This application is a U.S. national stage application of International Application No. PCT/JP2017/016878, filed on Apr. 28, 2017, the contents of which are incorporated herein by reference.
The present invention relates to a propeller fan including a blade having a notch in at least one of a leading edge and a trailing edge of the blade.
Patent Literature 1 discloses a fan including blades. Each blade has a sawtooth-like leading edge including multiple tapered projections. Each projection has two sloping outer-edge parts outwardly extending closer to each other and tip-side outer-edge part, serving as the tip of the projection, connecting distal ends of the two sloping outer-edge parts. The two sloping outer-edge parts form an acute angle. The tip-side outer-edge part is shaped to suppress collision between air flows rising up toward a suction surface of the blade. Patent Literature 1 describes that noise can be effectively reduced in the above-described configuration because collision between air flows rising up toward the suction surface of the blade can be reduced near the tip-side outer-edge part of each projection.
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2015-63912
The sawtooth-like leading edge of each blade in Patent Literature 1 includes curved base outer-edge parts each smoothly connecting proximal ends of the sloping outer-edge parts of the two adjacent projections. The two adjacent sloping outer-edge parts on opposite sides of each base outer-edge part form an acute angle. In such a configuration, stress generated by rotation of the blade locally increases in the base outer-edge parts, resulting in a reduction in strength of the blade.
The present invention has been made to solve the above-described problem, and aims at providing a propeller fan including a blade that exhibits enhanced strength while achieving noise reduction.
A propeller fan according to an embodiment of the present invention includes a shaft disposed on a rotation axis and a blade disposed adjacent to an outer circumferential surface of the shaft. The blade has a leading edge and a trailing edge. At least one of the leading edge and the trailing edge has a notch. The notch includes a pair of side edge-parts forming an acute included angle and bottom edge-part located between the pair of side edge-parts. The bottom edge-part includes at least one first protrusion having an obtuse included angle.
According to the embodiment of the present invention, part of the notch of the blade that is likely to undergo stress concentration can be distributed among the first protrusion and two recesses arranged on opposite sides of the first protrusion. In addition, the obtuse included angle of the protrusion can alleviate an increase in stress in each of the protrusion and the two recesses. Thus, the strength of the blade is enhanced while noise reduction effect achieved by the notch of the blade is maintained.
A propeller fan according to Embodiment 1 of the present invention will be described. The propeller fan is used in, for example, an air-conditioning apparatus or a ventilating apparatus.
Each blade 20 has a leading edge 21, a trailing edge 22, an outer edge 23, and an inner edge 24. The leading edge 21 is an edge part located forward in a rotating direction of the blade 20. The trailing edge 22 is an edge part located backward in the rotating direction of the blade 20. The outer edge 23 is an edge part located in an outer region of the blade 20, or located between an outer end of the leading edge 21 and an outer end of the trailing edge 22. The inner edge 24 is an edge part located in an inner region of the blade 20, or located between an inner end of the leading edge 21 and an inner end of the trailing edge 22. The inner edge 24 is connected to the outer circumferential surface of the boss 10.
At least one of the leading edge 21 and the trailing edge 22 of the blade 20 has at least one notch. The leading edge 21 of the blade 20 has a series of notches 30 arranged adjacent to the inner end of the leading edge 21. In an example illustrated in
The shapes of the notches 30 and 40 will now be described in detail, using the notch 30 as an example.
The angle formed by one side edge-part 31 and the other side edge-part 32 of the notch 30 is an included angle α (hereinafter, often referred to as an “included angle α of the notch 30”) defined between the side edge-part 31 and the side edge-part 32. In a case where the side edge-parts 31 and 32 are curves, the included angle α between the side edge-parts 31 and 32 is the angle formed by a tangent to the side edge-part 31 at an inflection point 103 thereof and a tangent to the side edge-part 32 at an inflection point 104 thereof. The notch 30 decreases in width inwardly or farther away from the edge, or upwardly in
The bottom edge-part 36 of the notch 30 includes a protrusion 33 (an exemplary first protrusion) protruding outward, or toward the edge. Two recesses 34 and 35 extending inward, or farther away from the edge, are arranged on opposite sides of the protrusion 33. The recess 34 overlaps the bottom edge-part 36 and the side edge-part 31. The recess 35 overlaps the bottom edge-part 36 and the side edge-part 32. The angle formed by a tangent to a part between the protrusion 33 and the recess 34 at an inflection point 105 and a tangent to a part between the protrusion 33 and the recess 35 at an inflection point 106 is an included angle β of the protrusion 33. The included angle β of the protrusion 33 is an obtuse angle (90 degrees<β<180 degrees). The protrusion 33 includes one or more arcs. Each of the recesses 34 and 35 includes one or more arcs.
The angle formed by the tangent at the inflection point 103 and the tangent at the inflection point 105 is an included angle γ1 of the recess 34. The angle formed by the tangent at the inflection point 104 and the tangent at the inflection point 106 is an included angle γ2 of the recess 35. It is preferred that at least one of the included angle γ1 and the included angle γ2 be an obtuse angle. In an example illustrated in
In a direction perpendicular to a straight line 110 passing through the tops 101 and 102 (for example, a tangent to the two adjacent projections 50), a maximum distance between the straight line 110 and the recess 34 corresponds to a depth D1 of the recess 34. Similarly, in the direction perpendicular to the straight line 110, a maximum distance between the straight line 110 and the recess 35 corresponds to a depth D2 of the recess 35. The depth D1 and the depth D2 may be the same as or may differ from each other. The protrusion 33 does not touch or cross the straight line 110 because the protrusion 33 is lower than the projections 50.
For example, the protrusion 33 is located in the middle part of the notch 30 in the radial direction of the blade 20. Specifically, when the distance between the top 101, serving as an outer end of the notch 30, and the rotation axis RC is referred to as r1 and when the distance between the top 102, serving as an inner end of the notch 30, and the rotation axis RC is referred to as r2, a circle having its center at the rotation axis RC and a radius (r1+r2)/2 overlaps the protrusion 33. Consequently, part of the protrusion 33 is located within the circle and the other part of the protrusion 33 is located outside the circle. As described above, it is preferred that at least part of the protrusion 33 included in the notch 30 be located in each of the inside and the outside of the above-described circle. If the notch 30 includes a plurality of protrusions, it is preferred that at least subset of the plurality of protrusions be located in both the inside and the outside of the above-described circle.
In contrast, the bottom edge-part 36 of each notch 30 in Embodiment 1 illustrated in
As described above, the propeller fan according to Embodiment 1 includes the boss 10 (exemplary shaft) disposed on the rotation axis RC and the blades 20 each having the leading edge 21 and the trailing edge 22 and arranged adjacent to the outer circumferential surface of the boss 10. At least one of the leading edge 21 and the trailing edge 22 has a notch 30 or a notch 40. The notch 30 or the notch 40 includes the pair of side edge-parts 31 and 32 forming an acute included angle α and the bottom edge-part 36 located between the pair of side edge-parts 31 and 32. The bottom edge-part 36 includes at least one protrusion 33 (exemplary first protrusion) having an obtuse included angle β.
This configuration allows a part of the notch 30 or the notch 40 that is likely to undergo stress concentration to be distributed among the protrusion 33 and the two recesses 34 and 35 arranged on the opposite sides of the protrusion 33. In addition, the obtuse included angle β of the protrusion 33 can alleviate an increase in stress in each of the protrusion 33 and the two recesses 34 and 35. Thus, the strength of the blade 20 is enhanced while the effect of reducing noise in the propeller fan and the effect of improving the efficiency of the propeller fan achieved by the notch 30 or 40 of the blade 20 are maintained.
In the propeller fan according to Embodiment 1, the protrusion 33 is located in the middle part of the notch 30 or the notch 40 in the radial direction of the blade 20. This configuration more effectively allows distribution of part of the notch 30 or the notch 40 that is likely to undergo stress concentration, thus further enhancing the strength of the blade 20.
In the propeller fan according to Embodiment 1, the protrusion 33 includes one or more arcs. This configuration can alleviate an increase in stress in the protrusion 33, thus further enhancing the strength of the blade 20.
In the propeller fan according to Embodiment 1, the notch 30 or the notch 40 includes the two recesses 34 and 35 arranged on the opposite sides of the protrusion 33. The included angle of at least one of the two recesses 34 and 35 (for example, the included angle γ1 of the recess 34) is an obtuse angle. This configuration can alleviate an increase in stress in at least one of the recesses 34 and 35, thus further enhancing the strength of the blade 20.
A propeller fan according to Embodiment 2 of the present invention will be described.
For the recesses 34 and 35 of each notch 40 in Embodiment 2, as illustrated in
A propeller fan according to Embodiment 3 of the present invention will be described.
For the recesses 34 and 35 of each notch 40 in Embodiment 3, as illustrated in
A propeller fan according to Embodiment 4 of the present invention will be described.
As illustrated in
A propeller fan according to Embodiment 5 of the present invention will be described.
As illustrated in
As described above, the propeller fan according to Embodiment 5 is configured such that the bottom edge-part 36 includes the protrusions 61, 62, 63, and 64 (exemplary first protrusions). Such a configuration allows a part that is likely to undergo stress concentration to be distributed among more locations, thus further enhancing the strength of the blade 20.
A propeller fan according to Embodiment 6 of the present invention will be described.
For the side edge-parts 31 and 32 of each notch 40, as illustrated in
In Embodiment 6, when air flows, represented by dashed lines in
For the pair of side edge-parts 31 and 32 in the propeller fan according to Embodiment 6, as described above, the side edge-part 32 located adjacent to the outer circumference of the propeller fan includes the protrusions 71, 72, 73, 74, and 75 (exemplary second protrusions). This configuration improves the aerodynamic performance of the blade 20, thus further reducing noise in the propeller fan and further improving the efficiency of the propeller fan.
A propeller fan according to Embodiment 7 of the present invention will be described.
As illustrated in
Embodiments 1 to 7 can be combined and implemented.
Filing Document | Filing Date | Country | Kind |
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PCT/JP2017/016878 | 4/28/2017 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2018/198300 | 1/11/2018 | WO | A |
Number | Name | Date | Kind |
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20030012656 | Cho et al. | Jan 2003 | A1 |
20060165526 | Cho et al. | Jul 2006 | A1 |
20120003097 | Cho et al. | Jan 2012 | A1 |
Number | Date | Country |
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100371607 | Feb 2008 | CN |
101379300 | Mar 2009 | CN |
103140684 | Jun 2013 | CN |
105275854 | Jan 2016 | CN |
205503552 | Aug 2016 | CN |
2015-063912 | Apr 2015 | JP |
2016-166600 | Sep 2016 | JP |
2016166600 | Sep 2016 | JP |
10-2013-0109515 | Oct 2013 | KR |
20130109515 | Oct 2013 | KR |
Entry |
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International Search Report dated Jul. 4, 2017 issued in corresponding international patent application No. PCT/JP2017/016878 (and English translation thereof). |
Extended European Search Report dated Mar. 24, 2020 issued in corresponding European patent application No. 17906931.5. |
Examination Report dated May 4, 2020 issued in corresponding AU patent application No. 2017411785. |
Office Action dated May 29, 2020 issued in corresponding CN patent application No. 201780089724.X. (with English translation). |
Examination Report dated Jul. 28, 2021 issued in corresponding IN patent application No. 201947039645. |
Number | Date | Country | |
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20200040736 A1 | Feb 2020 | US |