Patent Publication Number: US-2009237196-A1

Title: Method for manufacturing transformer, and transformer

Description:
TECHNICAL FIELD 
     This invention relates to a transformer which is used for a consumer electronics equipment and a manufacturing method for the transformer. 
     BACKGROUND OF THE INVENTION 
     A transformer is configured in a way such that a core is incorporated into a coil bobbin which is looped around with a coil wire. For the core, conventionally thin laminated silicon steel plates have been used. However, since there is a problem of beat noise in using the core, a ferrite core is used in substitution for the silicon steel plates. 
     For the core of the transformer, generally a core such as an EI-type core or an EE-type core is used. In such the core, outer legs and an inner leg are formed integrally, and a coil bobbin wound around with a coil is configured to be attached to the inner leg. In order to pursuit of efficiency in capacity, space, etc for the transformer comprising a ferrite core, it is important to secure a larger cross section of the core and accommodate the core in the smallest space. However, the transformer having the core integrally formed with an inner leg cannot be efficiently realized to be a large capacity, compact, low profile or space-saving transformer, etc. 
     There is disclosed in Japanese Patent Application Provisional Publication 2005-72261 a transformer which makes it possible to have a larger cross section of a core inner leg by dividing a core cross section into an upper section and a lower section and combining two O-type cores and an I-type core. According to the configuration of the transformer, since a cross section of side legs is divided into an upper section above the I-type core and a lower section beneath the I-type core, a ratio of dimensions of each core may be changed appropriately to realize a low profile transformer, etc. 
     The low profile transformer is configured with a coil bobbin in which the coil is wound around a circumference of a winding-drum section, an inner leg inserted into and penetrating an opening of the winding-drum section, an upper O-type core and a lower O-type which have openings in the center and are located so as to surround the coil bobbin and bind together vertically each of edges of the inner leg protruding from both sides of the winding-drum section. Terminal blocks of shapes of flanges are formed in both sides of the bottom of the coil bobbin. Terminals are implanted in the blocks. 
     DISCLOSURE OF THE INVENTION 
     The above mentioned transformer comprises a coil bobbin with a terminal block. The transformer is assembled in a way that after winding a coil around a circumference of the coil bobbin, a lower core is placed on the terminal block from above, an inner leg is inserted into the coil bobbin from side, and an upper core is placed from above. 
     Thus, there has been a problem that assemblability of the transformer is not so good, since the transformer is not configured to be assembled as stacking up components sequentially in the same direction. 
     In addition to a process of winding a coil around the coil bobbin, a process to insert an inner leg into the coil bobbin from side is needed, which makes the assembly process more complicated. 
     In view of the foregoing various issues, the present invention has been made. An object thereof is to provide a manufacturing method of a transformer which can attain good assemblability of a transformer comprising two O-type cores and an I-type core which is an inner leg, by dividing a core cross section into an upper section and a lower section and by configuring the transformer such that components can be stacked in the same direction or in the upward and downward directions in the assembly process, and to provide a transformer which is manufactured using the method. 
     A manufacturing method of a transformer according to an embodiment of the present invention comprises the step of: incorporating a first O-type core to be stacked on an upper surface of a terminal block having a shape of a frame which is implanted with terminals in bottom surfaces of terminal sections at both ends of the terminal block; incorporating a coil block comprising an I-type core and a coil wound around the I-type core to be stacked on the first O-type core; and incorporating a second O-type core having a shape of a frame to be stacked on the coil block. 
     According to the method, since the transformer is assembled by stacking up members in a direction, efficient assemblability is attained, and the method is suitable for mass production. 
     A transformer according to an embodiment of the present invention comprises: a terminal block having a shape of a frame which is implanted with terminals in a bottom surfaces of terminal sections at both ends of the terminal block; a first O-type core of a shape of a frame which is laid on an upper surface of the terminal block; a coil block including an I-type core of which both ends are placed on the first O-type core; a second O-type core having a shape of a frame which is placed on the I-type core of the coil block. 
     According to the configuration, since the transformer is assembled by stacking up members in a direction, efficient assemblability is attained, and the method is suitable for mass production. 
     In addition, when the terminal block is made to be a shape of a frame, the terminal block and a coil block may not interfere with each other, and a low profile transformer is easily realized. 
     Optionally, I-type core positioning sections having a shape of a plate are formed to stand upward at central parts of outer surfaces of both ends of terminal sections of the terminal block; core attaching sections having a shape of a plate are formed upward on inner surfaces of the terminal sections, an I-type core is placed between the I-type core positioning sections; and the first O-type core and the second O-type core are attached on outsides of the core attaching sections. 
     According to the configuration, an I-type core of the coil block is positioned by the I-type core positioning sections, which can prevent looseness and rattling of the I-type core in a core&#39;s axial direction. In addition, the second O-type core is incorporated while being positioned by the core attaching sections. 
     Optionally, there are provided pawl sections which are configured to engage with the second O-type core at outside of upper ends of the core attaching sections. 
     Alternatively or additionally, upper ends of the core attaching sections and the second O-type core are fixed with each other with adhesive. 
     With the configuration, incorporated components are hard to be loosened. 
     A production method of a transformer according to some of the embodiments of the present invention comprises incorporating an first O-type core having a shape of a frame on a terminal block having a window to be formed in a shape of a frame, being implanted with terminals in bottom surfaces of terminal sections at both ends of the terminal block, and having recessed portions formed in bottoms of connecting sections which connect both ends of the terminal block so that the first O-type core is stacked on the terminal block from below, incorporating a coil block comprising an I-type core and a coil wound around the core into the window of the terminal block from above, incorporating a second O-type core having a shape of a frame to be stacked on an upper surface of the coil block from above. 
     According to the method, since the transformer is assembled as stacking each members from upward and downward directions, efficient assemblability is attained, and the method is suitable for mass production 
     A transformer according to an embodiment of the present invention comprises a terminal block having a shape of a frame which is implanted with terminals in bottom surfaces of terminal sections at both ends of the terminal block, a first O-type core which is incorporated into recessed portions formed in a bottom of the terminal block, a coil block which has an I-type core and a coil wound around the core and is incorporated in a window of the terminal block from above, and a second O-type core having a shape of a frame which is placed on both ends of the I-type core of the coil block. 
     According to the method, since the transformer is assembled as stacking members in the upward and downward directions, efficient assemblability is attained, and the method is suitable for mass production. 
     Optionally, a window of a shape substantially the same as an outer shape of the coil block is formed in the terminal block, second O-type core attaching sections are formed to stand upward at both sides of the terminal sections of the window, in the second O-type core attaching sections, substantially U-shaped protrusions which receive ends of the I-type core are formed and core attaching pieces which extend outward in a shape of a flange at inner ends of the protrusions and of which upper ends protrude upward from upper ends of the protrusions are formed, and the second O-type core is located between the upper ends of the core attaching pieces and the upper ends of the protrusions. 
     According to the configuration, since a coil block is placed in a window of the terminal block, height dimension can be reduced to realize a low profile transformer. In addition, since the second O-type core attaching sections have substantially the same forms as an outer form of the coil block, the coil block located in the core can be positioned. Further, since a step is formed in the second O-type core attaching portion, and the second O-type core can be mounted in the step, thickness of the second O-type core can be covered by the step portion, height dimension can be reduced to realize a low profile transformer. 
     Optionally, there are provided pawl sections which are configured to engage with the second O-type core at outside of upper ends of the core attaching pieces. 
     Alternatively or additionally, upper ends of the core attaching pieces and the second O-type core are fixed with each other with adhesive. 
     In an aspect of one of some embodiments of the present invention, the coil block is a bobbinless coil block and comprises: a thin insulating material laid around a circumference of the I-type core; margin tapes laid on both ends of the insulating material; and a coil wound between the margin tapes. 
     According to the configuration, since the coil block is bobbinless, a bobbin is not necessary and a process to insert the I-type core into the bobbin is not also necessary. Further, since no bobbin is on a circumference of the I-type core, and a coil is placed on a thin insulating material, the I-type core and the coil are placed in a close distance, and excellent magnetic coupling is attained. 
     A manufacturing method of a transformer according to an embodiment of the present invention comprises the step of: incorporating a coil block comprising an I-type core wound around with a coil to be stacked on a first O-type core having a shape of a frame which has a window; incorporating a second O-type core having a shape of a frame and having a window to be stacked on the coil block; incorporating a first terminal block main body and a second terminal block main body which have a bisection structure to be stacked from outside on the second O-type core, placing terminal sections of the first and second terminal block main bodies on legs of the second O-type core, attaching inner ends of the pair of attachment pieces which are formed part from each other inside of each terminal section by inserting the pieces into terminal block locking grooves which are formed in the I-type core through the window of the second O-type core, and attaching the first and second terminal blocks. 
     According to the configuration, since the transformer is assembled by stacking up members in a direction, efficient assemblability is attained, and the method is suitable for mass production. 
     A transformer according to an embodiment of the present invention comprises: a first O-type core having a shape of a frame which has a window; a coil block comprising an I-type core incorporated in the first O-type core and a coil wound around the core; a second O-type core having a shape of a frame which has a window and is incorporated in the coil block; a first terminal block main body and a second terminal block main body which are placed on the second O-type core, wherein the first terminal block main body and the second terminal block main body include: terminal sections which are placed on legs of the second O-type core; and attaching pieces which protrude inside terminal sections in a direction of the I-type core and are attached to terminal block locking grooves formed in the I-type core, so that the first terminal block main body and the second terminal block main body are attached to the second O-type core. 
     According to the configuration, since the transformer is assembled by stacking up members in a direction, efficient assemblability is attained, and the method is suitable for mass production. 
     Optionally, the coil block comprises: a thin insulating material which is laid around a circumference of the I-type core; margin tapes which are laid on both ends of the insulating material, a coil which is wound between the margin tapes, wherein a terminal block locking groove is formed outside of the margin tapes around circumference of the I-type core. 
     According to the configuration, since the coil block is bobbinless, a bobbin is not necessary and a process to insert the I-type core into the bobbin is not also necessary. Further, since no bobbin is on a circumference of the I-type core, and a coil is placed on a thin insulating material, the I-type core and the coil are placed in a close distance, and excellent magnetic coupling is attained. 
     Optionally, the transformer further comprises pawl sections which are configured to engage with the first O-type core at outside of lower ends of the core attaching pieces. 
     Alternatively or additionally, lower ends of the core attaching pieces and the first O-type core are fixed with each other with adhesive. 
     In an aspect of an embodiment of the present invention, the transformer is wound with a tape on the circumference thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  shows an exploded perspective view of the first embodiment of the present invention. 
         FIGS. 2  ( a )-( c ) show explanatory drawings of an assembly process of a coil block used for an embodiment of the same as above. 
         FIG. 3  shows a perspective view of the first embodiment of the present invention. 
         FIG. 4  shows a central longitudinal section of the same as above. 
         FIG. 5  shows an example of prevention of loosening of assembled components of the first embodiment of the present invention. 
         FIG. 6  shows another example of prevention of loosening of assembled components of the first embodiment of the present invention. 
         FIG. 7  shows an assembly perspective view of another example of prevention of loosening of assembled components of the first embodiment of the present invention. 
         FIG. 8  shows an exploded perspective view of a second embodiment of the present invention. 
         FIG. 9  shows an assembly perspective view of the same as above. 
         FIG. 10  shows a central longitudinal section of the same as above. 
         FIG. 11  shows an exploded perspective view of a third embodiment of the present invention. 
         FIGS. 12  ( a )-( d ) show explanatory drawings of an assembly process of a coil block used for embodiment of the same as above. 
         FIG. 13  shows an assembly perspective view of the third embodiment of the present invention. 
     
    
    
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
           1 , 10  terminal block 
           1 A, 1 B terminal block main body 
           1   a  upper surface 
           1   b  terminal section 
           1   b ′ outer surface 
           1   c  connecting section 
           1   d  output groove 
           1   e  I-type core positioning section 
           1   f  window 
           1   g  core attaching section 
           1   g ′ pawl 
           1   h  I-type core mounting section 
           1   i  second O-type core attaching section 
           1   j  protrusion 
           1   k  core attaching piece 
           1   l  output section 
           2  first O-type core 
           2   b  one leg 
           2   c  link leg 
           3  I-type core 
           4  coil 
           5 ,  5 A coil block 
           5   b  terminal block locking groove 
           6  second O-type core 
           6   a  window 
           6   b  one leg 
           6   b ′ on one leg 
           6   c  link leg 
           7 ,  7 A terminal 
           8  insulating material 
           9  margin tape 
           10  terminal block 
           10   a  terminal section 
           10   b  one surface 
           10   c  output groove 
           10   d  other surface 
           10   e  inner surface 
           10   f  attaching piece 
         a adhesive 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, embodiments of the present invention are described with reference to the accompanying drawings. 
     First Embodiment 
       FIGS. 1-7  show exploded perspective views of small-size transformers according to embodiments of the present invention.  FIG. 1  shows an exploded perspective view of the first embodiment. 
     The transformer according to the embodiment is configured so that the transformer can be assembled by stacking a first O-type core  2 , a coil block  5  comprising an I-type core  3  and a coil  4  wound around a circumference of the core  3 , and a second O-type core  6  sequentially from one direction on a terminal block  1  of a straight pin type as shown in  FIG. 1 . 
     In other words, the first O-type core  2  is placed such that the first O-type core  2  is stacked on an upper surface la of the terminal block  1 . An outer form of a top plane of the terminal block  1  is configured to be a shape of a frame including a pair of terminal sections  1   b  which are facing to and apart from each other and have, in their inside, a rectangular window  1   f  in conformity with the first and second O-type cores  2  and  6 , and a connecting section  1   c  which connects the terminal section  1   b , and an upper surface  1   a  is flat to place the first O-type core  2  on the face. Further, terminals  7  of a straight pin type are implanted in underside of the terminal sections  1   b  formed at both ends, and output grooves  1   d  for leader lines are formed between adjacent terminals  7 . Further, recessed portions  1   c ′ are formed underneath of connecting sections  1   c.    
     In substantially central parts of the outer surfaces  1   b ′ side of each terminal sections  1   b , as shown in the figure, I-type core positioning sections  1   e  which extend in a vertical direction upward along the outer surfaces  1   b ′ are formed. 
     Further, core attaching sections  1   g , which are used to attach the I-type core  3  and to position the first O-type core  2  and the second O-type core  6 , are formed on the inner surface of the side of the window  1   f  to extend upward. The core attaching sections  1   g  are formed to extend upward at inside positions of the I-type core positioning sections  1   e  such that the core attaching sections  1   g  are parallel to the I-type core positioning sections  1   e.    
     In substantially central parts of the core attaching sections  1   g , I-type core mounting sections  1   h  having form of vertically long notches are formed. The I-type core mounting sections  1   h  are rectangular, the width dimension thereof corresponds to the width dimension of the I-type core  3 . Further, the core attaching sections  1   g  are formed over the whole internal surface of window  1   f  sides of terminal sections  1   b . The width dimensions of the core attaching sections  1   g  are equal to the corresponding width dimensions b of the windows  2   a  and  6   a  of the first O-type core  2  and the second O-type core  6 . 
     In the assembly process, the first O-type core  2  is placed from above to be stacked on the upper surface  1   a  of the terminal block  1  as shown with an arrow. The first O-type core  2  does not protrude outward from the terminal block  1 , and increase of a floor space is prevented. At this state, since the core attaching sections  1   g  are placed inside the window  2   a  of the first O-type core  2 , position shifts and looseness are prevented. Next, both ends of the I-type core  3  to which the coil is attached are set up into the I-type core mounting sections  1   h  of the core attaching sections  1   g  between the I-type core positioning sections  1   e  which are placed on each outer surfaces  1   b  of the terminal sections  1   b.    
     The coil block  5  comprising the I-type core  3  and the coil  4  are assembled as follows. 
     As shown in  FIG. 2  ( a ), a thin insulating material  8  such an insulating paper or an insulating tape is wound up around an outer peripheral portion excluding both ends of the I-type core  3 . 
     Next, as shown in  FIG. 2  ( b ), margin tapes  9  are wound around both ends of the insulating material  8  in prescribed times in a shape of a flange. 
     Next, the coil block  5  is assembled by winding a coil wire between the margin tapes  9  on the both ends to make the coil  4 . 
     As thus described, in the present invention, the coil block  5  is configured to be bobbinless by winding a coil wire around a circumference of the I-type core  3  via the insulating material  8 . 
     Since the coil block  5  are placed between a pair of the I-type core positioning sections  1   e  positioned facing to and apart from each other, the I-type core positioning sections  1   e  prevent looseness in the axial direction. Further, a lower surface of the I-type core  3  contacts the upper surface of the first O-type core  2 . 
     Next, the second O-type core  6  is placed to be stacked on the I-type core  3  of the coil block  5  from above, so that the second O-type core  6  contacts the I-type core  3  and makes a closed magnetic circuit. In this case, since the upper parts of the core fixing sections  1   g  are located inside the window  6   a  of the second O-type core  6 , position shifts and looseness of the second O-type core  6  can be prevented. 
       FIG. 3  and  FIG. 4  show a perspective view and a central longitudinal cross section of the transformer after assembly respectively. Looseness of comportments can be prevented by winding a tape T around a circumference. 
     Alternately, as shown in  FIG. 5 , looseness in an upward direction can be prevented by applying adhesive extending from ends of the core attaching sections  1   g  to the second O-type core  6 . 
     Alternatively, as shown in  FIG. 6  and  FIG. 7 , pawls  1   g ′ may be made at ends of the core attaching sections  1   g  so that the pawls  1   g ′ prevent looseness in an upward direction after press-fitting of the second O-type core  6 . 
     Further, leader lines of the coil  4  are tucked up to the terminals  7  appropriately and are connected by soldering as well known in the art, which is not particularly illustrated. 
     Second Embodiment 
       FIG. 8  shows a second embodiment according to the present invention. According to the embodiment, the transformer comprises terminals  7 A of an L-pin type and is configured such that the first O-type core  2 , the second O-type core  6  and the coil block  5  are stacked with respect to the terminal block  1  from above and from below. Further, assembling of the first O-type core  2  and the coil block  5 , etc., is innovated to realize a low profile transformer. 
     That is, an appropriate number of L-type terminals  7 A are implanted in the terminal sections  1   b  formed at both ends of the terminal block  1 . Bending sections of the L-shaped terminals  7 A are implanted in the terminal sections  1   b  and ends  7   a  for tucking up the leader lines protrude from the outer surfaces  1   b ′ of the terminal sections  1   b . The other ends  7   b  for mounting protrude from the bottom surfaces of the terminal sections  1   b′.    
     The first O-type attaching sections comprising recessed portions  1   c ′ are formed in bottoms of the connecting sections  1   c  connecting the terminal sections  1   b  at the both ends. 
     Shapes of the first O-type core attaching sections comprising the recessed portions  1   c ′ are shapes suitable to accommodate the first O-type core  2  beneath the terminal block  1 . 
     A window  1   f  of which a shape is substantially the same as a shape of the coil block  5  is formed in the terminal block  1 , and the coil block  5  is placed at the position. In addition, the coil block  5  is configured similarly to the above-mentioned first embodiment. 
     Both ends of the window  1   f , that is, each side of the terminal sections  1   b , have shapes corresponding to the end portions of the coil block  5 . The second O-type core attaching portions  1   i  are placed standing in vertical direction from the upper surface of the terminal block  1 . 
     The second O-type core attaching sections  1   i  is provided with protrusions  1   j  which protrude in the U shapes toward outer surface of the terminal sections  1   b ′ and accommodate, in its inside, the ends of the I-type core  3  having an almost U-shape, and core attaching pieces  1   k  which extend in the orthogonal direction to the projection of the protrusions  1   j  at the inner ends of the protrusions  1   j , that is, extend toward the connecting sections  1   c  in a shape of a flange are formed so that the edge of the margin tape  9  of the coil  4  of the coil block  5  is situated in the inside. 
     The core attaching pieces  1   k  are formed so that upper ends of the pieces are higher than upper ends of the protrusions  1   j . The difference in height is equal to thickness C of the second O-type core  6 , and the second O-type core  6  is placed on the upper ends of the protrusions  1   j . It is noted that at outer ends of the core attaching pieces  1   k , namely, on the sides of the connecting sections  1   c , output sections  11  are formed in shapes of notches to draw leader lines of the coil  4  to the terminal  7 A sides. 
     In the assembly process, the first O-type core  2  is placed stacking up beneath the recessed portions  1   c ′ in the bottom of the connecting sections  1   c  of the terminal block  1 . 
     Next, the coil block  5  is located in the window  1   f  and in the second O-type core attaching sections  1   i  such that the coil block  5  is stacked on the first O-type core  2  from above. 
     Next, the second O-type core  6  is placed to be stacked on the upper ends of the protrusions  1   j  from above, and on the upper surface of inner ends of the I-type core  3  located underneath are made to contact the lower surface of the second O-type core  6  to configure a closed magnetic circuit. 
       FIG. 9  shows an assembly perspective view. Leader lines of the coil  4  of the coil block  5  are drew out via through holes of the output sections  11 , and tucked up to the prescribed terminals  7 A. 
       FIG. 10  shows a central longitudinal section of  FIG. 9 . 
     Further, for prevention of loosening of components, a tape may be wound around a circumference of the assembled transformer as shown in  FIGS. 3 and 4  in the first embodiment. Alternatively, as shown in  FIG. 5 , adhesive may be applied to be extended from ends of the core attaching pieces  1   k  to the second O-type core  6 . Alternatively, as shown in  FIG. 7 , pawls may be made at ends of the core attaching pieces  1   k  to prevent loosening. 
     Third Embodiment 
       FIG. 11  shows an exploded perspective view of a third embodiment of the present invention. According to the embodiment of the present invention, the coil block  5 A and the second O-type core  6  are mounted to be stacked on the first O-type core  2 , and a terminal block  10  which is formed with two divided components is also mounted. 
     In the embodiment, as shown in  FIG. 11 , the first O-type core  2  and the second O-type core  6  have windows  2   a,    6   a  similarly to the first and second embodiments. 
     As shown in  FIG. 12  ( a ), the coil block  5 A comprises an I-type core  5   a  on which terminal block locking grooves  5   b  are formed inward from ends of the core, and a coil  4  which is wound around a circumference of the I-type core  5   a  between margin tapes  9 . The terminal block locking grooves  5   b  are formed on both sides of the both ends of the I-type core  5   a.    
     Then, as shown in  FIG. 12(   b ), a thin insulating material  8  such as an insulating tape or an insulating paper is wound between the terminal block locking grooves  5   b  which are formed on both sides of the both ends of the I-type core  5   a.    
     Next, as shown in  FIG. 9(   c ), a margin tape  9  is wound around at ends of the insulating material  8  in shapes of flanges. The margin tape  9  is placed inside of the terminal block locking grooves  5   b.    
     Next, as shown in  FIG. 12(   d ), a coil wire is wound between the margin tapes which are placed apart from each other to make the coil  4 , and the coil block  5 A is assembled. 
     Further, in the embodiment, as shown in  FIG. 11 , the terminal block  10  is configured with the first terminal block main body  1 A and the second terminal block main body  1 B which are apart from each other. 
     The first terminal block main body  1 A comprises a terminal section  10   a  configured with insulating resin on which appropriate number of straight type terminals  7  are implanted in the surfaces  10   b . Between adjacent terminals  7 , output grooves  10 C are formed for drawing out leader lines. A longitudinal shape of the terminal section  10   a  is formed to correspond to a length and a width of one of legs  6   b  of the O-type core  6 . The other surface  10   d  of the terminal section  10   a  is a flat surface, and is placed on one leg  6   b ′ of the second O-type core  6 . 
     A pair of attaching pieces  10   f  which are plates extending toward the coil block  5 A incorporated in the first O-type core  2  are formed on insides  10   e  of the terminal sections  10   a , namely the window  6   a  side of the second O-type core  6 . 
     Each of insides of the attaching pieces  10   f  is inserted into and attached to the terminal block locking grooves  5   b  which are formed on the both sides of the I-type core  5   a  in a vertical direction. Further, outer surfaces of the attaching pieces  10   f  contact with inner surfaces of link legs  2   c,    6   c  which are formed at ends of legs  2   b,    6   b  of the first O-type core  2  and the second O-type core  6  placed apart from each other and which link the legs to be fixed. 
     Since the second terminal block main body  1 B is formed similarly to the first terminal block main body  1 A, a corresponding member is indicated by the same reference number. 
     In the assembly process, as shown with a solid arrow line in  FIG. 11 , each of both ends of the I-type core  5   a  of the coil block  5 A is placed on the central part of the upper surface  2   b ′ of one of legs  2   b  of the first O-type core  2 . 
     Next, the second O-type core  6  is placed on both ends of the I-type core  5   a  to contact each other. 
     Next, bottom surfaces  10   d  of the first terminal block main body  1 A and the second terminal block main body  1 B are placed on one of legs  6   b  of the second O-type core  6  and the other leg  6   b  which are set apart and parallel with each other. In the case, each of insides of attaching pieces  10   f  of the first terminal block main body  1 A and the second terminal block main body  1 B are inserted into the terminal block locking grooves  5   b  of the I-type core  5   a  through the window  6   a  of the second O-type core  6 , and attached. 
     In the assembly, as shown with an arrow of broken line in  FIG. 11 , the first O-type core  2  may be incorporated in the coil block  5 A, and the assembled unit may be incorporated in the second O-type core  6 , and then the first terminal block main body  1 A and the second terminal block main body  1 B may be incorporated in the second O-type core  6  from above. 
       FIG. 13  shows a perspective view of an assembled transformer. To prevent loosening of members after assembly, as described in  FIG. 3  and  FIG. 4  in the first embodiment, a tape may be wound around the circumference. Alternatively, as described in  FIG. 5 , adhesive may be applied to upper portions of the attaching pieces  10   f  to extend to the first O-type core  2 . Alternatively, as described in  FIG. 7 , pawls may be made at ends of the attaching pieces  10   f  to prevent loosening.