JPH10196592A - Fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the vibration transmittivity of a vibrating mode of a blade part, and to obtain the high vibration isolation efficiency, by setting the flexural rigidity of plural ribs radially extended from a boss, so that the natural frequency of a torsional vibration system around a rotation axis of a fan, is lower than the frequency of the external force input from the rotation axis. SOLUTION: A propeller fan comprises a boss 5 into which a rotation axis 7 is inserted and fixed, a plural ribs 31 radially extended from the boss 5, a ring-shaped hub 2 connected with the outer edges of the ribs 31, and plural blades 1 mounted on an outer peripheral face of the hub 2. On this occasion, the thickness of an intermediate part of taper parts T respectively formed on the connecting parts at the boss 5 side and the hub 2 side, is thinned. By property designing the number of pieces, width and thickness of the ribs 31, the flexural rigidity of the ribs 31 can be determined so that the natural frequency of a torsional vibration system around the rotation axis 7 of the fan, is lower than the frequency of the external force input from the rotation axis 7. Thereby the vibration and the noise of the blade part can be reduced at low cost and with a simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fan incorporated in an air conditioner or the like and driven by a power source such as a motor.

[0002]

2. Description of the Related Art An example of a conventional propelleran is shown in FIG. 9, in which (A) is a partial longitudinal sectional view and (B) is a transverse sectional view taken along the line BB of (A). The fan 10 includes a boss 5 into which the rotating shaft 7 is inserted and fixed, a disk-shaped disk 4 connected to the front end of the boss 5, and a plurality (8 in the figure) extending radially from the boss 5.
B), a ring-shaped hub 2 connected to the outer peripheral edge of the disk 4 and the outer end of the rib 3, and a plurality of blades 1 attached to the outer peripheral surface of the hub 2. It is integrally molded with resin.

[0003]

When the fan 10 is driven by the motor 6 via the rotary shaft 7, the fan 10 is driven by the frequency component of torsional vibration based on the electromagnetic exciting force of the motor 6.
When the natural vibration mode of the wing 1 is excited and the wing 1 resonates, the wing 1 becomes a sound generator and generates noise.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its gist is a boss fixed to a rotating shaft driven by a power source. The natural frequency of the torsional vibration system around the rotation axis of the fan in the fan consisting of a plurality of ribs extending radially from the fan, a ring-shaped hub connected to the outer ends of these ribs, and a plurality of blades attached to the hub Wherein the bending rigidity of the rib is set so as to be smaller than the frequency of the external force input from the rotating shaft.

Another feature is that the bending rigidity of the rib is set as described above by appropriately designing at least one of the thickness, the width, and the number of the rib.

Another feature is that one or both of the connecting portions of the rib to the boss and the hub are tapered or rounded.

Another feature is that a folded portion is provided in the middle of the rib.

Another feature is that the ribs have a corrugated shape.

Another feature is that the rib is formed of a separate metal thin plate.

[0010] Still another feature is that the hub is divided for each of the blades, and an elastomer is interposed between a rib provided on the divided hub and a rib provided on a divided hub adjacent to the hub. I did it.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention is shown in FIG. 1, in which (A) is a partial longitudinal sectional view, and (B) is a transverse sectional view taken along the line BB of (A). is there. In the first embodiment, each rib 31 forms a tapered portion T at a connection portion on the boss 5 side and the connecting portion on the hub 2 side, and a thickness of an intermediate portion of the tapered portion T is reduced.

By appropriately designing the number, width and thickness of the ribs 31, the flexural rigidity of the ribs 31 is such that the natural frequency of the torsional vibration system around the rotation axis of the fan 10 is a factor of the external force input from the rotation axis 7. It is set to be lower than the frequency. The disk 41 is formed in an annular shape with a narrow width from the hub 2 toward the axis so as not to affect the torsional rigidity of the fan 10, but it can be omitted.

If the torsional vibration system around the rotation axis of the fan 10 is schematically represented as a free vibration of a one-mass system, its fundamental frequency fn
Is represented by (Equation 1).

[0014]

[Equation 1]

The vibration transmissibility Tr is represented by (Equation 2).

[0016]

[Equation 2]

FIG. 2 shows (Equation 2) with respect to a certain damping constant. As shown in FIG. 2, the fundamental natural frequency of the torsional vibration system around the rotation axis of the fan 10 is calculated from the natural frequency of one blade of the fan 10. By sufficiently reducing the vibration transmission coefficient, the vibration transmissibility is reduced, the response of the natural vibration mode of the blade 1 as a vibration or noise source is reduced, and the vibration isolation performance is improved.

As shown in FIG. 3, if the connecting portion of each rib 32 to the boss 5 and the hub 2 is formed in a round shape instead of the tapered portion T, the stress applied to the connecting portion can be reduced.

As shown in FIG. 4, if the length that affects the bending rigidity is increased by forming a folded portion U in the middle of each rib 33, the bending rigidity of the rib 33 can be reduced. Can be.

Further, as shown in FIG. 5, if a double folded portion W is formed symmetrically in the middle of each rib 34,
The bending stiffness of 34 can be further reduced.

As shown in FIG. 6, if each rib 35 is curved in a wave shape, the torsional rigidity can be reduced and the stress acting on each rib 35 can be reduced.

As shown in FIG. 7, the inner end of a rib 36 made of a thin metal plate is inserted into a groove 5a formed in the outer peripheral surface of the boss 5, and the outer end is formed in the inner peripheral surface of the hub 2. It can also be inserted into the groove 2a. By doing so, the bending rigidity of the rib 36 can be reduced, and at the same time, the strength can be improved.

In the embodiment shown in FIG. 8, the hub 2 is divided for each blade 1 to be independent, and the divided hubs 2A, 2A
Estramers 8 are interposed between adjacent ribs among ribs 3A, 3B, 3C, and 3D connected to B, 2C, and 2D, respectively. Thus, the material, shape,
A predetermined torsional rigidity can be obtained by appropriately selecting the dimensions.

Although not shown, the ribs 31, 32, 33, 34, 35, 36, and 3 A to 3 D in each embodiment are inclined with respect to the plane including the rotation axis so that the ribs have a blowing function. be able to. Further, the present invention is not limited to the propeller fan, but it is needless to say that it can be applied to any type of fan such as a radiant flow, a mixed flow, a multi-blade fan, a sirocco fan, and the like.

[0025]

According to the present invention, the bending stiffness of the ribs is set so that the natural frequency of the torsional vibration system around the rotation axis of the fan is smaller than the frequency of the external force input from the rotation axis. The vibration transmissibility of the mode can be reduced, and as a result, a high vibration isolation effect can be obtained, so that the noise radiated from the wings can be reduced.

If the bending stiffness of the rib is set by appropriately designing at least one of the thickness, width and number of the rib, vibration or noise of the wing portion of the fan can be reduced with a simple and inexpensive structure.

If one or both of the connecting portions of the rib to the boss and the hub are tapered or rounded, the strength of the connecting portion can be improved while reducing the bending rigidity of the rib.

By providing a folded portion in the middle of the rib, the bending rigidity of the rib can be easily reduced.

If the ribs are corrugated, the bending stiffness of the ribs can be easily reduced and the stress can be reduced.

If the rib is formed of a separate metal sheet, the strength of the rib can be improved while reducing the bending rigidity.

If the hub is divided for each blade and an elastomer is interposed between the rib provided on the divided hub and the rib provided on the divided hub adjacent to the rib, the material, shape and size of the elastomer can be reduced. By appropriately selecting, the torsional rigidity of the fan can be easily reduced.

[Brief description of the drawings]

FIGS. 1A and 1B show a first embodiment of the present invention, wherein FIG. 1A is a partial longitudinal sectional view, and FIG. 1B is a transverse sectional view taken along line BB of FIG. 1A.

FIG. 2 is a diagram showing a vibration transmissibility of the embodiment.

FIG. 3 is a partial cross-sectional view showing a second embodiment of the present invention and corresponding to FIG. 1 (B).

FIG. 4 is a partial cross-sectional view corresponding to FIG. 1B, showing a third embodiment of the present invention.

FIG. 5 is a partial sectional view showing a fourth embodiment of the present invention and corresponding to FIG. 1 (B).

FIG. 6 is a partial cross-sectional view corresponding to FIG. 1B, showing a fifth embodiment of the present invention.

FIG. 7 is a partial sectional view showing a sixth embodiment of the present invention and corresponding to FIG. 1 (B).

FIG. 8 is a transverse sectional view showing a seventh embodiment of the present invention.

9A and 9B show an example of a conventional fan, in which FIG. 9A is a partial longitudinal sectional view, and FIG. 9B is a transverse sectional view taken along the line BB of FIG. 9A.

[Explanation of symbols]

 6 Motor 7 Rotation axis 10 Fan 1 Wing 2 Hub 31 Rib 5 Boss T Taper

Claims (7)

[Claims] A boss fixed to a rotating shaft driven by a power source; a plurality of ribs extending radially from the boss;
In a ring-shaped hub connected to the outer ends of these ribs and a fan composed of a plurality of blades attached to the hub, the natural frequency of the torsional vibration system around the rotation axis of the fan is determined by an external force input from the rotation shaft. The bending rigidity of the rib is set so as to be lower than the frequency of the fan. 2. The fan according to claim 1, wherein the bending rigidity of the rib is set as described above by appropriately designing at least one of the thickness, width and number of the rib. 3. The fan according to claim 2, wherein one or both of the connecting portions of the rib to the boss and the hub have a tapered or round shape. 4. The fan according to claim 1, wherein a folded portion is provided at an intermediate portion of the rib. 5. The fan according to claim 1, wherein the rib has a corrugated shape. 6. The fan according to claim 1, wherein said rib is formed of a separate metal sheet. 7. The hub according to claim 1, wherein the hub is divided for each of the blades, and an elastomer is interposed between a rib provided on the divided hub and a rib provided on a divided hub adjacent to the hub. Item 7. The fan according to Item 1.