Abstract:
A coil assembly having a simplified bobbin structure and facilitating connection of a draw-out portion of a wire to a pin terminal. A coil assembly includes first and second pin support portions protruding in a protruding direction from a terminal base. First and second pin terminals protrude in the protruding direction from free end faces of the first and second pin support portions, respectively. The draw-out portion is electrically connected to an associated one of the pin terminals. The second pin support portion provides a protruding length from the terminal base greater than that of the first pin support portion, and the free end face of the second pin support portion is positioned downstream, in the protruding direction, of an imaginary linear draw-out portion directed linearly from the wire engaging portion to the first pin terminal, such that the second pin support portion is positioned and sized to intersect with the imaginary linear draw-out portion.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2010-50361 filed Mar. 8, 2010. The entire content of the priority application is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a coil assembly, and more particularly, to a type thereof including a bobbin having a terminal base, a plurality of terminal electrodes provided at the terminal base, and a plurality of coils wound over the bobbin and each having one end portion and another end portion electrically connected to associated terminal electrodes. 
     BACKGROUND 
     A coil assembly such as a transformer includes a bobbin and coils or conductive wires wound over the bobbin. The bobbin has generally cylindrical shape, and a plurality of wires each coated with an electrically insulation layer are wound over an outer peripheral surface of the bobbin. Each wire has a winding portion wound over the bobbin and draw-out portions at each end portion of the wire. 
     Japanese Patent Application Publication No. H08-111323 discloses a coil assembly in which a terminal base is provided at one axially end portion of a cylindrical portion. The terminal base is provided with a plurality of pin terminals protruding in a direction perpendicular to a circuit board when the coil assembly is surface-mounted on the board. The terminal base is provided with an engaging portion protruding outward so as to engage the draw-out portion of the wire and to direct the draw-out portion toward the pin terminal. Each end portion of the wire is wound over the pin terminal and is electrically connected thereto. 
     SUMMARY 
     In such conventional structure, the draw-out portion of the wire is drawn out of the winding portion and is engaged with the engaging portion, and is then drawn to the pin terminal. Therefore, cumbersome production of the coil assembly is required such as engaging the draw-out portion with the engaging portion and winding the draw-out portion over the pin terminal. Further, complicated bobbin structure results. 
     It is therefore, an object of the present invention to provide a coil assembly having a simplified bobbin structure and capable of facilitating the drawing out work of the draw-out portion toward the pin terminal. 
     This and other object of the present invention will be attained by a coil assembly to be mounted on a circuit board including a bobbin, at least one electrically conductive wire, first and second pin support portions, and first and second pin terminals. The bobbin is made from an electrically insulating material and includes a wound portion having an end portion, a wire engaging portion, and a terminal base positioned at the end portion. The at least one electrically conductive wire has an electrically insulation coating and includes a winding portion wound over the wound portion and draw-out portions each drawn out from the winding portion and engaged with the wire engaging portion. The first pin support portion and the second pin support portion protrude in a protruding direction from the terminal base. The first pin terminal protrudes in the protruding direction from a free end face of a first pin support portion and is supported thereto. The second pin terminal protrudes in the protruding direction from a free end face of the second pin support portion and is supported thereto. The draw-out portion is electrically connected to associated one of the pin terminals. The pin terminals are configured to extend through the circuit board in the protruding direction which is substantially perpendicular to a surface of the circuit board. The second pin support portion provides a protruding length from the terminal base greater than that of the first pin support portion, and the free end face of the second pin support portion is positioned downstream, in the protruding direction, of an imaginary linear draw-out portion directed linearly from the wire engaging portion to the first pin terminal, such that the second pin support portion is positioned and sized to intersect with the imaginary linear draw-out portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a perspective view of a coil assembly according to one embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of the coil assembly according to the embodiment; 
         FIG. 3  is a bottom view of the coil assembly according to the embodiment; 
         FIG. 4  is a front elevational view of the coil assembly according to the embodiment. 
         FIG. 5  is a front elevational view of a coil assembly according to a first modification to the embodiment; and 
         FIG. 6  is a front elevational view of a coil assembly according to a second modification to the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A coil assembly according to a first embodiment of the present invention will be described with reference to  FIGS. 1 through 4 . The coil assembly in this embodiment is a transformer including a core  10 , a bobbin  20 , and a conductive wire  50 . Throughout the description, a direction from an upper right portion to a lower left portion in  FIG. 1  will be referred to as “+X direction”, a direction opposite to the +X direction will be referred to as “−X direction”, a direction from a lower right portion to an upper left portion will be referred to as “+Y direction”, a direction opposite to the +Y direction will be referred to as “−Y direction”, a direction from the lower portion to the upper portion will be referred to as “+Z direction”, and a direction opposite to the +Z direction will be referred to as “−Z direction”. 
     As shown in  FIG. 2 , a pair of the cores  10  having a shape identical to each other are provided. Each core  10  is E-shaped and includes a bottom plate portion  10 A, a pair of side plate portions  10 B each extending from each end portion of the bottom plate portion  10 A, and a central stem portion  10 C extending from a longitudinally center portion of the bottom plate portion  10 A. Free end faces of the side plate portions  10 B of one of the cores  10  are in contact with free end faces of the side plate portions  10 B of the remaining one of the cores  10 , whereas a free end face of the central stem portion  10 C of one of the cores  10  is spaced apart by a predetermined distance from a free end face of the central stem portion  10 C of the remaining one of the cores  10 . 
     As shown in  FIG. 2 , the bobbin  20  has a sleeve portion  21  having a generally cylindrical shape and made from an electrically insulating resin. The sleeve portion  21  has a generally circular cross-section taken along a plane extending perpendicular to the X direction. The sleeve portion  21  has a cylindrical hollow space into which the central stem portions  10 C of the cores  10  are inserted. The sleeve portion  21  has an axial length of about 18 mm. The sleeve portion  21  corresponds to a wound portion. 
     A terminal base  31  is provided at one axial end of the sleeve portion  21 , and another terminal base  32  is provided at another axial end of the sleeve portion  21 . The terminal bases  31 ,  32  are made from an electrically insulation resin the same as that of the sleeve portion  21 , and are provided integrally with the sleeve portion  21 . Each terminal base  31 ,  32  extends in a direction parallel to the Y direction. 
     As shown in  FIG. 3 , the terminal base  31  has a bottom surface  31 Z provided with pin support portions  31 A,  31 B,  31 C,  31 D,  31 E,  31 F, terminal electrodes  31 G,  31 H,  31 I,  31 J,  31 K,  31 L, wire following wall portions  31 M,  31 N, and wire following rectangular protrusions  31 O,  31 P,  31 Q,  31 R,  31 S. Similarly, the terminal base  32  has a bottom surface  32 Z provided with pin support portion  32 A,  32 B,  32 C,  32 D,  32 E,  32 F, terminal electrodes  32 G,  321 J,  32 I,  32 J,  32 K,  32 L, wire following wall portions  32 M,  32 N, and wire following rectangular protrusions  32 O,  32 P,  32 Q,  32 R,  32 S. 
     The wire following wall portions  31 M,  31 N are positioned at extreme −X end position of the bottom surface  31 Z, and positioned at each end portion of the bottom surface  31 Z in the Y direction. The wire following wall portions  31 M,  31 N are plate shaped extending in Y direction and protruding in −Z direction. A base end portion of each wire following wall portion  31 M,  31 N is provided with a slope portion  31 T,  31 U each having a first region extending in +X direction and a second region extending in Y direction. The slope portions  31 T,  31 U correspond to engaging portions. 
     Similarly, the wire following wall portions  32 M,  32 N are positioned at extreme +X end position of the bottom surface  32 Z, and positioned at each end portion of the bottom surface  32 Z in the Y direction. The wire following wall portions  32 M,  32 N are plate shaped extending in Y direction and protruding in −Z direction. A base end portion of each wire following wall portion  32 M,  32 N is provided with a slope portion  32 T,  32 U each having a first region extending in +X direction and a second region extending in Y direction. The slope portions  32 T,  32 U correspond to engaging portions. 
     The wire following rectangular protrusions  31 O through  31 S are positioned between the wire following wall portions  31 M and  31 N and arrayed in Y direction. Neighboring wire following rectangular protrusions are spaced away from each other by a constant predetermined interval. Further, the wire following wall portion  31  is spaced away from the neighboring rectangular protrusion  31 O by the predetermined interval, and wire following wall portion  31 N is spaced away from the neighboring rectangular protrusion  31 S by the predetermined interval. The wire following rectangular protrusions  31 O through  31 S have quadrangular prism shape and extend in −Z direction. These wire following rectangular protrusions  31 O through  31 S correspond to the engaging portions. The same is true with respect to wire following rectangular protrusions  32 O,  32 P,  32 Q,  32 R,  32 S, and geometrical relationship to wire following wall portions  32 M,  32 N. 
     The pin support portions  31 A through  31 F are provided at extreme +X end portion of the bottom surface  31 Z, and are arrayed in Y direction with a constant interval. Each pin support portion has a cylindrical shape and extends in −Z direction from the bottom surface  31 Z. Each free end portion of each pin support portion is roundish shaped. The pin support portions  32 A through  32 F are provided at extreme −X end portion of the bottom surface  32 Z, and have geometrical relationship and configuration the same as those of the pin support portions  31 A through  31 F. 
     As shown in  FIG. 4 , the pin support portions  31 A,  31 , provided at extreme end portions in the Y direction provide a protruding length from the bottom surface  31 Z smaller than that of the pin support portions  31 B,  31 C,  31 D,  31 E. Further the protruding length of the pin support portions  31 A and  31 F is equal to each other, and protruding length of the pin support portions  31 B,  31 C,  31 D,  31 E is equal to one another. The same is true with respect to the protruding length from the bottom surface  32 Z regarding the pin support portions  32 A through  32 F. 
     As shown in  FIG. 4 , the pin support portion  31 B,  31 E next to the pin support portion  31 A,  31 L provide the protruding length such that an imaginary linear draw-out portion  50 A′ drawn from the slope portions  31 T,  31 U to peripheral surfaces of pin terminals  31 G,  31 L (described later) for winding over the pin terminals  31 G,  31 L can be positioned to overlap with the pin support portion  31 B,  31 E in the Z direction. In other words, a lower end face of the pin support portion  31 B,  31 E is positioned at −Z side with respect to the imaginary linear draw-out portion  50 A′, i.e., the lower end face of the pin support portion  31 B,  31 E is positioned downstream of the imaginary linear draw-out portion  50 ′ in the −Z direction. Stated differently, the imaginary linear draw-out portion  50 A′ is intersected with or crossed with the peripheral surface of the pin support portion  31 B,  31 E as shown in  FIG. 3 . The protruding length of the pin support portion  31 A,  31 F is about 1 mm smaller than that of the pin support portions  31 B,  31 ,  31 D,  31 E. 
     The same is true with respect to the pin support portions  32 A through  32 F, the sloped portions  32 T,  32 U, and the imaginary linear draw-out portion  50 A′. In  FIG. 4 , the imaginary draw-out portion  50 A′ is coincident with an actual draw-out portion  50 A in the front elevational view. 
     Terminal electrodes  31 G,  31 H,  31 I,  31 J,  31 K,  31 L in the form of pin terminals protrudes in −Z direction from free end surfaces of the pin support portions  31 A,  31 B,  31 C,  31 D,  31 E,  31 F coaxially therewith. A distance from the bottom surface  31 Z to each free end of each of the terminal electrodes  31 G through  31 L is equal to one another. The same is true with respect to the relationship among terminal electrodes  32 G,  32 H,  32 I,  32 J,  32 K,  32 L, the pin support portions  32 A,  32 B,  32 C,  32 D,  32 E,  32 F, and the bottom surface  32 Z. 
     Six conductive wires  50  are wound over the bobbin  20 . Each conductive wire  50  includes a copper wire coated with an electrically insulating layer. A first conductive wire  50  is directly wound over the sleeve portion  21 , and an insulating tape is formed over the winding portion. A second conductive wire  50  is wound over the first insulating tape, and then a second insulating tape is formed over the second winding portion. In this way, totally six conductive wires  50  and six insulating tapes including an uppermost tape  80  are alternately provided over the sleeve portion  21 . Each one end portion of each conductive wire  50  is wound over each base end portion of each of the terminal electrodes  31 G through  31 L at a position close to each of the pin support portions  31 A through  31 F and is electrically connected to each terminal electrode by soldering. Similarly, each another end portion of each conductive wire  50  is wound over each base end portion of each of the terminal electrodes  32 G through  32 L at a position close to each of the pin support portions  32 A through  32 F and is electrically connected to each terminal electrode by soldering. Each wire has a first part wound over the sleeve portion  21  as a winding portion, and a second part as draw-out portions  50 A drawn out from the winding portion to the terminal electrode. 
     More specifically, as shown in  FIG. 3 , on the terminal base  31 , draw-out portions  50 A electrically connected to the terminal electrodes  31 G,  31 L are drawn out from the winding portion and are engaged with the slope portions  31 T,  31 U and are contacted with the outer peripheral surfaces of the pin support portions  31 B,  31 E. The draw-out portions  50 A are then wound over the base end portions of the terminal electrodes  31 G,  31 L at a position close to the pin support portions  31 A,  31 F ( FIG. 4 ), and are then electrically connected to the terminal electrodes  31 G,  31 L by soldering. 
     On the other hand, other draw-out portions  50 A electrically connected to the terminal electrodes  31 H,  31 I,  31 J,  31 K are drawn out from the winding portion and are engaged with the wire following rectangular protrusions  31 O,  31 P,  31 Q,  31 R,  31 S. The draw-out portions  50 A are then wound over the base end portions of the terminal electrodes  31 H,  31 I,  31 J,  31 K at a position close to the pin support portions  31 B,  31 D,  31 C,  31 D,  31 E ( FIG. 4 ), and are then electrically connected to the terminal electrodes  31 H,  31 I,  31 J,  31 K by soldering. The same is true with respect to draw-out portions  50 A on the terminal base  32 . 
     Soldering of the draw-out portions  50 A to the terminal electrodes is performed by dipping the draw-out portions  50  wound over the terminal electrodes into a molten solder. More specifically, oblique posture of the terminal base  31  is maintained such that lower end faces of the two pin support portions  31 A,  31 B are on an identical horizontal plane parallel to a top surface of the molten solder, and the terminal base  31  is moved downward with maintaining the oblique posture so as to simultaneously dip the end portions of the draw-out portions  50 A on the terminal electrodes  31 G and  31 H. Thus, simultaneous soldering is achieved with respect to these end portions  50 A. The same is true with respect to the end portions of the draw-out portions  50 A in association with the terminal electrodes  31 K and  31 L. 
     Regarding soldering of the remaining draw-out portions  50 A to the remaining terminal electrodes  31 I,  31 J, these terminal electrodes  31 I,  31 J are moved downward into the molten solder while maintaining their vertical orientation with respect to the surface of the molten solder, so that the end portions of the draw-out portion  50 A in association with the terminal electrodes  13 I,  31 J are subjected to simultaneous soldering. The same is true with respect to the soldering of the draw-out portions to the terminal electrodes  32 G through  32 J. In this way, deposition of surplus solder onto the pin support portions  31 A through  31 F, and  32 A through  32 F can be prevented. 
     The imaginary linear draw-out portion  50 A′ intersects with the pin support portion  31 B as shown in  FIG. 3 , and the protruding length of the pin support portion  31 B from the bottom surface  31 Z of the terminal base  31  is greater than that of the pin support portion  31 A as shown in  FIG. 4 . Further, the protruding length of the pin support portion  31 B provides the free end (lower end) of the pin support portion  31 B positioned downstream of the imaginary linear draw-out portion  50 ′ in the −Z direction as shown in  FIG. 4 . Accordingly, this pin support portion  31 B can prevent the conductive wire  50  electrically connected to the terminal electrode  31 G from being mechanically interfered with the terminal electrode  31 H. 
     In the same way, the pin support portions  31 E,  32 B,  32 E can avoid mechanical interference of the draw-out portions  50 A electrically connected to the terminal electrodes  31 L,  32 G,  32 L with the terminal electrodes  31 K,  32 H,  32 K. 
     Various modifications are conceivable. For example, in the above-described embodiment, each draw-out portion  50 A is wound at each base portion of each terminal electrode at a position near each pin support portion. However, each draw-out portion or one of the draw-out portions can be wound at a portion other than the base end portion, for example, near the free end portion of each terminal electrode. 
     More specifically, as shown in  FIG. 5 , in a coil assembly  1 A shown in  FIG. 5 , the rightmost draw-out portion  50 A is wound over the first pin terminal  31 G and electrically connected thereto at a position remote from the free end face of the first pin support portion  31 A and positioned downstream, in the protruding direction (in the direction), of the free end face of the second pin support portion  31 B. The same is applied to the draw-out portion  50 A connected to the pin terminal  31 L. 
     With this arrangement, each free end portion of each terminal electrode can be simultaneously dipped into the molten solder while maintaining vertical orientation of terminal electrodes with respect to the surface of the molten solder for simultaneous soldering the all draw-out portions to the all terminal electrodes. 
     Further, in the above-described embodiment, protruding length of the pin support portion  31 B,  31 E (or  32 B,  32 E) is equal to that of the pin support portion  31 C,  31 D (or  32 C,  32 D). However, the protruding length of the pin support portion  31 B,  31 E ( 32 B,  32 E) can be different from that of the pin support portion  31 C,  31 D ( 32 C,  32 D). For example, in a coil assembly  1 B shown in  FIG. 6 , regarding pin support portion  31 B,  31 C′ protruding length of the most upstream side pin support portion  31 C′ can be greater than that of the pin support portion  31 B positioned immediate downstream of the pin support portion  31 C′ in the −Y direction. The same is true with respect to the pin support portions  31 D′,  31 E. Protruding length of the most upstream side pin support portion  31 D′ can be greater than that of the pin support portion  31 E positioned immediate downstream of the pin support portion  31 D′ in the +Y direction. Thus, mechanical interference of the draw-out portions  50 A electrically connected to the terminal electrodes  31 H,  31 K with the terminal electrodes  31 I,  31 J can be prevented by the elongated pin support portions  31 C′ and  31 D′. 
     Further, the number of the conductive wires and the terminal electrodes and shape of the bobbin and the core are not limited to the above-described embodiment. Furthermore, the coil assembly is not limited to the transformer. 
     While the invention has been described in detail with reference to the specific embodiment thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention.