Patent Publication Number: US-6990840-B2

Title: Conjoining apparatus using electromagnetic forming

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority of Korean Application No. 10-2003-0079034, filed on Nov. 10, 2003. 
   FIELD OF THE INVENTION 
   Generally, the present invention relates to a conjoining apparatus using electromagnetic forming. More particularly, the present invention relates to a conjoining apparatus using electromagnetic forming wherein an auxiliary ring of aluminum or copper material is inserted between a field shaper and a working object to conjoin a working object that does not easily form an induced magnetic field. 
   BACKGROUND OF THE INVENTION 
   In connection with weight reduction of a vehicle, the use of aluminum material has become more prevalent, and accordingly, research has been undertaken regarding how to conjoin steel and aluminum materials. The two materials are difficult to conjoin together because of their material differences, and therefore a vehicle body is usually formed entirely of steel or of aluminum. To overcome this problem, generally by conjoining different materials such as steel and aluminum, electromagnetic forming has been proposed. 
   However, prior art conjoining schemes for steel and aluminum using electromagnetic forming of steel have only been applicable to the case in which an aluminum member is disposed exterior to a steel member. This is because a sufficient induced magnetic field is formed only at the aluminum. That is, the steel does not form a sufficient induced magnetic field, so the aluminum should be disposed exterior to the steel or the capability of a conjoining apparatus must be very high in order to enable conjoining of an exteriorly disposed steel member therewith. 
   The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art. 
   SUMMARY OF THE INVENTION 
   An exemplary conjoining apparatus using electromagnetic forming according to an embodiment of the present invention includes: a field shaper for concentrating a magnetic field to a conjoining working object; a coil for generating and applying the magnetic field to the field shaper such that the field shaper can form a reactive force; a charging circuit for supplying electricity to the coil; and an auxiliary ring disposed between the field shaper and the working object, for generating an induced magnetic field, the auxiliary ring having a conductivity greater than steel. 
   In a further embodiment, a pair of grooves are formed on an interior side of the auxiliary ring. 
   Embodiments of the present invention thus provide a conjoining apparatus using electromagnetic forming having non-limiting advantages of easy conjoining of work pieces by inserting an auxiliary ring of aluminum or copper material between a field shaper and the working object to conjoin the working object when it does not easily form an induced magnetic field. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, serve to explain the principles of the invention: 
       FIG. 1  is a perspective view of a conjoining apparatus using electromagnetic forming according to a preferred embodiment of the present invention; 
       FIG. 2  is a sectional view of  FIG. 1  along a line IV—IV; 
       FIG. 3  is an exploded view of  FIG. 1 ; and 
       FIGS. 4–6  illustrate an electromagnetic forming process by use of an auxiliary ring according to an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
   The present invention is not limited to an embodiment described hereinafter, and may be realized in a variety of fashions. The present embodiment is only provided to fully describe the present invention and to fully convey the scope of the present invention to a person of ordinary skill in the art. 
   As shown in  FIGS. 1–6 , a conjoining apparatus  100  using electromagnetic forming according to an embodiment of the present invention is provided with a field shaper  10  for concentrating a magnetic field to a conjoining working object, a coil  20  for generating and applying the magnetic field to the field shaper  10  such that the field shaper  10  can form a reactive force, and a charging circuit  30  for supplying electricity to the coil  20 . An auxiliary ring  40  is disposed between the field shaper  10  and the working object  11 , for generating an induced magnetic field therebetween. The auxiliary ring  40  has conductivity greater than steel. 
   The field shaper  10  has a flange portion  13  projecting to the working object  11 , and the magnetic field is concentrated at the flange portion  13  such that the forming load is strengthened. The coil  20  is wound at an exterior of the field shaper  10 . 
   The coil  20  generates an instantaneous magnetic field and causes the field shaper  10  to apply a high pressure to the auxiliary ring  40  through the flange portion  13 . The coil  20  is connected to the charging circuit  30  such that the coil  20  receives electricity therefrom. The charging circuit  30 , having been charged with electric energy, instantaneously supplies the charged electricity to the coil  20  such that a great induced magnetic field is thereby generated. 
   The auxiliary ring  40  is a member inserted between the conjoining working object  11  and the field shaper  10 . The auxiliary ring  40  is made of a material that has higher conductivity than steel, such as aluminum or copper. As shown in  FIG. 6 , the auxiliary ring  40  has a pair of grooves  41  on an interior side thereof. The grooves  41  enable easy detachment of the auxiliary ring  40  from the working object  11  after conjoining, since a crack is formed at the grooves  41  by a pressure load on the auxiliary ring  40  during the conjoining. 
   An operation of the auxiliary ring  40  is as follows. When the working object  11  is made of a material having low conductivity such as steel, it is difficult to form a strong induced magnetic field therein. Therefore, it is difficult to apply a sufficient reactive force to the working object  11  by the field shaper  10 . In this case, the auxiliary ring  40  made of aluminum or copper that has high conductivity may form a strong induced magnetic field therein and accordingly receive a strong reactive force from the field shaper  10  through its projected portion  13  such that the auxiliary ring  40  deforms to in turn apply the reactive force to the working object  11 . 
   That is, in the case that a steel member  15  is to be conjoined exterior to an aluminum member  17 , an induced magnetic field cannot be easily formed at the steel member  15 , so the field shaper  10  cannot apply a strong reactive force to the steel member  15 . Therefore, in this case, an auxiliary ring  40  made of aluminum or copper having high conductivity is disposed exterior to the work piece  11  such that it may form a strong induced magnetic field, and accordingly form a reactive force by an interaction with the field shaper  10 . 
   Such an operation of the auxiliary ring  40  is explained in further detail with reference to  FIGS. 4–6 . 
   Firstly, as shown in  FIG. 4 , the auxiliary ring  40  is inserted exterior to the working object  11 , which includes the steel member  15  and aluminum member  17 . 
   Subsequently as shown in  FIG. 5 , the auxiliary ring  40  receives a radial compression pressure  43  by an electromagnetic interaction with the field shaper  10  and the coil  20 . Then, the auxiliary ring  40  subsides onto conjoining indentations  45  formed at either of the members  15  and  17  of the working object  11 . 
   Subsequently as shown in  FIG. 6 , cracks are formed along the grooves  41  by the compression pressure  43 , and the auxiliary ring  40  becomes easily detached from the conjoined working object by dividing it at the cracks. 
   As shown above, a conjoining apparatus using electromagnetic forming according to an embodiment of the present invention has the following effects. 
   A working object including steel that does not form a strong induced magnetic field may be easily electromagnetically formed by using an auxiliary ring, and the auxiliary ring may be easily detached from the conjoined working object. Therefore, in comparison with welding, this electromagnetic forming is sufficient for conjoining the working object and simplifies a process thereof. 
   While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.