Abstract:
In metal tubes for heat pipes and a method of manufacturing the metal tubes, a metal tube includes a tube defining an inner space, and at least one dividing portion extruding from an inner sidewall of the metal tube. The at least one dividing portion divides the inner space into a vapor channel and a liquid channel connected to the vapor channel. The metal tubes can prevent heat pipe form being dried out and improve heat dissipation efficiency of heat pipes.

Description:
BACKGROUND 
       [0001]    The present invention generally relates to heat pipes, and more especially, relates to metal tubes for heat pips and method of manufacturing the metal tubes. 
         [0002]    With continuous progress of operation rate of central process unit (CPU), more and more heat is produced when the CPU is in use. Conventional heat dissipation apparatus comprised of aluminum extrusion type heat sink and fan can&#39;t sufficiently dissipate heat generated by CPU; therefore, heat pipe is developed to meet the increased heat dissipation requirement. Generally, heat pipe is used accompany with heat sink. Inner structure design and amount of working fluid disposed in heat pipe are very important parameters that affect heat dissipation ability of heat pipe. When there is too much working fluid filled in the heat pipe the vapor channel in the heat pipe will be too small, as a result, heat dissipation efficiency of heat pipe decreases a lot; in contrast, when there is too little working fluid the heat pipe may be dried out, and even damaged. The present inventor provides a new metal tube for heat pipe and method of manufacturing the same. 
         [0003]    Conventional metal tubes used in heat pipes are usually made of seamless copper tube, for example, as disclosed in published Taiwan Patent Publication Nos. 200720614, 200720615 and 200720616. Capillaries are employed in these heat pipes as dividing grooves thereby structuring a number of vapor channels and liquid channels in the heat pipe. 
         [0004]    However, in these heat pipes, although the liquid channels and the vapor channels are separated from each other, vapor channels are formed at inner edge and outer edge of the liquid channels. As a result, when the working fluid in the heat pipes are gasified the produced steam doesn&#39;t move along a certain path, thus the steam and cooled working fluid interfere with each other thereby decreasing the heat dissipation efficiency. 
         [0005]    In addition, in a method of manufacturing such heat pipes, a dividing plate is wrapped with capillaries at first, and then the dividing plate is inserted into a metal tube, and finally working fluid is injected into the metal tube. Generally, a diameter of a heat pipe is very small; the capillaries wrapping step is very difficult, not to say of disposing the resulted structure in the metal tube and attaching the resulted structure to an inner sidewall of the metal tube. Therefore, there is a desire to develop metal tubes for heat pipes to simplify manufacturing process of heat pipes. 
       BRIEF SUMMARY 
       [0006]    The present invention provides a metal tube for heat pipe and a method of manufacturing the same. Vapor channel and liquid channel are directly formed in the metal tube, as a result, the heat pipe can be avoided from being dried out; furthermore, a heat dissipation rate and efficiency of the heat pip is greatly improved. 
         [0007]    In one exemplary embodiment, a metal tube includes a tube defining an inner space, at least one dividing portion extrudes from an inner sidewall of the metal tube. The at least one dividing portion divides the inner space into a vapor channel and a liquid channel connected to the vapor channel. 
         [0008]    In another exemplary embodiment, a method of manufacturing a metal tube for heat pipe includes steps of: a) providing a tube, a number of dividing portions extruding from an inner sidewall of the tube; and b) applying a pressure onto the dividing portions using a tool such that end surfaces thereof are adjoined with each other thereby defining a vapor channel and a liquid channel in an inner space of the tube. 
         [0009]    In still another exemplary embodiment, a method of manufacturing a metal tube for heat pipe includes steps of: a) providing a tube, at least one dividing portion extruding from an inner sidewall of the tube; and b′) applying a pressure onto the tube such that an end surface of the dividing portion adjoin an inner sidewall of the tube other thereby defining a vapor channel and a liquid channel in an inner space of the tube. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which: 
           [0011]      FIG. 1  is a flow chart of a method of manufacturing a metal tube of the present invention; 
           [0012]      FIG. 2  is a cross sectional view of a metal tube prior to being processed by a shaping tool; 
           [0013]      FIG. 3  is a cross sectional view of the metal tube after being processed by a shaping tool; 
           [0014]      FIG. 4  is a cross sectional view of the metal tube along another direction; 
           [0015]      FIG. 5  is a schematic view of the metal tube of  FIG. 3  being employed in a heat pipe; 
           [0016]      FIG. 6  is a schematic view illustrating a practical application of the heat pipe in  FIG. 5 ; 
           [0017]      FIG. 7  is a flow chart of a method of manufacturing a metal tube in accordance with a second embodiment; 
           [0018]      FIG. 8  is a cross sectional view of a metal tube in accordance with another embodiment; 
           [0019]      FIG. 9  is a cross sectional view of the metal tube of  FIG. 8  after being pressed; 
           [0020]      FIG. 10  is a cross sectional view of a metal tube in accordance with still another embodiment; and 
           [0021]      FIG. 11  is a cross sectional view of the metal tube of  FIG. 10  after being pressed. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The present invention will be described in detail accompany with the drawings as following. However, it is understood that the drawings illustrate the present invention, but not restrict the present invention. 
         [0023]    The present invention provides a metal tube used in heat pipes. As shown in  FIG. 3 , a metal tube  10  includes a tube  100 , two dividing portions  101 ,  102  extruding from an inner sidewall of the tube  100  thereby dividing an inner space of the tube  100  into a vapor channel  11  and a liquid channel  12 . In the present embodiment, a length of the liquid channel  12  is less than that of the vapor channel  11 , thus, two connecting sections  13  are provided at two ends of the vapor channel  11  (referring to  FIG. 4 ). 
         [0024]      FIG. 1  illustrates a flow chart of manufacturing the metal tube for heat pipes of the present invention in accordance with a first embodiment, and  FIGS. 2-4  illustrate cross sectional views of the metal tube in different steps. The method will be described in detail with reference to these figures. 
         [0025]    In step a), referring to  FIG. 2 , a tube  100  is provided, two dividing portions  101 ,  102  extruding from an inner sidewall of the tube  100 . In this step, the tube  100  is made of the material having high heat conductivity and heat dissipation ability such as copper, and the tube  100  can be circular or other shaped. During forming of the tube  100 , a special mold is disposed in the tube  100  thereby two arc shaped dividing portions  101 ,  102  are extruded from the inner sidewall of the tube  100 . 
         [0026]    In step (b), the two dividing portions  101 ,  102  are pressed using a tool  5  thereby forming a vapor channel  11  and a liquid channel  12  (as shown in  FIGS. 2 and 3 ). In the present embodiment, the tool  4  has a semi-circular groove  51  for applying a pressure to the two dividing portions  101 ,  102 . When adequate pressure is applied the plastic deformation occurs in the two dividing portions  101 ,  102  thereby forming the vapor channel  11  and the liquid channel. 
         [0027]    In addition, the method of manufacturing the metal tube of the present invention includes step c), in which the dividing portions  101 , 102  are machined using a tool to form a connecting section  13  (as shown in  FIG. 4 ) at two ends of the tube  100 . In this step, the tool can be a lathe tool or a milling cutter. Two ends of the dividing portions  101 ,  102  are removed thereby forming connecting sections  13  at the two ends respectively. Furthermore, it is understood that the step c) can also be performed prior to the step b). 
         [0028]      FIG. 5  illustrates a cross sectional view of a heat pipe including the metal tube in the above described embodiment. During a process of making the heat pipe, firstly, an end of the metal tube  10  is sealed by welding, and then a rod is inserted into the vapor channel  11 . In sequence, the metal powder is poured into the tube  100  and distributed in lower ends of the vapor channel  11 , the liquid channel  12 , and the lower connecting section  13 . The metal powder in the tube  100  is sintered such that great deals of capillaries  20  are formed in the lower end of the metal tube  10 . The working fluid is filled in the tube  10  and air in the tube  10  is removed by heating the tube  10  thereby forming a vacuum chamber in the tube  10 . Finally, another end of the tube  10  is sealed by pressing and a heat pipe is thereby obtained. 
         [0029]      FIG. 6  is a schematic view illustrating a practical application of the heat pipe in  FIG. 5 . An end of the heat pipe is surrounded by a heat sink  6 , and another end of the heat pipe is attached to an electronic device  7 . Heat generated by the electronic device  7  gasifies the working fluid  30  thereby producing a mass of working fluid steam. The working fluid steam will move in the vapor channel  11  along a direction toward to the heat sink  6  due to a pressure difference between the two ends of the tube till the working fluid steam entering the connecting section. The heat sink  6  absorbs heat contained in the working fluid steam and dissipates the heat out to the ambient air. Thus, the working fluid steam is cooled back to the working liquid; the cooled working fluid moves in a front end of the liquid channel  12  and reaches to the capillaries  20  under effect of gravity or pressure difference, and then the cooled working fluid moves in the capillaries  20  under capillary force. Finally, the cooled working fluid comes back to the end of the tube attached to the electronic device  7  and a heat dissipation circle is completed. Generally, the working fluid  30  has a very high specific heat capacity; furthermore, the heat dissipation circle is performed efficiently, as a result, the heat generated by the electronic device  7  is quickly removed. 
         [0030]      FIG. 7  is a schematic view of a method of manufacturing a heat pipe according to another embodiment. In this embodiment, a step b‘) is used to replace the step b) in the method of above described embodiment. In step b′), referring to  FIG. 8 , a metal tube  20  is pressed using a pressing tool. The metal tube  20  includes a cylinder tube  200 . A first dividing portion  201  and a second dividing portion  202  extrude from an inner sidewall of the tube  200  erectly and extend to each other. The metal tube  20  is pressed such that end surfaces of the first dividing portion  201  and the second dividing portion  202  are adjoined to each other thereby forming a vapor channel  21  and a liquid channel  22  in the tube  200 . 
         [0031]    In addition, as described in step c) of the method in the first embodiment, the dividing portions  201 ,  202  can be processed using a tool to form a connecting section at two ends of the tube  200 . Furthermore, it is understood that this step can be performed prior to or after the step b′). 
         [0032]      FIG. 10  illustrates a metal tube  30  of the present invention in accordance with a third embodiment. The metal tube  30  includes a tube  300 , and a dividing portion  301  extruding from an inner sidewall of the tube  300  erectly. Referring to  FIG. 11 , an outer surface of the metal tube  30  is pressed such that an end surface of the dividing portion  301  reaches to the inner sidewall of the tube  300  thereby dividing an inner space of the tube  300  into a vapor channel  31  and a liquid channel  32 . It is understood that the vapor channel  31  and the liquid channel  32  are connected at two ends of the tube  300  (not shown). 
         [0033]    The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein, including configurations ways of the recessed portions and materials and/or designs of the attaching structures. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.