Abstract:
An inductor has a case having an opening, a core accommodated in the case, a coil wound on a part of the core and a fixing member fixed to the case. The fixing member fixes the core by contacting a top surface of the core facing the opening and elastically biasing the core toward a bottom surface of the case. The fixing member further includes a first plate portion and a first contacting portion. The first plate portion is disposed between the top surface of the core and the opening of the case and extending in parallel with the top surface of the core. The first contacting portion extends from a fore-end portion of the first plate portion so as to be U-shaped and having a distal end portion elastically push-contacting the top surface of the core.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §119 from Japanese Patent Application No. 2008-273102 filed on Oct. 23, 2008. The entire subject matter of the application is incorporated herein by reference. 
     BACKGROUND 
     1.Technical Field 
     Aspects of the present invention relate to an inductor formed such that a core on which a coil is wound is accommodated in a case. 
     2.Related Art 
     Conventionally, an inductor is used as a reactor in an electric circuit. An example of such an inductor (reactor) is disclosed in International Publication No. WO 2007/108201 (hereinafter, referred to as &#39;201 publication). 
       FIG. 7  is a perspective view showing a configuration of a conventional reactor disclosed in &#39;201 publication. The reactor  101  is configured such that a core  120 , which is O-shaped when viewed from directly above, and a pair of coils  130 , which are wound around the core  120 , are accommodated in a case  110 . 
     A fixing member  140  is used to retain the core  120  in the case  110 .  FIG. 8  is a perspective view showing the fixing member  140  of the conventional reactor. As shown in  FIG. 8 , the fixing member  140  is made by bending a metal plate (e.g., a stainless-steel plate) into an L-shape at a corner portion  143 . In addition, an opening  145  is formed at a position in the vicinity of one of corners (upper left corner in  FIG. 8 ) of an upper plate  141 , which extends from the corner portion  143  in an horizontal direction, in order to fix the fixing member  140  to the case  110  with a bolt  152  inserted through the opening  145  ( FIG. 7 ). 
     A side plate  142 , which extends from the corner portion  143  in an vertical direction, is bended into a U-shape in the middle thereof. The second portion  142  is inserted into a space between an inner surface of a side wall  111 , which is one of side walls of the case  110 , and the core  120 . Thus, the side plate  142  biases the core  120  toward a side wall (not shown in  FIG. 7 ) opposed to the side wall  111 . 
     Furthermore, a slit  144  is formed in the middle of the upper plate  141  of the fixing member  140  ( FIG. 8 ) to divide the upper plate  141  into two parts. One part has the opening  145  as described above, and the other part of which a fore-end portion is bent downwardly and a leaf spring  141   a  is formed. In a state where the fixing member  140  is fixed to the case  110 , a fore-end of the leaf spring  141   a  elastically push-contacts a top surface of the core  120  and biases the core  120  toward a bottom surface of the case  110 . 
     As described above, the fixing member  140  retains the core  120  in case  110  by biasing the core  120  toward the side wall and the bottom surface of case  110 . 
     However, in the conventional reactor  101 , since the core  120  is biased toward the bottom surface of the case  110  with an elasticity produced by the leaf spring  141   a  itself, a stress concentration is likely to occur on the upper plate  141  of the fixing member  140 , in particular, at the end of the slit  144 . Therefore, there remain problems that the fixing member  140  may be broken by an excessive stress given to the upper plate  141  due to a big impact load. 
     SUMMARY 
     In consideration of the above problems, aspects of the invention provide an improved inductor of which a fixing member is irrefrangible even though an impact load is given to the inductor. 
     According to aspects of the present invention, there is provided an inductor including a case having an opening, a core accommodated in the case, a coil wound on a part of the core and a fixing member fixed to the case. The fixing member fixes the core by contacting a top surface of the core facing the opening and elastically biasing the core toward a bottom surface of the case. The fixing member further includes a first plate portion and a first contacting portion. The first plate portion is disposed between the top surface of the core and the opening of the case and extending in parallel with the top surface of the core. The first contacting portion extends from a fore-end portion of the first plate portion so as to be U-shaped and having a distal end portion elastically push-contacting the top surface of the core. 
    
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         FIG. 1  is a perspective view showing a reactor according to an embodiment of the present invention. 
         FIG. 2  is a cross-sectional side view showing the reactor according to the embodiment of the present invention. 
         FIG. 3  is a perspective view showing a fixing member  40  used in the reactor from an anterior view of the  FIG. 1 . 
         FIG. 4  is a perspective view showing the fixing member  40  used in the reactor from a posterior view of the  FIG. 1 . 
         FIG. 5  is a cross-sectional side view showing configurations around the fixing member  40  used in the reactor according to the embodiment of the present invention. 
         FIG. 6  schematically shows a behavior of the fixing member  40  when an external load is given to the reactor according to the embodiment of the present invention. 
         FIG. 7  is a perspective view showing a configuration of a conventional reactor. 
         FIG. 8  is a perspective view showing a fixing member  140  of the conventional reactor. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment according to aspects of the present invention will be described with reference to the accompany drawings. 
       FIG. 1  is a perspective view showing a reactor according to an embodiment of the present invention.  FIG. 2  is a cross-sectional side view showing the reactor according to the embodiment of the present invention. A reactor  1 , in an exemplary embodiment, is configured such that an approximately O-shaped core  20 , which is O-shaped when viewed from directly above, and a pair of coils  31  and  32 , which are wound around the core  20 , are accommodated in a case  10 , which is a box-shaped container, having an opening O on one of faces of the case  10 . A first end  31   a  of the coil  31  and a first end  32   a  of the coil  32  are connected together and configure a serially-cascaded circuit as a whole. A second end portion  31   b  of the coil  31  and a second end portion  32   b  of the coil  32  respectively protrude outside the case  10  through the opening O. The reactor  1  is installed into an electric circuit by connecting the second end portions  31   b  and  32   b  to the electric circuit. A coil body  31   c  of the coil  31  and a coil body  32   c  of the coil  32  are accommodated in the case  10  without protruding except for the second end portions  31   b  and  32   b.    
     Note that, in the following description, a horizontal direction and a vertical direction are defined according to an arrangement shown in  FIG. 2 , and an upper side of  FIG. 2  is defined as a top side of the reactor  1 , a right side of  FIG. 2  is defined as a right side of the reactor  1 . In addition, a virtual plane on the opening O is defined as a top plane. 
     In the exemplary embodiment, a fixing member  40  is used to fix the core  20 , the coils  31  and  32  to the case  10 . The fixing member  40  is formed by bending a metal plate such as stainless-steel plate into an L-shape at a first corner portion  43 . In addition, a fore-end portion  41   a  of an upper plate  41 , which extends from the first corner portion  43  in a horizontal direction, is downwardly bent into a U-shape so as to define a leaf spring. An incision  47  is formed on an area straddling the upper plate  41  and the fore-end portion  41   a  to adjust a spring force of the leaf spring. A fore-end portion  42   a  of a side plate  42 , which extends from the first corner portion  43  in a vertical direction, is upwardly bent into a U-shape so as to define a leaf spring. The fixing member  40  is fixed to the case  10  with volts  52  and the side plate  42  is inserted into a space, which is relatively narrower than a thickness of the leaf spring formed by the side plate  42 , between a right side wall  11  of the case  10  and the core  20 . Thus, the side plate  42  bent into a U-shape is compressed in the space between the right side wall  11  of the case  10  and the core  20 , and the fore-end portion  42   a  biases the core  20  toward a left side wall opposed to the right side wall  11 . 
     The upper plate  41  of the fixing member  40  is arranged above the core  20 , and the fore-end portion  41   a  bent downwardly elastically push-contacts a top surface of the core  20 . Thus, when the fixing member  40  is fixed to the case  10 , the top surface of the core  20  is pressed thereon with the fore-end portion  41   a  of the fixing member  40 . At this time, a base portion  41   b  of the fixing member  40 , the fore-end portion  41   a  of the fixing member  40  and the first corner portion  43  are upwardly deformed around a fulcrum point at which the fixing member  40  contacts with the right side wall  11 . Thus, the core  20  is biased by a repulsion force of such deformations. The bottom surface  13  of the case  10  is provided with bumps  14   a  and  14   b  to support a bottom surface of the core  20 , and the core  20  is pressed onto the bumps  14   a  and  14   b  because the fore-end portion  41   a  biases the core  20  toward the bumps  14   a  and  14   b.    
     Thus, the core  20  is fixed to/retained in the case  10  so as not to move because the core  20  is biased into an inner surface  12  of the left side wall  12  and the bumps  14   a  and  14   b    
     Hereinafter, the details of the fixing member  40  are described.  FIG. 3  is a perspective view showing the fixing member  40  from an anterior view of the  FIG. 1 , and  FIG. 4  is a perspective view showing the fixing member  40  from a posterior view of the  FIG. 1 . 
     As shown in  FIG. 4 , the fixing member  40  is provided with a pair of slits  44  which extend from both sides of the upper plate  41  to positions in the middle of the side plate  42 . Namely, the upper plate  41  corresponds to a portion extended from a part of the side plate  42  between the slits  44 . Fixing arms  45  for fixing the fixing member  40  to the case  10  ( FIG. 1 ) with the bolts  52  are formed outside of both of the slits  44 , i.e., the fixing arms  45  extends from a lower part of the side plate  42 . In addition, each fixing arm  45  is formed by bending a portion outside of the slit  44  perpendicular to the side plate  42  at a second corner portion  46  which is lower than the first corner portion  43 . Through-holes  45   a  are formed respectively at a fore-end portion of both of fixing arms  45 , and the fixing member  40  is fixed to the case  10  by the bolts  52  through the through-holes  45   a.    
       FIG. 5  is a cross-sectional side view showing configurations around the fixing member  40  at a state where the core  20 , the coil  31 , the coil  32 , and the fixing member  40  fixed to the case  10  with the bolts  52  are accommodated in the case  10 . In the exemplary embodiment, the fixing member  40  is inserted to a space between the right wall  11  and the core  20  and contacts with the right side wall  11  at a fulcrum point X which is located around the first corner portion  43  on the side plate  42 . Note that, as shown in  FIG. 4 , the slits  44  extend to the positions, which are lower than the fulcrum point X, in the middle of the side plate  42 . 
     In such a case, when an impact load is given to the reactor  1 , a major load is upwardly given to the fore-end portion  41   a  of the upper plate  41 . A behavior of the fixing member  40  in such a case is described below.  FIG. 6  is a cross-sectional side view showing a configuration around the fixing member  40  and also illustrating (1) a state where an external load from outside of the reactor  1  is not given to the fore-end portion  41   a  in solid line, and (2) a state where an external load from outside of the reactor  1  is given to the fore-end portion  41   a  in dashed line. 
     As shown in  FIG. 6 , when an upward load is given to the fore-end portion  41   a , the fore-end portion  41   a  and a flection portion B are deformed because the fore-end portion  41   a  is bent in a direction toward the base portion  41   b  (deformation α), and then the base portion  41   b  warps upwardly and the first corner portion  43  deformed because the fore-end portion  41   a  and a flection portion B are deformed (deformation β), and the first corner portion  43  warps upwardly (deformation γ). As described above, in the exemplary embodiment, when an upward load is given to the fore-end portion  41   a , three kinds of deformations α, β, and γ are caused. Therefore, a deformation volume of each of deformations α, β, and γ is kept low. In other words, in the fixing member  40  according to the exemplary embodiment, the fore-end portion  41   a  (deformation α), the flection portion B (deformation α), the base portion  41   b  (deformation β) and the first corner portion  43  (deformation β and γ) respectively function as leaf springs against a load externally given to the fore-end portion  41   a  upwardly. Thus, a stress concentration to the fixing member  40  is absorbed, and the fixing member  40  becomes to be irrefrangible even if an impact load is given to the reactor  1 . 
     In general, the stress concentration is incident on the end of a cutout portion such as slit end, but the slits  44  according to the exemplary embodiment exceed the fulcrum point X and extend to positions in the middle of the side plate  42 . Since an impact load is supported to the case  10 , i.e., at the fulcrum X, the impact load is scarcely given to a portion which is lower than the fulcrum point X. Therefore, an excessive stress concentration is not caused at the ends of the slits  44 . 
     As described above, the coil body  31   c  and the coil body  32   c  are accommodated in the case  10  without protruding. Therefore, a space P is secured between the case  15  and the top surface  21  of the core  20 . As shown in  FIG. 5 , when the fixing member  40  is fixed to the case  10 , a spacing d 1  from the top surface of the core  20  to a top end of the upper plate  40  and a spacing d 2  from the top surface of the core  20  to a top end  15  of the case  10  are almost the same. In other words, in the exemplary embodiment, a spacing from the top surface of the core to a top surface of the coil body  31   c  and  32   c  is approximately equal to a spacing from the fore-end portion  41   a  to the base portion  41   b . Thus, when the fixing member  40  is fixed to the case  10 , the upper plate  41  of the fixing member  40  is accommodated in the space P without protruding the top end of the fixing member  40  from the case  10 . In other words, the reactor  1  according to the exemplary embodiment allows the fixing member, which is superior in an impact resistance, to be used without making the case  10  larger by using the space P effectively.