JP2022101088A - Multiblade fan and indoor unit - Google Patents

Abstract

To suppress noise caused by blade pitch sounds which are generated during rotation of blades.SOLUTION: A multiblade fan 6 comprises a plurality of blades 12 extending in an axial direction of a rotary shaft and arrayed at a predetermined pitch around the rotary shaft. The plurality of blades include at least two blades in each of which a recess 20 recessed in a thickness direction of the blade is formed in the axial direction of the rotary shaft in at least one of a positive pressure surface 17a and a negative pressure surface 17b which are blade surfaces of the blade and in at least one of an inner peripheral side part 18a and an outer peripheral side part 18b of the blade. Regarding the blades which are adjacent to each other in an array direction of the plurality of blades, cross-sectional shapes orthogonal to the rotary shaft are different at a position where the recess is formed in any blade on the rotary shaft. Regarding the at least two blades, lengths of the recesses with respect to the axial direction of the rotary shaft are different from each other.SELECTED DRAWING: Figure 7

Description

The present invention relates to a multi-blade fan and an indoor unit.

A multi-blade fan is known that is extended along the axial direction of the axis of rotation and has a plurality of blades arranged around the axis of rotation. Examples of this type of multi-blade fan include a centrifugal fan and, for example, a cross-flow fan (through-flow fan) provided in an air conditioner (Patent Document 1).

Japanese Patent No. 2014-190543

In the above-mentioned multi-blade fan, a blade pitch sound (periodic sound), which is a wind noise of the airflow between the blades, is generated when the blades rotate, and becomes noise during rotation. This blade pitch sound is generally called an Nz sound, and its frequency is expressed by the product (N × z) of the rotation speed N of the multi-blade fan and the number z of the blades. The frequency of the blade pitch sound increases as the number of blades increases.

The disclosed technique has been made in view of the above, and an object thereof is to provide a multi-blade fan and an indoor unit capable of suppressing noise due to a blade pitch sound generated during rotation of a blade.

One aspect of the multi-blade fan disclosed in the present application is a once-through fan having a plurality of blades extending along the axial direction of the rotation axis and arranged at a predetermined pitch around the rotation axis. At least one of the positive pressure surface and the negative pressure surface, which are the blade surfaces of the blade, and at least one of the inner peripheral side portion and the outer peripheral side portion of the blade, recesses recessed in the thickness direction of the blade are along the axial direction of the rotation axis. The blades that are adjacent to each other in the arrangement direction of the plurality of blades, including at least two blades formed in the above direction, have different cross-sectional shapes perpendicular to the rotation axis at the position where a recess is formed in one of the blades on the rotation axis. , At least two blades have different lengths of recesses with respect to the axial direction of the axis of rotation.

According to one aspect of the multi-blade fan disclosed in the present application, noise due to blade pitch noise generated during rotation of the blade can be suppressed.

FIG. 1 is a cross-sectional view showing an indoor unit of an embodiment. FIG. 2 is a perspective view showing a multi-blade fan of the embodiment. FIG. 3 is a cross-sectional view showing the multi-blade fan of the embodiment. FIG. 4 is a schematic diagram for explaining an example of the blades of the multi-blade fan of the embodiment. FIG. 5 is a schematic diagram for explaining an example of the blades of the multi-blade fan of the embodiment. FIG. 6 is a schematic diagram for explaining an example of the blades of the multi-blade fan of the embodiment. FIG. 7 is a cross-sectional view showing a plurality of blades in the multi-blade fan of the embodiment. FIG. 8 is a cross-sectional view showing a modification 1 of a plurality of blades in the multi-blade fan of the embodiment. FIG. 9 is a cross-sectional view showing a modification 2 of a plurality of blades in the multi-blade fan of the embodiment. FIG. 10 is a plan view showing a modification 3 of a plurality of blades in the multi-blade fan of the embodiment. FIG. 11 is a perspective view showing a modification 4 of a plurality of blades in the multi-blade fan of the embodiment. FIG. 12 is a plan view showing a modification 5 of a plurality of blades in the multi-blade fan of the embodiment. FIG. 13 is a plan view showing a modification 6 of a plurality of blades in the multi-blade fan of the embodiment. FIG. 14 is a schematic diagram showing another example of a blade in the multi-blade fan of the embodiment. FIG. 15 is a cross-sectional view showing a modification 7 of a plurality of blades in the multi-blade fan of the embodiment. FIG. 16 is a diagram for explaining a noise level in the multi-blade fan of the embodiment.

Hereinafter, examples of the multi-blade fan and the indoor unit disclosed in the present application will be described in detail with reference to the drawings. The following examples do not limit the multi-blade fan and the indoor unit disclosed in the present application.

(Composition of indoor unit)
FIG. 1 is a cross-sectional view showing an indoor unit of an embodiment. FIG. 2 is a perspective view showing a multi-blade fan of the embodiment. As shown in FIG. 1, the indoor unit 1 of the embodiment is an indoor unit constituting a refrigerating cycle device, for example, an air conditioner (not shown), and has passed through a heat exchanger 5 and a heat exchanger 5. A main body casing 8 that houses a multi-blade fan 6 into which air flows, a fan casing 7 that forms a flow path for airflow sent from the multi-blade fan 6, a heat exchanger 5, a multi-blade fan 6, and a fan casing 7 inside. And prepare. The main body casing 8 has an air suction port 8a and an air outlet 8b.

As shown in FIG. 2, the multi-blade fan 6 includes an impeller 11 in which a plurality of blades 12 are arranged around a rotation axis 13. A plurality of impellers 11 are arranged in the axial direction X of the rotating shaft 13, and are connected by sandwiching a partition plate 14 between the impellers 11. End plates 15 supported by the rotating shaft 13 are provided at both ends of the rotating shaft 13 in the axial direction X, and both ends of the multi-blade fan 6 are supported by the rotating shaft 13.

Further, the impellers 11 are connected so as to be offset from each other in the circumferential direction around the rotation shaft 13, that is, in the arrangement direction of the plurality of blades 12. As a result, each impeller 11 has a phase difference in the blade pitch sound between the impellers 11 arranged in the axial direction X of the rotating shaft 13, so that the noise during rotation of the multi-blade fan 6 can be suppressed.

(Composition of multi-wing fan)
FIG. 3 is a cross-sectional view showing the multi-blade fan 6 of the embodiment. The multi-blade fan 6 of the embodiment is used as a so-called once-through fan in which the air flow penetrates the multi-blade fan 6 in a direction intersecting the axial direction X of the rotating shaft 13.

As shown in FIG. 2, the multi-blade fan 6 is extended along the axial direction X of the rotating shaft 13, and as shown in FIG. 3, a plurality of blades arranged around the rotating shaft 13 at a predetermined pitch P. 12 is provided. The blade surface 17 of the blade 12 is curved so as to be convex in a direction opposite to the rotation direction R of the multi-blade fan 6, and has a positive pressure surface 17a and a negative pressure surface 17b. The blade 12 has an inner peripheral side portion 18a located on the rotation center O side of the multi-blade fan 6 and an outer peripheral side portion 18b located on the side opposite to the rotation center O side.

4, 5 and 6 are schematic views for explaining an example of the blade 12 of the multi-blade fan 6 of the embodiment. As shown in FIG. 4, the plurality of blades 12 have a positive pressure surface 17a on the inner peripheral side portion 18a, a negative pressure surface 17b on the inner peripheral side portion 18a, a positive pressure surface 17a on the outer peripheral side portion 18b, and a negative pressure surface 17b on the outer peripheral side portion 18b. A wing having recesses 20 (20A to 20D) recessed in the thickness direction of the wing 12 from the outer diameters of the wing (positive pressure surface 17a and negative pressure surface 17b in FIG. 4) that can be seen on the inner side of the paper surface at four locations. Includes 12. It should be noted that the wing may have a recess 20 formed in at least one of the four locations. In other words, the plurality of blades 12 are recessed in at least one blade surface of the positive pressure surface 17a and the negative pressure surface 17b of the blade 12 and at least one end of the inner peripheral side portion 18a and the outer peripheral side portion 18b of the blade 12. There are 15 types of formation patterns as the cross-sectional shape of the wing 12 by the combination in which the wing 12 in which the wing 20 is formed is included and the recess 20 is formed in any of the four places.

Further, the wing 12 is formed so that the maximum wall thickness portion at which the thickness of the wing 12 is maximized is located on the inner peripheral side portion 18a side of the center of the chord. The recess 20 is formed on either the inner peripheral side portion 18a side or the outer peripheral side portion 18b side with respect to the maximum wall thickness portion (broken line in FIG. 4), for example.

As shown in FIG. 5, when the recess 20A is formed on the negative pressure surface 17b of the inner peripheral side portion 18a and the recess 20C is formed on the negative pressure surface 17b of the outer peripheral side portion 18b, the recesses 20A and 20C are one continuous portion. It may be formed as a recess 20. When the recess 20 (20A, 20C) continuous from the tip of the inner peripheral side portion 18a to the tip of the outer peripheral side portion 18b is formed in this way, the recess 20 (20A, 20C) is a blade in the axial direction X of the rotating shaft 18. The presence of the recess 20 (20A, 20C) can be visually recognized from the appearance of the negative pressure surface 17b of the blade 12 which is formed in a part of the wing 12. Similarly, as shown in FIG. 6, when the concave portion 20B is formed on the positive pressure surface 17a of the inner peripheral side portion 18a and the concave portion 20D is formed on the positive pressure surface 17a of the outer peripheral side portion 18b, the concave portions 20B and 20D are continuous with each other. It may be formed as one recess 20 to be formed. When the recess 20 (20B, 20D) continuous from the tip of the inner peripheral side portion 18a to the tip of the outer peripheral side portion 18b is formed in this way, the recess 20 (20B, 20D) is a blade in the axial direction X of the rotating shaft 18. It is formed in a part of 12, and the presence of the recess 20 (20B, 20D) can be visually recognized from the appearance of the positive pressure surface 17a of the blade 12.

In the multi-blade fan 6 of the present embodiment, for example, recesses 20 are formed in all of the plurality of blades 12, but the structure is not limited to this, and at least one of the plurality of blades 12 has a recess 20. Any structure may be used. Then, in the multi-blade fan 6 of the present embodiment, the blades adjacent to each other in the arrangement direction of the plurality of blades 12 are orthogonal to the rotation shaft 13 at the position where the recess 20 is formed in any of the blades on the rotation shaft 13. The cross-sectional shape is different. As a result, the frequency of the blade pitch sound can be made different between the adjacent blades 12 having different cross-sectional shapes.

Further, according to the multi-blade fan 6, it is possible to easily change the cross-sectional shape of each of the adjacent blades 12 by changing the formation pattern of the recess 20. Therefore, the frequency of the blade pitch sound can be easily changed between the adjacent blades 12.

Although not shown, the multi-blade fan 6 may have a structure in which, for example, a wing 12 having a recess 20 and a wing 12 having no recess 20 are arranged next to each other. In this structure, the noise of the multi-blade fan 6 can be suppressed by dispersing the frequency of the blade pitch sound between the blade 12 having the recess 20 and the blade 12 having no recess 20.

As described above, the fact that the cross-sectional shapes of the blades 12 are different between the adjacent blades 12 means that the cross-sectional shapes orthogonal to the axial direction X of the rotating shaft 13 of the adjacent blades 12 are different in the axial direction X of the rotating shaft 13. It means that the cross-sectional shapes of the blades 12 are different from each other when compared at the positions where the blades 12 pass through the recess 20. Such different cross-sectional shapes of the wing 12 include a structure in which the formation pattern of the recess 20 is different, a structure in which the cross-sectional shape of the recess 20 is different, and a structure in which the position of the recess 20 is different in the direction along the chord.

FIG. 7 is a cross-sectional view showing a plurality of blades 12 in the multi-blade fan 6 of the embodiment. As shown in FIGS. 3 and 7, for example, all of the plurality of blades 12 of the multi-blade fan 6 are adjacent to each other in the arrangement direction of the plurality of blades 12 in the cross section of the blade 12 orthogonal to the axial direction X of the rotation axis 13. The positions where the recesses 20 (20A to 20D) of the matching blades 12 are provided are different from each other. In the multi-blade fan 6, the positions where the recesses 20 of at least two blades 12 are provided are different from each other in the arrangement direction of the plurality of blades 12, and the two blades 12 may be arranged next to each other. The frequency of the blade pitch sound can be dispersed among adjacent blades 12 having different positions of 20.

Each recess 20 (20A to 20D) has a bottom surface 21a having an arcuate cross section. The recess 20 is formed over the axial direction X of the rotary shaft 13 in the blade 12, but may be formed in a part of the blade 12 in the axial direction X. Further, in one wing 12, the cross-sectional shape of the recess 20 is formed to have the same shape in the axial direction X of the rotating shaft 13, but the cross-sectional shape of the recess 20 in one wing 12 is the axial direction X of the rotating shaft 13. It may be formed to change along with.

(Modification 1)
FIG. 8 is a cross-sectional view showing a modification 1 of a plurality of blades 12 in the multi-blade fan 6 of the embodiment. As shown in FIG. 8, all of the plurality of blades 12 of the modification 1 have the blades 12 adjacent to each other in the arrangement direction among the plurality of blades 12 in the cross section of the blades 12 orthogonal to the axial direction X of the rotation axis 13. The number of recesses 20 (20A to 20D) is different from each other. As a result, the blade pitch sound can be dispersed among the adjacent blades 12. The number of recesses 20 of each blade 12 increases and decreases regularly along the rotation direction R of the multi-blade fan 6, but the structure is not limited to this, and may change irregularly.

(Modification 2)
FIG. 9 is a cross-sectional view showing a modification 2 of a plurality of blades 12 in the multi-blade fan 6 of the embodiment. As shown in FIG. 9, all of the plurality of blades 12 of the modification 2 have the blades 12 adjacent to each other in the arrangement direction among the plurality of blades 12 in the cross section of the blades 12 orthogonal to the axial direction X of the rotation axis 13. The cross-sectional shapes of the recesses 20 are different from each other. For example, the recess 20 extends from the distal end surface of the inner peripheral side portion 18a toward the outer peripheral side portion 18b, and has an end surface 21b of the recess 20 that intersects the negative pressure surface 17b. As a result, the frequency of the blade pitch sound can be dispersed among the adjacent blades 12. The cross-sectional shape of the recess 20 includes the depth of the recess 20 in the thickness direction of the blade 12, the length of the recess 20 in the direction along the chord, and the blade surface 17 and the end surface 21b in the cross section orthogonal to the axial direction X of the rotation axis 13. It suffices if the angles formed by the wheels are different. Further, in the multi-blade fan 6, for example, the modification 1 and the modification 2 may be combined, and the frequency of the blade pitch sound can be further dispersed among the adjacent blades 12.

(Modification 3)
FIG. 10 is a plan view showing a modification 3 of a plurality of blades 12 in the multi-blade fan 6 of the embodiment. As shown in FIG. 10, in the modified example 3, the cross-sectional shapes of the recesses 20 in the direction along the chord are the same among the blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12, and the axial direction X of the rotation axis 13 is X. The length H of the recess 20 is different from that of the recess 20. In the third modification, the length H of the recess 20 is different between the adjacent blades 12, so that, for example, in the DD cross section in FIG. 10, the cross-sectional shapes of the blades 12 between the adjacent blades 12 are different, so that the adjacent blades 12 are adjacent to each other. The frequency of the blade pitch sound can be distributed among the matching blades 12.

Although not shown, also in the modified example 3, the adjacent blades 12 are formed so that the length H of the recesses 20 is different in combination with the structures of the recesses 20 of the above-mentioned Examples, Modified Examples 1 and 2. May be done, and the effect of the embodiment is further enhanced.

(Modification example 4)
FIG. 11 is a perspective view showing a modification 4 of a plurality of blades 12 in the multi-blade fan 6 of the embodiment. The modified example 4 is an example in which the above-described embodiment and the modified example 3 are combined, and as shown in FIG. 11, in each of the plurality of blades 12, the positive pressure surface 17a and the inner peripheral side portion of the inner peripheral side portion 18a. A recess 20 is formed in any one of four locations: the negative pressure surface 17b of the 18a, the positive pressure surface 17a of the outer peripheral side portion 18b, and the negative pressure surface 17b of the outer peripheral side portion 18b, and the recess 20 is formed between the adjacent blades 12. Positions are different from each other.

In addition, in the modified example 4, in each of the plurality of blades 12, the length H of the recess 20 with respect to the axial direction X of the rotary shaft 13 and the cross section perpendicular to the axial direction X of the rotary shaft 13 along the blade surface 17. The widths of the extending recesses 20 differ from each other in the positions of the recesses 20 between the adjacent blades 12. In this way, the position, length H, and width of the recess 20 are different in all the blades 12, so that the change in the frequency of the blade pitch sound between the adjacent blades 12 is increased, and the frequency of the blade pitch sound is increased. By effectively dispersing, the noise caused by the wing pitch sound is further suppressed.

(Modification 5)
FIG. 12 is a plan view showing a modification 5 of a plurality of blades 12 in the multi-blade fan 6 of the embodiment. As shown in FIG. 12, in each of the blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12, a plurality of recesses 20 having the same cross-sectional shape orthogonal to the axial direction X of the rotating shaft 13 are provided in the axial direction of the rotating shaft 13. It is formed side by side with X. The number of recesses 20 arranged at intervals in the axial direction X of the rotating shaft 13 differs between the blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12. The number of recesses 20 of each blade 12 changes so as to repeatedly increase and decrease in a predetermined cycle along the rotation direction R of the multi-blade fan 6, but the structure is not limited to this and may change irregularly. .. In the modified example 5, the number of recesses 20 is different between the adjacent blades 12, so that, for example, in the EE cross section in FIG. 12, the cross-sectional shapes of the blades 12 between the adjacent blades 12 are different, so that the adjacent blades are adjacent to each other. The wing pitch sound can be dispersed among the twelve.

(Modification 6)
FIG. 13 is a plan view showing a modification 6 of a plurality of blades 12 in the multi-blade fan 6 of the embodiment. As shown in FIG. 13, in the blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12, the cross-sectional shape of the recesses 20 orthogonal to the axial direction X of the rotating shaft 13 and the recesses 20 arranged in the axial direction X of the rotating shaft 13 The number is the same, and the positions of the recesses 20 in the axial direction X of the rotating shaft 13 are different. The position of the recess 20 of each blade 12 gradually shifts toward one side in the axial direction X of the rotary shaft 13 along the rotation direction R of the multi-blade fan 6, but the position of the recess 20 is not limited to this structure. The position may change irregularly. In the modified example 6, the positions of the recesses 20 with respect to the axial direction X of the rotating shaft 13 are different between the adjacent blades 12, so that, for example, in the GG cross section in FIG. 13, the cross section of the blades 12 between the adjacent blades 12 is different. Due to the different shapes, the blade pitch sound can be dispersed among the adjacent blades 12.

(Modification 7)
FIG. 14 is a schematic diagram showing another example of the blade 12 in the multi-blade fan 6 of the embodiment. FIG. 15 is a cross-sectional view showing a modified example 7 of a plurality of blades 12 in the multi-blade fan 6 of the embodiment. As shown in FIG. 14, the wing 12 has recesses 20 (20F, 20G) formed in the inner peripheral side portion 18a and the outer peripheral side portion 18b, respectively. The recess 20 (20F, 20G) is formed in a part of the blade 12 in the axial direction X of the rotating shaft 13.

The bottom surface 21a of the recess 20F of the inner peripheral side portion 18a is curved in the same direction as the negative pressure surface 17b as the blade surface 17 on which the recess 20F is formed is curved. The bottom surface 21a of the recess 20F is a negative pressure surface 17b on which the recess 20F is formed from the tip of the inner peripheral side portion 18a as one end of the chord length L in the cross section of the blade 12 orthogonal to the axial direction X of the rotation shaft 13. It is formed as one curved surface that is smoothly continuous up to. Further, the recess 20F is formed by cutting out the tip of the inner peripheral side portion 18a in succession to the positive pressure surface 17a and the negative pressure surface 17b, and the chord length L is shortened by forming the recess 20F. ing.

Similarly, the bottom surface 21a of the recess 20G of the outer peripheral side portion 18b is curved in the same direction as the positive pressure surface 17a on which the recess 20G is formed is curved. The bottom surface 21a of the recess 20G is from the tip of the outer peripheral side portion 18b as one end of the chord length L to the positive pressure surface 17a on which the recess 20G is formed in the cross section of the blade 12 orthogonal to the axial direction X of the rotation shaft 13. It is formed as one smoothly continuous curved surface. Further, the recess 20G is formed by cutting out the tip of the outer peripheral side portion 18b in succession to the positive pressure surface 17a and the negative pressure surface 17b, and the chord length L is shortened by forming the recess 20G. There is.

In the bottom surface 21a formed as one curved surface as described above, since the recess 20 (20F, 20G) is formed in a part of the blade 12 in the axial direction X of the rotating shaft 18, the negative pressure surface 17b of the blade 12 The presence of the recess 20 (20F, 20G) can be visually recognized from the appearance of.

Further, the bottom surface 21a of the recess 20F is smoothly connected to the negative pressure surface 17b at a position on the inner peripheral side portion 18a side of the center of the chord. The bottom surface 21a of the recess 20G is smoothly connected to the positive pressure surface 17a at a position on the outer peripheral side portion 18a side of the center of the chord. The position where the bottom surface 21a of the recess 20 (20F, 20G) and the blade surface 17 are connected is not limited to the modification 7. Further, for example, when the tip surface of the inner peripheral side portion 18a of the blade 12 is formed so as to include an arcuate curved surface, the bottom surface 21a of the recess 20F is formed so as to intersect the arcuate curved surface. The bottom surface 21a is smoothly connected to the blade surface 17.

In this way, the bottom surface 21a of the recess 20F is formed so as to be smoothly continuous with the negative pressure surface 17b, and the bottom surface 21a of the recess 20G is formed so as to be smoothly continuous with the positive pressure surface 17a. Since the vortex generated in the airflow flowing along the blade surface 17 along the blade surface 17 is reduced and the turbulent flow generated on the downstream side of the blade 12 is suppressed, the pressure loss generated in the airflow along the blade surface 17 is suppressed, and the multi-blade fan 6 is operated. The power consumption of the driving motor (not shown) can be reduced. In other words, the air volume of the multi-blade fan 6 can be increased by reducing the pressure loss of the air flow along the blade surface 17 of the blade 12.

As shown in FIG. 15, the two blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 have different cross-sectional shapes, which are the sizes of the recesses 20 (20F, 20G) formed as described above. Therefore, the chord lengths L are different from each other. As a result, the frequency of the blade pitch sound can be changed between the adjacent blades 12, and the frequency of the blade pitch sound can be dispersed among the adjacent blades 12.

Even if the wing 12 is reduced to about 20% of the chord length L of the wing 12 before the recesses 20G and 20F are formed, as in the inner peripheral side portion 18a and the outer peripheral side portion 18b shown by the broken line in FIG. good. If the blade 12 is smaller than 20% of the chord length L, an appropriate flow path cannot be secured between the adjacent blades 12, turbulence occurs between the adjacent blades 12, and pressure is applied to the airflow between the blades 12. It is not preferable because it causes a loss.

(Action of recess)
As described above, the adjacent blades 12 of the multi-blade fan 6 have different cross-sectional shapes of each blade 12 due to having any of the recesses 20 in the embodiments 1 to 7, and therefore the blades of each blade 12 have different cross-sectional shapes. The frequency of the pitch sound changes. This makes it possible to disperse the frequency of the blade pitch sound among the adjacent blades 12, and suppress the noise caused by the blade pitch sound generated when the blades 12 rotate.

FIG. 16 is a diagram for explaining a noise level in the multi-blade fan 6 of the embodiment. In FIG. 16, the vertical axis indicates the noise level [dB], and the horizontal axis indicates the noise frequency [Hz]. In FIG. 16, the multi-blade fan 6 of the embodiment is shown by a broken line, and the multi-blade fan of the comparative example is shown by a solid line.

In the multi-blade fan of the comparative example, the blade 12 does not have the recess 20, the cross-sectional shape of the blade 12 is the same in the arrangement direction of the plurality of blades 12, and the blades 12 are arranged at equal pitches. As shown in FIG. 16, in the multi-blade fan 6 of the embodiment, the cross-sectional shape of the blade 12 having the recess 20 is different between the blades 12 adjacent to each other in the arrangement direction of the blade 12, so that the blades 12 are adjacent to each other. By changing the frequency of the pitch sound and distributing the frequency of the blade pitch sound among the adjacent blades 12, the noise level is near the primary frequency indicated by the arrow F1 and near the secondary frequency indicated by the arrow F2. Can be reduced.

(Ratio of inner and outer diameters of wings)
As shown in FIG. 3, the plurality of blades 12 of the multi-blade fan 6 described above have a diameter (inner diameter) of the inscribed circle C1 of the blade 12 with respect to the rotation center O of the rotating shaft 13 as A, and the circumscribed circle C2 of the blade 12. When the diameter (outer diameter) is B, the inner / outer diameter ratio (A / B) of the blade 12 is 0.720 or more and 0.800 or less. In the case of such an inner / outer diameter ratio (A / B) of the blade 12, noise can be reduced as compared with a multi-blade fan having no recess 20 by controlling the frequency of the blade pitch sound by the recess 20 in the embodiment. ..

Further, the inner / outer diameter ratio (A / B) of the blade 12 is expanded in order to increase the air volume of the multi-blade fan 6, and when the inner / outer diameter ratio (A / B) of the blade 12 exceeds 0.800, the multi-blade Since the wind speed passing between the blades 12 increases so as to penetrate the fan 6, there is a risk of causing deterioration of noise. Even in such a case, by controlling the frequency of the blade pitch sound by the recess 20, the air volume can be increased while avoiding the deterioration of the noise.

(effect)
As described above, the plurality of blades 12 of the multi-blade fan 6 are provided on at least one of the positive pressure surface 17a and the negative pressure surface 17b of the blade 12 and on at least one of the inner peripheral side portion 18a and the outer peripheral side portion 18b of the blade 12. The recess 20 recessed with respect to the thickness direction of 12 includes at least two blades 12 formed along the axial direction X of the rotating shaft 13. The blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 have different cross-sectional shapes orthogonal to the axial direction X of the rotating shaft 13 at the position where the recess 20 is formed in any of the blades 12 on the rotating shaft 13. The above-mentioned at least two blades 12 have different lengths of the recesses 20 with respect to the axial direction X of the rotating shaft 13. This makes it possible to disperse the frequency of the blade pitch sound between the adjacent blades 12 by changing the frequency of the blade pitch sound of the adjacent blades 12 in the plurality of blades 12, and when the blades 12 rotate. It is possible to suppress the noise caused by the generated wing pitch sound. Further, since the cross-sectional shape of the blade 12 can be easily changed by changing the position where the recess 20 is formed on the blade surface 17 of the blade 12, the frequency of the blade pitch sound can be easily changed between the adjacent blades 12. Can be made to.

Further, since the frequency of the blade pitch sound changes between the adjacent blades 12 by making the length H of the recess 20 different between the adjacent blades 12, the frequency of the blade pitch sound between the adjacent blades 12 is dispersed. It is possible to suppress the noise caused by the wing pitch sound.

Further, in the multi-blade fan 6, each recess 20 of the two blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 is any one of a positive pressure surface 17a, a negative pressure surface 17b, an inner peripheral side portion 18a, and an outer peripheral side portion 18b. The positions (formation patterns of the recesses 20) are different from each other. In this way, it is possible to easily change the cross-sectional shape of each blade 12 by changing the formation pattern of the recess 20 between the adjacent blades 12. Therefore, the frequency of the blade pitch sound between the adjacent blades 12 can be easily changed, and the frequency of the blade pitch sound between the adjacent blades 12 can be dispersed.

Further, in the multi-blade fan 6, the two blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 have different numbers of recesses 20 in the cross section of the blade 12 orthogonal to the axial direction X of the rotation axis 13. In this way, it is possible to easily change the cross-sectional shape of each of the adjacent blades 12 by changing the number of the recesses 20. Therefore, the frequency of the blade pitch sound between the adjacent blades 12 can be easily changed, and the frequency of the blade pitch sound between the adjacent blades 12 can be dispersed.

Further, in the multi-blade fan 6, the two blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 have different cross-sectional shapes of the recesses 20 in the cross-section of the blades 12 orthogonal to the axial direction X of the rotation axis 13. In this way, it is possible to easily change the cross-sectional shape of each of the adjacent blades 12 by changing the cross-sectional shape of the recess 20. Therefore, the frequency of the blade pitch sound between the adjacent blades 12 can be easily changed, and the frequency of the blade pitch sound between the adjacent blades 12 can be dispersed.

Further, in the multi-blade fan 6, the two blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 have different numbers of recesses 20 arranged in the axial direction X of the rotating shaft 13. In this way, it is possible to easily change the cross-sectional shape of each of the adjacent blades 12 by changing the number of the recesses 20 arranged in the axial direction X of the rotating shaft 13. Therefore, the frequency of the blade pitch sound between the adjacent blades 12 can be easily changed, and the frequency of the blade pitch sound between the adjacent blades 12 can be dispersed.

Further, in the multi-blade fan 6, the recess 20 of the blade 12 is formed in a part of the blade 12 in the axial direction X of the rotating shaft 13. The bottom surface 21a of the recess 20 (20F, 20G) is curved in the same direction as the blade surface 17 on which the recess 20 (20F, 20G) is formed is curved, and the bottom surface 21a is in the axial direction X of the rotation shaft 13. In the cross section of the orthogonal blade 12, it is formed as one continuous curved surface from one end of the chord length L to the blade surface 17 on which the recess 20 (20F, 20G) is formed. As a result, the vortex generated in the airflow flowing along the bottom surface 21a of the recesses 20F and 20G is reduced, and the turbulence generated on the downstream side of the blade 12 is suppressed, so that the pressure loss generated in the airflow along the blade surface 17 is suppressed. Is suppressed, and the power consumption of the motor (not shown) for driving the multi-blade fan 6 can be reduced. Therefore, the air volume of the multi-blade fan 6 can be increased by reducing the pressure loss of the air flow along the blade surface 17 of the blade 12.

Further, in the multi-blade fan 6, the concave portion 20 of the blade 12 is formed by cutting out the tip of either the inner peripheral side portion 18a or the outer peripheral side portion 18b in succession to the positive pressure surface 17a and the negative pressure surface 17b. .. As a result, it is possible to easily change the cross-sectional shape of each of the adjacent blades 12 by changing the chord length L. Therefore, the frequency of the blade pitch sound can be easily changed between the adjacent blades 12.

Further, in the multi-blade fan 6, the plurality of blades 12 have the blade 12 when the diameter of the inscribed circle C1 of the blade 12 with respect to the rotation center O of the rotation shaft 13 is A and the diameter of the circumscribed circle C2 of the blade 12 is B. The inner-outer diameter ratio (A / B) is 0.720 or more and 0.800 or less. As a result, in the case of such an inner / outer diameter ratio (A / B) of the blade 12, noise can be reduced as compared with a multi-blade fan having no recess 20 by controlling the frequency of the blade pitch sound by the recess 20.

Further, in the multi-blade fan 6, the plurality of blades 12 have an inner / outer diameter of the blade 12 when the diameter of the inscribed circle C1 of the blade 12 with respect to the rotation center O of the rotation shaft 13 is A and the diameter of the circumscribed circle C2 is B. The ratio (A / B) exceeds 0.800. When the inner / outer diameter ratio (A / B) of the blade 12 exceeds 0.800, the wind speed passing between the blades 12 so as to penetrate the multi-blade fan 6 may increase, which may cause deterioration of noise. By controlling the frequency of the blade pitch sound by the recess 20, the air volume can be increased while avoiding the deterioration of noise.

The multi-blade fan disclosed in the present application is used as a once-through fan in the examples, but is not limited to the once-through fan. The multi-blade fan may be applied to a centrifugal fan such as a sirocco fan, for example, and the same effect as that of the present embodiment can be obtained.

1 Indoor unit 5 Heat exchanger 6 Multi-blade fan 12 Wings 13 Rotating shaft 17 Wing surface 17a Positive pressure surface 17b Negative pressure surface 18a Inner peripheral side 18b Outer peripheral side 20 (20A to 20G) Recess 21a Bottom surface 21b End surface A, B diameter ( A / B) Inner / outer diameter ratio C1 Inscribed circle C2 Circumscribed circle H Length L Chord length X Axial direction

Claims (10)

A once-through fan that is extended along the axial direction of the axis of rotation and has a plurality of blades arranged at a predetermined pitch around the axis of rotation.
The plurality of blades are recessed in at least one of a positive pressure surface and a negative pressure surface, which are the blade surfaces of the blade, and at least one of the inner peripheral side portion and the outer peripheral side portion of the blade in the thickness direction of the blade. The recess contains at least two wings formed along the axial direction of the axis of rotation, including at least two wings.
The blades adjacent to each other in the arrangement direction of the plurality of blades have different cross-sectional shapes orthogonal to the rotation axis at the position where the recess is formed in any of the blades on the rotation axis.
The at least two blades are multi-blade fans in which the lengths of the recesses with respect to the axial direction of the rotation axis are different from each other. The two wings have the recess and
The concave portions of the two blades have different positions of the positive pressure surface, the negative pressure surface, the inner peripheral side portion, and the outer peripheral side portion.
The multi-wing fan according to claim 1. The two blades have different numbers of recesses in the cross section of the blade orthogonal to the axial direction of the rotation axis.
The multi-wing fan according to claim 1 or 2. The two blades have different cross-sectional shapes of the recesses on the end faces of the blades orthogonal to the axial direction of the rotation axis.
The multi-wing fan according to any one of claims 1 to 3. The two blades have different numbers of recesses arranged in the axial direction of the rotation axis.
The multi-wing fan according to any one of claims 1 to 4. The recess is formed in a part of the wing in the axial direction of the rotation axis.
The bottom surface of the recess is curved in the same direction as the blade surface on which the recess is formed is curved, and the bottom surface is formed from one end of the chord length in the cross section of the blade orthogonal to the axial direction of the rotation axis. It is formed as one curved surface continuous to the blade surface on which the recess is formed.
The multi-wing fan according to any one of claims 1 to 5. The recess is formed by cutting out the tip of either the inner peripheral side portion or the outer peripheral side portion so as to be continuous with the positive pressure surface and the negative pressure surface.
The multi-wing fan according to any one of claims 1 to 6. When the diameter of the inscribed circle of the blade with respect to the center of the rotation axis is A and the diameter of the circumscribed circle of the blade is B, the plurality of blades have an inner / outer diameter ratio (A / B) of 0.720 or more. It is 0.800 or less,
The multi-wing fan according to any one of claims 1 to 7. When the diameter of the inscribed circle of the blade with respect to the center of the rotation axis is A and the diameter of the circumscribed circle is B, the inner / outer diameter ratio (A / B) of the plurality of blades exceeds 0.800.
The multi-wing fan according to any one of claims 1 to 7. With a heat exchanger,
The multi-blade fan according to any one of claims 1 to 9, wherein air that has passed through the heat exchanger flows into the fan.
Equipped with an indoor unit.

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