JPH11132194A - Axial flow fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an air blowing noise, and increase an air blowing quantity by molding respective blades so that a cross section running along a circular arc in a prescribed radius forms a streamline shape in an axial flow fan by arranging plural blades along a peripheral surface of a cylindrical boss hub. SOLUTION: An axial flow fan of an air blower used for an outdoor unit of an air conditioner, is formed by arranging three blades 2 through a triangular rib 3 along a peripheral surface of a cylindrical boss hub 1 fitted to and installed on a rotary shaft of a fan motor. In the respective blades 2, its outer peripheral part 4 is formed into a curved shape where a front edge part 6 is projected larger than a connecting part 5 of the triangular rib 3 and the boss hub 1. In the respective blades 2, the front edge part 6 side is thick by being formed into a cross-sectional spindle shape, and has the almost same thickness toward a rear edge part 7 from an intermediate part, and is thin in a cross-sectional pointed shape over the front edge from the rear edge part 7 side, and a negative pressure surface is smoothly bent toward the rear edge part 7 and an outer peripheral part 4 from a maximum thickness part on the front edge part 6 side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blower which is disposed, for example, in an outdoor unit of an air conditioner and blows heat exchange air to the outside through a heat exchanger on a suction side, and particularly relates to a blade in an axial fan. .

[0002]

2. Description of the Related Art For example, in an outdoor unit of an air conditioner, a blower is disposed so as to be opposed to a heat exchanger.
In this blower, the fan suction side faces the heat exchanger, and the blowout side faces a blowout port provided on the front surface of the unit main body.

[0003] The structure of the blower is composed of a fan motor and a fan fitted to a rotating shaft of the fan motor. In selecting the shape of the fan, an axial fan is frequently used in order to promote the thinning of the outdoor unit, to reduce the internal space, and to ensure heat exchange efficiency with the heat exchanger.

The axial fan has a cylindrical boss hub fitted on a rotating shaft of a fan motor, and blades (hereinafter referred to as blades) provided along triangular ribs along the peripheral surface of the boss hub. Consists of Three or four blades are provided at predetermined intervals.

[0005]

The conventional blade has a uniform thickness in the cross section along the circular arc at the radius r, or has a thicker shape only at the leading edge.
When viewed from the negative pressure surface, these blades are not smoothly curved from the front edge to the rear edge.

[0006] Therefore, the boundary layer turbulence generated on the negative pressure surface is large, and a large vortex (wake vortex) is generated at the trailing edge of the blowout, thereby increasing the blowing noise. In particular, in the case where only the leading edge portion is thick, boundary layer turbulence increases at the boundary between the thick portion and the thin portion, which causes a large noise.

The position of the inflection point on the outer periphery of the blade is set differently from the length of the leading edge. When this inflection point position is larger than the front edge length, the airflow noise decreases, but the air volume decreases, and when the inflection point position is smaller than the front edge length, the air volume increases but the airflow increases. The noise increases.

It is also known that the load applied to the rotating fan motor varies depending on the position of the trailing edge of the blade connected to the triangular rib and the direction of rotation with respect to the rotation axis and the rotation direction.

In the conventional fan, since the blade mounting angle determined from the chord length of the blade and the fan height is set to be larger than the mounting angle with respect to the rotation axis direction and the rotation direction, the load on the motor also increases. I have.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the load on the fan motor, thereby reducing the blowing noise and increasing the blowing amount. Another object of the present invention is to provide an axial fan having a blade capable of improving the blowing performance.

[0011]

According to a first aspect of the present invention, there is provided an axial-flow fan comprising a plurality of blades along a peripheral surface of a cylindrical boss hub. An axial fan, wherein the blade is formed so that a cross section along an arc at a predetermined radius r forms a streamline shape.

According to a second aspect of the present invention, in the axial flow fan according to the first aspect, the negative pressure surface of the blade is smoothly curved from a maximum thickness portion on a front edge portion side to a rear edge portion and an outer peripheral portion. It is characterized by.

According to a third aspect of the present invention, in the axial flow fan according to the first aspect, the blade is perpendicular to a leading edge R and a trailing edge R passing through a midpoint of the length of each of the leading edge and the trailing edge. In the cross section along the line (perpendicular to the tangent), the ratio of the cross-sectional thicknesses of the leading edge and the trailing edge is: leading edge thickness: trailing edge thickness = 3: 1.
Is set to be

According to a fourth aspect of the present invention, in the axial flow fan according to the first aspect, the blade has a front edge length extending from a midpoint of an R portion formed between the outer circumference and the front edge toward the outer circumference. A blade inflection point P is provided at the same length as
It is characterized in that it projects from the leading edge to the above-mentioned inflection point toward the outlet side, and projects from the inflection point P to the trailing edge toward the suction side.

According to a fifth aspect of the present invention, in the axial flow fan according to the first aspect, a triangular rib serving as a blade mounting portion is formed between the boss hub and the blade, and an intersection between the triangular rib and a trailing edge portion. Is M, the intersection of the outer peripheral portion and the rear edge portion is N, and the center of rotation of the fan is O, the straight line ON =
(2.2 to 2.4) × the straight line OM.

According to a sixth aspect, in the axial fan according to the fifth aspect, an angle θ between the straight line ON and the straight line OM is defined.
Is set to be in the range of 15 ° to 20 °.

According to a seventh aspect of the present invention, in the axial flow fan according to the fifth aspect, an angle β formed between a straight line OS connecting an intersection S between the front edge portion and the outer peripheral portion and the center of rotation O of the fan and the straight line OM is , 95 ° to 105 °.

According to an eighth aspect of the present invention, in the axial flow fan according to the fifth aspect, an angle α formed between the straight line OM and a plane perpendicular to the fan rotation axis of the boss hub is equal to the straight line OM and the straight line ON.
Are set to be in the same range (15 ° to 20 °) as the angle θ formed by

According to a ninth aspect, in the axial flow fan according to the fifth aspect, an angle θ between the straight line OM and the straight line ON is provided.
Is set to satisfy γ> θ with respect to the blade mounting angle γ (sin γ = string length CL / fan height H).

By adopting the means for solving such a problem, the load on the fan motor is reduced, the blowing noise is reduced, and the blowing volume is increased to improve the blowing performance. Get.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described.
This will be described with reference to the drawings. FIG. 1 shows, for example, a positive pressure surface side which is an outlet side of an axial fan of a blower used for an outdoor unit of an air conditioner.

The axial flow fan includes a cylindrical boss hub 1 fitted on a rotating shaft of a fan motor (not shown), and blades 2 as wings provided along a peripheral surface of the boss hub 1.
Consists of

Then, a triangular rib 3 is interposed at the connecting portion of the boss hub 1 of the blade 2. The pressure side of the triangular rib 3 has a triangular frame shape, while the suction side, which is the suction side, is closed by a lid.

The above-mentioned plurality of blades 2
Of the triangular rib 3 and the connecting portion 5 of the boss hub 1 protrude largely to the front edge 6 on the rotation direction side, while the rear edge 7 on the anti-rotation direction side extends in a direction substantially orthogonal to the rotation direction. It is formed in a curved shape with a large radius of curvature.

FIG. 2A shows only one blade 2 taken out from the boss hub 1 and shown from the pressure side. When an arc having a predetermined radius r is drawn with the fan rotation center which is the center of the boss hub 1 as O, this arc-shaped line 3F-3
A cross section of the blade 2 cut along F is as shown in FIG.

That is, the blade 2 is thick at the front edge 6 side and is formed to have a spindle shape in cross section, has substantially the same thickness from the middle portion to the rear edge 7, and extends from the rear edge 7 side to the edge. It is formed to be thin with a sharp cross section throughout.

As shown in FIG. 5, on the negative pressure surface of the blade 2, the leading edge 6 extends from the line a to a along the maximum thickness portion of the streamlined section to the trailing edge 7 and the outer peripheral portion 4. It is smoothly curved toward.

As shown in FIGS. 2A and 2B again, in the blade 2, the middle portion 8 of the R portion formed between the outer peripheral portion 4 and the front edge portion 6 extends from the midpoint 8 to the outer peripheral portion 4 side. A blade inflection point P is provided at the same length as the length of the front edge 6 toward the blade.

As shown in FIG. 3 again, the cross section of the blade 2 in the direction of rotation of the axial fan is such that the portion from the leading edge 6 to the inflection point P projects toward the blowing side, and the portion from the inflection point P to the trailing edge 7. Has a compound curved surface protruding toward the suction side.

As shown in FIG. 6A, at the leading edge 6 and the trailing edge 7 of the blade 2, the midpoints b,
(B) and (C) show cross sections taken along perpendicular lines (perpendicular to the tangent line) 4B-4B and 4C-4C of the leading edge R and trailing edge R passing through c. .

FIG. 3B shows a cross-sectional shape on the front edge portion 6 side, and FIG. 3C shows a cross-sectional shape on the rear edge portion 7 side. That is, although the cross section of the trailing edge portion 7 has been described in FIG. 3 as being sharp, the minimum thickness is actually secured.

In this case, the portions 4B-4B, 4
In C-4C, the ratio of the cross-sectional thickness obtained by cutting the leading edge 6 and the trailing edge 7 is such that the leading edge 6 thickness: the trailing edge 7 thickness = 3: 1.
It is set to be.

As shown in FIG. 7, the intersection between the triangular rib 3 between the boss hub 1 and the blade 2 and the rear edge 7 is M, and the intersection between the outer peripheral portion 4 and the rear edge 7 is N. At this time, the straight line ON connecting the fan rotation center O and the intersection point N is set to be 2.2 to 2.4 times the straight line OM connecting the fan rotation center O and the intersection point M.

The angle θ between the straight line ON and the straight line OM is set to be in the range of 15 ° to 20 °. Also, the intersection of the front edge 6 and the outer periphery 4 is denoted by S,
The angle β between the straight line OS connecting the fan rotation center O and the straight line OM is set to be in the range of 95 ° to 105 °.

As shown in FIG. 8, the angle α between the straight line OM and the boss hub upper surface 1a perpendicular to the fan rotation axis OL.
Is the angle θ between the straight line OM and the straight line ON described above.
Is set in the same range of 15 ° to 20 °.

As shown in FIG. 9, the straight line OM and the straight line O
The angle θ made with N is the blade mounting angle γ (sin γ =
It is set to be smaller than the chord length CL / fan height H (γ> θ).

The blade 2 of the axial fan configured as described above has the following characteristics.
That is, the blade 2 has a streamlined cross section along an arc having a predetermined radius r. The negative pressure surface of the blade 2 is smoothly curved from the thickest portion on the front edge portion 6 side to the rear edge portion 7 and the outer peripheral portion 4. The cross section along the tangent line of the leading edge R and the trailing edge R passing through the midpoint of the length of the leading edge 6 and the trailing edge 7, where the leading edge thickness: the trailing edge thickness = 3: 1. It was set to become.

As a result, as shown in FIG. 4A, the boundary layer turbulence K generated by the wind flow on the blade 2 surface is reduced, and the wake vortex Z formed near the trailing edge 7 of the blowout is reduced. Noise is reduced.

On the other hand, as shown in FIG. 3B, the conventional blade 2A having a uniform thickness and the conventional blade 2B having a thicker front edge only as shown in FIG.
In both cases, the boundary layer turbulences Ka and Kb generated by the wind flow are large, and the wake vortices Za and K formed near the trailing edge.
Zb is generated large, and the blowing noise is large.

The blade 2 has the same length as the front edge portion 6 from the midpoint 8 of the R portion formed between the outer peripheral portion 4 and the front edge portion 6 toward the outer peripheral portion 4. A blade inflection point P was provided.

Depending on the position of the inflection point P, the blade 2
It is known that the flow of wind over a surface changes. When the position of the inflection point P on the outer peripheral portion 4 is larger than the length of the front edge portion 6, the blowing noise decreases but the air volume decreases. When the position of the inflection point P is smaller than the length of the front edge portion 6, the air volume increases, but the blowing noise increases. Therefore, as described above, the position of the inflection point P is set to the same length as the front edge portion 6, so that the balance between the blowing noise and the air volume is improved.

Further, the straight line ON is set to 2.2 to 2.4 × the straight line O.
M was set in the range. The angle θ between the straight line ON and the straight line OM was set in a range of 15 ° to 20 °. The angle β between the straight line OS and the straight line OM was set in the range of 95 ° to 105 °.

With these settings, as will be described later, effective conditions for the position of the trailing edge 7 on a plane perpendicular to the fan rotation axis OL and the position of the leading edge 6 with respect to the trailing edge 7 are set. It will be aligned.

That is, when viewed from a plane perpendicular to the fan rotation axis OL, the position of the rear edge 7 (the position of the straight line MN) is a straight line (reference line) connecting the fan rotation center O to the end N of the rear edge 7. The load on the rotating fan motor changes depending on the position with respect to the line (ON).

When the position of the trailing edge 7 (the position of the straight line MN) is above the drawing with respect to the reference line ON, in other words, the straight line O
If the angle θ between M and the straight line ON is large, the load on the fan motor increases.

Therefore, as described above, ON = 2.2.
２2.4 × OM, and θ = 15 ° -20 ° to optimize the position of the trailing edge 7 (the position of the straight line MN).
Furthermore, the position of the leading edge 6 with respect to the trailing edge 7 is also set to β = 95 to 105 °, so that the position of the leading edge 6 is optimized, and the load applied to the fan motor even when the air volume is large. Can be kept smaller.

The angle α between the straight line OM and the boss hub upper surface 1a is the angle θ between the straight line OM and the straight line ON,
The same range, 15 ° to 20 °, was set. The angle θ between the straight line OM and the straight line ON is the blade mounting angle γ (si
nγ = string length CL / fan height H) (γ>
θ).

The position of the trailing edge 7 in the direction of the fan rotation axis OL is determined by such an angle setting. That is,
8, when viewed from the XZ plane, the position of the trailing edge 7 (the position of the straight line MN) is any position relative to the reference line q of the blade XZ plane (the straight line extending from the boss hub upper surface 1a in the X direction). , The load applied to the rotating fan motor changes.

As the position of the trailing edge 7 (the position of the straight line MN) moves away from the boss hub upper surface 1a, that is, as the angle α between the straight line OM and the boss hub upper surface 1a increases, the load on the fan motor increases. .

Therefore, the previously described angle α = θ = 15 °
20 ° and a relationship of γ> θ is set, and the position of the trailing edge 7 in the direction of the fan rotation axis OL (the position of the straight line MN)
And the load on the fan motor can be kept small even with a large air volume.

[0051]

As described above, according to the present invention, since the cross section cut along the fan radius R is provided with a blade having a streamlined shape, the load on the fan motor is reduced and the blowing noise is reduced. In addition to this, there is an effect that the amount of air blow is increased and the air blowing performance is improved.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the present invention, as viewed from a positive pressure side of an axial fan.

FIG. 2A is a front view of the boss hub and one blade viewed from the positive pressure side in the embodiment. (B) is an enlarged view of a part of the blade.

FIG. 3 is a cross-sectional view of the embodiment along an arc at a radius R of the blade.

FIG. 4A is a characteristic diagram of a flow of wind along a blade according to the embodiment. (B) is a characteristic diagram of a wind flow along a conventional blade. (C) is a characteristic diagram of the wind flow along a different conventional blade.

FIG. 5 is a view for explaining positions of a leading edge maximum thickness portion, a trailing edge, a leading edge, and an outer peripheral portion as viewed from the blade negative pressure surface side in the embodiment.

FIG. 6A illustrates positions of perpendicular lines of a leading edge R and a trailing edge R passing through a middle point of each length of the leading edge and the trailing edge of the blade in the embodiment. Figure to do. (B) is sectional drawing which follows the 4B-4B line | wire of FIG. 6 (A). (C) shows FIG.
Sectional drawing which follows the 4C-4C line of (A).

FIG. 7A is a diagram illustrating the position of the trailing edge of the blade viewed from a plane perpendicular to the fan rotation axis according to the embodiment;
(B) is an enlarged view of a part of the blade.

FIG. 8 is a view for explaining the position of the trailing edge of the blade as viewed along the direction of the fan rotation axis according to the embodiment;

FIG. 9 is a diagram illustrating an attachment angle of the blade to the boss hub according to the embodiment.

[Explanation of symbols]

 1 boss hub, 2 blade, 4 front edge, 7 rear edge, 3 triangular rib.

Claims (9)

[Claims] 1. An axial flow fan comprising a plurality of blades provided along a peripheral surface of a cylindrical boss hub, wherein the blade has a streamline cross section along an arc at a predetermined radius r. An axial fan characterized by being formed into a shape. 2. The axial flow fan according to claim 1, wherein said blade has a negative pressure surface smoothly curved from a maximum thickness portion on a front edge portion side to a rear edge portion and an outer peripheral portion. 3. The blade according to claim 1, wherein the blade has a cross section along a tangent line (a line perpendicular to the tangent line) of the leading edge portion and the trailing edge portion passing through the midpoint of the respective lengths of the leading edge portion and the trailing edge portion. , The ratio of the cross-sectional thicknesses of the leading edge and the trailing edge is: leading edge thickness: trailing edge thickness = 3: 1
The axial flow fan according to claim 1, wherein the axial flow fan is set to: 4. The blade has a blade inflection point P at the same length as the front edge portion from the midpoint of the R portion formed between the outer peripheral portion and the front edge portion toward the outer peripheral portion. 2. The axial flow fan according to claim 1, wherein the axial flow fan is provided so as to protrude from the front edge portion to the inflection point toward the blowing side, and protrude from the inflection point P to the rear edge portion toward the suction side. 5. A triangular rib, which is a blade mounting portion, is formed between the boss hub and the blade. An intersection between the triangular rib and the rear edge is defined as M, and an intersection between the outer peripheral portion and the rear edge is defined as M. When N is set and the rotation center of the fan is set to O, the straight line ON =
2. The axial flow fan according to claim 1, wherein the axial flow fan is set so as to form (2.2-2.4) × straight line OM. 6. An angle θ between the straight line ON and the straight line OM.
The axial fan according to claim 5, wherein the angle is set to be in a range of 15 ° to 20 °. 7. A straight line OS connecting an intersection point S between the blade leading edge portion and the outer peripheral portion and a fan rotation center portion O;
6. The axial flow fan according to claim 5, wherein the angle β is set to be in a range of 95 ° to 105 °. 8. An angle α between the straight line OM and a plane perpendicular to the fan rotation axis of the boss hub is defined by a straight line OM and a straight line ON.
The axial flow fan according to claim 5, wherein the angle? Is set to be in the same range (15 to 20) as the angle? 9. An angle θ between the straight line OM and the straight line ON.
6. The axial flow fan according to claim 5, wherein is set so that γ> θ with respect to a blade mounting angle γ (sin γ = string length CL / fan height H).