Casing for centrifugal fan

The present invention relates to a structure of a casing of a centrifugal fan, which is effective in suppressing noise.

<patcit num="1"><text>Japanese Unexamined Patent Publication No. H05-231393</text></patcit>

The overall configuration and function of the centrifugal fan according to the present invention will be omitted because it is a technique that has been cultivated as seen in the above-mentioned well-known prior application, but for example, in the example of FIG. 4, the well-known centrifugal fan is used. , The bell mouth 1-1 forming the suction port of the casing 1 forms an arc surface 1-16 that gradually shrinks from the outer surface so as to form an arc-shaped cross section, that is, a so-called R-shaped multi-blade impeller 2 The tip edge of the impeller 2-1 facing the impeller 2-1 is formed in a substantially cylindrical shape 1-17.

As can be seen in FIG. 4, in the configuration of the bell mouth 1-1 according to the above-mentioned well-known technique, the pulsation of ventilation near the suction port due to the generation of the vortex 4 near the tip of the impeller 2-1 contributes to the noise. It is well known that the above-mentioned publicly known example of the prior application can be said to be an example of the improvement measures, and the above-mentioned effects are realized.

<p> However, in the conventional configuration as described above, various processes have to be added in order to obtain the means for realizing the effect, and measures / improvements for the conflicting requirements of continuous noise reduction and cost reduction are required. The reality was that it was.</p>

<p> The casing of the centrifugal fan according to the present invention has a suction port that opens in the axial direction and a discharge port that opens in the circumferential direction, so that the annular inner peripheral surface gradually expands from the upstream side to the downstream side. A cochlear-shaped casing formed and a rotatable multi-wing impeller internally arranged in the cochlear-shaped casing are provided, and the cross-sectional shape of the bell mouth provided on the periphery of the suction port of the casing is from the outer surface of the casing. It is formed so that it becomes a semicircular arc surface that gradually shrinks and expands within a range of approximately 180 °, or</p><p> The cross-sectional shape of the bell mouth provided on the periphery of the suction port of the casing is a small arc surface that gradually shrinks within a range of approximately 90 ° from the outer surface of the casing, and a great circle that communicates with the edge of the small arc surface and gradually expands. Formed to have an arcuate surface, or</p><p> An arcuate surface in which the cross-sectional shape of the bell mouth provided on the periphery of the suction port of the casing gradually shrinks within a range of approximately 90 ° from the outer surface of the casing and a conical surface that communicates with the edge of the arcuate surface and gradually expands. It is formed to prepare.</p>

<p> The casing of the centrifugal fan according to the present invention realizes an improvement effect that is compatible with the conflicting requirements of noise reduction that does not stay and cost reduction.</p>

Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a partial view for explaining the first embodiment of the present invention, in which air from the suction port of the casing 1 communicates with the semicircular arc surface 1-11 from the outside to the inside of the bell mouth 1-1. It shows how the suction ventilation 3 in the entire area of Impeller 2-1 of the multi-blade impeller 2 is smoothed by accompanying the flow along the line.

FIG. 2 is a partial view for explaining a second embodiment of the present invention, in which the air from the suction port of the casing 1 communicates with the small arc surface 1-12 on the outside of the bell mouth 1-1. It shows how the suction ventilation 3 in the entire area of Impeller 2-1 of the multi-blade impeller 2 is smoothed by accompanying the flow along the arcuate surface 1-13.

FIG. 3 is a partial view for explaining a third embodiment of the present invention, and is an inner conical surface in which air from the suction port of the casing 1 communicates with the outer arc surface 1-14 of the bell mouth 1-1. It shows how the suction ventilation 3 in the entire area of Impeller 2-1 of the multi-blade impeller 2 is smoothed by accompanying the flow along 1-15.

In any of the above examples, the generation of eddy current near the tip of the impeller in the conventional technique shown in FIG. 4 is suppressed, and FIG. 5 shows the conventional technique shown by the alternate long and short dash line and the first embodiment shown by the solid line (FIG. 1). ), The performance of the second embodiment (Fig. 2) shown by the broken line and the performance of the third embodiment (Fig. 3) shown by the dotted line are compared. In contrast to the technology (dashed line), the reduction effect is realized in all the examples.

The casing of the centrifugal fan according to the present invention can be widely used as a casing of a centrifugal fan that can achieve both noise reduction and cost reduction.

<figref num="1">It is explanatory drawing which concerns on 1st Example which concerns on this invention.</figref><figref num="2">It is explanatory drawing which concerns on 2nd Example which becomes a present invention.</figref><figref num="3">It is explanatory drawing which concerns on 3rd Example which concerns on this invention.</figref><figref num="4">It is explanatory drawing which concerns on the example which becomes the prior art.</figref><figref num="5">It is a figure which contrasts the performance of the example which becomes invention of this application, and the prior art example.</figref>

Code description

1 Casing 1-1 Bellmouth 1-11 Semicircular arc surface 1-12 Outer small arc surface 1-13 Inner large arc surface 1-14 Outer arc surface 1-15 Inner conical surface 1-16 R shape 1-17 Cylinder Shape 2 Multi-blade impeller 3 Inflow ventilation 4 Swirl