Centrifugal fan noise-lowering structure

A centrifugal fan noise-lowering structure includes a frame having an upper and a lower cover and a sidewall, which together internally define a receiving space communicable with an air inlet and an air outlet of the frame; a stator assembly located in the receiving space and fixedly mounted on the lower cover; and a rotor assembly correspondingly assembled to the stator assembly. The receiving space is internally defined a high pressure zone and a low pressure zone. The upper cover is provided with an airflow passage, which has an inlet located at a position corresponding to the high pressure zone, and an outlet located at a position corresponding to the low pressure zone. With the airflow passage, air in the high pressure zone can be guided to jet out to the low pressure zone to thereby reduce noise produced by the centrifugal fan during its operation.

FIELD OF THE INVENTION

The present invention relates to a centrifugal fan noise-lowering structure, and more particularly, to a centrifugal fan noise-lowering structure that includes an airflow passage provided on an upper cover or a lower cover of the centrifugal fan for guiding air to jet out to a low pressure zone in the fan, so as to reduce the noise produced by the fan during its operation.

BACKGROUND OF THE INVENTION

Since centrifugal fans, centrifugal compressors, centrifugal blowers and centrifugal pumps have the advantages of being capable of changing the flowing direction of a fluid (i.e. having fluid inlet and fluid outlet oriented to different directions), utilizing a centrifugal force to further increase the pressure of the fluid, being highly adaptable to different spaces (applicable to narrow space in, for example, a notebook computer for heat dissipation), and being simple in structure, they have wide applications in daily life, such as being used in notebook computers, hair dryers, vacuum cleaners, bathroom exhaust fans, kitchen range hoods, air-conditioning or related ventilation system for car engines, industrial equipment, and water-cooling towers. However, centrifugal fans, compressors, blowers and pumps would produce noise during their operation to form a serious and unacceptable problem. It is therefore necessary to improve the noise problem of the centrifugal type machines.

Most currently available centrifugal fan noise-lowering structures are focused on the optimization of the structural design of fan, such as adjusting the shape of fan blades, the geometry of air inlet, the style of volute, the throat gap design and the number of air guiding structures; or the mounting of additional active noise-eliminating devices or deafening devices. The conventional optimized structural designs have the disadvantage of narrow scope of application. That is, the locally optimized structural designs are uneasy to be widely applied. Usually, many optimized structural parameters must be re-calculated once the environment and operating conditions are changed. On the other hand, the mounting of additional noise-eliminating devices has the drawback of largely increased materials and manufacturing cost and occupying more space.

It is therefore an important target of the technical persons in this field to solve the disadvantages in the conventional centrifugal fan noise-lowering structures.

SUMMARY OF THE INVENTION

To effectively solve the above problems, a primary object of the present invention is to provide an airflow passage on one or both of an upper cover and a lower cover of a centrifugal fan for guiding air to jet out from a high pressure zone to a low pressure zone in a frame of the centrifugal fan, so as to reduce the noise produced by the centrifugal fan during its operation.

To achieve the above and other objects, the present invention provides a centrifugal fan noise-lowering structure. In a first embodiment, the centrifugal fan noise-lowering structure includes a frame, a stator assembly and a rotor assembly.

The frame has an upper cover, a lower cover and a sidewall. The upper cover is provided with an airflow passage, which has two opposite ends forming an inlet and an outlet, respectively. The upper cover, the lower cover and the sidewall together internally define a receiving space, which is communicable with an air inlet and an air outlet of the frame. The receiving space is internally defined a high pressure zone and a low pressure zone; the inlet of the airflow passage is located at a position corresponding to the high pressure zone, and the outlet of the airflow passage is located at a position corresponding to the low pressure zone. The stator assembly is located in the receiving space and fixedly mounted to an inner side of the lower cover; and the rotor assembly is correspondingly assembled to the stator assembly.

To achieve the above and other objects, a second embodiment of the centrifugal fan noise-lowering structure according to the present invention includes a frame, a stator assembly and a rotor assembly.

The frame has an upper cover, a lower cover and a sidewall. The upper cover is provided with a first airflow passage, and the lower cover is provided with a second airflow passage. The first airflow passage has two opposite ends forming a first inlet and a first outlet, respectively; and the second airflow passage has two opposite ends forming a second inlet and a second outlet, respectively. The upper cover, the lower cover and the sidewall together internally define a receiving space, which is communicable with an air inlet and an air outlet of the frame. The receiving space is internally defined a high pressure zone and a low pressure zone. The first and second inlets of the first and second airflow passages are located at positions corresponding to the high pressure zone, and the first and second outlets of the first and second airflow passages are located at positions corresponding to the low pressure zone. The stator assembly is located in the receiving space and fixedly mounted to an inner side of the lower cover; and the rotor assembly is correspondingly assembled to the stator assembly.

According to the present invention, the provision of the airflow passage on one or both of the upper cover and the lower cover can effectively guide air to jet out from the high pressure zone to the low pressure zone in the frame of the centrifugal fan to thereby reduce the noise produced by the centrifugal fan during its operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with some preferred embodiments thereof and by referring to the accompanying drawings. For the purpose of easy to understand, elements that are the same in the preferred embodiments are denoted by the same reference numerals.

Please refer toFIGS.1and2, which are exploded perspective view and assembled sectional view, respectively, of a centrifugal fan noise-lowering structure according to a preferred embodiment of the present invention. As shown, the centrifugal fan noise-lowering structure includes a frame11, a stator assembly12and a rotor assembly13.

The frame11includes an upper cover111, a lower cover112and a sidewall114. The upper cover111is provided with an airflow passage113, which has two ends forming an inlet1131and an outlet1132, respectively. The sidewall114is perpendicularly formed along an outer periphery of the lower cover112, such that the upper cover111, the lower cover112and the sidewall114together define a receiving space115between them. An air outlet116is formed at one side of the lower cover112, and an air inlet117is formed on the upper cover111at a location corresponding to the rotor assembly13. The receiving space115is communicable with the air outlet116and the air inlet117.

The receiving space115is internally defined a high pressure zone1151and a low pressure zone1152. The high pressure zone1151is located in the receiving space115farther away from the rotor assembly13and closer to an area of the lower cover112adjacent to the sidewall114. On the other hand, the low pressure zone1152is located in the receiving space115closer to the rotor assembly13. The inlet1121of the airflow passage113is located at a position corresponding to the high pressure zone1151, and the outlet1132of the airflow passage113is located at a position corresponding to the low pressure zone1152.

The stator assembly12is located in the receiving space115and fixedly mounted on an inner side of the lower cover112. The stator assembly12includes a plurality of silicon steels121and a circuit board122. The silicon steels121are stacked together and wound by a plurality of coils123. The coils123are electrically connected to the circuit board122.

The rotor assembly13is correspondingly assembled to the stator assembly12. The rotor assembly13includes a hub131, a disc-shaped section132radially outward extended from the hub131, a plurality of fan blades133formed on the disc-shaped section132, magnetic bodies134provided in the hub131, and a shaft135perpendicularly extended from an inner side of the hub131toward the stator assembly12. The magnetic bodies134and the silicon steels121are excited due to mutual induction.

A bearing cup14is perpendicularly formed on the inner side of the lower cover112. At least one bearing15is set in the bearing cup14to define a shaft hole151, in which the shaft135is inserted. The silicon steels121and the circuit board122of the stator assembly12are fitted around an outer side of the bearing cup14.

The present invention is described with a centrifugal fan. In a preferred embodiment thereof, the inlet1131of the airflow passage113of the fame11is located at the upper cover111near a radially outer side thereof to correspond to the high pressure zone1151; and the outlet1132of the airflow passage113of the frame11is located at the upper cover111near a throat thereof to correspond to the low pressure zone1152. In the preferred embodiment, the entire airflow passage113is formed in the upper cover111. The outlet1132defines a jet flow, which is located at a throat gap between the sidewall114and the rotor assembly13. The jet flow formed at this location can improve a recirculation zone at the throat (seeFIG.1) by reducing flow field pressure fluctuation in the recirculation zone and accordingly lowering the noise produced by the centrifugal fan during operation thereof.

More specifically, the inlet1131of the airflow passage113is provided at a location corresponding to the high pressure zone1151and the outlet1132of the airflow passage113is provided at a location corresponding to the low pressure zone1152. When the fan blades133of the rotor assembly13are rotated, air is forced and guided into the high pressure zone1151and the low pressure zone1152. The air is forced and guided by the rotor assembly13to flow into the airflow passage113via the inlet1131and then flows out of the airflow passage113via the outlet1132. In this way, the air can jet out of the outlet1132to the low pressure zone1152closer to the rotor assembly13to thereby achieve a noise lowering effect. The airflow passage113can be selectively provided on the upper cover111or the lower cover112, or on both of the upper cover111and the lower cover112(not shown). In the illustrated preferred embodiment, the airflow passage113is provided on the upper cover111. However, it is understood the present invention is not particularly limited thereto.

Please refer toFIG.3, which is an assembled sectional view of another embodiment of the centrifugal fan noise-lowering structure according to the present invention. This embodiment is generally structurally similar to the preferred embodiment but has an airflow passage113in the form of a pipe2. The pipe2is selectively provided on the upper cover111or the lower cover112, or is connected to between the upper cover111and the lower cover112. In this embodiment, the pipe2is not integrally formed with the upper and the lower cover111,112but is additionally assembled to the upper cover111and/or the lower cover112. InFIG.3, the illustrated pipe2is connected at two ends to the upper cover111. However, it is understood the present invention is not particularly limited thereto.

In the above embodiments, there can be a plurality of airflow passages113provided on the frame11. Further, the inlet1131and the outlet1132can have a round, a square, a triangular or a trapezoidal cross sectional shape; and the airflow passage113can have a cross sectional shape the same as or different from that of the inlet1131and the outlet1132.

The present invention is described with a centrifugal fan, and is characterized by providing an airflow passage on the upper cover or the lower cover of the centrifugal fan. When the rotor assembly rotates, a pressure difference is naturally formed at two opposite ends of the airflow passage due to the feature of a rotational machine, such that the flowing of air from the high pressure zone through the airflow passage to the low pressure zone can achieve a natural and self jetting effect. Since the fan noise is generated mainly due to the fluctuation of pressure in the air flow, the self jetting is able to accurately control the uneven low pressure zone or the low speed zone near the rotor assembly to thereby reduce the pressure fluctuation of the air flow in the low pressure or low speed zone and accordingly, reduce the noise generated by the fan during its operation.

In view that the rotor assembly and the volute, i.e. the frame, of the centrifugal fan tend to produce uneven low pressure/low speed zone, and that the fan noise is usually generated at some fixed positions, such as radial outer ends of fan blades near the air outlet, the throat, and areas between the upper and lower covers and the fan blades, the centrifugal fan noise-lowering structure of the present invention that utilizes self jet to lower fan noise can be widely applied to different centrifugal designs and operating conditions.

Further, since most of the centrifugal fans have upper and lower covers made of a metal material, it is relatively easy to add the airflow passage to the upper and/or the lower cover to achieve the noise-lowering structure. The centrifugal fan noise-lowering structure of the present invention has the advantages of wide applications, not requiring additional manufacturing equipment, and not requiring complicated structural design. With the structurally simple airflow passage, it is possible to improve the problems in the flow field, such as vortex and secondary flow appeared between the rotor assembly and the fan frame. The present invention not only enhances the feature of the centrifugal fan, but also lowers the noise generated by the centrifugal fan during its operation.