JP2020079567A - Centrifugal fan - Google Patents

Abstract

To provide a centrifugal fan capable of reducing noise, and capable of suppressing deterioration of ventilation efficiency due to reduction in the area of a blade, or improving the ventilation efficiency.SOLUTION: A centrifugal fan 1 comprises an annular side plate 2 having an air inlet 5, a main plate 3 provided oppositely to the side plate 2, and a plurality of blades 4 arranged at a predetermined interval in a rotation direction between the side plate 2 and the main plate 3. The blade 4 has a through hole 10 that penetrates a suction surface 8 and a pressure surface 9 and is not opened at a trailing edge 7.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a centrifugal fan used in a centrifugal blower.

Conventionally, a centrifugal fan used for a centrifugal blower is known.
The centrifugal fan described in Patent Document 1 has a plurality of concavo-convex shapes (hereinafter referred to as serrations) at the trailing edge of the blade. As a result, this centrifugal fan is configured such that the air blown from the pressure surface side of the trailing edge of the blade and the rear of the blade at the outlet of the flow passage formed between the blades (hereinafter, referred to as inter-blade flow passage). Noise is reduced by reducing the pressure difference at the boundary with the air blown from the negative pressure surface side of the edge.

Japanese Patent Laid-Open No. 4324474

  However, since the centrifugal fan described in Patent Document 1 has the serrations at the trailing edge of the blade, the area for performing the work of blowing out air near the trailing edge of the blade is reduced. Therefore, this centrifugal fan has a problem that the blowing efficiency is reduced. The ventilation efficiency refers to the amount of air blown by the fan with respect to the energy required to rotate the fan.

  In view of the above points, an object of the present invention is to provide a centrifugal fan capable of reducing noise and suppressing a decrease in air flow efficiency due to a reduction in blade area, or improving air flow efficiency. ..

In order to achieve the above object, the invention according to claim 1 is
In a centrifugal fan used in a centrifugal blower,
An annular side plate (2) having an air inlet (5),
A main plate (3) provided to face the side plate,
A plurality of wings (4) arranged at predetermined intervals in the rotational direction between the side plate and the main plate,
The blade has a through hole (10) which penetrates the suction surface (8) and the pressure surface (9) and which is not opened at the trailing edge (7).

  According to this, in the predetermined inter-blade flow path formed between the blades, the air flowing in the vicinity of the pressure surface passes through the through hole and is located on the rear side in the rotation direction from the predetermined inter-blade flow path. It flows to the other inter-blade flow path. Therefore, in the other inter-blade flow paths, the flow of air with a high flow velocity in the vicinity of the suction surface is pushed out toward the rear side in the rotational direction by the air that has flowed in from the through holes, and spreads to the pressure surface side with a slow flow velocity. , The flow velocity deviation at the outlet of the blade-to-blade passage approaches a uniform value. Therefore, the vortex formed near the trailing edge of the blade is reduced, so that noise can be reduced. The flow velocity deviation refers to the non-uniformity of the flow velocity at the outlet of the blade-to-blade flow passage.

  By the way, if the area of the blades is reduced by the through holes, there is a concern that the blowing efficiency may be reduced. On the other hand, in the invention according to claim 1, since the through hole is not opened at the trailing edge, the wall surface between the through hole and the trailing edge of the blade allows air to flow to the outside of the outlet of the inter-blade passage. It is possible to do the work of pushing. Therefore, this centrifugal fan has a wall surface between the through hole and the trailing edge of the blade to suppress the decrease in the air blowing efficiency due to the decrease in the blade area due to the through hole, or to improve the air blowing efficiency. can do.

  The reference numerals in parentheses that are given to the respective components and the like indicate an example of a correspondence relationship between the components and the like and specific components and the like described in the embodiments described later.

It is a perspective view of the centrifugal fan which concerns on 1st Embodiment. It is a side view which shows a part of centrifugal fan which concerns on 1st Embodiment. It is explanatory drawing for demonstrating the hole width which a blade has in the cross section perpendicular|vertical to the rotating shaft of a centrifugal fan. It is a side view which shows a part of centrifugal fan which concerns on 2nd Embodiment. It is a side view which shows a part of centrifugal fan which concerns on 3rd Embodiment. It is a side view which shows a part of centrifugal fan which concerns on 4th Embodiment. It is a side view which shows a part of centrifugal fan which concerns on 5th Embodiment. It is a side view which shows a part of centrifugal fan which concerns on 6th Embodiment. It is a side view which shows a part of centrifugal fan which concerns on 7th Embodiment. FIG. 10 is a cross-sectional view near the trailing edge of the blade taken along line XX of FIG. 9. It is explanatory drawing for demonstrating Powell's vortex sound theory. FIG. 6 is an analysis diagram showing a flow velocity distribution in an inter-blade passage in the case where serrations are provided at the trailing edges of the blades as a comparative example. As a first comparative example, it is a schematic diagram when serrations are provided on the trailing edge of the blade. As a second comparative example, it is a schematic diagram when serrations are provided on the trailing edge of the blade. As a third comparative example, it is a schematic diagram when serrations are provided on the trailing edge of the blade. As a fourth comparative example, it is a schematic diagram when serrations are provided on the trailing edge of the blade. It is a schematic diagram which shows an example of the shape of a through-hole. It is a schematic diagram which shows another example of the shape of a through-hole. It is a schematic diagram which shows another example of the shape of a through-hole. It is the figure which showed the exit of the flow path between blades in the perspective view of a centrifugal fan. FIG. 21 is an analysis diagram showing a flow velocity distribution when the blade is provided with serrations at the outlet of the inter-blade passage shown in FIG. 20. FIG. 21 is an analysis diagram showing a flow velocity distribution when a blade has a through hole at the outlet of the inter-blade passage shown in FIG. 20. Among the outlets of the inter-blade passage shown in FIG. 20, the flow velocity deviations are shown for the upper, middle, and lower portions of the blade in the case of the base shape, in the case of providing the blade with serrations, and in the case of providing the blade with through holes. It is a graph. 21 is a graph showing flow velocity deviations of the upper, middle, and lower portions of the blade among the outlets of the inter-blade passage shown in FIG. 20 in the case of the base shape and when the diameter of the through hole is changed. Of the outlets of the blade-to-blade passage shown in FIG. 20, a graph showing the flow velocity deviations of the upper, middle and lower portions of the blade when the base shape is used and when the positions of the through holes are changed in the radial direction of the centrifugal fan. is there. 7 is a graph showing specific noise and fan efficiency in the case of a base shape, when the blade is provided with serrations, in the case of the through hole of the first embodiment, and in the case of the through hole of the second embodiment. It is an analysis figure which shows the total pressure distribution of the air which flows along the positive pressure surface of a blade|wing in the case of a base shape. It is an analysis figure which shows the total pressure distribution of the air which flows along the positive pressure surface of a blade|wing, when the through-hole of 2nd Embodiment is provided in the blade|wing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the following embodiments, the same or equivalent portions will be denoted by the same reference numerals, and description thereof will be omitted.

(First embodiment)
The first embodiment will be described with reference to the drawings. The centrifugal fan of this embodiment is used for a centrifugal blower included in an air conditioner or a ventilation device.

  As shown in FIGS. 1 and 2, the centrifugal fan 1 includes a side plate 2, a main plate 3, and a plurality of blades 4. The side plate 2 is formed in an annular shape and has a suction port 5 for sucking air in the center thereof. The side plate 2 has a bell mouth shape that approaches the main plate 3 side from the suction port 5 at the center thereof toward the outer peripheral side. The outer peripheral portion of the side plate 2 may have an annular shape that is perpendicular to the rotation axis Ax of the centrifugal fan 1.

  The main plate 3 is formed in a disk shape and is provided so as to face the side plate 2. The main plate 3 has a shape such that its central portion projects toward the suction port 5 side. The motor fastening portion 31 provided at the center of the main plate 3 is fixed to the shaft of an electric motor (not shown).

  The plurality of blades 4 are arranged between the main plate 3 and the side plates 2 at predetermined intervals in the rotation direction. In the present embodiment, one side of the plurality of blades 4 in the rotation axis Ax direction is fixed to the main plate 3, and the other side of the rotation axis Ax direction is fixed to the side plate 2. That is, the main plate 3, the side plate 2, and the plurality of blades 4 are integrally formed. The blades 4 extend rearward in the rotational direction from the leading edge 6 toward the trailing edge 7. Therefore, this centrifugal fan 1 is a turbo fan. In the figure, the rotation direction of the centrifugal fan 1 is indicated by an arrow R.

  The centrifugal fan 1 rotates together with the shaft of the electric motor. When the centrifugal fan 1 rotates, the air sucked from the suction port 5 passes through the flow path between the plurality of blades 4 (hereinafter referred to as inter-blade flow path) from the leading edge 6 side to the trailing edge 7 side of the blade 4. Flow toward. The air flowing through the inter-blade passage is blown radially outward from the air outlet formed between the trailing edge 7 of the blade 4, the side plate 2 and the main plate 3.

  Each of the plurality of blades 4 has at least one through hole 10 penetrating the suction surface 8 and the pressure surface 9. The suction surface 8 is a surface of the blade 4 on the rear side in the rotation direction. The positive pressure surface 9 is a surface of the blade 4 on the front side in the rotation direction, and is also called a pressure surface. In the present embodiment, each of the plurality of blades 4 has a plurality of through holes 10. In addition, in FIG. 2, in order to distinguish each of the plurality of through holes 10, an alphabet is added to the end of the numeral reference. In the following description, an alphabet is added to the end of the numeral code of the through hole 10 as needed.

  The through hole 10 of the blade 4 is provided so as to satisfy the following requirements (A), (B), and (C). At least a part of the plurality of through holes 10 may satisfy the requirements (A), (B), and (C).

(A) The plurality of through holes 10 are provided on the trailing edge 7 side of the blade 4 with respect to the maximum sled position.
In FIG. 3, the maximum warp position formed between the leading edge 6 and the trailing edge 7 of the blade 4 is indicated by a dashed line W. The plurality of through holes 10 are provided in the blade 4 at a position between the maximum sled position and the trailing edge 7. The through hole 10 is provided at a position apart from the trailing edge 7 and does not open in the trailing edge 7. Therefore, the wall surface 41 of the blade 4 exists between the trailing edge 7 and the through hole 10.

(B) In the plurality of through holes 10, the hole width of the predetermined through hole 10 is the same or larger than the hole width of the other through holes 10 adjacent to the side plate 2 side of the predetermined through hole 10.
Here, as shown in FIG. 3, in the present specification, the distance D1 from the inner wall of the through hole 10 on the front edge 6 side to the front edge 6 and the inner wall of the through hole 10 on the rear edge 7 side to the front side. The difference ΔD from the distance D2 to the edge 6 is defined as the hole width. The hole width of the through hole 10 refers to the smaller one of the difference measured on the positive pressure surface 9 and the difference measured on the negative pressure surface 8. This is because the smaller hole width is the rate-determining factor for the air flow.

  As shown in FIG. 2, in the first embodiment, a plurality of through holes 10a to 10g arranged in the blade 4 from the side plate 2 side portion (hereinafter, referred to as an upper portion) to an intermediate portion (hereinafter, referred to as a central portion). The width is the same size. The hole width of the through hole 10h is larger than the hole width of the through hole 10g adjacent to the side plate 2 side of the through hole 10h. Moreover, the hole width of the plurality of through holes 10h to 10j arranged in the portion of the blade 4 on the main plate 3 side (hereinafter referred to as the lower portion) is the same.

  In the first embodiment, the shape of the plurality of through holes 10 is circular. Therefore, in the first embodiment, in the plurality of through holes 10, the hole diameter of the predetermined through hole 10 is the same as or larger than the hole diameters of the other through holes 10 adjacent to the side plate 2 side of the predetermined through hole 10. You can also say. The shape of the through hole 10 is not limited to the circular shape, and can be arbitrarily set, for example, an elongated hole, a polygon, or a D shape.

(C) The plurality of through holes 10 are parallel to the rotation axis Ax of the centrifugal fan 1 or the front edge of the predetermined through hole 10 with respect to the other through holes 10 adjacent to the side plate 2 of the predetermined through hole 10. It is provided on the 6 side.
As shown in FIG. 2, in the first embodiment, the plurality of through holes 10 a to 10 j are provided such that the center position of each through hole 10 is aligned parallel to the rotation axis Ax of the centrifugal fan 1.

  Regarding the first embodiment described above, the technical significance of the through hole 10 will be described after the configurations of second to seventh embodiments described later are described.

(Second to seventh embodiments)
The second to seventh embodiments will be described. The second to seventh embodiments are different from the first embodiment in the configuration of the through hole 10, and other aspects are the same as the first embodiment, and therefore only the portions different from the first embodiment will be described. explain. The through holes 10 of the second to seventh embodiments are also provided so that at least a part thereof satisfies the requirements (A), (B), and (C) described in the first embodiment.

(Second embodiment)
As shown in FIG. 4, in the second embodiment, the through holes 10a to 10e arranged in the central portion of the blade 4 have the same hole width. The hole width of the through hole 10f is larger than the hole width of the through hole 10e adjacent to the side plate 2 side. Further, the through holes 10f to 10h arranged in the lower portion of the blade 4 have the same hole width.

  Further, in the second embodiment, the through holes 10a to 10e arranged in the central portion of the blade 4 are provided such that the center position of each through hole 10 is aligned parallel to the rotation axis Ax of the centrifugal fan 1. The through holes 10g and h arranged in the lower portion of the blade 4 are provided on the front edge 6 side with respect to the other through holes 10 adjacent to the side plate 2 side of the predetermined through hole 10. Has been.

  Further, in the second embodiment, the through hole 10 is not provided in the upper portion of the blade 4 (that is, the portion of the blade 4 closer to the side plate 2 than the through hole 10a). This is based on experiments and simulations (hereinafter referred to as experiments) described later, and the noise reduction effect by the through holes 10 does not occur in a predetermined region of the blade 4 on the side plate 2 side. The predetermined area is appropriately set by experiments or the like according to the shape of the centrifugal fan 1.

(Third Embodiment)
As shown in FIG. 5, in the third embodiment, the through holes 10a to 10e arranged in the central portion of the blade 4 have the same hole width. The hole width of the through hole 10f is larger than the hole width of the through hole 10e adjacent to the side plate 2 side. Further, the through holes 10f to 10h arranged in the lower portion of the blade 4 have the same hole width.

Further, in the third embodiment, the through holes 10a to 10h arranged from the middle portion to the lower portion of the blade 4 are provided such that the center position of each through hole 10 is aligned in parallel with the rotation axis Ax of the centrifugal fan 1. There is.
Further, in the third embodiment, the through hole 10 is not provided in the upper part of the blade 4.

(Fourth Embodiment)
As shown in FIG. 6, in the fourth embodiment, each of the through holes 10b to 10j arranged from the upper part to the lower part of the blade 4 has a predetermined hole width of the through hole 10 adjacent to the side plate 2 side. Is larger than the hole width of the through hole 10.
In addition, in the fourth embodiment, the through holes 10a to 10j are provided such that the center position of each through hole 10 is aligned in parallel with the rotation axis Ax of the centrifugal fan 1.

(Fifth Embodiment)
As shown in FIG. 7, in the fifth embodiment, the through holes 10a and 10b are elongated holes. Also in this case, the hole width of the predetermined through hole 10b is larger than the hole width of the through hole 10a adjacent to the side plate 2 side.
In addition, in the fifth embodiment, the through holes 10a and 10b are provided such that the center positions of the through holes 10 are aligned parallel to the rotation axis Ax of the centrifugal fan 1.

(Sixth Embodiment)
As shown in FIG. 8, also in the sixth embodiment, the through holes 10a and 10b are elongated holes. Also in this case, the hole width of the predetermined through hole 10b is larger than the hole width of the through hole 10a adjacent to the side plate 2 side.
In addition, in the sixth embodiment, the through holes 10a and 10b are arranged such that the center position of the predetermined through hole 10b is in front of the center positions of the other through holes 10a adjacent to the side plate 2 side of the predetermined through hole 10b. It is provided on the edge 6 side. Specifically, the through hole 10b arranged in the lower portion of the blade 4 is inclined so as to approach the rotation axis Ax of the centrifugal fan 1 from the side plate 2 side toward the main plate 3 side.
In addition, in the sixth embodiment, the through hole 10 is not provided in the upper portion of the blade 4.

(Seventh embodiment)
As shown in FIGS. 9 and 10, in the seventh embodiment, the through hole 10 has a shape in which the opening area S2 of the pressure surface 9 of the blade 4 is larger than the opening area S1 of the suction surface 8 of the blade 4. ing. Even if the through hole 10 has such a shape, the same effect as that of the above-described first to sixth embodiments can be obtained.

  Specifically, in the seventh embodiment, the shape of the wall 11 on the trailing edge 7 side of the inner wall of the through hole 10 of the blade 4 corresponds to the suction surface 8 of the blade 4 located on the front side in the rotation direction of the blade 4. It is supposed to have a shape. Thereby, when a plurality of blades 4 are injection-molded, it is possible to make the die-cutting direction of the mold arranged between the blades 4 and the inner wall direction of the through hole 10 the same. Note that, as shown by an arrow M in FIG. 10, the die cutting direction of the mold arranged in the inter-blade flow passage during the injection molding is along the negative pressure surface 8 of the blade 4. Therefore, in the seventh embodiment, the blade 4 and the through hole 10 can be formed by one mold, and the manufacturing cost can be reduced.

(Technical significance of through holes)
Next, the technical significance of the through hole 10 will be described.
The through holes 10 of the first to seventh embodiments reduce noise generated by the rotation of the centrifugal fan 1. Further, the through holes 10 of the first to seventh embodiments are intended to suppress a decrease in the air blowing efficiency due to the reduction of the area of the blade 4 due to the through holes 10 or to improve the air blowing efficiency.

First, the reason why noise is generated by the rotation of the centrifugal fan 1 will be described with reference to FIG.
In FIG. 11, the speed of the main flow flowing through the outlet of the blade-to-blade flow path is indicated by an arrow v, and the axis of the vortex that is the noise source is indicated by an arrow ω. Here, according to Powell's vortex sound theory, the sound source term is represented by div(v×ω), and it is shown that the noise increases as the value increases. Div means divergence, and becomes large at the time of springing out and inhaling in a minute volume. Further, v means the mainstream velocity, and ω means the vorticity. That is, the noise is an outer product of the mainstream velocity v and the vorticity ω. Therefore, a large vortex is orthogonal to the main stream, and the place where it is generated or disappears becomes a sound. Therefore, noise can be reduced by reducing the vortex generated at the outlet of the inter-blade passage. In order to reduce the vortex generated at the outlet of the blade-to-blade passage, the variation in the flow velocity at the outlet of the blade-to-blade passage (that is, the flow velocity deviation) may be reduced.

  FIG. 12 shows the deviation of the flow velocity in the inter-blade passage when serrations are provided on the trailing edge 7 of the blade 4. In the flow path between the blades, the flow velocity near the suction surface 8 is fast, and the flow velocity near the pressure surface 9 is slow. Therefore, when serrations are provided on the trailing edge 7 of the blade 4, as shown by an arrow F, the air flowing in the vicinity of the positive pressure surface 9 in the predetermined inter-blade flow path passes through the notch of the serration, and the predetermined It flows to another inter-blade flow passage located on the rear side in the rotational direction of the inter-blade flow passage. Therefore, in the other inter-blade passages, the air having a high flow velocity flowing in the vicinity of the suction surface 8 is pushed out to the rear side in the rotational direction, and the flow velocity at the outlet of the inter-blade passage becomes closer to uniform. Therefore, the vortex formed near the trailing edge 7 of the blade 4 becomes smaller, and the noise is reduced. It should be noted that this was discovered by the research of the inventors.

13 to 16 are schematic diagrams showing a case where serrations are provided on the trailing edge 7 of the blade 4 as a comparative example of the present invention.
FIG. 13 shows the shape of a general serration 20. FIG. 14 shows a shape in which the notch portion of the serration 20 is deeply cut toward the front edge 6 side. FIG. 15 shows a shape in which the serrations 20 have a rectangular shape so that the flow velocity is partially reduced. FIG. 16 shows a shape in which the serration 20 is enlarged in the rotation axis Ax direction of the centrifugal fan 1. If the serration 20 has such a shape, it is possible to increase the flow rate of the air flowing from the inter-blade passage on the front side in the rotation direction to the inter-blade passage on the rear side in the rotation direction. However, in all of the serrations 20 shown in FIGS. 13 to 16, there is a problem that the ventilation efficiency is reduced due to the reduction of the area of the blade 4. Further, in all of the serrations 20 shown in FIGS. 13 to 16, the air flowing into the inter-blade passage from the notch is immediately blown out to the outside of the inter-blade passage. It is considered that the effect of pushing the air having a high flow velocity in the vicinity of 8 toward the positive pressure surface 9 side is weak.

  Therefore, the inventors have invented a structure in which the blade 4 is provided with the through hole 10 as shown in FIGS. 17 to 19. As a result, the air that has flowed from the position upstream of the trailing edge 7 of the blade 4 into the inter-blade flow passage on the rear side in the rotational direction via the through hole 10 is moved to the suction surface 8 of the suction surface 8 in the inter-blade flow passage. It is possible to improve the effect of pushing the air having a high flow velocity in the vicinity to the positive pressure surface 9 side. The shape of the through hole 10 can be any shape such as a triangle, a quadrangle, and a circle, but if the shape is a circle, the reduction of the blade 4 area can be minimized.

  20 to 22 show flow velocity distributions at the outlets of the inter-blade passages when the blade 4 is provided with the serrations 20 and when the blade 4 is provided with the through holes 10. FIG. 20 shows the positions of the outlets of the inter-blade passages shown in FIGS. 21 and 22. That is, FIG. 21 and FIG. 22 show the flow velocity distribution from the trailing edge 7 of the blade 4 on the front side in the rotational direction to the trailing edge 7 of the blade 4 on the rear side in the rotational direction at the outlet of the predetermined inter-blade passage. It is a numerical analysis figure by computational fluid dynamics). Specifically, FIG. 21 shows the velocity distribution at the outlet of the inter-blade passage when the serration 20 is provided on the blade 4. FIG. 22 shows the velocity distribution at the outlet of the inter-blade passage when the blade 4 is provided with the through holes 10.

Compared with the velocity distribution at the outlet of the inter-blade passage when the blade 4 is provided with the serrations 20 (see FIG. 21), the velocity distribution at the outlet of the inter-blade passage when the through hole 10 is provided in the blade 4 (see FIG. 21) 22), the fluctuation of the flow velocity is small as a whole. In particular, comparing the lower right portion of FIGS. 21 and 22, that is, the portion near the suction surface 8 of the blade 4 and the portion near the main plate 3, when the blade 4 is provided with the serrations 20, a flow with a high flow velocity is obtained. However, when the through hole 10 is provided in the blade 4, the flow velocity at that portion is slowed down and is uniformized with other portions.
In this way, in the case where the blade 4 is provided with the through holes 10, the flow velocity is made uniform as a whole as compared with the case where the blade 4 is provided with the serrations 20. This means that when the blade 4 is provided with the through-hole 10, air flows into the inter-blade flow passage from the upstream side of the trailing edge 7 of the blade 4 through the through-hole 10 and thus the air flow is negative in the inter-blade flow passage. It is considered that this is because the effect of pushing out the flow of air having a high flow velocity in the vicinity of the pressure surface 8 to the positive pressure surface 9 side is improved.

  Next, FIG. 23 shows a case where the blade 4 is not provided with the serrations 20 or the through holes 10 (hereinafter referred to as a base shape), a case where the blades 4 are provided with the serrations 20 and a case where the blade 4 is provided with the through holes 10. The difference in flow velocity at the outlet of the inter-blade passage is shown in the case of the provision of. The flow velocity deviation at the outlet of the blade-to-blade flow passage refers to the nonuniformity of the flow velocity when the flow velocity at the outlet of the blade-to-blade flow passage is viewed in the circumferential direction.

  As shown in FIG. 23, in the upper portion of the blade 4, the flow velocity deviation is larger when the serration 20 or the through hole 10 is provided in the blade 4 than in the base shape. However, in the upper part of the blade 4, since the flow rate of the main flow flowing through the outlet of the blade-to-blade passage is small, the influence on noise is small. However, it is preferable not to provide the through hole 10 in the upper portion of the blade 4 as in the second, third, and sixth embodiments shown in FIGS. 4, 5, and 8.

  On the other hand, in the middle portion and the lower portion of the blade 4, the flow velocity deviation is smaller when the serration 20 is provided on the blade 4 than in the base shape. Further, when the blade 4 is provided with the through hole 10, the flow velocity deviation becomes smaller. From this, it can be said that the noise can be further reduced by providing the through holes 10 in the blade 4 rather than providing the serrations 20 in the blade 4.

  Next, FIG. 24 shows the flow velocity deviation at the outlet of the inter-blade passage between the case of the base shape and the case of providing the blade 4 with the through holes 10 having different inner diameters. Specifically, when the plurality of through holes 10 are provided so as to be aligned in parallel with the rotation axis Ax of the centrifugal fan 1, the inner diameter of the plurality of through holes 10 is 1 mm and the inner diameter is 2 mm. And the inner diameter of which was set to 2.5 mm.

  At the upper portion of the blade 4, the flow velocity deviation is larger when the through hole 10 is provided in the blade 4 than in the base shape. However, in the upper part of the blade 4, since the flow rate of the main flow flowing through the outlet of the blade-to-blade passage is small, the influence on noise is small. However, unlike the second, third, and sixth embodiments shown in FIGS. 4, 5, and 8, it is preferable not to provide the through hole 10 in the upper portion of the blade 4.

On the other hand, in the middle part and the lower part of the blade 4, the flow velocity deviation is smaller when the through hole 10 having a larger inner diameter is provided in the blade 4 than when the through hole 10 having a smaller inner diameter is provided. From this, it can be said that the noise can be further reduced by providing the blade 4 with the through hole 10 having a large inner diameter.
Specifically, the flow velocity deviation is smaller in the lower portion of the blade 4 than in the middle portion of the blade 4 by increasing the inner diameter of the through hole 10. From this, it can be said that noise can be further reduced by making the inner diameter of the through hole 10 arranged in the lower portion of the blade 4 larger than the inner diameter of the through hole 10 arranged in the middle portion of the blade 4. Therefore, as shown in the requirement (B) described above, the plurality of through holes 10 have a predetermined through hole 10 having a width equal to that of the other through holes 10 adjacent to the side plate 2 side of the predetermined through hole 10. It is possible to further reduce noise by making the hole width the same or larger than the hole width.

  Next, FIG. 25 shows the flow velocity deviation at the outlet of the blade-to-blade flow passage in the case of the base shape and in the case of changing the position of the through hole 10 in the radial direction of the centrifugal fan 1. Specifically, when the plurality of through holes 10 are provided so as to be arranged parallel to the rotation axis Ax of the centrifugal fan 1, the distance between the center position of the plurality of through holes 10 and the trailing edge 7 of the blade 4 is set to 4 mm. And the distance between them was 14 mm.

  At the upper portion of the blade 4, the flow velocity deviation is larger when the through hole 10 is provided in the blade 4 than in the base shape. However, in the upper part of the blade 4, since the flow rate of the main flow flowing through the outlet of the blade-to-blade passage is small, the influence on noise is small. However, unlike the second, third, and sixth embodiments shown in FIGS. 4, 5, and 8, it is preferable not to provide the through hole 10 in the upper portion of the blade 4.

In the middle portion of the blade 4, the flow velocity deviation is smaller when the through hole 10 is provided at a position closer to the trailing edge 7 of the blade 4 than in the base shape. On the other hand, as compared with the case where the through hole 10 is provided at a position close to the trailing edge 7 of the blade 4, the flow velocity deviation becomes larger when the through hole 10 is provided at a position far from the trailing edge 7 of the blade 4. There is.
On the other hand, in the lower part of the blade 4, the flow velocity deviation is smaller when the through hole 10 is provided at a position closer to the trailing edge 7 of the blade 4 than in the base shape. Further, compared with the case where the through hole 10 is provided at a position near the trailing edge 7 of the blade 4, the flow velocity deviation is smaller when the through hole 10 is provided at a position far from the trailing edge 7 of the blade 4. There is.

  From this, it can be said that the noise can be further reduced by providing the through hole 10 at a position near the trailing edge 7 of the blade 4 in the middle portion of the blade 4. On the other hand, in the lower part of the blade 4, it can be said that the noise can be further reduced by providing the through hole 10 at a position far from the trailing edge 7 of the blade 4. Therefore, as shown in the requirement (C) described above, the plurality of through holes 10 are centrifugally separated from the other through holes 10 which are adjacent to the side plate 2 side of the predetermined through hole 10. By arranging the fan 1 in parallel to the rotation axis Ax or on the front edge 6 side, noise can be further reduced.

  Next, in FIG. 26, the through holes 10 are provided as in the case of the base shape, the case where the blades 4 are provided with the serrations 20 and the first embodiment and the second embodiment shown in FIGS. 2 and 4. The case shows the specific noise of the centrifugal fan 1 and the fan efficiency (that is, the blowing efficiency). In addition, in FIG. 26, the specific noise and the ventilation efficiency of the centrifugal fan 1 in the base shape are set to the reference value 0, and the difference of each form with respect to the reference value is shown.

Regarding the specific noise of the centrifugal fan 1, the case where the serrations 20 are provided on the blades 4 is smaller than that of the base shape. The specific noise is smaller when the through holes 10 are provided as in the first embodiment than when the serrations 20 are provided on the blade 4. Furthermore, the specific noise is smaller when the through hole 10 is provided as in the second embodiment than when the through hole 10 is provided as in the first embodiment.
Therefore, by providing the through holes 10 in the blade 4 as in the first embodiment, it is possible to reduce noise more than the serrations 20. Furthermore, unlike the second embodiment, the through hole 10 is not provided in the upper portion of the blade 4, and the through hole 10 in the lower portion of the blade 4 is arranged on the front edge 6 side, thereby further reducing noise. Is possible.

Regarding the air blowing efficiency of the centrifugal fan 1, the case where the blades 4 are provided with the serrations 20 is lower than that of the base shape. On the other hand, as compared with the case where the blade 4 is provided with the serrations 20, the case where the through hole 10 is provided as in the first embodiment suppresses the reduction in the blowing efficiency. Furthermore, when the through hole 10 is provided as in the second embodiment, the blowing efficiency is improved as compared with the base shape.
Therefore, as in the first embodiment, by providing the blade 4 with the through hole 10, it is possible to suppress a decrease in the blowing efficiency as compared with the serration 20. Further, unlike the second embodiment, the through hole 10 is not provided in the upper portion of the blade 4 and the through hole 10 in the lower portion of the blade 4 is arranged on the front edge 6 side, so that the ventilation efficiency is higher than that of the base shape. It is possible to improve.

Next, the reason why the ventilation efficiency is improved as compared with the base shape when the through hole 10 is provided as in the second embodiment will be described.
FIG. 27 shows the total pressure distribution of the air flowing through the pressure surface 9 of the blade 4 in the base shape. On the other hand, FIG. 28 shows the total pressure distribution of the air flowing through the positive pressure surface 9 of the blade 4 when the through hole 10 is provided as in the second embodiment.

  Compared with the total pressure distribution on the positive pressure surface 9 in the base shape (see FIG. 27), the total pressure distribution on the positive pressure surface 9 in the second embodiment (see FIG. 22) shows that the pressure near the trailing edge 7 of the blade 4 is 4 in the vertical direction (that is, the rotation axis Ax direction). Furthermore, compared with the total pressure distribution of the positive pressure surface 9 in the base shape (see FIG. 27), the total pressure distribution of the positive pressure surface 9 in the second embodiment (see FIG. 22) is similar to the trailing edge 7 of the blade 4 and the vicinity of the main plate 3. The pressure is increasing. This means that when the blade 4 is provided with the through-hole 10, air flows into the inter-blade flow passage from the position upstream of the trailing edge 7 of the blade 4 through the through-hole 10 and within the inter-blade flow passage. It is considered that the pressure of the air near the positive pressure surface 9 side increases the pressure near the trailing edge 7 of the blade 4 and the main plate 3.

Then, in the case where the through hole 10 is provided as in the second embodiment shown in FIG. 4, the through holes 10g and 10h arranged in the lower portion of the blade 4 are provided in other through holes 10 adjacent to the side plate 2 side. On the other hand, it is provided on the front edge 6 side. Therefore, the area of the wall surface 41 of the blade 4 between the through holes 10g, h and the trailing edge 7 becomes large, and the wall surface 41 can perform the work of pushing air out of the outlet of the inter-blade passage. Is.
Further, air flows into the inter-blade passage from the position upstream of the trailing edge 7 of the vane 4 through the through hole 10, and the air flow approaches the positive pressure surface 9 side in the inter-blade passage. Since the pressure on the trailing edge 7 of the blade 4 and in the vicinity of the main plate 3 increases, the amount of work on the wall surface 41 between the through holes 10g, h of the blade 4 and the trailing edge 7 increases. Therefore, when the through hole 10 is provided as in the second embodiment, the blowing efficiency is improved as compared with the base shape. It can be said that this also improves the blowing efficiency over the base shape, similarly in the sixth and seventh embodiments shown in FIGS. 8 and 9.

(Other embodiments)
The present invention is not limited to the above-described embodiments, but can be appropriately modified within the scope described in the claims. Further, the above embodiments are not unrelated to each other, and can be appropriately combined unless a combination is obviously impossible. Further, in each of the above-mentioned embodiments, it goes without saying that the elements constituting the embodiment are not necessarily essential unless explicitly stated as being essential and in principle considered to be essential. Yes. Further, in each of the above-described embodiments, when numerical values such as the number of components of the embodiment, numerical values, amounts, ranges, etc. are referred to, it is clearly limited to a particular number and in principle limited to a specific number. The number is not limited to the specific number, except in the case of being performed. Further, in each of the above-mentioned embodiments, when referring to the shape of the components and the like, the positional relationship, etc., the shape thereof, unless otherwise explicitly stated and in principle limited to the specific shape, the positional relationship, etc., It is not limited to the positional relationship or the like.

  (1) In each of the above-described embodiments, the turbofan is described as an example of the centrifugal fan 1, but the present invention is not limited to this, and the centrifugal fan 1 may be a radial fan, a sirocco fan, or the like.

  (2) Further, the plurality of through holes 10 included in the blade 4 may all have the same hole width.

  (3) Further, the plurality of through holes 10 included in the blade 4 may partially include a portion that does not satisfy the requirements of (A), (B), and (C).

  (4) Further, each of the blades 4 may have a single through hole 10.

  (5) In each of the above embodiments, the main plate 3, the side plate 2, and the plurality of blades 4 have been described as rotating integrally, but the present invention is not limited to this, and the main plate 3 and the plurality of blades 4 may also rotate. The configuration may be such that only the plurality of blades 4 rotate, or only the plurality of blades 4 may rotate.

(Summary)
According to the first aspect shown in some or all of the above-described embodiments, the centrifugal fan is used in a centrifugal blower. The centrifugal fan includes an annular side plate having an air suction port, a main plate provided to face the side plate, and a plurality of blades arranged between the side plate and the main plate at predetermined intervals in the rotation direction. The blade has a through hole that penetrates the suction surface and the pressure surface and is not opened at the trailing edge.

According to the second aspect, the through hole is provided on the trailing edge side of the maximum sled position formed between the leading edge and the trailing edge of the blade.
According to this, on the trailing edge side of the maximum warp position of the blade, the air in the predetermined inter-blade passage passes through the through hole and flows into another inter-blade passage located on the rear side in the rotation direction. Therefore, in the other inter-blade flow paths, the flow of air with a high flow velocity in the vicinity of the suction surface is pushed out toward the rear side in the rotational direction by the air that has flowed in through the through-holes, and spreads to the pressure surface side with a slow flow velocity. It is possible to make the flow velocity deviation at the outlet of the blade-to-blade flow path uniform. Therefore, since the vortex formed near the trailing edge of the blade becomes weaker, noise can be reduced.

  Further, the wall surface between the through hole and the trailing edge of the blade performs the work of pushing the air to the outside of the outlet of the inter-blade passage, thereby suppressing a decrease in the ventilation efficiency or improving the ventilation efficiency. be able to.

According to the third aspect, each of the plurality of blades has a plurality of through holes.
According to this, the position and opening area of the through hole can be arbitrarily adjusted while maintaining the rigidity of the blade.

  According to the fourth aspect, the difference between the distance from the inner wall on the front edge side of the through hole to the front edge and the distance from the inner wall on the rear edge side of the through hole to the front edge is defined as the hole width. At this time, the hole width of the predetermined through hole among the plurality of through holes is set to be the same as or larger than the hole widths of the other through holes adjacent to the side plate side of the predetermined through hole.

According to this, the noise reduction effect due to the through-holes in the blade on the main plate side, the portion in the vicinity of the middle of the main plate and the side plate of the blade, and the side plate side portion of the blade according to the experiments by the inventors. Was found to be different. Specifically, the noise reduction effect of the through hole is large at the main plate side portion of the blade, and the noise reduction effect of the through hole is small at the portion near the middle of the main plate and the side plate of the blade. It was found that there is almost no noise reduction effect due to the through hole.
Therefore, in the fourth aspect, among the plurality of through holes, the hole width of the predetermined through hole is the same or larger than the hole widths of the other through holes adjacent to the side plate side of the predetermined through hole. There is. As a result, the noise reduction effect can be further enhanced while suppressing the reduction of the blade area due to the through hole. Further, since the reduction of the blade area due to the through holes is suppressed, it is possible to suppress the reduction of the ventilation efficiency.

  According to a fifth aspect, among the plurality of through holes, the predetermined through hole is parallel to the rotation axis of the centrifugal fan or on the leading edge side with respect to other through holes adjacent to the side plate side of the predetermined through hole. It is provided.

According to this, the inventors' experiments and the like have revealed that the wall surface of the blade between the through hole and the trailing edge works to push air out of the outlet of the inter-blade passage. It was also found that the work amount was larger in the main plate side portion than in the side plate side portion of the blade.
Therefore, in a fifth aspect, among the plurality of through holes, a predetermined through hole is provided parallel to the rotation axis of the centrifugal fan or on the leading edge side with respect to another through hole adjacent to the side plate side of the predetermined through hole. It is provided. This makes it possible to increase the work amount of pushing air out of the outlet of the inter-blade passage by using the wall surface of the blade between the through hole and the trailing edge, particularly on the main plate side. is there. Therefore, this centrifugal fan can further suppress the reduction of the blowing efficiency or further improve the blowing efficiency.

  According to the sixth aspect, among the plurality of through holes, the predetermined through hole is parallel to the rotation axis of the centrifugal fan or on the front edge side with respect to the other through holes adjacent to the side plate side of the predetermined through hole. It is provided. The hole width of the predetermined through hole is the same as or larger than the hole width of other through holes adjacent to the side plate side of the predetermined through hole.

  According to this, among the wall surfaces of the blade between the through hole and the trailing edge, particularly the wall surface located on the main plate side can increase the work amount for pushing the air to the outside of the outlet of the inter-blade passage. It is possible. Further, the noise reduction effect can be further enhanced while suppressing the reduction of the blade area due to the through hole. Therefore, this centrifugal fan can reduce noise, suppress a decrease in air blowing efficiency, or improve air blowing efficiency.

  According to the seventh aspect, the through hole has a larger opening area on the pressure surface of the blade than on the suction surface of the blade.

  According to this, even if the through-hole has such a shape, it is possible to reduce noise and suppress a decrease in air-blowing efficiency, or improve air-blowing efficiency, as in the first to sixth aspects described above. .

  Further, if the shape of the trailing edge side of the inner wall of the through-hole of a given blade is made to correspond to the suction surface of the blade located on the front side in the rotation direction of the blade, when a plurality of blades are injection molded, the blades are The die cutting direction of the metal mold arranged between and the direction of the inner wall of the through hole are the same. The injection direction of the mold disposed in the blade flow passage during injection molding is the radial direction along the suction surface of the blade. Therefore, the blade and the through hole can be formed by one mold, and the manufacturing cost can be reduced.

1 Centrifugal Fan 2 Side Plate 3 Main Plate 4 Blade 5 Suction Port 7 Trailing Edge 8 Negative Pressure Surface 9 Positive Pressure Surface 10 Through Hole

Claims (7)

In a centrifugal fan used in a centrifugal blower,
An annular side plate (2) having an air inlet (5),
A main plate (3) provided to face the side plate,
A plurality of blades (4) arranged at a predetermined interval in the rotational direction between the side plate and the main plate,
A centrifugal fan, wherein the blade has a through hole (10) which penetrates the suction surface (8) and the pressure surface (9) and which is not opened at the trailing edge (7).   The centrifugal fan according to claim 1, wherein the through hole is provided closer to the trailing edge than a maximum sled position (W) formed between the leading edge and the trailing edge of the blade.   The centrifugal fan according to claim 1 or 2, wherein each of the plurality of blades has a plurality of the through holes. The difference (ΔD) between the distance (D1) from the inner wall on the front edge side to the front edge of the through hole and the distance (D2) from the inner wall on the rear edge side of the through hole to the front edge (ΔD) When defined as
Of the plurality of through holes, the hole width of the predetermined through hole is the same as or larger than the hole widths of the other through holes adjacent to the side plate side of the predetermined through hole. The centrifugal fan according to any one of claims 1 to 3.   Of the plurality of through holes, the predetermined through hole is parallel to the rotation axis (Ax) of the centrifugal fan or on the front edge side with respect to the other through holes adjacent to the side plate side of the predetermined through hole. The centrifugal fan according to any one of claims 1 to 4, which is provided. Among the plurality of through holes, the predetermined through hole is provided parallel to the rotation axis of the centrifugal fan or on the front edge side with respect to the other through holes adjacent to the side plate side of the predetermined through hole. And
The hole width of the predetermined through hole is the same as or larger than the hole widths of the other through holes adjacent to the side plate side of the predetermined through hole. Centrifugal fan.   The centrifuge according to any one of claims 1 to 6, wherein the through-hole has an opening area (S2) on the pressure surface of the blade that is larger than an opening area (S1) on the suction surface of the blade. fan.