1. Technical Field
The present disclosure generally relates to centrifugal fans, and particularly to a centrifugal fan having a low noise during operation.
2. Description of Related Art
In a portable electronic device such as a notebook computer, a centrifugal fan is generally used to dissipate heat generated by heat-generating electronic components such as CPU (central processing unit) etc. The centrifugal fan typically includes a housing and an impeller rotatably received in the housing. The impeller includes a hub and a plurality of plate-type blades extending radially outwardly from the hub.
With continuing development of the electronic technology, the electronic components are made to operate at a high speed and therefore generate a large amount of heat required to be timely dissipated. In order to improve a heat dissipation efficiency of the centrifugal fan, a typical way is to increase a revolving speed of the impeller. However, increasing the revolving speed may correspondingly cause a rise of a noise level of the centrifugal fan, which makes a user near the centrifugal fan feel uncomfortable.
Therefore, it is desired to provide a centrifugal fan to overcome the above described shortcoming.
Many aspects of the present disclosure can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Referring to
The impeller 20 includes a hub 21 and a plurality of blades 22 extending radially outwardly from the hub 21. A volute air passage channel 106 is defined between outmost free ends 221 of the blades 22 and an inner surface 125 of the sidewall 12. In the embodiment, the impeller 20 rotates counter-clockwise, as viewed from
Referring also to
A plurality of grooves 1231 is evenly defined in the outer surface 1232 along the height direction of the tongue 123. Each of the grooves 1231 extends along a lengthwise direction of the tongue 123. The grooves 1231 are parallel to the bottom plate 11 and spaced from each other. Each of the grooves 1231 extends from an outer end of the tongue 123 which is located adjacent to the air outlet 121 towards an inner end of the tongue 123 which is smoothly connected with the inner surface 125 of the sidewall 12. The tongue 123 has a bulge 1233 at a middle portion thereof, wherein the bulge 1233 is located closer to the outmost free ends 221 of the blades 22 than other portions of the tongue 123. A thickness of the tongue 123 decreases gradually from the bulge 1233 towards the inner and the outer ends of the tongue 123 along the lengthwise direction of the tongue 123, and decreases gradually from the bottom plate 11 towards the top cover plate 30 along the height direction of the tongue 123. Accordingly, a distance between the outer surface 1232 of the tongue 123 and the outmost free ends 221 of the blades 22 increases gradually from the bulge 1233 towards the inner and the outer ends of the tongue 123 along the lengthwise direction of the tongue 123, and increases gradually from the bottom plate 11 towards the top cover plate 30 along the height direction of the tongue 123. A minimum distance between the outer surface 1232 of the tongue 123 and the outmost free ends 221 of the blades 22 is formed between a portion of the bulge 1233 adjacent to the bottom plate 11 and the outmost free ends 221 of the blades 20.
In operation, the impeller 20 rotates and the blades 22 drive an airflow into the air passage channel 106 via the air inlets 111. The airflow is guided by the inner surface 125 of the sidewall 12 to flow along the air passage channel 106 from the tongue 123 towards the air outlet 121. Specifically, the airflow firstly flows into the air passage channel 106 along the outer surface 1232 of the tongue 123, then towards the air outlet 121 along the air passage channel 106, and finally to an outside of the centrifugal fan via the air outlet 121. Since the tongue 123 is protruded towards the outmost free ends 221 of the blades 20, an air pressure of the airflow entering into the air passage channel 106 is greatly increased. When the airflow blows on different points of the outer surface 1232 of the tongue 11, each blown point is a sound source which will generate a narrowband noise. However, due to the presence of the grooves 1231 on the curved outer surface 1232 of the tongue 123, the narrowband noises at different blown points are disturbed to have different frequencies and will not be superposed. Thus, the noise level of the present centrifugal fan is greatly reduced.
It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
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2008 1 0304903 | Oct 2008 | CN | national |
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Number | Date | Country | |
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20100092282 A1 | Apr 2010 | US |