A cross-flow fan, and blades of a cross-flow fan are provided. The cross-flow fan includes a rotary shaft; a plurality of blades that extends in a direction parallel to the rotary shaft and having a positive pressure surface and a negative pressure surface; and a connector that connects the rotary shaft and the plurality of blades. At least one protrusion that protrudes in a thickness direction and extends in a longitudinal direction of the plurality of blades is formed on the plurality of blades, and by means of the at least one protrusion formed on a blade surface, a flow separation phenomenon caused by friction with the blade surface is suppressed, thereby reducing noise generated by the cross-flow fan.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a U.S. National Stage Application under 35 U.S.C. § 371 of PCT Application No. PCT/KR2020/018036, filed Dec. 10, 2020, which claims priority to Korean Patent Application No. 10-2020-0023209, filed Feb. 25, 2020, whose entire disclosures are hereby incorporated by reference.

BACKGROUND

TA cross-flow fan, and more particularly, a cross-flow fan blade is disclosed herein.

Blower fans which suction and discharge air by rotation are classified into various types, such as a centrifugal fan, an axial fan, and a cross-flow fan, depending on a positional relationship between a rotary shaft and a flow direction. Among these blower fans, the cross-flow fan generally includes a rotary shaft and a blade extending long or lengthwise in a direction of the rotary shaft, and a large amount of air is suctioned in a transverse direction.

One of the factors that determines performance of the cross-flow fan is noise, and the noise of the cross-flow fan is mainly generated near the blade. The biggest cause of noise generation near the blades is a flow separation phenomenon caused by friction with a blade surface, more specifically, the noise is generated as separated flows near the blade prevent air from being suctioned into the cross-flow fan.

In order to solve the above problems a related patent KR 2011-0122220A discloses a protrusion structure formed in or on an outer edge of a blade, but there is a problem that a flow separation phenomenon occurring over a positive pressure surface and a negative pressure surface of the blade cannot be addressed. In order to solve the above problem, another related patent U.S. Patent Publication No. 2012/0171013A1 discloses a blade structure having a plurality of inflection points in a line of a camber line, but there is a problem in weak durability and insufficient adaptability to various flow angles.

An object of embodiments is to reduce noise generated by a cross-flow fan by reducing an amount of separated flows near a blade.

Another object of embodiments is to improve durability of the blade by changing a thickness of the blade and to have versatility for various flow angles.

Yet another object of embodiments is to maximize a noise reduction effect at a low manufacturing cost by designing the blade of the present disclosure based on a conventional blade specification.

The objects of embodiments are not limited to the objects mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above objects, a cross-flow fan according to an embodiment includes: a rotary shaft; a plurality of blades spaced apart from each other at a predetermined angle about the rotary shaft, each blade extending in a direction parallel to the rotary shaft and having a positive pressure surface and a negative pressure surface; and a connector connecting the plurality of blades and the rotary shaft. A protrusion protruding in a thickness direction of the blades on at least one surface of the positive pressure surface and the negative pressure surface and extending in a longitudinal direction of the blades is formed in each blade among the plurality of blades

The protrusion may extend from one (first) end to the other (second) end in the longitudinal direction of the each blade. The protrusion may be formed in each of the positive pressure surface and the negative pressure surface, and a protrusion formed in the positive pressure surface and a protrusion formed in the negative pressure surface may protrude in opposite directions to thereby form a pair of opposing protrusions. The opposing protrusions may have each a cross section of a circular shape.

The opposing protrusions may be formed as a plurality of opposing protrusions so as to be spaced apart from each other in a direction of a camber line of the each blade. One (first) of the plurality of opposing protrusions may be formed in an inner edge of the each blade, and the other (second) one of the plurality of opposing protrusions may be formed in an outer edge of the each blade. Centers of the opposing protrusions may be located on a camber line of the each blade.

Intervals between the plurality of opposing protrusions may be formed to divide a code line into equal parts when a foot of perpendicular is drawn onto the code line from a center of each of the opposing protrusions. Diameters of the plurality of opposing protrusions may be formed in such a way that an opposing protrusion located closer to the inner edge has a greater diameter.

The plurality of opposing protrusions may be connected by a beam. A thickness of the beam may decrease in a direction away from the inner edge.

A surface of the each blade including the protrusion may have a continuous curvature distribution.

The details of other embodiments are included in the detailed description and

DRAWINGS

According to the cross-flow fan of embodiments, there is one or more of the following effects.

First, as a flow separation phenomenon caused by friction with a blade surface is suppressed due to protrusions formed in the blade surface, it is possible to reduce noise generated by a cross-flow fan.

Second, by varying a thickness of a blade and a diameter of a protrusion along a camber line, it is possible to improve durability of the blade and to have adaptability to various flow angles.

Third, by designing the blade of the present disclosure based on shape specification of a conventional blade, it is possible to reduce noise without a significant change in manufacturing cost.

The effects of embodiments are not limited to the above-described effects, and other unmentioned effects will be clearly understood to those skilled in the art from the description of claims.

DETAILED DESCRIPTION

Advantages and features of embodiments and a method of achieving the same should become clear with embodiments described in detail below with reference to the accompanying drawings. However, embodiments are not limited to the embodiments disclosed below and may be realized in various other forms, the embodiments make the disclosure complete and are provided to completely inform one of ordinary skill in the art to which the embodiments pertain of the scope, and the embodiments are defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Hereinafter, embodiments will be described with reference to the drawings for explaining a cross-flow fan according to embodiments.

Referring toFIG.1, a blade3indicates a conventional blade3distinct from a blade30and40used in an embodiment, and this is merely to describe arrangement relationship among the blade3, a rotary shaft10, and a connector20and has nothing to do with the gist.

Referring toFIG.1, a cross-flow fan1includes the rotary shaft10capable of being rotated by power from an external power source (not shown), the blade3that suctions external air into the cross-flow fan1by rotation, and the connector20that connects the rotary shaft10and the blade3. There may be a plurality of blades3, and the plurality of blades3is spaced apart from each other at a predetermined angle relative to the rotary shaft10. The blade3may be disposed to be parallel with the rotary shaft10with a length in a direction of the rotary shaft10, and a plurality of connectors20may be spaced apart from each other in a direction of the rotary shaft10so as to connect the rotary shaft10and the blade3.

Hereinafter, with reference toFIG.2, symbols commonly used in blade design are defined for explanation.

An end located close to a rotary shaft on a surface of a blade is referred to as an inner edge E1, and an end located far from the rotary shaft is referred to as an outer edge E2. A portion where each of the inner edge E1 and the outer edge E2 is formed may have a semicircular shape, a diameter of the semicircular shape of the inner edge E1 is referred to as an inner diameter D1, and a diameter of the semicircular shape of the outer edge E2 is referred to as an outer diameter D2.

A curve passing through both the inner edge E1 and the outer edge E2 and connecting a midpoint of thickness of the blade is referred to as a camber line C, and a straight line connecting the inner edge E1 and the outer edge E2 is referred to as a code line L.

An angle between a direction of rotation and the camber line C at the inner edge E1 is referred to as an inner angle B1, and an angle between the direction of rotation and the camber line C at the outer edge E2 is referred to as an outer angle B2.

Hereinafter, a blade30according to an embodiment will be described with reference toFIG.3based on the description ofFIGS.1and2.

The blade30shown inFIG.3may be disposed to replace the conventional blade3in the configuration of the cross-flow fan1shown inFIG.1, and an arrangement and connection relationship with rotary shaft10and connector20may be the same as described with reference toFIG.1.

A surface of the blade30may include a positive pressure surface31receiving a positive pressure by rotation and a negative pressure surface32receiving a negative pressure by rotation. The inner edge E1 and the outer edge E2 may be formed at a portion where the positive pressure surface31and the negative pressure surface32meet each other.

As shown inFIG.1, a plurality of blades30may be spaced apart from the rotary shaft10at a predetermined angle, and accordingly, the plurality of blades30may be disposed in such a way that a negative pressure surface32of each blade30faces a positive pressure surface of a blade ahead while a positive pressure surface31of a corresponding blade30faces a negative pressure surface of a blade behind.

A positive pressure protrusion33athat protrudes in a thickness direction of the blade30may be formed in the positive pressure surface31, and a negative pressure protrusion33bthat protrudes in the thickness direction of the blade30may be formed in the negative pressure surface32. A plurality of positive pressure protrusions33aand a plurality of negative pressure protrusions33bmay be spaced apart from each other in a direction of the camber line C along the positive pressure surface31and the negative pressure surface32, respectively. The positive pressure protrusion33aand the negative pressure protrusion33bmay be formed in the inner edge E1 or the outer edge E2, respectively, and a cross-sectional shape thereof may have a semi-circular shape.

The positive pressure protrusion33aand the negative pressure protrusion33bmay be formed at positions symmetrical with respect to the camber line C, thereby forming a pair of opposing protrusions33. An opposing protrusion33may be formed to have a cylindrical shape in a cross-section view of the blade30.

The opposing protrusion33may be formed to extend from one (first) end to the other (second) end of the blade30in a longitudinal direction of the blade30. A plurality of opposing protrusions33may be spaced apart from each other in the direction of the camber line C, and may be parallel to the rotary shaft10.

FIG.4is a cross-sectional view taken along line IV-IV′ shown inFIG.3. The plurality of opposing protrusions33may be spaced apart in the direction of the camber line C, and a front opposing protrusion33F located innermost may be formed in the inner edge E1, and a rear opposing protrusion33L located outermost may be formed in the outer edge E2. Centers of the front opposing protrusion33F and the rear opposing protrusion33L may be located on the camber line C. In addition, the centers of the plurality of opposing protrusions33may be all located on the camber line C.

The plurality of opposing protrusions33may be formed at constant intervals. Positioning at the constant intervals means a case in which the code line L is divided into equal parts when a perpendicular line is drawn from a center of each opposing protrusion33to the code line L.

A curve3ain contact with all of the plurality of opposing protrusions33may be the same as the surface of the conventional blade shown inFIG.2, and accordingly, the blade30may be manufactured in a way of cutting the surface of the conventional blade so that the opposing protrusions33can be formed in the conventional blade.

The positive pressure surface31and the negative pressure surface32of the blade30may be each an assembly that includes a surface of an opposing protrusion33and a surface of a beam34. The beam34may function as a structure connecting the opposing protrusions33spaced apart from each other, and may have a flat plate shape.

The beam34may have the same curvature distribution as that of the surface of the conventional blade shown inFIG.2. Accordingly, the blade30may be manufactured by projecting the opposing protrusions33to contact a second virtual curve3b, a portion of which forms a surface of the beam34.

The plurality of opposing protrusions33may be formed so as to have a cross section of a cylindrical shape, and a diameter of each opposing protrusion33may increase in a direction toward the inner edge E1. A diameter of each opposing protrusion33may be inversely proportional to a distance of a center of a corresponding opposing protrusion33from the inner edge E1 along the camber line C.

A thickness of the beam34connecting each opposing protrusion33may increase in a direction toward the inner edge E1, and may be inversely proportional to a distance of a center of a corresponding opposing protrusion33from the inner edge E1 along the camber line C. The beam34may not be a beam34used to connect an opposing protrusion33, but may have a continuous curved plate that forms the basic framework of the blade30, and in this case, the opposing protrusion33may be in the shape that protrudes from the surface of the beam34. That is, in this case, a second imaginary curve3bmay be a surface of the beam34, and a thickness of the beam34may decrease in a direction from the inner edge E1 to the outer edge E2, and a ratio between a diameter of each opposing protrusion33and a thickness of the beam34at a position where a corresponding opposing protrusion33is formed may be constant.

A vortex may be formed in an area where the surface of the opposing protrusion33is converted to the surface of the beam34, and accordingly, air flowing along the surface of the blade30may cause friction not with the surface of the blade30, but with the vortex of relatively less frictional strength, thereby reducing an amount of separated flows. As each opposing protrusion33formed in each of the plurality of blades30are disposed to face an opposing protrusion in an adjacent blade, the above-described generation of vortex may be further enhanced by interaction of the opposing protrusions.

FIG.5is a cross-sectional view taken along line IV-IV′ shown inFIG.3according to another embodiment. In this case, the IV-IV′ cross-sectional view according to this embodiment indicates a cross-sectional view of a blade40according to this embodiment.

An opposing protrusion43of the blade40according to this embodiment may be formed so as to have a cross section of an elliptical-cylindrical shape. A positive pressure surface41and a negative pressure surface42formed by the blade40may have a continuous curvature distribution over an entire surface of the blade40, which is a slight difference from the blade30according to the previous embodiment in that a discontinuous curvature distribution is formed at a portion where an opposing protrusion33and beam34of the blade30contact each other. In this case, a region in which the surface of the opposing protrusion43is converted into the surface of the beam44may have a smooth curved shape.

Matters such as intervals and diameters of the opposing protrusions43of the blade40according to this embodiment are the same as or similar to those described in the previous embodiment, and thus, description thereof has been be omitted.

Hereinafter, effect of noise reduction improvement of a cross-flow fan according to an embodiment of the present disclosure will be described with reference toFIGS.6to8.

FIG.6is image contouring for comparison of flow velocity distribution in a cross-flow fan according to a related art and the cross-flow fan according to embodiments. In the overall flow velocity distribution of the image contouring, a blue area where a flow velocity is slowly distributed is wider on the left side, visually showing that an average flow velocity increases according to embodiments, and thus, it may be said that flow rate performance of the cross-flow fan is improved.

FIG.7is a graph for comparison in noise performance between a cross-flow fan according to a related art and a cross-flow fan according to embodiments. The X-axis of the graph represents an air volume flowing into a cross-flow fan, and the Y-axis represents a noise value measured at a corresponding air volume.

A line connecting rectangular dots indicates noise measurement values according to the related art, and a line connecting rhombus dots indicates noise measurement values according to embodiments. A smaller noise value is measured in the cross-flow fan according to embodiments in the overall air volume range, and it may be found that noise reduction performance is improved accordingly.

FIG.8is a graph for comparison in noise reduction performance between a cross-flow fan according to a related art and a cross-flow fan according to embodiments through noise spectrum analysis. The X-axis of the graph represents a frequency range of generated noise, and the Y-axis represents intensity of the generated noise in decibel (dB).

A black line on the graph indicates a noise spectrum of the cross-flow fan according to the related art, and a gray line indicates a noise spectrum of the cross-flow fan according to embodiments.

The noise intensity of the cross-flow fan according to embodiments in area A (800 to 1300 Hz) in the drawing is measured as about 5 dB lower than that of the related art, and it may be found that noise reduction performance is improved accordingly.

While embodiments have been illustrated and described above, the embodiments are not limited to the aforementioned specific embodiments, various modifications may be made by a person with ordinary skill in the technical field to which the embodiments pertain without departing from the subject matters that are claimed in the claims, and these modifications should not be appreciated individually from the technical spirit or prospect.