Centrifugal fan

Abstract

A centrifugal fan is described. The centrifugal fan is suitable for a portable electrical apparatus. A tongue shape is formed from a volute sidewall of a casing of the centrifugal fan. The volute sidewall is formed with at least one groove substantially extending horizontally at the tongue shape. Therefore, when the blades rotate to generate a wake flow to blow on a surface of the volute sidewall at the tongue shape, noise generated by the centrifugal fan can be reduced.

Description

RELATED APPLICATIONS

The present application is based on, and claims priority from, Taiwan application Ser. No. 93133855, filed Nov. 5, 2004, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a centrifugal fan, and more particularly, to a centrifugal fan with a surface of a volute sidewall at a tongue shape being formed with at least one groove substantially extending horizontally.

2. Description of the Related Art

A heat dissipation module is necessary to provide effective heat dissipation for a portable electrical apparatus, and especially for a notebook personal computer (PC), so as to allow the best performance. When heat accumulates in and cannot dissipate from the apparatus, the electrical devices and the apparatus as a whole cannot work normally. The computer system, in particular, will crash. However, in order to satisfy the market requirement for mobilization, sufficient space cannot be possibly formed in the casing of the notebook PC for natural convection. Because heat dissipation design for high-frequency devices has encountered its bottleneck, the heat dissipation module of the notebook PC tends to dissipate heat with forced convection generated by a centrifugal fan.

Reference is made to FIGS. 1 and 1A, which depict a perspective view and a top plan view showing a centrifugal fan of the prior art. The centrifugal fan 10, installed in a portable electrical apparatus such as a notebook PC, comprises a casing 11 and blades 31. The casing 11 has a volute sidewall 13 and a bottom plate 15, and the casing 11 defines a cavity 17 and an outlet 19. A volute channel 21 is jointly defined by the cavity 17 and the outlet 19, and a tongue shape 23 is formed from the volute sidewall 13 on a side of the outlet 19. The blades 31 are disposed vertically with a rotational axis 33 on the bottom plate 15 in the cavity 17. Rotation of blades 31 drives a horizontal airflow 25. The horizontal airflow 25 can be exhausted via dynamic and static pressures generated by the horizontal airflow 25 passing through the volute channel 21.

The outlet 19 of the prior art uses a curved surface and divergent duct with a constant cross-section, which means a surface 16 of the volute sidewall 13 at the tongue shape 23 is parallel to the rotational axis 33. This makes the airflow generate dynamic and static pressure, which resists outside force to achieve the effect of heat dissipation.

Reference is made to FIG. 2, which depicts a schematic diagram showing a wake flow generated by the centrifugal fan of the prior art blowing on the volute sidewall at the tongue shape. When the wake flow 35 generated by the blades 31 is blowing on the surface 16 of the volute sidewall 13 at the tongue shape 23, each blasting point 41 is generated and regarded as a sound source that generates narrow band noise 43. Because the surface 16 of the volute sidewall 13 at the tongue shape 23 is parallel to the rotational axis 33, according to the superposition principle, the narrow band noise 43 with a large amplitude 45 and constant blade pass frequency will be generated. Once it is necessary to enhance the efficiency of the heat dissipation, the flow rate and the wind velocity must be increased. However, the more the rotational speed and the flow rate are increased, the higher the frequency of the noise band is. Therefore, the noise is increasing. The trade off between the noise and the heat dissipation is a serious problem.

SUMMARY OF THE INVENTION

It is an aspect of the present invention to provide a centrifugal fan suitable for a portable electrical apparatus. A tongue shape is formed from the volute sidewall of a casing of the centrifugal fan. The volute sidewall is formed with at least one groove substantially extending horizontally at the tongue shape. Therefore, when the blades rotate to generate a wake flow to blow the surface of the volute sidewall at the tongue shape, noise generated by the centrifugal fan can be reduced.

According to the aforementioned aspect of the present invention, a centrifugal fan is provided, which is suitable for a portable electrical apparatus and comprises a casing having a bottom plate and a volute sidewall disposed on the bottom plate to define a cavity and an outlet. A tongue shape is formed from the volute sidewall on at least one side of the outlet; and blades are disposed vertically with a rotational axis on the bottom plate of the cavity. The volute sidewall is formed with at least one groove substantially extending horizontally at the tongue shape.

In a preferred embodiment of the present invention, the aforementioned portable electrical apparatus is a notebook PC.

In a preferred embodiment of the present invention, a surface of the aforementioned volute sidewall at the tongue shape is, for example, formed with on or more grooves substantially extending horizontally.

The surface of the volute sidewall at the tongue shape of the centrifugal fan of the invention is formed with at least one groove substantially extending horizontally, resulting in easy manufacture and improvement of the issue of noise caused by the centrifugal fan.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIGS. 1 and 1A depict a perspective view and a top plan view showing a centrifugal fan of the prior art;

FIG. 2 depicts a schematic diagram showing a wake flow generated by the centrifugal fan of the prior art blowing on the volute sidewall at the tongue shape;

FIG. 3 depicts a perspective view showing a centrifugal fan in accordance with a preferred embodiment of the present invention;

FIG. 4 depicts a schematic diagram showing a wake flow generated by the centrifugal fan in accordance with a preferred embodiment of the present invention blowing on the volute sidewall at the tongue shape;

FIG. 4A illustrates the location of the groove with respect to the blades in accordance with a preferred embodiment of the present invention;

FIG. 5 depicts a cross-sectional view of a surface of a volute sidewall at a tongue shape in accordance with another preferred embodiment of the present invention;

FIG. 6 depicts a cross-sectional view of a surface of a volute sidewall at a tongue shape in accordance with another preferred embodiment of the present invention;

FIG. 7A illustrates the blade pass frequency of a centrifugal fan where no groove is formed to the surface of the volute sidewall; and

FIG. 7B illustrates the blade pass frequency of a centrifugal fan where one groove is formed to the surface of the volute sidewall.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference is made to FIG. 3, which depicts a perspective view showing a centrifugal fan in accordance with a preferred embodiment of the present invention. The centrifugal fan 100 installed in a portable electrical apparatus such as a notebook PC, comprises a casing 111 and blades 131. The casing 111 has a volute sidewall 113 and a bottom plate 115, and the casing 111 defines a cavity 117 and an outlet 119. A volute channel 121 is jointly defined by the cavity 117 and the outlet 119, and a tongue shape 123 is formed from the volute sidewall 113 on a side of the outlet 119. The blades 131 are disposed vertically with a rotational axis 133 on the bottom plate 115 in the cavity 117, and preferably, the blades 131 are disposed vertically to the bottom plate 115. Rotation of the blades 131 drives a horizontal airflow 125. The horizontal airflow 125 can be exhausted via dynamic and static pressure generated by the horizontal airflow 125 passing through the volute channel 121. Meanwhile, when horizontal airflow 125 is generated by the blades 131 rotating, the blades 131 blow on a surface 116 of the volute sidewall 113 at the tongue shape 123. A groove 118 is formed on the tongue shape 123 and substantially extends horizontally to destruct the wave superposition resulted from a wake flow 135 (as shown in FIG. 4) generated by the blades 131 rotating on the surface 116 of the volute sidewall 113 at the tongue shape 123, so that the noise generated by the centrifugal fan can be reduced. According to this invention, the groove 118 may be integrally formed on the casing 111 by plastic injection molding, metal casting or metal stamping.

Reference is made to FIG. 4, which depicts a schematic diagram showing a wake flow 135 generated by the centrifugal fan in accordance with a preferred embodiment of the present invention blowing on the volute sidewall at the tongue shape. When the wake flow 135 generated by the blades 131 is blowing on the surface 116 of the volute sidewall 113 at the tongue shape 123 (as shown in FIG. 3), each blasting point 141 is generated and regarded as a sound source that generates narrow band noise 143. Because the surface 116 of the volute sidewall 113 at the tongue shape 123 is formed with a groove 118 substantially extending horizontally, the time at which each sound source is generated is different. Therefore, comparing to priot amplitude 45 (as shown in FIG. 2), the amplitude 145 can be substantially reduced as a result of less constructive interference of sound waves generated by the sound sources on different time; that is to say, the narrow band noise 143 is lessened.

According to this invention, a part of the groove 118 substantially extending horizontally on the surface 116 corresponds to where the wake flow 135 of the blades 131 is blown. For example, reference is made to FIG. 4A, the groove 118 formed on the surface 116 of the volute side wall 113 at the tongue shape 123 is located to face the blades 131 at a midpoint of a height direction of the blades 131. The groove 118 alternatively be located to face an upper side or a lower side with respect to the height direction of the blades 131, so long as a part of the groove 118 corresponds to where the wake flow 135 of the blades 131 are blown. In addition, the surface 116 of the volute sidewall 113 at the tongue shape 123 may also be formed with two ore more grooves 118 substantially extending horizontally. FIG. 4A depicts a perspective view showing a centrifugal fan in accordance with a preferred embodiment of the present invention, where the groove 118 substantially extending horizontally on the surface 116 is of a rectangular cross-section.

FIG. 5 depicts a cross-sectional view of a surface of a volute sidewall at a tongue shape in accordance with another preferred embodiment of the present invention, wherein the surface 116 is formed thereon with two grooves 118 each of rectangular cross-section. FIG. 6 depicts a cross-sectional view of a surface of a volute sidewall at a tongue shape in accordance with another preferred embodiment of the present invention, wherein the surface 116 is formed with a groove 118a of a rounded cross-section. However, this invention is not limited the above number or cross-sectional shapes of the grooves. Persons having ordinary skills in the relevant art should be able to comprehend this invention and utilizes other means, in accordance with the actual needs, to adjust the number or cross-sectional shapes of the grooves, or to combine plural grooves of different cross-sections on the surface, which are not described in detail herein.

As mentioned above, the groove 118 formed on the surface of the volute sidewall 113 at the tongue shape 123 can effectively reduce the amplitude 145 of the noise. Hence, the broader band noise is obtained to allow a user to experience a better quality of sound.

FIG. 7A illustrates the blade pass frequency of a centrifugal fan where no groove is formed to the surface of the volute sidewall. Significant blade pass frequency can be observed at the operation frequencies of 900 Hz and 1900 Hz. FIG. 7B illustrates the blade pass frequency of a centrifugal fan where one groove is formed to the surface of the volute sidewall. FIG. 7B clearly illustrates the significant reduction of the blade pass frequency at the operation frequencies of 900 Hz and 1900 Hz.

Therefore, according to the aforementioned preferred embodiments, one advantage of the centrifugal fan of the present invention is that the surface of the volute sidewall at the tongue shape of the centrifugal fan is formed with at least one groove substantially extending horizontally. Therefore, when the blades rotate to generate a wake flow to blow on the surface of the volute sidewall at the tongue shape, noise generated by the centrifugal fan can be reduced.

As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrated of the present invention rather than limiting of the present invention. It is intended that various modifications and similar arrangements be included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structure.

Claims

1. A centrifugal fan, suitable for a portable electrical apparatus, comprising:

a casing, the casing having a volute sidewall to define a cavity and an outlet, wherein a tongue shape is formed from the volute sidewall on at least one side of the outlet;

blades disposed around and vertically with a rotational axis on the casing; and

at least one groove set on the volute sidewall, the groove substantially extending horizontally at the tongue shape.

2. The centrifugal fan according to claim 1, wherein the portable electrical apparatus is a notebook personal computer (PC).

3. The centrifugal fan according to claim 1, wherein the groove has a rectangular cross-section.

4. The centrifugal fan according to claim 1, wherein the groove has a rounded cross-section

5. The centrifugal fan according to claim 1, wherein the groove is such located that a part of the groove faces the blades along a height direction of the blades.

6. The centrifugal fan according to claim 5, wherein the groove is such located that the groove faces the blades at a midpoint of the height direction of the blades.

7. A casing of centrifugal fan, suitable for a portable electrical apparatus, comprising:

a bottom plate;

a volute sidewall to define a cavity and an outlet, wherein a tongue shape is formed from the volute sidewall on at least one side of the outlet; and

at least one groove formed on the tongue shape of the volute sidewall, the groove substantially extending horizontally at the tongue shape.

8. The casing of centrifugal fan according to claim 7, wherein the portable electrical apparatus is a notebook PC.

9. The casing of centrifugal fan according to claim 7, wherein the groove has a rectangular cross-section.

10. The casing of centrifugal fan according to claim 7, wherein the groove has a rounded cross-section.

11. The casing of centrifugal fan according to claim 7, wherein the bottom plate rotatably supports blades thereon, and wherein the groove is such located that a part of the groove faces the blades along a height direction of the blades after the blades are supported on the bottom plate.

12. The casing of centrifugal fan according to claim 11, wherein the groove is such located that the groove faces the blades at a midpoint of the height direction of the blades.