document: BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a heat-dissipating device and a housing thereof, and more particularly to an axial fan having an increased intake airflow rate without modifying the assembling conditions with other elements so as to greatly enhance the heat-dissipating performance of the fan, and a housing for the fan. 
     2. Description of the Related Art 
     A typical electrical product usually includes electrical elements positioned in a closed housing in order to prevent the electrical elements from being contaminated with particles in the air. However, since the electrical element (such as a central processing unit (CPU) or circuit board) raises its temperature during operation, the element tends to be consumed and the lifetime thereof tends to be shortened if the element is continuously kept at the high-temperature condition. Thus, a fan is typically disposed in the housing to dissipate heat to the outside in order to prevent the electrical element from failing. 
     As shown in  FIG. 1 , a conventional fan  1  is mainly composed of a fan housing  11  and an impeller  12 . When the fan is operating, a motor may be used to drive the impeller  12  to rotate and to produce air streams flowing toward the electrical element in order to dissipate the heat generated from the electrical element. The fan housing includes an air inlet and an air outlet in communication with the air inlet via a central, cylindrical air passage  11   a . The air streams caused by the impeller  12  may freely flow into and out of the fan housing via the air passage. Furthermore, a plurality of tapered portions  13 , through which the air streams may smoothly flow into the air inlet side, are provided at the corners on the air inlet side of the air passage. In addition, a plurality of screw holes  14  is formed at four corners of the fan housing such that the fan may be mounted to a frame of an electrical apparatus (i.e., a computer) via the screw holes  14 . 
     However, due to the restriction in the dimension of the rectangular fan housing of the conventional fan, the air passage at the lateral side has to be reduced. The optimized design in the shape of the blade based on the curve of the air passage is also restricted, and the space and material of the fan housing are also wasted. Besides, due to the restriction in the construction of the fan housing, air may be taken into the fan only in the axial direction. However, it only can achieve very limited improvement effect in the increased intake airflow rate by doing so. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a heat-dissipating fan and a housing thereof, wherein an sidewall of the housing extends outwards to enlarge the intake airflow area thereof without modifying the assembling conditions between the existing fan and other heat dissipation elements, and the shape of the housing at the air outlet side is kept unchanged in order to enhance the heat-dissipating efficiency of the fan. The fan may be mounted to a system or other heat dissipation elements without changing the assembling conditions with the system and the heat dissipation elements. 
     Another object of the invention is to provide a heat-dissipating device and a housing thereof, wherein an sidewall of the housing extends outwards to enlarge its intake airflow area so that the impeller of the heat-dissipating device may increase its dimension with the outward extension of the housing. Thus, the airflow rate may be increased and the heat-dissipating efficiency may be enhanced. 
     Still another object of the invention is to provide a heat-dissipating fan and a housing thereof, wherein the air passage formed by the sidewall of the passage of the housing reduces gradually and evenly in its cross-sectional area. Thus, the air streams produced by the rotation of blades of the impeller of the heat-dissipating device can be effectively concentrated to the center and then blow to the center portion of the heat sink having the highest temperature when the heat sink is assembled with the heat-dissipating device so as to enhance its heat-dissipating efficiency. 
     According to the first aspect of the invention, the housing includes an outer frame having a passage for guiding air streams to flow from an opening to another opening, wherein an sidewall of the passage of one of the opening sides extends radially outwards so as to enlarge intake or discharge area for the air streams. 
     The sidewall of the passage extends radially outwardly with respect to a central axis of the passage in a symmetrical manner. In addition, the sidewall of the passage extends radially outwardly with respect to a longitudinal axis of the passage and beyond the peripheral edge of the outer frame. Alternatively, the sidewall of the passage extends radially outwardly with respect to a longitudinal axis of the passage in a frustum-conical or a frustum-elliptically conical manner. 
     Preferably, the sidewall of the passage is formed with an inclined portion or a beveled edge there around. 
     According to the second aspect of the invention, the housing includes an outer frame including an air inlet, an air outlet, and a passage for guiding air streams from the air inlet to the air outlet, wherein an sidewall of the passage at the air inlet side extends radially outwardly so as to enlarge an intake area of the air streams. 
     Preferably, the sidewall of the passage at the air inlet side extends radially outwardly with respect to a central axis of the passage in a symmetrical manner. Alternatively, the sidewall of the passage at the air inlet side extends radially outwardly with respect to a longitudinal axis of the passage and beyond the peripheral edge of the outer frame. Furthermore, the sidewall of the passage at the air inlet side extends radially outwardly with respect to a longitudinal axis of the passage in a frustum-conical or a frustum-elliptically conical manner. 
     Preferably, the sidewall of the passage is formed with an inclined portion extending from the air inlet to the air outlet. 
     Preferably, the radially outward extension of the sidewall of the passage at the air inlet side is partially cut off to form a notch in order to enlarge an intake area for lateral side air streams. 
     According to the third aspect of the invention, the heat-dissipating device includes an impeller and a housing for receiving the impeller, wherein the housing includes a passage for guiding air streams to flow from an opening to another opening, an sidewall of the passage at least one of the opening sides extends radially outwards so as to enlarge an intake/discharge area for the air streams. A dimension of a blade of the impeller increases along with the radially outwardly extending direction of the sidewall of the passage. 
     According to the fourth aspect of the invention, the heat-dissipating device includes an impeller and a housing for receiving the impeller, wherein the housing includes an air inlet, an air outlet, and a passage for guiding air streams from the air inlet to the air outlet, and an sidewall of the passage at the air inlet side extends radially outwards so as to enlarge an intake area of the air streams. 
     According to the fifth aspect of the invention, the heat-dissipating system includes a casing, at least one electrical element mounted within the casing, and a heat-dissipating device mounted on the casing for dissipating heat generated from the at least one electrical element when it operates, wherein the heat-dissipating device includes an impeller and a housing for receiving the impeller. Further, the housing includes a passage for guiding air streams to flow from an opening of the housing to another opening, and an sidewall of the passage at one of the openings extends radially outwardly with respect to a rotational axis of the heat-dissipating device so as to enlarge an intake/discharge area for the air streams. 
     Preferably, the heat-dissipating device is an axial fan. 
     Further, the heat-dissipating device includes a heat sink assembled with the housing. 
     According to the sixth aspect of the invention, the heat-dissipating system includes a casing, at least one electrical element mounted within the casing, and a heat-dissipating device mounted on the casing for dissipating heat generated from the at least one electrical element when it operates, wherein the heat-dissipating device includes an impeller and a housing for receiving the impeller. Further, the housing includes an air inlet, an air outlet, and a passage for guiding air streams to flow from the air inlet to the air outlet, wherein the sidewall of the passage at the air inlet side extends radially outwardly with respect to a rotational axis of the heat-dissipating device so as to enlarge an intake area for the air streams. 
     Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 
  
  
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view showing a conventional fan. 
         FIG. 2A  is a perspective view showing a heat-dissipating device according to a first preferred embodiment of the invention. 
         FIG. 2B  is a top view showing the heat-dissipating device of  FIG. 2A . 
         FIG. 2C  is a cross-sectional view showing the heat-dissipating device taken along a line A-A′ of  FIG. 2B . 
         FIG. 2D  is a cross-sectional view showing the heat-dissipating device taken along a line B-B′ of  FIG. 2B . 
         FIGS. 3A and 3B  are cross-sectional views showing several modified structures of the housing for the heat-dissipating device of the invention, wherein  FIG. 3A  also shows the direction of the flow field. 
         FIG. 4A  is a top view showing the housing for the heat-dissipating device according to another preferred embodiment of the invention. 
         FIG. 4B  is a cross-sectional view showing the heat-dissipating device taken along a line C-C′ of  FIG. 4A . 
         FIG. 5  is a top view showing a housing for the heat-dissipating device according to still another preferred embodiment of the invention. 
         FIG. 6  is a perspective view showing the heat-dissipating device according to another preferred embodiment of the invention. 
         FIG. 7  is a schematic illustration showing the heat-dissipating device of the invention mounted in a system frame having with electrical elements disposed therein. 
         FIG. 8A  is an exploded, cross-sectional view showing the assembly of the heat-dissipating device of the invention and the heat sink. 
         FIG. 8B  is a cross-sectional view showing the combination of the heat-dissipating device and the heat sink of  FIG. 8A . 
         FIG. 8C  is a perspective view showing the combination of the heat-dissipating device and the heat sink of  FIG. 8A . 
         FIG. 9  is a schematic illustration showing the assembly of the heat-dissipating device of the invention and the heat sink, which is disposed in the framework with electrical elements. 
         FIG. 10  is another schematic illustration showing the assembly of the heat-dissipating device of the invention and the heat sink, which is mounted on the casing. 
     
  
  
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 2A to 2D , which show a heat-dissipating device according to a first preferred embodiment of the invention. The heat-dissipating device  2  is mainly composed of a housing and an impeller  22 . The housing includes a rectangular outer frame  21  having an air inlet, an air outlet, and a passage  23  connecting the air inlet to the air outlet. An sidewall  23   a  of the passage extends radially outwards with respect to a rotational axis of the fan motor of the heat-dissipating device or an axis of passage, or even protrudes over the rectangular outer frame  21 . Since the air inlet side of the housing has a circular shape extending outwards, the bottom part of the housing is still kept as a rectangular shape, and screw holes  24  and their positions are kept unchanged, the way of assembling the housing with other elements is also kept unchanged. The dimension of the blade of the impeller can be enlarged along with the outward extension of the sidewall of the housing, and an inclined portion  231  can be formed at the sidewall of the housing, as shown in  FIG. 2C . The inclined portion  231  can greatly enlarge the intake airflow area and reduce noises of the turbulent flow produced owing to uneven intake airflow area of the conventional fan. In addition, an inclined portion  232  can also be designed at the sidewall of the air outlet side of the housing, as shown in  FIG. 2D , wherein the inclined portion  232  can significantly increase the heat-dissipating area of the air outlet side. 
     In addition to the designs of inclined portions towards different directions at the sidewall from the air inlet side to the air outlet side, the sidewall may be formed with an inwardly inclined portion from the air inlet side to the air outlet side of the housing, as shown in  FIGS. 3A and 3B . In this case, the air streams can be concentrated toward the center to provide better heat-dissipating performance for the heat-dissipating device that requires concentrated air streams. In addition, the fan housing assembly housing may be formed with a beveled edge at the air inlet side around the screw holes so that the intake airflow area can also be enlarged. 
     Furthermore, in addition to the sidewall of the passage at the air inlet side extending radially outwards and protruding over the rectangular outer frame  21 , the same designs may be configured at the air outlet side. In other words, the sidewall of the passage at the air outlet side also extends radially outwards and protrudes over the rectangular outer frame  21 , as shown in  FIGS. 4A and 4B , such that the sidewalls at the air inlet side and the air outlet side have a symmetrical structure with respect to a longitudinal axis L of the air passage including the same axis or a horizontal median plane H of the heat-dissipating device. 
     In addition that the sidewall of the passage at the air inlet side of the housing as shown in  FIG. 2A  evenly radially extends outwards in a circular manner, it can also be designed into an elliptic shape extending outwards in a symmetrical manner, as shown in  FIG. 5 . In other words, the sidewall of the passage at the air inlet side of the housing can extend radially outwards in a symmetrical manner with respect to the longitudinal axis L of the air passage, that is, in a right-and-left or upper-and-lower symmetry from the top view of the housing. 
     In addition to the outward extension of the sidewall of the housing, when the lateral side of the housing cannot be extended owing to the dimensional limitation, a part of the side wall of the housing may be cut off to form a notch or notches, as shown in  FIG. 6 . In this case, the intake airflow area at the lateral side can be enlarged, the air can be smoothly introduced, and the noise can also be reduced. 
     In practice, the heat-dissipating device  2  may be disposed within a system casing  3  in which electrical elements are mounted, as shown in  FIG. 7 . Several heat sources or electrical elements, which will generate a lot of heat during operation, are mounted on a circuit board  4 . The heat-dissipating device  2  of the invention is mounted to a proper position (close to the heat sources) to discharge air streams toward the heat sources or electrical elements. Thus, the heat-dissipating efficiency can be enhanced, and it is possible to prevent the electrical elements from being damaged owing to high-temperature conditions. 
     In addition, the heat-dissipating device  2  of the invention may also be used with a heat sink  31 , which may be mounted to the heat-dissipating device  2  by screws  32 , as shown in  FIGS. 8A to 8C . The assembly may be mounted to a central processing unit (CPU)  5 , as shown in  FIG. 9  and  FIG. 10 . That is, the bottom surface of the heat sink  31  is in close contact with the surface of the CPU  5 , and the heat generated by the CPU  5  during operation may be quickly conducted to the heat sink  31 . Then, the heat-dissipating device  2  produces cooling air streams to dissipate the generated heat. Moreover, the design of the inclined portion of the sidewall of the passage of the heat-dissipating device  2  of the invention may further be utilized to guide air streams toward the central portion of the heat sink having the highest temperature, and the heat-dissipating effects may be effectively achieved accordingly. 
     In summary, according to the aspect of the invention, the outward extension of the sidewall of the housing can greatly enlarge the air inlet area or air outlet area so as to enhance the heat-dissipating efficiency of the fan. In addition, the dimensions of the blades of the heat-dissipating fan can be enlarged along with the outward extension of the housing so that the airflow can be greatly increased and the heat-dissipating efficiency can be enhanced. Furthermore, the passage formed by the sidewall of the housing of the invention has a gradually reduced inner diameter formed from the inlet side to the outlet side (i.e., the formed passage has the inclined portion), and the air streams produced when the impeller rotates may be effectively concentrated to the central portion. Then, the air streams can directly flow toward the central portion of the heat sink having the highest temperature, and the heat-dissipating effects of the fan may be further enhanced. 
     While the invention has been described by way of examples and in terms of preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications.
summary: A heat-dissipating device and a housing thereof. The housing includes a passage for guiding an air stream flowing from an opening to another opening, wherein an sidewall of the passage at least one of the opening sides extends radially outwards with a rotational axis of the heat-dissipating device or the passage so as to enlarge intake or discharge area for the air streams. Accordingly, the intake airflow rate may be greatly increased and the heat-dissipating efficiency of the heat-dissipating device may be greatly enhanced without changing assembling conditions with other elements.