Abstract:
Disclosed is an inductor without a gap spacer. The inductor includes a bobbin having at least one round of wire wound thereon to serve as a coil of the inductor, a first magnetic member coupled with the bobbin, and a second magnetic member having a first end and a second end, wherein the second magnetic member is inserted into the bobbin from the second end thereof and the first end has a protrusion for allowing the second magnetic member to be partially inserted into the bobbin, thereby forming a gap between these two magnetic members.

Description:
FIELD OF THE INVENTION 
     The present invention is related to an inductor, and especially to an inductor without a gap spacer. 
     BACKGROUND OF THE INVENTION 
     As shown in FIGS. 1 a  and  1   b , a conventional inductor  10  includes a bobbin  20 , a U-shaped magnetic core member  30 , an I-shaped magnetic core member  50 , and a spacer  60 . Several rounds of wires are wound on the bobbin  20  to be employed as a coil of the inductor  10 . Because the magnetic core of the inductor  10  is constituted by the U-shaped magnetic core member  30  and the I-shaped magnetic core member  50 , this inductor  10  is commonly called a “UI inductor”. The U-shaped magnetic core member  30  has a concavity  35  on a side wall thereof. The U-shaped magnetic core member  30  is engaged with the bobbin  20  but the opening of the central hole of the bobbin  20  is exposed out of the concavity  35  of the U-shaped magnetic core member  30 . The spacer  60  is disposed between the adjacent magnetic core members  30 ,  50  to space the core members out of contact with each other, thereby reducing magnetic interference therebetween. The spacer  60  may be made of a non-magnetic material, such as plastic, aluminum or paint, which does not cause any magnetic interference between the two magnetic core members  30 ,  50  and the two magnetic core members  30 ,  50  may be fixed and held through the spacer  60  with a certain space therebetween. Typically, this spacer  60  is made of an insulating material and adhered to one end of the I-shaped magnetic core member  50 . The end of the I-shaped magnetic core member  50  with the spacer  60  is inserted into the central hole of the bobbin  20  through the concavity  35  for allowing the spacer  60  to be attached to the U-shaped magnetic core member  30  so as to assemble the inductor  10  as shown in FIG. 1 a . Briefly, the function of the spacer  60  is to form a gap between the I-shaped magnetic core member  50  and the U-shaped magnetic core member  30  so that the inductance of the inductor  10  can be changed by adjusting the spacer size. 
     However, when manufacturing such an inductor, there exists some problems as follows. 
     (1) When the I-shaped magnetic core member  50  is inserted into the hole of the bobbin  20 , the spacer  60  may be adhered to the inner wall of the central hole of the bobbin  20  due to its adhesive property. If the I-shaped magnetic core member  50  is forcedly inserted into the bobbin  20 , the spacer  60  may be deformed, thereby influencing the thickness of the spacer  60  and generating an error of the gap, so that the predetermined inductance can not be obtained. 
     (2) It is uneasy to precisely control the length of the I-shaped magnetic core member  50  inserted into the bobbin  20 . 
     (3) One end of the I-shaped magnetic core member  50  is attached to the U-shaped magnetic core member  30  only through the spacer  60 . When manufacturing the inductor, the gap may become larger because of the thermal expansion of the spacer so that the inductance of the inductor may be changed. 
     (4) If the gap is too large or the spacer  60  is too thick, the other end of the I-shaped magnetic core member  50  will be protruded over the edge of the bobbin  20 , or even over the pin  70  of the bobbin  20 , after inserting the I-shaped magnetic core member  50  into the central hole of the bobbin  20 . 
     (5) The size of the spacer  60  must be matched with that of the central hole of the bobbin  20 . If the size of the spacer  60  is too big, the I-shaped magnetic core member  50  can not be smoothly inserted into the central hole of the bobbin  20 . If the size of the spacer  60  is too small, the spaced area between the I-shaped magnetic core member  50  and the U-shaped magnetic core member  30  may be insufficient. 
     Therefore, it is desirable to develop an inductor without any above-described drawbacks and without needing a spacer to form a gap. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an inductor without a gap spacer. According to the present invention, the inductor includes a bobbin having at least one round of wire wound thereon to serve as a coil of the inductor, a first magnetic member coupled with the bobbin, and a second magnetic member having a first end and a second end, wherein the second magnetic member is inserted into the bobbin from its second end and the first end of the second magnetic member has a protrusion for allowing the second magnetic member to be partially inserted into the bobbin. 
     Preferably, the first magnetic member is a U-shaped type magnetic core member and the second magnetic member is an I-shaped type magnetic core member. The first and second magnetic members are made of one selected from a relatively soft magnetic material, Mn—Zn ferrite, Ni—Zn ferrite and a silicon steel plate, respectively, and employed as a magnetic core of the inductor. 
     Preferably, the protrusion of the second magnetic member has a recess formed on an upper surface thereof for allowing a tool to be inserted therein so as to grab the second magnetic member. The recess can be a hole. 
     Preferably, the second magnetic member is shortened in accordance with a thickness of a reference piece so as to form a gap between the second end of the second magnetic member and the first magnetic member. The height of the reference piece is greater than that of the side wall of the first magnetic member with the concavity. Certainly, the reference piece is removed before the inductor is assembled. 
    
    
     The present invention may best be understood through the following description with reference to the accompanying drawings, in which: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  is a perspective view of a conventional UI inductor; 
     FIG. 1 b  is an exploded view of the conventional UI inductor shown in FIG. 1 a;    
     FIG. 2 a  is a perspective view of a preferred embodiment of an inductor according to the present invention; 
     FIG. 2 b  is an exploded diagram showing the first method for manufacturing and assembling the inductor of the present invention; and 
     FIG. 2 c  is an exploded diagram showing the second method for manufacturing and assembling the inductor of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described more detailedly with reference to the following embodiments. It is to be noted that the following descriptions of the preferred embodiments of this invention are presented herein for the purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. 
     One preferred embodiment of the inductor of the present invention is shown in FIG. 2 a . Referring to FIGS. 2 a  and  2   b , the inductor  100  at least includes a bobbin  120 , a first magnetic member  130 , and a second magnetic member  150 . The bobbin  20  is wound by at least one round of wire which serves as a coil of the inductor  100 . The first magnetic member  130  is engaged with the bobbin  120 . The first magnetic member  130  has a concavity  135  on one side wall thereof for exposing the opening of the central hole of the bobbin  120 . The first magnetic member  130  and the second magnetic member  150  are employed as a magnetic core of the inductor  100 . The first and second magnetic members can be made of a soft magnetic material such as Mn—Zn ferrite, Ni—Zn ferrite or silicon steel plate. Preferably, the first and second magnetic members are crosssectionally U- and I-shaped magnetic core members, respectively. 
     The second magnetic member  150  has a first end and a second end. The first end of the second magnetic member  150  has a protrusion  155 , the height of which is high enough to prevent the second magnetic member  150  from being completely inserted into the bobbin  120 , that is, the protrusion  155  is stopped by the side wall of the first magnetic member with the concavity  135 . The second magnetic member  150  can be inserted into the bobbin  120  from the second end thereof through the concavity  135  of the first magnetic member  130 . 
     When adjusting the inductance of the inductor  100 , a reference piece  160  with a suitable thickness is disposed between the protrusion  155  of the second magnetic member  150  and the side wall of the first magnetic member  130  with the concavity  135  and closely attached to both of them so as to form a gap between the second end of the second magnetic member  150  and a side wall of the first magnetic member  130  opposed to that of the first magnetic member  130  with the concavity  135 . Thereafter, as a predetermined inductance is obtained, the thickness of the reference piece is measured. The second magnetic member  150  is shortened from the second end thereof according to the thickness of the reference piece  160  so as to form the gap after the shortened second magnetic member  150  is inserted into the bobbin  120 . The second magnetic member  150  can be shortened by any prior technique including but not limited to the polishing method. 
     It should be noted that the reference piece  160  is not the component of the inductor of the present invention but only used to measure the truncated length of the second magnetic member  150 . Therefore, it must be easily replaced and does not have the adhesive property. Its height must be greater than that of the side wall of the first magnetic member  130  with the concavity  135 . Its shape is not limited and any object with some degree of thickness can be adopted, for example, rectangle (as shown in FIG. 2 b ) or cylinder (as shown in FIG. 2 c ). 
     Due to the presence of the protrusion  155 , the shortened second magnetic member  150  is partially inserted into the bobbin  120 . After the shortened second magnetic member  150  is inserted into the bobbin  120 , the protrusion  155  will be stopped by the side wall of the first magnetic member  130  with the concavity  135 , thereby easily positioning the bobbin  120 , the first magnetic member  130 , and the second magnetic member  150 . In other words, the shortened second magnetic member  150  is pushed into the bobbin  120  until the protrusion  155  is stopped by the side wall of the first magnetic member  130  so as to precisely form the gap. Therefore, it is unnecessary to accurately calculate the length of the second magnetic member  150  inserted into the bobbin  120  like the prior art (or calculate the length of the second magnetic member  150  left out of the bobbin  120 ) or precisely fix the second magnetic member  150  relative to the first magnetic member  130 . If the measured or judged inductance of the inductor does not meet the requirement, the thickness of the reference piece  160  can be increased or decreased or the reference piece  160  is replaced by another one with a more suitable thickness so as to obtain a predetermined inductance value. 
     Specially, there is a recess  157  formed on the upper surface of the protrusion  155  for allowing a suitable tool to be inserted therein in order to grab the second magnetic member  150  as shown in FIGS. 2 a ˜ 2   c . The recess includes but is not limited to a hole  157  for inserting a needle therein. Therefore, the second magnetic member  150  of the inductor of the present invention can be grabbed by a clip with the needle, which is convenient for the manufacturing process. Certainly, the recess can also have other shapes such as cross, etc. 
     In conclusion, the design of the present invention can solve the problems encountered by the conventional inductor. First of all, because the inductor of the present invention does not need the gap spacer, some defects caused by the spacer can be eliminated, for instance, the problems caused by the adherence between the spacer and the inner wall of the central hole of the bobbin, the thermal expansion of the spacer, or the portion of the second magnetic member  150  protruded over the edge of the pin of the bobbin. In addition, because the second magnetic member  150  has a protrusion  155 , it is easy to control the length of the second magnetic member  150  inserted into the bobbin  120 . Furthermore, the reference piece  160  can be used repeatedly and its shape is not limited, thereby simplying the manufacturing process of the inductor. Moreover, the protrusion  155  has a recess for allowing users to insert a tool therein to grab the second magnetic member  150 . 
     While the invention has been described in terms of what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention need not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.