JP3469857B2 - Axial flow fan for cooling air circulation - Google Patents

Abstract

An axial flow fan for refrigerators is disclosed. In the axial flow fan of this invention, a hub(51) is mounted to the rotating shaft of a drive motor, with a plurality of blades(55) regularly fixed around the hub(51). A variety of designing factors of the blades, such as the number of blades, hub ratio, sweep angle, pitch angle and maximum camber ratio, are optimally designed to allow a smooth flow of cool air agreeable with both the large pressure loss and complex flow passage of refrigerators while accomplishing a reduction in air flow noise of the refrigerators. A vortex prevention means is provided on the concave back surface of the annular rim formed of the shroud for preventing discharged air from forming a vortex stream in back of the fan. <IMAGE>

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial flow fan for supplying air cooled by an evaporator in a refrigerator to a freezing compartment and a refrigerating compartment, and particularly to the number of rotating blades of the fan, hub ratio, sweep angle, Axial flow for cold air circulation in refrigerators that optimizes fan design factors such as pitch angle and maximum camber ratio to achieve low noise and reduces eddy currents around the fan to reduce flow resistance It's about fans.

[0002]

2. Description of the Related Art FIG. 11 is a perspective view of a conventional cold air circulating axial fan, and FIG. 12 is a cross-sectional view showing an end portion of a rotary blade of a cold air circulating axial fan. The structure and operation of the conventional axial fan for circulating the cool air of the refrigerator will be described with reference to FIGS. 11 and 12 .

The axial fan for circulating cold air is composed of a hub 1 connected to a rotary shaft of a blower motor and receiving a driving force of the blower motor, and a plurality of rotary blades 5 provided on the outer peripheral surface of the hub 1 at regular intervals. Composed. The rotating blades 5 are usually composed of three to four, the hub ratio, which is the diameter ratio of the outer diameter of the hub 1 to the fan, is 0.25 to 0.3, and the pitch angle of the rotating blades 5 is 25 ° to. It is 35 °.

Here, the pitch angle is an angle formed by a straight line connecting the leading edge and the trailing edge of the rotary blade 5 and a line in the radial direction, and how much the rotary blade 5 is inclined with respect to a plane perpendicular to the rotary axis. Means formed. However, depending on the fan design factors such as the number of rotating blades 5 of the axial fan for cold air circulation, the hub ratio, the pitch angle, etc. configured as described above, the pressure loss and the complicated flow of the refrigerator, which are increasing in size, are likely to occur. There has been a problem that the flow noise suitable for the road characteristics cannot be generated and the noise of the refrigerator increases.

In such an axial-flow fan, noise is generated when the rotating blade 5 that follows rotates hits the swirl zone generated while the rotating blade 5 in the front rotates while the rotating blade 5 is used as a reference. (Blade vortex
interaction) phenomenon occurs. In the recent design of axial fans, active research has been conducted to reduce such BVI phenomenon.

[0006] of the axial flow fan blade tip 5a, as shown in FIG. 1
As shown in FIG. 2 , the blade tip 5a has a slow cross-section formed by a pressure surface 5b, which is a side surface on which pressure due to air flow acts, and a negative pressure surface 5c, on which a negative pressure acts, on the opposite side surface of the pressure surface 5b. Therefore, the positive pressure recovery of the air from the pressure surface 5b of the rotary blade 5 to the negative pressure surface 5c occurs rapidly.

Therefore, the main frequency of the noise generated by the collision of the peripheral object and the flow due to the rotation of the rotating blade 5 is represented by a positive integer multiple of the product of the number of rotating blades 5 and the number of rotations. Blade passing frequency) becomes low. By the way, refrigerator compressors, machine room fans,
Since the door of a refrigerator for preventing noise that is generated by a fan for circulating cold air and then flows to the outside through various routes is generally formed so as to block high-frequency noise of 700 Hz or higher. The low BPF generated by the axial fan can hardly be blocked by the refrigerator door.

In other words, the conventional cool air circulation fan mainly produces a low-frequency band noise with a low BPF, and therefore, the shielding sound effect of the refrigerator door, that is, the noise reducing effect, can hardly be obtained. There is a problem that the noise flowing out from the outside becomes large.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to reduce the number of rotating blades so as to meet the noise reduction of a fan. An object of the present invention is to provide an axial fan for cold air circulation of a refrigerator, which optimizes fan design factors such as a hub ratio, a sweep angle, a pitch angle, a maximum camber ratio, etc. to reduce operating noise of the refrigerator.

[0010]

To achieve the above object, an axial fan for circulating cold air of a refrigerator according to the present invention comprises a hub connected to a rotating shaft of a blower motor and a peripheral surface of the hub at regular intervals. In the axial fan including a plurality of rotating blades provided, the rotating blade comprises at least seven, and a hub ratio, which is a ratio of a diameter of the hub to an outer diameter of the rotating blade, is 0.45 to 0.55. Yes,
The pitch angle of the rotating blade is 32 ° ± 2 ° for the rotating blade tip and 45 ° ± 2 ° for the rotating blade hub, and the maximum camber rate of the rotating blade is 11.5 ± 0.5 for the rotating blade tip. %, 8 ± 0.5% in the rotating blade hub, and the sweep angle of the rotating blade is 32 ° to 34 °.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view of an axial fan for circulating cold air according to the present invention, FIG. 2 is a front view and a plan view of the axial fan according to the present invention, and FIG. 3 is a rotary blade of the axial fan according to the present invention. FIG. 4 is a sectional view taken in a circumferential direction, and FIG. 4 is a sectional view showing an end portion of a rotating blade of an axial fan according to the present invention.

The structure and operation of the axial fan for circulating cold air of the refrigerator according to the present invention will be described with reference to FIGS. 1 to 4.
The axial fan for circulating cold air according to the present invention is shown in FIGS.
As shown in (1), it includes a hub 51 connected to the rotating shaft of the blower motor, and a plurality of rotating blades 55 provided on the outer peripheral surface of the hub 51 at regular intervals. The rotating blade 5
5 consists of at least 7 or more. More specifically, the number of the rotary blades 55 is most preferably 9 in consideration of various items such as efficiency, air volume, and air pressure.

The hub ratio, which is the ratio of the outer diameter (ID) of the hub 51 and the outer diameter (OD) of the fan, is 0.45 to 0.5.
The diameter of the hub 51 is distributed within the range of 55 ± 5 mm, and the outer diameter of the fan, that is, the outer diameter of the rotary blade 55 is distributed within the range of 110 ± 10 mm.

Sweep angle (θ) of the rotary blade 55
Are distributed in the range of 32 ° to 34 °. Here, the sweep angle (θ) is an angle formed by a straight line connecting the center of the rotating blade hub 55b and the center of the rotating blade tip 55a and a straight line connecting the center of the rotating blade hub 55b and the center of the hub 51. As shown, the rotary blade 55
Means how much is formed in front of the rotation direction.

Further, the pitch angle (Ψ) of the rotary blade 55
Is distributed at 32 ° ± 2 ° on the rotary blade tip 55a and 45 ° ± 2 ° on the rotary blade hub 55b. here,
The pitch angle (Ψ) is an angle formed by a straight line connecting the leading edge 57a and the trailing edge 57b of the rotary blade 55 and an X axis perpendicular to the Z axis which is the rotary axis, and the rotary blade 55 is the rotary axis Z. It means how obliquely it is formed with respect to the plane perpendicular to the axis.

The maximum camber position of the rotary blade 55 is 0.65, which is evenly distributed from the rotary blade hub 55b to the rotary blade tip 55a, and the maximum camber rate is 11.5% at the rotary blade tip 55a. It is distributed at 8% on the blade hub 55b.

Here, the maximum camber position is a position where the rotary blade 55 is farthest from a cord (CL) which is a straight line connecting the leading edge 57a and the trailing edge 57b of the rotary blade 55,
The distance between the straight line and the rotary blade 55 at this time is the maximum camber (C). The maximum camber rate is a ratio of the maximum camber (C) to the code length (CX) expressed as a percentage. The maximum camber position is
It is shown by the ratio of the distance (CP) between the leading edge 57a of the blade and the point on the cord where the maximum camber is located, with respect to the length (CX) of the cord.

The rake angle indicating the degree to which the rotary blade 55 is tilted with respect to the positive axial direction is zero. As described above, when the sweep angle (θ), the pitch angle (Ψ), and the maximum camber rate of the rotary blade 55 are made large, the fluid noise generated by the fan itself is reduced. In addition, the rotation of the rotary blade 55 increases the BPF, which is the main frequency of noise generated by collision of surrounding objects with the flow, and most of the BPF is blocked by the refrigerator door. Greatly reduced.

As shown in FIG. 4, the rotary blade tip 55a of the rotary blade 55 has a pressure surface 56b, which is a front surface on which air pressure acts, and a negative pressure surface 56a, on which a negative pressure acts, behind the pressure surface 56b. And is formed so as to bend with a predetermined curvature from the pressure surface 56b toward the suction surface 56a. At this time, the rotary blade tip 55
It is preferable that a has the same curvature as the radius of 0.1 times the fan diameter or less.

As described above, the rotary blade tip 55a
, The positive pressure recovery of the air passing from the pressure surface 56b to the negative pressure surface 56a gradually progresses.
The generation of the swirl zone that occurs after 5 is suppressed, and the BVI is weakened. The noise generation ratios due to the respective design factors of the axial fan according to the present invention configured and operated as described above are graphed in FIGS. 5, 6, 7, 8 and 9, respectively.

That is, the graph shown in FIG. 5 shows the noise ratio depending on the hub ratio. When the hub ratio is 0.45 to 0.55, the noise is 22.3 ± 0.2 dB, which is the minimum value.
Particularly, when the hub ratio is 0.5, the noise shows the lowest value.
The graph shown in FIG. 6 represents the noise factor according to the sweep angle (θ), and the sweep angle (θ) is 32 ° to 34 °.
The noise level is 22.4 ± 0.2 dB, which is the lowest value.

The graph shown in FIG. 7 shows the noise factor depending on the pitch angle (Ψ). The pitch angle (Ψ) is 32 ° ± 2 ° for the rotary blade tip 55a and 45 for the blade hub 55b.
When distributed as ° ± 2 °, noise is 22.3 ± 0.2 dB
And the lowest value. The graph shown in FIG. 8 shows the noise rate according to the maximum camber rate (CP). The maximum camber position (CP) is 0.65 and the maximum camber rate is uniformly distributed from the rotary blade hub 55b to the rotary blade tip 55a. Is 11.5% with the rotating blade tip 55a,
When distributed with the rotating blade hub 51 at 8%, the noise is 2
It represents a minimum value of 2.5 dB.

The graph shown in FIG. 9 shows the noise rate depending on the rake angle. When the rake angle is 0, the noise is 23
It represents the minimum value in dB. When the axial fan as described above is applied to a refrigerator, a front noise characteristic can be obtained as shown in FIG. Here, a graph showing the forward noise characteristic of the existing axial fan is shown in FIG. Comparing the graphs of (a) and (b) of FIG. 10 with each other, compared to the case where the existing axial fan is applied to the refrigerator, when the axial fan of the present invention is applied to the refrigerator, the ventilation noise of the refrigerator is forward. It can be seen that it is reduced by about 4.3 dB (A) from the standard.

[0024]

As described above, the axial fan for cold air circulation of the refrigerator according to the present invention has a number of rotating blades, a hub ratio, a sweep angle (θ), a pitch angle (Ψ), a maximum camber rate, and the like. By optimizing the design factors of the fan, it is possible to generate a flow of cold air suitable for a large pressure loss and complicated flow path characteristics of the refrigerator and to reduce fluid noise of the fan itself.

Further, in the axial fan according to the present invention, the BPF, which is the main frequency of noise generated by the collision of the surroundings and the flow due to the rotation of the rotating blade 55, is more than doubled than that of the existing fan, and therefore, most of the fan is used. Since the BPF is blocked by the refrigerator door, there is an advantage that the outflow noise of the refrigerator is significantly reduced.

Further, in the axial fan for circulating cold air according to the present invention, since the rotary blade tip 55a is bent with a predetermined curvature, the swirl zone generated after the rotary blade 55 is suppressed, and the swirl zone is continuously rotated. Rotating blade 55
There is an advantage that BVI, which is a phenomenon in which noise is generated while hitting each other, is weakened.

[Brief description of drawings]

FIG. 1 is a perspective view of an axial fan for cold air circulation according to the present invention.

FIG. 2 is a view showing an axial fan for circulating cold air according to the present invention, (a) is a front view and (b) is a plan view.

FIG. 3 is a cross-sectional view showing a state in which a rotating blade of an axial fan for circulating cold air according to the present invention is cut in a circumferential direction.

FIG. 4 is a cross-sectional view showing an end portion of a rotating blade of an axial flow fan for circulating cold air according to the present invention.

FIG. 5 is a graph showing a noise ratio according to a hub ratio of an axial flow fan for circulating cold air according to the present invention.

FIG. 6 is a graph showing a noise factor according to a sweep angle of an axial fan for cold air circulation according to the present invention.

FIG. 7 is a graph showing the noise rate according to the pitch angle of the axial fan for circulating cold air according to the present invention.

FIG. 8 is a graph showing the noise ratio according to the maximum camber ratio of the axial fan for cold air circulation according to the present invention.

FIG. 9 is a graph showing the noise rate due to the rake of the axial fan for cold air circulation according to the present invention.

FIG. 10 is a graph showing a front noise characteristic of a refrigerator in which a cold air circulating axial fan according to the related art and a cold air circulating axial fan according to the present invention are applied and compared.

FIG. 11 shows a conventional axial fan for circulating cold air .
It is a perspective view.

FIG. 12: Rotation of an axial fan for circulating cold air according to the prior art
It is sectional drawing which shows the edge part of a blade .

[Explanation of symbols]

51 ... Hub 55 ... Rotating blade 55a ... Rotating blade tip 55b ... Rotating blade hub 57a ... Leading edge 57b ... Trailing edge θ: sweep angle Ψ ... Pitch angle CP ... Maximum camber position

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-10-122194 (JP, A) JP-A-7-167095 (JP, A) JP-A-5-44694 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) F04D 29/38

Claims (5)

(57) [Claims] 1. An axial flow fan including a hub connected to a rotation shaft of a blower motor and a plurality of rotating blades provided on an outer peripheral surface of the hub at regular intervals, wherein the rotating blade comprises at least seven. The hub ratio, which is the ratio of the diameter of the hub to the outer diameter of the rotating blade, is 0.45 to 0.55, and the pitch angle of the rotating blade is 32 ° ± 2 ° at the rotating blade tip and at the rotating blade hub. 45 ° ± 2 °, the maximum camber rate of the rotating blade is 11.5 ± 0.5% for the rotating blade tip and 8 ± for the rotating blade hub.
The axial fan for circulating cold air, wherein the rotating blade has a sweep angle of 32 ° to 34 °. 2. The axial fan for circulating cold air according to claim 1, wherein the rotary blade comprises nine blades. 3. The cold air circulation shaft according to claim 1, wherein the maximum camber position of the rotary blade is 0.65 ± 0.05, and the rotary blade hub and the rotary blade tip are uniformly distributed. Flow fan. 4. The axial fan for circulating cold air according to claim 1, wherein the rotary blade tip of the rotary blade is bent from the pressure surface to the negative pressure surface with a predetermined radius of curvature. 5. The axial fan for cold air circulation according to claim 1, wherein the rake angle of the rotary blade is zero.