Abstract:
An air-applying device has an impeller having a center of rotation, and a case which contains the impeller. The case includes a first edge defining an inlet port of air which exposes the center of rotation, a second edge defining an outlet port of air, and a high-pressure region which presents upon operational rotation of said impeller. The high-pressure region is located within the case along a peripheral portion of the impeller. A distance between the center of rotation of the impeller and the first edge is shorter in the direction from the center of rotation to a center of the high-pressure region than from the center of rotation to region other than the high-pressure region.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from PCT International Application No. PCT/JP02/13529, filed Dec. 25, 2002, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a air-applying device for applying, from the periphery of an impeller, the air that has been drawn into the center of an impeller. The invention also relates to a cooling unit having such an air-applying device, and to an electronic apparatus, e.g., a portable computer, which contains such an air-applying device. 
     2. Description of the Related Art 
     Electronic apparatuses, such as portable computers, incorporate a microprocessor. The microprocessor generates heat while operating. The heat it generates increases with faster processing (clock) speeds and with the number of functions performed. A conventional electronic apparatus incorporates a cooling unit that positively cools the microprocessor. 
     The cooling unit is provided, along with the microprocessor, in the housing of the electronic apparatus. The cooling unit includes a heat sink and a centrifugal air-applying device. The heat sink is thermally connected to the microprocessor. The air-applying device applies cooling air to the heat sink. The air-applying device has an impeller and a case containing the impeller. The impeller may be rotated. The case has an air inlet port, a spiral chamber, and an air outlet port. The air inlet port opens to the center of rotation of the impeller. The spiral chamber surrounds the impeller. The air outlet port lies at the output end of the spiral chamber, or the downstream end thereof. 
     When the impeller is rotated, air is drawn to the center of rotation of the impeller from the interior of the housing or from outside the housing and flows to the periphery of the impeller. The air is then applied from the periphery of the impeller into the spiral chamber, by virtue of a centrifugal force. The spiral chamber is designed to convert the velocity energy of the air applied from the impeller, into pressure energy. In the chamber, the impeller collects the air and blows the air to the air outlet port. Through the air outlet port, the air is forced onto the heat sink, acting as cooling air. As a result, the heat is radiated from the microprocessor, thanks to the heat exchange between the microprocessor and the cooling air. The heat is expelled from the housing as the air flows from the housing. 
     In the air-applying device, the air flows from the periphery of the impeller into the spiral chamber, is collected in the chamber and supplied to the air outlet port. Therefore, the air pressure in the spiral chamber gradually increases from the input end of the chamber to the output end of the chamber. The air pressure abruptly falls at a position immediately before the outlet port. Hence, the chamber has a high-pressure region near its output end. 
     In the conventional air-applying device, the air inlet port, which has a perfectly circular cross section, is coaxial with the impeller and communicates with the spiral chamber. (See FIG. 10) Thus, the air in the chamber at a position that corresponds to the above-mentioned high-pressure region, may acquire a higher pressure than the air at the inlet port. If so, part of the air in the spiral chamber abruptly flows from the chamber and through the air inlet port. In other words, the air in the chamber leaks to the air inlet port of the case and may not be reliably guided from the air inlet port to the air outlet port. 
     Japanese Patent Application Publication (KOKAI) No. 10-326986 discloses a fan device in which air is prevented from abruptly flowing from the case to and through the air inlet port. In this fan device, a ring surrounds the impeller, guiding air to prevent an abrupt flow of air. 
     In the prior-art fan device, however, a ring that rotates together with the impeller and a structure that secures this ring to the blades of the impeller are necessary. 
     Inevitably, the impeller is complex in structure and composed of a large number of components. This increases the manufacturing cost of the fan device. 
     BRIEF SUMMARY OF THE INVENTION 
     Embodiments of the present invention provide an air-applying device used in a cooling unit and/or an electronic apparatus having a heat generating component. 
     According to an embodiment of the present invention, an air-applying device has an impeller having a center of rotation, and a case which contains the impeller. The case includes a first edge defining an inlet port of air which exposes the center of rotation, a second edge defining an outlet port of air, and a high-pressure region which presents upon operational rotation of said impeller. The high-pressure region is located within the case along a peripheral portion of the impeller. A distance between the center of rotation of the impeller and the first edge is shorter in the direction from the center of rotation to a center of the high-pressure region than from the center of rotation to region other than the high-pressure region. 
     According to the other embodiment of the present invention, an air-applying device includes an impeller having a center of rotation, and a case which contains the impeller. The case has a wall defining a chamber with an initiating point, a midpoint, and a terminating point defined in order along a rotating direction of the impeller. The case also has a first edge defining an inlet port of air which exposes the center of rotation, and a second edge defining an outlet port of air. A distance between the center and the first edge is variable, and the shortest distance falls within an angular region of the chamber between the midpoint and the terminating point. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
     FIG. 1 is a perspective view showing a portable computer according to a first embodiment of the present invention; 
     FIG. 2 is a perspective view showing a positional relationship between a housing and a cooling unit in the first embodiment; 
     FIG. 3 is a perspective view showing a positional relationship between a CPU and the cooling unit in the first embodiment; 
     FIG. 4 is an exploded perspective view showing the cooling unit in the first embodiment; 
     FIG. 5 is a plan view showing a air-applying device in the first embodiment; 
     FIG. 6 is a cross-sectional view cut along the line F 6 —F 6  shown in FIG. 5; 
     FIG. 7 is a cross-sectional view of the air-applying device, illustrating the position relation between the shape of the air inlet port and the high-pressure region where the air attains the highest pressure in the first embodiment; 
     FIG. 8 is a cross-sectional view of the air-applying device, showing the pressure distribution in the case in the first embodiment; 
     FIG. 9 is a plan view of the air-applying device, showing the air flow-rate distribution in an air inlet port formed into a non-circular opening in the first embodiment; 
     FIG. 10 is a plan view of a conventional air-applying device, showing the air flow-rate distribution in an air inlet port formed into a perfectly circular opening arranged coaxial with an impeller; and 
     FIG. 11 is a plan view of an air-applying device according to a second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Preferred embodiments according to the present invention will be described hereinafter with reference to the accompanying drawings. 
     FIGS. 1 and 2 show a portable computer  1  as an electronic apparatus. The portable computer  1  includes a main unit  2  and a display unit  3  supported on the main unit  2 . 
     The main unit  2  has a housing  4  shaped in the shape of a flat box. The housing  4  includes a bottom wall  4   a , a top wall  4   b , a front wall  4   c  and two sidewalls  4   d . The main unit  2  further has a keyboard  5 , which is mounted on the top wall  4   b.    
     The display unit  3  includes a display housing  6  and a liquid-crystal display panel  7 . The display panel  7  is set in the display housing  6 . Hinges (not shown) couples the display housing  6  to the rear edge of the housing  4 , allowing the display housing  6  to rotate. The liquid-crystal display panel  7  has a display screen  7   a . The display screen  7   a  is exposed through an opening  8  that is made in the front of the display housing  6 . 
     As shown in FIGS. 2 and 3, the housing  4  contains a printed circuit board  10  and a cooling unit  20 , the printed circuit board  10  extends along the bottom wall  4   a  of the housing  4 . A semiconductor package  11  as a heat generating component is mounted on the upper surface of the printed circuit board  10 . The semiconductor package  11  is the main component of the portable computer  1 , and has a base substrate  12  and an IC chip  13 , such as a CPU. The base substrate  12  is soldered to the upper surface of the printed circuit board  10 . The IC chip  13  is mounted to the center part of the upper surface of the base substrate  12 . While operating, the IC chip  13  generates heat in great quantities. The package  11  needs therefore to be cooled to keep operating in stable conditions. 
     The cooling unit  20  is a component for cooling the semiconductor package  11 . As shown in FIGS. 2 to  4 , the cooling unit  20  includes a heat-receiving block  21 , a heat sink  22 , a heat pipe  23 , and a centrifugal air-applying device  24 . 
     The heat-receiving block  21  is somewhat larger than the IC chip  13 . A spring member  25  secures the heat-receiving block  21  to the printed circuit board  10 . 
     The spring member  25  has a pushing plate  26  and four legs  27 . Screws  28  fasten the pushing plate  26  to the upper surface of the heat-receiving block  21 . The legs  27  extend in radial direction from the four corners of the plate  26 . Screws  30  fasten the legs  27 , at their distal ends, to the four bosses  29  of the printed circuit board  10 . The legs  27  act as springs, biasing the heat-receiving block  21  toward the semiconductor package  11 , the block  21  being secured to the pushing plate  26 . The heat-receiving block  21  is therefore is contact with and biased against the IC chip  13  and, hence, thermally connected to the IC chip  13 . 
     The heat sink  22  has a number of heat-radiating fins  32 . The heat sink  22  extends along the left sidewall  4   d  of the housing  4 , and opposes the exhaust port  33  made in this sidewall  4   d.    
     The heat pipe  23  is thermally connected at one end  23   a  to the heat-receiving block  21 , and at the other end  23   b  to the heat sink  22 . Therefore, the heat radiated from the IC chip  13  is transmitted to the heat-receiving block  21  and then transferred to the heat sink  22  via the heat pipe  23 . 
     As shown in FIGS. 3 to  6 , the centrifugal air-applying device  24  includes a case  35  and an impeller  36 . The case  35  is in the shape of a flat box and contains the impeller  36 . The case  35  is composed of a case body  37  and a cover  38 . The case body  37  has a bottom plate  39  and a sidewall  40 . The sidewall  40  stands from the circumference of the bottom plate  39 . Both the cover  38  and the bottom plate  39  are shaped like a disc and constitute the outer walls of the case  35 . The sidewall  40  is bent like an arc, constituting the circumferential wall of the case  35 . The cover  38  is fixed to the upper edge of the sidewall  40  and opposes the bottom plate  39  of the case body  37 . 
     The case  35  has two round inlet ports  42   a  and  42   b  and one outlet port  43 . One inlet port  42   a  is defined by an edge cut in the center part of the cover  38 , and the other inlet port  42   b  is defined by an edge cut in the center part of the bottom plate  39 . A motor support  44 , which is shaped like a disc, lies inside the inlet port  42   b . The inlet ports  42   a  and  42   b  oppose each other, spaced apart in the direction of thickness of the case  35 . The outlet port  43  opens in the sidewall  40  of the case body  37 , and defined by edges cut in the cover  38 , the bottom plate  39 , and the sidewall  40 . The shape of the outlet port  43  is oblong, extending along the diameter of the case  35 . 
     The case  35  lies on the bottom wall  4   a  of the housing  4 , with the outlet port  43  oriented to the exhaust port  33  of the housing  4 . Thus, the heat sink  22  is positioned, opposing the outlet port  43  of the case  35 , and is interposed between the outlet port  43  and the exhaust port  33 . 
     The impeller  36  has a boss  45  and a plurality of vanes  46 . The boss  45  is a hollow cylinder. The vanes  46  protrude from the circumference of the boss  45 , each extending along a tangent to the circumference of the boss  45 . The impeller  36  lies between the cover  38  and bottom plate  39  of the case  35 . The roots of the vanes  46  oppose the inlet ports  42   a  and  42   b , and are exposed therethrough. 
     The impeller  36  is coupled to a motor  47 , which is secured to the motor support  44 . The motor  47  may rotate the impeller  36  counter-clockwise as shown in FIGS. 5 and 7. When the impeller  36  is so rotated, a negative pressure develops in the inlet ports  42   a  and  42   b . Air is therefore drawn from outside the case  35 , toward the center of the impeller  36  through the inlet ports  42   a  and  42   b  as indicated by the arrow in FIG.  6 . The air thus drawn is forced to the circumference of the impeller  36  by virtue of a centrifugal force. 
     As FIGS. 4 to  6  show, the case  35  has a spiral chamber  48  that surrounds the impeller  35 . The spiral chamber  48  is configured to collect the air applied from the circumference of the impeller  36  and guides the air toward the outlet port  43 . It has the function of converting the velocity energy of the air into pressure energy. The shape of the spiral chamber  48  is defined by the sidewall  40  of the case body  37 . The sidewall  40  surrounds the impeller  36 . 
     As shown in FIG. 7, the spiral chamber  48  has an initiating point P 1  and a terminating point P 2 . The initiating point P 1  is adjacent to one end  43   a  of the outlet port  43 . The terminating point P 2  deviates from the initiating point P 1 , by a preset angle θ, in the rotation direction of the impeller  36 . The other end  43   b , which extends along the outlet port  43 , is located on a line extending from the terminating point P 2 . 
     The distance d between the sidewall  40  and the circumference of the impeller  36  is the shortest at the initiating point P 1  and gradually increases from the point P 1  toward the terminating point P 2 . 
     FIG. 8 represents the pressure distribution that is observed in the case  35  while the impeller  36  is rotating. As is evident from FIG. 8, the air pressure (Pa) in the case  36  is lowest at the roots of the vanes  46 , which are close to the center of the impeller  36 , and also at the position near the outlet port  43 . The air pressure gradually rises from the initiating point P 1  toward the terminating point P 2 , in the rotation direction of the impeller  36 . 
     The air pressure (Pa) in the case  35  increases toward the sidewall  40  that is located at the outermost part of the spiral chamber  48 . The high-pressure region  49 , where the air pressure (Pa) reaches its peak, lies closer to the terminating point P 2  than the midpoint P 3  and between the points P 2  and P 3 . 
     The high-pressure region  49 , which is defined by the positional relation between the case  35  and the impeller  36 , is illustrated in FIG.  7 . In FIG. 7, point A is the center of rotation of the impeller  36 , point B is the position of the other end  43   b  of the outlet port  43 , point C is the position of the one end  43   a  of the outlet port  43 . Line X connects points B and C, line Y passes point A and intersects with the line X at right angles, line Z connects point A and the terminating point P 2  of the spiral chamber  48 , and point D is the intersection of line Y and the sidewall  40 . The high-pressure region  47  is region PAD that is defined by the terminating point P 2 , point A and point D. The region PAD lies, with one end reaching terminating point P 2  and the other end located at some distance from the midpoint P 3  of the spiral chamber  48 . 
     Two projections  50  are provided on the edges of the inlet ports  42   a  and  42   b , respectively. Both projections  50 , which are shaped like an arc, protrude toward the center of rotation (i.e., point A) of the impeller  36 . The edge of either inlet port is circular and lies coaxial with the impeller  36 , except at the projection  50 . 
     The inlet ports  42   a  and  42   b  have a curvature that changes at the high-pressure region  49 , due to the projections  50 . Neither the inlet port  42   a  nor the inlet port  42   b  has a perfectly circular cross section. 
     As seen from FIG. 7, either edge of projection  50  protrudes toward the center of rotation (point A) of the impeller  36 , to the greatest extent at its middle part. In other words, the distance L between the middle part of either edge of projection  50  and the center (point A) is shorter than the distance between any other part of the projection  50  and the center (point A). The projections  50  arranged on the cover  38  and the bottom plate  39  are at the positions corresponding to the spiral chamber between the midpoint P 3  and the terminating point P 2 . The high-pressure region  49  lies on the line connecting the midpoint of the projection  50  and the center of rotation (point A) of the impeller  36 . 
     FIG. 9 illustrates the flow-rate distribution of the air flowing through the inlet ports  42   a  and  42   b  of the centrifugal air-applying device  24 , which have a non-circular opening. FIG. 10 shows the flow-rate distribution of the air flowing through a conventional inlet port, which corresponds to the inlet ports  42   a and  42   b  and which is formed into a perfect circle and coaxial with the impeller  36 . 
     As shown in FIG. 9, air flows at positive pressure in that region of either inlet port  42   a  or  42   b , which extends from the middle part of the projection  50  to near the initiating point P 1  of the spiral chamber  48 . In the remaining region of either inlet port, air flows at negative pressure. Thus, the air is drawn to the center of rotation of the impeller  36 . 
     As shown in FIG. 10, air flows partly at positive pressure, along that part of the rim of either inlet port  42   a  or  42   b , which extends from a point near the terminating point P 2  of the spiral chamber  48  to the initiating point P 1  thereof. 
     In the centrifugal air-applying device  24  shown in FIG. 9, part of the air flowing through the inlet ports  42   a  and  42   b  that are formed into a non-circular shape acquires a positive pressure. Nonetheless, its flow rate falls within the range of 0.1 to 0.5 m/s. In the centrifugal air-applying device  24  shown in FIG. 10, wherein the inlet ports  42   a  and  42   b  are formed into a perfect circle, that part of air which has a positive pressure flows through the ports  42   a  and  42   b  at a rate ranging from 0.4 to 1.0 m/s. Obviously, this flow rate is higher than in the device of FIG.  9 . In addition, the range of flow rate of the air flowing at the positive pressure is broader than in the device illustrated in FIG.  9 . 
     As seen from the above, the inlet ports  42   a  and  42   b , each being formed into a non-circular shape, reduce both the flow rate of the air flowing at a positive pressure and the flow-rate range thereof. 
     This may be because those parts of the edges of the inlet ports  42   a  and  42   b , which correspond to the high-pressure region  49 , are spaced away from the high-pressure region  49  due to the projections  50 . 
     Namely, air is prevented from leaking from the inlet ports  42   a  and  42   b  in the first embodiment, by changing the opening shapes of the inlet ports  42   a  and  42   b . The structure of the impeller  36  is not changed and is not complicated. Nor will the number of component increase. The centrifugal air-applying device  24  may yet be provided at a low cost and, hence, at a low price. 
     Moreover, air may be efficiently guided from the inlet ports  42   a  and  42   b  to the outlet port  43 . As a result, the efficiency of cooling the heat sink  22  that opposes the outlet port  43  rises, making it possible to enhance the cooling of the semiconductor package  11 . 
     In the first embodiment, a part of the edge of either inlet port projects toward the center of rotation of the impeller, rendering the shape of the inlet port non-circular. Nevertheless, this invention is not limited to this feature. 
     For instance, the inlet port may have a perfectly circular opening coaxial with the impeller. If this is the case, leakage-preventing sheets may be laid on the cover and bottom plate of the case having the inlet ports, thus forming the projected edge parts of the inlet ports, which correspond to the high-pressure region of the spiral chamber. 
     In this arrangement, the sheets function as a projected edge such that the edge (i.e., projected edge) of the inlet ports is closer toward the center of rotation of the impeller. The sheets make both inlet ports effectively have a non-circular opening. The sheets prevent the air from leaking at the inlet ports, as the projections do in the first embodiments. 
     FIG. 11 depicts the second embodiment of the present invention. 
     The second embodiment differs from the first in the shape of inlet ports  55 . It is basically the same in other structural aspects as the first embodiment. The components identical to those of the first embodiment are designated at the same reference numerals and will not be described. 
     As shown in FIG. 11, the cover  38  has an inlet port  55 , and the bottom plate (not shown) also has an inlet port. The inlet ports  55  have a perfectly circular opening and lie coaxial with each other. The inlet ports  55  are eccentric to the center of rotation (point A) of the impeller  36 , with their centers located away from the high-pressure region  49  of the spiral chamber  48 . 
     The center H of each inlet port  55  deviates, by a distance L, from the center of rotation (point A) of the impeller  36 . Thus, that part of the edge of either inlet port  55 , which corresponds to the high-pressure region  49 , projects toward the center of rotation (point A) of the impeller  36 . 
     In this arrangement, the inlet ports  55  are eccentric to the impeller  36 . Therefore, that edge part of either inlet port  55 , which corresponds to the high-pressure region  49 , protrudes away from the high-pressure region  49 . 
     Thus, air may be prevented from leaking at the inlet ports  55 , by positioning the inlet ports  55  eccentric to the impeller  36 . This contributes to the reduction of cost. 
     Electronic apparatuses according to the present invention are not particularly limited to portable computers. The present invention is applicable to various data processing apparatuses each including a circuit component that generates heat. 
     It may be seen that an embodiment of the invention may be characterized as a method of making an air-applying device includes the steps of positioning an impeller within a casing having an inlet and an outlet ports, and configuring one of the shape of the inlet port and the orientation of the inlet port with respect to the center of rotation of the impeller, such that leakage flow of air from within the casing to outside the casing through the inlet port is inhibited. It is understood that inhibiting the air flow as mentioned above need not result in complete prevention of all leakage air but may reduce such leakage air as compared to the prior art (FIG.  10 ). 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.