B indicating the tip portion of the stabilizer 10 was the highest. According to the unsteady CFD (Computational Fluid Dynamics) analysis, it is understood that the stagnation point repeatedly moves in the vicinity of the position B, and this movement leads to the pressure fluctuation, and the pressure fluctuation level at the position B is increased. The
As described above, in this embodiment, the sound absorbing structure 20 is provided at the tip portion of the stabilizer 10.
In addition, the front-end | tip part of the stabilizer 10 is defined based on the following.
As shown in FIG. 2B, the uppermost part of the stabilizer 10 is a position S ₀ , the innermost position is S ₁ , and the distance is S _d . Figure 2 (b) position _{S 2} in refers to the position of the stabilizer 10 lower surface are separated by position _{S d} min from the position _{S 1.} On the assumption above, the front end portion of the stabilizer 10, mainly in _{S 1,} refers to a moiety took width only 0.3 × Sd min _{S 0} and _{S 2} side.

  As shown in FIG. 2, the sound absorbing structure 20 includes a windshield 21 provided at the tip portion of the stabilizer 10, an inlet 23 </ b> A provided behind the windshield 21, and a passage 23 </ b> E and a passage 23 </ b> E that are U-shaped spaces connected to the inlet 23 </ b> A. A sound absorbing chamber 23 having a back wall 23D which is a dead end of the sound.

The windshield 21 separates the sound absorbing chamber 23 from the outside, and blocks the flow of air from the impeller 7 from passing through the sound absorbing chamber 23. It has a function of passing through the chamber 23. As a material having this function, a sponge used as a windshield for a microphone is listed. However, as long as the function is provided, a material other than the sponge can be used.
The windshield 21 is provided at the front end portion of the stabilizer 10 and has a circular cross section. The front end portion of the stabilizer 10 performs the original function of controlling the air flow.

The sound absorbing chamber 23 has a passage 23E having a cross-sectional shape extending in a U shape from the entrance 23A facing the windshield 21 toward the back wall 23D. The sound absorbing chamber 23 includes an inner wall surface 23B extending from the inlet 23A to the inner wall 23D, and an outer wall surface 23C extending from the inlet 23A to the inner wall 23D and provided outside the inner wall surface 23B at a predetermined interval. Both the wall surface 23B and the outer wall surface 23C have an arc shape in the cross section. The sound absorbing chamber 23 is partitioned inside the connecting portion 12 by an inlet 23A, an inner wall surface 23B, an outer wall surface 23C, and a back wall 23D. As a preferred form, a sheet-like sound absorbing material 24 is attached to the inner wall surface 23B. Yes. The sound absorbing material 24 can be attached not only to the inner wall surface 23B but also to the outer wall surface 23C.
As will be described in detail later, the pressure fluctuation induced in the sound absorbing chamber 23 after passing through the windshield 21 is reflected on the inner wall surface 23B and the outer wall surface 23C in the process of traveling through the passage 23E from the inlet 23A toward the back wall 23D. Is repeated to attenuate the pressure fluctuation.

As shown in FIG. 4, the stabilizer 10 is configured by assembling a main body segment 15 and a tip segment 17 prepared as separate members.
As shown in FIG. 4A, the main body segment 15 includes a groove 15A corresponding to the passage 23E (sound absorbing chamber 23), a protruding piece 15B provided at one end in the circumferential direction of the groove 15A, and a groove 15A. Abutting portion 15C provided at the other end portion in the circumferential direction, and a key 15D provided at the abutting portion 15C and fitted into the key groove 17C of the tip segment 17 are provided.
Further, as shown in FIG. 4A, the tip segment 17 is provided on the projecting portion 17A, the abutting portion 17B that abuts against the abutting portion 15C of the main body segment 15, and the abutting portion 17B. A key groove 17C into which 15 keys 15D are inserted, and a connecting piece 17D that connects the projecting portion 17A and the abutting portion 17B are provided.
As shown in FIG. 4B, when the tip segment 17 is assembled at a predetermined position of the main body segment 15, the convex portion 17A is inserted into the groove 15A, thereby forming a passage 23E. Assembling, the main body segment 15 and the front end segment 17 are aligned so that the key 15D of the main body segment 15 is inserted into the key groove 17C of the front end segment 17, and the abutting portion 15C and the abutting portion 17B of the front end segment 17 are aligned. Is fixed, for example, with an adhesive.
When the windshield 21 is assembled to the inlet 23A of the sound absorbing chamber 23 released in this state, the sound absorbing structure 20 is configured.

[Effect of sound absorbing structure 20]
Hereinafter, the effect of the sound absorbing structure 20 according to the present embodiment will be described.
The sound absorbing structure 20 includes a sound absorbing chamber 23 in which an inlet 23 </ b> A is closed by a windshield 21 provided at the tip of the stabilizer 10. Since the windshield 21 can block the air flow, it can maintain the function as the stabilizer 10 that controls the air flow generated by the impeller 7.

  In addition, since the windshield 21 passes the pressure fluctuation, the pressure fluctuation that has entered through the windshield 21 is guided to the sound absorption chamber 23. The pressure fluctuation induced in the sound absorbing chamber 23 is converted into heat energy by alternately reflecting the inner wall surface 23B and the outer wall surface 23C that define the sound absorbing chamber 23, as indicated by an arrow P in FIG. To reduce. Since the sound absorbing chamber 23 is a space closed by the inner wall surface 23B, the outer wall surface 23C, and the inner wall 23D except for the inlet 23A, the pressure fluctuation introduced into the sound absorbing chamber 23 is released from the sound absorbing chamber 23. There is no.

  As described above, the sound absorbing structure 20 employs a mechanism for absorbing sound by attenuation due to repeated reflection, and thus can be said to be a sound absorbing structure corresponding to pressure fluctuations in a wide frequency band. On the other hand, a mechanism for reducing noise by the principle of resonance as in Patent Document 1, for example, is effective for a specific frequency determined by the shape of the air chamber causing resonance, but has a wide frequency band. Can not cope with.

  Since the sound absorbing structure 20 is intended for pressure fluctuation at a specific position, that is, the distal end portion of the stabilizer 10, the sound absorbing chamber 23 is shaped so as to be inverted in a U shape from the inlet 23A corresponding to the specific position to the back wall 23D. Can do. Thereby, even if a linear space is small, the frequency | count that a pressure fluctuation | variation is reflected can be earned.

The “wedge shape” frequently used on the walls of an anechoic chamber converts sound into heat energy based on the principle of reflection, as in this embodiment. However, the “wedge shape” is limited to a shape having high symmetry because it has to deal with sound from all directions, that is, pressure fluctuation.
When pressure fluctuation is converted into thermal energy using the principle of reflection, the effect is increased by increasing the number of reflections. The sound absorbing chamber 23 is compact and has a large sound absorbing effect because the number of times the pressure fluctuation introduced from the inlet 23A reflects the inner wall surface 23B and the outer wall surface 23C is larger than the “wedge shape” sound absorbing chamber of the same distance. it can.

  The sound absorbing chamber 23 can be integrally formed by injection molding together with the stabilizer 10 except for the portion of the windshield 21. However, since the inner wall surface 23B has a form inverted in a U shape, the sound absorbing chamber 23 is integrated. It is not easy to form. Therefore, in the present embodiment, as shown in FIG. 4, by making the tip end segment 17 a separate member from the main body segment 15 as shown in FIG. 4, each of the main body segment 15 and the front end segment 17 can be easily manufactured. The manufacture and assembly of the stabilizer 10 can be facilitated through the easy attachment of the sound absorbing material 24 to the inner wall surface 23B of the tip segment 17.

The preferred embodiments of the present invention have been described above. However, the configuration described in the above embodiments can be selected or changed to other configurations as appropriate without departing from the gist of the present invention. .
First, the sound absorbing structure according to the present invention is preferably provided at the tip portion of the stabilizer 10 of the cross flow fan 6, but is not limited to this application, and is applied to other applications in which pressure fluctuations occur due to the flow of air. be able to.

Further, the passage 23E of the sound absorbing chamber 23 has a U-shape, but if there is a space for forming a passage having a required length in a straight line, the sound absorbing chamber having a straight passage may be formed. On the contrary, the U-shaped passage can be a meandering passage repeatedly.
The sound absorbing structure 20 is obtained by assembling the three members of the main body segment 15, the tip segment 17, and the windshield 21, but it does not exclude that the main body segment 15 and the tip segment 17 are integrally formed. Absent.
The sound absorbing material 24 is a concept that includes a material having a property of absorbing sound, for example, an object composed of a fiber material such as glass wool or a resin material such as urethane or polyester, and has a noise reduction effect. Any member can be used.

DESCRIPTION OF SYMBOLS 1 Indoor unit 2 Casing 3 Guide surface 4 Air inlet 5 Air blower 6 Cross flow fan 7 Impeller 7A Blade 7B Negative pressure surface 7C Pressure surface 7X Rotating shaft 8 Heat exchanger 9 Space | gap 10 Stabilizer 11 Opposing part 12 Connection part 13 Guide Part 15 Body segment 15A Groove 15B Protruding piece 15C Abutting part 15D Key 17 Tip segment 17A Protruding part 17B Abutting part 17C Key groove 17D Connecting piece 20 Sound absorbing structure 21 Windshield 23 Sound absorbing chamber 23A Inlet 23B Inner wall surface 23C Outer wall surface 23D Back wall 23E passage 24 sound absorbing material

Claims (6)

A sound-absorbing structure provided in a member that receives a flow of air generated by a blower source,
A windshield that blocks passage of the air flow but passes pressure fluctuations based on the air flow;
An inlet located behind the windshield, a passage connected to the inlet, and a back wall that is a dead end of the passage, and the pressure fluctuation that has entered the inlet through the windshield is reflected in the passage. A sound absorption chamber that attenuates by repeating
Sound absorbing structure characterized by that. The sound absorption chamber is
The passage includes an inversion portion;
The sound absorbing structure according to claim 1. The sound absorption chamber is
The passage is inverted in a U shape from the entrance toward the back wall,
The sound absorbing structure according to claim 1. The windshield is
Among the members, provided in a region including a point where the pressure fluctuation due to the received air flow is the largest.
The sound absorbing structure according to any one of claims 1 to 3. An impeller in which a plurality of blades are arranged in the circumferential direction;
A crossflow fan having a stabilizer disposed between the impeller and having a sound absorbing structure according to any one of claims 1 to 4,
The stabilizer is
A facing portion that faces the impeller, a guide portion that guides the airflow flowing out from the impeller to an air outlet, and a connecting portion that connects the facing portion and the guiding portion,
The sound absorbing structure is
Provided in the connecting portion,
An air conditioner characterized by that. The stabilizer is
A main body segment including a part of the facing portion, the guide portion, and the connecting portion;
A tip segment forming another part of the connecting portion,
The sound absorption chamber is
Formed between the body segment and the tip segment;
The air conditioning apparatus according to claim 5.

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