CROSS REFERENCE OF RELATED APPLICATION 
       [0001]    This is a Continuation application of a non-provisional application having an application Ser. No. 12/733,924, and a filing date of Mar. 24, 2010, which is a 371 national phase application of an international application number PCT/CN2008/071772 and filing date Jul. 28, 2008, which claimed priority of three foreign applications, #1: 200710077392.1, filing date: Sep. 29, 2007, filing country: CHINA; #2: 200810067796.7, filing date: Jun. 18, 2008, filing country: CHINA; and #3: 200810067795.2, filing date: Jun. 18, 2008, filing country: CHINA. The contents of these specifications, including any intervening amendments thereto, are incorporated herein by reference. 
     
    
     BACKGROUND OF THE PRESENT INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to an electronic heat dissipating device and portable computer, and more particularly to a flat radiator with heat pipe for cooling the electronic chips (CPU or GPU) in the portable computer, and a flat-panel computer with a screen cover and a keyboard. 
         [0004]    2. Description of Related Arts 
         [0005]    As the higher demands of thinner and multi-functional portable devices, especially the CPU and GPU, the thermal design for the heat dissipating of the whole system has become a bottleneck to the improvement of portable computer&#39;s performance. The radiator affixed to the CPU or GPU is like the shell on a snail, and it has occupied quite much room of the portable computer, so cutting down the thickness of portable computer is restricted by the radiator. 
         [0006]    The structure of the radiator of current notebook computer is as follows. It has a centrifugal fan with a shell which is usually a helicoid shaped shell and has a centralized air outlet. The air convective extended heat exchange surface, which is usually a fin structure, briefly called fin, is located at the air outlet. Usually heat pipes are used to transport the heat produced by the CPU to the fin. 
         [0007]    The disadvantages of this design include the followings. First, the air outlet is easily blocked, it will cause that the heat can&#39;t be dissipated. Second, the wind driven by the fan is directly vented after flowing through the fin, and is unable to be further utilized. Next, the shell of the fan takes up much room of the fan, so that in order to reduce the volume, the shape of the shell isn&#39;t standard helicoid shape, which results in much more air vortex loss, and asymmetrical air flow at the air outlet, and it is unbeneficial to heat dissipation. Last, because of the restriction of the line layout, the CPU should be located near the center of the motherboard, so that the distance between the fin and the CPU is so long that long heat pipes are needed, and the distance between the vaporizing area and the condensing area of the heat pipe is longer, and the heat transport capacity becomes less. 
       SUMMARY OF THE PRESENT INVENTION 
       [0008]    In order to overcome the disadvantages of the above, the present invention changes the position of the fin, so that the shell of the fan is left out, and the distance between the vaporizing area and the condensing area of the heat pipe is shortened, and an intensified heat transfer structure is introduced to reduce the size of the fin. So the radiator&#39;s structure is simpler, smaller and thinner, and the heat transfer capacity is higher. So we can make out thinner and more convenient portable computers with simpler structure. 
         [0009]    The blue print of the present invention is as follow: The radiator comprises heat pipe, air convective extended heat exchange surface and centrifugal fan. The shape of the whole radiator is flat shape like. The characteristics of the present invention are that: the air convective extended heat exchange surface is bonded or welded on the heat pipe; the air convective extended heat exchange surface surrounds the fan impeller, facing the air outlet of the fan impeller, so that the air from the fan impeller is blew directly into the air convective extended heat exchange surface. 
         [0010]    The fin structure of air convective extended heat exchange surface is the most popular, it is a kind of structure that increases the area of air convection heat exchange effectually and cuts down the size to make the radiator compact, for example, it is used in the condenser and evaporator of air-condition. The present radiator of CPU has this structure too. 
         [0011]    The pin structure is not popular because of the high manufacturing cost, but the air convection heat transfer coefficient is more than twice of the fin structure. Compact structure and small size are very important for notebooks, so the pin structure is also adopted too. 
         [0012]    Usually heat pipes are tubular structure, whose both ends are blocked, the interior is vacuum and filled with working fluid. The present invention adopts not only tubular structure, but also plate type. For the plate heat pipe, the ratio of its width with its thickness is so large that it can only be curved in the thickness direction. In the present invention, the ratio is decided to be more than 5, it is named a plate heat pipe differentiate from a tubular heat pipe. 
         [0013]    The outer circle of the centrifugal fan impeller is the air outlet of the impeller, when the impeller rotating, air flows out equably from the outer circle of the impeller. The air convective extended heat exchange surfaces are set to surround the impeller, and are facing to the air outlet of the impeller, so the air coming from the impeller goes into the air convective extended heat exchange surface directly. The advantages of this structure are as follows. 
         [0014]    1. Increasing the length of setting the air convective extended heat exchange surface, it results in that the speed of the air through the air convective extended heat exchange surface can be reduced, so as to have lower airflow resistance, and more air flux. 
         [0015]    2. The fan can be set at a position near the electronic chips, this structure shortens the distance between vaporizing area and condensing area of heat pipe very much, so as to increase the heat transport capacity of the heat pipe. 
         [0016]    3. Abandoning the fan shell is one of the most significant advantages, it decreases the room, weight and cost of the shell, the room of the diffusion channel in the shell is left out, and the air vortex loss in the shell is avoided. The air from the radiator can not be vented out of the mainframe shell directly, and can be used to cool other components. 
         [0017]    4. The air convective extended heat exchange surface can be arranged in square, polygon or other shapes to surround the impeller of the fan. However, the best way is to arrange the air convective extended heat exchange surface circularly around the impeller, and the gap between the heat exchange surface and the impeller is as small as possible. The reasons of the above are as described as follows: First, the air can flow uniformly through the air convective extended heat exchange surface, without the influence of some placket or block surrounding the impeller. Second, it further decreases the room between the air convective extended heat exchange surface and the impeller. 
         [0018]    Now the radiator of the present invention just only makes up of heat pipe, fan and air convective extended heat exchange surface, and there is no other part can be left out. The gap between impeller and air convective extended heat exchange surface is necessary for avoiding impeller to be collided or clamped. 
         [0019]    It explains hereinbefore that arranging the air convective extended heat exchange surface to surround the impeller of a fan is the most compact structure. In order to cut down the size of the radiator further, we can only make some improvement on the air convective extended heat exchange surface and the fan, for example: Adopting the structure of strengthening convection heat transfer, to increase the coefficient of the convection heat transfer; Increasing the density of the air convective extended heat exchange surface, it can increase the area of heat exchange surface not only, and also the coefficient of the convection heat transfer can be improved; Optimizing the design of the impeller and increasing the rotate speed to cut down the diameter or thickness of the impeller. 
         [0020]    In the present invention, at least half of the outer circle of the impeller is surrounded by the air convective extended heat exchange surface, it is just to indicate that the whole outer circle of the impeller should be utilized effectually to set the air convective extended heat exchange surface for decreasing idle room. 
         [0021]    There is no wind cover and centralized air outlet, so the position of the radiator is not limited very much, it can be placed anywhere on the motherboard following CPU and GPU as long as keeping the air inlet unblocked. The radiator becomes a smaller and lighter part which does not take up the much room in the notebook computer any more, so that radiator can be divided into some series according to the heat dissipating capacity and thickness, and to establish standardization of the radiator, so that we can establish a standardization of the notebook case and the motherboard. 
         [0022]    These and other objectives, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is the rear view of a flat radiator with heat pipe according to a preferred embodiment of the present invention, illustrating the shape of a tubular heat pipe and the rear view of a conduction block. 
           [0024]      FIG. 2  is the sectional view of A-A section of the  FIG. 1 , illustrating the air convective heat transfer part of a flat radiator with tubular heat pipe. 
           [0025]      FIGS. 3 and 4  are the sectional views of two kinds of the flat radiator according to the preferred embodiment of the present invention, the heat pipes are the flat type. 
           [0026]      FIGS. 5 ,  6 ,  8  and  9  are the front views of four kinds of the flat radiator according to the preferred embodiment of the present invention, the heat pipes are the flat type. 
           [0027]      FIGS. 7 and 10  are the rear views of two kinds of the flat radiator according to the preferred embodiment of the present invention, the heat pipes are tubular type. 
           [0028]      FIG. 11  is a sectional view of a flat type heat pipe. 
           [0029]      FIG. 12  is a sectional view of a corrugated type fin of the flat radiator according to the preferred embodiment of the present invention. 
           [0030]      FIG. 13  is a sectional view of a laminated type fin of the flat radiator according to the preferred embodiment of the present invention. 
           [0031]      FIGS. 14-16  are partially perspective views of the impeller and fin of the flat radiator according to the preferred embodiment of the present invention. 
           [0032]      FIG. 17  is a sectional view of a staggered short fin for intensifying heat convection transfer. 
           [0033]      FIG. 18  is a sectional view of a louvered short fin for intensifying heat convection transfer. 
           [0034]      FIGS. 19 and 20  are the perspective sectional views of two kinds of portable computer, the structure of which is different from the traditional notebook computer, and show a kind of the flat radiator of the present invention is used in this kind portable computer. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0035]      FIG. 1  shows the characteristic structure of one kind of the present invention radiator with tubular type heat pipe, wherein the air convective extended heat exchange surface is not shown in the  FIG. 1 . The heat pipe  2  surrounding impeller  3  is an integrative pipe, and its both ends are vaporizing segment which are on the back of conduction block  1 . There is an even surface called heat-absorbing surface on the obverse side of conduction block  1 . 
         [0036]    The conduction block  1  abuts against the impeller  3  to cut down the distance between the vaporizing area and the condensing area effectually. Because of the limit of bending radius, the heat pipe can not be bended to surround the whole impeller (360°), there is an opening near the conduction block  1 , as  FIG. 1  shows, one end of the heat pipe  2  is extended straight to the conduction block  1 , the other is curved to the conduction block  1 , so there is an opening between them. 
         [0037]      FIG. 2  shows the characteristic structure of an air convection heat transfer unit which comprises a fan  5 , a heat pipe  2  and the air convective extended heat exchange surface  4 . The heat pipe  2  is a tubular structure, the fan  5  is a centrifugal type, air flows axially in and radially out, as the arrow  6  shows, the outer circle of the impeller  3  is the air outlet of the impeller  3 . The air convective extended heat exchange surface  4  faces to the air outlet of the impeller  3 , the air coming from the impeller  3  goes into the air convective extended heat exchange surface  4  directly. In order to reduce the periphery size of the air convective extended heat exchange surface  4  which surrounds the impeller  3 , namely to reduce the size of the radiator, the gap between the impeller  3  and the air convective extended heat exchange surface  4  should be as small as possible, but we should make sure that the impeller  3  can not come into contact with the air convective extended heat exchange surface  4  or the heat pipe  2 . 
         [0038]      FIG. 3  shows the characteristic structure of one kind of the present invention radiator with plate structure heat pipe. The heat pipe  2  is a plate structure, and the air convective extended heat exchange surface  4  is set on the heat pipe  2  directly, and the next is the heat-absorbing surface  7 . The part of the heat pipe  2  at the fan is designed to be concave to increase the height of the blades of the impeller  3  and motor, so to increase the air flux without thickening the radiator. In order to prevent the hot air out of the radiator from flowing back to the air inlet of fan, the PCB  8  or a device fixed on the PCB  8  are used as one sidewall of the fan  5 , and an air inlet is opened there, as  FIG. 4  shows, it is good not only for separating the air inlet from the outlet effectually, but also decreasing the fan&#39;s thickness. In a portable computer, the air from the radiator can be used to cool other components and bring heat out of the computer case. In  FIG. 4 , the part of the heat pipe  2  on the heat-absorbing surface  7  is thickened, it is to make use of room effectually and to increase the circulation area of working fluid in the heat pipe, and to improve the heat transfer capacity. 
         [0039]      FIG. 5  shows the obverse characteristic structure of one kind of the present invention, and the heat pipe  2  is a plate structure, the air convective extended heat exchange surface  4  surrounds the impeller  3  circularly. The air convective extended heat exchange surface  4  is a pin structure, the heat-absorbing surface  7  abuts against the air convective extended heat exchange surface  4 . There are four screw holes  11  on the heat pipe  2  to fix the heat pipe  2 , to make the heat-absorbing surface  7  being pressed tightly on the electronic chip to be cooled, to reduce the contact thermal resistance. 
         [0040]    In  FIG. 6 , the heat pipe  2  is a plate structure too, there are two impellers  3  and air convective extended heat exchange surface  4  on the heat pipe  2 , the heat-absorbing surface  7  is between them. In  FIG. 7 , the heat pipe  2  is a tubular structure, and the conduction block  1  is fitted with the two impellers  3 . 
         [0041]    In order to reduce the distance between the vaporizing area and the condensing area, the two fans  5  are closed to heat-absorbing surface  7 , the part of the air convective extended heat exchange surface conflicting with the chip to be cooled is taken out, as  FIG. 6  shows, there are openings in the air convective extended heat exchange surface  4 .  FIG. 6  also shows that there are four nuts  12  which can be welded on the heat pipe  2 . 
         [0042]    When there are two or more chips to be cooled on a PCB, we can use this mean: one fan takes on two or more heat-absorbing surfaces, as  FIGS. 8-10  show. In  FIG. 8 , there are two heat-absorbing surfaces  7  on the heat pipe  2 , while only one fan  5 . In  FIG. 9 , there are two heat pipes  2  with one half of the air convective extended heat exchange surface  4  on each heat pipe  2 . The heat pipes  2  in  FIGS. 8 and 9  are a plate structure. In  FIG. 10 , the heat pipe  2  is a tubular structure. 
         [0043]      FIGS. 5-10  show that, the outer circle of the impeller is utilized fully to set the air convective extended heat exchange surface, more than half of the outer circle of the impeller is surrounded by the air convective extended heat exchange surface, there is no diffusion channel and fan shell which are needed in traditional radiator, the idle room is decreased. 
         [0044]      FIG. 11  shows a kind of plate type heat pipe, the heat pipe is made of two metallic plates with wick  14  inside, the two metallic plates are connected together with buckle and welding  13 , and there are welding points at the middle of the heat pipe inside, the intensity of this structure is high. Usually water is used as working liquid, when the temperature of water is more than 100° C., the pressure in the heat pipe is more than the atmospheric pressure. If there aren&#39;t enough welding points or lines, the heat pipe will be swelled, so there should be enough welding points. 
         [0045]    The fin  15  in  FIG. 12  is a corrugated structure, it is made of coiled sheet being rippled, and set on the heat pipe  2  usually by welding technology, because the contact area between the fin  15  and the heat pipe  2  is so small.  FIG. 13  shows a kind of laminated type fin, there is a hem at root of the fin  15 , and the hem clings on the heat pipe  2 . To make sure the distance between the fin blades even and for high production efficiency, there are location hems  16  at the root hem and the top hem each, just as  FIG. 13  shows. 
         [0046]    At the air outlet of the impeller, namely, the outer circle of the impeller, the air speed can be separated into radial velocity and circumferential velocity. If the impeller shape is different, the distribution of the radial velocity and circumferential velocity is different, for the forward curved blade, the circumferential velocity is higher than that of backwards curved blade. Whatever type of impeller the circumferential velocity exists, and its direction accords with the direction of the impeller rotating. 
         [0047]    When the fins set at the air outlet of the impeller are arrayed radially, there is an angle, called attack angle in aerodynamics, between the front edge of the fin and the direction of the airflow out of the impeller. When the attack angle is bigger, the flowing resistance of the air flowing through fins is bigger, and it will cause reducing of the air flux, that is bad for heat dissipation. In order to cut down the attack angle, the fin  15  surrounding the impeller  3  can be set to incline forward the rotating direction of the impeller  3 , as  FIG. 14  shows. 
         [0048]    We can also curve or bend the air inlet front edge of the fin  15  surrounding the impeller  3  against the rotating direction of the impeller  3 , as  FIG. 15  shows, the fin  15  is curved, the channels between the fin  15  blades would be diversion diffuser, so the fin  15  is not only used for air convection heat transfer, but also for diversion and diffusion. 
         [0049]    In order to cut down the fin size, intensified air convection heat transfer structure is used in the fin.  FIGS. 17 and 18  show two kinds of short fin structure for intensifying convection heat transfer, the fin as  FIG. 17  shows is the staggered short fin structure, and  FIG. 18  shows the louvered short fin structure. Their basic characters are: the surface which the air flows over is cut into several discontinuous segments, when the air washing every segment, the boundary layers are all at theirs start bit, so that the whole air convective heat exchange surface make use of the advantage of thinner boundary layer of start bit, so that less heat resistance and higher coefficient of air convection heat transfer. When setting fins of louvered structure to surround the impeller, we must pay attention to the bend direction of the louvered fin, the edge of air inlet should be bended against the rotating direction of the impeller, as  FIG. 16  shows. 
         [0050]    The portable computers shown in  FIGS. 19 and 20  comprise the mainframe  25  and the screen cover  30 , the keyboard  21  is set on the screen cover  30 , the display screen  19  is on the mainframe  25 , and there are the motherboard  8 , the battery and hard disc (not shown) in the mainframe  25 , the radiator of the CPU or GPU  9  is one kind of the present invention, the heat pipe  2  is a plate structure and is keep close to the back shell  27  of the mainframe  25 . The computer in the figures is in open state, the mainframe  25  stands up askew on the interior of the screen cover  30 , the screen cover  30  is as the base of the mainframe  25  and the vertical line of the center of gravity of the mainframe  25  is within the screen cover  30  to make it stable. The broken line in the figures expresses the closed state of the mainframe  25  and the screen cover  30 , the display screen  19  is covered by the screen cover  30  for protection, and the backside edge of the screen cover  30  is adjacent to the downside of the mainframe  25 . The heat pipe  2  is pasted on the wall of the back shell  27  in order to make use of the wall of the back shell  27  to be a heat dissipation surface, and the effect of radiation heat transfer and air convection heat transfer is best when the mainframe  25  is upright. 
         [0051]    The display screen is on the mainframe and the keyboard is on the screen cover, when in open state the mainframe stands up askew on the interior of the screen cover used, it is different from the traditional notebooks. The advantages include that: 1. the heat dissipating capacity is increased, the wall of the shell can be used as heat dissipation surface, and the air inlet and outlet are not blocked easily, as the figures show that the air inlet  20  is opened at the back shell  27 ; 2. it needs only a shell and the display shell is left out, so the computer thickness is decreased; 3. the keyboard can be of several kinds of structures, like the thin film key-press; 4. the screen cover not only protects the display screen, but also be as the base of the mainframe when upright, and we can set a battery in the screen cover as backup battery, which can be replaced conveniently. 
         [0052]    In  FIGS. 19 and 20 , the CPU or GPU  9  is set near the bottom of the mainframe  25 , the fan  5  and the air convective extended heat exchange surface  4  are up, wherein the heat pipe vaporizing area is below, the working liquid flows back by gravity, so the heat flux of this heat pipe is high, we can use the simple heat pipe of a heat siphon structure. The air outlet  23  should be as high as possible, just like the highest position shown in the figures, and the CPU or GPU chip is set as low as possible, The purposes are that: 1. the hot air in shell can be dissipated equably, other components can be also cooled; 2. using the empty room in shell, a pump effect is formed like a chimney to improve air convection and the whole heat dissipating. 
         [0053]    In  FIG. 19 , there are a backup battery  29  and a keyboard  21  on the screen cover  30 , the backup battery  29  is a plate structure and is set between the keyboard  21  and the backside edge of the screen cover  30 , they are on the same side and their thickness is the same. The mainframe  25  is sustained by the strut  28 . The connection between the screen cover  30  and the mainframe  25  is also the strut  28 . The power and electrical signal wires between the screen cover  30  and the mainframe  25  can be set in the struts  28 . The connection between the strut  28  and the mainframe  25  or the screen cover  30  can be designed to be divided without any tool, so that the mainframe  25  and the screen cover can be separated easily. Then, the mainframe  25  becomes a flat-panel computer, it will be convenient for users. 
         [0054]    In  FIG. 20 , there is no strut and there are two runners  32  on both sidewalls of the screen cover  30 , and there are sliding axles  31  on the mainframe  25 . The connection between the mainframe  25  and the screen cover  30  is by the connection between the runners  32  and the sliding axles  31 , the mainframe  25  can be sustained also by the sliding axles with the runners. There are electric touch points between the downside of the mainframe  25  and the screen cover  30  for the electrical connection between the mainframe  25  and the screen cover  30 . 
         [0055]      FIG. 20  shows that there is an opening  33  at the outside on the runner  32 , the sliding axle  31  on the mainframe  25  can slide off from the opening  33 , so the mainframe  25  can be separated easily from the screen cover  30  without any tool. In  FIG. 20 , the backup battery  29  is a plate structure too, and is set on the outer surface of the screen cover  30  and covers the whole outside of the screen cover  30 . The backup battery  29  can be designed having different kinds of capacities and thicknesses and be replaced at any moment. If long operation time is needed, user can choose a larger backup battery conveniently, the capacity of backup battery maybe more than the battery in the mainframe. When users need handiness, they can choose the lighter and thinner backup batteries. 
         [0056]    It is appreciated that the hard discs in the present invention include mechanism hard discs and solid state discs. 
         [0057]    It will thus be seen that the objects of the present invention have been fully and effectively achieved. It embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.
A flat heat pipe radiator and a new kind of portable computer are provided. The air convective extended heat exchange surface of the radiator surrounds the fan impeller and is facing the air outlet of the impeller, the heat transport distance in heat pipe is shortened, the fan shell and the diffusion channel in the shell can be left out, so the size, weight and cost of the radiator are decreased effectively. The restrictions to a radiator when installing are reduced, which helps to implement the standardization of the radiator series. The new kind of portable computer helps to decrease weight and thickness and improve the heat dissipation further.