An axial flow fan

Abstract

An axial flow fan includes a hub and a plurality of blades arranged on the circumference of the hub, wherein the placement angles between two adjacent blades are equal, and each blade uses a cut-out line to cut out materials of different weights at the outer edge of equal-diameter blades to achieve unequal blade centroid angles; when the number of blades is 3 and each blade has one cut-out line, each blade is provided with a first cut-out line, a second cut-out line and a third cut-out line, and the shapes of the first cut-out line, the second cut-out line and the third cut-out line are not completely the same to achieve unequal diameters at the cut-out portion of the blade outer edge. The unequal diameters and unequal centroid angles at the cut-out portion of the blade outer edge of the axial flow fan of the present invention, on the one hand, make the phase difference between two adjacent blades beating the air different, and on the other hand, can reduce the pulsation intensity of the blade beating the air at the fundamental frequency. The superposition of the above two aspects effectively reduces the sound pressure level of the fan and significantly improves the sound quality.

Description

Technical Field

[0001] The invention relates to a fan, in particular to an axial flow fan. Background Art

[0002] like Figure 4 , Figure 5 As shown, the shape and weight of each blade of the axial flow fans currently on the market are the same, so the position of the center of mass of each blade is the same, and the angle of the center of mass of each blade is equal. The pulsation intensity of each blade of the axial flow fan with this structure hitting the air is the same, and the phase difference between the interaction between two adjacent blades and the air is the same, so the rapid rotation of the fan will make this periodic excitation particularly obvious, and the coherent effect of this harmonic enhances the pulsation intensity at the pass frequency, so peaks appear at the fundamental frequency and harmonic values ​​in its discrete noise spectrum, making the sound pressure level of the axial flow fan relatively high and the noise relatively loud.

[0003] Therefore, further improvements are necessary. Summary of the invention

[0004] The purpose of the present invention is to provide an axial flow fan with simple structure, low noise, good sound quality and strong practicality, so as to overcome the shortcomings of the prior art.

[0005] An axial flow fan designed for this purpose includes a hub and a plurality of blades arranged on the circumference of the hub, wherein the angles between two adjacent blades are equal. The invention is characterized in that each blade uses a cutting line to cut materials of different weights at the outer edge of blades of equal diameter to achieve unequal angles of the blade center of mass.

[0006] The cut-off profile of each blade is one or more curves.

[0007] The number of the blades is 3 to 6.

[0008] When the number of the blades is 3 and each blade has one cutting line, each blade is provided with a first cutting line, a second cutting line and a third cutting line respectively, and the shapes of the first cutting line, the second cutting line and the third cutting line are not completely the same, so as to achieve unequal diameters at the cutting point of the outer edge of the blade.

[0009] The placement angles between two adjacent blades are a, b, and c respectively, and a=b=c.

[0010] The centroid angles between two adjacent blades are β1, β2, and β3 respectively, β1≠β2≠β3 or β1=β2≠β3 or β1≠β2=β3.

[0011] The plane projection outer angle of the axial flow fan is α2, the number of blades of the axial flow fan is N, and the relationship between α2 and N is:

[0012]

[0013] A circular sleeve is arranged in the middle of the wheel hub, and reinforcing ribs are connected between the sleeve and the inner wall of the wheel hub.

[0014] The axial flow fan of the present invention uses different shapes of cutting lines on each blade to cut materials of different weights on the outer edge of equal-diameter blades, so that the diameters and the centroid angles of the blade outer edge cutouts are unequal. On the one hand, the phase difference between two adjacent blades beating the air is different, and on the other hand, the pulsation intensity of the blade beating the air at the fundamental frequency can be reduced. The superposition of the above two aspects effectively reduces the sound pressure level of the fan and significantly improves the sound quality. It has the characteristics of simple structure, low noise, good sound quality and strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a front view of an axial flow fan in one embodiment of the present invention.

[0016] Figure 2 and Figure 3 Schematic diagram of the overall structure of an axial flow fan in different orientations according to an embodiment of the present invention.

[0017] Figure 4 and Figure 5 Schematic diagram of the overall structure of two traditional axial flow fans. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0019] See also Figure 1-Figure 3 The axial flow fan comprises a hub 1 and a plurality of blades 2 arranged on the circumference of the hub 1. The angles between two adjacent blades 2 are equal. Each blade 2 uses a cutting line to cut off materials of different weights at the outer edge of equal-diameter blades (N-1 blades 2 are allowed to have the same weight of cut materials, N is the number of blades, and the formula below explains) to achieve unequal angles of the center of mass of the blades 2 (the center of mass is the mass center of an object, referring to an imaginary point on a material system where the mass is considered to be concentrated).

[0020] The cut-off profile of each blade 2 is one or more curves.

[0021] The number of blades 2 is 3 to 6.

[0022] When the number of blades 2 is 3 and each blade 2 has one cut-out profile line, each blade 2 is respectively provided with a first cut-out profile line X, a second cut-out profile line Y and a third cut-out profile line Z. The shapes of the first cut-out profile line X, the second cut-out profile line Y and the third cut-out profile line Z are not completely the same, so as to achieve unequal diameters at the cut-out portion of the outer edge of the blade 2, thereby making the positions of the centroids of the blades 2 different, so as to achieve unequal angles of the centroids of the blades 2.

[0023] The placement angles between two adjacent blades 2 are a, b, and c, respectively, and a=b=c; the center of mass angles between two adjacent blades 2 are β1, β2, and β3, respectively, and β1≠β2≠β3 or β1=β2≠β3 or β1≠β2=β3.

[0024] A circular sleeve 1.1 is provided in the middle of the wheel hub 1, and a reinforcing rib 1.2 is connected between the sleeve 1.1 and the inner wall of the wheel hub 1.

[0025] The unequal distance angles of the blade centroids of the present invention need to satisfy the following relationship:

[0026]

[0027]

[0028]

[0029] Where N is the number of blades; β j The purpose of satisfying the above formula is that the center of mass of the entire axial flow fan reaches a dynamic balance state when it is on the axis of rotation, and the placement angles between two adjacent blades 2 are equal, which is to ensure that the fan will not vibrate more due to unequal spacing during operation, and will not excessively affect the aerodynamic performance of the fan due to unequal spacing.

[0030] The starting point of the cut-off line of the axial flow fan is O (see Figure 1 ) must meet the following requirements:

[0031] α2 / 2-10°≤α≤α2 / 2+10°

[0032] like Figure 4 As shown, the plane projection outer angle α2 of the traditional axial flow fan (equal diameter blades) needs to satisfy the following relationship:

[0033]

[0034] When the size of the plane projection outer angle α2 satisfies the above relationship, the fan has better aerodynamic performance, lower sound pressure level, and lower spectrum peak. That is, under the same air volume, when the size of the plane projection outer angle α2 satisfies the above relationship, the axial flow fan has lower noise value and better sound quality.

[0035] Working principle of axial flow fan:

[0036] For an equidistant fan, the pulsation intensity of each blade 2 hitting the air is the same, and the phase difference between the interaction between two adjacent blades 2 and the air is 2π / N. The rapid rotation of the fan will make this periodic excitation particularly obvious. The coherent effect of this harmonic enhances the pulsation intensity at the pass frequency, so peaks appear at the fundamental frequency and harmonic values ​​in its discrete noise spectrum. The expression of the fundamental frequency of rotation noise is:

[0037]

[0038] For unequally spaced fans, β j is a random variable, and the β between adjacent leaves 2 j The angles are usually different. j The value is randomly selected, so the frequency of blade 2 of the unequally spaced fan beating the air is different, the gas pressure pulsation generated is also different, and the phase difference between two adjacent blades 2 beating the air is also different. In the spectrum curve characteristics, the peak value of the unequally spaced fan at f1 is weakened into a smaller value distributed at the fundamental frequency and its multiples, and the total sound pressure level of the unequally spaced fan is also significantly reduced.

[0039] The unequal angles of the center of mass of the blades 2 of the axial flow fan are achieved by the unequal diameters of the outer edges of the blades 2. On the one hand, this makes the phase difference between the two adjacent blades 2 beating the air different. On the other hand, it can reduce the pulsation intensity of the blades 2 beating the air at the fundamental frequency. The combined effect of the above two aspects effectively reduces the sound pressure level of the fan and significantly improves the sound quality.

[0040] The above is a preferred embodiment of the present invention, which shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for illustrating the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. An axial flow fan, comprising a hub (1) and a plurality of blades (2) arranged on the circumference of the hub (1), wherein the angles between two adjacent blades (2) are equal, and characterized in that: Each blade (2) uses a cutting profile to cut off materials of different weights at the outer edge of the blades with equal diameters, so as to achieve unequal centroid angles of the blades (2); The number of the blades (2) is 3 to 6; When the number of the blades (2) is 3 and each blade (2) has one cutting profile line, each blade (2) is provided with a first cutting profile line (X), a second cutting profile line (Y) and a third cutting profile line (Z), respectively, and the shapes of the first cutting profile line (X), the second cutting profile line (Y) and the third cutting profile line (Z) are not completely the same, so as to achieve unequal diameters at the cutting portion of the outer edge of the blade (2); The plane projection outer angle of the axial flow fan is α2, the number of blades (2) of the axial flow fan is N, and the relationship between α2 and N is: ； The placement angles between two adjacent blades (2) are respectively a, b, and c, where a=b=c; The centroid angles between two adjacent blades (2) are β1, β2, and β3 respectively, β1≠β2≠β3 or β1=β2≠β3 or β1≠β2=β3; The starting cut-off point O of the cut-off line of the axial flow fan needs to meet the following range: α2 / 2-10°≤α≤α2 / 2+10°。 2. The axial flow fan according to claim 1, characterized in that: A circular shaft sleeve (1.1) is provided in the middle of the wheel hub (1), and a reinforcing rib (1.2) is connected between the shaft sleeve (1.1) and the inner wall of the wheel hub (1).

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