JPH1037894A - Centrifugal fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiblade impeller which can realize calmness by a centrifugal fan, especially by a small centrifugal fan. SOLUTION: In a centrifugal fan in which the outside diametral dimension of a multiblade impeller 3 mounted in is set to 250mm or below, and the number of blades is 50 or more, a ratio of the inlet side inner circumferential diameter of the multiblade impeller 3 to the outlet side peripheral diameter thereof is set in a range of from 0.4 to 0.75, an outlet angle β2 is set to 100 or more and an inlet angle β1 is set in a range of from 30 deg. to 85 deg., and also a circular arc surface whose size is more than 1/4 of the thickness of a blade 4 is formed at the corner of the inlet side inner circumferential surface of the blade 4, and the surface shape of the outlet side peripheral end 4-2 of the blade 4 forms an acute angled shape or a minute circular arc at an end by being thinned according as it approaches a peripheral end 4-1, and also both or one surface shape of front and rear surfaces is formed into a streamline shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement for quieting a centrifugal fan, especially a small-sized centrifugal fan.

[0002]

2. Description of the Related Art It is well known that a centrifugal fan has a large number of blades of an internal multi-blade impeller, so that the generation of eddy current is reduced and noise due to rotation is reduced. Although the use of a multi-blade impeller having two blades has been put to practical use, the interval between the impellers becomes narrower due to the increase in the number of blades. The radial blade structure is such that both the angle β1 and the exit angle β2 at the exit side outer peripheral edge are 90 °.

FIG. 5 is a schematic sectional view of a centrifugal fan 1 in which a multi-blade impeller 3 is rotatably supported inside a casing 2. FIG. 6 is a schematic front view of an example of a conventionally well-known multi-blade impeller 3. FIG. 6 shows that the number of blades 4 is 50, and each of the blades 4 has the same length from the inner peripheral edge 3-1 on the inlet side to the outer peripheral edge 2-2 on the outlet side, and is radially formed. It is well known that since the area of the flow path 5 is substantially determined by the gap between the adjacent blades at the inlet-side inner peripheral edge 3-1, the larger the number of blades, the lower the air flow.

[0004] In a radial blade structure in which the inlet angle β1 of the inner peripheral edge on the inlet side and the outlet angle β2 of the outer peripheral edge on the outlet side are both 90 °, the flow of air from the blade 4 is referred to as a separation phenomenon at the inflow portion of the air. Separation caused noise, and a vortex was likely to occur at the outlet when the air flowed out, which also caused noise.

[0005]

In the conventional configuration as described above, since both the entrance angle β1 and the exit angle β2 are 90 ° as described above, improvement in noise generation is required.

[0006]

SUMMARY OF THE INVENTION A centrifugal fan according to the present invention has a multi-blade impeller having an inlet side inner diameter and an outlet side outer diameter in the range of 0.4 to 0.75 and an outlet angle β2. Is greater than 100 ° and the inlet angle β1 is in the range of 30 ° to 85 °, and an arc surface having a size of 1/4 or more of the thickness of the blade is formed at the corner of the inner peripheral surface on the inlet side of the blade. The shape of the outer peripheral end surface of the blade on the outlet side becomes thinner as it approaches the outer peripheral end, forms a sharp angle or a minute arc at the tip, and is formed so that both or one of the front and rear surfaces has a streamlined surface shape.

[0007] In the above configuration, the air flow in the multi-blade centrifugal impeller used in the small centrifugal fan is smoothed, and the noise is generated by eliminating the separation phenomenon at the inlet and the vortex at the outlet. Can be reduced.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, in which the inlet angle β1 of the blade 4 at the inner peripheral edge 3-1 of the impeller is 30 °.
It is formed in the range of ~ 85 °.

In this example, the blade entrance angle β1 at the inner peripheral edge 3-1 of the impeller is reduced so that the inner peripheral edge 3-1 of the impeller is reduced.
It has been confirmed that the so-called peeling phenomenon in which air is released from the blade inner peripheral end surface 4-1 when air flows in from the blade is reduced. The entrance angle β1 is practically 30 ° to 8
The range of 5 ° is suitable in terms of smooth flow and eliminating noise due to separation.

FIG. 2 shows another example according to the present invention, in which the outlet angle β2 is set to 100 ° or more. As the outlet angle β2 increases, the centrifugal force given by the rotation of the impeller 3 is increased. When the flow is discharged from the outer peripheral edge 3-2 of the impeller, it is effective in reducing the generation of the vortex at the outer peripheral end 4-2 of the blade.

FIG. 3 is a partially enlarged view of a multi-blade impeller 3 which is a further improvement of the example of FIG. Especially in a small multi-blade centrifugal fan, the flow path 5 is restricted as the number of blades increases,
The influence of the thickness of the blade 4 becomes relatively large. In particular, the shape of the inner end face 4-1 on the inlet side causes turbulent air flow. It is effective to form a large arc of at least 1/4 of the length on both sides.

FIG. 4 is intended to further reduce the noise generation at the outlet side in addition to the above-mentioned improvement.
In order to eliminate the so-called boundary layer and to reduce the noise, the outer edge 4-2 of the blade is made thinner by sharpening the outer edge or reducing the diameter of the tip. It is an arc.

It is needless to say that the surface shape of the blade 4 between the inlet angle β1 and the outlet angle β2 is preferably a gentle arc surface or a cross-sectional streamline shape to facilitate the flow of air.

[0014]

The centrifugal fan according to the present invention has an inlet angle β1
In addition, the improvement of the outlet angle β2 and the improvement of the blade end surface and the surface shape can achieve the effect of realizing quietness, particularly with a small centrifugal fan.

[Brief description of the drawings]

FIG. 1 is a schematic front view of an example of a multi-blade impeller of a centrifugal fan according to the present invention.

FIG. 2 is a schematic front view of a second example of the multi-blade impeller of the centrifugal fan according to the present invention.

FIG. 3 is a partially enlarged view of an example of a blade improvement of the multi-blade impeller according to the present invention.

FIG. 4 is a partially enlarged view of another example of the blade improvement of the multi-blade impeller according to the present invention.

FIG. 5 is a schematic sectional view of an example of a centrifugal fan according to the present invention.

FIG. 6 is a schematic front view of an example of a multi-blade impeller of a prior art centrifugal fan.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Centrifugal fan 2 Casing 3 Multi-blade impeller 3-1 Inner peripheral edge 2-2 Outer peripheral edge 4 Blade 4-1 Inner peripheral end 4-2 Outer peripheral end 5 Flow path

Claims (5)

[Claims] 1. A casing and a multi-blade impeller rotatably supported inside the casing, wherein air is sucked from an inlet formed on one side wall of the casing to rotate the multi-blade impeller. A centrifugal fan impeller configured to apply centrifugal force to intake air and to send out high-pressure air from an outlet formed in a part of the outer peripheral surface of the casing. When the number is 50 or more, the ratio between the inner diameter on the inlet side and the outer diameter on the outlet side of the multiblade impeller is in the range of 0.4 to 0.75, and the inlet angle β1
Is constituted by 30 ° to 85 °. 2. A casing and a multi-blade impeller rotatably supported inside the casing, wherein air is sucked from an inlet formed on one side wall of the casing, and the multi-blade impeller rotates. A centrifugal fan impeller configured to apply centrifugal force to intake air and to send out high-pressure air from an outlet formed in a part of the outer peripheral surface of the casing. When the number is 50 or more, the exit angle β2 of the blades constituting the impeller
The centrifugal fan is configured to have an angle of 100 ° or more. 3. An arc-shaped surface having a size of not less than 1/4 of the thickness of the blade is formed at a corner of an inner peripheral surface on the inlet side of the blade constituting the impeller. 3. The centrifugal fan according to 2. 4. An outer peripheral end surface of an outlet side of a blade constituting an impeller is formed so as to become thinner as approaching the outer peripheral end and to be formed at an acute angle at a tip end.
4. The centrifugal fan according to 2, 3. 5. A blade forming an impeller, wherein a cross-sectional shape of an outer peripheral edge on an outlet side is a minute arc, and both or one surface shape of both front and rear surfaces is formed in a streamlined shape.
The centrifugal fan according to claim 1, 2 or 3, wherein: