Abstract:
A system for cooling interior and external housing surfaces of an electronic apparatus. The apparatus includes at least one electronic component, a heat transfer mechanism for transferring to an external surface of the apparatus heat generated by the electronic component, and a cooling mechanism for cooling the external surface of the apparatus. The cooling mechanism also includes an airflow generation device and an opening that enables airflow to simultaneously flow over at least one electronic component within the apparatus and over the external surface to dissipate the heat generated by the at least one electronic component.

Description:
PRIORITY CLAIM  
       [0001]     This application claims priority of Japanese Patent Application No. 2004-269416, filed on Sep. 16, 2004, and entitled, “Electronic Apparatus Comprising a Cooling Apparatus for Cooling Interior and External Housing Surfaces.” 
       BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field  
         [0003]     The present invention relates in general to the field of electronic apparatuses. More particularly, the present invention relates to the field of cooling electronic apparatuses. Still more particularly, the present invention relates to a system of cooling interior and external housing surfaces in electronic apparatuses.  
         [0004]     2. Description of Related Art  
         [0005]     Recently, for compact electronic apparatuses such as portable personal computers (PCs), the performance of internally provided electronic components has been improved and their installation density has been increased. As a result, during the operation of the compact electronic apparatuses, heat generated by the internally mounted electronic components has become a serious problem. Since there is a tendency that the thickness, weight, and size of the housings are reduced, the head generated by the electronic components tends to be retained internally. Therefore, to ensure the performance and the reliability of electronic components, there is a need for a system of removing generated heat quickly to cool the housings of a data processing system such as a PC.  
         [0006]     Since housings provided for compact electronic apparatuses have gotten smaller as the demand for more compact data processing systems increase, the installation of cooling apparatuses in the housings, such as fans, is difficult. Therefore, parts such as copper plates, aluminum plates, or heat pipes have been employed to move heat from heat generating sources to locations where the heat can be discharged. If the generated heat is not removed, the performance of the electronic components within the data processing system will degrade.  
         [0007]     According to one method for locating a fan inside a housing, a very small fan with a limited flow rate is employed. Since the density in which components is high, it is difficult for air impelled by the fan to be dispersed throughout the housing. This difficulty results in electronic components within the data processing system that do not received adequate cooling. When electronic components are inadequately cooled, erroneous operations or failures may occur, and the safely and reliability of the components may be degraded.  
         [0008]     According to another method for transferring head generated by an electronic component, heat is conveyed to the inner surface of a housing and is externally removed at its outer surface. Since the removal of heat from the outer surface of the housing depends on the natural transfer of heat based on the difference between atmospheric temperature and the surface temperature of the housing, the heat discharge effect is not satisfactory. Furthermore, since during operation, the temperature at the surface of the housing is high, a person who comes in contact with the surface will experience an uncomfortably hot sensation which may result in a burn if the contact with the housing surface continues for an extended period of time. Thus, since people tend to carry personal computers, such as mobile PCs, in their hands or use them in their laps, heat at the surfaces of the housings has also become a problem. From the viewpoint of the users, measures are required (e.g., temperature reductions and surface cooling) that will reduce the heat of housing surfaces that regularly come in contact with the user. As a conventional countermeasure, the surfaces of housings are covered with materials with low thermal conductivity, such as resin. According to this method, only a small amount of heat is removed from the housing surfaces, and only reduced cooling effects are provided for internal electronic components.  
         [0009]     Conventional techniques for the provision of cooling apparatuses in portable PCs are also disclosed in Japanese Utility Models No. 3064584 and No. 3043379, for example. However, these techniques are provided merely for the cooling PC housing interiors, not for reducing the temperatures of housing surfaces.  
       SUMMARY OF THE INVENTION  
       [0010]     A system for cooling interior and external housing surfaces of an electronic apparatus is disclosed. The apparatus includes at least one electronic component, a heat transfer mechanism for transferring to an external surface of the apparatus heat generated by the electronic component, and a cooling mechanism for cooling the external surface of the apparatus. The cooling mechanism also includes an airflow generation device and an opening that enables airflow to simultaneously flow over at least one electronic component within the apparatus and over the external surface to dissipate the heat generated by the at least one electronic component.  
         [0011]     The above-mentioned features, as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objects and advantages thereof, will be best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:  
         [0013]      FIG. 1  is an oblique rear view of an exemplary personal computer (PC) according to a preferred embodiment of the present invention;  
         [0014]      FIG. 2  is a cross-sectional view of the PC illustrated in  FIG. 1 .  
         [0015]      FIGS. 3A-3C  depict plan views of example locations and shapes of libs on a heat sink according to a preferred embodiment of the present invention; and  
         [0016]      FIG. 4  illustrates a cross-sectional view of the PC in  FIG. 2  where a duct is provided according to another preferred embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]     The present invention provides the cooling of the external surface of a housing for an electronic apparatus and of the electronic components (that generate heat during operation) that are disposed within the housing.  
         [0018]     The present invention will now be described by employing a portable PC as an example. However, those with skill in this art will appreciate that the present invention is not limited to a PC and can be applied for other types of electronic apparatus.  FIG. 1  is an oblique rear view of a portable PC  10  in which a preferred embodiment of the present invention may be implemented.  FIG. 2  is a cross-sectional view of the PC in  FIG. 1  taken in a direction indicated by A.  
         [0019]     A housing is formed of a core housing  12  and a cradle housing  14 . A CPU  18  mounted on a printed circuit board  16 , a heat sink  20  connected to the CPU  18  via a thermal conductive flexible member  19 , libs (LIB)  22  that secure the heat sink  20  to the core housing  16 , and electronic components  24  (not shown in details), such as a memory, various control ICs and an HDD, are arranged in the core housing  12 .  
         [0020]     A connector (not shown) for electric connection is provided at an end  33  of the core housing  12 , and is detachable to a connector (not shown) mounted on the printed circuit board that is located at the bottom of an opening  40  formed in the cradle housing  14  and is used for an interface (I/O)  46 . The core housing  12  is operated as a PC with being connected to the connector of the cradle housing  14 . During the operation, the temperature on the surface of the core housing  12  is increased very much. Since the core housing  12  can be removed from the cradle housing  14  and carried, the core housing  12  can be used as a PC by being attached to another cradle housing in a different place.  
         [0021]     The cradle housing  14  incorporates interfaces (I/Os) for a power source and external devices, such as a display device, a keyboard and a mouse), and have connectors  46  for these interfaces. A fan  30  is provided inside the cradle housing  14 , and by the fan  30 , air is taken through an opening  36  inside the cradle housing  14 , and is impelled from the fan  30  to the surface of the core housing  12 . An opening  42  is formed in the upper portion of the cradle housing  14 , so that the part of the air from the fan  30  is output through the opening  42  and drifted along a surface  29  of the core housing  12 , as indicated by arrows  44  (hereinafter referred to as an airflow  44 ).  
         [0022]     The amount of the airflow  44  depends on the capacity of the fan  30  and the sizes of the openings  36 ,  26 ,  28  and  42 . The airflow  44  does not necessarily reach the upper end of the core housing  12 , i.e., the vicinity of the opening  28 , but at least accelerate the discharge of heat transferred from the libs  22 . The amount of the airflow  44  is determined to satisfy the need. The fan  30  and the cradle housing  14  are tightly sealed except for the openings  36  and  42  to prevent the flow of air (air leaking) except for the airflows  44  and  32  (will be described later in detail). With this arrangement, the pressure inside the cradle housing  14  is higher than the surroundings, and air is easily moved to the core housing  12  where pressure is lower and the upper end  28 . By the airflow  44 , a surface  29  of the core housing  12  is cooled during the operation of the PC, and as a result, the temperature on the surface  29  is reduced. At the same time, the effects (cooling effects) for removing heat that is transferred from the CPU  18  to the heat sink  20  and the libs  22  to the core housing  12  are accelerated.  
         [0023]     The part of the air impelled by the fan  30  flows from the opening  26  of the core housing  12  to the core housing  12 , and is drifted along the core housing  12  as the airflow  32  that is to be externally discharged from the opening  28 . By this airflow  32 , the electronic components, such as the CPU  18 , that generate heat during the operation, the heat sink  20  and the reverse surface of the core housing  12  are cooled. As is described above, in the PC shown in  FIG. 2 , the airflows  44  and  32  flow at the same time along both the obverse surface and inside of the core housing  12 . As a result, the effects for cooling the electronic components in the core housing  12  are increased, and the rise of the temperature on the surface of the housing  12  can be suppressed. The same effects can be obtained by drifting the airflows  36 ,  32  and  44  in the direction opposite to the direction in  FIG. 2 .  
         [0024]     The libs  22  in  FIG. 2  are elongated in cross section, because the area where the core housing  12  and the heat sink  20  contact is increased and heat conduction from the heat sink  20  to the core housing  12  is more efficient. Further, this shape is not an obstacle in an air flow path and can provide an effective heat discharge function.  
         [0025]      FIGS. 3A, 3B  and  3 C are plan views of example locations and shapes of the libs  22  on the heat sink  20 . In  FIG. 3A , cylindrical libs  22  are located at four points  50 . In  FIG. 3B , L-shaped libs  22  are located at four points  52 . In  FIG. 3C , two elongated libs  22  are located at points  54 , as used for the PC in  FIG. 2 . The shapes, the sizes and the volumes of the libs  22  are optimized for a portable PC in accordance with the size of the housing of the PC, the amount of heat generated by incorporated electronic components, the location of a heat generation device on a substrate, the location where air is taken in from a fan, the amount of air impelled by the fan and the direction of an airflow. As a result, the amount of thermal conduction can be adjusted, and heat generated by the heat generation element can be efficiently transferred to the surface of the housing.  
         [0026]     In the example in  FIG. 2 , since the libs  22  are formed elongated, the strength whereby the heat sink  20  is secured to the housing is increased, and the deflection of the heat sink  20  seldom occurs when a load is imposed by connection with the CPU. Further, at least two libs  22  are arranged at an interval in order to obtain the path of the airflow  32  that flows in the core housing  12 .  
         [0027]     A thermal conductive material, such as an aluminum alloy, copper, stainless steel or a magnesium alloy, can be employed for the heat sink  20  and the libs  22 . When a heat sink and a heat pipe are employed together as a heat transfer mechanism, the cooling effects are more increased.  
         [0028]     The following experiment was conducted to examine the cooling effects provided by the airflow  44  that flows along the surface of the housing.  FIG. 4  is a cross-sectional view of a PC  10 ′ wherein a duct  34  is formed in the cradle housing  14  of the PC in  FIG. 2  to prevent the air impelled by the fan  30  from being discharged through the opening  42 . In the PC  10 ′ in  FIG. 4 , air impelled by the fan  30  enters the core housing  12 , and is drifted as an airflow  32  in the core housing  12  to be discharged from the upper opening  28 .  
         [0029]     For the PC  10  in  FIG. 2  and the PC  10 ′ in  FIG. 4 , the two elongated libs  22  (size: 2 mm×25 mm×1 mm, made of A15052) were attached to the heat sink  20  (size: 50 mm×100 mm×0.5 mm, made of A11050), and the cooling effects by using the airflow  44  that flows along the surface of the housing were examined. As a result, for the PC  10  in  FIG. 2  using the airflows  32  and  44 , the temperature on the housing surface  29  and the temperature of the CPU  18  could be reduced respectively by about 2° C. and by about 4° C., compared with the PC  10 ′ in  FIG. 4  employing only the airflow  32 . The data for the conditions in the experiment are as follows.  
         [0030]     CPU clock: 1 Ghz  
         [0031]     fan: 4200 rpm  
         [0032]     housing surface temperature: 
        48.9° C. with the airflow  44      50.8° C. with no airflow  44         
 
         [0035]     CPU temperature: 
        77.2° C. with the airflow  44      81.3° C. with no airflow  44      environmental temperature: 35° C.        
 
         [0039]     The present invention has been explained by using the PCs in FIGS.  1  to  4 . However, the present invention is not limited to these PCs. For example, instead of a fan using airflows, the cooling system for this invention may be a system where a coolant flows along a narrow pipe formed on the surface of the housing, or a system wherein a cooling device, such as a Peltier device, is located at a portion (heat spot) that becomes especially hot. According to the present invention, an appropriate cooling apparatus can be employed while taking into account the shape, the size and the heat generating condition of the electronic apparatus. So long as the cooling of the heat generating electronic components in the housing and cooling of the surface of the housing are performed at the same time, greater cooling effects of the invention can be obtained by using any type of cooling apparatus. It will be obvious for one having ordinary skill in the art that the present invention can be variously modified without departing from the scope of the subject of the invention.  
         [0040]     While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that the various changes in form and detail may be made therein without departing from the spirit and scope of the invention.