In inductance coils and transformers, magnetic cores according to an E core configuration or an E-I core configuration or a double-E core configuration are often used. The center leg of these magnetic cores has normally arranged thereon at least one winding. When a magnetic core according to an E-I core configuration is manufactured, an E core is combined with an I core. When a magnetic core according to a double-E core configuration is manufactured, two individual E cores are normally joined by gluing. Alternatively, frame cores are used together with I cores, the I core being then inserted as a center leg into the frame core and joined to two opposed sides of the frame core by gluing.
In the case of E cores, air gaps can be adjusted in grinding processes with very small manufacturing tolerances for the purpose of avoiding saturation influences, so that the AL value of a magnetic core can be adjusted by precise grinding. It is true that the winding process of these magnetic cores is not very complicated, since the coil to be wound has no core and is coupled to the core only during the assembly process, but joining two E core halves in a separate gluing process is highly disadvantageous. The disadvantage resides, on the one hand, in that the glued joint leads to a significant weak point in the finished component and, on the other hand, in that the gluing process represents a considerable cost and time factor in the production process. In addition, the two E core halves are separately molded in a molding press in the production process and are then removed from the moldings press. Subsequently, the two E core halves are sintered individually in two separate sintering processes. All this results in complicated handling for conventional production processes. Furthermore, due to the inevitable manufacturing tolerances occurring during sintering, it can no longer be guaranteed for two individually sintered core parts that the core formed by combining the two core parts is produced with the desired accuracy and, in particular, that the outer legs of two E core halves are arranged in plane-parallel opposed relationship with one another.
In addition, the manufacturing tolerances occurring in the sintered core halves result in a displacement at the transition from one core half to the next, when two E core halves that have been produced in this way are assembled. The resultant locations of displacement in the finished core represent for the magnetic field lines in the finished inductive component a constriction of the magnetically effective core cross-section. At said constriction, premature saturation of the core occurs and leads to a decrease in inductance. Furthermore, the field lines exit the ferrite area at saturation regions and saturation gaps during operation in the finished inductive component, so that additional losses will occur in the winding.
The frame core admittedly has the advantage that the core is produced from one piece and does therefore not necessitate any subsequent gluing process, a circumstance which leads to a significantly increased mechanical stability in comparison with glued core configurations and which, due to the non-existing gluing process, also leads to a simple production process, but it is here much more difficult to efficiently form air gaps in a frame core. For this reason, frame cores are excluded from many power applications.
Reference DE 10 2004 008 961 B1 describes a frame core with a center leg glued into said frame core.
Document DE 1 193 119 describes a framelike core component with a tuning pin inserted in a semi-cylindrical recess of the framelike core component.
Reference EP 004272 A2 discloses a method of manufacturing magnetic cores from molding material with soft-magnetic properties by molding a mixture of soft-magnetic material and a synthetic resin as a binder, a mixture of iron powder being here mixed with a thermosetting resin in liquid form and filled into a heated mold and then molded.
Reference DE 3909624 A1 describes an E-I core with an air gap, the air gap being formed in the I part of the core by means of molding.
Reference DE 2305958 A discloses a bipartite magnetic core with a sheared hysteresis loop, said magnetic core being sheared in an air gap-free manner by a solid non-magnetic or low-permeable body and the parts of the magnetic core being firmly interconnected, partially as directly as possible and partially via the body with a sheared hysteresis loop.
USPTO Backgrounds
USPTO Backgrounds