A fan includes an impeller and a frame. The frame is used for accommodating the impeller. The frame includes a plurality of static blade groups. Each of the static blade groups has a plurality of static blades. Moreover, at least one first static blade of a first static blade group and at least one first static blade of a second static blade group are symmetric with respect to a central axis of the frame.

FIELD OF THE INVENTION

The present invention relates to a fan, and more particularly to a fan capable of reducing noise effectively.

BACKGROUND OF THE INVENTION

With increasing development of science and technology, the performance of electronic devices is largely enhanced. Consequently, heat-dissipating devices or heat-dissipating systems become essential instruments for the electronic devices. During operation of an electronic device, the heat is generated by the electronic components of the electronic device. If the heat fails to be effectively dissipated away, the elevated operating temperature may result in damage, short circuit or deteriorated performance of the electronic device. For effectively removing the heat, it is important to install a high-performance heat-dissipating device within or beside the electronic device to exhaust the heat to the surroundings. Moreover, it is an important requirement to make efforts in increasing the efficiency of the heat-dissipating device.

A fan is one of the most popular heat-dissipating devices. Generally, the fan comprises a frame, static blades, a hub, and dynamic blades. The static blades are connected with the frame. The dynamic blades are connected with the hub. In addition, a motor (not shown) is installed within the hub. As the fan is driven to rotate by the motor, the dynamic blades arranged around the hub are synchronously rotated to produce airflow to dissipate heat.

For increasing the efficiency of the fan, the number of the static blades is usually in the range between 7 and 17. If the fan contains seven dynamic blades, the frequency of the noise generated by the fan is the multiple of 49˜119 Hz. For example, if the rotating speed of the fan is 2,500 rpm, the frequency of the noise generated by the fan is about 2,000˜5,000 Hz. As known, the hearing sensitivity of the human is dependent on the frequency of the sound. Generally, the frequency of the sound in the range between 2,500 Hz and 3,000 Hz is more sensitive to the human ears. Moreover, the sound in the low frequency range is less sensitive to the human ears. In other words, for maintaining or increasing the air pressure, the reduction of the noise is an important factor for selecting the fan.

SUMMARY OF THE INVENTION

The present invention provides a fan for reducing noise and effectively dissipating the heat away from an electronic device without deteriorating the original properties of the fan and solving the noise problems encountered by the prior arts.

In accordance with an aspect of the present invention, the fan includes an impeller and a frame. The frame is used for accommodating the impeller. The frame includes a plurality of static blade groups. Each of the static blade groups has a plurality of static blades. Moreover, at least one first static blade of a first static blade group and at least one first static blade of a second static blade group are symmetric with respect to a central axis of the frame.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a fan. Hereinafter, a fan according to a first embodiment of the present invention will be illustrated with reference toFIGS. 1A˜1G.FIG. 1Ais a front view of a fan according to a first embodiment of the present invention.FIG. 1Bis a perspective view of a portion of a frame of the fan shown inFIG. 1A.FIG. 1Cis a front view illustrating an impeller of the fan shown inFIG. 1A.FIG. 1Dis a perspective view of the impeller of the fan shown inFIG. 1A.FIGS. 1E˜1G are cross-sectional views of the impeller of the fan ofFIG. 1Calong different viewpoints. In this embodiment, the fan1is an axial-flow fan. The fan1comprises a frame10, an impeller2, and a motor (not shown). The impeller2and the motor are accommodated within the frame10. The motor is used for driving rotation of the impeller2. The fan1of this embodiment can be applied to a power supply, a server, a communication apparatus, a vehicular electronic system, a computer system or any other electronic system.

The frame10of the fan1comprises a frame body11, a base12, a plurality of static blade groups, and a wire-managing groove134. In this embodiment, the frame body11is a square frame body. Alternatively, in some other embodiments, the frame body11is a circular frame body. The frame body11comprises an axial part111and an externally-expanded part112as shown inFIG. 1B. An airflow channel is defined by the axial part111. The axial part111is connected with the externally-expanded part112. An outlet of the fan1is defined by the externally-expanded part112. Moreover, the inner wall of the externally-expanded part112comprises a plurality of flat regions X and an outwardly angled region Z positioned between each pair of adjacent flat regions X. The flat regions X can be located at corresponding lateral sides of the frame body11.

Moreover, each of the static blade groups comprises a plurality of static blades. In this embodiment, the frame10comprises four static blade groups1331,1332,1333and1334. Each static blade group has the same number of static blades. For example, each of the static blade groups1331,1332,1333and1334comprises one first static blade131and two second static blades132. The first static blade131is aligned with a corresponding flat region X, and thus the first static blade131extends between the base12and the corresponding flat region X. One end of the first static blade131is connected with the base12. The other end of the first static blade131is partially connected with the axial part111and partially connected with the flat region X of the externally-expanded part112. As used herein, the expression “the other end of the first static blade131is partially connected with the axial part111and partially connected with the flat region X of the externally-expanded part112” means that a part of the other end of the first static blade131is connected with the axial part111and the rest of the other end of the first static blade131is connected with the flat region X of the externally-expanded part112completely, so that the other end of the first static blade131is completely connected with and not spaced from the frame body11. Moreover, two second static blades132are arranged between every two adjacent first static blades131. Each second static blade132extends between the base12and the outwardly angled region Z that is adjacent to the corresponding flat region X. One end of the second static blade132is connected with the base12. The other end of the second static blade132is partially connected with the axial part111. Since the second end of the second static blade132is not connected with the outwardly angled region Z of the externally-expanded part112, the second static blade132has a suspension segment1321with respect to the externally-expanded part112as shown inFIG. 1B.

As known, since the static blade groups of the frame of the conventional fan are asymmetric, asymmetric flow fields are generated at the outlet of the fan. Under this circumstance, the conventional fan will result in serious vortex. In accordance with the present invention, the first static blades of two corresponding static blade groups are symmetric with respect to a central axis of the frame10. In this embodiment, the first static blades131of the two corresponding static blade groups1331and1332are symmetric with respect to the central axis of the frame10, and the first static blades131of the two corresponding static blade groups1333and1334are symmetric with respect to the central axis of the frame10. Consequently, the outlet formed by the externally-expanded part112is divided into four identical flow fields, which are arranged around each other. Different flow fields will not be interfered with each other. Thus, the airflow at the outlet of the fan can be uniformly diffused and the possibility of causing vortex will be minimized. In other words, the heat of the electronic system can be uniformly dissipated away by the fan.

In the above embodiment, each static blade group has the same number of static blades. Alternatively, in another embodiment, different static blade groups can have different numbers of static blades.FIG. 2is a front view of a frame of a fan according to a second embodiment of the present invention. The frame10′ comprises four static blade groups51,52,53and54. The static blade group51comprises three static blades, including one first static blade131and two second static blades132. The static blade group52comprises three static blades, including one first static blade131and two second static blades132, wherein the first static blade131is located beside one of the two second static blades132. The static blade group53comprises three static blades, including one first static blade131and two second static blades132, wherein the first static blade131is located beside one of the two second static blades132. In this embodiment, the first static blades131of the two corresponding static blade groups51and53are symmetric with respect to a central axis of the frame10′. The static blade group54only comprises one first static blade131. The first static blades131of the two corresponding static blade groups52and54are symmetric with respect to the central axis of the frame10′. Consequently, the frequency of the noise generated by the dynamic blades will not be too centralized.

Please refer toFIGS. 1C and 1Dagain. The impeller2comprises a hub21and a plurality of dynamic blades22. A motor (not shown) is disposed within the hub21for driving the impeller2to rotate. The dynamic blades22are arranged around the hub21, and connected with the hub21. As the impeller2is driven to rotate by the motor, the dynamic blades22are synchronously rotated to produce the airflow.

Each dynamic blade22comprises a blade body221and a connecting part222. The blade body221comprises a front edge2211, a rear edge2212, and a wing tip2213. The extending direction of the front edge2211and the rear edge2212is the same as the rotating direction of the impeller2. The wing tip2213is opposed to the connecting part222. Moreover, the wing tip2213is connected with the front edge2211and the rear edge2212. The wing tip2213is twisted and extended along the rotating direction of the dynamic blade22. Consequently, each dynamic blade22has a leading edge angle θ. The leading edge angle θ is defined between a farthest end point P of the front edge2211away from the center of the hub21and an end point Q at the junction between a root part of the front edge2211and the hub21. That is, the leading edge angle θ is defined between a first line passing through a center A of the hub21and a farthest end point P of the front edge2211and a second line passing through the center A of the hub21and an end point Q at the junction between a root part of the front edge2211and the hub21. In this embodiment, the leading edge angle θ is in the range between 15 degrees and 50 degrees, but is not limited thereto.

Due to the leading edge angle of each dynamic blade22, the noise can be effectively reduced. Moreover, since there is no obvious vortex in the flow field generated by the dynamic blade22, the fan can maintain the original properties.

The connecting part222is located at a root part of the blade body221, and connected with the hub21, the front edge2211and the rear edge2212. In this embodiment, the connecting parts222are disposed on a suction surface2214and a pressure surface2215of the blade body221of each dynamic blade22, respectively.

Please refer toFIGS. 1E-1F.FIG. 1Eis a cross-sectional view of the impeller ofFIG. 1Calong the line A′-A.FIG. 1Fis a cross-sectional view of the impeller ofFIG. 1Calong the line B-A.FIG. 1Gis a cross-sectional view of the impeller ofFIG. 1Calong the line C-A. The curvature radius R of the connecting part222is gradually decreased along the direction from the front edge2211to the rear edge2212. That is, as shown inFIG. 1C, the curvature radius R of the connecting part222is gradually decreased along the direction Y. InFIG. 1E, the connecting part222on the suction surface2214and the pressure surface2215of the blade body221has the curvature radius R1. InFIG. 1F, the connecting part222on the suction surface2214and the pressure surface2215of the blade body221has the curvature radius R2. InFIG. 1G, the connecting part222on the suction surface2214and the pressure surface2215of the blade body221has the curvature radius R3. It is found that R1>R2>R3.

Since the curvature radius R of the connecting part222is gradually decreased along the direction from the front edge2211to the rear edge2212, the angle of the connecting part222corresponding to the curvature radius R of the connecting part222is gradually decreased along the direction from the front edge2211to the rear edge2212. Under this circumstance, the structural strength of the dynamic blade22is enhanced, and the possibility of causing the vortex near the hub21will be reduced. Experiments showed that the conventional dynamic blade without the connecting part has a safety factor of 1.84 but the dynamic blade22of the present invention having the connecting part222with the varying curvature radius has a safety factor of 2.01. In other words, while the dynamic blade22is rotated at a high speed, the varying curvature radius of the connecting part222can enhance the structural strength of the dynamic blade22.

Hereinafter, a fan according to a third embodiment of the present invention will be illustrated with reference toFIGS. 3A-3D.FIG. 3Ais a front view of a fan according to a third embodiment of the present invention.FIG. 3Bis a perspective view of the fan shown inFIG. 3A.FIG. 3Cis a cross-sectional view illustrating the fan shown inFIG. 3A.FIG. 3Dis a cross-sectional view illustrating the fan shown inFIG. 3Aalong another viewpoint. In this embodiment, the fan6is a diagonal flow fan. The fan6comprises a frame61, an impeller2, and a motor3. The impeller2and the motor3are accommodated within the frame61. The motor3is used for driving rotation of the impeller2.

In this embodiment, the hub of the impeller2has a curved outer surface S1, and the dynamic blade of the impeller2has a curved outer surface S2. Moreover, the frame body62has a curved inner surface S3, and the curved outer surface S2 and the curved inner surface S3 are in parallel with each other. The frame61of the fan6comprises a frame body62, a base63, and a plurality of static blade groups. The frame body62comprises a plurality of flat regions X. The flat regions X are located at corresponding lateral sides of the frame body62.

InFIG. 3A, the frame61comprises four static blade groups641,642,643and644. Each static blade group has the same number of static blades. Each flat region X of the frame body62is connected with two first static blades131of a corresponding static blade group. Moreover, each of the static blade groups641,642,643and644comprises five static blades, including two first static blades131and three second static blades132. The two first static blades131are connected with a corresponding flat region X as shown inFIG. 3C. One end of the first static blade131is connected with the base63. The other end of the first static blade131is partially connected with the axial part111and partially connected with the flat region X of the externally-expanded part112. As shown inFIG. 3D, one end of the second static blade132is connected with the base63and the other end of the second static blade132is partially connected with the axial part111. Preferably, the connection portion between the second end of the second static blade132and the axial part111is lower than one third of the height of the second static blade132. Since the second end of the second static blade132is not connected with the externally-expanded part112, the second static blade132has a suspension segment1321with respect to the externally-expanded part112as shown inFIG. 3D.

As known, since the static blade groups of the frame of the conventional fan are asymmetric, asymmetric flow fields are generated at the outlet of the fan. Under this circumstance, the conventional fan will result in serious vortex. In accordance with the present invention, the first static blades of two corresponding static blade groups are symmetric with respect to a central axis of the frame61. In this embodiment, the static blades131of the two corresponding static blade groups641and642are symmetric with respect to the central axis of the frame61, and the first static blades131of the two corresponding static blade groups643and644are symmetric (see the dotted lines as shown inFIG. 3A). Consequently, the outlet formed by the frame body62is divided into four identical flow fields, which are arranged around each other. Different flow fields will not be interfered with each other. Thus, the airflow at the outlet of the fan can be uniformly diffused and the possibility of causing vortex will be minimized. In other words, the heat of the electronic system can be uniformly dissipated away by the fan.

FIG. 4is a plot illustrating the relationship between the airflow pressure and the noise (dB) of the fan ofFIG. 1Ain comparison with the conventional fan. In case that the fan of the present invention and the conventional fan produce the same airflow pressure (e.g. 46 mmAq), the noise resulted from the fan of the present invention is lower than the noise resulted from the conventional fan by up to 5 dBA. That is, the efficiency of reducing the noise by the fan of the present invention is superior to the conventional fan.

From the above descriptions, the present invention provides a fan. The fan comprises a frame. The frame comprises a plurality of static blade groups. Since at least one first static blade of a first static blade group and at least one first static blade of a second static blade group are symmetric with respect to a central axis of the frame, the outlet formed by the externally-expanded part of the frame is divided into a plurality of identical flow fields by the static blade groups. These flow fields are arranged around each other. Different flow fields will not be interfered with each other. Thus, the airflow at the outlet of the fan can be uniformly diffused and the possibility of causing vortex will be minimized. In other words, the heat of the electronic system can be uniformly dissipated away by the fan. As previously described, since the static blade groups of the frame of the conventional fan are asymmetric, asymmetric flow fields are generated at the outlet of the fan to result in serious vortex. In other words, the efficiency of reducing the noise by the fan of the present invention is superior to the conventional fan. Moreover, since each dynamic blade has a leading edge angle, the noise is effectively reduced, no obvious vortex is occurred in the flow field generated by the dynamic blade, and the fan can maintain the original properties. Moreover, since the curvature radius of the connecting part is gradually decreased along the direction from the front edge to the rear edge, the structural strength of the dynamic blade is enhanced and the possibility of causing the vortex near the hub is reduced.