Manufacturing method of fin unit

Abstract

In a manufacturing method of a fin unit for a heat sink for dissipating a heat from a heat source, the fin unit includes a plurality of fins radially arranged about its center axis, and a fin supporting portion connecting inner ends of the fins and supporting the fins. First, metal is heated. The heated metal is extruded and/or drawn through a die to obtain a metal body. One of the die and the metal body obtained through the die is rotated relative to the other about a center axis of a die hole of the die. The metal body is then cut, thereby obtaining the fin unit.

1 . A manufacturing method of a fin unit for a heat sink for dissipating heat from a heat source, the fin unit including a plurality of fins arranged about a center axis and a fin supporting portion connecting radially inner ends of the fins, the manufacturing method comprising the steps of:
 a) heating a metal;   b) extruding and/or drawing the metal from a die having a die hole to obtain a metal body, the die hole being shaped to correspond to the fins and the fin supporting portion;   c) rotating at least one of the metal body and the die relative to the other about a center axis of the die hole;   d) cutting the metal body to obtain the fin unit; wherein   at least a portion of each of the steps b) and c) are carried out simultaneously.   
   
   
       2 . The manufacturing method according to  claim 1 , wherein in the step c), the metal body is connected to a supporting member and the die is fixed relative to the metal body, and the metal body is rotated about the center axis of the die hole relative to the die by rotating the supporting member about the center axis of the die hole. 
   
   
       3 . The manufacturing method according to  claim 2 , wherein the supporting member is rotated by a first servo motor. 
   
   
       4 . The manufacturing method according to  claim 3 , wherein the step of extruding and/or drawing the metal from the die is performed via a second servo motor. 
   
   
       5 . The manufacturing method according to  claim 4 , wherein the first servo motor and the second servo motor are controlled in synchronization with each other to control a rate at which the metal body is obtained from the die and a rotation speed of the supporting member in accordance with a distance between a leading end of the metal body and the die. 
   
   
       6 . The manufacturing method according to  claim 1 , wherein a rotation speed of the metal body is changed to change an inclination angle of a portion of the metal body which corresponds to an outer peripheral edge of each of the fins with respect to the center axis of the die. 
   
   
       7 . The manufacturing method according to  claim 1 , wherein the metal is aluminum or aluminum alloy. 
   
   
       8 . The manufacturing method according to  claim 1 , wherein the metal body extends continuously substantially parallel to the center axis of the die, and includes a plurality of fin units each of which has the fins and the fin supporting portion and which are arranged substantially parallel to the center axis of the die. 
   
   
       9 . The manufacturing method according to  claim 1 , further comprising the step of:
 e) finishing an inner peripheral surface of the fin supporting portion which is hollow and obtained in step c).   
   
   
       10 . The manufacturing method according to  claim 1 , further comprising the step of:
 f) performing a heat treatment on the metal body or the fin unit.   
   
   
       11 . A fin unit manufactured by the manufacturing method according to  claim 1 . 
   
   
       12 . The fin unit according to  claim 11 , wherein each of the fins includes an inner portion connected to an outer peripheral surface of the fin supporting portion, and a plurality of outer portions extending radially outward from a radially outer end of the inner portion;
 the inner portion is defined by a single thin plate-shaped member, and each of the outer portions is defined by a single thin plate-shaped member; and   the outer portions overlap each other in a circumferential direction of the fin unit.   
   
   
       13 . The fin unit according to  claim 11 , wherein each of the fins extends radially outward from the fin supporting portion and are curved in a clockwise or counterclockwise direction when viewed along the center axis. 
   
   
       14 . A cooling device for cooling a heat source by dissipating heat transferred from the heat source, comprising:
 a heat sink including the fin unit according to  claim 11 ; and   a fan arranged on one axial side of the fin unit; wherein   the fan is arranged to deliver air to the heat sink.   
   
   
       15 . The cooling device according to  claim 14 , wherein a fan-side portion of each of the fins of the fin unit is inclined with respect to the center axis of the fin unit so as to be approximately parallel to an airflow from the fan. 
   
   
       16 . The cooling device according to  claim 14 , wherein an outer peripheral edge of a fan-side portion of each of the fins is inclined with respect to the center axis of the fin unit at an angle in a range from approximately 10 degrees to approximately 50 degrees.