JP2022114106A - Multiblade fan and indoor machine - Google Patents

Abstract

To suppress noise due to blade pitch noise generated when blades rotate, and to suppress channel resistance as compared with an unequal pitch arrangement.SOLUTION: A multiblade fan is equipped with a plurality of blades extended in an axial direction of a rotary shaft and arranged around the rotary shaft at predetermined pitches. The plurality of blades have an inner peripheral side part and an outer peripheral side part. The plurality of blades includes a blade having a stepped portion formed at a boundary between the inner peripheral side portion and the outer peripheral side portion by shifting the outer peripheral side portion in one direction in a thickness direction of the blade with respect to the inner peripheral side portion and coupling the inner peripheral side portion and the outer peripheral side portion. The blades adjacent to each other in the arranging direction of the plurality of blades are disposed while having different cross-sectional shapes orthogonal to the rotary shaft at a position on the rotary shaft where the stepped portion is formed on either one of the blades.SELECTED DRAWING: Figure 6

Description

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

2. Description of the Related Art A multi-blade fan is known that has a plurality of blades that extend along the axial direction of a rotating shaft and are arranged around the rotating shaft. Examples of this type of multi-blade fan include a centrifugal fan and a cross-flow fan provided in an air conditioner (Patent Document 1).

In the multi-blade fan described above, when the blades rotate, blade pitch sounds (periodic sounds), which are wind noises of the airflow between the blades, are generated and become noises during rotation. This blade pitch sound is generally called Nz sound, and the frequency is represented by the product (N×z) of the rotational speed N of the multi-blade fan and the number of blades z. The blade pitch sound has a higher frequency as the number of blades increases, and is determined by (frequency)=(rotation speed)×(number of blades).

Japanese Patent No. 2014-190543 Japanese Patent No. 60-17296

In a multi-blade fan, a structure is known in which blades are arranged with different pitches (hereinafter referred to as a non-uniform pitch arrangement) in order to suppress blade pitch noise (Patent Document 2). However, in the structure of unequal pitch arrangement, there is a possibility that the flow path resistance increases at the portion where the entire flow path along the blade surface between the adjacent blades becomes narrow.

The disclosed technology has been made in view of the above, and provides a multi-blade fan and an indoor fan that can suppress noise due to blade pitch noise that occurs when the blades rotate, and can suppress flow resistance compared to a non-uniform pitch arrangement. The purpose is to provide

One aspect of the multi-blade fan disclosed in the present application is a multi-blade fan including a plurality of blades extending along the axial direction of a rotating shaft and arranged at a predetermined pitch around the rotating shaft, wherein the plurality of blades has an inner peripheral side and an outer peripheral side, and when the inner peripheral side is used as a reference, the outer peripheral side of the plurality of blades is shifted in one direction in the blade thickness direction, and the inner peripheral side and the outer peripheral side are Blades adjacent to each other in the direction in which the blades are arranged, including blades having a stepped portion formed at the boundary between the inner peripheral side and the outer peripheral side by being connected, are connected to one of the blades on the rotating shaft. At the position where the stepped portion is formed, the cross-sectional shapes perpendicular to the rotation axis are arranged differently.

ADVANTAGE OF THE INVENTION According to one aspect of the multi-blade fan disclosed in the present application, it is possible to suppress noise due to blade pitch noise generated when the blades rotate, and to suppress flow path resistance as compared with a non-uniform pitch arrangement.

FIG. 1 is a cross-sectional view showing an indoor unit of an embodiment. FIG. 2 is a perspective view showing the 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 showing an enlarged example of blades of the multi-blade fan of the embodiment. FIG. 5 is an enlarged schematic diagram showing another example of the blades of the multi-blade fan of the embodiment. FIG. 6 is a cross-sectional view showing an example of stepped portions of a plurality of blades in the multi-blade fan of the embodiment. FIG. 7 is a cross-sectional view showing Modification 1 of the stepped portions of the plurality of blades in the multi-blade fan of the embodiment. FIG. 8 is a plan view showing Modification 1 of the stepped portions of the plurality of blades in the multi-blade fan of the embodiment. FIG. 9 is a plan view showing Modification 2 of the stepped portions of the plurality of blades in the multi-blade fan of the embodiment. FIG. 10 is a plan view showing Modification 3 of the stepped portions of the plurality of blades in the multi-blade fan of the embodiment. FIG. 11 is a diagram for explaining noise levels in the multi-blade fan of the embodiment.

Hereinafter, embodiments of the multi-blade fan and the indoor unit disclosed in the present application will be described in detail based on the drawings. It should be noted that the multi-blade fan and the indoor unit disclosed in the present application are not limited to the following examples.

(Indoor unit configuration)
FIG. 1 is a cross-sectional view showing an indoor unit of an embodiment. FIG. 2 is a perspective view showing the multi-blade fan of the embodiment. As shown in FIG. 1, the indoor unit 1 of the embodiment is an indoor unit that constitutes a refrigeration cycle device, for example, an air conditioner (not shown). A multi-blade fan 6 into which air flows, a fan casing 7 forming a flow path for the airflow sent from the multi-blade fan 6, and a main body casing 8 housing the heat exchanger 5, the multi-blade fan 6, and the fan casing 7 inside. And prepare. The body casing 8 has an air inlet 8a and an air outlet 8b.

The multi-blade fan 6 includes an impeller 11 in which a plurality of blades 12 are arranged around a rotating shaft 13, as shown in FIG. A plurality of impellers 11 are arranged in the axial direction X of the rotating shaft 13 , and the impellers 11 are connected to each other with a partition plate 14 interposed therebetween. End plates 15 having the rotating shaft 13 are provided at both ends of the rotating shaft 13 in the axial direction X, and the rotating shafts 13 at both ends of the multi-blade fan 6 are rotatably supported by bearings (not shown) of the fan casing 7 . ing.

The impellers 11 are connected to each other while being shifted in the circumferential direction around the rotating shaft 13 , that is, in the arrangement direction of the plurality of blades 12 . As a result, the impellers 11 lined up in the axial direction X of the rotating shaft 13 have a phase difference in blade pitch noise, so that noise when the multi-blade fan 6 rotates can be suppressed.

(Configuration of multi-blade 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 cross-flow fan in which air flows through the multi-blade fan 6 in a direction intersecting with the axial direction X of the rotating shaft 13 .

The multi-blade fan 6 extends along the axial direction X of the rotating shaft 13 as shown in FIG. 2, and has a plurality of blades arranged at a predetermined pitch P around the rotating shaft 13 as shown in FIG. 12 (equal pitch arrangement). A 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 pressure surface 17a and a suction surface 17b. The blade 12 is positioned on the side of the rotation center O of the multi-blade fan 6 and forms the blade surface of the blade 12, with an inner peripheral side portion 18a forming the blade surface of the blade 12 and positioned on the side opposite to the rotation center O side. and an outer peripheral side portion 18b. In the multi-blade fan 6 of the embodiment, the blades 12 are arranged in an even pitch arrangement, but the arrangement is not limited to an equal pitch arrangement, and the blades 12 may be arranged in an uneven pitch arrangement.

FIG. 4 is a schematic diagram showing an enlarged example of the blades 12 of the multi-blade fan 6 of the embodiment. As shown in FIG. 4 , the plurality of blades 12 are such that one blade surface 17 of the inner peripheral side portion 18 a and the outer peripheral side portion 18 b of the blades 12 and the other blade surface 17 have the thickness of the blade 12 . It includes a blade 12 that is shifted in one direction and has a stepped portion 20 that is formed by connecting an inner peripheral side portion 18a and an outer peripheral side portion 18b. In other words, in the multi-blade fan 6 of this embodiment, as an example, the outer peripheral side portion 18b is shifted in the rotation direction R of the multi-blade fan 6 along the thickness direction of the blades 12 with respect to the inner peripheral side portion 18a. The stepped portion 20 is formed, the inner peripheral side portion 18a and the outer peripheral side portion 18b are connected on the pressure surface 17a by the stepped portion 20 (end face 20a), and the inner peripheral side portion 18a and the outer peripheral side portion 18b are connected on the suction surface 17b. are connected by the stepped portion 20 (end face 20b). Here, the thickness direction of the blade 12 refers to a direction perpendicular to the direction along the chord of the blade 12 . In this case, the angle formed by the end surface 20a and the pressure surface 17a of the inner peripheral side portion 18a in the cross section perpendicular to the axial direction of the rotating shaft 13 is 90 degrees, but it may be larger than 90 degrees. Also, in the cross section perpendicular to the axial direction of the rotating shaft 13, the angle formed by the end surface 20b and the negative pressure surface 17b of the outer peripheral side portion 18b is 90 degrees, but it may be larger than 90 degrees.

In the multi-blade fan 6 of this embodiment, for example, all of the plurality of blades 12 are formed with the stepped portions 20, but the structure is not limited to this, and at least one blade 12 among the plurality of blades 12 has a stepped portion. Any structure having the portion 20 may be used. The multi-blade fan 6 of this embodiment has a cross-sectional shape (hereinafter referred to as , referred to as a cross-sectional shape of the blades 12 ) are arranged adjacent to each other in the arrangement direction of the plurality of blades 12 . In other words, the blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 have different cross-sectional shapes of the blades 12 crossing the blade surface 17 and along the blade chord. In the multi-blade fan 6, at least two blades 12 have different cross-sectional shapes in the arrangement direction of the plurality of blades 12, and it is sufficient that the two blades 12 are arranged adjacent to each other. 12, the frequency of the blade pitch sound can be varied.

In the multi-blade fan 6, the pressure surface 17a and the suction surface 17b are shifted in one direction in the thickness direction of the blades 12, and a stepped portion 20 is formed by connecting the inner peripheral side portion 18a and the outer peripheral side portion 18b. , only one of the inner peripheral side portion 18a and the outer peripheral side portion 18b is shifted in the thickness direction of the blades 12, so that there is a gap between adjacent blades 12 like a structure in which the blades 12 are arranged at uneven pitches. By narrowing the pitch of the entire flow path, an increase in flow path resistance can be suppressed. That is, the multi-blade fan 6 can suppress flow resistance between the adjacent blades 12 compared to a structure in which the blades 12 are arranged at uneven pitches. In other words, in the multi-blade fan 6, in the flow path between the adjacent blades 12, there is a risk that the flow path resistance will increase at the stepped portion 20. It is possible to avoid an increase in flow path resistance in the entire flow path between

For example, as shown in FIG. 4, the stepped portion 20 of the blade 12 of the multi-blade fan 6 forms a concave portion on the pressure surface 17a, and the suction surface 17b has a height corresponding to the depth of the concave portion on the pressure surface 17a. It corresponds to a structure that forms a convex portion of height. That is, in the thickness direction of the blade 12, the pressure surface 17a of the inner peripheral side portion 18a is recessed more than the pressure surface 17a of the outer peripheral side portion 18b by the stepped portion 20, and the suction surface 17b of the inner peripheral side portion 18a is located on the outer peripheral side. It protrudes from the negative pressure surface 17b of the portion 18b.

Here, although not shown, for example, a reference example in which a concave portion is formed on the pressure surface 17a without changing the suction surface 17b of the blade 12 will be compared with an embodiment in which the stepped portion 20 is formed in the blade 12. . In this case, the blade 12 having the stepped portion 20 in the embodiment has a concave portion formed on the pressure surface 17a and a convex portion formed on the suction surface 17b in the thickness direction of the blade 12, so that the suction surface 17b is changed. This is different from the reference example in which a concave portion is formed on the pressure surface 17a without the pressure surface 17a.

In the reference example in which a recess is formed in the pressure surface 17a without changing the suction surface 17b, only one blade surface 17 (pressure surface 17a) of the blade 12 is affected by the recess to create a phase difference in blade pitch noise. However, this action cannot be applied to the other blade surface 17 (suction surface 17b) of the blade 12 . On the other hand, according to the stepped portion 20 of the blade 12 in the embodiment, the pressure surface 17a is given the action of creating a phase difference in the blade pitch sound by the concave portion, and the convex portion creates a phase difference in the blade pitch sound. The negative pressure surface 17b is provided with an action to force the pressure.

In this way, the stepped portion 20 in the embodiment causes a phase difference in the blade pitch noise on both the pressure surface 17a and the suction surface 17b of the blade 12, thereby increasing the phase difference in the blade pitch noise. The effect of reducing noise is higher than in the example. Further, in the stepped portion 20 of the embodiment, by making the inclination angles of the end faces 20a and 20b of the stepped portion 20 (to be described later) different from each other, the pressure surface 17a causes a phase difference in blade pitch noise, and the suction surface 17b causes blade pitch noise. Since the timing of cutting the wind differs depending on the position of the blade 12, the phase of the noise differs, and they interfere to enhance the noise reduction effect.

Further, for example, in the reference example in which the recesses are formed only on one blade surface 17 of the blade 12, if the phase difference to be generated in the blade pitch noise is to be increased, it is necessary to form the recesses large. There is a problem that the mechanical strength of the blade 12 is lowered due to the thinning of the blade 12 . Furthermore, in the reference example, in order to secure the mechanical strength of the blades 12 while forming a large concave portion, the thickness of the blades 12 must be increased. is narrowed, and the flow path resistance between adjacent blades 12 is increased.

In the multi-blade fan 6, the outer peripheral side portions 18b of the blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 are aligned in the rotation direction R of the multi-blade fan 6 with respect to the inner peripheral side portions 18a. By shifting, narrowing of the flow path between the adjacent blades 12 can be avoided, and flow path resistance can be suppressed. As a result, pressure loss in the airflow passing along the blade surface 17 in the flow path between the blades 12 can be suppressed, and the power consumption of the motor (not shown) that drives the multi-blade fan 6 can be reduced. In other words, it is possible to increase the air volume of the multi-blade fan 6 by reducing the pressure loss of the airflow generated in the flow path between the adjacent blades 12 .

In each blade 12 adjacent to the arrangement direction of the plurality of blades 12, the direction in which the inner peripheral side portion 18a is shifted with respect to the outer peripheral side portion 18b is not limited to the rotation direction R of the multi-blade fan 6, The wings 12 may also be offset in the direction opposite to the direction of rotation R.

Although not shown, the multi-blade fan 6 may have a structure in which, for example, the blades 12 having the stepped portion 20 and the blades 12 without the stepped portion 20 are arranged adjacent to each other. Even with this structure, it is possible to make the frequencies different between the blades 12 having the stepped portion 20 and the blades 12 without the stepped portion 20, and the effect of suppressing the noise of the multi-blade fan 6 can be obtained. .

As described above, the blades 12 having different cross-sectional shapes between the adjacent blades 12 means that the cross-sectional shapes of the adjacent blades 12 perpendicular to the axial direction X of the rotating shaft 13 are It means that the blades 12 have different cross-sectional shapes when compared at the same position on the blades 12 passing through the stepped portion 20 . Such different blade 12 cross-sectional shapes include a structure in which the stepped portion 20 has a different cross-sectional shape, and a structure in which the stepped portion 20 has a different position in the direction along the blade chord.

(Cross-sectional shape of step)
The stepped portion 20 has two end surfaces 20a and 20b that intersect with the blade surface 17 of the blade 12, as shown in FIG. An end surface 20a of the stepped portion 20 on the side of the pressure surface 17a intersects the pressure surface 17a of the blade 12, and is formed across the pressure surface 17a on the side of the inner peripheral side portion 18a and the pressure surface 17a on the side of the outer peripheral side portion 18b. ing. Similarly, the end surface 20b of the stepped portion 20 on the side of the suction surface 17b intersects the suction surface 17b of the blade 12, and is formed across the suction surface 17b of the inner peripheral side portion 18a and the suction surface 17b of the outer peripheral side portion 18b. It is Moreover, the end face 20a and the end face 20b are located on the same plane. Further, the stepped portion 20 is formed over the axial direction X of the rotating shaft 13 in the blade 12 , but may be formed in a part of the blade 12 in the axial direction X.

In the structure in which the cross-sectional shape of the stepped portion 20 is different between adjacent blades 12, the amount of displacement of the pressure surface 17a of the outer peripheral side portion 18b with respect to the pressure surface 17a of the inner peripheral side portion 18a, that is, the displacement in the direction intersecting the blade surface 17 A structure in which the depth of the step portion 20 is different is included. In other words, this structure is a structure in which the widths of the end surfaces 20a and 20b of the stepped portion 20 in the direction intersecting the blade surface 17 are different. In addition, the structure in which the cross-sectional shape of the stepped portion 20 differs between the blades 12 includes a structure in which the end surfaces 20a and 20b have different inclination angles with respect to the blade surface 17, that is, a structure in which the angles formed by the blade surface 17 and the end surfaces 20a and 20b are different. included. In this way, in each stepped portion 20 between adjacent blades 12 in the arrangement direction of the plurality of blades 12, the flow direction and wind speed of the air passing over the surfaces of the end faces 20a and 20b can be made different. As a result, the pitch angles of the end surfaces 20a and 20b with respect to the blade surface 17 are different, so that the adjacent blades 12 can have different blade pitch noise frequencies.

Also, the depth of the stepped portion 20 is set to, for example, about 1/2 of the thickness of the blade 12 at the center of the blade chord length L, but the depth is not limited. If the thickness of the blades 12 is thin, it may not be possible to ensure the depth of the stepped portion 20 so that the frequency of the blade pitch sound varies appropriately between the blades 12 . In this case, the depth of stepped portion 20 may be formed to be equal to the thickness of blade 12 or may be formed to be greater than the thickness of blade 12 . In addition, the plurality of blades 12 includes blades 12 in which stepped portions 20 are formed such that end faces 20a and 20b are positioned at the maximum thickness portion where the thickness of blades 12 is maximized. For example, in the direction along the chord of the blade 12, the maximum thickness portion of the blade 12 is positioned closer to the inner peripheral side portion 18a than the center of the blade chord length L, and the stepped portion 20 is formed on the inner peripheral side portion 18a. is formed.

FIG. 5 is an enlarged schematic diagram showing another example of the blades 12 of the multi-blade fan 6 of the embodiment. As shown in FIG. 5, the blade 12 of another example is formed thinner than the blade 12 shown in FIG. In the stepped portion 20, the pressure surface 17a and the suction surface 17b, which are the blade surfaces 17 of the inner peripheral side portion 18a, are opposite to the pressure surface 17a and the suction surface 17b, which are the blade surfaces 17 of the outer peripheral side portion 18b. It is shifted larger than the thickness of the outer peripheral side portion 18b along the . In this way, the depth of the stepped portion 20 may be formed to be greater than the thickness of the portion of the blade 12 where the stepped portion 20 is formed.

In the blade 12 of the example shown in FIG. 17b is shifted more than the thickness of the outer peripheral side portion 18b along the end face 20b, so the end face 20a and the end face 20b of the stepped portion 20 are separated from each other in the direction along the chord. The distance between the end face 20a and the end face 20b is, for example, about the thickness of the outer peripheral side portion 18b along the end face 20b, so that the mechanical strength of the stepped portion 20 is ensured.

FIG. 6 is a cross-sectional view showing an example of the stepped portions 20 of the plurality of blades 12 in the multi-blade fan 6 of the embodiment. As shown in FIG. 6 , the blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 have different depths of the stepped portions 20 . It is formed so as to gradually increase with respect to R. The depth of the stepped portion 20 is not limited to the structure in which the depth of the step portion 20 gradually changes along the rotation direction R of the multi-blade fan 6. The depth of each stepped portion 20 may vary irregularly. The multi-blade fan 6 may be formed so that the stepped portions 20 of the adjacent blades 12 have different depths, so that the adjacent blades 12 can have different blade pitch noise frequencies.

(Modification 1)
FIG. 7 is a cross-sectional view showing Modification 1 of the stepped portions 20 of the plurality of blades 12 in the multi-blade fan 6 of the embodiment. FIG. 8 is a plan view showing Modification 1 of the stepped portions 20 of the plurality of blades 12 in the multi-blade fan 6 of the embodiment.

As shown in FIGS. 7 and 8, in Modification 1, the blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 have different positions of the stepped portions 20 in the direction along the chord. The position of 20 is formed so as to gradually change along the rotation direction R of the multi-blade fan 6 from the inner peripheral side portion 18a side to the outer peripheral side portion 18b side. The position of the stepped portion 20 is not limited to the structure in which the position of the stepped portion 20 gradually changes along the rotation direction R. The positions may vary randomly. The multi-blade fan 6 may be formed so that the positions of the stepped portions 20 are different between the adjacent blades 12, and the frequencies of the blade pitch sounds can be further differentiated between the adjacent blades 12.

Adjacent blades 12 may have different cross-sectional shapes by combining the depth of the stepped portion 20 and the position of the stepped portion 20, and all the blades 12 may have different cross-sectional shapes. may be formed.

In the multi-blade fan 6 shown in Figs. The cross-sectional shape of the blades 12 in one blade 12 may be formed so as to change along the axial direction X of the rotating shaft 13 .

(Modification 2)
FIG. 9 is a plan view showing Modified Example 2 of the stepped portions 20 of the plurality of blades 12 in the multi-blade fan 6 of the embodiment. As shown in FIG. 9 , in one blade 12 , the end surfaces 20 a and 20 b of the stepped portion 20 are inclined with respect to the axial direction X of the rotating shaft 13 , so that the cross-sectional shape of the blade 12 is aligned with the axis of the rotating shaft 13 . It is changing in direction X. Therefore, in one blade 12, the position of the stepped portion 20 in the direction along the blade chord (the position of the end surfaces 20a and 20b) changes according to the position of the rotating shaft 13 in the axial direction. In addition, since the thickness of the blade 12 in the direction along the chord is not uniform, the depth of the step 20 changes as the position of the step 20 in the direction along the chord changes.

In Modification 2, the two blades 12 have different inclination angles θ of the end surfaces 20a and 20b with respect to the axial direction X of the rotating shaft 13 in the arrangement direction of the plurality of blades 12, that is, the rotation direction R of the multi-blade fan 6. are placed next to each other. For this reason, for example, in the DD cross section in FIG. 9, the adjacent blades 12 have different cross-sectional shapes, so that the adjacent blades 12 can have different blade pitch noise frequencies.

The blade 12 having the stepped portion 20 described above is formed by injection molding using a molding die. It is formed by drawing in the orthogonal direction, that is, the axial direction X of the rotating shaft 13 . Therefore, by adjusting the draft angle of the blade 12 with respect to the mold when molding the blade 12, the inclination angle θ of the end surfaces 20a and 20b of the stepped portion 20 with respect to the axial direction X of the rotating shaft 13 can be easily changed. can. Therefore, by making the inclination angles θ of the end surfaces 20a and 20b of the stepped portion 20 with respect to the axial direction X of the rotating shaft 13 different between adjacent blades 12, the position and depth of the stepped portion 20 can be easily varied. can.

In the step portion 20, the end face 20a on the side of the pressure surface 17a and the end face 20b on the side of the suction surface 17b have different inclination angles with respect to the axial direction X of the rotating shaft 13. As shown in FIG. As a result, the phase in which the stepped portion 20 generates the blade pitch noise of the airflow on the pressure surface 17a side can be made different from the phase in which the stepped portion 20 generates the blade pitch noise of the airflow on the suction surface 17b side. Noise caused by blade pitch noise can be reduced. When the blade 12 molded by the molding die is pulled out from the molding die in the axial direction X of the rotating shaft 13, the end surface 20a of the stepped portion 20 is pulled in the direction opposite to the direction in which the blade 12 is pulled out from the molding die. The end surfaces 20a and 20b are inclined so that the position of the end surface 20b gradually approaches the outer peripheral side portion 18b as the position of .

(Modification 3)
FIG. 10 is a plan view showing Modified Example 3 of the stepped portions 20 of the plurality of blades 12 in the multi-blade fan 6 of the embodiment. As shown in FIG. 10 , in Modification 3, the cross-sectional shape of the stepped portion 20 in the direction along the chord is the same between the blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 , and The length H of the step portion 20 with respect to X is different. In Modified Example 3, since the length H of the stepped portion 20 is different between the adjacent blades 12, for example, in the EE cross section in FIG. The frequency of the blade pitch sound can be made different between adjacent blades 12 .

Although not shown, adjacent blades 12 may be formed so that the lengths H of the stepped portions 20 are different in combination with the structures of the stepped portions 20 of the above-described embodiment and modified examples 1 and 2. , the effect of the embodiment is further enhanced. Also, the multi-blade fan 6 may have the blades 12 of the embodiment and modified examples 1 to 3, respectively.

(Action of Stepped Part)
As described above, the adjacent blades 12 of the multi-blade fan 6 have one of the stepped portions 20 in the embodiment and modified examples 1 to 3, so that the cross-sectional shape of each blade 12 is different. The frequency of the wing pitch sound is made different between them. As a result, it is possible to disperse the frequency of the blade pitch sound between the adjacent blades 12 and suppress the noise caused by the blade pitch sound generated when the blades 12 rotate. In addition, since the inner peripheral side portion 18a and the outer peripheral side portion 18b of the blade 12 are connected by the stepped portion 20, a decrease in mechanical strength is suppressed.

FIG. 11 is a diagram for explaining the noise level in the multi-blade fan 6 of the embodiment. In FIG. 11, the vertical axis indicates the noise level [dB], and the horizontal axis indicates the noise frequency [Hz]. In FIG. 11, the multi-blade fan 6 of the example is indicated by a dashed line, and the multi-blade fan of the comparative example is indicated by a solid line.

In the multi-blade fan of the comparative example, the blades 12 do not have the stepped portion 20 and the blades 12 have the same cross-sectional shape in the arrangement direction of the plurality of blades 12 . As shown in FIG. 11, in the multi-blade fan 6 of the embodiment, the cross-sectional shape of the blades 12 having the stepped portion 20 is different between the blades 12 adjacent to each other in the arrangement direction of the blades 12, so that the blade pitch between the blades 12 is different. By making the sound frequencies different, the noise level can be reduced in the vicinity of the primary frequency indicated by arrow F1 and in the vicinity of the secondary frequency indicated by arrow F2.

(Inner/outer diameter ratio of blade)
The plurality of blades 12 of the multi-blade fan 6 described above, as shown in FIG. 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 blades 12, by varying the frequency of the blade pitch sound with the stepped portion 20 in the embodiment, noise can be reduced compared to a multi-blade fan without the stepped portion 20. can be reduced.

Further, the inner/outer diameter ratio (A/B) of the blades 12 is increased in order to increase the air volume of the multi-blade fan 6. When the inner/outer diameter ratio (A/B) of the blades 12 exceeds 0.800 As the wind speed passing between the blades 12 increases so as to penetrate the fan 6, there is a risk of causing an increase in noise. Even in such a case, by varying the phase of the blade pitch sound by the stepped portion 20, it is possible to increase the air volume while avoiding the deterioration of the noise.

(effect)
As described above, in the multi-blade fan 6, the plurality of blades 12 has the inner peripheral side portion 18a and the outer peripheral side portion 18b. A stepped portion 20 is formed at the boundary between the inner peripheral side portion 18a and the outer peripheral side portion 18b by being shifted in one direction in the thickness direction of the blade 12 and connecting the inner peripheral side portion 18a and the outer peripheral side portion 18b. Includes wings 12 . The blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 passing through the stepped portion 20 in the axial direction X of the rotating shaft 13 are arranged at a position where the stepped portion 20 is formed on one of the blades 12 on the rotating shaft 13. They are arranged with different cross-sectional shapes perpendicular to the rotating shaft 13 . As a result, by changing the frequency of the blade pitch sound of the adjacent blades 12 in the plurality of blades 12, noise caused by the blade pitch sound generated when the blades 12 rotate can be suppressed.

In addition, in the blades 12 of the multi-blade fan 6, the pressure surface 17a and the suction surface 17b are shifted in one direction in the thickness direction of the blades 12, so that the boundary between the inner peripheral side portion 18a and the outer peripheral side portion 18b. By having the formed stepped portion 20, only one of the inner peripheral side portion 18a and the outer peripheral side portion 18b is shifted in the thickness direction of the blades 12, so that the blades 12 are arranged at uneven pitches. Thus, an increase in flow path resistance in the entire flow path between adjacent blades 12 is suppressed. That is, the multi-blade fan 6 can suppress flow resistance between the adjacent blades 12 compared to a structure in which the blades 12 are arranged at uneven pitches.

In the multi-blade fan 6, the inner peripheral side portion 18a and the outer peripheral side portion 18b are connected at the stepped portion 20, so that the mechanical strength of the blades 12 can be suppressed from being lowered. In addition, in the multi-blade fan 6, the blade surfaces 17 of the inner peripheral side portion 18a are shifted in the thickness direction of the blades 12 with respect to the blade surfaces 17 of the outer peripheral side portion 18b, thereby forming the stepped portion 20. As a result, it is possible to avoid a large change in the thickness of the blade 12 in the direction along the chord, suppress the deterioration of the mechanical strength of the blade 12, and suppress the deterioration of the releasability when removing the blade 12 from the molding die. can be

In the multi-blade fan 6, two blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 have different positions of the stepped portions 20 in the direction along the blade chord. By making the positions of the stepped portions 20 different between the adjacent blades 12 in this way, the frequency of the blade pitch sound can be made different between the adjacent blades 12, so that the noise caused by the blade pitch sound can be suppressed. .

In the multi-blade fan 6 , two blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 have different inclination angles θ of the end faces 20 a and 20 b of the stepped portion 20 with respect to the axial direction X of the rotating shaft 13 . Thus, by making the inclination angles θ of the end surfaces 20a and 20b of the stepped portion 20 different, the position and depth of the stepped portion 20 in the direction along the blade chord can be easily changed. Further, by adjusting the draft angle of the blade 12 with respect to the molding die, the positions of the end surfaces 20a and 20b of the stepped portion 20 in the direction along the blade chord and the depth of the stepped portion 20 can be easily adjusted. As a result, it is possible to easily form a plurality of blades 12 having different cross-sectional shapes in the direction along the blade chord.

In the multi-blade fan 6 , two blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 have different lengths H of the stepped portions 20 in the axial direction X of the rotating shaft 13 . By making the length H of the stepped portion 20 different between the adjacent blades 12 in this way, the frequency of the blade pitch sound can be made different between the adjacent blades 12, so that the noise caused by the blade pitch sound can be suppressed. can be done.

In the multi-blade fan 6 , the blades 12 adjacent to each other in the arrangement direction of the plurality of blades 12 have different cross-sectional shapes of the blades 12 perpendicular to the axial direction X of the rotating shaft 13 . In this way, by making the frequencies of the blade pitch sounds different between all the adjacent blades 12 over the entire circumference in the arrangement direction of the plurality of blades 12, the effect of suppressing the noise caused by the blade pitch sounds can be further enhanced.

Further, in the multi-blade fan 6, one blade surface 17 of the inner peripheral side portion 18a and the outer peripheral side portion 18b is shifted with respect to the other blade surface 17 at each stepped portion 20 of the plurality of blades 12. The orientation is the same as the rotation direction R of the multi-blade fan 6 . Since the blades 12 are shifted in one direction with respect to the rotation direction R, the flow paths between the adjacent blades 12 are properly secured so that the flow paths between the adjacent blades 12 are not narrowed. The air volume of the multi-blade fan 6 can be increased by suppressing the pressure loss of the airflow between the blades 12.例文帳に追加In addition, the multi-blade fan 6 can reduce the power consumption for driving the multi-blade fan 6 because the flow resistance of the airflow between the adjacent blades 12 can be suppressed.

In the stepped portion 20 of the multi-blade fan 6, one of the inner peripheral side portion 18a and the outer peripheral side portion 18b has one blade surface 17 and the other blade surface 17 extends along the end surfaces 20a and 20b. is shifted more than the thickness of As a result, even when the thickness of the blades 12 is thin, the amount of displacement between the inner peripheral side portion 18a and the outer peripheral side portion 18b that are displaced in the thickness direction of the blades 12 is properly ensured, and the blade pitch noise is generated between the blades 12. can have different frequencies.

Further, in the multi-blade fan 6, when the diameter of the inscribed circle C1 of the blades 12 with respect to the rotation center O of the rotating shaft 13 is A, and the diameter of the circumscribed circle C2 of the blades 12 is B, the blades 12 has an inner/outer diameter ratio (A/B) of 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 blades 12, the stepped portion 20 makes the phase of the blade pitch sound different, thereby reducing noise compared to a multi-blade fan without the stepped portion 20. can.

In the multi-blade fan 6, the plurality of blades 12 have an inner and outer diameter The ratio (A/B) exceeds 0.800. If the inner/outer diameter ratio (A/B) of the blades 12 exceeds 0.800, the wind speed passing between the blades 12 so as to penetrate the multi-blade fan 6 may increase and cause noise deterioration. By varying the phase of the blade pitch sound by the stepped portion 20, it is possible to increase the air volume while avoiding the deterioration of the noise.

Although the multi-blade fan disclosed in the present application was used as a cross-flow fan in the embodiments, it is not limited to a cross-flow fan. The multi-blade fan may be applied to, for example, a centrifugal fan such as a sirocco fan, and the same effects as in this embodiment can be obtained.

1 Indoor unit 5 Heat exchanger 6 Multi-blade fan 12 Blade 13 Rotating shaft 17 Blade surface 17a Positive pressure surface 17b Suction surface 18a Inner peripheral side 18b Outer peripheral side 20 Stepped portion 20a, 20b End faces A, B Diameter (A/B) Inner/outer diameter ratio C1 Inscribed circle C2 Circumscribed circle H Length L Blade chord length X Axial direction θ Inclination angle

Claims (11)

A multi-blade fan having a plurality of blades extending along the axial direction of a rotating shaft and arranged at a predetermined pitch around the rotating shaft,
The plurality of blades have an inner peripheral side and an outer peripheral side,
When the inner peripheral side portion is used as a reference, the outer peripheral side portion of the plurality of blades is shifted in one direction in the thickness direction of the blades, and the inner peripheral side portion and the outer peripheral side portion are connected to each other. including a wing having a stepped portion formed at the boundary between the peripheral side portion and the outer peripheral side portion;
The blades adjacent to each other in the arrangement direction of the plurality of blades are arranged with different cross-sectional shapes perpendicular to the rotation shaft at a position where the stepped portion is formed on one of the blades on the rotation shaft. wing fan. The blades adjacent to each other in the arrangement direction of the plurality of blades have different positions of the stepped portions in the direction along the chord,
The multi-blade fan according to claim 1. The stepped portion has an end face that intersects with the blade surface of the blade,
The blades adjacent to each other in the arrangement direction of the plurality of blades have mutually different inclination angles of the end faces with respect to the axial direction of the rotating shaft,
The multi-blade fan according to claim 1 or 2. The stepped portion has a pressure side end face formed on the pressure side of the blade and a suction side end face formed on the suction side of the blade,
The end face on the pressure side and the end face on the suction side have different angles of inclination with respect to the axial direction of the rotating shaft,
A multi-blade fan according to any one of claims 1 to 3. The blades adjacent to each other in the arrangement direction of the plurality of blades have different lengths of the stepped portions in the axial direction of the rotating shaft,
A multi-blade fan according to any one of claims 1 to 4. The blades adjacent to each other in the arrangement direction of the plurality of blades have different cross-sectional shapes of the blades orthogonal to the axial direction of the rotating shaft,
A multi-blade fan according to any one of claims 1 to 5. The plurality of blades have the stepped portion, and in each stepped portion, the direction in which one of the blade surfaces of the inner peripheral side portion and the outer peripheral side portion is shifted with respect to the other blade surface is the multiplicity of directions. are oriented in the same direction with respect to the direction of rotation of the blade fan,
A multi-blade fan according to any one of claims 1 to 6. The stepped portion has an end face that intersects with the blade surface of the blade,
In the stepped portion, each blade surface of one of the inner peripheral side portion and the outer peripheral side portion is shifted from the other blade surface by a greater amount than the thickness of the other along the end surface.
A multi-blade fan according to any one of claims 1 to 7. The plurality of blades have an inner/outer diameter ratio (A/B) of 0.720 or more, where A is the diameter of an inscribed circle of the blades with respect to the center of rotation of the rotating shaft, and B is the diameter of the circumscribed circle of the blades. , is less than or equal to 0.800;
A multi-blade fan according to any one of claims 1 to 8. The plurality of blades have an inner/outer diameter ratio (A/B) exceeding 0.800, where A is the diameter of an inscribed circle of the blades with respect to the center of rotation of the rotating shaft, and B is the diameter of the circumscribed circles of the blades.
A multi-blade fan according to any one of claims 1 to 8. a heat exchanger;
The multi-blade fan according to any one of claims 1 to 10, into which air that has passed through the heat exchanger flows;
indoor unit.

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